JP7165064B2 - linear gauge - Google Patents

Description

The present invention relates to a linear gauge for measuring surface displacement of an object to be measured.

A grinding apparatus that grinds a workpiece held on a chuck table to a predetermined thickness with a grinding wheel while supplying grinding water is disclosed in Japanese Patent Laid-Open Publication No. 2002-200011. The height of the surface and the height of the upper surface of the workpiece held by the holding surface are measured, and the height difference is calculated as the thickness of the workpiece.

In addition, a linear gauge is used to measure the height of each surface as described above. Height measurement is made possible (see Patent Document 2, for example).

JP 2008-073785 A JP 2015-175758 A

The linear gauge as described above is equipped with an air bearing that supports the shaft without contact by ejecting air toward the side surface of the shaft so that no load is applied to the vertical movement of the shaft. The air used in the air bearing is exhausted along the side surface of the shaft toward the workpiece, so that the grinding dust generated in the grinding chamber is included as the grinding process is performed while the grinding water is being supplied. It prevents grinding spray from entering the linear gauge.

However, this exhaust of air generates a vortex around the shaft, dries the grinding spray, and causes the grinding dust contained in the grinding spray to adhere to the shaft, making the shaft unable to move up and down.
Therefore, in a linear gauge that measures the top surface height of an object to be measured by linearly moving the shaft in the vertical direction while supporting the shaft in a non-contact manner with an air bearing, air can be exhausted from the air bearing and the side surface of the shaft There is a problem of preventing the shaft from becoming unable to move up and down due to adhesion of grinding dust.

The present invention for solving the above-mentioned problems is a linear gauge for measuring the surface displacement of an object to be measured, which comprises a shaft having a probe at its tip which is brought into contact with the surface of the object to be measured, and a side surface of the shaft. a casing having a support surface for supporting the shaft as a solid, an air ejection port disposed on the support surface and allowing air to intervene between the side surface of the shaft and the support surface, and a shaft disposed below the casing. an exhaust port formed in a ring shape surrounding a side surface for exhausting the air ejected from the air ejection port along the side surface of the shaft toward an object to be measured; and a water film surrounding the exhaust port on the side surface of the shaft. to enable air to be exhausted from the exhaust port, and prevent deposits from adhering to the shaft and the probe due to the water film formed by the water film forming means. It is a linear gauge that protects against

It is preferable that the water film forming means includes a water supply nozzle having an annular water ejection port surrounding the exhaust port.

The water film forming means includes an annular pipe surrounding the shaft, a supply portion supplying water from one position of the annular pipe to the annular pipe, and a symmetrical position with respect to the center of the annular pipe. and a water jetting port for jetting water toward the object to be measured at the other position, wherein the water supplied from the supply part to the annular pipe flows through the annular pipe, and the axis of the shaft is generated. It is preferable that a force in the circumferential direction around the center remains when the water merges at the water spout so that the water covers the side surface of the shaft and flows toward the object to be measured to form the water film.

A linear gauge for measuring the surface displacement of an object to be measured according to the present invention comprises a shaft having a probe at its tip to be brought into contact with the surface of the object to be measured, and a casing having a support surface surrounding and supporting the side surface of the shaft. , an air ejection port disposed on the support surface and allowing air to intervene between the side surface of the shaft and the support surface, and an air ejection port formed in a ring shape disposed under the casing and surrounding the side surface of the shaft and ejected from the air ejection port. Since it is provided with an exhaust port that exhausts air along the side surface of the shaft toward the object to be measured, and a water film forming means that surrounds the exhaust port and forms a water film on the side surface of the shaft, the air from the exhaust port In addition, the water film formed by the water film forming means can protect the shaft and the probe from deposits such as grinding dust. Furthermore, since the air exhausted from the exhaust port and the water supplied from the water film forming means remove grinding dust from the surface of the object to be measured that the probe is in contact with, the measurement error of the displacement of the surface of the object to be measured is reduced. occurrence can be prevented.

In the linear gauge according to the present invention, the water film forming means includes a water supply nozzle having an annular water ejection port surrounding the exhaust port, so that the water film can be easily formed.

In the linear gauge according to the present invention, the water film forming means includes an annular tube surrounding the shaft, a supply portion supplying water from one position of the annular tube, and a water supply section symmetrical with respect to the center of the annular tube. and a water ejection port formed on the opposite side of the supply unit at the other position and ejecting water toward the object to be measured, so that the water supplied from the supply unit to the annular pipe flows through the annular pipe. The generated circumferential force around the axis of the shaft remains when water joins at the water spout, causing the water to cover the side of the shaft and flow toward the object to be measured, easing the water film. can be formed.

