JPS6234849A - Motor-drive steering device - Google Patents

Abstract

PURPOSE:To obtain a steering assist torque not influenced from the variation of a power supply voltage and secure a good steering feeling constantly, by correcting the control signal computed from detected values of steering torque and the steering rotation speed depending on the power supply voltage. CONSTITUTION:In the captioned device, motor control signals are generated by a motor control signal generating device 64 depending on the output signals from a steering torque detecting device 41 to detect the steering torque of the steering system and a steering rotation detecting device 45 to detect the rotation speed of the steering system. Adding to such a system, a power supply voltage detecting device 65 is furnished to detect the power supply voltage feeding to a motor driving device 55, and depending on the detected value of the power supply voltage, the motor control signal is corrected by a correcting device 66. A motor to generate a steering assist torque is controlled through the motor driving device 55 depending on the control signal after correction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric power steering device that generates auxiliary torque by a steering force booster using an electric motor.

(Prior Art) A conventional electric power steering device is equipped with a steering force booster powered by an electric motor and its control circuit, and detects the steering torque applied to the steering wheel. The control circuit generates an auxiliary torque to the electric motor based on this steering torque signal, thereby reducing the steering force on the steering wheel.In addition, the conventional control circuit is composed of an analog circuit, and the electric motor drive circuit is driven by PWM drive. are doing.

Therefore, it is easy to perform feedback control of the electric motor, and the electric motor can be controlled at a high speed, thereby improving appropriate steering performance. However, when the electric motor is similarly controlled by a microcomputer, due to the characteristics of the microcomputer, it is not possible to read many inputs at the same time, and the microcomputer operates based on certain clock pulses. This is due to the fact that a certain amount of space is required for signal processing.

In particular, with conventional feedback control that repeats feedback loops over and over again, it takes time to complete the control, which may reduce responsiveness, and it may not be possible to sufficiently follow various changes in the steering system, making it difficult to perform proper steering. It becomes difficult to aim for the direction of the feeling. Therefore, a microcomputer determines a control signal for the electric motor based on the steering torque detection signal and other detection signals related to steering rotation, and uses the control signal to operate the electric motor drive means to improve the motor's response performance without performing feedback control. ``Patent Application No. 60-9545'' and ``Patent Application No. 80-9548'' have been filed as an electric power steering device that can sufficiently respond to the operation of the steering device and provide an appropriate steering feeling. The application was filed by Junto.

(Problem to be Solved by the Invention) However, in the electric power steering device using the electric motor mentioned above, even if the determined control signal (given by the duty ratio) is constant, the electric motor driving means When the supplied power supply voltage fluctuates, the armature current that is its output will also fluctuate, and as a result, the auxiliary torque written will also fluctuate.

Figure 10 shows this control signal (horizontal axis) and armature current (vertical axis).
This is an experimental result showing the relationship between power supply voltage (VI"V4) as a parameter, and even if the control signal (duty ratio) is the same, the larger the power supply voltage is, the more It can be seen that the amount of auxiliary torque that can be obtained increases.

Therefore, when the temperature decreases in cold regions, etc., and the battery capacity decreases, or when the power supply decreases due to load effects, consumption, etc., the auxiliary torque obtained for the same control signal This causes a problem in that the desired torque cannot be obtained, and as a result, the steering feeling becomes low.

Therefore, an object of the present invention is to provide an electric power steering device that can obtain a torque of 90 mm even when the power supply voltage changes and can always provide a good steering feeling.

(Means and operations for solving the problems) FIG. 1 is an overall configuration diagram of an embodiment according to the present invention. When the power is turned on, the output signal of the steering torque detection means (41) is inputted to the electric motor control signal generation means (84), and this electric motor control signal generation means (64) is used for detecting the rotational speed of the steering system, for example. A control signal is determined based on the steering torque detection signal together with the information signal from the rotation detection means (45) and the like.

On the other hand, the power supply voltage detection means (85) is connected to the motor drive means (
The control signal is corrected by a correction means (66) based on the detected value of the power supply voltage, and then inputted to the motor drive means (55).

Therefore, when the power supply voltage supplied to the motor driving means (55) fluctuates, the control signal can be corrected in accordance with the fluctuation, and the motor can be controlled without being affected by the fluctuations in the power supply voltage.

