JPH0569840A - Power steering device for vehicle - Google Patents

Abstract

PURPOSE:To reduce a difference in a steering force between turning and returning by operating a control means according to a set value of a first setting means in turning and operating the control means according to a set value of a second setting means in returning. CONSTITUTION:In a micro computer constituting a control unit 60, '1.0' is set as a turning coefficient used for calculation of control current in turning, and as a returning coefficient, '0.8', which is smaller by 20%, for example, is set to be used for calculation of control current in returning. Due to the difference in these set values, an assisting force smaller in returning than in turning is reduced. Due to the difference in the set values between the turning coefficient KM and the returning coefficient KH, a steering force of a steering wheel 13 becomes appropriate according to the driving condition judged by a steering wheel angular velocity in turning. That is, the steering force which was lighter in the conventional example is made heavier by a reduced amount of the set value.

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
The sensor for detecting the vehicle speed of the automobile and the sensor for detecting the steering wheel angle are used for control to obtain appropriate steering characteristics according to the vehicle speed and the steering state. For example, the steering force is increased to make the steering wheel force lighter when steering in the stationary range and the low speed traveling range, and is reduced to be heavy when steering in the middle and high speed traveling range.

[0005]

By the way, according to the power steering device for a vehicle as described above, when the steering wheel is turned, for example, in the middle-high speed traveling range, a large steering wheel force is applied for stable steering. When you return the cut handle, you will get a fairly small handle force.

[0006] This is because the influence on the structure of the automobile causes the steering wheel force to be small in the returning even though the same assisting force acts in the cutting and the returning. This means that the steering operation is heavy at the time of turning and becomes light at the time of returning, and the change (hysteresis) in the steering force is large.

For this reason, the situation of the road surface directly from the steering wheel, which was felt at the time of turning, becomes difficult to catch at the time of returning, and the steering feeling is impaired. In particular, this steering feeling is one of the factors that make the automobile difficult to control, and therefore improvement is desired.

The present invention has been made in view of such circumstances, and an object thereof is to provide a vehicle power steering device capable of reducing a difference in steering wheel force between a cut and a return. To do.

[0009]

In order to achieve the above object, the vehicle power steering apparatus of the present invention is provided with a discriminating means for discriminating between a steering cut and a steering return, and assists according to the vehicle speed and the steering state. A first setting means for setting a value for generating a force is provided, and a second setting means for setting a value for generating an assist force smaller than the assist force generated by the set value of the first setting means is provided, and the determining means is also provided. According to the determination result of No. 3, the means for activating the control means according to the set value of the first setting means at the time of cutting and the means for activating the control means according to the set value of the second setting means at the time of cutting are provided.

[0010]

According to the vehicle power steering apparatus of the present invention, when the steering wheel is steered, cutting is performed while obtaining the assisting force generated according to the set value set in the first setting means. At this time, since the assist is performed according to the vehicle speed and the steering state, the steering operation becomes heavy in the middle and high speed traveling range, for example.

When the handle is returned after finishing the cutting, the return is performed by the assist force generated according to the set value set in the second setting means. At this time, since the set value set in the second setting means is a value that generates an assisting force smaller than the assisting force generated by the setting value of the first setting means, the steering operation at the time of returning becomes heavy. That is, the steering operation at the time of returning becomes heavy while keeping the same state at the time of cutting. This means that the handle force, which had been lightened at the time of returning, becomes heavy due to the setting value of the second setting means. Therefore, the difference between the steering force at the time of cutting and the steering force at the time of returning is reduced, and the change (hysteresis) in the steering force is reduced. Therefore, even when returning, it is possible to directly feel the road surface condition from the steering wheel. Therefore,
The steering feeling can be improved, and the characteristics that the vehicle can easily control can be obtained.

[0012]

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

FIG. 2 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, for example, a casing 3 having a rack 4 and a pinion 5 built therein. 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).

