JPH03284193A - Encoder - Google Patents

Abstract

PURPOSE:To improve the resolution of an encoder by emitting light through an optical system from a light-emitting element to rotor pole teeth in a motor, and sending the reflected optical signal to a photodetector through an optical system. CONSTITUTION:Optical fibers 12 are extended outside from the housing 3 of a stepping motor 1. One of the fibers is connected to a light-emitting element 14 such as a light-emitting diode or laser diode, while the other is connected to a photodetector 15 such as phototransistor or photodiode. The light output from the light-emitting element 14 is introduced through an optical transmission system 10 to the inside of the motor housing 3. The light is then emitting to rotor pole teeth 7a through an output end 12A, and an optical signal reflected from a pole teeth 7a is detected at a receiving end 12b in a predetermined position. The optical signal is transmitted to the photodetector 15 through an optical transmission system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Field of Industrial Application) The present invention relates to an encoder, and particularly to an encoder that detects the rotation angle of a stepping motor using rotor pole teeth.

(Prior Art) In general, stepping motors can rotate by a rotation angle corresponding to an input pulse signal, so they are suitable as an intermittent drive source, and have been widely used in recent years to drive feed mechanisms of various OA equipment.

Since this stepping motor can appropriately set the step angle using only pulse signals from the drive circuit, open-loop control is possible without using a sensor or the like to detect the rotation angle of the rotor. Therefore, it has the advantage that the entire motor drive system can be manufactured easily and at low cost.

However, open loop control has a problem in that if the load torque of the stepping motor is too large or the pulse frequency is too high, it will step out and it will be difficult to recover. In order to solve this problem, a sensor may be used to detect the rotation angle and a closed loop control that can monitor and control step-out may be used.

Hall elements and rotary enrotors are generally known as angle detection sensors used for this closed loop control.

FIG. 3 shows a stepping motor equipped with a Hall element, and reference numeral 20 in the figure indicates a housing of the motor. A PC board 22 is fixed to the inner surface of the housing 20 near the rotor 21. Then, the Hall element 2 is placed so as to face the rotor pole teeth 21a of this PC board 22.
3 is fixed. This Hall element 23 is the rotor 21
It is possible to detect a predetermined rotation angle by detecting changes in magnetic flux as a magnet or magnetic body approaches.

In addition, a rotary encoder consists of a slit disk or a disk whose peripheral edge is magnetized, which is attached coaxially to the rotating shaft at a position outside the motor, and an optical sensor such as a photointerrupter that can detect the rotation angle of this disk. Alternatively, it is composed of a magnetic sensor.

(Problems to be Solved by the Invention) However, in the above-described Hall element, the magnetic flux of the rotor spreads due to the influence of the magnet used, resulting in a decrease in resolution. For this reason, there is a problem in that highly accurate angle detection is difficult in a stepping motor whose rotor has a small pitch of pole teeth. In order to solve this problem, a magnetoresistive element (MR element) can be used in place of the Hall element, but this magnetoresistive element is expensive and has the same P as the Hall element.
There is a problem in that a C plate or the like must be provided inside the motor, making it impossible to downsize the motor.

On the other hand, encoders are used by attaching a slit disk etc. to the outside of the motor, but when installing it, it is difficult to determine the relative angular position with the rotor pole teeth inside the motor, and the disk and rotor pole teeth are slightly Even if there is a deviation, there is a problem that the rotation angle will be detected incorrectly.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an encoder for a stepping motor or the like that eliminates the problems of the above-mentioned conventional techniques, requires fewer parts, and exhibits high resolution.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention guides the light output from the light emitting element into the housing of the motor through the optical transmission system, so that the light emitting end faces the rotor pole teeth. and a light-emitting part that outputs light toward the rotor pole teeth, and a light-receiving end that receives the optical signal reflected by the rotor pole teeth,
It is characterized by comprising a light receiving section that transmits the optical signal to a light receiving element via an optical transmission system.

(Function) According to the present invention, the light output from the light emitting element is guided into the housing of the motor through the optical transmission system, and the light beam is directed from the light emitting end arranged to face the rotor pole teeth to the rotor pole teeth. The optical signal reflected on the rotor pole teeth is received by a light receiving end provided at a predetermined position, and this optical signal is transmitted to the light receiving element via an optical transmission system, which enables high resolution at low cost. A stepping motor can be provided with a high encoder.

(Embodiment) An embodiment of the encoder according to the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a normal HB type stepping motor, and the rotor 2 of this stepping motor 1 includes a shaft 5 supported by a bearing 4 mounted on a housing 3, and a shaft inserted into the shaft 5. It is composed of a directionally magnetized permanent magnet 6 and a rotor core 7 made of electromagnetic mild steel plates laminated and fixed on the outer periphery of the permanent magnet 6. A large number of pole teeth 7a are formed on the surface of this rotor core 7.

