JPH10278818A - Power steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device for a vehicle attempted to reduce a lateral difference of steering force on an actual vehicle. SOLUTION: A lateral difference to set off a lateral difference of a steering load of a vehicle is provided on a characteristic of assist force against handle input torque on a power steering device for the vehicle workability of a handle 10 of which is improved by adding specified assist force in accordance with the handle input torque to steering torque of the handle 10. That is, it is devised to drive an assist motor to set off the lateral difference of the steering load of the vehicle by providing the lateral difference on an assist command value.

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 used for a vehicle such as an automobile, and more particularly to a device suitable for an electric power steering system for reducing a left-right difference in steering force.

[0002]

2. Description of the Related Art Various types of power steering devices for vehicles such as automobiles have been proposed.
Among them, there is a configuration as shown in FIG. 6, and when a steering wheel is steered, an assisting force is determined by the steering wheel input torque, and there is a system in which an assist torque is added to the steering torque to improve the operability of the steering wheel. .

Here, in this power steering device, a force (rack axial force) required for steering a tire.
Is equal to the load at the time of steering. Also, the rack axial force is
It is represented by steering wheel input torque × gear ratio + assisting force. On the other hand, the assisting force is determined by the steering wheel input torque as shown in the characteristics of FIG.

[0004] Therefore, if the load at the time of steering is large, a rack axial force corresponding to the load is required, and furthermore, a handle input torque corresponding thereto is required. Therefore, the load at the time of steering (rack axial force) and the handle input torque are required. Figure 1
A characteristic like 0 will be shown. Therefore, in the case of a vehicle having a characteristic of steering wheel angle-steering load (rack axial force) as shown in FIG. 11, the steering characteristics are as shown in FIG.

[0005]

As shown in FIG. 9, in this type of conventional power steering apparatus, the characteristic of steering wheel input torque-assist force is symmetrical, but actual steering of the vehicle is performed. Due to the shape of the suspension, the influence of the center of gravity of the vehicle, and the like, the load state is often such that the steering load with respect to the steering wheel steering angle is not symmetrical as shown in FIG. 11, and as a result, as shown in FIG.
There is a problem that a left-right difference occurs in the steering force.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicular power steering device that reduces the left-right difference in steering force in an actual vehicle. is there.

[0007]

Means adopted by the first aspect of the present invention to solve this problem are described with reference numerals used in the embodiments. In a power steering device for a vehicle in which a predetermined assist force according to a torque is added to improve the operability of the steering wheel 10, the characteristic of the assist force with respect to the steering wheel input torque includes a right and left steering wheel which offsets a left and right difference in a steering load of the vehicle. A power steering device for a vehicle, characterized by having a difference.

That is, in a power steering apparatus for an automobile as shown in FIG. 6, an assist force is determined by a steering wheel input torque to assist a steering section. In many cases, the steering load is not symmetrical due to the shape or the displacement of the center of gravity of the vehicle, and the steering load with respect to the steering angle is not symmetrical.

Therefore, for example, as shown in FIG. 11, when there is a left-right difference in the relationship between the steering wheel angle and the steering load,
Since the steering load with respect to the steering wheel angle is large when turning right, as shown in FIG. 7, the characteristic of the assist force with respect to the steering wheel input torque is determined so that the turning with the right turn becomes larger, so that the steering load is reduced. Since it is possible to cancel the left-right difference, as shown in FIG.
The steering force characteristics can be made symmetrical.

That is, in the vehicle power steering apparatus according to the first aspect of the present invention, the steering wheel input torque-assisting force characteristic is changed so as to cancel the steering angle-steering load characteristic which is not symmetrical. As a result, the left-right difference in the steering force is reduced by the asymmetric configuration.

By the way, if the above-described configuration is to be realized by a conventional hydraulic power steering device,
Since the characteristics of the steering load vary depending on the type of vehicle, it is difficult to tune the hydraulic valve and the like, and there is a problem that the number of processing steps is complicated and the cost is increased.

