KR101605506B1 - Hydraulic weight-in-motion sensor having double-tube structure and device including the same - Google Patents

Abstract

Disclosed in the present invention is a hydraulic axle load detector using a double pipe. The hydraulic axle load detector comprises: a plurality of hydraulic tubes formed in a double pipe structure including an internal tube having a first internal space and an external tube having a second internal space between the internal tube; a connecting pipe which fixates hydraulic tubes on both sides; at least one vent hole disposed between the hydraulic tubes among the connecting pipes to be a moving passage of the atmosphere; and at least one fluid injecting pipe disposed in the connecting pipe to inject a fluid into the second internal space of the hydraulic tubes. Accordingly, excellent linearity and accurate measurement is able to be provided by reducing a temperature sensitivity of the hydraulic axle load detector.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shaft weight sensor using a dual pipe,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a hydraulic axis weight sensor using a dual pipe and a shaft weight sensing device including the same, and more particularly to a hydraulic axis weight sensor using a double pipe for measuring the weight of a moving vehicle, .

A weight-in-motion (WIM) sensor is used to measure the dynamic load of the moving vehicle to estimate the static load corresponding to the vehicle. Generally, the WIM sensor is an apparatus for detecting an overloaded vehicle to protect a road or a bridge. The WIM sensor detects the total weight of the vehicle by detecting and summing the axle weights of the vehicles in the traveling state of the vehicle, Device. These WIM systems are very important data for traffic situation monitoring to reduce accident frequency, reduce fuel consumption and reduce packaging cost.

Accordingly, various WIM sensors have been developed and are being sold on the market. The banding plate load cell, the most commonly used low-speed WIM sensor, provides relatively high accuracy. However, the installation cost is high, and the accuracy of the high-speed driving vehicle is low due to the slow response time. On the other hand, piezoelectric sensors are problematic in that their cost is low, but they do not work well at a low speed of less than 20 km / h.

Meanwhile, despite the high accuracy, the hydraulic load cell has been used only for limited applications such as static pressure measurement due to pressure variation due to temperature change in the sensor and unstable characteristic diaphragm. Therefore, there is a need for the development of new structures.

KR 10-1410378 B1 KR 10-0579008 B1

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a hydraulic type axial weight detector using a double pipe in order to reduce a coefficient of thermal expansion according to a temperature of a fluid and improve nonlinearity and response characteristics.

Another object of the present invention is to provide a shaft weight sensing device including the hydraulic shaft weight sensor using the double pipe.

In order to achieve the object of the present invention, the axial weight sensor according to an embodiment of the present invention includes a double pipe structure including an inner tube having a first inner space and an outer tube having a second inner space between the inner tube and the inner tube A plurality of hydraulic tubes formed; A connection pipe fixing the hydraulic tubes at both sides; At least one vent hole formed between the hydraulic tubes of the coupling pipe to prevent deformation of the coupling pipe and to be a moving passage of the atmosphere; And at least one fluid injection tube formed in the coupling tube for injecting fluid into the second internal space of the hydraulic tubes.

In an embodiment of the present invention, the first inner space of the hydraulic tubes may be filled with air, and the second inner space may be filled with a pressure transmission medium.

In an embodiment of the present invention, the pressure transmission medium may be a lithium chloride (LiCl) aqueous solution.

In an embodiment of the present invention, the axial weight detector may further include weighting portions formed at the upper center of the hydraulic tubes along the longitudinal direction of the hydraulic tubes to weight the hydraulic tubes.

In an embodiment of the present invention, the axial weight detector may further include weighting portions formed at the lower center of the hydraulic tubes along the longitudinal direction of the hydraulic tubes to weight the hydraulic tubes.

In an embodiment of the present invention, the width of each of the weighting portions may be narrower than the width of the corresponding hydraulic tube.

In an embodiment of the present invention, the weighting portions may be formed in the form of a plate.

