JPH052547B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric power steering device that controls a steering force booster using an electric motor that generates auxiliary torque in accordance with the speed of a traveling vehicle.

(Prior art) In a general steering device, the steering torque is small when driving at high speeds and increases when driving at low speeds. It is desirable to stop the booster, and an example of such an electric power steering device is disclosed in Japanese Patent Publication No. 53-38849.

In this electric power steering device, the clutch of the steering force booster is connected and driven when the steering torque is zero when transitioning from high-speed driving to low-speed driving, for example, when driving straight or when turning back, and when driving at low speed. On-off control is also performed to release the valve in the same way when transitioning from high-speed driving to high-speed driving, thereby preventing sudden changes in steering torque during steering.

(Problems to be Solved by the Invention) However, in the conventional electric power steering device described above, the clutch of the steering force booster is not driven when the vehicle speed is above a predetermined value or below a predetermined value and the steering torque is zero. Since the configuration is such that when turning from high speed to low speed where the steering torque is not zero, the high speed state is maintained, and the steering force booster is not activated, so at low speed However, the steering force is not reduced, and conversely, when turning from low speed to high speed, the steering force is too light because the steering force booster is activated even at high speed. Furthermore, when there is a sudden steering change, the steering torque passes through zero, so the steering force booster suddenly activates (from high speed to low speed).
It may be released (low speed → high speed). As a result, there is a problem that the steering stability and steering feel are deteriorated.

(Purpose of the Invention) Therefore, the present invention aims to reduce the transmission torque of the clutch means over time when the traveling vehicle speed increases beyond a predetermined value while a steering torque is applied, and then reduce the transmission torque to zero, while reducing the vehicle speed. The purpose of this invention is to improve steering stability and steering feel by increasing the transmission torque of the clutch means over time to a determined value when the torque decreases beyond a predetermined value.

(Means for solving problems and their effects) FIG. 1 is an overall configuration diagram of the present invention.

The device of the present invention includes a steering torque detection means 77, a vehicle speed detection means 86, and a clutch control signal generation means 7.
6A, vehicle speed determination means 76B, and correction means 76C.
and a clutch drive means 108. Clutch control signal generating means 76A and vehicle speed determining means 76
B and the correction means 76C are constructed using a microcomputer 76.

In the device of the present invention, when the ignition key switch is turned on, each detection signal is output from the steering torque detection means 77 and the vehicle speed detection means 86. When the steering wheel is steered, the clutch control signal generating means 76A determines the transmission torque of the clutch based on at least the steering torque detection signal of the steering torque detecting means 77 and outputs it as a clutch control signal.

On the other hand, the vehicle speed determination means 7 based on the steering torque detection signal and the vehicle speed detection signal from the vehicle speed detection means 86
At 6B, the vehicle speed is determined, and if the vehicle speed increases beyond a predetermined value, a decreasing correction request signal is output, while if the vehicle speed decreases by exceeding a predetermined value, an increasing correction request signal is output.

In the correction means 76C, the reduction correction request signal performs a reduction correction so that the transmission torque of the clutch means gradually decreases to zero at a predetermined rate, and the increase correction request signal causes the transmission torque to decrease from zero to zero at a predetermined rate. An incremental correction is made which is gradually increased to the determined value of the required transmission torque. and,
Clutch drive means 1 based on the corrected control signal
08 drives the clutch means.

(Embodiment) A preferred embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 2 is a longitudinal sectional view showing the electromagnetic booster of this embodiment bent at 90°. In Fig. 2, 1 is a steering column, 2 is a stator,
3 is a case, and 4 and 7 are an input shaft and an output shaft coaxially arranged with each other. In the electric power steering device of this embodiment, the inner end of the input shaft 4 is loosely fitted into the inner end of the output shaft 7, and these inner ends are connected by a torsion bar 8, so that the input shaft 4 is connected to the bearing 9. , 10, 11, the output shaft 7 is rotatably supported by bearings 11A, 13, 13A, respectively. Further, a steering rotation sensor 20 disposed around the input shaft 4, a steering torque sensor 24 disposed around the fitting portion of the input/output shafts 4 and 7, and a steering torque sensor 24 disposed around the output shaft 7. Electric motor 3
3. A configuration comprising a reduction gear device 50, an electromagnetic clutch (clutch means) 63, and a control device 75 that drives and controls the electric motor 33 and the electromagnetic clutch 63 based on detection signals from the steering rotation sensor 20 and the steering torque sensor 24. be.

