JPH06123639A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To detect runout of a spindle of a lathe or a machining center in a magnetic encoder. CONSTITUTION:A square sum detecting means 31 is constituted of a subtracter/ adder/multiplier of OP amplifiers or the like, detecting the square sum of the amplitude of two-phase sine wave signals of 90 deg. phase difference from a gear 1 made of a magnetic permeable material and groups of magnetic sensors 3, 4 and sending the sum to a low-pass filter 32. A first and a second abnormality detecting means 33, 34 compare the square sum passing through the low-pass filter 32 with predetermined values Ver1 and Ver2. When the square sum is not smaller than Ver1 or not larger than Ver2, the detecting mean so detect that a spindle is run out with outputting an alarm signal via an OR output means 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic encoder, and more particularly to a magnetic encoder having a function of detecting an abnormality of a rotating body which is an object to be detected.

[0002]

2. Description of the Related Art FIG. 4 is a schematic view showing an example of a conventional magnetic encoder. The gear 1 is made of a magnetically permeable material and is attached to a main shaft 2 of a machine tool that is a rotating body. The magnetic sensor groups 3 and 4 have permanent magnets (not shown), and the gear 1
And a predetermined air gap. The signals Ea and Eb output from the magnetic sensor groups 3 and 4 are sine wave signals corresponding to the rotational position of the gear 1 and are two-phase sine waves represented by the equations 1 and 2 having a phase difference of 90 degrees. Become a signal.

[Equation 1] Ea = V * SIN (x) + Voff

## EQU2 ## Eb = V * COS (x) + Voff Two-phase sine wave signals Ea and Eb sent to the comparison circuits 5 and 6.
Is compared with a predetermined level Voff and converted into a pulse signal. 2 sent to UP-DOWN pulse counter 7
The phase pulse signals are counted and the rotational position of the spindle 2 is detected.

FIG. 5 is a schematic view showing another example of a conventional magnetic encoder, which can detect with higher accuracy than the magnetic encoder of FIG. Sample and
The hold circuits 8 and 9 detect the instantaneous values of the two-phase sine wave signals Ea and Eb, and the analog-digital conversion circuit 10 and
The instantaneous value sent to 11 is converted into a digital signal and sent to the interpolation position detecting means 12. Interpolation position detection means 12
Is composed of a microcomputer, and detects the interpolated position x which is the position within one tooth of the gear 1 by performing the following steps 1 and 2 from the instantaneous value digital signals Sa and Sb. Step 1 ... Removal of DC component

[Equation 3] Sa-Voff

[Equation 4] Sb-Voff Step 2 ... Calculation of interpolation position x

X = ARCTAN (V * SIN (x) / V * COS (x)) = ARCTAN ((Sa-Voff) / (Sb-Voff)) Then, the interpolation position x and the UP-DOWN pulse counter And the output of 7 are combined by the combining means 13 and the main shaft 2
The highly accurate rotational position of is detected.

[0004]

The spindle of a lathe or a machining center may be in a very dangerous state when the spindle loses its balance during high-speed rotation or when the spindle is shaken during heavy cutting. However, the conventional magnetic encoder has a drawback that it cannot detect the main shaft shake. The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a magnetic encoder capable of detecting a spindle shake.

[0005]

According to the present invention, there is provided a magnetic sensor group, which has a gear made of a magnetically permeable material, a magnetizing body, and detects two-phase sinusoidal signals having a phase difference of 90 degrees from each other.
The present invention relates to a magnetic encoder provided with position detecting means for detecting a rotational position of a rotating body from a phase sine wave signal. The above object of the present invention is to detect the sum of squares of the two phase sine wave signal. A second abnormality detecting means for comparing the sum of squares with a first predetermined value and outputting an alarm signal when the sum of squares is smaller than the first predetermined value; A second abnormality detecting means for comparing the sum with a second predetermined value and outputting an alarm signal when the sum of squares is larger than the second predetermined value; and an output of the first abnormality detecting means. OR for outputting an OR output with the output of the second abnormality detecting means
And output means.

[0006]

In the present invention, the behavior of the spindle is grasped from the detection signal, and when it exceeds a predetermined value, it is judged that the spindle shake has occurred, and an alarm is output. Can be detected.

[0007]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of the magnetic encoder of the present invention in correspondence with FIG. Here, the gear 1, the magnetic sensor groups 3 and 4, the comparison circuits 5 and 6, and the UP-DOWN pulse counter 7 are the same as those described in the conventional example, and the description thereof will be omitted. The signals Ea and Eb output from the magnetic sensor groups 3 and 4 are represented by the equations 1 and 2, where Ea,
The amplitude V of Eb varies depending on the gap length between the magnetic sensor groups 3 and 4 and the gear 1. In the normal use range, the amplitude V is inversely proportional to the air gap length. Therefore, the void length can be known by knowing the amplitude V or the square of the amplitude V ^ 2. Therefore, the amplitude V or the square of the amplitude V ^.
If the change of No. 2 is investigated, the behavior of the spindle 2 can be known.

