JPH0725313B2 - Power steering device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electric power steering apparatus (power steering) that assists a force required for operating a steering wheel with a rotational force of a motor.

[Prior art]

The steering torque applied to the steered wheels is detected, and when the detected torque exceeds a predetermined dead zone, a drive current proportional to the detected torque is caused to flow through a motor for steering assistance to drive the motor, and An electric power steering apparatus has been developed in which a force required for steering is assisted by a rotational force of the motor to provide a driver with a comfortable steering feeling.

In such a power steering apparatus, when the steering assist force during high-speed traveling is large, there is a problem in that the steering feeling feels unstable and the steering feeling is unnatural due to the inertial force of the motor. Then, in order to solve the problem, a correction value based on the angular velocity of the steering wheel rotation obtained from the rotation detector of the motor and the vehicle speed obtained from the vehicle speed detector,
The control for reducing the steering assist force is performed by subtracting from the target value of the drive current flowing through the motor, and the fluctuation feeling and the unnaturalness of the steering feeling are suppressed.

[Problems to be Solved by the Invention]

However, when performing the control for reducing the steering assist force based on the angular velocity of the steering wheel rotation and the vehicle speed as described above, a rotation detector that detects the rotational position of the motor is necessary to obtain the angular velocity, but this rotation There is a problem that the power steering apparatus becomes expensive due to the provision of the detector.

The present invention has been made in view of such circumstances, and by obtaining the counter electromotive voltage of the motor from the terminal voltage and drive current of the motor, and by obtaining the rotational angular velocity of the motor and the relative steering angle of the steered wheels from the counter electromotive voltage. An object of the present invention is to provide an inexpensive power steering apparatus that can perform control related to steering assistance without providing a motor rotation detector.

[Means for Solving the Problems]

A power steering apparatus according to the present invention is a power steering apparatus including a steering assisting motor driven according to a steering torque applied to a steering wheel, wherein voltage detection means for detecting a terminal voltage of the motor, and The motor is detected from a plurality of data of current detection means for detecting a drive current of the motor, a predetermined detection result of the current detection means, and an average value of a plurality of detection results of the voltage detection means corresponding to the detection result. Internal resistance calculation means for calculating the internal resistance of the motor, and a counter electromotive voltage calculation for calculating the counter electromotive voltage of the motor from the calculation result of the internal resistance calculation means, the detection result of the voltage detection means and the detection result of the current detection means. Means, a rotational angular velocity calculation means for calculating the rotational angular velocity of the motor from the calculation result of the counter electromotive voltage calculation means, and a relative steering angle for calculating a relative steering angle from the calculation result of the counter electromotive voltage calculation means. Characterized by comprising a means out.

[Action]

The internal resistance of the motor is obtained from a plurality of data of the detected motor drive current and the corresponding average value of the terminal voltage detection results, and the product of the internal resistance and the drive current is subtracted from the terminal voltage. And the back electromotive force is obtained. The counter electromotive voltage is multiplied by the ratio of the rotational angular velocity to the counter electromotive voltage determined as a characteristic of each motor to obtain the rotational angular velocity of the motor. Then, the counter rudder voltage is integrated to obtain the relative steering angle. In this way, the rotational angular velocity and the steering position are obtained based on the motor drive current and the terminal voltage,
No motor rotation detector is required.

[Examples] The present invention will be specifically described below with reference to the drawings illustrating the examples. FIG. 1 is a partially cutaway front view of a power steering apparatus according to the present invention, and FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

In the figure, reference numeral 1 denotes a rack shaft, and a rack shaft case 2 which is fixed to a part of the vehicle body and has a cylindrical shape with the longitudinal direction being the left-right direction.
It is interpolated concentrically with this. Further, 3 is a pinion shaft, which is rotatably supported inside the pinion shaft case 4 continuously provided in the vicinity of one end of the rack shaft case 2 in a state in which its axis is oblique to the rack shaft 1.

