JP7637600B2 - Air Spindle Device - Google Patents

Description

This disclosure relates to an air spindle device that includes a housing and a spindle that is rotatably supported within the housing via air.

Conventionally, an air spindle device is known that has a housing and a spindle that is supported within the housing so that it can rotate freely via air.

Due to the structure of the air spindle device, it is difficult to give the spindle rigidity and rotate it at high speed. For this reason, the spindle may displace within the housing during machining, but no technology has been developed to measure the displacement of the spindle within the housing, and the displacement of the spindle that occurs during machining may make it impossible to perform machining work with high precision.

JP 2019-104066 A

The present disclosure has been made in consideration of these points, and aims to provide an air spindle device that can measure the amount of spindle displacement during machining and use this amount of spindle displacement to perform machining operations with high precision.

The present disclosure relates to an air spindle device comprising a housing, a spindle rotatably provided within the housing and holding a tool, a radial bearing provided in the housing and supporting the spindle in the radial direction via air, a thrust bearing provided in the housing and supporting the spindle in the axial direction via air, an x-direction displacement meter, a y-direction displacement meter, and a z-direction displacement meter that determine the amount of displacement of the spindle in each of the x-direction, y-direction, and z-direction relative to the housing, a movement mechanism that drives the housing, and a control unit, wherein the control unit controls the movement mechanism in a direction that corrects the amount of displacement of the spindle in each of the x-direction, y-direction, and z-direction based on signals from the x-direction displacement meter, the y-direction displacement meter, and the z-direction displacement meter.

The present disclosure relates to an air spindle device in which the control unit determines the load on the tool based on signals from the x-direction displacement gauge, the y-direction displacement gauge, and the z-direction displacement gauge.

The present disclosure relates to an air spindle device in which the x-direction displacement gauge and the y-direction displacement gauge are embedded in the radial bearing provided in the housing and measure the distance between the outer peripheral surface of the spindle.

The present disclosure relates to an air spindle device in which the z-direction displacement meter is embedded in the thrust bearing provided in the housing and determines the distance between the thrust bearing and a flange provided on the spindle.

The present disclosure is an air spindle device in which the z-direction displacement meter determines the displacement of the upper end of the spindle.

As described above, according to the present disclosure, the amount of displacement of the air spindle can be measured during machining, and this amount of displacement can be used to perform machining with high precision.

FIG. 1 is a schematic diagram showing an air spindle device according to the present disclosure. FIG. 2 is an overall configuration diagram of a machine tool equipped with an air spindle device. FIG. 3 is an enlarged view of FIG. 1 showing an x-direction displacement gauge and a y-direction displacement gauge. FIG. 4 is an enlarged view of FIG. 1 showing the z-direction displacement gauge. FIG. 5A is a diagram showing a change in the amount of displacement in the x direction according to the present disclosure. FIG. 5B is an enlarged view of FIG. 5A.

First, we will describe the entire machine tool equipped with the air spindle device disclosed herein.

As shown in Figs. 1 and 2, the air spindle device 100 is a device for machining a workpiece 3, which is a workpiece, by rotating the tool 1 attached to one end of the spindle 10 by driving the spindle 10 to rotate around its central axis. The air spindle device 100 is attached to a machine tool 200, and moves relative to the workpiece 3 by a moving mechanism 110 provided in the machine tool 200. The machine tool 200 is a numerically controlled (NC) machine tool, which controls the relative motion (position and speed) between the tool 1 and the workpiece 3 by numerical information, and executes a series of operations related to machining by a program 132. Specifically, the machine tool 200 is a machining center equipped with the air spindle device 100 and a tool exchange device 120, and various types of machining such as drilling, boring, and milling can be performed by replacing the tool 1 with the air spindle device 100.

In this embodiment, for example, a mold for an optical lens is considered as an example of the workpiece 3, and the mold is precisely machined by the machine tool 200. The air spindle device 100 and the machine tool 200 are capable of highly accurate measurement of the workpiece 3, and are therefore particularly suitable for precision machining that requires high accuracy, such as the manufacture of molds.

