JP2950097B2 - Power steering device for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering apparatus for a vehicle used for steering a front wheel of an automobile, for example.

[0002]

2. Description of the Related Art Some automobiles are equipped with a hydraulic power steering device so that a driver can perform steering by operating a light steering wheel.

In this power steering device, an input shaft connected to a steering wheel and an output shaft connected to a steered wheel (front wheel) are connected by a torsion bar, and the rotational force of the input shaft is controlled by a hydraulic assist system. To be communicated as

In the assist system, a rotary valve that is relatively displaced in accordance with the torsion bar torsion is provided between an input shaft and an output shaft. The rotary valve drives an engine-driven oil pump and a front wheel in a steering direction. Power cylinder is connected. Then, the hydraulic pressure obtained by the rotary valve relatively displaced by the rotation of the steering wheel is supplied to the power cylinder to generate an assist force.

That is, when the handle is rotated, the output shaft rotates via the input shaft and the torsion bar. At this time,
The rotation of the output shaft is hindered by the road surface resistance of the front wheels, the torsion bar is twisted by the road surface resistance, and the input shaft rotates extra by the torsion angle of the torsion bar.

As a result, a rotation difference (relative displacement) occurs in the rotary valve provided between the input shaft and the output shaft,
The hydraulic pressure generated by this rotation difference is supplied to the cylinder chamber of the power cylinder. By supplying hydraulic pressure to the power cylinder, the front wheels are steered in the rotation direction of the steering wheel, and the steering force is reduced.

On the other hand, in a conventional power steering apparatus, a reaction force mechanism for generating a reaction force in an assist system and a control valve for controlling the reaction force mechanism are provided, and the response of the handle is made variable by hydraulic pressure to turn the handle. There is one that improves the reversibility.

[0008] This reaction force mechanism will be described.

The input shaft (or the output shaft) is provided with a pair of projections projecting from both sides in the radial direction, and two pairs of the projections are provided along the axial direction.

The output shaft (or input shaft) is provided with a first reaction force piston which presses and urges a pair of protrusions on one side in the axial direction to rotate the input shaft from one direction to a relative rotation neutral position, The first reaction force piston is disposed at a diagonal position across the axis of the input shaft. Further, the output shaft is provided with a second reaction force piston for urging the pair of protrusions on the other side in the axial direction to rotate the input shaft from another direction to the relative rotation neutral position, and the second reaction force piston is a second reaction force piston. It is arranged diagonally across the axis of the input shaft symmetrically with the one reaction force piston.

The first reaction force piston and the second reaction force piston are brought into contact with the projection of the input shaft to apply a reaction force to the rotational force of the input shaft, that is, the steering force of the steering wheel. By controlling the driving oil pressure of the force piston and the second reaction force piston, the response of the handle can be changed.

[0012]

In the conventional power steering device, the relationship between the operating angle of the rotary valve and the hydraulic pressure generated from the rotary valve is uniquely determined by the torsion of the torsion bar accompanying the rotation of the steering wheel. ing. For this reason, the steering force cannot be appropriately controlled only by the displacement of the rotary valve, and the variable width of the steering force is restricted.

The hydraulic control of the control valve for driving the first and second reaction force pistons of the reaction force mechanism is uniquely performed based on a map determined by the steering angle of the steering wheel and the vehicle speed. I have. For this reason, the variable width of the steering force in the reaction force mechanism is restricted.

In a conventional reaction mechanism of a power steering apparatus, a pair of projections is provided on an input shaft (or an output shaft), and the pair of projections are two-staged in the axial direction of the input shaft (or the output shaft). , And a reaction force piston is provided for each radial projection, so that the power steering device becomes longer in the axial direction, which hinders a reduction in weight and size.

Further, the reaction force mechanism only applies a reaction force to the steering force of the steering wheel, so that the steering wheel does not return when the driver releases the steering wheel, particularly when the steering wheel is largely steered. In other words, the driver was forced to bear a large steering return.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a power steering apparatus capable of reducing a burden on a driver under a wide range of steering conditions and enabling steering according to the steering conditions. .

[0017]

According to a first aspect of the present invention, an output shaft connected to a steering wheel is connected to one end of a torsion bar, and an input shaft connected to a handle is connected to the other end of the torsion bar. A steering mechanism that steers the steered wheels in accordance with the steering operation of the steering wheel, a hydraulic pressure generation unit that generates a predetermined hydraulic pressure, and a hydraulic pressure generator that is provided between the input shaft and the output shaft of the steering mechanism. A rotary valve that is connected to the hydraulic pressure generation unit and that relatively displaces in accordance with the torsion of the torsion bar during steering operation of the steering wheel and outputs a hydraulic assist force; and that the steered wheels are hydraulically driven from the rotary valve. A cylinder mechanism that is driven in a steering direction, and is provided between the input shaft and the output shaft of the steering mechanism; It has a pressed part protrudingly provided on one of the output shafts, and has a pressing element provided on the other side of the input shaft or the output shaft to press the pressed part to both sides in the circumferential direction, A valve driving mechanism for generating an independent torsional moment in the torsion bar by pressing the pressed portion by driving a pressing element, and pressing element driving means for driving the pressing element of the valve driving mechanism by exciting a solenoid valve And an assist force obtained by rotating the rotary valve in the same direction as the torsion bar torsion direction and an assist force obtained by rotating the rotary valve in the opposite direction to the torsion bar torsion direction. A target assist force, which is a value, is set, and the presser of the valve drive mechanism is driven so that the target assist force is obtained when the steering wheel is operated. Rubeku, and a control means for excitation of the solenoid valve, control means,
A centering control function for generating an assist force for steering the steering wheel in a neutral state in a low-speed range where the vehicle speed is equal to or less than a predetermined value; a steering force control function for generating an assisting force in the same direction as the steering direction of the steering wheel in the low-speed range And a steering reaction force control function for generating an assist force in the same direction as or in the opposite direction to the steering direction of the steering wheel in a high-speed region where the speed of the vehicle is equal to or greater than a predetermined value. There is provided a means for increasing a command control voltage for exciting the electromagnetic valve until an angular velocity is generated, and gradually shifting the command control voltage to a value reduced by a predetermined value when a handle angular velocity is generated. And the centering controller of the control means.
When the handle is near neutral, the command
A means to gradually reduce the voltage in two stages
And features.

[0018]

When the steering wheel is steered, the torsion bar, which is to be twisted by the difference from the road surface resistance, is twisted in a predetermined direction by the valve drive mechanism so as to attain the target assist force. As a result, the rotary valve is initially driven by the valve drive mechanism, and thereafter, the rotary valve is driven by the torsion bar that is twisted by the difference from the road surface resistance, and the required hydraulic pressure is supplied to the cylinder mechanism.

The steering force obtained at this time is determined by the steering force of the output of the rotary valve in the region of the operating angle of the torsion bar which is twisted by the steering wheel operation, and the torsion direction of the torsion bar by the pressing element of the valve drive mechanism. Rotation of the torsion bar by the pusher of the valve drive mechanism and the light steering force (due to the fact that the pressure of the rotary valve rises faster than the steering by the steering wheel operation) generated by rotating the torsion bar And a heavy steering force (due to the fact that the pressure of the rotary valve rises later than the steering by the steering wheel operation) caused by the rotation in the opposite direction (opposite phase: decrease of the operating angle).

During the centering control, the command control voltage is increased until the steering wheel angular velocity is generated, and when the return speed is generated, the command control voltage is gradually shifted to a value obtained by lowering the command control voltage by a predetermined value. Is kept constant.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration of a power steering apparatus according to an embodiment of the present invention, FIG. 2 is a cross section showing a steering mechanism for steering the steered wheels (left and right front wheels) of an automobile, and FIG. FIG. 4 is a view taken along line IV-IV in FIG.
A line arrow is shown.

In FIG. 2, reference numeral 2 denotes a rack and pinion type steering gear which constitutes the steering mechanism 1.
And a pinion 5.

As shown in FIG. 1, one end of the rack 4 is connected to one front wheel 8 via a steering rod 6, a tie rod 6a and a knuckle 6b. Also,
The other end of the rack 4 is connected to the other front wheel 8 via a steering rod 6, a power cylinder device (cylinder mechanism) 7, a tie rod 6a, and a knuckle 6b.

