JPH0569842A - Power steering device for vehicle - Google Patents

Abstract

PURPOSE:To reduce fatigue of a driver at steady turning by providing a second setting means in which an assisting force larger than the assisting force of a first setting means according to steady turning state is set. CONSTITUTION:A control unit 60 has a function to judge if it is in the steady turning state, that is, a steering wheel 13 held or not from outputs of a steering angle sensor 62 and a steering angular velocity sensor 63. When brought into the steady turning state, a control means which has been operated so far by an assisting force set by a first setting means is operated according to the assisting force set by a second setting means. Here, as the assisting force set by the second setting means is set at a value larger than the assisting force set by the first setting means and suitable for steady turning, a holding force of the steering wheel is reduced at steady turning. Thus, burden of a driver becomes smaller and fatigue of the driver can be reduced.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An automobile (vehicle) is equipped with a hydraulic power steering device for steering with a light operation.

In such a power steering system, a steering mechanism for steering the front wheels (steering wheels) to the left and right in accordance with a steering operation from a steering wheel, an oil pump, a rotary valve, a power cylinder device, and a flow path connecting each component. Hydraulic assist system (hydraulic assist mechanism)
Is provided to supply the hydraulic pressure obtained by the rotary valve that is displaced by the rotation of the handle to the power cylinder device,
Generating an assist force is performed. However, the handle force cannot be properly controlled only by the displacement of the rotary valve.

Therefore, in the conventional power steering system, the assist force is variable by providing a reaction force mechanism for varying the reaction force in the assist system and a control valve (control means) for controlling this reaction force mechanism. To
An appropriate steering characteristic is obtained by controlling using a sensor that detects the vehicle speed of the automobile and a sensor that detects the steering wheel angle. For example, the steering force is appropriately increased to lighten the steering force during steering in the stationary range and the low speed traveling range, while the steering force is appropriately decreased to be increased during steering in the middle and high speed traveling regions.

[0005]

In an automobile, turning traveling with a constant steering wheel angle cut into a certain amount, that is, steady turning traveling is performed during driving conditions, for example, during high speed traveling on a highway or the like. is there. Specifically, when entering from one highway to the other crossing highway, there is a case where the vehicle travels on a substantially circular (large radius) approach road. It can be said that it is a steady turning drive.

By the way, in such a steady turning traveling state,
The steering wheel is in a so-called steering-held state in which the steering wheel is kept cut, and the driver must hold the steering wheel during this period.

[0007] However, similarly to holding a certain object for a long time, it becomes a burden gradually. Over time, the heavy steering force becomes a heavy burden on the driver.

Therefore, there is a drawback that the driver is easily tired during steady turning. In particular, since the steering force of the power steering device becomes heavier (assist force: small) as the vehicle speed increases, the above-mentioned drawbacks are noticeable in high-speed traveling.

The present invention has been made in view of such circumstances, and an object thereof is to provide a power steering device for a vehicle capable of reducing driver's fatigue during steady turning traveling. It is in.

[0010]

In order to achieve the above object, the vehicle power steering apparatus of the present invention is provided with means for detecting a steady turning traveling state, and first setting means according to the steady turning traveling state. Second setting means in which an assisting force larger than the assisting force of the second setting means is provided, and when the steady turning traveling state is detected, the assisting force of the first setting means is gradually changed to the assisting force of the second setting means. A means for operating the control means for varying the assist force according to the assist force to be transferred and the assist force of the second setting means in accordance with the detection of the steady turning traveling state is provided. ..

[0011]

According to the power steering apparatus for a vehicle of the present invention, for example, when the steering wheel is turned to a predetermined steering angle to enter a steady turning traveling state during traveling at middle and high speeds, the vehicle is operated by the assist force set up to the first setting means. The control means that has been operated operates according to the assist force set in the second setting means.

Since the assisting force set in the second setting means is set to a value larger than the assisting force set in the first setting means and suitable for a steady turning traveling state,
During steady-state turning, the steering holding force of the steering wheel becomes smaller than when the vehicle simply goes straight and is cut / returned. Therefore,
The driver holding the steering wheel is less burdened by it. That is, the driver's fatigue can be reduced.

Moreover, since the assist force (first setting means) corresponding to the vehicle speed and steering gradually changes to the target assist force (second setting means) according to the target steady turning traveling state, the driver is kept safe. The steering feeling is good without having to be aware that the steering force has changed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in FIGS.

FIG. 1 shows the construction of a power steering device for steering the left and right front wheels (steering wheels) of an automobile, and 2 is a rack and pinion type steering gear constituting the steering mechanism 1.

The steering gear 2 has a structure in which a rack 3 and a pinion 5 are built in a casing 3, for example. One end of the rack 4 is connected to one front wheel (not shown) of the vehicle via a steering rod 6, a tie rod, and a knuckle. The other end is connected to the other front wheel 8 (steering wheel) of the automobile through a steering rod 6, a power cylinder device 7, a tie rod, and a knuckle (neither is shown).

