JPH0436610A - Rotational angle detector - Google Patents

Abstract

PURPOSE:To simplify the constitution of this device, to attain the reduction in cost and to improve the durability by setting a winding axis in the moving direction of a movable magnetic body and providing a primary and secondary coils which are fitted to a base frame so as to surround the movable magnetic body. CONSTITUTION:When the movable magnetic body 3 is positioned right in a center to the primary coil 6, an AC power source 8 applies a specific voltage to the primary coil 6 and then voltages which are equal in amplitude are induced across the secondary coils 7a and 7b respectively. When a steering wheel 1a is operated in one direction based upon the reference position in this state and a rotary shaft 1 rotates, its rotary displacement is converted by a converting mechanism 5 into the linear displacement of the movable magnetic body 3. Consequently, the primary coil 6 and secondary coils 7a and 7b are changed in magnetic coupling state complementarily to each other. When the magnetic coupling is varied, an output voltage developed between output terminals (a) and (b) is nearly proportional to the angle of rotation of the rotary shaft 1. Therefore, the voltage is measured directly without providing any special converting circuit to detect the absolute value of the angle of rotation.

Description

[Detailed description of the invention] [Object of the invention (industrial application field)] The present invention detects the rotation angle of a rotating shaft,
In particular, the present invention relates to a rotation angle detection device suitable for detecting the absolute rotation angle of a rotating shaft that rotates many times, such as a steering wheel of an automobile.

(Prior Art) Conventionally, there have been the following devices for detecting the rotation angle of a rotating shaft such as a steering wheel of an automobile.

That is, for example, in a variable resistor, an electrode is placed in contact with a resistor, and as the rotating shaft rotates, the electrode slides on the contact surface of the resistor. The rotation angle is detected by measuring the resistance value that changes with rotation.

(Problem to be Solved by the Invention) However, in the conventional configuration as described above, the electrode is in contact with the resistor, so as it is used, wear and tear between the sliding electrode and the resistor occur. Poor electrical contact is likely to occur due to dirt, etc., making it difficult to extend the lifespan in terms of durability.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a rotation angle detection device that has a simple configuration and can be inexpensively improved in durability.

[Configuration of the Invention (Means for Solving the Problems) The rotation angle detection device of the present invention includes a rotation shaft rotatably supported on a base frame, and a conversion mechanism that converts the rotational displacement of the rotation shaft into a linear displacement. a movable magnetic body that is displaced in accordance with the linear displacement of the conversion mechanism; a primary coil that is attached to the base frame so as to surround the movable magnetic body with the moving direction of the movable magnetic body being the winding axis; The main feature is that it is configured with a secondary coil.

In this case, one secondary coil is placed on each side of the primary coil in the moving direction of the movable magnetic body, and two
It is preferable to connect two secondary coils to obtain a differential output.

(Function) According to the rotation angle detection device according to claim 1, when the rotation shaft rotates, the movable magnetic body is linearly displaced by the conversion mechanism, thereby changing the magnetic coupling state between the secondary coil and the secondary coil. changes. Therefore, by measuring this change as the voltage appearing in the secondary coil when voltage is applied to the primary coil, the rotation angle of the rotation axis can be detected.

According to the rotation angle detection device according to the second aspect, since the two secondary coils are connected to obtain a differential output, the terminal voltage of each secondary coil detected in the same manner as described above is When the magnetic body is located between the two secondary coils, they cancel each other out and the output voltage becomes zero. Then, as the rotary shaft is rotated from this state, the output voltage fluctuates, and the rate of change at this time is a value proportional to the rotation angle. Therefore, the output voltage can be read directly as the rotation angle.

(Example) Hereinafter, an example in which the present invention is applied to a rotation angle detection device for a steering wheel of an automobile will be described with reference to the drawings.

Figures 1 (a) and (b) show a lower cross-sectional view and a vertical side view of the overall configuration, respectively. In Figure 1, the rotating shaft 1
A steering wheel 1a is fixed to an upper end portion, and a cylindrical container-shaped base frame 2 is rotatably supported in the middle portion of the steering wheel 1a, with the base frame 2 being penetrated through its insertion holes 2a, 2b. 20 Inside the base frame 2, the rotary shaft 1 is formed with a threaded portion 1b, and a thick-walled cylindrical movable magnetic body 3 is formed with a threaded portion 3a that screws into the second threaded portion 1b.
or is inserted through the rotating shaft 1. A coil bobbin 4 is fixed to the base frame 2 on the outer peripheral side of the movable magnetic body 3 so as to surround it. In this case, the movable magnetic body 3 has an engaging convex portion 3b formed in the vertical direction on the outer circumferential surface, and the engaging convex portion 3b is formed on the inner circumferential surface of the coil bobbin 4.
An engagement recess 4a is formed to engage with. As a result, rotation of the movable magnetic body 3 in the rotational direction of the rotating shaft 1 is restricted. These constitute a conversion mechanism 5, in which when the rotating shaft 1 is rotationally displaced, the movable magnetic body 3 is linearly displaced in the vertical direction. A primary coil 6 is wound around the outer periphery of the coil bobbin 4 so as to be located in the center, and secondary coils 7a and 7b are wound around the outer periphery of the coil bobbin 4, respectively. In this case, the secondary coils 7a, 7b
are formed under similar conditions, and are arranged at vertically geometrically symmetrical positions with respect to the -order coil 6.