The lower end of the torsion bar 9 is connected to the pinion 5 of the steering gear 2 via an output shaft 5a (output shaft). The upper end of the torsion bar 9 is connected to an input shaft 11 (input shaft) through a valve unit 10 provided above the steering gear 2. Input shaft 11
Is connected to a handle 13 via a steering shaft 12. When the rotational displacement is input from the handle 13, the steering shaft 12, the torsion bar 9, the pinion 5, the rack 4, and the steering rod 6
The left and right front wheels 8 are steered via the steering wheel.

The valve unit 10 is provided above the steering gear 2 so as to surround the torsion bar 9.
A valve drive actuator 15 (valve drive mechanism) and a rotary valve 16 are provided at a portion from the upper portion of the steering gear 2 to the inside of the housing 14.
Are provided in order from the bottom.

The rotary valve 16 has a cylindrical outer valve 17 rotatably provided on the inner surface of the housing 14, and a cylindrical inner valve 18 combined with the outer valve 17 provided integrally with the input shaft 11. That is, the rotary valve 16 is configured such that when the torsion bar 9 is twisted by a rotation operation from the handle 13, a relative displacement occurs between the outer valve 17 and the inner valve 18.

An inflow port 17a formed in the outer valve 17 is provided with an inflow body 19 provided in the housing 3.
The outlet port 18 a formed in the inner valve 18 is connected to an outlet 20 provided in the housing 3. An output port (not shown) formed in the outer valve 17 communicates with a pair of output port portions 21 and 22 provided in the housing 3. The output ports 21 and 22 are connected to the power cylinder device 7.

In the power cylinder device 7, as shown in FIG. 1, a piston rod 24 is slidably provided in the cylinder 23 so as to penetrate the cylinder 23. A piston 25 is provided so as to partition on both sides (left and right) in the direction. A pair of input ports 26 and 27 communicating with the left and right chambers 25 a and 25 b partitioned by the piston 25 are connected to the output port portions 21 and 22 via flow paths 28 and 29.

The inlet body 19 of the housing 3 is
And a flow dividing unit 31 (one inlet part 31a and two outlet parts 31b, 31b are provided with orifice-equipped flow paths 31c,
31c) is connected to an oil pump 33 (oil pressure generating unit) with a relief valve driven by a driving engine 32 of the vehicle. In addition, the outlet 20 of the housing 3 is connected to an oil reservoir 35 via a flow path 34, and a hydraulic circuit for the power cylinder device 7 is configured.

Outer valve 17 of rotary valve 16
When the inner valve 18 and the inner valve 18 are displaced relative to each other, a hydraulic pressure corresponding to the steering force and the steering direction is transmitted from the rotary valve 16 to the chambers 25a, 2
5b. That is, the front wheels 8 are steered while being assisted by hydraulic pressure.

Next, the valve drive actuator 15 will be described.

An extended portion 37 is formed at a lower end portion of the input shaft 11 (a shaft portion immediately below the inner valve 18). The extended portion 37 is formed such that the lower end portion of the input shaft 11 extends downward along the axial direction of the torsion bar 9. It has been extended to. The casing 3 around the extension portion 37 has a large diameter portion, and a circular chamber 4 is provided in the large diameter portion.
7 are formed. Inside the chamber 47, a hollow circular large-diameter portion 38 integrally connected to the output shaft 5a is rotatably accommodated. The large diameter part 38 is connected to the outer valve 17 of the rotary valve 16 via a pin 36. An inner sleeve 39 is fitted over the entire outer peripheral surface of the large-diameter portion 38, and an outer sleeve 4 is mounted on the inner peripheral surface of the chamber 41 facing the inner sleeve 39.
0 is rotatably fitted.

As shown in FIGS. 3 and 4, the inside of the large-diameter portion 38 has a radius from two symmetrical points 180 degrees apart in the circumferential direction in the through hole 38a of the large-diameter portion 38. A flat recessed chamber 41 extending outward in the direction is formed.

The extended portion 37 covered by the large diameter portion 38 includes
Plate-like projections 42 (pressed portions) projecting outward in the radial direction from two symmetrical points 180 degrees apart in the circumferential direction are formed. Each of the overhang portions 42 is formed to have an outer shape smaller than the length and width of the chamber 41, and the overhang portion 42 is loosely fitted concentrically into the chamber 41. The gap between the plate-shaped overhanging portion 42 and the flat chamber 41 is set to a dimension in which a region necessary for compensating the operating angle of the rotary valve 16 can be set, and the torsion bar 9 has a predetermined angle with respect to the input shaft 11. It is designed to be twisted in a range.

Further, holes, for example, four circular holes 43 are formed symmetrically on both sides of the large-diameter portion 38 across the chamber 41 so as to be connected in series across the overhang 42. . Plungers 44a and 44b (pressing elements) are slidably fitted in the holes 43 symmetrically in the axial direction, respectively. Each of the plungers 44a and 44b has a projection 42a formed at the center of the tip, and the projection 42a presses the plate surface portion of the overhang portion 42. The total length of each of the plungers 44a and 44b is set shorter than the length of the hole 43. Hydraulic chambers 45 and 46 are provided in the holes surrounded by the rear end surfaces of the plungers 44a and 44b and the inner sleeve 39, respectively. Is formed. Hereinafter, of the four symmetrical hydraulic chambers 45 and 46, two ones on the clockwise rear side with respect to the chamber 41 are referred to as a first hydraulic chamber 45 and a chamber 41.
The two oil pressure chambers on the front side in the clockwise direction are referred to as second hydraulic chambers 46.

As shown in FIG.
A first annular oil passage 48 is provided at an upper portion of the outer peripheral surface of the inner sleeve 39, and a second annular oil passage 49 is provided at a lower portion of the outer peripheral surface of the inner sleeve 39.
Is provided. As shown in FIG. 3, the first annular oil passages 48 are connected to the two first hydraulic chambers 45 via first hole passages 50 a provided in the inner sleeve 39 corresponding to the positions of the respective first hydraulic chambers 45. Communicating. Further, as shown in FIG. 4, the second annular oil passage 49 is connected to the two second hydraulic chambers 46 via the second hole passage 50 b provided in the inner sleeve 39 corresponding to the position of each second hydraulic chamber 46. Communicating.

As shown in FIG. 2, the outer sleeve 40
A first annular oil passage 51 is provided at an upper portion of the outer peripheral surface of the outer sleeve 40, and a second annular oil passage 52 is provided at a lower portion of the outer peripheral surface of the outer sleeve 40.
Is provided. Reference numeral 53 in the drawing denotes an upper stage of the first annular oil passage 51, the first annular oil passage 51 and the second annular oil passage 5.
2 and O-rings for oil passage sealing provided at the lower stage of the second annular oil passage 52, respectively.

As shown in FIG. 3, the outer sleeve 40
The first annular oil passage 51 is provided with a first annular oil passage 51 formed in the casing 3.
The second annular oil passage 52 of the outer sleeve 40 communicates with the inlet / outlet body 54 and the second inlet / outlet body 5 formed in the casing 3.
5 is connected.

First inlet / outlet body 54 and second inlet / outlet body 55
Are flow passages 56 and 57, first and second control valves 58 and 59 each composed of a pressure regulating valve, and a flow dividing unit 60.
(One inlet part 60a and two outlet parts 60b, 60b are connected by orifice-equipped flow paths 60c, 60c) to the other outlet part 31b of the flow dividing unit 31, By operating the first and second control valves 58 and 59, the hydraulic pressure from the oil pump 33 divided by the flow dividing units 31 and 60 is applied to the inlet / outlet body 54 or the inlet / outlet body 5
5 is supplied. Each control valve 5
The return portions 8 and 59 are connected to the oil reservoir 3 by the flow path 34.
It is connected to 5.

The first annular oil passage 48 of the inner sleeve 39
The first annular oil passage 51 of the outer sleeve 40 communicates with the first annular oil passage 51 via first communication holes 61 provided in the outer sleeve 40. Further, the second annular oil passage 49 of the inner sleeve 39 and the second annular oil passage 52 of the outer sleeve 40 communicate with each other through second communication holes 62 provided in the outer sleeve 40.

The first and second control valves 58, 58 in the hydraulic circuit 64 (pressor driving means) configured as described above.
The operation of 59 and the action of the hydraulic pressure on the first and second hydraulic chambers 45 and 46 will be described with reference to FIGS. FIGS. 5A, 5B and 5C show the first and second hydraulic chambers 4.
6A, 6B, 6A, 6B,
FIG. 5C schematically shows the operation of the plungers 44a and 44b corresponding to FIG.

