JP2004125620A - Snow property measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a shear power and shear displacement in a compressed state of snow and also precisely measure a shear property including a shear elasticity of the snow. <P>SOLUTION: A base 2 is provided with a snow shear property measuring means 4 comprising a snow compression means 3 having a sample container 6 provided with a container body 6U and a transversal movement part 6L and accommodating the sampled snow and a pressing tool 8 for compressing the snow in the sample container 6 by pushing down or up a piston 7, a transversal pressing tool 41 for shearing the snow by moving the transversal movement part 6L in the direction of intersecting the compression direction, a shear power measuring tool 42 for measuring the shear force to the snow and a transversal movement distance measuring instrument 43 for measuring a transversal movement distance of the transversal movement part 6L. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a snow characteristic measuring device capable of measuring a shear force and a shear displacement when snow is sheared in a compressed state to measure a shear characteristic of snow.
[0002]
2. Description of the Related Art
For example, the running performance on snow of winter tires such as snow tires and studless tires is greatly affected by the snow quality. Therefore, in the R & D of winter tires, when accurately comparing and evaluating the running performance of snow tires on snow, only test data measured under the same snow condition, that is, test data measured at the same time on the same course, are compared with each other. And it is a significant hindrance to R & D.
[0003]
Therefore, the present inventor conducted research to quantify and display snow quality. as a result,
(1) Among the characteristics of snow, that is, the characteristics of snow, which have a large influence on the running performance on snow, there are compression characteristics and shear characteristics. By quantifying and displaying these, it is possible to grasp the snow quality substantially.
{Circle around (2)} Even in test data measured under any one of different conditions such as the location of the test course, the date and time of the test, and the weather conditions at the time of the test, the compression characteristics and the shear characteristics of the snow are not affected. In the case where they substantially coincide with each other, it has been determined that the test data can be compared and evaluated.
[0004]
By quantifying the compression and shear characteristics of such snow, it is also possible to correct test data measured under various snow qualities with the compression and / or shear characteristics of the snow, It is expected that the comparison between test data measured under different snow conditions can be realized. Furthermore, such quantification can also be used as snow model data when computer simulation of tire running performance on snow is performed.
[0005]
Of these, the "shear characteristic" is a well-known relationship between a shear displacement and a shear stress generated when a shear stress is applied to snow in a compressed state, as shown by a curve m schematically shown in FIG. In the early stage of the shearing, the shear stress has a certain elastic modulus (referred to as shear elastic modulus) and increases sharply, then changes gradually, and when the X mark is reached, snow breaks (shear breakage) occurs. I do. At this time, the shear modulus and the shape of the curve m differ depending on the snow quality, and greatly affect traction and the like.
[0006]
In the field of construction, a one-sided shear test device is used as a device for measuring the shear fracture characteristics of soil (for example, see Non-Patent Document 1).
[0007]
[Non-patent document 1]
Kunio Yasukawa, Kiyoshi Imanishi, Yoshitaka Tateishi, "Edology and Soil Mechanics", Ohmsha, p120-123
[0008]
However, since this apparatus is intended for soil, the structure of the apparatus is complicated and large, which makes it difficult to measure outdoors. Since the shear characteristics of snow are greatly affected by weather conditions and regions, it is important to bring a measuring device to the place where the snow to be measured exists and measure the sampled snow at the same time as sampling. However, the large size of the above-mentioned device makes it difficult to do so, and the shear characteristics cannot be measured accurately.
[0009]
Also, when snow is compressed, the temperature tends to rise with the decrease in volume and melt (pressure melting). However, it is difficult to prevent pressure melting due to the complicated structure of the above-described device. The measurement of the shear properties cannot be performed accurately.
