JPH0443163A - Controller for power steering device - Google Patents

Abstract

PURPOSE:To eliminate the trouble that the incompatibility feeling is given in steering in the course of the steering wheel return by controlling the applied electric current to a booster so as to gradually vary in the reduction direction of the assisting force, during the time from the start of return of a steering wheel to the reach of a prescribed angle. CONSTITUTION:A power steering device is equipped with a booster 12 for applying an assisting force to a working member 11 for steering a steering wheel, and the assisting force given by the booster 12 is varied by a controller 15 according to the torque and applied electric current which are applied on a rotary shaft 16. Further, a calculating output means 2 which calculates the applied electric current according to the traveling state and output the applied electric current into the controller 15 is provided. In this case, a return judging means 1 for detecting the steering wheel return state which changes in the direction in which the steering angle detected by a steering angle sensor 46 becomes nearly zero is installed, and during the time when the return angle of the steering wheel 46 reaches a prescribed angle from the start of the detection for the steering wheel returned state, the applied electric current which is calculated by a calculating output means 12 is gradually changes in the reduction direction, by an addition calculating means 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is provided in connection with a power booster that provides assist force, and is applied to an applied current that is calculated based on driving conditions such as vehicle speed, steering angle, and steering wheel torque. Accordingly, the present invention relates to a control device for a power steering device including a control device for controlling the assist force by a force multiplier.

(Prior art) For example, in a control device for a hydraulic power steering device, a control current corresponding to vehicle speed, steering angle, etc. is applied to an electromagnetic control valve of the control device to control the steering wheel torque of the power steering device. This is known. According to this technique, satisfactory results can be obtained regarding the characteristics when the handle is turned, but there is a problem that the return of the handle feels bad.

To solve this problem, the technology disclosed in Japanese Patent Application Laid-Open No. 62-279170 detects that the steering angle is changing toward the neutral position in a power steering system having a steering force control device using a reaction force mechanism. A return determining means is provided, and in response to the output of the return determining means, the opening degree of the electromagnetic control valve is controlled to increase the hydraulic pressure supplied to the reaction force mechanism, so that the steering wheel returns smoothly when the steering wheel returns. That's what I do.

In addition, in relation to this, in order to prevent the oil pressure to the reaction force mechanism from changing and the steering wheel torque to change every time the steering wheel is returned for correction when the steering wheel is turned, the return angle of the steering wheel is adjusted so that the steering wheel starts returning. It has also been considered to maintain the same hydraulic pressure as at the time of cutting until a predetermined angle is reached.

(It's what the invention aims to solve!) However, with this type of technology, the steering wheel torque suddenly changes when the steering wheel is returned to a predetermined angle. There is.

An object of the present invention is to eliminate such discomfort by gradually changing the current applied to the force booster in the direction of decreasing the assist force from when the steering wheel starts returning until it reaches a predetermined angle. do.

(Means for Solving the Problems) For this purpose, the power steering device control device according to the present invention has the following features:
As shown in FIG. 1, an actuating member 11 for steering the steering wheel
a rotating shaft 16 that connects the operating member to the steering handle 46; a force increasing device 12 that provides assist force to the operating member 11; In a power steering device comprising a control device 15 that changes the assist force, and a calculation output means 2 that calculates the applied current according to the driving state of the vehicle and outputs it to the control device 15, the steering handle Steering angle sensor 45 that detects the steering angle of 46
a return determination means 1 for detecting a steering wheel return state in which the steering angle detected by the steering angle sensor is changing toward O; and a return angle of the steering wheel 46 detected by the steering angle sensor 45. further comprising an additional calculation means 3 for gradually changing the applied current calculated by the calculation output means 2 in a direction in which the assisting force decreases from the start of detection of the return state of the steering wheel by the return determination means 1 until a predetermined angle is reached. It is characterized by:

(Function) When the steering wheel is turned, the calculation output means 2 calculates the applied current according to the driving state of the automobile and outputs it to the control device 15, whereby the force multiplier 12 applies an assist force to the actuating member 11 to perform power steering. It will be done. When the return determination means 1 determines that the steering wheel is in the returned state, the calculation output means 2 similarly calculates the applied current according to the running state of the automobile, and the additional calculation means 3 calculates the applied current by the steering angle sensor 45. The assist force is gradually changed in the direction of decreasing until the detected return angle of the steering wheel 46 reaches a predetermined angle after the return determination means 1 starts detecting the return state of the steering wheel 46, and this changed applied current is used as a control wave. Output to W15. Due to this, the steering wheel torque when returning the steering wheel is
From when the steering wheel starts returning to when the steering wheel reaches a predetermined angle, the steering wheel gradually changes in a direction in which the steering wheel feels good.