When the first and second control valves 58 and 59 do not operate, no hydraulic pressure acts on the first hydraulic chamber 45 and the second hydraulic chamber 46.

When only the first control valve 58 is operated, FIG.
6A, the pressure oil from the oil pump 33 is supplied to the first hydraulic chamber 45, and the plunger 44
The b presses the overhang portion 42 to generate a torsional moment in the torsion bar 9 in the normal rotation direction (right direction) of the rotary valve 16, for example. That is, as shown in FIG. 27, the valve operating angle of the rotary valve 16 is slightly increased.

When only the second control valve 59 is operated, as shown in FIGS. 5 (b) and 6 (b),
Is supplied to the second hydraulic chamber 46 and the plunger 4
4a presses the overhang portion 42 to generate a torsional moment in the torsion bar 9 in the reverse rotation direction (left direction) of the rotary valve 16, for example.

Therefore, the first and second control valves 58, 5
By the switching operation of No. 9, a torsional moment can be generated independently of the torsion bar 9.

When the first and second control valves 58 and 59 are operated, as shown in FIGS. 5C and 6C, the pressure oil from the oil pump 33 is supplied to the first and second hydraulic pressures. Room 45,
The plungers 44a and 44b press the overhang 42 from both sides. In this state, the equivalent rigidity of the torsion bar 9 is enhanced, and for example, the sense of response and the sense of stability when the handle 13 is near neutral can be increased.

As shown in the map of FIG. 7, the first and second control valves 58 and 59 are supplied to the first and second inlet / outlet members 54 and 55 as the control voltage (V) increases. A control valve is used to increase the pressure.

A control unit (ECU) 70 is connected to the solenoids 58a, 59a of the first and second control valves 58, 59 as control means composed of a microcomputer and its peripheral circuits. E
The CU 70 has a vehicle speed sensor 71 for detecting the running speed (vehicle speed: Vel) of the automobile, a steering wheel angle sensor 72 for detecting the steering angle of the steering wheel 13 (steering angle: θh), and a torque acting on the steering wheel 13 (steering torque: tq2). Is connected.

With this control system, the assist force obtained by rotating the rotary valve 16 in the same direction as the torsion bar 9 is twisted, and the rotary valve 16 is rotated in the direction opposite to the torsion bar 9 torsion direction. The range of the target assisting force is set by the assisting force obtained in step (1), and the plungers 44a and 44b are driven so as to achieve the assisting force, so that the torsion bar 9 generates a necessary torsional moment.

For this reason, the ECU 70 includes the handle 13
A function is set to determine whether is operated forward (right) or reverse (left), and a function for obtaining a target torque required for operating the handle 13 at this time is set. Thus, the assist force obtained by rotating the rotary valve 16 in the same direction as the torsion bar 9 in the torsion bar 9 is added to the range of the target assist force, that is, the assist force obtained by the torsion bar 9 twisted by the steering of the steering wheel 13. An assist force region is set by combining the above and an assist force obtained by rotating the rotary valve 16 in a direction opposite to the torsion direction of the torsion bar 9.

The ECU 70 calculates a control voltage value for the solenoids 58a and 59a by determining whether to set a mode for controlling the steering force of the steering wheel 13 or a centering mode for maintaining the neutrality of the steering wheel 13. Function is set.

The ECU 70 further stores the current steering wheel 1
3, the function of judging a change in the steering wheel angle (steering wheel angular velocity: θh); operating the first control valve 58 in accordance with the above calculation result (twisting the torsion bar 9 in the same direction as the direction of the relative displacement of the rotary valve 16) A function for operating the second control valve 59 (generating a torsional moment on the torsion bar 9 in the direction opposite to the direction of the relative displacement of the rotary valve 16) is set in accordance with the above calculation result. ing. As a result, the plungers 44a and 44b are driven to generate the required torsional moment on the torsion bar 9 so that the target assist force is obtained.

Next, the control operation in the ECU 70 will be specifically described with reference to FIGS. 8 to 21 show control flowcharts of the power steering device. FIGS. 22 and 23 show timing charts in the low-speed assist control of the power steering device.

The ECU 70 is started by an ON signal of an ignition key switch (IG).

In step S1, initial values are set, each control flag is set to 0 (non-execution side), and all variables are set to 0. In addition, various coefficients are set at preset values.

In step S2, the neutral signal (Hc value) of the handle 13 is read, and in step S3, the handle angle θh detected by the handle angle sensor 72 is read. Thereafter, the steering wheel angle θh is calculated by the steering wheel angle calculation routine in step S4.

The steering angle calculation routine in step S4 will be described with reference to FIG. In step S4,
Until the Hc value of the handle 13 is turned ON, the handle angle θ
h is set to 0, and safety is secured when the IG is turned ON while the steering is at a large steering angle.

As shown in FIG. 13, it is determined in step S4-1 whether the Hc value is ON. If the Hc value is determined to be ON, the steering wheel angle θh is set to 0 in step S4-2,
In step S4-3, the state of the handle neutral flag Hcflag is determined. In step S4-3, Hcflag =
0, that is, when it is determined that the handle 13 is not neutral, it is determined in step S4-4 that Hcflag = 1, that is, the handle 13 is neutral, and the process returns to the main flowchart. In step S4-3, it is determined that Hcflag is not 0. If so, the process returns to the main flowchart.

On the other hand, if it is determined in step S4-1 that the Hc value is not ON, then Hcfl is determined in step S4-5.
It is determined whether ag = 0 or not. If Hcflag = 0, the steering wheel angle θh is set to 0 in step S4-6, and the process returns to the main flowchart. Hcfla in step S4-5
If it is determined that g is not 0, it is determined in step S4-7 whether the steering wheel 13 is steered right or left. In the case of right steering, the read value is added to the steering wheel angle θh in step S4-8 (θh = θh + CNT) and the process returns to the main flowchart. In the case of left steering, the read value is subtracted from the steering wheel angle θh in step S4-9 ( θh = θh-CNT), and returns to the main flowchart.

In step S4, the Hc value is finally turned on.
Until the steering wheel angle θh is set to 0, control execution start conditions are not set in subsequent processes.

Returning to the main flowchart, as shown in FIG. 8, in steps S5, S6 and S7, the steering wheel angular velocity θhs, the vehicle speed Vel detected by the vehicle speed sensor 71, and the steering torque tq2 detected by the torque sensor 73 are read. . Thereafter, the steering cycle is detected in the steering cycle detection routine in step S51.

The steering cycle detection routine in step S51 will be described with reference to FIG. In step S51, when the steering torque fluctuates in a short cycle, that is, when the steering that does not respond to the vehicle is repeated, the command control voltage Vol to the first and second control valves 58 and 59 is reduced to 0.
To prevent the generation of assist force.

As shown in FIG. 21, step S51-1
It is determined whether or not the steering torque tq2 is equal to or greater than a preset positive control determination torque threshold Tq00. If it is determined that the steering torque tq2 is equal to or greater than the positive control determination torque threshold Tq00, it is a storage variable in step S51-2. The high set hiset is set to 1, and in step S51-5, the timer Shtim
Count. In step S51-1, the steering torque tq
If it is determined that 2 is less than the positive control determination torque threshold value Tq00, it is determined in step S51-3 whether or not the value is equal to or less than a preset negative control determination torque threshold value -Tq00. If it is determined that the value is equal to or less than the negative control determination torque threshold value -Tq00, in step S51-4, the high set hisse
t is set to 0, and the timer Sht is set in step S51-5.
is counted, and a negative control judgment torque threshold value -Tq
If it is determined that the value exceeds 00, the timer Shitim is counted in step S51-5.

In step S51-6, it is determined whether or not the timer Shitim is equal to or greater than 100. Immediately after the start of operation, since the timer Shitim is 0, step S51-7 is performed.
It is determined whether the high set hiset is not equal to the previous high set, the low set losset, and immediately after the start of operation, the high set hiset and the low set loss
Since both et are equal to 0, it is determined in step S51-8 whether the memory mf is 2 or more.

If it is determined in step S51-6 that the timer Shitim is 100 or more, it is not determined that the time is short,
The output voltage flag Volflag is set to 1 so that the first and second control valves 58 and 59 are excited, and the memory mf and the timer Shtim are set to 0, and the process proceeds to step S51-8. Step S51
If it is determined in -7 that the high set hiset and the low set loset are not equal, 1 is added to the memory mf in step S51-10, and the timer Shtim is set to 0 (reset) in step S51-11, and step S51 is performed.
Go to 51-8.

