JPH03217376A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE:To keep off any heavy-current discharge at time of stationary steering locking and so on by controlling an electric motor so as to decrease its assist force according to an increase of steering angle speed when it is more than the specified car speed, but to increase it according to the increase of the steering angle speed when it is less than the specified one. CONSTITUTION:An electric motor 30 is connected to a steering mechanism 20, assisting the steering torque for a steering wheel. On the other hand, the steering torque and angle of this steering wheel are detected by each of means 41, 42, while car speed is detected by means 44. On the basis of each detected result, feed basic control over the motor 30 is performed so as to assist the steering torque according to the steering torque of the steering wheel, and feed compensation control over the motor 30 is also performed so as to decrease its assist force according to an increase of steering angle speed when it is more than the specified car speed, but to increase it according to the increase of the steering angle speed when it is less than the specified one, respectively by a means 71.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in electric power steering devices.

(Prior Art) Conventionally, electric power steering devices include a steering mechanism that steers wheels by receiving steering torque from a steering wheel, and a steering mechanism that steers wheels by receiving steering torque from a steering wheel, for example, as disclosed in Japanese Patent Application Laid-Open No. 132465/1982. There is known a vehicle that includes an electric motor mechanically connected to the steering wheel, and controls power supply to the electric motor according to the steering torque of the steering wheel so that the electric motor assists the steering torque of the steering wheel.

In this system, the assist force decreases as the steering angular speed increases, improving the convergence of the steering wheel during hands-off driving, and providing an appropriate response during sudden steering operations to improve steering feel. Improving.

(Problem to be Solved by the Invention) By the way, when the steering wheel is locked in such an electric power steering device and the steering wheel cannot be steered any further, if the steering torque is further increased in the locking direction and the lock continues, the electric power steering device will lock. Due to the configuration of the motor control system,
Excessive current flows through the electric motor, causing the battery to run down.

■As the amount of work required to the alternator increases rapidly, the engine load suddenly increases and engine stall occurs.

■If the battery voltage drops, for example, the microcontroller needs to be reset.

Other harmful effects may occur. Such problems tend to occur when the vehicle is locked.

The present invention has been made with attention to these points,
The purpose of this is to use the steering torque, vehicle speed, and steering angle data used to control the electric motor in an electric power steering system to generate a large current in the electric motor when the steering wheel is locked at a predetermined vehicle speed or below. The purpose is to prevent the flow of

(Means for solving the problem) In order to achieve the above object, the present invention basically controls the assist force according to the steering torque of the steering wheel, and increases the steering angular velocity when the vehicle exceeds a predetermined vehicle speed. The assist force is decreased in accordance with the steering angle speed, and the assist force is increased in accordance with the increase in the steering angular speed below a predetermined vehicle speed.

Specifically, the solution taken by the present invention, as shown in FIG. An electric motor 30 for unsteering the steering torque of the wheel, a steering wheel torque detecting means 41 for detecting the steering torque of the steering wheel, a steering wheel angle detecting means 42 for detecting the steering angle of the steering wheel, and a steering wheel angle detecting means 42 for detecting the speed of the vehicle. the vehicle speed detection means 44, the above-mentioned steering wheel torque detection means 41, the steering wheel steering angle detection means 42, and the vehicle speed detection means 4.
The electric motor 30 receives the output of 4 and assists the steering torque according to the steering torque of the steering wheel.
In addition to executing basic control to control the power supply to the The configuration includes a control means 71 that executes correction control to control power supply to the motor 30.

(Function) With the above configuration, in the present invention, the power supply to the electric motor 30 is controlled by the control means 7 based on the steering torque detected by the steering wheel torque detection means 41, and the electric motor 30 controls the steering wheel. The steering torque is assisted and transmitted to the steering mechanism 20.

