JPH09203625A - Rotation position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a rotation angle of a rotation shaft along an entire periphery of 360 deg. and also to improve durability by detecting without contact. SOLUTION: A disk-like translucent plate 4 is fixed in a slant state to a rotation shaft 3 provided to pass through a base 1 and an outer case 2. The translucent plate 4 is a planar transparent plate with a predetermined thickness and a refractive index of (n), it is designed to refract light incident slantly with respect to a direction perpendicular to a surface. A gradient angle is set to θ. An LED(light emitting diode) 5 for projecting a light beam P along an axial line of the rotation shaft 3 and a PSD (semiconductor position detection element) 6 for receiving the light beam P are provided oppositely across the translucent plate 4. When the translucent plate 4 rotates according to rotation of the rotation shaft 3, a direction where the light beam P is refracted by the plate 4 varies, and by detecting this by the PSD 6, corresponding rotation angles can be detected along the entire periphery without contact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational position detecting device for detecting the rotational position of a rotary shaft.

[0002]

Conventionally, as a device for detecting the rotational position of a rotary shaft, a potentiometer or the like constituted by using a variable resistor whose resistance value changes in accordance with a rotation angle is used to electrically detect the rotational position. There is a device in which a signal corresponding to the rotation angle is obtained by detecting the signal.
Further, such a variable resistance type has an advantage that it can have a simple and inexpensive structure.

However, in these devices, the brush rotates on the surface of the resistor constituting the variable resistor in a state of being in electrical contact with the surface of the resistor to detect the potential at the position of contact, thereby detecting the rotational position. Since the system is used, there is a problem that the resistance and brush wear due to long-term use and characteristic changes occur, or the detection potential fluctuates due to the generation of noise due to abrasion powder, which results in a decrease in durability and reliability. There was a practical problem in that respect.

Further, in such a general potentiometer, the contact surface of the brush is constituted by cutting out a part of the resistor coated in an annular shape and taking out electrodes from both ends thereof. However, since the cutout portion cannot be detected in principle, there is a problem that it is difficult to detect the rotation angle over the entire range of 360 ° as long as such a structure is used. .

The present invention has been made in view of the above circumstances, and an object thereof is to have excellent durability for long-term use and to rotate over the entire range of 360 ° by eliminating undetectable portions. An object is to provide a rotational position detecting device capable of detecting an angle.

[0006]

SUMMARY OF THE INVENTION A rotational position detecting device of the present invention is a refraction device which is formed of a flat plate-shaped light-transmissive member having a predetermined thickness and is fixed in a state of being penetrated at a predetermined angle with respect to a rotating shaft. A member, a light projecting element for projecting light to the refracting member in the axial direction of the rotating shaft, and a position that opposes the light projecting element with the refracting member sandwiched between the member and the refracting plate. A position detecting element that receives light incident through the light receiving element and outputs a light receiving signal corresponding to the light receiving position, and a detecting unit that detects the rotational position of the rotary shaft based on the light receiving signal from the position detecting element. It is characterized in that it is configured by providing.

According to the above configuration, the light beam output from the light projecting element enters the position detecting element via the refraction member. At this time, since the refraction member is fixed in a state of being inclined with respect to the rotation axis, the light beam from the light projecting element is incident at an incident angle corresponding to the inclination angle. Therefore, the light ray that has entered the refracting member from the light projecting element is refracted according to the inclination angle of the light, enters the inside of the refracting member, and when the light passes through the refracting member and exits again, the light ray is rotated by the refraction again. It will proceed in the direction along the axis.

As a result, the position of the light beam incident on the position detecting element is shifted by the distance according to the law of refraction due to the inclination of the refraction member. At this time, since the tilt direction of the refracting member changes corresponding to the rotational position of the rotation axis, the light receiving position on the light receiving surface of the position detecting element is a circle whose radius is the distance of the deviation amount changed by the refracting member. Will move up. Therefore, the detecting means can calculate and obtain the rotational position of the rotary shaft from the light receiving position based on the detection signal from the position detecting element.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a steering wheel rotation angle detecting device will be described below with reference to the drawings. In FIGS. 1 and 2 showing the outline of the overall configuration, a disk-shaped substrate 1 has a cylindrical outer case 2 mounted on the top thereof.
A rotary shaft 3 is provided inside the outer case 2 so as to penetrate therethrough, and a transparent plate 4 serving as a refraction member is fixed to the inside of the outer case 2. The translucent plate 4 is fixed in a state of penetrating with an angle θ with respect to the radial direction of the rotating shaft 3, and has a refractive index of n (for example, n =
A resin having a light-transmitting property of about 1.5) is formed on a disc having a predetermined thickness.