More specifically, the input shaft 4 is divided into a first shaft 5 and a cylindrical second shaft 6, and a steering wheel, which is a handle, is fixed to the outer end side of the first shaft 5 (the right end side in the figure). A cylindrical second shaft 6 is connected to the inner end via a rubber bush 14 for preventing vibration transmission. Further, as shown in FIG. 3, an annular member 15 having a protrusion 15a projecting in the radial direction is integrally fixed to the first shaft 5.
is inserted into a notched groove 6a formed on one end side (right end side in the figure) of the second shaft 6 with an appropriate gap. Therefore, the first shaft 5 and the second shaft 6 are elastically connected by the rubber bush 14, and
After being twisted by a predetermined angle due to the gap, the first shaft 5 and the second shaft 6 engage with each other, and the rubber bush 14 is inserted in the twisting direction.
The structure is such that a load exceeding a predetermined torque is not applied to the Incidentally, 16 is a circlip for preventing it from coming off.

In addition, on the other end side of the second shaft 6 (left end side in the figure),
As shown in FIGS. 4a to 4c, grooves 17 along the axial direction
are formed at 180° intervals, and projecting pieces 7a that protrude in the axial direction from the inner end side of the output shaft 7 whose diameter has been enlarged to correspond to the grooves 17 are inserted into each groove 17 at predetermined intervals. A small diameter portion formed on the other end side of the second shaft 6 is supported within the enlarged diameter portion of the output shaft 7 via a bearing 11. Further, a torsion bar 8 is disposed along the axis in the hole formed on the inner end side of the second shaft 6 and the output shaft 7, and one end side (right end side) of the torsion bar 8 is connected to the second shaft by a pin 18. 6, while the other end of the torsion bar 8 is fixed to pin 1.
9 is fixed to the output shaft 7. The outer end of the output shaft 7 is connected to another shaft on the load side by a spline formed therein. Therefore, the steering torque applied to the input shaft 4 by the steering wheel is transmitted to the output shaft 7 and the load side through the torsion of the torsion bar 8. Incidentally, the rigidity of the rubber bush 14 is higher than that of the torsion bar 8.

As shown in FIG. 5, the steering rotation sensor 20 includes a plurality of protrusions 21 protruding from the outer periphery of the second shaft 6 at equal intervals in the radial direction, and a plurality of protrusions 21 attached to the steering column 1 so as to sandwich the protrusions 21. It is composed of an attached photocoupler (photoelectric pickup) 22, receives transmitted light interrupted by the protrusion 21, converts the received light into a pulsed electric signal, and outputs it.

The steering torque sensor 24 includes a cylindrical movable iron core 25 provided on the outer periphery of a fitting portion between the second shaft 6 and the output shaft 7 so as to be displaceable in the axial direction, and a steering column 1.
It is constituted by a differential transformer consisting of a coil portion 28 fixed to the inner circumference. The movable iron core 25 is connected to each projecting piece 7a of the output shaft 7, as shown in FIGS.
Elongated holes 25a and 25b are provided to engage with pins 26 protruding from the second shaft 6, and pins 27 protruding from the second shaft 6 at an angle of 90 degrees with respect to these pins 26, respectively. The elongated hole 25a is formed along the axial direction, while the elongated hole 25b is formed inclined at a predetermined angle with respect to the axial direction. Therefore, when an angle difference occurs between the second shaft 6 and the output shaft 7 in the circumferential direction, the long hole 25b and the pin 26 and the long hole 25a and the pin 27
Due to the engagement relationship, the movable core 25 moves in the axial direction, and the movable core 25 is displaced in response to the steering torque applied to the second shaft 6. Also,
Coil section 28 provided around movable iron core 25
is a primary coil 29 into which a pulse signal is input;
It consists of a pair of secondary coils 30 and 31 coaxially disposed on both sides of a primary coil 29 that outputs an output signal corresponding to the displacement of the movable iron core 25. Therefore, when an angular difference occurs between the second shaft 6 and the output shaft 7 due to twisting of the torsion bar 8, the axial displacement of the movable iron core 25 is converted into an electrical signal and output.

Next, the electric motor 33 includes a cylindrical stator 2 that is integrally fixed to the steering column 1 and the case 3 by bolts 34, and at least one pair of magnets 36 that are fixed to the inner surface of the stator 2.
A rotor 3 rotatably arranged around an output shaft 7
It consists of 7. The rotor 37 has bearings 12 and 1
The stator 2 is rotatably mounted on the output shaft 7 via the bearings 11A and 13A.
and a cylindrical shaft 38 supported by the case 3, an iron core 39 having a skew groove on the outer periphery of the cylindrical shaft 38,
Multiple windings 41 are sequentially and integrally wrapped around each other, and a minute air gap is provided between the magnet 36 and the multiple windings 41. Further, the cylindrical shaft 38 is provided with a commutator 43 connected to the multiplex winding 41 . Further, brushes 46 that press against the commutator 43 are housed in brush holders 47 fixed to the case, and lead wires connected to the brushes 46 are taken out of the stator 2 through non-magnetic pipes. Note that the electric motor 33 generates auxiliary torque using multiple windings 41, a commutator 43, and a brush 46.
It consists of