The machine tool 200 shown in FIG. 2 includes an air spindle device 100, a movement mechanism 110, and a tool exchange device 120. The machine tool 200 and the air spindle device 100 also include a control unit 130 that controls each of these components.

The moving mechanism 110 is configured to move the air spindle device 100 and the workpiece 3 relative to each other. In this case, the moving mechanism 110 can move the air spindle device 100 and the workpiece 3 relative to each other in at least three orthogonal axial directions, which are the up-down direction and two orthogonal directions in a horizontal plane. When moving the air spindle device 100 and the workpiece 3 relative to each other, only one of the air spindle device 100 and the workpiece 3 may move, or both the air spindle device 100 and the workpiece 3 may move. In this embodiment, as shown in FIG. 2, the moving mechanism 110 holds the air spindle device 100 and moves the air spindle device 100 in the z direction, which is the up-down direction, and in the x direction in a horizontal plane (left-right direction in FIG. 2), and moves the workpiece 3 in the y direction (forward and backward directions perpendicular to the paper surface in FIG. 2) perpendicular to the x direction in the horizontal plane.

The specific configuration of the movement mechanism 110 will be described below. As shown in FIG. 2, the machine tool 200 is a gate-type machining center. The machine tool 200 includes a table 140 on which the workpiece 3 is placed, and a bed 141 that supports the table 140 so that it can move in the y direction. The machine tool 200 also includes a pair of columns 142 arranged on both sides of the bed 141 in the x direction, and a crossbar 143 that is hung across the upper ends of the pair of columns 142. The crossbar 143 extends in the x direction so as to straddle the top of the table 140 and the bed 141. The crossbar 143 supports a saddle 144 so that it can move in the x direction. The saddle 144 supports a head 145 that holds the air spindle device 100 so that it can move in the z direction.

In this embodiment, the moving mechanism 110 includes a z-axis moving mechanism 111 that moves the head 145 in the z direction, an x-axis moving mechanism 112 that moves the saddle 144 in the x direction, and a y-axis moving mechanism 113 that moves the table 140 in the y direction. Each of the z-axis moving mechanism 111, the x-axis moving mechanism 112, and the y-axis moving mechanism 113 includes, for example, a servo motor 114 with a built-in position detector, and a linear motion mechanism (not shown) driven by the servo motor 114. The moving mechanism 110 may have more than three moving axes. For example, the moving mechanism 110 may have a rotation axis that rotates the head 145 around the axis in the y direction (tilting the tool 1 of the air spindle device 100 with respect to the horizontal plane) and a rotation axis that rotates the table 140 around the z axis (rotating the workpiece 3 in the horizontal plane).

The tool exchange device 120 has the function of removably holding multiple types of tools 1 and replacing the tools 1 attached to the spindle 10 of the air spindle device 100. The tool exchange device 120 also removably holds the contact sensor 2 in addition to the tool 1. In other words, the tool exchange device 120 is configured to removably hold the tool 1 and the contact sensor 2 on the spindle 10 of the air spindle device 100.

As shown in FIG. 2, the control unit 130 is configured to control the overall operation of the machine tool 200. The control unit 130 is configured with a processor such as a CPU. Specifically, the control unit 130 has a memory unit 131 in which various programs 132 for controlling the machine tool 200, including a machining program for the workpiece 3, are stored. The processor executes the programs stored in the memory unit 131, causing the processor to operate as the control unit 130 of the machine tool 200. As a result, the control unit 130 controls the operation of the air spindle device 100, the movement mechanism 110, and the tool exchange device 120. The control unit 130 is provided, for example, in a control panel of the machine tool 200, and is connected to a display unit (not shown) and an input unit (not shown) of the control panel.

Next, the air spindle device 100 according to the present disclosure will be described. As shown in FIG. 1, the air spindle device 100 according to the present disclosure includes a housing 50, a spindle 10 rotatably provided within the housing 50, and a tool 1 held at the lower end of the spindle 10. In this case, the tool 1 is attached and held at the lower end of the spindle 10 via a tool holder 40.

