Touch probe and contact detection method

Abstract

To provide a touch probe with which it is possible to detect contact with high sensitivity without relying on the direction of contact of a workpiece to a stylus.SOLUTION: Provided is a touch probe comprising: a cylindrical housing 14 which is attached to a movable arm of a coordinate positioning device; a bearing part 20; a stylus shaft 12 which is contactlessly held; a stylus 11; magnetic repulsion parts 25, 31 that urge the stylus shaft 12 to a pause position by a repulsion force between a first magnet disposed to the stylus shaft 12 and a second magnet disposed to the housing 14 so as to face the first magnet; sensors 34, 35, 36 that output a change of stress in the magnetic repulsion parts 25, 31, as an electric signal, that is caused by a change of the repulsion force upon contact of the stylus 11 with a workpiece; and a control device. The control device has a calculation part that detects contact by the electric signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a touch probe and a contact detection method. [Background technology]

[0002] Touch probes are known that are used in coordinate positioning machines (e.g., coordinate measuring machines, machine tools, etc.) that contact a stylus with a workpiece (object to be measured), detect a signal related to the contact, and detect the position of the workpiece's surface.

[0003] As an example of such a touch probe, Patent Document 1 describes a contact detection device comprising: a central member having contacts that contact the object to be measured; a case having at least three seats for seating the central member and tiltably holding the central member; first detection means having stress-sensitive elements disposed on each seat and outputting a first detection signal based on pressure applied through the central member; second detection means having seating contacts formed on the stress-sensitive elements of each seat and outputting a second detection signal when at least one seating contact opens due to a change in the position of the contacts; and an electrical circuit that, when the second detection signal is output from the second detection means within a set time after the first detection signal is output from the first detection means, generates a contact signal at the time the first detection signal is output. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Publication number 7-4488 Summary of the Invention [Problem to be solved by the invention]

[0005] The touch probe according to the invention described in Patent Document 1 can detect contact with high sensitivity by combining detection based on the opening and closing of seated contacts and detection based on changes in stress.

[0006] However, there was room for improvement in that contact detection by opening and closing a limited number of seats meant that the sensitivity varied depending on the direction, and furthermore, the configuration in which the stylus came into contact with the seat meant that deformation due to impact and wear was inevitable, and responsiveness and sensitivity decreased with use.

