Stylus

Abstract

To provide a stylus that suppresses wear-out of a stylus tip of a measurement probe tip, or damage occurring in a workpiece, extends a durable life, and can suppress damage occurring in a measurement workpiece.SOLUTION: A stylus, which is provided in a tip of a measurement probe, has a stylus chip that contacts with a measured object in an outer peripheral surface; and a stylus shaft that has one end connected to the stylus chip. The stylus chip has a hard coating in an outer periphery, and when defining a protrusion of the hard coating equal to or more than height 1 μm locally occurring from the outer peripheral surface as a coating protrusion, an area of 0.10 mm*0.10 mm in which the number of coating protrusions of the stylus chip outer periphery surface is equal to or less than five pieces can be selected.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a stylus that is attached to the tip of a measuring probe for a two-dimensional or three-dimensional measuring device, and in particular to a measuring probe suitable for scanning measurement. [Background technology]

[0002] Two-dimensional or three-dimensional measuring devices are used to measure precision mechanical parts such as gears. Measurement probes are used to come into contact with the surfaces of precision mechanical parts and measure the surface shapes. Among the measurement methods, a continuous measurement method called scanning measurement has a much larger number of measurement points than point measurement, and the reliability of the measurement results is improved.

[0003] However, when scanning measurement is performed, the number of measurement points increases, and unless the measurement speed is increased, the measurement takes a long time, resulting in a problem of poor measurement efficiency. If the measurement speed is increased, new problems may arise, such as wear or breakage of the stylus tip that constitutes the stylus attached to the tip of the measurement probe, chipping of the tip, and scratches on the workpiece to be measured. If the stylus tip at the end of the stylus wears out or breaks, or if the tip is chipped during scanning measurement, the measurement must be repeated or the reliability of the acquired data may be compromised. Furthermore, if the stylus tip body is made of a superhard material with excellent wear resistance in order to extend the durable life due to wear of the stylus tip, not only will it be expensive, but there will also be a higher risk of the stylus tip breaking or chipping. It is believed that these problems are influenced not only by the measurement pressure and measurement speed, but also by the hardness, surface properties, toughness, etc. of the contact surface of the stylus tip.

[0004] In this regard, for example, Patent Document 1 discloses a stylus whose ball tip is treated to reduce friction with a DLC (diamond-like carbon) film that has high hardness and high wear resistance, with the aim of providing a three-dimensional measuring device and a probe used therein that are capable of realizing high-precision, high-speed and stable scanning measurement. Moreover, Patent Document 2 discloses a method for manufacturing a stylus having such a tip ball that has been treated to reduce friction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-201105 A [Patent Document 2] JP 2019-190999 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the inventors have discovered that when a high-hardness coating treatment such as those described in Patent Documents 1 and 2 is applied to the stylus tip, while it is desirable to improve efficiency by further increasing the measurement speed, it may not always be possible to simultaneously prevent peeling, wear, and damage to the coating applied to the stylus tip and prevent scratches on the measured workpiece, depending on conditions such as the object to be measured and the measurement speed. In other words, there is a problem that the conventionally disclosed styli may have insufficient durability in terms of the lifespan of the stylus tip and insufficient prevention of scratches on the workpiece to be measured. The present invention has been developed in consideration of these problems, and its objective is to provide a stylus that can reduce wear on the stylus tip at the end of the measurement probe and scratches on the workpiece, thereby extending the durable life of the stylus and suppressing scratches on the workpiece being measured. [Means for solving the problem]

[0007] The present inventors have conducted research to solve the above problems, and have found that the above problems are largely related to the presence of protrusions that occur when a hard coating is formed on the outer periphery of the stylus tip. DLC coatings formed by chemical vapor deposition (CVD) using hydrocarbon gas as a raw material are generally characterized by the fact that they generate fewer protrusions due to the film formation method, but are inferior in wear resistance to DLC coatings formed by physical vapor deposition (PVD) using solid carbon as a raw material. For this reason, DLC coatings formed by the PVD method are suitable for members where wear and scratches are a problem. However, the present inventors have found that the above problems occur when DLC coatings formed by the PVD method generate more protrusions than those formed by the CVD method. As a result of examining various conditions for forming a hard coating on the outer periphery of the stylus tip, they have found that the above problems can be solved by forming a hard coating that satisfies specific conditions on the outer periphery of the stylus tip, and have completed the present invention.

