JPH06258154A - Optical rotary-torque detector - Google Patents

Abstract

PURPOSE:To suppress the rotating ripples of an optical rotary-torque detector. CONSTITUTION:This optical rotary-torque detector has a torsion bar 3, which links two rotary shafts 1 and 2, a pair of opposedly placed rotary slit plates 4 and 5, which are fixed to the respective rotary shafts 1 and 2, a light emitting element 6, which is arranged at one surface side of the pair, and a photodetector 7, which is arranged at the other surface side of the pair, receives the transmitted light and detects the relative torsions of two rotary shafts 1 and 2. The slit plate 4 has a track slit holes 8, which are aligned in the circumferential direction at an equal angle. The individual slit hole 8 has the spiral shape, which is expressed by the expression R=atheta<1/2> (a: constant) when the radius from the center O of the rotary slit plate is made to be R and the angle is made to be theta. The track has the width in the radial direction including just the integer number of the spiral-shaped slit holes 8. The other slit plate has the slit holes in the spiral shape by the same way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical rotary torque detecting device. More specifically, the present invention relates to an optical rotary torque detection device including a pair of rotary slit plates fixed to a pair of rotary shaft ends connected by a torsion bar, and a light emitting element and a light receiving element. Such an optical rotational torque detecting device is incorporated in, for example, an electric power steering system.

[0002]

2. Description of the Related Art An optical rotary torque detecting device having the above structure is disclosed in, for example, Japanese Patent Laid-Open No. 63-284442. As shown in FIG. 8, a conventional optical rotational torque detecting device includes a torsion bar 103 that connects two rotating shafts 101 and 102 to each other, and a rotating bar 101 and a rotating bar 101, respectively.
A pair of rotary slit plates 104 and 105 fixed to the pair 102 and facing each other, a light emitting element 106 arranged on one surface side of the pair, and a transmitted light received on the other surface side of the pair to rotate two It is provided with a light receiving element 107 that detects a relative twist of the shafts 101 and 102.

FIG. 9 shows a pair of rotary slit plates 104 and 10.
6 is a schematic perspective view showing a slit pattern formed in FIG. The upper rotary slit plate 104 has substantially rectangular slit holes 108 formed at a predetermined pitch along the entire circumference. Similarly, the slit holes 109 having the same shape and the same pitch are formed along the entire circumference in the circumferential direction of the lower rotary slit plate 105.
Are formed. In the neutral state where relative twist is not generated in the pair of rotation shafts, the upper slit hole 108 and the lower slit hole 109 are completely aligned. Therefore,
The amount of transmitted light is maximum. When a twist occurs between both rotary shafts, relative displacement occurs between the pair of rotary slit plates 104 and 105, and the slit holes 108 and 109 are displaced from each other. Therefore, the amount of transmitted light is reduced. Since the amount of transmitted light changes according to the amount of twist, the twist can be detected based on the output of the light receiving element 107.

[0004]

Two rotary shafts 101,
When 102 rotates integrally with a certain twist relationship, a ripple occurs in the amount of light received by the light receiving element. Since this rotation ripple causes an error, it needs to be suppressed. In order to suppress the rotational ripple, it is necessary to simultaneously detect the light that has passed through the plurality of slit holes, so that the circumferential width of the light receiving element must be at least equal to the pitch of the slit holes. For this purpose, the arrangement pitch of the slit holes must be made sufficiently small with respect to the circumferential width dimension of the light receiving element and the light emitting element. However, if the slit hole pitch is reduced, the maximum twist angle detection range of the pair of rotary slit plates becomes smaller, which causes a problem that measurement accuracy deteriorates. On the contrary, if the dimensions of the light receiving element and the light emitting element are relatively increased as compared with the slit hole pitch, there arises a problem that the area increases and the cost of parts increases. In view of the problems of the prior art, it is an object of the present invention to provide an optical rotational torque detection device that can use a light receiving element and a light emitting element having a circumferential width dimension smaller than a slit hole pitch.

[0005]

In order to solve the above-mentioned problems of the prior art and achieve the object of the present invention, the following means were taken. That is, the optical rotational torque detecting device according to the present invention has, as its basic constituent elements, a torsion bar connecting two rotating shafts, and a pair of rotating slit plates fixed to the respective rotating shafts and facing each other, The light emitting element is arranged on one surface side of the pair, and the light receiving element is arranged on the other surface side of the pair and receives transmitted light to detect a relative twist of the two rotating shafts. As a feature of the present invention, each rotary slit plate has a track composed of slit holes arranged at equal angles in the circumferential direction. Each slit hole has a spiral shape represented by the following relational expression when the radius R from the slit plate center and the angle θ are set. Also, the track has a radial width that includes just an integer number of spiral-shaped slit holes.