As shown in FIG. 2, the pinion shaft 3 is composed of an upper shaft 3a and a lower shaft 3b which are coaxially connected to each other via a torsion bar 5, and the upper shaft 3a is installed in a pinion shaft case 4 by a ball bearing 40. It is supported and its upper end is interlocked with the steering wheel via a universal joint (not shown). The lower shaft 3b is supported in the pinion shaft case 4 by a four-point contact ball bearing 41 at a position near the upper end of the lower shaft 3b with the lower portion thereof appropriately protruding from the lower opening of the pinion shaft case 4. The four-point contact ball bearing 41 is fitted onto the lower shaft 3b from the lower end side thereof,
Due to the step formed near the upper end of the lower shaft 3b and the collar 42 fitted from the lower end side and caulked and fixed to the outer peripheral surface,
After being pinched on both sides of the inner ring and axially positioned outside the lower shaft 3b, the lower ring 3b is fitted into the pinion shaft case 4 together with the lower shaft 3b, and is formed in the lower part of the case 4. By the annular shoulder and the lock nut 43 screwed to the case 4 through the opening, both sides of the outer ring are clamped and positioned in the pinion shaft case 4 in the axial direction, and the lower shaft 3b is attached. Apply the acting radial load and bidirectional axial load.

In the middle of the lower shaft 3b protruding from the pinion shaft case 4, there are formed pinion teeth 30 having an appropriate length in the axial direction thereof. When fixed to the upper side of the rack shaft case 2 with a fixing bolt 44, a rack formed inside the rack shaft case 2 at a position near one end of the rack shaft 1 over a suitable length in the axial direction. The lower shaft 3b and the rack shaft 1 are meshed with the teeth 10 and are engaged with each other with their axes intersecting each other. The lower shaft 3b extends further downward than the engagement position with the rack shaft 1, and has a lower end portion coaxial with the lower shaft 3b, and a large bevel gear 31 is fitted with its tooth forming surface facing downward. The large bevel gear 31 is supported by a needle roller bearing 33 in a bevel gear housing 20 that is continuously provided below the rack shaft case 2 in a manner surrounding the large bevel gear 31. Therefore, the lower shaft 3b is made up of rack teeth by the four-point contact ball bearing 41 and the needle roller bearing 33.
It is supported on both sides of the meshing position between the 10 and the pinion teeth 30, and the amount of bending of the lower shaft 3b at the meshing position is kept within a predetermined allowable range.

Further, at the meshing position of the rack tooth 10 and the pinion tooth 30, there is provided a rack guide 12 for pressing the rack shaft 1 by the urging force of the push spring 11 toward the pinion shaft 3 so that they are meshed with each other without a gap. The rack shaft 1 is supported while being held by the rack guide 12 and the lower shaft 3b from both sides in the radial direction at the meshing position, and the rack shaft case on the opposite side of the continuous position with the pinion shaft case 4 is supported. It is supported by a bearing bush 13 fitted inside the end of the rack shaft 2, and is movable in the axial direction of the rack shaft case 2. The left and right ends of the rack shaft 1 protruding from both sides of the rack shaft case 2 are connected to tie rods 15 and 15 connected to left and right wheels (not shown) via separate ball joints 14 and 14, respectively. The wheels are steered to the left and right by the movement of the rack shaft 1 in the axial direction.

Reference numeral 6 in FIG. 2 denotes a torque sensor for detecting a steering torque applied to the steering wheel. The torque sensor is externally fitted to the upper shaft 3a and rotates together therewith, and the lower end face of the torque sensor is centered on the shaft center of the upper shaft 3a. A resistor holding member 60 formed of an annular resistor, and a detector that is externally fitted to the lower shaft 3b and rotates together therewith, and a detector that is in sliding contact with one point in the radial direction on the resistor at its upper end face. The detector holding member 61 thus formed constitutes a potentiometer. The upper shaft 3a of the pinion shaft 3 rotates about its axis according to the rotation of the steering wheel, but the road surface resistance acting on the wheels acts on the lower shaft 3b via the rack shaft 1,
The torsion bar 5 interposed between the two shafts is twisted according to the steering torque applied to the steering wheel. Torque sensor 6
Is the upper shaft 3a and the lower shaft 3b as the torsion bar 5 is twisted.
The relative displacement in the circumferential direction generated between and is output as a potential corresponding to the sliding contact position between the detection element and the resistor. When the torsion bar 5 is not twisted, in other words, steering wheel operation is performed. The initial adjustment is made so as to output a predetermined reference potential when not performed. Torque sensor 6
Is output to the control unit 7 in time series, and the control unit 7 compares the signal with the reference potential to recognize the direction and the magnitude of the steering torque, and is arranged as described later. A drive signal is issued to the steering assisting motor 8.

