JP4373297B2 - Processing equipment - Google Patents

Description

  The present invention relates to a machining apparatus, and more particularly, to a configuration of a detection means for detecting machining stress applied to a tool or a workpiece in a machining apparatus such as a machine tool.

  In general, a tool or workpiece mounted on a machine tool is subjected to an axial processing stress when the workpiece is processed. If the processing stress is excessive, the tool or the workpiece may be damaged. For example, when turning, a tool or workpiece is attached to the spindle shaft, and cutting is performed while rotating the tool or workpiece. In this case, stress in the rotational direction is applied to the tool or workpiece. And stress in the axial direction.

  For example, if you want to make a relatively deep hole with a very small diameter in the workpiece, use a small diameter drill, but the small diameter drill has low strength and also forms a deep hole in the workpiece. As a result, the processing stress increases, so the drill often breaks, the processing efficiency is low, and the processing cost increases.

Therefore, there is provided a machining device that detects the rotational load and feed load of a tool and interrupts the feed operation of the tool when the detected value exceeds a predetermined load limit value with the rotational load and feed load as variables. It is known (for example, refer to Patent Document 1 below). In this processing apparatus, the feed operation is controlled so that the detected values of the rotational load and feed load of the tool do not exceed the load limit values, so that the tool can be prevented from being damaged by the rotational load and feed load. In this processing apparatus, the bearing body is supported in the form of a cantilever by the flexible support body that constitutes the feed deformation portion, and the bearing body is directly engaged with the spindle shaft in the axial direction. A strain sensor is attached to the support member, and the deformation amount of the support member is detected by the strain sensor. As a general method for detecting the load on a tool, a method for measuring the power consumption (current value) of a drive motor that generates a driving force for rotating or feeding a tool is known.
JP 2001-341014 A

  However, the above-described processing apparatus has a problem that it is difficult to accurately detect a processing stress because the detection sensitivity and the detection error of the deformation amount are easily changed depending on the mounting state of the strain sensor with respect to the support. In addition, since it is necessary to provide a detection point in the middle of the power transmission path for transmitting the driving force in the feed direction, there is a problem that the degree of freedom in design is small and the design change is difficult.

  In addition, in the method of detecting the power load of the drive motor, the transmission load of the power transmission path from the drive motor to the tool is also detected, so that it is possible to accurately detect the weak machining load that a small diameter drill can withstand. There is a problem that is difficult.

  Therefore, the present invention solves the above-mentioned problems, and the problem is that it is possible to detect the processing stress received by the tool or the workpiece with high accuracy and to have a degree of freedom in design such as the position of the detection point. An object of the present invention is to provide a processing apparatus having a detection means that is high and can be easily provided in various apparatuses.

In view of such circumstances, a machining apparatus according to the present invention includes a spindle shaft on which a tool or a workpiece is fixed, and a support body including a bearing structure that rotatably supports the spindle shaft via a fluid in an axial direction. And a detecting means for detecting a processing stress received by the tool or workpiece, the detecting means including a detection electrode fixed to the spindle shaft, and the axial direction with respect to the detection electrode A fixed electrode disposed oppositely and connected to the support in a state fixed at least in the axial direction, and detection for directly or indirectly detecting a capacitance between the detection electrode and the fixed electrode And a circuit.

  According to the present invention, when the tool or workpiece is subjected to a processing stress in the axial direction, the fluid of the bearing structure is interposed between the spindle shaft and the support that rotatably supports the spindle shaft through the fluid in the axial direction. A relative displacement in the axial direction occurs against the pressure, and this changes the capacitance between the detection electrode and the fixed electrode. Therefore, the amount of displacement is found by detecting the capacitance using the detection circuit. To do. In this case, by using a bearing structure that is axially supported via a fluid, the amount of axial displacement between the spindle shaft and the support is between the machining stress experienced by the tool or workpiece. Since it has a positive correlation, it is possible to know the machining stress in the axial direction received by the tool or workpiece by the amount of displacement. In the present invention, since the relative displacement in the axial direction between the spindle shaft and the support is detected by a change in capacitance, even a slight displacement of the bearing structure caused by machining stress can be measured with high accuracy. In addition, since the relative displacement between the spindle shaft and the support body can be detected in a non-contact manner, it is not necessary to provide a new contact portion in addition to the spindle shaft bearing structure by the support body. Is not required, and the detection means does not depend on the mechanical contact state, so that the change in detection sensitivity can be reduced. In addition, it is only necessary to detect the relative displacement between the spindle shaft and the support body regardless of the transmission path of the feed driving force, so the position of the detection point can be set freely, increasing the degree of design freedom. Therefore, it is possible to easily provide detection means for various processing apparatuses.

