JPH0725314B2 - Rudder angle midpoint detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a steering angle midpoint detection device for detecting the midpoint of the steering angle of a steering mechanism, and more particularly to an improvement aimed at improving the midpoint detection accuracy. .

[Prior art]

In the power steering apparatus that assists the steering force based on the detection result of the steering torque applied to the steering wheel, the steering angle is usually selected as one of the steering conditions.

Conventionally, as a means for detecting the steering angle, one using a sensor such as a potentiometer for detecting the movement of the steering wheel shaft or the rack shaft is known.

With such a steering angle detecting means, when the vehicle goes straight,
The output of the sensor is adjusted and determined so as to have a predetermined output value, and the midpoint of the steering angle is detected thereby.

[Problems to be Solved by the Invention]

However, in the conventional rudder angle detecting means, the output value of the sensor corresponding to the midpoint of the rudder angle is determined in advance, so that it may change due to the secular change of the characteristic value of the steering mechanism such as the camber and the toe-in and the change due to the maintenance of the steering mechanism. However, there is a problem in that a predetermined output value of the sensor and a midpoint of a steering angle at which the vehicle goes straight ahead are deviated from each other, and the midpoint cannot be accurately detected.

Therefore, in order to eliminate the above deviation and detect the midpoint with high accuracy, it becomes necessary to correct the output value of the sensor at regular intervals or every time maintenance is performed.

The present invention has been made in view of such circumstances, and determines that the vehicle is traveling straight when the steering torque is smaller than the torque setting value according to the vehicle speed and the angular speed is smaller than the angular speed setting value according to the vehicle speed. Detecting the steering angle at that time, detecting the midpoint of the steering angle, eliminating the need to correct the output value of the sensor, and obtaining a steering angle midpoint detection device with improved midpoint detection accuracy. To that end.

[Means for Solving the Problems]

A rudder angle midpoint detection device according to the present invention is a device for detecting the midpoint of the rudder angle of a steering mechanism that converts the rotation of a steering wheel of a vehicle into a lateral movement for steering, and detects the vehicle speed of the vehicle. Vehicle speed detecting means, a torque sensor for detecting a steering torque applied to the steering wheel, a steering position detecting means for detecting a steering position of the steering mechanism, and an angular velocity detecting means for detecting an angular velocity of a steering angle of the steering mechanism. A means for comparing a steering torque set value preset according to the vehicle speed with a steering torque detected by the torque sensor; an angular velocity set value preset according to the vehicle speed; and the angular velocity detecting means. Means for comparing the detected angular velocity,
When the steering torque is smaller than the steering torque setting value and the angular velocity is smaller than the angular velocity setting value, the midpoint of the steering angle is detected from the steering position of the steering mechanism detected by the steering position detecting means. And means.

[Action]

In the present invention, the steering torque, the vehicle speed, and the angular velocity of the steering angle are detected, and when the vehicle speed is higher than a constant value, a comparison between the steering torque setting value and the magnitude of the steering torque preset according to the vehicle speed and The angular velocity set value preset according to the vehicle speed is compared with the magnitude of the angular velocity, and when the steering torque is smaller than the steering torque set value and the angular velocity is smaller than the angular velocity set value, it is considered that the vehicle is traveling straight. , The midpoint of the steering angle is detected by the steering position of the steering mechanism.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment thereof. FIG. 1 is a partially cutaway front view of a power steering apparatus using a steering angle midpoint detecting device according to the present invention, and FIG. 2 is II-II of FIG.
FIG. 3 is an enlarged sectional view taken along line III-III in FIG. 1 showing the structure of a rotation detector which is steering position detecting means.

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 externally fitted to the lower shaft 3b from the lower end side thereof, and a step portion formed near the upper end of the lower shaft 3b and externally fitted from the lower end side to be caulked and fixed to the outer peripheral surface. After being positioned on the outer side of the lower shaft 3b in the axial direction by being held by the collar 42 on both sides of the inner ring, the lower shaft 3b and the lower shaft 3b are fitted into the pinion shaft case 4 from the lower opening. An annular shoulder portion formed in the lower portion of the case 4 and a lock nut 43 screwed into the case 4 through the opening are clamped on both sides of the outer ring so as to extend axially in the pinion shaft case 4 inside. It is positioned and applies a radial load acting on the lower shaft 3b and an axial load in both directions.