[0007] Therefore, an object of the present invention is to provide a touch probe that can detect contact with high sensitivity regardless of the direction of contact between the stylus and the workpiece. Another object of the present invention is to provide a contact detection method. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0009] [1] A touch probe attached to a movable arm of a coordinate positioning device and used to detect contact with a workpiece, the touch probe comprising: a cylindrical housing; a bearing portion arranged inside the housing; a stylus shaft supported in a non-contact manner by the bearing portion; a stylus arranged at the tip of the stylus shaft and contacting the workpiece; a magnetic repulsion portion that urges the stylus shaft to a rest position by the repulsive force between a first magnet arranged on the stylus shaft and a second magnet arranged in the housing so as to face the first magnet; a sensor that outputs, as an electrical signal, a change in stress in the magnetic repulsion portion caused by a change in the repulsive force due to a change in the distance between the first magnet and the second magnet when the stylus comes into contact with the workpiece; and a control device, the control device having a calculation portion that detects the contact by the electrical signal. [2] The touch probe described in [1], wherein the bearing portion has a third magnet arranged along the inner surface of the housing, and a fourth magnet is arranged on the outer surface of the stylus shaft so as to face the third magnet, and the rotation of the stylus shaft is regulated by the attractive force generated by the third magnet and the fourth magnet. [3] The touch probe described in [2], wherein the stylus shaft has a flange portion formed to extend in a perpendicular direction, the fourth magnet is arranged on the flange portion, and at least a portion of the third magnet is arranged so as to face the fourth magnet on the housing above and below the flange portion along the axial direction of the stylus shaft. [4] The touch probe according to [3], wherein the third magnet and the fourth magnet are permanent magnets. [5] A touch probe described in any of [1] to [4], wherein the magnetic repulsion portion includes a first magnetic repulsion portion whose repulsive force acts along the axial direction of the stylus shaft, and a second magnetic repulsion portion whose repulsive force acts along a direction perpendicular to the stylus shaft, and the first magnetic repulsion portion includes a second flange portion arranged on the stylus shaft so as to protrude in the perpendicular direction, the first magnet arranged on the second flange portion, and the second magnets arranged on the housing above and below the second flange portion along the axial direction so as to face the first magnet, respectively. [6] The touch probe described in [5], wherein the second magnetic repulsion portion includes the first magnet arranged on the outer periphery of the stylus shaft and the second magnet arranged on the inner periphery of the housing so as to face the first magnet. [7] A touch probe described in any of [1] to [6], wherein the magnetic repulsion unit includes the second magnets arranged evenly in the inner circumferential direction of the housing, the sensors are arranged corresponding to each of the second magnets, and the calculation unit calculates at least one selected from the group consisting of the displacement direction and displacement amount of the stylus axis based on the difference in output of the sensors. [8] The touch probe according to any one of [1] to [7], wherein the sensor includes a strain gauge. [9] A contact detection method for detecting contact with a workpiece using the touch probe according to any one of [1] to [8]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a touch probe that can detect contact with high sensitivity regardless of the direction of contact between the stylus and the workpiece. Also, according to the present invention, it is possible to provide a contact detection method. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram of a touch probe according to an embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged view (cross-sectional view) of the ENL portion of FIG. [Figure 3] 1A and 1B are explanatory diagrams of the bearing portion, where (a) is an axial cross-sectional view of the tip portion of the housing including the bearing portion, (b) is a BB' cross-sectional view, (c) is a CC' cross-sectional view, and (d) is a DD' cross-sectional view. [Figure 4] 10A and 10B are explanatory diagrams of another embodiment of the bearing part, in which (a) is an explanatory diagram of the arrangement of the permanent magnets in the bearing part, and (b) is an exploded view thereof. [Figure 5] 10A and 10B are explanatory diagrams of another embodiment of the bearing part, in which (a) is an explanatory diagram of the arrangement of the permanent magnets in the bearing part, and (b) is an exploded view thereof. [Figure 6] FIG. 2 is a cross-sectional view of the touch probe taken along line AA′. [Figure 7] 2 is a cross-sectional view of a touch probe taken along line AA' for illustrating another form of the first magnetic repulsive portion. FIG. [Figure 8] FIG. 2 is a cross-sectional view taken along the line AA′ for explaining a method for detecting contact between the stylus and the workpiece. [Figure 9] 10 is an axial (XY) cross-sectional view of a rear end portion of a housing including a second magnetic repulsion portion. FIG. [Figure 10] FIG. 10 is an axial cross-sectional view of the rear end portion of the touch probe for explaining a method of detecting contact between the stylus and the workpiece. [Figure 11] FIG. 2 is a functional block diagram of a touch probe. [Figure 12] 1 is a flowchart of a method for detecting contact with a workpiece using a touch probe. [Figure 13] 10 is an axial (XY) cross-sectional view of a rear end portion of a housing including a second magnetic repulsion portion. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0013] The embodiment shown below is an example that embodies the technical concept of the present invention, and the technical concept of the present invention does not limit the materials, shapes, structures, and arrangements of the components to the following embodiment. The drawings are schematic. Therefore, the relationship and ratio between thickness and planar dimensions may differ from the actual ones, and the relationship and ratio between dimensions may also differ between the drawings.

[0014] [Touch probe] A touch probe according to an embodiment of the present invention (hereinafter also referred to as "this touch probe") is a touch probe that is attached to a movable arm of a coordinate positioning device and is used to detect contact with a workpiece, and comprises a cylindrical housing, a bearing portion arranged inside the housing, a stylus shaft supported non-contact by the bearing portion, a stylus arranged at one end of the stylus shaft and that contacts the workpiece, a magnetic repulsion portion that urges the stylus shaft to a rest position by the repulsive force between a first magnet arranged on the stylus shaft and a second magnet arranged in the housing so as to face the first magnet, a sensor that outputs as an electrical signal a change in stress in the magnetic repulsion portion that occurs when the stylus shaft is displaced from the rest position due to contact between the stylus and the workpiece, changing the distance between the first magnet and the second magnet, and the repulsive force changes, and a control device, the control device having a calculation portion that detects contact by the electrical signal.

[0015] First, the hardware configuration of this touch probe will be explained with reference to Figures 1 and 2. Figure 1 is an explanatory diagram of this touch probe, and Figure 2 is an enlarged view (cross-sectional view) of the ENL portion.

[0016] The touch probe 100 has a stylus 11 including a contact 10 for contacting a workpiece (object to be measured), and a stylus shaft 12 connected to the stylus 11 via a connection part 13 . The stylus shaft 12 is housed inside a cylindrical housing 14 and is supported non-contact by a bearing portion 20, a first magnetic repulsion portion 25 provided midway along the stylus shaft 12, and a second magnetic repulsion portion 31 provided at the end of the stylus shaft 12 opposite the stylus 11.