The spindle 10 is supported in the radial direction by a radial bearing 31 provided in the housing 50 through air (also called air). Similarly, the spindle 10 is supported in the axial direction by a thrust bearing 32 provided in the housing 50 through air (also called air).

The thrust bearing 32 and the radial bearing 31 form the air bearing mechanism 20.

In this embodiment, as shown in FIG. 1, the spindle 10 has a shaft portion 11 of a predetermined length and a flange portion 12 that is provided midway along the shaft portion 11 and has a diameter larger than that of the shaft portion 11. The spindle 10 is disposed in a storage hole 50A in the housing 50.

As shown in FIG. 1, the air bearing mechanism 20 has a bearing member 30 that is fixed in the storage hole 50A of the housing 50 and rotatably supports the spindle 10 via an air gap, and this bearing member 30 consists of the above-mentioned radial bearing 31 and thrust bearing 32. Of these, the radial bearing 31 has an inner diameter with a predetermined radial gap 33 between it and the outer circumferential surface of the shaft portion 11, and has air outlet holes 34 that blow air into the radial gap 33. The thrust bearing 32 is formed integrally with the radial bearing 31, has a predetermined thrust gap 35 between it and the end face of the flange portion 12, and has air outlet holes 36 that blow air into this thrust gap 35.

As described above, the housing 50 is formed with a storage hole 50A that stores the spindle 10 in the central axial direction, and an air supply port 23 for the air bearing is formed on the outside of the housing 50. In addition, an air supply passage 25 is formed inside the housing 50, which connects the air supply port 23 for the air bearing to the air outlet holes 34 and 36 of the radial bearing 31 and thrust bearing 32.

The air spindle device 100 also includes an air source 60 that supplies air to the radial bearing 31 and thrust bearing 32, and a fluid circuit 70 that is connected between the air source 60 and the air bearing air supply port 23 and controls the pressure supply of air to the air bearing air supply port 23. This allows compressed air at a predetermined pressure to be supplied from the air source 60 to the radial bearing 31 and thrust bearing 32 via the fluid circuit 70. The supplied air pressure may be, for example, about 0.3 MPa or more and about 0.7 MPa or less.

Next, the drive unit 80 that drives the spindle 10 will be described. The drive unit 80 drives the spindle 10 to rotate. The drive unit 80 is connected to the upper end of the spindle 10 and is configured to directly drive the spindle 10 to rotate around the central axis. The drive unit 80 is an electric motor capable of high-speed rotation of about 60,000 rpm, and is a built-in motor built into the housing 50. The motor can be a synchronous motor or an induction motor, but specifically, the drive unit 80 is configured by such an induction motor. The induction motor generates an induced current in the rotor 82 by a rotating magnetic field generated in the stator 81, and rotates the rotor 82 by the interaction between the magnetic field generated by the induced current and the rotating magnetic field of the stator 81. The rotor 82 is fixed to the spindle 10, while the stator 81 is fixed inside the housing 50 so as to surround the radial outside of the rotor 82.

As shown in Figures 1 to 4, an x-direction displacement meter 41 and a y-direction displacement meter 42 are provided on the lower part of the housing 50 to measure the amount of displacement of the spindle 10 in the x and y directions relative to the housing 50.

The x-direction displacement gauge 41 and the y-direction displacement gauge 42 are used to measure the displacement of the spindle 10 in the x and y directions, and are arranged at positions spaced 90° apart in a plan view on the outer periphery of the spindle 10 in Figures 1 and 3. The x-direction displacement gauge 41 is arranged to extend horizontally within an opening 41A formed by penetrating the housing 50 and the radial bearing 31 in the horizontal direction, and the x-direction displacement gauge 41 is used to measure the horizontal distance between the outer periphery of the shaft portion 11 of the spindle 10.

The signal from the x-direction displacement meter 41 is then sent to the control unit 130.

