Thermal overload relay

Abstract

In the present invention, a trip operation of a reversal mechanism (24) is performed by a differential lever (23) being pivoted by being pushed against a push shifter (22a) from the outside in the radial direction with a position at which the differential lever engages with a pull shifter (22b) as the pivot center, and a compensation bimetal contact surface (74) that is provided to the differential lever displacing a compensation bimetal (31). In addition, there is provided a compensation bimetal displacement amplifying means that amplifies the displacement of the compensation bimetal by, in an overloaded state in which an overcurrent flows, stopping of the displacement of the pull shifter and a subsequent displacement of the push shifter, whereby the differential lever is pivoted.

Description

[Technical Field]

[0001] The present invention relates to a thermal overload relay. [Background technology]

[0002] When an overcurrent continues to flow, a thermal overload relay trips by bending the bimetal due to heat, and protects the main circuit from overload by shutting off the electromagnetic contactor or molded case circuit breaker. In the thermal overload relay of Patent Document 1, when the bimetal arranged between multiple partitions on the inside of the case is heated by a heater and bent, the push shifter and pull shifter are displaced, causing the differential lever to move, and the displacement of the differential lever is transmitted to the compensating bimetal of the reversing mechanism, resulting in a trip state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-165492 Summary of the Invention [Problem to be solved by the invention]

[0004] In the thermal overload relay of Patent Document 1, the bimetal may bend and come into contact with a partition wall provided inside the case before the relay starts tripping. In an overload state (a state in which an overcurrent continues to flow), the bimetal is hot, and there is a risk that the partition wall that the hot bimetal comes into contact with may be burned. The object of the present invention is to provide a thermal overload relay that can initiate tripping in an overload state early, thereby reducing the risk of damage caused by the high-temperature bimetal coming into contact with the case partition. [Means for solving the problem]

[0005] A thermal overload relay according to one aspect of the present invention includes a case containing multiple partitions, multiple bimetals individually housed between the partitions, a push shifter and a pull shifter arranged to cover the ends of the partitions and engage with the free ends of the bimetals and displace when the bimetals bend, a differential lever that is pushed and driven by the displacement of the push shifter and the pull shifter, and a reversing mechanism that transmits the driven movement of the differential lever to the compensating bimetal to reverse the contacts and perform a tripping operation. The differential lever rotates when pushed from the radial outside by the push shifter around a position where it engages with the pull shifter, and the compensating bimetal contact surface on the differential lever displaces the compensating bimetal, thereby tripping the reversing mechanism. Furthermore, a compensating bimetal displacement amplification means is provided that, in an overload state where an overcurrent is flowing, first stops the displacement of the pull shifter, and then the push shifter displaces, rotating the differential lever and amplifying the displacement of the compensating bimetal. [Effects of the Invention]

[0006] According to the thermal overload relay of the present invention, by performing a tripping operation in an overload state early, the risk of damage caused by the high-temperature bimetal coming into contact with the partition wall of the case can be reduced. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing the inside of a thermal overload relay according to an embodiment of the present invention with the cover removed. FIG. [Figure 2] This is an oblique view showing the inside of a thermal overload relay from the side where the adjustment dial is provided. [Figure 3] FIG. 2 is a perspective view showing the inside of the thermal overload relay from the side where the push shifter, pull shifter, and differential lever are arranged. [Figure 4] FIG. 10 is a diagram showing the positions of the push shifter, pull shifter, and differential lever in a thermal overload relay under normal conditions. [Figure 5] FIG. 2 is a perspective view showing a differential lever according to an embodiment. [Figure 6] 1A and 1B are a side view and a cross-sectional view showing a differential lever according to an embodiment; [Figure 7] This figure shows the state in which the push shifter and pull shifter are displaced in an overload state in a thermal overload relay, and the differential lever is subsequently moved. DETAILED DESCRIPTION OF THE INVENTION

[0008] Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc., may differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Furthermore, it goes without saying that the drawings may include parts with different dimensional relationships and ratios. Furthermore, the embodiments shown below are merely examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the materials, shapes, structures, arrangements, etc. of the components to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims. In the following description, the three mutually orthogonal directions will be referred to as the vertical direction, the width direction, and the depth direction for the sake of convenience.

