JPH026271A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE:To obtain favorable traveling stability and steering feeling by effecting the optimum control matched with each input in either case of the normal input or the reverse input of a steering torque which is generated in a steering system. CONSTITUTION:The steering torque of a steering system is detected by a steering torque detecting means and, on the other hand, it is judged whether the above steering torque is a normal torque from a steering wheel side or a reverse torque therefrom by a normal/reverse input judging means. The steering torque detected value which is detected by the steering torque detecting means is differentiated by a steering torque differentiating means and, on the other hand, the reference current value at the time of reverse input is determined by a reference current value determining means based on the steering torque detecting value, while determining the correcting current value at the time of reverse input by a correcting current value determining means based on the steering torque differentiated value. A control means controls the drive of an electric motor in accordance with the driving current corresponding to a normal/reverse input.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electric power steering device that applies steering assist torque to a steering system by the rotational force of an electric motor.
In particular, even if the steering torque generated in the steering system is input from the steered wheels (reverse input), running stability and steering feel are not impaired.

[Conventional technology]

Conventionally, an electric power system determines whether the steering torque generated in the steering system is a normal human force from the steering wheel side or a reverse input from the steered wheels, and drives and controls the electric motor based on the determination result. As a steering device,
For example, patent application No. 63-6870 filed earlier by the present applicant.
There is something listed in No. 3.

This conventional technology includes means for determining whether the steering torque generated in the steering system is a positive input or a reverse input, and a drive current to the electric motor is determined depending on whether the steering torque is a positive input or a reverse input. I was changing the value of the value.

That is, when it is determined that the steering torque is a positive input, like other power steering devices, it allows light steering when parking, etc., and also prevents driving safety from being impaired when driving at high speeds. In addition, when it is determined that the steering torque is a reverse input, a proportional gain is applied when calculating the drive current value from the steering torque to prevent the running direction of the steered wheels from changing unexpectedly due to unevenness of the running road surface, etc. is made larger than when there is a positive input to generate a large steering assist torque in the steering system, improving the vehicle's running stability and steering feel.

[Problem to be solved by the invention]

However, since it takes a certain amount of time after the steering torque is detected until the steering assist torque is generated in the steering system, it is difficult to determine the drive current value based only on the steering torque as in the conventional technology described above. In this configuration, it takes time to settle the steering torque when the rate of change of the steering torque is large, so torque vibration occurs in the steering system.
There was a problem in that running stability and steering sensation were impaired.

In addition, in order to eliminate the above-mentioned torque vibration generated in the steering system, the present applicant has proposed a method for controlling the steering torque as described in, for example, JP-A-62-29465 and JP-A-62-34846. The present invention proposes an invention in which a driving current value of an electric motor is determined based on a detected value and a steering torque differential value.

However, with these conventional solutions, although the above problems with positive input can be solved, in order to ensure driving safety at high speeds, the drive current value, that is, the steering assist torque, decreases depending on the vehicle speed. Since the control had to be performed, there was an unresolved problem that if a reverse input steering torque was generated in the steering system, running stability and steering feel would be impaired.

Therefore, this invention was made by focusing on the unresolved problems of the prior art described above, and it is determined whether the steering torque generated in the steering system is a positive input from the steering wheel side or a positive input from the steered wheels side. A means for determining whether the input is a reverse input is provided, and when the steering torque is a reverse input, a reference current value determined based on the steering torque and a corrected current value determined based on the differential value of the steering torque are provided. An object of the present invention is to provide an electric power steering device that can perform optimal control for reverse input by determining a drive current value for an electric motor according to the following.

[Means for Solving the Problems] In order to achieve the above object, the electric power steering device of the present invention includes an electric motor that generates a steering assist torque in the steering system, as shown in the basic configuration diagram of FIG. , a steering torque detection means for detecting the steering torque of the steering system, a forward/reverse input determination means for determining whether the steering torque is a forward input or a reverse input, and the electric motor when the steering torque is a forward input. positive input current value determining means for determining a drive current value for the steering torque based on the steering torque; a steering torque differentiating means for differentiating the detected steering torque value to obtain a differential steering torque value; a reference current value determining means for determining a reference current value at the time of reverse input; a corrected current value determining means for determining a corrected current value at the time of reverse input based on the steering torque differential value; and when the steering torque is a reverse input. drive current value determining means for determining a drive current value for the motor based on the reference current value and the corrected current value; and when the determination result of the forward/reverse input determining means is positive input, the positive input Drive control means for driving and controlling the motor in accordance with the drive current value determined by the current value determining means and in accordance with the drive current value determined by the drive current value determining means when the determination result is a reverse input; Equipped with. In addition,
The gains (amplification factors) of the reference current value determining means and the corrected current value determining means may be variable depending on the vehicle speed.

[Operation] While the steering torque of the steering system is detected by the steering torque detection means, it is determined whether this steering torque is an input from the steering wheel side (positive input) or an input from the steered wheels side (reverse input). is determined by the forward/reverse input determining means.