In step S51-8, whether or not the memory mf is 2 or more, that is, in step S51-7, the high
The state in which t is not equal to the row set losset is determined twice or more, and whether the steering torque tq2 has changed to positive or negative in a short time (steps S51-1, S51-).
3) is determined. When it is determined that the memory mf is 2 or more, the steering torque tq2 fluctuates in a short cycle, and thus the output voltage flag Volfl is determined in step S51-12.
ag to 0 and the first and second control valves 58 and 5
Step S51-1 so as not to perform the excitation in Step S51-1.
At 3, the low set and the high set hiset are made equal.

If it is determined in step S51-8 that the memory mf is less than 2, it is determined in step S51-14 whether the absolute value | θh | of the steering wheel angle θh is 10 deg or less. If the absolute value | θh | is equal to or smaller than 10 deg, the output voltage flag Volflag is set to 1 in step S51-15, and the process proceeds to step S51-13, where the absolute value | θh
When | exceeds 10 deg, step S51-1 is performed as it is.
Proceed to 3. In steps S51-14 and S51-15, the output voltage flag Vo is set when the steering wheel angle θh is near the neutral position.
lflag is always set to 1.

FIG. 25 shows the relationship between the high set hiset and the steering torque tq2. As shown in the figure, the steering torque tq2 has a positive control determination torque threshold Tq00.
, The high set hiset = 1 is set until the negative control determination torque threshold value -Tq00 is exceeded. Also,
The steering torque tq2 is equal to the negative control determination torque threshold value-Tq0.
The high set hiset = 0 from when the value exceeds 0 to when the value exceeds the positive control determination torque threshold Tq00. In the steering cycle detection routine, the output voltage flag Volflag is set to 0 and the first and second control valves 58 and 59 are excited only when the high set hiset has changed two or more times (one cycle) in a short time. Not to generate any assist force.

When the output voltage flag Volflag = 0, 0 is output as the command control voltage Vol to the first and second control valves 58 and 59 as described later in steps S52 and S53 of FIG. .

For example, referring to FIG. 25, the flow of control from point A to point B with point A as the start of operation will be described.

At the point A, after it is determined NO in the step S51-1, the result is YES in the step S51-3, and the high set hiset = 0 is set in the step S51-4.
The timer Shtim is counted, and since the count has not reached 100, the high set hi is set in step S51-7.
set is compared with the row set lostet. Initially, both are 0, so the result is NO. In step S51-8, the memory mf is compared with 2, and after looking at the steering wheel angle | θh |, in step S51-13, the low set lowset = high set hiset is set. Hereinafter, the same control is repeated,
By the time point a, the timer Shitim is set to 1 in step S51-6.
If it is not less than 00, the timer Shti is set in step S51-9.
Reset m. If Shtim is 100 or less by the point a, the time count is repeated.

At the point a, the answer is YES in the step S51-1 and in the step S51-2 the high set hiset = 1
Again, in step S51-5, the timer Shitim
Count, and since the count has not reached 100,
In step S51-7, the high set hiset and the low set loset are compared. Previously, step S51-13
In step S51-7, YES is set in step S51-7, and 1 is added to the memory mf in step S51-10.
In step S51-11, the timer Shitim is reset. In step S51-8, after the memory mf is set to NO as compared with 2 and the steering wheel angle | θh |
-13 low set lowset = high set hiset
Set to. Hereinafter, in step S51-6, the timer Sht
When im is 100 or less, step S5 is performed until point B is reached.
The control in which 1-7 is NO is repeated.

At point B, the answer is NO in step S51-1, the answer is YES in step S51-3, and the
At 51-4, the high set hiset = 0. Last time,
Since the timer Shtim has been reset in step S51-11, the timer Shtm is reset in step S51-5.
Since the count im has not reached 100, the high set hiset and the low set loset are compared in step S51-7. Previously, step S51-
13 and the row set losset = high set hiset =
Since it is set to 1, step S51-7 is YES
In step S51-10, 1 is added to the memory mf, and in step S51-11, the timer Shtim is reset. The memory mf becomes 2, the result is YES in step S51-8, and the output voltage flag Wolflag is set to 0 in step S51-12. Output voltage flag Vo
If lflag = 0, step S in FIG.
At 52 and S53, the command control voltage Vol to the first and second control valves 58 and 59 is set to 0.

That is, if the steering torque fluctuation continues for one cycle (from point A to point B) within a certain time (the count of the timer Shitim is less than 100 twice), it is determined that the steering torque fluctuation has occurred in a short cycle. , Output voltage flag Volflag
= 0, the command control voltage Vol is set to 0, and the assist control at the time of so-called tweaking is stopped.

If the steering torque tq2 is within the range of the control determination torque thresholds Tq00 and -Tq00 for a set time (count of the timer Shitim is 100), the output voltage flag Volflag is set to 1 in step S51-9, and the normal operation is performed. Control returns to.

As described above, in the steering cycle detection routine,
The plungers 44a and 44b are not operated at the time of a steering cycle that is short enough for the vehicle not to respond, so that unnecessary energy consumption and durability of the device are not reduced.

Returning to the main flow chart, as shown in FIG. 8, it is determined in step S8 whether the vehicle speed Vel is 15 km / h or more. If the vehicle speed Vel is 15 km / h or more, the vehicle speed flag is determined in step S9. By setting Vflag = 1, high-speed reaction force control can be executed. If it is determined in step S8 that the vehicle speed Vel is less than 15 km / h, it is determined in step S10 whether the vehicle speed Vel is 10 km / h or less. If the vehicle speed Vel is 10 km / h or less,
In step S11, the vehicle speed flag Vflag is set to 0, and control on the low speed side can be executed. Step S9 and Step S
After setting the vehicle speed flag Vflag to 0 or 1 in step 11, the state of the vehicle speed flag Vflag is determined in step S12. If the vehicle speed flag Vflag = 1, step S1 is executed.
Control of steering reaction force at high speed running in 3 (steering reaction force function:
(Described later), and if the vehicle speed flag Vflag is not 1, the main flowchart shown in FIG. 9 is executed.

When the vehicle speed Vel is 10 km / h or less, the assist control on the low speed side is performed. The centering control (centering control function) for assisting the steering wheel 13 in a neutral state depending on the driving conditions and the steering force of the steering wheel 13 are assisted. Steering force control (steering force control function).

As shown in FIG. 9, in step S14, it is determined whether or not the centering control is being performed, that is, the centering flag Cfl
It is determined whether or not ag = 1, and the centering flag Cfl
If ag = 1 is not satisfied, the steering torque t is determined in step S15.
The control determination torque threshold value Tq0 of q2 is set to a value of Tq00 which is a preset value. Centering flag C
If flag = 1, the steering torque tq is determined in step S16.
The control determination torque threshold Tq0 of 2 is a value obtained by multiplying a preset value Tq00 by a coefficient Kc (for example, 2 to 4) (Tq00 <Kc · Tq00).

That is, as shown by the dashed line in FIG. 23B, during the centering control (Cflag = 1), the control determination torque threshold value Tq0 is increased, and the steering torque tq2 is greatly reversed due to the inertia of the steering wheel 13. Even when turned,
The centering control is continued within the range of the control determination torque threshold Tq0.

In step S15 or step S16, the steering torque t in the steering force control or the centering control.
After the control determination torque threshold value Tq0 of q2 is set,
In the control setting routine of step S17, it is determined whether to perform the steering force control or the centering control.

The control setting routine in step S17 will be described with reference to FIG. In step S17, whether to perform steering force control (steering force control flag tqflag =
1), the steering force control is reset (tqf
lag = 0) It is determined whether the centering control can be executed.

As shown in FIG. 14, step S17-1
It is determined whether the absolute value | tq2 | of the steering torque is equal to or greater than the control determination torque threshold value Tq0. Immediately after the start of the operation, it is determined in step S14 that Cflag is not 1, so that the control determination torque threshold Tq0 becomes the set value Tq00.

When the absolute value | tq2 | of the steering torque tq2 is equal to or larger than the control determination torque threshold value Tq0, step S1 is executed.
At 7-2, the steering force control flag tqflag is set to 1 to enable the execution of the steering force control. Next, step S17-3
To set the control timer tqT to 0, and
At -4, Cflag = 0 is set to reset the centering control, and the process returns to the main flowchart.