It is a perspective view showing an example of a linear gauge. FIG. 4 is a cross-sectional view showing an example of a linear gauge; FIG. 4 is a cross-sectional view for explaining an example of water film forming means; FIG. 5 is a cross-sectional view for explaining another example of the water film forming means;

A linear gauge 4 according to the present invention shown in FIG. It is possible to measure the height position of the surface Wa of the object W, which changes with time due to grinding or the like.

The linear gauge 4 shown in FIGS. 1 and 2 surrounds and supports, for example, a direct-acting shaft 40 having a probe 400 at its tip that contacts the surface Wa of the object W to be measured, and a side surface 40a of the shaft 40. a casing 41 having a support surface 41a; an air ejection port 42 disposed on the support surface 41a and allowing air to intervene between the side surface 40a of the shaft 40 and the support surface 41a; An exhaust port 43 formed in a ring shape surrounding the side surface 40a and exhausting the air ejected from the air ejection port 42 along the side surface 40a of the shaft 40 toward the object W to be measured; and a water film forming means 44 for forming a water film on the side surface 40a.

The shaft 40 has, for example, a cylindrical outer shape, and a probe 400 is detachably connected to its lower end side. The probe 400 in this embodiment has a lower end 400c made of diamond or the like and formed in a rounded spherical shape.

As shown in FIG. 1, the upper end side of the shaft 40 extending in the vertical direction (Z-axis direction) is connected to, for example, the lower surface side of a rectangular plate-like fixing plate 490 by a fixing nut 491 .
The linear gauge 4 has a flat plate-like support plate 480 that faces the fixed plate 490 in the Z-axis direction and is parallel to the fixed plate 490 . As shown in FIG. 2, the shaft 40 passes through a circular hole 480a of the support plate 480, and the lower end side of the shaft 40 and the probe 400 connected to the lower end side of the shaft 40 are pushed from the lower surface of the support plate 480. It protrudes downward.

The linear gauge 4 includes, for example, a rotation restricting means 50 that restricts rotation about the axial direction (Z-axis direction) of the shaft 40 supported by the casing 41 in a non-contact manner. The rotation restricting means 50 includes a block-shaped first magnet 501 and a magnetic field directed in a direction repulsive to the magnetic field possessed by the first magnet 501. At least two second magnets 502 extending in the Z-axis direction parallel to the axial direction of 40, and a guide rod 503 connected to the first magnet 501 to move the first magnet 501 in the Z-axis direction It is configured.

The upper end side of the guide rod 503 is connected to the fixed plate 490 and extends parallel to the extending direction of the shaft 40 . A first magnet 501 is fixed to the lower end side of the guide rod 503 . The two second magnets 502 are fixed to the side surface of the casing 41 with the first magnet 501 interposed therebetween. Then, the repulsion between the first magnet 501 and the second magnet 502 keeps the horizontal distance between the second magnet 502 and the guide bar 503 constant, and the direction of the guide bar 503 changes. never Therefore, since the guide rod 503 whose orientation is fixed is connected to the shaft 40 via the fixing plate 490, even if the shaft 40 is formed in a cylindrical shape, the movement of the shaft 40 in the rotational direction is prevented by the rotation restricting means 50. can be regulated.
It should be noted that the shape of the shaft 40 is not limited to a cylindrical shape, and may be configured in a non-rotating shape, that is, a non-cylindrical shape. Therefore, it may be a polygonal prism or an elliptical prism. Also, it may have a columnar shape in which only one surface is flat and the other surface is curved. Correspondingly, the support surface 41 a of the casing 41 may also be formed in accordance with the shape of the shaft 40 . In this case, the linear gauge 4 may not be provided with the rotation restricting means 50 .

The casing 41 has, for example, a rectangular parallelepiped frame 410 disposed on the upper surface of the support plate 480. The shaft 40 can be inserted through the frame 410 to support the side surface 40a of the shaft 40 without contact. It is configured. In this embodiment, the shaft 40 is formed in a cylindrical shape, and correspondingly, the frame 410 is formed with a receiving hole 41d having a circular cross section for receiving the shaft 40 .
The frame body 410 includes a support surface 41a that surrounds the side surface 40a of the shaft 40 with a uniform gap therebetween, and air that surrounds the side surface 40a of the shaft 40 and supports the side surface 40a of the shaft 40. On the other hand, a plurality of air ejection ports 42 ejected from the support surface 41a, an air inlet 410c connected to an air supply source 60 such as a compressor, and a flow path communicating between the air inlet 410c and each air ejection port 42. 410d.

