JP2017140688A - Smart tool holder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting behavior continuous monitoring system in a machining line capable of grasping in advance a symptom of unsteady behavior such as tool breakage, which solves the problem of unexpected troubles in machine work, such as tool cutting edge breakage, tool fracture and cutting edge abnormal wear that are caused by, e.g., entanglement of chips or presence of interstitial foreign matter (inclusions) contained in a surface hardened layer or a work material, in particular in difficult-to-machine materials such as high strength materials and high heat resistance materials.SOLUTION: In a tool holder, a machining force detection sensor is positioned as closely to a machined point as possible to minimize the length of a machining force transmission path from the machined point to the detection sensor and minimize the reciprocating inertia and the rotating inertia on that force transmission path. In addition, the tool holder has an attenuation function for inhibiting generation of vibration induced by the machining force. Thereby, a frequency band allowing measurement of the machining force is made higher.SELECTED DRAWING: Figure 2

Description

  The present invention grips a tool such as a drill or an end mill and fits it to the spindle of a machine tool to perform machining, and has a function of detecting a load generated at a machining point at the time of machining, that is, a machining force, when generating chips during machining. It relates to a tool holder.

  At the time of machining, the cutting edge of the tool is worn with the continuation of machining, and the machining accuracy deteriorates. For this reason, it is common to provide thresholds for the cutting distance and the number of pieces that can be machined with one tool cutting edge, and to replace the tool cutting edge before the machining accuracy exceeds the machining tolerance. When the wear of the cutting edge of the tool progresses constantly with the cutting distance, such tool life can be dealt with by threshold management of the processing force and the number of processing. However, in reality, unpredictable unsteady cutting edge damage such as abnormal wear or chipping of the tool cutting edge frequently occurs. For such unsteady cutting edge damage, the tool life cannot be managed from the threshold based on the above rule of thumb. For this reason, it continues to be used even after the tool cutting edge is abnormally worn or chipped, often resulting in a decrease in yield such as successive defective products. In addition, as a safety measure to avoid such troubles, the cutting distance until the replacement of the tool cutting edge is set short to increase the tool cost, or the processing conditions are set low to reduce the machining efficiency. I have problems such as inducing.

  In response to these issues, machining forces have been measured by measuring the driving power consumed to rotate the spindle motor of machine tools and measuring the vibration of spindle heads and workpieces. Attempts have been made to detect the unsteady cutting edge damage in-process based on the measured machining force.

  Of these methods, the former method of measuring the driving power of the spindle motor during machining is being applied to machining sites because the detection of driving power is relatively simple. However, even when the spindle motor rotates without load, a lot of driving power is consumed due to mechanical loss such as electrical loss of the spindle motor and friction of the motor bearing. On the other hand, in the finishing process, etc., the power consumption required for chip generation is small, and the power consumed for machining to be detected is buried in the drive power of the spindle drive motor, and the rotational inertia of the spindle drive motor However, there is a problem that it is not possible to faithfully measure a small fluctuation in instantaneous power consumption such as a cutting edge defect.

  In order to instantly detect the chipping behavior of the cutting edge, it is necessary to be able to measure the machining force up to a high frequency band. For that purpose, the location of the machining force, that is, the machining point and the detection of the machining force are detected. It is important to make the distance from the end as close as possible and to minimize the rotation inertia and reciprocation inertia from the processing point to the detection end. For this reason, in Literature 1 and Literature 2, a secondary shaft is provided on the tool side of the main shaft to reduce rotational inertia and increase the upper limit of the machining torque measurement band. However, this detection method has a detection function in the spindle, so even if only the detection system breaks down, the spindle cannot be used while the detection system is repaired, and the operating rate of the machine tool body is reduced. Decrease significantly.

  On the other hand, when trying to detect the processing force of a tool in-process with a tool holder that holds the tool by fitting it to the spindle of the machine tool, the tool and the tool holder are always used in pairs. Therefore, each tool holder prepared for each tool must have a detection function.

  In addition, in Document 3, the machining force acting on the main shaft can be detected by measuring the relative displacement between the shaft of the hydrostatic bearing and the bearing. However, the inertia of the built-in type rotor shaft is large, no consideration is given to the detection signal of this inertia, and the measurement band is limited to be extremely low. Moreover, since piping is connected to the housing of the fluid dynamic bearing, it is not premised on rotation, and application to a rotating tool is not assumed.

  Reference 4 also shows an example in which the machining force acting on the tool blade edge is replaced with a bending moment acting on the tool by this machining force, and detection is possible with an axial magnetostrictive film. It is fixed to the main body and cannot be easily attached and detached, which is essential for tool change. Further, the rolling bearing on the main shaft side is fixed in the axial direction, and the rolling bearing on the cutting edge side has a free bearing arrangement in the axial direction. On the other hand, in consideration of the fact that the machining accuracy is determined by the position of the cutting edge, the fixed fulcrum that should be as close to the cutting edge as possible is arranged on the main shaft side in the known example, and is not practical.

  On the other hand, Documents 5 to 10 show a tool unit that has a built-in mechanism capable of detecting the limit value of the machining load and can hold the tool. However, in either case, only a function as an overload torque or overload thrust limiter is provided, and a time-dependent change in machining load torque or load thrust cannot be detected. In particular, continuous load fluctuations that change from moment to moment cannot be measured from circumferential and axial deviations detected intermittently corresponding to steps equally distributed in the circumferential direction. Instantaneous behavior such as blade chipping, tool breakage, and entanglement of chips cannot be detected, and the processing force that leads to tool breakage prediction cannot be grasped.