[0017] The touch probe 100 also has a window 32 provided in the top of the housing 14 and a circuit board 33 arranged inside the window 32, and furthermore, a battery (not shown) is arranged inside the housing 14. A control device and the like that control each part of the touch probe 100 are arranged on the circuit board 33.

[0018] At the end of the housing 14 opposite the stylus 11 is a shank 15. Via this shank 15 the touch probe 100 is attached to a movable arm of a coordinate positioning apparatus or the like.

[0019] Next, moving inside the cylindrical housing 14, the stylus shaft 12 has a first flange portion 16 formed to protrude in the direction perpendicular to the shaft (XY direction). Permanent magnets 17, 18, and 19 that make up a bearing portion 20 are arranged around this along the inner periphery of the housing 14.

[0020] Permanent magnets 17 and 19 (third magnets) are arranged on the upper (Z+ direction) and lower (Z- direction) sides, respectively, of first flange portion 16 along the axial direction (Z direction) of stylus shaft 12. Permanent magnet 18 (third magnet) is arranged so as to face the end face of first flange portion 16 in the direction perpendicular to the axis (XY direction).

[0021] Figure 3 is an explanatory diagram of the bearing portion 20, where Figure 3(a) is an axial cross-sectional view of the tip portion 40 of the housing 14 including the bearing portion 20, Figure 3(b) is a BB' cross-sectional view, Figure 3(c) is a CC' cross-sectional view, and Figure 3(d) is a DD' cross-sectional view.

[0022] The stylus shaft 12 has a first flange portion 16 that protrudes in a direction perpendicular to the shaft (XY direction, outer periphery). A permanent magnet 37 (fourth magnet) is disposed on this first flange portion 16. In other words, the fourth magnet is disposed on the outer periphery of the stylus shaft 12. Furthermore, the permanent magnet 19, which is arranged on the upper side (Z+ direction) along the axial direction of the stylus shaft 12 relative to the first flange portion 16, faces the permanent magnet 37. Furthermore, the orientations of the magnetic poles of the permanent magnets 37 and 19 are adjusted so that a (magnetic) attractive force acts between them. In other words, in terms of the relationship between the N (positive) pole 190 and S (negative) pole 191 of the permanent magnet 19, and the N pole 370 and S pole 371 of the permanent magnet 37, the S pole 191 and the N pole 370 are closest to each other, and are arranged so that an attractive force can easily act.

[0023] Similarly, the permanent magnet 17, which is arranged on the lower side (Z-direction) along the axial direction of the stylus shaft 12 with respect to the first flange portion 16, faces the permanent magnet 37. In addition, the orientations of the magnetic poles of the permanent magnets 37 and 17 are adjusted so that an attractive force acts between them. In other words, in terms of the relationship between the north pole 170 and south pole 171 of the permanent magnet 17, and the north pole 370 and south pole 371 of the permanent magnet 37, the south pole 171 and the north pole 370 are closest to each other, and are arranged so that attractive force can easily act.

[0024] Furthermore, a permanent magnet 18 is arranged in the housing 14 so as to face the permanent magnet 37 arranged in the first flange portion 16 in a direction perpendicular to the axis (XY direction). The magnetic poles of this permanent magnet 18 are adjusted so that an attractive force acts between it and the permanent magnet 37. That is, the north pole 190 and south pole 191 of the permanent magnet 19, the north pole 370 of the permanent magnet 37 and the south pole 181 of the permanent magnet 18 are closest to each other, and are arranged so that attractive forces can easily act.

[0025] By arranging the permanent magnets as described above, the permanent magnet 37 (fourth magnet) arranged in the first flange portion 16 and the permanent magnets 17, 18, and 19 (third magnets) arranged to face it in the axial and perpendicular directions, respectively, generate attractive forces. This attractive force restricts the rotation of the stylus shaft 12. In other words, the bearing portion 20 functions as a non-contact support rotation stopper. The bearing portion 20 also has the function of biasing the stylus shaft 12 toward approximately the center inside the housing 14, and together with magnetic repulsion portions 25 and 31 described below, biases the stylus shaft 12 toward the rest position.

[0026] The above is one example of the configuration of the bearing 20, and the configuration of the bearing of this touch probe is not limited to the above. For example, the orientation of the magnetic poles of each permanent magnet can be changed as appropriate. Furthermore, although the touch probe 100 has one bearing 20, this touch probe may have multiple bearings. In addition to those that utilize magnetic force (attraction force), known air bearings can also be used.

[0027] Figures 4 and 5 are explanatory diagrams of other embodiments of the bearing unit 20. Figures 4(a) and 5(a) are explanatory diagrams of the arrangement of the permanent magnets in the bearing unit 20, and Figures 4(b) and 5(b) are exploded views thereof. Note that the housing 14 and stylus shaft 12 are omitted from the drawings.

