JPH02161312A - Rotary encoder - Google Patents

Abstract

PURPOSE:To exactly control rotating speed and position of a motor at a low cost with a small-sized device by providing a broad light translucent part having the transmissivity which is the intermediate of the transmissivity of light shielding parts and light transparent parts on an encoder rotating plate having the light shielding parts and the light transparent parts. CONSTITUTION:The encoder rotating plate having the light transparent parts 1 and the black-printed light shielding parts 2 is provided broadly with the light translucent part 3 having the transmissivity of about the intermediate level of the transmissivity of the light transparent parts 1 and the light shielding parts 2. The detection position X of a photointerruptor 5 is set at the translucent part 3 in the static state which is the initial position of the rotary encoder combined with such encoder rotating plate 4 and the photointerruptor 5 as a detecting sensor. The light translucent part 3 may be used for detecting the prescribed intermediate part or end part in addition to the initial position. The stable encoding signal is obtd. at the low cost with the small size.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a rotary encoder that rotates in conjunction with the movement of a motor and performs servo control etc. by outputting pulses according to the rotational position. be.

[Conventional technology]

Conventionally, rotary encoders have been proposed for the purpose of constant speed rotation control and position control of motors. A rotary encoder is a position sensor that outputs a pulse proportional to the rotation angle of an input shaft, and there are two types: an absolute type (FIG. 9a) and an incremental type (FIG. 9b). 9th
In the figure, 51 is an encoder shaft, 52 is an encoder rotating plate, 53 is a fixed mask, 54 is a light emitting diode, and 55
is a photodiode. Further, in FIG. 9, 56 is a human face slit, 57 is a B-phase slit, and the positional difference between the A-phase and B-phase is 90°. Furthermore, using the principle of a rotary encoder, in order to perform simple C servo control in the classification of small consumer devices, the encoder rotating plate has a light-shielding part and a light-transmitting part, as shown in Figure 1O. There is also known a photointerrupter 5 comprising a transparent sheet and a light emitting diode and a photodiode integrated.

[Problem that the invention is trying to solve] However,
The above conventional examples each have the following problems.

First of all, in an abunlute type or an incremental type rotary encoder, the encode output signal is extremely accurate, and as a result, high quality DC servo control can be performed. However, as is clear from its structure, the device itself has a large number of components and is large and expensive. Furthermore, since a plurality of light emitting diodes and photodiodes are used, the number of external computer circuits increases, resulting in high layer costs. Therefore, this type of device is suitable for large, expensive equipment that requires high precision, but it is suitable for consumer use, that is, equipment that is low in price and small in size.
It is particularly inappropriate for devices that are meant to be carried.Therefore, for such low-cost, small-sized devices, an extremely simplified rotary encoder as shown in Figure 10 is recommended. This type of device can reduce the cost considerably, and the signal accuracy is at a reasonable level, and this signal allows speed control and position control to a certain extent.However, in recent years, Due to demands for higher quality and lighter weight, this type of rotary encoder also needs to be further downsized and highly accurate. (It has become essential to do so. However, with the increase in resolution, optical sensors such as photointerrupters have also been improved in transmission efficiency and detection ability, but this is not sufficient. As the pitch between light and dark of the transparent part is narrowed, the amplitude of the bright and dark levels of the output signal decreases, causing variations in the performance of the optical sensor.
Depending on the surrounding environmental conditions, there is a possibility that an accident may occur where the output from the encoder cannot be determined.

In order to prevent such accidents, if compensation is attempted in an electric circuit, the circuit becomes considerably complicated and requires complicated adjustments, which increases the cost.

[Means for Solving the Problems (and Effects)] According to the present invention, in a rotary encoder that detects the rotational position of a motor, an encoder rotary plate having a light shielding part and a light transmitting part has a light shielding part and a light transmitting part. By providing a wide semi-transparent part with a light transmittance between the two parts, and using this semi-transparent part to detect a predetermined position of the encoder rotary plate and use it as a home position, etc., a small device can be used. Moreover, it is possible to obtain a stable encode signal at low cost, and it is possible to accurately control the rotational speed and position of the motor.

〔Example〕

Fig. 1 shows an encoder rotary plate made of a transparent sheet having a light-shielding part and a light-transmitting part used in the rotary encoder of the present invention. Parts 3 and 3 are semi-transparent parts whose light transmittance, which is a feature of the present invention, is at a level intermediate between that of the light-transmitting part 1 and the light-shielding part 2. FIG. 2 is an enlarged view of the semi-transparent part 3 in FIG. 1, and shows an example of a black printing pattern.
) has a checkerboard shape, and (C) has an arc shape. In particular, (c) does not have a high frequency component of a bright/dark pattern in the direction of rotation of the encoder, so it is most effective for stable signal detection. Further, in the embodiment shown in FIG. 2, since the semi-transmissive characteristic is created by a black and white pattern, there is also the effect that paint having an intermediate level of density is unnecessary.

