JPH06281514A - Optical torque detector - Google Patents

Abstract

PURPOSE:To improve the detection accuracy of an optical torque detector and stabilize the operation. CONSTITUTION:Constituted are of a tortion bar 3 connecting two revolution shafts 1, 2, a pair of revolution slit plates 4, 5 fixed to each revolution axes 1, 2 and facing to each other, a light emitting element 8 and a light receiving element 7 arranged face to face over the pair, and a processing circuit 50 for detecting the relative twist of the two revolution shafts 1, 2 based on the output of the light receiving element 7. The light receiving element 7 has 4 light reception region A RA, B RB in total separated it each two in the radial direction and the circumferential direction. The processing circuit 50 adds and processes the output form the two light reception regions on the same track and every track with adding amplifiers 51, 52. The result of addition is processed by difference with a differential amplifier 53 to detect a twist torque.

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 a device that optically detects a relative rotational twist amount between an input shaft and an output shaft connected by a torsion bar. Such an optical rotational torque detecting device is applied to, for example, an electric power steering of an automobile.

[0002]

2. Description of the Related Art Conventionally, as a rotational torque detecting device, a structure using a strain gauge and a slip ring, a structure using a potentiometer and a slip ring, a structure for detecting a change in inductance based on a torsional displacement of a rotating shaft, etc. are known. . However, the first structure requires a skill to attach the strain gauge to the rotary shaft, which causes a problem in mass productivity. In addition, since the slip ring is a contact type, it has poor durability. In the second structure, since the potentiometer uses a brush as a contact, there is a problem in durability and stability of the contact due to vibration or shock. The third structure is a non-contact type, so there is no problem in terms of durability, but it is easily affected by the surroundings due to the fact that it uses the detection of magnetic inductance. It has the drawback of becoming In addition, in these conventional methods, only the torque information is obtained, and another detection device is required to obtain the rotation information.

In addition to these conventional systems, there is known an optical type rotary torque detecting device capable of simultaneously detecting both torque information and rotation information, for example, Japanese Patent Laid-Open No. 63-2844.
No. 42 publication. As shown in FIG. 8, the conventional optical rotation torque detecting device has two rotary shafts 101, 1
A torsion bar 103 is provided for connecting the 02 to each other. A pair of rotary slit plates 104 and 105 facing each other are attached to the rotary shafts 101 and 102, respectively. Through this pair, the light emitting element 106 and the light receiving element 107
Are opposed to each other. A relative twist between the two rotary shafts 101 and 102 is detected based on the output of the light receiving element.

FIG. 9 shows a pair of rotary slit plates 104 and 10.
5 shows the slit pattern shape formed on each of Nos. 5 and 5. On the surface of the upper rotary slit plate 104, slit holes 106 are formed at a predetermined pitch along the circumferential direction. Similarly, slit holes 107 are formed in the lower slit plate 105 at the same cycle. A pair of rotating shafts 10
In the neutral state where there is no relative twist displacement between the first and second slits 102, the slit holes 106 and 107 are aligned with each other, and the amount of light transmitted from the light emitting element 106 is maximized. On the other hand, when a relative torsional displacement is generated between both rotary shafts, the slit hole 10
Since 6, 107 are displaced from each other, the effective slit opening area is reduced and the amount of transmitted light is reduced. The light receiving element 107 outputs a detection signal proportional to a change in the amount of received light, and twist information can be obtained. or,
When the pair of rotary shafts 101 and 102 are connected together by the torsion bar 103 and integrally rotate, the pair of slit plates 104 and 105 also rotate accordingly. At this time, since the slit holes 106 and 107 are arranged along the entire circumference, the amount of light received by the light receiving element 107 changes intermittently with the passage thereof. By monitoring the change, rotation information can also be obtained.