[0009] [Configuration of thermal overload relay] 1 to 3 are diagrams showing the inside of a case 12 of a thermal overload relay 11 according to one embodiment of the present invention with a cover (not shown) removed. As shown in FIG. 1, the thermal overload relay 11 has a case 12 inside which are provided three-phase U, V, and W bimetal elements 21U, 21V, and 21W, a shifter 22, a differential lever 23, a reversing mechanism 24, and a reset rod 25. The three-phase bimetals 21U, 21V, and 21W are formed as plates extending in the depth direction and aligned in the vertical and depth directions, with the front end in the depth direction being a fixed end and the rear end being a free end. Each bimetal 21 is connected at its front end in the depth direction to a main terminal and at its rear end in the depth direction to one end of a heater 26. The heater 26 is wound around the three-phase bimetals 21U, 21V, and 21W, and its other end is connected to a connection terminal 27 at its front end in the depth direction. The connection terminal 27 is connected to an electromagnetic contactor (not shown). The three-phase bimetals 21U, 21V, and 21W are normally straight, but in an overload state (a state in which an overcurrent continues to flow), the free ends 21Ua, 21Va, and 21Wa bend toward the other widthwise side and push the shifter 22.

[0010] The reversing mechanism 24 is a mechanism that reverses the contacts when an overcurrent is detected, i.e., closes the a-contact and opens the b-contact, and as shown in Figures 1 and 2, it is equipped with a compensating bimetal 31, a release lever 32, a tension spring 33, a movable plate 34, a leaf spring 35, an interlocking plate 36, and an adjustment dial 37. The compensating bimetal 31 extends in the depth direction and is formed in the shape of a flat plate along the depth direction and the vertical direction, with the front side in the depth direction fixed to the release lever 32 and the back side in the depth direction being the free end which engages with the differential lever 23. The release lever 32 extends in the depth direction and is formed in the shape of a plate along the depth direction and the vertical direction, and is rotatably supported by a support shaft along the vertical direction, with the rear side in the depth direction in contact with the tension spring 33. The tension spring 33 pulls the movable plate 34 toward the rear side in the depth direction. An adjustment dial 37 for setting the settling current is provided on the case 12, and the end portion of the release lever 32 on the front side in the depth direction is engaged with the circumferential surface of an eccentric cam 37a provided integrally with the adjustment dial 37 on the rear side in the depth direction. When the adjustment dial 37 is turned, the free end of the compensating bimetal 31 is displaced in the width direction via the release lever 32 which is engaged with the circumferential surface of the eccentric cam 37a.

[0011] The movable plate 34 is flat and extends in the depth and vertical directions, and its near side in the depth direction can be displaced in the width direction with its far side in the depth direction as a fulcrum. The upright position of the movable plate 34 serves as a fulcrum, and when a force acts on one or the other side in the width direction, the movable plate 34 tilts to one or the other side in the width direction due to the tension of the tension spring 33. Normally, the movable plate 34 tilts to one side in the width direction, but when an overload occurs, it is pushed by the release lever 32 via the compensating bimetal 31, causing it to tilt to the other side in the width direction. The far side in the depth direction of the movable plate 34 is connected to one of the auxiliary terminals, and a movable contact is formed on its near side in the depth direction.

[0012] The leaf spring 35 is a flat plate extending in the depth direction and aligned in the depth and vertical directions, with the rear side in the depth direction connected to the other auxiliary terminal and a fixed contact formed on the front side in the depth direction facing the movable plate 34. Under normal conditions, the movable contact of the movable plate 34 is separated from the fixed contact of the leaf spring 35, but when an overload occurs, the movable plate 34 tilts to the other side in the width direction, causing the movable contact of the movable plate 34 to come into contact with the fixed contact of the leaf spring 35. These fixed contact and movable contact constitute an a-contact, and a trip state is achieved when the a-contact is closed.

[0013] Interlocking plate 36 is formed in the shape of a plate extending in the width and depth directions, is rotatably supported by a vertical support shaft, and its rear side in the depth direction engages with movable plate 34. Interlocking plate 36 rotates in conjunction with movable plate 34, thereby opening and closing the contacts on the back side of interlocking plate 36 (not shown in FIG. 1). That is, under normal circumstances, the movable contact is in contact with the fixed contact, but when an overload occurs, interlocking plate 36 rotates, causing the movable contact to separate from the fixed contact. These fixed contact and movable contact constitute a b-contact, and a trip state is achieved when the b-contact opens.