One end of an air supply pipe 600 such as a metal pipe or a flexible resin tube communicates with the air inlet 410c via a joint 410e. is connected.

In the casing 41 configured as described above, the air supplied from the air supply source 60 to the air supply pipe 600 is ejected from each air ejection port 42 in a direction perpendicular to the side surface 40a of the shaft 40, thereby 40 can be supported in a non-contact state by surrounding it with air through a gap.

On the support plate 480, a direct drive means 20 for linearly moving the shaft 40 in the Z-axis direction is arranged. As shown in FIGS. 1 and 2, the direct-acting drive means 20 is, for example, a piston cylinder. The cylinder tube 201 includes at least a piston rod 202 inserted into the cylinder tube 201 and having a lower end attached to the piston 200, and air inlets 203a and 203b for introducing air into the cylinder tube 201. As shown in FIG. The upper end side of the piston rod 202 can contact the lower surface of the fixed plate 490 , and the base end side of the cylinder tube 201 is fixed to the upper surface of the support plate 480 .

Air flow paths 204a and 204b communicate with the air inlets 203a and 203b, respectively.

When the shaft 40 is lifted in the direction away from the surface Wa of the object W to be measured by the linear motion driving means 20, the solenoid valve 603 is energized and the air supply source 60 communicates with the air flow path 204b. Air supplied from the supply source 60 flows into the air inlet 203b. By supplying air into the cylinder tube 201 from below, the piston 200 is raised inside the cylinder tube 201 . After the piston rod 202 is brought into contact with the lower surface of the fixed plate 490, the piston rod 202 is further raised to raise the fixed plate 490, thereby raising the shaft 40 connected to the fixed plate 490.

On the other hand, when the shaft 40 is lowered in the direction of approaching the surface Wa of the object W to be measured by the linear motion driving means 20, the solenoid valve 603 is energized and the air supply source 60 communicates with the air flow path 204a. , the air supply source 60 injects a predetermined amount of air into the air inlet 203a, supplies air from above into the cylinder tube 201, and causes a predetermined amount of air to flow out from the air inlet 203b. As a result, the upper end of the piston rod 202 is in contact with the lower surface of the fixed plate 490 and the piston rod 202 descends at a regulated speed. The speed at which shaft 40 descends is limited. Then, the shaft 40 is lowered until the lower end 400c of the probe 400 contacts the surface Wa of the object W to be measured.

As shown in FIGS. 1 and 2, a height position reading means 25 is arranged at one corner of the lower surface of the fixed plate 490 . The height position reading means 25 includes a scale 250 whose upper end is fixed to the lower surface of the fixed plate 490 and extends in the -Z direction parallel to the extending direction (Z-axis direction) of the shaft 40; , and a support column 252 to which the reading portion 251 is fixed. The support column 252 is fixed to the side surface of the support plate 480 and extends in the +Z direction. The reading unit 251 is fixed to the side surface of the support column 252 and faces scales 250a formed on the side surface of the scale 250 at equal intervals in the Z-axis direction. The reading unit 251 is, for example, an optical type that reads the reflected light of the graduation 250a of the scale 250, and converts the read value of the graduation 250a of the scale 250 into the height position of the lower end 400c of the stylus 400 of the shaft 40. , the height position of the surface Wa of the object W to be measured can be read.

As shown in FIGS. 2 and 3, a water supply nozzle 441 having, for example, a substantially cylindrical outer shape is detachably attached to the lower surface of the support plate 480 by means of a threaded portion 441a formed on the upper portion thereof. A through hole 441 b having a circular cross section is formed in the center of the water supply nozzle 441 for the shaft 40 to pass through in the thickness direction (Z-axis direction). An exhaust port 43 formed in a ring shape surrounding the side surface 40a of the shaft 40 exhausts the air ejected from the air ejection port 42 along the side surface 40a of the shaft 40 toward the object W to be measured.
The centers of the through hole 441b, the circular hole 480a of the support plate 480, and the circular receiving hole 41d of the casing 41 are substantially aligned, and in this embodiment, they have the same diameter.

