JPH0794226B2 - Electric power steering device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electric power steering device for reducing an steering torque of a steering system by generating an auxiliary torque by an electromagnetic booster using an electric motor, and particularly to a control. Regarding control at the time of starting the device.

(Prior Art) Generally, an electric power steering apparatus includes an electromagnetic booster that uses an electric motor as a power source and a control device for the electromagnetic booster. The control device detects the steering torque applied to the steering wheel and generates an auxiliary torque in the electric motor based on the detection signal to reduce the steering force.

(Problems to be Solved by the Invention) However, in the above-described conventional electric power steering device, when the key switch of the vehicle is turned on, the control device is immediately activated to start the operation. When the key switch is turned on while torque is being applied, the auxiliary torque generating electric motor that has been stopped until then is started, and the applied steering force suddenly decreases. Such a sudden decrease in the steering force deteriorates the starting feeling, and the steering wheel rotates against the driver's will, which deteriorates the sense of luxury.

(Object of the Invention) Therefore, in the present invention, when the control device is started, the electric motor control signal is corrected such that the electric motor control signal gradually increases to its determined value with time, so that the steering torque at the start of the control device is large. In this case, it is an object of the present invention to provide an electric power steering apparatus that gently increases the auxiliary torque applied to the steering system by the electric motor and has a good starting feeling and a high-class feeling.

(Means for Solving Problems and Its Action) FIG. 1 is an overall configuration diagram of the present invention.

In FIG. 1, when the key switch of the ignition key is turned on, each detection signal is output from the steering torque detecting means (1) and the initial state detecting means (3). The electric motor control signal generating means (2) determines and outputs the electric motor control signal based on the steering torque signal output from the steering torque detecting means (1). In the correction means (4), when the detection signal indicating the starting state is input from the initial state detection means (3), it is corrected so as to gradually increase the electric motor control signal to the determined value of the electric motor control signal, The electric motor is driven and controlled by the electric motor drive means (5) based on the corrected electric motor control signal. Therefore, even if the steering torque is applied to the steering wheel at the time of starting, the auxiliary torque of the electric motor gently increases, so that the starting feeling becomes good.

(Embodiment) An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a perspective view showing a partial cross section of the electromagnetic booster of this embodiment. In FIG. 2, (6) is a steering wheel, (7) is an input shaft, (8) is a steering rotation sensor,
(9) is an output shaft, (10) is a steering torque sensor, (11) is an electric motor, (12) is a control device, and (13) is a power supply.

In the electric power steering apparatus of this embodiment, an output shaft (9) of the electromagnetic booster is connected to a constant velocity joint (not shown), a rack and pinion, a tie rod, a nax, etc. to steer the rotation of the steering wheel (6). It is possible to steer the vehicle by converting it into swinging motion of the wheels.

More specifically, one end of the input shaft (7) is integrally provided with the steering wheel (6), and the other end is the output shaft (9).
Is engaged with. Steering torque sensor (1
A steering rotation sensor (8) is provided between the steering wheel (6) and the steering wheel (6).

The steering rotation sensor (8) has a toothed pulley (15) wound around a toothed pulley (7a) integrally provided on the input shaft (7) via a timing belt (14) on its rotor. The DC generator (16) is integrally provided and detects the rotation direction and the rotation speed of the input shaft (7). This DC generator is connected to the control device described later.

The steering torque sensor (10) is composed of a movable iron core (17) and a differential transformer (18) provided at an engaging portion between the input shaft (7) and the output shaft (9), and the input / output shaft (7). ), (9) relative rotation is converted into a magnetic core movable core (17) fitted to the outer periphery of the output shaft (7) into an axial displacement, and this displacement is transferred to the outer periphery of the movable core (17). It is converted into an electric signal by a differential transformer (18) fitted with an appropriate gap.
A torsion bar (not shown) is connected between the input and output shafts. One end of the torsion bar is integrally provided with the input shaft (7) and the other end is provided with the output shaft (9). ing. Therefore, the axial displacement of the movable iron core (17) is
It is proportional to the torsion of the torsion bar, that is, the steering torque. The differential transformer (18) is provided with a primary winding (18a) at its center and secondary windings (18b) and (18c) at both ends thereof.
An AC signal from the control device (12) is input to a) and the secondary winding (18) is proportional to the displacement from the middle position of the movable core.
The action direction and magnitude of the steering torque output as a change in the differential electric signal from b) and (18c) are detected. The secondary windings (18b) and (18c) are connected to the control device (12), respectively.