The y-direction displacement gauge 42 is disposed at a position 90° apart from the x-direction displacement gauge 41 in a plan view. In this embodiment, an opening 42A is formed at a position 90° apart from the opening 41A in a plan view, penetrating the housing 50 and the radial bearing 31 in the horizontal direction. The y-direction displacement gauge 42 is provided to extend horizontally within this opening 42A, and the horizontal distance between the outer circumferential surface of the shaft portion 11 of the spindle 10 can be determined by this y-direction displacement gauge 42. A signal from the y-direction displacement gauge 42 is sent to the control unit 130.

A z-direction displacement meter 43 is provided in the housing 50 above the flange portion 12 to measure the amount of displacement of the spindle 10 in the z direction relative to the housing 50.

In this embodiment, an opening 43A is provided above the flange portion 12 of the spindle 10, penetrating the housing 50 and the thrust bearing 32 in the vertical direction, and a z-direction displacement meter 43 is arranged to extend vertically within this opening 43A. The z-direction displacement meter 43 can be used to determine the vertical distance between the flange portion 12 of the spindle 10. A signal from the z-direction displacement meter 43 is sent to the control unit 130.

In addition, any displacement gauges can be used as the x-direction displacement gauge 41, y-direction displacement gauge 42, and z-direction displacement gauge 43, which are used to determine the displacement of the spindle 10 in the x-direction, y-direction, and z-direction relative to the housing 50, as long as they can measure the distance between the spindle 10.

For example, the x-direction displacement gauge 41, the y-direction displacement gauge 42, or the z-direction displacement gauge 43 can be a capacitance sensor, an eddy current sensor, or a laser light irradiation sensor.

In addition, in this embodiment, an example has been shown in which the z-direction displacement meter 43 is provided inside the housing 50 to measure the distance between the flange portion 12 of the spindle 10, but this is not limiting. The z-direction displacement meter 43 may be provided on the upper part of the housing 50, and the vertical distance between the upper end of the spindle 10 may be measured using this z-direction displacement meter 43.

Next, we will explain the operation of this embodiment with such a configuration.

First, as shown in FIG. 1, compressed air (also called compressed air) from an air source 60 is sent to the housing 50 side via a fluid circuit 70, and the compressed air is supplied to both the radial bearing 31 and the thrust bearing 32 from the air bearing air supply port 23 of the housing 50. As a result, the spindle 10 is supported in a non-contact state in the radial direction by the radial bearing 31 via air, and in a non-contact state in the axial direction by the thrust bearing 32 via air. As a result, the spindle 10 is supported rotatably around the central axis by the air pressure supplied to the radial bearing 31 and the thrust bearing 32, with movement in the axial direction (Z direction) and radial direction (XY direction) restricted in a non-contact state.

In this state, the spindle 10 is rotated by the drive unit 80, and the tool 1 attached to the spindle 10 rotates at high speed. Then, the air spindle device 100 and the workpiece 3 are moved relative to each other by the movement mechanism 110, and the tool 1 is brought into contact with the workpiece 3, thereby performing cutting on the workpiece 3.

During this time, the x-direction displacement meter 41 measures the horizontal distance between the outer circumferential surface of the shaft portion 11 of the spindle 10, the y-direction displacement meter 42 measures the horizontal distance between the outer circumferential surface of the shaft portion 11 of the spindle 10, and the z-direction displacement meter 43 measures the vertical distance between the flange portion 12 of the spindle 10. The signals from the x-direction displacement meter 41, the y-direction displacement meter 42, and the z-direction displacement meter 43 are sent to the control unit 130.

The measurement results from the x-direction displacement meter 41, the y-direction displacement meter 42, and the z-direction displacement meter 43 sent to the control unit 130 correspond to the x-direction displacement amount, the y-direction displacement amount, and the z-direction displacement amount of the spindle 10 relative to the housing 50, respectively, and these x-direction displacement amount, y-direction displacement amount, and z-direction displacement amount are stored in the memory unit 131 of the control unit 130.

