JP2002251948A - Thermal overload relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an operation characteristic of a thermal overload relay and to improve an assembly structure so as to miniaturize the relay and to reduce the cost thereof in conjunction with the expansion of an overload detection determination range. SOLUTION: This thermal overload relay comprises a reversing mechanism for opening/closing contacts comprising an assembly composed of main bimetals 2 bent and displaced based on a carried current, a release lever 4 driven by the displacement of a shifter 3 interlocked with the main bimetal, a movable plate 8, a reversing spring 9 and a bearing member 12, and a contact mechanism, and opens and closes b-contacts 10 and 11, and a-contacts 16, 16 by the reverse operation of the reversing mechanism when the bent displacement amount of the main bimetals exceeds a specified value. The release lever is reversely operated by directly pressing it against the surface of the movable plate of the reversing mechanism, a lift-off type contact mechanism using a movable contact spring 16a is employed for the a-contacts, and the generation power- displacement characteristic of the main bimetals is matched with the load displacement characteristic of the release lever, so that the generation energy of the main bimetals is effectively utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal overload relay (thermal relay) used in combination with an electromagnetic contactor or the like.

[0002]

2. Description of the Related Art The thermal overload relay described above is used for a main bimetal that is bent and displaced by heating of an energizing current, a release lever that is driven by a displacement of a shifter that is interlocked with the main bimetal, and a contact opening and closing device that is driven by a release lever. And a contact mechanism, and when the amount of bending displacement of the main bimetal exceeds a specified value, the reversing mechanism performs a reversing operation to open and close the contact.

Here, the reversing mechanism is provided with a substantially U-shaped movable plate which is swingably supported by a bearing member with a tip of a leg as a fulcrum, and a movable plate and the lower portion of the movable plate with the fulcrum interposed therebetween. And a reversing spring (a linear tension coil spring) stretched between the support arm and the support arm. Further, in order to cause the reversing mechanism to perform reversing operation by bending displacement of the main bimetal, conventionally, as disclosed in Japanese Utility Model Publication No. 3-9234, the tip of the release lever interlocking with the main bimetal is pushed by the reversing spring. Then, the movable plate is turned over.

FIGS. 5 (a) and 5 (b) show a thermal overload relay disclosed in the above publication, and FIGS. 6 and 7 show schematic views of the relay and the structure of its reversing mechanism, respectively. Show. First, in FIG. 5A, 1 is a main body case, 2 is a main bimetal heated by a heating element (not shown) through which a main circuit current flows (only one phase of a three-phase circuit is shown),
3 is a shifter connected to the tip of the main bimetal 2, 4 is a release lever arranged in combination with a temperature compensating bimetal 5 and opposed to a reversing mechanism described later, 6 is an adjustment link connected to the upper end of the release lever 4, 7 is an adjustment link 6, an adjusting dial for adjusting the set current value connected to the top of the movable member via a cam mechanism; 8, an oscillating movable plate of an inverting mechanism; 9, an inverting spring attached to the movable plate 8 (filament tension coil spring); Reference numeral 10 denotes a normally closed movable contact (b contact) as an auxiliary contact, and 11 denotes a fixed contact thereof.

Here, the movable plate 8 of the reversing mechanism is made of an inverted U-shaped metal plate as shown in FIG.
The movable plate 8 is swingably supported by abutting a leading end (lower end) of a on a V-shaped groove 12a formed in the bearing member 12 as a knife edge. The reversing spring 9 is formed by forming a coil 9a and a hook 9b on a spring wire as shown in FIG. 5B, and is provided between the upper end of the movable plate 8 and the support arm 13 disposed below the movable plate. The hooks 9b at both ends are hooked and stretched, and at this position, the distal end 4a of the release lever 4 described above.
Is in contact with the middle of the spring streak. In FIG. 6, 15 is a fixed contact of a normally open output contact (a contact), 16 is a movable contact,
Reference numeral 17 denotes a slider for opening and closing the movable contact 16 in conjunction with the movement of the movable plate 8.

