JPH07122308A - Electrical equipment earth terminal structure - Google Patents

Abstract

PURPOSE:To prevent the connection loosening of an earth cable caused by thermal expansion and thermal contraction, prevent the damage of a holder, and facilitate the connection work of an external earth cable connection terminal by installing an earth terminal in an insulating material holder. CONSTITUTION:A through hole 27 with a hexagonal large diameter part 27 is installed so as to pass through inside and outside in a cylindrical boss 26 of a synthetic resin holder 24 to which an earth inductance is installed. A metallic female screw 28 with tapped holes 28b, 28c at the opposite ends, also having a hexagonal head 28a at the base end is inserted into the through hole 27. A connection terminal 29 is connected to the tip of the female screw 28 by fastening an internal screw 30. A connection terminal 31a of an external earth cable 31 is connected to the base end of the female screw 28 by fastening an external screw 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground terminal structure for an electric device in which a holder made of an insulating material is provided with a ground terminal.

[0002]

2. Description of the Related Art Generally, in electric equipment, for example, a ground terminal is provided on the back surface of the main body, and an external ground wire is connected to the ground terminal when the equipment is installed. In some electric devices, noise transmitted through the power supply line, the ground line, etc. may adversely affect other devices. Therefore, in recent years, in order to reduce the noise, a ground inductance is provided between the cabinet and the ground terminal. In this case, since it is necessary to electrically insulate between the cabinet and the ground terminal, the ground terminal is provided in the holder made of an insulating material that holds the ground inductance. A conventional ground terminal structure of this type is shown in FIG.

That is, a through hole 3 is formed in a holder 2 made of synthetic resin which is attached to a cabinet 1 on the back side of an electric device, and a hexagonal large diameter portion 3a formed on the outer surface side of the through hole 3 is inside. The hex nut 4 is housed in the. The metal long screw 5 is inserted into the through hole 3 with the spring washer 6 inserted.
Is inserted from the inside (right side in the drawing) and is tightened to the hexagon nut 4. At this time, the connection terminal 7 of the ground wire connected to the ground inductance is sandwiched between the head 5a of the long screw 5 and the spring washer 6.
On the other hand, the tip end of the long screw 5 projects beyond the hexagon nut 4 and projects to the outer surface of the holder 2, and the hexagon nut 9 for connection is tightened with the connection terminal 8 of the external ground wire sandwiched therebetween, thereby The ground wire is designed to be connected.

[0004]

By the way, in a microwave oven or the like, there is a circumstance that the temperature of the cabinet 1 is relatively high during use. Therefore, as the use is repeated, the holder 2 and the long screw 5 may be removed. Thermal expansion and contraction occur. However, since the difference in expansion and contraction rates between the synthetic resin holder 2 and the metal long screw 5 is relatively large, even if the holder 2 and the long screw 5 are fixed without rattling at the beginning of installation. , Rattling will gradually occur on both sides.

In the above conventional structure, the connection terminal 7 of the ground wire on the inner side is sandwiched between the inner wall surface of the holder 2 and the head 5a of the long screw 5, so that the holder 2 and the long screw 5 are connected. When rattling occurs, the connection of the connection terminal 7 of the internal ground wire is loosened. Further, if the long screw 5 is excessively fastened to the hexagon nut 4, the holder 2 may be damaged due to a large fastening force.

Also, the connection terminal 8 of the external ground wire is a hexagon nut 9 for connection when the microwave oven is installed at home.
Although it is connected to the long screw 5 by the above, the tightening work of the hexagon nut 9 for connection requires a tool such as a spanner or box driver which is not usually prepared in ordinary households, and therefore the connection of the external ground wire is required. There was a problem that the connection work of the terminal 8 could not be easily performed.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent loosening of the connection of the ground wire due to thermal expansion and thermal contraction and to prevent damage to the holder. Another object of the present invention is to provide a ground terminal structure for an electric device that can be connected to an external ground wire and can be easily connected.