[0014] The reset rod 25 is an operating element for recovering from a tripped state, and is formed in a generally cylindrical shape with its axis extending in the depth direction. It is disposed on the other side of the case 12 in the vertical direction and the other side of the width direction. The reset rod 25 is supported by the case 12 so as to be displaceable in the depth direction and rotatable about its axis, and is further biased toward the front side in the depth direction by a leaf spring (not shown) extending in the vertical direction. The reset rod 25 has an initial position, a manual reset position, and an automatic reset position. The initial position is a position where the front side in the depth direction protrudes beyond the case 12. The manual reset position is a position where the reset rod 25 is simply pushed toward the rear side in the depth direction from the initial position. The automatic reset position is a position where the reset rod 25 is pushed toward the rear side in the depth direction from the initial position and rotated approximately 90 degrees clockwise as viewed from the front side in the depth direction, thereby maintaining the position in the depth direction.

[0015] When the reset rod 25 is pushed toward the rear in the depth direction in the tripped state, the leaf spring 35 and movable plate 34 are pushed toward one side in the width direction by the rear end in the depth direction, and so if the overload is resolved, the contact a opens again and the contact b closes. On the other hand, if the reset rod 25 is pushed toward the rear in the depth direction in the tripped state and turned clockwise by approximately 90 degrees as viewed from the front side in the depth direction, the reset rod 25 maintains its position in the depth direction. Then, the leaf spring 35 and movable plate 34 are pushed toward one side in the width direction by the rear end in the depth direction, and so if the overload is resolved, the contact a automatically opens again and the contact b closes.

[0016] 3, the shifter 22 is composed of an insulating push shifter 22a and a pull shifter 22b that are supported by the case 12 so that their thicknesses are flush with each other. When an overload condition occurs, the three-phase bimetals 21U, 21V, and 21W bend, and the free ends 21Ua, 21Va, and 21Wa move to the other side in the width direction, displacing the push shifter 22a to the other side in the width direction. Along with the displacement of the push shifter 22a, the pull shifter 22b and the differential lever 23 also displace. When a phase loss occurs, the unbent bimetal of the phase with the missing phase restricts the displacement of the pull shifter 22b, so that the push shifter 22a displaces in the same way as when an overload condition occurs.

[0017] 3, the case 12 is formed with partition walls 41 to 43 and a girder plate 44, which are arranged at a predetermined interval in the width direction inside the case 12. On the other vertical side of the partition walls 41 and 43, protrusions 45a1 and 45a2 are aligned along the width direction and formed to protrude in a columnar shape. On one vertical side of the partition walls 41 and 43, protrusions 45b1 and 45b2 are aligned along the width direction and formed to protrude in a columnar shape.

[0018] 4, the push shifter 22a has an elongated hole 51 formed on one side in the width direction, into which the protrusion 45a1 of the partition wall 41 fits, and an elongated hole 52 formed on the other side in the width direction, into which the protrusion 45b2 of the partition wall 42 fits. The push shifter 22a also has engagement pieces 53 to 55 formed on one side in the vertical direction, and a tip 56 formed to protrude on the other side in the width direction opposite to the engagement piece 55. 4, the pull shifter 22b has an elongated hole 58 formed on one widthwise side, into which the protrusion 45b1 of the partition wall 41 fits, and an elongated hole 59 formed on the other widthwise side, into which the protrusion 45b2 of the partition wall 43 fits. Furthermore, the pull shifter 22b has engagement pieces 60 to 62 formed on the other vertical side, and an engagement groove 65 formed on the other widthwise side of the pull shifter 22b that opens on the other vertical side and extends to one side.

[0019] FIG. 5 is a perspective view showing the differential lever 23, FIG. 6(a) is a view of the differential lever 23 as seen from the other side in the width direction, and FIG. 6(b) is a cross section taken along line AA in FIG. 6(a). The differential lever 23 has a pair of opposing plates 70, 71 formed on one side in the vertical direction. The pair of opposing plates 70, 71 are formed as flat plates extending in the vertical and width directions, face each other while being spaced apart in the depth direction, and are connected by a cylindrical support shaft 72 extending in the depth direction. The distance between the pair of opposing plates 70, 71 is slightly greater than the thickness of the girder plate 44 of the case 12, and the diameter of the support shaft 72 is slightly smaller than the groove width of the engagement groove 65 of the pull shifter 22b. The other side in the vertical direction of the differential lever 23 has an end surface 73 that is a flat surface extending in the vertical and depth directions and facing one side in the width direction. In addition, the other side in the vertical direction of the differential lever 23 has a compensating bimetal contact surface 74 that is a curved surface extending in the depth direction and convex toward the other side in the width direction.