In such a configuration, in a steady state, the shifter 3 connected to the main bimetal 2 is retracted to the right, and the movable plate 8 of the reversing mechanism is tilted to the position shown in FIG. Contact 10/11 is ON, normally open contact 15/16
Is OFF. When an overcurrent flows through a heat element (not shown) of the main bimetal 2 from this state, the heat of the heat element causes the main bimetal 2 to bend and displace, pushing the shifter 3 in the direction of arrow P, and via the temperature compensating bimetal 5. The release lever 4 is rotated. As a result, the distal end portion 4a of the release lever 4 pushes the line of the reversing spring 9 and deflects the spring line into a "-" shape. In this case, when an overload current flows through the main circuit and the amount of bending displacement of the main bimetal 3 exceeds a specified value, the movable plate 8 is released via the release lever 4.
Turns the normally closed contact 10/11 OFF and the normally open contact 15/16 ON by turning the tip of the leg as a fulcrum, and trips the electromagnetic contactor by the contact output. The resetting of the contact mechanism is performed by setting the reset rod 14 shown in FIG. 5A to an automatic return position and a manual return position.

[0007]

However, the conventional thermal overload relay having the above-mentioned structure has the following problems in terms of operation characteristics, assemblability of the reversing mechanism, and the like. Here, FIGS. 8A to 8C show operation characteristics of the conventional structure shown in FIG. 6A shows the generated force-displacement characteristic A of the main bimetal 2, the movable plate reaction force-displacement characteristic B when the movable plate 8 is reversed, and the contact point F with the reversing spring 9 (FIG. 6).
) Represents the reaction force-displacement characteristic C acting on the release lever 4, and (b) shows the movable plate 8 which drives the contact mechanism to the open / close position.
-Displacement characteristic D and reaction force of a and b contact mechanisms-
A displacement characteristic E is shown, and FIG. 7C shows a load-displacement characteristic F accompanying the reversing operation of the movable plate 4.

That is, the generated force of the main bimetal 2 is a force that pushes the shifter 3 by the curvature generated by the temperature rise, and the generated force is large during the small displacement where the movement of the main bimetal is restricted from the reversing mechanism side. Since the accumulated energy is released as the displacement of the main bimetal increases for the first time when the reversing mechanism moves, the generated force decreases. on the other hand,
The spring pressing force at the point F required to reversely drive the movable plate 8 of the reversing mechanism increases with the displacement until the movable plate 8 urged by the reversing spring 9 reverses from the steady position. When the plate exceeds the dead point or the movable plate reaction force B shown in FIG. 8A falls below the contact b reaction force shown in FIG. Declines sharply. When the contact mechanism is opened and closed, a contact pressure is applied between the contacts by the force generated by the movable plate 8 which is spring-biased by the reversing spring 9. Is bent to close the contact.

As can be seen from the characteristic diagram, the generated force-displacement characteristic D of the movable plate 8 and the reaction force-displacement characteristic E required for the opening and closing drive of the contact mechanism have substantially the same tendency. On the other hand, in the first half region of the reversing operation of the reversing mechanism, the release lever 4 pressing the reversing spring 9 and the generated force-displacement characteristic A of the main bimetal.
In the reaction force-displacement characteristic C, the directions of increase and decrease are opposite to each other, and the movable plate reaction force acting on the release lever 4 becomes zero when the movable plate 8 exceeds the dead point. For this reason, in the first half of the reversing operation, the generated force of the main bimetal 2 is reduced by the reversing spring 9.
While the large generated force required to invert the movable plate 8 by bending the movable plate 8 is required, the generated force (stored energy) of the main bimetal is not used as the driving force in the latter half range shaded in FIG. become.

Also, in the hinge structure in which the tip of the movable plate 8 is supported by the V-shaped groove 12a of the bearing member 12 as a knife edge as shown in FIG. As shown by (c), the load-displacement characteristic F when the movable plate 8 performs the reciprocating reversal operation becomes the hysteresis characteristic. This hysteresis characteristic adversely affects the operation characteristics of the thermal overload relay. In addition, the main bimetal 2 needs to be designed in thickness, dimensions, and the like so as to secure the bimetal characteristic in consideration of the hysteresis characteristic. As a result, the main bimetal becomes large, and the setting range of the overcurrent detection is increased. Is narrowed.

[0011] Further, in the conventional reversing mechanism shown in FIG.
Therefore, it is difficult to automatically assemble the reversing mechanism by an assembling robot or the like, and the present situation is that the reversing mechanism relies on manual work. The present invention has been made in view of the above points, and a purpose of the present invention is to provide a thermal overload relay improved so as to solve the above-described problems and improve the operation characteristics, and to realize automatic assembly of a reversing mechanism. To provide.