The steering assisting motor 8 transmits its rotational force to the lower shaft 3b via an electromagnetic clutch 16, a planetary gear speed reducer 9 and a small bevel gear 32 that meshes with the large bevel gear 31 and has a smaller diameter than this. Is.

The electromagnetic clutch 16 has an annular shape and is an intermediate case of the motor 8.
A coil portion 161 fixed to 81, a main driving portion 162 which is fitted onto one side of a rotating shaft 80 of the motor 8 coaxially therewith, and which rotates together with the rotating shaft 80, and a disk-shaped main driving portion 162. The main part 162 is opposed to the part 162 by electromagnetic force generated by energizing the coil part 161.
The motor 8
Is engaged and disengaged.

The planetary gear speed reducer 9 is fitted in the engagement / disengagement portion 163, rotates, and has a sun gear. One end of the planetary gear reduction gear 9 is supported by a bearing fitted in the main drive portion, and the other end is fitted in a planet carrier 93 described later. A sun shaft 90 supported by a fixed bearing, a ring-shaped outer ring 91 fixed to a casing end surface 82 of the motor 8 coaxially with the rotating shaft 80, an inner peripheral surface of the outer ring 91 and the Sun axis 90
A plurality of planet gears 92, 92 that rotate around the sun gear's outer peripheral surface, respectively, rotate about their respective axes and revolve around the axis of the sun gear, and these planet gears 92, 92, respectively. It is composed of a planet carrier 93 which is axially supported, has an outer diameter smaller than that of the motor 8, and is integrated with the motor 8 and the electromagnetic clutch 16 on one side of the rotary shaft 80. Planetary gear reducer 9
The output shaft 94 is fitted and fixed in the axial center position of the planet carrier 93 located coaxially with the rotation shaft 80 of the motor 8 and is projected to the outside of the casing by an appropriate length. The small bevel gear 32 is fitted to the tip of the output shaft 94 with its tooth forming surface facing the tip side, and the bevel gear 32 together with the output shaft 94 is connected to the planet gears 92, 92 ... It is designed to rotate according to the revolution of the.

The motor 8, the electromagnetic clutch 16, and the planetary gear speed reducer 9 are arranged such that their axes are substantially parallel to the axis of the rack shaft 1 with the small bevel gear 32 inside.
A large bevel gear 31 which is internally fitted to the housing 20 and in which the small bevel gear 32 is fitted to the lower end of the lower shaft 3b inside the housing 20.
And is fixed to a bracket 2a provided outside the rack shaft case 2. Backlash adjustment between the large bevel gear 31 and the small bevel gear 32 is performed by the planetary gear reduction device 9
Can be easily fitted into the bevel gear housing 20 by changing the thickness and / or the number of shims provided at the abutting portion between the casing of the planetary gear speed reducer 9 and the bevel gear housing 20.

In addition to the output signal of the torque sensor 6 described above, an output signal of a vehicle speed detector 18 for detecting a vehicle speed is input to the control unit 7, and a drive signal for driving the motor 8 is controlled by the control described later. Is output.

Next, the control by the control unit 7 will be described.

FIG. 3 is a block diagram showing the configuration and control operation of the control unit.

The torque detection signal of the torque sensor 6 advances its phase,
A phase compensating unit 71a for stabilizing the system is provided to a midpoint detecting unit 71h for determining the steering angle midpoint of the steering mechanism, and the torque detecting signal is phase-compensated and compensated in the phase compensating unit 71a. The detected torque Tc is given to the subtractor 74a.

