JP7074335B2 - Manufacturing method of variable friction coefficient block body - Google Patents

Description

The present invention relates to a method for manufacturing a block body having a variable friction coefficient that can change the friction coefficient of the surface by controlling the formation state of surface irregularities, and in particular, the exposed state of the woven fabric embedded in the vicinity of the surface to the surface. The present invention relates to a method for manufacturing a variable friction coefficient block body that can be controlled to change the friction coefficient.

The coefficient of friction of the surface can be reduced, increased or adjusted depending on the formation state of the surface unevenness. Such a structure is applied to a belt conveyor for transporting an object, a feed roller of various machines, and the like.

For example, in Patent Document 1, the friction coefficient of the conveyor belt can be lowered and the accumulation of dust can be suppressed by embedding a woven cloth in the rubber surface of the conveyor belt for transporting the load and giving the protrusion structure arranged on the surface. It is said that it can be done. Further, in Patent Document 2, in a rubber member used for a sliding portion such as a bearing or a shaft seal, the porous carbon material particles are dispersed in a rubber composition and then crosslinked to cause friction as compared with other rubbers. It is said that the coefficient can be made smaller and the sliding characteristics can be improved.

On the other hand, a variable friction coefficient block body that can change the friction coefficient during machine operation by variably controlling the formation state of surface irregularities has also been proposed.

For example, in Patent Document 3, a woven cloth is embedded in the surface of the rubber body and superposed on the wavy shape of the rubber body to periodically give a protrusion of the woven cloth to give a larger change width of the friction coefficient. The obtained friction coefficient variable sheet body is disclosed. As a method for producing such a sheet body, a liquid rubber elastic body precursor liquid is poured into a woven fabric on a flat glass substrate and permeated, and the cured PDMS plate-like body is pressed against the elastic body sheet. After thermosetting, it is peeled off from the glass substrate to obtain a sheet body having a variable friction coefficient. When uniaxial in-plane compression of the weft in the yarn axis direction is applied to this using a small compressor, undulations are formed and periodic protrusions of the woven fabric are superimposed on the undulations.

In addition, Non-Patent Document 1 also discloses a variable friction coefficient sheet body including a protrusion structure arranged on the surface of a rubber body. A plain fabric made of nylon 66 fibers is placed on the surface of a silicone rubber base material, impregnated with an uncured liquid which is a precursor of silicone rubber, and heat-cured while being pressurized. At this time, when the rubber base material is stretched in the uniaxial direction and the stretching is released after curing, compressive strain is applied in the surface direction, the embedded woven fabric layer buckles, and a periodic wrinkle structure is formed. It is.

International Publication No. 2015/186435 Pamphlet Japanese Unexamined Patent Publication No. 2016-060846 Japanese Unexamined Patent Publication No. 2017-190537

"Peculiar increase in static friction force on wrinkles on the surface of woven rubber embedded rubber"; Takuya Osono, Kei Teraoka: Tribologist, Vol. 62, No. 8 (2017) pp. 532-536

In the above-mentioned variable friction coefficient sheet or block body, if the periodic structure of the protrusions due to the woven fabric or the undulation of the main body in which the woven fabric is embedded becomes uneven, a given change in the friction coefficient cannot be obtained. This tendency is particularly remarkable in the application to large-area members required for robots and the like.

The present invention has been made in view of such a situation, and an object thereof is friction that can change the friction coefficient by controlling the exposure state of the woven fabric embedded in the vicinity of the surface to the surface. In a method for manufacturing a variable coefficient sheet or a block body, it is an object of the present invention to provide a method capable of efficiently manufacturing a variable friction coefficient sheet or a block body capable of giving a stable change in the friction coefficient.

The manufacturing method according to the present invention is a manufacturing method of a friction coefficient variable block body capable of changing the friction coefficient by controlling the exposure state of the woven fabric embedded along the surface of the rubber elastic body to the surface. The woven fabric is placed on a table, and an uncured liquid which is a precursor of the rubber elastic body is applied from above, and the woven fabric is impregnated with the pressing member while being pressed against the base. It is characterized by including a step of curing a curing liquid to form a presheet body, and a sticking step of sticking the presheet body to a sticking surface of a main body made of the rubber elastic body.

