JPH03112778A - Controller for power steering device - Google Patents

Abstract

PURPOSE:To control returning of a handle in an optimum manner by decreasing assist force, when a steering angle and a steering angular speed are larger than the respective lower limit value, further decreasing the assist force by a predetermined proportion, when reversely the steering angle and the steering angular speed are smaller than the lower limit valve, in a return condition of the handle. CONSTITUTION:A lower steering device 10 is provided with at least a variable mechanism 13, which is provided with an electromagnetic valve 30 for changing the steering characteristic between input and output shafts 14 and 15 in accordance with an applied current, and a means 5 for outputting the applied current, controlled in accordance with a running condition of an automobile, to the variable mechanism 13. Now when a returning condition of a handle 46 is decided by a means 2, assist force is decreased when a steering angle of the handle 46, detected by a sensor 45, is, for instance, larger than a steering angle lower limit value, stored in a means 3, further when a steering angular speed, calculated in a means 1, is, for instance, larger than a steering angular speed lower limit value, stored in the means 3, and the above described applied current is controlled by a means 4.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention changes steering characteristics between an input shaft and an output shaft according to applied current according to vehicle speed, steering angle, steering wheel torque, etc. to generate assist force. The present invention relates to a control device for a power steering device equipped with a variable mechanism for controlling.

<Prior art> In a power steering system, there is a servo valve between an input shaft and an output shaft that is operated by relative rotation of both shafts, and a variable valve that changes the steering characteristics between the two shafts according to the applied current. A mechanism is provided in which the supply and discharge of working fluid to both working chambers of the power cylinder that provides assist force is controlled by the servo valve, and at this time, the current applied to the variable mechanism is varied according to driving conditions such as vehicle speed and steering angle. I'm letting you do it.

One of these is a return detection means that detects that the steering angle is changing toward the neutral position, and when it is determined that the steering wheel is in a returned state, the assist force is reduced to improve the return of the steering wheel. A handle return control that performs such control is disclosed in Japanese Patent Laid-Open No. 62-279170.

<Problems to be Solved by the Invention> In conventional steering wheel return control, when the steering angle changes in a direction approaching the neutral position, it is determined that the steering wheel is in the return state, and the current applied to the variable mechanism is changed to an assist force. Although the applied current is controlled to be small, the applied current is constant regardless of the magnitude of the steering angle or steering angular velocity. Therefore, when returning the steering wheel from a position with a large steering angle,
Alternatively, if the steering wheel is returned at a high steering angular velocity, the driver may be confused that the steering wheel returns poorly.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned problems, and includes a steering angle sensor that detects a steering angle of a steering wheel, and a steering angular velocity calculation that calculates a steering angular velocity from the steering angle. means for determining whether the steering wheel is in a returned state based on the steering angular velocity and the steering angle; a storage means for storing a predetermined lower limit value of the steering angle and a predetermined lower limit value of the steering angular velocity; When it is determined that the steering angle is in the return state, if the steering angle is larger than a predetermined lower limit of steering angle and the steering angular velocity is larger than a predetermined lower limit of steering angular velocity, the applied current is controlled to reduce the assist force. However, if the steering angle is smaller than a predetermined lower limit of steering angle or the steering angular velocity is smaller than a predetermined lower limit of steering angular velocity, the rate at which the assist force is reduced is reduced in accordance with the decrease in the steering angle and steering angular velocity. The present invention is characterized in that it has a control means for controlling the applied current in a direction in which the current is applied.

<Operation> The steering angle sensor detects the steering angle of the steering wheel, and the steering angular velocity calculation means calculates the steering angular velocity by differentiating the steering angle. The determining means determines whether the steering wheel is in the returned state or in the turned state based on the direction of the steering angle and the direction of the steering angular velocity. When the determining means determines that the steering wheel is in the returned state, the control means changes the driving state of the vehicle if the steering angle is larger than a predetermined lower limit of steering angle and the steering angular velocity is larger than a predetermined lower limit of steering angular velocity. The applied current is controlled so that the assist force is minimized with respect to the applied current calculated accordingly, so that the return of the handle is maximized. In addition, if the steering angle is smaller than a predetermined steering angle or the steering angular velocity is smaller than a predetermined steering angular velocity, the applied current calculated according to the driving state of the vehicle will be assisted according to the decrease in the steering angle and steering angular velocity. By outputting an applied current that is controlled to reduce the rate of force reduction,
Reduce the force of the return of the handle.