In the example shown in Document 11, a “strain gauge” is used as a detector. For detection methods using strain gauges, it is essential to distinguish between the strain of members caused by the load being measured, the so-called load strain, and the fateful thermal strain associated with temperature changes at the measurement location. Even if you take measures such as using a strain gauge that compensates for the resistance change according to the thermal expansion coefficient of the member, or putting a strain gauge in a symmetrical place with respect to the load and building a bridge circuit to compensate for the temperature effect, it is ^10-6 orders Alternatively, it is very difficult to measure a micro strain within that range with high accuracy.

  For this reason, generally, the rigidity of the place where the strain gauge is applied is intentionally lowered to cause a large strain. In consideration of these matters, in the example of this document, there is a concern that the method of ensuring detection sensitivity may adversely affect the machining system, such as chatter vibration due to a decrease in rigidity and degradation of machining dimensional accuracy.

  In Reference 11, as a means for supplying power to the rotating detection system, power is supplied to the rotating tool holder by self-power generation accompanying rotation similar to an automatic wristwatch. However, with this power generation method, it is not possible to perform an operation check before work when the main shaft is not rotating, or calibration of detection accuracy outside the machine. In order to enable these operations, there is a problem that a new power supply means is required.

  On the other hand, regarding the method of supporting the countershaft that grips the tool, when a load is applied between the inner ring and the outer ring of the rolling bearing, the rolling elements interposed between the inner ring and the outer ring and the rolling surfaces of both wheels It is widely known that local elastic deformation is caused at the contact point and the spindle rigidity is lowered, and improvement of the support rigidity of the spindle is an important issue for a spindle of a machine tool that performs heavy cutting. On the other hand, as an example of positively utilizing this elastic deformation, evaluating the load acting on the shaft by detecting the elastic deformation amount is performed.

  In the known example shown in Document 12, the axial load is measured by detecting a change in the time interval passing through the concave groove on the assumption that the main shaft rotates at a constant speed. However, in a non-rotating stop state, neither axial load measurement nor measurement accuracy calibration is possible. Further, the amount of torsional deformation is measured intermittently at the rotation angle interval, and a rapid change in the axial load occurring within this angle interval cannot be detected. Thus, the measurable frequency band is limited to a very low level. For example, even if chipping occurs at the cutting edge, the rapid load change behavior cannot be detected. In the example of FIG. 6 of Document 12, it can be read that a concave groove is arranged at every rotation angle of 90 °, and the load change is measured only at this angular interval, so that it occurs within a smaller rotation angle. A change in machining force cannot be detected.

  In addition, although the phase difference of the detection signal using a plurality of sensors is mentioned, it is not possible to measure a rapid time change of the axial load only by increasing the measurement accuracy of the detection angle position.

  References 13 and 14 are application examples for measuring the load from the road surface when the load received from the tire of the vehicle is received by a bearing box in which a pair of angular contact bearings are combined on the back. In these two known examples, an encoder in which magnets are equally arranged is attached to a rotating body, and a load received from a tire is detected by an elastic displacement of a shaft by a magnetic detection element fixed to a bearing box. However, the known example of Document 14 is based on the premise that the rotating body is rotating, and the detection sensitivity cannot be calibrated while stationary. In Reference 14, the elastic displacement in the radial direction is measured near the center between a pair of angular contact bearings combined on the back, but the elastic displacement is minimized in consideration of the bending moment from the tire. Measuring at a close position. On the other hand, in Reference 13, although the detection sensor is moved to the vehicle body side to increase the detection sensitivity, there is a concern that the dynamic rigidity of the attachment location of the sensor and the detected end is lowered.

JP2011-93061A JP2007-229826A JP 7-314292 A JP-A-9-174384 JP-A-6-304848 JP-A-8-90320 JP-A-9-285946 7-94106 7-96181 JP-A-9-285946 JP-A-6-114688 JP2012-157963 JP 2006-317420 A JP2004-3918

  As described above, in the machining line, it is an object to realize a measuring means that enables in-process measurement of a machining force up to a high frequency band and can detect sensitively to a rapid machining force change. To that end, the rotational inertia and reciprocating inertia from the machining point to the measurement point are suppressed to a small level, making it possible to measure the machining force up to the high frequency band, and to make it applicable to machining lines. The challenge is to improve cost performance by simplifying the structure.

  In order to solve the above problems, the tool holder according to the present invention does not connect the elastic support system constituting the detection unit in series, but has a simple structure to improve measurement performance and to be inexpensive. .

  For this reason, the tool holder according to claim 1 has a tapered portion that can be fitted to the main shaft of the machine tool, and a chuck that grips the tool at the tip, and is a counter shaft that is arranged coaxially with the tapered portion. And two types of support portions that are interposed between the tapered portion and the countershaft and support the countershaft, and are mounted on the countershaft to detect elastic displacement or elastic strain of the subshaft with respect to the taper portion. A detection sensor that performs detection, a signal processing unit that processes a detection signal from the detection sensor, a transmission unit that transmits the processed signal, and a power supply unit that supplies power to the detection sensor, the signal processing unit, and the transmission unit. It is a tool holder, and the support part is of two types, a radial bearing arranged on the front end side of the countershaft and a spline bearing arranged on the rear end side, and the detection sensor is The elastic displacement of the secondary shaft with respect to the tapered portion in at least one of the four directions consisting of the axial direction of the main axis, two directions orthogonal to each other in a cross section perpendicular to the axial center, and the torsional direction around the axial center Is detected.

  The tool holder according to claim 2 is the tool holder according to claim 1, wherein the tapered portion includes an outer cylinder fixed to the tapered portion and an inner cylinder fixed to the outer cylinder. The shaft is inserted into the inner cylinder, and the detection sensor is mounted on one of the two types of support parts, the outer cylinder or the inner cylinder.