(Effects of the Invention) As described above, according to the present invention, the steering wheel torque when returning the steering wheel makes it feel like the steering wheel returns gradually becomes better, so the steering wheel torque suddenly changes and there is no difference in steering. It doesn't give a sense of harmony.

(Example) The present invention will be explained below using examples shown in FIGS. 1 to 17.

As shown in FIGS. 1 and 112, the power steering device 10 includes a power cylinder (
The control device E15 includes a servo valve 17 provided on a rotary shaft 16 that connects the operating rod 11 and the steering handle 46 via a rank-binion mechanism and a handle shaft 47; It is constituted by a reaction force mechanism 18 equipped with an electromagnetic control valve 3o.

A supply pump 20 such as a vane pump driven by an automobile engine has a built-in bypass valve 21, which allows a constant flow rate Q of working fluid to flow through a discharge passage 23 to a diversion valve 2.
2. The diversion valve 22 distributes a constant flow rate Q of working fluid to the servo valve passage 23a and the reaction force control passage 23b at constant flow rates Ql and Q2, respectively. Servo valve passage 2
3a is connected to the power cylinder 12 via the servo valve 17, and the reaction force control passage 23b is connected to the reaction force mechanism 18 and the electric am oi 30. When an electric pump is used as the supply pump 2o, the bypass valve 21 is not necessary.

The servo valve 17 is a known rotary type open center four-port throttle switching valve, and is operated by twisting of the rotating shaft 16 based on the handle torque applied to the steering handle 46. In the neutral steering state where no steering wheel torque is generated, the servo valve 17. Each boat 17a~
17d are communicated with each other without substantial restriction. In this state, the pressure generated in the working fluid supplied from the supply pump 20 to the supply boat 17a (hereinafter referred to as gear generation pressure)
is low, and both distribution boats 17c and 17d have the same low pressure, so the power cylinder 12 is not operated. If the steering handle 46 is rotated in one direction and a steering wheel torque is generated,
The servo valve 17 is deviated from the neutral state and the supply boat 17a
and one distribution port) 17c (or 17d), and between the discharge boat 17b and the other distribution boat 17d (or 17c). As a result, the gear generation pressure of the working fluid from the supply boat 17a increases, and the working fluid flows from the other distribution boat 17d (or 17c) to the power cylinder 12 through the negative distribution passage 24b (or 24a).
The working fluid in the other working chamber flows from the other distribution passage 24a (or 24b) into one distribution port) 17c (or 17d) to generate an assist force.
) and is discharged to the reservoir 25 via the discharge boat 17b. This assist force increases the steering force acting on the actuating rod 11, and is transmitted to the steering wheels via the steering link mechanism of the enclosure.

The reaction mechanism 18 includes a plunger 18b fitted into an insertion hole 18c formed on the output side of the rotation shaft 16, and a plunger 18b formed on the input side of the rotation shaft 16 on both sides in the circumferential direction that engages with the tip of the plunger 18b. This is a known type having an inclined surface 18d as a main component. Then, the pressure of the working fluid introduced into the rear part of the plunger 18b via the boat 18a is changed to an electric current! The control well 30 changes the torsion spring characteristics between the input and output sides of the rotating shaft 16, thereby changing the operating characteristics of the servo valve 17 that controls the supply and discharge of working fluid to both working chambers of the power cylinder 12. It is. The electromagnetic stab valve 30 is normally fully closed, and the solenoid 30
The degree of opening increases as the current applied to a increases, and eventually becomes fully open.

As shown in Figure jI2, the electronic control unit 50 includes a central processing unit (hereinafter simply referred to as CPU) 51, a memory dedicated to m output (hereinafter simply referred to as ROM) 52, and a writable memory (hereinafter simply referred to as ROM).
53 (hereinafter simply referred to as RAM) is a main component, and the solenoid 3 of the electromagnetic control valve 30 is connected to the CPU 51 via an enclosure interface and a solenoid drive circuit.
0a is connected to control the applied current.

Further, a vehicle speed sensor 40 and a steering angle sensor 45 are connected to the CPU 51 via an enclosure interface. This steering angle sensor 45 is provided on the handle shaft 47,
It detects the steering angle θ of the steering wheel 46 by generating a steering angle pulse every predetermined small steering angle, and the vehicle speed sensor 40
is provided on the output shaft 43 of the transmission 42 that transmits the driving force of the engine 41 to the rear wheels, and detects the vehicle speed V.

The ROM 52 stores the vehicle speed V, steering angle θ, and steering angular velocity d of the applied current output to the solenoid 30a of the electromagnetic sub-control valve 3o.
Characteristics for θ/dt and handlebar return angle are stored. The characteristics of the applied current ■ are the characteristics of the base current ■8, the characteristics of the correction current 11, and the first, second, and 11!4 correction coefficients +, k2. It consists of the characteristics of ka, and each characteristic is the fourth
This is shown as a characteristic map in FIGS.