<Example> Hereinafter, an example of the present invention will be described based on FIGS. 1 to 6. In FIGS. 1 and 2, a power steering device 10 having an input shaft 14 and an output shaft 15 has an output using a servo valve 11 and a reaction force mechanism 13 provided between both shafts 14 and 15, and a rack and pinion mechanism. The input shaft 14 is connected to a steering handle 46 via a handle shaft 47, and the power cylinder 12 is connected to a shaft 15.
The second rack par 12a is connected to the steering wheels of the circuit via a steering linkage.

A supply pump 20 such as a vane pump driven by an automobile engine has a built-in bypass valve 21, whereby a constant flow IQ of working fluid is supplied to a diversion valve 22 via a discharge passage 23. The diversion valve 22 transfers this constant flow iQ of working fluid to the servo valve passage 23a and the reaction force control passage 23b.
A constant flow rate Q1 and Q2 are distributed to each of them.

The servo valve passage 23a is connected to the power cylinder I2 via the servo valve 11, and the reaction force control passage 23b is connected to the reaction force mechanism 13 and the electromagnetic control valve 30.

The servo valve 11 is a known rotary oven center type four-boat throttle switching valve, and is operated by relative rotation between the input shaft 14 and the output shaft 15 based on the handle torque applied to the steering handle 46. In the neutral state where no handle torque is generated, the supply boat 11a
The supplied working fluid flows equally through the left and right passages and is discharged from the discharge boat 11b to the reservoir 25. In this state, the redistribution port t-11c and lid have equal low pressure, so the power cylinder 12 is not operated. When the steering handle 46 is operated, the servo valve 11 is deviated from its neutral state to move between one distribution boat (for example, l1c) and the discharge boat 11b, and between the other distribution boat (for example, 11d) and the supply port 11a. The area of the passage between them is narrowed, and the gear generation pressure generated in the servo valve passage 23a increases. This working fluid is passed from one distribution boat (for example 11C) to one distribution passage (for example 24a) to the power cylinder 1.
2 to generate an assisting force, and the working fluid in the other chamber passes from the other distribution passage (e.g. 24a) to the other distribution boat (e.g. 11d) to the discharge boat 11.
b is discharged into the reservoir 25. This assist force is configured to increase the steering output torque of the output shaft 15 and to be transmitted to the steering wheels.

The reaction mechanism 13 includes a plunger 13b fitted into an insertion hole 13c provided on the output shaft 15 side of the servo valve 11, and a plunger 13b fitted on the input shaft 14 side of the servo valve 11.
An inclined surface 13d inclined on both sides in the circumferential direction engages with the tip of the
This is a well-known device whose main components are: Then, the pressure of the working fluid introduced into the rear part of the plunger 13b via the boat 13a is changed by the electromagnetic control valve 30 to change the torsion spring characteristics between the input shaft 14 and the output shaft 15, and the servo valve 11 is actuated. By changing the characteristics, the characteristics of the steering output torque with respect to the steering wheel torque are changed. This electromagnetic control valve 30 normally has the smallest opening, and as the current applied to the solenoid 30a increases, the opening gradually increases until it is fully open.

As shown in FIG. 2, the electrical control device 50 has a microprocessor (hereinafter referred to as CPU) 51, a read-only memory (hereinafter referred to as ROM) 52, and a writable memory (hereinafter referred to as RAM) 53 as main components. CPU5
A solenoid 30a of an electromagnetic control valve 30 is connected to the solenoid 30a of the electromagnetic control valve 30 via an enclosure fence and a solenoid drive circuit to control the current applied thereto.

Further, a steering angle sensor 45 and a vehicle speed sensor 40 are connected to the CPU 51 via an enclosure fence.

The steering angle sensor 45 is connected to the handle shaft 47 and detects the steering angle θ of the steering handle 46.