The speed reduction device 50 includes a two-stage planetary gear mechanism 51 and 52 arranged around the output shaft 7.
The planetary gear mechanism 51 at the front stage includes a common internal gear 53 formed on the inner peripheral surface of the case 3, a sun gear 38a formed on the outer periphery of the other end side (the left end side in the figure) of the cylinder shaft 38, and these. Three planetary gears 5 meshed with
4, and a first carrier member 55 that pivotally supports the planetary gear 54. The planetary gear mechanism 52 in the latter stage includes the common internal gear 53 and a sun gear 56a formed on the outer periphery of a cylinder 56 that is encircled around the output shaft 7 and integrally connected to the first carrier member 55.
, three planetary gears 57 that mesh with these, and a second carrier member 58 that pivotally supports these planetary gears 57. Moreover, this second carrier member 5
A cylindrical body 60 supported by the output shaft 7 is integrally connected to the inner edge of the case 8 via a bearing 59, while a cylindrical body 61 along the inner circumference of the case 3 is integrally connected to the outer edge thereof. , internal teeth 61a are formed in the circumferential direction on the inner circumferential surface of this cylindrical body 61. Therefore, when the rotor 37 of the electric motor 33 rotates, the rotation of the rotor 37 is transferred to the cylinder 61 via the cylinder shaft 38, the planetary gear 54, the first carrier member 55, the planetary gear 57, and the second carrier member 58. It is transmitted while being decelerated.

The electromagnetic clutch 63 has a rotor 64 that
It is rotatably supported via a bearing 66 by an annular body 65 spline-coupled to the outer periphery of the output shaft 7, and is fixed to the output shaft 7 via an annular elastic member 67 that absorbs torsional vibrations. Further, the rotor 64 is formed in a cylindrical shape, and extends to the periphery of the cylindrical body 60 of the second carrier member 58, and has a pair of projections 64a that protrude radially from the inner surface of this extending portion toward the outer periphery of the output shaft 7. is installed protrudingly. These protrusions 64a
As shown in FIG. 6, the groove 65a is inserted into a cutout groove 65a formed in the annular body 65 with a required gap in the circumferential direction, and has an engaging relationship with the annular body 65 in the circumferential direction. are doing. Therefore, the rotor 64 and the output shaft 7 are located within the gap, that is, the rotor 6
Until the projection 64a of No. 4 and the ring body 65 are engaged, they are in an elastically connected state. Further, external teeth 64b are formed on the outer periphery of the extending portion of the rotor 64, and the second carrier member 58 of this extending portion
A disk-shaped support plate 64c is provided in a protruding manner on the opposite side. Between this support plate 64c and the second carrier member 58, a disc-shaped plate 68 having a groove on its outer periphery that engages with the internal teeth 61a of the cylindrical body 61 is provided.
and disk-shaped plates 69 having grooves on their inner peripheries that mesh with the external teeth 64b of the rotor 64 are arranged alternately to constitute a multi-plate clutch mechanism. In addition,
In the figure, 70 is a stopper for the plate 69. Further, a frame body 71 having a U-shaped longitudinal section is fixed to the case 3, and a ring-shaped excitation coil 72 is housed within the frame body 71. The excitation coil 72 is connected to a control device 75 through a lead wire. There is. Therefore, the electromagnetic force generated as the excitation coil 72 is energized attracts the plates 69 and 68 toward the excitation coil 72, so that the rotational torque of the electric motor 33 transmitted via the reduction gear device 50 is multi-plate. It is transmitted to the output shaft 7 through the clutch mechanism and the protrusion 64a of the rotor 64.

Next, the control device 75 will be explained based on FIG. 7.

In FIG. 7, 76 is a microcomputer, and this microcomputer 76 is used to generate the clutch control signal generating means 76 shown in FIG.
A, vehicle speed determination means 76B, and correction means 76C are configured.

The microcomputer 76 receives each detection signal S1 to S6 from the steering torque detection means 77, the steering rotation detection means 82, the vehicle speed detection means 86, and the abnormality detection means 114.

The steering torque detection means 77 includes the steering torque sensor 24, a drive unit 78 that divides and outputs the clock pulse _T1 inside the microcomputer 76 to the primary coil 29 of the steering torque sensor 24, and Corresponding rectifier circuits 79A and 79B that rectify the electrical signals obtained from the secondary coils 30 and 31, respectively, and low-pass filters 80A and 80B that remove high frequency components.
and an A/D converter 81 which converts each analog electrical signal from the low-pass filters 80A and 80B into digital signals and inputs them to the microcomputer 76 as steering torque detection signals S ₁ and S ₂ . The steering rotation detection means 82 includes the steering rotation sensor 20 and the steering rotation sensor 20.
In the photocoupler 22, the protrusion 2 of the second shaft 6
A pulse conversion circuit that supplies power to two light-emitting parts whose phases differ by approximately 90 degrees with respect to 1, and converts the electric signal output by the light-receiving part facing each light-emitting part into an appropriate pulse signal and outputs it. 83, a waveform shaping circuit 84 that shapes this output signal, and a steering speed signal having a frequency proportional to the steering rotation speed in the steering direction based on the pulse signal output from the waveform shaping circuit 84 and the clock pulse of the microcomputer 76. S ₃ or S ₄ accordingly, for example as in FIG.
In clockwise rotation, a pulse signal proportional to the steering rotational speed is generated from _S3 , at which time S=0; conversely, in case of counterclockwise rotation, a pulse signal proportional to the steering rotational speed is generated from _S4 , at this time S3= ₀ . and a drive unit 85 that outputs a signal that becomes 0. Further, the vehicle speed detection means 86 includes, for example, a vehicle speed sensor 89 consisting of a magnet 87 that rotates together with the speedometer cable and a reed switch 88 that is turned on and off as the magnet rotates, and a reed switch 88 that supplies power to the reed switch 88. A pulse conversion circuit 90 that outputs the intermittent pulse signal as a pulse signal.
and a waveform shaping circuit 91 that shapes and outputs this output signal, and the output signal _S5 from this waveform shaping circuit 91 is a pulse signal with a frequency proportional to the vehicle speed.

