JP3078376B2 - Tool abnormality detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool abnormality detecting device for detecting an abnormality such as breakage or wear of a tool attached to a machine tool.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Publication No. Sho 54-6101, for example, a tool abnormality detecting device has two springs interposed between a spindle and a transmission member for transmitting power to the spindle. In some cases, a change in the cutting load acting on the spindle is detected based on the degree of bending of the two springs, thereby detecting breakage of the cutting tool, a decrease in sharpness, and the like.

Also, a strain sensor is attached to a ring provided on the outer periphery of the bearing portion of the spindle, and the degree of distortion of the ring due to the thrust force of the spindle is electrically extracted, and a tool abnormality is detected from a change in the strain signal. Some have done so.

[0004]

In the former case of the above-mentioned prior art, in order to detect the bending of the spring, the position of the spindle is actually changed by a predetermined amount, and if the degree of bending of the spring does not change, the abnormality of the tool is detected. There is a problem that it is impossible to know the delicate state of the tool, and that the bending of the spring adversely affects the machining.

In the latter case of the above-mentioned prior art, a lead wire for a strain sensor must be wired up to the outer peripheral portion of the bearing, which makes the device electrically complicated.
The bearing is heated to a considerable temperature during machining, and the effect of the strain caused by the temperature rise is large, so that the delicate state of the tool cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to provide a tool abnormality detection device having a simple configuration and high detection accuracy.

[0006]

SUMMARY OF THE INVENTION According to the present invention, pistons provided to be movable in a minute amount in the axial direction are opposed to each other at the front and rear ends in the axial direction of a bearing of a spindle to which a tool is attached, with the bearings interposed therebetween. A cylinder section holding each of the pistons, and a hydraulic pipeline which is continuous with each of the cylinder sections and independently forms a closed pipeline on each side of the axial front and rear ends of the bearing. This is a tool abnormality detecting device in which oil is sealed at a predetermined pressure in a section and each hydraulic pipeline, and a pressure sensor for detecting the pressure of the hydraulic pipeline is connected to each hydraulic pipeline.

[0007]

According to the tool abnormality detecting device of the present invention, a machining resistance generated when a tool attached to a machine tool is broken or worn is converted into a change in oil pressure via a piston, and the oil pressure is detected by a pressure sensor. Therefore, the axial movement amount of the bearing is a minute amount, but a large pressure change appears, and it is possible to accurately detect a tool abnormality in real time.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. The tool abnormality detecting device of this embodiment is provided on a machine tool having a spindle 12 on which a tool 10 such as a drill is mounted, a bearing 14 holding the spindle 12, and a spindle housing 16 holding these bearings 14 and the like. It was done. The outer ring at the front end in the axial direction of the bearing 14 is held in the axial direction by a piston 18 that can move by a minute amount δ1 in the axial direction with respect to the outer ring. The outer ring at the rear end in the axial direction of the bearing 14 is also On the other hand, it is held in the axial direction by a piston 20 that can move by a minute amount δ2 in the axial direction. The piston 18 is mounted so as to move δ1 in a cylinder portion 24 formed in the front housing 22, and the piston 20 is provided so as to move δ2 in a cylinder 26 formed in the spindle housing 16.

As shown in FIG. 3, six cylinder portions 24 are provided at equal intervals around the spindle 12 in the front housing 22, and the cylinder portions 24 are connected by a communication passage 40. Further, the cylinder portion 26 is similarly formed in the spindle housing 16. The cylinder portions 24 and 26 are respectively connected to the front housing 22
The hydraulic lines 32 and 34 are connected to the connecting lines 28 and 30 formed in the spindle housing 16, respectively. Hydraulic lines 32, 34
Are connected to the atmosphere via air vent valves 36 and 38, respectively. The front housing 22, as shown in FIG.
It is attached to the spindle housing 16 by bolts 42, and is initially attached with a gap of about 1 mm between the front housing 22 and the spindle housing 16.

The cylinders 24 and 26 are connected to a hydraulic device 50 via valves 43 and 44 and check valves 46 and 48. Further, pressure sensors 52 and 54 are connected to the hydraulic lines 34 and 36, respectively. The bearing 14 is connected to a lubricating oil supply line 52 provided in the spindle housing 16, and is provided so that the lubricating oil circulates through the bearing 14.

The method of using the tool abnormality detecting device of this embodiment is as follows. First, with the valves 36.38.43 and 44 closed,
Oil is sealed in the hydraulic lines 32 and 34 at a predetermined pressure. In this state, the outer ring of the bearing 14 is held at the predetermined pressure by the pistons 18 and 20 on both sides. Here, each of the hydraulic lines 32, 34 independently forms a closed line, and each of the hydraulic lines 32, 34
The pressure inside will vary independently.

