JPH09123926A - Motor-driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide optimum steering assist force at the time of steering reversing while restricting power consumption under a steering blocked condition by prohibiting or restricting the decrease correction of a target current signal based on steering torque for a prescribed time after a steering torque signal is reversed. SOLUTION: In the control means 15 of this motor-driven power steering device 1, a target current signal setting means 21 sends a target current signal for a steering torque signal to a multiplying means 27, and performs the decrease correction of the target current signal by multiplying a correcting coefficient based on the steering torque signal from a correcting means 22 to control a motor 10 through a drive means 16 by the target current signal. At this time, a correction restricting means 23 switches the steering torque signal sent to a correction condition discriminating means 25 based on the polarity reversing signal of the steering torque signal, for example, to zero value for a prescribed time, thus prohibiting the decrease correction of the target current signal based on steering torque in the opposite direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus that reduces the steering force of a driver by causing the power of an electric motor to act on a steering system as a steering assist force, and more particularly to a steering thrust control near a rack end. The present invention relates to an electric power steering device that improves the deterioration of steering feel.

[0002]

2. Description of the Related Art A conventional electric power steering device is
As disclosed in Japanese Patent Application Laid-Open No. 64-9064 by the applicant of the present application, steering force detecting means for detecting the steering force (steering torque) of the steering system, or steering speed of the steering force detecting means and the steering system (steering rotation speed). ) Is detected, and an overload prevention means is provided, and when the steering force exceeds a predetermined value, or when the steering force exceeds a predetermined value and the steering speed is equal to or less than the predetermined value, overload prevention is performed. The means is operated to reduce the electric current of the electric motor for applying the steering assist force to the steering system.

The conventional electric power steering apparatus having such a structure is, for example, of a rack and pinion type, even though the rack shaft is moved to the maximum steering position (abutting the rack end) by the steering operation of the driver. If the steering force is applied to the steering wheel, or if the steering wheel cannot be steered due to an obstacle on the road, the steering force is applied. Exceeds a prescribed value, or the steering force exceeds a prescribed value and the steering speed is below a prescribed value (hereinafter referred to as "steering state"), and unnecessary current flowing to the motor is reduced. As a result, the power consumption of the electric motor is reduced, and a switching element (for example, power F
(ET: field effect transistor) and the like are prevented from being deteriorated or damaged.

[0004]

The conventional electric power steering system detects the steering thrust state as described above by the steering force (steering torque) and the steering speed (steering rotation speed) or the electric motor rotation speed. , The electric current flowing through the electric motor was reduced to limit the unnecessary steering assist force generated by the electric motor.However, when the steering operation is performed in the opposite direction after detecting the steering thrust state (hereinafter, steering torque The operation that changes from one to the other is referred to as "steering back"). In order to recover from the steering thrust state, the electric motor is stopped even though a sufficient steering assist force is required. Since the motor is suddenly rotated in the opposite direction, the inertial force of the electric motor detects the thrusting state of the steering system again and the steering assist force of the electric motor is reduced. Since it is limited, it is not possible to obtain sufficient steering assist force corresponding to steering operation,
There is a problem that causes deterioration of steering feeling.

In particular, when the steering assisting force is reduced or returned to the original state, when a method of reducing or returning with time is used, the steering wheel is suddenly turned back in the opposite direction after detecting the thrusting state of the steering wheel. However, since the steering assist force is not yet returned to the original state, there is a problem that the steering thrust state is detected.

Further, such a phenomenon may occur when the steering wheel is turned back when the steering wheel is not in the thrusting state.

In order to prevent the steering assist force from being restricted when the steering wheel is turned back, it is necessary to make the steering thrust condition detection condition strict.
There is a problem that the detection of the original steering thrusting state is delayed, and the power consumption of the switching element that constitutes the electric motor or bridge circuit increases.

The present invention has been made to solve the above problems, and its purpose is to limit the power consumption when the steering wheel is in a thrusting state and to obtain an optimum steering assist force when the steering wheel is turned back. To provide a device.

[0009]

In order to solve the above-mentioned problems, the control means of the electric power steering apparatus according to claims 1 and 2 has a predetermined time after the steering torque signal is changed from one direction to the opposite direction. Is equipped with a correction limiting means for prohibiting or limiting the reduction correction of the target current signal based on the steering torque.

In the electric power steering apparatus according to the present invention, the control means is provided with the correction limiting means for prohibiting or limiting the reduction correction of the target current signal based on the steering torque in the opposite direction for a predetermined time when the steering is turned back. With respect to the steering operation in the opposite direction, the decrease correction can be prohibited or limited to compensate the steering characteristic corresponding to the steering torque.