[0020] 4, push shifter 22a is disposed so as to be displaceable in the width direction by fitting elongated hole 51 onto protrusion 45a1 of partition wall 41 of case 12 and fitting elongated hole 52 onto protrusion 45a2 of partition wall 43. Also, engagement piece 53 of push shifter 22a engages with free end 21Ua of U-phase bimetal 21U from the other side in the width direction, and engagement piece 54 engages with free end 21Va of V-phase bimetal 21V from the other side in the width direction. Engagement piece 55 engages with free end 21Wa of W-phase bimetal 21W from the other side in the width direction. 4, pull shifter 22b is disposed so as to be displaceable in the width direction by fitting elongated hole 58 onto protrusion 45b1 of partition wall 41 of case 12 and elongated hole 59 onto protrusion 45b2 of partition wall 43. Furthermore, engagement piece 60 of pull shifter 22b engages with free end 21Ua of U-phase bimetal 21U from one side in the width direction, engagement piece 61 engages with free end 21Va of V-phase bimetal 21V from one side in the width direction, and engagement piece 62 engages with free end 21Wa of W-phase bimetal 21W from one side in the width direction.

[0021] As shown in Fig. 4, the differential lever 23 is pivotally supported on the case 12 about the support shaft 72 such that a pair of opposing plates 70, 71 sandwich the digit plate 44 of the case 12 and the support shaft 72 fits into the engagement groove 65. The end face 73 facing one side in the width direction of the differential lever 23 engages with the tip 56 of the engagement piece 55 of the push shifter 22a. The free end of the compensation bimetal 31 of the inversion mechanism 24 engages with the compensation bimetal contact surface 74 facing the other side in the width direction of the differential lever 23.

[0022] Then, as shown in Fig. 4, in the normal state where the three-phase bimetals 21U, 21V, 21W are not curved, the push shifter 22a provides a gap of dimension D1 between the protrusion 45a1 of the partition wall 41 fitted into the long hole 51 and the opening edge 51a on one side in the width direction of the long hole 51. Also, in the normal state, the pull shifter 22b provides a gap of dimension D2 between the protrusion 45b1 of the partition wall 41 fitted into the long hole 58 and the opening edge 58a on one side in the width direction of the long hole 58. Note that the pull shifter 22b is formed with a long hole 59 into which the protrusion 45b2 of the partition wall 43 also fits on the other side in the width direction, and a gap of dimension D2 is provided between the protrusion 45b2 and the opening edge on one side in the width direction of the long hole 59 in the same manner as the relationship between the long hole 58 and the protrusion 45b1 described above. Since they have the same function, only the engagement state of the long hole 58 and the protrusion 45b1 will be described in the following explanation.

[0023] Here, in this embodiment, when the three-phase bimetals 21U, 21V, 21W are maximally curved in the overload state, the displacement amount of the free ends 21Ua, 21Va, 21Wa (hereinafter referred to as the overload bimetal displacement amount) is defined as D3. The bimetal displacement amount D3 in this overload state is set to be smaller than the gap D1 of the push shifter 22a in the normal state (D3 < D1). Also, the bimetal displacement amount D3 in the overcurrent state is set to be larger than the gap D2 of the pull shifter 22b in the normal state (D3 > D2). Therefore, the relationship among the bimetal displacement amount D3 in the overload state, the gap D1 of the push shifter 22a in the normal state, and the gap D2 of the pull shifter 22b in the normal state is set as in the following formula (1). D2 < D3 < D1 …… Formula (1)

[0024] Furthermore, when the adjustment dial 37 is turned toward a larger scale (the direction in which the settling current increases), the release lever 32, which engages with the circumferential surface of the eccentric cam 37a, rotates clockwise, causing the free end of the compensating bimetal 31 connected to the release lever 32 to move toward the other side in the width direction. The compensating bimetal 31 indicated by the dashed line in FIG. 4 is the position at which the compensating bimetal 31 is displaced to the other side in the width direction by the greatest extent when the adjustment dial 37 is turned to the maximum scale (the scale at which the settling current is maximized). When the adjustment dial 37 is turned to the maximum scale, the compensating bimetal 31 is displaced toward the other side in the width direction by a dimension D4 from the reference position of the compensating bimetal 31 indicated by the solid line. This dimension D4 is referred to as the maximum displacement of the compensating bimetal. In this embodiment, the relationship between the maximum displacement amount D4 of the compensating bimetal and the gap D2 of the pull shifter 22b in the normal state is set as shown in the following formula (2). D4 < D2 ...Formula (2)

[0025] [Operation] Next, the main operations of this embodiment will be described with reference to FIGS. 4, the push shifter 22a and the pull shifter 22b are located on one side in the width direction, and the compensating bimetal 31 is disposed in a state of extending in the vertical direction. The push shifter 22a provides a gap D1 between the protrusion 45a1 of the partition wall 41 fitted into the elongated hole 51 and the opening edge 51a on one side in the width direction of the elongated hole 51, and the pull shifter 22b provides a gap D2 between the protrusion 45b1 of the partition wall 41 fitted into the elongated hole 58 and the opening edge 58a on one side in the width direction of the elongated hole 58.