[0008] The present invention relates to a stylus provided at the tip of a measurement probe, The stylus has a stylus tip that contacts an object to be measured at an outer circumferential surface thereof, and a stylus shaft having one end connected to the stylus tip, The stylus tip has a hard coating on its outer periphery, When a hard coating protrusion that occurs locally from the outer periphery and has a height of 1 μm or more is defined as a coating protrusion, The present invention relates to a stylus capable of selecting an area of ​​0.10 mm x 0.10 mm on the outer circumferential surface of the stylus tip in which the number of coating protrusions is 5 or less. Effect of the Invention

[0009] According to the present invention, it is possible to provide a stylus tip in a measurement probe of a two-dimensional or three-dimensional measuring device that can reduce wear and breakage of the stylus tip at the tip of the measurement probe, extend its durable life, and suppress scratches on the workpiece being measured. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing an example of the configuration of a measurement probe. [Diagram 2] 1A and 1B are schematic cross-sectional views showing the vicinity of the contact portion of the stylus tip, in which (a) is an example in which the shape of the stylus tip is spherical, and (b) is an example in which the shape of the abacus is shaped. [Diagram 3] 1 is a photograph showing coating protrusions on a hard coating. [Figure 4] 1 is a photograph showing an inspection device for a wear test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] One embodiment of the present invention comprises: A stylus provided at the tip of a measurement probe, The stylus has a stylus tip that contacts an object to be measured at an outer circumferential surface thereof, and a stylus shaft having one end connected to the stylus tip, The stylus tip has a hard coating on its outer periphery, When a hard coating protrusion that occurs locally from the outer periphery and has a height of 1 μm or more is defined as a coating protrusion, The stylus is capable of selecting an area of ​​0.10 mm x 0.10 mm on the outer periphery of the stylus tip in which the number of coating protrusions is 5 or less. Specific embodiments of the present invention will be described below. However, unless otherwise specified, the configurations described in the following embodiments are not intended to limit the technical scope of the invention.

[0012] The stylus according to this embodiment can be provided at the tip of a measurement probe of a measurement device. The configurations of the measuring device and the measuring probe are not particularly limited, and the present invention can be applied to, for example, a three-dimensional measuring device for measuring precision mechanical parts such as gears and its measuring probe.

[0013] <Stylus> A measurement probe equipped with a stylus according to this embodiment will be described with reference to FIG. Fig. 1 is a schematic diagram showing an example of a measurement probe equipped with a stylus according to this embodiment. The stylus attached to the measurement probe is composed of a stylus shaft and a stylus tip. In Fig. 1, the up-down direction is the "radial direction" and the left-right direction is the "axial direction". 1 has a stylus shaft 10 and a stylus tip 11 provided at the tip side of the stylus shaft 10, and one end of the stylus shaft 10 is connected to the stylus tip 11. Measurement is performed by bringing the outer circumferential surface of the stylus tip 11 into contact with the object to be measured. The stylus tip 11 has a hard coating on its outer periphery.

[0014] In this specification, the "contact portion" refers to the portion of the outer circumferential surface of the stylus tip 11 where the stylus tip 11 comes into contact with the object to be measured. Depending on the shape of the stylus tip 11 and the object to be measured, the entire outer circumferential surface of the stylus tip 11 can be the contact portion, but an example is the portion of the outer circumferential surface of the stylus tip 11 that is farthest from the central axis of the stylus shaft 10, as shown by reference numeral 12 in Figures 2(a) and (b).

[0015] In the example shown in FIG. 1, the shape of the stylus shaft 10 is cylindrical and the shape of the stylus tip 11 is abacus-shaped, but the shape of the stylus shaft 10 is not particularly limited and may be a cone or a rectangular parallelepiped. The shape of the stylus tip 11 may be, for example, a barrel shape, a sphere shape, a hemisphere shape, a cone shape, a cylinder shape, or a disk shape. Fig. 2(a) shows a sphere shape, and (b) shows an abacus shape.