The water film forming means 44 (hereinafter referred to as the water film forming means 44 of Embodiment 1) shown in FIGS. ing.
For example, a water supply port 441 d is formed on the side surface of the water supply nozzle 441 , and the water supply port 441 d communicates with the water ejection port 441 c inside the water supply nozzle 441 . In the example shown in FIGS. 2 and 3, the water jet port 441c is formed in a cylindrical shape that decreases in diameter toward the lower end side of the water supply nozzle 441, and the water that has moved from the water feed port 441d to the water jet port 441c Although the flow is directed toward the center of the water supply nozzle 441 and descends, it is not limited to this.

One end of a water supply pipe 460 is connected to the water supply port 441d, and the other end of the water supply pipe 460 is provided with a water supply source 461 configured by a pump or the like and capable of supplying water (for example, pure water). are in communication.

The operation of the linear gauge 4 when measuring the displacement of the surface Wa of the object W to be measured by the linear gauge 4 will be described below with reference to FIGS. 2 and 3. FIG.
2 and 3, the object W to be measured is held by suction on a chuck table 10 (not shown in FIG. 3) of a grinding device (not shown), and is thinned by a grinding wheel that rotates while being supplied with grinding water. there is That is, the object W to be measured is sucked and held by a holding surface 10a made of a porous member or the like, which communicates with a suction source (not shown) of the chuck table 10, with the surface Wa facing upward. Rotating around an axial axis.

As shown in FIG. 2, the linear gauge 4 is mounted on a support base 11 and positioned above the object W to be measured. During the grinding of the workpiece W, the linear gauge 4 is used to measure the displacement of the surface Wa of the workpiece W to monitor changes in the thickness of the workpiece W. FIG.
The direct drive means 20 lowers the shaft 40 in the -Z direction to approach the object W to be measured. Specifically, the air supply source 60 shown in FIG. 2 causes a predetermined amount of air to flow into the air inlet 203a to supply air to the inside of the cylinder tube 201 at a regulated speed. The piston 200 is moved downward (-Z direction). As a result, the shaft 40 is lowered until the lower end 400c of the stylus 400 contacts the surface Wa of the object W to be measured while limiting the lowering speed due to the fixed plate 490 and the shaft 40's own weight. In this way, by limiting the descending speed of the fixed plate 490 and the shaft 40 by the linear motion driving means 20, the impact when the lower end 400c of the probe 400 contacts the object W to be measured can be reduced.

At this time, by supplying air from the air supply source 60 to the air inlet 410c and ejecting air from the air ejection port 42 between the side surface 40a of the shaft 40 and the support surface 41a of the casing 41, the casing 41 is , the shaft 40 can be vertically lowered in the Z-axis direction while supporting the side surface 40a of the shaft 40 in a non-contact manner.

When the probe 400 comes into contact with the surface Wa of the object W to be measured as the shaft 40 descends, the reading unit 251 reads the scale 250a of the scale 250 when the lower end 400c of the probe 400 contacts the surface Wa of the object W to be measured. .
After that, the amount of air supplied from the air supply source 60 to the air inlet 203a is adjusted so that the shaft 40 can move freely according to the change in the thickness of the object W to be measured, in other words, the displacement of the surface Wa of the object W to be measured. The displacement of the surface Wa of the object W to be measured can be sequentially measured by the linear gauge 4 by sequentially reading the changing scale 250a with the reading unit 251.

While measuring the displacement of the surface Wa of the object W to be measured by the linear gauge 4, the air supplied from the air ejection port 42 between the side surface 40a of the shaft 40 and the support surface 41a of the casing 41 It descends inside the housing hole 41 d of the casing 41 along the side surface 40 a of the casing 40 , passes through the circular hole 480 a of the support plate 480 , and reaches the water supply nozzle 441 .
The air descends through the through hole 441 b along the side surface 40 a of the shaft 40 also in the water supply nozzle 441 and is exhausted toward the object W to be measured from the annular exhaust port 43 .

While the linear gauge 4 is measuring the displacement of the surface Wa of the object W to be measured, water is supplied from the water supply source 461 and flows into the water supply nozzle 441 from the water supply port 441d. . Then, the water is jetted toward the side surface 40a of the shaft 40 from the annular water jet port 441c surrounding the exhaust port 43, and flows downward toward the object W while covering the side surface 40a of the shaft 40 as a water film. go. As a result, the air is exhausted from the exhaust port 43, and the water film formed by the water film forming means 44 protects the shaft 40 and the probe 400 from deposits. That is, even if the grinding spray containing the grinding dust flies around the shaft 40 and the probe 400 protruding downward from the water supply nozzle 441, the water film prevents it from coming into contact with the side surface 40a of the shaft 40 and the probe 400. Flaking and drying and sticking are also prevented.

