JP5051184B2 - Thermal overload relay - Google Patents

Description

  The present invention relates to a bimetal heater unit support structure mounted on a thermal overload relay (thermal relay) used in combination with an electromagnetic switch or the like.

  First, regarding the thermal overload relay described above (for a three-phase circuit), a conventional structure (see, for example, Patent Document 1) is shown in FIGS. In the figure, 1 is a heater unit corresponding to each of the R, S, and T phases in which the heater conductor 3 is wound around the main bimetal 2, 1 a is a mounting bracket provided at the upper end of the heater unit 1, and 4 is a main bimetal for each phase. 2 is a shifter that is linked to the front end (output end) across 2 and 5 is a release lever facing the end of the shifter 4, 6 is an output contact mechanism that opens and closes by driving the release lever 5, and 7 is release A reversing spring linked between the lever 5 and the output contact mechanism 6, 8 an adjustment link linked between the release lever 5 and the adjustment dial 9, 10 a reset button, and 11 a lead of a main circuit connected to the electromagnetic switch A conductor (bar conductor), 12 is a load side terminal, and 13 is an external terminal of an output contact. These components are assembled in an outer case 14 of a molded resin molded product to constitute a thermal overload relay.

Here, the outer case 14 is a molded resin molded product, in which the heater unit 1 for each phase of R, S, T is arranged on the left and right, and a unit chamber 14a for individually accommodating each element, and an output contact mechanism 6 are provided. A chamber for accommodating the chamber and a chamber for accommodating an operation mechanism (such as the release lever 5) that links the heater unit 1 and the output contact mechanism 6 are defined, and the chambers are separated by a partition wall 14b. . The heater unit 1 is fixed to the back wall of the unit chamber 14a with screws via a mounting bracket 1a.
The operation of the thermal overload relay configured as described above is well known. When an overcurrent exceeding the settling current flows through the main circuit, the main bimetal 2 is bent and displaced by the heat generated by the heater conductor 3, and the shifter 4 is pushed. The output contact mechanism 6 is switched through the release lever 5 and the reversing spring 7. In the thermal overload relay (2E thermal relay) with the phase loss protection function, an operation amplification link mechanism having a phase loss detection function is employed as the shifter 4.

On the other hand, recently, as shown in FIG. 6, a heater unit 1 for each phase is placed in the outer case 14 as a new type with a downsized thermal overload relay and improved assembly of the heater unit. An assembly in which the heater unit 1 is press-fitted and supported to the outer case 14 without using a fixing screw after defining a unit chamber 14a for accommodating each element and a chamber 14c for accommodating the output contact mechanism 6 and the operation unit on the left and right sides. Thermal overload relays with a structure have been developed.
Next, a single structural diagram of the heater unit 1 in FIG. 6 is shown in FIG. 7, and an external view of the outer case 14 is shown in FIG. First, in the heater unit 1 shown in FIG. 7, the base (lower end side) of the main bimetal 2 is fitted into a slot opening in the center of the plate surface of the support plate 15 (pressed product of electrogalvanized steel sheet) to form a T joint. In addition to joining (for example, fillet-welding the periphery of the bimetal by laser welding), the heater conductor 3 is wound around the peripheral surface of the main bimetal 2 and both ends of the conductor are connected to the plate surface of the main bimetal 2 and the load side terminal 12. Further, it is configured by an assembly in which the lead conductor 11 of the main circuit is joined to the support plate 15.

  Further, the outer case 14 shown in FIG. 8 protrudes from the left and right partition walls 14b toward the center on the bottom side of the unit chamber 14a corresponding to each phase of R, S, and T that accommodates the heater unit 1. A rib 14d is provided, and when the heater unit 1 is assembled, the support plate 15 is pushed into the rib 14d and the bottom wall of the outer case 14 from the front of the outer opening of the outer case 14 and is press-fitted. The bimetal 2 is supported in a vertical upright posture.

