A surface microtopography measurement sensor

Abstract

The present invention discloses a surface micro-topography measurement sensor for measuring the topography of a workpiece to be measured, comprising: a stylus for measuring the micro-topography; a stylus shaft, one end of which is connected to the stylus and is used to move up and down following the stylus when the stylus measures the micro-topography; a magnetic constant force module connected to the other end of the stylus shaft for adjusting the measurement force between the stylus and the workpiece to be measured; a stylus shaft air bearing module surrounding the outer periphery of the stylus shaft for suspending the stylus shaft; and a displacement measurement module arranged directly above the stylus shaft for measuring the displacement of the stylus shaft in the vertical direction. In the present invention, an air gap is formed on the outer surface of the stylus shaft by the stylus shaft air bearing module to ensure that the stylus shaft is suspended and the friction is minimized, thereby improving the measurement accuracy of the stylus. The measurement force between the stylus and the workpiece to be measured can be adjusted by the magnetic constant force module so that the stylus transmits the surface topography of the workpiece to the sensor more truly.

Description

Technical Field

[0001] The present invention relates to the field of surface micro-topography measurement, and particularly to a surface micro-topography measurement sensor. Background Art

[0002] All along, surface micro-topography has been a hot topic in the field of precision engineering. Among them, surface roughness is a technical index used to describe the micro-geometric shape error of parts and is also an important method for evaluating machining processes. In manufacturing fields such as precision machinery, instruments, and ultra-precision machining, surface roughness is a parameter that is taken seriously, and the research on its measurement theory and the development of measurement instruments have always been the key concerns of people.

[0003] Roughness measuring instruments can be divided into stylus type and non-stylus type according to the measurement principle. The measurement principle of traditional stylus roughness measuring instruments is that after the stylus moves relative to the surface of the workpiece to be measured, the stylus undulates vertically with the surface of the workpiece to be measured, and then a sensor is used to measure this small undulation, and finally the surface information of the workpiece to be measured is obtained through signal processing.

[0004] The stylus roughness measuring instrument includes a lever type and a vertical type according to the measurement structure. Among them, due to the characteristics of its measurement structure, the lever stylus roughness measuring instrument has an inevitable cosine error when measuring the surface height undulation, which ultimately affects the overall accuracy of the roughness measuring instrument. Although this systematic error can be compensated by some means such as an angle sensor, in the field of nano-measurement, this is still an inevitable error and will introduce more uncertainties when evaluating the overall uncertainty of the instrument. Therefore, compared with the lever structure, the method of vertically measuring the surface micro-undulation has a smaller systematic error in principle and satisfies the Abbe principle. The key to a roughness measuring instrument is its sensor system. Therefore, it is necessary to invent a new type of surface micro-topography measurement sensor. Summary of the Invention

[0005] The purpose of the present invention is to provide a surface micro-topography measurement sensor for improving measurement accuracy.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] A surface micro-topography measurement sensor for measuring the topography of a workpiece to be measured, comprising:

[0008] A stylus for measuring the micro-topography;

[0009] A stylus shaft, one end of which is connected to the stylus and is used to move up and down following the stylus when the stylus measures the micro-topography;

[0010] A magnetic constant force module, connected to the other end of the stylus shaft, for adjusting the measuring force between the stylus and the workpiece to be measured;

[0011] A stylus shaft air bearing module, surrounding the periphery of the stylus shaft, for suspending the stylus shaft;

[0012] A displacement measurement module, arranged directly above the stylus shaft, for measuring the displacement of the stylus shaft in the vertical direction.

[0013] Optionally, the surface microtopography measurement sensor further includes a fixing plate, which is respectively connected to the stylus shaft, the magnetic constant force module and the displacement measurement module, and is used for fixing the stylus shaft, the magnetic constant force module and the displacement measurement module.

[0014] Optionally, the magnetic constant force module includes a force control link, a ring permanent magnet, a ring coil and a coil holder;

[0015] The force control link includes a first force control link and a second force control link. One end of the first force control link is connected to the other end of the stylus shaft, and the first force control link is perpendicular to the stylus shaft; the other end of the first force control link is connected to one end of the second force control link, the second force control link is perpendicular to the first force control link, and the second force control link and the stylus shaft are on the same side of the first force control link;

[0016] The ring permanent magnet is sleeved on the second force control link;

[0017] The coil holder includes an upper coil holder and a lower coil holder, and both the upper coil holder and the lower coil holder are fixed on the fixing plate;

[0018] The ring coil includes an upper ring coil and a lower ring coil. The upper ring coil is sleeved on the upper coil holder, and the lower ring coil is sleeved on the lower coil holder;

[0019] The ring permanent magnet is located between the upper ring coil and the lower ring coil, and the ring permanent magnet is parallel and coaxial with the upper ring coil and the lower ring coil.

