JPS6041289B2 - position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position detector that detects, for example, the rotation speed or rotation angle of a rotating shaft of a motor using an encoder and is used for feed control of the motor.

For example, a position detector that performs feedback control of a motor is equipped with a rotating disk around which many slits are arranged in parallel around the rotating shaft of the motor, and an optical detection element that detects the slits in the rotating disk. The element holder is fixed to a stationary part such as one end face of the motor, but recently it has become possible to control stepping motors as well as common DC motors using this type of position detector. It is being said.

However, when such a fault detector is applied to a stepping motor, it is necessary to adjust the position of the output waveform of the element holder equipped with the detection element to accurately match the excitation position of the stepping motor. There is. Conventionally, this adjustment was made by displacing the rotating disk with respect to the motor's rotating shaft, but if a set screw is attached vertically to fix the rotating disk to the motor's rotating shaft, the rotating disk can be adjusted vertically. The positional relationship between the rotating disk and the rotating disk is likely to shift, and when tightening the set screws described above, the gap between the rotating disk and the element holder containing the sensing element must be adjusted accurately at the same time.Therefore, the adjustment work is difficult. However, it is extremely troublesome and has the disadvantage of being low in productivity. The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a guide means for guiding an element holder equipped with a detection element so that it can be moved and adjusted around the center of rotation of a rotating disk. Accordingly, it is an object of the present invention to provide a position detector which can be easily positioned and adjusted to an accurate position and which can greatly improve productivity.

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

1 is a double-shaft stepping motor, whose rotation axis la
A rotating disk 2 is fixed to one end of the rotary disk.

This rotating disk 2 consists of a boss portion 3 having a koji hole 3a that competes with the rotation axis la, and a thin disk portion 5 having a large number of slits 4 lined up at regular intervals on the outer periphery. One side of the outer screen of the stepping motor 1 facing the disc 2 is finished to be perpendicular to the rotation axis la to form a mounting surface 6 as a mounting member. It is fixed to the rotating shaft la with the interval between it and the attached surface 6 adjusted to a predetermined dimension. Reference numeral 7 denotes an annular groove as a guide portion formed in an annular shape around the rotation axis la on the mounting surface 6, and two parallel straight grooves 8, 8 extending from the annular groove 7 to the outer edge of the mounting surface 6 are formed. It is engraved on the mounting surface 6.

9, 9 are two screw holes drilled in the mounting surface 6, one screw hole 9 is aligned with the other straight groove 8, and the other screw hole 9 is located near the other straight groove 8. There is.

An element holder fixed on the mounting surface 6 with setscrews 11, 11 screwed into the vertically threaded holes 9, on which the rotating disk 2 is attached.
A groove portion 12 having a U-shaped cross section is provided in loose contact with the outer peripheral portion of the element holder 10, and two circular protrusions 13 as engagement members which are iron-fitted in the annular groove 7 are provided on the lower surface of the element holder 10. 1
3 are provided in a protruding manner with an interval equal to the interval between the straight grooves 8, 8.

Reference numerals 14 and 14 denote elongated holes provided in the element holder 1 so that the aforementioned setscrews 11 and 11 are passed through, and these holes are formed in an arc shape centered on the rotation axis la of the stepping motor 1. There is. Reference numeral 15 denotes a printed circuit board screwed and fixed to the upper surface of the element holder 10. This is provided with an electric circuit to be described later, and the aforementioned element holder 10 and the printed circuit board 15 constitute an encoder unit 16. .

Now, FIG. 6 shows the electric circuit of the encoder unit 16 and the receiving device 17 that receives the signal from the encoder unit 16, and this will be described below.

18 is a positive power supply line, 19 is a ground line, and a series circuit of a resistor 20 and a light emitting diode 21 is connected between them, and the light emitting diode 21 is connected downward from the top surface of the groove 12 of the element holder 10'. It is installed so that it emits a beam of light.

22 and 23 are a resistor and a negative diode connected in series between the positive power line 18 and the ground line 19, and their common connection point 24 is led out from the encoder unit 16 via an intermediate level power line 25. ing.

Photodiodes 26 and 27 are mounted on the lower surface of the groove 12 of the element holder 10, and a mask 28 is provided on the lower surface of the groove 12 to cover the photodiodes 26 and 27 as detection elements.