In that case, when the vehicle speed detected by the vehicle speed detecting means 44 exceeds a predetermined vehicle speed, the assist force decreases in accordance with the increase in the steering angle speed determined from the output of the steering wheel angle detecting means 42, and when the vehicle speed is below the predetermined vehicle speed, the assist force decreases as described above. Since the power supply to the electric motor 30 is corrected and controlled so that the assist force increases as the steering angular speed increases, a suitable response can be obtained during sudden steering operations during normal driving, improving the steering feeling and improving the steering feel. Sufficient assist force is obtained when steering or when driving at extremely low speeds, reducing the steering force. Furthermore, when the steering wheel is locked, the movement of the steering wheel stops and the steering angular velocity becomes zero, so there is no assist force and the electric motor 30
The power supply to the engine is stopped, and even if the steering torque continues to increase, a large current will not flow, which prevents problems such as battery depletion, engine stalling, and battery voltage drop due to a sudden increase in the amount of work required of the alternator. .

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows an embodiment of the invention. In the figure, reference numeral 1 denotes left and right front wheels of a vehicle, which are connected to the vehicle body via steering knuckles (not shown) so as to be rotatable around a vertical axis. A knuckle arm (not shown) is attached to this steering knuckle. These two wheels 1 are steered by a steering mechanism 20.

The above steering mechanism 20 will be explained.

The knuckle arms of the left and right wheels 1 are connected by a rack joint 21, and a rack 22 is provided at the center of the rack joint 21. On the other hand, a steering shaft 24 is provided in the vehicle body. One end of the steering shaft 24 is introduced into the vehicle interior, and the steering wheel 2 is attached to the end.

Further, a pinion 23 is attached to the other end of this steering shaft 24, and this pinion 23 is attached to the rack 24.
It meshes with 2. Therefore, when the steering wheel 2 is rotated, the left and right wheels 1 are steered left and right by the steering mechanism 20 in response to the steering torque.

Steering shaft 24 of the steering mechanism 20
An electric motor 30 is mechanically connected to. That is, the drive shaft of the electric motor 30 is connected to the steering shaft 24 via a gear mechanism, and the drive shaft of the electric motor 30 is connected to the steering shaft 24 via a gear mechanism.
The steering torque of the steering wheel 2 is assisted by the driving torque of the steering wheel 2. The driving torque of the electric motor 30 is determined according to the current value supplied to the electric motor 30. A clutch 32 is provided on the drive shaft of the electric motor 30, and in the event of an abnormality, the transmission of the drive torque of the electric motor 30 to the steering shaft 24 is interrupted to perform fail-safe operation. The above electric motor 30
and clutch 32 are controlled by controller 40.

The steering shaft 24 is provided with a pair of torque sensors 41 as steering wheel torque detection means, and the torque sensors 41 detect the steering wheel 2.
The steering torque is detected. Further, the steering shaft 24 is provided with a pair of steering angle sensors 42 as a steering wheel angle detection means.
The steering angle of the steering wheel 2 is detected by this. The reason why a pair of torque sensors 41 and a pair of steering angle sensors 42 are provided is to detect a failure of the sensors. That is, by taking the difference between the output signals of the two sensors, if this difference is a constant value, it can be estimated that there is a failure. Furthermore, this vehicle is provided with a rotational speed sensor 43 for detecting the engine rotational speed, a vehicle speed sensor 44 as vehicle speed detection means for detecting the speed of the vehicle, and a voltage sensor 45 for detecting the voltage of the alternator. The transmission connected to the engine also has a bus switch 46 that detects the shift state to the reverse position.
is provided. Output signals from these sensors 41 to 46 are input to the controller 40.

A schematic configuration of the controller 40 is shown in FIG. In the figure, 50 is a CPU, and this CPU 50 is driven by a constant voltage circuit 51.

Reverse switch 46, voltage sensor 45, vehicle speed sensor 4
4. The output signal of the rotation speed sensor 43 is sent to the digital buffer 5
2 and input to the CPU 50. In that case, the output signals of reverse switch 46 and voltage sensor 45 are passed through a waveform processing circuit and counters 53, 54. Further, the output signals of the pair of torque sensors 41 and steering angle sensor 42 are processed by an annular buffer 55, and further
The signal is A/D converted by the D converter 56 and then input to the CPU 50.