[0016] The material of the base material of the stylus shaft 10 and the stylus tip 11 is not particularly limited and may be a magnetic or non-magnetic material, such as, but not limited to, steel, ruby, cemented carbide, etc. In addition, a material with little thermal expansion and contraction is preferable.

[0017] <Hard coating> The stylus tip 11 has a hard coating on its outer periphery. The hard coating may cover at least a part of the outer periphery of the stylus tip 11, including the contact portion, but from a manufacturing standpoint, it is preferable that the hard coating covers the entire outer periphery of the stylus tip 11. The hard coating may also cover at least a part of the outer periphery of the stylus shaft 10. The stylus tip 11 may have a different coating or underlayer between the substrate and the outermost hard coating of the stylus tip 11. When multiple coatings are present, hereinafter the term "hard coating" refers to the outermost hard coating unless otherwise specified.

[0018] The composition of the hard coating is not particularly limited, but from the viewpoint of excellent wear resistance, it is preferably at least one selected from the group consisting of DLC coating, chromium nitride coating, and titanium nitride coating. Also, it is more preferably a DLC coating, and more preferably a so-called hydrogen-free DLC coating having a hydrogen content of 5.0 at% or less. The hydrogen content may be 2 at% or less, 1 at% or less, or 0.5 at% or less.

[0019] The present inventors have discovered that the coating protrusions present on the surface of the hard coating are related to the balance between the wear of the stylus tip 11 and the suppression of scratches occurring on the measured workpiece. In this specification, a coating protrusion is a hard protrusion having a height of 1 μm or more that is locally generated from the outer periphery of the stylus tip when the hard coating surface on the outer periphery of the stylus tip is measured under the following conditions. This refers to the protrusion of the membrane.

[0020] The method for measuring the number of coating protrusions will be described below. FIG. 3 shows photographs of coating protrusions on the surface of a hard coating observed under the following conditions. Hard coating: Hydrogen-free DLC coating Hydrogen content 0.3 at% Film thickness 4 μm Measuring instrument: Keyence laser microscope VK-X100 Measurement magnification: 50x objective lens Measurement field of view: 0.20mm x 0.27mm For example, φ1.7×1.6 in FIG. 3 indicates that the major axis of the coated protrusion is 1.7 μm and the height of the coated protrusion is 1.6 μm. <Method for measuring the number of film protrusions> The protrusions on the hard coating surface are measured by the following method. Using a laser microscope VK-X100 manufactured by Keyence Corporation, a microscope image and three-dimensional data of the target surface are obtained with a 50x objective lens. The measurement field of view is 0.20 mm x 0.27 mm. The measurement field of view may be changed as appropriate depending on the size and shape of the stylus tip, which is the target. After trimming the captured image to an arbitrary 0.10 mm x 0.10 mm field of view, the automatic noise removal function of the laser microscope analysis application is used to remove abnormal data values ​​at the time of image acquisition, and the inclination of the outer peripheral surface at the time of measurement is corrected to a flat surface by automatic surface tilt correction. After that, a horizontal line is drawn in the image on the profile screen, and protrusions with a height of 1 μm or more relative to the outer peripheral surface are measured, and the number of protrusions is counted as the number of coating protrusions present in the 0.10 mm x 0.10 mm area. The diameter of the protrusions may also be measured when measuring the height.

[0021] In this embodiment, when the number of coated protrusions is measured by the above method, a region of 0.10 mm×0.10 mm in which the number of coated protrusions is 5 or less can be selected. It is even more preferable to be able to select an area of ​​0.10 mm x 0.10 mm in which the number of coating protrusions is 3 or less. By forming a hard coating so that such an area of ​​0.10 mm x 0.10 mm can be selected, scratches during measurement can be suppressed.