FIG. 2 shows the electrical configuration, in which the secondary coil 6 is connected to an AC power source 8 and a predetermined voltage is applied to it, and the secondary coils 7a and 7b are generated by the primary coil 6. They are connected in series so that the phase of the induced voltage is opposite, and both terminals are used as output terminals a and b, and this output terminal a.

A load resistor 9 is connected between the terminals 5 and 5.

Next, the operation of this embodiment will be described with reference to FIG. 3 as well.

First, when the movable magnetic body 3 is located exactly in the center with respect to the primary coil 6, when a predetermined voltage is applied to the primary coil 6 from the AC power source 8, a voltage of the same amplitude is applied to each of the secondary coils 7a and 7b. is induced. That is, by having a geometrically symmetrical positional relationship, the -order coil 6 and each secondary coil 7a.

7b becomes equal, and each secondary coil 7
The induced voltages of a and 7b become equal.

As mentioned above, since the secondary coils 7a and 7b are connected to obtain a differential output, the output voltages appearing between the output terminals a and b at this time are eventually canceled out and become zero.

Now, with the above-mentioned state as the reference position, when the steering wheel 1a is operated in any direction from this state and the rotating shaft 1 is rotated, this rotational displacement is converted into a linear displacement of the movable magnetic body 3 by the above-mentioned conversion mechanism. converted. As a result, the magnetic coupling state between the secondary coil 6 and each of the secondary coils 7a and 7b changes in a complementary manner. That is, for example, if the magnetic coupling between the secondary coil 6 and the secondary coil 7a increases, the magnetic coupling between the secondary coil 6 and the secondary coil 7b decreases. When the magnetic coupling changes in this way, the output voltage appearing between the output terminals a and b is approximately proportional to the rotation angle of the rotating shaft 1, as shown in FIG. Therefore, without providing a special conversion circuit etc.
By directly measuring the voltage, the absolute value of the rotation angle can be detected.

According to this embodiment, the conversion mechanism 5 converts the rotational displacement of the rotary shaft 1 into the linear displacement of the movable magnetic body 3 as the cumulative displacement amount, and the secondary coil 7a.

Since the differential output of the voltage induced in 7b is detected, unlike the conventional method in which sliding electrodes are provided, there is no part that causes electrical contact failure, resulting in excellent durability. Since it is proportional to the angle, it is possible to achieve a long life at low cost with a simple configuration without separately providing an arithmetic circuit or the like.

In the above embodiment, the present invention has been described for the case where the present invention is used to detect the rotation angle of a steering wheel, but the present invention is not limited to this, and can be applied to any device that detects the absolute value of the rotation angle of a rotating shaft. , various modifications are possible without departing from the gist.

[Effects of the Invention] According to the rotation angle detection device according to claim 1, the conversion mechanism converts the rotational displacement of the rotating shaft into a linear displacement of the movable magnetic body, and the primary coil changes according to the position of the movable magnetic body. The absolute value of the rotation angle of the rotating shaft is detected by electrically detecting changes in the magnetic coupling between the coil and the secondary coil, which eliminates the conventional problem of electrical contact failure due to sliding electrodes. In contrast, it has an excellent effect of improving durability at low cost with a simple structure.

According to the rotation angle detection device according to claim 2, since the two secondary coils detect the differential output of the induced voltage due to the displacement of the movable magnetic body, in addition to the above effects, the rotation angle of the rotation shaft is Since it is possible to obtain an output voltage proportional to the angle, an excellent effect can be achieved in that it can be easily achieved without separately providing an arithmetic circuit or the like.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIGS. 1(a) and (b)
) are a cross-sectional bottom view and a vertical cross-sectional side view of the overall configuration, FIG. 2 is an electrical configuration diagram, and FIG. 3 is an output voltage characteristic diagram. In the drawing, 1 is a rotating shaft, 1a is a steering wheel, 2
3 is a base frame, 3 is a movable magnetic body, 4 is a coil bobbin, 5 is a conversion mechanism, 6 is a primary coil, 7a and 7b are secondary coils, 8 is an AC power source, and a and b are output terminals.

Claims (2)

[Claims] 1. A rotating shaft rotatably supported by a base frame, a conversion mechanism that converts the rotational displacement of this rotating shaft into linear displacement, a movable magnetic body that is displaced in accordance with the linear displacement of this conversion mechanism, and a movable magnetic body that is A rotation angle detection device comprising a primary coil and a secondary coil wound around the base frame so as to surround the movable magnetic body with the moving direction as a winding axis. 2. One secondary coil is placed on each side of the primary coil in the moving direction of the movable magnetic body, and the two secondary coils are connected to obtain a differential output. The rotation angle detection device according to claim 1.