[0008]

A ground terminal structure for an electric device according to the present invention is provided with a holder made of an insulating material, which is attached to an outer wall of an electric device main body, and a holder made to communicate with the inside and outside of the outer wall. A through hole having a large diameter portion on the outer surface of the holder, a female screw member made of a conductive material to be inserted into the through hole from the outside, and a female screw member provided at the base end portion of the female screw member and fitted into the large diameter portion. Head part for preventing the female screw member from being pulled out at a position where the tip of the female screw member slightly protrudes from the through hole, screw holes formed at both ends of the female screw member, and a screw hole on the tip side of the female screw member. An internal screw for connecting the connection terminal of the internal ground wire to the female screw member, and an external screw for connecting the connection terminal of the external ground wire to the female screw member by tightening the screw hole on the base end side of the female screw member. With side screws To have the feature.

In this case, it is effective that the holder can be made of synthetic resin, and that the structure in which the female screw member and the through hole are prevented from rotating. The female screw member may be hollow, and the head portion of the female screw member and the large-diameter portion of the through hole may both be formed in a hexagonal shape.

[0010]

According to the above-mentioned means, the internal side wire is connected to the tip portion of the female screw member by tightening the inner side screw into the screw hole on the tip side of the female screw member protruding from the through hole of the holder. Connected while being sandwiched between the side screw and the external screw, tighten the external screw into the screw hole on the base end side of the female screw member so that the connection terminal of the external ground wire is connected to the base end of the female screw member and the external screw. It is connected while being sandwiched between.

Therefore, the tightening of each screw does not exert a large tightening force on the holder, and the female screw member is provided so as to have a backlash with respect to the holder, so that the expansion of the female screw member and the holder occurs. ， Even if the difference in shrinkage ratio is relatively large, the connection of each ground wire will not loosen. Since the external ground wire connection terminal is connected by tightening the external screw, a general tool such as a screwdriver may be used. Can be done easily.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a microwave oven will be described below with reference to FIGS. First,
FIG. 5 shows an external appearance of a main body 11 of a microwave oven which is an electric device, and an outer wall of the main body 11 is composed of a cabinet 12 made of a metal having a rectangular box shape. And cabinet 1
An earth terminal 13, which will be described later, is provided below the second back plate 12a (see FIGS. 1 and 3).

FIG. 4 schematically shows a partial electric circuit configuration of the microwave oven, in which a pair of power supply lines 15 and 16 connected to the plug 14 are connected to the first and second doors. It is connected to a magnetron oscillator circuit 19 via switches 17 and 18, respectively. Further, between the power lines 15 and 16, a monitor switch 20, which performs an operation reverse to that of the door switches 17 and 18, a heater 21 and its switch 22 are connected in parallel. The magnetron oscillator circuit 19 is body-grounded to the cabinet 12.

A ground inductance 23 for reducing noise is provided between the cabinet 12 and the ground terminal 13. The earth inductance 23 is formed by winding a winding around a core, and as shown in FIG. 3, the earth inductance 23 is held by a holder 24 made of an insulating material, for example, a synthetic resin such as polypropylene. Further, the ground terminal 13 is also provided in a state of being electrically insulated from the cabinet 12 by the holder 24. The ground terminal 13 is connected to an external ground 25 such as a ground rod embedded in the ground.

Now, the structure of the ground terminal 13 will be described mainly with reference to FIGS. 1 to 3. First,
As shown in FIG. 3, the holder 24 has an attachment portion 24a to which the earth inductance 23 is attached, and an integral cylindrical boss portion 26 that protrudes leftward in the figure at the lower portion thereof. Is configured. This holder 2
4 is attached to the inner surface side of the back plate 12a of the cabinet 12, and at this time, the tip of the boss portion 26 projects to the outer surface side through the through hole 12b formed in the back plate 12a. It is supposed to do.

As shown in FIG. 1, the boss portion 26 includes
A through hole 27 is provided so as to penetrate the inside and outside. The through hole 27 has a large diameter portion 27 a on the outer surface of the boss portion 26.
Is formed in a so-called stepped shape, and in the present embodiment, the large diameter portion 27a is formed in a hexagonal shape.

A female screw member 28 made of a conductive material is inserted into the through hole 27 of the boss portion 26. In this case, the female screw member 28 is made of a metal such as copper, a copper alloy, and stainless steel having excellent corrosion resistance and conductivity, and has a hollow cylindrical pipe shape as a whole as shown in FIG. A hexagonal large-diameter head portion 28a is integrally provided (at the left end portion in FIG. 1).

