JPH0236313A - Gap adjusting method for magnetic encoder - Google Patents

Abstract

PURPOSE:To adjust a gap of about + or -10mum electrically by rotating a magnetic drum, finding a Lissajour waveform by using an A-phase and a B-phase signal obtained from a magnetic sensor, and adjusting the gap by using the Lissajour waveform. CONSTITUTION:The A-phase and B-phase signals obtained by the magnetic sensor 1b by rotating the magnetic drum 1a are inputted to a Lissajous waveform processing part 3. Then the processing part 3 finds the radii Si (i=1, 2...) of the Lissajour waveform at specific timing and compares the radii SH and SL of the Lissajour waveform when the proper gap is maximum and minimum. Then when Si < SH, an LED which indicates that the maximum value of the proper gap is exceeded illuminates to display an alarm ALM 1. When Si > SL, on the other hand, an LED indicating that the proper gap is not reached illuminates to display an alarm 2. Then the displays of the alarms ALM1 and ALM2 are used to adjust the fitting height of a sensor 1b from outside a gear box.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a gap adjustment method for a magnetic encoder, and particularly to a magnetic encoder having a magnetic rotary drum inserted into a spindle and a magnetic sensor disposed facing each other. This relates to a method for adjusting the gap W4 of an encoder.

<Prior Art> In machining centers, milling machines, etc., it is necessary to rotate a spindle (main shaft) at a specified speed and to stop it at a specified rotational direction position. To this end, the main shaft is equipped with a magnetic encoder for detecting the position of one rotational speed.

FIG. 10 is an explanatory diagram of a magnetic encoder mounted on the main shaft of a machine tool.

In FIG. 10, the magnetic encoder 11 (shaded area) is composed of a cylindrical magnetic drum lla and a magnetic sensor llb, and the magnetic drum lla and the magnetic sensor llb are arranged opposite to each other with a predetermined gap interposed therebetween. The magnetic sensor llb is configured to generate an output signal (sine wave signal, cosine wave signal) according to the rotation of the magnetic drum lla. The main shaft (spindle) 12 is equipped with a case (gear box) so that it can rotate via a bearing unit 13.
15, the magnetic drum lla is fixed to the spindle 12 via a holder 11c, and the magnetic sensor lla is
b is fixed to the gear box 15 with an attached flange Ild. Note that 14 is a gear.

Generally, when assembling the magnetic encoder 1, the clearance adjustment between the magnetic tram lla and the magnetic sensor llb is mechanically performed using a gap gauge or the like.

<Problems to be Solved by the Invention> However, when the magnetic encoder must be attached to the main shaft 12 of a machining center, milling machine, etc. inside the gear box 15 as shown in FIG. Although adjustments can be made mechanically, there is a problem in that the clearance between the magnetic sensor and the magnetic 1-ram cannot be adjusted mechanically using a gap gauge or the like.

Furthermore, in a magnetic encoder, a change in the clearance between the magnetic tram and the magnetic sensor by just 10 μm changes the amplitude and output waveform shape of the output signal output from the magnetic sensor. On the other hand, in order to increase the resolution through interpolation, etc., it is necessary to ensure that the signal output amplitude is maximum and the signal waveform to be close to a sine wave. It is necessary to adjust the clearance with an accuracy of approximately ±10 μm. However, the method of mechanically adjusting the gap using a conventional gap gauge etc.
There is a problem in that it takes a lot of man-hours to adjust with an accuracy of about m, and it also requires a method to prevent damage to the magnetic drum or magnetic sensor.

From this point on, it is an object of the present invention to provide a magnetic encoder that can adjust the gap between the magnetic drum and the magnetic sensor even if it is inside a gear box, etc., and that can adjust the gap with an accuracy of about ±10 μm. The purpose is to provide an adjustment method.

<Means for Solving the Problems> FIG. 1 is a block diagram of an apparatus that implements a magnetic encoder gap adjustment method according to the present invention.

1 is a magnetic encoder, 1a is a magnetic drum, 1b is a magnetic sensor, 2 is an oscilloscope, 3 is a Lissajous waveform processing unit, and ALMI, AI, and M2 are alarms.

<Operation> By rotating the magnetic drum 1d of the magnetic encoder 1, in which magnetic bodies are magnetized at a predetermined pitch, the magnetic sensor 1
A Lissajous waveform is obtained using the A-phase signal and B-phase signal obtained from b, and displayed on the oscilloscope 2, and the gap P between the magnetic drum 1a and the magnetic sensor 1b is adjusted with reference to the Lissajous waveform. In addition, in the Lissajous waveform processing unit 3, where the amplitude of the A-phase signal at a predetermined timing is X, and the amplitude of the B-phase signal at a predetermined timing is Y, the radius of the Lissajous waveform is determined at V■71. By comparing the radius of the Lissajous waveform obtained with the maximum value SH and minimum value SL of the appropriate gap, it is determined whether the gap between the magnetic drum 1a and the magnetic sensor 1b is appropriate, and the radius of the Lissajous waveform obtained is determined as the appropriate gap. If the clearance is above the maximum value, the alarm ALMI will be displayed, and if it is below the minimum value of the appropriate clearance, the alarm ALM will be displayed.
Display 2.