[0010]
Therefore, the present invention makes it easy to carry the device to the measurement location, for example, by making the structure simple and compact, so that the sampled snow can be measured at the same time as the sampling at the location, and the snow is altered by pressure melting at the time of measurement. It is an object of the present invention to provide a snow characteristic measuring device capable of measuring snow characteristics including a shear elastic modulus with high accuracy and greatly contributing to quantification of snow quality.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a snow characteristic measuring device that measures a shear force and a shear displacement when snow is sheared in a compressed state to measure a shear characteristic of the snow,
On the base,
A sample container having a straight cylindrical shape capable of storing sampled snow, and comprising a container body and a laterally movable portion capable of moving in a direction intersecting with the compression direction, and sliding with the inner cavity of the sample container; A snow compression means comprising a piston that abuts against the upper or lower surface of the snow in the lumen, and a pusher that compresses the snow by pushing down or pushing up the piston with a load applying tool;
And a lateral pressing tool having a lateral load applying tool for shearing snow in the sample container by moving the lateral moving unit,
A shear force measuring instrument for measuring the shear force on the snow,
The present invention is characterized in that there is provided snow shear characteristic measuring means comprising a lateral displacement measuring device for measuring the shear displacement of snow by measuring the lateral displacement of the lateral displacement section.
[0012]
The invention according to claim 2 is characterized in that at least a part of the sample container is exposed to the outside and supported by the base.
[0013]
According to a third aspect of the present invention, there is provided a cooling device capable of cooling the sample container and preventing snow in the sample container from melting under pressure.
[0014]
According to a fourth aspect of the present invention, the shear force measuring instrument is a load cell interposed between the lateral moving portion and the lateral load applying instrument.
[0015]
Further, in the invention according to claim 5, the sample container is characterized in that a clearance between the container main body and the laterally moving portion is 3.0 mm or less.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to illustrated examples. FIG. 1 is a perspective view showing a snow characteristic measuring device of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a side view thereof.
[0017]
1 to 3, a snow characteristic measuring apparatus 1 of the present embodiment is configured by providing a base 2 with a snow W compressing unit 3 and a shearing characteristic measuring unit 4, thereby reducing the shear modulus of the snow. The shear properties including are measured with high precision.
[0018]
The base 2 includes, for example, a plate-like base 2A horizontally supported in a height-adjustable manner by legs 5 provided at four corners, and a column 2B standing upright on the base 2A. This allows installation of the device outdoors at the measurement site.
[0019]
The compression means 3 has a straight cylindrical sample container 6 capable of storing the sampled snow W, and a piston 7 abutting on the upper surface of the snow W in the sample container 6. In the present embodiment, at least a pusher 8 for compressing the snow W is provided. In this example, a pusher 8 is further provided which includes a distance measuring device 10 for measuring a distance of the push-down of the piston 7. The pusher 8 may be configured such that the piston 7 is brought into contact with the lower surface of the snow W and the snow W is compressed by pushing up the piston 7.
[0020]
As shown in FIG. 4, the sample container 6 is, for example, a container having a bottom having a rectangular cylindrical shape for storing sampled snow W. In this example, the front surface thereof is made of, for example, an acrylic resin, a polycarbonate resin, or the like. Is formed so that the compressed state and the sheared state of the snow W inside can be seen through. In this example, the case where the sample container 6 is formed of an upper container body 6U and a lower lateral moving portion 6L that can move laterally in a direction intersecting with the compression direction with the container body 6U is illustrated. The lateral moving portion 6L is guided by a guide rail 11 laid on the base 2A so as to be laterally movable.
[0021]
The container body 6U is detachably held by the support 2B via holding means 13. In this example, the holding means 13 has a pair of vertical holding plate pieces 13A protruding forward from the support portion 2B, and inserts the container body 6U into a space between the holding plate pieces 13A, 13A. Hold. In addition, the holding plate piece 13A can hold the container body 6U floating from the lateral moving portion 6L. In this example, the clearance (gap) between the lower end of the container body 6U and the upper end of the lateral moving portion 6L is 3. It is configured to be adjustable to 0 mm or less, preferably 1.0 mm or less, more preferably 0.5 mm or less.
[0022]
Here, when snow compresses, it has the property of changing the snow quality, for example, the temperature rises as the volume decreases and pressure melting occurs.Therefore, in order to accurately measure the shear characteristics, the temperature rise due to the compression is suppressed by suppressing the temperature rise due to the compression. It is important to prevent melting. For this purpose, at least a part of the sample container 6 is exposed to the outside and supported by the base 2, and the inside snow W is naturally cooled together with the sample container 6 from the exposed portion, and / or dry ice or the like. It is preferable to apply forced cooling by attaching to the exposed portion.