  The tool holder according to claim 3 is the tool holder according to claim 1 or 2, wherein each of the radial bearing and the spline bearing has an outer ring fixed to the inner cylinder, and the auxiliary shaft is parallel to the axial direction. It has a plurality of spline grooves, and these spline grooves are attached to the spline bearing while fitting the steel balls of the spline bearing, and are fixed to the inner ring of the radial bearing.

  The tool holder according to claim 4 is the tool holder according to any one of claims 1 to 3, wherein the radial bearing or the spline bearing has a steel ball that allows elastic deformation, and is caused by the elastic deformation. The diameter of the steel ball with respect to the curvature of the contact surface of the steel ball in each bearing is determined so that the elastic displacement of the counter shaft is within a desired range.

  The tool holder according to claim 5 is the tool holder according to any one of claims 1 to 4, wherein the radial bearing is constituted by a radial ball bearing, and the spline bearing is constituted by a ball spline bearing.

  A tool holder according to a sixth aspect is the tool holder according to any one of the first to fifth aspects, wherein the auxiliary bearing in two directions orthogonal to each other in a cross section perpendicular to the axis of the main shaft is in the vicinity of the radial bearing. A detection sensor for detecting the elastic displacement of the shaft is arranged.

  A tool holder according to a seventh aspect is the tool holder according to any one of the first to sixth aspects, wherein the spline bearing is provided in two directions including an axial direction of the main shaft and a torsion direction around the axial center. Among them, a detection sensor for detecting at least one direction is arranged.

  The tool holder according to claim 8 is the tool holder according to any one of claims 1 to 7, wherein at least one of the two types of support portions is in the axial direction of the main shaft and in a cross section perpendicular to the axial center. It has a damping function in at least one direction out of two directions orthogonal to each other and four directions including a twisting direction around the axis.

  A tool holder according to a ninth aspect is the tool holder according to the eighth aspect, wherein at least one of the two types of support portions is fixed to the support body while forming a minute gap with the auxiliary shaft. The damping function is exhibited by a squeeze effect generated by filling the gap with a fluid.

  The tool holder according to claim 10 is the tool holder according to claim 9, wherein the fluid is a magnetic fluid, and the ring member is formed of a magnetic body having a magnetic force, and the magnetic body is in contact with the gap. By causing a magnetic field loop, the magnetic fluid leakage suppressing function is exhibited.

  In the tool holder of the present invention, the auxiliary shaft integrated with the tool is elastically supported by the tapered portion having the same axial center at the two supporting portions separated from each other. By measuring using the detection sensor, the machining force transmitted from the machining point can be detected. Here, the closer the detection sensor is to the processing point, the more the reciprocal inertia and rotational inertia from the processing point to the detection sensor can be further suppressed, and the attenuation of the processing force and processing torque is suppressed. The frequency can be increased, and the processing force up to a higher frequency band can be detected with high reliability. Therefore, it is possible to quickly detect a minute chipping or breakage of the tool cutting edge in real time.

It is a model figure of the measurement system for demonstrating the principle of this invention. It is a figure which shows the static force relationship when the inertia of a processing system in FIG. 1 and a measurement system is disregarded. It is sectional drawing which shows the tool holder of one Embodiment of this invention. It is a structure schematic diagram of the processing force detection system which has the tool holder of FIG. The BB arrow line view in FIG. 3 is shown. It is the figure which showed the components around a radial bearing, and an assembly procedure. It is sectional drawing of the DD arrow in FIG. It is the figure which showed the components around a spline bearing, and the assembly procedure. It is CC arrow line view in FIG. It is sectional drawing of the AA arrow in FIG. It is sectional drawing of the EE arrow in FIG. It is the figure which showed the example of calculation of the elastic displacement of a load direction when a perpendicular load works. It is a FF arrow line view in FIG. It is a GG arrow line view in FIG. It is a figure which shows the example of a calculation of the elastic displacement of the load direction by a vertical load when pressing the steel ball made from bearing steel to the raceway surface with load 1N. It is a figure which shows the power supply system of the tool holder in 2nd Embodiment. It is the II arrow directional view in FIG. It is a HH arrow line view in FIG. It is the figure which showed the modification of the rotating coil. It is the figure which showed the explanatory table of the symbol used for FIG.

  The tool holder of the present invention has a machining force detection function, and a machining force detection sensor is disposed as close to the machining point as possible, and a machining force transmission path from the machining point to the detection sensor is provided. It has been greatly shortened to sufficiently suppress the reciprocating inertia and rotational inertia of this force transmission path, and has a damping function that suppresses the generation of vibration due to machining force, and has increased the frequency band in which machining force can be measured. is there.

  First, the configuration of the measurement system leading to the present invention will be described using the model diagram of the measurement system shown in FIG. FIG. 1A shows a general machining force measurement model according to the prior art, and FIG. 1B shows a machining force measurement model according to the present invention. FIG. 1C shows the coordinate axis system in FIGS. 1A and 1B, with the machining point O as the origin, the Z axis in the direction of the main axis, and the in-plane perpendicular to the main axis. The X axis and the Y axis are taken in the direction orthogonal to each other, and the θ axis is taken in the torsion direction around the Z axis. Among the processing forces applied to the tool cutting edge, the component forces acting in the three axes of the X, Y and Z axes are Px, Py and Pz, respectively, and the torsional moment acting around the spindle axis is Mt. Including Mt, it is called the four component force of the processing force. Here, all or a part of the four component forces is set as a measurement target of the machining force.

  Since the four component forces of the working force acting on the machining point O of the tool cutting edge cannot be measured directly, it is transmitted to the measurement position (measurement points A, B, C in FIG. 1 (a)) away from the machining point. The incoming force or the accompanying elastic strain is measured, but the transmission path of this force greatly affects the measurement characteristics of the machining force. That is, if the machining force is quasi-static or in a very low frequency band, the four component forces of Px, Py, Pz, and Mt are calculated from the corresponding measured values Fx, Fy, Fz, and Qt, respectively. It can be obtained simply by converting. FIG. 2 shows the correspondence between these symbols.