According to such an invention, since the surface layer portion that affects the protrusions and surface waviness caused by the woven fabric can be manufactured separately from the main body portion, a stable friction coefficient change can be provided without being affected by the shape and properties of the main body portion. The obtained friction coefficient variable sheet or block body can be efficiently manufactured, and in particular, even a large area and thick block body can be manufactured with high accuracy.

In the above-mentioned invention, the sticking step may be characterized by including a step of preliminarily stretching the sticking surface. According to such an invention, in particular, it is possible to efficiently manufacture a variable friction coefficient sheet or a block body which can form undulations on the surface without being affected by the shape and properties of the main body portion and can give a stable change in the friction coefficient. ..

In the above-described invention, the sticking step may be characterized in that a surface in contact with the pressing member is pasted on the sticking surface. According to such an invention, the woven fabric can be accurately applied to the vicinity of the surface, and a variable friction coefficient sheet or a block body capable of giving a stable change in the coefficient of friction can be efficiently manufactured.

(A) Surface photograph (large magnification), (b) Surface photograph (small magnification), (c) Cross-sectional photograph, and (d) Cross-sectional perspective view of the variable friction coefficient block body obtained by the manufacturing method according to the present invention. Is. It is a surface photograph of the state where the periodic swell of the friction coefficient variable block body was generated. In the friction coefficient variable block body, (a) a surface photograph of periodic protrusions formed by superimposing on undulations, a diagram showing a surface shape in a direction orthogonal to the compression direction, and (b) a projection formation mechanism will be described. It is a perspective view of a woven cloth. It is sectional drawing which shows the manufacturing method by the comparative example of the friction coefficient variable block body. It is sectional drawing which shows the manufacturing method by Example of the friction coefficient variable block body. It is a surface photograph of the friction coefficient variable block body manufactured by the comparative example 1. FIG. It is a surface photograph of the friction coefficient variable block body manufactured by Example. It is a list of evaluation test results of the friction coefficient variable block body. It is a graph which shows the measurement result of the friction coefficient of a friction coefficient variable block body.

First, the friction coefficient variable block body manufactured by the manufacturing method according to the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, the variable friction coefficient block body 10 includes a woven fabric 2 and a laminated portion 5 made of a rubber elastic body on the main surface of a plate-shaped main body portion 1 made of a rubber elastic body. The woven fabric 2 is embedded in the laminated portion 5 along the surface thereof and directly below the woven fabric 2, so that the main surface is formed flat as a whole and a part of the woven fabric 2 can be exposed. The woven fabric 2 is composed of a biaxial woven fabric in which orthogonal warp threads 2a and weft threads 2b are woven.

As shown in FIG. 2, the variable friction coefficient block body 10 is compressed by being compressed in a direction along the main surface of the woven fabric 2 so that either the warp threads 2a or the weft threads 2b are compressed. Repeated periodic "waviness" of ridges 3a and valleys 3b in the direction is formed on the main surface of the woven fabric 2 on the embedded side. Also, by releasing the compression (distortion), it returns to the original flat shape. That is, the "waviness" can be reversibly formed. The height of the ridge 3a with respect to the valley 3b of the swell changes according to the strain in the compression direction, and changes, for example, in the range of 0 to 0.2 times the period length of the swell. The formation of such "waviness" is also called "surface buckling".

The swell as described above can be formed by using the main body 1 as a material having a low elastic modulus and the woven fabric 2 as a material having a high elastic modulus. At this time, for example, the ratio (Ea / Eb) of the elastic modulus (Ea) of the main body 1 to the effective elastic modulus (Eb) of the warp threads 2a and the weft threads 2b in the yarn axis direction is preferably 10 ^-1 or less. Further, the cycle length of the swell can be adjusted by the ratio of the Young's modulus of the main body 1 and the woven fabric 2 and the thickness of the woven fabric 2.