In an embodiment of the present invention, the fluid injection tube includes: a first injection tube for injecting fluid into the second internal space; And a second injection tube for removing the atmosphere from the second inner space.

In an embodiment of the present invention, the hydraulic tubes may be formed of stainless steel.

According to another aspect of the present invention, there is provided an axial weight sensing device including: a lower substrate; A plurality of hydraulic tubes formed on the lower substrate in a double pipe structure including an inner tube having a first inner space and an outer tube having a second inner space between the inner tube and the inner tube; A connection pipe fixing the hydraulic tubes at both sides; An upper substrate to cover the hydraulic tubes and the connection tube, and to transmit an external load to the hydraulic tubes; And a pressure sensor for measuring the weight change by measuring the internal pressure change of the hydraulic tubes along the rod.

In an embodiment of the present invention, the first inner space of the hydraulic tubes may be filled with air, and the second inner space may be filled with a pressure transmission medium.

In an embodiment of the present invention, the pressure transmission medium may be a lithium chloride (LiCl) aqueous solution.

In an embodiment of the present invention, the axial weight sensing device may further include an upper weighting portion formed of weighting portions formed at the upper center of the hydraulic tubes along the longitudinal direction of the hydraulic tubes to weight the hydraulic tubes.

In an embodiment of the present invention, the axial weight sensing device may further include a lower weighting portion formed of weighting portions formed at the lower center of the hydraulic tubes along the longitudinal direction of the hydraulic tubes, the weighting portions weighting the hydraulic tubes.

In an embodiment of the present invention, the width of each of the weighting portions may be narrower than the width of each corresponding hydraulic tube.

In an embodiment of the present invention, the upper weight portion or the lower weight portion may each be formed in the form of a plate.

In an embodiment of the present invention, the hydraulic tubes may be formed of stainless steel.

In the embodiment of the present invention, the axial weight sensing device may further include at least one vent hole formed between the hydraulic tubes of the coupling pipe to prevent deformation of the coupling pipe and to be a moving passage of the atmosphere .

In an embodiment of the present invention, the axial weight sensing device may further include at least one fluid injection tube formed in the coupling tube for injecting fluid into the second internal space of the hydraulic tubes.

In an embodiment of the present invention, the fluid injection tube includes: a first injection tube for injecting fluid into the second internal space; And a second injection tube for removing the atmosphere from the second inner space.

According to the hydraulic shaft weight detector and the sensing device using the double pipe, the hydraulic load cell is made of a double tube structure composed of an outer tube and an inner tube so as to reduce the temperature sensitivity. The fluid is injected into the pressure transfer medium between the tubes. At this time, as the pressure transmission medium, a solution having a low thermal expansion coefficient is injected so as to more effectively reduce the temperature-dependent sensitivity. In addition, when a lithium chloride (LiCl) aqueous solution is used as a pressure-transmitting medium, the temperature sensitivity of the double tube can be remarkably reduced.

Accordingly, the hydraulic load cell can have advantages of excellent corrosion resistance, excellent tensile strength, and large thermal expansion coefficient. In addition, such a double-tube hydraulic load cell has low temperature dependency and exhibits excellent linearity and measurement accuracy as a result of the static load test. According to this characteristic, it is possible to provide an accurate and efficient WIM sensor by using the hydraulic load cell having a double pipe structure.