[0005]

In the conventional optical rotational torque detecting device shown in FIGS. 8 and 9, the relative rotational displacement of the pair of slit plates is directly used for torque detection as a light amount change. However, this method has a problem in that a change in the amount of emitted light due to temperature dependence of the light emitting element, deterioration of life, etc. is directly captured as a torque change, and a detection error occurs due to various fluctuation factors. Further, since the amount of transmitted light changes intermittently with the rotation of the slit plate, rotational ripple occurs in the output of the light receiving element. It is necessary to suppress this rotational ripple in order to perform stable torque detection. Conventionally, in order to remove this ripple, the light transmitted through a plurality of slit holes is detected at the same time. Therefore, a large effective area is required for the light emitting element and the light receiving element, which is disadvantageous in terms of manufacturing cost. On the contrary, when the effective areas of the light emitting element and the light receiving element are not increased, it is necessary to reduce the arrangement pitch of the slit holes. In this case, it is necessary to reduce the stress strain of the torsion bar to reduce the maximum torsional displacement amount. Since a minute change is detected, there is a problem that measurement accuracy deteriorates.

[0006]

In view of the above-mentioned problems of the prior art, the present invention suppresses the detection error of the optical rotational torque detecting device and eliminates the output fluctuation due to the rotational ripple to achieve stable torque detection. The purpose is to enable. The following measures have been taken in order to achieve this object. That is, the optical rotational torque detection device according to the present invention has, as its basic components, a torsion bar that connects two rotating shafts, and a pair of rotating slit plates that are fixed to the rotating shafts and face each other. A light emitting element and a light receiving element which are arranged to face each other via this pair, and a processing circuit which detects a relative twist of the two rotary shafts based on the output of the light receiving element. As one of the features of the present invention, one rotating slit plate has a slit width corresponding to four times or more of the amount of twist on one side at the time of maximum torque as one cycle, and slit holes for half the cycle are equally spaced all around. It has 2 tracks. The other rotary slit plate is provided with two slit holes, which are out of phase with each other in the track reverse direction by 1/4 cycle, along the entire circumference. The light receiving element has a light receiving region which is divided into two in two in the radial direction and the circumferential direction (rotational direction). Each light receiving area is (n + 1
/ 2) The width in the circumferential direction is equal to the period (where n is an integer). In such a configuration, the processing circuit adds the outputs from the two light receiving regions on the same track for each track, and detects the torsion torque by the difference processing of the addition result. Further, this processing circuit compares outputs from two light receiving areas on the same track with each other and simultaneously detects rotation. Further, the processing circuit controls the light emitting element so that the total sum of the outputs from all the light receiving areas is always kept constant.

[0007]

According to the present invention, the outputs from the two light receiving regions arranged along one of the two tracks are added. These outputs change complementarily to each other, and the addition result becomes a signal having a constant level. This level increases, for example, according to the amount of twist. Further, the outputs from the two light receiving regions arranged along the other track are also added. This output is also complementary to each other, and the addition result has a predetermined level. On the contrary, this level decreases in accordance with the change in twist. Therefore, both addition results change differentially, and the torsion torque can be detected stably and highly accurately by performing the difference processing. As described above, the outputs from the two light receiving areas on the same track are complementary to each other. Therefore, when this is compared, a pulse signal corresponding to the rotation is obtained, and the rotation information can be easily detected. In addition, the operation is further stabilized by automatically controlling the light amount of the light emitting element so that the total sum of the outputs from all the light receiving regions is always kept constant.

[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 block diagram showing the basic configuration of an optical rotational torque detecting device according to the present invention. The device comprises a torsion bar 3 which connects an input shaft 1 and an output shaft 2 to each other so as to be rotatable. An input side slit plate 4 is attached to the end surface of the connecting portion of the input shaft 1. Similarly, an output side slit plate 5 is attached 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 receiving element 7 is arranged below the input side slit plate 4 via a fixed mask plate 6.
A light emitting element 8 is fixedly arranged on the upper side of the output side slit plate 5 so as to face the light receiving element 7. A processing circuit 50 is connected to the light receiving element 7, and the relative twist of the pair of input shaft 1 and output shaft 2 is detected based on the output thereof. At the same time, rotation detection is also performed.