The control means according to the second aspect can detect the steering thrust state more accurately than the control means according to the first aspect.

The control means of the electric power steering apparatus according to a third aspect of the present invention is characterized by comprising time gradual increase / decrease means for gradually increasing / decreasing the correction correction of the target current signal and the subsequent correction correction.

In the electric power steering apparatus according to the present invention, the control means is provided with the time gradual increase / decrease means for gradually increasing / decreasing the target current signal decrease correction and the subsequent return correction. During the restoration correction, the electric motor current is gradually decreased and increased over time, and the steering assist force acting on the steering system can be smoothly decreased and increased.

The control means of the electric power steering apparatus according to the present invention prohibits the decrease correction for the steering torque in the opposite direction for a predetermined time after executing the decrease correction of the target current for one of the steering torques or It is characterized in that a limiting means for limiting is provided.

In the electric power steering apparatus according to the present invention, the control means prohibits the decrease correction for the steering torque in the opposite direction for a predetermined time after executing the decrease correction of the target current for either one of the steering torques, or Since the limiting means for limiting is provided, in the case of having a correcting means for continuously changing the decrease correction and the return correction with time, the decrease correction is prohibited or restricted to cope with the steering torque at the time of sudden steering back. The steering characteristics can be compensated.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The electric power steering apparatus of the present invention corrects the electric motor current to decrease when the condition that the steering torque exceeds the predetermined value or the condition that the steering torque exceeds the predetermined value and the steering rotation speed falls below the predetermined value are satisfied. The reduction correction control that reduces the power consumption of the electric motor and the switching element that constitutes the electric motor drive circuit is prohibited or limited, and the steering characteristic corresponding to the steering torque is obtained when the steering wheel is turned back to obtain the optimum steering feeling. Is to be done.

FIG. 1 is an overall configuration diagram of an electric power steering apparatus according to the present invention. In FIG. 1, an electric power steering apparatus 1 includes a universal joint 3 on a steering shaft 2 provided integrally with a steering wheel 17.
A manual steering force generating means 6 is connected to a pinion 5A of a rack & pinion mechanism 5 provided in a steering gear box 4 via a connecting shaft 3 provided with A and 3B.

The rack shaft 7 is provided with rack teeth 7A which mesh with the pinion 5A, and reciprocates by these meshes.
The left and right front wheels 9 as steering wheels are connected to both ends thereof via tie rods 8.

In this way, the steering wheel 1
At the time of seven-wheel steering, the front wheel 9 is steered by manual steering via the normal rack-and-pinion type manual steering force generating means 6 to change the direction of the vehicle.

In order to reduce the steering force by the manual steering force generating means 6, an electric motor 10 for supplying a steering assist force is arranged coaxially with the rack shaft 7, and a ball screw mechanism 11 provided coaxially with the rack shaft 7. Converted to thrust through the rack shaft 7
(Ball screw shaft 11A).

A steering torque sensor 12 for detecting the direction and magnitude of the driver's manual steering torque is arranged in the steering gear box 4, and the steering torque of an analog electric signal corresponding to the steering torque detected by the steering torque sensor 12 is arranged. The signal T _S is provided to the control means 15. Alternatively, a steering torque sensor 12 for detecting the direction and magnitude of the driver's manual steering torque, and a steering rotational speed sensor 13 for detecting the direction and magnitude of the steering rotational speed of the steering wheel 17 operated by the driver are arranged. steering torque signal T _S of the analog electric signal sensor 12 corresponding to the steering torque detected, controls each of the steering rotational speed signal N _S of the analog electric signal steering rotational speed sensor 13 corresponding to the steering rotational speed detected means 15 To provide.

It should be noted that instead of the steering rotation speed sensor 13, an electric motor rotation speed sensor for detecting the rotation speed of the electric motor 10 may be provided to calculate the steering rotation speed N _S from equation (1).

[0023]

N _S = K ₁ (N _M −dT _S / dt) where K ₁ is a constant, N _M is the motor rotation speed, dT _S / d
t is a differential value of the steering torque T _S

An electric motor rotation speed sensor is arranged in place of the steering rotation speed sensor 13, and the electric motor rotation speed signal (N _M ) detected by the electric motor rotation speed sensor is supplied to the control means 15 instead of the steering rotation speed N _S. It may be configured to.

Further, an electric motor voltage sensor and an electric motor current sensor are provided instead of the electric motor rotation speed sensor, and the electric motor voltage V _M detected by the electric motor voltage sensor and the electric motor current I _M detected by the electric motor current sensor are used. The rotation speed N _M can also be calculated.