1 is a perspective view of an axial weight sensing apparatus according to an embodiment of the present invention.
2 is a plan view of the axial weight sensor of FIG.
3 is a cross-sectional view of the axis weight sensor of FIG.
4 is a hydraulic tube of a single tube structure for comparison with the hydraulic tube of the double tube structure of the present invention.
5 is a hydraulic tube of various structures for comparison with the hydraulic tube of the dual pipe structure of the present invention.
FIG. 6 is a graph showing temperature characteristics according to the widths of the hydraulic tubes of the single-tube structure of FIG.
7 is a graph showing the non-linearity of the hydraulic tubes of the single-tube structure of FIG. 4 according to their widths.
8 is a graph showing temperature characteristics of hydraulic tubes of various structures of FIG.
9 is a graph showing the non-linearity of the hydraulic tubes of various structures of FIG.
10 is a graph showing the temperature characteristics of the pressure transmission medium of the double pipe structure of the present invention.
11 is a plan view of a weighting portion of a shaft weight sensing device according to another embodiment of the present invention.
12 is a cross-sectional view of the axial weight sensor including the weighted portion of FIG.
13 is a graph showing the characteristics of the axial weight sensing device according to the width of the weighted portion of FIG.
FIG. 14 is a graph showing the error rate of the shaft weight sensing device according to the width of the weighted portion of FIG.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

1 is a perspective view of an axial weight sensing apparatus according to an embodiment of the present invention. 2 is a plan view of the axial weight sensor of FIG. 3 is a cross-sectional view of the axis weight sensor of FIG.

The axial weight sensing device (1) according to the present invention uses a double pipe structure to improve the performance of a hydraulic load cell. Specifically, a dual tube is used to reduce the coefficient of thermal expansion according to the temperature of the fluid and to improve nonlinearity and response characteristics, and a fluid having a low thermal expansion coefficient is injected between the tube and the tube.

1, a shaft weight sensing device 1 includes a hydraulic axis weight sensor 10, an upper substrate 20, a lower substrate 30, and a pressure sensor 50. [

The shaft weight sensing device 1 may be formed on or embedded in the ground on a road, a toll gate, a tunnel entrance, or the like. The longitudinal direction of the shaft weight sensing device 1 may be a direction perpendicular to the traveling direction of the vehicle.

The upper substrate 20 is a portion to which an external load is directly applied and transmits the load (for example, a dynamic load of the vehicle) externally applied to the hydraulic shaft weight sensor 10.

The hydraulic axis weight sensor 10 includes a plurality of hydraulic tubes 11 formed between the upper substrate 20 and the lower substrate 30. The hydraulic axis weight sensor 10 applies a double-tube structure to the hydraulic tubes 11 to reduce the pressure change with respect to temperature to improve the accuracy of the axial weight sensing device 1, . The hydraulic axis weight sensor 10 will be described in detail later.

The lower substrate 30 supports the hydraulic axis weight sensor 10 from below and the pressure sensor 50 measures the internal pressure change of the hydraulic axis weight sensor 10 along the rod to measure the weight do.

The shaft weight sensing device 1 is not limited to the above configuration, and various configurations may be additionally added or omitted as necessary. For example, it may further include a temperature sensor for measuring the temperature of the hydraulic axis weight sensor 10, and may include an identification module capable of identifying a traveling vehicle, a warning module for generating a warning sound when the weight is exceeded, A display module for displaying the weight of the vehicle, and the like.

2, the hydraulic axis weight sensor 10 includes a plurality of hydraulic tubes 11, a connecting tube 13 for fixing the hydraulic tubes 11 on both sides and a vent hole 15, Tubes 17,18.

The connection pipe 13 may fix both sides of the hydraulic tubes 11 and at least one or more of the vent hole 15 and the fluid injection pipes 17 and 18 may be formed.

The vent hole 15 minimizes the deformation of the connection pipe 13 due to a change in load or pressure, thereby maximizing the effect of the hydraulic tubes 11. For example, the vent hole 15 may be formed between the plurality of hydraulic tubes 11.

The vent hole 15 serves to minimize the temperature unbalance at the time of temperature change by allowing the atmosphere to move within the hydraulic axis weight sensor 10, And the like can be easily installed.

The fluid injection pipes 17 and 18 may be an inlet for injecting fluid when injecting fluid and an outlet for removing air using a vacuum pump.

Each of the hydraulic tubes 11 has a double pipe structure. Specifically, it includes an inner tube 11a having a first inner space and an outer tube 11b having a second inner space between the inner tube 11a and the inner tube 11a. Such a double structure increases the internal volume due to the elastic deformation of the inner tube 11a by the pressure, and can reduce the sudden pressure change due to the temperature.