In addition, the vehicle speed detection signal of the vehicle speed detector 18 is the midpoint detection unit 71.
h, a command current function unit 73a that generates a command current I of the motor 8 described below, and a steering angle θ output from a steering angle determination unit 71i described below are given, and the command current I is determined according to the steering angle θ and the vehicle speed V. Change current function part that determines the change current Ia that changes the characteristics of
73b and the subtraction signal function unit 73c for generating the subtraction signal Sr for subtracting the value of the torque detection signal and the instruction current I, respectively.

The terminal voltage of the motor 8 is detected by a voltage detection circuit 71b provided on the output side of a PWM drive circuit 72 described later, and the drive current of the motor 8 is obtained by inserting a current detection resistor (not shown) in the motor line. It is detected by a current detection circuit 71c that detects a current.

The detection results of the voltage detection circuit 71b and the current detection circuit 71c are given to the internal resistance calculation unit 71d and the counter electromotive voltage calculation unit 71e, and the internal resistance calculation unit 71d calculates the internal resistance R of the motor based on these detection results. _M is calculated, and the calculation result is given to the counter electromotive voltage calculation unit 71e. The back electromotive force calculation unit 71e calculates the back electromotive force V _{G of the} motor 8 from the detection results of the voltage detection circuit 71b and the current detection circuit 71c and the calculation result of the back electromotive force calculation unit 71e. Calculator 71f
And the relative steering angle calculation unit 71g.

The rotation angular velocity calculation unit 71f calculates the rotation angular velocity ω of the motor 8 based on the calculation result of the back electromotive force calculation unit 71e, and the calculation result is given to the subtraction signal function unit 73c. In the relative steering angle calculation unit 71g, the relative steering angle θr is calculated based on the calculation result of the counter electromotive voltage calculation unit 71e, and the calculation result is given to the midpoint detection unit 71h and the steering angle determination unit 71i.

The midpoint detection unit 71h calculates the steering angle midpoint θm from the torque detection signal, the vehicle speed V, the rotational angular velocity ω, and the relative steering angle θr, and supplies the calculation result to the steering angle determination unit 71i. The steering angle determination unit 71i calculates the steering angle θ of the steered wheels from the midpoint θm and the relative steering angle θr, and the calculation result is the change current function unit.
Given to 73b.

The changing current function unit 73b obtains the changing current Ia from the steering angle θ and the vehicle speed V, and supplies this to the instruction current function unit 73a. Then, in the instruction current function unit 73a, the instruction current I is generated based on the input torque T, the vehicle speed V and the change current Ia,
The instruction current I is given to the subtractor 74b.

In the subtraction signal function unit 73c, the relationship between the rotation angular velocity ω and the subtraction signal Sr is functionalized according to the value of the vehicle speed V, and the subtraction signal Sr is obtained from the rotation angular velocity ω and the vehicle speed V. Sr is given to the first gain compensator 75a and the second gain compensator 75b.

The first gain compensator 75a calculates a subtraction torque Tr to be subtracted from the compensation detection torque Tc by multiplying the input subtraction signal Sr by a predetermined value, and the calculation result is the subtractor.
Given to 74a.

The subtractor 74a performs an operation of subtracting the subtraction torque Tr from the input compensation detection torque Tc, and the subtraction result is given to the instruction current function unit 73a as the input torque T. In the instruction current function unit 73a, the input torque T and the instruction current I
Is expressed as a function according to the value of the vehicle speed V, an instruction current I is obtained from the input torque T and the vehicle speed V, and the instruction current I is given to the subtractor 74b.

In the second gain compensator 75b, the subtraction current Ir to be subtracted from the instruction current I is calculated by multiplying the input subtraction signal Sr by a predetermined value, and the calculation result is the subtracter 74.
given to b.

The subtractor 74b performs an operation of subtracting the subtraction current Ir from the input current I input, and the subtraction result is given to the subtractor 74c.

In the subtractor 74c, the feedback signal from the current detection circuit 71c is reduced, and the subtraction result is PWM (Pulse-
It is given to the motor 8 via a Width Modulation (pulse width modulation) drive circuit 72. The current detection circuit 71c is configured to detect the current including the flywheel current of the motor, and the current loop is stable.

