JP2000079537A - Closely adhering condition detector device for tool holder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a highly accurate detection whether a tool holder is mounted or not in a tapered hole of a main spindle in an abnormal condition. SOLUTION: In this device, three or more sheets of resistance strain gages 1, 2, 3, 4 are individually provided on a surface of a tool side end face of a spindle, respective first coils 5, 6, 7, 8 connected to these resistance strain gages 1, 2, 3, 4 are provided to appear on a side surface of the tool side end face of the spindle, on the other hand, second coils 9, 10, 11, 12 are provided on a spindle head so as to correspond to the first coils 5, 6, 7, 8, a bridge circuit is formed by using the second coils 9, 10, 11, 12, and an abnormal clamp condition of a tool holder is detected by a bridge output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool holder close contact detecting device for detecting whether a tool holder is inserted into a tapered hole of a spindle in a close contact state, that is, in a normal state.

[0002]

2. Description of the Related Art In a machine tool equipped with an automatic tool changer, rotation of a spindle is transmitted to a tool via a tool holder in a state where the tool holder is correctly inserted into a tapered hole of the spindle. Expected. However, it is difficult to maintain such a state at all times, and in rare cases, chips or the like are caught between the tapered hole of the main shaft and the tool holder, so that the processing accuracy is reduced, or in the worst case, The tool was damaged.

In order to detect the state of close contact of the tool holder, various devices have been devised. Primarily,
A spindle rotatably supported by a cylindrical casing, a center shaft provided inside a shaft hole of the spindle, rotating integrally with the spindle, and having a chuck portion at its tip for gripping the bottom of the tool holder; Spring means for urging the center shaft to the rear side, and a piston rod of a hydraulic cylinder that can move forward and backward to move the center shaft forward and backward and control whether the chuck unit clamps or unclamps the tool. In a spindle for a machine tool, an abnormality detection shaft spring-biased in a forward direction is inserted into a shaft hole of a piston rod of the hydraulic cylinder. The front end of the detection axis contacts the rear end of the central axis,
A tool clamp abnormality detection device for a machine tool spindle, characterized in that the rear end of the abnormality detection shaft is pressed back to a predetermined position by being pressed by the center axis and an abnormality detection switch for detecting an abnormality is provided by the retraction. (Japanese Utility Model Publication No. 4-51922).

Second, compressed air is supplied between the shank of the tool holder and the tapered surface on the tool side of the spindle head to check the close contact between the shank and the tapered surface. Means for detecting have been proposed.

[0005] Third, as shown in FIG.
Is installed face-to-face with a tool 33 fitted in a tapered hole 34 of a spindle 31 rotatably supported on a spindle head 28 via a bearing 29 to measure a change in distance, that is, a displacement. Eddy current or tool 3 flowing through
Means for detecting the capacitance that accumulates between the sensor 3 and the shake sensor 30 (detection end) has been proposed.

[0006]

However, the first means is that when the chuck portion is broken or the like, the center axis is moved backward by the tensile force of the disc spring, and the abnormality detecting axis is moved to the compression coil. The detector is pressed backward against the spring force of the spring, and the detection object of the abnormality detection axis is detected by the abnormality detection switch. From this structure, it is difficult to detect unless it becomes a considerable abnormal state. Having. For example, when it is indistinguishable from the normal state that the tool holder is clamped with foreign matter such as chips slightly remaining in the tapered hole, such an abnormal state is overlooked by such means. I will.

In the second means, since the pressure switch to be detected is operated after the compressed air pressure is stabilized, it takes a long time to detect an abnormal state, and the work procedure in the subsequent process is disturbed. Have.

The third means is that the displacement hardly changes when a small chip 35 of a few microns as shown in FIG. 6 is bitten between the surface of the tapered hole 34 and the shank 32. If the main shaft 31 is rotated at a high speed while being clamped in an abnormal state, the tool 33 may be broken,
The machining surface may chatter, or the accuracy of roundness and surface roughness may be reduced.

The present invention solves the drawbacks of the conventional means and provides a tool holder that can accurately detect whether or not a tool is normally inserted into a tapered hole of a main spindle. It is an object to provide a state detection device.

[0010]

The present invention adopts the following means in order to solve the above-mentioned problems. That is,
According to the first aspect of the present invention, at least three or more resistance strain gauges are separately provided on the surface of the tool side end face of the main spindle, and the first coil connected to each of the resistance strain gauges faces the side surface of the tool side end face of the main spindle. On the other hand, a second coil is provided on a non-rotating body portion on the outer periphery that rotatably supports the main shaft so as to face the first coil, and a bridge circuit is formed using the second coil. An apparatus for detecting a contact state of a tool holder, wherein an abnormal clamping state of the tool holder is detected by a bridge output of the circuit.

The invention according to claim 2 is the device for detecting the close contact of a tool holder according to claim 1, wherein the number of resistance strain gauges is three or four.

Further, according to a third aspect of the present invention, there is provided an apparatus for detecting a close contact state of a tool holder according to the first or second aspect, wherein the resistance strain gauges are provided at equal intervals on the same circumference on the tool-side end surface of the spindle. It is.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. However, the drawings are merely for explanation, and some modifications may be made without departing from the spirit of the present invention. FIG. 1 is a schematic cross-sectional view of a spindle head to which an embodiment of a tool holder close contact detection device according to the present invention is applied. In FIG. 1, a spindle 16 is rotatable on a spindle head 17 via a bearing 18. It is supported by

In FIG. 1, it is assumed that the tool holder 26 is fitted in the tapered hole 23 of the main shaft 16, so that the tip portion 25 of the clamp rod 19 pushes up or down the steel ball 24 for clamping. By engaging the tool holder 26 and the stub 27, the tool holder 26 and thus the tool are clamped to the main shaft 16.

