JP2003028706A - Weight sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a weight sensor stable in a characteristic, of which the output is precluded from getting unstable caused by plastic deformation of a sensor substrate. SOLUTION: In this sensor, a stopper 13 and a stopper 22 are provided to regulate vertical-directional motion of the sensor substrate 14 by allowing extension to a detecting member 23 side in order to provide in a fixed member 11 and a fixed member 21 a space with respect to the sensor substrate 14 therebetween.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weight sensor which detects strain generated by an external force generated by the weight of a human being or the weight of a vehicle such as an automobile by a strain detecting element provided on a sensor substrate.

[0002]

2. Description of the Related Art As a conventional weight sensor of this type, one disclosed in Japanese Patent Application Laid-Open No. 8-29273 is known.

A conventional weight sensor will be described below with reference to the drawings.

FIG. 7 is a perspective view of a conventional weight sensor, and FIG. 8 is a circuit diagram of the same weight sensor.

In FIGS. 7 and 8, 1 is a fixing member made of metal. Reference numeral 2 denotes a sensor substrate formed by applying an insulating layer to the surface of a metal made of an elastic material, one end of which is fixed to the fixing member 1, and the strain detecting element 3 and the strain detecting element 3 are electrically connected to the upper surface thereof. 3 bias resistors 4
Is provided, and the strain detecting element 3 and the bias resistor 4 form a bridge circuit. An electrode 5 is provided on the upper surface of the sensor substrate 2. A detection member 6 is fixed to the other end of the sensor substrate 2.

The operation of the conventional weight sensor configured as described above will be described below.

When an external force acts on the detecting member 6, the sensor substrate 2 is deformed by this external force. A strain detecting element 3 and three bias resistors 4 are provided on the surface of the sensor substrate 2, and the strain detecting element 3 is proportional to the deformation amount of the sensor substrate 2.
The resistance value of changes. Since the strain detecting element 3 and the three bias resistors 4 form a bridge circuit, the external force applied to the detecting member 6 is detected by the electrode 5 in the bridge circuit.

[0008]

However, in the above conventional structure, when an external force exceeding the elastic range of the sensor substrate 2 is applied to the detection member 6, the sensor substrate 2 is plastically deformed, and as a result, the detection member 6 is deformed. Even when the external force of 6 is removed, residual strain remains on the sensor substrate 2, which causes a problem that the output of the weight sensor becomes unstable.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a weight sensor having stable characteristics without the output becoming unstable.

[0010]

In order to achieve the above object, the present invention has the following constitution.

The invention according to claim 1 of the present invention is
The fixing member is provided with a stopper that extends toward the detection member so as to provide a gap between the sensor member and the sensor substrate and restricts the vertical movement of the sensor substrate. When an external force exceeding the elastic range of the substrate is applied, the sensor substrate contacts the stopper, so the sensor substrate does not plastically deform, and as a result, residual strain remains on the sensor substrate even when the external force of the detection member is removed. The effect of stabilizing the output of the weight sensor can be obtained.

The invention according to claim 2 of the present invention is
The stopper is provided on both the upper side and the lower side of the sensor board.This allows the sensor board to contact the stopper even when an external force exceeding the elastic region in either the upward direction or the downward direction is applied to the detection member. Since they are in contact with each other, the effect of stabilizing the output of the weight sensor can be obtained even when an external force exceeding both elastic regions in the vertical direction is applied.

The invention according to claim 3 of the present invention is
The first fixing member and the second fixing member are provided with stoppers that extend toward the detecting member so as to provide a gap between the first fixing member and the second fixing member and that regulate the vertical movement of the sensor substrate. As a result, when an external force exceeding the elastic range of the sensor substrate is applied to the detection member, the sensor substrate contacts the stopper, so that the sensor substrate is not plastically deformed, and as a result, even when the external force of the detection member is removed. Since the residual strain does not remain on the sensor substrate, the effect of stabilizing the output of the weight sensor can be obtained.

The invention according to claim 4 of the present invention is
It has a structure in which the stopper is in contact with the sensor substrate, and the stopper plate is in contact with the spacer, so that the first fixing member, the second fixing member, and the sensor substrate have the same thickness as the spacer. Since the gap between the two is set, it is possible to easily provide a stopper that regulates the vertical movement of the sensor substrate.

The invention according to claim 5 of the present invention is
The stopper plate of the first fixing member and the stopper plate of the second fixing member are connected to each other, whereby the stopper plate has no free end, so that when the sensor substrate abuts on the stopper. The stopper plate is less likely to be displaced, and as a result, the function as a stopper is improved, which is an effect.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) In the following, Embodiment 1 will be used to explain the invention particularly described in claims 1 and 2.