[0026]

N _M = (V _M -K ₂ * I _M ) / K ₃ where K ₂ and K ₃ are constants

The control unit 15 various arithmetic unit microprocessor-base, processing means, signal generating means, constituted by a memory or the like, the motor control signal V _O corresponding to the steering torque signal T _S (e.g., an ON signal and a PWM signal To generate a mixed signal of (1) to drive and control the motor driving means 16.

Further, the control means 15 controls the steering torque signal T
_S , or steering torque signal T _S, and control of correction means for reducing and correcting the target current signal ( _IMS ) corresponding to the steering torque signal T _S based on the steering rotation speed signal N _S or the motor rotation speed (N _M ). a correction limiting means prohibits or limits the condition steering torque signal T _S exceeds a predetermined value or the steering torque signal T _S exceeds a predetermined value, and the steering rotational speed signal N _S or motor rotation speed, (N _M) When the value is below a predetermined value, the reduction correction control of the correction means for canceling the correction of the target current signal ( _IMS ) is released, or the reduction correction is limited to show the steering characteristic at the time of turning the steering wheel to the steering torque signal. Corresponding to T _S.

Further, the control means is a time gradual reduction means, a time
A target current signal (I _MS) Decrease correction,
Alternatively, the target current signal (I_MS) Decrease or
The steering characteristics are smoothed by gradually changing the increase over time.
Change easily.

The motor driving means 16 is constituted by a bridge circuit composed of, for example, four power FET (field effect transistor) switching elements, and the motor voltage V _M is supplied based on the motor control signal V _O supplied from the control means 15. Is output to drive the electric motor 10.

FIG. 2 is a block diagram of the essential parts of the electric power steering apparatus according to the first aspect. In FIG.
The control means 15 of the electric power steering device 1 includes a target current signal setting means 21, a correction means 22, and a correction limiting means 2.
3. The drive control means 24 is provided.

The target current signal setting means 21 comprises an A / D conversion means, a memory such as a ROM, and the steering torque sensor 12
The steering torque signal T _S fed into a steering torque signal T _D digital from, into a target current signal I _MS which is set in advance based on the steering torque signal T _D, to the steering torque signal T _D supplying a target current signal I _MS to the multiplication means 27 of the correction means 22.

The steering torque signal in FIG. 8 (T _D) - indicates a target current signal (I _MS) characteristic diagram. As shown in FIG. 8, the target current signal setting means 21 supplies a positive polarity target current signal _IMS (+) to the steering torque signal T _D (+ polarity) corresponding to the steering torque in the right direction. On the other hand, for the steering torque signal T _D (-polarity) corresponding to the steering torque in the left direction, the target current signal _IMS (-) of negative polarity is supplied.

The correction means 22 is a correction condition determination means 25,
Correction coefficient generation means 26, comprising a multiplication unit 27, the correction coefficient K _H a (0 <K _H ≦ 1) generated based on the steering torque signal T _S supplied from the steering torque sensor 12, the correction coefficient K _H The target current signal I _MS is multiplied to obtain the target current signal I _MS
Is corrected to decrease the target current signal I _MSH to drive control means 24.
To supply.

The correction condition judging means 25 comprises a comparing means,
The steering torque signal T _Q (the same as the steering torque signal T _S ) supplied to the switching means 30 is compared with the reference torque value T _F , and the steering torque signal T _S exceeds the reference torque value T _F (T _S > T _R ). In this case, the correction judgment signal J _H (for example, H level) is provided to the correction coefficient generating means 26.

The reference torque value T _F is set to a value corresponding to a sufficiently large steering torque signal T _S such as the steering wheel thrusting state.

The correction coefficient generation means 26 outputs a predetermined correction coefficient K _H (0 <K _H <1) and an L level correction judgment signal J _H when the H level correction judgment signal J _H is supplied, for example. When supplied, the correction coefficient K _H (= 1) that gradually increases to 1 in a predetermined time is supplied to the multiplication means 27.

FIG. 3 is a block diagram of the essential parts of one embodiment of the correction coefficient generating means. In FIG. 3, the correction coefficient generating means 26 includes a correction coefficient setting means 41 and a time gradual increase / decrease means 4.
2 is provided. The correction coefficient setting means 41 includes a memory such as a ROM, stores coefficients of 1 and K _C less than 1 in advance, and corrects the correction coefficient 1 based on the L level correction determination signal J _H , while the H level correction determination is performed. A binary correction coefficient K _X having a correction coefficient K _C less than 1 is output to the time gradual increase / decrease means 42 based on the signal J _H.