If it is determined in step S17-1 that the absolute value | tq2 | of the steering torque tq2 is smaller than the control determination torque threshold value Tq0, the process proceeds to step S17-5.
Then, it is determined whether or not the command control voltage Vol to the solenoid units 58a, 59a for operating the second control valves 58, 59 is 0. If the command control voltage Vol has already been output, the process returns to the main flowchart. Step S17
If it is determined in step -5 that the command control voltage Vol is 0, the control timer tqT is counted in step S17-6 (tqTCNT), and in step S17-7, the value of the control timer tqT is 0.5 seconds or more. Judge. If the control timer tqT has not reached 0.5 second, the process returns to the main flowchart. If the control timer tqT has reached 0.5 second or longer, the steering force control flag t is determined in step S17-8.
By setting qflag = 0 (steering force control reset), centering control can be executed, and the process returns to the main flowchart.

That is, when the command control voltage Vol is 0 V and the state where the absolute value | tq2 | of the steering torque tq2 is smaller than the control determination torque threshold Tq0 is 0.5 seconds or more (section in FIG. 23). A), the centering control becomes executable. If the absolute value | tq2 | of the steering torque tq2 is equal to or larger than the control determination torque threshold Tq0, the immediate steering force control can be executed.

Thus, even if the value of the steering torque tq2 becomes temporarily smaller than the control determination torque threshold value Tq0 due to the torque fluctuation during the steering of the steering wheel 13, it is short (less than 0.5 second). There is no transition to centering control. Further, when the value of the steering torque tq2 becomes equal to or larger than the control determination torque threshold value Tq0, the steering can be immediately shifted to the steering force control, so that the steering wheel 13 can be stopped immediately even in the centering control.

After executing the control setting routine in step S17, the steering force control flag tqfla is set in step S18.
It is determined whether g = 1 or not, and the steering force control flag tqfla
When g = 1, the steering force control shown in FIG. 10 is executed. When the steering force control flag tqflag is not 1, that is, when the steering force control flag tqflag = 0, the centering control shown in FIGS. 11 and 12 is performed. Execute.

The steering force control shown in FIG. 10 will be described.

If it is determined in step S18 of FIG. 9 that the steering force control flag tqflag = 1, the process proceeds to step S18.
A steering direction is determined by a direction determination routine of 19.

The direction determining routine in step S19 will be described with reference to FIG. In the determination of the steering direction in step S19, the determination of the steering torque tq2 is performed using the reverse control determination torque threshold value (± Tq0), and the determination of the steering wheel angular velocity θhs is performed based on the value of the reverse steering wheel angular velocity. is there.

As shown in FIG. 15, step S19-1
It is determined whether or not the steering torque tq2 is equal to or more than (negative side control determination torque threshold value) -Tq0, and the steering torque tq2
If the value is equal to or more than the negative control determination torque threshold value -Tq0 (toward the positive side), the vehicle is set to the right steering state, and in step S19-2, it is determined whether the steering wheel angular velocity θhs is equal to or more than -5 deg / S.

If the steering wheel is actually steered to the right, the steering wheel angular velocity θhs becomes larger than -5 deg / S.
It is determined whether or not the steering direction flag tflag = 0 (left steering) in 9-3. If the steering direction flag tflag = 0, the previous target steering torque (described later) is determined in step S19-4.
Dtq1 (the initial value is set to 0) is set to 0, and in step S19-5, the steering direction flag t
It is assumed that flag = 1 is set to right steering control. If the steering is not rightward, the steering wheel angular velocity θhs ≦ −5 deg / S, and the flow returns to the main flowchart. Step S1
If it is determined in 9-3 that the steering direction flag tflag is not 0, the process proceeds as it is, and in step S19-5, the steering direction flag tflag is set to 1 and right steering control is performed.

That is, when right steering control is performed with the steering direction flag tflag = 1, as shown by the solid line in FIG. 24, the steering torque tq2 is determined by the left steering side control determination torque threshold value -Tq0, and Handle angular velocity θh
The determination of s is made based on the value of the negative steering wheel angular velocity on the left steering side.

If it is determined in step S19-1 that the steering torque tq2 is not equal to or greater than the negative control determination torque value -Tq0, then in step S19-6 the steering torque tq2 is equal to or less than the positive control determination torque threshold Tq0. If the steering torque tq2 is equal to or less than the positive-side control determination torque threshold Tq0 (toward the negative side), the steering is set to the left steering state, and if the steering angular velocity θhs is equal to or greater than 5 deg / S in step S19-7. Determine whether or not. If it is determined in step S19-6 that the steering torque tq2 is not equal to or less than the positive control determination torque threshold Tq0, and if it is determined in step S19-7 that the steering wheel angular velocity θhs is equal to or greater than 5 deg / S, Since the left steering state is not set, the process returns to the main flowchart.

In the actual left steering state, the steering wheel angular velocity θhs becomes smaller than 5 deg / S.
At -8, it is determined whether or not the steering direction flag tflag = 0 (right steering). If the steering direction flag tflag = 1, the torque difference dtq1 is set to 0 at step S19-9, and at step S19-10, the steering direction flag tflag is set. = 0 and left steering control. If it is determined in step S19-8 that the steering direction flag tflag is not 1, the process proceeds as is, and in step S19-10, the steering direction flag tflag = 0.
As left steering control.

That is, when the left steering control is performed with the steering direction flag tflag = 0, as shown by the dotted line in FIG. 24, the determination of the steering torque tq2 is performed based on the control determination torque threshold value Tq0 on the right steering side, and Angular velocity θhs
Is determined based on the value of the positive steering wheel angular velocity on the right steering side.

Therefore, when determining the steering direction of the steering force control, the determination of the steering torque tq2 is performed using the reverse control determination torque threshold value (± Tq0) and the steering wheel angular velocity θ
Since the determination of hs is made based on the value of the steering wheel angular velocity in the opposite direction, the steering torque fluctuation and the steering wheel angular velocity fluctuation occur due to various disturbances, noises, etc., and the steering torque tq2 and the steering wheel angular velocity θhs temporarily change to positive or negative. However, the steering direction does not repeatedly change (hunting phenomenon), and the steering direction can be switched quickly. To eliminate the hunting phenomenon, a filter circuit may be configured, but in this case, a delay occurs in determining the steering direction.

Returning to the main flowchart, when the steering direction is determined in the direction determination routine of step S19,
In step S20, it is determined whether the steering direction flag tflag = 1. According to the steering direction, step S21 (tf
lag = 1) or step S22 (tflag =
In 0), a torque difference dtq2 between the target steering torque ttq and the steering torque tq2 is calculated.

The target steering torque ttq in the low-speed steering force control is a preset value, which is set in step S1 in FIG.

Right steering (steering direction flag tqflag =
In the case of 1), in step S21, the value of the target steering torque ttq is subtracted from the value of the steering torque tq2 to obtain a torque difference dtq2.
And In the case of left steering (steering direction flag tqflag = 0), in step S22, the value of the target steering torque ttq is added to the value of the steering torque tq2, and the result in a negative state is defined as the torque difference dtq2.

After calculating the torque difference dtq2 according to the steering direction, the first and second control valves 58 and 59 are calculated in the torque control voltage calculation routine in steps S23 and S24.
The command control voltage Vol to be output to is calculated. Steps S23 and S24 perform the same processing.

The torque control voltage calculation routine in steps S23 and S24 will be described with reference to FIG. The command control voltage Vol in steps S23 and S24 is determined by increasing the command control voltage Vol when the torque difference dtq2 from the target steering torque ttq is a positive value larger than the previous torque difference dtq1. If it is smaller than this, the command control voltage Vol is reduced over time.

