JPH0675816B2 - Mounting structure for machine tool detector - Google Patents

Description

Detailed Description of the Invention

[Industrial applications]

The present invention relates to a mounting structure for a machine tool detector that detects a cutting force or a cutting resistance during machining of a workpiece.

[Prior art]

In recent years, with the practical use of production systems such as FMC and FMS, machine tools such as machining centers and NC lathes have become unmanned, and in-process measurement of cutting conditions for monitoring abnormalities during workpiece machining has become possible. The measurement of cutting force and cutting force, which is strongly desired and has a great relation to tool abnormalities, has become a major issue. Conventionally, for the measurement of cutting force and cutting resistance, strain measurement performed by incorporating a strain gauge or a crystal oscillator into a jig or the like, and measurement of a load current of a spindle motor have been attempted.

[Problems to be Solved by the Invention]

However, in strain measurement, since the detector is expensive and the rigidity of the detector itself is low, it is easily damaged when an excessive force is applied. In both strain measurement and motor load current measurement, when measuring a small cutting force or cutting resistance such as a small diameter drill or tap, the detection sensitivity is low, so it is affected by noise etc. It is difficult to measure the cutting force and cutting resistance, which has been a major factor in preventing unmanned operation of machine tools. The present invention has been made in view of such conventional problems, and has rigidity to withstand a large cutting force and cutting resistance,
In addition, the high detection sensitivity enables accurate detection of even small cutting forces and cutting resistances, providing a mounting structure for machine tool detectors that can properly perform inner process measurement for unmanned operation. The purpose is to do.

[Means for Solving the Problems]

To achieve this object, according to the present invention, a through hole 5 for allowing a feed screw shaft 11 of a machine tool to penetrate through the center of a circular film sheet having electrode layers 3a and 3b formed on both surfaces of a piezoelectric material layer 2 is formed. A mounting structure of a machine tool detector that detects a cutting force or a cutting resistance of a machine tool by a piezoelectric sensor 1 formed in an annular shape by forming a support bearing 15a at the axial end of the feed screw shaft 11. 15b
Fit the inner ring of the support bearing 15
The piezoelectric sensor 1 is sandwiched by the spacer rings 20a, 20b between the thrust direction end faces of the outer rings 19, 21 of the a, 15b and the end face 18a of the bearing hole 18a in which the accommodating portion of the piezoelectric sensor 1 is formed. Further, the feed screw shaft 11 is attached so as to penetrate the through hole 5. The present invention also forms an annular shape by forming a through hole 5 for the feed screw shaft 11 of a machine tool to penetrate in the center of a circular film sheet having electrode layers 3a and 3b formed on both surfaces of the piezoelectric material layer 2. The mounting structure of a machine tool detector that detects the cutting force or cutting resistance of a machine tool by the piezoelectric sensor 1 described above, and the inner rings of the support bearings 15a and 15b are fitted to the axial ends of the feed screw shaft 11. At the same time, a housing portion for the piezoelectric sensor 1 is formed on the thrust bearing sides of the outer rings 19, 21 of the support bearings 15a, 15b, and the piezoelectric sensor 1 is housed in the housing portion and the feed screw shaft is formed.
11 is attached so as to penetrate the through hole 5, and the spacer ring 25 is incorporated into the outer ring 19 of the support bearing 15b.

[Action]