[0020] Optionally, the stylus shaft includes a stylus fixing part and a piston rod;

[0021] One end of the stylus is located inside the stylus fixing part, one end of the piston rod is connected to the magnetic constant force module, and the other end of the piston rod is connected to the stylus fixing part; the stylus fixing part, the piston rod and the stylus are all coaxial.

[0022] Optionally, the stylus shaft air bearing module includes an air bearing and a guiding block, and the air bearing is sleeved outside the piston rod;

[0023] The stylus shaft further includes guiding hemispheres that match the number of the guiding blocks; each of the guiding hemispheres is connected to the piston rod, and the guiding hemispheres are uniformly arranged around the piston rod in a plane.

[0024] For each of the guiding blocks, there is a guiding hemisphere in contact with the guiding block, and the guiding block and the guiding hemisphere jointly keep the piston rod always in a vertical state.

[0025] Optionally, a reflecting component is arranged on the part of the stylus located inside the stylus fixing component.

[0026] Optionally, the reflecting component includes a cylindrical column sleeved on the stylus and a reflecting layer, and the reflecting layer is arranged on the surface of the cylindrical column.

[0027] Optionally, the material of the cylindrical column is glass-ceramics.

[0028] Optionally, the material of the reflecting layer is silver.

[0029] Optionally, the fixing plate includes a fixing plate mounting hole and a lens mounting groove.

[0030] In the present invention, an air gap is formed on the outer surface of the stylus shaft through the stylus shaft air bearing module, ensuring that the stylus shaft floats and has the minimum friction, and improving the accuracy of stylus measurement. The measurement force between the stylus and the workpiece to be measured can be adjusted through the magnetic constant force module, so that the stylus transmits the surface topography of the workpiece to the sensor more realistically. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 is the device structure diagram of the surface micro-topography measurement sensor of the present invention;

[0033] Figure 2 is the structural schematic diagram of the stylus shaft air bearing module;

[0034] Figure 3 is the structural schematic diagram of the stylus shaft;

[0035] Figure 4 is the structural schematic diagram of the fixing plate.

[0036] Symbol description:

[0037] Stylus shaft - 1; Stylus fixing part - 11; Piston rod - 12; Guide hemisphere - 13; Stylus shaft air bearing module - 2; Air bearing - 21; Guide block - 22; Magnetic constant force module - 3; Force control link - 31; Ring permanent magnet - 32; Upper ring coil - 331; Lower ring coil - 332; Coil holder - 34; Displacement measurement module - 4; Reflection part - 41; Fixed plate - 5; Lens mounting groove - 51; Fixed plate mounting hole - 52; Stylus - 6. Detailed implementation manners

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] The purpose of the present invention is to provide a surface microtopography measurement sensor for improving the measurement accuracy.

[0040] To make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0041] Figure 1 It is a structural diagram of the surface microtopography measurement sensor device of the present invention; Figure 2 It is a schematic structural diagram of the stylus shaft air bearing module; Figure 3 It is a schematic structural diagram of the stylus shaft; Figure 4 It is a schematic structural diagram of the fixed plate, as Figures 1 - 4 shown, the surface microtopography measurement sensor of the present invention includes a stylus 6, a stylus shaft 1, a magnetic constant force module 3, a stylus shaft air bearing module 2, and a displacement measurement module 4.

[0042] The stylus 6 is used to measure the microtopography of the surface of the workpiece to be measured.

[0043] One end of the stylus shaft 1 is connected to the stylus 6, and the stylus shaft 1 is used to move up and down following the stylus 6 when the stylus 6 measures the microtopography of the surface of the workpiece to be measured.

[0044] The stylus shaft 1 specifically includes a stylus fixing part 11 and a piston rod 12.

[0045] One end of the stylus 6 is located inside the stylus fixing part 11. A reflection part 41 is provided on the part of the stylus 6 located inside the stylus fixing part 11.

[0046] The reflection component 41 includes a cylindrical column sleeved on the stylus 6 and a reflection layer. The reflection layer is disposed on the surface of the cylindrical column.

[0047] The material of the cylindrical column is preferably glass-ceramics, but is not limited to glass-ceramics. Those skilled in the art can select different materials according to actual needs.

[0048] The material of the reflection layer is preferably silver, but is not limited to silver.

[0049] The reflection component 41 is used to reflect the laser of the displacement measurement module 4 to achieve displacement measurement.

[0050] One end of the piston rod 12 is connected to the magnetic constant force module 3, and the other end of the piston rod 12 is connected to the stylus fixing member 11.

[0051] The stylus fixing member 11, the piston rod 12, and the stylus 6 are all coaxial.

[0052] To ensure that the stylus shaft 1 always remains vertical during the measurement process, the stylus shaft 1 further includes a guiding hemisphere 13.

