JPS6247064Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a pressure detection diaphragm used in a pressure gauge, and is particularly intended to provide a pressure detection diaphragm having a simple structure and having a diaphragm stretched at a constant tension.

A pressure detection diaphragm is generally constructed by attaching diaphragm support rings 2 and 3 to the periphery of a diaphragm 1, as shown in FIG. That is, the diaphragm 1 and the rings 2 and 3 are welded on the outer circumferential sides of the rings 2 and 3, and these three parts are integrated and then installed in a housing (not particularly shown) constituting the pressure gauge.

If there is slack in the diaphragm 1, there will be a drawback that the output will suddenly change or the zero point will shift due to the Bekotski phenomenon when the pressure difference between the front and back sides of the diaphragm 1 is around zero. For this reason, the diaphragm 1 is generally supported with a constant tension applied thereto. In order to apply a constant tension to the diaphragm 1 while attached to the rings 2 and 3, for example, the diaphragm 1 can be welded to the rings 2 and 3 while a constant tension is applied to the diaphragm 1, or the rings 2 and 3 from the outer circumferential direction, diaphragm 1 is welded to rings 2 and 3 in this state, and then the compression force is released and rings 2 and 3 return to their original shapes to initialize diaphragm 1. It has also been considered to apply tension to the diaphragm 1, or to press-fit rings with tapered surfaces into the rings 2 and 3, and apply tension to the diaphragm 1 through this press-fitting. However, when such a manufacturing method is adopted, a special jig is required and mass production is difficult. Another drawback is that it is difficult to make the tension applied to the diaphragm 1 uniform between products.

The purpose of this invention is to provide a pressure detecting diaphragm that is easy to manufacture and allows the tension to be easily made uniform among products.

In this invention, a ring made of a shape memory alloy that has the property of forming a matrix state at room temperature is fitted onto the inner periphery of rings 2 and 3 that support the diaphragm 1, and this ring is expanded at room temperature. The structure is such that a constant tension is applied to the diaphragm 1 via the rings 2 and 3.

As is well known, shape memory alloys are mainly alloys of nickel and titanium, and exhibit a matrix state and a martensite state depending on the temperature. In the matrix state, it has the characteristics of a normal metal and is extremely hard. If it is cooled from this state to a temperature below the martensitic transformation completion temperature, it becomes soft and can be deformed into any shape. However, when the temperature is returned to normal, it enters the matrix state and returns to its original shape. The martensitic transformation end temperature can be set to any temperature depending on the blending ratio of the components. In general, it usually becomes martensite at low temperatures, but there are also shape memory alloys that become martensite at high temperatures.

An embodiment of this invention will be described below in detail with reference to the drawings.

In this invention, a ring 4 as shown in FIG. 2 is formed of a shape memory alloy which is in a matrix state within the operating temperature range of the diaphragm, for example within the range of -50 DEG C. to 150 DEG C. The outer diameter D ₂ of this ring 4 is larger than the inner diameter D ₁ (see Fig. 1) of the diaphragm support rings 2 and 3 in the matrix state.
Form the relationship D ₂ > D ₁ .

The ring 4 formed of this shape memory alloy is heated to a temperature below the martensitic transformation completion temperature, for example -200°C.
It is cooled down to martensite. When it becomes martensite, the shape memory alloy becomes soft and can be deformed into any shape. Therefore, the martensite is deformed so that the outer diameter _of the ring 4 becomes an outer diameter _D8 smaller than the inner diameter D1 of the rings 2 and 3, as shown in FIG. The ring 4' in this deformed state is fitted into the diaphragm support rings 2 and 3 as shown in FIG. 4, and in this state it is returned to room temperature.

At room temperature, the shape memory alloy becomes the matrix state and the second
It returns to the shape shown in the figure and becomes very hard. By returning to the matrix state, the outer diameter of the ring 4 becomes
Returning to D ₂ , the diaphragm support rings 2 and 3 are pushed apart to reach the state shown in FIG. 5. Since the force with which ring 4' returns to its original shape is very large, support rings 2 and 3 are pushed apart with great force. The diaphragm 1 can thus be tensioned via the support rings 2 and 3. Here, the inner diameter D ₁ of support rings 2 and 3 and the outer diameter D ₂ of ring 4 in the matrix state
A constant tension can be applied to the diaphragm 1 by setting the relationship between the diameters to have a constant ratio.

As explained above, according to this invention, the ring 4 is made of a shape memory alloy, and the ring 4 is transformed into a ring 4' in martensite whose outer diameter is smaller than the inner diameter of the diaphragm support rings 2 and 3. The ring 4 returns to its original outer diameter D ₂ by fitting it into the support rings 2 and 3 and returning it to room temperature in that state to bring the shape memory alloy into a matrix state. Therefore, due to this change in shape, the support ring 2
and 3 can be given a large expansion force.

Therefore, according to this invention, manufacturing is easy because it is only necessary to cool the ring 4 made of a shape memory alloy to a temperature below the martensitic transformation completion temperature. However, the cooling temperature does not require strict temperature control since it is only necessary to cool the material to a temperature below the martensitic transformation end temperature. Therefore, the cooling device can also be inexpensive. Further, by making the ratio of the inner diameter D ₁ of the diaphragm support rings 2 and 3 to the outer diameter D ₂ of the ring 4 in the matrix state as specified, the tension applied to the diaphragm 1 can be made constant. Therefore, a pressure detection diaphragm with less variation in tension can be obtained, and a uniform product can be obtained. Also, the inner diameter of rings 2 and 3
By appropriately selecting the ratio between D ₁ and the outer diameter D ₂ of the ring 4, there is also the advantage that the tension of the diaphragm 1 can be set arbitrarily.

In the above description, the support rings 2 and 3 are attached to both sides of the diaphragm 1, but the ring 2 is attached only to one side.
This invention can also be applied to a pressure detection diaphragm with 3 or 3 attached.

[Brief explanation of the drawing]

Figure 1 is a sectional view for explaining the structure of a conventional pressure detection diaphragm, Figures 2 and 3 are sectional views showing a ring made of a shape memory alloy used in this invention, and Figure 4 is a sectional view for explaining the structure of a conventional pressure detection diaphragm. FIG. 5 is a cross-sectional view showing an example of the manufacturing process for obtaining the pressure-detecting diaphragm of this invention. FIG. 5 is a cross-sectional view showing an example of the pressure-detecting diaphragm of this invention. 1: Diaphragm, 2, 3: Diaphragm support ring, 4: Ring made of shape memory alloy.

Claims (1)

[Scope of utility model registration request] A ring is fixed to the peripheral edge of at least one surface of the diaphragm, and a ring-shaped shape memory alloy whose outer diameter is larger than the inner diameter of the ring is fitted into the inner peripheral surface of the ring in a matrix state. A diaphragm for pressure detection in which tension is applied to the diaphragm through the ring.