The lower end of a torsion bar 9 is connected to the pinion 5 of the steering gear 2. The upper end of the torsion bar 9 penetrates the valve unit 10 provided on the upper portion of the steering gear 2 and is connected to the input shaft 11 and the steering shaft 12. The end of the steering shaft 12 is the handle 1
When the rotational displacement is input from the steering wheel 13, the front wheels 8 and 8 (only one of which is not shown) are steered via the steering shaft 12, the torsion bar 9, the pinion 5, the rack 4, and the steering rod 6. It's horny.

In the valve unit 10, a housing 14 is installed in the upper part of the casing 3 so as to surround the torsion bar 9, and a reaction mechanism 15 (control means) and a rotary valve 16 are provided inside the housing 14 from below. The structure is used.

As is well known, the rotary valve 16 is provided with a cylindrical outer valve 17 on the inner surface of the housing 14,
The input shaft 11 is provided with a cylindrical inner valve 18 which is combined with the outer valve 17. That is, the rotary valve 16 is configured such that when the torsion bar 9 is twisted by the handle force 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 has an inflow port body 19 provided in the housing 3.
The outflow port 18a formed in the inner valve 18 communicates with the outflow port body 20 provided in the housing 3. The output port formed on the outer valve 17 communicates with a pair of output port portions 21 and 22 provided on the housing 3. This output port section 21,2
2 is connected to the power cylinder device 7.

That is, in the power cylinder device 7, the piston rod 24 is slidably provided so as to penetrate the cylinder 23, and the cylinder 2 is provided in a part of the piston rod 24.
Piston 25 so that 3 is divided into both sides in the longitudinal direction (left and right)
Is provided and configured. A pair of input ports 2 communicating with the left and right chambers 25a and 25b partitioned by the piston 25
6, 27 are connected to the output port sections 21, 22 via the flow paths 28, 29.

An oil pump 40 having a relief valve driven by an automobile engine (not shown) and an oil reservoir 4 are provided between the inflow port body 19 and the outflow port body 20.
2 are connected via a flow path 43. With this hydraulic circuit, according to the relative displacement between the outer valve 17 and the inner valve 18 of the rotary valve 16, the rotary valve 16 can supply the hydraulic pressure according to the steering force and the steering direction to the chambers 25a and 25b of the power cylinder device 7. I am trying. That is, the front wheels 8, 8 can be steered while hydraulically assisting the steering wheel force. As the oil pump 40, a pump having a characteristic that the discharge flow rate to the rotary valve 16 changes according to the pump rotation speed is used.

Further, the reaction force mechanism 15 includes an inner valve 17
Of the input shaft 11, that is, the lower end of the input shaft 11 is extended downward. On the outer peripheral surface of the pressed portion 30, as shown in FIG.
One recess 31 is formed at equal intervals. Further, in the portion inside the housing 14 around the pressed portion 30, each recess 3 is formed.
The reaction force plungers 32 are respectively provided at the portions facing the position 1
A holder 33, which is movably installed inside, is provided. A convex portion 34 that engages with the concave portion 31 is provided at the tip of each reaction force plunger 32. Further, a chamber 35 is formed behind each reaction force plunger 32. Each chamber 3
5 communicates with the inflow port 39 provided in the housing 14 via the annular flow path 36, and the hydraulic force is supplied from the inflow port 39 so that the pressed portion 30 is sandwiched by the reaction force plungers 32. I try to press it. That is,
As the hydraulic pressure in each chamber 35 increases, the input shaft 11 is strongly pressed. As a result, a feeling of reaction (reaction force) is generated in the handle 13. Reference numeral 37 is a return path provided in the holder 33 for communicating the flow path 36 with the outlet body 20 through the space inside the inner valve 18, and 38 is an orifice provided in the return path 37. .

On the other hand, as shown in FIG. 1, the reaction force mechanism 1 is provided between the oil pump 40 and the oil reservoir 42.
Pressure control valve 41 for controlling the supply pressure of 5
(Control means: hereinafter referred to as PCV41) is provided. The PCV 41 includes a spool valve body 4 in a cylindrical cylinder space 46 formed inside a valve housing 45.
7 is provided slidably. This spool valve body 4
The lower end of 7 is connected to a plunger 49 of a solenoid 48 installed in the lower part of the valve housing 45, and according to the excitation control of the solenoid 48, the spool valve body 47
The entire structure of the above can be displaced upward. The spool valve body 47 is returned by a spring 50 provided at the upper end of the cylinder space 46.

