JPH034620Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a control device for an electric power steering device for an automobile.

Prior Art In automobiles, in order to reduce the need for steering wheel operations when turning the steering wheel, a torque sensor is provided to detect the steering torque during the steering operation, and this converts the steering torque into an electrical quantity. An electric power steering device has already been developed that variably controls the output of the electric device in response to changes in the steering torque and performs power assist in accordance with the steering torque (see, for example, Japanese Patent Publication No. 41246/1983).

Problems to be solved by the invention In the electric power steering system as described above, an auxiliary steering force is applied that is approximately proportional to the steering torque regardless of the vehicle speed, so it is difficult to provide sufficient auxiliary steering when stationary or when driving at low speeds. If you try to apply more force to the vehicle, there is a problem in that the steering force becomes too light when driving at high speeds, which tends to lead to excessive turning of the steering wheel.

An object of the present invention is to provide an electric power steering device that can deal with this problem.

Means for Solving the Problems The present invention provides an electric power steering device in which current is controlled to an electric motor according to the torsional torque of a steering shaft, and the electric motor provides power assist in the steering direction. The assist direction motor current command value of the output torque value instruction function section that issues the assist direction motor current command value based on the addition signal obtained by adding the sensor voltage addition coefficient signal determined by the vehicle speed and the torsional torque signal of the steering shaft and the vehicle speed are The direction of power assist and the output torque of the electric motor are controlled by the multiplication signal of the multiplication calculation section which generates a signal multiplied by a vehicle speed coefficient signal which gradually becomes smaller as the speed increases. It is something.

Effect: By adopting the above configuration, the present invention moves the assist direction motor current command value having one basic function in parallel with the torsional torque signal of the steering shaft according to the vehicle speed, and the assist direction motor current that has been shifted in parallel. The slope of the command value can be gradually made gentler as the vehicle speed increases.

Embodiments The present invention will be described in detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and the portion surrounded by chain lines shows the conventional structure.

First, a general control mode of an electric power steering device will be explained with reference to FIG.

Reference numeral 1 denotes a torsional torque sensor that generates a torsional torque signal of the steering shaft. The polarity of the torsional torque signal from the torsional torque sensor 1 is determined by a positive/negative determining unit 2, and the output direction of the electric motor 8 is determined by an electric motor drive unit 4. is determined, and the absolute value of the torsional torque signal of the torsional torque sensor 1 is determined by the absolute value converter 3.

Reference numeral 5 denotes an output torque value indicating function unit which issues an assist direction motor current command value with respect to the absolute value of the torsion torque signal, and the duty control unit 6 controls the assist direction motor current command value and the armature current detection unit 7.
The duty ratio is determined so that the motor current matches the assist direction motor current command value by comparing the output of Power assist by torque is provided to the steering mechanism 9.

With conventional electric power steering devices such as those mentioned above, if an attempt is made to provide sufficient power assist when stationary or driving at low speeds, the steering force becomes too light when driving at high speeds, which tends to lead to excessive turning of the steering wheel. As mentioned above, this problem occurs.

In the present invention, as shown in FIG. 1, in addition to the conventional torsional torque sensor 1 that emits a torsional torque signal of the steering shaft, a vehicle speed sensor 10 that detects the vehicle speed is used.
and an addition calculation constant function unit 11 that generates a sensor voltage addition coefficient signal _S0 that gradually decreases as the vehicle speed increases; and a vehicle speed coefficient indicator function that generates a vehicle speed coefficient signal that gradually decreases as the vehicle speed increases. an addition calculation unit 13 which uses the unit 12 to generate an addition signal of the absolute value S of the torsional torque signal of the torsional torque sensor 1 and the sensor voltage addition coefficient signal S ₀ obtained by the addition calculation constant function unit 11; and the output torque; A multiplication calculation section 14 is provided which generates a multiplication signal of the assist direction motor current command value of the value instruction function section 5 and the vehicle speed coefficient signal obtained by the vehicle speed coefficient instruction function section 12.