Further, in the present invention, the detection electrode is more that you have been fixed to the spindle shaft, it is possible to enhance the positional accuracy of the detection electrodes relative to the spindle axis, it is possible to improve the detection accuracy of the machining stress .

  In the present invention, it is preferable that the detection electrodes have a pair of fixed electrodes that are opposed to each other from the same side and are insulated from each other, and the detection circuits are conductively connected to the pair of fixed electrodes, respectively. . According to this, when the distance between the fixed electrode and the detection electrode changes due to the relative displacement in the axial direction between the spindle shaft and the support, the capacitance between the pair of fixed electrodes depends on the distance. Since the capacitance changes, the amount of the relative displacement can be known by detecting the capacitance with a detection circuit. Therefore, there is no need to conductively connect the detection electrode to the detection circuit, and in particular, when the detection electrode is fixed to the spindle shaft, it is not necessary to provide an electrical contact from the detection electrode rotating with the spindle shaft to the detection circuit. The wiring structure can be simplified and the detection state can be stabilized.

  In this invention, it is preferable that the said detection electrode is opposingly arranged by the side which moved to the direction of the said process stress with respect to the said fixed electrode. According to this, when the tool or workpiece is subjected to a processing stress, the spindle shaft moves relative to the support in the direction of the above processing stress, so that the detection electrode also has a processing stress with respect to the fixed electrode. Move in the direction of. Therefore, since the detection electrode is disposed opposite to the fixed electrode on the side where it moves in the direction of the processing stress, the detection electrode moves in a direction relatively away from the fixed electrode when receiving the processing stress. Therefore, it can be configured so that a contact accident between the detection electrode and the fixed electrode does not occur regardless of the magnitude of the processing stress. In other words, since the contact between the detection electrode and the fixed electrode does not occur regardless of the magnitude of the processing stress, the distance between the two electrodes can be sufficiently reduced. The detection sensitivity or detection accuracy of the stress or the displacement amount can be increased.

  In the present invention, the bearing structure is preferably configured to support the spindle shaft in the axial direction via a compressive fluid. According to this, since the support body supports the spindle shaft in the axial direction via the compressive fluid, the movement of the spindle shaft in the axial direction with respect to the support becomes smooth. Can be increased. In particular, by configuring a hydrostatic bearing that applies a compressible fluid at a predetermined (constant) pressure, the correlation characteristics between the machining stress and the relative displacement of the spindle shaft can be stabilized. It can be further increased.

  According to the present invention, it is possible to detect a machining stress applied to a tool or a workpiece with high accuracy, and to provide a high degree of design freedom such as the position of a detection point, and can be easily provided in various devices. The outstanding effect that the processing apparatus which has a means is realizable can be produced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view showing the main part of the processing apparatus according to the first embodiment of the present invention. The processing apparatus 100 includes a spindle shaft 101 and a support body 103 that rotatably supports the spindle shaft 101. A gripping mechanism 102 such as a collet chuck is attached to the end of the spindle shaft 101, and a tool T such as a drill or a reamer is gripped and fixed to the gripping mechanism 102. The support body 103 includes a bearing structure 104. The bearing structure 104 includes a rolling bearing such as a ball bearing and a roller bearing, a slide bearing, and other known bearing structures, and rotatably supports the spindle shaft 101. The spindle shaft 101 is axially supported via a fluid such as oil.