[0026] When an overcurrent starts to flow, the three-phase bimetals 21U, 21V, and 21W are curved by the heating of the heater 26, and the free ends 21Ua, 21Va, and 21Wa move toward the other side in the width direction. Due to the movement of the free ends 21Ua, 21Va, and 21Wa toward the other side in the width direction, the engaging pieces 53 to 55 of the push shifter 22a are pushed to the other side in the width direction and displaced. Due to the displacement of the push shifter 22a, the protrusion 45a1 approaches the opening edge 51a on one side in the width direction of the long hole 51, and the protrusion 45a2 approaches one side in the width direction of the long hole 52. Also, along with the displacement of the push shifter 22a, the pull shifter 22b is also displaced to the other side in the width direction. Due to the displacement of the pull shifter 22b, the protrusion 45b1 approaches the opening edge 58a on one side in the width direction of the long hole 58. Also, the differential lever 23 is displaced to the other side in the width direction together with the push shifter 22a and the pull shifter 22b. Due to the displacement of this differential lever 23, the free end of the compensation bimetal 31 engaged with the compensation bimetal contact surface 74 of the differential lever 23 is also displaced to the other side in the width direction.

[0027] And, as shown in FIG. 7, in an overload state where the overcurrent continues to flow, the push shifter 22a and the pull shifter 22b that continue to be displaced simultaneously to the other side in the width direction have a smaller gap D2 of the pull shifter 22b than the gap D1 of the push shifter 22a (D2 < D1). Therefore, the protrusion 45b1 engages with the opening edge 58a on one side in the width direction of the long hole 58 of the pull shifter 22b, and the displacement of the pull shifter 22b to the other side in the width direction stops. Although the displacement of the pull shifter 22b stops, the push shifter 22a continues to be displaced to the other side in the width direction due to the movement of the free ends 21Ua, 21Va, and 21Wa to the other side in the width direction. Then, the tip 56 of the push shifter 22a pushes the end face 73 of the differential lever 23 to the other side in the width direction. The differential lever 23 rotates counterclockwise around the support shaft 72 engaged with the engaging groove 65 of the pull shifter 22b whose displacement has stopped, and the compensation bimetal contact surface 74 displaces the free end of the compensation bimetal 31 to the other side in the width direction. As a result, the reversing mechanism 24 becomes a trip state where the a contact is closed and the b contact is opened because the free end side of the compensation bimetal 31 is displaced to the other side in the width direction.

[0028] [Action and effect] Next, the effects of this embodiment will be described. In an overload state, when the push shifter 22a and the pull shifter 22b continue to simultaneously displace to the other side in the width direction, the protrusion 45b1 of the partition wall 41 engages with the opening edge 58a on one side of the elongated hole 58 in the width direction of the pull shifter 22b, stopping the displacement of the pull shifter 22b. The push shifter 22a continues to displace to the other side in the width direction, and the tip 56 of the push shifter 22a presses the end face 73 of the differential lever 23. This pressing action of the push shifter 22a causes the differential lever 23, whose support shaft 72 is engaged with the engagement groove 65 of the pull shifter 22b, to rotate counterclockwise about the support shaft 72, and the compensating bimetal contact surface 74 significantly displaces the free end of the compensating bimetal 31 to the other side in the width direction. In this way, in an overload state, the displacement of the pull shifter 22b stops first, and the displacement of the push shifter 22a rotates the differential lever 23, amplifying the displacement of the free end of the compensating bimetal 31, enabling the tripping operation of the reversing mechanism 24 to begin early.

[0029] Therefore, the tripping operation can be started early before the high-temperature bimetals 21U, 21V, 21W bend and come into contact with the partition walls 41-43, thereby reducing the risk of damage to the partition walls 41-43. Furthermore, as is clear from the relationship D2 < D3 in the above-mentioned formula (1), the gap D2 in the normal state between the elongated hole 58 provided in the pull shifter 22b and the protrusion 45b1 of the partition wall 41 is set to a value smaller than the overload bimetal displacement D3 of the bimetals 21U, 21V, 21W in the overload state. Therefore, before the free ends 21Ua, 21Va, 21Wa of the high-temperature bimetals 21U, 21V, 21W come into contact with the partition walls 41 to 43, the displacement of the pull shifter 22b stops, the rotation of the differential lever 23 begins, and the tripping operation of the reversing mechanism 24 can be reliably initiated.