As shown in FIG. 3, the variable friction coefficient block body 10 can be formed by superimposing periodic protrusions 4 on the intersections of the warp threads 2a and the weft threads 2b in a swell when compressed. That is, the protrusion 4 is formed by controlling the exposure state of the woven fabric 2 to the surface.

As shown in FIG. 3A, undulations in the same direction are formed by compression in the lateral direction of the paper surface. That is, it forms a swell with ridges 3a and valleys 3b extending perpendicular to the compression direction. At this time, when the height of the top of the ridge 3a is measured along the extending direction of the ridge 3a (vertical direction on the paper surface), for example, a peak 4a having a height of about 10 μm is observed. That is, the protrusion 4 having the shape of the peak 4a is formed in synchronization with the ridge 3a of the swell.

Also referring to FIG. 3B, first, when no stress is applied to the woven fabric 2, the surface of the variable friction coefficient block body 10 is flat. On the other hand, for example, when the main body 1 (see FIG. 1) is compressed along the main surface so as to compress the weft 2b, the tensile stress in the direction perpendicular to this, that is, in the extending direction of the warp 2a, is applied to the main body 1. Occurs in. Due to the tensile stress, the main body 1 is stretched in the extending direction of the warp 2a, and at the same time, the warp 2a is pulled and stretched so as to approach a straight line. As a result, the degree of bending at the intersection of the weft 2b knitted so as to pass above and below the warp 2a is increased. At this time, the protrusion 4 is formed at the portion of the intersection with the warp 2a where the weft 2b is located on the surface side. That is, the periodic protrusions 4 are formed in synchronization with the formation of the swell, that is, superimposed on the swell. The height of the protrusion 4 is 0 when no compression is applied. That is, the heights of the intersections of the warp threads 2a and the weft threads 2b are the same. On the other hand, the height of the protrusion 4 becomes the highest when the warp 2a is stretched by in-plane compression in the weft 2b direction, and becomes the same height as the diameter of the weft 2b when the warp 2a is made linear. The same applies even if the compression direction is changed between the warp threads 2a and the weft threads 2b.

The variable friction coefficient block body 10 changes the shape of its main surface from a flat shape to form a swell by applying compressive stress, and at the same time, increases the exposure of the woven fabric 2 to the surface to form protrusions 4. Form. That is, a periodic uneven structure is formed in which the undulations and the protrusions 4 are superimposed. Here, the area of contact with an object having a shape that does not enter the swell valley 3b becomes smaller by forming the swell than when it is flat. In addition to this, the variable friction coefficient block body 10 forms the protrusions 4 in synchronization with the formation of the waviness, so that the contact area is further reduced. This makes it possible to increase the range of change in the coefficient of friction of the surface with respect to the object in contact. That is, the coefficient of friction is changed by controlling the exposure state of the laminated portion 5 to the surface of the laminated portion 5 by the rubber elastic body of the woven fabric 2.

Next, regarding the method for manufacturing such a variable friction coefficient block body 10, the test results of manufacturing the variable friction coefficient block body by each of the comparative examples and the examples will be described.

[Block body of comparative example]
As shown in FIG. 4, the variable friction coefficient block body is prepared separately by, for example, infiltrating the uncured or melted liquid state material which is the precursor of the main body 1 into the woven fabric 2 to fill the void portion thereof. It was manufactured by a method of crimping to the surface of a solid main body 1 to cure or solidify the precursor. That is, it is a manufacturing method by crimping in one step.

