JPH0542881A - Power steering device - Google Patents

Abstract

PURPOSE:To provide a power steering device which changes a steering assist amount according to the degree of fatigue based on the operation of a driver. CONSTITUTION:A lapse time (t) after a vehicle ignition switch being operated to an ON condition is obtained as a parameter showing the degree of the fatigue of a driver (S1, S5), and a vehicle velocity V from a vehicle velocity sensor is read as an actual vehicle velocity Vact (S2). In addition, a change vehicle velocity Vmod is determined by determining a vehicle velocity change amount DELTAV according to a lapse time (t) and subtracting it from the actual vehicle velocity Vact, and at the same time a reference electric current Io in accordance with it is fed to a solenoid valve to control a steering assist amount (S3, S4). As a result, a light-hearted steering feeling at which the longer the lapse time (t) is, that is, the higher the fatigue degree of the driver is, the larger the steering assist amount is, is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device for a vehicle, and more particularly to a technique for further reducing the fatigue caused to a driver by steering.

[0002]

2. Description of the Related Art As one mode of a power steering device, there is already a device which assists a steering force applied to a steering wheel of a vehicle by a driver and changes the steering assist amount by not only the steering force but also other parameters. ..

This type of power steering device includes a vehicle speed sensitive type in which the steering assist amount is changed according to the vehicle speed (an example of which is described in Japanese Patent Laid-Open No. 58-180381), and engine speed. There is known a rotation speed-sensitive type in which the steering assist amount is changed accordingly.

Further, as a form of changing the steering assist amount, a direct steering assist amount is set according to a steering force (to be precise, a relation between the steering force and a road surface reaction force received by the steered wheels from the road surface) and other parameters. There is known a direct assist amount changing type for changing the. One example of this is to change the amount of oil supplied from the oil pump to the power cylinder via the control valve in accordance with the steering force and other parameters. Further, as a change form of the steering assist amount, the steering assist amount is changed according to the steering force, while the steering resistance is changed according to other parameters, so that the substantial steering assist amount (the steering assist amount according to the steering force is changed). An indirect assist amount change type in which the steering resistance is indirectly changed) is also known.
In this example, the amount of oil supplied from the oil pump to the power cylinder via the control valve is changed according to the steering force, while the steering resistance of the steering wheel is changed according to other parameters.

The steering resistance may be generated, for example, as a frictional force of a steering wheel or a member that moves integrally with the steering wheel, or a hydraulic pressure that biases the steering wheel or a member that moves integrally with the steering wheel toward a neutral position. It can also be generated as a reaction force.

[0006]

The driver usually becomes physically and mentally tired when driving for a long time. Since the driver feels that the steering feel is heavier when the fatigue is large than when the fatigue is small, it is required that the steering force is smaller when the fatigue is large than when the fatigue is small.

[0007] In addition, in the beginning of the driving period, the driver is not accustomed to driving, and careful steering is required to provide a satisfying steering feeling. However, a light steering feeling is required.

However, the conventional power steering system is not designed so as to change the steering assist amount according to the degree of fatigue or the degree of familiarity, and thus change the steering force. Therefore, the conventional device has a problem that the driver has to steer with the same force as usual even when the tiredness or habituation is high, and the driver causes a little great fatigue. That is, the power steering device originally aims to reduce fatigue caused by steering, but the conventional power steering device has a problem that the fatigue cannot be sufficiently reduced.

The present invention has been made to solve this problem.

[0010]

As shown in FIG. 1, the gist of the present invention is to assist a steering force applied to a steering wheel of a vehicle by a driver, and to change the steering assist amount in addition to the steering force. (A) Fatigue / familiarity-related parameter detection means for detecting a fatigue / familiarity-related parameter that changes according to the driver's fatigue caused by driving or the degree of familiarity with driving 1 and (b) Steering assist amount change that changes the amount of steering assist so that it is greater when the degree of fatigue or habituation is higher than when it is low, using at least the parameters related to fatigue and habituation as other parameters. And means 2 and means.