Japanese Patent Laying-Open No. 2005-116370 (FIG. 3)

As for the outer case 14 of the thermal overload relay, recently, it has become the mainstream to change the material of the outer case from a thermosetting resin to a thermoplastic resin due to environmental, resource recycling, and productivity problems. ing.
By the way, the outer case 14 is made of a thermoplastic engineering plastic, and the support plate 15 of the heater unit 1 is press-fitted to the lower surface of the outer casing 14 across the ribs 14d provided on the left and right partition walls 14b of the unit chamber 14a. In the assembly structure in which the main bimetal 2 is held in an upright posture, the following problems remain regarding the support function of the heater unit 1.
That is, the width and thickness of the support plate are set so that the margin of press-fitting of the support plate 15 with respect to the opening of the unit chamber 14a and the rib 14d is about 0 to 0.2 mm, and the heater is added to the unit chamber 14a of the outer case 14 In the assembled state in which the unit 1 is press-fitted and supported, residual stress due to the press-fitting of the support plate 15 is applied to the ribs 14d (cantilever structure) protruding from the left and right partition walls 14b toward the center, and the shifter 4 ( 5), the mechanical reaction force acting on the tip of the main bimetal 2 from the switching contact mechanism and the stress caused by the heat transfer from the heater unit 1 due to the heat generated by the heater conductor 3 are added for a long time. During actual use, the rib 14d has a creep deformation characteristic of the thermoplastic resin (the thermoplastic resin is inferior to the thermosetting resin in creep resistance). ) Occurs. For this reason, the position of the main bimetal 2 is tilted and the bimetal tip position linked to the shifter 4 (see FIG. 5) is slightly deviated from the position adjusted and set at the time of assembly of the thermal relay. The operating characteristics of the thermal relay may fluctuate with respect to the value.

Further, when the rib 14d is press-fitted so that the plate surface of the support plate (flat plate) 15 is pressed against the entire length of the lower surface of the rib 14d with a flat cross section having the same thickness from the root to the tip as shown in the drawing, A pushing load due to the reaction force is applied, and the residual stress becomes the highest at the base portion of the rib 14d. In addition, when the press-fitting allowance increases due to the dimensional variation of the support plate 15 and the like, the residual stress of the ribs also increases. As a result, cracks occur at the roots of the ribs 14d and the heater unit 1 can be maintained in a normal upright posture. There is also a risk of disappearing.
The present invention has been made in view of the above points.For ribs protruding from the left and right partition walls of the unit chamber of the outer case so as to press-fit and support the support plate of the heater unit, the residual stress of the rib accompanying the press-fitting of the support plate is measured. Reducing the creep deformation and maintaining the main bimetal in an upright posture even in long-term actual use, and improving the reliability of the heater unit support structure for a thermal overload relay with high reliability The purpose is to provide.

To achieve the above object, according to the present invention, a main bimetal heater unit connected to each phase of the main circuit, and an output contact mechanism linked to the main bimetal of each phase via a shifter and a release lever The thermal overload relay is configured to be mounted on the heater unit, and the heater unit has a structure in which the base of the main bimetal around which the heater conductor is wound is joined to the center of the support plate by a T joint, A plurality of unit chambers are arranged to house the heater units of each phase side by side on the left and right sides, and ribs projecting from the left and right side walls are provided on the bottom side of the unit chambers. In what supported the main bimetal in an upright posture by press-fitting the support plate on the lower surface side,
The plate surface contact position of the support plate with respect to the rib is limited to the front end side of the rib so as to be press-fitted and supported (claim 1), and specifically, configured in the following manner.
(1) In the above configuration, a convex stepped portion that bulges toward the plate surface of the support plate is formed on the leading end side of the rib, and the plate surface of the support plate is pressed against the convex stepped portion to erect the heater unit. It is press-fitted and supported in the posture (claim 2).
(2) In the configuration described above, a convex stepped portion that bulges toward the tip end of the rib is formed in the central region of the plate surface of the support plate, and the heater unit is erected by pressing the convex stepped portion against the tip of the rib. It is press-fitted and supported in the posture (claim 3).
(3) In the above-described configuration, the left and right width dimensions of the support plate are set to be smaller than the opening of the unit chamber, and a stepped pedestal for positioning and holding the support plate at the center of the chamber is provided on the bottom side of the unit chamber so as to face the rib. Then, a support plate is press-inserted between the pedestal and the rib to press-support the heater unit in an upright position.