The steering torque detection value detected by the steering torque detection means is differentiated by the steering torque differentiating means, while the reference current value at the time of reverse input is determined by the reference current value determination means based on the steering torque detection value, and the steering torque Based on the differential value, the corrected current value at the time of reverse input is determined by the corrected current value determining means.

Further, the positive input current value determination means determines a drive current value for the electric motor when the steering torque is a positive input based on the steering torque detection value of the steering torque detection means, and also determines the drive current value. The means determines a drive current value for the electric motor when the steering torque is a reverse input, based on the reference current value and the corrected current value.

When the determination result of the forward/reverse input determination means is positive input, the drive control means drives and controls the electric motor according to the drive current value determined by the current value determination means at the time of positive input; If the determination result is a reverse input, the electric motor is drive-controlled in accordance with the drive current value determined by the drive current value determining means.

Then, when a positive input is made, a steering assist torque corresponding to the steering torque is generated in the steering system, which allows light steering operations such as when parking the vehicle.If the steering assist torque is reduced according to the vehicle speed, high-speed Driving safety will not be compromised.

For example, even if a reverse input steering torque occurs in the steering system due to a steering wheel running over a protrusion on the road surface, if the forward/reverse input determination means determines that the input is a reverse input, the steering torque detection value and the steering Since the steering assist torque is generated according to the torque differential value, that is, the steering assist torque is generated according to the magnitude of the steering torque and the rate of change of the steering torque, the running direction of the steered wheels is quickly corrected and the running stability of the vehicle is improved. As a result, the steering feeling becomes better because the reverse input steering torque is not transmitted to the steering wheel.

In addition, the reverse input steering torque is generated when the steered wheel runs over a protrusion on the road surface or due to vibrations caused by unbalanced wheels, etc., so when the vehicle speed changes, the reverse input steering torque also changes. When the gains of the reference current value determining means and the correction current value determining means are made variable according to the vehicle speed, by appropriately selecting the relational characteristics between the vehicle speed and each gain, it is possible to ensure that the reverse input is controlled by the optimal motor output. The steering torque can be canceled out.

〔Example〕 Embodiments of the present invention will be described below based on the drawings.

FIGS. 2 to 17 show an embodiment of the present invention.

First, to explain the structure, as shown in Fig. 2, the symbol ■ is a steering shaft, and the steering wheel 2 is attached to its upper end, and the lower end thereof is shown in an enlarged cross-section in Fig. 3. As shown, a stub shaft 1a, which is an input shaft forming a part of the steering shaft 1, is spline-coupled, and a lower part of the stub shaft 1a is inserted into a gear box 4 of a rack-and-pinion steering gear 3. .

The stub shaft 1a passes through a hole in a ring-shaped bearing holder 5 that closes an opening 4a on the steering wheel 2 side of the gear box 4, and is inserted into the bearing holder 5 through a bearing 6 fitted in the hole. is rotatably supported. The bearing holder 5 is positioned on the gear box 4 by a snap ring 7, and is sealed with the stub shaft 1a by an oil seal 8.

Further, in the gear box 4, a pinion shaft 9, which is an output shaft integrally provided with a pinion gear 9a, is disposed coaxially below the stub shaft 1a, and is externally fitted on both sides of the pinion gear 9a in the axial direction. 2 bearings10.
The pinion shaft 9 is rotatably supported by the gear box 4 via the gear box 11 . The pinion gear 9a is
It meshes with the rack 12a of the rack shaft 12 in the gear box 4, and tie rods 1 are provided at both ends of the rack shaft 12.
3.13 are swingably connected to each other, and a knuckle 15.15 that rotatably supports the wheels 14, 14 is swingably connected to the outside of each tie rod 13.13.

16 are two bearings 10 fitted onto the pinion shaft 9
, 11 is a nut for applying preload, 17 is a nut 1
6 is a cap screwed into a screw hole provided in the gear box 4 for attaching and detaching the gear box 4, 18 is a rack retainer, and 19 is an adjustment bolt.

Further, the stub shirt 1-12 has a pipe shape, and a torsion bar 20 as an elastic body is inserted into the hole thereof, and the end on the steering wheel 2 side and the stub shaft la are connected by a pin 21. They are fastened together to form one body in the rotational direction, and the opposite end thereof is inserted into an axial hole 9b facing the end surface of the pinion shaft 9 on the stub shaft 1a side, and is fastened to the pinion shaft 9 by a pin 22. and are integrated in the direction of rotation. Furthermore, the stub shaft l of the pinion shaft 9
A hub 9c protruding toward the stub shaft la side and a flange 9d protruding radially outward are formed at the end of the stub shaft la, and the lower end of the stub shaft la passing through the hole of the hub 9c and the hub Needle roller bearing 2 is installed between 9c and 9c.
3 is interposed.

