Surface pressure measuring device

A surface pressure measuring device includes an abutting plate, a lift, a probe, a piezo actuator and a controller. A pinhole is formed in the abutting plate at an abutting surface that abuts a target. The lift causes the target to abut the abutting surface such that the target is compressed to a predetermined thickness. The probe is inserted through the pinhole to be movable in an axial direction of the pinhole. The piezo actuator holds a state in which a tip surface is flush with the abutting surface as the probe resists a repulsive force received from the target while the lift causes the target to abut the abutting surface. The controller calculates a local surface pressure of the target from a load applied to the probe and an area of the tip surface of the probe.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-153066 filed on Aug. 3, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a surface pressure measuring device.

2. Description of Related Art

Measurement of a local surface pressure of a target surface when a predetermined load is applied to a target or the target is compressed to a predetermined thickness is needed. For example, in some cases, a surface pressure in a predetermined local portion of a gasket when the gasket formed of rubber is compressed to a predetermined thickness may be measured. Devices configured to measure a surface pressure of a target are disclosed in, for example, Japanese Patent Application Publication No. 2009-68991 (JP 2009-68991 A) and Japanese Patent Application Publication No. 2012-21924 (JP 2012-21924 A).

The surface pressure measuring device in JP 2009-68991 A includes a sheet having a plurality of convex sections, and a pressure measuring material that develops a color upon receiving pressure. The color of the pressure measuring material varies according to a magnitude of the pressure. In the surface pressure measuring device, a pressure measuring material is affixed to apex surfaces of the plurality of convex sections of the sheet and the sheet is attached to a target. A surface pressure applied to each convex section is determined according to the color of the pressure measuring member. In the surface pressure measuring device in JP 2012-21924 A, a plurality of probes are disposed in a two-dimensional array such that tips thereof form a planar surface. A target is pressed against the tips of the plurality of probes. The surface pressure measuring device in JP 2012-21924 A can obtain a surface pressure distribution of the surface of the target from the load applied to the probes.

SUMMARY

In the surface pressure measuring device in JP 2009-68991 A, a certain area is required for a pressure measuring material, and it is not suitable for measuring an extremely small local surface pressure of the surface of the target. In the surface pressure measuring device in JP 2012-21924 A, a plurality of probes are disposed in a two-dimensional array. Position resolution when the surface pressure distribution is measured depends on a diameter of the probe. For example, in measuring the surface pressure distribution at a resolution of tens of microns, the plurality of probes having a diameter of tens of microns should be densely disposed in a two-dimensional array. Accordingly, the surface pressure measuring device in JP 2012-21924 A is not suitable for measuring an extremely small local surface pressure of the surface of the target. When only one probe of the surface pressure measuring device in JP 2012-21924 A is used, since a load applied to the entire target is the load applied to the probe, a local surface pressure when the entire target is compressed to a predetermined thickness cannot be measured. The technology disclosed herein discloses a surface pressure measuring device capable of measuring an extremely small local surface pressure of a target surface when a predetermined load is applied to a target or the target is compressed to a predetermined thickness.

A surface pressure measuring device disclosed herein includes an abutting plate that abuts a target, a first actuator, a second actuator, a probe, a load sensor and a controller. The abutting plate has an abutting surface that abuts the target, and a hole is in the abutting surface. The first actuator is configured to cause the target to abut the abutting surface with a predetermined load. Alternatively, the first actuator is configured to cause the target to abut the abutting surface such that the target is compressed to a predetermined thickness. The probe has the tip surface that is exposed at the abutting surface side and is configured to be inserted through the hole to be movable in an axial direction thereof. The second actuator supports the probe. The second actuator is configured to hold a state in which the tip surface of the probe is flush with the abutting surface as the probe resists a repulsive force received from the target while the first actuator causes the target to abut the abutting surface. The load sensor is configured to measure a load applied to the probe when the second actuator holds the state in which the tip surface of the probe is flush with the abutting surface. The controller is configured to calculate a surface pressure applied to the tip surface of the probe from a measured value of the load sensor and an area of the tip surface of the probe. The surface pressure is a local surface pressure of a place that abuts the probe of the target.

In the above-mentioned surface pressure measuring device, the tip surface of the probe exposed from the hole is flush with the abutting surface of the abutting plate. The controller measures a surface pressure of a place that abuts the tip surface of the probe while the abutting surface of the abutting plate including the tip surface of the probe applies the load to the entire target. The above-mentioned surface pressure measuring device can measure a surface pressure of a local place that abuts the tip surface of the probe when the abutting plate applies a predetermined load to the entire target (or the entire target is compressed to a predetermined thickness). As a diameter of the hole of the abutting plate and an area of the tip surface of the probe are reduced, an extremely small local surface pressure of the target surface can be measured.