As a feature of the present invention, the output side slit plate 5 has a width corresponding to four times or more the one-sided twist amount at the maximum torque (a width corresponding to two or more the two-sided twist amount).
As a cycle T, slit holes having a width of ½ of the cycle T are provided at equal intervals over the entire circumference for two tracks. The input side slit plate 4 is provided with two tracks over the entire circumference of which slit holes are out of phase with the output side slit holes in the opposite direction of each track by ¼ cycle. The light receiving element 7 has light receiving areas A, RA, B, and RB divided into two in the radial direction and the circumferential direction (rotational direction) of the slit plate. Each light receiving region has a circumferential width equal to (n + 1/2) period. The processing circuit 50 adds the outputs from the two light receiving regions on the same track for each track,
The torsion torque is detected by the difference processing of the addition result. Specifically, the outputs from the two light receiving areas A and RA located on the outer track (the reference symbols indicating the outputs are the same as the reference symbols of the corresponding light receiving areas)
The addition amplifier 51 performs addition processing. The outputs from the two light receiving regions B and RB located on the inner track are added together by the adding amplifier 52. The addition result (A + RA) and (B + RB) are subjected to a difference process by the differential amplifier 53, and a torque signal output representing a torsion torque is obtained. Further, the outputs from the two light receiving regions A and RA on the outer track are compared with each other by the differential amplifier 54,
A phase output is obtained. Similarly, the outputs from the two light receiving regions B and RB located on the inner track are the differential amplifier 55.
Are compared with each other to obtain a B-phase output. The pair of A-phase output and B-phase output constitutes a rotation signal output, and the integrated rotation amount and rotation direction of the input shaft 1 and the output shaft 2 can be detected. Further, the outputs of the summing amplifiers 51 and 52 are added to each other by the summing amplifier 56 in the subsequent stage. Summing amplifier 5
A light emitting element controller 57 is connected to the output stage of 6,
The light amount of the light emitting element 8 is automatically controlled so that the total sum of the outputs from all the light receiving regions A, RA, B and RB is always kept constant.

Next, specific examples of main components will be described in detail with reference to FIGS. 2 to 5. First of all, FIG. 2 is a schematic partial plan view showing the slit pattern shape of the output side slit plate 5. The output side slit plate 5 is provided with two tracks along the circumferential direction. Slit holes 11 are arranged on the outer track at a predetermined cycle T all around.
In this example, the period T is set to a width corresponding to four times the one-sided twist amount at the maximum torque. It may be more than this. Each slit hole 11 has a circumferential width dimension equal to T / 2. Slit holes 12 are arranged all around the inner track at a cycle T. This slit hole 12 also has a circumferential width dimension corresponding to T / 2. The outer track slit holes 11 and the inner track slit holes 12 are arranged in the same phase.

FIG. 3 is a schematic partial plan view showing the pattern shape of the input side slit plate 4. This slit plate 4 also has two tracks along the circumferential direction. On the outer track, slit holes 9 are arranged all around in a cycle T.
The slit hole 9 has a width dimension corresponding to T / 2.
This slit hole 9 is out of phase with the corresponding slit hole 11 of the output side slit plate 5 by T / 4 in the counterclockwise direction. Slit holes 10 are also arranged all around the inner track at a cycle T. This slit hole 10 has a width dimension of T / 2, and the phase thereof is shifted by T / 4 in the clockwise direction with respect to the corresponding slit hole 12 formed in the inner track of the output side slit plate 5.

FIG. 4 is a schematic plan view showing the pattern shape of the fixed mask plate 6. Transmission patterns 13 and 14 are provided corresponding to the outer tracks. Further, transmission patterns 15 and 16 are provided corresponding to the inner tracks. The transmission patterns 13 and 14 are out of phase with each other by T / 2 along the circumferential direction. Similarly, the transmission patterns 15 and 16 are also out of phase with each other by T / 2. On the other hand, the transmission patterns 13 and 15 have the same phase relationship with each other, and the transmission pattern 1 and
4 and 16 are also in phase with each other.