<Embodiment> FIG. 1 is a block diagram of an apparatus that implements a gap adjustment method for a magnetic encoder according to the present invention.

1 is a magnetic encoder, 1a is a magnetic drum, 1b is a magnetic sensor, 2 is an oscilloscope, 3 is a Lissajous waveform processing section, and ALMI and ALM2 are alarms. FIG. 2 is a block diagram of the magnetic encoder 1, and in the figure, 1a is a magnetic drum.

Magnetic ICs forming minute multipolar structures are magnetized at a predetermined pitch. ■b is a magnetic sensor, and the magnetic drum 1a
The magnetizing magnetic flux of the magnetic body 1c is detected.

The magnetic drum 1a is typically a non-magnetic cylinder with a diameter of 50 mm with magnetic paint baked on the side surface, and the pitch is approximately 120 mm.
Multipolar magnetization of μm is performed.

Further, the magnetic sensor 1b is composed of a magnetoresistive element main body in the form of a permalloy thin film pattern formed on glass, and a wiring pattern for forming an electric circuit. The shape and dimensions of the main body pattern correspond to the magnetization pattern of the drum, and it is possible to obtain an output signal according to the amount of rotation of the drum.

The operating principle of the magnetic encoder will be explained using FIG. The magnetoresistive element MR has a characteristic that the electrical resistance value R when a current is passed in the longitudinal direction of the pattern decreases when a magnetic field H perpendicular to the electrical resistance value R is present. For this reason,
When the pattern of the magnetoresistive element MR is arranged in correspondence with the magnetization pattern of the drum, as shown in FIG. 3(a),
In other words, when the magnetoresistive elements MRa and MRb are arranged with a phase shift of λ/2 (λ indicates the pitch of the magnetized pattern), the magnetoresistive element MRa.

The resistance value of MRb becomes smaller alternately as the magnetized pattern moves, and in the state shown in FIG. 3(a), the magnetoresistive element M
The resistance value of Ra becomes small, and the resistance value of magnetoresistive element MRb becomes large. As a result, the output terminal our (Fig. 3(b)
), the rotation of the drum (i.e. movement of the magnetization pattern)
Accordingly, an alternating current signal output can be obtained.

Incidentally, the magnetic sensor 1b is actually shown in FIG. 3(C).

As shown in (d), the magnetoresistive element ai (i=1°2・
By combining ・, 4), bi (i=1, 2, . . . , 4) to form a bridge configuration, the output voltage is increased and the temperature characteristics are improved. By arranging another magnetoresistive element bi at a position shifted by 1/4 wavelength with respect to the pattern pitch, the output terminal 0U
The A-phase signal output necessary for the incremental encoder is obtained from Tl, and the B-phase signal output is obtained from output terminal 0UT2.

4 to 6 are display examples of the A-phase and B-phase output from the magnetic encoder 1 displayed on the oscilloscope 29. In each figure (a), the amplitude scale is shown on the vertical axis of the oscilloscope 2. , is an example of displaying curves of phase A and phase B when time t is plotted on the horizontal axis.7 In each figure (b), the amplitude of phase A at a predetermined timing is entered on the horizontal axis (X axis) of the oscilloscope 2,
This is a display example of a Lissajous waveform obtained by putting the B-phase amplitude on the vertical axis (Y@).

FIG. 4 shows that the gap between the magnetic drum 1a and the magnetic sensor 1b is
For example, this is a display example when the distance is in the range of 110 μm to 120 μm. At this time, the waveforms of the A and B phases become close to sine waves or cosine waves (see Figure 4 (a)), and the Lissajous waveform also becomes close to a circle (see Figure 4 (b)), which means that the output signal It can be seen that the amplitude of is also sufficiently secured, making it an ideal gap.

Figure 5 shows an example display when the gap is 1, for example, 100 μm or less, and the Lissajous waveform is distorted into a rectangular shape (see Figure 5 (b)), indicating that the waveform has many high frequency components. I understand.

Figure 6 shows an example of a display when the gap is, for example, 130 μm or more, and the amplitude of the output signal becomes smaller (Figure 6 (
It can be seen that the diameter of the Lissajous waveform also becomes smaller (see FIG. 6(b)). Note that in this case, signal processing is improved.

From the above, it can be seen that there is a close correlation between the gap between the magnetic drum 1a and the magnetic sensor 1b and the A-phase and B-phase waveforms.

Using this relationship, a method for adjusting a gap in a magnetic encoder according to the present invention will be explained. In addition, as shown in FIG. 10, the magnetic encoder is assembled to the main shaft, and the appropriate clearance between the magnetic drum and the magnetic sensor is, for example, 110 mm.
It is assumed that the range is from μm to 120 μm.

