JP2012129156A - Thermal type overload relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the support mechanism of a heater unit in order to maintain its operation characteristics stably without being affected by deformation of a press-fitted support part caused by electric conduction and heat generation in the heater unit accommodated in an enclosure case.SOLUTION: A thermal type overload relay incorporates a heater unit 4 of a main bimetal 7 connected to each phase of a main circuit and a contact make-and-break mechanism linked to the main bimetal via a shifter in an enclosure case 1 made of mold resin and consisting of a case body 2 and a case cover 3. The heater unit 4 is constructed in such a way that the base part of its main bimetal 7 is joined to a support plate 8 by a T joint, and that the case body 2 and the case cover 3 have press-fitting ribs 2d and 3a formed integrally therewith, which sandwiches the support plate 8 of the heater unit 4 in between from front and rear, the front and the rear parts of the support plate 8 being inserted under pressure into the press-fitting ribs 2d and 3a to hold the main bimetal 7 in an upright posture, whereby the posture of the main bimetal 7 is restrained from changing to a direction of curvature as will be caused by relaxation of residual stresses in, or creep deformation of, resin molded articles.

Description

  The present invention relates to a thermal overload relay (thermal relay) used in combination with an electromagnetic contactor, and more particularly to a support structure for a heater unit housed in an outer case thereof.

  The thermal overload relay described above is made of molded resin with a main bimetal heater unit connected to each phase (three-phase circuit) of the main circuit and a contact switching mechanism linked to the main bimetal of each phase via a shifter (See, for example, Patent Document 1).

  The operation of this thermal overload relay is well known, and when an overcurrent exceeding the settling current flows in the main circuit, the main bimetal is bent by the heat generated by the heater conductor, pushing the shifter, and via the release lever. The contact opening / closing mechanism is switched. In the thermal overload relay with a phase loss protection function, a differential amplification link type shifter having a phase loss detection function is employed as the shifter.

  On the other hand, recently, the heat of an assembly structure in which the heater unit is press-fitted and supported by a screwless fixing method that does not use a fixing screw in the unit chamber of each phase that is defined inside the outer case and accommodates the heater unit. Dynamic overload relay products have been developed, and conventional structures are shown in FIGS.

  First, in FIG. 5, reference numeral 1 denotes an outer case made of mold resin, which includes a box-shaped case main body 2 and a case cover 3 covered with an open end face of the case main body 2. As shown, a heater unit 4 corresponding to each of the R, S, and T phases of the three-phase circuit, a contact opening / closing mechanism 5, and a shifter 6 that links between the main bimetal of the heater unit 4 and the operation lever of the contact opening / closing mechanism 5 are incorporated. It is. FIG. 7 is an assembly diagram of the heater unit 4, the output contact mechanism 5, and the shifter 6 (the S-phase heater unit is omitted).

  Here, as shown in FIG. 8, the heater unit 4 has a base portion (lower end side in the figure) of the main bimetal 7 in a slot opening in the center of the plate surface of the support plate 8 (pressed product of electrogalvanized steel sheet). Fitting and T joint joining (for example, fillet welding of the peripheral edge of the bimetal by laser welding), the heater conductor 9 is wound around the peripheral surface of the main bimetal 7 and both ends of the conductor are connected to the plate surface of the main bimetal 7 , And the load-side terminal 10, and an assembly in which a lead conductor 11 connected to the electromagnetic contactor is drawn from the support plate 8. The heater unit 4 is press-fitted into the case and supported in an upright posture by a screwless fixing method that does not use screws as described below with respect to the case body 2 of the outer case 1.

  That is, as shown in FIG. 9 (FIG. 9 is drawn with the top of the unit case 1 shown in FIG. 5 turned upside down), the case main body 2 of the outer case 1 has one heater unit 4 for each phase. Unit chambers 2a corresponding to the respective R, S, T phases to be accommodated are defined on the left and right sides through the partition wall 2b, and each unit chamber 2a has left and right sides corresponding to the support plate 8 of the heater unit 4. A bifurcated press-fitting rib 2c (see FIG. 10B) is formed so as to protrude from the partition wall 2b toward the center of the unit chamber. When the heater unit 4 is assembled into the case main body 2, the support plate 8 is inserted between the press-fitting ribs 2c by inserting from the open end surface of the case main body 2 as shown by the arrows in FIG. , (B), the main bimetal 7 is supported in an upright posture with the plate surface facing left and right.