Further, an internal thread is formed on the inner peripheral portion of the internal thread member 28, for example, as a whole, so that the internal threaded hole 28b is formed at the tip of the internal thread member 28 (on the right end side in the figure). Is formed, and an external screw hole 28c is formed at the base end portion (left end side in the drawing) of the female screw member 28. The length dimension of the female screw member 28 is slightly larger than the length dimension of the through hole 27 (thickness dimension of the boss portion 26).

The female screw member 28 thus constructed is
As shown in FIG. 1, the holder 24 is provided by being inserted into the through hole 27 of the boss portion 26 from the outside. At this time, the head portion 28 a is the large diameter portion 2 of the through hole 27.
By being fitted into the inside 7a, the female screw member 28 is brought into a fixed positioning state to prevent the female screw member 28 from being pulled inward (to the right in the drawing), and is also prevented from rotating with the through hole 27. It is like this. Further, in this state, the tip of the female screw member 28 is slightly moved from the through hole 27 (for example, 0.
3 mm) and the base end portion (head portion 28a) of the female screw member 28 also protrudes slightly from the through hole 27 (large diameter portion 27a).

A U-shaped connecting terminal 29a of an internal ground wire 29 led out from the ground inductance 23 is connected to the tip of the female screw member 28 by a metal internal screw 30. This connection is performed by tightening the internal screw 30 into the internal screw hole 28b of the female screw member 28 with the connecting terminal 29a inserted in the outer periphery of the internal screw 30. As a result, the connection terminal 29a of the internal ground wire 29 is connected to the female screw member 2
8 is connected between the front end surface portion 8 and the head portion 30a of the internal screw 30. Further, at this time, the head portion 30a of the inner side screw 30 is made larger in diameter than the through hole 29, so that the female screw member 28 has a slight amount (0.
3 mm) of rattling is retained in the holder 24.

On the other hand, the cabinet 12 of the female screw member 28
The external ground wire 31 connected to the external ground 25, for example, a U-shaped connecting terminal 31a, is connected to the base end exposed on the outer surface of the back plate 12a of the back plate 12a by a metal external screw 32. Has become. This connection is also for external screw 32
With the connection terminal 31a inserted in the outer periphery of the female screw member 28, the external screw 32 is tightened in the external screw hole 28c of the female screw member 28. The screw 32 is connected while being sandwiched between the head 32a of the screw 32.

The connection terminal 31 of the external ground wire 31
The connection with a is made when the microwave oven is installed at home, for example. Therefore, in the product state at the time of factory shipment, the external ground wire 31 is not connected to the main body 11 and is, for example, an accessory. The external screw 32 may be an accessory together with the external ground wire 31, but may be loosely attached to the external screw hole 28c of the female screw member 28 in advance.

In the structure of the earth terminal 13 constructed as described above, the tightening of the screws 30 and 32 does not exert a large tightening force on the holder 24 made of synthetic resin, and the holder 24 is not damaged. There is no invitation. Further, since the female screw member 28 is provided so that there is some play in the holder 24 in advance, the difference in expansion and contraction rates between the female female screw member 28 made of metal and the holder 24 made of synthetic resin is relatively large. However, the connection between the ground wires 29 and 31 does not loosen.

Then, the connection terminal 31 of the external ground wire 31
For the connection work of a, the external screw 32 is temporarily loosened from the external screw hole 28c using a tool such as a screwdriver, the connection terminal 31a is fitted on the outer periphery of the external screw 32, and then the external screw 32 is again attached. Since it is performed by tightening the screw into the external screw hole 28c, even when the work is performed at home, it is possible to use a general tool such as a screwdriver and to simply perform the work.

As described above, according to the present embodiment, the connection terminals 29a and 31a of the ground wires 29 and 31 respectively have the end portions of the female screw member 28 and the head portions 30a and 32 of the screws 30 and 32, respectively.
The connection terminal 7 is sandwiched between the holder 2 and the head 5a of the long screw 5 by tightening the long screw 5 to the hexagon nut 4 as in the conventional case. It is possible to prevent loosening of the connection of the ground wires 29 and 31 due to thermal expansion and contraction, unlike the case of being attached and connected.