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

FIG. 2 is a vertical view showing the electromagnetic booster (1) of this embodiment bent at a 90" cut plane. In FIG.
1) is an electric power steering device.

(2) is the steering column, (3) is the stator, (4
) and (5) are an input shaft and an output shaft arranged coaxially.

The inner end of the human power shaft (4) is rotatably supported within the inner end of the output shaft (5) via a bearing (11), while these inner ends are connected by a torsion bar (12).
The input shaft (0 is connected to the output shaft (0) by the bearings (11) and (13)
5) are rotatably supported by bearings (14) and (15), respectively. Further, a steering rotation sensor (16) is arranged around the input shaft (4), a steering torque sensor (17) is arranged around the fitting part of the input/output shaft (0 and (5)), and a steering torque sensor (17) is arranged around the fitting part of the input/output shaft (0 and (5)).
5) The electric motor (1B) and reducer (19
), steering rotation sensor (18) and steering torque sensor (
17), and a control device (20) that drives and controls the electric motor (18) based on each detection signal from the motor (17).

To explain in more detail, the steering rotation sensor (16) is as follows.

DC power generation fi (113a) fixed to the outer periphery of column (2)
). This generator (lea) has its rotating shaft disposed along the axis of the input shaft (4), and corresponds to the pulley (+6b) attached to the end of the input shaft (4).
A belt groove (4a) is formed on the outer periphery of the belt 4).

The belt (
+6c) is passed, and the generator (tea) rotates as the human power shaft (4) rotates, and a detection signal corresponding to the rotation direction and rotation speed of the input shaft (4) is output.

” - The steering torque sensor (17) consists of a cylindrical movable iron core (1?a) provided on the outer periphery of the fitting part of the human power shaft (4) and the output shaft (5) so as to be displaceable in the axial direction, and a steering column. It is constituted by a differential transformer consisting of a coil part (17b) fixed to the inner periphery. The movable iron core (17a) has a pin (17e) protruding from each projecting piece (5a) of the output shaft (5), and a human power shaft (4
) respectively engage the pins (17F) protruding from the long holes (1
7g) and (17h), and a movable iron core (17a).
When there is an angular difference between the input shaft (4) and the output shaft (5) in the circumferential direction, it will be displaced in the axial direction due to their cohesive relationship, and this displacement amount is 1j for the input shaft (4). , corresponding to the available steering torque. The movable iron core (+7a) has a central part made of magnetic material, and a good conductor non-magnetic material (
+7i) is provided in one piece. Also, r+ (moving iron core (+78) is connected to a non-magnetic material spring (+?D) from the right end.
This prevents lost motion due to the gaps between the pins (+7e), (17F) and the long holes (17g), (17h). The coil part (17b) disposed around the movable core (17a) includes a primary coil (17k) to which AC signals such as pulses are manually input, and a +1 [dynamic core (17b)].
A pair of secondary coils (17a) are placed on both sides of the primary coil (17k) to output an output signal corresponding to the displacement of the coil (17a).
It consists of (7 sentences) and (17m). Therefore, as the torsion bar (12) twists, the input shaft (4) and output shaft (5)
The angular difference becomes an axial displacement of the IIT dynamic iron core (17a), which is converted into an electrical signal by the secondary coils (171) and (17m) and output.

The electric motor 42 (u+) has a stator (3) provided integrally on the steering column (2) and a stator (3
) at least a pair of magnets (3a) fixed to the inner peripheral surface of the
, a rotor (18a) rotatably disposed around the output +l+(5), and a spring (18c) arranged radially within a brush holder (18b) fixed to the stator (3).
) and a brush (18d) pressed by the zero rotor (
18a) includes a cylinder shaft (18e) rotatably supported by bearings (21) and (22), and this cylinder sleeve (18e)
) Laminated core (18f) with skew grooves on the outer periphery
.

Multiple windings (18g) are sequentially wrapped in a single ring, and a small gap is provided around the outer periphery of the magnet (3a) and the iron core (18F). In addition, the cylinder shaft (18e) is equipped with multiple windings (18g
) and a commutator (18h) connected to the brush (18h).
8d) is pressed.

The speed reduction mechanism (19) consists of a two-stage M star mechanism (23) and (24) arranged around the output shaft (5), tJ
The stage planetary mechanism (23) is provided on the inner circumferential surface of the case (25), and is elastically supported by a spring (2B) on a contact portion (3a) formed between the case (25) and the stator (3). The ring roller (27) and the cylindrical shaft (18e
) is engaged with the other end side (left end side in the figure), and is provided so as to be movable in the axial direction and rotatable together in the circumferential direction.

