JPH0559266U - Load cell - Google Patents

Abstract

(57) [Abstract] [Purpose] The strain gauge and the resistance for output temperature compensation are made to match the transient temperature characteristics to easily realize a highly accurate and stable load cell against sudden temperature changes in the surrounding environment. [Structure] By inserting a thermal insulator 6 between the load cell body 1 and the output temperature compensating section 5 and changing the thickness and material of the insulator, the transient of the output temperature compensating resistor 4 and the strain gauge 2 is changed. It was formed so that the response characteristics with respect to temperature were almost equal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a load cell that corrects temperature characteristics.

[0002]

[Prior Art]

 As a conventional strain gauge type load cell, there is one having a structure as shown in FIG. In the figure, 1 is a load cell body made of aluminum or the like, 2 is a strain gauge, 3 is a strain generating part, 4 is an output temperature compensating resistor, 5 is an output temperature compensating part, 7 is a load moving part, and 8 is a fixed part. Is. The load cell body 1 has a rectangular Roberval shape, and has four strain-generating portions 3 at the upper and lower portions, and strain gauges 2 are attached to the respective strain-generating portions. It is designed to be converted into and taken out. Further, the output temperature compensating resistor 4 is installed in the thick portion of the load cell body 1 as disclosed in Japanese Utility Model Laid-Open No. 56-144332, and corrects the output variation due to the temperature change of the load cell. is doing.

Usually, in such a conventional load cell, when the temperature rises, the output thereof shifts to the plus side due to the characteristics of the metal material of the load cell. Therefore, a compensating resistor is provided on the excitation voltage side of the load cell bridge circuit, whose resistance value becomes positive as the temperature rises, and if the ambient temperature around the load cell moves to the positive side, the excitation voltage applied to the load cell bridge will decrease. The circuit is configured in order to cancel the fluctuation of the output value with respect to the temperature of the load cell and correct it to obtain the desired performance. In order to correct the load cell output with high accuracy, the compensating resistor must behave the same with respect to the strain gauge and temperature, so it is optimal to install it in the same place, but the strain gauge is If the strained portion that is bonded is very thin and a compensating resistor is attached, basic load detection will be hindered and the load cell performance will not be fully exhibited. Therefore, the structure is such that no compensation resistor is installed in the thin-walled strain element. Considering the above, in Japanese Utility Model Publication No. 62-17693, there is no significant difference between the temperature of the strain gauge part and the output temperature compensating resistor provided in the rigid part in the center near the strain generating part. Has been done.

[0004]

[Problems to be solved by the device]

 In recent years, there has been a demand for high-precision load cells. In the conventional load cell structure described above, the strain gauge part where the strain gauge is installed is thin, and the part where the temperature compensation resistor is installed is a thick part There is a difference in heat capacity between them, and even if both parts are relatively close to each other, when the ambient temperature changes transiently, the difference in response to each heat causes an output error and accurate measurement is performed. Things are getting harder. Further, the output temperature compensator and the load cell body were simply fixed to each other with an adhesive or the like, and no consideration was given to transient temperature changes in the surroundings.

In the strain gauge type load cell, the output temperature characteristic is conventionally compensated only in the steady temperature state, but in the present invention, the transient temperature characteristic of the output temperature compensating resistor is set. Focusing on the fact that it can be controlled by one side, by eliminating the difference between the transient temperature characteristic of the strain gauge and the characteristic of the output temperature compensation resistor, it is possible to perform appropriate output correction even when the ambient temperature changes transiently. The goal is to provide a highly accurate and stable load cell.

[0006]

[Means for Solving the Problems]

 This invention is a strain gauge type load cell, in which the resistance and strain gauge for output temperature compensation are changed by changing the thickness and material of the thermal insulator inserted between the load cell body and the installation portion of the resistance for output temperature compensation. It is characterized in that the response characteristics to the transient temperature of are formed to be almost equal.

[0007]

[Action]

 By selecting the thickness and material of the thermal insulator to be inserted between the output temperature compensation resistor and the thick portion of the load cell, the transient temperature characteristic of the strain gauge and the transient temperature characteristic of the output temperature compensation resistor can be adjusted. They can be matched, and a stable load cell can be realized even when the ambient temperature changes rapidly.

[0008]

【Example】

 The first embodiment is shown in FIGS. 1 and 4. In FIG. 1, the load cell of the present invention has almost the same configuration as the load cell described in FIG. 6 described above, and includes a load cell body 1, a strain gauge 2, a strain-flexing portion 3, an output temperature compensation resistor 4, and an output temperature compensation. The part 5, the load movable part 7, and the fixed part 8 are the same as in the conventional example. The difference is that a thermal insulator 6 is inserted between the output temperature compensator and the load cell body, and the thickness and material of the insulator are selected to select the transient temperature characteristics of the strain gauge 2 and the output temperature compensating resistor 4. This is because the transient temperature characteristics of are matched. Fig. 4 is the circuit diagram above. A bridge circuit is formed by four strain gauges 2, an output temperature compensation resistor 4 is connected to the input side, and an exciting voltage is applied to the input terminal 9 to output the output terminal. It is configured to output a voltage corresponding to the load applied to the load cell from 10.