Next, the operation of the control unit 7 as described above will be described.

FIG. 4 is a flowchart showing a procedure of control for reducing the steering assist force according to the vehicle speed and the rotational angular velocity of the steered wheels.

First, in step 1, the torque detection signal and the vehicle speed V are read from the torque sensor 6 and the vehicle speed detector 18, respectively,
The terminal voltage and drive current of the motor 8 are read from the voltage detection circuit 71b and the current detection circuit 71c, respectively.

Next, the phase compensation unit 71a converts the torque detection signal into the compensation detection torque Tc (step 2). Then, the rotational angular velocity ω of the motor 8 is calculated by the subroutine for calculating the rotational angular velocity and the relative steering angle (step 3).

The calculation subroutine of the rotational angular velocity and the relative steering angle shown in FIG. 5 will be described below.

FIG. 5 is a flowchart showing a subroutine for calculating the rotational angular velocity and the relative steering angle, and FIG. 6 is an internal resistance R _{M of the} motor 8.
FIG. 6 is a graph showing a method for obtaining the above, and in FIG. 6, the vertical axis represents the terminal voltage and the horizontal axis represents the drive current, and the relationship between them is shown.

First, in the internal resistance calculation unit 71d, as shown in FIG. 6, a plurality of (n) terminal voltages corresponding to each of a plurality of sampled current values I ₁ and I ₂ of a predetermined drive current I _M. The detected values V ₁ n and V ₂ n are sampled (step 31), these sampled values are averaged as shown in the following equations (1) and (2), and the respective voltage average values V ₁ and V ₂ are calculated. (Step 32).

V ₁ = ΣV ₁ n / n (1) V ₂ = ΣV ₂ n / n (2) Then, from these current values I ₁ and I ₂ and voltage average values V ₁ and V _{2, the following} formula (3) is obtained. The internal resistance R _M of the motor 8 is calculated by the linear approximation method as shown in (step 33).

In this way, the detected values of the terminal voltage V _M are averaged to obtain the terminal voltage V _M
When the internal resistance R _M of the motor 8 is obtained by linearly approximating the relationship between the drive current I _M and the drive current I _M , the counter electromotive voltage component included in the detected value of the terminal voltage V _M is removed, so that the internal resistance R _M is Accurately required.

Next, the counter electromotive voltage calculator 71e calculates the counter electromotive voltage V _G from the internal resistance R _M , the terminal voltage V _M and the drive current I _M as shown in the following equation (4) (step 34).

V _G = V _M −R _M · I _M (4) When the counter electromotive voltage V _G is calculated, the rotational angular velocity calculation unit is calculated.
In 71f, as shown in the following equation (5), the counter electromotive voltage V _G is multiplied by the motor power generation constant K _M , which is the ratio of the rotational angular velocity ω to the counter electromotive voltage V _G determined as the characteristic of each motor, and the rotation of the motor 8 is performed. The angular velocity ω is calculated (step 35).

ω = K _M · V _G (5) Further, as shown in the following equation (6), the rotational angular velocity ω is integrated to obtain the relative steering angle θr (step 36).

θr = KΣω (6) However, K: proportional constant Next, returning to FIG. 4, description will be made.

In step 4, the subtraction signal Sr is calculated from the vehicle speed V and the rotational angular velocity ω input in the subtraction signal function unit 73c and output to the first gain compensation unit 75a and the second gain compensation unit 75b.

In the subtraction signal function unit 73c, as shown in FIG. 7, the subtraction signal Sr increases in proportion to the increase of the rotational angular velocity ω, and this proportional relationship has vehicle speeds V ₁ , V ₂ , V ₃ (where V ₁ < Depends on V ₂ <V ₃ ),
As the vehicle speed V increases, the ratio of the subtraction signal Sr to the input rotational angular velocity ω increases. Therefore, the subtraction signal Sr increases as the vehicle speed V and the rotational angular velocity ω increase. Then, the first gain compensator 75a
Then, the subtraction signal Sr is multiplied by a predetermined value to obtain a subtraction torque Tr, and the second gain compensating section 75b multiplies the subtraction signal Sr by a predetermined value to obtain a subtraction current Ir.