Specifically, a plate-shaped body of silicone rubber having a thickness of 2 mm was used as the main body 1, and this was uniaxially stretched with a strain of 12% in the direction along the main surface. The dimensions of the main surface are 180 mm × 180 mm. As the woven fabric 2, a plain woven fabric made of nylon 6,6 fibers having a diameter of 35 μm with a distance between the fibers of about 80 μm is used, and the woven fabric 2 is provided with a polydimethylsiloxane (PDMS) sol which is a precursor of silicone rubber. It was placed on the main body 1 which was impregnated with 11 and stretched. Next, a base 21a and a pressing member 21b made of two plate-shaped support glasses are arranged below and above, respectively, and sandwiched so as to be crimped at a constant pressure, while squeezing out the surplus PDMS sol 11 (arrows). (See S), the PDMS sol was cured by holding at room temperature (295 K) for 24 hours. Finally, the base 21a and the pressing member 21b were peeled off to obtain a variable friction coefficient block body (comparative example). By peeling off the base 21a and the pressing member 21b, the strain due to the stretching given in advance was released, and a swell having a period of about 700 μm was generated on the surface. The pressure for crimping was set to 12 kPa and 60 kPa, respectively, and the pressure was created as a variable friction block body according to Comparative Example 1 and Comparative Example 2, respectively.

[Block body of example]
As shown in FIG. 5, the block body of this example was manufactured by crimping in two stages. In this manufacturing method, the woven fabric 2 is placed on the base 21a, the uncured liquid which is the precursor of the rubber elastic body is applied from above, and the pressing member 21b is pressed against the base 21a without being pressed. The pre-sheet body forming step, which is the first step of crimping to form the pre-sheet body 2'by impregnating the woven fabric 2 with the curing liquid and curing the woven fabric 2, and the pre-sheet body 2'with the upper surface of the main body 1 as the pasting surface are attached. It has a pasting step which is a second stage crimping.

Specifically, as shown in FIG. 5A, in the presheet body forming step, first, the woven fabric 2 was placed on the base 21a which is the support glass and impregnated with the PDMS sol 11. Further, it is sandwiched from above by another supporting glass, a pressing member 21b, and sandwiched so as to be crimped at a constant pressure of 12 kPa, and while squeezing out the surplus PDMS sol 11 (see arrow S), 24 at room temperature (295 K). The PDMS sol was cured for a long time to obtain a presheet body 2'containing the woven fabric 2.

Next, as shown in FIG. 5B, in the pasting step, first, the main body 1 made of a 2 mm thick silicone rubber sheet is uniaxially stretched in the direction along the main surface with a strain of 12%. A presheet body 2'coated with PDMS sol 11 on the lower surface was placed on the upper surface as a sticking surface. Similar to the comparative example, the dimensions of the main surface are 180 mm × 180 mm. The base 21a and the pressing member 21b arranged one above the other are sandwiched so as to be crimped at a constant pressure of 12 kPa or less, and the surplus PDMS sol 11 is squeezed out (see arrow S) and held at room temperature (295 K) for 24 hours. The PDMS sol was cured, and the presheet body 2'was attached to the main body 1. Finally, the base 21a and the pressing member 21b were peeled off to obtain a variable friction coefficient block body (Example). By peeling off the base 21a and the pressing member 21b, the strain due to the stretching given in advance was released, and a swell having a period of about 700 μm was generated on the surface.

[Evaluation test]
Surface observation was performed on each of the samples (variable friction coefficient blocks) obtained in Examples 1 and 2 described above, and surface topography was obtained using an optical microscope and a laser cofocal optical microscope. In addition, the sliding friction coefficient was measured for each sample using a pin-on-plate type friction tester. In addition to conducting these evaluation tests in a state where swells are generated, the main body 1 is stretched so as to give a distortion of 12% in the same direction as when the main body 1 is uniaxially stretched at the time of manufacture, and the same applies even in a state without swells. An evaluation test was conducted.

In the surface topography, the cross-sectional image, the transmission image, and the laser reflection image were obtained, and the difference in the height of the surface depending on the part was obtained. The difference in height is such that the portion of the intersecting portion where the warp 2a and the weft 2b intersects and forms the protrusion 4 is A, and the portion between the other adjacent intersections (for example, the intersection of the two intersections on the weft 2b). B, the position between the two adjacent warp threads 2a and the position between the two adjacent weft threads 2b, that is, the position of the opening portion of the woven fabric 2, and the difference in height between A and B. , The difference in height between A and C was calculated respectively.