  On the other hand, when Px, Py, Pz, and Mt of the machining force varying at the machining point O work, the force is transmitted in series from the machining point O to the measurement points A, B, and C. As the distance from the point O increases, the reciprocal inertia and rotational inertia on the force transmission path increase, and accordingly, the upper limit of the frequency band that can be detected by the detection sensor decreases.

  Therefore, in the present invention, the processing force is not a serial force transmission path to the respective measurement points A, B, and C such as Px and Py, Pz, and Mt described above, but as shown in FIG. The measurement points A ′, B ′, and C ′ are all on a secondary shaft that can be regarded as a rigid body, and a reciprocal inertia and a rotational inertia are suppressed by adopting an integrated detection method that can be regarded as a pseudo same location. By adopting a method of detecting elastic displacement caused by the contact stiffness of the sphere, the machining force measurement system has a simple structure.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following drawings, the same members are denoted by the same reference numerals, and description thereof is omitted or simplified. The drawings schematically show the configuration of the invention, a part of the configuration is omitted or simplified, and the dimensions are not necessarily the same as the actual apparatus. First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows a sectional view of the tool holder 1 of the first embodiment, and FIG. 4 shows an outline of a system configuration for detecting a processing force including the tool holder.

  The countershaft 6 having a chuck 5 at one end capable of gripping the tool 4 is shown in the model diagram of FIG. 1 with respect to the inner cylinder 7 and the outer cylinder 16 screwed and integrated with the inner cylinder. A steel ball and a race surface are connected via a rotatable radial bearing 11 at a position corresponding to the support point A 'and a reciprocating spline bearing 12 at a position corresponding to the support point B' shown in the model diagram of FIG. The outer cylinder 16 shares the spindle axis with the tool 4, the chuck 5, the countershaft 6, the inner cylinder 7 and the tapered portion 3, and is fixed to the tapered portion 3 with screws. ing.

  In FIG. 5, the BB arrow line view in FIG. 3 is shown. The radial bearing 11 is in metal contact between the steel balls 11a and the race surfaces of the inner ring 11b and the outer ring 11c. When a load is applied in the radial direction (that is, the direction perpendicular to the axis) or the axis of the main shaft, Produces elastic deformation at the micron to micron level.

  FIG. 6 shows the state of the assembly around the radial bearing 11. FIG. 7 shows a cross-sectional view taken along the DD line of the cross section passing through the main axis in FIG. 6, and the insertion state of the auxiliary shaft 6 is indicated by an imaginary line in FIG. In addition, the inner cylinder 7 and the outer cylinder 16 in FIG. 6 have drawn the cross section cut into 1/2, in order to help an understanding. First, a magnet disc 34 having an equal thickness having a magnetic field in the thickness direction is fitted to the outer periphery of the space ring 31, and side plates A (made of soft magnetic material are provided on both sides of the space ring 31 and the magnet disc 34. 32) and the side plate B (33) are bonded and integrated in a sandwich shape, and then the inner diameter is slightly larger than the outer diameter of the auxiliary shaft 6 to form a micro gap of 30 to 80 μm in diameter during assembly. To be. The minute gap is filled with the magnetic fluid 60 by vacuum suction, and then the inner ring 11 b of the radial bearing 11 is press-fitted, and the inner ring is fixed in the axial direction of the auxiliary shaft 6 by the bearing nut 35.

  The outer ring 11c is fitted by the end plate 17 in which the outer diameters of the sandwiched magnet disc 34 and the outer ring 11c of the radial bearing that are partly assembled with the countershaft are fitted into the inner cylinder 7 and the O-ring 58 is incorporated in the inner periphery. The magnet disk 34 and the outer ring 11c are fixed in the direction of the main shaft axis by the set screw 36.

  The side plate A (32) and the side plate B (33) are provided with nuisance on the inner peripheral side, and the four members of the side plate B (33), the magnet disc 34, the side plate A (32), and the outer ring 11c. Is fixed to the inner cylinder 7 so that the elastic displacement in the axial direction of the inner ring 11b is not restrained.

  Here, the vibration in the radial direction of the auxiliary shaft induced by the machining force is caused by the magnetic fluid filled between the inner diameter of the side plate A (32), the space ring 31 and the side plate B (33) and the auxiliary shaft 6. Damped and damped by the squeeze effect of the magnetic fluid.

  FIG. 8 shows the components around the spline bearing 12 and their assembly procedure. In order to facilitate understanding, a half cut cross section passing through the axial centers of the space ring 37, the side plate C (38), the side plate D (39) and the magnet disk 40 is shown, and the spline bearing 12 and the torque base 43 are also shown. A part is also shown broken.

  Four spline grooves 6a parallel to the direction of the main shaft axis are formed on the outer periphery of the sub shaft 6, and the main shaft axis is similarly formed at four angular positions at which the outer ring 12d of one spline bearing 12 faces. Four spline grooves 12c parallel to the direction are formed, and four steel balls whose diameters are selected are incorporated in each spline groove so as to give a slight preload between the two spline grooves. These four steel balls are sandwiched between two spacer rings 12a to limit the movement of the steel balls in the direction of the main shaft axis to a clearance fit.