Band-shaped annular grooves 51 and 52 are formed on the outer peripheral surface on the upper stage side and the outer peripheral surface on the lower stage side of the spool valve body 47. Further, inside the spool valve body 47, an annular groove 51
A through passage 53 is formed so as to connect the ring groove 52 with the ring groove 52. The communication state between the inflow port 54 provided in the valve housing 45 can be varied between the annular groove 51 and the peripheral surface portion around the annular groove 51.
The inflow port 54 communicates with the flow path 43 connected to the oil pump 40. The annular groove 52 is always in communication with the output port 55 provided in the valve housing 45. The output port 55 corresponds to the reaction mechanism 15 described above.
Is connected to the inflow port 39 through the flow path 56.

The annular groove 51 and the inflow port 39 are set when the axial force of the plunger 49 is the largest (when the plunger 49 is protruded to the uppermost position; for example, the Max current value is 1.0).
A), the inflow port 39 is set to a state of being blocked (closed), and as the axial force of the plunger 49 becomes smaller (current value becomes smaller) (plunger 49 lowers), communication is performed,
At that time, the communication area is increased. As a result, according to the excitation of the solenoid 48, the handle 1
A feeling of reaction (reaction force) is generated in 3 (assist force: small). A drain passage 57 is formed inside the spool valve body 47 so as to pass through a coaxial center portion for the drain, and the drain passage 57 is connected to the oil reservoir 42 via an outflow port 58 provided in the valve housing 45. To the flow path 43 connected to the. The hydraulic circuit configured in this way constitutes an assist system 44 (assist mechanism) for assisting the steering of the front wheels 8 and 8 together with the control system.

The solenoid 48 is provided with a control unit 60 composed of a microcomputer and its peripheral circuits. Further, the control unit 60 includes a vehicle speed sensor 61 for detecting the vehicle speed of the automobile, a steering wheel angle sensor 62 for detecting the steering angle of the steering wheel 13, a steering wheel angular velocity sensor 63 for detecting the steering angular velocity of the steering wheel 13, and a response in normal mode and sports. A mode changeover switch 64 for changing over to the mode is provided and constitutes a control system for controlling the hydraulic pressure acting on the reaction force plunger 49.

By using the circuit of this control system, the difference between the steering wheel force at the time of cutting and the steering wheel force at the time of returning is reduced, the steering wheel force is changed according to the steering wheel angular velocity at each cutting, and the steering wheel force is changed at the time of steady turning. I am making it smaller. The control unit 60 has the following functions.

That is, the control unit 60 has a vehicle speed map in which the reference current AN corresponding to the vehicle speed is divided into modes (normal, sports) as shown in FIG.
A steering speed map shown by a solid line for obtaining a steering state coefficient (a value required for obtaining a control current value of the solenoid 48) according to the steering wheel angular velocity as shown in FIG. 4, and as shown by a solid line in FIG. A steering holding map is set for obtaining the control value AM (control current of the solenoid 48) during steady turn traveling according to various vehicle speeds. It should be noted that each of the maps has a value that produces an optimum assist force.

The control unit 60 has a function of judging whether the steering wheel is in a steering state or a neutral state based on the outputs of the steering wheel angle sensor 62 and the steering wheel angular velocity sensor 63. It has a function of judging whether it is time, and a function of judging whether it is a normal mode or a sports mode by turning on / off the mode changeover switch 64.

The control unit 60 also reads the reference current A corresponding to the vehicle speed from the map of FIG. 3 and the coefficient Kθ corresponding to the steering wheel angular velocity at the time of cutting and returning from the map shown in FIG. , Coefficient K
Using θ, a predetermined mathematical expression “A × KθM (memorized coefficient K
θ) × KM ”, it has a function of calculating a control current for obtaining an appropriate assist force according to the vehicle speed and steering.

Here, a coefficient KM which is different at the time of cutting and at the time of returning is given to the above formula in advance. Specifically, the microcomputer constituting the control unit 60 is set with “1.0” as a cutting coefficient used for calculating the control current at the time of cutting, and as a return coefficient used for calculating the control current at returning, for example, "0.8" is set to be 20% smaller, and the assist force is set smaller at the time of returning from the difference between these set values than at the time of cutting.

The control unit 60 has a function of detecting the peak value of the steering wheel angular velocity at the time of cutting from the steering wheel angular velocity sensor 63 and calculating the control (driving) current according to the coefficient Kθ read from the detected value. is doing. As a result, the handle force is changed according to the angular velocity of the handle for each cut.