As shown in FIGS. 4(a) and 4(b), the base current Ii decreases as the absolute values of the vehicle speed V and the steering angle θ increase. In the conventional technology in which no special control is performed when the handle returns, only this base current Is is applied to the electromagnetic control valve 3o, and in this case, the return of the handle feels heavy.

As shown in FIG. 5, the correction current 11 is O until the vehicle speed V reaches a certain value, then rapidly increases and then returns to O with a two-step break, and thereafter changes to O. I1
As shown in FIG. 6(a), 1 for 1 correction coefficient corresponds to the steering angle θ.
As the value increases, it increases rapidly, reaches a certain value, and then gradually decreases to O.

As shown in FIG. 6(b), the second correction coefficient 2 increases from a certain value as the steering angular velocity dθ/dt increases, is maintained at a constant value for a while, and then suddenly decreases to 0. As shown in FIG. 6(c), the fourth correction coefficient 4 increases in a quadratic manner until the handle return angle reaches a predetermined angle α, and then becomes a constant value. As shown in FIG. 7(a), this steering wheel return angle is the return angle from an arbitrary maximum position of the steering angle θ, and is determined by the steering angle sensor 45 from when the steering wheel return flag F, which will be described later, becomes 1. It is obtained by counting the steering angle pulses. Although each of these characteristics is stored in the ROM 52 as a characteristic map in this embodiment, it may also be stored as an experimental formula or a functional formula.

The ROM 52 also stores a control program that sets the steering wheel return flag F to 1 when the value of the steering angular velocity dθ/dt calculated based on the constantly changing steering angle θ is negative (that is, the return state).

The ROM 52 further contains vehicle speed V, steering angle θ, and steering angular velocity d.
Based on θ/dt and handle return angle, Figure 4~m! From the characteristics shown in FIG. 6, the base current Is, the correction current 11, and the first . Second and fourth correction coefficient kit k2. Calculate L,
When F=1, an applied current of I=Is is output to the electromagnetic control valve 30, and when F=1, I"Is LX
A control program for outputting an applied current of k+Xk2Xkj to the electromagnetic control valve 30 is stored.

Next, the control operation of the above embodiment will be explained with reference to the flowchart shown in FIG.

When the main switch of the car is turned on, the electronic control device 50
sets each variable to O or a predetermined initial value. Vehicle speed V and steering angle θ that change moment by moment in the driving state of the car
are detected by the vehicle speed sensor 40 and the steering angle sensor 45, and their current values are input into the registers of the enclosure. C
The PU 51 calculates the handle return flag F based on the control program for the enclosure, and executes processing operations based on the control program shown in the flowchart in FIG. 313 each time an interrupt signal is input at predetermined short intervals.

First, in step 101 of the flowchart shown in Figures 1 and 3, the CPU 51 calculates the current vehicle speed V stored in the register.
After reading the steering angle θ and the vehicle speed V, the base current θ is calculated based on the vehicle speed V and the steering angle θ using each characteristic map stored in the ROM 52 in step 102. In subsequent step 103, the CPU 51 sets the vehicle speed V to a predetermined value v.
1, if v < V + (if running at low speed), the control operation proceeds to return control 110, and if v < V +
Otherwise (if the vehicle is traveling at medium to high speeds), the control operation proceeds to the steering force control 220.

In return control 110, which is a main part of the present invention, first, if F, which is separately calculated in step 111, is not 1, that is, the handle is not in the return state, the CPU 51 returns to step 11.
In step 3, the applied current is set to the base current I11, and in step 120, this applied current I is output to the solenoid 30a of the electromagnetic control valve 30. As a result, the handle torque in the handle cutting state becomes the same value as the conventional one.

If F=1 in step 111, that is, the handle is returned, the CPU 51 executes the control operation in step 112.
In step 120, the applied current l is calculated using the previously calculated base current ■8, ll+k++k2+ kA calculated from each characteristic map, and the following formula %, and in step 120,
This applied current is output to the solenoid 30a of the electromagnetic control valve 30. This applied current is not only kA but also Is,
Although it varies depending on It, k+, and k2, if the vehicle speed V, steering angle θ, and steering angular velocity dθ/dt are the same, as is clear from the characteristics of kA, the steering wheel return angle gradually decreases until it reaches a predetermined angle α. decreases and then remains constant. The characteristic of 4 for the 114 correction coefficient only needs to be such that the handlebar return angle gradually increases from O until it reaches a predetermined angle α, and does not have to increase in a quadratic curve as shown in FIG. 6(c). Good too.