An LED (light emitting diode) 5 as a light projecting element is provided on the upper surface of the outer case 2, and its optical axis is set in the axial direction of the rotary shaft 3. The substrate 1 is provided with a PSD (semiconductor position detecting element) 6 as a position detecting element at a position facing the LED 5 with the light transmitting plate 4 interposed therebetween. The PSD 6 is capable of two-dimensionally detecting the light receiving position of the light spot from the LED 5, and outputs a detection signal corresponding to the light receiving position.

FIG. 3 shows the electrical construction of the detecting means. As a terminal for outputting a light receiving signal indicating the two-dimensional position of the PSD 6 as a current signal, an output terminal X1 corresponding to each of the X direction and the Y direction. , X2 and output terminal Y
1, Y2 are derived. Then, each output terminal X1,
X2, Y1, and Y2 are connected to the voltage conversion circuits 7, 8, 9, and 10 so that the current signals are output in the state of being converted into voltage signals.

The output terminals of the voltage conversion circuits 7 and 8 are connected to the input terminals of the adder circuit 11 and the subtractor circuit 12, respectively. The output terminals of the voltage conversion circuits 9 and 10 are connected to the input terminals of the adder circuit 13 and the subtractor circuit 14, respectively. The output terminals of the adder circuits 11 and 13 are connected to the input terminal of the adder circuit 15, and the output terminal of the adder circuit 15 is connected to the energization path of the LED 5 via the current adjusting circuit 16.

The current adjusting circuit 16 adjusts the output current, that is, the energizing current to the LED 5 so that the value of the voltage signal input from the adding circuit 15 matches a predetermined value, whereby the amount of light received by the PSD 6 is constantly maintained. It is controlled so as to be constant. The output terminal of the subtraction circuit 12 is connected to a terminal x that outputs a signal indicating a deviation in the x direction, and the output terminal of the subtraction circuit 14 is connected to a terminal y that outputs a signal indicating a deviation in the y direction. There is.

Next, the operation of this embodiment will be described with reference to FIGS. First, the principle of detecting the rotation angle of the rotary shaft 3 will be briefly described. That is, LED
When a light ray P output from the light source 5 and parallel to the axial direction of the rotating shaft 3 is incident on the transparent plate 4, as shown in FIG. 4, the traveling direction is bent by refraction to the inside of the transparent plate 4, and When the light exits from the rear light-transmitting plate 4, the light is refracted again and is bent, so that the light rays P are parallel to the axial direction of the rotating shaft 3 and travel. However, since the light beam P has passed through the transparent plate 4 at this time, the optical path of the light beam P is displaced by a deviation distance δ from the position when it is output from the LED 5.

Therefore, the light ray P incident on the upper surface side of the light transmitting plate 4 is refracted at each position in the direction corresponding to the inclination and is output to the lower surface side, so that it is displaced as shown by the arrow in FIG. . This means that the position of the light ray P corresponding to the rotation of the light transmissive plate 4 is changed as the light transmissive plate 4 is rotated, as shown in FIG. When the light plate 4 is not provided, the position of the light receiving surface that receives the light beam P is set as the origin O, and the origin O is moved around the circumference corresponding to the deviation distance δ.

Now, such a deviation distance δ is determined by the transparent plate 4
From the inclination angle θ, the thickness h, and the refractive index n, it can be calculated as in the following equation (1). That is, the deviation distance δ can be obtained by obtaining the traveling direction of the light ray P inside the light transmitting plate 4 according to the law of refraction and calculating the position at which the light ray P exits from the light transmitting plate 4.