Next, the rotary encoder output detection method of the present invention will be explained using FIGS. 3, 4, and 5. FIG. 3 is a diagram showing the light-dark pattern of the encoder rotary plate 4 and the positional relationship of the photointerrupter 5 used as a detection sensor in a static state, which is the initial position of the rotary encoder of the present invention. X in FIG. 3 is the actual detection position, which in the initial state is located on the semi-transparent part of FIG. 1. FIG. 4 is a diagram showing an example of the configuration of a detection circuit. In FIG.
7 is a comparator that compares the output of the operational amplifier 6. Next, the operation will be explained. In FIG. 3, when a motor (not shown) starts rotating, the encoder rotary plate 4 starts rotating in the rotational direction shown in the figure. Then, the signal SL in FIG. 5(a) is outputted to PI in FIG. 4 as the motor rotates.

The signal 81 in FIG. 5(a) is AC amplified by the operational amplifier 6 in FIG. 4, and the signal 82 in FIG. 5(a) is output. Note that VCI and VC2 in FIG. 4 correspond to VCI and VC2 in FIG. 5(a). Here, the reason why AC amplification is used instead of DC amplification is that since the DC component of Sl is large, only the AC component is extracted and amplified. Next, the output of the operational amplifier 6 is input to the comparator 7, compared with the comparison reference voltage VC2, and output as a rectangular wave as shown in FIG. 5(b). In this way, by rotating the encoder rotating plate in conjunction with the rotation of the motor, a corresponding output signal can be obtained with a simple circuit. Here, if the semi-transparent part shown in FIG. 1, which is the initial position, is a completely light-shielding part or a transparent part, this part is wide and has the characteristics of AC amplification. Due to the time constant of R, there is a possibility that the first few pulses of the bright/dark signal cannot be detected, making it impossible to detect the signal with a simple circuit as shown in FIG. By providing this, the level of the signal S1 from the initial position becomes near the intermediate level of the AC level, and pulses after the initial position can be reliably detected and malfunctions can be prevented.

Note that the wide semi-transparent part may be used not only for initial position detection but also for detecting a predetermined intermediate part or end part.

Next, as an example of applying the rotary encoder of the present invention, an embodiment will be described in which the rotary encoder of the present invention is applied to control the opening speed and aperture diameter of a half-open shutter of a camera. FIG. 6 is a diagram showing the mechanism of the present invention, FIG. 7 is a block diagram showing the circuit configuration, and FIG. 8 is a flow chart.

In FIG. 6, reference numeral 11 denotes a motor that opens the shutter, and is fixed on the base plate 31. As shown in FIG. 12 is a pinion gear press-fitted into the shaft of the motor 11, and a first reduction gear 13.12 is fitted to the gear shafts 31a and 31b of the main plate 31. The rack gear 15 is slid along the shafts 31g and 31f of the base plate 31 via the second reduction gear 14.

16 is a rack spring attached to the spring hook 31c of the main plate 31, one end of which is attached to the protrusion 31d of the main plate, and the other end of which is attached to the rack gear 1.
5, and presses the rack gear 15 against the stopper 31e of the main plate.

A shaft 19 of a clutch 18 is attached through the hole 15b of the rack gear 15, and a clutch spring 17 is also attached to the shaft 19 to bias the clutch 18 clockwise.

20 is a shirt top plate whose protrusion 20b is pushed by the end 18a of the clutch 18 and rotates counterclockwise around the hole 20a. The outer circumferential portion 20c of the shutter plate 20 is a gear, and drives the gear portion of the encoder rotary plate 4. 22 is a return spring for the encoder rotating plate, and 25 is a photointerrupter that reads the bright and dark pattern of the encoder rotating plate.

24 and 25 are shutter blades, 24a and 25a are openings forming an aperture, and elongated holes 24b and 25b are driven by projections 20d and 20e of the shutter plate 20.

Numerals 26 to 30 are suction type magnets, and 26 is an armature, which is attracted upward when energized and hits the protrusion 18b of the clutch 18 with 26a, causing the 18a and the shaft plate protrusion 2 to be drawn together.
0b is disengaged. 27 is an armature shaft, 28 is a yoke, 29 is a coil, and 30 is a coil shaft that passes through the coil and is attached to the yoke 28.

Further, in FIG. 7, 41 is a photometry circuit that measures the brightness of the subject, 42 is a release signal generation circuit that detects that a release switch (not shown) is pressed and generates a signal, and 43 is a control circuit for the entire shutter. 44 is a constant speed control circuit that performs constant speed control based on the signal from the photointerrupter 5 which is the output waveform of the rotary encoder with respect to the shutter opening speed; 45 is a motor that drives the motor 11; A drive circuit 11 is a motor that opens the shutter and initializes gears etc. after the shutter is closed;
6 is a magnet drive circuit that drives a clutch release magnet 47 for rapidly closing the shutter by a spring force; 47 is a magnet; Further, 48 is a photointerrupter waveform shaping circuit that shapes the waveform of a signal from the photointerrupter 5 that detects the signal of the encoder rotary plate interlocked with the shutter opening member, and is configured as shown in FIG. Further, 5 is a photo interrupter.