  Here, “supporting in the axial direction through the fluid” means that the axial direction has a gap that can allow relative displacement in the axial direction that can be detected by the detecting means described later, and oil, grease, or the like is provided in the gap. This means that the fluid is intervening. In the case of the present embodiment, the relative displacement that can be detected by the detection means described later is sufficiently smaller than the thickness of the lubricant film incorporated in a general bearing structure. If there is, it can be used as the bearing structure 104 of the present embodiment.

  A pair of fixed electrodes 105A and 105B are fixed to the support 103. The pair of fixed electrodes 105A and 105B are in a state of being insulated from each other through a gap or an insulator. Further, a detection electrode 106 fixed to the spindle shaft 101 is disposed opposite to the fixed electrodes 105A and 105B in the axial direction. The detection electrode 106 is disposed on the side opposite to the attachment side of the tool T with respect to the pair of fixed electrodes 105A and 105B. More specifically, the fixed electrodes 105A and 105B are fixed to the support 103 in a posture exposed to the opposite side to the tool T in the axial direction, and the tool T is fixed to the tool T with respect to the fixed electrodes 105A and 105B. The detection electrode 106 is disposed opposite to the opposite side. Note that the detection circuit described later is configured to detect the capacitance Cx between the fixed electrodes 105A and 105B.

  Although not shown in FIG. 1, the spindle shaft 101 is usually configured to be rotationally driven by a rotational drive mechanism configured by a drive motor or the like. The spindle shaft 101 is configured to be movable in the axial direction relative to the workpiece by a feed drive mechanism that sends the tool T relative to the workpiece (not shown) in the axial direction. In this case, the spindle shaft 101 may be moved in the axial direction, or a fixed base that fixes a workpiece (not shown) may be moved in the axial direction with respect to the spindle shaft 101. It should be noted that a workpiece may be attached to the spindle shaft 101 instead of the tool T. In this case, the tool T is fixed to a tool post (not shown).

  FIG. 2 is a perspective plan view illustrating a state in which the planar shapes of the fixed electrode and the detection electrode of the processing apparatus 100 are viewed in the axial direction. The pair of fixed electrodes 105 </ b> A and 105 </ b> B are each configured to have a planar shape that avoids a penetrating region of the spindle shaft 101, specifically, a semicircular arc shape. The detection electrode 106 is configured to have an annular planar shape, specifically a ring shape, avoiding the penetrating region of the spindle shaft 101 so as to face both the pair of fixed electrodes 105A and 105B. . In this embodiment, since the detection electrode 106 is fixed to the spindle shaft 101, when the spindle shaft 101 is rotationally driven, the detection electrode 106 is also rotationally driven. In this case, as shown in the illustrated example, if the opposing area between the fixed electrodes 105A and 105B and the detection electrode 106 does not change even when the detection electrode 106 rotates, the capacitance due to the rotation of the detection electrode 106 is reduced. Since changes can be eliminated or reduced, more accurate detection can be performed.

FIG. 3 is an equivalent circuit diagram showing a circuit structure constituted by the fixed electrodes 105A and 105B and the detection electrode. The electrostatic capacitance Cx between the fixed electrodes 105A and 105B is an electrostatic capacitance Ca constituted by the fixed electrode 105A and the detection electrode 106, and an electrostatic capacitance Cb constituted by the fixed electrode 105B and the detection electrode 106. It is expressed by a series circuit. Here, the electrode interval between the fixed electrode 105A and the detection electrode 106 is da, the electrode facing area is Sa, the electrode interval between the fixed electrode 105B and the detecting electrode 106 is db, the electrode facing area is Sb, and ε is a dielectric. If rate,
1 / Cx = 1 / Ca + 1 / Cb = da / εSa + db / εSb (1)
Is established. However, in this embodiment, da = db, Sa = Sb, and Ca = Cb. When the distance between the fixed electrodes 105A and 105B and the detection electrode 106 changes, the electrode intervals da and db simultaneously change by the same amount. Therefore, if the capacitance between the fixed electrodes 105A and 105B is detected, the capacitance between the fixed electrodes 105A and 105B and the detection electrode 106 is detected. As a result, the fixed electrodes 105A and 105B are detected. It is possible to know the relative displacement in the axial direction between the detection electrode 106 and the detection electrode 106, that is, the relative displacement in the axial direction between the spindle shaft 101 and the support 103.