In order to solve this problem, the invention according to claim 2 has been devised. In order to solve the problem, a predetermined assist command determined by the steering torque of the steering wheel 10 is provided. In the electric power steering device for an electric vehicle, which drives the assist motor to add an assist force to the steering torque according to the steering torque to improve the operability of the steering wheel, a left and right difference is provided in the assist command value to reduce the steering load of the vehicle. An electric vehicle power steering device characterized in that an assist motor is driven so as to cancel the left-right difference.

That is, as shown in FIG. 3, an assist command value (current command value) is determined by an electric control unit (ECU 50) based on a steering wheel input torque signal corresponding to the steering torque of the steering wheel 10, and a drive is performed based on the assist command value. As shown in FIG. 4, in an electric vehicle power steering apparatus that drives an assist motor 40 via a circuit to add an assist force to a steering torque, as shown in FIG. Only by providing the left and right difference in the motor current characteristic with respect to the torque, the left and right difference of the steering load can be offset, and the existing configuration can be used as it is, so that adjustment according to the vehicle type can be easily performed and some cost increase is required. In other words, an electric vehicle power steering device with reduced left-right steering force It can be current.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, an example in which the present invention is applied to an electric vehicle power steering device will be described.

First, in FIG. 2, when the steering wheel 10 is operated, the steering torque is applied to the input shaft 1 of the gear case 11.
1a, and drives the rack 12 via a pinion at the lower end of the output shaft 11b. This rack 12 changes the direction of wheels 14 via a steering link 13.

On the other hand, as shown in FIG.
1, a torque sensor 20 detects a steering torque, a vehicle speed sensor 30 detects a vehicle speed, and an electric signal thereof is input to an electric control device (ECU 50). EC
U50 is the input from the torque sensor 20 and the vehicle speed sensor 3
A predetermined assist command value (current command value) is determined based on the input from 0, transmitted to a drive circuit via each limiter, and the drive circuit
0 is driven.

The torque of the assist motor 40 is transmitted to the input shaft 16a of the gear case 16 via the electromagnetic clutch 15.
And drives the rack 12 via a pinion at the lower end of the output shaft 16b. This rack 12 has a handle 10
The drive shaft 10b is driven by the output shaft 16b of the assist motor 40 together with the output shaft 11b, so that the operability of the steering wheel 10 is significantly improved.

In this embodiment, the handle 10
The ECU 50 performs return control to improve the return of the motor, and the motor rotation speed estimation calculation means 54 estimates and calculates the rotation speed of the assist motor 40 from the current detection value of the assist motor 40 and the motor terminal voltage value. When the rotation direction of the assist motor 40 obtained from the numerical value and the input direction of the steering torque obtained from the torque sensor 20 are different from each other, the polarity determination unit 53 that determines that the steering wheel 10 is in the return state is in the return state. When it is determined that the return command value determined from the vehicle speed is added to the assist command value, the return of the steering wheel 10 is improved.

Further, in this embodiment, the differential command value determined by the differential amount of the steering torque input from the torque sensor 20 and the vehicle speed input from the vehicle speed sensor 30 is converted into an assist command value (current command value). The addition compensates for the phase lag of the control system.

It is the present invention to reduce the left-right difference in the steering force of the steering wheel 10 due to the left-right difference in the steering load generated for each type of vehicle in such an electric vehicle power steering apparatus. , As described above,
As shown in FIG. 4, the left-right difference in the steering load can be canceled only by providing the left-right difference in the motor current characteristic with respect to the steering wheel input torque, that is, only by providing the left-right difference in the assist command value. I have.