[Equation 2]

Preferably, the light receiving element has a pair of light receiving areas divided in the radial direction, and a change in the amount of light received by the relative displacement of both rotary slit plates increases in one light receiving area and decreases in the other light receiving area. Thus, the twist detection is performed based on the difference between the outputs from both light receiving regions. More preferably, each of the divided light receiving areas is further divided into two by diagonal lines substantially parallel to the spiral-shaped slit, and outputs from the redivided areas are subjected to difference processing to detect rotation. In this case, the light receiving element may have a longitudinal shape in which the width dimension in the circumferential direction is significantly smaller than the width dimension in the radial direction, and may be provided with a light receiving region divided into four substantially in the radial direction. Note that automatic light amount control of the light emitting element may be performed so that the sum of the outputs from all the light receiving regions becomes constant.

[0007]

According to the present invention, the rotary slit plate has a track consisting of spiral-shaped slit holes arranged in the circumferential direction at an equal angular pitch. The radial width of this track is set so as to include just an integer number of spiral-shaped slit holes. When the size of the light receiving element is set according to the radial width, the integer number of spiral slit holes can be included even in a light receiving element having a light receiving region whose circumferential width is narrower than the pitch. At this time, the spiral shape satisfies the specific relationship shown in the above formula, and the total effective opening area of the slit holes that regulate the transmitted light entering the light receiving element is constant regardless of the rotational position of the slit plate. Therefore, even if the circumferential width of the light receiving element is set smaller than the arrangement pitch of the slit holes, the rotational ripple of the light receiving amount does not occur.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a basic configuration of an optical rotational torque detecting device according to the present invention. (A)
As shown in FIG.
And a torsion bar 3 connecting the output shaft 2 to each other. The input side slit plate 4 is provided on the end face of the connecting portion of the input shaft 1.
Is fixed. The output side slit plate 5 is also fixed to the end surface of the connecting portion of the output shaft 2. The pair of slit plates 4 and 5 are arranged to face each other. A light emitting element 6 is fixedly arranged above the output side slit plate 5. A light receiving element 7 is fixedly arranged below the input side slit plate 4 and faces the light emitting element 6.

FIG. 1B is a plan view showing the pattern shape of the slit plate 4. The other slit plate 5 also has a similar pattern shape. As shown in the figure, the slit plate 4 has a track composed of a plurality of slit holes 8 arranged in the circumferential direction at an equal angular pitch. Each slit hole 8 has a spiral shape represented by a predetermined relational expression. The light receiving element 7 is arranged so as to match the radial width of the track.
As is apparent from the figure, the circumferential width of the light receiving element 7 is smaller than the arrangement pitch of the slit holes 8. However, the light-receiving area of the light-receiving element 7 includes just an integral number (two in the illustrated case) of spiral-shaped slit holes 8.

The radius from the rotation center O of the slit plate 4 is R
When the angle from the standard rotation position P ₀ is θ, the spiral shape 8a of the slit hole 8 is set so as to satisfy the following relational expression.

[Equation 3] Similarly, the spiral shape 8b satisfies the above relational expression with the standard rotational position P ₁ deviated from the standard rotational position P _{0 by} the width angle θ ₁ of the slit hole 8 as a standard. Similarly, all the other slit holes 8 are also arranged at equal angular pitches so as to satisfy the above relational expression. When the spiral shape of all the slit holes 8 satisfies the above relational expression, the sum of the opening areas of the slit holes 8 that restrict the transmitted light entering the light receiving element 7 is as follows regardless of the rotational position of the slit plate 4. It becomes constant as shown by the relational expression. Therefore, according to the present invention, the rotational ripple of the received light amount does not occur.

[Equation 4] In the above relational expression, θ ₁ represents the width angle of the slit hole 8, and D
Represents the width angle of the light receiving element 7, and n represents the number of slit holes included in the radial track width.