The middle part of the lower shaft 3b protruding from the pinion shaft case 4 has pinion teeth 30 of a proper length in the axial direction.
When the pinion shaft case 4 is fixed to the upper side of the rack shaft case 2 by a fixing bolt 44, one end of the rack shaft 1 is formed inside the rack shaft case 2. A rack tooth 10 formed at a position near the portion and having an appropriate length in the axial direction is meshed with each other, and the lower shaft 3b and the rack shaft 1 are engaged with each other with their axial centers crossed. The lower shaft 3b extends further downward than the position of engagement with the rack shaft 1, and has a lower end portion coaxial with the lower shaft 3b and fitted with a large bevel gear 31 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 lower shaft 3b
Is supported by the four-point contact ball bearing 41 and the needle roller bearing 33 on both sides of the meshing position of the rack teeth 10 and the pinion teeth 30, and the amount of bending of the lower shaft 3b at the meshing position is It is kept within a predetermined tolerance.

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. 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 projecting on both sides of the rack shaft case 2 are connected through separate ball joints 14, 14, respectively.
The left and right wheels (not shown) are connected to tie rods 15 and 15 respectively connected to the left and right wheels, and 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 inputted to the control unit 7, which compares the signal with the reference potential to recognize the direction and the magnitude of the steering torque, and which is provided as described below for steering assist. A drive signal is issued to the motor 8 of.

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 and is driven by an electromagnetic force generated by energizing the coil part 161.
The engaging / disengaging portion 163 is engaged with and disengages the rotational force of the motor 8.

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. The small bevel gear 32 together with the output shaft 94 is connected to the planet rollers 92, 92 ... It is designed to rotate according to the revolution of the.

The motor 8, the electromagnetic clutch 16, the planetary roller speed reducer 9
Means that these shaft centers are substantially parallel to the shaft center of the rack shaft 1 and are fitted into the bevel gear housing 20 as the inner side of the small bevel gear 32, and the small bevel gear inside the housing 20. 32 is a large bevel gear fitted to the lower end of the lower shaft 3b.
It is engaged with 31 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 fitting the casing of the planetary roller reduction gear 9 and the bevel gear housing 20 together when the planetary roller reduction gear 9 is fitted in the bevel gear housing 20. This can be easily performed by changing the thickness and / or the number of shims to be inserted in the.

Further, a rotation detector 17 for detecting the rotation position of the motor 8 is provided on the other side of the rotation shaft 80 of the motor 8, and the rotation detector 17 is a disc externally fitted on the other side of the rotation shaft 80 of the motor 8. Make a state,
It is composed of a magnet plate 170 having two north poles and two south poles, and two reed switches 171 and 171 mounted around the magnet plate 170 with a predetermined mounting angle β (β = 135 ° in this embodiment). FIG. 4 is a waveform diagram showing the output waveform of the rotation detector. Since the two reed switches 171, 171 are mounted with the mounting angle β of 135 °, the output waveforms are output with a 90 ° phase shift. Since each of these outputs four waveforms in one rotation, the rotation detector 17 has a resolution of 1/16 of one rotation by detecting the rising and falling edges.

The rotation detector 17 can detect the rotation speed from 0 and can detect the relative position of the rotor, as compared with a conventional rotation detector such as a tachogenerator.

In addition, it is smaller than the photo interrupter type rotary encoder, is resistant to high temperatures, is less subject to aging, and is less expensive. Furthermore, since the output waveform is a pulse output, the detection result can be easily loaded into a CPU such as a microcomputer.

In addition to the output signal of the torque sensor 6 described above, the output signal of the rotation detector 17 and the output signal of the vehicle speed detector 18 for detecting the vehicle speed are input to the control unit 7, and the control described below is performed to the motor. 8 and a drive signal for driving the electromagnetic clutch 16 are output.