Further, precision of “flushness” between the tip surface of the probe and the abutting surface depends on required measurement precision of the surface pressure. As the required measurement precision of the surface pressure is increased, an allowable error in a degree of “flushness” between the tip surface of the probe and the abutting surface is reduced.

The surface pressure measuring device disclosed herein may further include a third actuator configured to move the abutting plate relative to the target to change a place at which the target abuts the probe. In this case, the controller calculates the surface pressure at a plurality of places of the target and outputs a surface pressure distribution of the target. In the surface pressure measuring device including the third actuator, a size of the tip surface of the probe and movement resolution of the probe determine a resolution (a position resolution) of surface pressure distribution measurement. For example, when the tip surface of the probe is a circle having a diameter of 10 microns and the movement resolution of the probe of the third actuator is 10 microns, the surface pressure measuring device has a position resolution of 10 microns. The surface pressure measuring device disclosed herein can measure the surface pressure distribution with a high position resolution.

The probe may include a tip and an intermediate section thicker than the tip. In this case, the hole formed in the abutting plate may include a small diameter section through which the tip of the probe is inserted, and a large diameter section having a diameter larger than that of the small diameter section and through which the intermediate section is inserted. A strong probe can be realized while setting the tip surface as a small area. In the surface pressure measuring device disclosed herein, like the device in JP 2012-21924 A, there is no need to densely dispose a plurality of probes. Therefore, a probe in which only a tip is thin and a connecting portion (an intermediate section) is thick may be employed. Then, as the intermediate section is fitted into the large diameter section of the hole, the probe can be supported by the intermediate section having a large diameter.

The above-mentioned surface pressure measuring device may further include a first laser range finder configured to measure a position of the hole of the probe in the axial direction. In addition, the controller may store a position of the hole of the probe in the axial direction when the tip surface is flush with the abutting surface, and control the second actuator such that the tip surface is flush with the abutting surface based on measurement data of the first laser range finder.

The above-mentioned surface pressure measuring device may further include a placing table placed on the target. In addition, the first actuator may be configured to move the placing table.

The above-mentioned surface pressure measuring device may further include a second laser range finder installed on the placing table and configured to measure a distance between the placing table and the abutting plate. In addition, the controller may acquire measurement data measured by the second laser range finder and control the first actuator to change the distance between the placing table and the abutting plate based on the measurement data measured by the second laser range finder.

In the above-mentioned surface pressure measuring device, the first actuator may be configured to move the abutting plate.

Details of the technology disclosed herein will be described in the following “Detailed Description of Embodiments.”

DETAILED DESCRIPTION OF EMBODIMENTS

A surface pressure measuring device2of an embodiment will be described with reference to the accompanying drawings.FIG. 1is a schematic cross-sectional view of the surface pressure measuring device2.FIG. 2is an enlarged view of a portion in a circle designated by reference numeral II inFIG. 1. The surface pressure measuring device2can measure a local surface pressure when a target100placed on a placing table6is compressed to a predetermined thickness. The target100is a gasket formed of, for example, an elastic material. The surface pressure measuring device2can measure a surface pressure distribution of the gasket (the target100).

The surface pressure measuring device2includes a base3, an XY stage4, a lift5, the placing table6, an abutting plate7, a probe20, a load sensor9, a piezo actuator10, a controller12, and two laser range finders31and32. Further, in a coordinate system in the drawings, an X axis and a Y axis represent horizontal directions, and a Z axis represents a vertical direction.

The XY stage4is provided on the base3. The lift5is attached onto the XY stage4, and the placing table6is attached onto the lift5. The target100is placed on the placing table6. The XY stage4can move the lift5and the placing table6within a horizontal plane. As described below, the abutting plate7and the probe20configured to measure a surface pressure are disposed over the placing table6(over the target100). A place of the target100abutting a tip surface23aof the probe20corresponds to a surface pressure measurement place. The XY stage4can change a place of the target100that abuts the tip surface23aof the probe20. The XY stage4is an actuator configured to move the target100relative to the probe20to change an abutting place of the target100with the probe20. The XY stage4is controlled by the controller12.

