JP3245971B2 - Vacuum condenser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable vacuum capacitor used for an oscillation circuit, an amplification circuit of a high power transmitter, a tank circuit of an induction heating device, or the like.

[0002]

2. Description of the Related Art High voltage and current ratings, tuning ratios,
In recent years, variable vacuum capacitors have been used for large power capacitors because of their excellent self-healing properties.

FIG. 3 is a sectional structural view of a typical variable vacuum capacitor of this type. For example, a side portion is formed by a ceramic 12 having copper flanges 11a and 11b at both ends, and this side portion is fixed. A vacuum vessel 10 for filling a high-proof vacuum dielectric is formed by being closed by the conductor 13 and the metal lid 14.

[0004] Inside the fixed conductor 13, a plurality of substantially cylindrical electrode plates having different inner diameters are provided concentrically at regular intervals to form the fixed electrode 15, and the fixed electrode 15 is formed.
The movable electrode 16 is formed by providing a plurality of cylindrical electrode plates having different inner diameters on the movable conductor 18 so that they can be inserted into and removed from each electrode gap in a non-contact state. On the back surface of the movable conductor 18, a cylindrical movable lead 18a slidably supported in a substantially airtight manner by a bearing 17 serving as a guide is attached integrally.

Reference numeral 19 denotes a bellows made of an elastic soft metal. The bellows 19 are provided so that the movable conductor 18 (movable electrode 16) can slide while keeping the inside of the vacuum vessel 10 airtight.
One end is joined to the inner wall and the bearing 17 and the other end is connected to the back of the movable conductor 18 or the movable lead 18a.
Bonded to the surface. Thereby, air around the surface of the bearing 17 and the surface of the movable lead portion 18a is kept airtight, and a vacuum seal is performed. The bellows 19 also serves as a current path between an external power supply terminal (not shown) provided on the lid 14 and the movable electrode 16 in addition to the vacuum seal.

When adjusting the capacitance of the vacuum capacitor having the above-mentioned structure, for example, as shown in FIG. 4, a tap is cut on the inner wall of the movable lead portion 18a, and the tap is provided with a headed capacitance adjusting screw. 20 is screwed. Then, a motor shaft 22 is coupled to the head of the capacitance adjusting screw 20 via a coupling 21, and a rotational force is applied by a motor 23. As a result, the movable lead 18a slides in contact with the inner surface of the bearing 17 to change the position of the movable conductor 18, and the value of the capacitance generated between the fixed electrode 15 and the movable electrode 16 changes continuously. The capacitance adjusting screw 20 may be manually rotated.

[0007]

When the capacitance screw 20 is adjusted, if the distance between the movable electrode 16 and the fixed electrode 15 is not constant, the withstand voltage value locally decreases. Therefore, it is desirable that the gap between the inner surface of the bearing 17 and the surface of the movable lead portion 18a be as small as possible. However, this causes the following problem.

When the movable lead portion 18a is slid, the volume of the inner space of the container partitioned by a surface portion including the bellows 19, the surface of the movable lead 18a, and the surface of the bearing 17 changes. For example, when the movable lead 18a is pulled out, the volume is reduced. At this time, the air in the space must be discharged to the outer space as shown by an arrow in FIG. 5, but as the gap becomes smaller, the flow of air is hindered, which resists the force pulling the movable lead portion 18a. It becomes a force and hinders operability in adjusting the capacitance. On the other hand, when the movable lead portion 18a is inserted into the container, the space inside the container increases, and air needs to be flown in. However, this is hindered by similar circumstances. Therefore, for example, as shown in FIG.
When the capacitance is adjusted by using a motor, a motor having a large driving force must be selected, and the cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the gap between the inner surface of the bearing 17 and the surface of the movable lead portion 18a. It is to provide a vacuum capacitor.

[0010]

According to the present invention, there is provided a vacuum capacitor comprising: a movable conductor having a cylindrical movable lead attached to the back side of a movable electrode; and the movable lead being substantially moved in the direction of the fixed electrode in the vacuum vessel. A bearing that slidably supports in a hermetically sealed state, and a bellows that keeps at least the periphery of the bearing surface and the surface of the movable lead portion in a vacuum vessel in an airtight manner; In a vacuum capacitor that changes the volume of an inner space of a container partitioned by a surface portion including a bearing surface and the movable lead portion surface, a bearing inner surface at a portion contacting the movable lead portion surface and a movable lead at a portion contacting the bearing inner surface A groove having a predetermined cross-sectional shape that allows air to flow between the inner space of the container and the outer space when at least one of the outer surface and the movable lead portion slides while being supported by the bearing. Characterized in that the formation of the.

The groove is spirally or linearly formed in the sliding direction of the movable lead, and has a substantially semicircular or substantially rectangular cross section.

[0012]

Since air flows between the inner space of the container and the outer space through the groove on the surface of the movable lead or the inner surface of the bearing, even if the movable lead is slid while being supported by the bearing in a substantially airtight state. The force does not increase as before. The flow path of the air is shortened by forming the groove portion in a straight line. On the other hand, if the groove is formed in a spiral shape, the air flow path becomes slightly longer, but the resistance due to air is reduced over the entire circumference of the movable lead.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Since the present invention is a partial modification of the structure of the conventional vacuum capacitor, the same components as those shown in FIG. 3 are denoted by the same reference numerals and the description thereof will be omitted.

In the present embodiment, a groove is formed in the contact surface between the inner surface of the bearing 17 and the surface of the movable lead portion 18a in the vacuum capacitor having the conventional structure, and air is formed between the inner space of the container and the outer space through the groove. Is to be distributed.