FIG. 2 shows a relative positional relationship between a slit hole formed in the entrance side slit plate (hereinafter referred to as an entrance side slit hole) and a slit hole formed in the exit side slit plate (hereinafter referred to as an exit side slit hole). It is a schematic diagram which shows the specific example of.
In this example, two tracks, an inner track and an outer track, are provided for differentially detecting the torsional torque. The incident side slit hole 8 is commonly provided for the two tracks. on the other hand,
The exit side slit hole 9 is divided into an outer track and an inner track. The phase of the exit side slit hole 9 of the outer track is shifted from the entrance side slit hole 8 by ¼ pitch in the counterclockwise direction. On the other hand, the exit side slit hole 9 of the inner track is set to 1 in the clockwise direction with respect to the entrance side slit hole 8.
The phase is shifted by / 4 pitch. In this way, the phases of the inner track and the outer track are opposite to each other. The overlapping portions of the entrance slit holes 8 and the exit slit holes 9 form individual openings 10. Individual openings 1
The area of 0 changes according to the relative displacement of the entrance side slit plate and the exit side slit plate.

The light receiving element 7 has a pair of light receiving regions (A + RA) and (B + RB) divided in the radial direction so as to correspond to the outer track and the inner track. According to the relationship of the opposite phases between the tracks described above, the change in the amount of received light due to the relative displacement of both slit plates is set to increase in one light receiving region and decrease in the other light receiving region. Therefore, the torsion torque can be detected by taking the difference between the output (A + RA) of the outer light receiving area and the output (B + RB) of the inner light receiving area. In the following, in order to simplify the description, the light receiving region and its output will be denoted by the same reference numeral. The light receiving area (A + RA) on the outer side is further divided into two by oblique lines substantially parallel to the spiral-shaped slit holes 8 and 9.
The outputs from the subdivided areas A and RA have a complementary relationship with each other. Therefore, the outputs A and RA from the subdivided area can be differentially processed to obtain an A-phase signal, which is used for rotation detection. Similarly, the inner light receiving area is further divided into two parts by diagonal lines substantially parallel to the spiral slit hole. The outputs from the subdivided areas B and RB can be subjected to the difference processing to obtain a B-phase signal. This signal is also used for rotation detection. Further, the rotation direction can be detected from the phase relationship between the pair of A-phase signal and B-phase signal.

As a modification of this embodiment, the light receiving element 7 can be formed into a longitudinal shape or a linear shape by making the circumferential width dimension significantly smaller than the radial width dimension. In this case, the above-mentioned light receiving regions A, RA, B and RB can be obtained by dividing the light receiving element 7 into four substantially in the radial direction.

FIG. 3 is a schematic diagram showing an improvement of the specific example shown in FIG. Basically, it has the same shape as the specific example shown in FIG. 2, and corresponding parts are given corresponding reference numerals to facilitate understanding. The improvement is that the exit side slit hole 9 of the outer track is shifted in phase clockwise from the entrance side slit hole 8 by a quarter pitch, while the exit side slit hole 9 of the inner track is shifted to the entrance side slit hole 8. On the other hand, it is offset counterclockwise. In this way, by reversing the shift direction from the specific example shown in FIG. 2, the incident side slit hole 8 and the emitting side slit hole 9 can be made to overlap each other on the side where the slit edges are not sharp. Compared to the example shown in FIG. 2, it is possible to reduce the influence of a dimensional error caused by the processing accuracy of the apex of the edge portion of the slit hole that occurs when the slit hole is formed by photoetching, for example.

FIG. 4 is a block diagram showing an example of the configuration of a processing circuit connected to the optical rotational torque detecting device shown in FIG. As described above, the light receiving element 7 has four light receiving areas A,
It is divided into RA, B, and RB. The output of each light receiving region is input to the processing circuit 20. The pair of outputs A and RA are added by the adding amplifier 21. Similarly, the pair of outputs B and RB are added by the adding amplifier 22. The addition result (A + RA), (B + RB) is the differential amplifier 2
Then, the torque signal (A + RA)-(B + RB) representing the amount of torsional torque is output by the difference processing by the signal No. 3. The pair of outputs A and RA are differentially processed by the differential amplifier 24 to obtain an A-phase output (A-RA). Similarly, a B-phase output (B-RB) is obtained by differentially processing the pair of outputs B and RB by the differential amplifier 25. These A-phase output and B-phase output are signal outputs indicating the rotation amount and the rotation direction. In addition, the addition results of the above-described addition amplifiers 21 and 22 are further added by the addition amplifier 26 in the subsequent stage. The light-emitting element controller 27 determines the total light-receiving area addition result (A + RA + B + R).
The light amount of the light emitting element 6 is automatically controlled so that B) is always constant. As a result, the sensitivity of the torque signal output does not change due to the influence of temperature and the like.