[0023]
At this time, in order to further enhance the cooling effect, it is necessary to secure a large number of exposed portions. Therefore, in this example, a substantially entire wide area of the front surface of the container body 6U and the peripheral surface of the laterally moving portion 6L is externally provided. Exposed.
[0024]
Next, the pusher 8 includes a piston 7 that contacts the upper surface of the snow W in the sample container 6 and a load application device 15 that compresses the snow W by applying a load to the piston 7 and pressing it down. At the same time, the load applying device 15 is configured to be able to grasp the applied load.
[0025]
The piston 7 has a piston head 7A (shown in FIGS. 2 and 3) that can slide on the inner surface of the sample container 6, and a trunk portion that has a smaller diameter than the piston head 7A and extends integrally upward. 7B, and a load applying device 15 is coaxially connected to the upper end of the body portion 7B.
[0026]
Here, in the piston head 7A, frictional heat such as Teflon (trademark of DuPont) or the like is used in order to suppress the generation of frictional heat with the bore surface during sliding and to prevent melting of snow due to frictional heat. It is preferable to use a polyfluoroethylene resin having a low resistance. In this piston head 7A, if the clearance between the piston head 7A and the inner cavity surface is small, a small amount of water existing between the piston head 7A and the inner cavity surface during compression or sample encapsulation will cause the environmental temperature at the time of measurement. As a result, there is a problem that the piston 7 is frozen and the piston 7 cannot slide, or the compression force cannot be accurately transmitted to the snow. Therefore, the clearance is preferably set to 0.05 to 1.0 mm, more preferably 0.1 to 0.5 mm.
[0027]
In addition, as shown in FIG. 1, in the present embodiment, the load applying tool 15 is formed by using a ball screw mechanism. The load applying device 15 includes a lift 18 that is vertically movably guided by a guide 17 provided on the support 2B, a lower end pivotally connected to the lift 18 and a handle 19A for manual operation at an upper end. It has a vertical screw shaft 19 formed and a nut fitting 20 fixed to the upper end of the support column 2B via a mounting plate and screwed with the screw shaft 19. In this example, the case where the lift 18 and the upper end of the piston 7 are connected via the connecting member 21 is illustrated, but they may be directly connected without the connecting member 21.
[0028]
As described above, in the load applying device 15 of the present example, the screw shaft 19 is screwed forward by the handle operation, so that the screw shaft 19 can be lowered integrally with the elevating platform 18 to push down the piston 7 connected coaxially. Thereby, the snow W in the sample container 6 can be compressed. At this time, the reaction force from the snow W which is the load applied to the piston 7, that is, the compressive force to the snow W, in this example, is between the piston 7 and the joint member 21 or between the lifting table 18. It can be measured by a sensor such as a load cell interposed. As the sensor, various types such as a piezoelectric force sensor using a piezoelectric effect and a magnetostrictive force sensor using a magnetostriction phenomenon can be appropriately used.
[0029]
In addition to the ball screw mechanism, for example, a weight whose mass has been measured in advance may be used as the load applying tool 15. That is, the weight is placed directly on the elevator 18 or on the vertically supported piston 7 to push down the piston 7 and compress the snow W. At this time, the compressive force applied to the snow W can be represented by the sum of the masses of the piston 7 and the weight (when the platform has the lift 18 or the like, the mass of the lift 18 or the like is also included). Is measured in advance, the compression force can be grasped. In such a case, the device structure can be further simplified and downsized, which is more preferable in terms of enhancing portability.
[0030]
In this example, a case is shown in which a distance measuring device 10 for measuring the distance of pressing down of the pusher 8 is provided in order to measure the volume change due to the compression of the snow W. Can be eliminated. In this example, a so-called linear scale including a detection scale 10A and a detection head 10B for detecting a moving distance along the detection scale 10A is used as the distance measuring device 10, as shown in FIG. The detection scale 10A is vertically attached to the column 2B via a mounting bracket, and the detection head 10B is attached to the lift 18 so as to be integrally movable. In addition, various types of optical scales and electromagnetic scales can be used as appropriate as the linear scale.