Next, in step 5, in the subtractor 74a, the compensation detection torque T
The subtraction torque Tr is subtracted from c to obtain the input torque T.

In step 6, the command current function unit 73a generates a command current I for the motor 8 from the input torque T and the vehicle speed V.
FIG. 8 shows a method of determining the instruction current I.

FIG. 8 is a graph showing the characteristic of the relationship between the instruction current I and the input torque T in the instruction current function unit 73a, where the vertical axis is the instruction current I and the horizontal axis is the input torque T. The positive side of the input torque T on the horizontal axis is the input torque T in the case of right steering.
The negative side shows the input torque T for left steering. The positive side of the instruction current I indicates the current for rotating the motor 8 in the right steering direction, and the negative side indicates the current for rotating the motor 8 in the left steering direction.
Further, the alternate long and short dash line changes the above characteristics that differ depending on the vehicle speeds V ₁ , V ₂ , V ₃ ... And the broken line changes according to the changing current Ia when returning the steering wheel determined by the steering angle θ and the vehicle speed V in the changing current function unit 73b. The instruction current I is shown.

Further, -D to D indicate dead zones, and the input talc T for steering to the right (or left) by steering wheel operation is the dead zone -D to D.
When exceeding the range, the instruction current I of the motor 8 increases as the input torque T increases, and the steering assist force by the motor 8 increases. In this case, the instruction current I increases until the input torque T reaches the low torque set value −Ts to Ts, regardless of the input vehicle speed V, and when it exceeds this, the relationship between the input torque T and the instruction current I becomes large. Vehicle speed V ₁ , V ₂ , V ₃ … (V ₁ <V ₂ <V ₃ )
The command current I for the input torque T decreases as the vehicle speed increases.

For example, when operating the steering wheel to the right (or left) and then returning the steering wheel, if the input torque T falls within the dead zones −D to D, the change current −Ia (or Ia) indicated by the broken line is the instruction current. Then, when the input torque T is within the dead zone -D to D, the instruction current I is constantly controlled to this change current -Ia (or Ia), and the motor 8 is driven with a constant torque. As a result, the steering assist force when returning the steering wheel becomes constant.

The absolute value of the change current Ia increases as the vehicle speed V input to the change current function unit 73b decreases. As a result, the instruction current I increases as the vehicle speed V decreases, and the steering wheel return force is increased. I try to make it bigger. Due to the function characteristics as described above, the indicated current function part
In 73a, when the steering input torque T is a low torque, the command current I is determined regardless of the vehicle speed, so that an unnatural steering feeling due to the inertia of the motor 8 is suppressed.

Then, in step 7, the subtracter 74b subtracts the subtraction current Ir from the instruction current I, and in step 8, the motor 8 is driven by the instruction current I after the subtraction.

Decreasing the instruction current I in this way is effective in increasing the steering torque when the input torque T is in the dead zone in the instruction current function unit 73a. This is because the steering assist is not performed within the dead zone, and the ratio of the output torque, which is the torque actually applied to the steering device, to the input torque T, which is the torque due to the steering wheel operation, is smaller than outside the dead zone. This is because the subtraction effect of I is large.

However, the subtraction effect in the dead zone is larger than that in the dead zone only by subtraction from the instruction current I, and a discontinuous steering feeling is felt. Therefore, the subtraction torque Tr is subtracted from the compensation detection torque Tc on the upstream side of the instruction current function unit 73a. By subtracting, the subtraction effect outside the dead zone is increased. This is because if the subtraction torque Tr is subtracted from the compensation detection torque Tc before the instruction current I is generated, the instruction current I is zero when the input torque T is in the dead zone, and thus the subtraction effect on the instruction current I is lost. This is because the effect is obtained only when the input torque T is outside the dead zone.