[0028] The arrangement of the permanent magnets in the bearing portion 20 in FIGS. 4 and 5 differs from that in FIG. 3 in that doughnut-shaped (cylindrical) permanent magnets are used. However, in either arrangement, the orientation of the magnetic poles of each permanent magnet is adjusted so that an attractive force easily acts on the permanent magnet 37 arranged in the first flange portion 16. In Fig. 4 and Fig. 5, the open area represents the north pole, and the shaded area represents the south pole.

[0029] Next, the configuration of the magnetic repulsion portion that has the function of biasing the stylus shaft 12 to the rest position will be described. 1 and 2, the touch probe 100 has two magnetic repulsive units 25, 31. The magnetic repulsive units 25, 31 are composed of a first magnet arranged on the stylus shaft 12 and a second magnet arranged on the inner periphery of the housing 14, and the repulsive force between the first magnet and the second magnet biases (balances) the stylus shaft 12 to the rest position.

[0030] First, first magnetic repulsion portion 25 is disposed midway along stylus shaft 12. Note that the position of first magnetic repulsion portion 25 is not limited to the above, and it can be disposed at any part of stylus shaft 12.

[0031] The first magnetic repulsion portion 25 is composed of a first magnet and a second magnet facing the first magnet. First, the first magnet is composed of permanent magnets 21, 22, 23, and 38 (permanent magnet 38 is arranged on the back side of permanent magnet 22, separated by stylus shaft 12, in the drawing) that are evenly arranged (arranged at 90° intervals) around the circumference of stylus shaft 12. Next, the second magnet is made up of four electromagnets 24 evenly spaced along the inner circumferential surface of the housing 14 so as to face each of the first magnets.

[0032] Next, the arrangement of the first magnet and the second magnet will be described in detail. Figure 6 is a cross-sectional view of the touch probe 100 taken along line AA'. Permanent magnets 21, 22, 23, and 38 are arranged at approximately 90° intervals around the outer periphery of stylus shaft 12. Note that touch probe 100 has a permanent magnet as the first magnet, but the first magnet may also be an electromagnet. If the first magnet is a permanent magnet, it does not require a power supply, and is therefore more suitable as the magnet for stylus shaft 12, which is supported in a non-contact manner relative to housing 14.

[0033] Meanwhile, four electromagnets 24 are arranged at approximately 90° intervals on the inner periphery of the housing 14. These electromagnets 24 face the first magnets (permanent magnets 21, 22, 23, 38) arranged along the outer periphery of the stylus shaft 12, respectively. The orientation of the magnetic poles of the electromagnets 24 is adjusted so that a repulsive force acts between them and the corresponding first magnets (permanent magnets 21, 22, 23, 38).

[0034] In Figure 6, each of the first magnets, permanent magnets 21, 22, 23, and 38, is arranged so that its north pole faces radially outward and its south pole faces radially inward, but the orientation of the magnetic poles of the first magnets in the touch probe according to the embodiment of the present invention is not particularly limited, and they may be oriented so as to generate a repulsive force relative to the electromagnet 24 arranged opposite them.

[0035] Furthermore, in the first magnetic repulsion portion 25 of Figure 6, the first magnet and the second magnet are each composed of four magnets (four pairs of magnets), but the number of magnets constituting the first magnet and the second magnet is not limited to the above as long as it can bias the stylus shaft 12 to the rest position. In particular, from the viewpoint of making it easier to bias the stylus shaft 12 toward the rest position, the number of first magnets and second magnets is preferably three or more, more preferably four or more, and preferably twelve or fewer, and even more preferably ten or fewer. Furthermore, the first magnets and second magnets are preferably evenly spaced at n equal intervals (n = number of first or second magnets; intervals of approximately 360 / n°) along the outer periphery of the stylus shaft 12 and along the inner periphery of the housing 14. By arranging them evenly, the amount and / or direction of displacement of the stylus shaft 12 can be more easily calculated in a calculation unit (described later).

[0036] 6, each electromagnet 24 is arranged so that the north pole faces in the radial direction toward the stylus axis 12. However, the method for adjusting the direction of the magnetic pole in the first magnetic repulsion portion 25 is not limited to the above. Fig. 7 is an AA' cross-sectional view of a touch probe for explaining another embodiment of the first magnetic repulsion portion 25. In the case of Fig. 7, the opposing permanent magnet 22 and electromagnet 24 are adjusted so that the directions of the magnetic flux they generate are the same, and the magnetic poles of each magnet and electromagnet are formed so as to loop counterclockwise (or clockwise) as SN / SN / SN / SN. In other words, the permanent magnets 22, 21, 38, 23 and electromagnet 24 are configured so that their N poles (or S poles) are aligned in one direction along the circumferential direction of the stylus shaft 12. With the above-described configuration, the stylus shaft 12 is biased toward approximately the center (rest position) of the housing 14 by the repulsive force generated between the permanent magnet and the electromagnet.

