JPH0989643A - Balance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a balance which restrains a step-shaped change in a zero point in a first measuring operation after a change in an ambient temperature in the balance in which a lever is provided with an elastic flucrum member whose material is different from that of the lever. SOLUTION: Seat plates 10 composed of a material whose coefficient of linear expansion is the intermediate value between the coefficient of linear expansion of a lever 5 and that of an elastic fulcrum member 8a or 9 are inserted into the mounting part of the lever 5 and the elastic fulcrum member 8a and into the mounting part of the lever 5 and the elastic fulcrum member 9. Thereby, a thermal stress which is generated in contact faces of the respective members in the mounting parts of the respective members can be halved in a change in an ambinet temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balance, and more particularly to a balance of a type in which a load acting on a dish is transmitted to a load sensitive section by a lever having an elastic fulcrum.

[0002]

2. Description of the Related Art In an electromagnetic balance type electronic balance or the like, generally, a tray is supported on a movable column whose displacement direction is restricted only to the vertical direction by a Roberval mechanism, and the movable column is connected to one end of a lever. , By its lever,
It is often the case that the load acting on the pan is reduced at a rate according to the lever ratio and transmitted to the load sensitive section.

The lever in such a balance is usually supported so as to be swingable with respect to the balance frame by an elastic fulcrum, and the movable column and the lever are connected by an elastic connecting member.

The elastic fulcrum is usually composed of a strip-shaped member of iron-based constant elastic material, and the elastic connecting member is also usually a strip-shaped member of iron-based material. On the other hand, the lever, the balance frame, the movable column, etc. are made of an aluminum material. Then, as illustrated in FIG. 1 as a perspective view in the vicinity of the attachment portion of these different materials, the elastic fulcrum member E (or the elastic connecting member) is
The lever L (or the balance frame and the movable column) is fixed by a screw S in a state where the flat surfaces of the two are in contact with each other.

[0005]

By the way, in the balance equipped with the lever and the elastic fulcrum member and the elastic connecting member made of different materials as described above, conventionally, when the environmental temperature changes, the sample after the environmental temperature changes. In some cases, the zero point changed stepwise during measurement. This step change of the zero point is 1 when the environmental temperature changes greatly.
Remarkably appears in the second measurement.

An object of the present invention is to eliminate the change of the zero point in the measurement after the environmental temperature change in the balance having the lever and the elastic fulcrum which are made of different materials.

[0007]

A structure for achieving the above object will be described with reference to FIGS. 3 and 4 showing an embodiment thereof. The balance of the present invention is different from the balance frame 2. Lever 5 oscillatably supported via elastic fulcrum members 8a and 8b, and movable column 3 which supports plate 1 and is displaceable in the vertical direction, are connected to each other by elastic connecting member 9. In the balance configured so that the load acting on the plate 1 is transmitted to the load sensitive portion 7 by the lever, the elastic expansion point members 8a and 8b and the elastic connecting member 9 are attached to the lever 5 at the mounting portions thereof having linear expansion coefficients of the lever. 5 and the mating member (the elastic fulcrum members 8a and 8b or the elastic connecting member 9) are interposed, and the seat plate 10 made of a material having a substantially intermediate value is inserted.

[0008]

[Function] In a balance having a structure in which an elastic fulcrum member of a material different from that of the lever is screwed to the lever, the reason why the zero point changes stepwise at the time of measurement after the environmental temperature changes is that both materials are used. There is a difference in the coefficient of linear expansion between the two.

That is, for example, the material of the lever is aluminum (coefficient of linear expansion 23 × 10 ⁻⁶ / deg), and the material of the elastic fulcrum member is iron-based alloy (coefficient of linear expansion 11 × 10 ⁻⁶ / de).
g), the two members have a dimensional difference corresponding to the expansion difference of 12 × 10 ⁻⁶ due to the change of the ambient temperature.
As shown in FIG. 1, assuming that the size of the mounting portion of the lever L and the elastic fulcrum member E, that is, the size h × w of each side of the portions in contact with each other is 10 × 10 mm, the temperature change 1
12 ° 10 ^-6 × 10 = on each side per ° C
A dimensional difference of 12 × 10 ⁻⁵ mm occurs, and if there is a temperature change of 10 ° C., a dimensional difference of 12 × 10 ⁻⁴ = 1.2 μm occurs on each side. Since the elastic fulcrum member E is strongly tightened to the lever L by the screw S, the slip due to the above-mentioned dimensional difference does not easily occur on the contact surface between these two members, and the elastic fulcrum member E remains stationary after the environmental temperature changes. In the state, as schematically shown in FIG. 2A, expansion (or contraction) in the vicinity of the contact surface is blocked by the fastening force of the screw S, and the force to expand (or contract), that is, the thermal stress is It remains as an internal stress in each material. The magnitude of the residual stress depends on the amount of change in the ambient temperature.If the amount of change exceeds a certain value, the sample to be measured is placed in that state, and the shock, etc.
As shown in FIG. 2B, a slight slip occurs on the contact surface between the two members, and the internal stress is released. This appears as a step change of the zero point described above.

