JPH0313114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a control device for an electric power steering device for an automobile.

BACKGROUND TECHNOLOGY In order to reduce the need for steering wheel operations during steering in automobiles, a torque sensor is provided to detect steering torque during steering operations, and the steering torque detected by the torque sensor is converted into an electrical quantity. Electric power steering devices have already been developed in which the output of an electric motor is variably controlled according to changes in the amount of electricity, and the electric motor provides power assist in the steering direction according to the steering torque. (For example, see Japanese Patent Publication No. 45-41246).

Problems to be Solved by the Invention In general, the steering wheel operation in a car is heavy when stopped (stationary) and when driving at low speeds, and becomes light when driving at high speeds. If the output characteristics of the electric motor are set so as to make the stationary shift sufficiently light in In a transient state in which the output starts to be output, the steering wheel feels strange in some way, and the problem is that it has a negative effect on the steering feel, especially when driving at high speeds.

The present invention aims to solve the above-mentioned problems.

Means for Solving the Problems The present invention provides an electric power steering device in which a first motor output instruction value is determined based on a steering torque signal of a torque sensor that detects steering torque and generates a steering torque signal. a first motor output instruction function section configured to control the first motor output instruction value in accordance with the vehicle speed such that it becomes larger at low vehicle speeds and becomes smaller as the vehicle speed becomes higher; and the steering of the torque sensor. a second motor output instruction function unit that determines a second motor output instruction value based on a function in which the steering torque signal gradually rises to a very gentle slope from zero or extremely close to zero in response to the torque signal; The output of the electric motor is controlled by the added value of the first motor output instruction value and the second motor output instruction value, and the output of the electric motor is used to perform power assist in the steering direction of the steering mechanism. It is characterized by:

Operation In the above configuration, the first motor output instruction function section causes the power assist by the electric motor to be large and the steering force to be light when the vehicle is stopped or at low speed, and the power assist by the electric motor to be small when driving at high speed. In addition, the second motor output instruction function section provides a slight output to the electric motor in the range where the motor output instruction value of the first motor output instruction function section is still zero. This significantly reduces the discomfort in handling during a transient state in which the motor output instruction value of the second motor output instruction function section rises from zero, and smooths out the steering feel especially when driving at high speeds. It is possible.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a torque sensor that is installed, for example, in a steering shaft portion and detects steering torque during a steering operation and generates a torque signal S corresponding to the steering torque. The signal is input to the first motor output instruction function section 2 and the second motor output instruction function section 3.

The first motor output instruction function unit 2 receives the torque signal S as shown in FIG. 2, for example, as shown in FIG.
As shown by So, the first motor output instruction value A1 is set based on the first motor output instruction function which is zero when the torque signal value is less than the predetermined value So and rises at a predetermined inclination angle when the torque signal value is equal to or greater than So. The second motor output instruction function section 3
For example, as shown in FIG. 4, the second motor output command value A2 is based on the second motor output command function that gradually rises at a very gentle slope from zero or very close to zero with respect to the torque signal S.
It is becoming more and more determined.

And the first and second motor output command values A1, A2
The electric motor 6 is configured to output an output according to the output instruction value A via the electric motor drive section 5 at the added value A=A1+A2, and power assist the steering mechanism 7 with the output.

The first and second motor output instruction function units 2 and 3
Among them, the first motor output instruction function section 2 controls the first motor output according to the vehicle speed signal v of the vehicle speed sensor 4 so that as the vehicle speed increases, the output instruction value A1 with respect to the torque signal value becomes smaller. It is designed to change the indicator function.

That is, the vehicle speed signal v from the vehicle speed sensor 4 is added to the torque signal S as shown by the solid line in FIG. 1, and is inputted to the first motor output instruction function section 2 as s+v. For example, if the vehicle speed signal vo when the vehicle speed is zero is set to zero, s+v=s, and the first motor output instruction function unit 2 adjusts the first motor output based on the basic function indicated by the symbol vo in FIG. indicated value
Determine A1.

If the vehicle speed signal v1 during medium speed driving is set to a certain negative number, s+v1 is a function of the torque signal shown by the solid line as shown by the dotted line in Fig. 2.
The value specified by the function is shifted in parallel to the negative side, that is, downward, by the negative coefficient corresponding to v1,
In the first motor output instruction function section 2, v1 in FIG.
The first motor output instruction value A1 is determined based on the function obtained by translating the basic function to the right side, as expressed by the sign The value A1 is considerably lower than when the vehicle is stopped, that is, when the vehicle speed signal is vo.

If the absolute value of the negative addition coefficient to be added to the torque signal S is set so that it increases as the vehicle speed increases, during high-speed driving, as shown by the sign v2 in Fig. 3, The instruction function of the first motor output instruction function section is in the same state as if it were further translated in parallel to the right, and during high-speed running, the first motor output instruction value is determined based on the function indicated by the sign v2.
A1 is determined, and the first motor output instruction value A1 for the torque signal S becomes even lower than that during the above-mentioned medium speed running.