A notch 9e is provided in the hub 9c of the pinion shaft 9, and a protrusion 1b to be inserted into the notch 9e is provided at the lower end of the stub shirt 1-13. Forming a stopper, the stub shaft 1a
and the relative rotational displacement between the pinion shaft 9 and the pinion shaft 9 (
For example, about 5 degrees). Further, a worm wheel 24 is fitted on the outside of the hub 9c, and a screw 25 that passes through the worm wheel 24 and screws into the flange 9d allows the worm wheel 24 and the nion shaft 9 to be integrated in the rotational direction. ing. And worm wheel 24
The worm 2 is rotatably supported by the gear box 4.
6 are in mesh with each other, and a rotating shaft of a motor 27 serving as an electric motor is connected to the shaft portion of the worm 26. A control device 30, which will be described later, is connected to the motor 27, and the motor 27 is driven and controlled by a control signal output from the control device 30.

Further, a disk-shaped substrate 28 formed of a highly insulating material such as phenol resin is fitted onto the stub shaft 1a and disposed between the convex portion 1b and the bearing 6. A post 28a protruding toward the convex portion 1b and a boss 28b protruding toward the bearing 6 are formed on the radially inner side of the disk-shaped substrate 28. Metal bushes 29a and 29b are attached to both bosses 28a and 28b, respectively. At the same time, the metal bushes 29b of the six bearings are fixed to the stub shaft 1a by caulking, and the stub shaft 1a and the disc-shaped substrate 2 are connected to each other.
8 are integrated in the rotational direction and the axial direction.

On the surface of the disk-shaped substrate 28 on the worm wheel 24 side, two electric resistance members 31 and 32 made of conductive plastic elements (CP elements), etc., and both electric resistance members are arranged in a shape as shown in FIG. A good electrical conductor such as a slip ring with a low resistance value connecting 31.32.
34 and a good electrical conductor 35.36 arranged concentrically on the outside of each electrically resistive member 31.32. The electrical resistance members 31 and 32 are provided concentrically with respect to the axis of the disc-shaped substrate 28 and spaced apart from each other by 180 degrees,
These constitute a resistance member for torque detection, and as described later, the amount of twist corresponding to the steering torque generated between the stub shaft 1a and the pinion shaft 9 is detected as a voltage value.

Further, on the surface of the disc-shaped substrate 28 on the bearing 6 side, a ring-shaped electric resistance member 40 made of a CP element or the like with a part cut in the circumferential direction is disposed in the shape shown in FIG. Four electrically conductive conductors 41 in a ring shape completely continuous in the direction
．． 42, 43, and 44 are printed concentrically around the axis. The electrical resistance member 40 is a steering angle detection resistance member of the stub shirt 1-1H, and is located second from the inside, and its discontinuous portion forms an electrical dead zone to be described later.

The steering angle detecting resistance member 40 has one end connected to a terminal 41a of a good electrical conductor 41 for a power line located innermost, and the other end connected to a good electrical conductor 41 for a ground line located third from the inside. 42 terminals 42a are connected. The terminal 41a of the electrical conductor 41 for the power line is connected to the electrical electrical conductor 34 for connection formed on the opposite surface via the rivet 45, and the terminal 42a of the electrical electrical conductor 42 for the earth line
The electrically conductive conductor 3 for connection formed on the opposite surface via 6
Connected to 3. Furthermore, the electrically conductive material 43 located fourth from the inside is connected to the torque detection electrically electrically conductive material 36 formed on the opposite surface via a rivet 47, and the electrically electrically conductive material 44 located at the outermost 48 to the torque detecting electrical conductor 35 formed on the opposite surface.

Further, a rotary member 50 and a ring member 51 made of highly insulating resin are rotatably fitted onto the metal bushes 29a and 29b, respectively, and the disc-shaped substrate 28 and the rotary member 50 and ring member 51 are connected to each other. Between them are wave springs 52 and 53 forming a ring 4k as shown in FIG.
are interposed, and the axial movement of the rotating member 50 toward the worm wheel 24 due to the urging force of the wave spring 52 is restricted by the snap ring 54 via a flat washer, and the movement due to the urging force of the wave spring 53 is restricted by the snap ring 54. Ring member 5
1 to the bearing 6 side is restricted by a snap ring 55 via a flat washer.

The rotating member 50 has a protrusion 50a that protrudes toward the worm wheel 24, a disc-shaped substrate 28, and a ring member 51.
A connecting pin 56 that is inserted into a hole provided in the worm wheel 24 and whose tip protrudes toward the bearing 6 is press-fitted into the protrusion 50a. , whereby the worm wheel 24 and the rotating member 50 are integrated in the rotational direction. A seal ring 57 that contacts the inner circumferential surface of the opening 4a of the gear box 4 is attached to the peripheral edge 50b of the rotating member 50, so that the lubricant stored on the worm wheel 24 side is transferred to the disc-shaped substrate. This prevents it from entering the 28 side.

Further, two comb-shaped current collecting members 58 and 59 are attached to two locations of the rotating member 50, as shown in FIG. Electric piece 5
8a and 59a are the torque detection electric resistance members 31.3
2 and the other current collector piece 58b,
59b are in individual contact with the electrically conductive conductors 35 and 36.