In such a mounting structure for a machine tool detector of the present invention, the thrust bearing end faces of the outer rings 19, 21 of the support bearings 15a, 15b and the end face of the bearing hole 18a in which the accommodating portion of the piezoelectric sensor 1 is formed. Since the piezoelectric sensor 1 is mounted between the spacers 18a so as to be sandwiched by the spacer rings 20a and 20b, the piezoelectric sensor 1 can be mounted on the machine tool without significantly changing the structure of the machine tool itself. The present invention further includes an outer ring 19 of the support bearings 15a and 15b,
Since the storage portion of the piezoelectric sensor 1 is formed on the thrust direction side of 21, the piezoelectric sensor 1 can be integrally incorporated in the support bearings 15a and 15b, and therefore a storage space for the piezoelectric sensor 1 is separately secured in the bearing hole 18a. Since it is not necessary, the piezoelectric sensor 1 can be attached to the machine tool without significantly changing the structure of the machine tool itself. Further, in the mounting structure for the machine tool detector of the present invention, since the detector is a film sheet piezoelectric sensor,
Even if it receives a large cutting force or cutting resistance, it will not be damaged due to the high rigidity of the detector, and since the film thickness is thin, the deformation of the detector will be minimal even if it receives a cutting force or cutting resistance, Does not affect processing accuracy. Further, the sensitivity of the detector can be easily increased by increasing the area of the piezoelectric sensor, and by further increasing the area, the load per unit area can be reduced and the rigidity can be further increased. In addition, because of its high detection sensitivity, it has a wide measurement range from 1 Kgf to over 1,000 Kgf and can accurately measure the cutting force and cutting resistance even with small diameter drills and taps with small cutting force and cutting resistance.

