KR20170119283A - A strain gauge and a pressure sensor comprising thereof - Google Patents

Abstract

According to an embodiment, the pressure sensor includes a diaphragm; And a strain gauge including a plurality of electrodes and a plurality of resistors and being glass-bonded to the diaphragm, wherein at least one of the plurality of resistors is disposed in a space between two electrodes of the plurality of electrodes, .

Description

A STRAIN GAUGE AND PRESSURE SENSOR COMPRISING THEREOF

The following description relates to a pressure sensor.

The pressure sensor is a mechanism for measuring pressure, for example, may include a strain gauge. A strain gauge is a measuring instrument that measures strain when an object is deformed by an external force. The strain gauge can be attached to an object and measured. When the alloy wire is deformed in the tensile direction, its length is increased, the cross-sectional area is decreased, and the electrical resistance is increased, and the increment can be measured.

The object of the embodiment is to provide a pressure sensor capable of miniaturizing the sensor packaging.

According to an embodiment, the pressure sensor includes a diaphragm; And a strain gauge including a plurality of electrodes and a plurality of resistors and being glass-bonded to the diaphragm, wherein at least one of the plurality of resistors is disposed in a space between two electrodes of the plurality of electrodes, .

The plurality of resistors may be four resistors arranged in the form of a Wheatstone bridge circuit.

A first resistor and a second resistor of the four resistors are located in the middle of the strain gage, and a third resistor and a fourth resistor of the four resistors may be respectively located at the left end and the right end of the strain gauge.

The third resistor and the fourth resistor may each include a plurality of piezoresistors arranged in the same direction.

Each of the first resistor and the second resistor may include at least one piezoresistive member arranged in the same direction as the plurality of piezoresistors.

The plurality of electrodes and the plurality of resistors may be physically connected in series to form one closed loop.

Wherein at least one of the plurality of resistors comprises: a plurality of piezoresistors; And at least one connecting body for connecting the plurality of piezoresistors in series.

The plurality of piezoresistors may be silicon wires.

The plurality of piezoresistors may be arranged long in a direction parallel to each other.

The stress strain of the at least one connecting body may be lower than the stress strain of the plurality of piezoresistors.

The at least one resistance may be disposed at a position where the diaphragm is deformed to the maximum.

The at least one resistance may be disposed at the center of the diaphragm.

The pressure sensor according to the embodiment is advantageous in terms of cost as compared with the conventional pressure sensor. Also, the sensor diaphragm can be robustly designed, and the entire sensor packaging can be miniaturized.

1 is a diagram illustrating a strain gage according to one embodiment.
2 is a partial cross-sectional view of a pressure sensor including the strain gauge of FIG.
FIG. 3 is a graph showing the strain value of each distance measured by the pressure sensor of FIG. 2; FIG.
4 is a view showing a strain gage according to another embodiment.
5 is a simplified schematic diagram of the strain gauge of FIG.
6 is a partial cross-sectional view of a pressure sensor including the strain gauge of FIG.
FIG. 7 is a graph showing values of strain by distance measured by the pressure sensor of FIG. 6; FIG.
8 is a graph simultaneously showing the graphs shown in Figs. 3 and 7, respectively.
9 and 10 are graphs showing strain distributions according to pressure acting on the diaphragm of the pressure sensor of FIG.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals whenever possible, even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the difference that the embodiments of the present invention are not conclusive.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected or connected to the other component, Quot; may be "connected," "coupled," or "connected. &Quot;

The components included in any one embodiment and the components including common functions will be described using the same names in other embodiments. Unless otherwise stated, the description of any one embodiment may be applied to other embodiments, and a detailed description thereof will be omitted in the overlapping scope.

1 is a diagram illustrating a strain gage according to one embodiment.

Referring to FIG. 1, a strain gauge 10 according to an embodiment includes a first resistor R1, a second resistor R2, a first electrode 11, a second electrode 12, and a third electrode 13). Both ends of the first resistor R1 are connected to the first electrode 11 and the third electrode 13 and both ends of the second resistor R2 are connected to the second electrode 12 and the third electrode 13 . The strain gage 10 according to one embodiment may be referred to as a half bridge strain gauge.

The first resistor R1 may include a plurality of piezoresistors R11 arranged in parallel with each other and a coupler R12 connecting the plurality of piezoresistors R11 in the vertical direction. For example, a silicon wire may be used as the piezoresistor R11. The connector R12 may be made of, for example, aluminum.

The stress strain of the connector R12 may be smaller than that of the plurality of piezoresistors R11. According to the above configuration, the stress strain of the first resistor R1 becomes largest in the longitudinal direction of the plurality of piezoresistors R11.

The second resistor R2 may have the same structure as the first resistor R1 and the resistor of the second resistor R2 may be arranged in the same direction as the resistor R1 of the first resistor R1 .