Further, in the control unit 60, based on the outputs of the steering wheel angle sensor 62 and the steering wheel angular velocity sensor 63, a steady turning traveling state, that is, the steered steering wheel 13 is obtained.
Has a function of determining whether or not the steering wheel is a steering wheel. The control unit 60 has a function of reading the control current value according to the vehicle speed from the steering holding map of FIG. Further, the control unit 60 calculates a change amount between the control current value AM read from the steering holding map and the control current value A (straight running state) which is obtained only according to the vehicle speed map before steering, and corresponds to the change amount. It has a function of gradually shifting from the calculated control current value (according to the vehicle speed map and the steering map) to the control current value read from the steering holding map by the number of steps. Further, the control unit 60 has a function of driving the solenoid 48 according to the shifting control current value, and from these functions, when the vehicle is in a steady turning traveling state, the assist force set at the time of cutting is gradually increased. The assist power is changed to be suitable for steering. The value set in the steering holding map is set to a value (assist force: large) larger than the control current value A of the solenoid 48 obtained according to the vehicle speed map. The flowcharts of FIGS. 6 to 10 show the control operation in the control unit 60. Next, the control operation in the control unit 60 will be described with reference to the flowchart.

The control unit 60 is activated by the ON signal of the ignition key switch of the automobile.
Then, first, in step S1, the initial setting is performed, the cut flag FLF indicating that the handle 13 has been cut is "0", the return flag FLR indicating that the handle 13 has returned is "0", and the memory Kθ value KθM is “1.0”, the cut / return coefficient KM is “1.0”,
The change flag counter CNT is set to "0", and the change flag CHF indicating that the cut has been changed to the return is set to "1".

Then, in step S2, a hold flag HFL indicating that the steering wheel 13 is being held.
G is set to "0", the timer HTM that counts the steering time of the steering wheel 13 is set to "0", and the control flag CFLG is set to "0".

Thereafter, in steps S2 to S5, the vehicle speed V detected by the vehicle speed sensor 61 and the steering wheel angle θ of the steering wheel 13 detected by the steering wheel angle sensor 63.
H, the steering wheel angular velocity θh of the steering wheel 13 detected by the steering wheel angular velocity sensor 63 is read.

At step S6, the steering wheel angular velocity θ
It is determined whether or not the absolute value of h is larger than “30 deg / s”. Further, in step S7, the steering wheel angle θ
It is determined whether or not the absolute value of H is larger than “5 deg”. From these, it is determined whether the vehicle is currently in a straight traveling state (around steering neutral) or in a steered state.

That is, when the vehicle is in a straight traveling state as indicated by a region α on the left side of FIG. 11, the steering state is near neutral (absolute value θh> 30 deg / s, absolute value θH).
> 5 deg).

If the vehicle is traveling straight ahead, step S
Resetting of steering holding control in 8 (hold flag HF
After setting LG to "0", timer HTM to "0", control flag to "0" and KθM value of "1.0" in step S9 shown in FIG. 7, step S10
Proceed to.

In step S10, the current steering mode of the vehicle is changed from on / off of the mode changeover switch 64 to
It is determined whether the "normal mode" suitable for normal driving or the "sport mode" suitable for sports driving.

If the "normal mode" is determined at this time, the process proceeds to step S11. In this step S11, the control current value AN corresponding to the current vehicle speed of the vehicle is read from the normal mode diagram shown by the "vehicle speed-control current" map in FIG. As a result, the reference drive current is obtained. In step S12, the corrected control current value A is obtained according to the arithmetic expression “AN × KθM × KM”.

Then, in step S13, the current of the obtained control current value A is supplied to the solenoid 48. Specifically, when the vehicle speed is low, the solenoid 48 is supplied with a drive current of 1.0 A (Max) at which the axial force of the plunger 49 is the largest. As a result, the plunger 49 of the solenoid 48 projects to the uppermost position, and holds the spool valve element 47 of the PCV 41 at the position where the inflow port 54 is blocked. That is, the discharge pressure of the oil pump 40 does not act on each chamber 35 of the reaction mechanism 15. As a result, there is no force to press the reaction force plunger 32 against the pressed portion 30 of the input shaft 11, and this state continues during neutral steering.

When the vehicle speed is high, a driving current of 1.0 A or less is supplied, the current difference, the prudjan 49 is held in the lowered position, the inflow port 54 is opened, and the current discharge pressure of the oil pump 40 is the reaction force. It is supplied to each chamber 35 of the mechanism 15.

That is, when the vehicle speed is high, the pressure portion 30 of the input shaft 11 is pressed by the reaction force plunger 32 by the discharge pressure of the oil pump 40, and the handle 1
Make 3 an appropriate weight.

If the "sport mode" is determined in step S10, the process proceeds to step S14, and FIG.
The control current value A corresponding to the current vehicle speed of the automobile is read from the sports mode diagram indicated by the "vehicle speed-control current" map of.

With the control current value A as a reference, the corrected control current value A is obtained in the same manner as in steps S12 and S13, and the reaction force plunger 3 of the reaction force mechanism 15 is obtained.
Control 2 By repeating these steps,
Appropriately control the steering force for straight running under all conditions. Next, it is assumed that the steering wheel 13 is turned to the left side, for example, as shown by a β region in FIG.