【Example】

FIG. 1 is a cross-sectional view showing a detector used in the mounting structure for a machine tool detector according to the present invention, and FIG. In FIG. 1, a detector 1 as a transducer that detects a force due to a cutting force or a cutting resistance has a piezoelectric material layer 2 using a piezoelectric material in the center, and electrode layers 3a and 3b are provided on both surfaces of the piezoelectric material layer 2. The insulating sheets 4a and 4b are fixed to the outside of the electrode layers 3a and 3b by adhesion or the like, and the piezoelectric material layer 2 and the electrode layers 3a and 3b form a film sheet type piezoelectric sensor. Specifically known as piezoelectric film
A piezoelectric element typified by PZT can be used, and this piezoelectric element has a film shape and a thickness of about 0.2 mm. In addition, even if the Young's modulus is small, the deformation when a load is applied is very small, so as will be made clear later, even if it is directly incorporated into the feed screw mechanism of a machine tool, the processing accuracy due to the deformation of the piezoelectric element will be small. It doesn't matter. Furthermore, since the piezoelectric constant of the piezoelectric element (generated charge amount per unit force) is constant regardless of the size of the area that receives the force, increasing the area reduces the load per unit area without lowering the sensitivity. The rigidity can be increased. In FIG. 1, the detector 1 further has a through hole 5 formed in the center for penetrating a feed screw shaft of a machine tool, and the detector 1 is attached and fixed as shown by an imaginary line in FIG. You may make it provide the bolt through hole 6 for doing. According to the detector 1 shown in FIGS. 1 and 2, it is possible to measure over a wide range from 1 kgf to 1000 kgf by switching the capacitor capacity of the charge amplification circuit (charge amplifier) that extracts the detection output of the detector 1. And a resolution of about 100 gf can be realized. Next, the mounting structure of the present invention to the machine tool of the detector 1 shown in FIGS. 1 and 2 will be described. First, although there are various types of NC machine tools provided with a detector, the NC lathe shown in FIG. 3 and the vertical machining center shown in FIG. 4 are typical ones. In the NC lathe shown in Fig. 3, the motion for cutting the workpiece is in two directions of X and Z axes as shown by the arrow, and in the machining center of Fig. 4, it is in three directions of X, Y and Z axes. is there. Here, taking the machining center of FIG. 4 as an example, movements in the X, Y, and Z-axis directions for cutting a workpiece are all obtained by converting the rotation of a pulse motor into a linear movement by a ball screw mechanism. That is, in FIG. 5, the movement of the saddle 12, which is provided on the bed 7 so as to be movable in the Y-axis direction, in the Y-axis direction is
The feed screw shaft 10a is rotated by the pulse motor 9a provided in the saddle 12 to transmit the linear movement of the feed nut 11a screwed to the feed screw shaft 10a to the saddle 12. The movement of the work table (not shown) installed on the saddle 12 in the X-axis direction is such that the pulse motor 9b provided on the saddle 12 rotates the feed screw shaft 10b to screw it onto the feed screw shaft 10b. Transmits linear movement of feed nut 11b to the work table. Further, in the Z-axis direction movement of the spindle head 14 by the column 13, the feed screw shaft 10c is rotated by the pulse motor 9c provided in the column 13, and the linear movement of the feed nut 11c screwed onto the feed screw shaft 10c is performed by the spindle head. Move to Z-axis by telling 14. As is clear from the conversion into linear motion by the ball screw mechanism shown in FIG. 5, the axial component force Fa applied to the feed screw shafts 10a to 10c at the time of machining the work is the cutting force Fc in each direction and the slide force. It is given as the sum of the frictional resistance Ff on the surface. Fa = Fc + Ff (1) Therefore, according to the present invention, the detector 1 shown in FIGS. 1 and 2 may measure the component force Fa in the axial direction of the feed screw shaft in the formula (1). Install on a machine tool. Although it is possible experimentally to separately measure the cutting force Fc shown in the equation (1), it is possible to use the detector 1 in the actual machine.
However, in the present invention, the detector 1 can measure the force Fa obtained by adding the frictional resistance Ff to the cutting force Fc. Thus friction resistance
Since the cutting force Fc is measured by adding Ff, the frictional resistance Ff also increases or decreases in proportion to the cutting force Fc, so even if the frictional resistance Ff is included, the sum of the two should be measured as the actual cutting force. There is no problem with. Further, since the frictional resistance is considerably smaller than the cutting force, there is no practical problem. FIG. 6 is an explanatory view showing an embodiment of the detector mounting structure of the present invention. In this embodiment, the detector is provided on the ball screw support bearing of the feed screw shaft. To do. In FIG. 6, a feed screw shaft 10 screwed with a feed nut 11 connected to a work table or a tool table is a pair of support bearings in which a left shaft end is incorporated in a bearing portion 17.
It is rotatably supported by 15a, 15b, and the right shaft end is rotatably supported by a ball bearing 15c.The ball bearing support bearing part 17 incorporating the support bearings 15a, 15b is provided with 2 The detector 1 shown in Fig. 2 is attached. The mounting structure of the detector 1 on the bearing 17 is as shown in FIG. That is, the detector 1 has the support bearing 15 located inside.
It is assembled between b and the end surface 18a of the bearing hole 18 on the fixed side. Specifically, the detector 1 is installed in a state of being sandwiched between the pair of spacer rings 20a and 20b between the outer ring (outer ring) 19 of the support bearing 15b and the end surface 18a of the bearing hole 18, and Support bearing built in outside
The detector 1 is clamped and fixed by bolting the presser foot 22 from the outside to the end surface of the outer ring 21 of 15a. In addition, the spacer rings 20a and 20b that sandwich the detector 1 from both sides are L
An O-ring having a V-shaped cross-section, and the inner and outer sliding contact surfaces seal the detector 1 incorporated inside.
23 intervening. In the mounting structure in which the detector 1 is incorporated in the bearing portion 17 of the feed screw shaft 10 shown in FIGS. 6 and 7 as described above, the cutting resistance from the work table or the cutting from the tool base during cutting is performed. The force acts in the axial direction of the feed screw shaft 10 by the horizontal movement of the feed nut 11 due to the rotation of the feed screw shaft 10, and through the outer ring 19 of the support bearing 15b provided in the bearing portion 17 the spacer rings 20a and 20b. Join the detector 1 sandwiched inside. Specifically, when a load corresponding to the cutting force or cutting resistance in the left direction is applied to the feed screw shaft 10, the compressive force of the detector 1 is reduced, and the feed screw shaft is adjusted to the cutting force or cutting resistance in the right direction. When a force is applied, the compressive force of the detector 1 increases conversely. Of course, since the capacitor provided in the feedback circuit of the charge amplification circuit that takes out the detection output of the detector 1 when the cutting process is started is discharge reset and the voltage output is in the initial state, the movement of the feed nut 11 is moved. It is possible to take out an output voltage having different polarities depending on the direction and proportional to the cutting force or cutting resistance received by the feed screw shaft 10. FIG. 8 shows the bearing portion 1 of the lead screw shaft 10 shown in FIGS.
FIG. 9 is a cross-sectional view showing another built-in structure for incorporating the detector 1 in 7. That is, in the embodiment shown in FIGS. 6 and 7, a space for incorporating the detector 1 has to be newly added to the bearing hole 18 for incorporating the support bearings 15a and 15b. Accompany. Therefore, in the structure shown in FIG. 8, the detector 1 is mounted without changing the bearing hole 18. That is, in the embodiment of FIG. 8, the detector housing 24 is formed by cutting out the right end of the outer ring 19 of the support bearing 15b, and the detector 1 is assembled in the detector housing 24 to form the outside. To L-shaped spacer ring 25, and an O-ring 23 for sealing the detector 1 is provided on the inner and outer contact surfaces of the spacer ring 25. In the mounting structure of FIG. 8 as described above, the detector 1 can be assembled integrally with the support bearing 15b, so that a mounting space for the detector is separately secured in the bearing hole 18 as shown in FIG. No need, more practical. In the above-mentioned embodiment, the case where the detector is incorporated into the feed screw mechanism of the work table or the tool base is taken as an example, but similarly, the feed nut provided in the feed screw mechanism of the main spindle system is used. Alternatively, the detector may be incorporated in the support bearing.