Next, the discrimination unit 133 of the control unit 130 determines the load applied from the workpiece 3 to the tool 1 based on the x-direction displacement amount, the y-direction displacement amount, and the z-direction displacement amount in the memory unit 131.

The specific results of the x-direction displacement measured by the x-direction displacement meter 41 are shown in Figures 5A and 5B.

Figure 5A shows the change in displacement in the x direction, and Figure 5B is an enlarged view of Figure 5A.

As shown in Figures 5A and 5B, when machining workpiece 3 using tool 1, the amount of x-direction displacement increases sharply in response to the load applied to tool 1 from workpiece 3 immediately after tool 1 comes into contact with workpiece 3, and this amount of x-direction displacement remains a constant value.

Next, when the tool 1 leaves the workpiece 3 and contact ends, the amount of displacement in the x direction decreases.

In this case, it is known that the amount of x-direction displacement is proportional to the load in the x-direction applied from the workpiece 3 to the tool 1. Therefore, the discrimination unit 133 of the control unit 130 can determine the load in the x-direction applied from the workpiece 3 to the tool 1 based on the amount of x-direction displacement.

In the same manner, the discrimination unit 133 of the control unit 130 can determine the load in the y direction applied to the tool 1 from the workpiece 3 based on the amount of y direction displacement sent from the y direction displacement meter 42.

In the same manner, the discrimination unit 133 of the control unit 130 can determine the z-direction load applied to the tool 1 from the workpiece 3 based on the z-direction displacement amount sent from the z-direction displacement meter 43.

In this embodiment, the discrimination unit 133 of the control unit 130 further corrects the positional deviation of the tool 1 relative to the workpiece 3 based on the amount of displacement in the x direction, the amount of displacement in the y direction, and the amount of displacement in the z direction.

In other words, when the spindle 10 has an x-direction displacement, a y-direction displacement, and a z-direction displacement relative to the housing 50, this means that the position of the tool 1 relative to the workpiece 3 is misaligned.

In this embodiment, the discrimination unit 133 of the control unit 130 drives and controls the movement mechanism 110 based on the x-direction displacement amount, the y-direction displacement amount, and the z-direction displacement amount. In this case, the movement mechanism 110 moves the entire air spindle device 100 including the housing 50 slightly in the x-direction, y-direction, and z-direction.

Specifically, the x-axis movement mechanism 112 of the movement mechanism 110 moves the entire air spindle device 100, including the housing 50, slightly in a direction that corrects the amount of x-direction displacement (a direction that offsets the amount of x-direction displacement), thereby correcting the x-direction positional deviation of the tool 1 relative to the workpiece 3.

For example, if the displacement of the spindle 10 in the x direction relative to the housing 50 is "+a", the entire air spindle device 100 including the housing 50 is moved slightly in the x direction by "-a". This makes it possible to correct the positional deviation of the tool 1 in the x direction relative to the workpiece 3.

Similarly, the y-axis movement mechanism 113 of the movement mechanism 110 moves the entire air spindle device 100, including the housing 50, slightly in a direction that corrects the amount of displacement in the y direction (a direction that offsets the amount of displacement in the y direction), thereby correcting the positional deviation of the tool 1 in the y direction relative to the workpiece 3.

The z-axis movement mechanism 111 of the movement mechanism 110 also moves the entire air spindle device 100, including the housing 50, slightly in a direction that corrects the amount of z-direction displacement (a direction that offsets the amount of z-direction displacement), thereby correcting the positional deviation of the tool 1 in the z direction relative to the workpiece 3.

As described above, according to this embodiment, the control unit 130 can determine the x-direction load applied from the workpiece 3 to the tool 1 based on the x-direction displacement amount sent from the x-direction displacement meter 41, can determine the y-direction load applied from the workpiece 3 to the tool 1 based on the y-direction displacement amount sent from the y-direction displacement meter 42, and can determine the z-direction load applied from the workpiece 3 to the tool 1 based on the z-direction displacement amount sent from the z-direction displacement meter 43.