  With the above configuration, in the assembled state in which the heater unit is press-fitted and supported in the unit chamber of the outer case, the support plate of the heater unit abuts only on the tip portion of the rib and is separated from the root portion of the rib. A pressing load is not directly applied to the root portion from the support plate. Therefore, in the rib of the cantilever structure, the intermediate portion between the tip portion and the root portion is bent to receive the press-fitting load, and the stress applied to the root portion is reduced as compared with the conventional assembly structure. As a result, even if the material of the outer case is made of thermoplastic resin, the amount of creep deformation that occurs in the rib with long-term use can be reduced, and the upright posture set at the beginning of assembly of the heater unit can be maintained. This improves the reliability of the thermal overload relay by maintaining stable overcurrent protection operating characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of 1st Example by this invention, (a) is an external appearance perspective view of the assembly state which assembled | attached the heater unit to the unit chamber of an outer case, (b) is an enlarged front view of the A section in (a). is there. 2A and 2B are supplementary explanatory views of FIG. 1, in which FIG. 1A is a perspective view illustrating a main part structure in a unit chamber, and FIG. 1B is a perspective view of an assembled state corresponding to FIG. It is a block diagram of 2nd Example by this invention, (a) is an external appearance perspective view of the assembly state which mounted the heater unit in the unit chamber of an outer case, (b) is an enlarged front view of the A section of (a), (C) is a perspective view showing the principal part structure in a unit chamber, (d) is a perspective view of the assembly state corresponding to (b). It is a block diagram of 3rd Example by this invention, (a) is the external appearance perspective view of the assembly state which assembled | attached the heater unit to the unit chamber of an outer case, (b) is an enlarged front view of the A section of (a), (C) is a perspective view showing the principal part structure in a unit chamber, (d) is a perspective view of the assembly state corresponding to (b). It is an assembly structure figure of the thermal overload relay of the conventional product, (a) is a front view, (b) is a side view. FIG. 6 is an overhead view of an assembled state in which a heater unit of a new type outer case different from FIG. It is a perspective view showing the assembly structure of the heater unit single-piece | unit in FIG. It is a perspective view showing the state just before incorporating the heater unit in FIG. 6 in an outer case.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on the examples shown in FIGS.

First, FIG. 1 and FIG. 2 show the configuration of Embodiment 1 according to claim 2 of the present invention.
In this embodiment, as in the conventional structure of FIG. 6, with respect to the rib 14d formed to protrude from the left and right partition walls 14b of the unit chamber 14a of the outer case 14 toward the center, a convex stepped portion is formed on the lower surface side of the tip of each rib 14d. 14d-1. When the heater unit 1 is press-fitted from the front of the front of the unit chamber 14a, the support plate 15 is pressed against the convex step portion 14d-1 as shown in FIG. It is trying to support the press fit. Reference numeral 14e denotes a pedestal of a support plate receiver provided at the bottom of the unit chamber 14a so as to face the lower side of the rib 14d, and the support plate 15 is sandwiched between the rib 14d and the pedestal 14e.
With the above configuration, in the state in which the heater unit 1 is press-fitted and supported in the unit chamber 1a of the outer case 14 as shown in FIG. 1A, the support plate 15 contacts only the convex step portion 14d-1 with respect to the rib 14d. In contact with each other (see FIGS. 1B and 2B), the root portion of the rib 14d and the both ends of the support plate 15 are separated from each other. Therefore, the pressing load applied to the rib 14d by the pressing reaction force of the support plate 15 is concentrated on the P portion shown in FIG. 1B, and the rib 14d (cantilever beam) is brought into contact with the root portion by this pressing load. The intermediate portion between them is bent upward with springiness to support the support plate 15. Thereby, the residual stress which arises in the root part of rib 14d by press-fitting of support plate 15 becomes small. In addition, the amount of creep deformation over time caused by the reaction force from the switching mechanism of the thermal overload relay and the heat transfer from the heater unit 1 is reduced, and the heater unit 1 is set at the beginning of assembly. Stable maintenance of upright posture. As a result, stable operation characteristics can always be secured even in actual use of the thermal overload relay for a long period of time, and the reliability of the product can be improved.