Then, it is determined that the steering wheel 13 is turned off by determining whether or not the steering wheel angular velocity is greater than 30 deg / s in step S6, and the change flag CFLG including steps S14 and S15 in FIG. After reset processing, step S
Proceed to 20. In step 20, it is determined whether or not “θH × θh” is larger than “0”, that is, whether the current steering state is the cut or the return. Here, if the handle 13 is cut like the region β, the value in step S20 becomes larger than "0" (positive) by the above calculation.

That is, the process proceeds to step S21, and in this step S21, it is determined whether or not there is a return before this cutting. That is, this is determined by whether or not the return flag FLR is set to "1".

The first cut does not return before that, that is, since the return flag FLR is reset to "0", the process proceeds to steps S22 to S24, the change flag CHF is reset to "0", and the cut flag is set. FL
F is set to "1" and the cut coefficient KM is set to "1.0". Then, the diagram indicated by the solid line of the "steering speed map" in FIG. 4 is set as it is as the map on the cutting side. As a result, the setting of the cut is made when the return is not performed before the cut.

Subsequently, in step S25 shown in FIG. 9, the coefficient Kθ corresponding to the absolute value of the steering wheel angular velocity θh read from the map on the cutting side indicated by the solid line shown in the “steering velocity map” of FIG. read. As a result, the coefficient Kθ corresponding to the steering state of the steering wheel angular velocity θh is obtained. Next, at step S26, it is judged if the change flag CHF is "1". Here, this cut is not a cut after returning. That is, the change flag CHF is set to "0" in step S22.

Therefore, the process proceeds to step S27. In this step S27, the coefficient Kθ read from the steering speed map is the coefficient value KθM (coefficient KM) stored in memory.
(Maximum value of), it is less than or equal to.

Here, as shown in FIG. 11, the steering wheel angular velocity is small at the beginning of the cut and gradually increases to reach a peak. In this behavior, "3
For 0 deg / s or more, “Kθ ≦ KθM” is satisfied. Then, the process proceeds to step S28, KθM is updated (peak hold) to Kθ read in step 25, and then the process proceeds to step S10. In steps S10 to S14, the processing described above is performed.

That is, the control current value AN corresponding to the current vehicle speed is read from the map of the "normal" or "sports" mode, and the corrected control current value A is calculated according to the arithmetic expression "AN × KθM × KM". And solenoid 4
Drive eight.

Here, as shown in FIG. 4, Kθ set in the solid line (cut side) diagram has a large value in a region where the steering wheel angular velocity θH is small, and a small value in a region where the steering wheel angular velocity θh is large, and an intermediate region. Is a fluctuating intermediate value, and a value smaller than KθM is read from this region, and the calculated control current A is a smaller control current A than in the straight traveling state.

This means that the current difference, the plunger 49 is held at the lowered position, and the current discharge pressure of the oil pump 40 is supplied to each chamber 35 through the inflow port 54 which opens as the plunger 49 descends.

That is, the pressed portion 30 of the input shaft 11 is pressed by the reaction force plunger 32, and the handle force during steering is adjusted to an appropriate weight (= appropriate assist force) according to the driving situation determined by the steering wheel angular velocity. To do. By repeating such steps, the handlebar force is properly controlled moment by moment during the time when the handlebar 13 in the β region of FIG. 11 is turned off.

Further, when the notch is finished like the region γ in FIG. 11 and the notched handle 13 is immediately returned, the process proceeds from step S6 to step S14 to step S20. The value calculated in this step S20 is " The value is smaller than 0 (negative).

That is, the return side is determined, and step S3
Go to 0. In this step S30, it is judged whether or not there is a cut before this returning. this is,
It is determined whether or not the cut flag FLF is set to "1". Here, at the time of the previous cutting, since the cutting flag FLF is set to "1" in the above step S23, this return is a return after the cutting.

Therefore, step S61 and step S62
To reset the cutting flag FLF to "0",
The change flag CHF is set to "1". This resets the return after cutting.

Then, in step S34, the return flag FLR is set to "1", and then in step S35, the return coefficient KM is set to "0.8". As a result, FIG.
20% from the cut side of the solid line shown above, which is indicated by the broken line
The low diagram is set as the "steering speed map".

Then, in step S25, the coefficient Kθ corresponding to the absolute value of the steering wheel angular velocity θh is read from the diagram on the return side of the "steering velocity map" indicated by the broken line, and in step S26 the change flag CHF is set to "1". It is determined whether or not

At this time, since the change flag CHF is set to "1" in step S62, the process proceeds to step S50, and the change flag CHF is counted as once. Then, in step S51, it is determined whether or not the count is "2". The count here determines a steering cycle in which cutting, returning, and cutting are repeated. Since the count of the counter is "once", the process proceeds to step S27.

In step S27, the coefficient K read from the map of the steering speed is the same as in the previous cut.
It is determined whether θ is smaller than or equal to the stored coefficient value KθM (maximum value of the coefficient KM).