[0012]

According to the present invention, there is provided a main bimetal which is bent and displaced by heating of an electric current, a release lever which is driven by a displacement of a shifter which cooperates with the main bimetal, and a release lever. This is a thermal overload relay that consists of a contact opening / closing reversing mechanism and a contact mechanism. A movable plate supported by the bearing member such that the reversing mechanism swings around a tip of a leg portion as a fulcrum, and a tension spring stretched between the movable plate and the support arm disposed below the movable plate with the fulcrum interposed therebetween. Wherein the release lever is directly pressed against the plate surface of the movable plate of the reversing mechanism to perform the reversing operation (claim 1). By adopting a lift-off type contact mechanism that obtains the contact pressure between the contacts by a spring (claim 2), the operating force can be improved by effectively utilizing the generated force of the main bimetal in the inversion drive of the inversion mechanism without waste. To

According to the present invention, in order to eliminate backlash and frictional resistance between the movable plate of the reversing mechanism and the bearing member,
The movable plate of the reversing mechanism and its bearing member are integrally connected via an elastic hinge portion (Claim 3). Further, in order to realize automatic assembly of the reversing mechanism, a tension spring of the reversing mechanism is provided by a leaf spring. The reversing mechanism is formed as a molded product such as PET resin or a composite formed product combining a leaf spring with the movable plate, the bearing member and the movable member. The extension spring is formed integrally (claim 5).

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.
This will be described with reference to the embodiment of FIG. In FIG. 1, members corresponding to those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted. That is, in the embodiment shown in FIG. 1, a slide-type lever 4a is linked to the release lever 4, and this release lever 4
a is directly pressed against the plate surface of the movable plate 8 to cause the reversing mechanism to perform a reversing operation, and this point is different from the conventional structure shown in FIG. A required contact pressure is applied to the normally open a contact 16 which opens and closes in conjunction with the lever 4a with the fixed contact 15 by the bending force of the contact spring 16a. A lift-off type contact is used in which the child spring 16a is bent and retracted. Thus, in the illustrated steady state (a contact OFF), the lever 4
The bending spring force of the contact spring 16a is applied to a.

In this configuration, when the main bimetal 2 is bent and displaced due to an overcurrent, the lever 4a moves rightward from the position shown in the drawing via the shifter 3 and the release lever 4, and the movable plate 8 of the reversing mechanism is directly pushed to perform the reversing operation. . As a result, the normally closed contact b is turned off, and the normally open contact a is turned on. The reset after the operation is performed manually or automatically by the reset operation rod 14 as in the conventional case.

Next, the operating characteristics of the configuration of the embodiment are shown in FIG.
Shown in That is, the reaction force-displacement characteristic G applied to the release lever 4 with respect to the generated force-displacement characteristic A of the main bimetal 2
(The combined characteristic of the load-displacement characteristic H of the contact a and the load-displacement characteristic I of the movable plate 8 of the reversing mechanism: G = H + I) is a characteristic having the same tendency as the generated force-displacement characteristic A of the bimetal as shown in the figure. Becomes In the drawing, P1 represents the position of the operating rod during automatic setting, and P2 represents the position of the operating rod during manual setting.

As can be seen from the operation characteristics, the reversing mechanism and the contact mechanism can be driven by effectively utilizing the energy generated by the main bimetal 2 with little waste as compared with the conventional system. Since less energy is required, the setting range of overcurrent detection, which has been a problem in the past, can be greatly expanded, and the size of the main bimetal can be reduced accordingly.

Next, a third embodiment of the present invention will be described with reference to FIGS. First, in the embodiment shown in FIG. 3A, the movable plate 8 of the reversing mechanism and the bearing member 12 are integrally formed so as to be integrally connected via a thin elastic hinge portion 18. According to this configuration, as compared with the pivot type hinge structure in which the knife edge and the V-shaped groove are combined as shown in FIG. The load-displacement characteristic F has no hysteresis as shown in FIG. 3 (b), and the operating characteristic can be greatly improved as compared with the conventional characteristic shown in FIG. 8 (c).

Here, in order to form the above-mentioned elastic hinge portion 18, Cu-based material is used as the material of the movable plate 8 and the bearing member 12.
A metal material having a large elastic limit, such as a Zn-Al alloy or a Ni-Ti alloy, or a PET resin can be used. In addition, the inventors conducted a durability test on the reversing mechanism made of PET resin, and it was confirmed that the reversing mechanism can sufficiently withstand the reversal operation test as many as 6000 times.