The mask 28 has four slit holes 29 corresponding to the photodiodes 26 and four slit holes 30 corresponding to the photodiodes 27 at the same pitch as the slits 4 provided in the rotating disk 2. The slit hole 29 on one side and the slit hole 3 on the other side
0 are located on circumferences with different radii around the rotation axis la, and are provided at positions different from each other by 1/4 pitch. (See Figure 5). Therefore, photodiode 2
The anodes of 6 and 27 are connected to the common connection point 24, and the cathode of one photodiode 26 is connected to the resistor 3.
The cathode of the photodiode 27 is connected to the positive power source line 18 through a resistor 32. 33 and 34 are obeamps, and their non-inverting input terminals are respectively connected to the common connection point 24.
The inverting input terminal of one obeamp 33 is connected to the cathode of the photodiode 26, and the inverting input terminal of the other obeamp 34 is connected to the cathode of the photodiode 27.

36 and 36 are resistors connected between the inverting input terminal and the output terminal of each obeamp 33, 34, and of the above configuration, the light emitting diode 21 and photodiode 26, 2
Components other than 7 are arranged on a printed circuit board 15, and each positive power terminal of the oven amplifiers 33 and 34 is connected to a positive power line 18, and each negative power terminal is connected to a ground line 19. On the other hand, 37 and 38 are the receiving device 1
These inverting input terminals are connected to the oven amplifiers 33 and 33 through resistors 39 and 40, respectively.
34, and feedback resistors 41 and 42 are connected between the inverting input terminals and output terminals of these operational amplifiers 37 and 38, respectively.

Further, reference numeral 43 denotes an oven amplifier constituting a non-inverting type buffer, whose non-inverting input terminal is connected to the intermediate level power supply line 25, and its output terminal is connected to the base of an NPN type transistor 44 for increasing the voltage. The emitter of the transistor 44 is connected to the ground line 19 via a resistor 45. The emitter of this transistor 44 is connected to the inverting input terminal of the amplifier 43 and is connected to the resistor 46.
and 47 to the respective non-inverting input terminals of the amplifiers 37 and 38. 48 has transistor 4 at one end
The other end of the resistor is connected to the collector of 4, and the other end of the resistor is connected to the positive power supply line 18.

The positive power terminals of the oven amplifiers 37, 38, and 43 are connected to the positive power line 18, and the negative power terminals of the oven amplifiers 37, 38, and 43 are connected to the ground line 19. Next, the operation of this embodiment configured as described above will be explained.