Each of the time gradual increasing / decreasing means 42 has two kinds of function calculating means and timer means, and when the correction judgment signal J _H is switched from L level to H level, the correction judgment signal J _H is at L level. The fall time T _A is calculated by calculating and outputting a predetermined function (for example, a linear function) from the correction coefficient 1 to the correction coefficient K _C at which the correction determination signal J _H is H level.
Then, the correction coefficient K _C (0 <K _C <1) having a constant value is supplied to the multiplication means 27 as the correction coefficient K _H from the falling time T _{A to the} predetermined time T _K.

On the other hand, the correction judgment signal J _H changes from H level to L
When switched to the level, the correction coefficient K _C from the up correction coefficient 1 another predetermined function (e.g., a linear function) by calculating and outputting a continuously increased at the rising time T _B, time (T _K + T _B) after the correction the correction coefficient 1 factor K _H
Is supplied to the multiplication means 27.

FIG. 4 shows an example of a time characteristic diagram of the correction coefficient. In FIG. 4, when the correction determination signal J _H switches from L level to H level, the correction coefficient K _H is
From time t = 0 to time t = T _A 1 linear function (K _H = -α
* T + 1), the decrease correction is performed, and the time t = T _A
The correction coefficient K _C (constant value) is maintained until a predetermined time T _K thereafter.

On the other hand, when the correction judgment signal J _H is switched from the H level to the L level at the predetermined time T _K , the correction coefficient K _C is a one-hour function (K K) from the time T _K to the time (T _K + T _B ). _{When H} = K _C + β * t), the restoration correction is performed to increase to the correction coefficient 1, and the correction coefficient 1 is maintained after the time (T _K + T _B ). Note that the rising slope β is set to be larger than the falling slope α.

The multiplying means 27 includes a multiplication function of multiplier or software control, the correction coefficient K _H supplied from the correction coefficient generator 26, the multiplication of the target current signal I _MS supplied from the target current signal setting unit 21 process running (K _H * I _MS), provides the target current signal target current signal _{I MSH (= K H * I} MS) drive control means 24 for the I _MS decreased corrected by the correction factor K _H.

The correction limiting means 23 is the polarity reversal detecting means 2
8, the timer means 29, a switching unit 30, the steering torque signal T _S for a predetermined time and supplies the correction condition determining means 25 based on the polarity inversion signal P _H of the steering torque signal T _S supplied from the steering torque sensor 12 During T _K , the steering torque signal T _O (for example, set to 0 value) is switched, and this steering torque signal T _O (for example, set to 0 value) is supplied to the correction condition determination means 25 as the steering torque signal T _Q. .

The polarity reversal detection means 28 detects a change in the polarity (left and right steering direction) of the steering torque signal T _S supplied from the steering torque sensor 12, and outputs a polarity reversal signal P _H corresponding to the polarity change to the timer means 29. Output to.

FIG. 5 is a block diagram of the essential parts of the polarity inversion detecting means according to the present invention. In FIG. 5, the polarity reversal detection means 28 includes a steering torque conversion means 43 and a comparison means 44.
Is provided. The steering torque converting means 43 is a single power source (5V power source) in which virtual ground is a midpoint potential (for example, 2.5V).
It is composed of a driving differential amplifier, the neutral point (T _S = 0) of the steering torque signal T _S is set to the neutral potential (2.5 V), and the steering torque signal T _S of positive polarity (for example, rightward) is 2. The torque detection voltage V _DT (> 2.5V) exceeding 5V is detected, and the negative polarity (eg, leftward) steering torque signal T _S is detected below the torque detection voltage V _DT of 2.5V (<2.5).
V) and supplies the torque detection voltage V _DT corresponding to the direction and magnitude of the steering torque signal T _S to the comparison means 44.

The comparison means 44 has a comparator or a soft control comparison function and compares the torque detection voltage V _DT supplied from the steering torque conversion means 43 with the reference value V _R (= 2.5 V) to detect the torque. When the voltage V _DT exceeds the reference value V _R (= 2.5 V) (V _DT > V _R ), for example, an H level polarity inversion signal P _H is generated, while the torque detection voltage V _DT is the reference value V V. below _{R (= 2.5V) (V DT} <V R) in case L
Providing a timer means 29 the polarity inversion signal P _H level occurs.

FIG. 6 shows a characteristic diagram of the polarity inversion detecting means according to the present invention. (A) drawing the steering torque (T _L, T _R) - torque detection voltage (V _DT) characteristic diagram, (b) a torque detection voltage (V _DT) - a polarity inversion signal (P _H) characteristic diagram. (A)
As shown in the figure, right steering torque T _R (plus polarity)
Correspondingly the torque detection voltage V _DT sets a value greater than 2.5V, the torque detection voltage V _DT corresponding to the left steering torque T _L (negative polarity) is set to a value below 2.5V in.