[0031]
Next, the shear characteristic measuring means 4 includes a lateral pushing tool 41 having a lateral load applying tool 40 for shearing the snow W in the sample container 6 by moving the lateral moving portion 6L of the sample container 6; A shear force measuring instrument 42 for measuring the shearing force of the snowboard, and a lateral movement distance measuring device 43 for measuring the shear displacement of snow by measuring the lateral movement distance of the lateral movement section 6L.
[0032]
Further, in the present embodiment, the lateral load applying device 40 is formed using a ball screw mechanism substantially similar to the load applying device 15. That is, as shown in FIG. 2, the lateral load applying tool 40 has a movable table 47 guided by the guide rail 11 on the base 2A so as to be able to move laterally, and a lateral inner end pivotally attached to the movable table 47. A horizontal screw shaft 46 having a handle 46A for manual operation at an outer end thereof, and a nut fitting 45 fixed to the base 2A via a mounting plate and screwed with the screw shaft 19. I can. Although the moving table 47 and the piston 7 are connected via the connecting member 48 in this embodiment, they may be connected directly without using the connecting member 48.
[0033]
As described above, in the lateral pushing tool 41 of the present example, the screw shaft 46 forming the lateral load applying tool 40 moves inward by screwing by operating the handle, and moves the lateral moving unit 6L via the moving table 47. Thereby, the snow W in the sample container 6 can be sheared. At this time, the reaction force received from the snow W, that is, the shearing force, can be measured by the shearing force measuring device 42 which is a load cell provided between the lateral moving portion 6L and the lateral load applying device 40 in this example. In this example, a case where the load cell is housed and held in the joint member 48 is illustrated. In addition to the load cell, various devices such as a piezoelectric force sensor using a piezoelectric effect and a magnetostrictive force sensor using a magnetostrictive phenomenon can be appropriately adopted as the shear force measuring device 42.
[0034]
The shear displacement of the snow W at that time is measured by a lateral movement distance measuring device 43 that measures the lateral movement distance of the lateral movement portion 6L. In the present embodiment, a linear scale including a detection scale 43A and a detection head 43B for detecting a moving distance along the detection scale 43A is used as the lateral movement distance measurement device 43, similarly to the distance measurement device 10. I have. The detection scale 43A is horizontally attached to the base 2A via a mounting bracket, and the detection head 43B is attached to the movable table 47 so as to be integrally movable. Various types of optical scales and electromagnetic scales can be used as appropriate as the linear scale.
[0035]
Since the snow characteristic measuring device 1 is configured as described above, it is convenient to carry the device, for example, it can be formed in a simple and compact structure. Therefore, it is possible to bring the device to a place where the snow to be measured exists and measure the sampled snow at that place and simultaneously with the sampling.
[0036]
The sample container 6 exposes at least a part thereof, in this example, substantially the entire front surface of the container body 6U and the entire peripheral surface of the lateral moving portion 6L to the outside. Therefore, when measuring outdoors, the wide exposed portion can be exposed to cold outside air, and the snow inside can be naturally cooled. In addition, it becomes possible to measure the shear characteristics of snow with high accuracy.
[0037]
In particular, it is preferable to provide a cooling unit 23 that can forcibly cool the sample container 6 in order to more reliably suppress the snow from being altered due to the pressure melting. In the present embodiment, the cooling means 23 is a so-called cooling spray 23A containing a liquid gas such as LP gas, and when compressed, can be forcibly cooled by spraying onto the exposed portion of the sample container 6 to remove snow inside. Pressure melting can be more reliably suppressed.
[0038]
Next, the case where the snow shear characteristic is measured using the snow characteristic measuring apparatus 1 of the present embodiment will be described.
[0039]
Bring the device to the place where there is snow to be measured (measurement site) and install it. A snow sample collected at the measurement site is stored in the sample container 6 and the sample container 6 is set in the apparatus 1. Thereafter, by operating the handle of the load applying device 15, the piston 7 is pressed down, and the snow is gradually compressed until the output from the load cell (compression force measuring device) corresponding to the compression force reaches a predetermined value.