[0017]

[Equation 1]

On the light receiving surface of the PSD 6, light is received at a corresponding point on the circumference of a circle having a radius δ according to the position of the light transmitting plate 4 which rotates with the rotation of the rotating shaft 3. PSD6
Outputs a light reception signal as a signal corresponding to each of the x direction and the y direction. Therefore, when the rotation angle is α, the values of the x and y light reception signals obtained corresponding to this are as shown in FIG. Make a big change. Then, the angle α corresponding to the light receiving position can be obtained by the following equation (2) based on the signals indicating the respective positions of x and y.

[0019]

[Equation 2]

In this case, the value of the angle α indicating the rotational position corresponds to the following range depending on the signs of the values of x and y.

(Equation 3)

The signals actually output from the PSD 6 are X1, X2 and Y1, Y2 corresponding to the x direction and the y direction from the respective terminals, and these are expressed by the following equations (3), (4). ) By performing the calculation shown in
The above-mentioned signals x and y are obtained. In this case, L is set as the length of one side of the light receiving surface of the PSD 6.

[0022]

(Equation 4)

The above calculation is performed and output by the electrical configuration shown in FIG. The PSD 6 outputs a light receiving signal corresponding to the light receiving position from each terminal of X1, X2, Y1, and Y2. Letting each signal be X1, X2, Y1, Y2, these are converted into voltage signals via the amplifiers 7 to 10 and then added by the adder 11 corresponding to the x direction and corresponding to the y direction. The signals are added by the adder 13, and the addition results are further added by the adder 15 to obtain a signal corresponding to the total received light current.

Since the current adjusting circuit 16 controls the current to the LED 5 so that the total received light current is constant, the values of X2 + X1 and Y1 + in the equations (3) and (4).
The value of Y2 can be controlled as a substantially constant value, and can be regarded as a constant together with the value of L. Since the difference values X2-X1 and Y2-Y1 described in the numerator of the equations (3) and (4) are calculated by the subtraction circuits 12 and 14, respectively, the signals output from the terminals x and y. Based on the above, the rotation angle α is obtained by performing the arithmetic processing corresponding to the above-mentioned formula (2).

According to this embodiment as described above, the transparent plate 4 is fixed to the rotating shaft 3 while being inclined by the angle θ, and the path of the light beam P from the LED 5 is refracted by the rotation of the rotating shaft 3 by refraction. Since it is changed, the PSD 6 can receive the light beam P at a position corresponding to the rotation angle α of the rotation shaft 3 in a non-contact state, and the durability for long-term use can be improved. At the same time, the rotation angle α of the rotation shaft 3 can be accurately detected with a simple and inexpensive structure.

FIG. 8 and FIG. 9 show a second embodiment of the present invention, and the portions different from the first embodiment will be described below. That is, the PSD 17 is of the improved surface division type, and has four output terminals A to D as shown in FIG.
Are provided at the four corners of the light-receiving surface, and there are portions where the electrical configuration as the detecting means is changed as shown in FIG. 8 due to such a difference in configuration.

In FIG. 8, the output terminals A to D provided at the four corners of the PSD 17 are voltage conversion circuits 18 to 2, respectively.
The signal output from the PSD 17 as a current signal is converted into a voltage signal by being connected to 1. In the four addition circuits 22 to 25, the addition inputs of the addition circuit 22 are voltage conversion circuits 20 and 21, the addition inputs of the addition circuit 23 are voltage conversion circuits 18 and 19, and the addition input of the addition circuit 24 is a voltage conversion circuit. Conversion circuits 18 and 21, and addition inputs of the addition circuit 25 are voltage conversion circuits 19 and 20.

The addition outputs of the addition circuits 22 and 23 are used as the subtraction input of the subtraction circuit 26, and the addition outputs of the addition circuits 24 and 25 are used as the subtraction input of the subtraction circuit 27 and the addition input of the addition circuit 28. The addition output of the addition circuit 28 is connected to the LED 5 via the current adjustment circuit 16. The subtraction outputs of the subtraction circuits 26 and 27 are configured to be output to the outside as an x-direction detection signal and a y-direction detection signal.

According to the above configuration, when the light receiving operation is performed in the same manner as in the first embodiment, the detection circuit in the detection circuit based on the light receiving signals output from the electrodes A to D provided at the four corners of the PSD 17 at this time. , The x-direction and y-direction detection signals can be obtained as follows. Here, the values when the magnitudes of the current signals output from the electrodes A to D are converted into voltage signals by the voltage conversion circuits 18 to 21 are shown as the same signs A to D, respectively. .