The hydraulic tubes 11 may be formed of stainless steel, for example, SUS304. When SUS304 is used, it can have advantages such as excellent corrosion resistance, good tensile strength, and large thermal expansion coefficient.

3, the first inner space inside the inner tube 11a is filled with air, and the second inner space between the inner tube 11a and the outer tube 11b is filled with the pressure transmitting medium 12, (pressure transfer medium). The pressure transmission medium 12 may use a fluid having a low coefficient of thermal expansion. For example, a lithium chloride (LiCl) aqueous solution may be injected as the pressure transmission medium 12. In addition, since the inner surface of the inner tube 11a is exposed to the atmosphere and the contact area is widened, the temperature unbalance caused by temperature and fluid temperature difference can be reduced.

The load applied to the hydraulic axis weight sensor 10 greatly affects the pressure of the hydraulic tubes 11. If an elastic deformation occurs in the range of the tensile strength of the hydraulic tubes 11, the magnitude of the pressure depends on the applied load, the thickness of the tube, the design of the tube and the elasticity of the material.

The load applied to the upper substrate 20 provides mechanical energy to the hydraulic tubes 11, so that the pressure of the hydraulic tubes 11 changes. In the present invention, a double tube structure is applied to the hydraulic tubes (11), and a single tube structure tube is tested to verify its characteristics.

Referring to Fig. 4, stainless steel grade 304 (SUS304) was used as the tube material and cut to 600 mm. The tube was set to a thickness of 1.1 mm and a height of 10 mm, and the width was made in three types. That is, tubes having a single tube structure (T11, T12, T13) having widths of 10 mm, 20 mm and 30 mm, respectively, were provided. For this purpose, the SUS304 tube is treated by CNC, which can be connected by argon welding at regular intervals.

In the hydraulic tubes 11, the pressure transmission medium uses water (H ₂ O), and the thermal expansion coefficient is 214 × 10 ^-6 / ° C. The thermal expansion coefficient of water (H ₂ O) is 4.14 times larger than that of SUS304. The temperature sensitivity of the hydraulic tubes 11 results from the difference in thermal expansion coefficient between the pressure transmission medium and the tube structure.

Referring to FIG. 5, a single tube type tube and a double tube type tube were compared for an experiment on temperature characteristics. A single tube T21, a solid core tube T22 and a double tube structure T23 according to the present invention can be identified. In another experiment, the temperature characteristics of the double tube structure by a pressure transfer medium containing lithium chloride (LiCl) was performed.

The temperature characteristics for a single tube with three different widths having the same height and thickness of FIG. 4 are shown in FIG. The temperature sensitivity of the single tube structure was investigated by increasing the temperature from 10 ° C to 60 ° C in the chamber.

Referring to FIG. 6, the temperature dependence of the pressure change is considerably observed in the tube due to the difference in thermal expansion coefficient between the pressure transmitting medium and the solid metal structure. The temperature dependence of the pressure change in a tube of a single tube structure can be reduced by increasing the ratio of the width to the height of the tube (W / H).

FIG. 7 is a result of measuring a change in the internal pressure of the tube when a load of 0 to 5,000 kg is applied to a tube having a single tube structure. As shown in Fig. 7, as the width of the tube increases, the nonlinearity of the hydraulic tubes increases.

By designing the width of a single tube, the temperature dependency is significantly reduced. However, the change in the area of the load is caused by the change in the internal pressure, which increases the nonlinearity. The nonlinearity of the single tube structure resulting from the change of the load area is due to the internal pressure change.

Table 1 below shows the number of tubes in FIG.

Tube W (mm) H (mm) T (mm) T21 Outer tube 15 15 1.5 T22 Outer tube 15 15 1.5 Inner solid 10 10 10 T23 Outer tube 15 15 1.5 Inner tube 10 10 0.9

The temperature was increased from 10 ° C to 60 ° C in the chamber under the same conditions.