Furthermore, a protrusion 5a provided on the bearing holder 5 is engaged with the ring member 51, thereby preventing the ring member 51 from rotating. 6 of such ring member 51
At these locations, comb-like current collecting members 60a and 60b having a shape as shown in FIG. 8 are provided.

61.62, 63.64 are installed. The two current collecting members 60a and 60b are arranged so as to be in sliding contact with the electrical resistance member 40 for detecting the steering angle at positions rotationally displaced by 180 degrees from each other, and when the vehicle is traveling straight, one current collecting member 60 is in contact with the electric resistance member 40. It is set to be located at the center of the resistance member 40.

Other four current collecting members 61. 62. 63. 64
are arranged so as to be in sliding contact with the four electrically conductive conductors 41, 42, 43, and 44 individually.

These six current collecting members 60a, 60b, 61°62.6
3.64 is connected to the control device 30 via six harnesses 65.
and a power source 66 such as a battery, the electric circuit configuration of which is shown in FIG.

An electrical resistance member 3 for detecting steering torque is provided before and after the power source 66.
Two fixed resistors 67 and 68 are provided in series with 1.32 and the steering angle detection electric resistance member 40, respectively, and the refixed resistors 67 and 68 connect each electric resistance member 31, 32.
．． By applying a potential difference to 40, when the electric circuit is in a normal state, the output voltage according to the steering force changes from the maximum output value 'I''I+ to the minimum output value T, as shown in FIG.
, and its output voltage is supplied to the control bag W30 as the steering torque detection signal DT.

When a steering operation is performed by turning the steering wheel 2, the magnitude of the steering force is determined by the amount of relative rotational change between the stub shaft 1a and the pinion shaft 9, which are connected via the torsion bar 20. appears as Therefore, the disk-shaped substrate 28 rotates together with the stub shaft 1a.
The amount of relative rotational change that occurs between the pinion shaft 9 and the rotating member 50 that rotates integrally with the electric resistance member 31 or 3
By looking at the amount of change in the output voltage based on the change in the resistance value of 2, it is possible to detect the steering force applied to the steering mechanism by the driver. In this case, two current collecting members 58
．． 59 is set to be located at the center of each electrical resistance member 31, 32 when the vehicle is traveling straight,
Therefore, an output voltage having a characteristic as shown in FIG. 10 is output depending on the steering force. In this embodiment, two combinations of the electric resistance member and the current collection member were provided, but this was done in consideration of the safety of torque detection, and it is possible to detect the steering torque with at least one combination. can.

Further, the magnitude of the steering angle appears as an absolute rotational change amount between the stub shaft 1a and the gear box 4. Therefore, the amount of absolute rotational change that occurs between the disk-shaped substrate 28 that rotates integrally with the stub shaft 1a and the ring member 51 that is non-rotatably supported by the gear box 4 is converted into a resistance value change of the electrical resistance member 40 for steering angle. The steering angle of the steering mechanism can be detected by looking at the amount of change in the output voltage based on the output voltage. Note that the steering angle detected at this time is the steering angle on the stub shaft Ia side.

In this case, in this embodiment, the steering angle is detected at two locations rotationally displaced by 180 degrees from each other. That is, as a normal steering angle detection signal, when the vehicle is traveling straight, the electric resistance member 4
The signal E detected by the first current collecting member 60a set at the center of 0 is used. This is a discontinuous point (electrical dead zone) of the electrical resistance member 40 within a range of approximately 360 degrees.
Therefore, only the above-mentioned steering angle detection signal E is used when the absolute rotational change amount is within about 360 degrees at a small steering angle and a medium steering angle.

On the other hand, the electrical resistance member 40 has an electrical dead zone that is a discontinuous part of about 10 to 20 degrees, and the electrical resistance member 40 enters the electrical dead zone at about 180 degrees. Since the output voltage of the steering angle detection signal E becomes zero, in this case, the steering angle detection signal E is corrected by the correction signal F detected by the second current collecting member 60b. (see publication). Then, as shown in FIG. 11, the output voltage E according to the steering angle is equivalent to changing between the maximum output value El+ and the minimum output value EL, so those output voltages E and F are the same as those for the steering angle. Angle detection signal D
θ is supplied to the control device 30, and the steering angle θ□ is calculated.

Further, a vehicle speed sensor 30a is connected to the control device 30, which detects, for example, the rotational speed of the output shaft of a transmission and outputs a vehicle speed detection signal DV consisting of a periodic pulse signal corresponding thereto. The control device 30 includes an A/D converter that converts the detected analog voltage value into a digital value;
A microcomputer (not shown) that includes an interface circuit, an arithmetic processing unit, and a storage device as an input/output device and calculates a driving current value for the motor 27 based on the detected detection value, and a calculation result by this microcomputer. a D/A converter that converts a digital value into an analog value; and a D/A converter that converts a digital value into an analog value, and
It has at least a drive circuit (not shown) for driving the .