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

  By the way, recently, due to the recycling of resources, it has become mainstream to manufacture the outer case 1 by changing the material of the outer case 1 from a thermosetting resin to a thermoplastic resin. For this purpose, the support plate 8 of the heater unit 4 is press-fitted between the left and right press-fitting ribs 2c formed in the unit chamber 2a of the case body 2 made of a thermoplastic resin (engineering plastic) as described above, and the main bimetal. In the support structure in which 7 is held in an upright posture, the following problems remain regarding the posture retainability of the main bimetal 7.

  That is, residual stress is produced in the molding process of the molded resin. Further, when the support plate 8 is press-fitted across the press-fitting ribs 2 c protruding from the left and right partition walls 2 b toward the center in the unit chamber 2 a of the case body 2 as described above, In addition to the bending stress generated in the press-fitted rib 2c, in the actual use state of the thermal overload relay, heat generated by energization of the heater conductor 9 is transferred to the press-fitted rib 2c, and creep deformation and stress relaxation peculiar to the thermoplastic resin occur. It becomes like this. Moreover, the deformation amount of the press-fitting rib 2c due to the creep and stress relaxation is not constant, and therefore the tip position of the press-fitting rib 2c holding the support plate 8 from the left and right is relatively displaced in the vertical direction. As a result, the standing posture of the main bimetal 7 slightly tilts in the left-right direction as indicated by the arrows shown in FIG. 10B. As a result, the relative position of the main bimetal 7 to the shifter 6 facing the tip of the main bimetal 7 is initially set. The operating characteristics of the thermal overload relay will fluctuate due to slight displacement from the assembly position.

  Conventionally, in order to deal with such a problem, a current corresponding to an overload is applied to the heater unit 2 in the inspection and adjustment processes performed on the assembled product to reproduce the thermal use environment. After testing, the shifter facing the tip of the main bimetal is trimmed to adjust the operating characteristics as specified.

  However, the assembled products are individually energized one by one and wait until they reach the prescribed annealing temperature before testing the operating characteristics, and then adjusting the operating characteristics by trimming the shifter based on the results. It takes a long working time. For this reason, the production lead time is prolonged, and the advantage of the assemblability of press-fitting and supporting the heater unit 4 to the outer case 1 by a screwless fixing method cannot be fully utilized.

  The present invention has been made in view of the above points, and is a screwless fixing method in which a support plate of a heater unit is press-fitted into a press-fitting rib formed inside an outer case made of mold resin to support a main bimetal in an upright posture. A thermal overload relay with an improved heater unit support structure so that the operation characteristics can be maintained stably without being affected by the stress of the press-fitting ribs caused by energization of the heater unit, heat generation, and creep deformation. The purpose is to provide.

In order to achieve the above object, according to the present invention, a main bimetal heater unit connected to each phase of the main circuit, and a contact opening / closing mechanism linked to the main bimetal of each phase via a shifter are made of a mold resin outer shell. A thermal overload relay housed in a case, wherein the heater unit has a structure in which a base of a main bimetal around which a heater conductor is wound is joined to a support plate with a T-joint, and the heater unit of each phase is oriented in the left-right direction. In what is arranged and accommodated in the outer case consisting of the case body and case cover,
The outer case is integrally formed with a press-fitting rib that sandwiches the support plate of the heater unit from the front and rear for each unit chamber of each phase defined in the outer case, and the front and rear portions of the support plate are formed on the press-fitting rib. And the main bimetal of each phase is supported in an upright posture (Claim 1), and specifically, configured as described below.
(1) The press-fitting rib provided inside the outer case is formed separately in the back of each unit chamber defined in the case body and the inner surface of the case cover so that the support plate is press-fitted and supported from the front and rear. (Claim 2).
(2) In the preceding item (1), the press-fitting ribs formed in the inner part of the case main body are formed such that the left and right side edges thereof are separated from the wall surface of the case main body so as to have flexibility.
(3) At the front and rear end portions of the support plate of the heater unit, a low step portion having a reduced thickness is formed so as to release the pressing contact with the press-fitting ribs and press-fitted and supported (claim 4).