  FIG. 4 shows an example of a detection circuit that measures the capacitance Cx. This detection circuit is a relaxation oscillation circuit including a capacitance Cx. However, in addition to the relaxation oscillation circuit, any oscillation circuit having a capacitance Cx as a circuit constant, such as a Wien bridge oscillation circuit, can be used, and other detection circuits other than the oscillation circuit can be used. Is possible.

  Further, in this embodiment, it has been confirmed that there is a positive correlation between the relative movement amount of the spindle shaft 101 and the support body 103 in the axial direction and the machining stress that the tool T receives in the axial direction. This is because, in the bearing structure 104, the spindle shaft 101 is pivotally supported by the support body 103 via a fluid such as oil, so that the machining stress received by the spindle shaft 101 increases against the spindle shaft 101 fluid. This is presumably because the amount of movement relative to the rear in the axial direction (the side opposite to the tool T in the axial direction) increases. Therefore, by detecting the relative movement amount of the spindle shaft 101 with respect to the support 103 in the axial direction based on the characteristics shown in the graph of FIG. 7 to be described later, the machining stress applied to the tool T can be known.

  In the present embodiment, since the electrostatic capacitance between the fixed electrodes 105A and 105B fixed to the support 103 and the detection electrode 106 fixed to the spindle shaft 101 is detected, the detection electrode 106 together with the spindle shaft 101 By rotating, the variation in capacitance is averaged in the rotation direction, and detection errors caused by relative angular deviations (posture deviations) between the fixed electrodes 105A and 105B and the detection electrodes 106 can be reduced. It is possible.

  Further, in the present embodiment, it is not necessary to detect the potential of the detection electrode 106 by measuring the capacitance between the pair of fixed electrodes 105A and 105B facing the detection electrode 106 from the same side. Since it is not necessary to provide a rotation-permissible electrical contact structure between the rotating detection electrode 106 and the detection circuit, the wiring structure can be easily configured.

  Furthermore, in the present embodiment, the detection electrode 106 is arranged on the side moved in the direction of the processing stress with respect to the fixed electrodes 105A and 105B (that is, the right side in FIG. 1), so that the processing stress increases. Since the detection electrode 106 is merely separated from the fixed electrodes 105A and 105B, it is possible to eliminate the possibility that the electrodes collide with each other. In addition, this makes it possible to reduce the electrode interval in advance, so that the detection sensitivity and accuracy can be increased.

  Next, a processing apparatus according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a schematic side view of the main part of the present embodiment, and FIG. 6 is an enlarged vertical sectional view of the main part. The machining apparatus 200 according to the second embodiment includes a spindle shaft 201, a gripping mechanism 202, a support 203, a bearing structure 204, fixed electrodes 205A and 205B, and a detection electrode 206, as in the first embodiment. ing. Here, the configuration other than the bearing structure 204 is basically the same as that of the first embodiment, including the configuration of the detection circuit described above, and thus the description thereof is omitted.

  In the present embodiment, as shown in FIG. 6, a rotation-side bearing portion 211 protruding in the radial direction is fixed to the outer periphery of the spindle shaft 201, and a cylindrical radial bearing portion 204 </ b> A is provided on the outer periphery side of the rotation-side bearing portion 211. The thrust bearing portions 204B and 204C are respectively disposed in the axial direction of the end surface of the rotation-side bearing portion 211, and the radial bearing portion 204A and the thrust bearing portions 204B and 204C are fixed to each other. The radial bearing portion 204A is provided with fluid introduction portions 204p at a plurality of locations, and is connected to fluid supply means (for example, one that supplies dry compressed air) not shown. Then, the fluid supplied from the fluid supply means is supplied to the gap between the radial bearing portion 204A and the thrust bearing portions 204B and 204C and the rotation-side bearing portion 211 via the fluid introduction portion 204p. A pressure bearing is configured. The fluid supplied in this way is discharged into the interior through openings 201x and 201y provided in the hollow spindle shaft 201.