That is, the addition calculation constant function unit 11 is configured to emit a sensor voltage addition coefficient signal _S0 that gradually decreases as the vehicle speed increases, as shown in FIG. By inputting the addition signal S+S ₀ obtained by adding ₀ to the torsion torque signal S by the addition calculation section 13 to the output torque value instruction function section 5, an assist direction motor current command value curve having one basic function for the torsion torque signal is generated. Third
As shown in the figure, it can be moved in parallel according to the vehicle speed.

In Fig. 3, i ₀ represents the assist direction motor current command value when the vehicle speed is zero, and as the vehicle speed increases, it gradually moves to i ₁ and i ₂ . The assist direction motor current command value gradually decreases as the vehicle speed increases.

In the above, when the sensor voltage addition coefficient signal _S0 generated by the addition calculation constant function unit 11 is configured to gradually increase as the vehicle speed increases, the addition calculation unit 13 generates the sensor voltage addition coefficient signal S0. Subtraction signal S obtained by subtracting ₀ from the torsional torque signal S
By inputting -S ₀ to the output torque value indicating function section 5, the same result as above can be obtained.

However, when S-S ₀ <0, S-S ₀ =0.

The vehicle speed coefficient indicating function unit 12 is configured to issue a vehicle speed coefficient signal that gradually decreases from 1 as the vehicle speed increases, as shown in FIG. By multiplying by the assist direction motor current command values i ₀ , i ₁ , i ₂ for each vehicle speed of the output torque value instruction function unit 5, the assist direction motor current command that moves in parallel with the vehicle speed as shown by the dotted line in FIG. 3 is obtained. The slopes of the values i ₀ , i ₁ , and i ₂ can be made more gentle as the vehicle speed increases.

Effects of the Invention As described above, according to the invention, there is provided an electric power steering device in which the electric current to the electric motor is controlled according to the torsional torque of the steering shaft, and the electric motor provides power assist in the steering direction. , the assist direction motor current command value of the output torque value instruction function section that issues the assist direction motor current command value based on the addition signal obtained by adding the sensor voltage addition coefficient signal determined by the vehicle speed and the torsional torque signal of the steering shaft. A simple configuration is adopted in which the direction of power assist by the electric motor and the output torque are controlled by the multiplication signal of the multiplication calculation section that generates a multiplication signal with a vehicle speed coefficient signal that gradually decreases as the vehicle speed increases. By doing so, the assist direction motor current command value having one basic function with respect to the torsional torque signal of the steering shaft is moved in parallel according to the vehicle speed, and
The slope can be made gentler at any angle as the vehicle speed increases, and power assist suitable for each vehicle speed can be provided, which can bring about great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and the area surrounded by chain lines shows the conventional structure. Fig. 2 is a sensor voltage addition coefficient signal characteristic diagram, Fig. 3 is an explanatory diagram showing how the assist direction motor current command value curve for the steering shaft torsional torque signal changes in parallel and inclination as the vehicle speed increases; FIG. 4 is a vehicle speed coefficient signal characteristic diagram. 1... Torsional torque sensor, 2... Positive/negative discrimination section,
3... Absolute value conversion section, 4... Electric motor drive section,
5... Output torque value instruction function unit, 6... Duty control unit, 7... Armature current detection unit, 8... Electric motor, 9... Steering mechanism, 10... Vehicle speed sensor,
DESCRIPTION OF SYMBOLS 11... Addition calculation constant function part, 12... Vehicle speed coefficient instruction function part, 13... Addition calculation part, 14... Multiplication calculation part.

Claims (1)

[Scope of utility model registration request] In an electric power steering device that controls current to an electric motor according to the torsional torque of the steering shaft and provides power assist in the steering direction using the electric motor, a sensor voltage addition coefficient signal determined by the vehicle speed and a sensor voltage addition coefficient signal determined by the vehicle speed are used. The assist direction motor current command value of the output torque value instruction function section that issues the assist direction motor current command value based on the addition signal obtained by adding the torsional torque signal of the steering shaft and the vehicle speed that gradually decreases as the vehicle speed increases. 1. A control device for an electric power steering device, characterized in that the direction of power assist and the output torque of an electric motor are controlled by the multiplication signal of a multiplication calculation unit that generates a multiplication signal with a coefficient signal.