The lift5is an actuator configured to move the placing table6vertically. The abutting plate7is disposed over the placing table6. The abutting plate7is fixed to the base3by posts3a. When the placing table6is raised by the lift5, the target100comes in contact with a lower surface of the abutting plate7. The lower surface of the abutting plate7is referred to as an abutting surface7ahereinafter. The laser range finder32is attached to the placing table6. The laser range finder32measures a distance from the surface of the placing table6to the abutting surface7a, i.e., a distance between the placing table6and the abutting plate7. Measurement data is transmitted to the controller12. The controller12can freely change a distance between the placing table6and the abutting plate7using the lift5based on the measurement data of the laser range finder32.

A pinhole7bis formed in the abutting plate7. A tip23of the probe20passes through the pinhole7b. As shown inFIG. 2, the tip surface23aof the probe20is exposed from the pinhole7bat the abutting surface7aside of the abutting plate7.

The probe20includes the tip23having a small diameter, and an intermediate section22having a large diameter and following the tip23. The intermediate section22is thicker than the tip23. For example, a diameter D1(seeFIG. 2) of the tip23is 10 microns. A diameter of the intermediate section22is 2 mm. A diameter D2of the pinhole7bof the abutting plate7is, for example, 12 microns, and the tip23of the probe20is fitted into the pinhole7bwith a clearance of 1 micron.

The abutting plate7has a large diameter hole7cthat follows the pinhole7b. A diameter of the large diameter hole7cis much larger than the diameter of the pinhole7b. The tip23of the probe20is inserted through the pinhole7b, and the intermediate section22of the probe20is inserted through the large diameter hole7c. InFIG. 1, while a gap is formed between the large diameter hole7cand the intermediate section22, a clearance between the large diameter hole7cand the intermediate section22is also about 1 micron. A relative position of the probe20with respect to the abutting plate7in an XY plane in the drawings is determined by fitting of a large diameter hole7cand the intermediate section22. The relative position of the probe20with respect to the abutting plate7in the XY plane can be determined by the large diameter hole7cand the intermediate section22without applying a load to the thin tip23of the probe20.

The probe20has a rear end that is supported by the piezo actuator10with intervention of the load sensor9. The piezo actuator10is supported by a support block8fixed onto the abutting plate7. The piezo actuator10expands and contracts in a Z direction (an upward/downward direction) in the drawings. That is, the piezo actuator10can advance and retract the probe20in the upward/downward direction. In other words, the probe20is inserted to advance and retreat in the pinhole7bby the piezo actuator10. A vertical stroke of the piezo actuator10(a stroke of the probe20) is about 100 microns. The probe20is supported such that the tip surface23ais substantially flush with the abutting surface7aof the abutting plate7. As will be described below in detail, the controller12controls a position of the probe20in the upward/downward direction using the piezo actuator10such that the tip surface23ais flush with the abutting surface7a.

The laser range finder31is attached to the support block8. The laser range finder31measures a position in the upward/downward direction of a flange24installed at a rear end of the probe20. That is, the laser range finder31measures a position of the probe20in the upward/downward direction. The controller12stores the position of the flange24when the tip surface23ais flush with the abutting surface7a. The controller12controls the piezo actuator10such that the tip surface23aof the probe20is always flush with the abutting surface7abased on the measurement data of the laser range finder31.

When the tip surface23aof the probe20receives an upward load, the load sensor9is contracted and the probe20is slightly raised. The controller12expands the piezo actuator10such that the tip surface23aof the probe20is flush with the abutting surface7a. The load sensor9measures a load received when the tip surface23aof the probe20is flush with the abutting surface7a. Further, the controller12adjusts the measurement data of the load sensor when no load is applied to the tip surface23ato a zero point upon starting of the surface pressure measuring device2. The weight of the probe20is removed from a measured value of the load sensor in the zero-point adjustment. Accordingly, the controller12can accurately obtain the load received when the tip surface23aof the probe20is flush with the abutting surface7afrom the measurement data of the load sensor9.

A method of manufacturing a surface pressure of the target100by the surface pressure measuring device2will be described. The controller12controls the XY stage4such that a surface pressure measurement place of the target100is disposed immediately under the tip surface23aof the probe20. Next, the controller12controls the lift5such that the target100comes in contact with a range including the tip surface23aof the abutting surface7a. The controller12raises the placing table6using the lift5and compresses the target100to a predetermined thickness based on the measurement data of the laser range finder32. That is, the controller12raises the placing table6using the lift5such that a gap between the placing table6and the abutting plate7is equal to a target thickness of the target100.