Next, the operation of the above embodiment will be explained with reference to FIGS. 12 to 17.

When the ignition switch is turned on, the control device 30
The power is turned on, and the steering torque detection signal DT, steering angle detection signal D0□, and vehicle speed detection signal DV are supplied to the microcomputer configuring the control device 30. This microcomputer is constantly executing other processing programs, and executes the process shown in FIG. 12 as an interrupt process every predetermined time (for example, 5m5ec).

First, in step (■) in FIG. 12, the steering torque detection signal D is
T, the steering angle detection signal Dθ□, and the vehicle speed detection signal DV are read, and then the process proceeds to step (2), where the steering torque T, steering angle θ is determined based on each detection signal read in the step (2).
11 and vehicle speed (2) are calculated and stored in a predetermined storage area of the storage device.

Next, the process moves to step (2), and it is determined whether or not the steering torque T calculated in step (2) is "0". In other words, if no steering torque is generated in the steering system, there is no need to apply steering assist torque to the steering system, so if the determination in step (2) is rYEsJ,
Step (2) The processing program shown in FIG. 12 is ended without executing the following processing.

On the other hand, if the determination in step ■ is rNOJ, that is, the steering torque T is generated in the steering system, the process moves to step ■, and the detected steering torque T is input from the steering wheel side (positive input). It is determined whether the input is from the wheel side (reverse input) by executing the subroutine process shown in FIG.

First, in step (2) in FIG. 13, the steering angle θ8. which is the rotation angle of the input shaft (stub shaft la) is determined. , and the detected steering torque T,. Based on the rotation angle θ of the output shaft (pinion shaft 9). , is calculated. Note that the subscript indicates that the value is a detection value detected in the same processing as k.

Here, the steering torque T of the steering system, , is determined by the following equation (1), assuming that the spring constant of the torsion bar 20 is .

1゛. 1-kTX(al((k)-θ,.,)...
(11) Therefore, the rotation angle θ2(k) of the output shaft is calculated based on the following equation (2), which is a modification of the above equation (1).

θP (k) ””θIT (kl T (k)
/k life・・・・(2) Next, move to step @ and calculate the current rotation angle θ of the input shaft and output shaft.
H (kl, θP (kl) and the same rotation angle θII (k-11 + θP (k-11) in the previous process, based on the following formulas (31, (41), the rotational angular velocity of the input shaft and output shaft Calculate r, .1. Shio, .

0 +l in =θ1lkl−θH(k−1+
”・・・(3)υ, 2.=θP (k)−θP
(k-11...(4) Next, proceed to step 0, and in order to determine the magnitude relationship of the absolute values of the rotational angular velocities of the input shaft and output shaft calculated in the step @, the difference between them is determined. The value S is calculated based on the following equation (5).

5=16Hn, l l lj□kl l ・
(5) Here, FIG. 14 shows each rotation angle θ0 of the input shaft and output shaft. This is a graph showing the relationship between θ and steering torque T in time series.
In the same figure (bl represents the time of reverse input, respectively).

Then, each rotation angle θ8. The time point when θ2 takes the extreme value and the time point when the steering torque T is "0" are expressed as t, ~t6 on the time axis.
and each time point t, xt6 and the interval R8 to R2 between each time point
The rotational angular velocity θi(., υ, (k) of the input shaft and output shaft of
, steering torque T (rightward direction is positive), and step 0
The polarity with the difference value S calculated in is summarized in the list shown in Figure 15. Based on this list, it is determined whether the current steering torque is a positive input in the process after step (■) in Figure 13. Determine whether it is a reverse input. Note that diagonal lines in this list indicate cases where the polarity cannot be limited to one or the other.

That is, in step ■, it is determined whether the steering torque T is positive (rightward), and if T>O, step [
phase].

In step [phase], the rotational angular velocity of the input shaft θ8. . , is greater than or equal to 0, and if it is determined to be greater than or equal to 0, the process moves to step [phase] and determines whether or not the rotational angular velocity υP (kl exceeds 0 or not) of the output shaft. Here, the judgment at this step [phase] is rYE
In the case of sJ, interval R1 at the time of positive input or time point 1 at the time of positive input. Since the current steering torque is determined to be a positive input, the process moves to step @ and sets the flag F to "1".
” and the subroutine processing ends.

On the other hand, if the determination in step q) is "NO", the process moves to step [phase], and it is determined whether the difference value S exceeds 0 or not. The judgment at this step [phase] is rYE
In the case of sJ, the current steering torque is determined to be normal human power because it is either section R6 at the time of a positive input or time point L6 at the time of a positive input, and the process moves to step O where the flag F is set to "1".
” and the subroutine processing ends.

Furthermore, if the determination in step [phase] is rNOJ, it is determined that the current steering torque is a reverse input because it is either section R3 at the time of reverse input or time t3 at the time of reverse input;
The process moves to step [phase], sets the flag F to "0", and ends the subroutine processing.