A linear gauge 4 for measuring the surface displacement of an object W to be measured according to the present invention includes a shaft 40 having a probe 400 at its tip to be brought into contact with the surface Wa of the object W to be measured and a side surface 40a of the shaft 40. A casing 41 having a support surface 41a for supporting, an air ejection port 42 disposed on the support surface 41a and allowing air to intervene between the side surface 40a of the shaft 40 and the support surface 41a, and a shaft disposed under the casing 41. An exhaust port 43 formed in a ring shape surrounding the side surface 40a of the shaft 40 and exhausting the air ejected from the air ejection port 42 along the side surface 40a of the shaft 40 toward the object to be measured W, and the shaft surrounding the exhaust port 43. Since the water film forming means 44 for forming a water film on the side surface 40a of the shaft 40 is provided, the air can be discharged from the exhaust port 43, and the water film formed by the water film forming means 44 causes the shaft 40 to move. Also, it is possible to protect the probe 400 from adhering matter such as grinding dust. Further, the air exhausted from the exhaust port 43 and the water supplied from the water film forming means 44 remove grinding waste from the surface Wa of the object W with which the probe 400 contacts as shown in FIG. Since it flows on the surface Wa of the object W to be measured, it is possible to prevent the linear gauge 4 from causing an error in measuring the displacement of the surface Wa of the object W to be measured.

In the linear gauge 4 according to the present invention, the water film forming means 44 includes a water supply nozzle 441 having an annular water ejection port 441c surrounding the exhaust port 43, thereby facilitating the formation of the water film. becomes possible.

The linear gauge 4 according to the present invention may include water film forming means 45 shown in FIG. 4 instead of the water film forming means 44 shown in FIGS.
The water film forming means 45 includes an annular tube 450 that surrounds the shaft 40, a supply portion 451 that supplies water from one position 450a of the annular tube 450 (position on the +X direction side in FIG. 4), and an annular tube 450. Water that is formed on the opposite side of the supply part 451 at the other position 450b (the position on the -X direction side in FIG. 4) symmetrical to the one position 450a with respect to the center and jets water toward the object W to be measured. and a spout 452 . In this embodiment, the constituent elements of the water film forming means 45 are arranged in a substantially columnar body 459 attached to the lower surface of the support plate 480, for example.

A screw portion 459a is formed on the upper surface of the column 459, and the column 459 is detachably attached to the lower surface of the support plate 480 by the screw portion 459a. A through-hole 459b having a circular cross section is formed in the center of the column 459 for the shaft 40 to pass through in the thickness direction (Z-axis direction). It has approximately the same diameter and is centered with the circular hole 480a.

The lower end side of the through hole 459b is formed in a ring shape which is arranged under the casing 41 and surrounds the side surface 40a of the shaft 40. It becomes the exhaust port 43 which exhausts toward. The exhaust port 43 has a larger diameter than the through hole 459b in the example shown in FIG. 4, but is not limited to this.

The supply part 451 is formed, for example, so as to extend horizontally from the side surface of the column 459 into the inside of the column 459 and further downward, and inside the column 459 at one position 450 a of the annular tube 450 . are in communication. One end of the water supply pipe 460 is connected to the supply portion 451, and the other end of the water supply pipe 460 communicates with a water supply source 461 configured by a pump or the like and capable of supplying water (for example, pure water). is doing.
The water ejection port 452 extends, for example, linearly from the other position 450 b of the annular pipe 450 toward the center of the column 459 and communicates with the exhaust port 43 .

While the displacement of the surface Wa of the object W is being measured by the linear gauge 4 having the water film forming means 45, the side surface 40a of the shaft 40 and the support surface of the casing 41 from the air ejection port 42 shown in FIG. 41a descends inside the accommodation hole 41d of the casing 41 along the side surface 40a of the shaft 40, passes through the circular hole 480a of the support plate 480, and reaches the column shown in FIG. Body 459 is reached.
The air descends through the through hole 459 b along the side surface 40 a of the shaft 40 also in the column 459 and is exhausted from the exhaust port 43 toward the object W to be measured.

While the displacement of the surface Wa of the object W to be measured is being measured by the linear gauge 4 having the water film forming means 45 shown in FIG. It flows into the column body 459 . The water supplied from the supply part 451 to one position 450a of the annular tube 450 is divided into two and flows in the annular tube 450 in the clockwise direction and the counterclockwise direction when viewed from the +Z direction, and as a result, Circumferential force about the axis of the shaft 40 in the Z-axis direction is generated in each of the two split waters.