[0037] When the stylus 11 is not in contact with the workpiece, in other words, when no contact pressure is applied to the stylus 11 from the workpiece, the stylus shaft 12 is biased by the magnetic repulsion portion 25 toward the approximate center of the housing 14, which is its resting position (the resting position in the XY plane). On the other hand, when the stylus 11 comes into contact with the workpiece, the stylus shaft 12 is displaced from this rest position. When the contact between the stylus 11 and the workpiece is released, the repulsive force acts as a restoring force, and the stylus shaft 12 returns to the rest position. One of the features of the touch probe 100 is that it detects the displacement of the stylus shaft 12 from the rest position by focusing on the change in repulsive force caused by the change in the distance between the magnets that make up the magnetic repulsion portion.

[0038] Returning to FIG. 6, a sensor for outputting a change in the repulsive force in the magnetic repulsive portion 25 as an electric signal will now be described. The housings 14 on the outer periphery of each electromagnet 24 are each formed thin, with a space Cav outside of them, and the housing 14 has a partial double-cylinder structure at the magnetic repulsion section 25. The sensor 34 is located within the space Cav and is bonded to the outside of this thin section. The sensor 34 is a strain gauge and is adjusted so that it can detect minute bending strain in the thin section. Specifically, it is adjusted so that it can detect bending strain using a known bridge circuit such as the two-gauge method.

[0039] Figure 8 is a cross-sectional view taken along line AA' to explain a method for detecting contact between the stylus 11 and a workpiece (contact detection method). While Figure 6 shows the state in which the stylus 11 (stylus shaft 12) is biased to the rest position before contact with the workpiece, Figure 8 shows the state in which the stylus 11 has come into contact with the workpiece and the stylus shaft 12 has been displaced in the X-direction.

[0040] When the stylus shaft 12 is in the rest position, the repulsive forces generated in each set of the first magnet and the second magnet that constitute the first magnetic repulsion section are approximately equal, and the repulsive forces applied to the stylus shaft 12 are balanced overall. On the other hand, when the stylus 11 comes into contact with the workpiece and the stylus shaft 12 is displaced in the X-direction, the distance (spacing) between the pair of magnets in the X-direction (the first magnet and the pair of opposing second magnets) becomes shorter, and the repulsive force generated becomes larger. On the other hand, the repulsive force generated between the pair of magnets in the X+ direction becomes smaller.

[0041] In the X-direction, the smaller spacing between the magnet pairs generates a larger repulsive force than in the balanced state, applying a (small) bending stress to the thin-walled housing 14. The strain gauge sensor 34 detects the strain caused by this bending stress and outputs it as an electrical signal. In other words, it outputs the change in the stress applied to the housing 14 as an electrical signal.

[0042] The above has described the case where the stylus shaft 12 is displaced in the X-direction, but because each set of magnets in the first magnetic repulsion section is evenly spaced along the circumferential direction, it is possible to calculate the amount and / or direction of displacement of the stylus shaft 12 based on the electrical signals output from each sensor 34. In other words, regardless of the direction of contact, it is possible to detect with high sensitivity the amount and / or direction of displacement, mainly in the X and Y directions.

[0043] Returning to FIGS. 1 and 2, the configuration of the second magnetic repulsion portion 31 for detecting the displacement of the stylus shaft 12 in the Z direction will now be described. First, the second magnetic repulsion portion 31 is disposed at the rear end of the stylus shaft 12 (the end opposite the stylus 11). Note that the position of the second magnetic repulsion portion 31 is not limited to the above, and it may be disposed midway along the stylus shaft 12.

[0044] The second magnetic repulsion portion 31 is composed of a first magnet and a second magnet facing the first magnet. First, the first magnet is disposed on a second flange portion 28 formed at the end of the stylus shaft 12 so as to protrude in a direction perpendicular to the axis of the stylus shaft 12 . More specifically, the first magnet is composed of a permanent magnet 27 arranged on the surface of the second flange portion 28 in the Z-direction and a permanent magnet 29 arranged on the surface in the Z+ direction.

[0045] On the other hand, the second magnet facing this is composed of four electromagnets 26 evenly spaced (spaced at 90° intervals) around the inner circumference of the housing 14 so as to face (face) the permanent magnet 27, and four electromagnets 30 evenly spaced around the inner circumference of the housing 14 so as to face the permanent magnet 29.