The present invention can be applied to, for example, a vehicle speed-sensitive power steering device or a rotation speed-sensitive power steering device.

Further, the present invention can be applied to, for example, a hydraulic power steering device that uses an oil pump as a power source for steering assist, or an electric power steering device that uses an electric motor.

Further, the fatigue-related / familiarity-related parameter in the present invention is, for example, when the ignition switch of the vehicle is turned on.
It can be the time that has elapsed since the N state was operated, or the travel time relating to travel of that time. This is because it is usual that the degree of fatigue and the degree of familiarity increase with the passage of time. Furthermore, the vehicle ignition switch is turned on.
It can also be the distance that the vehicle has traveled since the vehicle was operated in the state. This is because it is usual that the degree of fatigue and the degree of familiarity increase as the distance increases.

Further, the present invention can be applied to, for example, a direct assist amount changing type power steering device or an indirect assist amount changing type power steering device. In the latter case, for example, the value obtained by subtracting the corrected steering resistance that is uniquely determined from the fatigue / familiarity-related parameters from the reference steering resistance that is uniquely determined from the vehicle speed or engine speed as another parameter is the final value. The present invention may be implemented in the form of steering resistance, or the final steering resistance may be a value that is uniquely determined from both the vehicle speed or engine speed and the parameters related to the degree of fatigue and familiarity. it can.

[0015]

In the power steering apparatus according to the present invention, the fatigue degree / habituation degree related parameter detecting means 1 detects the fatigue degree / habituation degree related parameter, and the steering assist amount changing means 2 at least the fatigue degree / habituation degree. The steering assist amount is changed based on the related parameter, and as a result, the steering assist amount is changed in consideration of the driver's fatigue level or habituation level.

Specifically, the steering assist amount changing means 2 changes the steering assist amount so that the steering assist amount becomes larger when the fatigue level or the habituation level is higher than when the fatigue level or habituation level is low. Therefore, a light steering feeling is always realized in relation to the driver's fatigue level.
A lighter steering feeling is realized when the degree of habituation is high than when it is low.

[0017]

As described above, according to the present invention, the steering assist amount can be changed in consideration of the driver's fatigue level or habituation, so that the driver does not apply an excessively large steering force to the steering wheel. In addition, the effect of further reducing the fatigue due to steering can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic type, indirect assist amount changing type, and vehicle speed sensitive type power steering system according to an embodiment of the present invention will be described in detail below with reference to the drawings.

In the power steering system which is an embodiment of the present invention, as shown in FIG.
The oil in 0 is pumped up by a vane pump 12 driven by an engine of a vehicle (not shown) serving as an oil pump and supplied to the power cylinder 14. The vane pump 12 incorporates a flow control valve (not shown) so that the amount of oil discharged from the vane pump 12 is kept constant regardless of the rotational speed of the vane pump 12, that is, the rotational speed of the engine. The power cylinder 14 converts the oil pressure of the oil supplied from the vane pump 12 into a mechanical force to assist the steering force of the left and right front wheels, which are steering wheels, and moves in the left and right direction of the vehicle to steer the left and right front wheels. A power piston 20 fixed to the control rack 18 for changing the angle, and a right cutting pressure for steering the left and right front wheels to the right direction and a left cutting pressure for steering the left and right front wheels to the left are selectively provided on the power piston 20. And a cylinder right chamber 22 and a cylinder left chamber 24 which act on.

A steering gear box (hereinafter simply referred to as a gear box) 30 is provided between the reservoir tank 10, the vane pump 12, and the power cylinder 14 described above. In the gear box 30, one end of a torsion bar 32, whose one end is rotatably connected to a steering wheel (not shown), has the other end of the pinion gear 3.
4 and the pinion gear 3
The tooth portions 4 are meshed with the tooth portions of the control rack 18. That is, the steering gear mechanism of this power steering apparatus is a rack and pinion type.