The light beam from the light emitting diode 21 reaches the photodiodes 26 and 27 via the slit 4 of the rotating disk 2 and the slit holes 29 and 30 of the mask 28, and the photodiode 2
6 and 27, the current that flows increases in proportion to the amount of light that reaches them. That is, for example, the amount of light that reaches the photodiode 26 becomes the maximum when the slit 4 and the slit hole 29 match, and becomes the minimum when the slit 4 and the slit hole 29 are shifted by a half pitch from each other. When the light intensity and the slit hole 29 are shifted by 1/4 pitch from each other, the light intensity becomes intermediate between the maximum light intensity and the minimum light intensity. Further, the amount of light reaching the photodiode 27 similarly changes depending on the positional relationship between the slit 4 and the slit hole 30. As an example, when a 10V DC power supply is applied to the positive power supply line 18 of the encoder unit 16 and the zener voltage of the zener diode 23 is set to 5V, each of the non-inverting inputs of the amplifiers 33 and 34 A voltage of 5V is applied to the terminal via an intermediate level power supply line 25. On the other hand, the resistance value of the resistor 31 is set in advance by, for example, laser trimming, so that the current i3 flowing through the resistor 31 and the current i26a flowing through the photodiode 26 are equal when an intermediate amount of light is applied to the photodiode 26. The current flowing through the resistor 35 is 0,
Since the inverting input terminal of the obeamp 33 is at the same potential as the non-inverting input terminal, the output terminal of the obeamp 33 is equal to the inverting input terminal, and therefore equal to the voltage of the intermediate level power supply line 25, which is approximately 5V. Next, photodiode 26
When the maximum amount of light is applied to the photodiode 26, the current i2b flowing through the photodiode 26 becomes twice the aforementioned intermediate amount of light i26a. At this time, since the inverting input terminal and the non-inverting input terminal of the obeamp 33 are at the same potential and the current 13 flowing through the resistor 31 does not change, the insufficient amount flows through the resistor 35 to the photodiode 26 as shown by i35b, and i3 , and the values of i short b are approximately equal. And at this time Obeamp 3
The voltage at the output terminal 3 is higher than the voltage at the intermediate level power supply line 25 by a voltage corresponding to (resistance value R35 of the resistor 35) x j false b, and the voltage at this output terminal is higher than the voltage at the intermediate level power supply line 25. It is adjusted by trimming or the like and set to a predetermined value. Further, when the amount of light given to the photodiode 26 becomes the minimum amount of light, the current flowing through the photodiode becomes 0, and the inverting input terminal and the non-inverting input terminal of the oven amplifier 33 are at the same potential, and the current i flowing through the resistor 31 changes. Therefore, the resistor 35 has a current i3, and an amount equal to c
flows, and the voltage at the output terminal of the obeamp 33 at this time is higher than the voltage at the intermediate level power supply Marisen 25 (resistance value R35) ×
The voltage corresponding to i35c is lowered. That is, i$ and i
Since 35b, i and c are substantially equal, the voltage difference between the maximum voltage and the intermediate level of the output terminal of the oven amplifier 33 is approximately equal to the voltage difference between the minimum voltage and the intermediate level, and therefore the rotating disk 2
When is rotated by the rotating shaft la of the stepping motor 1, a voltage waveform that changes in a waveform as shown in FIG. 7a is outputted to the output terminal of the oven amplifier 33. Similarly, the resistance value of the resistor 32 is set by laser trimming or the like so that the output terminal of the obeamp 34 becomes equal to the voltage of the intermediate level electric wire 25 when an intermediate amount of light is applied to the photodiode 27. The resistance value of the resistor 36 is set by laser trimming or the like so that the output terminal of the oven amplifier 34 is approximately equal to the maximum output voltage of the oven amplifier 33 when the amount of light is given, and the output terminal of the oven amplifier 34 is set at the voltage shown in FIG. A voltage waveform that changes in a waveform as shown in is output. Since the slit holes 29 and 30 are shifted by 1'4 pitches, the output waveform from the oven amplifier 33 and the output waveform from the oven amplifier 34 are different in phase by about 90 degrees, and therefore the output waveform from the oven amplifier 34 is sin The output signal from the obeamp 35 becomes a cos signal. The output signals from these amplifiers 33 and 34, that is, the output from the encoder unit 16, are DC-amplified by amplifiers 37 and 38 in the receiver 17, respectively, and sent to an arithmetic unit (not shown). In this case, the intermediate level power line 25 from the encoder unit 16 is connected to the receiving device 17, and is applied to each non-inverting input terminal of the obe amplifiers 37 and 38 via a buffer circuit consisting of an obe amplifier 43 and a transistor 44. Therefore, the obeamp 37
and 38 amplify the sine signal and cosine signal from the encoder unit 16 with the intermediate level voltage of the encoder unit 16 as the center value. Now, when the encoder 6 is fixed to the mounting surface 6, it is necessary to match the sine signal and cosine signal of the encoder I6 with the input specifications of the arithmetic device in advance with respect to the stop position of the rotating shaft la. For example, si
The n signal is set to an intermediate level voltage and the cos signal is set to the maximum voltage (see Z in FIG. 7). This is done by loosening the set screw 11 and moving the element holder 10 while observing the sine signal and cosine signal from. That is, the element holder 10 has projections 13 inserted into the annular groove 7, and these projections 13 and the annular groove 7 serve as guides for guiding the element holder 10 so that it can move around the center of rotation of the rotating disk 2. Since it constitutes a means, when the protrusion 13 is moved while being stirred around the inner circumference of the annular groove 7, it will move accurately on the storm D circle with respect to the rotation center of the rotating disk 2, After moving the element holder 10 in this way, set the set screw 11 at the predetermined position.
Fix it with. In this case, the rotating disk 2 and the element holder 10
The gap between the rotary disk 2 and the groove 12 is necessarily a constant value because the distance between the rotary disk 2 and the mounting surface 6 is fixed at a constant value when the rotating disk 2 is fixed to the rotating shaft la. As is clear from the above description, in this embodiment, an annular groove 7 centered around the rotation of the rotating disk 2 is provided on the mounting surface 6, and the protrusion 13 of the element holder 10
is engaged with the annular groove 7 and the element holder 10 is moved while engaging the tab 13 with the annular groove 7.
0 and the rotating disk 2 is adjusted so that the output waveform of the element holder 10 becomes a predetermined value, so the position of the rotating shaft la and the rotating disk 2 is rotated during this adjustment. There is no need for adjustment, and therefore the element holder 10 can be moved and adjusted while keeping the gap between the rotating disk 2 and the element holder 10 constant.