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

FIG. 5 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,
Phase compensation circuit 71a for stabilizing the system, angular acceleration detection circuit 71b for detecting the angular acceleration of the rotation of the steered wheels, midpoint detection circuit 71c for determining the midpoint of the steering mechanism that is the gist of the present invention, motor Lock detection circuit 71 for detecting lock of 8
f, angular velocity detection circuit 71g that detects the angular velocity ω of the steering wheel rotation
And a torque function unit 73g that generates a function according to the absolute value | T | of the steering torque T. Further, the vehicle speed detection signal of the vehicle speed detector 18 includes a lock detection circuit 71f, a midpoint detection circuit 71c, and a vehicle speed function unit 7 for generating a function according to the vehicle speed V.
3f, the angular acceleration of the steering wheel output from the angular acceleration detection circuit 71b is given, and the inertial force during acceleration / deceleration of the motor 8 and the inertial force around the foot of the vehicle are corrected according to the angular acceleration and the vehicle speed V. A change current that changes the characteristic of the instruction current I according to the steering angle θ and the vehicle speed given the steering angle θ output from the correction current function unit 73b that determines the correction current Ic and the steering angle determination circuit 71d described later. They are respectively input to the changing current function unit 73c that determines Ia.

Further, the rotation detection signal of the rotation detector 17 is a lock detection circuit.
71f, the midpoint detection circuit 71c, the angular acceleration detection circuit 71b, the angular velocity detection circuit 71g, and the rotation detection signal and the midpoint position of the midpoint detection circuit 71c are input to the steering angle determination circuit 71d that determines the steering angle θ. .

The lock detection circuit 71f detects the rotation of the motor 8 when the torque and the vehicle speed are larger than respective predetermined values by the input rotation detection signal, vehicle speed detection signal and torque detection signal,
Accordingly, the presence or absence of lock is detected, and its output signal is given to the electromagnetic clutch 16 via the drive circuit 72b.

The output ω of the angular velocity detection circuit 71g is given to the angular velocity function unit 73d that generates a function according to the angular velocity. The function portion 73d is supplied with the change current Ia, and the change current Ia is applied with an offset amount. The output signal of the phase compensation circuit 71a and the change current Ia are given to the instruction current function unit 73a which generates the instruction current I to the motor 8. Further, the output signal of the vehicle speed function unit 73f is given to the torque function unit 73g, and the torque function fd corresponding to the vehicle speed is output. The output is given to the subtraction current function unit 73e, and the subtraction current Ir is generated by the output of the angular velocity function unit 73d and the output. The output signal of the instruction current function unit 73a is input to the subtractor 74c, where the subtraction current Ir which is the output of the subtraction current function unit 73e is subtracted, and the subtraction result is given to the adder 74a.

The output signal of the correction current function unit 73b is added to the adder 74a, and the addition result is given to the subtractor 74b.

In the subtractor 74b, the feedback signal from the current detection circuit 71e that detects the consumption current of the motor 8 is subtracted from the addition result, and the subtraction result is PWM (Pulse-Width Modu
lation: pulse width modulation) It is given to the motor 8 via a drive circuit 72a.

Next, the operation will be described.

FIG. 6 is a flowchart showing the lock detection control. In step 10, it is determined whether or not the ignition switch (not shown) is turned on. If not, the vehicle speed V of the vehicle speed detector 18 is read in step 11.
Whether the vehicle speed V is greater than the vehicle speed threshold Vs ₁ is determined by step 1
When it is determined in step 2 and is large, the steering torque T from the torque sensor 6 is read in step 13 below. The steering torque T
Is larger than the torque threshold Ts ₁ in step 14, and if larger, the rotational position of the motor 8 from the rotation detector 17 is read in step 15, and the value indicates whether the motor 8 is rotating in step 16. If it is not rotating, the process returns. If it is not rotating, it is determined that the motor 8 is locked. In step 17, the electromagnetic clutch 16 is turned off, and the motor 8 and the planetary gear speed reducer 9 The connection with is disconnected and the steering mechanism is freed from the motor 8. Then, in step 18, a lock alarm (not shown) is turned on and the process returns.

On the other hand, when it is determined in step 10 that the engine is rising, the electromagnetic clutch 16 is turned off in step 19, and the motor 8 is turned on in step 20. When the motor 8 is turned on, it is determined in step 21 that a predetermined time has elapsed, and then the rotational position of the motor 8 is read from the rotation detector 17 in step 22, and it is determined in step 23 whether or not the motor 8 is rotating by the value. If it is determined that the motor 8 is rotating, the motor 8 is turned off in step 24, and the electromagnetic clutch 16 is turned on in step 25. Step
When it is determined in 23 that the motor 8 is not rotating, the lock alarm is turned on in step 26 and the process returns.

Next, detection of angular acceleration and motor inertial control using the same will be described.

FIG. 7 is a flowchart showing calculation of angular acceleration and control of motor inertia using the calculation.

