JP2579381B2 - Vehicle steering force control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle steering force control device, and more particularly to a vehicle steering force control device equipped with an airbag.

(Related Art) In recent years, from the viewpoint of improving vehicle safety, so-called airbag-equipped vehicles that instantaneously inflate airbags (airbags) to protect occupants at the time of a vehicle collision have begun to spread.

The airbag is usually stored in the vehicle interior equipment (dashboard or steering wheel) in front of the occupant, and instantly deploys with the energy of explosives etc. in response to a sudden change in acceleration at the time of collision. I have.

By itself or in combination with a seat belt, occupants can be protected very effectively.

(Problems to be Solved by the Invention) However, in such a vehicle equipped with an airbag, since the storage position of the airbag on the driver side is within the steering wheel, the center of gravity of the steering wheel is biased, and as a result, the steering wheel There is a problem that the operation feeling deteriorates.

That is, in FIG. 8, when the airbag is stored inside the steering wheel, the airbag body, the deployment mechanism, and the like are often set slightly off the center of rotation of the steering wheel. This is a design consideration to avoid interference with a horn circuit provided at the center of the steering wheel.

However, since the airbag body and the deployment mechanism are considerably heavier than the various components constituting the steering wheel, the center of gravity of the steering wheel is biased, and, for example, as shown in FIG. 9 (a). As a result, the steering wheel operation when the position of the center of gravity moves upward is felt heavy, and when the operation is performed in the opposite direction (see FIG. 4B), the steering wheel operation is felt lightly. However, there is a problem that the steering feeling is deteriorated.

The present invention has been made in view of such a problem, and has as its object to improve the steering feeling of a vehicle equipped with an airbag.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a steering force control device for a vehicle that controls increase or decrease of an auxiliary steering force of power steering using at least a steering angle of a steering wheel as one parameter. Determine the amount of variation in steering force based on the mass of the steering wheel and the offset amount from the center of rotation of the steering wheel to the center of gravity,
The power steering hydraulic pressure increase / decrease control value is corrected so as to cancel the fluctuation amount.

(Function) In the present invention, the control value for increasing / decreasing the power steering assist steering force is corrected based on the mass of the steering wheel and the offset amount from the center of rotation to the center of gravity, and the assist such that the steering force fluctuation of the steering wheel is canceled. A steering force is generated.

That is, when the steering force is felt to be heavy, the auxiliary steering force is corrected in the increasing direction to reduce the sensible steering force, while when the steering force is felt to be light, the auxiliary steering force is decreased. As a result of the correction to increase the sensible steering force, the steering feeling of the vehicle equipped with the airbag is particularly improved.

Hereinafter, the present invention will be described with reference to the drawings.

1 to 7 are diagrams showing an embodiment of a vehicle steering force control device according to the present invention.

In FIG. 1, reference numeral 20 denotes a steering wheel steered by a driver.
The steering force input to the front wheel 22 is transmitted to the front wheel 22 via the rack and pinion gear 21 and
22 is to be steered.

The rack and pinion gear 21 is provided in a hydraulic actuator 23.
The hydraulic pressure adjusted by the rotary valve 24 is introduced into the two chambers A and B, and the piston 25 is moved by an urging force corresponding to the oil pressure difference between the chambers A and B.
In the axial direction to generate an auxiliary steering force for the front wheel 22.

The direction and magnitude of the auxiliary steering force are determined by the relative rotation amount (described later) of the rotary valve 24 and the amount of hydraulic pressure flowing into and out of the rotary valve 24. The amount of hydraulic pressure is determined by a solenoid valve.
It is controlled by the amount of current (control current i) flowing through 27.

2 and 3, the rotary valve 24 includes an outer body 24a and an inner body 24b, and a relative rotational displacement corresponding to a twist amount of a steering shaft (not shown) is given between these bodies. . The outer body 24a has a plurality of ports, that is, a port P ₁ connected to a hydraulic discharge port of the pump 28, and a hydraulic actuator 23.
A port P ₂ connected to the one chamber A, a port P ₃ connected to the other chamber B, and two ports P ₄ and P ₅ connected to the solenoid valve 27 are formed, and a reservoir tank is formed in the inner body 24b. drain port P ₆ to be connected to 29 are formed.

When steering the steering wheel 20, relative rotational displacement corresponding to the steering force is generated between the outer body 24a and the inner body 24b, the discharge was introduced to port P ₁ oil pressure, for example, a hydraulic actuator 23 via the port P ₃ port P ₆ in the later part is supplied to the chamber B which has passed through the solenoid valve 27 via the port P _4, via the port P ₅
Drained to On the other hand, the hydraulic pressure chamber A is sent to the drain port P ₆ via the port P _2.