As shown in (b), the polarity determination signal P _H
Generates an H level signal when the torque detection voltage V _DT exceeds 2.5 V (reference value V _R ), and the torque detection voltage V _DT
There is the case below 2.5V (reference value V _R) configured to generate an L level signal. The rising and falling of the polarity determination signal P _H may have a hysteresis characteristic centered on 2.5 V (reference value V _R ).

The timer means 29 is composed of, for example, a retriggerable monomultivibrator having a toggle characteristic, and the rising and falling of the polarity determination signal P _H supplied from the polarity inversion detection means 28 is used as a trigger for a predetermined time T _K. A timer signal T _K (for example, H level) is generated and the timer signal T _K is provided to the switching means 30.

The switching means 30 has a switching function and a memory,
The steering torque signal T detected by the steering torque sensor 12 based on the timer signal T _K provided from the timer means 29.
And _S, pre-steering torque signal is set to the memory T _O (e.g., 0 value) to switch the supply to the correction condition determining means 25 as a steering torque signal T _Q.

For example, when the timer signal T _K is L level, the steering torque signal T _{S is selected} , and when the timer signal T _K is H level, the steering torque signal T _O (for example, 0 value) is selected.

[0053] Thus, the steering torque signal T _S of the steering torque sensor 12 detects, for example, since a switching means 30 for switching the steering torque signal T _O 0 value in the timer signal T _K, the timer signal T _{When K} is at the H level, the steering torque signal T _Q of 0 value is output, and the correction condition determination means 25 outputs the L level correction determination signal J _H.
Supplies, since outputs the correction coefficient K _H of the coefficient 1 to the multiplier unit 27, a target current signal I outputted from the multiplier 27
_MSH becomes equal to the target current signal I _MS (I _MSH = I _MS ),
It can be inhibited decrease correction of the target current signal I _MS based on the steering torque in the opposite direction.

By setting the correction coefficient K _H when the L level correction determination signal J _H is supplied to a value which is sufficiently larger than the correction coefficient K _{C and} smaller than the coefficient 1, the steering torque in the opposite direction is set. It is also possible to limit the reduction correction of the target current signal I _MS based on it.

The drive control means 24 uses PI (proportional / integral)
A controller or PID (proportional / integral / derivative) controller, control signal generation means, etc. are provided, and PI control or PID is applied to the target current signal _IMSH provided from the multiplication means 27.
The control is performed and the electric motor drive signal 16 is supplied with the electric motor control signal V _{O including} a PWM signal corresponding to the target current signal I _{M SH} and a mixed signal of ON / OFF signals.

As described above, in the electric power steering apparatus according to the first aspect, the control means decreases the target current signal based on the steering torque for a predetermined time after the steering torque signal is changed from one direction to the other direction. Since the correction limiting means for inhibiting or limiting the correction is provided, it is possible to inhibit or limit the reduction correction when the steering wheel is turned back to compensate the steering characteristic corresponding to the steering torque.

In the electric power steering apparatus according to the third aspect of the invention, the control means is provided with the time gradual increase / decrease means for gradually increasing / decreasing the target current signal decrease correction and the subsequent return correction. During the recovery correction after that, the electric motor current can be gradually decreased and increased over time, and the steering assist force acting on the steering system can be smoothly decreased and increased.

FIG. 7 is a block diagram of the essential parts of an electric power steering apparatus according to the second aspect. In FIG.
The control means 45 of the electric power steering device 40 includes a target current signal setting means 21, a correction means 33, a correction limiting means 23, and a drive control means 24. The control means 45
Target current signal setting means 21 and drive control means 2 constituting
4 has the same configuration as the control means 15 shown in FIG.
Since the same operation is provided, the description will be omitted.

The correction means 33 is a correction condition determination means 34,
The correction condition determining means 34 is provided with the correction coefficient generating means 26 and the multiplying means 27, and the correction condition determining means 34 is supplied with the steering torque signal T _S and the steering rotation speed signal N _S supplied from the steering rotation speed sensor 13 or the electric motor. The difference from the correction condition determination means 25 of the correction means 22 shown in FIG. 2 is that the correction determination signal J _H is output based on the electric motor rotation speed signal N _M supplied from the rotation speed sensor 14.

The correction condition judging means 34 comprises a comparing means,
Reference torque value T _{F in the} same torque direction as the steering torque signal T _S
(Right reference torque value T _FR , left reference torque value T _FL ), reference steering rotation speed value N _{F in the} same direction as the steering rotation speed signal N _S (right reference steering rotation speed value N _FR , left reference steering Rotation speed value N _FL ) or motor rotation speed signal N
The reference motor rotation speed value N _MF (right direction reference motor rotation speed value N _MFR , left direction reference motor rotation speed value N _MFL ) in the same direction as _M is compared.