FIG. 1 is an exploded perspective view of a weight sensor according to Embodiment 1 of the present invention, FIG. 2 is a perspective view thereof, and FIG. 3 is a circuit diagram of a sensor substrate which is a main part thereof.

In FIGS. 1 to 3, reference numeral 11 denotes a first fixing member made of metal, which is provided with a first fixing portion 12 on the upper surface and a first stopper 13 so as to extend laterally. is there. Reference numeral 14 denotes a sensor substrate formed by forming an insulating layer on the surface of a metal made of an elastic material, one end of which is fixed to the first fixing portion 12 of the first fixing member 11, and one strain detecting element is provided on the upper surface. 15 and this strain detecting element 15
There are three bias resistors 16 electrically connected to the. Further, on the upper surface of the sensor substrate 14, the power electrode 17,
First output electrode 18, second output electrode 19 and GND
An electrode 20 is provided, and the electrodes 17 to 20 are electrically connected to the strain detecting element 15 and the bias resistor 16 to form a bridge circuit as shown in FIG. Reference numeral 21 is a second fixing member, and the second fixing portion 2 is provided on the lower surface.
2 is provided, one end of the sensor substrate 14 is fixed to the second fixing portion 22, and a second stopper 23 is provided so as to extend laterally. A detection member 24 made of metal is fixed to the other end of the sensor substrate 14.

Next, the method of assembling the weight sensor constructed as described above will be described.

First, after a glass paste (not shown) is printed on a metal base substrate (not shown) having elasticity prepared in advance, it is baked at about 850 ° C. for about 45 minutes to form the sensor substrate 14. .

Next, a metal glaze-based carbon paste is printed on the upper surface of the sensor substrate 14, and about 85
Baking is performed at 0 ° C. for about 45 minutes to form the strain detecting element 15 and the three bias resistors 16 on the upper surface of the sensor substrate 14.

Next, a silver paste is printed on one end of the upper surface of the sensor substrate 14 and baked at about 850 ° C. for about 45 minutes to supply the power electrode 17, the first output electrode 18, and the second output electrode 1.
9. Form the GND electrode 20.

Next, after the lower surface at one end of the sensor substrate 14 is fixed to the upper surface of the first fixing portion 12 of the first fixing member 11 with an adhesive, the sensor substrate 14 facing the first fixing portion 12 is fixed. The second fixing portion 22 of the second fixing member 21 is fixed to the upper surface of the with an adhesive.

Finally, the detecting member 24 is fixed to the other end of the sensor substrate 14.

The operation of the weight sensor according to the first embodiment of the present invention constructed and assembled as described above will be described below.

When an external force such as weight acts on the detecting member 24 from above, the external force deforms the sensor substrate 14 downward due to the downward displacement of the detecting member 24. A strain detecting element 15 is provided on the upper surface of the sensor substrate 14 at a position where the sensor substrate 14 is deformed, and a bias resistor 16 is provided at a position where the sensor substrate 14 is not deformed. The resistance value of the strain detection element 15 changes.

Since the strain detecting element 15 and the three bias resistors 16 form a bridge circuit, when the voltage of 5 V is applied between the power supply electrode 17 and the GND electrode 20, the first output electrode 18 and The weight applied to the detection member 24 is detected by the potential difference output from the second output electrode 19.

Here, considering the case where an external force exceeding the elastic range of the sensor substrate 14 is applied to the detection member 24, in the weight sensor according to the first embodiment of the present invention, a space between the fixing member 11 and the sensor substrate 14 is provided. Since the stopper 13 is provided so as to extend toward the detection member 24 so as to form a gap and regulate the downward movement of the sensor substrate 14, the detection member 24 is provided.
When an external force exceeding the elastic range of the sensor substrate 14 is applied to the sensor substrate 14, the sensor substrate 14 comes into contact with the stopper 13, and as a result, the sensor substrate 14 is not plastically deformed, and even when the external force of the detection member 24 is removed. Residual strain does not remain on the sensor substrate 14, and the effect that a weight sensor with stable output characteristics can be provided can be obtained.