【The invention's effect】

As described above, according to the present invention, the piezoelectric sensor 1 is provided between the thrust-direction end surfaces of the outer rings 19, 21 of the support bearings 15a, 15b and the end surface 18a of the bearing hole 18a in which the accommodating portion of the piezoelectric sensor 1 is formed. Is mounted so as to be sandwiched by the spacer rings 20a and 20b, the piezoelectric sensor 1 can be mounted on the machine tool without significantly changing the structure of the machine tool itself. Furthermore, since the accommodating portion for the piezoelectric sensor 1 is formed on the thrust bearing side of the outer rings 19, 21 of the support bearings 15a, 15b, the piezoelectric sensor 1 can be integrally incorporated in the support bearings 15a, 15b, and therefore the bearing holes Since it is not necessary to separately secure a storage space for the piezoelectric sensor 1 in 18a, the piezoelectric sensor 1 can be used without significantly changing the structure of the machine tool itself.
Can be attached to a machine tool. Further, as an effect peculiar to the embodiment, in the mounting structure of the machine tool detector of the present invention, a film sheet piezoelectric sensor is used as a detector for detecting the cutting force or the cutting resistance of the machine tool. Therefore, the detection sensitivity to load changes is high.For example, by switching the capacitor capacity of the charge amplification circuit that extracts the detection output of the detector, a high cutting force or cutting resistance of 1 kgf to 1000 kgf can be obtained. Can be measured with
As a result, not only tool abnormality but also feedback control for obtaining a constant cutting force or cutting resistance based on the detection output of the cutting force or cutting resistance is possible. Further, since the detector uses a piezoelectric sensor in the form of a film sheet, the deformation in the thickness direction of the detector is very slight even when receiving a force corresponding to the cutting force or the cutting resistance due to the thin film pressure. Even if it is installed in the bearing part of the feed nut or the feed screw shaft, it does not affect the machining accuracy of the machine tool. Further, since the sensitivity of the detector is constant even if the area of the piezoelectric sensor is changed, the load per unit area can be reduced by increasing the area of the piezoelectric sensor, and thus the rigidity of the detector can be increased. . Furthermore, because it is a detector that uses a film sheet piezoelectric sensor, it is extremely thin with a thickness of 0.2 mm or less, is small, and is lightweight, so it is easy to directly detect the cutting force or cutting resistance of machine tools. Can be incorporated. Furthermore, because it is a detector that uses a film sheet piezoelectric sensor. Mass production is easy, and the cost of the detector can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a detector used in the mounting structure for a machine tool detector of the present invention; FIG. 2 is a plan view showing the detector of FIG. 1 partially broken away; Is an explanatory view of an NC lathe; FIG. 4 is an explanatory view of a vertical machining center; FIG. 5 is an exploded view showing a ball screw mechanism of the machining center; FIG. 6 is an implementation structure of a machine tool detector of the present invention. Fig. 7 is an explanatory view showing an example; Fig. 7 is an explanatory view showing the bearing portion of Fig. 6 taken out; Fig. 8 is an explanatory view showing a mounting structure in which a detector is integrally assembled with a support bearing. 1: Detector 2: Piezoelectric material layer 3a, 3b: Electrode layer 4a, 4b: Insulation sheet 5: Through hole 6: Bolt hole 7: Bed 9a to 9c: Pulse motor 10, 10a to 10c: Lead screw shaft 11, 11a ~ 11c: Feed nut 12: Saddle 13: Column 14: Spindle head 15a, 15b: Support bearing 15c: Ball bearing 17: Bearing part 18: Bearing hole 19, 21: Outer ring (outer ring) 20a, 20b, 25: Spacer Ring 22: Presser foot 23: O-ring 24: Detector storage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kihachiro Toho 150 Nikamicho, Takaoka-shi, Toyama Prefecture Central Research Institute, Toyama Prefectural Industrial Technology Center (72) Inventor Masahiro Kakuzaki 25-4 Tomodawari, Iino, Toyama, Toyama Prefecture Toyama (56) Reference JP-A-49-86067 (JP, A) JP-A-50-7182 (JP, A) JP-A-62-188649 (JP, A) JP-A-60- 85854 (JP, A)