Thus, the subtraction current Ir is effective when the input torque T is within the dead zone with respect to the increase of the steering torque, while the subtraction torque Tr is effective when the input torque T is outside the dead zone. First gain compensator 75a and second gain compensator 75b
By adjusting the respective gains, it is possible to suppress the discontinuity in the subtraction control of the output torque during high-speed traveling.

FIG. 9 is a flow chart showing the return control of the steering wheel.
First, at step 40, the input torque T is read, and at step 41, it is judged whether or not the input torque T is within the dead zone. If the input torque T is within the dead zone, the midpoint calculation routine described later is executed at step 42. It is determined whether or not it has ended.
When the midpoint calculation is completed, the relative steering angle θr of the steered wheels is read from the relative steering angle calculation unit 71g in step 43, and then in step 44, the steering angle θr and the steering angle midpoint θm are used to determine the steering angle. The determination unit 71i determines the steering angle θ (= θr−θm).

When the steering angle θ is determined, the changing current Ia is obtained by the changing current function unit 73b from the steering angle θ and the vehicle speed V in step 45, and the value and direction of the instruction current I is calculated by the instruction current function unit 73a.

On the other hand, if it is determined in step 41 that the dead zone is not reached, the process returns, and if midpoint calculation is not completed in step 42, the relative steering angle θr of the steered wheels is calculated in step 46 by the relative steering angle calculation unit.
The value is read from 71g, and in step 47, the change current Ia is calculated by the minimum steering angle value determined in the later-described left / right determination routine, and the value and direction of the instruction current I are calculated.

Further, FIG. 10 is a flowchart showing a method for calculating the steering angle midpoint. In the midpoint calculation routine, in step 50, the vehicle speed V
Is read, and it is determined in step 51 whether the vehicle speed V is higher than the threshold value Vs _{2. If} it is larger, the torque set value Ts ₂ according to the vehicle speed is determined in step 52, and then the torque detection value is read in step 53. In step 54, it is determined whether the detected torque value is smaller than the torque set value Ts ₂ . If it is smaller, the rotational angular velocity set value ωs according to the vehicle speed is determined in step 541, then the rotational angular velocity ω calculated by the rotational angular velocity calculation unit 71f is read in step 542, and the rotational angular velocity ω is set in step 543. It is determined whether or not it is smaller than ωs. When it is small, it is determined that the vehicle is traveling straight, the number of times when it is small is counted in step 55, and the relative steering angle θr at that time is calculated in step 56.
Read from g. Then, in step 57, the relative steering angle θr is added to the total of the relative steering angles θr up to the last time, the addition result is divided by the number of counts to obtain the steering angle midpoint, and the value of the steering angle midpoint is updated. If the vehicle speed V is smaller than the threshold value Vs _{2 in} step 51, or the detected torque value is larger than the torque setting value Ts ₂ or the rotational angular velocity ω is larger than the rotational angular velocity set value ωs, the routine returns. As a result, when the detected torque value becomes zero, such as when the hand is released when the steering wheel is returned, it is not determined that the vehicle is going straight, and therefore the time for calculating the midpoint is shortened.

It should be noted that until the midpoint calculation is completed, the return control is performed by the right / left determination routine described below.

FIG. 11 is a flowchart showing a procedure for determining the left and right positions of the steering angle. In this left / right determination routine, the vehicle speed V is read in step 60, and it is determined in step 61 whether the vehicle speed V is higher than the threshold value Vs _{3, and} if it is higher, the torque detection value is stepped.
It is read in 62, and this torque detection value is integrated in step 63, and it is determined whether or not the direction of the integrated value is right. When it is right, the right value of the minimum steering angle is updated in step 65, and when it is left, the left value of the minimum steering angle is updated in step 64 and the process returns.

