JPS61125964A - Electric power steering device - Google Patents

Abstract

PURPOSE:To prevent an electric motor from being damaged by excessive heat by arranging an electric generator, which outputs electric voltage in response to the number of engine revolution, as an electric power source to assist steering torque in addition to an electric generator in an electric charging system. CONSTITUTION:No.2 generator 23 is connected with an engine 20 as an electric power source for an electric motor 16 by way of a belt transmission device. A control circuit 24, to which electric voltage generated by the generator 23 is applied, controls the current value to be applied to the electric motor 16 in response to torque signals outputted form a torque sensor 15. When a handle 11 is operated, torque is detected for its positive or negative value by the torque sensor 15. The control circuit 24 controls on only the direction of rotation of the electric motor 16 based on the signal from the torque sensor 15, but also controls the output current of the generator 23 to be applied to the electric motor 16 allowing the output torque of the electric motor 16 to be controlled in response to the torque of the handle.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electric power steering device in which steering torque is assisted by an electric motor.

<Prior Art> Generally, in an electric power steering system in which steering torque is assisted by an electric motor, a battery and a generator (alternator) are used as power supply sources for the electric motor.
is used. Such a generator is driven by an engine, and the amount of power generated varies depending on the engine rotation speed, but the generated voltage is controlled by a voltage regulator, and the battery voltage is adjusted to 12
It is designed to adjust to a constant voltage of V.

<Problems to be Solved by the Invention> In a power steering system, it is necessary to provide torque assistance, so an electric motor using a low-voltage battery as a power source is used to generate the necessary torque.

This requires a high current and causes problems such as motor seizure, which necessitates a larger motor, making it unsuitable for use in actual vehicles. For this reason, with batteries as a power supply source, the required torque cannot be produced because it is limited by the capacity of the buff steering wheel, and the steering torque cannot be sufficiently assisted.1. ＞
There's a problem.

As shown in FIG. 1, in addition to the charging system generator 21, a generator 23 that outputs a generated voltage according to the rotational speed of the engine 20 is provided, and this generator 23 is used to generate a steering torque. A control circuit 24 is provided for controlling the output current supplied to the electric motor 16 in accordance with the steering wheel torque detected by the torque sensor 15.

<Operation> Therefore, according to the present invention, when the torque sensor 15 detects the steering wheel torque based on the steering wheel operation, the control circuit 24 controls the current supplied to the electric motor 16 whose power supply source is the generator 23. As a result, the electric motor 16 is started with a torque corresponding to the steering wheel torque, and acts to assist the steering wheel torque to perform steering operations easily.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 10 indicates a handle shaft. A steering handle 11 is attached to one end of the handle shaft 10, and a pinion shaft 13 supported on a gear box 12 is coupled to the other end. The pinion shaft 13 is meshed with a rack shaft 14 fitted in the gear box 12.
Although not shown, both ends of the steering wheel are connected to steering wheels via ball joints or the like.

A torque sensor 5 is provided on the handle shaft 10 to detect the handle torque applied to the steering handle 11 and its direction. Also, on the handle shaft 10, an electric motor 6 that assists the handle torque is connected to a gear 17.
are connected via.

Reference numeral 20 indicates an engine of an automobile, and a first generator 21 is connected to this engine 20 via a belt transmission device.
A battery 2'2 is connected to this generator 21 to constitute a charging system. The generator 21 has a built-in voltage regulator,
This voltage regulator controls the field current flowing through the field coil, thereby controlling the generated voltage.
Appropriate power is supplied to various electrical devices regardless of the rotational speed of the battery 22, and the battery 22 is appropriately charged.

A second generator 23 as a power supply source for the electric motor 16 is also connected to the engine 20 via a belt transmission. The second generator 23 is configured to output a generated voltage according to the rotational speed of the engine 20, and this generated voltage is applied to the control circuit 24. Thus, the control circuit 24 controls the current value supplied to the electric motor 16 according to the torque signal output from the torque sensor 15, and controls the output characteristics of the electric motor 16 with respect to the steering wheel torque as shown in FIG. It looks like this. In addition, Fig. 3 shows the power generation tJ when the field current is kept constant.
The external load characteristics of S123 are shown.

In the above-described configuration, when the steering handle 11 is operated, the torque sensor 15 detects the steering wheel torque and whether the torque is positive or negative. Based on the signal from the torque sensor 15, the control circuit 24 controls the rotational direction of the electric motor 16, and also controls the output current of the generator 23 to be applied to the electric motor 16 to increase the output torque of the electric motor 16 to the second level. Control is performed according to the steering wheel torque as shown in the figure. As a result, the steering torque applied to the steering wheel 11 is assisted by the electric motor 16, allowing the steering operation to be performed easily.

<Effects of the Invention> As described above, the present invention provides, in addition to a charging system generator,
The configuration is equipped with a generator that outputs a generated voltage according to the engine speed, and this generator is used as the power supply source for the electric motor that assists the steering torque, so the electric motor can be started with high voltage and low current. This has the effect of preventing motor seizure and the like, and also allowing a small motor to obtain the necessary torque.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show an embodiment of the present invention, and FIG. 1 is a system diagram showing an electric power steering device, and FIG. 2 is a diagram showing the output torque of the electric motor with respect to the steering torque. , FIG. 3 is a diagram showing the external load characteristics of the generator. 11... Steering handle, 15... Torque sensor, 1
6... Electric motor, 20... Engine, 23...
Generator, 24...control circuit.

Claims (1)

[Claims] (1) In an electric power steering system that starts an electric motor based on the steering wheel torque applied to the steering wheel to assist the steering torque, the electric motor is activated based on the steering torque applied to the steering wheel. a control circuit for controlling the electric motor according to the handle torque or the like using the output of the generator, the generator being provided as a power supply source for the electric motor; Electric power steering device.