When the target100abuts the abutting surface7a, the surface pressure measurement place of the target100also abuts the tip surface23aof the probe20. The surface pressure measurement place of the target100adds a load to the probe20in an upward direction. The load sensor9in contact with the rear end of the probe20is contracted by the load. As described above, the controller12controls the piezo actuator10such that the tip surface23aof the probe20is flush with the abutting surface7a.FIG. 3shows a state in which an upper surface of the target100is adhered to the abutting surface7aof the abutting plate7. If there is no probe20, the surface pressure measurement place of the target100swells in the middle of the pinhole7b(reference numeral100aofFIG. 3). The probe20having the tip surface23athat is flush with the abutting surface7apushes back the portion100athat swells in the middle of the pinhole7bof the target100, and the surface of the target100is flattened. A repulsive force thereof is added to the probe20. The piezo actuator10holds the tip surface23aof the probe20to be flush with the abutting surface7aas the probe20resists a repulsive force received from the target100while the lift5causes the target100to abut the abutting plate7. The load sensor9detects the load at this time. The controller12calculates a surface pressure added to the tip surface23aof the probe20from a measured value of the load sensor9and an area of the tip surface23aof the probe20. The surface pressure corresponds to a surface pressure of a surface pressure measurement place of the target100. The controller12calculates a surface pressure of a place (a surface pressure measurement place) of the target100in contact with the tip surface23afrom the measurement data of the load sensor9and the area of the tip surface23aof the probe20and stores the surface pressure in a storage device13.

Advantages of the surface pressure measuring device2will be described. The abutting plate7in contact with the target100serving as a target for measuring a surface pressure has the pinhole7bin the abutting surface7a. The tip surface23aof the probe20is exposed through the pinhole7b. The tip surface23ais flush with the abutting surface7a. Since the tip surface23aof the probe20is buried in the pinhole7b, the abutting surface7apresses the target100uniformly as if there were no pinhole7b. Accordingly, the same surface pressure as when the flat abutting surface7awith no pinhole7bapplies the load uniformly is generated in the surface of the target100. Meanwhile, the load applied to the probe20buried in the pinhole7bis measured by the load sensor9. The load measured by the load sensor9corresponds to a local surface pressure of the target100when the flat abutting surface7ais pressed uniformly. Even when the area of the tip surface23aof the probe20is small, since the tip surface23ais surrounded by the abutting surface7a, a state in which the abutting surface7acompresses the target uniformly is held. The surface pressure measuring device2can measure the local surface pressure when the target is compressed uniformly. The surface pressure measuring device2can measure a local microscopic surface pressure of the target surface as a size of the tip surface23aof the probe20and an area of the pinhole7bare reduced.

A clearance between the tip23of the probe20and the pinhole7band precision of “flushness” between the tip surface23aof the probe20and the abutting surface7aare determined depending on the measurement precision of the surface pressure. As the required measurement precision of the surface pressure is increased, the clearance is reduced and an allowable error in a degree of “flushness” between the tip surface23aand the abutting surface7ais reduced. When the required measurement precision of the surface pressure is low, the clearance may be correspondingly large and the allowable error in the degree of “flushness” between the tip surface23aand the abutting surface7ais also increased.

The surface pressure measuring device2can also measure the surface pressure distribution when the target100is compressed uniformly. The controller12changes an abutting place of the target100with the probe20using the XY stage4and measures a surface pressure of a new place. The controller12calculates surface pressures at a plurality of places of the target100and outputs a surface pressure distribution of the target100to the storage device13.

FIG. 4shows an example of a measurement result of a surface pressure distribution. In a bar graph G1ofFIG. 4, a surface pressure distribution of the target100is shown in a Y direction of a coordinate system in the drawing. InFIG. 4, the pinhole7band the probe20are not shown. A position resolution dR of the surface pressure distribution depends on a diameter of the tip surface23aof the probe20and a position resolution of movement of the XY stage4. When both the diameter of the tip surface23aand the position resolution of the XY stage are 10 microns, the position resolution dR of the surface pressure measurement of the surface pressure measuring device2is 10 microns.

FIG. 5shows an example of another measurement result of a surface pressure distribution. A bar graph G2ofFIG. 5shows a surface pressure distribution of a target200in the Y direction of the coordinate system in the drawing. InFIG. 5, the pinhole7band the probe20are not shown. The target200is a gasket having three lips. Even in this example, the position resolution dR of the surface pressure distribution depends on the diameter of the tip surface23aof the probe20and a position resolution of movement of the XY stage4. When both the diameter of the tip surface23aand the position resolution of the XY stage are 10 microns, the position resolution dR of the surface pressure measurement of the surface pressure measuring device2is 10 microns.

Items of consideration in the technology described in the embodiment will be described. The probe20includes the thin tip23and the intermediate section22having a large diameter and that continues to the tip23. A strong probe can be realized while setting the tip surface23aas a small area. In addition, the intermediate section22is fitted into the large diameter hole7cformed to continue to the pinhole7b. A position of the probe20in the XY plane is determined by fitting of the large diameter hole7cand the intermediate section22.