On the other hand, the electric motor control signal output from the CPU 50 is D/A converted by a D/A converter 57 and then input to the electric motor 30 via a current control circuit 58, a driver 60, and a power circuit 61. In this case, the current control circuit 58 receives a signal from the fail-safe logic circuit 59, and in the event of a failure, the current supply to the electric motor 30 is cut off and the clutch 32 is disengaged. Also, 62
is a current detection circuit that detects the current value of the power circuit 6], and the output of this current detection circuit 62 is input to the current control circuit 58, and the output of the A/D converter 5 is input to the current control circuit 58.
The signal is input to the CPU 50 after being A/D converted at step 6.

Further, 63 is a current control circuit that controls the current supplied to the control system of the clutch 32, and 64 is a drive circuit that controls the drive system of the clutch 32. The output of this drive circuit 64 is detected by a monitor circuit 65 and input to the CPU 50.

Next, the control of the controller 1/roller 40 will be explained based on the flow shown in FIG. 4. After the start, first, in step S], the vehicle speed v1, the steering torque T1, the steering angle θH, and the differential value θH of the steering angle θH are read. Then, in step S2, various control amounts are calculated. That is, based on FIG. 5, the steering torque T
The assist force AT is calculated based on the differential value θH of the steering angle θH based on FIG. 6, and the correction value α is calculated based on the vehicle speed V based on FIGS. 7 and 8. , β is calculated. Next, in step S3, the vehicle speed V is set to the predetermined vehicle speed V. Determine whether the value is greater than or not. Vehicle speed V is ■. If it is larger, the process advances to step S4.

In step S4, the assist force A by the electric motor 30 is calculated from "A-α・AT-β・AθH", the current value supplied to the electric motor 30 is controlled according to this assist force A, and the process returns. Here, as shown in FIG. 5, the assist force AT is set larger according to the increase in the steering torque T, and the larger the steering torque T is, the larger the assist force A is set, and the steering force of the driver is reduced. . In this case, as shown in FIG. 7, the correction value α is set to decrease as the vehicle speed V increases, so that the higher the vehicle speed becomes, the smaller the assist force A becomes, thereby ensuring steering stability. Further, as shown in Fig. 6, the assist force AθH is set to be large according to the differential value θH of the steering angle θH, that is, the increase in the steering angle speed, and the larger the steering angle speed is, the greater the reduction in the assist force A becomes, and the sudden steering operation At certain times, the feeling of resistance increases and the steering feeling becomes better. In this case, as shown in FIG. 8, the correction value β is set to increase as the vehicle speed V increases, so that the higher the vehicle speed is, the greater the reduction in the assist force A becomes, and the feeling is improved.

Further, in step S3, the vehicle speed V is set to V. In the following cases, proceed to step S5. In step S5, the assist force A by the electric motor 30 is calculated by "A=γ・AT・AθH#, and the value of the current supplied to the electric motor 30 is controlled according to this assist force A, and the process returns. Here, the assist force AT
is set to increase as the steering torque T increases as described above, and the assist force AθH is set to increase as the steering angular velocity increases as described above. The larger T and the larger the steering angular speed, the larger the assist force A becomes. Therefore, when the vehicle is stationary or when steering at a very low speed, a sufficient assist force is obtained and the driver's steering force is reduced. Note that γ is a correction coefficient determined through experiments.

Furthermore, in this case, when the station is locked, the steering angular velocity becomes zero, so the assist force AθH becomes zero as shown in FIG. No current will flow through. Therefore, at the time of stationary lock, the electric motor 30
This prevents a large current from flowing through the engine, preventing problems such as a dead battery, engine stalling due to a sudden increase in the amount of work required of the alternator, and battery voltage drops.