In measuring the sliding friction coefficient, a sample is attached to a plate with high rigidity, a spherical glass indenter with a radius of 12.7 mm is pressed with a load of 1.5 N, and the direction is perpendicular to the direction in which the ridge of the swell extends. It was moved at a speed of 10 mm / s for 1 second, and the resistance force in the moving direction was measured with a force gauge and used as the frictional force. Further, each sample was measured 5 times, and the average value of the frictional force was divided by the load to obtain the sliding friction coefficient.

As shown in FIG. 6, in the surface observation of Comparative Example 1, the light was reflected unevenly, the woven fabric 2 was not exposed in the portion P that appeared to shine white, and the surface was covered with a thin silicone rubber. ..

On the other hand, as shown in FIG. 7, in the surface observation of the example, the unexposed portion P of the woven fabric 2 was not observed, and the woven fabric 2 was uniformly exposed to exhibit a good surface.

Further, as shown in FIG. 8, in Comparative Example 1, an unexposed portion of the woven fabric 2 was observed on the surface from the surface topography. In such a portion, the difference in surface height is only about 2 to 3 μm even in the state where the swell is generated, and it is considered that the contact area with the contacting object cannot be increased and the friction coefficient cannot be reduced. This was supported by the measurement of the coefficient of friction, which will be described later.

Further, in Comparative Example 2, although the woven fabric 2 can be sufficiently exposed in the state where the swell is generated (with swell), the difference in height is large in the state without swell (without swell). The distance between A and B is about 4 μm, but the distance between A and C is about 16 μm. That is, it is considered that the surface is not flat even in a state without swell, and the coefficient of friction cannot be changed significantly. This is also supported by the measurement of the coefficient of friction, and will be described later.

In the embodiment, the woven fabric 2 can be sufficiently exposed with undulations, and the difference in surface height can be as large as about 9 μm between AB and 21 μm between A and C, while there is no undulation. In, it was possible to make it as small as about 1 μm between AB and about 2 μm between A and C. That is, the contact area with the object in contact with the swell can be reduced to reduce the friction coefficient, and the contact area with the object with no swell can be increased to increase the friction coefficient.

As shown in FIG. 9, regarding the measurement result of the friction coefficient, in the embodiment, the friction coefficient was reduced when there was swell, and the friction coefficient was increased when there was no swell. In Comparative Example 1, the coefficient of friction was increased in the case of no swell as in the embodiment, but the coefficient of friction could not be reduced so much in the case of swell, and the difference in the coefficient of friction depending on the presence or absence of swell was reduced. .. In Comparative Example 2, the coefficient of friction was small regardless of the presence or absence of swell.

That is, in Comparative Example 1, the unexposed portion P of the woven fabric 2 was generated, and the friction coefficient could not be reduced even in the state where the swell was generated. On the other hand, in the past experience, when the main surface has a small area of about 50 mm × 50 mm or less, the friction coefficient can be increased in a state where the swell is generated without forming such an unexposed portion P. .. That is, the unexposed portion P of the woven fabric 2 is likely to occur when the area is 100 mm × 100 mm or more, for example, when the area is 180 mm × 180 mm as in Comparative Example 1. This is because the surplus of the uncured liquid (PDMS sol 11), which is the precursor of the rubber elastic body, is squeezed out in the one-step crimping manufacturing method, but the amount of the uncured liquid to be discharged by the squeezing out. It can be said that unevenness occurred depending on the part. In particular, the main body 1 is a rubber elastic body, and it is easy to allow excess uncured liquid to remain due to its elastic deformation during crimping, and as a result, the woven fabric 2 cannot be partially exposed as described above. It is thought that it was.