As shown in FIG. 16, step S23-1
It is determined whether or not the torque difference dtq2 is a positive value. If the value is a positive value, the torque difference dtq2 and the previous torque difference dtq1 (dtq1 is set to 0 in the first time) are determined in step S23-2. Be compared. When it is determined in step S23-2 that the torque difference dtq2 is equal to or larger than the previous torque difference dtq1, the torque difference dtq2 is set to 5 in step S23-3.
It is determined whether or not it exceeds 0, and an upper limit 50 of the torque difference dtq2 is set. If the torque difference dtq2 is equal to or less than 50, the process directly proceeds to step S23-4, where the torque difference dt
When q2 exceeds 50, the torque difference dtq2 is set to 50 in step S23-5, and the process proceeds to step S23-4. In step S23-4, dtq1 is replaced with dtq2, and the value of the torque difference dtq2 is set as the torque difference dtq1. Next, in step S23-6, the torque difference dtq1 is multiplied by the torque control proportional coefficient _KT , and the voltage 2.5V of the dead zone of the first and second control valves 58 and 59 is added to add the command control voltage Vol.
And

If it is determined in step S23-1 that the torque difference dtq2 is a negative value, or
If it is determined in Step 2 that the torque difference dtq2 is smaller than the previous torque difference dtq1, the previous torque difference dtq1 is lowered by one point in Step S23-7. Since the previous torque difference dtq1 needs to maintain a positive value, step S2
In 3-8, it is determined whether the previous torque difference dtq1 is a positive value. If the previous torque difference dtq1 is a positive value, the process directly proceeds to step S23-9, and if the previous torque difference dtq1 is a negative value, the process proceeds to step S23-9.
At 23-10, the previous torque difference dtq1 is set to 0, and the routine proceeds to step S23-9. In step S23-9, it is determined whether or not the command control voltage Vol is equal to or lower than 2.5V. If the instruction control voltage Vol in step S23-9 is determined to exceed the 2.5V, multiplied by a torque control proportional coefficient K _T in the torque difference dtq1 in step S23-12, the first and second control valves 58 , 59 dead zone voltage 2.5
The command control voltage Vol is obtained by adding V.

Step S23-6 and step S23
After calculating the command control voltage Vol at -12, step S
At 23-13, it is determined whether or not the command control voltage Vol exceeds 3.5 V, and the upper limit of the command control voltage Vol is set. When the command control voltage Vol is 3.5 V or less, the process returns to the main flowchart. When the command control voltage Vol exceeds 3.5 V, the command control voltage Vol is set to 3.5 V in step S23-14, and the process returns to the main flowchart.

That is, when the torque difference dtq2 is a positive value larger than the previous torque difference dtq1, the upper limit of this value is set to 50
And calculate the command control voltage Vol to obtain the torque difference dt.
When q2 is a negative value, the previous torque difference dtq1 is reduced by one point to calculate the command control voltage Vol. Only when the difference between the target steering torque ttq and the target steering torque ttq is large due to the fluctuation of the steering torque tq2 during steering, the command control voltage Vol is calculated. Is increased, and when the difference is negative, the command control voltage Vol is gradually decreased with the passage of time.

Thus, even if the steering torque fluctuates during the steering, the frequency of the fluctuation of the command control voltage Vol can be reduced.

Returning to the main flowchart, after calculating the command control voltage Vol in steps S23 and S24, in the case of right steering, the command control voltage V is calculated in step S25.
is output, and in the case of left steering, a command control voltage Vol is output in step S26. That is, in step S25,
A command control voltage Vol is output to a solenoid portion 58a of the first control valve 58 (hereinafter, referred to as a first control valve 58), and a solenoid portion 59a of the second control valve 59 (hereinafter, referred to as a second control valve 58).
0V is output to the control valve 59 to assist the steering force of the steering wheel 13 during right steering. Step S
At 26, the command control voltage Vol is output to the second control valve 59 and 0V is output to the first control valve 58 to assist the steering force of the steering wheel 13 during left steering.

Thus, the steering force control on the low speed side is executed.

Next, the centering control on the low speed side will be described with reference to FIGS. The centering control is for controlling the handle 13 to return to the neutral position.
Is steered to a neutral position.

If it is determined in step S18 shown in FIG. 9 that the steering force control flag Tqflag is not 1, it is determined in step S27 shown in FIG. 11 whether the absolute value | θh | of the steering wheel angle θh is not less than 120 deg. Is determined. If the absolute value | θh | is 120 deg or more, the flowchart shown in FIG. 12 is executed.

When the absolute value | θh | is 120 deg or more,
As shown in FIG. 12, it is determined in step S28 whether the centering flag Cflag = 0. First, since the centering flag Cflag = 0, step S2
9, the centering flag Cflag is set to 1 and
In step S30, the command control voltage Vol is set to 3.5V. After setting the command control voltage Vol to 3.5 V, it is determined in step S31 whether or not the steering wheel angle θh is 0 or more. If the steering wheel angle θh is 0 or more, the return direction flag Haflag is set to 1 at step S32 to return to the right (steering to the left), and if the steering wheel angle θh is negative, the return direction flag Haflag is set to 0 at step S33 to return to the left. (Steer back to the right). Step S
32, after setting the return direction flag Haflag in step S33, the centering control output routine in step S34 shown in FIG. 11 is executed.

In step S31, the absolute value | θh | of the steering wheel angle θh is equal to or greater than 120 degrees (step S27: FIG. 1).
It is determined whether the steering wheel angle θh at the time of 1) is positive or negative, and the returning direction of the steering wheel 13 is changed according to the determination result at this time in step S3.
2. Since the angle is set in step S33, the steering wheel angle θ
When h becomes small, the return direction does not change even if the sign of the steering wheel angle is reversed due to tire twisting or the like.

The centering control output routine in step S34 will be described with reference to FIG.

As shown in FIG. 19, step S34-1
It is determined whether the return direction flag Haflag = 1 or not.
In the case of rightward return (Haflag = 1), step S34
At -2, the command control voltage Vol is output to the second control valve 59 and 0 V is output to the first control valve 58. (FIG. 22
See section B where the left control voltage rises in (d). )
Conversely, in the case of leftward return (Haflag = 0), step S
At 34-3, the command control voltage Vol is output to the first control valve 58, and 0V is output to the second control valve 59. In steps S34-2 and S34-3, the command control voltage V
After outputting ol, the process returns to the main flowchart.

After returning to the main flow chart, it is determined in step S52 whether or not the output voltage flag Volflag = 0, and if the output voltage flag Volflag = 0 (see FIG. 21 described above), the process proceeds to step S53. The first and second control valves 58 and 59 are set to 0V. That is, it is determined whether or not so-called tweaking is being performed. In the case of tweaking, the assist control is stopped. After that, through the flowcharts of FIGS. 8, 9 and 11, FIG.
In step S28 of step 2, the centering flag Cflag =
It is determined whether it is 0 or not. At this time, the centering flag Cf
Since lag = 1, the command control voltage slow-up routine of step S35 is executed.

The command control voltage slow-up routine in step S35 will be described with reference to FIG. In the command control voltage slow-up routine, at the start of the centering control, the command control voltage Vol is increased until the handle angular velocity θhs is generated, and the command control voltage Vol is gradually shifted to a value reduced by a predetermined value when the handle angular velocity θhs is generated. , The handle 13 is always returned at a constant return speed regardless of the road surface μ.

As shown in FIG. 18, step S35-1
It is determined whether or not the steering angular velocity θhs is equal to or greater than the set value Shv.
At 5-2, 0.02 V is added to the command control voltage Vol to obtain a new command control voltage Vol. At step S35-3, the maximum voltage Volmax is changed from the command control voltage Vol by 0.25V.
Set to a lower value. Next, in step S35-4, it is determined whether or not the command control voltage Vol is equal to or higher than 4.5 V, and 4.5 is determined.
If it is not less than V, the command control voltage Vo is determined in step S35-5.
The flow returns to the main flowchart with 1 = 4.5V. If the command control voltage Vol is less than 4.5 V, it is determined in step S35-6 whether the command control voltage Vol is 2.5 V or less, and if it is 2.5 V or less, step S35-7.
, The command control voltage Vol = 2.5 V and the process returns to the main flowchart. If the command control voltage exceeds 2.5 V, the process returns to the main flowchart.

That is, until the steering wheel angular velocity θhs reaches the set value, the command control voltage Vol is increased by 0.02 V at a time until it reaches 4.5 V (see section C in FIG. 22D).