[0053] Each of the guiding hemispheres 13 is respectively connected to the piston rod 12, and each of the guiding hemispheres 13 is uniformly arranged around the piston rod 12 in a plane.

[0054] In this embodiment, the guiding hemisphere 13 is hemispherical.

[0055] The magnetic constant force module 3 is connected to the other end of the stylus shaft 1, and the magnetic constant force module 3 is used to adjust the measurement force between the stylus 6 and the workpiece to be measured.

[0056] Wherein, the magnetic constant force module 3 further includes a force control link 31, a ring permanent magnet 32, a ring coil, and a coil holder 34.

[0057] The force control link 31 includes a first force control link and a second force control link. The first force control link is connected to the other end of the stylus shaft 1, and the first force control link is perpendicular to the stylus shaft 1. The other end of the first force control link is connected to one end of the second force control link. The second force control link is perpendicular to the first force control link, and the second force control link and the stylus shaft 1 are located on the same side of the first force control link;

[0058] The ring permanent magnet 32 is sleeved on the second force control link;

[0059] The coil holder 34 includes an upper coil holder and a lower coil holder, and both the upper coil holder and the lower coil holder are fixed on the fixing plate 5;

[0060] The annular coil includes an upper annular coil 331 and a lower annular coil 332. The upper annular coil 331 is sleeved on the upper coil holder, and the lower annular coil 332 is sleeved on the lower coil holder.

[0061] The annular permanent magnet 32 is located between the upper annular coil 331 and the lower annular coil 332, and the annular permanent magnet 32 is parallel and coaxial with the upper annular coil 331 and the lower annular coil 332.

[0062] When the upper and lower suspension coils pass through currents with the same magnitude and opposite directions, a constant magnetic field will be generated near the center of the coil axis. Under the action of the electromagnetic field, the annular permanent magnet 32 overcomes gravity to keep a constant measuring force between 0.75 mN and 1 mN between the stylus 6 and the surface of the workpiece to be measured. And according to the hardness of the surface material of the workpiece to be measured, the magnitude of the measuring force can be adjusted by changing the magnitude of the coil current.

[0063] The stylus shaft air bearing module 2 surrounds the periphery of the stylus shaft 1, and the stylus shaft air bearing module 2 is used to suspend the stylus shaft 1.

[0064] The stylus shaft air bearing module 2 specifically includes an air bearing 21 and a guide block 22; the air bearing 21 is sleeved outside the piston rod 12.

[0065] The stylus shaft 1 acts as the piston rod 12 of the air bearing 21 and makes a reciprocating motion in the air bearing 21. Since the air bearing 21 will form an air film between the inner wall surface and the stylus shaft 1, the influence of friction on the dynamic response is greatly reduced, and the sufficient stiffness of the air film can keep its motion in the vertical direction.

[0066] For each of the guide blocks, there is a guide hemisphere 13 in contact with the guide block, and the guide block and the guide hemisphere 13 jointly keep the piston rod always in a vertical state.

[0067] In this embodiment, the number of the guide blocks and the guide hemispheres 13 is three each.

[0068] The three guide blocks 22 and the three guide hemispheres 13 on the stylus shaft 1 form a vertical guiding reference, and the guide hemispheres 13 are tangent to the guide blocks 22 respectively.

[0069] When the stylus 6 works, the guide hemisphere 13 and the guide block 22 are in point-contact friction, and both the guide block 22 and the guide hemisphere 13 are made of low-friction self-lubricating materials. While serving as a vertical guide, the guide block 22 also restricts five of the six degrees of freedom of the stylus shaft 1, preventing it from rotating and tilting, thus avoiding the resulting systematic errors.

[0070] The displacement measurement module 4 is arranged directly above the stylus shaft 1, and the displacement measurement module 4 is used to measure the displacement of the stylus shaft 1 in the vertical direction.

[0071] The displacement measurement module 4 further includes a reflection component 41 and a laser interferometer.

[0072] The laser interferometer is built above the stylus shaft 1, and the optical path center of the laser interferometer coincides with the axis of the stylus shaft 1.

[0073] For the convenience of installation, the surface micro-topography measurement sensor of the present invention further includes a fixing plate 5.

[0074] The fixing plate 5 is respectively connected to the stylus shaft 1, the magnetic constant force module 3 and the displacement measurement module 4. The fixing plate 5 is used to fix the stylus shaft 1, the magnetic constant force module 3 and the displacement measurement module 4.

[0075] The fixing plate 5 is provided with a fixing plate mounting hole 52 and a lens mounting groove 51, and the lens mounting groove 51 is used to mount a lens.

[0076] The surface micro-topography measurement sensor of the present invention further provides the following technical effects:

[0077] 1. The present invention adopts the vertical guiding reference of the air bearing and the V-block. While ensuring that the stylus shaft floats and has the minimum friction, it also avoids problems such as rotation and inclination of the stylus shaft during the working process, so that the stylus can transfer the surface topography of the workpiece to the sensor more truly.