On the other hand, if the judgment in step ① is rNOJ,
Move to step [phase], and the rotational angular velocity of the output shaft is Op<.

is greater than or equal to 0. If the determination in this step @ is "NO", the current steering torque is determined to be a reverse input since it is limited to the section R1 at the time of reverse input, and the process moves to step [phase] and flag F is set. It is set to "0" and the subroutine processing ends.

In addition, if the judgment at step 0 is rYESJ, proceed to step ■, and judge whether the difference value S exceeds 0. If it is judged that the difference value S exceeds 0, if it is judged that the difference value S exceeds 0, then Since it is either time t4 or section R3 at the time of reverse input, it is determined that the current steering torque is a reverse input, and step [
phase], the flag F is set to "0", and the subroutine processing ends.

Furthermore, if the determination in step ① is rNOJ, the current steering torque is determined to be a positive input because it is limited to section R2 during normal human power, and the process moves to step 0 to flag F.
is set to "1" and the subroutine processing ends.

On the other hand, if it is determined in step @ that the steering torque T is less than or equal to O, that is, the steering torque is in the left direction, the process proceeds to step 0.

In step 0, it is determined whether the input shaft rotational angular velocity 6□(.
1. Then, it is determined whether or not exceeds O. here,
If the determination in step 0 is [YESJ, it is either interval R7 at the time of reverse input or time t6 at the time of reverse input, so the current steering torque is determined to be a reverse input, and step 7 [ phase], the flag F is set to "0", and the subroutine processing ends.

On the other hand, if the determination in step [phase] is "NO", the process moves to step [phase], and it is determined whether the difference value S exceeds 0 or not. The judgment at this step [phase] is rY
In the case of EsJ, the time point 1 at the time of reverse input. or section R2 at the time of reverse input, it is determined that the current steering torque is a reverse input, and the process moves to step [phase] where flag F is set.
is set to "0" and the subroutine processing ends.

Further, if the determination in step [phase] is rNOJ, the current steering torque is determined to be a positive input because it is either time t4 at the time of positive input or interval R2 at the time of positive input;
The process moves to step [phase], sets the flag F to "1", and ends the subroutine processing.

On the other hand, if the determination at step 0 is rNOJ,
Shifting to step 0, the rotational angular velocity of the output shaft e p n+
is greater than or equal to 0. If the determination at step 0 is rNOJ, the current steering torque is determined to be a positive input since it is limited to the section R4 at the time of positive input, and the process moves to step [phase] and flag F is set to "1". ” and ends the subroutine processing.

Also, if the judgment at step 0 is rYEsJ, move to step 0 and judge whether or not the difference value S exceeds 0. If it is judged that the difference value S exceeds 0, then Since it is either section R1 or point 3 at the time of positive input, the current steering torque is determined to be a positive input, and step [
phase], the flag F is set to "1", and the subroutine process ends.

Furthermore, if the determination at step 0 is rNOJ, the current steering torque is determined to be a reverse input since it is limited to the section R4 at the time of reverse input, and the process moves to step [phase] and flag F is set to "0" and the bluech processing ends.

When the subroutine processing shown in Fig. 13 is finished, the first
2, the differential value ΔT of the steering torque is calculated according to the following equation (6).

ΔT = T tar T (1-1......(
6) Note that the steering torque differential value may be a value obtained by multiplying the steering torque differential value ΔT by a predetermined differential coefficient determined by the interruption time or the sampling time of the steering torque.

Next, the process moves to step (2), and it is determined whether the flag F set in the subroutine processing of FIG. 13 is "1". This flag F is set to "1" if the detected steering torque is a positive input, and is set to rQ if the detected steering torque is a reverse input.
The positive and negative human power can be determined by

If rYEsJ is determined in this step (2), the process moves to step (2) and the driving current value (2) at the time of positive input to the motor 27 is determined. To explain this simply, based on the vehicle speed ■ and the steering torque T obtained in step ■, the gain is determined by referring to a memory table showing the relationship between the steering torque and the steering assist torque using the vehicle speed V as a parameter. Then, the standard steering assist torque T1 is calculated based on the following equation (7).
Calculate. Note that the gain of 1 is set to have a characteristic that decreases as the vehicle speed V increases.

TII=, X (T-α)...
(7) Note that α in this equation (7) is the set value of the steering assist start torque.

Then, the standard steering assist torque T obtained by the above equation (7),
The differential value ΔT1 of the reference steering assist torque T, , is calculated according to (8) 2 below, according to the reference steering assist torque "Fmo" obtained a certain time ago, and the differential coefficient of 2.

ΔTII=kZ X (T, -T,.)...
...(8) Then, add the reference steering assist torque T obtained from the above equation (7) and the differential value ΔT obtained from the above (8) 2 to determine the steering that should actually be applied to the steering system. The auxiliary torque T is calculated, and the drive current value I corresponding to this steering auxiliary torque T4 is calculated, for example, with reference to a memory table showing the relationship between the steering auxiliary torque and the drive current value as shown in FIG. do.