[0046] 9 is an axial (XY) cross-sectional view of the rear end portion 41 of the housing 14, including the second magnetic repulsion portion 31. As shown in FIG.

[0047] The second magnetic repulsion portion 31 has a second flange portion 28 formed at the end of the stylus shaft 12 so as to protrude in a direction perpendicular to the shaft, and a permanent magnet 27 arranged on its lower (Z-direction) surface. The permanent magnet 27 is disk-shaped and has substantially the same shape and size as the second flange portion 28, and is arranged so that the N pole 270 is in the Z-direction and the S pole 271 is in the Z+ direction.

[0048] Four electromagnets 26 are arranged on the inner surface of the housing 14 below the permanent magnet 27 (in the Z-direction) so as to face the permanent magnet 27. The electromagnets 26 are evenly spaced (at 90° intervals) around the inner periphery of the housing 14, and the orientation of their magnetic poles is adjusted so that a repulsive force acts on the permanent magnet 27.

[0049] The second magnetic repulsion portion 31 also has a permanent magnet 29 arranged on the upper (Z+ direction) surface of the second flange portion 28. The permanent magnet 29 is disk-shaped and has the same shape and size as the permanent magnet 27, and is arranged so that the N pole 290 is in the Z+ direction and the S pole 291 is in the Z- direction.

[0050] Four electromagnets 30 are arranged on the inner surface of the housing 14 above the permanent magnet 29 (in the Z+ direction) so as to face the permanent magnet 29. The electromagnets 30 are arranged evenly (at 90° intervals) around the inner periphery of the housing 14, and the orientation of their magnetic poles is adjusted so that a repulsive force acts on the permanent magnet 29.

[0051] In Figure 9, the first magnets, permanent magnets 27 and 29, are arranged so that their north poles face in the Z+ and Z- directions, respectively. However, the orientation of the magnetic poles of the first magnets in the touch probe according to the embodiment of the present invention is not limited to the above, and may be oriented in any direction that generates a repulsive force relative to the electromagnets 26 and 30 arranged opposite them.

[0052] Also, in Figure 9, a "magnet set" is composed of one first magnet (permanent magnet 27, 29) and four second magnets (electromagnets 26, 30), but the number of magnets that make up the first magnet and the second magnet is not limited to the above as long as it can bias the stylus shaft 12 to the rest position. In particular, from the viewpoint of making it easier to bias the stylus shaft 12 toward the rest position, the number of second magnets is preferably at least three, more preferably four or more, and preferably twelve or fewer, and more preferably ten or fewer. Furthermore, the second magnets are preferably arranged evenly along the inner circumferential direction of the housing 14 at n equal intervals (n=number of second magnets; intervals of approximately 360 / n°).

[0053] With the above configuration, a repulsive force is generated between the permanent magnet and the electromagnet, and therefore the stylus shaft 12 is biased to the rest position (a predetermined position in the Z direction).

[0054] Next, a sensor for outputting a change in the repulsive force in the magnetic repulsive portion 31 as an electric signal will be described. The housings 14 on the outer periphery of the electromagnets 26, 30 are each formed thin, with a space Cav outside them, forming a partial double-cylinder structure. Sensors 35, 36 are bonded to the outside of these thin sections. Sensors 35, 36 are strain gauges, and are adjusted to be able to detect minute bending strain in the thin sections.

[0055] Figure 10 is an axial cross-sectional view of the rear end portion 41 of the touch probe to explain a method for detecting contact between the stylus 11 and the workpiece. Figure 10 shows a state in which the stylus 11 comes into contact with the workpiece and the stylus axis is displaced in the Z+ direction.

[0056] When the stylus shaft 12 is in the rest position, the repulsive forces generated in each set of the first magnet and the second magnet are approximately equal, and the repulsive forces applied to the stylus shaft 12 are balanced as a whole. On the other hand, when the stylus 11 comes into contact with the workpiece and the stylus shaft 12 is displaced in the Z+ direction, the repulsive force generated between the pair of magnets in the Z+ direction (the pair of the first magnet and the opposing second magnet) increases, while the repulsive force generated between the pair of magnets in the Z- direction decreases.

[0057] In the Z+ direction, the gap between the magnet pairs becomes smaller, which generates a larger repulsive force than when the repulsive forces are balanced, and a (small) bending stress is applied to the thin-walled housing 14. The sensors 35 and 36, which are strain gauges, detect the strain caused by this bending stress and output it as an electrical signal. In other words, they output the change in stress applied to the housing 14 as an electrical signal.

