JPH1047350A - Air bearing spindle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the displacement of a spindle stably without being adversely affected by inductance of a cable by building a displacement sensor circuit for detecting the displacement of the spindle, in a housing. SOLUTION: A board 8 of a sensor circuit 9 is built in a housing 3 along with a displacement gage 5. In order to protect the sensor circuit 9 from noise and to prevent an electric shock accident caused by the leak or the like of a motor 4, the housing 3 is earthed. The sensor circuit 9 is so formed that a resonance point of a resonance circuit changes according to the position of a spindle 1 and in association with this, the amplitude of sine wave changes. The sine wave changed in amplitude is therefore converted into DC voltage by a rectifying circuit, and a signal indicating the position of the main spindle is outputted as DC voltage to the outside through a low-pass filter for eliminating high frequency noise. The position of the spindle 1 can thereby be outputted stably to the outside only by supplying a stable power source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air bearing spindle, and more particularly to an air bearing spindle in which a spindle is supported in a housing by a fluid bearing including an air bearing and displacement of the spindle is detected.

[0002]

2. Description of the Related Art Heretofore, there has been a problem that a small-diameter hole is easily broken during machining because the diameter of the tool is small.
For this reason, attempts have conventionally been made to prevent the overload applied to the tool or to detect or predict the breakage of the tool by monitoring the machining state. Some devices detect a reaction force by displacement of a main shaft. In particular, when the main shaft is supported by a hydrostatic bearing, vibration during rotation caused by the bearing can be extremely reduced, so that even a minute machining reaction force can be detected as a displacement of the shaft.

FIG. 3 is a sectional view showing an example of such a spindle. 3, a main shaft 1 is supported by a hydrostatic bearing 2 in a non-contact manner with respect to a housing 3, and a motor 4 is provided.
Is driven to rotate. A non-contact displacement meter 5 is provided at one end of the main shaft 1 to detect the displacement of the main shaft 1. Spindle 1
A drill 6 is attached to the other end of. The output of the displacement meter 5 is supplied to a displacement detection circuit 7 to output a detection signal.

[0004]

When an eddy current type is used as the displacement gauge 5 built in the spindle shown in FIG. 3, the eddy current is applied to the main shaft 1 installed opposite to the coil serving as the sensor section. When the main shaft 1 is displaced and the main shaft 1 is displaced, the inductance of the coil changes due to the influence of the eddy current. Therefore, the displacement of the shaft can be detected by monitoring the inductance.

Conventionally, in a spindle using such a sensing method, a displacement detection circuit 7 comprising an electronic circuit for detecting a displacement of the main shaft 1 is provided outside the spindle as shown in FIG. That is, it is configured to be separated into two blocks of the displacement meter 5 and the displacement detection circuit 7. In this case, the cable connecting the coil and the inductance detecting section needs to be as long as possible in consideration of convenience in use. However, since the cable is connected to the sensor in series, the inductance detection unit also detects the inductance of the cable at the same time. For this reason, if the cable is violently moved, the sensor output may fluctuate even if the position of the spindle 1 does not change, and a signal unnecessary for detecting the displacement of the spindle may be taken in at the same time.

Moreover, if the displacement detection circuit provided outside is moved or the length of the cable between the spindle body and the displacement detection circuit is changed, the displacement detection circuit needs to be adjusted.

SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide an air bearing spindle capable of detecting a stable shaft displacement without being affected by the above-mentioned adverse effects.

[0008]

The invention according to claim 1 is
In a bearing spindle in which a main shaft is supported in a housing by an air bearing, a displacement sensor circuit for detecting displacement of the main shaft is built in the housing.

In the invention according to claim 2, the housing according to claim 1 is grounded. In the invention according to claim 3, claim 1
The displacement sensor circuit includes a sensor provided facing the end face of the main shaft, an oscillation circuit for giving an oscillation output to the sensor, a rectification circuit for rectifying the output of the sensor, and a high frequency included in the output of the rectification circuit. A filter circuit for removing noise.

[0010]

FIG. 1 is a sectional view of a spindle showing an embodiment of the present invention, and FIG. 2 is a block diagram of a sensor circuit used in the present invention.

In this embodiment, as shown in FIG. 1, a displacement sensor 5 and a substrate 8 of a sensor circuit 9 are provided in a housing 3.
Is built-in. Further, the housing 3 is grounded in order to protect the sensor circuit from noise and to prevent an electric shock accident due to leakage of the motor 4 or the like.

As shown in FIG. 2, the sensor circuit includes an oscillation circuit 11, a sensor section 12, a rectifier circuit 13, and a low-pass filter 14. The oscillation circuit 11 generates a sine wave and supplies it to the sensor unit 12. The sensor unit 12 is configured by a resonance circuit in which a sensor coil L and a resonance capacitor C are connected in parallel, and an eddy current is generated in the main shaft 1 facing the sensor coil L by a sine wave sent to the sensor coil L, and the main shaft 1 The inductance changes depending on the distance between the sensor coil L and the sensor coil L. For this reason, the resonance point of the resonance circuit changes depending on the position of the main shaft 1, and the amplitude of the sine wave changes accordingly.
The sine wave whose amplitude has changed is converted into a DC voltage by the rectifier circuit 13, and a signal indicating the position of the main shaft is output to the outside as a DC voltage via a low-pass filter 14 for removing high-frequency noise.

Therefore, by incorporating the sensor circuit shown in FIG. 2 in the housing 3 of the spindle shown in FIG.
Can be output stably.

[0014]

As described above, according to the present invention, since the displacement sensor circuit for detecting the displacement of the main shaft is built in the housing, it is not necessary to route the cable to the outside. Adverse effects can be minimized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle showing an embodiment of the present invention.

FIG. 2 is a block diagram of a sensor circuit used in the present invention.

FIG. 3 is a sectional view of a conventional spindle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main shaft 2 Hydrostatic bearing 3 Housing 4 Motor 5 Displacement gauge 6 Drill 8 Substrate 9 Sensor circuit 11 Oscillation circuit 12 Sensor part 13 Rectification circuit 14 Low-pass filter

Claims (3)

[Claims] 1. A bearing spindle for supporting a main shaft in a housing by an air bearing, wherein a displacement sensor circuit for detecting displacement of the main shaft is built in the housing. 2. The air bearing spindle according to claim 1, wherein said housing is grounded. 3. The displacement sensor circuit includes: a sensor provided to face an end surface of the main shaft; an oscillation circuit for providing an oscillation output to the sensor; a rectification circuit for rectifying an output of the sensor; The air bearing spindle according to claim 1, further comprising a filter circuit for removing high frequency noise included in an output of the rectifier circuit.