The solenoid valve 27 interposed in the hydraulic path is
The cross-sectional area of the passage is changed in accordance with the magnitude of the control current i, and the amount of hydraulic pressure supplied to one of the chambers A and B of the hydraulic actuator 23 is controlled in accordance with the size of the cross-sectional area of the passage. , And is controlled based on signals such as vehicle speed.

For example, when the vehicle speed is low, the control current i is increased to reduce the cross-sectional area of the passage, and the hydraulic pressure supplied to one of the chambers A and B of the hydraulic actuator 23 is increased. When the vehicle speed is high, the control current i
And the hydraulic pressure supplied to one of the chambers A and B of the hydraulic actuator 23 is reduced.

Thereby, controllability at low vehicle speed and stability at high vehicle speed are ensured.

Returning to FIG. 1, 30 is a control unit,
The control unit 30 receives a signal from a vehicle speed sensor 31 that detects the vehicle speed V, a signal from a steering sensor 32 that detects the steering angle θ of the steering wheel 20, and a signal from a stop lamp switch 33, an inhibitor switch 34, a parking switch 35, and the like. The arithmetic processing of the auxiliary steering force is executed using various signals as parameters, and a control current i corresponding to the arithmetic result is generated.

This calculation processing calculates an increase / decrease control value of the auxiliary steering force according to the vehicle speed (or according to the engine speed), and
A steering force variation is calculated based on the mass of the steering wheel 20 and the offset from the center of rotation of the steering wheel 20 to the center of gravity, and the increase / decrease control value is corrected so as to cancel the variation. In the figure, BAT represents a battery, IGN represents an ignition switch, and ENG represents an engine.

In such a configuration, the control current i applied to the solenoid valve 27 is given by the following equation.

i = i _O + i _C (θ, V) where i _O : reference current according to vehicle speed In the equation, i _C (θ, V) is a function of the steering angle θ and the vehicle speed V. In the example, by adding this function,
The hydraulic pressure of the power steering is controlled in accordance with the amount of steering, and the steering force fluctuation due to the offset of the center of gravity of the steering wheel 20 is canceled.

FIG. 4 is a model diagram when the center of gravity of the steering wheel 20 is eccentric from the center of rotation by a distance r, that is, when the mass m of the steering wheel is offset by the distance r. It is a model corresponding to the steering wheel that was used.

The steering force fluctuation amount F _V in such a model is obtained from the balance equation of energy when the steering wheel is steered to a steering angle θ to (θ + Δθ) as in the following equation.

F _V · r _W · Δθ = m · g · r ｛− [cos (θ + Δθ)] − [− cos θ]｝ = m · g · r ｛−cos θ · cos (Δθ) + sin θ · sin (Δθ) + cos θ｝ ... ... Since Δθ is very small, cos Δθ ≒ 1, sin Δθ ≒ Δθ
Then, the above equation becomes the following equation. F _V · r _W · Δθ = m · g · r · sin θ · Δθ... Eliminating Δθ on both sides, “Mass m is distance An arithmetic expression of the steering force fluctuation amount F _V when offset by r can be obtained. Then, the "steering force variation component graph with respect to the steering angle" in FIG. 5 can be obtained from this equation.

F _V = (r / r _W ) m · g · sin θ where r: offset amount r _W : steering wheel diameter Here, the steering force F when there is an offset of distance r
Is the steering reaction force F _O in the case of offset zero, because given the size plus the steering force variation F _V by the offset r, can be expressed by the following equation.

To F = F _O + F _V ...... Generally, the steering force characteristics of the power steering, the rod 26 the thrust of the hydraulic actuator 23 (the rack shaft force) and F _R, is expressed by the following equation.

F _R = _PO · A + (F · r _W / r _P ) where r _P : pitch radius of pinion gear r _W : steering wheel diameter P _O : hydraulic A: pressure receiving area of piston 25 F: steering force , when the steering force accompanying the offset r varies, since the steering force variation F _V is applied to the above equation, the rack shaft force F _R is given by the following equation.

F _R = P _O · A + ｛(F _O + F _V ) r _W / r _P …… From the above, in order to cancel the steering force fluctuation, the control hydraulic pressure P _C that cancels F _V in the above equation It may be determined, specifically, if you put equal to the following equation and the above equation, except for the steering force variation _{F V, F R = P C} · a + (F O · r W / r P) ...... control it can be calculated pressure P _C.