FIG. 1A shows a state in which a spiral groove 1 is formed on the surface of a movable lead 18a, and FIG.
Indicates a state in which a linear groove 2 is formed. It is sufficient that these grooves 1 and 2 are formed in the sliding range of the movable lead portion 18a, that is, in a portion that is in contact with the inner surface of the bearing 17, and the cross-sectional shape is substantially semicircular or substantially rectangular.

In the vacuum capacitor having such a structure, when the movable lead 18a is moved up and down at the time of adjusting the capacitance, the volume of the space in the container partitioned by the surface including the bellows 19, the surface of the movable lead 18a and the surface of the bearing 17 is obtained. Changes,
Since air flows between the inner space of the container and the outer space through the grooves 1 and 2, even if the movable lead 18a is supported by the bearing 17 in a substantially airtight state, the resistance increases as in the related art. There is no. Therefore, the fixed electrode 15 and the movable electrode 1
6, while maintaining a constant distance from the air, the conventional problem of resistance due to air can be solved.

A linear groove 2 as shown in FIG.
In this case, the flow path of the air is shortened, and quick adjustment becomes possible. On the other hand, in the spiral groove 1 as shown in FIG.
Although the air circulation path is slightly longer, the movable lead 18a
, The rotational driving force of the entire adjustment work is reduced.

FIG. 2A shows a state in which a spiral groove 3 is formed on the inner surface of the bearing 17, and FIG. 2B shows a state in which a linear groove 4 is formed. It is sufficient that these grooves 3 and 4 are formed in a range in contact with the surface of the movable lead portion 18a, that is, in the example shown in the drawing, a pair of convex portions is formed, and the cross-sectional shape thereof is substantially semicircular or rectangular.

Even when the grooves 3 and 4 are formed on the inner surface of the bearing 17 as described above, an air flow path between the inner space of the container and the outer space is secured when the movable lead 18a slides, and the same effect as described above is obtained. can get.

FIGS. 1A and 1B show an example in which one groove portion 1 and 2 are formed, and FIGS. 2A and 2B show an example in which a pair of groove portions 3 and 4 are formed. 4 to 4 may be formed in a plurality or pairs, respectively, or may be formed on both the surface of the movable lead portion 18a and the inner surface of the bearing 17. Further, the linear grooves 2 and 4 may be formed in the sliding direction of the movable lead 18a, and are not necessarily restricted by the illustrated example.

[0021]

As is apparent from the above description, according to the vacuum capacitor of the present invention, when the movable lead portion slides while being supported by the bearing, the space between the inner space of the container and the outer space is formed through the groove. Since air flows between them, there is an effect that the resistance due to air is significantly reduced. Accordingly, the gap between the inner surface of the bearing and the surface of the movable lead portion can be reduced as much as possible, and a decrease in the withstand voltage at the time of adjusting the capacitance can be effectively prevented. In addition, when the capacitance is adjusted using a motor, a motor having a low torque can be selected, and the drive mechanism including the motor can be reduced in size and cost.

By forming the groove in a spiral shape in the sliding direction of the movable lead, the driving force is made uniform over the sliding range. On the other hand, by forming the groove in a straight line, rapid sliding is achieved. Becomes possible. Further, by making the cross-sectional shape of the groove portion substantially semicircular or substantially rectangular in cross-section, processing becomes easy, and air resistance during distribution decreases.

[Brief description of the drawings]

FIG. 1 is an explanatory view of one embodiment of the present invention, in which (a) shows a state in which a spiral groove is formed on the surface of a movable lead,
(B) shows a state in which a linear groove is formed.

FIG. 2 is an explanatory view of another embodiment of the present invention, wherein (a) shows a state in which a pair of spiral grooves are formed on the inner surface of the bearing, and (b)
Indicates a state in which a linear groove is formed.

FIG. 3 is a sectional structural view of a variable vacuum capacitor to which the present invention is applied.

FIG. 4 is an explanatory diagram of a capacitance adjusting mechanism in the vacuum capacitor.

FIG. 5 is a partially enlarged view of a vacuum capacitor for explaining a conventional problem.

[Explanation of symbols]

 1-4 groove 13 fixed conductor 15 fixed electrode 16 movable electrode 17 bearing 18 movable conductor 18a movable lead 19 bellows

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-B-46-24938 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01G 5/00-5/40

Claims (4)

(57) [Claims] A movable conductor having a cylindrical movable lead attached to the back side of the movable electrode; and a bearing for slidably supporting the movable lead in a substantially airtight state toward the fixed electrode in the vacuum vessel. A bellows for holding air in the bearing surface and the movable lead portion airtight in a vacuum container, and a surface portion including the bellows, the bearing surface, and the movable lead portion surface as the movable lead portion slides. In the vacuum capacitor which changes the volume of the space inside the container partitioned by the above, at least one of the inner surface of the bearing in contact with the surface of the movable lead portion and the surface of the movable lead portion in contact with the inner surface of the bearing is supported by the bearing. And a groove having a predetermined cross-sectional shape for allowing air to flow between the space inside the container and the external space when the movable lead slides. 2. The device according to claim 1, wherein the groove is formed in a spiral shape along the entire circumference of the movable lead and in the sliding direction.
The described vacuum condenser. 3. The vacuum capacitor according to claim 1, wherein the groove is formed substantially linearly in a sliding direction of the movable lead. 4. The vacuum capacitor according to claim 1, wherein a cross-sectional shape of the groove is substantially semicircular or substantially rectangular.