  Further, a nonmagnetic space ring 37 is inserted in the inner periphery of the magnet disk 40, and both sides thereof are bonded in a state of being sandwiched between a soft magnetic side plate C (38) and a side plate D (39). Further, a minute gap having a diameter of 30 μm to 80 μm is formed between the inner diameter of the side plate C and the space ring and the auxiliary shaft 6, and the magnetic fluid 41 is filled in the gap. The end surface of the space ring 37 and the right side surface of the side plate D (39) are finished to be flush with each other after assembly, and when the torque base 43 is assembled to the countershaft 6, the space ring 37 and the side plate D (39) A small gap of 15 μm to 40 μm is formed between the torque base 43, chamfered on the inner periphery of the spacer ring 37, and a concentric relief groove 45 provided on the torque base 43. When the spline bearing 12 and the torque base 43 are assembled to the countershaft 6 and fastened to the countershaft screw portion 6c with the nut 7, a ring-shaped gap is formed between the torque base 43 and the space ring 37. 46 is formed.

  A magnetic fluid 41 is filled in the minute gaps in the cylindrical direction and the thrust direction. With this magnetic fluid, the vibration in the radial direction of the sub shaft and the vibration in the direction of the main shaft axis can be suppressed. The air gap 46 formed by the chamfered portion of the spline bearing 12 and the escape groove 45 is not completely filled with magnetic fluid, and a part of the air remains as a pool of air. By being present, the incompressibility of the magnetic fluid is released, and the mutual interference between the vibration in the axial direction of the auxiliary shaft 6 and the vibration in the direction perpendicular to the axis is relaxed to a negligible level. In addition, radial bearings 11 are arranged at two locations on the countershaft 6, that is, the supporting point A ′ in FIG. 1B, and spline bearings 12 are arranged at the supporting point B ′, both of which have dampers filled with magnetic fluid in a minute gap. By arranging them in parallel, the damping effect can be exhibited not only in the vibration mode in the translation direction but also in the vibration mode in the pitching direction with respect to the spindle axis.

  Note that the nut 47 is made of a copper alloy, and the torque base 43 is screwed to the countershaft 6 to enhance the loosening prevention effect of the screw fastening.

  FIG. 9 shows a CC arrow view in FIG. 3, and FIG. 10 shows an AA arrow view in FIG.

  The torque base 43 is screwed and fixed to the auxiliary shaft 6 by a copper alloy nut 47. On the other hand, a pair of T sensors 49 arranged symmetrically about the rotational axis are screwed and fixed to a T sensor base 48 via a sensor substrate 50, and the T sensor base is fixed to the inner cylinder 7 by bolts 53. ing. Here, the T sensor 49 is provided with a measurement terminal 69 (69 ') on the surface, and the measurement terminal 69 (69') is pressed against the torque dog 44 facing to be able to detect displacement in the rotation direction. The surface opposite to the T-sensor of the torque dog is opposed to the land 51 and the square ring magnet 52 surrounding the land with a minute gap of 15 μm to 40 μm, and the minute gap is filled with a magnetic fluid 57. Yes.

  In addition, the inner cylinder 7 from the outer cylinder 16 is fixed in the axial direction with a suspension bolt through the through hole 56.

  11 is a cross-sectional view taken along line EE in FIG. 3 is a cross-sectional view perpendicular to the axis adjacent to the radial bearing 11. FIG. A pair of X-axis sensor 13 and Y-axis sensor 13 ′ are attached to the inner cylinder 7 in two directions of the X axis and the Y axis perpendicular to each other, and the relative elastic displacement in the direction perpendicular to the axis of the auxiliary shaft 6 with respect to the inner cylinder 7. The X direction component forces Fx and Y of the machining force applied to the tool cutting edge from the difference between the two opposing X-axis sensors 13 and the difference between the two Y-axis sensors 13 'perpendicular to them. The directional component force Fy is converted using the conversion formula shown in FIG. Note that fine adjustment of the detection signals of the X-axis sensor and the Y-axis sensor is performed by changing the thickness of the shim in various ways.

  For the Z-direction component force Pz of the machining force, the Z-axis sensor 14 installed on the Z sensor base screwed to the outer cylinder 16 causes the rear shaft 6 between the rear end surface of the auxiliary shaft 6 and the outer cylinder. The elastic displacement in the axial direction is measured, and converted as if this elastic displacement and Pz are proportional. As the X-axis sensor 13, the Y-axis sensor 13 ′, the T sensor 49, and the Z-axis sensor 14, known sensors can be used, for example, an overcurrent displacement sensor, a capacitance displacement sensor, an optical displacement sensor, or the like. Can do. Furthermore, the X-axis sensor 13 and the Y-axis sensor 13 ′ may be installed on the front support 11, the rear support 12, and the outer cylinder 16 to measure relative displacement with respect to the auxiliary shaft.

  In the conventional example, the effect of thermal strain due to temperature change on the processing force detection was an issue, but here we measured the elastic strain in the direction perpendicular to the thermal strain in question, thereby minimizing the impact. ing.

  Here, FIG. 12 shows a correlation between the load acting on the steel ball and the component force acting on the countershaft in the radial bearing 11 and the spline bearing 12 in this embodiment, and a calculation example of detection sensitivity when detecting the displacement of the acting force. Show. FIG. 20 illustrates the symbols used in the figure. The elastic displacement on the vertical axis in FIG. 12 is proportional to the detection sensitivity. In FIG. 12, (a) column is an X direction component force and Y direction component force, FIG. 12 (b) column is a Z direction component force, FIG. 12 (c) column is a description of rotational moment, load and detection sensitivity. These are the examples of preload 0.

  Here, the elastic displacement at the contact point between the steel ball and the race surface is proportional to the 2/3 power of the load acting on both, and the detection sensitivity decreases as the load increases. Guided by the law. The proportional constants α, β, and γ for the detection sensitivity of Px, Py, Pz, and Mt shown in the figure depend on the diameter of the steel ball and the radius of curvature of the race surface, and also vary depending on the material in contact. It depends on the preload at the time of assembly.