FIG. 5 is a schematic plan view showing a light receiving area pattern of the light receiving element 7 divided into four parts. As shown in the figure, the light receiving element 7 has light receiving regions 17 to 20 which are divided into two in the radial direction and the circumferential direction, respectively. Each light receiving region has a circumferential width equal to or greater than T / 2.
The present invention is not limited to this, and the light receiving region may have a circumferential width generally represented by (n + 1/2) T. The pair of light receiving regions 17 and 18 are arranged in alignment with the outer track and output outputs A and RA, respectively.
The other pair of light receiving areas 19 and 20 are arranged in alignment with the inner track, and output signals B and RB, respectively. As is clear from comparison between FIG. 5 and FIG. 4, the mask pattern 13 is aligned with the light receiving region 17, and the mask pattern 1
4 is aligned with the light receiving region 18, the mask pattern 15 is aligned with the light receiving region 19, and the mask pattern 16 is aligned with the light receiving region 20.

The operation of the optical rotational torque detecting device shown in FIG. 1 will be described in detail with reference to FIGS. 6 and 7. Figure 6
FIG. 4 is a schematic diagram showing a relative positional relationship among the input side slit plate 4, the output side slit plate 5 and the fixed mask plate 6 due to the twist displacement. In the neutral state shown in (a), the amount of twist is zero. At this time, in the outer track, the slit hole 9 of the input side slit plate and the slit hole 11 of the output side slit plate overlap each other by T / 4 in the left half region of the light receiving element to form an opening 21 indicated by hatching. Similarly, in the inner track, the slit hole 10 of the input side slit plate and the slit hole 12 of the output side slit plate 12 in the right half side region of the light receiving element.
Opening 22 shown by hatching with and overlapping by T / 4 minutes
Is formed. As can be seen from the figure, the openings 21, 22 in the inner and outer tracks have equal areas.

Next, as shown in (b), when a rotational torque is applied to the output shaft 2 in the counterclockwise direction in the drawing, the torsion bar 3 is twisted, and the relative position of the input side slit plate 4 and the output side slit plate 5 is changed. In the state of (b) in which the gear is shifted and rotated to the limit of the detected torque, the opening 21 of the outer track described above is T
The opening 23 is enlarged to 1/2 minute. On the other hand, the opening 22 of the inner track is reduced so that its area becomes zero.

The state shown in (c) is when the torque is applied to the output shaft 2 in the clockwise direction in the drawing to the limit of the detected torque, and the torsion bar 3 is twisted and the input side slit plate 4 and the output side slit plate 5 are twisted. The relative position of shifts. As a result,
The outer track opening 2 in the neutral state shown in (a)
1 disappears. On the other hand, the opening 22 of the inner track in the neutral state becomes the opening 24 enlarged to T / 2 minutes.

FIG. 7 is a waveform diagram showing the output from each light receiving region when the input side slit plate 4 and the output side slit plate 5 rotate while maintaining the relative positional relationship. In addition, (a), (b), and (c) of FIG. 7 are (a) and (b) of FIG.
It corresponds to (b) and (c) respectively. When the pair of slit plates integrally rotate in the neutral state shown in (a), complementary outputs A and RA are obtained from the outer tracks. The pair of outputs are in opposite phase to each other. This output changes periodically as it passes through the opening 21. Since both outputs A and RA are complementary to each other, the addition result A +
RA has a predetermined DC voltage level VA. This voltage level VA is proportional to the area of the opening 21. Similarly, a pair of outputs B and RB complementary to each other are obtained from the inner track. The addition result B + RB also has a predetermined DC voltage level VB according to the area of the opening 22. In the neutral state, the inner track opening 21 and the outer track opening 22 have the same area. Therefore, the result of the differential processing of VA and VB becomes a DC voltage of 0 level, and the neutral state is detected. As is apparent from the waveform (a), when the difference processing of the outputs RA and A is performed, a pulse signal corresponding to the rotation is obtained and the A phase output is obtained. Similarly, a pulse signal corresponding to the rotation is obtained by performing a difference process between the output B and the output RB, and a B-phase output is obtained. Since the A-phase output and the B-phase output are out of phase with each other by T / 4, not only the rotation amount but also the rotation direction can be detected.