A lower end portion 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 above 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 tube 9 is twisted by the handle force from the handle 13, a relative displacement is generated 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, a 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.

Between the inlet body 19 and the outlet body 20, an oil pump 40 with a relief valve driven by an automobile engine (not shown) and an oil reservoir 4 are provided.
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.

The reaction 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. 2, a 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.

On the outer peripheral surface on the upper side and the outer peripheral surface on the lower side of the spool valve body 47, band-shaped annular grooves 51, 52 are formed. 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 setting of the annular groove 51 and the inflow port 39 is performed when the axial force of the plunger 49 is the largest (when the plunger 49 is projected to the highest position; for example, the Max current value 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 this control system circuit, the difference between the steering wheel force at the time of cutting and the steering wheel force at the time of returning is reduced, and the steering wheel force is changed according to the steering wheel angular velocity for each cutting. The control unit 60 has the following functions.

That is, the control unit 60 has a vehicle speed map in which the reference current A corresponding to the vehicle speed is divided into modes (normal and sports) as shown in FIG. 4, and the steering wheel angular velocity as shown in FIG. A steering speed map shown by a solid line for determining a steering state coefficient (a value required to determine the control current value of the solenoid 48) is set.

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. 4 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 the steering state.

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", which is 20% smaller, is set, and due to the difference between these set values, the assisting force that is smaller than that when cutting is made smaller when returning.

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. Figure 1
The flow chart of the control unit 6
The control operation within 0 is shown. 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 counter CNT is set to "0", and the change flag CHF indicating that the cut has changed to the return is set to "1".

Thereafter, in steps S2 to S4, 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 S5, it is judged if the steering wheel angle θH is larger than "5 deg". Further, in step S6, the steering wheel angular velocity θh is “30 deg.
/ S ”is determined. 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. 9, the steering state is near neutral (absolute value θH> 5 deg, absolute value θh> 30d.
eg / s).

If the vehicle is traveling straight ahead, step S
After step 7 and step S8, the process proceeds to step S9, and it is determined from the on / off state of the mode changeover switch 64 whether the current steering mode of the vehicle is the "normal mode" suitable for normal traveling or the "sport mode" suitable for sports traveling. To be done.

If the "normal mode" is determined at this time, the process proceeds to step S10. In step S10, the control current value A 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 S11, the corrected control current value A is obtained according to the arithmetic expression “A × KθM × KM”.

Next, in step S12, 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.

In the case of a high vehicle speed, a drive current of 1.0 A or less is supplied, the current difference is maintained in the lowered position of the plajan 49, 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 S9, the process proceeds to step 13, in which the current vehicle speed is changed from the sports mode diagram shown in the "vehicle speed-control current" map of FIG. The corresponding control current value A is read.

With the control current value A as a reference, the corrected control current value A is obtained and the reaction force plunger 3 of the reaction force mechanism 15 is obtained, as in steps S11 and S12.
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 cut to the left, for example, from the straight running state to turn the vehicle into a turning state.

Then, the steering wheel angle in step S5 is 5e.
It is determined that the handle 13 is turned off by at least one of the determination as to whether it is greater than g and the determination as to whether the steering wheel angular velocity is greater than 30 deg / s in step S6, and the process proceeds from step S5, S6 to step S14. , “ΘH × θh” is greater than “0”, that is, it is determined whether the current steering state is a cut or a return. Here, if the handle 13 is cut like the area β in FIG. 9, the value in step S14 becomes a value (positive) larger than “0” by the above calculation.

That is, the process proceeds to step S20, and in this step S20, 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".

There is no return before the first cut, that is, since the return flag FLR is reset to "0", the process proceeds to steps S21 to S23, 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. 5 is set as it is as the diagram on the cut side. As a result, the setting of the cut is made when the return is not performed before the cut.