The microcomputer 76 has an I/O port,
It is composed of a memory, a calculation section, and a control section. Also. A power supply circuit 92 that drives the microcomputer 76 and the like includes a relay circuit 96 connected to the + terminal of an on-vehicle battery 93 via an ignition key switch 94 and a fuse 95;
A constant voltage circuit 97 is connected to the output side of the relay circuit 96, and power is supplied from the A terminal on the output side of the relay circuit 96 to a motor drive means 100 and an electromagnetic clutch drive means 108, which will be described later. Power is supplied from the B terminal of the circuit 97 to the microcomputer 76 and other control units. Therefore, when the key switch 94 is turned on, the microcomputer 76 processes each of the input detection signals S ₁ to _{S 6} according to the program written in the memory, and generates control signals T ₃ , T ₄ , T ₅ , and a current control signal T ₆ for driving the electromagnetic clutch are outputted to the motor drive means 100 and the electromagnetic clutch drive means 108, respectively, to drive and control the electric motor 33 and the electromagnetic clutch 63.

The motor drive means 100 includes a drive unit 1
01, relays 102 and 103, and transistors 104 and 105. The bridge circuit consists of relays 102 and 10.
3 is connected to the A terminal of the power supply circuit 92,
The emitters of transistors 104 and 105 are connected to the common side (ground) via a resistor 106. The excitation coils of each relay 102, 103 and the bases of transistors 104, 105 are connected to the output side of the drive unit 101.
The armature winding 41 of the electric motor 33 is connected between the collectors of the motor 5. The drive unit 1
01 controls relay 102 or 103 based on control signals T ₃ and T ₄ from microcomputer 76.
ON, the transistor 105 or 104 is enabled to be driven, and a pulse signal whose pulse width is converted (PWM modulated) by the control signal _T5 is output to the base of either the transistor 104 or 105. Therefore, in the motor drive means 100, one relay 102 and the transistor 10
The direction of rotation of the motor 33 is controlled by energizing the relay 103 and the transistor 104, or by energizing the other relay 103 and the transistor 104.
PWM control of transistors 104 and 105 is performed by a pulse signal applied to the base of transistor 05. A voltage (A terminal) with a pulse width according to PWM control is applied to the electric motor 33, and the electric motor 33 is controlled to generate an auxiliary torque corresponding to the steering torque applied to the steering wheel.

The electromagnetic clutch driving means 108 consists of a drive unit 109 and a transistor 110. The collector of the transistor 110 and the power supply circuit 92
The excitation coil 7 of the electromagnetic clutch 63 is connected between the A terminals of the
2 are connected. The emitter of the transistor 110 is connected to the common side through a resistor 111,
The base is connected to the output side of the drive unit 109. Furthermore, the drive unit 109 outputs a pulse signal whose pulse width has been converted based on the control signal _T4 to the transistor 110. Therefore, the smell of the electromagnetic clutch drive means 108 is
Current control signal from microcomputer 76
PWM control of the transistor 110 is performed by the drive unit 109 based on _T4 , and the torque coupling force of the electromagnetic clutch 63 is controlled accordingly.

Further, in this embodiment, abnormality detection means 114 for detecting abnormalities in the electric motor 33 and the electromagnetic clutch 63 is provided. This abnormality detection means 114
is an amplifier 11 that amplifies the terminal voltage of the resistor 106.
5A, an amplifier 115B that amplifies the terminal voltage of the resistor 111, low-pass filters 116A and 116B that remove high frequency components, and these detected voltages are converted into a digital signal _S6 and input to the microcomputer 76. A/D converter 117
It is composed of. This abnormality detection means 114
For example, an abnormality in the electric motor 33 or the electromagnetic clutch 63 is detected by the terminal voltage of each resistor 106 and 111, and in the case of an abnormality, a relay control signal T ₂ is output to the relay circuit 96 of the power supply circuit 92.
It is used for abnormality diagnosis etc. to stop the supply of power from 2.

