JPH09273944A - Encoder apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an apparatus by improving a space factor. SOLUTION: The encoder apparatus is provided with an encoder plate 14 rotating in association with the rotation of a rotary body 10 and a photointerrupter consisting of a light-emitting part 2 and a photodetecting part 1 arranged via an outer circumferential part of the encoder plate 14. The light- emitting part 2 is disposed between the encoder plate 14 and rotary body 10, and the photodetecting part 1 is set at the opposite side to the rotary body 10 with respect to the encoder plate 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder device for detecting the amount of rotation of a rotating body such as a motor.

[0002]

2. Description of the Related Art Conventionally, a driving device for driving a driven body by a motor has been widely used in electronic devices in various fields. For example, even in a camera, automatic focus adjustment for stopping driving of a photographing lens to a focusing position. Used in equipment. The lens drive control device of the camera requires an encoder device for detecting the amount of movement and the moving speed of the lens necessary for control. Generally, a photo interrupter mechanism is used in this encoder device. That is, the slits are provided at equal intervals on a rotary plate that rotates with the movement of the taking lens, and the slits are counted by a photo interrupter in which a light emitting unit and a light receiving unit are arranged to face each other with the rotary plate sandwiched between them. The rotation amount and the rotation speed of the rotary plate are detected by the photo interrupter output signal, and the lens movement amount and the lens movement speed are calculated from them.

As this photo interrupter, a U-shaped one in which a light emitting portion and a light receiving portion are integrally formed so as to face each other is generally used. For example, fair fair 6-43769
The publication discloses an example in which a U-shaped photo interrupter is used in a lens drive control device of a camera. FIG.
The configuration is shown in FIG. The encoder plate 41 is attached to the drive shaft 30 of the drive motor 20 through the friction of the compression spring 39.
And the encoder gear 38 fixed integrally with the encoder plate 41 is fitted. The encoder plate 41 and the encoder gear 38 generate a frictional force between the encoder plate 41 and the encoder gear 38 with the washers 35 and 36 by the spring force of the compression spring 39, thereby rotating integrally with the motor drive shaft 20. The frictional force of the compression spring 39 is larger than the lens driving force of the drive shaft 30,
Moreover, when the lens reaches the moving end and the encoder gear 38 stops, the size is such that it slips with respect to the washers 35 and 36. When the lens reaches the moving end and the encoder gear 38 stops, the drive shaft 30 moves to the motor 2
Rotates against frictional force until the power supply to 0 is cut off.

The encoder plate 41 integrated with the encoder gear 38 is formed with slits extending radially from the center, and slits which are light transmitting portions and light shielding portions between the slits are periodically arranged. There is. One of the portions of the photo interrupter 42 that extend in parallel with the U-shape has a light emitting portion, which emits light toward a light receiving portion arranged at the other facing portion, and the light receiving portion receives the light. A part of the encoder plate 41 is arranged so as to enter the U-shaped portion of the photo interrupter 42. When the encoder plate 41 rotates, the light reaching the light receiving unit from the light emitting unit of the photo interrupter 42 through the slit of the encoder plate is periodically blocked, and the light reaching the light receiving unit is converted into an electric signal, thereby converting the pulse signal into a pulse signal. Output. The number of the pulse signals indicates the rotation amount of the encoder plate 41, that is, the rotation amount of the motor drive shaft 30, and the lens drive amount and the lens drive speed can be detected from this and the reduction ratio to the lens drive shaft (not shown).

[0005]

As described above, when the lens movement amount is detected by the rotation amount of the encoder plate directly connected to the motor drive shaft, backlash of the reduction gear occurs between the drive shaft of the motor, which is the drive source, and the encoder plate. Since the error between the detected rotation amount and the rotation amount of the motor drive shaft is reduced, it is convenient for accurate control. However, when a general U-shaped photo interrupter is arranged near the motor, there are the following problems.