The control unit 130 also controls the movement mechanism 110 based on the x-direction displacement amount, y-direction displacement amount, and z-direction displacement amount, and the movement mechanism 110 moves the entire air spindle device 100 including the housing 50 slightly in the x-direction, y-direction, and z-direction. In this case, the movement mechanism 110 moves the entire air spindle device 100 including the housing 50 slightly in a direction that corrects (cancels) the x-direction displacement amount, y-direction displacement amount, and z-direction displacement amount. This makes it possible to correct the positional deviation in the x-direction, y-direction, and z-direction of the tool 1 relative to the workpiece 3. This makes it possible to perform high-precision machining of the workpiece 3 using the tool 1.

In addition to the x-direction displacement gauge 41, y-direction displacement gauge 42, and z-direction displacement gauge 43 shown in the above embodiment, a y-direction rotational displacement gauge for determining the rotational displacement of the spindle 10 relative to the housing 50 around the y-direction axis, and a z-direction rotational displacement gauge for determining the rotational displacement of the spindle relative to the housing 50 around the z-direction axis may be installed. In this case, the entire air spindle device 100 having the housing 50 can be moved slightly based on the signals from the y-direction rotational displacement gauge and the z-direction rotational displacement gauge to eliminate the rotational displacement around the y-direction axis and the z-direction axis by the movement mechanism 110, thereby correcting the positional deviation in the rotational direction around the y-direction axis and the z-direction axis.

REFERENCE SIGNS LIST 1 Tool 3 Workpiece 10 Spindle 11 Shaft portion 12 Flange portion 20 Air bearing mechanism 23 Air supply port for air bearing 25 Air supply path 30 Bearing member 31 Radial bearing 32 Thrust bearing 33 Radial gap 34 Air ejection hole 35 Thrust gap 36 Air ejection hole 40 Tool holding portion 41 x-direction displacement meter 41A Opening 42 y-direction displacement meter 42A Opening 43 z-direction displacement meter 43A Opening 50 Housing 50A Storage hole 60 Air source 70 Fluid circuit 80 Drive portion 81 Stator 82 Rotor 110 Movement mechanism 111 Z-axis movement mechanism 112 X-axis movement mechanism 113 Y-axis movement mechanism 130 Control portion

Claims (5)

In the air spindle device,
Housing and
a spindle rotatably mounted within the housing and configured to hold a tool;
a radial bearing provided in the housing and supporting the spindle in a radial direction via air;
a thrust bearing provided in the housing and supporting the spindle in the axial direction via air;
an x-direction displacement meter, a y-direction displacement meter, and a z-direction displacement meter for determining displacement amounts in an x-direction, a y-direction, and a z-direction of the spindle relative to the housing;
A moving mechanism that drives the housing;
A control unit.
the moving mechanism includes an x-axis moving mechanism, a y-axis moving mechanism, and a z-axis moving mechanism;
An air spindle device in which the control unit controls the x-axis movement mechanism, the y-axis movement mechanism, and the z-axis movement mechanism of the movement mechanism in directions that correct the displacement amounts of the spindle in each of the x-direction, y-direction, and z-direction based on signals from the x-direction displacement meter, the y-direction displacement meter, and the z-direction displacement meter. The air spindle device according to claim 1, wherein the control unit determines the load on the tool based on signals from the x-direction displacement gauge, the y-direction displacement gauge, and the z-direction displacement gauge. The air spindle device according to claim 1 or 2, wherein the x-direction displacement gauge and the y-direction displacement gauge are embedded in the radial bearing provided in the housing and measure the distance between the outer peripheral surface of the spindle. An air spindle device according to any one of claims 1 to 3, wherein the z-direction displacement meter is embedded in the thrust bearing provided in the housing and determines the distance between the thrust bearing and a flange provided on the spindle. An air spindle device according to any one of claims 1 to 3, wherein the z-direction displacement meter measures the displacement of the upper end of the spindle.