_{That, P O · A + {(} F O + F V) r W / r P} = P C · A + (F O · r W / r P) ...... ∴P C · A = P O · A + F V · r W / r _P …… P _C = P _O + F _V · r _W / A · r _P …… By substituting the previous equation into the equation, P _C = P _O + r · m · g · sin θ / A · r _P …… , it is possible to obtain the control pressure P _C from the above equation.

Control pressure P _C is controlled by a control current i applied to the solenoid valve 27, the control current i is set through for example running test.

Here, the control current i is set by first measuring the power steering oil pressure P for various steering angles θ by steering the steering wheel, and as shown in FIG. 6 (a), a “steering angle-power steering oil pressure characteristic diagram ( θ-P characteristic diagram) ". At this time, the hydraulic pressure data when the current is changed (± nΔi) based on the predetermined solenoid current i _O is collected. The hydraulic pressure characteristic at i = i _O on the created θ-P characteristic diagram is P _O.

Then, plot the control hydraulic pressure P _C calculated in accordance with Equation on theta-P characteristic diagram. Figure 6 the broken line represents the P _C characteristic (theta-P _C characteristics) of (a).

Then, set the "steering angle θ- control current i characteristic (theta-i characteristic)" for realizing the theta-P _C characteristic, the correction current i _C of interest (theta) (FIG. 6 (b )), And, if necessary, these measurements to settings are repeated for each vehicle speed V to obtain a correction current characteristic i _C as a function of the steering angle θ and the vehicle speed V.
(Θ, V) is obtained.

The correction current characteristic i _C (θ, V) obtained in this manner is stored in the control unit 30 and is applied to the solenoid valve 27 by referring to the characteristic corresponding to the steering angle θ when the steering wheel 20 is turned. The control current i is corrected (see the previous equation).

Therefore, in this embodiment, the control current i to the solenoid valve 27 is obtained by adding the correction current i _C (θ, V) as a function of the steering angle θ and the vehicle speed V to the reference current i _O , and this control current i Is generated so as to generate an auxiliary steering force corresponding to the steering angle fluctuation component F _V associated with the steering angle θ included in the correction current i _C (the steering force fluctuation component F _V accompanying the offset amount r of the mass m). The steering force fluctuation component can be canceled, and the seventh
As shown in the figure, the steering force of the steering wheel 20 can be stabilized, and the steering feeling of the vehicle equipped with the airbag can be improved.

As described above, in the embodiment, the vehicle equipped with the airbag, in which the steering feeling is particularly problematic, is described as an example. However, the present invention can be effectively applied to a vehicle equipped with a crafter switch on the steering wheel.

Further, in the embodiment, the hydraulic power steering device is described as an example, but the power steering device is not limited to this and may be a known electric motor type power steering device.

(Effect) According to the present invention, the steering force fluctuation can be canceled by the auxiliary steering force, and the steering feeling of a vehicle equipped with an airbag can be particularly improved.

[Brief description of the drawings]

1 to 7 are diagrams showing an embodiment of a vehicle steering force control apparatus according to the present invention, wherein FIG. 1 is a system configuration diagram, FIG. 2 is a hydraulic system diagram of essential parts, and FIG. Is a cross-sectional view of the rotary valve and the solenoid valve, FIG. 4 is a model diagram of a steering wheel in which the position of the center of gravity is eccentric, FIG. 5 is a graph of a steering force fluctuation component Fv with respect to the steering angle,
FIG. 6 is an actual measurement diagram of the power steering oil pressure and the control current with respect to the steering angle, and FIG. 7 is a characteristic diagram of the steering force with respect to the steering angle. 8 and 9 are views showing a conventional example, FIG. 8 is an external view of a steering wheel in which the airbag is stored, and FIG. 9 is a state diagram when the center of gravity moves upward or downward. . 20 ... steering wheel, 21 ... rack and pinion gear, 22 ... front wheel, 23 ... hydraulic actuator, 24 ... rotary valve, 25 ... piston, 26 ... rod, 27 ... solenoid valve, 30 ... ... control unit, 31 ... vehicle speed sensor, 32 ... steering angle sensor, 33 ... stop lamp switch, 34 ... inhibitor switch, 35 ... parking switch.

Claims (1)

(57) [Claims] 1. A steering force control apparatus for a vehicle, wherein at least a steering angle of a steering wheel is used as one parameter to control an increase / decrease of an auxiliary steering force of a power steering, a mass of the steering wheel and a distance from a rotation center of the steering wheel to a center of gravity of the steering wheel. A steering force control device for a vehicle, wherein a variation amount of a steering force is obtained based on an offset amount, and an increase / decrease control value of an auxiliary steering force of the power steering is corrected so as to cancel the variation amount.