In the gear box 30, a control valve 40 mainly having a control valve shaft 36 and a rotary valve 38 each having a plurality of radial oil passages, a reservoir tank 10, a vane pump 12, a cylinder right chamber 22, and a cylinder. It is provided in a state of being connected to the left chamber 24. Control valve shaft 36
Has a cylindrical shape and is inserted to the outside of the torsion bar 32 with an appropriate gap. One end of the cylindrical bar is fixed to the torsion bar 32 by a pin 42, while the other end is floated from the torsion bar 32. ing. Rotary valve 3
8 is a cylindrical control valve shaft 36
It is fitted to the outside of the machine in an oil-tight and slidable manner, and
It is oil-tightly fixed to the gear housing 44 on its outer peripheral surface. The control valve 40 utilizes the phenomenon that if the torsion bar 32 is twisted by the driver's steering, the relative phase of the control valve shaft 36 with respect to the rotary valve 38 changes by the amount of the twist. Tank 10, vane pump 12, cylinder right chamber 22 and cylinder left chamber 2
The switching of the oil passage between 4 and the control of the throttle area of each oil passage are performed, whereby the operating direction of the power cylinder 20 (that is, the power assist direction of the steering force) and the steering direction of the steering wheel The operating force (that is, the power assist amount of the steering force) is controlled.

In the gear box 30, there is further provided a hydraulic reaction force acting device 50 which causes a force for suppressing the rotation of the steering wheel to act as a hydraulic reaction force.
The hydraulic reaction force acting device 50 includes four plungers 54 opposed to both side surfaces of a pair of levers 52 extending from the outer peripheral surface of the control valve shaft 36 in the diametrical directions thereof in opposite directions. And four hydraulic reaction chambers 58 that apply hydraulic pressure to the back surface of each plunger 54 in order to apply hydraulic reaction force to the side surfaces of each lever, and the hydraulic pressure generated in each hydraulic reaction force chamber 58 (hereinafter referred to as reaction pressure). ) And a solenoid valve 60 for changing The plunger 54 and the hydraulic reaction chamber 58 are incorporated in the pinion gear 34.

In the gear box 30, a shunt valve 64 is further provided.
Is also provided. The diversion valve 64 diverts the oil discharged from the vane pump 12 to the control valve 40 side and the solenoid valve 60 side, and even if the difference between the hydraulic pressure on the control valve 40 side and the hydraulic pressure on the solenoid valve 60 side fluctuates. The oil from 12 is always supplied to the solenoid valve 60 side at a constant flow rate. The shunt valve 64 to the solenoid valve 60
The oil supplied to the valve is throttled by the solenoid valve 60, so that a reaction pressure is generated in each hydraulic reaction chamber 58. Since the solenoid valve 60 is designed to have a smaller opening area (smaller flow area between the flow dividing valve 64 and the reservoir tank 10) as the current supplied to the solenoid valve 60 is smaller, the solenoid valve 60 is eventually The smaller the supply current, the higher the reaction force pressure generated in each hydraulic reaction chamber 58.

The control valve 40 side and the hydraulic reaction force chamber 58 side are connected to each other via a fixed orifice 68. When the pressure on the control valve 40 side rises (during steering), the oil is made to flow to the hydraulic reaction force chamber 58 side to increase its hydraulic pressure, thereby providing a steering feeling that is responsive when steering in the middle / high speed range. It is being realized.

The solenoid valve 60 is a power steering computer (hereinafter simply referred to as a computer).
Controlled by 70. The ROM of the computer 70 stores in the ROM the relationship between the vehicle speed V and the reference current I ₀ (V) (the relationship represented by the graph in FIG. 3), and the elapsed time t after the ignition switch of the vehicle is operated in the ON state. The relationship between the vehicle speed V change amount ΔV (t) (represented by the graph in FIG. 4), the steering assist control program (program represented by the flowchart in FIG. 5), and the like are stored.

Since the relationship between the vehicle speed V and the reference current I ₀ is represented by the graph of FIG. 3, the hydraulic reaction force, that is, the steering resistance is reduced at low speed and stationary steering, and steering is reduced. While the amount of assist increases and a light steering feeling is realized, the hydraulic reaction force, that is, steering resistance increases at medium and high speeds, and the amount of steering assist decreases and a comfortable steering feeling is realized.