Here, as shown in FIG. 11, the steering wheel angular velocity is small at the beginning of returning and gradually increases to reach a peak. In this behavior, "30d
For “eg / s or more”, “Kθ ≦ KθM” is satisfied. That is, the process proceeds to step S27, KθM is updated (peak hold) to Kθ read in step 25, and then the process proceeds to step S10. Then, step S10 to step S
Proceeding to 14, the processing described above is performed.

That is, the control current value AN corresponding to the current vehicle speed is read from the map of the "normal" or "sports" mode, and the corrected control current value A is calculated according to the arithmetic expression "AN × KθM × KM". And solenoid 4
Drive eight.

Here, as shown in FIG. 4, Kθ set by the dashed line diagram on the return side has a large value in a region where the steering wheel angular velocity θh is small, is small in a region where the steering wheel angular velocity θh is large, and is in an intermediate region. Is a fluctuating intermediate value and is 20% smaller than that at the time of cutting, so the control current A calculated at step S12 is "20" smaller than the control current A calculated at the time of previous cutting by such a value. % "Less control current A is calculated.

Then, the plunger 49 is held at a position lower than the position at the time of cutting, and through the inflow port 54 which opens as the plunger 49 descends.
The current discharge pressure of the oil pump 40 is supplied to each chamber 35. As a result, the pressed portion 30 of the input shaft 11 is pressed by the reaction force plunger 32 more strongly than at the time of cutting. Here, this original handle 1
If the returning operation is continued after the returning processing of step 3, the determination in step S30 is changed.

That is, since the cutting flag FLF is reset to "0" in the above step S61, regarding the returning after the returning operation of the handle 13 performed after the cutting, the current returning is performed before that by the step S30. Is determined to have not been performed. Then, the process proceeds to step S33, and the change flag CHF is reset to "0". This sets this return as not a replacement for the notch.

Then, like the initial return (return after cutting), the return flag FLR is set to "1" in step S34, the return coefficient KM is set to "0.8" in step S35, and step S25. In step S26, the coefficient Kθ corresponding to the absolute value of the steering wheel angular velocity θh is read from the diagram on the return side indicated by the broken line in the “steering speed map”, and then the process proceeds to step S26. Step S26
At, it is determined whether the change flag CHF is "1".

Since the change flag CHF is reset to "0" in step S33,
The process proceeds to step S26, and thereafter, the same processing as in the initial return (return after cutting) is repeated. By repeating such steps, during the time when the handle 13 in the γ region of FIG. 11 is returned, the handle force is appropriately controlled moment by moment with the passage of time. On the other hand, when the handlebar 13 that has been returned is subsequently cut to the right side to be turned, the process proceeds from step S20 to step S21.

In this case, since the flag indicating the cut after the return is set, that is, the return flag FLR is set to "1" in step S34, the process proceeds to steps S40 to S41 by the determination of step S21, and the return is performed. The flag FLR is reset to "0" and the change flag CHF is set to "1". This resets the cut after returning. Next, step S2
3. Proceeding to step S24, the cut flag FLF is set to "1" and the cut coefficient KM is set to "1.0".

Then, in step S25, the coefficient K corresponding to the absolute value of the steering wheel angular velocity θh is determined from the diagram on the cutting side indicated by the solid line in the "steering velocity map" of FIG.
Read θ. As a result, the current steering wheel angular velocity θh
The coefficient Kθ corresponding to the steering state of is calculated. Next, at step S26, it is judged if the change flag CHF is "1".

In this case, since the change flag CHF is set to "1" in step S41,
In step S50, the change flag CHF is counted. Succeedingly, in a step S51, it is determined whether or not the count is "2".

Here, in step S50, the change flags CHF at the time of both returning and cutting are counted, so the number of times is "2". The count “2” here indicates one steering cycle in which the notch, the return, and the notch are one steering. As a result, the process proceeds to step S53, the counter is reset to "0" in step S53, and then the process proceeds to step S28. In step S28, K? M is updated to K? Read in step S25, and then the process proceeds to steps S10 to S14.

Here, what large value Kθ is,
That is, even if the value is larger than KθM, the KθM value that serves as a reference thereafter is set by updating (KθM cancellation for each steering cycle). After step S10, the control current A corresponding to the traveling situation is calculated and the solenoid 48 is driven, as in the case of the previous cutting. If the cutting operation is continued after the initial cutting of the handle 13, the determination in step S21 is changed.

That is, since the return flag FLR is reset to "0" in step S40, the current cutting is returned to the previous cutting in step S21 for the cutting after the initial cutting operation of the handle 13. Determine that it is not. That is, the process proceeds to step S22 and the change flag CHF
Is reset to "0". This sets this notch as not a replacement.