A sun roller (28) is formed with a friction surface (28b) on its outer periphery, and a planetary roller (2) is interposed between these and has a friction surface (29b) formed on its outer periphery.
9) and a first carrier member (30) that pivotally supports this planetary roller (29). The planetary mechanism in the latter stage (
24) includes the common ring roller (27) and the first carrier member (30) fitted around the output shaft (5).
), a sun roller (31) whose friction surface is the outer periphery of a cylindrical body integrally connected to The second carrier member (33) is pivotally supported, and the inner end of the second carrier member (33) is attached to a ring body (34) that is fitted around the rear end of the output shaft (5). The ring body (34) is rotatably supported via a bearing (15) by a support member (35) attached to the case (3) side, and is attached to the rear end of the output shaft (5). They are connected by spline connections.

Now, 1; ring roller (27), each sun roller (2
8), (31) and planetary roller (29),
The ring rollers (32) are each made of metal (e.g., iron, aluminum, etc.) and have grooves with a V-shaped cross section into which each friction surface can be fitted.
and planetary rollers (29), (32) are (27b
)..., (29b)..., (32b)... are divided in the axial direction at each end of the approximately V-shaped groove,
For this amount; 1.11 each divided member (27a)...
(29a)..., (32a)... are provided so as to be able to move independently in the axial direction.

In such a configuration, steering torque is applied to the input shaft (4), torque is transmitted from the input shaft (4) to the output shaft (5) via the steering wheel (I2), and the steering torque (17) is also applied to the steering torque. When the direction of the steering torque and the torque tIl' are detected by the rotation sensor (16), the control device (
20) performs signal processing, a control voltage is supplied to the multiplex winding (18g) via the brush (+8d), and the electric motor (18) is rotated in the same direction as the steering torque. The rotational torque of the rotor (18a) of the electric motor (18) is decelerated by the reduction mechanism (19), and the planetary mechanism (23) in the previous stage,
The latter stage is transmitted to the output shaft (5) via the star mechanism (20).

Next, the 1-th control signal t; (20) will be explained based on FIG.

In FIG. 3, (67) is the control section, (40)
is a microcomputer, (47) if A/D
It is a computer.

The steering torque detection means (41) divides the clock pulse inside the microcomputer (40) to output the steering torque sensor (17) and the second coil (17k) of the steering torque sensor (17). , a drive unit that converts into a rectangular wave or sine wave alternating current and amplifies it) - (42
), and each electric signal j,'f obtained from the secondary coil (llj) and (17m) corresponding to the displacement of the movable iron core (17a)
It consists of rectifier circuits (43A) and (43B) that rectify the voltage, respectively, and low-pass filters (44A) and (44B) that remove the crystal frequency component and convert it into a stable DC voltage.

The steering rotation detection means (45) is a steering rotation sensor (16).
DC generator (LEA) and this DC generator (LEA)
Subtraction circuits (48A), (48B) that subtract the outputs of and detect their direction and magnitude, and low-pass filters (48A), (48B) that convert these outputs into stable DC voltages.
8B).

The microcomputer (40) includes an I10 port, memory, arithmetic section, control section, clock generator, and the like. The power supply circuit (49) that drives the microcomputer (40) etc. is an in-vehicle battery (50).
Connect the ignition key key switch (51) to the (+) terminal of the
), a relay circuit (53) that is connected via a fuse (52) and cuts off the power in the event of an abnormality, and this relay circuit (5
A constant voltage circuit (54) connected to the output side of the relay circuit (53) supplies power to a motor drive means (55), which will be described later, from the A terminal on the output side of the relay circuit (53). 54) supplies an If source to the microcomputer (40), each detection means (41), (45), and other control units. At this time, the power supply voltage supplied to the motor drive means (55) is
Voltage detection sensor (Ei5
A). This voltage detection sensor (65A)
For example, the power supply voltage is divided by resistance and sent to the A/D converter (4).
7) consists of resistors, etc. When the key switch (51) is turned on in the configuration of -1- below, the microcomputer (40) activates each detection means (41) based on the command.
, (45), output signals S1 to S5 of (f35A) to A
/D converter (37) converts the signal into digital, processes it according to the program written in the memory, and outputs control signals T2, T3 and T4' for driving the electric motor J11 (18) to the motor drive means (55), Electric motor (1
8) Drive and control.