In the present invention, the lever 5 and the elastic fulcrum member 8a,
8b and between the lever 5 and the elastic connecting member 9,
The seat plates 10 having a coefficient of linear expansion intermediate between those of the members to be fixed to each other are screwed in the inserted state to reduce the difference in thermal expansion between the members in contact with each other by half. It is intended to eliminate or mitigate such a zero point change.

That is, according to the structure of the present invention, as schematically shown in FIG. 5, the lever 5 and the elastic fulcrum members 8a, 8 are provided.
b (or elastic connecting member 9) do not contact each other,
Since each of them is screwed in contact with the seat plate 10, the difference in expansion at the contact surface of each member due to a change in environmental temperature is halved compared to the conventional case. Therefore, the limit temperature change amount at which the step change of the zero point occurs is doubled as compared with the conventional one, and even when the temperature change amount exceeds the limit, the zero point change amount is half that of the conventional one. Become.

[0012]

FIG. 3 is an overall view of a mechanism of an embodiment in which the present invention is applied to an electromagnetic balance type electronic balance, and FIG. 4 is a perspective view showing only the vicinity of the lever 5 thereof. is there.

A dish 1 for placing a sample to be measured is supported by a movable column 3 which is vertically movable with respect to a balance frame 2. The movable column 3 is fixed to the other ends of the upper and lower beams 3a and 3b which are fixed to the balance frame 2 at one end and which are parallel to each other, and these are the Roberval mechanism (parallel guide).
Thus, the inclination of the movable column 3 and the inclination of the dish 1 are suppressed.

The load to be measured acting on the movable column 3 via the dish 1 is swingably supported on the balance frame 2,
A lever 5 having one end connected to the movable column 3 and the other end fixed to the coil 4a of the electromagnetic force generating device 4 constitutes a servo mechanism having the electromagnetic force generating device 4, the displacement sensor 6 and the like as constituent elements. It is transmitted to the known load sensitive section 7. The load sensitive portion 7 is a lever 5 which is caused by a load to be measured acting on the dish 1.
Is detected by the displacement sensor 6, and the magnitude of the current flowing through the coil 4a of the electromagnetic force generator 4 is determined in order to generate an electromagnetic force such that the detected displacement value becomes 0 to balance the lever 5. The magnitude of the load to be measured is determined from the magnitude of the current required to balance the lever 5. In addition to the coil 4a, the electromagnetic force generator 4 includes a permanent magnet 4b,
The yoke 4c and the pole piece 4d are included.

The lever 5 has a substantially cruciform shape as a whole, on a plane perpendicular to the central axis in the longitudinal direction, and
The balance frame 2 is swingably supported at two positions equidistant from the center axis via elastic supporting members 8a and 8b, respectively. Elastic fulcrum member 8a,
8b is a ferrous alloy material rich in elasticity formed into a substantially strip shape and provided with a flexible portion in the center thereof. One end is attached to the lever 5 and the other end is attached to the balance frame 2 with a screw S.
The lever 5 and each elastic fulcrum member 8 are fixed by
A seat plate 1 to be described later is provided between the elastic support members 8a and 8b and between the elastic fulcrum members 8a and 8b and the balance frame 2, respectively.
0 is inserted.

Further, the lever 5 and the movable column 3 are made of the same iron-based alloy material as the elastic fulcrum members 8a, 8b and formed in a substantially strip shape, and are elastically connected to each other by providing two flexible portions at their intermediate portions. The members 9 are connected to each other. One end of the elastic connecting member 9 is attached to the lever 5 and the other end is attached to the movable column 3 by screws S.
The seat plate 10 is inserted exactly between the elastic connecting member 9 and the lever 5 and between the elastic connecting member 9 and the movable column 3 as well.

The materials of the lever 5, the movable column 3 and the balance frame 2 are aluminum, and the elastic fulcrum members 8a, 8 which are iron-based alloy materials.
Each seat plate 1 inserted between b and the elastic connecting member 9.
0 is formed of a material having a value approximately midway between the linear expansion coefficient of aluminum and the linear expansion coefficient of an iron-based alloy, such as austenitic stainless steel or a copper alloy.

According to the above-described embodiment of the present invention, when the ambient temperature changes, between the member made of aluminum such as the lever 5 and the elastic fulcrum members 8a, 8b and the elastic connecting member 9 made of an iron alloy. However, a difference in dimensional change occurs depending on the difference in the linear expansion coefficient, but the lever 5 and the elastic fulcrum member 8
Since a, 8b, and the lever 5 and the elastic coupling member 9 are not in direct contact with each other, and the seat plate 10 having a linear expansion coefficient between these two is interposed therebetween, As schematically shown, the difference in dimensional change between the contact surfaces of the respective members is approximately 1/2 as compared with the case where the seat plate 10 is not inserted, and as a result, the thermal stress generated at the contact surfaces of the respective members is substantially 1 /
It becomes 2.