Next, the action will be explained.

FIG. 8 is a flowchart outlining the electromagnetic clutch control processing according to the vehicle speed performed by the microcomputer 76, and P ₁ to _{P 43} in the figure indicate each step of the flowchart.

Ignition key switch 94 is ON
When the power is turned on, power is supplied to the microcomputer 76 and other circuits, and control begins. First, in the microcomputer 76, each register, RAM (random, access, memory)
Clear all the taters within. Then, in step P ₁ , the steering torque detection S ₁ and S ₂ are read sequentially, and in step P _2, it is diagnosed whether the read value is normal or not, and if it is above, the control signal is
_T2 turns off the relay circuit 96, stops all operations, and returns to manual steering. Here, since the torque sensor 24 is composed of an operating transformer, the steering torque T _S and S 1 and S ₂ are shown as shown in Fig. 14, and the sum of S ₁ and _{S 2 is} a constant value. As is well known. So (S ₁ +
It is diagnosed whether S ₂ )/2 is within a predetermined range, and if it is not within a predetermined range, it is determined that the torque sensor is malfunctioning. If the read steering torque detection signals S ₁ and S ₂ are normal, proceed to step P ₃ ,
In step _P3 , calculate S ₁ - S ₂ and calculate the steering torque T (=
T _S ) and memorize it.

Next, the detection signal S ₃ from the steering rotation detection means 82,
_S4 is read in sequence and each of t _s3 and t _s4 is sequentially measured in step _P5 , and the difference t between them is calculated in step _P6 to determine the rotation direction. For example, for clockwise rotation, t = t _S3 (t _S4 = 0), for left rotation, t = -t _S4
(t _S3 =0).

A motor control signal is stored in the memory with the steering torque T as the upper address and the period t as the lower address.
Table 1 is constructed in which T ₅ is stored. Here, since the control signal _T5 is for PWM driving the motor drive 100, the duty ratio (the ratio of the "H" engine during one cycle is stored).The duty ratio (T is the resistance of the multiple winding 41) R _M is the induced voltage constant, K is the motor rotation speed, I _M is the armature current,
When the power supply voltage is V _CC , it is expressed as T ₅ = (DUTY%) = R _M · I _M /V _CC −KN × 100 (However, the inductance of multiple windings must be sufficiently small.) In the case of an electric power steering device, it is preferable that the armature current I _M corresponds to the steering torque, and the motor rotation speed N corresponds to the steering rotation speed. Therefore, the steering torque T and armature current
If I _M is set in a proportional relationship as shown in Fig. 9, and the steering rotation speed N _S and motor rotation speed N are set in a proportional relationship as shown in Fig. 10, then T ₅ = (DUTY%) = K ₁ · Since it is expressed as R _M・T/V _CC −KK ₂ (1/t) (K ₁ and K ₂ are proportional constants), by storing this calculated value in Table 1, the steering torque T and steering rotation can be calculated. T ₅ can be immediately called by addressing with the well-known t corresponding to the speed N _S . The value of the duty ratio is stored in the microcomputer 76 as an 8-bit parallel signal, and is provided with a circuit that can programmably vary the duty ratio using the 8-bit parallel signal. series pulse with duty ratio
_T5 is output. Therefore, although the fresh fish signal _T5 actually output from the microcomputer 76 and the duty ratio processed inside the microcomputer 76 are different, they have the same meaning and will be treated as equivalent below.

It is determined whether the value of the control signal _T5 is negative or not in step _P8 , and if it is positive, the control signal (motor rotation direction) is changed to _T3 =1, _T4 =0 in step _P9 .
(Rotate right). If it is negative, proceed to step _P8 , convert the control signal _T5 to positive,
(motor rotation direction) control signal T ₃ = 0, T ₄ = 1
(Rotate clockwise).

Next, in step _P12 , the control signal _T5 is set, and in step _P13 , it is determined whether _T5 is positive or not. If it is negative or zero, the process jumps to step _P14 , and (motor rotation direction) The control signal is set to T ₃ =T ₄ =0, and the relays 102, 103 and transistors 104, 105 are turned off, and in step _P15 , the output to the control signals T5 _{, T6} is stopped, and the motor 33,
Stop the operation of the electric clutch 63 and proceed to step
Return to P ₁ . In other words, the state of manual steering is maintained. If control signal T ₅ is positive, step P ₁₆
and outputs the control signals T ₃ and T ₄ so that T ₃ =1, T ₄
= 0, the relay 102 is turned on, the transistor 105 is in a controllable state, and if T ₃ = 0, T ₄ = 1, the relay 103 is turned on, the transistor 104 is in a controllable state, and the process proceeds to step _P17 .
In step _P17 , in order to provide a second dead zone, a predetermined value b is further subtracted, and the result is processed as the control signal _T5.In step _P18 , it is determined whether _T5 is positive, and whether it is negative or zero. If so, jump to step P ₁₅ (set the control signals T ₅ and T ₆ to zero to stop the operation and return to step P _1. If the control signal T ₅ is positive, proceed to step P _19. This completes the motor rotation direction. The control signals T ₃ and T ₄ of are output, and the control signal T ₅ of the motor power is determined (hereinafter referred to as the determined value),
It is in a state where it is only waiting for output processing. Here, the reason why the first dead zone and the second dead zone are provided for the control signal _T5 is that relays have a large activation delay compared to transistors, and if they are activated at the same time as the control signal _T5 , the duty ratio of the control signal _T5 will change from zero. This is to prevent the steering torque from suddenly decreasing and reducing the steering feel because it is not output but is suddenly output from a certain value.