According to the above configuration, the strain gage 10 can be sensitive to a specific direction (longitudinal direction of the piezoresistor R11 of the first resistor R1) in the other direction. Normally, the diaphragm 1a is formed in a circular shape, and the deformation of the diaphragm 1a is symmetric with respect to the center of the diaphragm 1a in the radial direction (i.e., in the biaxial direction) according to the pressure acting on the hollow 1c Shape. When the strain gauge 10 is sensitive to a specific direction (i.e., the uniaxial direction), it is possible to reduce the problem that an error in the measurement value is generated due to the deformation with respect to the direction orthogonal thereto, It is possible to measure a relatively accurate strain rate even if the center of the diaphragm 10 is not exactly aligned with the center of the diaphragm 1a.

2 is a partial cross-sectional view of a pressure sensor including the strain gauge of FIG.

2, the pressure sensor 1 includes a diaphragm 1a, a side wall 1b for supporting the diaphragm 1a, a hollow 1c surrounded by the diaphragm 1a and the side wall 1b, And two strain gauges 10 disposed on the diaphragm 1a. On the other hand, the width of the hollow portion 1c may be referred to as "A", the thickness of the side wall 1b may be referred to as "B", and the thickness of the diaphragm 1a may be referred to as "C".

The diaphragm 1a may be formed of an inorganic material. The diaphragm 1a may be, for example, a metal or ceramic material. The strain gauge 10 is disposed on the upper side of the diaphragm 1a and the diaphragm 1a may be thinner than the side wall 1b. In this case, a stress change may be caused to the maximum at the portion where the strain gauge 10 is arranged by the pressure or other external force.

The diaphragm 1a is deformed corresponding to the pressure acting on the hollow 1c and the deformation amount of the diaphragm 1a can be measured using the two strain gauges 10. [ In this case, gaseous frit bonding can be applied to attach the strain gauges 10 to the diaphragm 1a. In this case, each of the glasses 1d applied to the diaphragm 1a by glass bonding, A minimum gap d is required between the two strain gauges 10 so that they do not overlap each other. Depending on the minimum spacing d, the glasses 1d to which the respective strain gages are attached may not overlap each other. If the glasses 1d overlap each other, the measurement values may become inaccurate due to mutual interference between the two strain gauges, and the minimum spacing d is indispensably required to improve the accuracy of the sensor. For this reason, the size of the diaphragm using the half bridge strain gage has a limitation in reducing the diaphragm due to the minimum interval d.

On the other hand, the reason for using glass frit bonding in fixing the strain gage to the diaphragm is as follows. First, heat treatment is required to remove the residual stress in the diaphragm with strain gauge attached, because the general epoxy adhesive can not withstand the heat treatment temperature. Second, in order to derive the strain value of the strain gauge predicted from the diaphragm, elastic modulus and thermal expansion conditions must be considered. Under these conditions, it is impossible to obtain a strain value of a predicted strain gauge by using an organic bonding material to which carbon is added. Accordingly, a glass material which is an inorganic bonding material is used.

FIG. 3 is a graph showing the strain value of each distance measured by the pressure sensor of FIG. 2; FIG.

Referring to FIG. 3, since two strain gauges 10 are disposed apart from each other with an interval d, a dead zone is generated as shown in the graph of FIG.

On the other hand, miniaturization of the diaphragm can be considered for the miniaturization of the sensor. Hereinafter, an embodiment in which the strain gauge is changed to reduce the size of the diaphragm and, as a result, the entire pressure sensor can be miniaturized will be described.

FIG. 4 is a view showing a strain gage according to another embodiment, and FIG. 5 is a simplified schematic diagram of the strain gauge of FIG.

4 and 5, the strain gauge 20 according to another embodiment includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, A second electrode 22, a third electrode 23, and a fourth electrode 24, as shown in FIG. Both ends of the first resistor R1 are connected to the first electrode 21 and the second electrode 22 and both ends of the second resistor R2 are connected to the second electrode 22 and the third electrode 23 And both ends of the third resistor R3 and the fourth electrode 24 are connected to the first electrode 21 and the fourth electrode 24 and both ends of the fourth resistor R4 are connected to the third electrode 23 and the fourth electrode 24, Lt; / RTI > In other words, the strain gauge 20 can be understood to include four resistors arranged in the form of a Wheatstone bridge circuit. The strain gauge 10 according to another embodiment may be referred to as a full bridge strain gauge.

The first resistor R1 may include a plurality of piezoresistors R11 arranged in parallel with each other and a coupler R12 connecting the plurality of piezoresistors R11 in the vertical direction. For example, a silicon wire may be used as the piezoresistor R11. The connector R12 may be made of, for example, aluminum. The four resistors can be understood to include silicon wires, which are physically and electrically connected, respectively.

The stress strain of the connector R12 may be smaller than that of the plurality of piezoresistors R11. According to the above configuration, the stress strain of the first resistor R1 becomes largest in the longitudinal direction of the plurality of piezoresistors R11.