In Comparative Example 2, the pressure at the time of crimping was set high so that all the excess uncured liquid was discharged. Therefore, the woven fabric 2 could be sufficiently exposed. However, there was a large difference in height in the absence of swell. It is considered that this is because the difference in the height of the surface is increased due to the non-uniformity of the partial thickness of the woven fabric 2 at the time of crimping. That is, in the woven fabric 2, since the intersecting portion (the portion A in FIG. 8) where the warp threads 2a and the weft threads 2b intersect is the thickest, the main body portion 1 is deformed so as to be sunk during crimping. On the other hand, the main body 1 is hardly deformed at the position of the thin portion, particularly the opening portion of the woven fabric 2 (the C portion in FIG. 3). Therefore, it is probable that the springback was larger in the A part than in the C part after the crimping, and the difference in height was increased even in the state where there was no swell.

On the other hand, in the example, by crimping in two steps, it was possible to improve the discharge of excess uncured liquid and to flatten the surface shape in a state without waviness. That is, in the first-stage crimping (see FIG. 5A), since the elastic deformation of the base 21a is small, it is difficult to tolerate the residual of excess uncured liquid, and the uncured liquid is discharged well. Further, in the crimping of the presheet body 2'in the second stage (see FIG. 5 (b)), even if the uncured liquid on the back surface (attached surface) of the presheet body 2'is insufficiently discharged, the presheet body 2 is used. It is probable that the woven fabric 2 could be uniformly exposed as a whole without directly affecting the surface of the variable friction coefficient block body, which is the surface of ‘’. Since the laminated portion 5 is manufactured separately from the main body portion 1, the woven fabric 2 can be uniformly exposed without being affected by the shape and properties of the main body portion 1, thereby providing a stable friction coefficient change in the variable friction coefficient block body. obtain. This makes it possible to accurately manufacture a block body having a variable friction coefficient even if the block body has a large area and is thick.

Further, in this embodiment, although the crimping process is increased by one as compared with Comparative Example 1 and Comparative Example 2, the crimping process does not require a particularly difficult operation, and the yield is good, that is, the friction coefficient variable block is efficiently performed. The body can be manufactured.

As described above, according to the above-described embodiment, the friction coefficient variable sheet that can give a stable friction coefficient change even in a large-area friction coefficient variable block body having a main surface of 100 mm × 100 mm or more. And blocks can be manufactured efficiently.

The variable friction coefficient block body 10 may have the main body 1 as a sheet body, and can be similarly manufactured as a variable friction coefficient sheet body. Further, a similar friction coefficient variable block body can be obtained as long as it causes surface buckling that forms waviness on the surface by compression without preliminarily stretching one axis in the crimping step.

Further, the surface in contact with the pressing member 21b in the presheet body forming step may be attached to the attachment surface of the main body portion 1 in the attachment step. Since the surface of the presheet body 2'that is in contact with the base 21a is the surface of the variable friction coefficient block body 10, the woven fabric 2 can be placed in the vicinity of the surface with high accuracy, and the change in the friction coefficient can be stably obtained. be able to.

Although the examples according to the present invention and the modifications based on the present invention have been described above, the present invention is not necessarily limited to this, and those skilled in the art deviate from the gist of the present invention or the scope of the attached claims. Without doing so, various alternative and modified examples could be found.

1 Main body 2 Woven fabric 2'Presheet body 10 Variable coefficient of friction block body 11 PDMS sol (uncured liquid)
21a Base 21b Pressing member

Claims (2)

A method for manufacturing a variable friction coefficient block body capable of changing the friction coefficient by controlling the exposure state of the woven fabric embedded along the surface of the rubber elastic body to the surface.
The woven fabric is placed on a base, an uncured liquid which is a precursor of the rubber elastic body is applied from above, and the woven fabric is impregnated with the pressing member while being pressed against the base. The process of curing the uncured liquid to form a precursor and
A method for manufacturing a block body having a variable friction coefficient, which comprises a step of stretching a sticking surface of a main body made of a rubber elastic body in advance and sticking the presheet body to the sticking surface. The method for manufacturing a block body having a variable friction coefficient according to claim 1 , wherein the sticking step is to stick a surface in contact with the pressing member to the sticking surface.

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