Further, in the weight sensor according to the first embodiment, the first stopper 13 is provided on the lower side of the sensor substrate 14 and the second stopper 23 is provided on the upper side of the sensor substrate 14, so that the detection member 24 is provided. When an external force exceeding the upward elastic region is applied, the sensor substrate 14 contacts the second stopper 23, and when an external force exceeding the upward elastic region is applied, the sensor substrate 14 is the second stopper. As a result, the weight sensor having a stable output characteristic can be provided even when an external force exceeding the vertical elastic region is applied.

(Embodiment 2) In the following, Embodiment 2 will be used to describe the invention of claims 3 to 5 of the present invention.

FIG. 4 is a side sectional view of a weight sensor according to the second embodiment of the present invention, FIG. 5 is a top view of the same, and FIG.

4 to 6, reference numeral 31 denotes a first fixing member, which is a cylindrical metal fitting 32, an upper spacer 33 press-fitted to the outer periphery of the fitting 32, and the upper spacer 33. A first stopper plate 34 fixed to the upper surface, a lower spacer 35 provided below the upper spacer 33, and a second stopper plate 36 fixed to the lower surface of the lower spacer 35. It is composed by.

The upper spacer 33 and the first stopper plate 34 constitute an upper stopper 34a, and the lower spacer 35 and the second stopper plate 36 constitute a lower stopper 36a. Three
Reference numeral 7 is a second fixing member, which is a cylindrical metal fitting 3
8, an upper spacer 39 press-fitted to the outer periphery of the mounting bracket 38, a third stopper plate 40 fixed to the upper surface of the upper spacer 39, and a lower side provided below the upper spacer 39. The spacer 41 and a fourth stopper plate 42 whose upper surface is fixed to the lower surface of the lower spacer 41.
It is composed of and.

The upper spacer 39 and the third stopper plate 40 constitute an upper stopper 40a, and the lower spacer 41 and the fourth stopper plate 42 constitute a lower stopper 42a. Also, the first stopper plate 34 and the third stopper plate 40 are connected to each other, and the second stopper plate 36 and the fourth stopper plate 42 are connected to each other.

Further, in the weight sensor according to the second embodiment of the present invention, the first stopper plate 34 and the third stopper plate 40 are connected to each other, and the second stopper plate 36 and the fourth stopper plate 40 are connected. Since the plate 42 is connected to each other, the first stopper plate 34, the third stopper plate 40, the second stopper plate 36, and the fourth stopper plate 34
Since the stopper plate 42 has no free end, when the sensor substrate 43 comes into contact with the first stopper plate 34, the third stopper plate 40, the second stopper plate 36, and the fourth stopper plate 42, Stopper plate 34, third stopper plate 40, second stopper plate 36 and fourth stopper plate
The stopper plate 42 is less likely to be displaced, and the function as a stopper is improved.

Reference numeral 43 denotes a sensor substrate, which has a fixing hole 44 at one end as shown in FIG.
And one end of the sensor substrate 43 is sandwiched between the upper spacer 33 and the lower spacer 35. Further, a fixing hole 45 is also provided in the vicinity of the other end side of the sensor board 43, and a mounting metal fitting 38 is fitted into the hole 45, and the other end side of the sensor board 43 is connected to the upper spacer 39 and the lower side. It is sandwiched between the side spacers 41.

A power supply electrode 46 is provided on the other end of the sensor substrate 43, and the power supply electrode 46 is provided on the upper surface of the sensor substrate 43. One end of the first strain detection element 47 and the second strain detection element 47. The first strain detecting element 4 is electrically connected to one end of the strain detecting element 48 by the circuit pattern 43a.
The other end of 7 is electrically connected to the first output electrode 49. Furthermore, the other end of the second strain detection element 48 is electrically connected to the second output electrode 50, and the other end of the second strain detection element 48 is electrically connected to one end of the third strain detection element 58. In addition, the other end of the third strain detecting element 58 is electrically connected to the GND electrode 51.

A fourth strain detecting element 52 is provided on the upper surface of the sensor substrate 43, and one end of the fourth strain detecting element 52 is connected to the other end of the first strain detecting element 47 and the first output electrode. In addition to being electrically connected to 49, the other end of the fourth strain detection element 52 is electrically connected to the GND electrode 51. Further, a central hole 53 is provided from the upper surface to the lower surface at substantially the center of the sensor substrate 43. Then, the first strain detecting element 47, the second strain detecting element 48, the third strain detecting element 58, the fourth strain detecting element 52, the power supply electrode 46, the first output electrode 49, and the second output electrode. A bridge circuit is constituted by 50, the GND electrode 51 and the circuit pattern 43a.