Next, the operation of vehicle speed control according to the present invention will be explained.
In step _P19 , the detection signal _S5 from the vehicle speed detection means 86 is read, and in step _P20 , the period _tv of the read signal _S5 is measured. Vehicle speed signal S ₅
Since is a frequency proportional to the vehicle speed, the period t _v also corresponds to the vehicle speed. In the next step _P21 , it is determined whether the period _tv is smaller than a predetermined value. When the vehicle speed is greater than a predetermined value, the period t _v is smaller than the predetermined value C, and when the vehicle speed is smaller than the predetermined value, the period t _v is larger than the predetermined value C. Therefore, if the vehicle speed is smaller than the predetermined value, the cycle t _v is greater than the predetermined value C, so the process proceeds to step _P22 . Here, signals A, F, and G for storing the previous control state are sent to the microcomputer 7.
6. Provided inside. When F=G=0, it is a low-speed stable region, that is, a region where control is performed using the determined value _T5 , and when F=G=1, it is a high-speed stable region, that is, when the motor control signals _T3 , _T4 , T ₅ and electromagnetic clutch control signal T ₆ are all zero, and the operation is stopped. Furthermore, F=1, G=0 is a low speed or high speed unstable region, that is, a state in which the vehicle speed exceeds a predetermined value and the control signals T ₅ and T ₆ are being reduced over time but have not yet been reduced to zero. , or indicates a state in which the vehicle speed has fallen below a predetermined value, the control signals T ₅ and T ₆ are being increased over time, and the control state has not yet reached the determined value. And A
indicates the correction value. In step _P22 , it is determined whether the previous control was in a high speed state. Since the initial data are all set to zero at the time of start, the process of F=0 is performed and after indicating the low speed stable region, the process proceeds to step _P24 , where the motor armature current from the abnormality detection means 114 is The detection signal S ₀ corresponding to I _M is read, and in step P ₂₅ , _{T 6 =} (DUTY%) = G _M・R ₁・I _M /V _CC ×100 (I _C : Clutch current, R _C : Resistance of electromagnetic clutch,
A table 2 is configured in which calculated values of G _M ; amplifier 115A, R ₁ ; resistance of resistor 106 are stored. Here, as shown in Figure 11, the armature current of the motor is
Since I _M corresponds to the steering torque T, T ₆ , that is, the clutch control signal also corresponds to the steering torque T. Here again, the value of the duty ratio is stored in the microcomputer 76 as an 8-bit parallel signal, and is equipped with a circuit that can programmably vary the duty ratio using this 8-bit parallel signal. A series pulse T ₆ with a duty ratio stored in is output.
Therefore, although the control signal _T6 actually output from the microcomputer 76 and the duty ratio processed inside the microcomputer 76 are different, they have the same meaning and will be treated as equivalent hereinafter. In step _P25 , a control signal _T6 with a pulse width proportional to the armature current corresponding to the steering torque signal is set from table 1 with the detection signal _S6 as an address.
Proceed to step _P26 . In step _P26 , the control signals _T5 and _T6 , which are the determined values, are outputted to drive the electric power steering device using PWM, and in step _P27 , the detection signal _S6 from the abnormality detection means 114 and the control signals _T5 , A comparison with T ₆ is made and if the predetermined range is not reached, the relay circuit 96 is turned off by the control signal T ₂ to stop all controls and return to manual steering. If the width is within the predetermined range, the process returns to step _P1 and the same control is repeated.