As shown in FIG. 4, the relationship between the elapsed time t and the vehicle speed change amount ΔV increases as the elapsed time t increases until the elapsed time t reaches the constant value t _0. After reaching t ₀ , the saturation value ΔVsat is kept constant.

Next, the operation of the computer 70 will be described in detail with reference to FIG. The vehicle ignition switch is O
When the computer 70 is operated in the N state and the power of the computer 70 is turned on, first, in step S1 (hereinafter, simply represented by S1; the same applies to other steps), the value of the elapsed time t is reset to zero. Then, in S2, the vehicle speed V detected by the vehicle speed sensor 72 is changed to the actual vehicle speed V.
Read as act.

Subsequently, in S3, the vehicle speed change amount ΔV corresponding to the current value of the elapsed time t is determined using the relationship shown in FIG. 4, and the value obtained by subtracting the vehicle speed change amount ΔV from the actual vehicle speed Vact is the changed vehicle speed. Vmod. However, when the changed vehicle speed Vmod thus determined is smaller than 0, it is changed to 0. Further, the reference current I ₀ corresponding to the changed vehicle speed Vmod is determined by using the relationship shown in FIG.

The change speed Vmod herein may mean a virtual vehicle speed V corresponding to the reference current I ₀ in the case of obtaining the reference current I ₀ of the proper size in relation to the degree of fatigue based on the operation of the driver To do. That is, in this step, the degree of driver's fatigue is expressed as the vehicle speed change amount ΔV, and the value of the actual vehicle speed Vact is changed by the vehicle speed change amount ΔV, so that the steering assist amount corresponds to the driver's degree of fatigue. The reference current I ₀ of a magnitude that increases by a certain amount is determined, and in turn, the reference current I ₀ of a magnitude that always realizes a light steering feeling in relation to the degree of fatigue of the driver is determined.

Then, in S4, the reference current I _{0 is set.}
Is supplied to the solenoid valve 60, and in S5, the current value of the elapsed time t is increased by a fixed small time Δt,
Then, the process returns to S2.

Therefore, for example, when the actual vehicle speed Vact changes as shown by the solid line graph in FIG. 6 as the elapsed time t increases, the changed vehicle speed Vmod is shown by the broken line graph in FIG. Will be changed to.

As is apparent from the above description, in the present embodiment, the computer 70 has S1 and S shown in FIG.
5 constitutes a fatigue degree / habituation degree related parameter detection means 1 of a type in which the elapsed time t is detected as a fatigue degree / habituation degree related parameter, and the hydraulic reaction force acting device 50 and the computer 70 of FIG. The part that executes S2 to S4 constitutes the steering assist amount changing means 2 of the type that uses the actual vehicle speed Vact and the elapsed time t as other parameters.

In the above-described embodiment, the value of the vehicle speed V is virtually changed according to the elapsed time t, so that the magnitude of the current supplied to the solenoid valve 60 according to the elapsed time t is indirectly determined. However, the magnitude of the current supplied to the solenoid valve 60 can be directly determined according to the elapsed time t. Hereinafter, one embodiment of this will be described in detail with reference to the drawings, but since this embodiment has many parts in common with the previous embodiment, the same reference numerals are used for the description and the text The description is omitted.

RO of the computer 70 in the present embodiment
M represents the relationship between the vehicle speed V and the reference current I ₀ (V) (the relationship represented by the graph in FIG. 3), the elapsed time t after the ignition switch of the vehicle is operated in the ON state, and the reference current. The relationship between the change amount ΔI (t) of I ₀ (V) (the relationship represented by the graph of FIG. 7), the steering assist control program (the program represented by the flowchart of FIG. 8) and the like are stored. ..

As shown in FIG. 7, the relationship between the elapsed time t and the current change amount ΔI increases as the elapsed time t increases until the elapsed time t reaches the constant value t _0. After reaching t ₀ , the saturation value ΔIsat is kept constant. This is the same as the relationship between the elapsed time t and the vehicle speed change amount ΔV shown in FIG.