Then, in step S24, the coefficient Kθ corresponding to the absolute value of the read steering wheel angular velocity θH is read from the diagram on the notch side indicated by the solid line shown in the “steering velocity map” of FIG. As a result, the coefficient Kθ corresponding to the steering state of the steering wheel angular velocity θ is obtained. Next,
In step S25, the change flag CHF is "1".
It is determined whether or not. Here, this cut is not a cut after returning. That is, the change flag CHF is set to "0" in step S21.

Therefore, the process proceeds to step S26. In this step S26, 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. 9, the steering wheel angular velocity shows a behavior that it is small at the beginning of cutting and gradually increases and reaches a peak. In this behavior, "3
For 0 deg / s or more, “Kθ ≦ KθM” is satisfied. Then, the process proceeds to step S27, KθM is updated (peak hold) to Kθ read in step 24, and then the process proceeds to step S9. In steps S9 to S13, the processing described above is performed.

That is, the control current value A 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 "A × KθM × KM". Then, the solenoid 48 is driven.

Here, as shown in FIG. 5, Kθ set in the solid line (cutting 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 steering wheel force is appropriately controlled moment by moment during the time when the steering wheel 13 in the β region of FIG. 9 is turned off.

Further, when the notch is finished like the region γ in FIG. 9 and the notched handle 13 is immediately returned, the process proceeds from step S5, S6 to step S14, but the value calculated in this step S14 is "0". Smaller value (negative)
Becomes

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. That is, this is determined by whether or not the cutting flag FLF is set to "1". Here, at the time of the previous cut, in step S22, the cut flag FL
Since F is set to "1", this return is a return after 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. Next, after proceeding to step S34 and setting the return flag FLR to "1",
In step S35, the return coefficient KM is set to "0.8".

As a result, the "steering speed map" is shown in FIG.
20% from the cut side of the solid line shown above, which is indicated by the broken line
Set as a low diagram. Then, in step S24, 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 speed map” indicated by the broken line, and in step S25 whether or not the change flag CHF is “1”. Is determined.

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 S26.

In step S26, 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. 9, 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 24, and then the process proceeds to step S9. Then, step S9 to step S13
Then, the processing described above is performed.

That is, the control current value A 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 "A × KθM × KM". Then, the solenoid 48 is driven.

Here, as shown in FIG. 5, Kθ set in the 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 fluctuates in an intermediate region. The control current A calculated in step S11 is 20% smaller than the control current A calculated at the time of the previous cut because it is an intermediate value that is 20% smaller than that at the time of cut. A small control current A is calculated.

That is, the control current A calculated as shown in FIG. 6 has a gain "20%" lower than that of the control current A on the cut side. Specifically, FIG.
In the diagram of, when the steering is turned, as indicated by reference sign a,
If a current value of "0.6 A" is supplied to the solenoid 48, a lower current value of "0.5 A" is supplied to the solenoid 48 when the solenoid 48 is returned.

Then, the plunger 49 is held at a position lower than the position at the time of cutting, and through the inflow port 54 that 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 return after the returning operation of the handle 13 performed after the cutting, the current return 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, similarly to the above-described initial return (return after cutting), the return flag is set to "1" in step S34, the return coefficient KM is set to "0.8" in step S35, and in step S24. After 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 of the “steering speed map”, the process proceeds to step S25. In step S25, it is determined whether the change flag CHF is "1".

Since the change flag CHF has been 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 these steps, the handle force is appropriately controlled moment by moment during the time when the handle 13 in the γ region of FIG. 9 is returned. 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 S14 to step S20.

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 S20, 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
2. In step S23, the cut flag FLF is set to "1" and the cut coefficient KM is set to "1.0".

Subsequently, in step S24, 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 S25, 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. In step S51, the count is "2"
It is determined whether or not.

Here, in step S50, the change flags CHF at the time of returning and at the time of cutting are respectively counted, so the number 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 S27. In this step S27, KθM read in step 24 is K
After updating to θ, the process proceeds to steps S9 to S13.