First, in step 30, the torque T from the torque sensor 6 is read, then in step 31, the angular acceleration detection circuit 71b reads the rotation speed ωm of the motor 8 from the rotation detector 17,
In step 32, the angular acceleration of the steering wheel is calculated by the following calculation.

T = K (θi−θ ₀ ) Where K is the spring constant of the torsion bar, n is the reduction ratio Next, the influence of the inertial force of the motor 8 and the inertial force around the wheels around the wheel, which is determined in advance by the correction current function unit 73b, is corrected by the angular acceleration given to the steering wheel and the vehicle speed V obtained in step 33. Find the correction current Ic. Next, the correction current Ic obtained in step 34 is input to the adder 74a and added with the instruction current I obtained in the instruction current function unit 73a.
As a result, when the angular acceleration at the start and end of the steering assist by the motor 8 is detected, the correction current Ic corresponding to the inertial force and the inertial force around the foot is added to the instruction current I. The ring is improved.

Next, the calculation of the midpoint of the steering angle and the steering wheel return control using the calculation will be described, which is the gist of the present invention.

FIG. 8 shows the steering wheel return control, FIG. 9 shows the calculation of the midpoint of the steering angle,
FIG. 10 is a flowchart showing a procedure for determining the left and right positions of the steering angle. Further, FIG. 11 is a graph showing the characteristic of the relationship between the motor current and the torque in the instruction current function unit 73a,
The vertical axis represents the instruction current I, and the horizontal axis represents the torque T. Further, the broken line shows the characteristic when the vehicle speed is high, and the alternate long and short dash line shows the characteristic when the vehicle speed is low.

In FIG. 8, first, the torque T is read in step 40, and it is determined in step 41 whether or not the torque T is in the dead zone. If the torque T is in the dead zone, the midpoint calculation routine described later in step 42 is executed. It is determined whether or not is completed. When the midpoint calculation is completed, the rotational position of the motor 8 is read from the rotation detector 17 in step 43, and then in step 44 the steering angle determination circuit 71d is determined by the rotational position and the midpoint.
Determines the steering angle θ. When the steering angle θ is determined, the changing current Ia is changed in step 45 by the steering angle θ and the vehicle speed V.
Then, the value and direction of the instruction current I are calculated by the instruction current function unit 73a.

On the other hand, if it is determined in step 41 that it is not in the dead zone, the process returns, and if midpoint calculation is not completed in step 42, the rotational position of the motor 8 is read from the rotation detector 17 in step 46, and will be described later in step 47. The change current Ia is calculated from the minimum steering angle value determined in the left / right determination routine, and the value and direction of the instruction current I are calculated.

In the midpoint calculation routine shown in FIG. 9, the vehicle speed V is read in step 50, and it is determined in step 51 whether the vehicle speed V is higher than the threshold value Vs _{2. If} it is larger, in step 52 the torque set value corresponding to the vehicle speed is set. defining a ts _2, then reads the torque T at step 53, the torque T at step 54 determines whether the torque set value Ts ₂ smaller. When it is smaller, the angular velocity set value ωs according to the vehicle speed is determined in step 541, then the angular velocity ω of the steering angle detected by the angular velocity detection circuit 71g from the change of the motor rotational position is read in step 542, and the angular velocity ω is read in step 543. Is smaller than the angular velocity setting value ωs. When it is small, it is determined that the vehicle is moving straight, the number of times when it is small is counted in step 55, and the rotational position of the motor 8 at that time is read in step 56. Then, in step 57, the rotational position is added to the total of the rotational positions up to the previous 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.
When the vehicle speed V is smaller than the threshold value Vs _{2 in} step 51, the torque T is larger than the torque setting value Ts _{2 in} step 54, or the angular velocity ω is larger than the angular velocity setting value ωs in step 543, the routine returns. Thus, when the torque T 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 the midpoint detection accuracy is improved.

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

In the left / right determination routine shown in FIG. 10, the vehicle speed V is determined in step 60.
In step 61, it is determined whether or not the vehicle speed V is larger than the threshold value Vs ₃ , and when it is larger, the torque T is read in step 62, the torque T is integrated in step 63, and whether the direction of the integrated value is right or not. judge. 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.