Next, FIG. 3 shows the configuration of Embodiment 2 according to claim 3 of the present invention. In this embodiment, contrary to the first embodiment described above, a convex step portion 15a bulging toward the tip side of the rib 14d is formed in the central area of the upper surface of the support plate 15 of the heater unit 1, When the heater unit 1 is assembled into the unit chamber 14a, the convex step portion 15a of the support plate 15 is pushed into the tip end portion of the rib 14d so that the heater unit 1 is press-fitted and held in an upright posture.
According to this configuration, as shown in FIG. 3B, the support plate 15 abuts only on the tip portion of the rib 14d (P portion in FIG. 3B) and is separated from the root portion of the rib 14d. Press-fit in the state. Therefore, as described in the first embodiment, the load due to the press-fitting of the support plate 15 is applied to the tip portion of the rib 14d, thereby reducing the residual stress at the base portion of the rib 14d, and the thermal overload. It is possible to reduce the creep deformation of the rib 14d due to the long-term actual use of the relay and maintain stable operation characteristics.

Next, FIG. 4 shows the configuration of Embodiment 4 according to claim 4 of the present invention. In this embodiment, the width D of the support plate 15 of the heater unit 1 is set to be smaller than the opening of the unit chamber 14a, and the support plate 15 is positioned and held at the center position in the room. Stepped pedestals 14 f are formed on the bottom side on the left and right sides, and the interval L between the stepped portions 14 f-1 of each stepped pedestal 14 f is set in accordance with the lateral width D of the support plate 15.
When the heater unit 1 is assembled in the unit chamber 14a of the outer case 14, the support plate 15 is aligned with the stepped portion 14f-1 of the stepped pedestal 14f and press-fitted between the rib 14d from the front ( (See FIG. 4E) The heater unit 1 is press-fitted and held in an upright position.
Thereby, in the press-fit support state of the heater unit 1, as shown in FIG. 4B, the support plate 15 is held in contact with only the tip end portion of the rib 14d. Therefore, as in the first and second embodiments, the residual stress and creep deformation applied to the base of the rib 14d can be reduced, and the operating characteristics of the thermal overload relay can be stably maintained.

DESCRIPTION OF SYMBOLS 1 Heater unit 2 Main bimetal 14 Outer case 14a Unit chamber 14b Partition wall 14d Rib 14d-1 Convex step 14f Stepped base 15 Support plate 15a Convex step

Claims (4)

This is a thermal overload relay that consists of a main bimetal heater unit connected to each phase of the main circuit and an output contact mechanism linked to each phase main bimetal via a shifter and release lever in the outer case. The heater unit has a structure in which the base of the main bimetal around which the heater conductor is wound is joined to the center of the support plate by a T-joint, and the outer case houses the heater units of each phase side by side. A plurality of unit chambers are defined, and ribs protruding from the left and right side walls are provided on the bottom side of the unit chambers. The support plate is press-fitted on the lower surface of the ribs so that the main bimetal stands upright. In what supported the posture,
A thermal overload relay, wherein the plate surface contact position of the support plate with respect to the rib is press-fitted and supported on the tip side of the rib.   The thermal overload relay according to claim 1, wherein a convex step portion that bulges toward the plate surface of the support plate is formed on a tip side of the rib, and the plate surface of the support plate is formed on the convex step portion. A thermal overload relay characterized by pressing and supporting the heater unit in an upright position.   The thermal overload relay according to claim 1, wherein a convex step portion that bulges toward a tip end side of the rib is formed in a central area of the plate surface of the support plate, and the convex step portion is formed at the tip end of the rib. A thermal overload relay characterized by pressing and supporting the heater unit in an upright position. 2. The thermal overload relay according to claim 1, wherein the left and right width dimensions of the support plate are set smaller than the opening of the unit chamber, and the support plate is placed in the center of the room at the bottom side of the unit chamber so as to face the rib. A thermal overload relay, wherein a stepped base for positioning and holding is formed, and a heater plate is press-fitted and supported in an upright position by inserting a support plate between the base and the rib.

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