As shown in FIG. 4, a small U-shaped package used for a photo interrupter of a camera or the like is generally formed such that opposing parallel portions have the same size. That is, the light emitting portion and the light receiving portion have the same height (dimension p in FIG. 4) and thickness (dimension q in FIG. 4). The light-emitting portion side of the photo interrupter is only a light source such as an infrared LED, while the light-receiving portion side includes a light-receiving element such as a photo interrupter and a comparator or preamplifier for making the output a Hi or Lo digital output. Electronic circuit is required. Therefore, the light receiving portion side needs a space which is several times larger in volume than the light emitting portion side. Therefore, the parallel portions facing each other of the U-shaped package are sized to accommodate a large light receiving portion.

On the other hand, when the photo interrupter 42 is arranged near the motor 20 as shown in FIG.
41m on the side of the motor 20 and the end surface 20a of the motor 20
In the space between and, the one parallel portion 42a of the U-shaped photo interrupter 42 facing each other and the substrate 21 for fixing the motor 20, the gear train, and the photo interrupter 42 are provided because the encoder plate 41 can rotate. Must be placed with a gap of. Therefore, the distance between the surface 41m of the encoder plate 41 and the end surface 20a of the motor 20 needs to be equal to the sum of the thickness u of the parallel portion 42a and the thickness t of the substrate 21, plus the gap k. Therefore, the encoder plate 41
And the end surface 20a of the motor 20 need to be additionally provided on the motor drive shaft, and the front end 30s of the drive shaft 30 and the rear surface 20 of the motor 20 are correspondingly correspondingly (length n in FIG. 3).
The distance D of b becomes large.

In the case of a single-lens reflex camera, the distance from the mount surface for mounting the lens to the film surface is set to a predetermined dimension in order to ensure compatibility of the interchangeable lens, so D must be smaller than that. I won't. The length of the compression spring 39 for friction needs to be a certain length in order to generate a predetermined frictional force, and the thickness of the encoder gear 38 cannot be unduly thin in order to secure the strength of the gear teeth. Therefore, in order to obtain an extra distance between the encoder plate 41 and the end surface 20a of the motor 20, the motor 20
There is no choice but to shorten the length L of. Then, the power of the motor drops, so the lens drive speed drops,
There is a problem that the torque of the lens that can be driven can be limited (especially when the temperature drops).

As a countermeasure against this, the photo interrupter 42
It is conceivable that the above package is arranged outside the outer diameter of the motor 20, but if this is done, the diameter of the encoder plate 41 must also be increased so that the encoder plate 41 does not interfere with the gear 40 at the next stage of the encoder gear 38. Therefore, the distance between the encoder gear 38 and the second-stage gear 40 must be increased, and the entire gear train becomes large.

As another measure, the substrate 21 is cut out at the portion where the photo interrupter 42 is in contact with the substrate 21, and the photo interrupter 42 (parallel portion 42a) is embedded in the space, and the encoder plate 41 and the motor are A method of shortening the distance between the end faces 20a is also conceivable. But,
Since the U-shaped photo interrupter 42 has a large height (dimension p in FIG. 4) and a large depth (dimension in the direction perpendicular to the paper surface in FIG. 4) as described above, the photo interrupter 42 is moved toward the motor 20. In order to bring them closer, the substrate 21 must be cut out larger than that, and a large hole is formed in the substrate near the motor mounting portion. As a result, the mechanical strength of the substrate for fixing the motor 20 is reduced, the motor 20 is tilted by the force perpendicular to the motor shaft received by the encoder gear 38 when the motor shaft rotates, and the motor 20 vibrates during rotation. There is a problem that noise is generated.

The present invention has been made in view of the above problems, and an object thereof is to improve the space factor and to downsize the device.

[0012]

In order to achieve this object, the encoder device of the present invention comprises an encoder plate (14) that rotates in conjunction with the rotation of a rotating body (10) and an encoder plate (14). Light emitting part (2) arranged with the outer peripheral part sandwiched
And a photo interrupter including a light receiving unit (1), the light emitting unit (2) is disposed between the encoder plate (14) and the rotating body (10), and the light receiving unit (1) is It is arranged on the opposite side of the encoder plate (14) from the rotating body (10).