{Circle around (1)} In this compressed state, a handle operation is performed on the lateral load applying tool 40 to gradually move the lateral moving portion 6L of the sample container 6 laterally, so that the container body 6U and the lateral moving portion 6L move between the container main body 6U and the lateral moving portion 6L. We shear snow. At that time, the lateral movement distance (shear displacement of snow) and the output (shear stress) from the load cell (shear force measuring instrument) are simultaneously measured. In addition, it is preferable that the lateral moving speed of the lateral moving unit 6L be in a range of 0.01 to 5 mm / sec.
[0040]
Thereby, from the measured lateral movement distance and the output from the load cell, as shown in FIG. 4, the shear characteristic, which is the relationship between the shear stress of the snow and the shear displacement, is known. From this, the shear modulus can be obtained.
[0041]
At this time, in order to suppress the temperature rise of the snow due to the compression and to suppress the fluctuation of the snow quality due to the pressure melting or the like, at the time of the compression, the cooling spray 23A is sprayed onto the exposed portion of the sample container 6 to perform the forced cooling. Thereby, the shear characteristics including the shear modulus can be measured more accurately.
[0042]
FIG. 3 shows the shear characteristics (measured temperature −2 ° C.) of the snow sample at the snow temperature −2 ° C. collected in the Nayoro test at a compressive force of 5 kgf / cm ² .
[0043]
As described above, particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.
[0044]
【The invention's effect】
Since the present invention is configured as described above, it is possible to easily carry the device to a measurement location, for example, to form the device with a simple and compact structure, and to measure the sampled snow simultaneously with sampling at that location. In addition, it is possible to suppress the alteration of snow due to pressure melting at the time of measurement, and it is possible to measure the shear characteristics of snow, including the shear modulus, with high accuracy, which can greatly contribute to the quantification of snow quality.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a snow characteristic measuring device according to the present invention.
FIG. 2 is a front view thereof.
FIG. 3 is a side view thereof.
FIG. 4 is a diagram showing a relationship between a shear stress and a shear displacement measured by the present apparatus.
FIG. 5 is a diagram illustrating a shear characteristic among snow characteristics.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Snow characteristic measuring device 2 Base 3 Snow compressing means 4 Shear characteristic measuring means 6 Sample container 6U Container main body 6L Lateral moving part 7 Piston 8 Pusher 15 Load applying tool 23 Cooling means 40 Lateral load applying tool 41 Lateral pressing tool 42 Shear force measuring instrument 43 Lateral moving distance measuring instrument

Claims (5)

A snow characteristic measuring device that measures a shear force and a shear displacement when shearing in a state where snow is compressed and measures a shear characteristic of the snow,
On the base,
A sample container having a straight cylindrical shape capable of storing sampled snow, and comprising a container body and a laterally movable portion capable of moving in a direction intersecting with the compression direction, and sliding with the inner cavity of the sample container; A snow compression means comprising a piston that abuts against the upper or lower surface of the snow in the lumen, and a pusher that compresses the snow by pushing down or pushing up the piston with a load applying tool;
And a lateral pressing tool having a lateral load applying tool for shearing snow in the sample container by moving the lateral moving unit,
A shear force measuring instrument for measuring the shear force on the snow,
A snow characteristic measuring device, comprising: a snow shear characteristic measuring means comprising a lateral moving distance measuring device for measuring a shear displacement of snow by measuring a lateral moving distance of the lateral moving portion. The snow characteristic measuring device according to claim 1, wherein at least a part of the sample container is exposed to the outside and supported by the base. The snow characteristic measuring device according to claim 1 or 2, further comprising a cooling unit that can cool the sample container and prevents the snow in the sample container from melting under pressure. The snow characteristic measuring device according to any one of claims 1 to 3, wherein the shear force measuring device is a load cell interposed between the lateral moving portion and the lateral load applying device. The snow characteristic measuring device according to any one of claims 1 to 4, wherein the sample container has a clearance between the container main body and the laterally moving portion of 3.0 mm or less.

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