Generally, the gear 1 is mounted with a slight eccentricity, but since the amount of eccentricity is usually suppressed to a certain level or less according to the specifications, the amplitude V or the square of the amplitude V ^ 2 is a certain value. To a certain value. If the main shaft 2 shakes, the air gap length becomes a value outside the specified range, and the amplitude V or the square of the amplitude V ^ 2 also becomes a value outside the predetermined range.

The sum of squares detecting means 31 comprises a multiplier, an adder, and a subtractor, which are constituted by an OP amplifier or the like. First, the DC component Voff is removed from Ea and Eb by a subtractor. The respective signals from which the DC component Voff has been removed are squared by a multiplier, then added by an adder, and sent as a square sum signal to a low pass filter 32 which is a general RC filter. Then, a high frequency component of several hundred KHz or more due to electromagnetic noise included in the sum of squares signal is removed and sent to the first abnormality detecting means 33 and the second abnormality detecting means 34. In the first abnormality detecting means 33, the sum of squares signal passed through the low-pass filter 32 and a predetermined voltage level Ver1 are compared by a comparator, and when the sum of squares signal is larger than the predetermined voltage level Ver1, an alarm is output. It Second abnormality detecting means 34
Then, the sum of squares signal that has passed through the low-pass filter 32 and the predetermined voltage level Ver2 are compared by a comparator, and an alarm is output when the sum of squares signal is smaller than the predetermined voltage level Ver2. In the OR output means 35, the OR of the alarm signal of the first abnormality detecting means 33 and the alarm signal of the second abnormality detecting means 34 is taken, and the OR signal of the first abnormality detecting means 33 or the second abnormality detecting means 34 is obtained. When either of them is an alarm, an alarm is output to notify the abnormality of the spindle 2.

FIG. 2 is a schematic view showing another example of the magnetic encoder of the present invention in correspondence with FIG. In this case as well, the components other than the abnormality detection unit 41 are the same as those described in the conventional example, and the description thereof will be omitted. The abnormality detecting unit 41 is processed by the same microcomputer as the interpolation position detecting means 12. The specific processing content of the abnormality detection unit 41 is as shown in the flowchart of FIG. Step S1: Read V1 = Ea-Voff and V2 = Eb-Voff. Step S2: W = V1 ² + V2 ² is calculated, and the sum of squares W of the amplitude is calculated. Step S3: If the sum of squares W of the amplitude is larger than the predetermined value Werr1, go to the alarm process of step S5, and if not, go to the next step S4. Step S4: If the sum of squares W of the amplitudes is smaller than the predetermined value Werr2, go to the alarm process of step S5, and if not, end the process.

In each of the above embodiments, the sum of squares of the amplitude is detected and the sum of squares of the amplitude is compared with a predetermined value. The alarm may be detected in the same manner as in the above-described embodiment by taking the square root of and detecting the amplitude itself.

[0012]

As described above, according to the magnetic encoder of the present invention, the rotational shake of the spindle can be detected. Therefore, it is possible to detect the abnormal situation of the spindle promptly and take a measure such as stopping the spindle. It can be avoided, and work safety can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a magnetic encoder of the present invention.

FIG. 2 is a schematic view showing another example of the magnetic encoder of the present invention.

FIG. 3 is a flowchart showing the processing contents of an abnormality detection unit of the magnetic encoder of the present invention shown in FIG.

FIG. 4 is a schematic diagram showing an example of a conventional magnetic encoder.

FIG. 5 is a schematic diagram showing another example of a conventional magnetic encoder.

[Explanation of symbols]

 31 sum-of-squares detection means 32 low-pass filter 33 first abnormality detection means 34 second abnormality detection means 35 OR output means 41 abnormality detection unit

Claims (3)

[Claims] 1. A magnetic sensor group for detecting a two-phase sine wave signal having a gear made of a magnetically permeable material and a magnetizing body and having a phase difference of 90 degrees from each other, and a rotating body based on the two-phase sine wave signal. In a magnetic encoder provided with position detecting means for detecting a rotational position, a sum of squares detecting means for detecting a sum of squares of AC components of the two-phase sine wave signal, and the sum of squares and a first predetermined value In comparison, a first abnormality detecting means for outputting an alarm signal when the sum of squares is smaller than the first predetermined value,
Second abnormality detecting means for comparing the sum of squares and a second predetermined value, and outputting an alarm signal when the sum of squares is larger than the second predetermined value; and the first abnormality detecting means. And an OR output means for outputting an OR output of the output of the second abnormality detecting means and the output of the second abnormality detecting means. 2. The magnetic encoder according to claim 1, wherein the sum of squares is passed through a low pass filter and then compared with the first and second predetermined values. 3. The magnetic encoder according to claim 1, wherein the square sum detecting means detects a square root of the square sum.