  In the illustrated example, the fluid is supplied only from the outer peripheral side of the rotation-side bearing portion 211. However, in order to ensure the axial support force in the thrust direction, the thrust bearing portions 204B and 204C are respectively provided. It is desirable to provide a fluid introduction portion so that fluid is supplied from both sides in the axial direction toward the end surface of the rotation-side bearing portion 211. For example, a part of the inner surface of the thrust bearing portions 204B and 204C is made of a porous material, and a fluid is supplied to the porous material, so that the fluid passes through the porous material, and a large number of surface fine particles of the porous material. A fluid can be supplied from the hole, and the end surface of the rotation-side bearing portion 211 can be supported in the axial direction.

  In the bearing structure 204 which is a hydrostatic bearing of the present embodiment, the bearing load is supported by a compressive fluid such as air. In the present embodiment, the gap between the end surface of the rotation-side bearing portion 211 and the inner surfaces of the thrust bearing portions 204B and 204C is not particularly limited, but is, for example, in the range of 5 to 100 μm, typically about 10 μm.

  10A is an exploded perspective view showing the mounting structure of the fixed electrodes 205A and 205B, FIG. 10B is an exploded longitudinal sectional view, and FIG. 10C is a longitudinal sectional view showing an assembled state. As shown in FIG. 10 and FIG. 7, in the present embodiment, the bearing structure 204 (specifically, the thrust bearing portion 204 </ b> C) is composed of a fixing member 221 made of an insulator and a conductor. The shield member 222 and the fixing member 223 made of an insulator are fixed in a stacked state, and the fixed electrodes 205A and 205B are fixed to the fixing member 223. As shown in FIG. 6, the detection electrode 206 is fixed to the spindle 201 via a fixing member 225 made of an insulator. The shield member 222 is conductively connected to a conductive case member 224 that covers the fixed electrodes 205A and 205B and the detection electrode 206, and is conductively connected to the circuit board 226 via the case member 224. The fixed electrodes 205A and 205B are conductively connected to the circuit board 226 via wirings not shown.

  In this embodiment, as shown by a dotted line in FIG. 4, the shield member 222 and the case member 224 act as a shield line for connecting the capacitance Cx and the detection circuit (operational amplifier). , Conductively connected to the output of the voltage follower connected to the input of the inverting amplifier.

  FIG. 7 is a graph showing the relationship between the displacement amount of the electrode interval between the fixed electrodes 205A and 205B and the detection electrode 206 and the oscillation frequency output from the detection circuit. As shown in this graph, it can be seen that the oscillation frequency changes greatly even if the electrode spacing slightly changes. Thus, by detecting the change in the electrode interval by the change in the capacitance, it becomes possible to perform highly accurate detection.

  FIG. 8 is a graph showing the relationship between the load in the thrust direction (axial direction) of the bearing structure 204 and the displacement amount of the electrode interval. As can be seen from this graph, the load in the thrust direction and the displacement amount of the electrode interval have a positive correlation, more specifically, a proportional relationship. Therefore, when a machining stress in the axial direction is applied to the tool T, a load in the thrust direction of the bearing structure 204 is generated, and the electrode interval is displaced according to the characteristics shown in FIG. Can know.

  FIG. 9 shows the thrust bearing performance of the bearing structure 204, and the load capacity in the thrust direction and the gap in the thrust direction when air is supplied through the fluid introduction part 204p at a constant pressure of 0.5 MPa. It is a graph which shows the relationship between (the space | interval of the end surface of the rotation side bearing part 211, and the inner surface of thrust bearing part 204B, 204C). As can be seen from this graph, the load capacity increases rapidly as the gap in the thrust direction decreases. In other words, when the machining stress increases and the spindle shaft 201 moves relatively rearward in the axial direction, the gap between the rear end surface of the rotation-side bearing portion 211 and the inner surface of the thrust bearing portion 204C decreases, and the bearing The load capacity of the structure 204 will also increase rapidly.