The solid core tube T22 having a small capacity of the pressure transmission medium having a large coefficient of thermal expansion can reduce the temperature dependency of the sensor. As shown in Fig. 8, the double tube structure T23 can be reduced in pressure change by 46% in accordance with the temperature change at 30? As compared with the single tube structure T21.

In a tube with a double tube structure, the temperature dependence of the sensor can be reduced since the pressure is absorbed by the deformation of the inner tube. 9, the nonlinearity of the double pipe structure can be reduced to 67.19% under the same load condition.

Table 2 below shows the number of tubes used in FIG.

Tube
W (mm) H (mm) T (mm)
T24 Outer tube 25 15 1.5 Inner solid 20 10 0.9

The temperature dependency of the hydraulic tube may also be reduced using a solution of low thermal expansion coefficient. Lithium chloride (LiCl) has a freezing point and a lower thermal expansion coefficient than water. 10 shows characteristics when lithium chloride (LiCl) is used as a pressure-transmitting medium in a double tube structure. Referring to FIG. 10, a lithium chloride (LiCl) aqueous solution can further reduce the thermal expansion coefficient of water.

Thus, the present invention can provide a new type of hydraulic load cell for a WIM sensor having a double tube structure, thereby reducing the temperature sensitivity and improving the accuracy of weight measurement.

11 is a plan view of a weighting portion of a shaft weight sensing device according to another embodiment of the present invention.

The axial weight sensing device 2 according to the present embodiment includes substantially the same configuration as the axial weight sensing device 1 and the hydraulic axis weight sensor 10 of FIG. 1 except for the sensing portions 60 and 70 do. Therefore, the same components as those of the axial weight sensing device 1 and the hydraulic axial weight sensor 10 of FIG. 1 are denoted by the same reference numerals, and repeated descriptions are omitted.

11, the axial weight sensing device 2 according to the embodiment of the present invention compensates the step of the hydraulic tubes 11 generated when the plurality of hydraulic tubes 11 are welded and assembled, And a weighting part for weighting the center of the teeth 11 to induce a constant elastic deformation. Accordingly, the error rate of the shaft weight sensing device 1 can be reduced.

The weighting portion includes an upper weight portion 60 and a lower substrate 30 formed between the upper substrate 20 and the hydraulic axis weight sensor 10 and a lower weight portion 70 formed in the hydraulic axis weight sensor 10 ). Depending on the embodiment, it may include one or both of the upper weighting portion 60 and the lower weighting portion 70.

The upper weighting portion 60 and the lower weighting portion 70 may be formed in the form of a plate to facilitate fabrication and assembly. Each of the upper weighting portion 60 and the lower weighting portion 70 may include weighting portions corresponding to the hydraulic tubes 11, respectively. Each weight portion may extend along the longitudinal direction of the hydraulic tubes 11, and the width of each weight portion may be narrower than the width of the corresponding hydraulic tube.

Referring to FIG. 13, the characteristics of the hydraulic axis weight sensor 10 according to the widths of the respective weighting portions are shown. As the width of the weighting portion is narrow, the pressure change according to the load shows linearity. Further, as shown in FIG. 14, as the width of the weighted portion becomes narrower, the error rate of the hydraulic axis weight sensor 10 can be reduced to improve the accuracy.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. You will understand.

The hydraulic type WIN sensor according to the present invention has a double tube structure of an outer tube and an inner tube so as to reduce the temperature sensitivity and a hydraulic pressure cell between the outer tube and the inner tube A solution having a thermal expansion coefficient can be injected to more effectively reduce the sensitivity depending on the temperature. Accordingly, the present invention can be widely applied to a technical field for controlling an overload vehicle regardless of an external environment, and the market related to the present invention is considered to be wide. In addition, there is a high demand for a device and a system for measuring the weight of the vehicle and the control of the overloading of the vehicle.