Then, similarly to the initial cut (cut after return), the cut flag is set to "1" in step S23, the cut coefficient KM is set to "1.0" in step S24, and step S25.
In step S26, the coefficient Kθ corresponding to the absolute value of the steering wheel angular velocity θh is read from the diagram on the cut side indicated by the solid line of the “steering speed map”, and then the process proceeds to step S26.

Here, since the change flag CHF is reset to "0" in step S22, the process proceeds to step S27, and thereafter, the same processing as the initial cut (cut after return) is repeated. By repeating such steps, during the time when the handle 13 is turned, the handle force is appropriately controlled moment by moment as the time elapses.

When the cut handle 13 is returned, the above-described returning process is performed, and the handle force is appropriately controlled moment by moment during the time during which the handle 13 is returned. On the other hand, following this return, it is assumed that the steering wheel 13 is turned to the left side and the vehicle makes a steady turning traveling (during middle-high speed traveling). When the steering wheel 13 is cut, it is processed according to the control routine based on the steering wheel angular velocity described above.

When the movement of the handle 13 stops from this cut, the determination in step S7 is changed. That is, since the handle 13 is cut and stopped, it is determined in step S7 that the handle angle is larger than 5 deg, and the process proceeds to step S70 shown in FIG.

In step S70, it is determined whether or not the hold flag HFLG is "1". That is, in this step S70, it is determined whether or not this state is the state after cutting.

Since the hold flag HLFG has been reset to "0" in step S2,
In step S71, the hold flag HFLG indicating that the routine has proceeded to the steering holding force routine is set to "1", and the timer HTM is reset. afterwards,
Proceeding to step S10, the solenoid 48 is driven according to the control current value A obtained only by the vehicle speed map, as in the case of straight running.

The control by the vehicle speed is continued by the subsequent determination in step S70, the timer count in step S72, and the timer count in step S73.

Meanwhile, in step S6, "the steering wheel angular velocity is smaller than 30 deg / s", and step S6
In FIG. 7, if the state that “the steering wheel angle θH is larger than 5 deg” is continuously discriminated for a predetermined time, for example, 3 seconds, the steering wheel 13 stops moving at the cut position, that is, in FIG. It is determined that the steering wheel 13 is being held, as indicated by δ. That is,
It is detected during these three seconds whether or not the steering is being held.

If the steering wheel 13 is turned or returned again during the detection of the steering holding condition, that is, during the detection, the process proceeds from step S6 to step S14, and the control routine by the steering wheel angular velocity described above is performed. .. When it is determined in step S73 that the steering is being held (continuous for 3 seconds), the process proceeds to step S74. In step S74, it is determined whether the control flag CFLG is "1". That is, it is determined whether or not the steering holding force is controlled. Since the control flag CLFG has been reset to "0" in step S2, the process proceeds to steps S75 to S77.

That is, in step S75, as shown in FIG.
The control current value AM corresponding to the current vehicle speed of the automobile is read from the diagram indicated by the solid line of "vehicle speed-current". As a result, the control current value of the solenoid 48 suitable for steering is obtained. At step S76, the current control current value A
The change amount between M and the control current value A obtained only by the vehicle speed map at the present step S12 is obtained by the following formula. Δi = (AM-A) / (2 / INT) where IN
T: interval That is, the addition amount per step in 2 seconds is obtained.

In step S77, after the control flag CFLG indicating that such processing has been set to "1", the process proceeds to step S10, and the solenoid 48 is driven according to the control current value AN obtained by "vehicle speed-current". To do.

Again, through steps S7, S70, S72 and S73, step S
When it reaches 74, the control flag CFLG is set to "1" in step S77 this time.
It proceeds to step S80.

In step S80, the counter adds the calculated addition amount to the control current value A. As a result, the control current value A (current value obtained from the vehicle speed map) approaches the control current value AM (current value obtained from the steering holding map).

After that, the routine proceeds to step S81, where it is judged if the control current value A (current value obtained by the vehicle speed map) becomes the control current value AM (current value obtained by the steering holding map) or not. If not, proceed to step S13. The solenoid 48 is driven by the added control current value A.

Then, the solenoid 48 is added by the addition of the current value.
Plunge 49 of the above protrudes upward from the current position and closes the inflow port 54. As a result, the pressure acting on each chamber 35 of the reaction force mechanism 15 decreases, and the force for pressing the pressed portion 30 of the input shaft 11 decreases.
As a result, the assist force is increased and the steering force, that is, the steering holding force is reduced.

By repeating such steps, the control current value A obtained from the vehicle speed map gradually shifts stepwise to the control current value AM obtained from the steering holding map as shown in the ε region in FIG. For example, when the control current value A shown by the chain double-dashed line as shown in FIG. 5 is the X value (during Nomar), this gradually shifts to the Y value of the corresponding control current value AM of the solid line.