The subtraction signal function unit 73c is a function unit that obtains the subtraction signal Sr corresponding to the relationship between the input rotational angular velocity ω and the vehicle speed V. The subtraction signal Sr increases as the rotational angular velocity ω increases, and The value corresponding to the rotational angular velocity ω increases as V increases. In the subtraction signal function unit 73c, the subtraction torque Tr and the subtraction current obtained based on the subtraction signal Sr obtained in accordance with the relationship as described above.
Ir is subtracted from the compensation detection torque Tc and the instruction current I.
As a result, during high speed traveling, the subtraction signal Sr becomes larger than during low speed traveling, and the instruction current I is suppressed to a low level.
The feeling of swaying of the vehicle body due to steering at high speed is suppressed. In addition to this, excessive return of the steering wheel at the time of returning the steering wheel is prevented.

In this embodiment, when the internal resistance of the motor is obtained, the terminal voltage is sampled in correspondence with each of the plurality of current values, but the present invention is not limited to this, and each of the current values has a predetermined range. The detection effective width is provided, the terminal voltage is sampled for the current value in this predetermined range, and the internal resistance of the motor is obtained by the linear approximation method as described above based on the average value of the sampled value and the current value. May be. Moreover, as the sampling values of the terminal voltage and the current value, those obtained by the moving average calculation may be used.

〔effect〕

As described in detail above, in the power steering apparatus according to the present invention, the counter electromotive voltage of the motor is obtained from the terminal voltage and the drive current of the motor, and the rotational angular velocity and the relative steering angle of the motor are obtained from the counter electromotive voltage. The present invention has excellent effects such that it is possible to perform control relating to steering assistance without providing the rotation detector of 1. and is inexpensive.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of a power steering apparatus according to the present invention, FIG. 2 is an enlarged sectional view taken along the line II-II of FIG. 1, and FIG. FIG. 4 is a block diagram showing the operation, and FIG. 4 is a flowchart showing a procedure of control for reducing the steering assist force according to the vehicle speed and the rotational angular velocity of the motor.
FIG. 5 is a flowchart of a subroutine for calculating the rotational angular velocity and the relative steering angle, FIG. 6 is a graph showing a method for obtaining the internal resistance of the motor, and FIG. 7 is a relationship between the subtraction signal in the subtraction signal function unit and the rotational angular velocity. 8 is a graph showing the characteristics of the relationship between the command current and the input torque in the command current function section, FIG. 9 is a flowchart showing the steering angle return control, and FIG. 10 is a graph showing the steering angle. FIG. 11 is a flowchart showing a method for calculating the midpoint, and FIG. 11 is a flowchart showing a procedure for determining the left and right positions of the steering angle. 6 ... Torque sensor, 8 ... Motor 18 ... Vehicle speed detector, 71b ... Voltage detection circuit 71c ... Current detection circuit, 71d ... Internal resistance calculation unit 71e ... Back electromotive force calculation unit, 71f ... Rotation Angular velocity calculation unit 71g ...... Relative steering angle calculation unit, 73c …… Subtraction signal function unit

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-63-240467 (JP, A) JP-A-62-34846 (JP, A) JP-A-2-256562 (JP, A) JP-A 58- 188751 (JP, A) Actual development Sho 58-64324 (JP, U) edited by The Institute of Electrical Engineers, "Handbook of Electrical Engineering" (reprint), December 15, 1969, Issued by The Institute of Electrical Engineers, P. 540 From right bottom, line 26-P. 542 right column 15 lines

Claims (1)

[Claims] 1. A power steering apparatus including a steering assisting motor driven according to a steering torque applied to a steering wheel, comprising: a voltage detecting means for detecting a terminal voltage of the motor; and a drive current of the motor. The internal resistance of the motor is calculated from a plurality of data of a current detection unit to detect, a predetermined detection result of the current detection unit, and an average value of a plurality of detection results of the voltage detection unit corresponding to the detection result. An internal resistance calculating means, a counter electromotive voltage calculating means for calculating a counter electromotive voltage of the motor from the calculation result of the internal resistance calculating means, the detection result of the voltage detecting means and the detection result of the current detecting means, Rotational angular velocity calculation means for calculating the rotational angular velocity of the motor from the calculation result of the electromotive voltage calculation means, and relative steering angle calculation for calculating the relative steering angle of the steered wheels from the calculation result of the counter electromotive voltage calculation means. Power steering apparatus characterized by comprising a means.