1, 2: Axial weight sensing device 10: Hydraulic axis weight sensor
11: Hydraulic tubes 11a: Inner tubes
11b: outer tube 12: pressure transmission medium
13: Connector 15: Vent hole
17, 18: fluid injection tube 20: upper substrate
30: Lower substrate 50: Pressure sensor
60: upper weight portion 70: lower weight portion

Claims (20)

A plurality of hydraulic tubes formed in a double pipe structure including an inner tube having a first inner space and an outer tube having a second inner space between the inner tube and the inner tube;
A connection pipe fixing the hydraulic tubes at both sides;
At least one vent hole formed between the hydraulic tubes of the connection pipe and serving as a traveling passage of the air; And
And at least one fluid injection tube formed in the coupling tube for injecting fluid into a second interior space of the hydraulic tubes.
The method according to claim 1,
Wherein the first inner space of the hydraulic tubes is filled with air and the second inner space is filled with pressure transmission medium.
3. The method of claim 2,
Wherein the pressure transmitting medium is a lithium chloride (LiCl) aqueous solution.
The method according to claim 1,
Further comprising weighting portions formed at the upper center of the hydraulic tubes along the longitudinal direction of the hydraulic tubes to weight the hydraulic tubes.
The method according to claim 1,
Further comprising weighting portions formed at the lower center of the hydraulic tubes along the longitudinal direction of the hydraulic tubes to weight the hydraulic tubes.
6. The method according to any one of claims 4 and 5,
Wherein the width of each of the weighting portions is narrower than the width of the corresponding hydraulic tube.
6. The method according to any one of claims 4 and 5,
Wherein the weighting portions are formed in the form of a plate.
The fluid injection device according to claim 1,
A first injection tube for injecting fluid into the second internal space; And
And a second injection tube to remove the atmosphere from the second interior space.
The method according to claim 1,
Wherein the hydraulic tubes are formed of stainless steel.
A lower substrate;
A plurality of hydraulic tubes formed on the lower substrate in a double pipe structure including an inner tube having a first inner space and an outer tube having a second inner space between the inner tube and the inner tube;
A connection pipe fixing the hydraulic tubes at both sides;
An upper substrate to cover the hydraulic tubes and the connection tube, and to transmit an external load to the hydraulic tubes; And
And a pressure sensor for measuring a weight change by measuring the internal pressure change of the hydraulic tubes according to the load.
11. The method of claim 10,
Wherein the first inner space of the hydraulic tubes is filled with air and the second inner space is filled with a pressure transmission medium.
12. The method of claim 11,
Wherein the pressure transmitting medium is a lithium chloride (LiCl) aqueous solution.
11. The method of claim 10,
Further comprising an upper weight portion formed at the upper center of the hydraulic tubes along the longitudinal direction of the hydraulic tubes, the upper weight portion being composed of weight portions that weight the hydraulic tubes.
11. The method of claim 10,
Further comprising a lower weighting portion formed of weighting portions formed in the lower center of the hydraulic tubes along the longitudinal direction of the hydraulic tubes to weight the hydraulic tubes.
14. A method according to any one of claims 13 and 14,
Wherein the width of each of the weighting portions is narrower than the width of each corresponding hydraulic tube.
14. A method according to any one of claims 13 and 14,
Wherein the upper weight portion or the lower weight portion are each formed in the form of a plate.
11. The method of claim 10,
Wherein the hydraulic tubes are formed of stainless steel.
11. The method of claim 10,
Further comprising at least one vent hole formed between the hydraulic tubes of the coupling pipe to serve as a moving path of the atmosphere.
11. The method of claim 10,
Further comprising at least one fluid injection tube formed in the coupling tube for injecting fluid into the second interior space of the hydraulic tubes.
The fluid injection device according to claim 10,
A first injection tube for injecting fluid into the second internal space; And
And a second injection tube for removing the atmosphere from the second internal space.

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