Claims (2)

[Claims] 1. A circular film sheet having electrode layers 3a and 3b formed on both sides of a piezoelectric material layer 2 is formed in an annular shape by forming a through hole 5 through which a feed screw shaft 11 of a machine tool penetrates in the center thereof. A mounting structure of a machine tool detector for detecting a cutting force or a cutting resistance of a machine tool by the piezoelectric sensor 1 described above, wherein a support bearing 15 is provided at an axial end of the feed screw shaft 11.
While fitting the inner rings of a and 15b, the thrust bearing end faces of the outer rings 19 and 21 of the support bearings 15a and 15b and the end face 18a of the bearing hole 18a in which the accommodating portion of the piezoelectric sensor 1 is formed. A mounting structure for a machine tool detector, characterized in that the piezoelectric sensor 1 is mounted so as to be sandwiched by spacer rings 20a, 20b, and the feed screw shaft 11 penetrates the through hole 5. 2. A circular film sheet having electrode layers 3a and 3b formed on both sides of a piezoelectric material layer 2 is formed in an annular shape by forming a through hole 5 through which a feed screw shaft 11 of a machine tool penetrates at the center thereof. A mounting structure of a machine tool detector for detecting a cutting force or a cutting resistance of a machine tool by the piezoelectric sensor 1 described above, wherein a support bearing 15 is provided at an axial end of the feed screw shaft 11.
While accommodating the inner rings of a and 15b, a housing portion of the piezoelectric sensor 1 is formed on the thrust bearing sides of the outer rings 19 and 21 of the support bearings 15a and 15b, and the piezoelectric sensor 1 is housed in the housing portion.
A mounting structure for a machine tool detector, characterized in that the feed screw shaft 11 is mounted so as to pass through the through hole 5, and the spacer ring 25 is incorporated in the outer ring 19 of the support bearing 15b.