First, (D + C) is calculated in the adder circuit 22 and (A + B) is calculated in the adder circuit 23 corresponding to the x direction. These correspond to positive and negative signals in the x direction, and when the difference between these signals is calculated by the subtraction circuit 26, a signal [(D +
C)-(A + B)]. Also, y
Depending on the direction, the adder circuit 24 calculates (A + D) and the adder circuit 25 calculates (B + C). These correspond to positive and negative signals in the y direction, and when the difference between these signals is calculated by the subtraction circuit 27,
It can be obtained as a signal [(A + D)-(B + C)] corresponding to the y direction.

The detection signals thus obtained in the x and y directions correspond to the total current value (A + B +).
C + D), the x direction and y
It can be obtained as a direction detection signal. Such arithmetic processing is performed by the following equation (5),
The arithmetic processing shown in (6) is performed. That is, the detection signal in the x direction can be obtained as in equation (5) when the length of one side of the light receiving surface is L, and the detection signal in the y direction is similarly obtained as in equation (6). You can get it.

[0032]

(Equation 5)

In the actual detection circuit, the addition circuit 28 calculates the added value (A + B + C + D) of all outputs, and the current adjusting circuit 16 controls the energizing current to the LED 5 so that this value becomes constant. Therefore, the value indicating the total current can be regarded as a constant, and can be obtained as the detection signals in the x-direction and the y-direction without substantially performing the division process.
Therefore, according to the second embodiment as described above, it is possible to obtain the same effects as those of the first embodiment.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. PSD
May be other type such as double-sided split type
Further, a CCD other than the PSD can be used as the position detecting element. The refraction member may be any material such as glass or resin as long as light can be transmitted. The light emitting element may use a laser. The light emitted by the light projecting element may be visible light or infrared light.

[0035]

According to the rotational position detecting device of the present invention, the refracting member is fixed in a state where the refracting member is penetrated while being inclined at a predetermined angle with respect to the rotating shaft, and the light projected from the light projecting element is directed to the refracting member. The light projecting element is configured to receive light by a position detecting element arranged at a position facing the refracting member and to detect the rotational position of the rotary shaft based on a light receiving signal from the position detecting element by the detecting means. By changing the tilt direction of the refraction member according to the rotation position of the shaft, it becomes possible to detect the rotation position of the rotation shaft as a different light receiving position in a non-contact state, which makes it durable for long-term use. It is possible to improve the property, and it is possible to detect the rotation angle of the rotating shaft over the entire circumference (360 °) without interruption.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional side view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional plan view

FIG. 3 is an electrical configuration diagram

FIG. 4 is an operation explanatory view showing a locus of a light ray passing through the transparent plate.

FIG. 5 is an operation explanatory view showing a deviation direction of a light ray due to refraction within a disc.

FIG. 6 is an operation explanatory view showing a light receiving surface and a light receiving position of the PSD.

FIG. 7 is a diagram showing changes in a light receiving position signal corresponding to a rotation angle.

FIG. 8 is a view corresponding to FIG. 3 showing a second embodiment of the present invention.

FIG. 9 is a view corresponding to FIG.

[Explanation of symbols]

1 is a substrate, 2 is an outer case, 3 is a rotating shaft, 4 is a light transmitting plate (refractive member), 5 is an LED (light projecting element), and 6 and 17 are PSDs.
(Position detection element), 7 to 10, 18 to 21 are voltage conversion circuits, 11, 13, 15, 22 to 25, 28 are addition circuits,
Reference numerals 12, 14, 26 and 27 are subtraction circuits, and 16 is a current adjustment circuit.

Claims (1)

[Claims] 1. A refraction member which is formed of a flat plate-shaped light-transmissive member having a predetermined thickness dimension and is fixed in a state of penetrating the rotation shaft at an inclination of a predetermined angle; A light projecting element that projects light from the axial direction and a light projecting element that is arranged at a position facing the light projecting element with the refraction member interposed therebetween. A rotational position detection device comprising: a position detection element that outputs a corresponding light reception signal; and a detection unit that detects a rotational position of the rotary shaft based on a light reception signal from the position detection element.