Further, since a large tightening force does not act on the holder 24, even if the holder 24 is made of synthetic resin, the damage can be prevented. Further, in this case, when selecting the material of the holder 24, it is not necessary to consider expansion, contraction rate, and strength so much, and there is an advantage that the conventional spring washer 6 can be eliminated. You can

Then, the connection terminal 31 of the external ground wire 31
Since the connection a is made by the external screw 32, the conventional connecting hexagonal nut 9 is used, and thus a tool such as a spanner or box driver which is not usually prepared in a general household is required. Unlike the ones, you can use a general tool such as a screwdriver,
The work can be easily performed even in a general household.

In the above embodiment, both the head portion 28a of the female screw member 28 and the large diameter portion 27a of the through hole 27 are formed in a hexagonal shape to prevent them from rotating, but the hexagonal shape is not the only option. Without a circular shape such as a square,
Similar anti-rotation effect can be exhibited, and the anti-rotation of both can be achieved, for example, by making both the female screw member and the entire through hole into a polygonal shape, or forming a concavo-convex relationship partially.

In the above embodiment, the female screw member 28 has a hollow pipe shape, but it may have a solid rod shape with screw holes formed only at both ends thereof. In addition, as the material of the holder, not only synthetic resin but also ceramic or the like can be adopted, and it can be applied not only to the microwave oven but also to various electric devices. It can be implemented by appropriately changing it.

[0030]

As is apparent from the above description, according to the grounding terminal structure of the electric device of the present invention, the female screw member made of the conductive material is rattled in the through hole of the holder made of the insulating material. The internal terminal and the external ground wire connecting terminals are connected by tightening the screws in the screw holes formed at both ends of the female screw member. It is possible to prevent the looseness of the connection of the ground wire, to prevent the holder from being damaged, and to achieve the excellent practical effect that the work of connecting the connection terminal of the external ground wire can be facilitated. It is a thing.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is an enlarged vertical side view of a ground terminal portion.

FIG. 2 is a perspective view of a female screw member.

FIG. 3 is a vertical sectional side view of a main part.

FIG. 4 is a diagram schematically showing an electric circuit configuration.

FIG. 5 is a side view of the microwave oven.

FIG. 6 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

In the drawings, 11 is a main body of an electric device, 12 is a cabinet, 1
2a is a back plate, 12b is a through hole, 13 is a ground terminal, 23 is a ground inductance, 24 is a holder, 25 is an external ground, 26 is a boss portion, 27 is a through hole, 27a is a large diameter portion, 2
8 is a female screw member, 28a is a head portion, 28b is an internal screw hole, 28c is an external screw hole, 29 is an internal ground wire, and 29 is an internal ground wire.
a is a connection terminal, 30 is an internal screw, 31 is an external ground wire, 31a is a connection terminal, and 32 is an external screw.

Claims (5)

[Claims] 1. A holder made of an insulating material, which is attached to an outer wall portion of an electric device body, and a through hole having a large diameter portion on an outer surface portion of the holder, which is provided so as to communicate the inside and the outside of the outer wall portion. A female screw member made of a conductive material which is inserted into the through hole from the outside, and a distal end portion of the female screw member which is provided at a base end portion of the female screw member and which is fitted into the large diameter portion and slightly projects from the through hole. At the position where the female screw member is retained, a screw hole formed at each end of the female screw member, and a screw hole on the distal end side of the female screw member, and the connection terminal of the internal ground wire is fastened to the female screw member. A ground terminal structure for an electric device, comprising: an internal screw to be connected; and an external screw tightened in a screw hole on a proximal end side of the female screw member to connect a connection terminal of an external ground wire to the female screw member. 2. The ground terminal structure for an electric device according to claim 1, wherein the holder is made of synthetic resin. 3. The earth terminal structure for an electric device according to claim 1, wherein a rotation stop structure is provided between the female screw member and the through hole. 4. The ground terminal structure for an electric device according to claim 1, wherein the female screw member is hollow. 5. The ground terminal structure for an electric device according to claim 1, wherein the head portion of the female screw member and the large diameter portion of the through hole are both formed in a hexagonal shape.