On the other hand, when the clamp rod 19 is pushed to the left as viewed in the drawing, the steel ball for clamping 24 fits into the recess 20 of the clamp rod 19, and the engagement between the tool holder 26 and the stub 27 is released. To be unclamped. Reference numeral 21 denotes a temporary holding hard ball, which faces the tool holder 26 from the hole of the main shaft 16 by a spring 22 and prevents the tool holder 26 from being detached from the unclamped state to the automatic tool change, thereby ensuring safety.

Reference numerals 1 and 3 denote resistance strain gauges.
Is mounted on the surface 15a of the tool-side end surface 15 in an insulated state from the outside. As shown in FIG. 3, the resistance strain gauges 2 and 4 are also provided at equal intervals on the surface 15a of the tool-side end face 15 of the main shaft 16 like the resistance strain gauges 1 and 3. The number of resistance strain gauges is three or more. This is because it is difficult to accurately detect the close contact state with two or less sheets. On the other hand, if the number is 5 or more, the effect is the same as the case of 4 sheets, which is a problem in cost. Also,
It is preferable to provide four sheets at equal intervals, as shown in FIG. 1, in order to easily form a bridge. It is preferable from a practical point of view that the resistance strain gauge is adhered to the strain body and this strain body is embedded in the surface 15a of the tool side end surface 15 and used.

In FIG. 2, resistance strain gauges 1, 2, 3, 4
Form a closed circuit with the first coils 5, 6, 7, and 8, respectively. The second corresponding to each first coil
The coils 9, 10, 11, and 12 are provided to form a bridge circuit abcd. Points a and c are respectively connected to the power supply 13, and points b and d are connected to the detection unit 14. When the tool holder 26 is fitted and mounted in the tapered hole 23 of the main shaft 16 and abnormally clamped, the degree of crimping of the resistance strain gauge is different, the balance of the bridge circuit is broken, and a bridge output is obtained at the detection unit 14. . Thereby, the abnormality of the close contact state of the tool holder is detected.

The operation of the present invention will now be described with reference to FIGS. First, the spindle 16 is rotating during machining, but as shown in FIG.
When the tool of the spindle 16 is changed in
Are localized (h-i), and are electrically fixed at a fixed phase, and the first coils 5, 6, 7, 8 are fixed at certain positions in the turning direction, and the second coils 9, 6, respectively. Positioning is performed so as to correspond to 10, 11, and 12. Next, in the automatic tool change (b) of FIG. 4, the automatic tool changer starts to operate (j-o). Further, in the unclamping / clamping (c), the clamp rod 1
9 is pushed to the left as viewed in FIG. 1, the steel ball for clamping 24 fits into the recess 20 of the clamp rod 19,
The engagement between the tool holder 26 and the stub 27 is released, and an unclamped state is formed (k-1). By the action of the tool changing arm, the temporary holding steel ball 21 is pressed down against the spring 22 to unclamp the old tool holder.

Next, in the detection (d), when a new tool holder 26 is fitted and mounted in the tapered hole 23 of the main shaft 16 in a normal close contact state, a bridge output is not generated in the detection unit 14 and automatic detection is performed. The tool changing operation of the tool changing device is completed, and machining is started. On the other hand, when the new tool holder 26 is fitted and mounted in an abnormal state, the detecting unit 1
4, a bridge output is generated, an abnormal signal is transmitted through a signal generator (not shown), the machine tool is stopped, and a retry of automatic tool change is performed.

[0020]

According to the first or second aspect of the present invention, an abnormal state of the tool holder is detected with high accuracy and accuracy in a short time.
Consequently, breakage of the tool is prevented. According to the third aspect of the present invention, an abnormal state of the tool holder is detected more stably and more accurately than the first or second aspect of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a spindle head to which an embodiment of a tool holder contact state detecting device according to the present invention is applied.

FIG. 2 is a conceptual explanatory view of one embodiment of a tool holder close contact detection device of the present invention.

FIG. 3 is an explanatory view according to the present invention in which a resistance strain gauge is provided on the surface of a tool-side end surface of a spindle.

FIG. 4 is a time chart when the tool holder close contact detection device of the present invention is used.

FIG. 5 is a cross-sectional view of a conventional tool holder close contact detection device.

FIG. 6 is a cross-sectional view when chips are bitten in FIG.

[Explanation of symbols]

 1, 2, 3, 4 Resistance strain gauge 5, 6, 7, 8 First coil 9, 10, 11, 12 Second coil 13 Power supply 14 Detecting unit 15 Tool-side end surface of main shaft 16 Main shaft 17 Main shaft head 19 Clamp rod 23 Taper hole 26 Tool holder

Claims (3)

[Claims] At least three or more resistance strain gauges are separately provided on the surface of a tool-side end surface of a main spindle, and a first coil connected to each of the resistance strain gauges faces a side surface of a tool-side end surface of the main shaft. On the other hand, a second coil is provided on the non-rotating body portion on the outer periphery that rotatably supports the main shaft so as to face the first coil, and a bridge circuit is formed using the second coil. An apparatus for detecting a contact state of a tool holder, wherein an abnormal clamping state of the tool holder is detected by a bridge output of a circuit. 2. The device according to claim 1, wherein the number of strain gauges is three or four. 3. The tool holder close-contact detecting device according to claim 1, wherein the resistance strain gauges are provided at equal intervals on the same circumference on the tool-side end surface of the spindle.