Further, the second strain detecting element 48 and the fourth strain detecting element 52 are provided at positions symmetrical to each other with the central hole 53 as a center and at the inner side in the longitudinal direction of the sensor substrate 43, and The first strain detection element 47 and the third strain detection element 58 are provided at positions symmetrical to each other with the central hole 53 as the center and located outside the sensor substrate 43 in the longitudinal direction. Reference numeral 54 denotes a detection member, which is the sensor substrate 4
Cylindrical sleeve 5 press-fitted into the central hole 53 in FIG.
5, and an upper spacer 56 and a lower spacer 57 made of resin fitted on the outer circumference of the sleeve 55.

The method of assembling the weight sensor configured as described above will be described.

First, the holes 44, 45 and the central hole 5 are previously prepared.
After printing a glass paste (not shown) on the metal base material (not shown) provided with 3, the sensor substrate 43 is formed by firing at about 850 ° C. for about 45 minutes.

Then, a metal glaze-based carbon paste is printed on the upper surface of the sensor substrate 43, and the temperature is about 85.
Baking at 0 ° C. for about 45 minutes, the first surface of the sensor substrate 43
The strain detecting element 47, the second strain detecting element 48, the third strain detecting element 58, and the fourth strain detecting element 52 are formed.

Next, a silver paste is printed on the upper surface of the sensor substrate 43 and baked at about 850 ° C. for about 45 minutes to supply the power electrode 46, the first output electrode 49, the second output electrode 50, and GN.
The D electrode 51 and the circuit pattern 43a are formed.

Next, the central hole 53 in the sensor substrate 43.
After press-fitting the sleeve 55 into, the upper spacer 56 is press-fitted into the upper side of the sleeve 55, and the lower spacer 57 is press-fitted into the lower side.

Next, after the mounting member 32 is press-fitted into the hole 44 in the sensor substrate 43, the upper spacer 33 is press-fitted from the upper side of the mounting member 32 and the lower spacer 35 is press-fitted from the lower side.

Next, after the mounting member 38 is press-fitted into the hole 45 in the sensor substrate 43, the upper spacer 39 is press-fitted from the upper side of the mounting member 38 and the lower spacer 41 is press-fitted from the lower side.

Next, the first stopper plate 34 and the second stopper plate 40 connected to each other are brought into contact with the upper surface of the upper spacer 33, and the third stopper plate 40 is connected to the upper spacer. It is placed so that it contacts the upper surface of 39.

At this time, the upper stopper 34a and the upper stopper 40a are connected to the upper spacer 33 and the upper spacer 39, and the first stopper plate 34 and the third stopper 39 which are in contact with the upper spacer 33 and the upper spacer 39, respectively.
Since it is configured by the stopper plate 40 of FIG. 3, the thickness of the upper spacer 33 and the upper spacer 39 provides a gap between the upper stopper 34a and the upper stopper 40a and the sensor substrate 43. As a result, the sensor substrate 43 can be easily separated. The effect that the upper stopper 34a and the upper stopper 40a that restrict the upward movement can be provided is obtained.

Finally, the second stopper plate 36 and the fourth stopper plate 42 connected to each other are brought into contact with the lower surface of the lower spacer 35, and the fourth stopper plate 42 is lowered. The lower side of the side spacer 41 is fixed so as to come into contact with the lower surface of the side spacer 41.

At this time, the lower stopper 36a and the lower stopper 42a are connected to the lower spacer 35 and the lower spacer 41, and the second stopper plate 36 and the second stopper plate 36 and the second spacer 41 which are in contact with the lower spacer 35 and the lower spacer 41, respectively. Four
Since it is configured with the stopper plate 42 of No. 3, the thickness of the lower spacer 35 and the lower spacer 41 provides a gap between the lower stopper 36a and the lower stopper 42a and the sensor substrate 43, and as a result, easily. The effect is that the lower stopper 36a and the lower stopper 42a for restricting the downward movement of the sensor substrate 43 can be provided.

The operation of the weight sensor constructed as above will be described below.

When an external force acts on the detecting member 54 from above, the sensor substrate 43 is deformed by this external force. Then, the first strain detection element 4 provided on the upper surface of the sensor substrate 43.
7 and the third strain detecting element 58 are subjected to tensile stress, the resistance values of the first strain detecting element 47 and the third strain detecting element 58 increase, and the second strain detecting element 48 and the fourth strain detecting element 58 increase. Compressive stress is applied to the detection element 52, and the resistance values of the second strain detection element 48 and the fourth strain detection element 52 become small. Since the first strain detecting element 47, the second strain detecting element 48, the third strain detecting element 58, and the fourth strain detecting element 52 form a bridge circuit, the first output electrode 49 and The external force applied to the detection member 54 is detected by the potential difference output from the second output electrode 50.