The electric motor drive means (55) includes a drive unit (51 (
) and FET (field effect transistor) (57), (
5B).

(59), (60) and series circuits of resistors and capacitors connected in parallel to these (6B), (87), (8B)
, (89).

In the bridge circuit, the respective drain terminals of FET (57) and (60) are connected to the A terminal of the power supply circuit (48), while their source terminals are connected to the other FET (5
8) and (58), respectively.

The source terminals of FETs (48) and (49) are each connected to the common side.

F E T (57), (58), (59), (Go)
The gate terminals of each of the F E
The source terminal of T (57) and the source terminal of FET (80) are connected to the armature winding (18g) of the motor (18).
It is connected to the. The drive unit (5B) is
Based on the motor rotation direction control signals T2 and T3 from the microcomputer (40), FET (57) is turned ON, and at the same time, FET and T (59) are enabled to be driven, and a motor drive signal T4 consisting of a PWM signal is activated. °
Drive FET (59) based on , or simultaneously drive FET (Go) ON.
(5B) is enabled to drive, and the FET (58) is driven based on a motor drive signal T4° consisting of a PWM signal. Therefore, in the electric motor drive means (55),
ON drive of one FET (57) and FET
(59) PWM drive, or the other F E T (80
) and the PWM drive of FET (5B), the electric motor (18) receives control signals T2, T3 and T4°.
The direction of rotation and its power (rotation speed and torque) are controlled accordingly.

Next, the operation based on this configuration will be explained.

FIG. 4 is a flowchart showing an outline of the motor control process in the microcomputer (40), and the P
1 to P13 represent each step of the flowchart.

When the key switch (51) of the ignition key is turned on, power is supplied to the microcomputer (40) and other circuits to start control. First, in the microcomputer (40), data in each register and RAM are cleared in step PI. Then, in steps P2 and P3, the steering torque detection signals S1 and S2 are sequentially read, and in step P4, the 5l-S2
is calculated and set as the steering torque T. Here, since the steering torque sensor (17) is constituted by a differential transformer, the relationship between the steering torque and the detection signals s, s2, and T is shown as shown in FIG.

In step P5, in order to classify the acting direction of the steering torque T into n, it is determined whether it is positive or negative. If positive or zero, step P6 sets F=0 and proceeds to step P9; if negative, proceeds to step P7, sets F=1, and then steps P
8, absolute value conversion, that is, T=-T processing is performed. Here, F indicates the sign of the steering torque T, that is, the direction of action. In step P9, the contents of the memory whose address is the absolute value T of the steering torque are called. In the memory, the armature current I of the electric motor m (18) corresponding to the absolute value T of the steering torque shown in FIG. 6, the armature winding,
A table 1 is configured in which a product of resistances R of brushes, wiring, etc., ie, a duty conversion value D(T) of RM and IM is stored. Therefore, in step P9, the contents of the memory corresponding to the address according to the absolute value T of the steering torque,
That is, the duty conversion value D (T) of RM/IM is called and the process proceeds to step PIG. In step P1o, the value of F is determined in order to give a sign to the addressed duty conversion value D (T). If F=0, the steering torque is zero or positive, so the duty converted value D (T) is transferred as is, and if F=1, the steering torque is negative, so the process proceeds to step pH and the duty converted value D ( T) is transferred and stored as a negative value, and the process proceeds to step PI2.

Next, in step P121'P13, the steering rotation speed detection signals S3 and S4 from the steering rotation detection means (45) are sequentially read, and the process proceeds to step P14. In step P14, S3-54 is calculated. is the steering rotation speed S. Here, detection signals S3, S4, and S from the steering rotation detection means (45) are shown as shown in FIG.

In step PI5, in order to determine the direction of the steering rotational speed S, it is determined whether it is positive or negative. If S is positive or zero, the process advances to step P16 and F=0. If S is negative, the process proceeds to step P17, where F=1 is set, and then absolute value conversion, that is, 5=-S processing is performed at step pH+. In step PIG, the contents of the memory whose address is the absolute value S of the steering rotational speed are called. In memory,
In order to determine the rotational speed SM of the electric motor (18) corresponding to the absolute value S of the steering rotational speed shown in FIG. A table 2 is configured in which the duty conversion value D (S) is stored. Therefore, the absolute value S of the steering rotation speed
The memory contents corresponding to the address, ie, the duty conversion value of SM, are called.