Therefore, when the elastic fulcrum members 8a, 8b or the elastic connecting members 9 are directly screwed to the lever 5 without inserting the seat plate 10, the difference in dimensional change due to the change in environmental temperature is caused. Assuming that the lower limit of the temperature change amount at which a slip occurs on the contact surface between them and a step-like zero point change is 10 ° C., in the embodiment of the present invention with the seat plate 10 interposed, Only when there is a temperature change of 20 ° C. does the contact surface slip and the zero point changes.
On the contrary, in the embodiment of the present invention, even if the zero point changes due to the slip on the contact surface of different members due to the change of the environmental temperature, the change amount of the zero point is the same when the temperature changes. In the conventional configuration, the slip amount is about 1/2
Therefore, it is about half that of the conventional one.

Here, in the above-described embodiment, the seat plate 10 is also attached to the elastic fulcrum members 8a and 8b and the balance frame 2, and also to the mounting portions of the elastic connecting member 9 and the movable column 3.
, But these are not necessary. That is, it is the lever 5 and the elastic fulcrum member 8a that have the greatest influence on the occurrence of the step-like zero point change due to the environmental temperature change.
8b and the elastic coupling member 9 are different in expansion, and the seat plate 10 may be inserted into at least these mounting portions. However, as in the above embodiment, the elastic fulcrum member 8
By inserting the seat plate 10 into all of the a, 8b and the elastic connecting member 9 that are attached to different materials, the effect of suppressing the zero point change is further improved.

Further, regarding the screw S for fixing the elastic fulcrum members 8a and 8b and the elastic connecting member 9 to the lever 5, the balance frame 2 and the like, the size of the screw S itself also changes due to the change of the environmental temperature, Depending on the difference in linear expansion coefficient between the lever 5 to which the screw S is fixed and the elastic fulcrum members 8a, 8b, etc., the fastening force of the screw S, that is, the lever 5
The tightening pressure between the seat plate 10 and the elastic fulcrum members 8a, 8b, etc. changes. This change in the tightening pressure causes a change in the magnitude of the internal stress, which is the limit of slip between the members. Therefore, if the linear expansion coefficient of the screw S is set to an approximately intermediate value between the linear expansion coefficient of the lever 5 and the linear expansion coefficient of the elastic fulcrum members 8a and 8b or the elastic connecting member 9 that is a member to which the lever 5 is attached. The change in tightening pressure due to temperature change is reduced, and the effect of suppressing change in the zero point is further improved.

In addition to the electromagnetic force balance type electronic balance as in the above-mentioned example, the present invention can be applied to any balance of the type in which the load acting on the dish by the lever is transmitted to the load sensitive section.
Of course, it can be similarly applied to any balance.

[0023]

According to the present invention, between the elastic fulcrum member and the elastic connecting member which are screwed to the lever and are made of a material different from that of the lever, an intermediate linear expansion coefficient of both materials is provided. Since a seat plate having a linear expansion coefficient is interposed, the thermal stress generated on the contact surfaces at the mounting portions of each member due to the difference in the dimensional change of each member due to the change in environmental temperature is about 1/2, It is possible to significantly reduce the stepwise change of the zero point at the first measurement after the environmental temperature change.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structural example of a mounting portion between a conventional lever and a dissimilar member such as an elastic fulcrum member.

FIG. 2 is an explanatory diagram of a reason why a zero point change occurs in the structure shown in FIG. 1 at the first measurement after a change in environmental temperature.

FIG. 3 is an overall view of a balance mechanism according to an embodiment of the present invention.

FIG. 4 is a perspective view showing only the vicinity of the lever 5 for extraction.

FIG. 5 is a diagram illustrating the operation of the embodiment of the present invention.

[Explanation of symbols]

 1 Dish 2 Balance Frame 3 Movable Columns 3a, 3b Beam 5 Lever 7 Load Sensitive Parts 8a, 8b Elastic Support Member 9 Elastic Connection Member 10 Seat Plate S Screw

Claims (1)

[Claims] 1. A lever, which is swingably supported by a balance frame via an elastic fulcrum member, and a movable column, which is vertically displaceable by supporting a plate, are interconnected by an elastic connection member. In the balance configured so that the load acting on the dish is transmitted to the load sensitive portion by the lever, the linear expansion coefficient is respectively attached to the mounting portion of the elastic fulcrum member and the elastic coupling member to the lever. A balance characterized in that a seat plate made of a material having an intermediate value of is inserted.