The surface pressure measuring device2of the embodiment can measure a local surface pressure in a state in which the target100is compressed to a predetermined thickness. The surface pressure measuring device2can measure a local surface pressure in a state in which a load having a predetermined magnitude is applied to the entire target100. In this case, a load measurement sheet is sandwiched between the placing table6and the target100. The controller12pushes the target100against the abutting plate7using the lift5. The controller12pushes the target100against the abutting plate7such that the load received by the target100coincides with a predetermined target load based on the measurement data by the load measurement sheet. The controller12measures a local surface pressure of the target100using the probe20in this state. Further, when the stiffness of the entire target100is known, a unique relationship is established between the load applied to the target100and the thickness after compression. Accordingly, in this case, application of the predetermined load to the target is substantially equivalent to compression of the target100to the predetermined thickness.

The piezo actuator10holds a state in which the tip surface23aof the probe20is flush with the abutting surface7awhile the lift5causes the target100to abut the abutting surface7a. The piezo actuator10holds the state in which the tip surface23ais flush with the abutting surface7afrom the beginning when the abutting surface7aabuts the target100. In other words, the lift5causes the target100to abut the abutting surface7awhile the piezo actuator10holds the state in which the tip surface23ais flush with the abutting surface7a. The controller12of the surface pressure measuring device2may control the lift5and the piezo actuator10in the following sequence instead of the above-mentioned sequence. The controller12stops supply of power to the piezo actuator10until the lift5is moved to compress the target100to a predetermined target thickness. Here, a portion of the target100pushes the probe20into the middle of the pinhole7b. The controller12controls the piezo actuator10after the target100is compressed to the predetermined target thickness, and holds the state in which the tip surface23aof the probe20is flush with the abutting surface7a. After that, the controller12calculates a surface pressure of a place that abuts the tip surface23abased on the measurement data of the load sensor9. However, in the former sequence (the sequence in which the lift5causes the target100to abut the abutting surface7awhile the piezo actuator10holds the state in which the tip surface23ais flush with the abutting surface7a), the surface pressure measurement precision is expected to increase.

In the case of the surface pressure measuring device2of the embodiment, the target100(the placing table6) is moved to change a relative position of the target100with respect to the probe20. Reversely, the abutting plate7including the probe20may be moved to change the relative position.

The surface pressure measuring device2of the embodiment sandwiches the target100with the flat placing table6and the abutting plate7having the flat abutting surface7a. The surface pressure measuring device may employ a cylindrical abutting plate, and a columnar placing table (attachment column) with a variable diameter. When such an abutting plate and such an attachment column are employed, a local surface pressure can be measured in a state in which the entire ring-shaped shaft seal gasket is compressed. Specifically, the ring-shaped shaft seal gasket is attached to the attachment column with the variable diameter. The attachment column attached to the gasket enters the cylindrical abutting plate. The diameter of attachment column is enlarged and the gasket is uniformly compressed. In this state, a local surface pressure of the gasket is measured using the probe exposed from the pinhole of the abutting plate.

The pinhole7bof the embodiment and the large diameter hole7cthat is continuous therefrom correspond to “a hole provided in an abutting plate” of the claims. The pinhole7bcorresponds to an example of “a small diameter section” of the claims, and the large diameter hole7ccorresponds to an example of “a large diameter section” of the claims. The lift5of the embodiment corresponds to an example of “a first actuator” of the claims. The piezo actuator10of the embodiment corresponds to an example of “a second actuator” of the claims. The XY stage4of the embodiment corresponds to an example of “a third actuator” of the claims. The first actuator may function as the third actuator. For example, a stage (an XYZ stage) capable of moving a table two-dimensionally may function as the first actuator and the third actuator. The laser range finder31of the embodiment corresponds to an example of “a first laser range finder” of the claims. The laser range finder32of the embodiment corresponds to an example of “a second laser range finder” of the claims.

The third actuator may be an XY stage using a ball screw or may be an actuator configured to move a placing table two-dimensionally using a link mechanism.

While specific examples of the present disclosure have been described above, these are merely exemplary and do not limit the scope of the claims. Various modifications and variations of the specific examples exemplified above are included in the technology disclosed in the claims. Technical components described in the specification or the drawings exhibit technical usefulness alone or in various combinations, but do not limit the combinations of the claims at the time the application is filed. In addition, the technology disclosed in the specification or the drawings can achieve a plurality purposes at the same time and has technical usefulness by itself by achieving one of the purposes.