On the other hand, when the change current Ia is obtained from the steering angle θ in the return control as shown in FIG. 11, the instruction current I for the return control of the steered wheels when the torque is within the dead zone is changed according to the change current Ia. For example, when the vehicle speed V is high, as shown by the broken line, when the torque T enters the dead zone, the rate of increase of the instruction current I is increased, and the motor 8 is controlled so as to speed up the return to the middle point. When it is small, when the torque T enters the dead zone as shown by the chain line, the rate of increase of the instruction current I is reduced and the motor 8 is controlled so as to delay the return to the middle point.

Next, the angular velocity control of the steering wheel will be described. FIG. 12 is a flowchart showing the angular velocity control of the steering wheel. First, in step 70, the rotational position of the motor 8 is read by the output of the rotation detector 17. Next, in step 71, obtain the steering angle from the rotational position,
An offset amount is given to the angular velocity function unit 73d based on the change current Ia according to the steering angle. Next, in step 72, the vehicle speed V is read, and in step 73, the torque T is read. Next, in step 74, the vehicle speed function section 73f obtains the vehicle speed function fv from the vehicle speed V, and the torque control section 73g calculates the vehicle speed function fv from the vehicle speed function fv.
To decide. Next, at step 75, the angular velocity ω is detected, and the angular velocity function fω taking into account the offset amount is obtained. Next, the subtraction current Ir is obtained by the subtraction current function unit 73e from the angular velocity function fω and the velocity control amount fd obtained in step 76, and this is input to the subtractor 74c, whereby the current corresponding to the torque T and the angular velocity ω is obtained. Subtract from the indicated current I.

In the present embodiment, the case where the device of the present invention is used for the return control of the steered wheels of the electric power steering device has been described, but the present invention is not limited to this and can be used for other controls. Needless to say.

Further, in the present embodiment, the rotation detector for detecting the rotation position of the motor is used as the steering position detecting means, but the present invention is not limited to this, and the steering mechanism such as the displacement of the rack shaft, the turning position of the steering wheel shaft, etc. Any means can be used as long as the relative position of can be detected.

〔The invention's effect〕

As described above, according to the present invention, the steering torque, the vehicle speed and the angular velocity are detected, and when the steering torque is smaller than the steering torque setting value preset according to the vehicle speed and the angular velocity is smaller than the angular velocity setting value, Since the steering position of the steering mechanism is detected and the midpoint of the steering mechanism is detected from the detected steering position, the midpoint can be detected at the relative steering position, and the correction of the midpoint of the steering position detection means is unnecessary. In addition to improving the accuracy of midpoint detection, the applicant previously filed (Japanese Patent Application No.
-248309), it is further determined by the angular velocity of the steering angle whether or not the vehicle is going straight.Therefore, when the steering wheel is returned, the steering wheel is released and there is no need to judge that the vehicle is going straight when the torque becomes zero. Further, it has an excellent effect such that the calculation time of the midpoint calculation can be shortened.

[Brief description of drawings]

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. 3 is a structure of a rotation detector. III-I in FIG.
Fig. 4 is an enlarged sectional view taken along line II, Fig. 4 is a waveform diagram showing the output waveform of the rotation detector, Fig. 5 is a block diagram showing the configuration and operation of the control unit, and Figs. 6 to 10 explain each control operation. 11 is a graph showing the characteristic of the relationship between the motor current and torque in the command current function section, and FIG. 12 is a flowchart of angular velocity control. 6 ... Torque sensor, 8 ... Motor, 17 ... Rotation detector, 18 ... Vehicle speed detector, 71c ... Midpoint detection circuit, 71d ...
Rudder angle determination circuit, 71g ... Angular velocity detection circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B62D 119: 00

Claims (1)

[Claims] 1. An apparatus for detecting a midpoint of a steering angle of a steering mechanism for converting a turning wheel of a vehicle into a lateral movement for steering, a vehicle speed detecting means for detecting a vehicle speed of the vehicle, A torque sensor for detecting a steering torque applied to the steering wheel, a steering position detecting means for detecting a steering position of the steering mechanism, an angular velocity detecting means for detecting an angular velocity of a steering angle of the steering mechanism, and a vehicle speed according to the vehicle speed. Means for comparing a preset steering torque setting value with a steering torque detected by the torque sensor; an angular velocity set value preset according to the vehicle speed; and an angular velocity detected by the angular velocity detecting means. And a means for comparing, the steering torque is smaller than the steering torque set value, and the angular velocity is smaller than the angular velocity set value, detected by the steering position detecting means. Means for detecting the midpoint of the steering angle from the steering position of the steering mechanism.