JPH0994736A - Ae detecting method of rotating element utilizing oil film and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting an AE signal at a bearing part clearly without having any effect of attenuation of the AE signal or generated noise. SOLUTION: From a viewpoint that an AE signal propagates in an oil film at a very high speed, a stationary jig 2 provided with an AE sensor is mounted in proximity to a rotating tool holder (rotating element) 3 to form an oil film 9 at a clearance between the rotating tool holder 3 and the stationary jig 2 and detect the AE signal propagating in the rotating tool holder 3 from a cutting point M, utilizing the oil film 9 as a signal transmitting medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil film formed and interposed in a gap between a rotating body such as a rotary tool and a fixing jig having an AE sensor, and the oil film is propagated in the rotating body as a signal transmission medium. The present invention belongs to a detection method and a detection device that detect an AE signal more clearly.

[0002]

2. Description of the Related Art Understanding the state of a tool during cutting in real time is an important technique for improving productivity by enabling automation and unmanned / night operation.
As a method of detecting such an abnormal state of the tool, conventionally, an AE sensor has been provided near the tool of the machine tool, and A
The E signal was detected, and the abnormal state of the tool was determined based on the rise in the signal level compared to the normal state. Note that A
E stands for Acoustic Emission
TIC Emission) is a signal that is generated when the energy accumulated inside is released when a solid material such as a metal is destroyed.
Signals in the ultrasonic region of Hz to several MHz are targeted.
This signal is also generated when scraping metal or breaking a cutting tool.

[0003]

However, in end mills and drills, which occupy most of the cutting work, since the tool is a rotating body, it is difficult to directly detect the AE signal generated from the cutting work point. Met. Therefore, conventionally, an AE sensor is attached to the outer wall of the stationary spindle head to detect the AE signal propagating in the rotary tool held by the bearing inside thereof, but the AE signal is attenuated at the bearing. The detection accuracy was significantly reduced due to the influence of noise generated in the bearings and bearings, and it was not a satisfactory detection method. Therefore, noise generated in the bearing and AE in the bearing can be detected with a simple and accurate detection method.
It has been awaited to realize a method for more clearly detecting an AE signal generated from a rotating body such as a rotary tool without being affected by signal attenuation or the like.

[0004]

SUMMARY OF THE INVENTION The present invention aims to solve such problems. In particular, the AE signal is attenuated in the air and hardly propagates, so that the path through which the signal propagates must be in a solid or a liquid. When air is present in the gap between the rotating body and the sensor fixing jig as in this method, a signal transmission medium such as a liquid is required to fill the gap. The inventor of the present invention has found that the AE signal propagates in the oil film at an extremely high speed, and the oil film has a high viscosity unlike water and has a good adhesion on the surface of the rotating body. Paying attention to the fact that an oil film can be accurately formed and intervened for a certain period of time, an AE sensor fixing jig, particularly preferably an AE sensor fixing jig formed in a semi-annular shape that fits a part of the outer shape of the rotating body. Attached close to the rotating body, forming an oil film in the gap and interposing,
An object of the present invention is to provide a method and an apparatus for detecting an AE of a rotating body using an oil film, which uses the oil as a signal transmission medium to detect an AE signal propagating in the rotating body. That is, the present solution means are as listed below. (1) A fixing jig having an AE sensor attached is mounted in proximity to a rotating body, an oil film is formed and interposed in a gap between the rotating body and the fixing jig, and the oil film propagates in the rotating body as a signal transmission medium. An AE detection method for a rotating body using an oil film, which is characterized in that a signal is detected. (2) In a rotary tool of a machine tool, a fixing jig equipped with an AE sensor is attached in the vicinity of a rotating tool holder, an oil film is formed in a gap between the rotating tool holder and the fixing jig, and the oil film is signaled. Cutting as a transmission medium,
A method for detecting an AE of a rotary tool using an oil film, wherein an AE signal generated from a machining point such as a hole and propagating in the rotary tool holder is detected. (3) A fixing jig equipped with an AE sensor is provided in a semi-circular shape close to the surrounding of the rotary tool holder, and an automatic oil agent for forming an oil film in the gap between the rotating body and the fixing jig. An AE detection device for a rotary tool utilizing an oil film, characterized in that a supply device is attached, and an AE sensor is attached so that its sensing portion can come into contact with the oil film. (4) The AE detecting device for a rotary tool using an oil film according to the item (3), wherein the fixing jig is made of an oil-free bearing material.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view illustrating an embodiment of an AE detection method of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA, showing a plan view of a fixing jig to which an AE sensor is attached. In the figure, 1 is an AE sensor, 2 is a fixing jig, 3 is a rotary tool holder, 4 is a spindle head, 5 is an automatic oil supply device,
6 is a cutting tool, and 9 is an oil film. A spindle 4a is rotatably held by a bearing 4b on a stationary spindle head 4 of a machine tool such as a milling machine, a drilling machine, or a machining center used for cutting such as end milling and drilling, and the lower end of the spindle 4a. A rotary tool holder 3 for mounting a cutting tool 6 is integrally connected to the. Thus, as the main shaft 4a rotates, the cutting tool 6 at the lower end rotates to cut the work 7 fixed on the table 8 and generate an AE signal by cutting. In addition, M is a cutting processing point of the cutting tool 6, and is an AE signal generation point.