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of an encoder device according to the present invention.

In FIG. 1, the drive shaft 11 of the motor 10
Further, the encoder gear 13 is fitted through the frictional force of the friction spring 12. Unlike the example of Japanese Utility Model Publication No. 6-43769, the slitted encoder plate 14 is not integrated with the encoder gear 13 but is joined with a certain amount of play in the rotational direction. FIG. 2 shows a plan view of the encoder plate 14. The encoder plate 14 has two protrusions 14a, and the two protrusions 13a of the encoder gear 13 are engaged with each other with the same inner diameter and outer diameter as the protrusion 14a with a predetermined gap in the rotation direction. By the frictional force generated by the spring force of the friction spring 12,
The rotation of the motor shaft 11 is integrally transmitted to the encoder gear 13, and the protrusion 13a also rotates. From the place where the protrusion 13a hits the protrusion 14a, the protrusions 13a and 14a
The rotation of the encoder gear 13 is integrally transmitted to the encoder plate 14 by the mutual engagement. When the motor shaft 11 rotates in the opposite direction, only the encoder gear 13 has the protrusion 13
While the backlash between a and the projection 14a is blocked, the rotation occurs, and when the projections 13a and 14a hit, the encoder plate 14 also starts to rotate in the opposite direction.

The reason why the play is provided between the encoder gear 13 and the encoder plate 14 is to determine the moving end when the lens reaches the moving end. As described above, when the lens reaches the moving end and the encoder gear 13 stops,
The motor shaft 11 continues to rotate while sliding by the frictional force of the friction spring 12. At this time, it is necessary to detect that the encoder gear 13 is stopped and determine that the lens has reached the moving end to cut off the energization of the motor. Normally, this detection is performed by the photo interrupter for a predetermined time. When it does not occur, it is detected that the encoder plate 14 is stopped. However, while the motor shaft 11 continues to rotate, even if the encoder gear 13 does not rotate, the friction between the friction spring 12 and the washer 17 causes a slight vibration. Therefore, encoder gear 1
When the encoder plate 3 and the encoder plate 14 are completely integrated, the vibration is transmitted to the encoder plate 14 and the photo interrupter may generate a pulse even if the encoder plate 14 is not rotating. Edge detection may be delayed or impossible. This play is provided to prevent the transmission of vibration to the encoder plate 14.

The photo interrupter is constructed by arranging a light receiving portion 1 and a light emitting portion 2 which is different from the light receiving portion 1 so as to face each other with an outer peripheral portion of the encoder plate 14 provided with a slit provided therebetween. Light receiving part 1 with built-in light receiving element and electronic circuit
Is a package that is considerably larger than the light emitting unit 2 including only the infrared LED. Therefore, a small light emitting unit 2 is arranged between the encoder plate 14 and the motor 10. Light emitting unit 2 and light receiving unit 1
Are integrally held by a holding member 3 formed of a thin plate, and the holding member 3 is fixed to the second substrate 6 with screws.

Since the height h1 from the encoder plate 14 to the back surface of the light emitting portion 2 is smaller than the height h2 from the encoder plate 14 to the back surface of the light receiving portion 1, the motor 10 is fixed between the light emitting portion 2 and the motor 10. Both the first substrate 5 and the mounting portion 4a of the holding member 4 for rotatably holding the encoder gear 13 and the separate encoder plate 14 to the first substrate 5 can be arranged. If this is a photo interrupter of a U-shaped package capable of housing the light receiving unit 1, a space shown by a chain line in FIG. 1 is required on the light emitting side, and both the first substrate 5 and the mounting portion 4 a of the holding member 4 are required. Cannot be placed.