Further, the vehicle speed sensor 40 is constituted by a tachometer connected to the output shaft 43 of the transmission 42 that transmits the driving force of the engine 41 to the rear wheels 44.
The vehicle speed V is detected based on the frequency of the pulse signal generated from the pulse signal.

The ROM 52 stores control characteristics of the applied current i applied to the solenoid 30a of the electromagnetic control valve 30 with respect to the steering angle θ and the vehicle speed V. This control characteristic is such that the applied current i decreases as the steering angle θ increases, and the applied current i decreases as the vehicle speed V increases, and is stored as a characteristic map or function equation. There is.

In this embodiment, in normal driving conditions, the applied current i is increased to increase the opening degree of the electromagnetic control valve 30 in response to a decrease in the vehicle speed V and a decrease in the steering angle θ, and the applied current i is increased to increase the opening degree of the electromagnetic control valve 30, and the The input shaft 14 and the output shaft 1 are
The torsion spring characteristics between 5 and 5 are soft. Therefore, vehicle speed V
As the steering angle θ decreases, the assist force ratio increases.

Then, the determination means 2 based on the flowchart disclosed in, for example, Japanese Patent Laid-Open No. 62-279170,
When it is determined that NEGA=1, that is, the handle is in the returned state, the applied current is decreased to reduce the opening degree of the electromagnetic control valve 30, the working fluid pressure applied to the reaction force mechanism 13 is increased, and the input shaft 14 is The torsion spring characteristics between the output shaft 15 and the output shaft 15 are stiffened, the assist force ratio is reduced, and return control is performed to improve the return of the steering wheel by the restoring force from the tires.

At this time, the control means 4 applies the applied current determined as follows to the solenoid 30a of the electromagnetic control valve 30. That is, in the initial state, the electric control device 50
Each variable is set to a predetermined initial value, and the vehicle speed V and steering angle θ, which change every moment while the vehicle is running, are detected by the vehicle speed sensor 40 and the steering angle sensor 45, and their current values are stored in the registers of the circuit. is input. CPU5
1, each time an interrupt signal is input at a predetermined short time interval,
The processing operations shown in FIG. 3 are executed.

In step 100 of the flowchart in FIG. 3, the vehicle speed V and steering angle θ are read, and in step 101,
After reading the base current (2) obtained from the circuit map according to the vehicle speed V and the steering angle θ, in step 102, the steering angle θ is differentiated to calculate the steering angular velocity θ. Thereafter, in step 103, the above-mentioned determining means 2 determines whether the steering wheel direction is the turning direction or the returning direction.

If it is determined that the direction of the steering wheel is the return direction, then in step 104, a variable Xθ corresponding to the steering angle θ is read. As shown in Figure 4, the variable Xθ becomes 0 when the steering angle θ is O, and becomes 1 when it is larger than θ, and when the steering angle θ increases, the variable Xθ changes in a straight line from 0 to 1. is increasing. Furthermore, in step 105, a variable Xθ corresponding to the steering angular velocity θ is read. As shown in FIG. 5, the variable Xθ becomes 0 when the steering angular velocity θ is O, and θ1
At θ2, it becomes 1, and at 0<θ<θ1, the variable Xθ increases linearly from O to 1 as the steering angular velocity θ increases, and θ2
At θ3, the variable Xθ becomes 0 as the steering angular velocity θ increases.
It decreases linearly from 1 to 1.

Then, in step 106, the variable Xθ read in step 104 and the variable Xθ read in step 105 are
is multiplied by the return current correction value 1com to calculate the control current Δi. This correction value 1cova changes to become smaller as the vehicle speed increases, and as a map, the ROM 52
is stored in If it is determined in step 103 that the steering direction of the steering wheel is the turning direction, the control current Δi is set to O in step 107.

Then, in step 108, the control current Δi is subtracted from the base current ■ read in step 101, and the output current I0 is
In step 109, the output current I0 is applied to the solenoid 30a of the electromagnetic control valve 30, and CP
U51 stops execution of the processing operation according to the flowchart of FIG.

From then on, each time an interrupt signal is output at a predetermined time,
The CPU 51 repeatedly executes the processing operation according to the flowchart of FIG.