[0022] The coating protrusions on the surface of the hard coating can occur when the hard coating is formed on the outer periphery of the stylus tip 11. The coating protrusions are formed when giant molten particles called droplets, which are generated when raw materials are evaporated by plasma, adhere to the coating. The inventors have found that by setting the height and number of these coating protrusions within a specific range, it is possible to suppress both stylus wear and scratches on the measurement workpiece.

[0023] The maximum height of the coating projections is preferably 8 μm or less, more preferably 7 μm or less, and particularly preferably 5 μm or less. When the maximum height of the coating projections is 8 μm or less, deep scratches during measurement can be suppressed. The major axis of the coated protrusions is preferably 12 μm or less, more preferably 9 μm or less, and particularly preferably 7 μm or less. When the major axis of the coated protrusions is 12 μm or less, deep scratches during measurement can be suppressed.

[0024] The nanoindentation surface hardness of the hard coating is preferably 12 to 30 GPa. The surface hardness of the hard coating is 12 GPa or more, so that the wear of the stylus tip 11 is reduced. In addition, when the surface hardness of the hard coating is 30 GPa or less, peeling of the hard coating is suppressed. This is preferable from the viewpoint of control and manufacturing. The surface hardness of the hard coating is more preferably 15 to 28 GPa. stomach. Generally, when considering wear resistance, a hard coating having a high hardness is preferred. However, if the hardness of the hard coating is too high, the hard coating tends to peel off, so it is preferable to keep the hardness within the above range. The surface hardness of the hard coating can be adjusted by the material of the hard coating and the processing conditions during coating. can.

[0025] The thickness of the hard coating in the 0.10 mm x 0.10 mm region is preferably 3 to 10 μm. On the other hand, if the thickness of the hard coating exceeds 10 μm, there is a risk of the hard coating peeling off and it may be difficult to control the height of the protrusions of the hard coating. The lower limit of the thickness may be 3 μm or more, or 5 μm or more. The upper limit of the thickness may be 8 μm or less, or 6 μm or less. If the thickness of the hard coating is 3 μm or more, the wear suppression effect of the hard coating is easily exerted, which is preferable. When other coatings or underlayers are present between the substrate of the stylus tip and the outermost hard coating, the total thickness including these is preferably within the above range. The thickness of the hard coating can be appropriately adjusted by adjusting the conditions during the coating formation.

[0026] In addition, the inventors have found that when the object to be measured has a gear-like shape, the stylus intermittently hits the object during measurement, and the impact easily causes chipping (breakage) of the stylus. From the viewpoint of suppressing this, the hard coating is designed to reduce the plastic deformation work (W plast ) is preferably 6.0 nJ or more.

[0027] Plastic deformation work (plastic deformation energy) (W plast ) is the amount of work expended by the indenter pressing into the coating surface in the nanoindentation test to deform the coating, the amount of work expended in plastic deformation that results in the coating remaining deformed even after the indenter is removed. In addition, the amount of elastic deformation work (elastic deformation energy) (W elast ) is the amount of work released when the indenter is unloaded and the coating returns to its original shape. plast ) is an index that characterizes a coating that is prone to plastic deformation when a foreign object is pressed into the coating surface. The plastic deformation work (W plast ) is preferably 6.0 nJ or more, since peeling of the coating due to an impact load during measurement can be suppressed. Furthermore, the plastic deformation work (W plast ) is more preferably 6.4 nJ or more. plast ) is not particularly limited, but if it is too large, it is not possible to maintain a hardness that satisfies the wear resistance requirements, so it is preferable that it is 10.5 nJ or less.

[0028] The nanoindentation test is performed using a Fisher Instruments nanoindentation measuring instrument, model HM-2000, with a Vickers indenter under the following conditions: indentation load 100mN, loading time to maximum indentation load 30s (seconds), holding time 5s (seconds), and unloading time 30s (seconds). The plastic deformation work and elastic deformation work of the hard coating, as well as the nanoindentation hardness, are calculated using the load-indentation depth curve obtained in the nanoindentation test. The measured value is the average value of the measured values ​​at three points around the circumference of the hard coating around the outer periphery of one stylus tip in the circumferential direction of the hard coating.