In the state of (b), the opening 23 of the outer track
Has expanded to the maximum range. Therefore, outputs A and RA having a large amplitude are obtained. The direct current voltage VA corresponding to the area of the opening 23 is obtained by adding the pair of outputs. On the other hand, the inner track opening has disappeared. Therefore, the outputs B and RB are close to 0 level, and the addition result B + R
B also has an output voltage VB close to 0 level. By performing difference processing of both addition results, a torque signal output according to the amount of twist can be obtained.

In the state of (c), the opening of the outer track almost disappears and the opening 24 of the inner track is enlarged. Therefore, the outputs A and RA of the outer tracks are close to the 0 level, and the addition result is the voltage VA close to the 0 level. on the other hand,
The amplitudes of the outputs B and RB from the inner track are increasing. The DC voltage level VB of the addition result B + RB also increases. By taking the difference between both addition results, a torque signal output according to the amount of twist can be obtained. The twisting direction can be detected by the polarity of the torque signal output.

As described above, since it is possible to compensate by utilizing the fact that the addition output fluctuates corresponding to the torque change and the A phase and the B phase change in opposite directions, stable torque information can be obtained. . Also, rotation information can be obtained by comparing the waveforms. Further, by controlling the light emitting element so that the added output of all the waveforms becomes constant, the temperature and the rotation speed are not affected.

[0021]

As described above, according to the present invention, the relative position is changed in the pair of slit plates, thereby changing the transmitted light amount. By detecting this change in the amount of light in the four-divided light receiving regions and performing addition processing and difference processing, it is possible to obtain an effect that accurate and stable torque measurement can be performed without contact. In addition, since it also functions as an encoder, it is possible to obtain accurate and stable rotation information at the same time.

[Brief description of drawings]

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

FIG. 2 is a partial plan view showing a pattern shape of an output side slit plate.

FIG. 3 is a partial plan view showing a pattern shape of an input side slit plate.

FIG. 4 is a plan view showing a pattern shape of a fixed mask plate.

FIG. 5 is a plan view showing a divided region of a light receiving element.

FIG. 6 is an operation explanatory diagram of the optical rotation torque detection device shown in FIG. 1.

FIG. 7 is an operation waveform diagram of the optical rotation torque detection device shown in FIG.

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

9 is a schematic perspective view showing a pair of slit plates incorporated in the conventional structure shown in FIG.

[Explanation of symbols]

 1 input shaft 2 output shaft 3 torsion bar 4 input side slit plate 5 output side slit plate 6 fixed mask plate 7 light receiving element 8 light emitting element 9 slit hole 10 slit hole 11 slit hole 12 slit hole 50 processing circuit

Claims (3)

[Claims] 1. A torsion bar connecting two rotary shafts, a pair of rotary slit plates fixed to the rotary shafts and facing each other, and a light emitting element and a light receiving element which are arranged to face each other with the pair interposed therebetween. In the optical rotational torque detecting device including a processing circuit that detects a relative twist of two rotary shafts based on the output of the light receiving element, one rotary slit plate has a twist amount of 4 on one side at the maximum torque. One-half the width corresponding to more than twice the half
The slit holes for the period are provided at equal intervals for two tracks along the entire circumference, and the other rotating slit plate is a slit whose phase is shifted by ¼ period in the track reverse direction with respect to the slit hole. The light receiving element has two tracks along the entire circumference, and the light receiving element has a light receiving area divided into two in the radial direction and two in the circumferential direction, and each light receiving area is (n +
½) (where n is an integer) has a width in the circumferential direction, and the processing circuit adds the outputs from two light receiving regions on the same track for each track, and adds the outputs. An optical rotational torque detecting device characterized by detecting a twisting torque by difference processing of the result. 2. The optical rotary torque detecting device according to claim 1, wherein the processing circuit performs rotation detection by comparing outputs from two light receiving areas on the same track with each other. 3. The optical rotational torque detecting device according to claim 1, wherein the processing circuit controls the light emitting element so as to always keep a total sum of outputs from all light receiving regions constant.