[0058] While the above description has been given for the case where the stylus axis is displaced in the Z+ direction, the same applies to the Z- direction. Furthermore, since the sets of magnets in the second magnetic repulsion section are arranged approximately evenly along the circumferential direction of the housing 14, the amount and / or direction of displacement of the stylus axis can be calculated based on the electrical signals output from each sensor 35, 36. In other words, regardless of the direction of contact, the amount and / or direction of displacement, mainly in the Z direction, can be detected with high sensitivity.

[0059] Next, a description will be given of the function of each part of the touch probe 100. FIG. The touch probe 100 has a control device 80 housed in the housing 14, and the control device 80 has a control unit 81, a magnetic force control unit 82 that supplies power to the second magnet, the electromagnet 24 (26, 30), and controls the generation of magnetic force, a first magnet, the permanent magnet 21 (22, 23, 27, 29, 38), arranged on the stylus shaft 12, a calculation unit 83 that detects contact between the stylus 11 and the workpiece based on the output (electrical signal) of the sensor 34 (35, 36), and a communication unit 84 that outputs (out) the detection results of the calculation unit 83 to the outside.

[0060] The control unit 81 includes, as hardware, a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), memory, a power supply (battery), an A / D converter, etc., and controls each part of the touch probe 100 to realize its functions.

[0061] The magnetic force control unit 82 has a function of supplying power to the electromagnet 24 (26, 30), which is the second magnet, to generate magnetic force and control the magnitude and direction of the magnetic flux, and is realized by the CPU executing a program stored in the memory of the control unit 81. Note that if the second magnet is a permanent magnet, the touch probe 100 does not need to have the magnetic force control unit 82.

[0062] The sensor 34 has a function of outputting, as an electrical signal, a change in stress caused by a change in repulsive force resulting from a change in the distance between the permanent magnet 21 (22, 23, 27, 29, 38), which is the first magnet, and the electromagnet 24 (26, 30), which is the second magnet, when the stylus 11 comes into contact with the workpiece and the stylus shaft 12 is displaced from its rest position. The sensor 34 (35, 36) includes, as hardware, a strain gauge and / or a piezoelectric element.

[0063] The calculation unit 83 has a function of detecting contact between the stylus 11 and the workpiece based on an electrical signal from the sensor 34 (35, 36). The calculation unit 83 is realized by the CPU executing a program stored in the memory of the control unit 81. The communication unit 84 has a function of wirelessly transmitting the detection result by the calculation unit 83 to an external device (for example, a host computer).

[0064] Next, the operation of the touch probe 100 will be described. FIG. 12 is a flowchart of a method for detecting contact with a workpiece using the touch probe 100 (contact detection method). First, in step S1, the stylus 11 is brought into contact with the workpiece. Before the stylus 11 comes into contact with the workpiece, the stylus shaft 12 is biased to a rest position.

[0065] When the stylus 11 comes into contact with the workpiece, stress generated by the contact displaces the stylus shaft 12. Specifically, the stylus shaft 12 is displaced in the XY direction and / or the Z direction (step S2).

[0066] When the stylus shaft 12 is displaced, the distance (spacing) between the first magnet arranged on the stylus shaft 12 and the second magnet arranged on the housing 14 changes (step S3). This changes the stress (repulsive force) generated between the "pair of magnets" in the magnetic repulsion section 25 (31), and the output (electrical signal) of the corresponding sensor changes (step S4).

[0067] The calculation unit 83 detects contact of the stylus 11 with the workpiece based on the difference in output from each sensor. Specifically, one method is to determine that the stylus 11 has contacted the workpiece when the output from one or more sensors changes beyond a predetermined threshold. Such a threshold may be stored in advance in the memory of the control unit 81.

[0068] Furthermore, the calculation unit 83 calculates the amount of displacement and / or the direction of displacement of the stylus shaft 12 from the difference in output between the sensors (step S5). The amount and direction of displacement of the stylus shaft 12 can also be used to calculate the coordinate position of the contact 10 (i.e., the workpiece surface).

[0069] Next, in step S6, contact information with the workpiece detected by the calculation unit 83 is transmitted to the outside by the communication unit 84 (step S6). This contact information only needs to include at least the fact that contact with the workpiece has been detected, and may also include the calculation result of the coordinate position of the contact piece 10 (workpiece surface) in addition to the above.

[0070] As described above, the touch probe 100 comprises a stylus shaft 12 supported non-contactingly on the housing 14, a magnetic repulsion section 25 (31) for urging the stylus shaft 12 to its rest position, and a sensor 34 (35, 36) for outputting the displacement of the stylus shaft 12 from its rest position as an electrical signal due to a change in repulsive force, and therefore can detect contact with excellent sensitivity regardless of the direction of contact.