For example, the rightward steering torque signal T _S exceeds the rightward reference torque value T _FR (T _S > T _FR ), and the rightward steering rotation speed signal N _S is the rightward reference steering rotation speed value N _FR.
Below (N _S ≦ N _FR ) or rightward motor rotation speed signal N _M
Is the right reference motor rotation speed value N _MFR or less (N _M ≤
N _MFR ), the correction signal J _H (for example, H level)
To the correction coefficient generating means 26. In addition, the leftward steering torque signal T _S , the leftward steering rotation speed signal N _S, or the leftward electric motor rotation speed signal N _M is the leftward reference torque value T _FL , the leftward reference steering rotation speed value N _FL, or the leftward reference steering rotation speed value N _FL , respectively. When the direction reference motor rotation value N _MFL and the above conditions are satisfied, the correction signal J _H (for example, H level) is provided to the correction coefficient generating means 26.

The reference torque values T _F (T _FR , T _FL ),
Each of the reference steering rotation speed value N _F (N _FR , N _FL ) or the reference motor rotation speed value N _MF (N _MFR , N _MFL ) is a sufficiently large steering wheel when the steering position is near the rack end by the steering operation. The torque signal T _S , the sufficiently small steering rotation speed signal N _S or the electric motor rotation speed signal N _M are set, but can be changed by the condition changing means 31 of the correction limiting means 23.

The correction coefficient generating means 26 has the structure shown in FIG. 3, and when the correction signal J _H (for example, H level) is supplied from the correction condition judging means 34, the correction coefficient K _{H having the} characteristic shown in FIG. To the multiplying means 27, and the multiplying means 27 multiplies the correction coefficient K _H by the target current signal I _MS , and drives the target current signal I _{M SH} which is the target current signal I _MS reduced and corrected by the correction coefficient K _H. Supply to the control means 24.

The correction limiting means 23 includes a timer means 29 and a condition changing means 31, and the torque direction of the correction signal J _H supplied from the correction condition judging means 34 and the steering torque signal T _S detected by the steering torque sensor 12. Based on the signal F, reference torque value T _F (right direction reference torque value T _FR , left direction reference torque value T _FL ), reference steering rotation speed value N _F (right direction reference steering rotation speed value N _FR , left direction reference steering Rotational speed value N _FL )
Alternatively, the reference motor rotation speed value N _MF (right reference motor rotation speed value N _MFR , left reference motor rotation speed value N _{M FL} ) is provided to the correction condition determination means 34.

Further, the correction limiting means 23 has a reference torque value T _F (T _FR , T _FL ) and a reference steering rotation speed value N _F (N _FR , N).
_FL ) or reference motor rotation speed value N _MF (N _MFR , N _MFL )
For each of the two different reference values, for example, the reference torque value T _F (T _FR , T _FL ) and a larger correction reference torque value T _FG (T _FRG , T _FLG ), the reference steering rotation speed value N _F
(N _FR , N _FL ) and a smaller correction reference steering rotation speed value N _FS (N _FRS , N _{FL S} ) or reference motor rotation speed value N
_MF (N _MFR , N _MFL ) and a smaller value of the correction reference motor rotation speed value N _MFS (N _MFRS , N _MFLS ) are set, and based on the conditions determined by the correction signal J _H and the torque direction signal F. Each of the reference values and the correction reference value are selected and provided to the correction condition determining means 34.

The timer means 29 has the same construction as that shown in FIG. 2, and when the L level correction signal J _H is supplied, it outputs the L level timer signal T _K , for example, while it outputs the H level. When the correction signal J _H is supplied to the condition changing means 31, the H level timer signal T _K is supplied for a predetermined time.

The condition changing means 31 is provided with a memory such as a comparing means and a ROM, and a reference torque value T _F (T _FR , T _FL ) and a corrected reference torque value T _FG having a larger value based on a design value or an experimental value in advance. (T _FRG , T _FLG ), reference steering rotation speed value N
Correction reference of _F (N _FR , N _FL ) and smaller value Steering rotation speed value N _FS (N _FRS , N _FLS ) or reference motor rotation speed value N _MF (N _MFR , N _MFL ) and correction reference of smaller value Set the motor rotation speed value N _MFS (N _MFRS , N _MFLS ).

The comparing means determines the steering condition based on the torque direction signal F and the timer signal T _H , selects each reference value from the memory based on the steering condition, and determines the corresponding reference value as the correction condition. Means 34.