According to the detection method of the present invention, the fixing jig 2 to which the AE sensor 1 is attached is attached close to the rotary tool holder 3, and an oil film 9 is formed in the gap between the rotary tool holder 3 and the fixing jig 2. , The oil film 9 as a signal transmission medium,
It is characterized in that the AE signal generated from the AE signal generation point M by cutting and propagating in the rotary tool holder 3 is detected more clearly. Then, in order to carry out the detection method, the rotary tool holder 3 is brought close to the surrounding thereof, and the facing portion 2a thereof is formed into a semicircular shape by forming an arc shape of about 90 ° and rising in an L shape. Attach the sensor fixing jig 2 to the spindle head 4 via the two holding rods 2b and 2b.
It hangs down and adheres to the bottom surface of. It is desirable that the fixing jig 2 be located as close as possible to the cutting point M on the holder and close to the holder 3 so as not to contact the holder 3. On the side of the spindle head 4, the rotary tool holder 3
An automatic oil agent supply device 5 for forming and interposing an oil film 9 in a gap formed between the and the opposing portion 2a of the fixing jig 2 is attached. Then, to the facing surface of the facing portion 2a of the fixing jig 2, the oil agent is supplied from the oil agent automatic supply device 5 through the supply pipe 5a, and the oil agent is provided on the outer periphery of the rotating rotary tool holder 3 which is opposed. The oil film 9 is formed by continuously adhering to the surface in a cylindrical shape and filling the gap with the facing portion 2a of the fixing jig 2. Further, on the fixing jig 2, the AE sensor 1 is attached so that the sensing portion 1a thereof projects toward the rotary tool holder 3 side and can come into contact with the generated oil film 9. Thus, the AE signal generated at the cutting point M can be detected through the path of the cutting tool 6-> rotary tool holder 3-> oil film 9-> AE sensor 1. In addition, general-purpose A
Since the E sensor is inferior in oil resistance, when using it, it is preferable to coat the sensor sensing portion 1a with an oil resistant coating resin or the like for oil resistance treatment. Alternatively, the sensor sensing unit 1a may be closely fixed to the back surface of the facing portion 2a of the fixing jig 2 (the right surface of the facing portion 2a in FIG. 2) to indirectly sense the AE signal. .
In this case, it is preferable that the right side of the facing portion 2a is deeply carved to reduce the wall thickness, and the AE sensor sensing portion 1a is closely fixed to the back of the carved portion.

Further, in order to always generate a stable oil film in the above-mentioned gap, an oil groove is engraved in the circumferential direction on the facing surface of the fixing jig 2, and an excess oil agent is formed at the lower end of the fixing jig 2. A discharge port and a discharge pipe 5b for discharging the are provided. An oil-free bearing material (for example, "Tarkite A" (trade name: WS Shamban, USA) polytetrafluoroethylene resin-based low friction coefficient wear resistance is provided on the facing portion 2a of the fixing jig 2. Material)) is used. Further, the oil agent to be supplied for generating the oil film 9 is an oil agent having a relatively high viscosity (for example, an industrial lubricant oil of lubricating oil “Dafney mechanical oil 220” (trade name: viscosity ISO VG220 manufactured by Idemitsu Kosan Co., Ltd.)). To be done. The viscosity of the oil is ISO VG4
6 to 320 is preferable. Further, when the AE detection device utilizing the oil film of the present invention is attached to the machine tool, the cutting tool 6
It is necessary to have a configuration capable of automatic tool exchange due to wear, damage, etc. of the tool, and for example, to attach the AE sensor fixing jig 2 close to the automatic tool changer (ATC) arm grip of the tool holder. But that ATC
It is necessary to install it in a position that does not interfere with the arm turning range. The detection method of the present invention is a gear, a turbine blade,
The same can be applied to detection of an abnormal state of a rotor such as a rotor.

[0008]

EXAMPLE In order to confirm the effectiveness of the AE detection method using the oil film of the present invention, an experiment was conducted to detect tool damage during cutting using an end mill. FIG. 3 shows an experimental example of this detection method. 4 is a block diagram for explaining the experimental method of FIG. 4, FIG. 4 is an explanatory view showing three mounting positions of the AE sensor in the present experiment, and FIG. 5 is a diagram showing the average total number of AE events per pass and the flank wear width of the present experimental result. FIG. 6 is a graph showing the relationship.
FIG. 4 is an explanatory diagram of a flank wear width of a cutting tool. The cutting process of this experiment is a side process of S50C material using a high speed steel end mill with a diameter of 10 mm as a cutting tool. In this experiment, a new product, flank wear width 6b (Fig. 6) was 0.09 mm,
Prepare four end mills of 0.17 mm and 0.31 mm, and use 3 passes (1 pass is 1
AE transmitted at that time after side processing of 20 mm)
As shown in FIG. 4, an AE sensor 1 according to the detection method of the present invention, an AE sensor 1b attached to the outer surface of the spindle head,
The AE sensor 1C attached to the surface of the table receives the AE sensor at three places and transmits it to the analyzer. In the analyzer, the AE signal is amplified and detected and output to the comparator. The comparator has a predetermined threshold level, and the output signal exceeding this threshold level is counted. The average total number of AE events per pass was determined.