  With regard to the support structure that holds the main bimetal in an upright position by pressing the support plate of the heater unit into the press-fitting rib formed inside the outer case, the support plate is clamped from the front and rear by the press-fitting rib from the conventional structure. As a result, the vertical displacement between the front press-fitting rib and the rear press-fitting rib occurs due to the effects of creep deformation and stress relaxation caused by energization and heat generation of the heater unit. However, since the tip of the main bimetal supported upright on the support plate is not displaced in the bending direction of the bimetal, the operation characteristics of the thermal overload relay can be secured stably. As a result, it is possible to shorten the production lead time by omitting the annealing process of the press-fitting ribs which is performed by energizing the heater unit in the product inspection and adjustment process after assembly as in the conventional structure.

  In addition, the front side press-fitting rib formed on the case body of the outer case has a flexible property in the longitudinal direction of the press-fitting rib by separating the left and right side edges from the partition wall of the unit chamber. The bimetal support plate can be accurately press-fitted and held.

  Furthermore, by forming low stepped portions at the front and rear end portions of the main bimetal support plate, when the support plate is press-fitted into the press-fit rib, an excessive pressing load is applied to the base portion of the press-fit rib so that the rib You can avoid troubles that break.

FIG. 2 is a support structure diagram of a heater unit housed in an outer case of a thermal overload relay according to an embodiment of the present invention, in which (a) is a perspective view of an internal structure in which a part of the outer case is cut; It is principal part sectional drawing of (a). It is an enlarged view of the arrow A part in FIG. 1, and the B part, Comprising: (a) is an enlarged view of the arrow A part, (b) is an enlarged view of the state which removed the heater unit from the press-fitting rib of (a), (C) It is an enlarged view of arrow B part. It is explanatory drawing showing the assembly procedure which accommodates the heater unit in FIG. 1 in the case main body of an outer case. FIGS. 4A and 4B are diagrams illustrating an assembly stage in which a heater unit is press-fitted and supported on the case main body of FIG. 3, and FIGS. 4A and 4B are a side view and a bottom plan view, respectively, with a part of the case main body cut. It is an overhead view of the conventional product of a thermal overload relay. It is a perspective view showing the internal structure of FIG. FIG. 7 is an assembly drawing of internal structural components in FIG. 6. It is an external appearance perspective view showing the structure of the heater unit in FIG. It is explanatory drawing showing the assembly procedure which accommodates the heater unit in FIG. 6 in the case main body of an outer case. It is a figure showing the assembly stage which press-fitted and supported the heater unit to the case main body of FIG. 9, (a) is the perspective view seen from the open surface side of the case main body, (b) is the arrow A section in (a). It is an expanded sectional view.

Embodiments of the present invention will be described below based on the examples shown in FIGS. In addition, in the figure of an Example, the same code | symbol is attached | subjected to the member corresponding to FIGS. 5-10, and the description is abbreviate | omitted.
In the thermal overload relay of the illustrated embodiment, the outer case 1 and the heater unit 4 accommodated therein are basically the same as the conventional structure, but the support structure of the heater unit 4 is as follows. Further, the support plate 8 of the heater unit 4 is changed to be press-fitted and supported from the front and rear.

  That is, in the conventional structure of FIG. 10, the press-fitting ribs 2c for supporting the heater unit 4 inside the case body 2 of the outer case 1 are formed on the left and right sides of the support plate 8 along the partition wall 2b of the unit chamber 2a. On the other hand, in the embodiment of the present invention, as shown in FIG. 1, the back of the unit chamber 2 a defined inside the case body 2 facing the front and rear of the support plate 8, and the case cover 3 have a bifurcated structure. The press-fitting ribs 2d and 3a are formed, and the support plate 8 is sandwiched between the press-fitting ribs 2d and 3a to support the main bimetal 7 in an upright posture. In addition, the enlarged view of the arrow A part and B part of FIG. 1 is shown to Fig.2 (a)-(c).

