JPH0821826B2 - Ladder type electric filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a ladder in which a plurality of series resonators and parallel resonators are inserted together with a terminal plate, an insulating plate, etc. in a case whose one surface is open. Type electric filter.

<Prior Art> In this type of ladder-type electric filter, it is necessary to hold each mounting member such as a resonator closely.

Therefore, conventionally, after inserting each mounting member into the case, the spacer is press-fitted at the outermost end so that each mounting member is brought into a tightly closed state.

However, this method requires a press-fitting step in which the spacer is forcedly pushed into the minute gap, so that the assembly is troublesome, and the wall thickness of the spacer is limited to a thickness that can be inserted. However, there is a drawback in that each mounting member is apt to rattle, and in some cases a connection failure may occur.

On the other hand, there is also one that uses a leaf spring instead of the spacer.

This device can be inserted relatively easily by utilizing its elasticity, and since each mounting member is pressed against each other by spring pressure, there is an advantage that the mounting member can be held tightly.

However, the case accommodating the mounting member is made of a synthetic resin material such as PBT. For this reason, when a filter is constructed, a contact pressure is required to hold the resonator, but this internal pressure causes the resin case to soften on the high temperature side in the temperature characteristics of the filter.
When the case expands and loosens inside, the leaf spring expands, and the elasticity of the leaf spring decreases, which makes it impossible to hold each mounting member with a stable pressure, resulting in unstable characteristics. There was a flaw.

It is an object of the present invention to stabilize the filter characteristics by making the contact pressure of each mounting member inside the case as constant as possible even if the case expands and contracts due to the ambient temperature atmosphere. <Means for Solving Problems> The present invention relates to a ladder type in which a plurality of series resonators and parallel resonators are inserted together with a terminal plate, an insulating plate, etc. in a synthetic resin case having an opening on one side. In the electric filter, a curved leaf spring made of a shape memory alloy in a transformation region from the martensite phase to the austenite phase at a use temperature is inserted in the case.

<Function> A shape memory alloy made of an alloy of nickel and titanium is
It exhibits a martensite phase at low temperatures and an austenite phase at high temperatures.

Here, the transformation end temperature in the martensite phase region is usually −80.
By selecting the composition of the alloy etc. in the range of up to 80 ℃,
It can be set relatively arbitrarily. Further, the austenite transformation end temperature can be usually set in the range of -10 to 110 ° C. The transformation range from the martensite phase region to the austenite phase region is −80 to 110.
It can be set over a wide range of ° C.

By the way, looking at the relationship between the temperature from the martensite phase region to the austenite phase region and the spring property, there is a characteristic that the spring property increases as the temperature rises in the transformation region from the martensite phase region to the austenite phase region. .

Here, the graph of FIG. 3 shows the relationship between the temperature and the repulsive force of the leaf spring. Here, this repulsive force is expressed as a load required to give a constant strain to a leaf spring having a predetermined curvature.

As is clear from this figure, in the martensite phase region, a gradual decrease in springiness is observed with increasing temperature, but when it goes out of this phase region and enters the transformation region, it rises sharply. In the austenite phase region, it exhibits stable characteristics with respect to temperature.

Therefore, when the curved leaf spring shown in FIG. 2 is formed by the shape memory alloy in this transformation region and mounted in the case, the temperature atmosphere around the case rises. The expansion expands the internal volume and expands the leaf spring. Due to this expansion, the spring elasticity of the ordinary leaf spring is reduced. However, since the springiness of the leaf spring increases in proportion to the temperature rise, even if the leaf spring expands as the volume increases, the springiness also increases, so that the elastic force does not decrease. Therefore, even if the case expands, each mounting member is pressed tightly and stably in the storage space, and the holding force of each resonator can be made constant.

In addition, in FIG. 3, the temperature characteristic of phosphor bronze generally used as a material of a terminal board is shown for comparison. That is,
It is understood that ordinary metals do not have the above temperature characteristics.

<Embodiment> Referring to FIG. 1, reference numeral 1 denotes a rectangular case made of an insulating material, and a case 2 is formed with a storage space 2 having an open top surface. In the storage space 2, the terminal plate 4a from the front to the end, the series resonator 5 having a large thickness, the terminal plate 4
Several sets of mounting members in which b, the terminal plate 6, the thin parallel resonator 7, the terminal plate 8, and the insulating plate 9 are arranged in a row to form one set are housed.

Electrodes are formed on the front and rear surfaces of the resonators 5 and 7,
Each terminal plate 4a, 4b, 6, 8 in contact with the resonator 5, 7 is made of phosphor bronze as a base material, and its surface is silver-plated, and its surface portion is electrically connected to the electrode. In order to ensure the above, the respective press-contact ridges 10 are formed. Also, the terminal boards at both ends
The connecting projections 11 are formed on the shoulders on one side of the 4a and 4a, and the connecting projections 12 are formed on the shoulders on the other side of the plurality of terminal plates 8. Therefore, in the mounted state, on the upper surface of the case 1, the connecting protrusions 11 of the terminal plate 4a project at one end on one side and the connecting protrusions 12 of the terminal plate 8 on one side in a row. Will be projected. Furthermore, the terminal plate 4b has a U-shaped cross section, and the contact surfaces on which the ridges 10 for pressure welding are formed are connected to the electrodes of the series resonators 5 to connect the series resonators 5 in series. There is. The row of the series resonators 5 can be electrically connected by the connecting protrusions 11 of the terminal plates 4a, 4a at the end.

Then, a sealing plate 15 is attached to the opening of the case 1, and then a sealing agent 16 such as epoxy resin is filled.

As shown in FIG. 2, a leaf spring 13 made of a shape memory alloy is formed at the outermost portion of each of the above-mentioned mounting members so as to generate a spring action by forming a curved cross section inward as shown in FIG.
Has been inserted. Moreover, the leaf spring 13 uses a material in the transformation region from the martensite phase region to the austenite phase region at the use temperature.

In this transformation range, the springiness increases with increasing temperature. Therefore, even if the case 1 expands due to the temperature rise and the volume of the storage space 2 expands, the leaf spring 13 expands without lowering the spring elasticity and presses the terminal plate 4a and the like inward. Then, in the case 1, the respective mounting members are held without loosening each other.

<Effects of the Invention> As described above, the present invention inserts a leaf spring made of a shape memory alloy in a transformation region from the martensite phase region to the austenite phase region at a use temperature into a case to tightly attach each mounting member. Since it is intended to realize the above, even if the volume of the case increases due to temperature rise, the spring elasticity of the leaf spring can be continuously maintained, and the inside of the case can be kept in a tight state with a constant pressure. It has excellent effects such as stable characteristics.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a ladder type electric filter according to an embodiment of the present invention, FIG. 2 is a perspective view of a leaf spring 13, and FIG. 3 shows repulsive force and temperature of a leaf spring made of a shape memory alloy. It is a graph which shows a relationship. 1; case, 2; storage space, 4a, 4b; terminal plate, 5a; series resonator, 6; terminal plate, 7; parallel resonator, 8; terminal plate, 13; leaf spring

Claims (1)

[Claims] 1. A ladder type electric filter comprising a plurality of series resonators and parallel resonators inserted together with a terminal plate, an insulating plate and the like in a synthetic resin case having an opening on one side, at operating temperature, A ladder type electric filter characterized in that a curved leaf spring made of a shape memory alloy in a transformation region from a martensite phase to an austenite phase is inserted in a case.