The electric motor (11) is provided in a position substantially parallel to the output shaft (9) and incorporates a speed reducer. The output shaft of this electric motor (11) is integrally provided with a toothed small diameter pulley (19).
A timing belt (21) is wound between the toothed small-diameter pulley (19) and the toothed large-diameter pulley (20) integrally provided on the output shaft (9) to rotate the electric motor (11). It is decelerated via the belt (21) and transmitted to the output shaft (9). The electric motor (11) is connected to and controlled by the control device (12).

The control device (12) will be described with reference to FIG.
As can be seen from the figure, the motor control signal generating means (2), the initial state detecting means (3) and the correcting means (4) are
A steering torque detecting means (1) including an A / D converter (23) and a microcomputer unit (24).
The detection signal from the steering rotation detecting means (22) and the detection signal from the steering rotation detecting means (22) are read based on a command from the microcomputer unit (24) via the A / D converter (23) to determine a motor control signal to determine the motor. Output to the driving means (5),
The electric motor drive means (5) drives and controls the electric motor (11) in the steering direction based on the electric motor control signal.

More specifically, the steering torque detecting means (1) divides the steering torque sensor (10) and the reference clock signal T1 of the microcomputer unit (24) and converts the divided frequency into an AC signal to convert the steering torque sensor (10). ) And a torque interface circuit (25) for rectifying and smoothing the outputs of the secondary windings (18b) and (18c), respectively.
The respective outputs S1 and S2 of this interface circuit (25) are A
Input to the / D converter (23).

The steering rotation detecting means (22) is the steering rotation sensor (8).
And a steering rotation / interface circuit (26) that converts and amplifies the sensor output according to the polarity, respectively. The output S3, S of the interface circuit (26)
4 is input to the A / D converter (23).

The electric motor control signal generating means (2), the initial state detecting means (3), and the correcting means (4) are composed of an A / D converter (23) and a microcomputer unit (24), and A / D according to the control software described later. The signals S1 to S4 from the D converter (23) are read, the motor control signal is determined and output. The initial state detection means (3) detects whether or not the control device is in the initial state, and in the case of the initial state, the correction means (4) uses the detection signal to control the motor so that the motor control signal gradually increases to the determined value. It has the function of correcting the signal.

The electric motor drive means (5) controls the rotation direction and power of the electric motor (11) based on the electric motor control signals T2 and T3.

Next, the control software which is the operation will be described.

FIG. 4 is a flow chart showing an outline of the control processing in the microcomputer unit (24), and steps P0 to P14 in the figure show respective steps of the flow chart.

When the key switch of the ignition key is turned on, power is supplied to the microcomputer unit (23) and other circuits to start control (P0). First, in the microcomputer unit (23), initialization (P1) such as setting of I / O ports, RAM, data in registers, and clearing is performed, and arbitrary symbols N and D are set to N.
= 0 and D = 0 are set. Next, the steering torque detection signals S1, S2
Is read (P2), and the steering torque T is calculated (P3). That is, the processing of T ← S1-S2 is performed, the sign is checked, and if it is negative, the sign flag "1" is set and stored in the register, then T is converted into an absolute value and stored in the register. Next, the steering rotation detection signals S3 and S4 are read (P4), and the steering rotation speed S is calculated (P5). That is, S ← S3-S4 is processed, the sign flag is checked, and if negative, the sign flag "1" is set and stored in the register, and then S is converted into an absolute value and stored in the register.

Next, at step P6, the electric motor control signals T2 and T3 are determined by the steering torque T and the steering speed S. That is, the data D1 is taken out from the table storing the duty data D for determining the auxiliary torque of the electric motor whose address is the absolute value T of the steering torque, and the encoded value from the sign flag of the steering torque is set as D1. Further, the data D2 is taken out from the table storing the duty data D2 that determines the rotation speed of the electric motor whose address is the absolute value S of the steering rotation speed, and the encoded value from the code flag of the steering rotation speed is D2. Then, the data D1 and D2 are added, and if the sign is positive, for example, the control signal T2 indicating the rotation direction is T2 = 01,
If it is negative, T2 = 10. If it is zero, T2 = 00. Further, the value obtained by adding is converted into an absolute value, and this value is used as the control duty of the electric motor, that is, the voltage control signal T3.