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 S9, the control current A corresponding to the traveling situation is calculated and the solenoid 48 is driven, as in the case of the previous cut. If the cutting operation is continued after the initial cutting of the handle 13, the determination in step S20 is changed.

That is, since the return flag FLR is reset to "0" in the above step S40, regarding the cutting after the initial cutting operation of the handle 13, the current cutting is returned to the previous cutting in step S20. Determine that it is not. That is, the process proceeds to step S21 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 returning), the cut flag is set to "1" in step S22, the cut coefficient KM is set to "1.0" in step S23, and step S24.
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 cutting side indicated by the solid line of the “steering speed map”, and then the process proceeds to step S25.

Here, since the change flag CHF is reset to "0" in step S21, the process proceeds to step S26, and thereafter, the same process 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-mentioned return processing is performed, and the handle force is appropriately controlled moment by moment during the time during which the handle 13 is returned.

As described above, due to the difference between the set values of the cut coefficient KM and the return coefficient KM, the handle force of the handle 13 becomes an appropriate weight according to the driving condition judged by the steering wheel angular velocity at the time of cut, and the return is performed. Time becomes heavier and moderate (assist force: small). In other words, conventionally
At the time of returning, the handle force that had been lighter becomes heavier as the set value is lowered.

Therefore, the difference (hysteresis) in the handle force at the time of cutting and at the time of returning can be reduced.
That is, when the incision and the return are driven by a constant drive current of the solenoid 48 as shown in FIG. 8, the difference in the handle force between the incision and the return is large as shown by the chain double-dashed line. When the current value is changed between the cut and the return as described above, the difference in the handle force between the cut and the return is reduced. Therefore, even at the time of returning, as in the case of cutting, the situation of the road surface can be directly felt from the steering wheel 13, and the steering feeling can be improved.
Moreover, the improved steering feel can provide the vehicle with characteristics that are easy to control.

[0078]

As described above, according to the present invention,
It is possible to reduce the difference between the steering wheel force when the steering wheel is turned and when the steering wheel is returned, that is, the hysteresis of the steering wheel force.
Therefore, even when returning, it is possible to directly feel the road surface condition from the steering wheel, as in the case of cutting. Therefore, the steering feeling can be improved, and the characteristics that are easy to control in the vehicle can be obtained.

[Brief description of drawings]

FIG. 1 is a flowchart showing steering control of a power steering system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a power steering device according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of the reaction force mechanism taken along the line AA in FIG.

FIG. 4 is a diagram of a vehicle speed and a reference control current of a solenoid.

FIG. 5 is a diagram showing a steering wheel angular velocity and a coefficient according to a steering situation.

FIG. 6 is a diagram of a steering wheel angular velocity on a cut side and a return side and a drive current of a solenoid.

FIG. 7 is a diagram showing a specific change in current value during cutting and returning.

FIG. 8 is a diagram showing that the change in steering wheel force is reduced by changing the current during cutting and returning.

FIG. 9 is a diagram showing a change in a steering wheel angle from a straight traveling state to a slalom traveling state, and a steering wheel angular velocity, a Kθ value, and a solenoid drive current which change according to the steering wheel angle.

[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 (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B62D 137: 00 (72) Inventor Takeo Takeo 5-3-8 Shiba 5-chome, Minato-ku, Tokyo Mitsubishi Motors Corporation Incorporated (72) Inventor Tadao Tanaka 5-33-8, Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation

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 provided on the hydraulic assist mechanism. The control means for varying the assist force generated by the hydraulic assist mechanism, the discrimination means for discriminating between the turning and the returning of the steering, and the value for generating the assist force according to the vehicle speed and the steering state are set. From the first setting means and the assisting force generated by the set value of the first setting means,
Based on the second setting means that sets a value for generating a small assisting force, and the determination result of the determining means, the first setting means when cutting.
A power steering device for a vehicle, comprising: a means for operating the control means according to a set value of the setting means, and a means for operating the control means according to the set value of the second setting means at the time of returning.