When the tool 10 is operated and machining is performed, a force is applied to the spindle 12 in the axial direction due to cutting resistance or the like during the machining, and the force is transmitted to the pistons 18 and 20 via the bearing 14. , And hydraulic lines 32 and 34
And the pistons 18 and 20 move a small amount to the right in the drawing, the gap δ1 slightly increases, and the gap δ2 slightly decreases. As a result, the pressure in the hydraulic pipeline 32 decreases, and the pressure in the hydraulic pipeline 34 increases. This increase or decrease is detected by the pressure sensors 52 and 54, and the output value is calculated by a calculation device (not shown). In addition, a change in the machining resistance value in the axial direction can be detected with high sensitivity.

The axial force due to the machining resistance of the tool is shown in FIG.
Can be detected and displayed as a differential pressure between the pressure sensors 52 and 54, and when the operation is stopped, a predetermined reference value a
The differential pressure is stored inside. When the machining is performed normally, the machining resistance is within a certain range, and the differential pressure is detected below the reference value b. When the wear of the tool 10 exceeds the limit, the machining resistance increases, the axial force increases, and when the tool 10 exceeds a predetermined reference value b, it is understood that the tool is worn beyond the reference. further,
When an abnormal force is applied and a situation such as breakage of the tool occurs, a differential pressure is detected at a peak, and a situation such as breakage of the tool is detected.

The tool abnormality detecting device of this embodiment converts the force applied to the bearing into a change in the oil pressure by the oil sealed in the closed conduit, detects the differential pressure of the oil pressure, and thereby reduces the machining resistance in the axial direction. Since the detection is performed, a subtle change can be detected sensitively. In addition, even if the temperature of the oil rises due to the processing, the differential pressure is monitored, so that both oil pressures rise and cancel each other, so that there is no influence.

In the present invention, in addition to the above-described embodiment, the shapes and positions of the piston and the cylinder can be appropriately set, and the arrangement of the hydraulic pipeline, the type of the pressure sensor, and the like can be appropriately selected. .

[0016]

According to the tool abnormality detecting device of the present invention, the axial front and rear ends of the bearing of the spindle to which the tool is mounted are held by the piston, and the hydraulic pipeline is connected to each cylinder having the piston. The oil is sealed at a predetermined pressure in the cylinder portion and each hydraulic line, and the processing resistance during processing is detected by detecting the pressure in the hydraulic line, so that the processing resistance can be accurately and easily detected. It can be detected and is not affected by temperature or vibration. In addition, by detecting the differential pressure of the hydraulic line, the machining resistance can be detected with high accuracy, and delicate changes such as tool wear can be constantly monitored. Also, since the oil in the hydraulic pipeline is placed in a static pressure state, no power is required for generating the oil pressure while monitoring the processing state, and the apparatus is simple,
It does not use wasted energy. Furthermore, the bearing will be supported in the axial direction with high rigidity by pressure using oil, which is an incompressible fluid, substantially through the piston, and will absorb vibrations during machining with oil. Due to the damping action of this oil, the influence of vibration during machining is unlikely to appear on the detected pressure.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of a tool abnormality detecting device according to the present invention.

FIG. 2 is a partial vertical sectional view of the machine tool according to the embodiment.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a graph showing a relationship between a differential pressure detected according to the embodiment and a state of a tool.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Tool 12 Spindle 14 Bearing 16 Spindle housing 18, 20 Piston 24, 26 Cylinder part 32, 34 Hydraulic pipeline 50 Hydraulic device 52, 54 Pressure sensor

Claims (2)

(57) [Claims] 1. A piston, which is provided to be movable by a minute amount in the axial direction, is attached to the front and rear ends in the axial direction of a bearing of a spindle to which a tool is attached, facing each other with a bearing interposed therebetween, and each of the pistons is held. Cylinder part
A hydraulic line which is continuous with each cylinder portion and independently forms a closed line on each side of the front and rear ends in the axial direction of the bearing is provided, and oil is applied to the cylinder portion and each hydraulic line at a predetermined pressure. A tool abnormality detecting device, wherein a pressure sensor for sealing and detecting the pressure of the hydraulic line is connected to each hydraulic line. 2. The tool abnormality detecting device according to claim 1, wherein a difference between the pressures of the hydraulic lines is detected by the pressure sensor.