  The signal processing transmission unit 8 includes a detection signal amplification unit from the detection sensor, an A / D conversion unit for the amplified detection signal, and a transmission unit having an antenna. The transmission unit and a personal computer (hereinafter referred to as “PC”). In the meantime, wireless communication is performed by the inexpensive and versatile Wi-Fi method, and the processing force data received by the PC is displayed in a graph on the PC screen and sent to the machine tool. Used as a control command.

  The signal processing transmission unit 8 is covered with a waterproof cover 10 and is protected from moisture such as processing liquid. In this embodiment, a signal transmission module is incorporated in the signal processing transmission unit, and the detection signal is transmitted from the inside, and therefore, a waterproof cover made of nylon resin rich in radio signal transparency is employed.

  In addition, as a power supply means to this rotating tool holder, it shows in FIG. 13 which showed the FF arrow line view in FIG. 4 or FIG. 4, and FIG. 14 which is the GG arrow line view in FIG. As described above, the sector yoke 22 made of a soft magnetic material having a peripheral groove and fixed to the quill 20 of the machine tool through the fixed spacer 21 having a cooling function, and the sector yoke made of the soft magnetic material A fixed coil 23 wound around an outer peripheral groove, a soft magnetic disk 9 having a concentric groove at the outer peripheral position facing the sector yoke with a small gap therebetween, and a coated copper wire wound around the concentric groove By forming a non-contact transformer with the rotating coil 18 and supplying AC power from the oscillation amplifier 27 to the fixed coil 23, alternating current with the same frequency is induced in the rotating coil 18. A DC power source is obtained from the induced AC through a rectifier circuit and a voltage regulator.

  Here, the reason why the fixed-side sector yoke 22 is formed in a sector rather than the entire circumference is to avoid interference with the fork of an ATC (Automatic Tool Change) when replacing the tool holder. For this reason, a high voltage inversely proportional to the angle of inclusion of the fixed coil with respect to the rotating coil 18 is changed from the oscillation amplifier 27 to the fixed coil 23. The same effect can be obtained even when the number of turns of the rotating coil with respect to the fixed coil is set to the number of turns inversely proportional to the included angle.

  Further, when the fixed coil 23 is energized, the temperature of the sector yoke rises. Therefore, a liquid passage hole is provided in the fixed spacer 21, and during operation, the machining liquid is cooled to suppress the temperature rise of the sector yoke 22.

  For work with a short operating time, it is not always necessary to use the non-contact power feeding method as described above. A stationary position where the battery is built in the tool holder and stored in the ATC stocker, etc. However, it is obvious that the same effect can be obtained even if the storage battery is charged and this storage battery is used as a power source during measurement mounted on the spindle.

  Further, in this embodiment, the stationary coil and the rotating coil are opposed to each other to form a non-contact transformer, and the power is supplied to the rotating body. In addition to this, an LCR resonance circuit in which a capacitor and a resistor are combined can be configured to supply power to a signal processing / transmission unit that rotates in a non-contact manner. In this case, power can be supplied in a non-contact manner even when the fixed coil and the rotating coil are not far away from each other, even if they are further apart.

In this embodiment, the distance from the tool cutting edge, that is, the processing point, to the steel ball position of the radial bearing that is the support point close to the chuck is a, and the spline that is the support point far from the chuck from the steel ball position of the radial bearing. If the distance to the ball position of the bearing 12 is L and the load applied to the machining point in the direction perpendicular to the axis is P, the load applied to the radial bearing in the direction perpendicular to the axis is: (1 + a / L) P
Load on spline bearing: (a / L) P
By making it possible to detect the elastic displacement in the direction perpendicular to the axis in the vicinity of the radial bearing, a load with high sensitivity approximately (1 + a / L) times the load of the support point obtained by conversion from the elastic displacement. A P detection signal is obtained.

  That is, since the load in the direction perpendicular to the axis applied to the radial bearing is larger by P than the load in the direction perpendicular to the axis applied to the spline bearing, the structure that increases the support rigidity of the radial bearing, which is a support point close to the chuck to which a large load is applied. Is desirable. Thereby, since the rigidity of a tool blade edge can be improved, more stable processing can be performed and processing force can be detected with high sensitivity even in processing with a large processing load.

Here, a design method of the support rigidity will be described with reference to FIG. FIG. 15 shows an example of trial calculation of displacement at the contact point when a concave spherical surface is contacted with a Φ1.5 mm steel ball (elasticity in the load direction due to a vertical load when a steel ball made of bearing steel is pressed against the raceway surface with a load of 1N. It is a figure which shows the calculation example of a displacement. Thus, the support rigidity can be designed freely by changing the diameter of the steel ball and the curvature of the concave spherical surface. In addition, by applying a so-called preload in advance, a substantial radius of curvature R ₂ of the concave spherical surface in the drawing can be increased, the gradient of [elastic displacement / 2R ₂ ] can be decreased, and rigidity can be increased. be able to. The above description is given for one steel ball and a concave spherical surface. However, when the number of steel balls increases, the same description is effective only by multiplying the proportional coefficient accordingly. Further, as apparent from FIG. 12, the relationship between the detection sensitivity, that is, the elastic displacement and the load is generally inversely proportional to the 1/3 power of the load. By performing the gain correction so as to become more convenient, the convenience of processing load detection is further enhanced. It should be noted that the above-described support rigidity and processing force detection sensitivity are naturally in a trade-off relationship, and the support rigidity and detection sensitivity corresponding to the processing load are selected.

  For example, in the case of a large-diameter hole, since the axial Fz is relatively larger than Fx and Fy, the radius of curvature of the raceway surface with respect to the steel ball of the radial bearing is reduced, and the rigidity in this direction is increased. Thus, the processing force can be measured in a more stable processing state. Similarly, in the end mill machining with a small diameter, the rigidity design of the radial bearing and the spline bearing according to various machining applications is possible, such as the rigidity design of the support point with the increased sensitivity of Fx and Fy.