  Here, with respect to the press-fitting rib 2d formed in the unit chamber of the case body 2 so as to face the front end of the support plate 8, the left and right side edges of the press-fitting rib 3d are shown in FIGS. 2 (b) and 4 (b). A slit g is formed so as to be separated from the wall surface of the partition wall 2b, so that the rib is flexible. On the other hand, the press-fitting rib 3 a formed on the case cover 3 so as to face the rear end of the support plate 8 is formed so as to protrude from the inner surface of the cover toward the unit chamber of the case body 2.

  The support plate 8 is also pressed at its front and rear end portions to form a recessed low step portion 8a as shown in FIG. 1B, and the support plate 8 is pressed against the press-fitting ribs 2d and 3a. When inserted, the step Δh of the low step portion 8a escapes and an excessive pressing load is applied to the base side of the press-fitting ribs 2d and 3a, so that stable press-fitting support is obtained.

  According to the above support structure, the residual stress is relaxed and creep deformation occurs in the press-fitting ribs 2d and 3a that press-support the support plate 8 from the front and back due to the heat generated by energization of the heater unit 4. Even if the postures of the plate 8 and the main bimetal 7 are inclined, the operation characteristics of the thermal overload relay can be maintained in a stable state without being affected by this.

  That is, the posture variation of the main bimetal 7 caused by the stress relaxation of the press-fitting ribs 2d and 3a accompanying the energization and heat generation of the heater unit 4 and the creep deformation is the front-rear direction represented by the arrows in FIG. On the other hand, the main bimetal 7 does not affect the position in the bending direction even if the upright posture is tilted in the front-rear direction, and therefore the relative position with respect to the shifter 6 (see FIG. 7) facing the tip of the main bimetal 7 and the operation characteristics are changed. There is no.

  As a result, in the inspection and adjustment process performed after product assembly, the heater unit is energized and the heat generated from the heater case is annealed and the operation characteristics are checked and adjusted by eliminating the time and effort required for annealing. In addition to shortening the production lead time, it is possible to maintain the operating characteristics stably and improve the reliability of the product even in the long-term use of the thermal overload relay.

DESCRIPTION OF SYMBOLS 1 Outer case 2 Case body 2a Unit chamber 2d Press-fitting rib 3 Case cover 3a Press-fitting rib 4 Heater unit 5 Contact opening / closing mechanism 6 Shifter 7 Main bimetal 8 Support plate 8a Low step part 9 Heater conductor

Claims (4)

A thermal overload relay in which a main bimetal heater unit connected to each phase of the main circuit and a contact opening / closing mechanism linked to the main bimetal of each phase via a shifter is housed in an outer case made of molded resin, The heater unit has a structure in which a base portion of a main bimetal around which a heater conductor is wound is joined to a support plate by a T-joint. In what was held and held,
The outer case is integrally formed with a press-fitting rib that sandwiches the support plate of the heater unit from the front and rear for each unit chamber of each phase defined in the outer case, and the front and rear portions of the support plate are formed on the press-fitting rib. A thermal overload relay, characterized in that the main bimetal of each phase is supported in an upright posture by press-fitting.   The thermal overload relay according to claim 1, characterized in that the press-fitting rib provided in the outer case is divided into a back part of each unit chamber defined in the case body and an inner surface of the case cover. Thermal overload relay.   The thermal overload relay according to claim 2, wherein the press-fitting ribs formed in the inner part of the case body have left and right side edges separated from the wall surface of the case body. relay.   The thermal overload relay according to any one of claims 1 to 3, wherein a low stepped portion is formed at the front and rear ends of the support plate of the heater unit to release the pressing contact with the press-fitting rib. Thermal overload relay.