On the other hand, a stator core 8 formed by laminating electromagnetic mild steel plates is fixed to the inner surface of the housing 3. Pole teeth 8a facing the pole teeth 7a of the rotor core 7 are formed on the inner surface of the stator core 8, and slots 9 are formed on the inner surface of the stator core 8.
are formed at predetermined intervals. An excitation winding 10 is wound around the stator core 8 at this slot 9 position. The basic step angle of this stepping motor can be set by the excitation method for this excitation winding and the above-mentioned pole tooth pitch.

In this embodiment, the rotor core 7 has the number of pole teeth Nr-50 and the tooth pitch θ=7.2°, and the resolution is improved by the excitation force method of the excitation winding 10 of the adjacent stator core 8. be able to.

At this time, two small-diameter mounting holes 11 are provided in the housing surface holding the bearing 4. This mounting hole 1] is bored at a position facing the pole teeth 7a of the rotor core 7. Optical fibers 12 are fitted into each of the mounting holes 11, and the tips of the optical fibers 12 extend to the vicinity of the pole tooth position 7a of the rotor core 7 while being supported and fixed to a resin holder 13. has been done.

The tip of this optical fiber 12 is polished so that it can be used as a sensor head or a light guide, and one of the two tips can be used as a light emitting end 12A and the other as a light receiving end 12B. There is.

That is, the optical fiber 12 is extended to the outside from the housing 3 of the stepping motor 1, one of which is connected to a light emitting element 14 such as a light emitting diode or a laser diode, and the other is connected to a light emitting element 14 such as a phototransistor or photodiode. It is connected to the light receiving element 15.

Next, details of a rotation angle detection section using an encoder according to the present invention will be explained with reference to FIG.

FIG. 2 shows a portion of the stator core 8 and the rotor core 7, as well as a light emitting end 12A and a light receiving end 12B of an optical sensor installed near the rotor core. Since the light-emitting end], 2A and the light-receiving end 1.2B have predetermined directional characteristics, the rotor pole teeth 7a are located within the overlapping region of the light-emitting region where the light output extends and the sensitive region where light can be received. . Therefore, the light emitting end 12A and the light receiving end 12B are fixed to the housing 3 so as to form a predetermined angle.

Since the present invention is configured as described above, the continuous light irradiated from the light emitting end 12A to the pole tooth position 7a of the rotor 7 rotating at a constant rotation speed as shown in FIG. The light is reflected by the pole teeth 7a at the right timing and is received by the light receiving end 12B as a pulse wave. This pulse wave is then transmitted to the light receiving element 15 via the optical fiber 12, and then converted into a predetermined pulse signal through an amplifier and a waveform shaper.

As described above, the rotation angle of the stepping motor can be detected from the pulse signal and the number of pole teeth.

Incidentally, by arranging a plurality of sets of the above-mentioned optical sensors at predetermined intervals at the positions of the rotor pole teeth, the deviation can be canceled out, and as a result, the detection precision of the rotation angle can be improved.

Furthermore, the encoder according to the present invention is applicable not only to the stepping motor having rotor pole teeth as described above, but also to other types of motors in which the rotor has slots for excitation windings. In other words, since the continuous light irradiated onto the rotating rotor of the motor passes through the slot position, this reflected light can be detected as a pulse wave, and the motor rotation speed etc. can be detected using this pulse signal. It becomes possible.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a light beam is irradiated from the light emitting end in the motor toward the rotor pole teeth using the leading force from the light emitting element through the optical transmission system, and the light beam is directed toward the rotor pole teeth. The reflected optical signal is received at the light-receiving end, and this optical signal is transmitted to the light-receiving element via the optical transmission system.
In a stepping motor or the like, the structure is simple and an encoder exhibiting high resolution can be installed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the encoder according to the present invention, FIG. 2 is a perspective view showing an embodiment of the detection situation with the encoder according to the present invention, and FIG. 3 is a conventional rotation angle detection method. FIG. 2 is a cross-sectional view showing an example of a sensor. 1...Stepping motor, 2...Rotor, 3...
Housing, 5... Shaft, 6... Permanent magnet, 7
...Rotor core, 8...Stator core, 12...
Optical fiber, 14... light emitting element, 15... light receiving element.

Claims (1)

[Claims] a light emitting section that guides light output from the light emitting element into the motor housing through an optical transmission system, has a light emitting end facing the rotor pole teeth, and outputs light toward the rotor pole teeth; and the rotor pole teeth. What is claimed is: 1. An encoder comprising: a light receiving end that receives an optical signal reflected by a light receiving element; and a light receiving section that transmits the optical signal to a light receiving element via an optical transmission system.