A second embodiment is shown in FIG. The difference between this embodiment and the first embodiment is that in the first embodiment, the output temperature compensator 5 is provided in the thick portion near the fixed portion 8 on the opposite side of the load movable portion 7, but in the second embodiment. This is the same as the other points except that it is provided in a thick portion located in the middle of the strain-flexing portion 3. The same parts as in FIG. 1 are designated by the same reference numerals. The circuit is also the same as in FIG.

A third embodiment is shown in FIG. The difference between this embodiment and the first embodiment is that in the first embodiment, the output temperature compensator 5 is provided on a surface perpendicular to the hole including the strain-flexing part 3 in the thick part near the fixing part 8. However, in the third embodiment, it is provided on the surface of the fixing portion 8 side in the hole including the strain-flexing portion 3, and the other points are the same. The same parts as in FIG. 1 are designated by the same reference numerals. The circuit is also the same as in FIG.

In each of the above-described embodiments, the load cell body 1 side on which the output temperature compensating resistor 4 is installed has a thick portion, and has a characteristic that it is hard to heat and cool in terms of heat capacity. On the other hand, the output temperature compensator 5 has a small heat capacity because it is installed on a thin metal plate. Therefore, in FIGS. 1 to 3, when there is no thermal insulator 6 and they are placed in contact with each other, the output temperature compensating resistor 4 becomes insensitive to temperature due to the influence of the thick portion in terms of heat capacity. When placed away from each other by, for example, providing a space between them, it has the property of becoming sensitive to temperature. Considering the case where the ambient temperature rises transiently, the output of the strain gauge 2 itself tries to increase to the positive side, but the output temperature compensating resistor 4 inserted on both sides of the bridge circuit tries to suppress it in the opposite direction. To do. At this time, since the heat transfer characteristics differ depending on the positional relationship between the output temperature compensating section 5 and the thick portion of the load cell main body 1, the transient temperature characteristic of the output temperature compensating resistor 4 slightly changes and both of them change. Experiments have shown that insufficient or over-compensation occurs depending on the positional relationship.

The results of the above experiment are shown in FIG. (A) is a characteristic diagram when the output temperature compensator 5 and the load cell body 1 are arranged in contact with each other, and the output of the strain gauge 2 itself is increased to the positive side as shown in the second graph from the top. To do. On the other hand, the voltage applied to the bridge circuit by the output temperature compensating resistor 4 tends to increase to the negative side as shown in the third graph from the top, but as mentioned above, it is difficult to warm up due to the heat capacity of the thick portion of the load cell. Response to changes is delayed. Therefore, the output of the load cell has an overcompensated transient temperature characteristic with a peak on the positive side, as shown in the lower graph. (B) is a characteristic diagram when the output temperature compensating section 5 and the load cell body 1 are arranged apart from each other. Since the output temperature compensating resistor reacts sensitively to temperature, the bridge by the output temperature compensating resistor 4 is shown. The voltage applied to the circuit rapidly increases to the negative side. Therefore, the output of the load cell has a transient temperature characteristic with a peak on the negative side and insufficient compensation. (C) is a characteristic diagram when the thermal insulator 6 is inserted between the output temperature compensating section 5 and the load cell body 1, and the voltage applied to the bridge circuit by the output temperature compensating resistor 4 is thermal. Due to the influence of the insulator 6, the strain gauge 2 tries to increase to the minus side so as to be close to the output of the strain gauge 2 itself. Therefore, the output of the load cell has a good transient temperature characteristic. This thermal insulator 6 is extremely simple because a double-sided tape having a thickness of, for example, about 0.4 mm to 0.6 mm may be bonded.

[0013]

[Effect of the device]

 According to this invention, by inserting a thermal insulator between the output temperature compensating resistor and the thick block portion of the load cell body and changing the thickness and the material, the strain gauge and the output temperature compensating resistor can be changed. Since the transient temperature characteristics of can be made almost equal, there is an effect that a highly accurate and stable load cell can be easily realized against a sudden temperature change of the surrounding environment.

[Brief description of drawings]

FIG. 1 is a front view and a side view of a load cell according to a first embodiment of the present invention.

FIG. 2 is a front view and a side view of a load cell according to a second embodiment of the present invention.

FIG. 3 is a front view and an AA sectional view of a load cell according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of the first to third embodiments of the present invention.

FIG. 5 is a characteristic diagram showing the effect of this invention.

FIG. 6 is a front view and a side view of a conventional load cell.

[Explanation of symbols]

 1 Load cell main body 2 Strain gauge 3 Load cell strain element 4 Output temperature compensation resistor 5 Output temperature compensation part 6 Thermal insulator 7 Load cell load movable part 8 Load cell fixed part 9 Bridge circuit input terminal 10 Bridge circuit output Terminal

Claims (1)

[Scope of utility model registration request] 1. The transient temperature of the output temperature compensating resistor and the strain gauge pasting part is changed by changing the thickness and material of the thermal insulator inserted between the load cell body and the installation part of the output temperature compensating resistor. A strain gauge type load cell characterized by being formed so that the response characteristics are substantially equal.