  In the present embodiment, the bearing structure 204 is composed of a hydrostatic bearing using a compressive fluid, so that the relative movement between the spindle shaft 201 and the support 203 in the axial direction becomes smooth and the thrust is thrust. Since the correlation characteristic between the change in the gap in the direction and the load in the thrust direction becomes good, the detection sensitivity to the processing stress is increased, and the detection accuracy can be improved.

  In each of the above embodiments, the output of the detection circuit is connected to a control device (not shown), and when this output (ie, processing stress) exceeds a predetermined value, the processing is interrupted or the feeding operation is interrupted. Various controls such as reducing the feed speed or the like may be performed. This can prevent or reduce breakage of tools and workpieces. As the control device, an MPU (microprocessor unit), a programmable controller, or the like can be used.

  In addition, the processing apparatus and the detection means of the present invention are not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention. For example, in each of the above embodiments, an example of a processing apparatus having a spindle shaft to which a tool T is attached has been described. However, a processing apparatus having a spindle axis to which a workpiece is attached instead of a tool may be configured. . The processing apparatus of the present invention includes various processing devices and processing tools such as a machine tool such as a lathe and other turning devices, a polishing device, and a surface treatment device.

The schematic side view which shows the principal part of the processing apparatus of 1st Embodiment. The plane perspective view which shows the state which saw through the structure of the detection means of the processing apparatus of 1st Embodiment in the axial direction. The equivalent circuit diagram of the detection means of the processing apparatus of 1st Embodiment. The circuit diagram of the detection circuit of the processing apparatus of 1st Embodiment. The schematic side view which shows the principal part of the processing apparatus of 2nd Embodiment. The longitudinal cross-sectional view of the principal part of the processing apparatus of 2nd Embodiment. The graph which shows the characteristic of the detection means of the processing apparatus of 2nd Embodiment. The graph which shows the characteristic of the bearing structure of the processing apparatus of 2nd Embodiment. The graph which shows the load capability of the bearing structure of 2nd Embodiment. The exploded perspective view (a), the exploded sectional view (b), and the assembly sectional view (c) which show the attachment structure of the fixed electrode of a 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,200 ... Processing apparatus, 101,201 ... Spindle axis | shaft, 102,202 ... Gripping mechanism, 103,203 ... Supporting body, 104,204 ... Bearing structure, 105A, 105B, 205A, 205B ... Fixed electrode, 106,206 ... Detection electrode, 204A ... radial bearing, 204B, 204C ... thrust bearing, 204p ... fluid introduction, 211 ... rotation side bearing, 221,223,225 ... fixing member, 222 ... shield member, 224 ... case member, 226 ... Circuit board

Claims (4)

A spindle shaft to which a tool or a workpiece is fixed, a support having a bearing structure that rotatably supports the spindle shaft via a fluid in an axial direction, and a processing stress received by the tool or the workpiece are detected. A processing device having a detecting means for performing
The detection means includes a detection electrode fixed to the spindle shaft, and a fixed electrode which is disposed to face the detection electrode in the axial direction and is connected to the support body at least in the axial direction. And a detection circuit that directly or indirectly detects a capacitance between the detection electrode and the fixed electrode.   The detection electrode includes a pair of fixed electrodes that are opposed to each other from the same side and insulated from each other, and the detection circuit is conductively connected to the pair of fixed electrodes. The processing apparatus according to 1.   The processing apparatus according to claim 1, wherein the detection electrode is disposed to face the fixed electrode on a side moved in the direction of the processing stress.   4. The processing apparatus according to claim 1, wherein the bearing structure is configured to support the spindle shaft in the axial direction via a compressive fluid. 5.

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