Next, when the vehicle speed exceeds a predetermined value and the period _tv of the detection signal _S5 becomes smaller than the predetermined value C, the step
After the determination process in _P21 , the process proceeds to step _P28 , where signal processing F=1 indicating that the vehicle speed has exceeded a predetermined value is performed, and the process proceeds to step _P29 , where it is determined that the previous control was in the high-speed stable region. determine whether the
Currently, G=0 because the previous control was in the low speed stable region. Therefore, proceed to step P ₂₀ ,
At step _P30 , the correction value A is subtracted from the control signal _T5 , but since A=0 now, _T5 and step _P31
Now, add A=A+1 and set step _P30 to 1.
Proceed to step _P32 in which the number of passes is memorized.
In step _P32 , it is determined whether the control signal _T5 is positive or not. If it is positive, it is still necessary to decrease _T5 , so the process jumps to step _P24 , and then
In steps P ₂₄ and P ₂₅ , the control signal T ₆ is called from table 1, and in step P ₂₆ , the PWM control signals T ₅ and T ₆ are output, and in step P ₂₇ , the fault is diagnosed and if normal, the process returns to step P ₁ . Then it reaches P ₃₀ again and T ₅ = T ₅
-1 processing is performed, and T ₅ is 1 from the above determined value.
T ₅ is decreased over time, and T ₆ is also decreased as time passes through steps _{P 30 and P 25 .}
, which is reduced over time in response to the reduced auxiliary torque of the motor, ie the armature current. Then, when T ₅ becomes zero, it is determined in step P ₃₂ and the process proceeds to step P _33. After setting the reduction correction value A to zero, the signal G indicating the high-speed stable region is set to 1, and in step P ₃₄ , T ₃ =T. ₄ = T ₅ = T ₆ = 0 is output to stop the operation of the electric power steering device and return to manual steering. Then, proceed to step P ₃₅ for fault diagnosis and if normal, proceed to step P ₁₉ .
Hejump. In the high-speed stable region, the step
Steps P ₂₈ , P ₂₉ , P ₃₃ , _{P 34} ,
A loop of P ₃₅ , P ₁₉ , and P ₂₀ is repeated to function as a constant manual steering wheel.

Next, the vehicle speed decreases from the high-speed stable region to a predetermined value, and a determination is made in step _P21 . When the process proceeds to step _P27 , this time F=1, so the determination in step _P23 jumps to step _P36 , and here the previous It is determined whether the state was in the high-speed stable region or not, and since it was in the high-speed stable region last time, G = 1, and the process advances to step _P37 , where the increase correction value A of the control signal _T5 reaches the determined value. It is determined whether the announcement is stable or not, and since it was in the stable announcement area last time, the step
A=0 is processed by _P33 . Therefore, in the determination at step _P37 , since A is smaller than _T5 , the process proceeds to step _P38 , and after processing _T5 = 0, step _P38
Then, the increase correction value A is increased by 1, the process jumps to step _P24 , and the control signal _T6 is output via steps _P24 and _P25 .
is called from table 1, and in step _P26 ,
It outputs PWM control signals T ₅ and T ₆ and undergoes a failure diagnosis in step P ₂₇ and returns to step P ₁ if normal.
Then, step P ₃₈ is reached again, where T ₅ =1
T ₅ is corrected by 1 from the previous value, and is increased with time each time it passes through steps P ₃₈ and P ₃₉ , and T ₆ is also adjusted to increase the auxiliary torque of the electric motor at steps P ₂₄ and P ₂₅ . , i.e. increases over time in response to the armature current. and control signal
When _T5 is increased and corrected to the determined value, A= _T5 at step _P37 , and the process jumps to step _P23 to enter the low speed stable region. Control is performed using the determined value, and the electric power steering device operates normally.

Next, the low speed or high speed unstable region will be explained.
This unstable region is an unstable region in which the vehicle speed changes oscillatorily around a predetermined value. For example, when transitioning from low speed to high speed, the vehicle speed exceeds the predetermined value and the reduction correction of T ₅ and T ₆ starts, but before it is finished. Smoothness when the vehicle speed decreases again or when transitioning from high speed to low speed, the vehicle speed drops below the predetermined value and the increase correction of T ₅ and T ₆ starts, and the vehicle speed exceeds the predetermined value again before it is finished. This enables precise control.

Steps P ₂₇ , P ₂₈ , P ₂₉ , P ₃₀ ,
Control is performed via P ₃₁ , P ₃₂ , P ₂₄ , P ₂₅ , P ₂₆ , and P ₂₇ , and if this is repeated, for example, 10 times, A=0.
For T ₅ , T ₅ −9 is output for the determined value, and T ₆
is correspondingly reduced along with the armature current. Next, when the vehicle speed decreases and falls below a predetermined value, step _P22 ,
After passing through P ₂₃ and P ₃₆ , jump to step P ₄₀ and A=
A-9, that is, A=9, is calculated, and after step _P41 , B= _T5-9 is calculated, which matches the previous value.
Then, in step _P42 , it is determined whether B, that is, the control signal is smaller than the previously determined value;
is smaller than T ₅ by 9, so proceed to step P ₄₃ , transfer B to T ₅ , jump to step P ₂₄ ,
A control signal _T5 corresponding to the armature current called in steps _P24 and _P25 is determined, and _T5 and _T6 are sequentially output. If the vehicle speed continues to decrease, steps P ₂₂ , P ₃₆ , P ₄₀ , P ₄₁ , P ₄₂ , P ₄₃ , P ₂₄ , P ₂₅ ,
After passing through P ₂₆ and P ₂₇ , T ₅ and T ₆ are increased and corrected over time, and when the determined values are reached, the process jumps from step P ₄₂ to step P ₂₃ and returns to the low speed stable region. Therefore, even if the vehicle speed exceeds a predetermined value and falls below the predetermined value before the reduction correction is completed, the reduction correction value A is stored and the increase correction is performed from that state. On the other hand, even if the vehicle speed becomes equal to or higher than the predetermined value before the increase correction is completed after the vehicle speed becomes less than the predetermined value and the increase correction control is started, the increase correction value A is stored and the decrease correction can be performed from this state. I can do it.