Proceed to step P20.

In step P20, the value of F is determined in order to give a sign to the addressed duty conversion value D(S).

If F=O, the steering rotational speed is positive, so the duty conversion value D (S) is transferred as is; if F=1, the steering rotational speed is negative, so the process proceeds to step P21, and the duty conversion value D ( S) is transferred and stored as a negative value, and in step P22, the duty conversion value D (T) based on the steering torque T and the duty conversion value D (S) based on the steering rotational speed are added, and this i+f
Let i be T4.

Thereafter, a program is executed to correct the obtained control signal T4 in accordance with fluctuations in the power supply voltage supplied to the motor section/driving means (55).

First, in step P23, the voltage detection sensor (65
The detected value S5 of A) is read and set as V, and the next step P2
At step 4, the contents of the memory whose address is this detection value ■ are called out. As shown in FIG. 9, a correction coefficient K for the control signal T4 corresponding to the power supply voltage V is defined in the memory. Then, in step P25, the control signal is multiplied by this correction coefficient to perform correction, and this value is set as T4°.

Step P2 [1 is the sign 1 of this corrected value T4' in order to differentiate the acting direction of the auxiliary torque to be output by Tl)
Determine. If T4' is positive or zero, step P2? It is determined whether the history is lTE or zero, and if it is zero, T2=Ta=O in step P2 [1, and if positive, T2=1 and Tl=0 in step P29, and in step P32. are output respectively. On the other hand, f of T4'
If ff is negative, T2=OIt in step P3G
Tz=1 and T4° in step P31.
After setting the absolute value of T4 to a new value, step P32
The values of T2 and T3 are outputted at step P3.
At step 3, the value of T4' is output.

In this way, the direction of the torque to be assisted is determined by the sign of T4°, that is, the values of T2 and T3, and the absolute value of the torque to be assisted is determined by the absolute value of T4°, and as shown in FIG. drive unit of drive means (55))
(5B).

At this time, the value of T4', that is, the control signal, is corrected in accordance with the fluctuations in the power supply voltage supplied to the motor drive means (55), so the motor (18) is not affected by the fluctuations in the power supply voltage. This means that stable control is performed and a good steering feel is always obtained.

(Effect of the invention) As is clear from the above description, according to the present invention.

When the power supply voltage supplied to the motor drive means fluctuates, the motor control signal can be corrected in accordance with this fluctuation, and therefore the desired output torque can be obtained without being affected by the fluctuations in the power supply voltage. .

As a result, it is possible to provide an electric power steering device that provides a good steering feeling at all times.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram according to an embodiment of the present invention, FIG. 2 is a longitudinal side view showing an electric power steering device bent at a 90° cut plane, and FIG. 3 is an overall configuration diagram of a control device. FIG. 4 is a flowchart showing an outline of the control process, FIG. 5 is a diagram showing the detection characteristics of the steering torque detection means, FIG. 6 is a diagram showing the relationship between the steering torque detection value and the duty conversion value, and FIG.
FIG. 8 is a diagram showing the detection characteristics of the steering rotation detection means, FIG. 8 is a diagram showing the relationship between the detected steering rotation speed value and the duty conversion value,
FIG. 9 is a diagram showing the relationship between the power supply voltage detection value and the correction coefficient, and FIG. 10 is a diagram showing the relationship between the duty value (control signal) and armature current (output value) with respect to the power supply voltage. And in the drawing. (1B)...Electric motor, (45)...Steering rotation detection means, (55)...
. . . Motor drive means, (64) . . . Motor control signal generation means, (65A) . . . Power supply voltage detection means. (66)...Correction means, (67)...Control signal

Claims (1)

[Claims] Steering torque detection means for detecting steering torque of a steering system; motor control signal generation means for determining and outputting a control signal for the electric motor based on a detection signal from the detection means; and driving the electric motor based on the control signal from the means. In an electric power steering device comprising a motor drive means, a power supply voltage detection means for detecting a voltage of a power supply supplied to the motor drive means is provided, and the control signal is corrected based on a detection signal of the power supply voltage detection means. An electric power steering device characterized in that a means is provided.