Here, the sensor substrate 4 in the weight sensor
Considering a case where an external force exceeding the elastic range of the sensor substrate 43 is applied to 3, the weight sensor according to the second embodiment of the present invention is provided with the first stopper plate 34 on the upper portion of the first fixing member 31. As the upper stopper 34a, and also as a lower stopper 36a by providing a second stopper plate 36 on the lower portion, and further as a second fixing member 37.
The third stopper plate 40 is provided on the upper part of the upper stopper 40a, and the fourth stopper plate 42 is provided on the lower part of the lower stopper 42a. The upper stopper 34a, the upper stopper 40a, the lower stopper 36a and the lower stopper 36a Since the side stopper 42a is extended to the detection member 54 side so as to form a gap between the sensor substrate 43 and the sensor substrate 43 and serves as a stopper for restricting the vertical movement of the sensor substrate 43, the detection member 54 has an elastic region of the sensor substrate 43. When an external force exceeding the above is applied, the sensor substrate 43 comes into contact with the upper stopper 34a and the upper stopper 40a or the lower stopper 36a and the lower stopper 42a. As a result, the sensor substrate 43 is not plastically deformed. Even when the external force of 54 is removed, the sensor substrate 4 To eliminate that residual strain remains, thereby, in which there is an advantage that it is possible to provide a stable weight sensor output characteristics.

In the weight sensor according to the second embodiment of the present invention, the first strain detecting element 47, the second strain detecting element 48, the third strain detecting element 58 and the fourth strain detecting element 47 are provided on the upper surface of the sensor substrate 43. However, the bridge circuit may be configured by providing a bias resistor instead of the second strain detecting element 48, the third strain detecting element 58 and the fourth strain detecting element 52. The same effect can be obtained.

[0055]

As described above, according to the present invention, the fixing member is provided with the stopper that extends toward the detecting member so as to provide a gap between the fixing member and the sensor substrate and restricts the vertical movement of the sensor substrate. Therefore, if an external force exceeding the elastic range of the sensor substrate is applied to the detection member, the sensor substrate will contact the stopper, and the sensor substrate will not be plastically deformed.Therefore, even if the external force of the detection member is removed, The residual strain does not remain, and the weight sensor with stable output can be provided.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a weight sensor according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is a circuit diagram of the sensor board.

FIG. 4 is a side sectional view of a weight sensor according to a second embodiment of the present invention.

FIG. 5 is a top view of the same.

FIG. 6 is a top view of the sensor substrate.

FIG. 7 is a perspective view of a conventional weight sensor.

FIG. 8 is a circuit diagram of the main part of the same.

[Explanation of symbols]

11, 21, 31, 37 Fixing member 13, 23, 34a, 36a, 40a, 42a Stopper 14, 43 Sensor substrate 15, 47, 48, 52, 58 Strain detecting element 16 Bias resistance 24, 54 Detection member 33, 35, 39,41 spacer

Claims (5)

[Claims] 1. A sensor provided with a fixing member, and a bridge circuit having one end fixed to the fixing member and having at least one strain detecting element and a bias resistor electrically connected to the strain detecting element on the upper surface. The sensor substrate is provided with a substrate and a detection member that is fixed to the other end of the sensor substrate and is movable in the vertical direction, and extends toward the detection member side so that a gap is provided between the fixed member and the sensor substrate. A weight sensor with a stopper that regulates the vertical movement of the. 2. The weight sensor according to claim 1, wherein stoppers are provided on both the upper side and the lower side of the sensor substrate. 3. A first fixing member, a second fixing member provided apart from the first fixing member, one end fixed to the first fixing member and the other end second. The first fixing member and the second fixing member include a sensor substrate fixed to the fixing member and provided on the upper surface thereof with a bridge circuit including at least two strain detecting elements, and a detection member fixed to substantially the center of the sensor substrate. A weight sensor provided with a stopper that extends toward the detection member so as to provide a gap between the fixing member and the sensor substrate and restricts the vertical movement of the sensor substrate. 4. The weight sensor according to claim 3, wherein the stopper comprises a spacer that abuts against the sensor substrate, and a stopper plate that abuts against the spacer. 5. The weight sensor according to claim 4, wherein the stopper plate of the first fixing member and the stopper plate of the second fixing member are connected to each other.