The flank wear width 6b is the width of wear on the flank 6a (FIG. 6) of the cutting edge of the cutting tool and is generally used as a reference value for tool life, but in this experiment as well. As the flank wear width increased, the total number of AE events was detected, which supports this fact. The results of this experiment are shown graphically in FIG.
Compared to the case where the AE sensor is attached to the spindle head and table as the detection method, the AE output is large and the total number of AE events is detected even though the threshold level is set to a large value. It has been confirmed that the wear progress state of can be judged more clearly. Also, from this, it was proved that the detection method of the present invention can be incorporated into a cutting tool condition monitoring system and can be fully utilized.

[0010]

As is apparent from the above detailed description, according to the present invention, the following various effects can be expected. (1) The AE signal propagating in the rotating body is not detected via the bearing portion, but the oil film is detected as a signal transmission medium. Therefore, noise generated in the bearing portion, attenuation of the AE signal in the bearing portion, etc. More unambiguous detection is possible without being affected. (2) Unlike water, etc., the oil film has high viscosity and good adhesion on the surface of the rotating body.
Since it is possible to form and intervene the oil film in the gap of the fixing jig to which the E sensor is attached for a certain period of time, it is possible to detect the AE signal in a stable and reliable manner. (3) When this detection method is applied to the detection of damage to the rotary tool of a machine tool, the AE signal can be detected directly from the vicinity of the cutting point without being affected by the bearing, and more reliable detection of tool damage is possible. Not only is it possible, but various processing methods (end milling, drilling, dry, wet processing, etc.)
It is possible to detect tool damage in the tool and establish a practical and highly reliable in-process tool condition monitoring system. (4) Since it can also be applied to machine tools equipped with an ATC device, automatic tool replacement due to tool wear, chipping, etc. is possible, and real-time tool status monitoring of multi-step machining that requires tool replacement is possible. Become. (5) By using only the oil film for the oil agent and having a function of discharging the excess oil agent, it is possible to cope with all cutting environments (dry type, wet type).

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an embodiment of an AE detection method of the present invention.

FIG. 2 is a cross-sectional view taken along line AA of FIG. 1 and is a plan view of a fixing jig to which an AE sensor is attached.

FIG. 3 is a block diagram illustrating an experimental method of an experimental example of the present detection method.

FIG. 4 is an explanatory diagram showing three attachment positions of the AE sensor according to the present experiment.

FIG. 5 is a graph showing the relationship between the total number of average AE events per pass and the flank wear width of the experimental results.

FIG. 6 is an explanatory diagram of a flank wear width of a cutting tool.

[Explanation of symbols]

1 AE sensor 1a Sensing part 1b AE sensor mounted on the outer wall of the spindle head 1c AE sensor mounted on the surface of the table 2 Fixing jig 2a Facing part 2b Holding rod 3 Rotating tool holder 4 Spindle head 4a Spindle 4b Bearing 5 Automatic oil supply Equipment 5a Supply pipe 5b Discharge pipe 6 Cutting tool 6a Flank surface 6b Flank wear width 7 Machining work 8 Table 9 Oil film M Cutting point

Claims (4)

[Claims] 1. A fixing jig to which an AE sensor is attached is attached close to a rotating body, an oil film is formed and interposed in a gap between the rotating body and the fixing jig, and the oil film propagates in the rotating body as a signal transmission medium. A method for detecting an AE of a rotating body using an oil film, characterized in that the AE signal is detected. 2. In a rotary tool for a machine tool, a fixing jig having an AE sensor is attached in the vicinity of the rotating tool holder, and an oil film is formed and interposed in a gap between the rotating tool holder and the fixing jig. As a signal transmission medium,
A method for detecting an AE of a rotary tool using an oil film, wherein an AE signal generated from a machining point such as cutting or drilling and propagating in the rotary tool holder is detected. 3. A fixing jig having an AE sensor is provided in a semi-circular shape in the vicinity of the surrounding of the rotary tool holder,
An automatic oil agent supply device for forming and interposing an oil film in the gap between the rotating body and the fixing jig is additionally provided, and an AE sensor is attached so that its sensing portion can come into contact with the oil film. AE detection device for rotary tools that uses an oil film. 4. The AE detecting device for a rotary tool utilizing an oil film according to claim 3, wherein the fixing jig is made of an oil-free bearing material.