  As described above, according to the tool holder 1 of the present embodiment, the X-axis direction, the Y-axis direction, and the Z-axis direction between the race surfaces of the inner and outer rings of the radial bearing arranged at the support point close to the chuck and the steel balls are used. Fx, Fy, and Fz are detected from the amount of elastic deformation, and Mt is detected from the elastic deformation in the rotational direction between the spline groove of the spline bearing disposed at the support point far from the chuck and the steel ball. In other words, the detection sensor is as close as possible to the machining point, and the reciprocating inertia and rotational inertia from the machining point to the detection sensor are made smaller, so that it is possible to detect the machining force up to a higher frequency band. This makes it possible to instantaneously detect a minute chipping or breakage of the cutting edge.

  Normally, in the elastic support system of the tool composed of the front stage support body and the rear stage support body, there is a concern that vibration is induced by the processing force, but in the present embodiment, the radial support 11 and the spline bearing 12 are included. By adding a damping function that utilizes the squeeze effect between both supports and the inner cylinder or outer cylinder, the processing is stabilized and the processing force up to a higher frequency band can be accurately detected. .

  Furthermore, in this embodiment, since it is comprised so that non-contact electric power feeding to the rotating tool holder 1 is attained, it is relieved from the complexity of the charge operation | work which had to be repeated regularly.

  In addition, a highly versatile Wi-Fi system is adopted as a communication means, and by using a commercially available general-purpose Wi-Fi module, measurement data can be wirelessly communicated and a processing force detection function is provided. Tool holders can be constructed at low cost.

  In this type of measurement system, the measurement value is generally easily affected by temperature, but in this embodiment, the processing force is detected by a change in displacement in a direction perpendicular to the thermal expansion direction due to temperature. The feature is that the processing force detection signal is extremely insensitive to thermal expansion due to temperature rise. That is, the temperature influence on the detection signal can be suppressed and the reliability of the measurement value can be improved.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 16 is a cross-sectional view of the tool holder 1 according to the second embodiment, FIG. 17 is a cross-sectional view taken along the line II in FIG. 16, and FIG. 18 is a cross-sectional view taken along the line HH in FIG. In the first embodiment, the stationary coil 23 wound around the outer periphery of the sector-like sector yoke 22 is different from the rotating coil 18 wound around the outer periphery of the rotating soft magnetic disc 9 in the radial direction of the soft magnetic disc 9. It was arrange | positioned in the position which the outer periphery which spaced apart the micro gap | interval.

  On the other hand, in the second embodiment, a concentric groove is provided on the end surface near the outer periphery of the soft magnetic disk 9 ', and a rotating coil 18' wound with a coated copper wire is embedded in this groove. On the other hand, a sector yoke 22 'made of a soft magnetic material is arranged with a slight gap with respect to the end face of the soft magnetic disk. Arc-shaped grooves having the same radius as the rotating coil 18 'are provided on the upper and lower surfaces of the sector yoke, and a fixed coil 23' wound with a coated copper wire is embedded. The sector yoke 22 'is fixed to the quill 20 via a fixed spacer 21' so that both the fixed coil 23 'and the rotating coil 18' are opposed to each other with a sub-millimeter order gap. In this way, the same non-contact power feeding is possible even if the fixed coil 23 ′ and the rotating coil 18 ′ are arranged in the end face direction.

  In the second embodiment, the fixed coil arcs are opposed to each other in the range of about 1/3 of the rotating coil. However, this is considered so as not to become an obstacle when the automatic tool change is performed. If it does not become an obstacle when changing tools, or if it is possible to slightly increase the attachment / detachment stroke when changing tools, a ring-shaped fixed coil is used instead of the arc-shaped fixed coil facing partly. In addition, the same non-contact power feeding is possible by making the rotating coil and the stationary coil face each other over the entire circumference.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be easily made without departing from the spirit of the present invention. Can be inferred.

  For example, in each of the above embodiments, the rotating coils 18 and 18 ′ wound with the coated copper wire are used, but instead of this, as shown in FIG. 19, the rotating coil wound with the coated copper wire is used. A rotating coil reinforced by aligning and winding high tensile strength resin fibers on the outer periphery may be used. In response to the recent demand for high-speed rotation of several tens of thousands of revolutions per minute, the coated copper wire winding alone breaks due to the centrifugal force of the copper wire itself. Therefore, in this modification, the outer circumference of the wound rotating coil is wound with a polyamide resin fiber, and the gap between the windings is reinforced with an adhesive to reinforce it, enabling use at higher rotational speeds. Yes.

  In the first embodiment, the magnetic fluid is filled in the minute gap to suppress the vibration. However, even if the minute gap is filled with a general-purpose fluid such as machine oil, the fluid in the minute gap is caused by the capillary phenomenon. It is confirmed that the damping effect similar to that described above can be obtained. In this case, the magnet disks 34 and 40 and the square ring magnet 52 do not need to have magnetism, and any material can be used as long as it is hard enough to form a predetermined minute gap.

  Furthermore, in the first embodiment, the waterproof cover 10 made of nylon resin is used as the waterproof cover 10. However, the waterproof cover 10 made of resin is also made of a nylon resin material that is highly permeable to radio transmission from the internal signal processing / transmission unit 8. The force exceeds the breaking strength of the nylon resin, resulting in damage. Therefore, for such high-speed rotation, high-speed rotation is enabled by using a waterproof cover made of GFRP (Glass Fiber Reinforced Plastics) molded with a resin reinforced with glass fiber. Note that this is not the case when the detection signal from the signal processing / transmitting unit 8 is transmitted by an antenna provided outside the waterproof cover, and it is not necessary to select a material in consideration of electromagnetic waves for the waterproof cover.