On the other hand, if it is determined that the input is "NO" in step (2), that is, it is a reverse input, the process proceeds to step (2), and based on the vehicle speed (2) determined in step (2), the first value stored in advance in the storage device is determined. + is calculated for the proportional control gain by referring to the memory table showing the relationship between the vehicle speed and the proportional control gain shown in FIG. 17(a), and the relationship between the vehicle speed and the differential control gain shown in FIG. 17(b) is calculated. 2 is calculated as the differential control gain by referring to the storage table shown in FIG.

The function table shown in FIG. 17 (al and (b)) is
As will be explained in detail later, the characteristic is a combination of a characteristic in which a larger control gain is obtained as the vehicle speed (2) increases, and a characteristic in which a maximum gain is obtained at a predetermined vehicle speed (2).

Next, the process moves to step (2), and the following (9) is calculated based on the steering torque T obtained in step (2), the differential value T obtained in step (2), and each control gain obtained in step (2). The drive current value (■) for the motor 27 at the time of reverse input is calculated according to the formula, and the process moves to step @la.

1 = + XT + 2 XΔT + Io...
・(9) Note that the first term (Kl 'r) in the above equation (9)
corresponds to the reference current value at the time of reverse input, and the second term (KgΔT)
corresponds to the corrected current value at the time of reverse input, and the third term ■. is the motor dark current, which is added to eliminate the dead zone of the motor 27.

Then, in step @la, it is determined whether or not to turn to the right based on the polarity of the steering torque T, for example, and when it is determined that it is to turn to the right, the process moves to step [phase] b, and the step Alternatively, the drive current value I calculated in step (2) is output to a drive circuit (not shown) so as to rotate the motor 27 in the right direction, thereby generating a steering assist torque in the right rotation direction in the steering system.

If it is determined in step @la that the turning is to the left, the process moves to step @lC, and the motor 27 is rotated to the left using the drive current value ■ calculated in step ■ or step ■. The output signal is outputted to a drive circuit (not shown) to generate a steering assist torque in the left rotation direction in the steering system.

Then, if the steering torque is a positive input, a steering assist torque is generated in the direction of the steering operation and the steering operation is lightened, but in this case, the reference steering assist torque T□ obtained by the above equation (7) is Since this characteristic decreases as the vehicle speed increases, it prevents the vehicle from becoming unsteady due to too light steering during high-speed driving, and a large drive current value is calculated when driving at low speed or when stationary. Therefore, the steering operation can be performed easily, and furthermore, the above step
When calculating the drive current value ■ at the time of positive input in
Even if the torque fluctuation is steep, a steering assist torque is generated that can quickly stabilize the torque fluctuation, so a smooth steering feeling can be obtained.

Even if the steering torque is a reverse input, the steering torque T
Since the motor 27 is driven according to the drive current value I calculated according to the above equation (9) based on the steering torque differential value ΔT, the magnitude and rate of change (differential A steering assist torque is generated in the steering system according to the value).

Here, the reverse input steering torque is generated by a composite force of a component caused by a disturbance such as a steered wheel running over a protrusion on the road surface, and a component caused by vibration caused by wheel imbalance, but the former is caused by a component caused by a change in vehicle speed. The higher the speed, the more severe the impact will be at the time of collision between the protrusion and the steered wheel, which will increase as the vehicle speed increases. The maximum frequency occurs when the frequency is (10 to 2011z), and the predetermined frequency occurs when the predetermined vehicle speed Vs (approximately 120 km/h) is determined depending on the vehicle type.

Therefore, as shown in Fig. 17 (al and (bl), if the values of 1 and 2 are increased for each control gain as the vehicle speed (■) increases, it is possible to If a large control gain can be obtained at the predetermined vehicle speed V, the component caused by wheel imbalance can be canceled out, so optimal control for reverse inputs can be performed. becomes possible.

Therefore, as in equation (9) above, the steering torque T and the 17th
The value obtained by multiplying the proportional control gain determined based on the function table shown in Figure (a) by and the steering torque differential value ΔT
and the value obtained by multiplying the differential control gain determined according to the function table shown in Figure 17fb) by 2, and the motor dark current ■
. and the addition result is the drive current value I at the time of reverse input.
In this embodiment, it is possible to quickly and reliably cancel out the reverse input steering torque by the rotational force of the motor 27, so that when the steering angle of the steered wheels is about to change due to the reverse input steering torque during steering, etc. Also, since the steering angle is quickly and reliably corrected, the running stability of the vehicle is not impaired, and as a result, reverse input steering torque is not transmitted to the steering wheel, so a good steering feeling can be obtained. I can do it.

Note that the electrical resistance members 31 and 32 and the electrically conductive material 31
, 32, 35.36 and current collecting member 58° 59.63.6
4 constitutes a steering torque detecting means, the processing of steps (2) to (phase) constitutes a forward/reverse input determining means, and the processing of step (2) constitutes a steering torque differentiating means. , fbl, the reference current value determining means and the corrected current value determining means are constituted by the processing of the step (2) and the step (2), the current value determining means at the time of positive input is constituted by the processing of the step (2), and the step A drive current value determining means is constituted by (2), and a drive control means is constituted by a drive circuit (not shown) and the processes of step (2) and steps [phase] a to step @lC.