That is, in the conventional structure, when adjusting the positional relationship between the rotating shaft and the rotating disk, the gap between the rotating disk and the element holder had to be adjusted at the same time, making the adjustment work very difficult.
In this embodiment, even if the element holder 10 is moved, the gap between the element holder 10 and the rotating disk 2 does not change at all, so the positional relationship between the element holder 10 and the rotating disk 2 is maintained at an accurate position. Positioning can be done easily, so adjustment can be done in a short time and productivity can be greatly improved. Further, in this embodiment, a power supply section consisting of a resistor 22 and a zener diode 23 for setting the intermediate level of the amplifiers 33 and 34 is provided inside the encoder unit 16, and this intermediate level power supply is connected to the outside of the encoder unit 16. Since the intermediate level power supply is drawn out via the power source 26 to provide an intermediate level between the amplifiers 37 and 38 for expansion in the receiver 17, a single power supply is required as a power source for the amplifiers 33, 34, 37, and 38. It is economical because it does not require an expensive power supply with two positive and negative power supplies, and since the encoder unit 16 operates with a single power supply, the encoder unit 16 can be easily adjusted by itself. can do. In addition, since the intermediate level voltage of the encoder unit 16 is taken out to the outside and used as the intermediate level of the obe amplifiers 37 and 38 of the receiving device 17, the obe amplifiers 33, 34 and 37,
All 38 intermediate level voltages can be made the same, and even if the intermediate level voltage of the encoder unit 16 varies between products, there will be no difference in the intermediate level voltage between the encoder unit 16 and the receiving device 17. Troublesome adjustment work such as adjusting each intermediate level voltage of the encoder unit 16 and the receiving device 17 individually is no longer necessary, and overall assembly and adjustment work can be made easier, especially when replacing the encoder unit 16. The receiving device 17 side does not require any adjustment and can be easily replaced. In the above embodiment, the annular groove 7 as a guide part is provided on the mounting surface 6 as a mounting member, and the protrusion 13 as an engaging member is provided on the element holder 10'.
An engaging portion may be provided on the side, and an arcuate guide portion may be provided on the element holder 10 side. Furthermore, it can be applied to DC motors other than stepping motors.

As is clear from the embodiments described above, the present invention can provide a position detector that can be easily adjusted to an accurate mounting position and can greatly improve productivity.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and Fig. 1 is a perspective view, Fig. 2 is a plan view showing the mounting surface of the stepping motor, Fig. 3 is a bottom view of the encoder, and Fig. 4 is a diagram of the encoder. FIG. 5 is an exploded perspective view, FIG. 5 is an enlarged plan view of the encoder mask, FIG. 6 is an electric circuit diagram, and FIG. 7 is a diagram showing voltage waveforms. In the drawing, 1 is a stepping motor, la is a rotating shaft, 2 is a rotating disk, 4 is a slit, 6 is a mounting surface (mounting member), and 7
10 is an annular groove (guide portion), 10 is an element holder, 13 is a protrusion (engaging member), 15 is a printed circuit board, 16 is an encoder unit, 17 is a receiving device, 21 is a light emitting diode, 2
5 is the back of the intermediate power source, 26 and 27 are photodiodes, 28 is a mask, 29 and 30 are slit holes, 33
, 34, 37, 38 and 43 are obeamps, respectively, and 44 is a transistor. Figure 3 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A rotary disk with a large number of slits arranged in parallel around the periphery, an element holder equipped with a detection element for detecting the slits, and a mounting member to which the element holder is attached, and which is attached to the element holder. A guide part provided on either the element holder or the mounting member, and a guide part that engages with the guide part to allow the element holder to move around the center of rotation of the rotating disk. What is claimed is: 1. A position detector characterized in that a position detector is provided with a guide means comprising an engaging member that guides the user.