The remaining resistors R2, R3 and R4 may have the same structure as the first resistor R1 and the other resistors R2, R3 and R4 may have the same structure as the resistors of the first resistor R1 0.0 > R11. ≪ / RTI >

The first resistor R1 and the fourth resistor R4 may have a shape symmetrical to each other with respect to the center of the strain gauge 20. [

The second resistor R2 and the third resistor R3 may have a shape symmetrical to each other with respect to the center of the strain gauge 20. [

According to the above configuration, the strain gage 10 can be sensitive to a specific direction (longitudinal direction of the piezoresistor R11 of the first resistor R1) in the other direction.

6 is a partial cross-sectional view of a pressure sensor including the strain gauge of FIG.

6, the pressure sensor 2 may include a diaphragm 2a, a side wall 2b, a hollow 1c, and one strain gauge 20 disposed on the diaphragm 2a. The strain gauge 20 may be fixed to the diaphragm 2a by glass bonding. The glass applied to the diaphragm 2a by glass bonding is denoted by 2d. On the other hand, the width of the hollow portion 2c may be referred to as "A", the thickness of the side wall portion 2b may be referred to as "B", and the thickness of the diaphragm 2a may be referred to as "C". Since the pressure sensor 2 can measure the strain of the diaphragm 2a using only one strain gauge 20, the spacing d is not required unlike the embodiment described in Figs. 1 to 3, The width A 'can be reduced, and as a result, the entire pressure sensor 2 can be miniaturized. In other words, by applying the full bridge strain gage 20, it is possible to eliminate the minimum interval d portion necessary when the half bridge strain gage 10 is used, so that the width A 'of the hollow 1c can be reduced, Is possible.

FIG. 7 is a graph showing values of strain by distance measured by the pressure sensor of FIG. 6, and FIG. 8 is a graph simultaneously illustrating the graphs of FIGS. 3 and 7, respectively.

Referring to FIGS. 7 and 8, it can be seen that there is no dead area unlike the embodiment described in FIGS. 1 to 3 described above. Since the diaphragm 2a has the largest deformation at the portion farthest from the side wall 2b, that is, at the center portion of the diaphragm 2a, the maximum strain value that can be detected through the strain gauge 20 is 8 by G shown in FIG. In other words, the sensitivity of the strain gauge 20 can be improved.

7 and 8 are shown in the table below.

Table 1 shows the results obtained when the half bridge strain gage 10 and the full bridge strain gage 20 were applied to the same diaphragm, respectively. It can be seen that, in a pressure sensor employing a half bridge strain gage 10, the thickness of the sensor diaphragm must be made thinner in order to measure the same strain as the full bridge strain gage 20.

Table 2 shows the results of designing with the same sensitivity. In order for the pressure sensor employing the half bridge strain gauge 10 to have the same sensitivity as the pressure sensor to which the full bridge strain gauge 20 is applied, the thickness of the sensor diaphragm must be made thinner, And the durability is lowered. In other words, a more robust design is possible by using the full bridge strain gauge 20.

9 and 10 are graphs showing strain distributions according to pressure acting on the diaphragm of the pressure sensor of FIG.

Referring to FIGS. 9 and 10, it can be seen that the directionality of the strain sensed at each resistance of the strain gage 20 is as shown in the following table.

The pressure sensor according to the embodiment is advantageous in terms of cost as compared with the conventional pressure sensor. Also, the sensor diaphragm can be robustly designed, and the entire sensor packaging can be miniaturized.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that various changes, modifications, or substitutions may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (12)

Diaphragm; And
A plurality of electrodes, and a strain gauge including a plurality of resistors and being glass-bonded to the diaphragm,
Wherein at least one of the plurality of resistors is disposed in a space between two electrodes spaced apart from each other among the plurality of electrodes. The method according to claim 1,
Wherein the plurality of resistors are four resistors arranged in the form of a Wheatstone bridge circuit. 3. The method of claim 2,
Wherein a first one of the four resistors and a second one of the four resistors are located in the middle of the strain gauge,
And a third one of the four resistors and a fourth one of the four resistors are located at the left end and the right end of the strain gauge, respectively. The method of claim 3,
And the third resistor and the fourth resistor each comprise a plurality of piezoresistors arranged in the same direction. 5. The method of claim 4,
Wherein the first resistor and the second resistor each include at least one piezoresistive element disposed in a long direction in the same direction as the plurality of piezoresistors. The method according to claim 1,
Wherein the plurality of electrodes and the plurality of resistors are physically connected in series to form one closed loop. The method according to claim 1,
Wherein at least one of the plurality of resistors comprises:
A plurality of piezoresistors; And
And at least one connecting body connecting the plurality of piezoresistors in series. 8. The method of claim 7,
Wherein the plurality of piezoresistors are silicon wires. 8. The method of claim 7,
Wherein the plurality of piezoresistors are arranged long in a direction parallel to each other. 8. The method of claim 7,
Wherein the stress strain of the at least one connecting body is lower than the stress strain of the plurality of piezoresistors. The method according to claim 1,
Wherein the at least one resistance is disposed at a position where the diaphragm is deformed to the maximum. The method according to claim 1,
Wherein the at least one resistance is disposed at the center of the diaphragm.

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