[0030] Furthermore, even if the adjustment dial 37 is turned to its maximum setting due to an incorrect operation, as is clear from the relationship D4 < D2 in equation (2) above, the compensating bimetal 31 is only displaced up to the maximum compensation bimetal displacement D4, which is smaller than the gap D2 of the pull shifter 22b in the normal state. For this reason, in an overload state, the displacement of the free end of the compensating bimetal 31 is amplified as described above. Therefore, even if the adjustment dial 37 is turned to its maximum setting, the tripping operation of the reversing mechanism 24 can be initiated early, preventing damage to the electrical equipment. [Explanation of symbols]

[0031] 11 Thermal overload relay 12 cases 21U, 21V, 21W Bimetal 21Ua, 21Va, 21Wa Free end of bimetal 22 Shifter 23 Differential lever 24 Reversal mechanism 25 Reset Stick 26 Heater 27 Connection terminal 31 Compensating Bimetal 32 Release lever 33 Tension spring 34 Movable plate 35 Leaf spring 36 Interlocking plate 37 Adjustment dial 37a Eccentric cam 22a push shifter 22b pull shifter 41~43 Bulkhead 44 digit board 45a1 Protrusion (push shifter protrusion) 45a2 Protrusion 45b1 Protrusion (pull shifter protrusion) 45b2 Protrusion 51 Oblong hole (push shifter oblong hole) 52 slot 53~55 Engagement piece 56 Tip 58 Oblong hole (pull shifter oblong hole) 59 Slot 60~62 Engagement piece 65 Engagement groove 70,71 Opposing plate 72 Spindle 73 End face 74 Compensating bimetal contact surface

Claims

1. A plurality of partition walls provided inside the case; a plurality of bimetals individually housed between the plurality of partition walls; a push shifter and a pull shifter that are disposed to cover the ends of the partition walls and engage with the free ends of the bimetal to be displaced when the bimetal is bent; a differential lever that is pushed and driven by the displacement of the push shifter and the pull shifter; a reversing mechanism that transmits the driven movement of the differential lever to a compensating bimetal to reverse the contacts and perform a tripping operation, the differential lever is rotated by being pushed by the push shifter from the radially outer side around a position where it engages with the pull shifter as a rotation center, and a compensating bimetal contact surface provided on the differential lever displaces the compensating bimetal, thereby causing a tripping operation of the reversing mechanism; A thermal overload relay characterized in that, in an overload state where an overcurrent is flowing, the displacement of the pull shifter stops first, and then the push shifter is displaced, thereby rotating the differential lever and amplifying the displacement of the compensating bimetal.

2. The compensating bimetal displacement amplifier means a push shifter slot whose long axis direction extends in the displacement direction of the push shifter; a pull shifter slot having a major axis extending in the displacement direction of the pull shifter; a push shifter protrusion protruding from an end of the partition wall and slidably fitted into the push shifter slot; a pull shifter protrusion protruding from an end of the partition wall and slidably fitted into the pull shifter slot, a distance D1 from when the push shifter is displaced from a normal state in which the bimetal is not bent until the push shifter protrusion engages with one opening edge in the long axis direction of the push shifter elongated hole; a distance D2 between the pull shifter projection and one opening edge of the pull shifter slot in the longitudinal direction when the pull shifter is displaced from the normal state; If the displacement of the free end when the bimetal is bent to the maximum in the overload state is D3, 2. A thermal overload relay according to claim 1, wherein the relationship is set as expressed by the following formula (1): D2 < D3 < D1... Formula (1)

3. an adjustment dial is provided for adjusting a settling current, and when the scale of the adjustment dial is turned in a direction in which the settling current increases, the compensating bimetal of the reversing mechanism is set to move away from the contact surface of the compensating bimetal of the differential lever by a predetermined displacement; 3. The thermal overload relay according to claim 2, wherein when the scale of the adjustment dial is turned in the direction in which the settling current is maximized, the maximum displacement of the compensating bimetal is D4, and the distance D2 from the normal state until the pull shifter engages with the pull shifter protrusion and stops is expressed by the following equation (2): D4 < D2... Formula (2)

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