According to the above flow, the power supply to the electric motor 30 is controlled so as to receive the outputs of the steering wheel torque detection means 41, the steering wheel angle detection means 42, and the vehicle speed detection means 44, and to assist the steering torque according to the steering torque of the steering wheel. In addition to executing basic control, power is supplied to the electric motor 30 so that the assist force decreases as the steering angular speed increases when the vehicle speed exceeds a predetermined vehicle speed, and increases as the steering angular speed increases below the predetermined vehicle speed. It constitutes a control means 71 that executes correction control.

Therefore, in the above-mentioned embodiment, the predetermined vehicle speed V at the time of stationary lock, etc. In the following, steering wheel 2
If the motor 30 is locked and steering is no longer possible, the power supply to the electric motor 30 is stopped, preventing problems such as battery drain due to large current discharge, engine stalling due to sudden increase in the amount of work required of the alternator, and battery voltage drop. can.

(Effects of the Invention) As explained above, according to the electric power steering device of the present invention, there is a steering mechanism that steers the wheels by receiving the steering torque of the steering wheel; It is equipped with an electric motor that assists the steering torque of the wheels, and performs basic control to control power supply to the electric motor to assist the steering torque according to the steering torque of the steering wheel, and also controls the steering angular speed when the vehicle speed exceeds a predetermined vehicle speed. As the steering angle speed increases, the assist force decreases as the steering speed increases, and when the vehicle speed is below a predetermined speed, the assist force increases as the steering angular speed increases. If the steering wheel locks and becomes unable to steer any further when the vehicle speed is below a specified speed, the power supply to the electric motor is stopped, the battery drains due to large current discharge, and the engine stalls due to a sudden increase in the amount of work required of the alternator. , it is possible to prevent problems such as battery voltage drop.

[Brief explanation of drawings]

The drawings show embodiments of the invention, and FIG. 1 is a block diagram showing the configuration of the invention. Figure 2 and the following diagrams show an example. Figure 2 is an overall schematic configuration diagram, Figure 3 is a configuration diagram of the controller, Figure 4 is a flowchart diagram showing controller control, and Figure 5 is a diagram showing steering torque and assist force. 6 is a map diagram showing the relationship between the differential value of the steering angle and the assist force, and FIGS. 7 and 8 are map diagrams showing the relationship between the vehicle speed and the correction value. 2... Steering wheel 20... Steering mechanism 30... Electric motor 41... Torque sensor (handle torque detection means) 4
2... Rudder angle sensor (steering wheel angle detection means) 44...
・Vehicle speed sensor (vehicle speed detection means) 71...Control means No. 4 Fig. 2...Steering wheel 20・Steering mechanism 30...Electric motor 41...Torque sensor (knot/torque detection means) 4
21 Rudder angle sensor (turn-on steering angle detection means) 44/Vehicle speed sensor (vehicle speed detection means) 71 Control means 2nd Fig. ■ Fig. 5 e+-+ Fig. 6 Fig. ■ Fig. 7 ■ Fig. 8

Claims (1)

[Claims] (1) A steering mechanism that receives the steering torque of the steering wheel to steer the wheels; an electric motor that is mechanically connected to the steering mechanism and assists the steering torque of the steering wheel; and a system that detects the steering torque of the steering wheel. Steering wheel torque detection means; Steering wheel angle detection means for detecting the steering angle of the steering wheel; Vehicle speed detection means for detecting the speed of the vehicle; Outputs of the steering wheel torque detection means, the steering wheel angle detection means, and the vehicle speed detection means. In response to this, basic control is executed to control the power supply to the electric motor to assist the steering torque according to the steering torque of the steering wheel.
Control that executes correction control that controls power supply to the electric motor so that when the vehicle speed exceeds a predetermined vehicle speed, the assist force decreases as the steering angular speed increases, and when the vehicle speed is below the predetermined vehicle speed, the assist force increases as the steering angular speed increases. An electric power steering device characterized by comprising means.