Next, the operation will be explained with reference to FIGS. 6 to 8. When the release switch of the camera is pressed, a signal is sent from the release signal generation circuit 42 to the control circuit 43. Control circuit 43
The photometry circuit 41 is driven by Sl to detect the brightness of the subject as luminance information, and based on this information, an appropriate aperture diameter and the corresponding number of encoder pulses are calculated in S2. Next, in S3, the drive of the motor 11 is started, the pinion 12 of the motor 11 rotates counterclockwise, and the first reduction gear 13 is rotated.
rotates clockwise, and the second reduction gear 14 rotates counterclockwise to rotate the clutch gear 15 and the shafts 31g and 31f of the base plate 31.
Slide it to the right along.

Since the clutch 18 attached to the clutch gear 15 is biased downward by the clutch spring 17, its end 18a pushes the protrusion 20b of the shirt flap plate 20 to rotate the shirt flap plate 20 counterclockwise (S4). ).

The shirt flap plate 20 rotates the encoder rotary plate 4 clockwise against the spring 22 using a gear portion 20c on the outer periphery, and causes the photointerrupter 5 to output a pulse corresponding to the rotation angle of the shirt flap plate 20. is waveform-shaped in the photointerrupter waveform shaping circuit 48, counted in S5, and inputted to the constant speed control circuit 44 to become a reference signal for constant speed control. At this time, at the same time, the protrusion 20d on the lower surface of the shirt flap plate 20 drives the blade 24, and the blade 20e drives the blade 25 by fitting into the respective elongated holes 24b and 25b.
Exposure is performed through the opening formed by a and 25a.

As the shutter plate rotates counterclockwise, the number of pulse counts from the photointerrupter 5 increases, and the number of pulses 24a and 25
The aperture created by a is opened, but it is determined in 86 whether or not the count number calculated in S2 has been reached according to the brightness of the subject measured in advance, and when this count number is reached. In S7, the magnet coil 29 is energized by the magnet drive circuit 46, and the armature 26
is sucked upward, so 26a hits projection 18b of clutch 18 upward, causing 18a and shirt plate projection 20b to
The engagement with is released.

Then, the shirt flap plate 20 rapidly returns clockwise due to the action of the return spring 22, and the blade 24. 25 is closed (S8). After that, the magnet is also de-energized.

Then, in S9, by energizing the motor 11 in the opposite direction, the pinion 12, the first reduction gear 13, and the second reduction gear 1
4, the clutch gear 15 slides back to the left and finally reaches the end 18 of the clutch 18 on the rack gear.
a again engages with the protrusion 20b of the shirt shirt plate 20, returning to the initial state.

〔Effect of the invention〕

As explained above, according to the present invention, in a rotary encoder that controls the rotational speed and position of a motor, an encoder rotary plate having a light-shielding part and a light-transmitting part is provided with a light-transmitting part between the light-shielding part and the light-transmitting part. By providing a wide semi-transparent part with a certain width and using this semi-transparent part for detecting a predetermined position of the encoder rotary plate as a home position, etc., it is possible to create a small device, low cost, and simple operation. The detection circuit can obtain a wide and stable encoded signal, which has the effect of enabling accurate motor rotational speed control and position control.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the encoder rotary plate used in the present invention, FIGS. 2(a) to (c) are diagrams each showing an example of the configuration of a semi-transparent part, and FIG. 3 is a diagram showing an example of a pulse detection mechanism. Layout diagram, Figure 4 is a diagram showing an example of the encoded signal detection circuit, Figure 5 (a),
(b) is a partial waveform diagram of the fourth illustrated circuit. FIG. 6 is a diagram showing a mechanism example of a half-open shutter using the rotary encoder of the present invention, FIG. 7 is a block diagram showing a circuit configuration of a half-open shutter using the rotary encoder of the present invention, and FIG. It is a flowchart showing the operation of a half-open shutter using the rotary encoder of the invention. 9A and 9B are diagrams showing examples of a conventional absolute type encoder and an incremental type encoder, respectively, and FIG. 1O is a diagram showing an example of a conventional encoder using a transparent plate. 4 is an encoder rotating plate, 5 is a photointerrupter, 6 is an operational amplifier, and 7 is a comparator.

Claims (2)

[Claims] (1) In a rotary encoder that detects the rotational position of a motor, the encoder rotary plate, which has a light-shielding part and a light-transmitting part, has a wide semi-transparent part with a light transmittance between that of the light-shielding part and the light-transmitting part. A rotary encoder, wherein the semi-transparent part is used for detecting a predetermined position of the encoder rotary plate. (2) Claim (1) characterized in that the rotary encoder is used for controlling the opening speed or opening diameter of shutter blades of a manually-opened shutter, or both.
) rotary encoder.