First, the radius SH (see Figure 1, oscilloscope display) of the Lissajous waveform at the maximum value (for example, 120 μm) of the appropriate gap and the radius SL at the minimum value (for example, 110 μm).
is determined in advance and input to the Lissajous waveform processing section 3. still,
The radius of the Lissajous waveform is where X is the amplitude of the A-phase signal obtained by the magnetic sensor at a predetermined timing, and Y is the amplitude of the B-phase signal at a predetermined timing.

(5<Geto-Tr Find it by calculating.

Now, after assembling the magnetic encoder, the magnetic drum 1a
By rotating the magnetic sensor 1b, the A-phase and B-phase signals obtained from the magnetic sensor 1b are input to the Lissajous waveform processing section 3.

Then, the Lissajous waveform processing section 3 calculates the radius Si of the two surge waveforms at the predetermined timing Ti (i=1, 2, . . .) using the method described above, and calculates the radius S of the two surge waveforms.
i is compared with the radii SH and SL of the Lissajous waveform at the maximum and minimum values of the appropriate gap. However, if the gap becomes larger, the radius of the Lissajous waveform will become smaller at all timings;

At a certain timing, the radius of the two waveforms of the beam surge increases.

As a result of the comparison, it was found that the radius Si of the Lissajous waveform obtained at all timings was less than the radius S of the maximum value of the appropriate gap (
If Si<SH) (see Figure 7), an alarm ALML is displayed by lighting up the LED, which means that the maximum value of the suitable lE gap has been exceeded. On the other hand, (Si)S exceeds the minimum radius SL of the appropriate clearance at some timings.
If L) (see Fig. 8), an LED indicating that the proper clearance has not been reached is lit to display an alarm ALM2.

Then, using the display of alarms ALM1 and ALM2,
Alternatively, by observing the two surge waveforms displayed on the oscilloscope 2, the mounting height of the magnetic sensor 1b is adjusted from the outside of the gearbox (that is, the gap adjustment).

Although the method described above uses the Lissajous waveform processing unit 3 to automatically determine the appropriate gap, it is also possible to visually observe the surge waveform displayed on an oscilloscope or by visually observing the surge waveform without using the Lissajous waveform processing unit 3. You can also adjust the gap by In this case, as shown in FIG. 9, the two waveforms of the surge surge at the maximum value of the appropriate gap Umax (-dotted chain line) and the two waveforms of the surge surge at the minimum value U1in are displayed in advance on the screen (display section) of the oscilloscope 2, as shown in FIG. , (double chain II)
After the magnetic encoder is assembled, the obtained two surge waveforms Ui may be superimposed and displayed on the display section of the oscilloscope 2 to visually judge whether the gap is appropriate.

<Effects of the Invention> According to the present invention, by rotating the magnetic drum, a Lissajous waveform is obtained using the A-phase signal and the B-phase signal obtained from the magnetic sensor, and the clearance is adjusted using the Lissajous waveform. With this structure, even if the gap between the magnetic drum and the magnetic sensor is inside a gear box or the like, the gap can be adjusted, and the gap can be electrically adjusted to about ±10 μm.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus that implements a magnetic encoder gap adjustment method according to the present invention. FIG. 2 is a configuration diagram of the magnetic encoder of the present invention. FIG. 3 is an explanatory diagram of the operating principle of the magnetic encoder of the present invention, FIGS. 4 to 6 are display examples of an oscilloscope, and FIGS. 7 to 9 are detailed explanatory diagrams of the present invention. FIG. 10 is an explanatory diagram of a magnetic encoder installed. 1. Magnetic encoder. 1a...Magnetic drum. 1b...Magnetic sensor. 2.Oscilloscope. 3. Lissajous waveform processing section. ALM1, ALM2... Alarm patent applicant Fanuc Corporation agent Patent attorney Chimima Saito No. 3 (a) (b) Figure 3 (C) (d) (a) Figure 4 (b) Figure 57 Figure 7 Ma■ 9th

Claims (3)

[Claims] (1) A magnetic drum with magnetic material magnetized at a predetermined pitch,
Phases A and B are 90° out of phase with each other due to the magnetoresistive element.
A gap adjustment method for a magnetic encoder configured to generate two-phase signals and having a magnetic sensor disposed opposite to a magnetic drum with a predetermined gap therebetween, by rotating the magnetic drum. A method for adjusting a gap in a magnetic encoder, comprising: determining a Lissajous waveform using an A-phase signal and a B-phase signal obtained from a magnetic sensor, and adjusting the gap using the Lissajous waveform. (2) When the amplitude of the A-phase signal at a predetermined timing obtained from the magnetic sensor is X, and the amplitude of the B-phase signal is Y, find the radius of the Lissajous waveform by √(X^2+Y^2), and calculate the Lissajous The magnetic encoder according to claim (1), wherein it is determined whether the gap is appropriate by comparing the radius of the waveform with the radius of the Lissajous waveform at the maximum value and minimum value of the appropriate gap. How to adjust the gap. (3) An alarm is displayed when the radius of the determined Lissajous waveform is greater than or equal to the maximum value of the appropriate gap, and an alarm is displayed when the radius is less than or equal to the minimum value of the appropriate gap. The magnetic encoder gap adjustment method described in (2).