On the other hand, in step S35-1, the steering angular velocity θhs is equal to or greater than the set value Shv, ie, the steering angular velocity θh
If it is determined that s has occurred, the command control voltage Vol is reduced by 0.01 V in step S35-8, and
9, the command control voltage Vol becomes the maximum voltage Volmax (FIG. 2).
2 (d)) is determined. If the command control voltage Vol exceeds the maximum voltage Volmax, the process directly proceeds to step S35-4, where the maximum voltage Volmax is set.
In step S35-8, the command control voltage Vo
The control to lower 1 by 0.01 V is repeated (see section H in FIG. 22D). If it is determined in step S35-9 that the command control voltage Vol is equal to or lower than the maximum voltage Volmax, the command control voltage Vol is set to the maximum voltage Volmax in step S35-10, and steps S35-4 and S35 are performed.
After -6, the process proceeds to step S34 in FIG. The command control voltage Vol is the steering wheel angle θh in step S27 of FIG.
Is maintained at the value of the maximum voltage Volmax until the absolute value | θh |

That is, if it is determined in step S35-1 that the steering wheel angular velocity θhs has occurred, the command control voltage Vo
1 is reduced by 0.01 V at a time (step S35-8), and the maximum voltage Volmax which is a value reduced by a predetermined value (0.25V).
Transition slowly. As a result, when the return speed is generated in the steering wheel 13, the command control voltage Vol is gradually shifted to a value reduced by a predetermined value, and the return speed can be kept constant regardless of the condition of the road surface μ.

Returning to the main flowchart, the centering control proceeds and if it is determined in step S27 shown in FIG. 11 that the absolute value | θh | of the steering wheel angle θh is less than 120 deg, it is determined in step S36 whether the centering flag Cflag = 0. It is determined whether or not.

At step S36, centering flag Cf
If it is determined that lag = 0, the process proceeds to step S34,
When it is determined that the centering flag Cflag = 1,
In step S37, the absolute value | θh |
It is determined whether it is 5 degrees or more. Absolute value | θh | is 45
deg or more, that is, the absolute value | θh |
If it is not less than 120 ° and less than 120 °, it is determined whether or not the centering flag Cflag = 1 in step S38. If the centering flag Cflag = 1, the command control voltage slow-up routine is executed in step S35, and the centering flag Cflag is not 1. In this case, the command control voltage slowdown routine of step S39 is executed.

The command control voltage slowdown routine in step S39 will be described with reference to FIG. In the command control slowdown routine, the command control voltage Vol at the end of the centering control is gradually reduced in two stages, and the handle 13 is stopped smoothly.

As shown in FIG. 17, step S39-1 is executed.
It is determined whether or not the command control voltage Vol is 3.3 V or more. If the command control voltage Vol is 3.3 V or more, the command control voltage Vol is reduced by 0.02 V in step S39-2, and the new command control voltage V
and proceeds to step S34 in FIG. This is repeated until the command control voltage Vol becomes less than 3.3 V to reduce the command control voltage Vol by 0.02 V (FIG. 22).
(See section E in (d)).

In step S39-1, command control voltage Vol
Is determined to be less than 3.3 V, step S3
It is determined whether or not the command control voltage Vol is 2.3 V or more in 9-3. If the command control voltage Vol is 2.3 V or more, the command control voltage Vol is reduced by 0.005 V in step S39-4 to obtain a new command control voltage Vol. The process proceeds to step S34 in FIG. This is repeated until the command control voltage Vol becomes less than 2.3 V, and the command control voltage Vol is reduced by 0.005 V at a time (see section F in FIG. 22D).

When the command control voltage Vol decreases, step S
If it is determined in Step 39-3 that the voltage is less than 2.3 V, Step S3
In step 9-5, the command control voltage Vol is set to 0 V, and step S3 is performed.
In 9-6, the centering flag Cflag is set to 0, and the process returns to the main flowchart.

On the other hand, if it is determined in step S37 shown in FIG. 11 that the absolute value | θh | of the steering wheel angle θh is less than 45 degrees, the centering flag Cfl is determined in step S40.
It is determined whether or not ag = 2. Centering flag Cf
If lag = 2, the process proceeds to step S39. If the centering flag Cflag is not 2, the centering flag Cflag = 2 is set in step S41 and step S34.
Proceed to.

The centering flag Cflag = 2 is an execution flag of the command control voltage slowdown routine in step S39 when the absolute value | θh | of the steering wheel angle θh once becomes less than 45 degrees. That is, the steering wheel angle θ
When the absolute value | θh | of h is less than 45 deg, the centering flag Cflag is set to 2 and then the steering wheel 13 is returned too much by disturbance or the like, and the absolute value | θ of the steering wheel angle θh is set.
Even if h | becomes 45 degrees or more, Cf in step S38
lag = 1 is negative, and the process proceeds to the command control voltage slowdown routine of step S39.

As described above, the centering control on the low speed side is executed. In this centering control, even if the handle 13 is released, a torsional moment is generated in the torsion bar 9 by the control valves 58 and 59, and the handle 13 can be steered to the neutral position. The weight can be greatly reduced, and the steering wheel 13 is not left while being steered.

In this centering control, the return direction of the handle 13 is determined by the sign of the handle angle θh when the absolute value | θh | of the handle angle θh is 120 degrees or more. The control direction does not change even if the steering wheel changes, and the steering wheel 13 is over-controlled to the opposite side in anticipation of tire twisting or the like (FIGS. 22, 23 (a)).
(The middle P point), so that the handle 13 can be reliably returned to the vicinity of the neutral position.

When the steering wheel 13 is returned, the command control voltage Vol is increased until the steering wheel angular velocity θhs is generated. After the return, the command control voltage Vol is gradually shifted to a value reduced by a predetermined value, and the return speed is excessive. Because it is preventing
The return speed of the handle 13 can be made constant without being affected by the road surface μ. Further, when the steering wheel 13 is near neutral, the command control voltage Vol is gradually reduced in two steps, so that a sudden movement of the steering wheel 13 at the time of stopping can be prevented. For this reason, it is possible to smoothly start and stop the return of the handle 13.

Next, a description will be given of a high-speed steering reaction force control at a vehicle speed Vel of 15 km / h or more.

In step S12 in FIG. 8, Vflag
= 1, that is, when it is determined that the vehicle speed Vel is 15 km / h or more, a steering reaction force control routine of step S13 is executed.

The steering reaction force control routine in step S12 will be described with reference to FIG. In the control of the steering reaction force in step S12, the target steering torque tq is obtained from the vehicle speed Vel and the steering wheel angle θh, and the command control voltage Vol is determined according to the difference between the target steering torque tq and the actual steering torque tq2.
And the control direction.

As shown in FIG. 20, step S13-1
Calculates the target torque tq suitable for the current vehicle speed Vel and the steering wheel angle θh. That is, Vel-K shown in FIG.
A vehicle speed sensitive steering wheel angle torque coefficient KTV corresponding to the current vehicle speed Vel is read from the TV map, and a target torque tq is obtained by multiplying the vehicle speed sensitive steering wheel angle torque coefficient KTV by the steering wheel angle θh. In step S13-2, the steering torque t
The torque difference dtq2 is obtained by subtracting the target torque tq from q2.

In step S13-3, it is determined whether or not the torque difference dtq2 is equal to or greater than the set value -dtq on the right steering side. If it is equal to or greater than the set value -dtq, in step S13-4, the steering direction flag tflag is set to 1 and the right steering control is performed. As step S1
Proceed to 3-5. In step S13-3, the torque difference dtq2
Is smaller than the set value -dtq, in step S13-6, the torque difference dtq2 is changed to the set value d on the left steering side.
It is determined whether it is equal to or less than tq. When the torque difference dtq2 is equal to or smaller than the set value dtq, the steering direction flag tflag is set to 0 in step S13-7, and the left steering control is performed in step S13.
The process proceeds to -5, and if the torque difference dtq2 exceeds the set value, the process directly proceeds to step S13-5.

Here, the reason why the set value is set to ± dtq is that the set value has a range so that the steering direction does not change even if a torque fluctuation occurs temporarily due to disturbance or the like.

After the steering direction is determined, step S13
At -5, the command control voltage Vol is calculated. That is, the set value dtq is subtracted from the absolute value | dtq2 | of the torque difference dtq2, and this value is multiplied by a coefficient KoV to obtain a command control voltage Vol.

At step S13-8, the command control voltage Vol
Is negative or not, and if negative, step S13
At -9, the command control voltage Vol is set to 0, and step S13-
When the result is positive, in step S13-11, the dead band voltage 2.5V of the control valve is added to the command control voltage Vol, and the process proceeds to step S13-10 as a new command control voltage Vol.

In step S13-10, the steering direction flag t is set.
It is determined whether flag = 1 or not, and the steering direction flag tfl
If ag = 1, the command control voltage Vol is output to the first control valve 58 and 0 V is output to the second control valve 59 in step S13-12, and the steering direction flag tflag is set.
If = 0, the first control valve 58 is set in step S13-13.
And the command control voltage Vol is output to the second control valve 59.