If v<V+ is not found in step 103, the CPU5
1 executes the control operation shown in the steering force control 220 to calculate the applied current, and outputs it to the solenoid 30a of the electromagnetic control valve 30 in step 120. Note that this steering force control 220 is not a main part of the present invention, so only a flowchart is shown and detailed explanation is omitted.

When step 120 is completed, the CPU 51 temporarily suspends execution of the processing operation according to the flowchart of FIG. Thereafter, each time an interrupt signal is output at predetermined short intervals, the CP
U51 repeatedly executes the processing operation according to the flowchart in Fig. 113, and controls the opening degree of the electromagnetic control valve 30 as usual when the handle is in the forward position, and until the handle return angle reaches a predetermined angle α when the handle is returned. The opening degree of the electromagnetic control valve 3o is gradually reduced from that in the cutting state.

The return control 110 shown in FIG. 113 will be explained in more detail with reference to FIG. 7. As shown in FIG.
2, when the handle return flag F becomes 1 at time t1, the fourth correction coefficient k
Since a increases up to a predetermined angle α, the applied current gradually decreases ψ from time t1 to time t2, as shown in FIG. 17(b). As a result, the opening degree of the electromagnetic control valve 30 is similarly reduced, and the assist force applied to the actuating rod 11 is also reduced. Therefore, the force in the return direction of the handle gradually increases,
The return of the steering wheel gradually changes so that it feels better.

Note that FIG. 9 is an example of a conventional technique (not publicly known) by the applicant, and in the return control 210, the operation when the handle is not returned is the same as that of the present invention (see steps 211 and 214). ), in the case of the handle returning state, the applied current is kept at the base current 1 @ until the handle returning angle reaches the predetermined angle α, step 212;
Thereafter, the applied current calculated by the following formula (% formula %) (see step 213) is output to the solenoid 30a of the electromagnetic control valve 30. With this technology, as shown in Figure 8, the applied current ψ decreases rapidly at time L2 when the handle return angle reaches a predetermined angle α, and the handle torque suddenly decreases during the return of the handle. As the steering wheel changes, the return of the steering wheel suddenly feels good and creates a strange feeling.

On the other hand, in the above-mentioned embodiment, the steering wheel torque changes so that returning the steering wheel gradually feels better, so that the steering does not feel strange when returning the steering wheel.

In the above embodiment, return control is performed when driving at low speed,
Although the steering force control is performed when the vehicle is running at medium to high speeds, the present invention may also be implemented so that the return control is performed regardless of the vehicle speed.

Further, in the above embodiment, a case was explained in which a reaction force type steering force control device was used, but the present invention is applicable to the case where a reaction force type steering force control device is used. It can also be implemented using a bypass-type steering force control device that is provided with an electromagnetic control valve that bypasses the gap. Further, in this embodiment, the steering wheel return flag F is determined by the steering angle sensor 45, but the determination may be made by a steering angle sensor and a torque sensor that detects the steering wheel torque. Further, each characteristic map may change stepwise instead of changing continuously as in the embodiment.

Further, the present invention can also be implemented in an electric power steering device.

[Brief explanation of drawings]

Fig. 111 is a diagram showing the configuration of a control device for a power steering device according to the present invention, Figs. Flowchart, I! Figure 4 is a characteristic diagram of the base current, Figure 15 is a characteristic diagram of correction current, Figure 6 is a characteristic diagram of each correction coefficient, and Figure 7 is a characteristic diagram of each correction coefficient.
The figure is a diagram showing the steering angle and the state of change in applied current with respect to the steering angle. 8 and 119 show an example of the prior art made by the applicant, IF5 is a diagram showing changes in applied current, and FIG. 9 is a flowchart of a control program. Explanation of symbols 1...Return judgment means, 2...Calculation output means. 3... Additional calculation means, 11... Operating member (operating rod), 12... Power booster (power cylinder), 15.
...Control device, 16... Rotating shaft, 20... Supply pump, 4S... Steering angle sensor, 46... Steering handle.

Claims (1)

[Claims] an actuating member that steers the steering wheel; a rotating shaft that connects the actuating member to a steering handle; a force increasing device that applies an assisting force to the operating member; and a force increasing device that applies an assist force to the rotating shaft in accordance with a torque applied to the rotating shaft and an applied current. A power steering device comprising: a control device that changes the assist force applied by the device; and a calculation output means that calculates the applied current according to the driving state of the vehicle and outputs it to the control device, wherein the steering wheel a steering angle sensor that detects the steering angle of the steering wheel, and a return determination means that detects a steering wheel return state in which the steering angle detected by the steering angle sensor is changing toward zero;
Until the return angle of the steering wheel detected by the steering angle sensor reaches a predetermined angle after the return determination means starts detecting the return state of the steering wheel, the applied current calculated by the calculation output means is applied to the assist force. 1. A control device for a power steering device, comprising additional calculation means for gradually changing the power in a decreasing direction.