Here, the left-right difference in the steering load changes depending on the load state of the vehicle (for example, when the vehicle is occupied by one person, when the vehicle is fully occupied, or the load state of luggage). Therefore, as shown in FIG. 5, the left / right difference of the steering load is automatically detected by the load state detecting means 60 such as the number of occupants switch and the load sensor, and the left / right difference is determined by the left / right difference determining means 61 according to the detected value. By adding to the original current command value, obtaining the left / right difference by automatic correction of the assist command value, and performing steering control based on this, it is possible to always obtain the optimum steering feeling regardless of the fluctuation of the load state of the car. become able to.

If the driver can arbitrarily switch the difference between the left and right assist command values by operating a switch or the like, a steering sensation according to the user's preference can be obtained, and a load sensor and the like can be obtained. The load state detecting means 60 becomes unnecessary, and cost can be reduced.

[0023]

As described in detail above, the power steering apparatus for a vehicle according to the present invention offsets the steering load of the vehicle from side to side by providing a left-right difference in the characteristic of the assist force with respect to the steering wheel input torque. This has the effect of reducing the left-right difference in the steering force of the actual vehicle.

In particular, in the invention according to the second aspect, the left-right difference in the steering load can be canceled by only providing the left-right difference in the assist command value, and the existing configuration can be used as it is. This makes it possible to achieve an extremely excellent effect that an electric vehicle power steering apparatus in which the left-right difference in the steering force is reduced can be realized easily without making any adjustment and without increasing the cost.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a first embodiment in which the present invention is applied to an electric power steering apparatus for an automobile.

FIG. 2 is a block diagram illustrating the structure of the first embodiment.

FIG. 3 is a block diagram illustrating a system according to a first embodiment.

FIG. 4 is a graph showing assist command value characteristics (handle input torque-motor current characteristics) in the first embodiment.

FIG. 5 is a block diagram of another embodiment in which the assist command value is automatically corrected according to the load state of the vehicle in the first embodiment.

FIG. 6 is a block diagram illustrating a system according to a second embodiment in which the present invention is applied to a hydraulic power steering apparatus for an automobile.

FIG. 7 is a graph showing a steering wheel input torque-assisting force characteristic in the second embodiment.

FIG. 8 is a graph showing a steering wheel angle-steering wheel input torque (steering force) characteristic in a state where the left-right difference is corrected.

FIG. 9 is a graph showing a conventional steering wheel input torque-assisting force characteristic.

FIG. 10 is a graph showing a conventional steering wheel input torque-steering load (rack axial force) characteristic.

FIG. 11 is a graph showing a steering angle-steering load (rack axial force) characteristic including a left-right difference.

FIG. 12 is a graph showing a steering angle-steering wheel input torque (steering force) characteristic including a left-right difference.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Handle 20 Torque sensor 30 Vehicle speed sensor 40 Assist motor 50 Electric control unit (ECU) 53 Polarity discriminating means 54 Motor rotation speed estimation calculating means 60 Load state detecting means 61 Left-right difference determining means

Claims (4)

[Claims] 1. A power steering apparatus for a vehicle, in which a predetermined assisting force corresponding to a steering wheel input torque is added to a steering wheel steering torque to improve the operability of the steering wheel, a characteristic of the assisting force with respect to the steering wheel input torque. To
A power steering device for a vehicle, wherein a left / right difference is provided for canceling a left / right difference in a steering load of the vehicle. 2. An electric vehicle power for driving an assist motor to add an assist force to the steering torque according to a predetermined assist command value determined by the steering torque of the steering wheel, thereby improving the operability of the steering wheel. An electric vehicle power steering device, wherein a left-right difference is provided in the assist command value, and the assist motor is driven so as to offset a left-right difference in a steering load of the vehicle. 3. The electric type according to claim 2, wherein a left / right difference in the steering load of the vehicle is detected by a load state detecting means, and the left / right difference in the assist command value is controlled in accordance with the detected value. Vehicle power steering device. 4. The system according to claim 2, wherein the driver can arbitrarily switch the left / right difference between the assist command values.
An electric vehicle power steering device as described in the above.