That is, in the high-speed steering reaction force control, the control direction and the command control voltage Vol are determined by the torque difference dtq2 between the target torque tq and the steering torque tq2, and when the steering torque tq2 is large (particularly at the start of steering). Assist control is performed, and when the steering torque tq2 is small, reaction force control is performed, and a linear steering force is obtained.

As described above, the steering reaction force control function calculates the target steering torque of the steering wheel 13 (target torque tq),
Means are provided for determining the magnitude and direction of the assist force such that the steering torque tq2 becomes the target steering torque in accordance with the calculated torque difference dtq2 between the target steering torque and the actual steering torque tq2.

By the above-described steering force control and centering control on the low speed side and steering reaction force control on the high speed side, it is possible to realize a steering operation with a small burden under any steering conditions such as stationary, high-speed running, and sports running. it can.

As shown in the diagram of FIG. 28, the characteristic of the generated hydraulic pressure of the rotary valve 16 obtained in the above-described control is in-phase by the plunger 44a based on the absence of the control by the plungers 44a and 44b. A wide hydraulic range is obtained by adding upper and lower limits of the hydraulic range by the control and the hydraulic range by the reverse phase control by the plunger 44b.

For example, in the case of stationary steering, as shown in FIG. 29 (a), the conventional power steering device has a heavy steering start and requires a considerably large steering force over the entire steering angle range. By applying the control of the present invention, as shown in FIG. 29B, a characteristic is obtained in which the start of steering is light and the steering force changes in accordance with the steering angle. Further, in the case of steering in slalom running, as shown in FIG. 30 (a), the hysteresis is large and lacks a sense of response near neutral, but when the control of the present invention is applied, as shown in FIG. 30 (b). Characteristics with small hysteresis and a sense of response near neutral are obtained.

Therefore, it is possible to cope with environmental conditions such as long-distance high-speed running and aging of the driver. In addition, even in a vehicle equipped with additional functions such as a four-wheel drive vehicle and a four-wheel steering vehicle, the burden of steering operation is increased. Can be reduced.

In the above embodiment, the two control valves 5
Although the plungers 44a and 44b were driven using 8, 59, the invention is not limited to this.
Even if the plungers 44a and 44b are driven using the electromagnetic switching valve 75 for switching the position in the same manner as in the above embodiment,
A similar effect is achieved.

In the above-described embodiment, the overhang is provided on the input shaft and the plunger is provided on the output shaft. However, the invention is not limited to this, and the plunger is provided on the input shaft, the overhang is provided on the output shaft, and the torsion bar is provided. A torsional moment may be generated.

[0151]

According to the power steering apparatus for a vehicle of the present invention, the variable width of the steering force can be greatly increased, and the burden on the driver at the time of restoring the vehicle can be greatly reduced, and high-speed running, sports running, etc. Steering force according to the driving conditions can be obtained. Therefore, it is possible to cope with environmental conditions such as long-distance high-speed driving and aging of the driver, and further reduces the burden of steering wheel operation on vehicles equipped with additional functions such as four-wheel drive vehicles and four-wheel steering vehicles. can do.

In the centering control, the command control voltage is increased until the steering wheel angular velocity is generated, and the command control voltage is gradually shifted to a value reduced by a predetermined value when the return speed is generated. Regardless, the return speed can be kept constant, and the sense of discomfort can be reduced.

Further, since the pressed member of the valve driving mechanism is pressed by the pressing element from both sides in the circumferential direction of the input / output shaft,
The valve drive mechanism does not become longer in the axial direction of the input / output shaft, and the device can be reduced in weight and size.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a power steering device according to one embodiment of the present invention.

FIG. 2 is a sectional view of a steering mechanism.

FIG. 3 is a view taken along the line III-III in FIG. 2;

FIG. 4 is a view taken along line IV-IV in FIG. 2;

FIG. 5 is an explanatory diagram of the action of hydraulic pressure on a hydraulic chamber.

FIG. 6 is an explanatory diagram of the operation of the plunger corresponding to FIG. 5;

FIG. 7 is a graph showing a map of a characteristic of a discharge pressure according to a control voltage of a control valve.

FIG. 8 is a control flowchart of the power steering device.

FIG. 9 is a control flowchart of the power steering device.

FIG. 10 is a control flowchart of the power steering device.

FIG. 11 is a control flowchart of the power steering device.

FIG. 12 is a control flowchart of the power steering device.

FIG. 13 is a control flowchart of the power steering device.

FIG. 14 is a control flowchart of the power steering device.

FIG. 15 is a control flowchart of the power steering device.

FIG. 16 is a control flowchart of the power steering device.

FIG. 17 is a control flowchart of the power steering device.

FIG. 18 is a control flowchart of the power steering device.

FIG. 19 is a control flowchart of the power steering device.

FIG. 20 is a control flowchart of the power steering device.

FIG. 21 is a control flowchart of the power steering device.

FIG. 22 is a timing chart in low-speed assist control of the power steering device.

FIG. 23 is a timing chart in low-speed assist control of the power steering device.

FIG. 24 is a diagram illustrating a determination state of a steering torque.

FIG. 25 is a diagram illustrating a change in steering torque.

FIG. 26 is a graph showing a map of a vehicle speed-sensitive steering wheel angle torque coefficient according to the vehicle speed.

FIG. 27 is a cross-sectional view illustrating a state when the operating angle of the rotary valve is displaced to the leading side.

FIG. 28 is a graph showing the input and output pressures of a rotary valve whose operating angle has changed.

FIG. 29 is a graph showing a steering force at the time of stationary steering as compared with a conventional steering force.

FIG. 30 is a graph showing a steering force during slalom traveling steering as compared with a conventional steering force.

FIG. 31 is an overall configuration diagram of a power steering device according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 steering mechanism 5a output shaft 7 power cylinder device 8 front wheel 9 torsion bar 11 input shaft 13 handle 15 valve drive actuator 16 rotary valve 33 oil pump 42 overhang portions 44a, 44b plunger 58 first control valve 59 second control valve 64 Hydraulic circuit 70 Control unit (ECU)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tadao Tanaka 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-5-112249 (JP, A) JP Hei 5-69840 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B62D 6/02

Claims (2)

(57) [Claims] An output shaft connected to a steering wheel is connected to one end of a torsion bar, and an input shaft connected to a handle is connected to the other end of the torsion bar, and the steering wheel is operated in accordance with a steering operation of the handle. A steering mechanism that steers, a hydraulic pressure generating unit that generates a predetermined hydraulic pressure, and is provided between the input shaft and the output shaft of the steering mechanism, and is connected to the hydraulic pressure generating unit to perform steering operation of the steering wheel. A rotary valve that outputs a hydraulic assist force by relative displacement according to the torsion bar torsion; a cylinder mechanism that drives the steered wheels in a steering direction with hydraulic pressure from the rotary valve; and the input shaft of the steering mechanism. A pressurized portion provided between the output shaft and the input shaft or the output shaft. It has a pressing element provided on the other side of the input shaft or the output shaft to press the pressing part to both sides in the circumferential direction, and is independent of the torsion bar by the pressing of the pressed part by the driving of the pressing element. A valve drive mechanism for generating a torsional moment, a presser drive means for driving the presser of the valve drive mechanism by exciting an electromagnetic valve, and rotating the rotary valve in the same direction as the torsion direction of the torsion bar. A target assist force, which is a target value of the assist force obtained by rotating the rotary valve in a direction opposite to the torsion direction of the torsion bar, is set. Control means for exciting the electromagnetic valve to drive the presser of the valve drive mechanism so as to be a target assist force, The control means has a centering control function for generating an assist force for steering the steering wheel in a neutral state in a low-speed range where the speed of the vehicle is equal to or less than a predetermined value, and generates an assisting force in the same direction as the steering direction of the steering wheel in the low-speed range. A steering force control function to generate an assist force in the same direction as or in the opposite direction to the steering direction of the steering wheel in a high-speed range where the speed of the vehicle is equal to or more than a predetermined value. The control function includes means for increasing a command control voltage for exciting the electromagnetic valve until the steering wheel angular velocity occurs, and gradually shifting the command control voltage to a value reduced by a predetermined value when the steering wheel angular velocity occurs. A power steering device for a vehicle, comprising: 2. The control device according to claim 1, wherein
The centering control function determines that the handle is near neutral.
The command voltage is gradually reduced in two stages.
Power steering for a vehicle, comprising means for causing
Ring device.