[0071] (Other forms of magnetic repulsion part) FIG. 13 is an axial (XY) cross-sectional view of the rear end portion 41 of the housing 14, including the second magnetic repulsion portion. In Figure 13, instead of strain gauges, sensors are provided, which include a piezoelectric element 90 that outputs mainly Z-direction compression as an electrical signal from changes in the repulsive force generated in the second magnet, electromagnet 26, and a piezoelectric element 91 that outputs mainly Z+ direction compression as an electrical signal from changes in the repulsive force generated in the second magnet, electromagnet 30. Four piezoelectric elements 90, 91 are arranged at equal intervals of approximately 90° along the inner circumference of the housing 14. These correspond to the electromagnets 26, 30, which are the second magnets, respectively, and the amount and / or direction of displacement can be detected from the difference in their outputs.

[0072] According to the above configuration, it is possible to output, as an electrical signal, a change in the repulsive force that accompanies displacement of the second flange portion 28 mainly in the Z direction. Note that although the Z axis direction is described in the drawings, the same applies to the magnetic repulsive portion 25, i.e., the X and Y directions. [Explanation of symbols]

[0073] 10 contact, 11 stylus, 12 stylus shaft, 13 connection portion, 14 housing, 15 shank, 16 first flange portion, 17-19, 21-23, 27, 29, 37, 38 permanent magnet, 20 bearing portion, 24 electromagnet, 25 first magnetic repulsion portion, 26, 30 electromagnet, 28 second flange portion, 31 second magnetic repulsion portion, 32 window, 33 substrate, 34-36 sensor, 40 tip portion, 41 rear end portion, 80 control device, 81 control portion, 82 magnetic force control portion, 83 calculation portion, 84 communication portion, 90, 91 piezoelectric element, 100 touch probe

Claims

1. A touch probe attached to a movable arm of a coordinate positioning device and used to detect contact with a workpiece, A cylindrical housing; a bearing portion disposed inside the housing; a stylus shaft supported in a non-contact manner by the bearing portion; a stylus disposed at the tip of the stylus shaft and contacting the workpiece; a magnetic repulsion unit that urges the stylus shaft toward a rest position by a repulsive force between a first magnet disposed on the stylus shaft and a second magnet disposed on the housing so as to face the first magnet; a sensor that outputs, as an electrical signal, a change in stress in the magnetic repulsion portion, the change occurring as a result of the repulsion force being changed due to a change in the distance between the first magnet and the second magnet when the stylus comes into contact with the workpiece, and a control device; The control device includes a calculation unit that detects the contact by the electrical signal.

2. the bearing portion has a third magnet arranged along an inner circumferential surface of the housing, and a fourth magnet is arranged on an outer circumferential surface of the stylus shaft so as to face the third magnet, 2. The touch probe according to claim 1, wherein rotation of the stylus shaft is restricted by an attractive force generated between the third magnet and the fourth magnet.

3. the stylus shaft has a flange portion formed to protrude in the orthogonal direction, the fourth magnet being disposed on the flange portion; 3. The touch probe according to claim 2, wherein at least a portion of the third magnet is arranged to face the fourth magnet on each of the housings above and below the flange portion along the axial direction of the stylus shaft.

4. The touch probe of claim 3 , wherein the third magnet and the fourth magnet are permanent magnets.

5. the magnetic repulsion unit includes a first magnetic repulsion unit whose repulsive force acts along the axial direction of the stylus shaft, and a second magnetic repulsion unit whose repulsive force acts along a direction perpendicular to the stylus shaft, The first magnetic repulsion portion includes: a second flange portion disposed on the stylus shaft so as to protrude in the orthogonal direction; the first magnet disposed on the second flange portion; The touch probe according to any one of claims 1 to 4, further comprising: second magnets arranged on the housing above and below the second flange portion along the axial direction so as to face the first magnets, respectively.

6. The second magnetic repulsion portion includes the first magnet disposed on the outer periphery of the stylus shaft; The touch probe according to claim 5 , further comprising: the second magnet disposed on an inner periphery of the housing so as to face the first magnet.

7. the magnetic repulsion portion includes the second magnets that are uniformly arranged in an inner circumferential direction of the housing, the sensors are disposed corresponding to the second magnets, 7. The touch probe according to claim 1, wherein the calculation unit calculates at least one selected from the group consisting of a displacement direction and a displacement amount of the stylus shaft based on the difference in output from the sensors.

8. A touch probe according to any preceding claim, wherein the sensor comprises a strain gauge.

9. A contact detection method for detecting contact with the workpiece using the touch probe according to any one of claims 1 to 8.

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