[0029] In addition, the total work load (also called total deformation work load, W) calculated by the following formula (1) measured by the nanoindentation test total ) is preferably 18.0 nJ or more. Although there is no particular upper limit to the total work amount, it is preferable that the upper limit is 24.0 nJ or less. By satisfying the above range, it is possible to achieve both good abrasion resistance and prevention of peeling of the coating due to impact load during measurement. W total = W plast + W elast (1)

[0030] Furthermore, the plastic deformation power (η plast ) is preferably 32.4% or more, and further, The plastic deformation power is more preferably 33.0% or more, and even more preferably 34.0% or more. The upper limit of the plastic deformation power is not particularly limited, but is preferably 45.0% or less. By satisfying the above range, it is possible to achieve both good abrasion resistance and prevention of peeling of the coating due to impact load during measurement. η plast = (W plast / W total ) × 100(%) (2)

[0031] In addition, the nanoindentation hardness (HIT) and the plastic deformation work (W plast ) ratio (HIT / W plast ) is preferably 4.5 GPa / nJ or less, and more preferably 4.1 GPa / nJ or less. plast ) ratio (HIT / W plast The lower limit of ) is not particularly limited, but is preferably 1.5 GPa / nJ or more. By satisfying the above range, it is possible to achieve both good abrasion resistance and prevention of peeling of the coating due to impact load during measurement.

[0032] Examples of the film formation method for forming a hard coating on the stylus tip 11 (film formation process) include physical vapor deposition (PVD) methods such as ion plating and sputtering. PVD is preferred from the viewpoint of providing the abrasion resistance of the DLC coating required for stylus measurement. PVD (physical vapor deposition) is a type of vapor deposition method in which particles emitted from a target are attached to a substrate to form a film on the surface of a substance, and can also be called physical vapor deposition. PVD methods can include ion plating, vacuum deposition, ion beam deposition, sputtering, FCVA (Filtered Cathodic Vacuum Arc), and the like. It can also include chemical vapor deposition (CVD) methods such as thermal CVD and plasma CVD.

[0033] The number and size of the film protrusions of the hard coating can be set to the desired value by adjusting the manufacturing method of the hard coating. More specifically, for example, by lowering the arc current value, which is one of the film formation parameters, the surface temperature of the melting point called the arc spot that occurs on the target surface during vacuum arc discharge can be lowered, and the molten particles called droplets that cause the film protrusions can be reduced. In addition, by reducing the diameter of the aperture, which is the path through which carbon ions released from the target adhere to the substrate, the droplets that fly out from the target can be trapped within the path, and the number of droplets in the coating can be reduced.

[0034] The plastic deformation work measured by the nanoindentation test can be adjusted to a desired value by adjusting the manufacturing method of the hard coating. More specifically, when forming a hard coating using the FCVA method, the desired value can be achieved by adjusting the applied pulse bias voltage, the substrate temperature during the formation of the hard coating, the chamber pressure (vacuum degree), the arc current, the purity of the target, and the like.

[0035] When the hard coating includes a DLC coating, the DLC coating may be a DLC coating containing hydrogen, or may be a so-called hydrogen-free DLC. For example, the proportion of hydrogen elements may be 5.0 at% or less. A DLC coating with a high hydrogen content has lower wear resistance than a DLC coating without hydrogen. The method for forming the hydrogen-free DLC coating can be a known method, such as an ion plating method or a sputtering method.