Finally, the operation of the optical rotational torque detecting device shown in FIG. 4 will be described with reference to FIGS. When the relative position of the input side slit plate and the output side slit plate changes due to the torsion of the torsion bar, the sum of the outputs of the light receiving regions A and RA increases and the sum of the light receiving regions B and RB decreases. As a result, a pair of addition outputs (A + RA) as shown in FIG.
(B + RB) is obtained. A torque signal is obtained by performing differential amplification on the results of both additions. When the relative positions of both slit plates are constant and rotating, (A + RA), (B +
Since each sum of RB) has a constant value regardless of the rotational position, the torque signal does not change due to the rotation.

On the other hand, while the slit plate is rotating, the outputs A, RA, B and RB of the four-divided light receiving areas are shown in FIG.
As shown in, the AC signal is synchronized with the passing period of the slit hole. At this time, the outputs A and RA are in opposite phase to each other.
Further, the outputs B and RB are also in antiphase relation with each other.

By differentially amplifying the pair of outputs A and RA, an A-phase output (A-RA) as shown in FIG. 7 is obtained. Similarly, by differentially amplifying the pair of outputs B and RB, a B-phase signal (B-RB) as shown in FIG. 7 is obtained.
The A-phase signal and the B-phase signal are out of phase with each other by 90 °.
The rotation direction can be specified depending on whether the B-phase signal is the advanced phase or the delayed phase with respect to the A-phase signal. Also, A phase signal or B
The amount of rotation can be measured by counting the peaks of the phase signals.

[0019]

As described above, according to the present invention, the slit hole formed in the rotary slit plate has a spiral shape according to a predetermined relational expression, so that the slit hole has a small circumference with respect to the slit hole pitch. Even if a light receiving element having a width dimension in the direction is used, it is possible to suppress the rotation ripple and obtain a stable torque output.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic structure of an optical rotational torque detection device according to the present invention.

FIG. 2 is a schematic diagram showing a relative positional relationship between an entrance slit hole and an exit slit hole.

FIG. 3 is a schematic diagram showing a relative positional relationship between an entrance slit hole and an exit slit hole.

FIG. 4 is a block diagram showing a specific example of a processing circuit connected to the optical rotational torque detection device shown in FIG.

5 is an explanatory diagram of the operation of the processing circuit shown in FIG.

FIG. 6 is an operation waveform diagram of the processing circuit of the same.

FIG. 7 is an operation waveform diagram of the processing circuit of the same.

FIG. 8 is a schematic diagram showing an example of a conventional optical rotation torque detection device.

9 is a perspective view showing a pattern shape of a slit plate incorporated in the optical rotary torque detection device shown in FIG.

[Explanation of symbols]

 1 Input axis 2 Output axis 3 Torsion bar 4 Input side slit plate 5 Output side slit plate 6 Light emitting element 7 Light receiving element 8 Slit hole

Claims (5)

[Claims] 1. A torsion bar connecting two rotary shafts, a pair of rotary slit plates fixed to the rotary shafts and facing each other, a light emitting element arranged on one surface side of the pair, and a pair of rotary slit plates of the pair. In an optical rotary torque detector equipped with a light receiving element that is arranged on the other surface side and receives transmitted light and detects the relative twist of the two rotary shafts, each rotary slit plate is equiangular in the circumferential direction. It has a track consisting of arrayed slit holes, and each slit hole has a spiral shape expressed by the following relational expression when the radius R from the center of the rotary slit plate and the angle θ are set, and the track is just an integer number. An optical rotational torque detecting device having a radial width including a spiral-shaped slit hole. [Equation 1] 2. The light receiving element has a pair of light receiving regions divided in a radial direction, and a change in the amount of received light due to relative displacement of both rotary slit plates increases in one light receiving region and decreases in the other light receiving region. The optical rotational torque detecting device according to claim 1, wherein twist detection is performed based on a difference between outputs from both light receiving regions. 3. A light receiving area is further divided into two parts by diagonal lines substantially parallel to the spiral-shaped slit holes, and outputs from the redivided areas are subjected to difference processing to detect rotation. Item 2. The optical rotation torque detection device according to item 2. 4. The optical element according to claim 3, wherein the light receiving element has a longitudinal shape having a width dimension in the circumferential direction which is significantly smaller than a width dimension in the radial direction and has a light receiving region divided into four substantially in the radial direction. Rotary torque detector. 5. The optical rotary torque detecting device according to claim 2, wherein the light emitting element is controlled so that the sum of the outputs from all the light receiving regions becomes constant.