Next, the operation of the computer 70 will be described in detail with reference to FIG.

When the ignition switch of the vehicle is operated to the ON state and the power of the computer 70 is turned on, first, in step S11, the value of the elapsed time t is reset to zero. Then, in S12, the vehicle speed sensor 7
The actual vehicle speed Vact is read from 2.

Subsequently, in S13, the current change amount ΔI corresponding to the current value of the elapsed time t is calculated using the relationship shown in FIG.
Is determined, and the reference current I ₀ corresponding to the actual vehicle speed Vact is determined using the relationship shown in FIG. Furthermore, the reference current I
A value obtained by adding the current change amount ΔI to ₀ is set as the change current Imod. That is, in this step, the degree of fatigue of the driver is expressed as the current change amount ΔI, and the current change amount ΔI is expressed.
By changing the value of the reference current I _{0 with} I, the change current Imod of a magnitude that increases the steering assist amount by an amount commensurate with the degree of fatigue of the driver is determined, and as a result, it is always related to the degree of fatigue of the driver. The magnitude of the change current Imod that achieves a light steering feel is determined.

Then, in S14, the changed current I
mod is supplied to the solenoid valve 60, the current value of the elapsed time t is increased by a fixed small time Δt in S15, and then the process returns to S12.

Therefore, for example, when the reference current I ₀ changes as shown by the solid line graph in FIG. 9 as the elapsed time t increases, the change current Imod is shown by the broken line graph in FIG. It will change like this.

As is apparent from the above description, in the present embodiment, the fatigue of the type in which the portion of the computer 70 which executes S11 and S15 of FIG. 8 detects the elapsed time t as the fatigue degree / familiarity related parameter. Of the degree / familiarity-related parameter detecting means 1 and the hydraulic reaction force acting device 50
The part of the computer 70 that executes S12 to S14 in the figure constitutes a steering assist amount changing means 2 of a type that uses the actual vehicle speed Vact and the elapsed time t as other parameters.

The embodiments of the present invention have been described above in detail with reference to the drawings. However, other than these, various modifications, based on the knowledge of those skilled in the art, without departing from the scope of the claims.
Of course, the invention can be implemented in an improved manner.

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing the structure of the present invention.

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

FIG. 3 is a graph showing a relationship between a vehicle speed V and a reference current I ₀ used by the power steering device.

FIG. 4 is a graph showing a relationship between an elapsed time t used by the power steering device and a vehicle speed change amount ΔV.

FIG. 5 is a flowchart showing a steering assist control program used by the power steering device.

FIG. 6 is a graph showing an example of the relationship between the elapsed time t, the actual vehicle speed Vact, and the changed vehicle speed Vmod when the power steering device is used.

FIG. 7 is a graph showing a relationship between an elapsed time t and a current change amount ΔI used by a power steering device according to another embodiment of the present invention.

FIG. 8 is a flowchart showing a steering assist control program used by the power steering device.

FIG. 9 is a graph showing an example of the relationship between the elapsed time t, the reference current I _0, and the change current Imod when the power steering device is used.

[Explanation of symbols]

 12 vane pump 14 power cylinder 32 torsion bar 38 rotary valve 40 control valve 50 hydraulic reaction force acting device 60 solenoid valve 70 power steering computer 72 vehicle speed sensor

Claims (1)

[Claims] 1. A power steering apparatus for assisting a steering force applied to a steering wheel of a vehicle by a driver, and changing the steering assist amount not only by the steering force but also by other parameters. Or a fatigue degree / habituation degree related parameter detecting means for detecting a fatigue degree / habituation degree related parameter that changes according to the degree of familiarity with driving, and using at least the fatigue degree / habituation degree related parameter as the other parameter A power steering apparatus, comprising: steering assist amount changing means for changing the steering assist amount so that the amount of steering assist is greater when the degree of fatigue or familiarity is higher than when the degree of fatigue is low.