At the time of normal steering operation, the reference torque value T _F (T _FR , T _FL ), the reference steering rotation speed value N
_F (N _FR , N _FL ) or reference motor rotation speed value N _MF (N
_MFR , N _MFL ) is provided to the correction condition determination means 34.

From the normal steering operation state, for example,
The steering torque signal T _{S in} the right direction, the steering rotation speed signal N _{S in the} right direction, or the motor rotation speed signal N _MS in the right direction is supplied to the condition determining means 34, and the steering torque signal T _S in the right direction and the reference torque in the right direction are supplied. Value T _FR , steering speed signal N to the right
_S and rightward reference steering rotation speed value N _FR or rightward motor rotation speed signal N _MS and rightward reference motor rotation speed value N
_MFR are compared respectively, the steering torque signal T _S in the right direction corresponding to a state in which steering torque is applied in the further rightward from the thrust addressed state of right steering is greater than the right direction reference torque value T _FR, and rightward steering When the rotation speed signal N _S is equal to or lower than the right reference steering rotation speed value N _FR or the right motor rotation speed signal N _MS is equal to or lower than the right reference motor rotation speed value N _MFR , the H-level correction signal J _H is _output. The target current signal _IMS is output and corrected with the correction coefficient K _H.

On the other hand, when the H level correction signal J _H is output, the H level timer signal T _H is output for a predetermined time.
Based on the timer signal T _H and the torque direction signal F, the condition determination means 31 replaces the leftward reference torque value T _FL with the larger leftward correction reference torque value T _FLG and the leftward reference steering rotation speed value N _FL . Instead, a smaller leftward correction reference steering rotation speed value N _FLS or a smaller leftward reference motor rotation speed value N _MFL is used instead of a smaller leftward correction reference motor rotation speed value N _MFLS in the correction condition determination means 34. In order to supply, if the steering is turned back within the predetermined time T _K and the large left steering torque signal T _S , the small left steering rotation speed signal N _S or the motor rotation speed signal N _MS acts, the correction signal is supplied. In order to keep J _H at the L level, the target current signal I _MS corresponding to the left direction by turning the steering wheel is returned.
The reduction correction of can be prohibited.

When the steering steering is turned back from the state where the target current signal I _MS is corrected to decrease by the leftward steering torque, the reference values in the rightward direction are similarly changed to correspond to the rightward direction. prohibiting decrease correction of the target current signal I _MS.

As described above, in the electric power steering apparatus according to the second aspect of the present invention, the control means, the control means, and for a predetermined time when the steering wheel is turned back, the correction correction to decrease the target current signal based on the steering torque in the opposite direction is prohibited or Since the correction limiting means for limiting is provided, it is possible to inhibit or limit the reduction correction for the steering operation in the opposite direction to compensate the steering characteristic corresponding to the steering torque.

Further, in the electric power steering apparatus according to the fourth aspect, the control means causes the correction correction for the steering torque in the opposite direction for a predetermined time after the correction correction for the target current is executed for one of the steering torques. Since the limiting means for prohibiting or limiting the steering torque is provided, the steering torque can be suppressed by prohibiting or limiting the reduction correction at the time of a sudden steering turnback in the case where the correction means is configured to continuously change the reduction correction and the return correction with time. It is possible to compensate the steering characteristics corresponding to

[0075]

As described above, in the electric power steering apparatus according to the first and second aspects, the control means decreases the target current signal based on the steering torque in the opposite direction for a predetermined time when the steering wheel is turned back. A correction limiting means for prohibiting or limiting the correction is provided, and the steering characteristic corresponding to the steering torque can be compensated by prohibiting or limiting the reduction correction for the steering operation in the opposite direction. It is possible to obtain the optimum steering feeling when the steering wheel is turned back while limiting the power consumption of the electric motor and the electric motor driving means.

The correction limiting means according to the second aspect can more accurately set the inhibition or the limitation of the reduction correction at the time of turning the steering wheel, so that a more optimal steering feeling can be obtained.

In the electric power steering apparatus according to the third aspect of the present invention, the control means is provided with the time gradual increase / decrease means for gradually increasing / decreasing the target current signal decrease correction and the subsequent recovery correction. At the time of correction, the electric motor current is gradually decreased and increased over time to smoothly decrease and increase the steering assist force acting on the steering system, so that a natural steering feeling without being caught can be obtained.

The control means of the electric power steering apparatus according to the fourth aspect prohibits the decrease correction for the steering torque in the opposite direction for a predetermined time after executing the decrease correction of the target current for one of the steering torques or A steering characteristic corresponding to the steering torque by prohibiting or limiting the reduction correction at the time of a sudden steering back when the steering control device is provided with a limiting device for limiting and the reduction correction and the restoration correction are continuously changed with time. Therefore, even if the steering wheel is suddenly turned back, a stable steering feeling without getting caught can be obtained.