In the above embodiment, means for detecting the rotation angle θ□ of the input shaft (stub shaft la) and means for detecting the relative amount of twist between the input shaft and the output shaft (pinion shaft 9) (steering torque Detecting means) are provided, and the rotation angle θ2 of the output shaft is calculated based on these detected values. However, the rotation angle θ11 .
The rotation angle θ of the output shaft and the steering torque T have the relationship shown in Equation 11 above, so if any two values are detected, the other values can be calculated. The present invention is not limited to the combination of detection devices, and may be configured such that an output shaft rotation angle detection device and a steering torque detection device are provided to calculate the input shaft rotation angle θ□.
Alternatively, a configuration may be adopted in which a rotation angle detection device for the input shaft and the output shaft is provided to calculate the steering torque T.

〔Effect of the invention〕

As explained above, according to the electric power steering device of the present invention, the steering torque generated in the steering system is
Provide a means to determine whether it is a positive input or a reverse input,
If it is determined that the input is a positive input, the electric motor is driven by the drive current value determined according to the steering torque, while if it is determined that the input is a reverse input, the reference current value and the drive current value based on the steering torque are determined. Since the electric motor is driven by the drive current value determined according to the correction current value based on the steering torque differential value, when operating the steering wheel, the steering assist torque is applied according to the positive input steering torque. Since the steering torque can be generated, the steering operation can be performed lightly, and even if a reverse input steering torque is generated, the steering torque can be quickly and reliably canceled without generating torque vibration in the steering system. Therefore, the running stability of the vehicle is not impaired, and since the steering torque of the reverse input is not transmitted to the steering wheel, there is an effect that a good steering feeling can be obtained.

The proportional control gain when determining the reference current value based on the steering torque detection value and the differential control gain when determining the corrected current value based on the steering torque differential value are made variable according to the vehicle speed, and the By appropriately setting the relationship with the control gain, it becomes possible to perform optimal control.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing the overall configuration of an embodiment of the present invention, FIG. 3 is a sectional view taken along line mm in FIG. The figure shows one side of the disk-shaped substrate, FIG. 5 shows the other side of the disk-shaped substrate, FIG. 6 is a perspective view of the wave spring, and FIGS. 7 and 8 show the current collecting member, respectively. A perspective view, FIG. 9 is an electric circuit diagram, FIG. 10 is a graph showing the relationship between steering torque and output voltage, and FIG.
Figure 1 is a graph showing the relationship between steering angle and output voltage.
Fig. 2 is a flowchart showing the processing procedure inside the microcomputer, Fig. 13 is a flowchart showing the subroutine processing of Fig. 12, and Fig. 14 shows the relationship between the rotation angle of the input shaft and output shaft and the steering torque. This is a graph shown in series, where (a) is the case when the input is normal, and (b) is when the input is the reverse. Fig. 15 is a list showing the polarity of the rotational angular velocity of the input shaft and output shaft, steering torque, and difference value, and Fig. 16 is a graph showing the relationship between the steering assist torque and the drive current value at the time of positive input. , FIG. 17 is a graph showing the relationship between each control gain and vehicle speed used when determining the drive current value at the time of reverse input. 1a...Stub shaft, 9...Pinion shaft, 20...Torsion bar 27...Motor ('t
'JJJ 1m), 28... Disc-shaped member, 30.
...Control device, 40...Electric resistance member, 50... Rotating member, 60a, 60b... Current collecting member. Funeral diagram Funeral diagram Funeral diagram Funeral diagram Funeral diagram Figure 14 (a) Figure 15 = -7 Torf TM

Claims (2)

[Claims] (1) An electric motor that generates a steering assist torque in a steering system, a steering torque detection means that detects the steering torque of the steering system, and a forward/reverse input that determines whether the steering torque is a forward input or a reverse input. determining means; positive input current value determining means for determining a drive current value for the electric motor when steering torque is a positive input based on the steering torque; and differentiating the detected steering torque value to obtain a steering torque differential value. Steering torque differentiation means to obtain, reference current value determining means for determining a reference current value at the time of reverse input based on the detected steering torque value, and correction for determining a corrected current value at the time of reverse input based on the steering torque differential value. a current value determining means; a driving current value determining means for determining a driving current value for the electric motor when the steering torque is a reverse input based on the reference current value and the corrected current value; If the determination result is a positive input, the drive current value determined by the current value determination means at the time of positive input is determined, and if the determination result is a reverse input, the drive current value determined by the drive current value determination means is determined. An electric power steering device comprising: drive control means for controlling drive of the electric motor according to a current value. (2) Claim (1) wherein the gains of the reference current value determining means and the corrected current value determining means are variable depending on the vehicle speed.
The electric power steering device described.