In the embodiment shown in FIG. 4, the movable plate 8, the bearing member 12, and the elastic hinge portion 18 are provided as described with reference to FIG.
Is integrated with a resin, and the reversing spring 19 made of a resin is replaced by a reversing spring 19 made of a resin.
Are formed integrally with the movable plate 8. here,
The reversing spring 19 made of resin has a plurality of rhombus-shaped segment plates (perforated) 19a connected in a bead shape, and is formed simultaneously with the resilient hinge 18 when the reversing mechanism is molded. In addition, the rhombic segment plates 19a are continuous on the same plane,
The segment 19 may be bent in a zigzag manner, and the segment at the tip is locked to the support arm 13 in a state where a tensile force is applied to the segment 19 at the assembly position of the reversing mechanism. It performs the same function as a spring.

Further, according to this embodiment, since the movable plate 8 and the reversing spring 19 are formed integrally, the small holes formed in the movable plate 8 in the assembling process as in the conventional structure shown in FIG. The work of hooking the hook 9b of the reversing spring 9 made of the spring wire is not required, thereby enabling automatic assembly by an automatic machine without relying on manual work.

[0022]

As described above, according to the configuration of the present invention, the operating characteristics of the thermal overload relay can be improved, and the setting range of the overcurrent detection can be greatly expanded as compared with the conventional one. At the same time, the mechanical energy required for the main bimetal is small. In addition, by using the structure of claims 3 to 5 of the present invention together with the reversing mechanism, it is possible to reduce the size and cost of the thermal overload relay and to enable automatic assembly of the reversing mechanism. Further, it is possible to provide a thermal overload relay exhibiting excellent effects in terms of manufacturing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a thermal overload relay according to an embodiment of the present invention.

FIG. 2 is an operation characteristic diagram of the thermal overload relay having the configuration of FIG. 1;

FIG. 3 shows a reversing mechanism according to claim 3 of the present invention,
(a) is a configuration perspective view of the reversing mechanism, and (b) is a load-displacement characteristic diagram of the movable plate.

FIG. 4 is a perspective view showing the configuration of a reversing mechanism according to a fourth embodiment of the present invention;

FIG. 5 is a configuration diagram of a conventional thermal overload relay, in which (a) is an assembly structure diagram of the product, and (b) is an enlarged perspective view of a release lever and a reversing spring in (a).

FIG. 6 is a diagram schematically showing the structure of FIG. 5;

FIG. 7 is a perspective view showing the configuration of a reversing mechanism in FIG. 6;

8A and 8B are operating characteristic diagrams of the thermal overload relay having the configuration shown in FIG. 6, wherein FIGS.

[Explanation of symbols]

 Reference Signs List 2 Main bimetal 3 Shifter 4, 4a Release lever 8 Movable plate of reversing mechanism 9 Reversing spring 10, 11 Normally closed contact 12 Bearing member 13 Support arm 15, 16 Normally open contact 16a Contact spring 18 Elastic hinge 19 Resin reversing spring

Claims (5)

[Claims] 1. A main bimetal which is bent and displaced by heating of an electric current, a release lever which is driven by a displacement of a shifter interlocked with the main bimetal, a reversing mechanism for opening and closing a contact driven by the release lever, and a contact mechanism. A thermal overload relay in which a reversing mechanism inverts and opens and closes contacts when the amount of bending displacement of the bimetal exceeds a specified value, and the reversing mechanism can swing on a bearing member with the tip of a leg as a fulcrum. The release lever is directly pressed against the plate surface of the movable plate of the reversing mechanism. A thermal overload relay characterized in that it is adapted to perform a reversing operation. 2. A thermal overload relay according to claim 1, wherein a lift-off type contact mechanism for obtaining a contact pressure between the contacts by a movable contact spring is used as the contact mechanism. Load relay. 3. The thermal overload relay according to claim 1, wherein the movable plate of the reversing mechanism and the bearing member are integrally connected via an elastic hinge portion. Type overload relay. 4. The thermal overload relay according to claim 1, wherein the reversing spring of the reversing mechanism is integrally connected to the movable plate as a leaf spring. 5. The thermal overload relay according to claim 3, wherein the reversing mechanism is a resin molded product, and the movable plate,
A thermal overload relay, wherein a bearing member and a reversing spring are integrally formed.