As described above, when the steering wheel is in the returned state, the steering angle θ is larger than θ and the steering angular velocity θ is θ1<θ<θ2
In the case of , the correction value Icon of the return current is subtracted from the base current ■, and the assist force is controlled to be the smallest.
When the steering wheel is stopped and the steering wheel is suddenly turned when the steering angular velocity θ is outside the range of θ1 < θ < θ2 near the vertical position where the steering wheel return is best, the steering angle θ and the steering angular velocity are Control current Δi reduced according to θ
is subtracted from the base current (■) to reduce the rate at which the assist force decreases, thereby decreasing the degree of return of the steering wheel. That is, by adjusting the return current depending on the magnitude of the steering angle θ and the magnitude of the steering angular velocity θ, it is possible to change the degree of return of the steering wheel.

Note that in this embodiment, the opening degree of the electromagnetic control valve 30 is changed by the applied current, and the working fluid pressure applied to the reaction force mechanism 13 is increased/decreased to change the steering force, but the present invention is not limited to this. Instead, the present invention can also be applied to bypass control in which the steering force is changed by controlling a variable valve disposed between a high pressure chamber and a low pressure chamber of a hydraulic cylinder using a control current.

<Effects of the Invention> 4 As described above, according to the present invention, when the steering wheel is in the return state and the steering angle θ is larger than θ1 and the steering angular velocity θ is larger than θ1, the return current is changed from the base current ■. The correction value 1com is subtracted to control the assist force to be the smallest, so that the steering wheel returns best. In addition, when the steering angle θ is smaller than θ1 near neutral and the steering angular velocity θ is smaller than θ8, the correction value Icom of the return current is reduced according to the decrease in the steering angle θ and the steering angular velocity θ. The control current Δi is subtracted from the base current (■), so that the rate at which the assist force decreases is decreased, and the degree of return of the steering wheel is decreased. In this way, by adjusting the return current depending on the magnitude of the steering angle θ and the magnitude of the steering angular velocity θ, it is possible to change the degree of steering wheel return to the optimum weight.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a control device for a power steering device according to the present invention, FIGS. 2 to 5 show an embodiment of the present invention, and FIG.
The figure is an overall explanatory diagram, Figure 3 is a flowchart of the control program in the determination means, and Figure 4 is the steering angle θ and the variable Xθ.
FIG. 5 is a diagram showing the relationship between the steering angular velocity θ and the variable Xθ. 1... Steering angular velocity calculation means, 2... Judgment means, 4.
... Control means, 5... Output means, 11... Servo valve, 12... Power cylinder, 13... Variable mechanism, 1
4... Input shaft, 15... Output shaft, 20... Supply pump, 30... Solenoid control valve, 40... Vehicle speed sensor,
45... Steering angle sensor, 46... Steering handle.

Claims (1)

[Claims] (1) An input shaft connected to the steering wheel, an output shaft connected to the steering wheels, a power cylinder that provides assist force to the output shaft, and a power cylinder that operates in accordance with the relative rotation between the two shafts. a variable mechanism comprising: a servo valve that controls supply and discharge of working fluid sent from a supply pump to both working chambers of the power cylinder; and a solenoid valve that changes steering characteristics between the two shafts in accordance with applied current; and a power steering device comprising an output means for outputting the applied current controlled according to the running state of the vehicle to the variable mechanism, a steering angle sensor for detecting a steering angle of the steering wheel, and a steering angle sensor for detecting a steering angle of the steering wheel; a steering angular velocity calculating means for calculating a steering angular velocity; a determining means for determining whether the steering wheel is in a return state based on the steering angular velocity and the steering angle; and a memory for storing a predetermined lower limit value of the steering angle and a predetermined lower limit value of the steering angular velocity. and when the determining means determines that the steering wheel is in the returned state, the assisting force is reduced if the steering angle is larger than a predetermined lower limit of steering angle and the steering angular velocity is larger than a predetermined lower limit of steering angular velocity. If the steering angle is smaller than a predetermined lower limit value of steering angle or the steering angular velocity is smaller than a predetermined lower limit value of steering angular velocity, the rate at which the assist force is reduced is adjusted to A control device for a power steering device, comprising a control means for controlling the applied current in a direction in which the applied current is decreased in accordance with a decrease in steering angular velocity.