  As described above, according to the present invention, by providing a tool holder having a function of detecting a machining force, machining data during machining can be constantly collected, and a constantly monitoring system for machining behavior can be constructed. In particular, tool cutting edge defects and abnormal wear that frequently occur during machining of stainless steel, nickel alloy, titanium alloy, etc., which have high strength and heat resistance, can be predicted at the initial stage of minor damage, and defective defects in the processed product can be suppressed. .

DESCRIPTION OF SYMBOLS 1 Tool holder 2 Main axis | shaft 3 Tapered part 4 Tool 5 Chuck 6 Sub axis | shaft 6a Spline groove 6b Bearing part 6c Sub axis screw part 7 Inner cylinder 8 Signal processing and transmission part 9, 9 'Soft magnetic disc 10 Waterproof cover 11 Radial bearing 11a Steel ball 11b Inner ring 11c Outer ring 12 Spline bearing 12a Spacer ring 12b Steel ball 12c Spline groove 12d Outer ring 13 X axis sensor 13 'Y axis sensor 14 Z axis sensor 15 T sensor base 16 Outer cylinder 17 End plate 18, 18' Rotating coil 19 Z sensor base 20 Quill 21, 21 'Fixed spacer 22, 22' Sector yoke 23, 23 'Fixed coil 24 Terminal block 25 Terminal box 26 Waterproof connector 27 Oscillator amplifier 28 Lead wire 29 Receiver 30 Personal computer, PC
31 Space ring 32 Side plate A
33 Side plate B
34 Magnet disc 35 Bearing nut 36 Set screw 37 Space ring 38 Side plate C
39 Side plate D
40 Magnet disk 41 Magnetic fluid 42 Fixing hole 43 Torque base 44 Torque dog 45 Escape groove 46 Air gap 47 Nut 48 T sensor base 49 T sensor 50 Sensor substrate 51 Land 52 Square ring magnet 53 Bolt 54 Sensor substrate 55 Stop screw 56 Through hole 57 Magnetic fluid 58 O-ring 59 O-ring 60 Magnetic fluid 61 Reinforcement coil 67 Yoke fixing bolt 68 Lead wire 69, 69 'Measuring terminal 70 Spindle axis

Claims (10)

A tapered portion capable of fitting with the spindle of the machine tool;
A countershaft having a chuck for gripping a tool at the tip, and arranged coaxially with the tapered portion;
Two types of support portions that are interposed between the tapered portion and the auxiliary shaft and support the auxiliary shaft;
A detection sensor mounted on the countershaft to detect elastic displacement or elastic strain of the countershaft with respect to the tapered portion;
Signal processing means for processing a detection signal from the detection sensor and transmission means for transmitting the processed signal;
A tool holder comprising a power supply means for supplying power to the detection sensor, signal processing means and transmission means,
The support portion is of two types, a radial bearing disposed on the front end side of the counter shaft and a spline bearing disposed on the rear end side,
The detection sensor has the taper portion in at least one direction out of four directions including an axial direction of the main shaft, two directions orthogonal to each other in a cross section perpendicular to the axial center, and a torsional direction around the axial center. A tool holder for detecting elastic displacement of a counter shaft. The tapered portion includes an outer cylinder fixed to the tapered portion and an inner cylinder fixed to the outer cylinder,
The countershaft is inserted into the inner cylinder,
2. The tool holder according to claim 1, wherein the detection sensor is mounted on one of the two types of support portions, the outer cylinder, or the inner cylinder. In the radial bearing and the spline bearing, each outer ring is fixed to the inner cylinder,
The countershaft has a plurality of spline grooves parallel to the axial direction, and the spline grooves are attached to the spline bearing while inserting the steel balls of the spline bearing and are fixed to the inner ring of the radial bearing. The tool holder according to claim 1, wherein the tool holder is a tool holder.   The radial bearing or the spline bearing has a steel ball which allows elastic deformation, and the contact surface of the steel ball in each bearing has a desired range so that the elastic displacement of the secondary shaft due to the elastic deformation falls within a desired range. The tool holder according to any one of claims 1 to 3, wherein a diameter of the steel ball with respect to a curvature is determined.   The tool holder according to any one of claims 1 to 4, wherein the radial bearing is configured by a radial ball bearing, and the spline bearing is configured by a ball spline bearing.   2. A detection sensor for detecting an elastic displacement of the auxiliary shaft in two directions orthogonal to each other in a cross section perpendicular to the axis of the main shaft is disposed in the vicinity of the radial bearing. The tool holder in any one of 5 thru | or 5.   The detection sensor for detecting at least one direction is arrange | positioned in the vicinity of the said spline bearing among the two directions which consist of the axial direction of the said main axis | shaft, and the twist direction around an axial center. Tool holder according to one of the above.   At least one of the two types of support portions is at least one of four directions including an axial direction of the main shaft, two directions orthogonal to each other in a cross section perpendicular to the axial center, and a torsional direction around the axial center. On the other hand, it has a damping function, The tool holder in any one of Claim 1 thru | or 7 characterized by the above-mentioned.   At least one of the two types of support portions includes a ring member that is fixed to the support while forming a minute gap between the counter shaft and the damping function fills the gap with fluid. The tool holder according to claim 8, wherein the tool holder is exhibited by a squeeze effect generated by.   The fluid is a magnetic fluid, and the ring member is made of a magnetic material having a magnetic force, and the magnetic material exhibits a function of suppressing leakage of the magnetic fluid by generating a magnetic field loop with respect to the gap. The tool holder according to claim 9, wherein the tool holder is provided.

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