Then, when the water splits into two and flows through the annular pipe 450 and reaches the water jetting port 452 and merges, the force in the circumferential direction remains, so that the water passes through the exhaust port 43 and the shaft 40 moves. The water that has moved to the side surface 40a becomes a water film having a spiral flow, for example, and descends toward the object W while covering the side surface 40a. As a result, the air is exhausted from the annular exhaust port 43, and the water film formed by the water film forming means 45 protects the shaft 40 and the probe 400 from deposits. That is, even if the grinding spray containing the grinding dust is scattered around the shaft 40 and the probe 400 protruding downward from the column 459, the water film prevents the spray from contacting the side surface 40a of the shaft 40 and the probe 400. It also prevents it from drying out and sticking.

As described above, in the linear gauge 4 according to the present invention, the water film forming means 45 includes the annular tube 450 that surrounds the shaft 40, the supply portion 451 that supplies water from one position 450a of the annular tube 450, and the annular tube 450. A water ejection port 452 that is formed on the opposite side of the supply part 451 at the other position 450b symmetrical to the one position 450a with respect to the center of the pipe 450 and that ejects water toward the object W to be measured. , the force in the circumferential direction about the axis of the shaft 40 generated by the water supplied from the supply part 451 to the annular pipe 450 flowing through the annular pipe 450 remains when the water joins at the water jet port 452. As a result, the water covers the side surface 40a of the shaft 40 and flows toward the object W to easily form a water film.

It goes without saying that the linear gauge 4 according to the present invention is not limited to the example provided with the water film forming means 44 or the water film forming means 45 described above, and may be implemented in various forms within the scope of the technical idea. . Further, the outer shape of each component of the linear gauge 4 shown in the accompanying drawings is not limited to this, and can be changed as appropriate within the range where the effects of the present invention can be exhibited.

W: Object to be measured Wa: Surface of object to be measured 4: Linear gauge 40: Shaft 40a: Side surface of shaft 400: Probe 400c: Lower end of probe 41: Casing 410: Frame 41d: Accommodating hole 41a: Support surface 410c : Air inlet 410d: Flow path 42: Air ejection port 43: Exhaust port 44: Water film forming means
441: water supply nozzle 441a: screw portion 441b: through hole 441c: water spout 441d: water supply port 46: water supply source 460: water supply pipe 490: fixed plate 491: fixed nut 480: support plate 480a: circular hole 50 : Rotation Regulating Means 501: First Magnet 502: Second Magnet 503: Guide Rod 60: Air Supply Source 600: Air Supply Pipe 603: Solenoid Valve
20: Linear drive means 200: Piston 201: Cylinder tube 202: Piston rod 203a, 203b: Air inlet 204a, 204b: Air flow path 25: Height position reading means 250: Scale 250a: Scale 251: Reading unit 252: Support column 11: Support table 10: Chuck table 10a: Holding surface 45: Water film forming means 450: Annular tube 451: Supply unit 452: Water jet 459: Column

Claims (3)

A linear gauge for measuring surface displacement of an object to be measured,
a shaft having a stylus at its tip that is brought into contact with the surface of the object to be measured;
a casing having a support surface surrounding and supporting the sides of the shaft;
an air ejection port disposed on the support surface and allowing air to intervene between the side surface of the shaft and the support surface;
an exhaust port disposed under the casing and formed in a ring shape surrounding the side surface of the shaft for exhausting the air ejected from the air ejection port toward the object to be measured along the side surface of the shaft;
a water film forming means for surrounding the exhaust port and forming a water film on the side surface of the shaft;
A linear gauge that enables air to be exhausted from the exhaust port and protects the shaft and the probe from adhesion by a water film formed by the water film forming means. 2. A linear gauge according to claim 1, wherein said water film forming means comprises a water supply nozzle having an annular water jet surrounding said exhaust port. The water film forming means is
an annular tube surrounding the shaft;
a supply unit that supplies water to the annular tube from one position of the annular tube;
a water ejection port that ejects water toward the object to be measured at the other position symmetrical to the one position with respect to the center of the annular tube;
Circumferential force around the axis of the shaft generated by the water supplied from the supply unit to the annular pipe flowing through the annular pipe remains when the water merges at the water spout. 2. The linear gauge according to claim 1, wherein water covers the side surface of said shaft and flows toward said object to be measured to form said water film.

Images