[0036] The hard coating may contain other elements, such as, but not limited to, Si, Ti, W, Cr, Mo, Nb, and V. When these elements are contained, the total amount of these elements is 40 It is preferably at % or less. Furthermore, the stylus substrate may be provided with an underlayer containing Cr, Ti, Si, etc. By providing the underlayer, it is possible to improve the adhesion between the substrate of the stylus tip and the hard coating. The stylus according to this embodiment is completed through the above steps, but surface treatment such as buffing may be applied after film formation. EXAMPLES

[0037] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0038] As shown in Table 1, the material of the stylus tip and the hard coating on the periphery were adjusted to produce styli according to Examples 1 and 2 and Comparative Examples 1 to 3. [Table 1] The amount of wear of each stylus tip shown in Table 2 was determined by carrying out the following wear test. [Table 2]

[0039] <Wear test> A probe was attached to the inspection device shown in Figure 4 and brought into contact with a cylindrical workpiece under the conditions below, and the workpiece was rotated for the specified test time shown in Table 2. The part of the stylus tip that came into contact with the workpiece was observed under a microscope before and after the test, and the amount of wear was calculated. Test conditions Push-in amount (force): 150μm (approx. 25g) Stylus tip: Abacus type φ1.5mm Workpiece diameter: φ70mm Work material: Alloy tool steel Work surface roughness: Ra1.5mm Workpiece rotation speed: 1.5 rpm (scanning speed 5.5 mm / sec)

[0040] <Evaluation of scratches on workpiece> Regarding scratches caused on the workpiece by contact with the stylus tip, a reciprocating abrasion tester was used to test under the following conditions, which are stricter than the above-mentioned abrasion test. Test conditions Pressing load: 2.5N Stroke: 50mm Speed: 100 strokes / min Lubricant: None (no lubrication = dry) Upper specimen: stylus tip Lower test piece: Chromium molybdenum steel with mirror-finished surface Test time: 30 seconds The evaluation criteria were to measure the depth and number of scratches on the lower test piece after the test, and if scratches of 1.5 μm or more were generated, it was rated as NG, and if none were generated, it was rated as OK. In addition, if five or more scratches of 0.5 μm to 1.5 μm in depth were generated, it was rated as ×, if 1 to 4 scratches were generated, it was rated as ○, and if none were generated, it was rated as ◎. The results are shown in Table 3. [Table 3]

[0041] As is clear from the above examples, by providing the stylus tip of this embodiment at the tip of the measurement probe, it is possible to perform measurement work while reducing wear on the stylus tip and suppressing scratches on the workpiece to be measured. [Explanation of symbols]

[0042] 1 Stylus 10 Stylus shaft 11 Stylus Tip 12 Contact part 13 Probe

Claims

1. A stylus provided at the tip of a measurement probe, The stylus has a stylus tip that contacts an object to be measured at an outer circumferential surface thereof, and a stylus shaft having one end connected to the stylus tip, The stylus tip has a hard coating on its outer periphery, When a hard coating protrusion having a height of 1 μm or more that occurs locally on the outer peripheral surface is defined as a coating protrusion, A stylus capable of selecting a 0.10 mm x 0.10 mm area on the outer circumferential surface of the stylus tip in which the number of coating protrusions is 5 or less.

2. 2. The stylus of claim 1, wherein the hard coating has a thickness of at least 3 μm and less than 10 μm in the 0.10 mm×0.10 mm area.

3. The nanoindentation hardness of the hard coating is 12 GPa or more and 30 GPa or less.

2. The stylus of claim 1.

4. The hard coating is a DLC hard coating having a hydrogen content of 5.0 at% or less.

2. The stylus of claim 1.

5. The hard coating has a plastic deformation work (W ｐｌａｓｔ ) is 6.0 nJ or more; 2. The stylus of claim 1.

6. The hard coating has a total work load (W) calculated by the following formula (1) measured at a load of 100 mN by the nanoindentation test. ｔｏｔａｌ ) is 18.0 nJ or more; 2. The stylus of claim 1. W ｔｏｔａｌ = W ｐｌａｓｔ +W ｅｌａｓｔ (1)

7. The hard coating has a plastic deformation power (η ｐｌａｓｔ ) is 32.4% or more, 2. The stylus of claim 1. or ｐｌａｓｔ = (W) ｐｌａｓｔ / W ｔｏｔａｌ ) × 100 (%) (2)

8. The hard coating has a ratio (HIT / Wplast) of nanoindentation hardness (HIT) to plastic deformation work (Wplast) measured at a load of 100 mN by the nanoindentation test of 4.5 GPa / nJ or less. A stylus according to any preceding claim.

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