Next, in step P7, it is judged if the control processing of the electric power steering device is the first time, that is, if it is in the starting state. If it is in the starting state, N set in step P1 is N = 0, so the routine jumps to step P8, and if the duty value (T3) is zero in step P6, that is, no steering torque acts on the steering wheel. If not started, D at start
Since = 0, DUTY = D, the process proceeds from step P8 to step P9, and after processing N ← 1 in step P9, the process proceeds to step P10, in which the control signal T2 is output to change the rotation direction of the electric motor. The control signal T3 is set, the control signal T3 indicating the control duty is output, and the process returns to step P2. In this case, if DUTY = D = 0, T = 00 and the rotation direction is not set.

Then, after passing from step P2 to step P6 and then to step P7, at this time, N = 1, so that the process directly proceeds to step P10, and the motor control in the normal state which is not the starting state is performed.

If the steering torque acts on the steering wheel during the starting state and the value is large, in step P8
Since DUTY> D (D = 0 in this case), step P12
Then, in step P12, the process N ← 0 for maintaining the starting state is performed, the value in the D register is incremented in step P13, this value is set as the duty value in step P14, and the process proceeds to step P10. Then, in step P10, the rotation direction is set, and in step P11, the duty value registered in step P13 is output. And
Next, in steps P12 through P8,
Further, the duty value is increased by one step, and the process of isocrementing D is repeated until DUTY = D or DUTY <0 in step P8, and gradually increases with the passage of time to the previously determined duty value. When DUTY = D or DUTY <0 in step P8, the process of N ← 1 is performed in step P9 and then step P10 is reached. After that, the normal control is performed without proceeding to step P8 and step P12. Be done.

Therefore, when the steering torque is applied to the steering wheel when the control device starts, the torque of the electric motor is gently increased, so that the starting feeling can be improved.

The present invention is not limited to the above embodiments and modifications, and various other embodiments and modifications are possible within the technical scope of the present invention, and equivalent components can be replaced. It is obvious to a person skilled in the art that it is possible. For example, in the above embodiment, control is performed such that the electric motor control signal is linearly gradually increased toward the determined value, but the duty value is increased by tracing a curve having a positive or negative curvature. May be. Further, in the above embodiments, the explanation is made assuming that the engine is started, but the same applies to the case where a failure is found in the failure diagnosis and the reset operation is performed when the failure is normally recovered later. is there. That is, for example, when the engine is operating and the reset operation is performed while applying torque to the steering system, the steering torque does not suddenly change.

As described above, according to the present invention, the control signal of the electric motor is corrected and controlled so that the torque of the electric motor is gradually increased to the required torque in the starting state when the control device is started. Thus, it is possible to obtain an electric power steering device which is stable and has good responsiveness at the time of starting the control device, has a good starting feeling, and has a high-class feeling.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of the present invention, FIGS. 2 to 4 show an electric power steering device according to an embodiment of the present invention, and FIG. 2 is a perspective view showing an electromagnetic booster thereof. Third
FIG. 4 is a schematic configuration diagram of the control device, and FIG. 4 is a flowchart showing an outline of control processing. In the drawings, (1) is steering torque detecting means, (2) is electric motor control signal generating means, (3) is initial state detecting means, and (4).
Is a correction means, (5) is an electric motor drive means, and (11) is an electric motor.

Claims (1)

[Claims] 1. Steering torque detecting means for detecting steering torque of a steering system, and electric motor control signal generating means for determining and outputting an electric motor control signal based on at least a steering torque signal output from the steering torque detecting means. In an electric power steering apparatus including an electric motor drive unit that drives an electric motor based on a control signal output from the electric motor control signal generation unit, an initial operation detection unit that detects an operation start state of the electric motor control signal generation unit, ,
An electric power steering apparatus comprising: a correction unit that corrects the electric motor control signal so as to gradually increase the electric motor control signal to its determined value with time based on a detection signal from the detection unit.