Therefore, the relationship between armature current Ia, clutch current Ic, and time t in this case is as shown in FIG. 12, time t=
From _t3 to t= _t4 , if the vehicle speed v decreases beyond the predetermined value _v2 , the transmission torque of the electromagnetic clutch 63 increases in response to the auxiliary torque of the electric motor 33 which is increased. Since it gradually increases until it reaches the determined value, the steering feeling and steering stability are improved. Furthermore, power consumption can be reduced as in the case of increasing vehicle speed.

As described above, in this embodiment, since the transmission torque of the electromagnetic clutch is controlled over time in response to changes in vehicle speed, it is possible to improve the steering feeling and steering stability. In addition, power consumption can be reduced by controlling the transmission torque of the electromagnetic clutch over time, and there is no need to provide hysteresis in the predetermined value for comparing the vehicle speed v, as in this embodiment, and it is always stable at the predetermined value. It can be operated by

(Effect of the invention) As is clear from the above explanation, according to the present invention,
While steering torque is being applied, when the vehicle speed increases beyond a predetermined value, the transmission torque of the clutch means decreases over time and then becomes zero, while when the vehicle speed decreases beyond a predetermined value, the clutch means transmits the torque. By increasing the torque over time to a determined value, it is possible to reduce power consumption, and also to smoothly stop the electric power steering device when the vehicle speed changes from low to high speed and return to manual steering, and conversely when changing from high speed to low speed. It shows a smooth connection without sudden changes when moving or when operating the electric power steering device from the manual steering, and continuously even when the vehicle speed changes vibrationally around a predetermined value. Therefore, the stop and operation of the electric power steering device can be controlled stably and smoothly while the vehicle speed is always at a predetermined value.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram of the present invention, Figures 2 to 14
The figure shows an embodiment of the electric power steering device of the present invention, and FIG. 2 shows the electromagnetic booster.
A vertical cross-sectional view shown by bending at a 90° cutting plane, FIG. 3 is a cross-sectional view taken in the direction of the − arrow in FIG. 2, FIG. 4 a is a cross-sectional view taken in the − arrow direction of FIG. 2, and FIGS. 4 b, c are the plan view and side view of the movable iron piece, and Figure 5 is - in Figure 2.
6 is a sectional view taken along the - arrow in FIG. 2, FIG. 7 is an overall configuration diagram of the control device, FIG. 8 is a flow chart showing an outline of the control process, and FIG. 9 is a diagram showing the steering torque. Diagram showing the relationship between and armature current, No. 10
Figure 11 shows the relationship between the steering rotation speed and motor rotation speed, Figure 11 shows the relationship between the armature current and clutch current, and Figure 12 shows the relationship between the clutch current and time as the vehicle speed increases and FIG. 13 is a pulse waveform diagram showing the steering rotational speed signal, and FIG. 14 is a diagram showing the relationship between the steering torque and its detection signal. In the drawing, 63... an electromagnetic clutch which is a clutch means, 76... a microcomputer constituting a clutch control signal generating means, a vehicle speed determining means and a correction means, 76A... a clutch control signal generating means, 76B... a vehicle speed determining means, 76C...Correction means, 77...Steering torque detection means, 86...Vehicle speed detection means, 108...Clutch drive means, S1,
S2...Steering torque detection signal, S3...Steering speed detection signal, S4...Vehicle speed detection signal, T4...Clutch control signal.

Claims (1)

[Claims] 1. An electric motor that generates an auxiliary torque corresponding to the steering torque of the steering system, a clutch means that connects and disconnects the electric motor and the steering system, and a clutch that detects the steering torque of the steering system based on a detection signal from the steering torque detection means that detects the steering torque of the steering system. An electric power steering device comprising a clutch control signal generating means for determining a transmission torque of the means and outputting a clutch control signal, and a clutch driving means for driving the clutch means in accordance with the control signal,
A vehicle speed detecting means for detecting the vehicle speed, a vehicle speed determining means for determining whether the vehicle speed has increased or decreased from a predetermined value based on a detection signal from the vehicle speed detecting means, and a vehicle speed determining means for determining the vehicle speed based on an output signal from the vehicle speed determining means. The clutch is configured to reduce the transmission torque of the clutch means over time when the vehicle speed increases beyond a predetermined value, and increase the transmission torque of the clutch means over time to the determined value when the vehicle speed decreases beyond a predetermined value. An electric power steering device comprising: a correction means for correcting a control signal.