Then, the processing is repeated, and the process proceeds to step S81 again, and in this step S81, when it is determined that the control current value A obtained from the vehicle speed map becomes the same value as the control current value AM obtained from the steering holding map. , Step S
After advancing to 82 and resetting the addition amount, step S8
After 3, the process proceeds to step S13. As a result, the solenoid 48 is driven according to the control current value AM.

Thereafter, the timer H in step 72
When TM measures 5 seconds, the process proceeds to step S84 according to the determination of "whether the timer count has elapsed for 5 seconds" in step S83, and after the time measurement is stopped, the process proceeds to step S13. After that, while the steering wheel 13 is being held, that is, during the steady turning traveling,
Will continue.

When the steering wheel 13 is cut or returned again during this steering holding, the process proceeds from step S6 to step S14, and the control routine based on the steering wheel angular velocity described above is performed.

By such control, the steering wheel 13 during steady turning is not the assisting force according to the vehicle speed and the steering state in which steering stability is emphasized, but the assisting force in which steering holding property of the steering wheel 13 is emphasized, that is, the above-mentioned. It will be assisted with a larger assist force than the steering stability.

Therefore, the force required to hold the steering wheel 13 can be small, and the steering wheel 1 can be operated during steady turning.
The driver holding the steering wheel 3 can reduce the burden of holding the steering wheel 13. Therefore, fatigue of the driver can be reduced. Moreover, since the assist force gradually changes to the target steady turning traveling state, the driver does not need to be aware of the change in the steering holding force.

[0099]

As described above, according to the present invention,
When the vehicle turns into a steady turning traveling state by turning a steering wheel at a predetermined steering angle, the control means that has been operated by the assisting force set in the first setting means until now is set in the second setting means. The assist force is greater than the assist force of the setting means. Therefore, the driver holding the steering wheel is less burdened by it. That is, fatigue of the driver can be reduced.

Moreover, the assist force (first setting means) corresponding to the vehicle speed and steering gradually changes to the assist force (second setting means) corresponding to the target steady-state turning traveling state, so that the driver is kept safe. The steering feeling is good without having to be aware that the steering force has changed.

[Brief description of drawings]

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

FIG. 2 is a sectional view of the reaction force mechanism taken along the line AA in FIG.

FIG. 3 is a diagram showing a map formed by a vehicle speed and a solenoid reference control current.

FIG. 4 is a diagram showing a map formed by a steering wheel angular velocity and a coefficient according to steering.

FIG. 5 is a diagram showing a map formed by a vehicle speed and a control current suitable for steering.

FIG. 6 is a flowchart of control of the power steering device.

FIG. 7 is a flowchart showing a vehicle speed control routine connected to FIG. 6;

8 is a flowchart showing the first half of the control routine based on the steering wheel angular velocity, which is connected to FIG.

FIG. 9 is a flowchart showing the latter half of the same.

10 is a flowchart showing a control routine for controlling the steering holding force, which is connected to FIG.

FIG. 11 is a diagram showing changes in the steering wheel angle, the steering wheel angular velocity, and the solenoid drive current when going from a straight traveling state to a slalom traveling state or a steady turning traveling state.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Steering mechanism, 2 ... Steering gear, 7 ... Power cylinder device, 8 ... Front wheel (steering wheel), 9 ... Torsion bar, 10 ... Valve unit, 11 ... Input shaft, 13 ... Steering wheel, 15 ... Reaction force mechanism (control) Means), 16 ... Rotary valve, 30 ... Pressed portion, 3
2 ... Reaction force plunger, 40 ... Oil pump, 41 ... Pressure control valve (control means), 42
... Oil reservoir, 44 ... Assist system (hydraulic assist mechanism), 47 ... Spool valve element, 48 ... Solenoid, 49 ...
Plunger, 60 ... Control unit, 61 ... Vehicle speed sensor, 62 ... Steering wheel angular velocity sensor, 63 ... Steering wheel angle sensor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Takeo 5-3-8, Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation (72) Inventor Tadao Tanaka 5-33-8, Shiba, Minato-ku, Tokyo Mitsubishi Automotive Industry Co., Ltd.

Claims (1)

[Claims] 1. A steering mechanism for steering a steered wheel according to a steering operation from a steering wheel, a hydraulic assist mechanism provided on the steering mechanism for hydraulically assisting steering of the steered wheel, and a hydraulic assist mechanism provided on the hydraulic assist mechanism. The control means for varying the assist force generated by the hydraulic assist mechanism, the first setting means for setting the assist force according to the vehicle speed and the steering, and the control means according to the assist force of the first setting means A means for activating the steady turning traveling state, a means for detecting a steady turning traveling state, a second setting means for setting an assist force larger than the assist force of the first setting means according to the steady turning traveling state, and the steady turning traveling Upon detection of the state, the assist force of the first setting means is gradually changed to the assist force of the second setting means. And a means for operating the control means in accordance with the assisting force of the transition and the assisting force of the second setting means in accordance with the detection of the steady turning traveling state. Power steering device.