Therefore, it is possible to provide an electric power steering apparatus which can provide a stable steering feeling even when the steering wheel is suddenly turned back while limiting the electric power consumption of the electric motor and the electric motor driving means.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an electric power steering device according to the present invention.

FIG. 2 is a block diagram of a main part of the electric power steering apparatus according to claim 1.

FIG. 3 is a block diagram of a main part of an embodiment of a correction coefficient generating means.

FIG. 4 is an example of a time characteristic diagram of a correction coefficient.

FIG. 5 is a block diagram of the essential parts of the polarity inversion detection means according to the present invention

FIG. 6 is a characteristic diagram of the polarity reversal detection means according to the present invention.

FIG. 7 is a block diagram of an essential part of the electric power steering apparatus according to claim 2;

[8] the steering torque signal (T _D) - target current signal (I _MS) characteristic diagram

[Explanation of symbols]

1, 40 ... Electric power steering device, 2 ... Steering shaft, 3 ... Connection shaft, 3A, 3B ... Universal joint, 4 ... Steering gear box, 5 ... Rack and pinion mechanism, 5A ... Pinion, 6 ... Manual steering force generation Means, 7 ... Rack shaft, 7A ... Rack teeth, 8 ... Tie rod, 9 ... Front wheel,
10 ... Electric motor, 11 ... Ball screw mechanism, 11A ... Ball screw shaft, 12 ... Steering torque sensor, 13 ... Steering rotation speed sensor, 14 ... Electric motor rotation speed sensor, 15, 45 ... Control means, 16 ... Electric motor drive means, 17 ... Steering wheel, 21 ... Target current signal setting means, 22, 33 ... Correction means, 23 ... Correction limiting means, 24 ... Drive control means, 2
5, 34 ... Correction condition determination means, 26 ... Correction coefficient generation means, 27 ... Multiplication means, 28 ... Polarity inversion detection means, 29 ...
Timer means, 30 ... switching means, 31 ... condition changing means, 4
1 ... Correction coefficient setting means, 42 ... Time gradual increase / decrease means, 43 ...
Steering torque conversion unit, 44 ... comparator, I _MS, I _MSH ...
Target current signal, J _H ... correction determination signal, K _C , K _H , K _X ... correction coefficient, N _F ... reference steering rotation speed value, N _M ... motor rotation speed signal, N _MF ... reference motor rotation speed value, N _S ... steering rotational speed signal, P _H ... polarity inversion _{signal, T A, T B, T} K ... predetermined time, T _F ... reference torque value, T _S ... steering torque signal, V _DT ...
Torque detection voltage, V _M ... Motor voltage, V _O ... Motor control signal.

Claims (4)

[Claims] 1. A motor for applying an auxiliary steering force to a steering system, a steering torque sensor for detecting a steering torque of the steering system, and driving of the motor based on at least a steering torque signal detected by the steering torque sensor. In the electric power steering apparatus, the control means for controlling the electric power steering apparatus is provided with a correcting means for reducing and correcting a target current signal for controlling the drive of the electric motor when the steering torque signal exceeds a predetermined value. An electric power steering apparatus comprising: a correction limiting unit that prohibits or limits the correction correction of the target current signal based on the steering torque for a predetermined time after the steering torque signal is changed from one direction to the other direction. . 2. A motor for applying an auxiliary steering force to a steering system, a steering torque sensor for detecting a steering torque of the steering system, a steering rotation speed sensor for detecting a steering rotation speed of the steering system, or a rotation of the electric motor. An electric motor rotation speed sensor for detecting a speed and a control means for controlling the drive of the electric motor based on the steering torque signal detected by at least the steering torque sensor are provided, and the steering torque signal exceeds a predetermined value and the steering rotation is performed. In the electric power steering apparatus including a correction unit that reduces and corrects a target current signal that controls the drive of the electric motor when the speed or the electric motor rotation speed is lower than a predetermined value, the control unit is a steering torque signal from one direction. The target current signal decreases based on the steering torque for a predetermined time after changing to the opposite direction. An electric power steering apparatus characterized by comprising a correction limiting means prohibits or limits the positive. 3. The control means includes a time gradual increase / decrease means for gradually increasing / decreasing the target current signal decrease correction and the subsequent return correction.
Alternatively, the electric power steering device according to claim 2. 4. The control means comprises correction limiting means for prohibiting or limiting reduction correction for steering torque in the opposite direction for a predetermined time after executing reduction correction of the target current for one of the steering torques. The electric power steering apparatus according to claim 3, wherein