In this way, the photointerrupter can be constructed by using the light emitting section 2 and the light receiving section 1 as separate packages.
This is more effective when the light receiving unit 1 is large. For example, 2
This is a case of configuring a phase photo interrupter. Light receiving part 1
4 light receiving elements (see FIG. 5) are provided, and if the relationship between the four light receiving elements 1a to 1d and the slit of the encoder plate 14 is changed to the positional relationship shown by the dashed line in FIG. Two half-wavelength shifted pulses are obtained from the output changes of 1a to 1d. It is shown in FIG. If the rising and falling edges of these two pulses are read as pulses, 4 pulses can be generated in one cycle of one phase, and the encoder plate 14 can be made to have a narrow interval between slits without increasing the frequency. Since the number of pulses generated per revolution of 14 can be increased, more accurate control becomes possible.

Further, since the rotation direction of the encoder plate 14 can be detected from the phase difference θ between the two pulses, control using the rotation direction can also be performed. For example, when driving to invert the lens, even if the motor is energized in the reverse direction, the motor drive shaft does not immediately invert due to the inertia of the entire lens drive mechanical system. At this time, if the rotation direction of the encoder plate 14 is not known, only the rotating pulse can be detected, so that the accurate rotation amount after the motor shaft actually starts reversing cannot be detected. By detecting the direction of rotation, the exact amount of rotation from the beginning of reversal can be known, and accurate control can be performed.

Such a two-phase photo interrupter is
Since four light-receiving elements are required, the light-receiving section becomes particularly large. Since only one light emitting part is required as in the case of one phase, the difference in the size of the required space is further widened. If this is put in a U-shaped package, the light-emitting side will have a large wasted space due to the package. When the light receiving portion becomes large, it is particularly effective to form the light emitting portion and the light receiving portion in separate packages as in the present invention, and to arrange the light emitting portion having a smaller number of elements in a smaller space. Is.

In the above-described embodiment, the light-emitting portion 2 and the light-receiving portion 1 of the photo interrupter are described as separate members, but they are fixed to the same (common) holding member and the light-emitting portion 2 is fixed. The light receiving unit 1 and the light receiving unit 1 may be integrally configured.

[0023]

As described above, according to the encoder device of the present invention, the light emitting part (2) is arranged between the encoder plate (14) and the rotating body (10), and the light receiving part (1) is provided. , The encoder plate (14) is disposed on the opposite side of the rotating body (10), and therefore the rotating body (10) and the encoder plate (1
It is possible to reduce the size of the device by improving the space factor between the device and 4).

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an encoder device according to the present invention.

FIG. 2 is a plan view showing an embodiment of an encoder device according to the present invention.

FIG. 3 is a cross-sectional view showing an example of a conventional encoder device.

FIG. 4 is a plan view showing an embodiment of an encoder device according to the present invention.

FIG. 5 is a plan view showing an embodiment of an encoder device according to the present invention.

FIG. 6 is a waveform diagram showing an embodiment of an encoder device according to the present invention.

[Explanation of symbols]

 1 Photointerrupter light receiving part 2 Photointerrupter light emitting part 3 Holding member 10 Motor 11 Motor drive shaft 12 Friction spring 13 Encoder gear 14 Encoder plate

Front page continuation (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03B 13/36 G02B 7/11 P H03M 1/24 G03B 3/00 A

Claims (4)

[Claims] 1. An encoder plate that rotates in association with rotation of a rotating body, and a photointerrupter composed of a light-emitting portion and a light-receiving portion that are arranged with the outer peripheral portion of the encoder plate sandwiched between the encoder plate and the light-emitting portion. An encoder device, wherein a portion is arranged between the encoder plate and the rotating body, and the light receiving portion is arranged on a side opposite to the rotating body with respect to the encoder plate. 2. The encoder device according to claim 1, wherein the encoder plate is arranged coaxially with the rotating body. 3. The encoder device according to claim 1, wherein the light receiving section has four light receiving elements, and the photo interrupter detects a rotation amount and a rotation direction of the encoder plate. 4. The encoder device according to claim 1, wherein the light emitting portion and the light receiving portion are fixed to the same holding member so as to face each other and are integrally formed.