[0078] 2. The present invention adopts a magnetic constant force control module. By changing the current magnitude in the upper and lower coils, it overcomes the self-weight of the stylus shaft itself to ensure that the measurement force between the stylus and the workpiece to be measured is maintained between 0.75 mN and 1 mN, and can change the current magnitude in the coil to adapt to workpieces with various different surface materials. And the magnetic constant force control module leads out the measurement cycle through a connecting rod to achieve the purpose of leading out the heat source and reducing the thermal expansion error.

[0079] 3. The present invention uses the laser interference method to measure the minute displacement change of the stylus, which has the characteristics of high precision, high resolution, low uncertainty, etc., and realizes the traceability to the definition of the meter, so that the roughness value can be directly measured.

[0080] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same and similar parts among the embodiments can be referred to each other.

[0081] In this article, specific examples are used to elaborate on the principles and implementation modes of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation modes and application scopes. To sum up, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A surface micro-topography measurement sensor for measuring the topography of a workpiece to be measured, characterized in that, The surface microtopography measurement sensor includes: A stylus for measuring the microtopography; A stylus shaft, one end of which is connected to the stylus and is used to move up and down following the stylus when the stylus measures the microtopography; A magnetic constant force module, connected to the other end of the stylus shaft, for adjusting the measurement force between the stylus and the workpiece to be measured; the magnetic constant force module includes a force control link, a ring permanent magnet, a ring coil, and a coil holder; the force control link includes a first force control link and a second force control link, one end of the first force control link is connected to the other end of the stylus shaft, and the first force control link is perpendicular to the stylus shaft; the other end of the first force control link is connected to one end of the second force control link, the second force control link is perpendicular to the first force control link, and the second force control link and the stylus shaft are on the same side of the first force control link; the ring permanent magnet is sleeved on the second force control link; the coil holder includes an upper coil holder and a lower coil holder, and both the upper coil holder and the lower coil holder are fixed on a fixed plate; the ring coil includes an upper ring coil and a lower ring coil, the upper ring coil is sleeved on the upper coil holder, and the lower ring coil is sleeved on the lower coil holder; the ring permanent magnet is located between the upper ring coil and the lower ring coil, and the ring permanent magnet is parallel and coaxial with the upper ring coil and the lower ring coil; A stylus shaft air bearing module, surrounding the periphery of the stylus shaft, for suspending the stylus shaft; the stylus shaft acts as a piston rod of an air bearing and makes a reciprocating motion in the air bearing; A displacement measurement module, arranged directly above the stylus shaft, for measuring the displacement of the stylus shaft in the vertical direction; the displacement measurement module further includes a reflection component and a laser interferometer, the laser interferometer is built above the stylus shaft, and the optical path center of the laser interferometer coincides with the axis of the stylus shaft.

2. The surface microtopography measurement sensor according to claim 1, characterized in that The surface microtopography measurement sensor further includes a fixed plate, which is respectively connected to the stylus shaft, the magnetic constant force module, and the displacement measurement module, and the fixed plate is used to fix the stylus shaft, the magnetic constant force module, and the displacement measurement module.

3. The surface microtopography measurement sensor according to claim 1, characterized in that The stylus shaft includes a stylus fixing component and a piston rod; One end of the stylus is located inside the stylus fixing component, one end of the piston rod is connected to the magnetic constant force module, and the other end of the piston rod is connected to the stylus fixing component; the stylus fixing component, the piston rod, and the stylus are all coaxial.

4. The surface microtopography measurement sensor according to claim 3, characterized in that, The stylus shaft air bearing module includes an air bearing and a guide block, and the air bearing is sleeved outside the piston rod; The stylus shaft further includes a guide hemisphere matching the number of the guide blocks; each guide hemisphere is connected to the piston rod, and each guide hemisphere is evenly arranged around the piston rod in a plane; For each guide block, there is a guide hemisphere in contact with the guide block, and the guide block and the guide hemisphere jointly keep the piston rod always in a vertical state.

5. The surface microtopography measurement sensor according to claim 3, characterized in that, A reflection component is arranged on the part of the stylus located inside the stylus fixing component.

6. The surface microtopography measurement sensor according to claim 5, characterized in that, The reflection component includes a cylindrical column sleeved on the stylus and a reflection layer, and the reflection layer is disposed on the surface of the cylindrical column.

7. The surface microtopography measurement sensor according to claim 6, wherein The material of the cylindrical column is glass-ceramics.

8. The surface microtopography measurement sensor according to claim 6, characterized in that The material of the reflection layer is silver.

9. The surface microtopography measurement sensor according to claim 2, wherein The fixing plate includes a fixing plate mounting hole and a lens mounting groove.

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