Even if the output of the electric motor 6 is controlled via the electric motor drive unit 5 using only the first motor output instruction value A1 of the first motor output instruction function unit 2 in this way,
When the vehicle is stationary or running at low speeds, the power assist by the electric motor 6 is large and the steering force is lightened, and when the vehicle is running at high speeds, the power assist by the electric motor 6 is small to provide handling with appropriate responsiveness (weight). However, in general, in a mechanism that uses the output of an electric motor to provide power assist, when the electric motor starts outputting from a state of zero output, some kind of vibration may occur due to the inertia and backlash of the electric motor itself. The first motor of the first motor output instruction function section 2, which is controlled by the vehicle speed as described above, If the motor output is controlled only by the output instruction value A1, there will be a problem with the smoothness of handling near the rise of the instruction function from zero, and this will have the disadvantage of worsening the steering feel, especially when driving at high speeds.

Therefore, in the present invention, a second motor output instruction function unit 3 is provided which determines a motor output instruction value A2 according to the torque signal S based on an instruction function as shown in FIG. 4, which is not related to vehicle speed. indicated value
The output of the electric motor 6 is determined by the motor output instruction value A which is the sum of A2 and the motor output instruction value A1 of the first motor output instruction function section 2 which is controlled by the vehicle speed. .

With this configuration, the electric motor 6
As shown in FIG. 5, the steering mechanism 7 is operated at the motor output instruction value A determined by the instruction function represented by the sign vo' when stopped, v1 when running at medium speed, and v2' when running at high speed. Power assist in the steering direction is performed in the range where the steering torque T is generated due to resistance such as friction within the steering mechanism 7 during steering operation, but the steering mechanism 7 has not actually started moving yet. The electric motor 6 receives the second motor output instruction value.
The electric motor 6 generates an output by A2, and at the time when the first motor output command value A1 is added to the above A2 to perform practical power assist, the electric motor 6 is already generating output at the output command value A2 as described above. Since only the magnitude of the output of the electric motor 6 changes,
The change in output is extremely smooth, and there is almost no discomfort in handling, and as mentioned above, the electric motor 6 starts outputting power only when the steering mechanism 7
is within the range of the resistance of the steering mechanism before it actually starts moving, so vibrations of the electric motor are absorbed by the resistance of the steering mechanism and are hardly transmitted to the steering wheel etc., and the first motor output instruction function section 2 Even during high-speed driving, where the rise of the indicator function from zero is considerably delayed, an extremely smooth steering feel can be obtained.

In addition, the purpose of increasing the power assist to lighten the steering force when stationary or driving at low speeds, and decreasing the power assist to obtain moderately responsive handling when driving at high speeds is to increase the power assist when driving at low speeds, and to obtain moderately responsive handling by decreasing the power assist when driving at high speeds. It goes without saying that the output instruction value A1 can be used satisfactorily.

In the above embodiment, the sum signal s+ of the vehicle speed signal v of the vehicle speed sensor 4 and the torque signal S of the torque sensor 1 is
In this example, the first motor output instruction value is determined based on v. Motor output instruction function section 2
For example, input the above multiplication coefficient (for example,
1.0, 0.7, 0.5, etc.), the slope angle of the basic function is configured to become gentler as the vehicle speed increases, and the slope angle becomes gentler depending on the vehicle speed. Even if the output instruction value A1 is determined, the same function as above can be achieved.

Although not shown in FIG. 1, it goes without saying that the direction of steering is detected and the electric motor drive section 5 switches and controls the direction of the output of the electric motor 6 based on this detection.

Effects of the Invention As described above, according to the present invention, in an electric power steering device, with an extremely simple configuration, the power assist is increased when stationary or when driving at low speeds, the steering force is lightened, and the power assist is applied when driving at high speeds. In addition to fully satisfying the purpose of obtaining an appropriate steering force with a small torque, it also improves the connection between the electric motor output during steering and significantly improves the steering feel, especially when driving at high speeds. , which can bring about great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Figure 2 is a torque signal characteristic diagram for steering torque.
3 is a first motor output instruction value characteristic diagram of the first motor output instruction function section of FIG. 1, FIG. 4 is a second motor output instruction value characteristic diagram of the second motor output instruction function section of FIG. 1, FIG. 5 is a characteristic diagram of the added value of the first motor output command value and the second motor output command value. DESCRIPTION OF SYMBOLS 1...Torque sensor, 2...First motor output instruction function section, 3...Second motor output instruction function section, 4
...Vehicle speed sensor, 5...Electric motor drive unit, 6...
...Electric motor.

Claims (1)

[Claims] 1 A first motor output instruction value is determined based on a steering torque signal of a torque sensor that detects steering torque and issues a steering torque signal, and the first motor output instruction value varies depending on the vehicle speed; A first motor output indicating function part is controlled so that the output decreases as the vehicle speed increases, and the steering torque signal is controlled to decrease from zero or extremely close to zero according to the steering torque signal of the torque sensor. The second function is based on the function that gradually rises with a gentle slope.
a second motor output instruction function unit that determines a motor output instruction value, and controls the output of the electric motor with the added value of the first motor output instruction value and the second motor output instruction value, and A control device for an electric power steering device, characterized in that power assist in a steering direction of a steering mechanism is performed using the output of an electric motor.