circuit breaker

Abstract

To provide a circuit breaker which can efficiently achieve suppression effect in permanent deformation of a bimetal by reducing stress applied to the bimetal.SOLUTION: A thermal tripping device 50 comprises: a bimetal upper base 52 fastened to a tip end of a bimetal 51; a bimetal upper part 54; and a bimetal upper spring 56 which biases the bimetal upper part 54 in a direction of a trip bar with a load greater than a tripping load of an opening / closing mechanism part. A distance between a holding part 56b of the bimetal upper spring 56 and a biasing part 56a of the bimetal upper spring 56 with respect to the bimetal upper part 54 becomes longer after rotation of the bimetal upper part 54 than it is before the rotation of the bimetal upper part 54. A rotation shaft 53 of the bimetal upper part 54 is provided on the opposite side to the holding part 56b of the bimetal upper spring 56 across the bimetal upper part 54.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a circuit breaker with a thermal trip device having a bimetal. [Background technology]

[0002] Circuit breakers compatible with electrical circuits containing harmonic components are equipped with thermal trip devices, which are configured to operate a trip bar using a bimetal that bends and deforms when an overcurrent occurs in the electrical circuit, thereby tripping the switching mechanism.

[0003] In Patent Document 1, a rotating part that is biased by a spring and can rotate is provided at the tip of the bimetal. The thermal trip device in Patent Document 1 includes a bimetal upper base fixed to the tip of the bimetal, a bimetal upper that is rotatably provided on the bimetal upper base and has an overcurrent characteristic adjustment member fixed thereto that faces the trip bar across a gap, and a bimetal upper spring that is held by the bimetal upper base and always biases the bimetal upper with a load that is equal to or greater than the trip load of the opening and closing mechanism, and when an overcurrent occurs in the electrical circuit, the bimetal bends and rotates the bimetal upper against the bimetal upper spring, driving the trip bar via the overcurrent characteristic adjustment member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 103015 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the bimetal upper is rotatable relative to the bimetal upper base, but the position of the rotation axis is on an extension of the longitudinal direction of the plate-shaped bimetal upper, so the rate of increase in the spring load of the bimetal upper spring as the bimetal upper rotates is large, which increases the stress applied to the bimetal, resulting in the problem that the effect of suppressing permanent deformation of the bimetal cannot be efficiently achieved.

[0006] The present disclosure has been made in view of the above, and has an object to provide a circuit breaker that reduces the stress applied to the bimetal and efficiently suppresses permanent deformation of the bimetal. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the object, the circuit breaker disclosed herein includes a switching mechanism that drives switching contacts that open and close an electric circuit, and a thermal trip device that drives a trip bar using a bimetal that bends when an overcurrent occurs in the electric circuit, thereby tripping the switching mechanism. The thermal trip device includes a bimetal upper base fixed to the tip of the bimetal, a bimetal upper that is rotatably mounted on the bimetal upper base and faces the trip bar across a gap, and a bimetal upper spring that is held by the bimetal upper base and urges the bimetal upper toward the trip bar with a load greater than the trip load of the switching mechanism. The distance between the holding portion of the bimetal upper spring and the urging portion of the bimetal upper spring relative to the bimetal upper is longer after the bimetal upper rotates than before. The rotation axis of the bimetal upper is located on the opposite side of the bimetal upper from the holding portion of the bimetal upper spring, with the bimetal upper in between. [Effects of the Invention]

[0008] The circuit breaker of the present disclosure has the effect of reducing the stress applied to the bimetal, thereby efficiently suppressing permanent deformation of the bimetal. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view showing a configuration of a circuit breaker according to a first embodiment; [Figure 2] 1 is a cross-sectional view showing a configuration of a circuit breaker according to a first embodiment; [Figure 3] FIG. 1 is an enlarged side view showing the configuration of a circuit breaker tripping device according to a first embodiment; [Figure 4] FIG. 1 is an enlarged perspective view showing a configuration of a thermal tripping device for a circuit breaker according to a first embodiment; [Figure 5] FIG. 1 is an enlarged perspective view of a main part of a thermal tripping device of a circuit breaker according to a first embodiment, viewed from another angle; [Figure 6] FIG. 1 is a cross-sectional view showing a state in which a circuit breaker according to a first embodiment is opened; [Figure 7] FIG. 1 is an enlarged side view showing a state in which the thermal tripping device of the circuit breaker according to the first embodiment has pushed the trip bar to a maximum trip position; [Figure 8] 8 is an enlarged side view showing a state in which the bimetal is further bent and the bimetal upper is rotated from the state shown in FIG. 7 in the thermal tripping device of the circuit breaker according to the first embodiment. [Figure 9] 1 is an enlarged side view illustrating a state before and after rotation of a bimetal upper in a thermal tripping device of a circuit breaker according to a first embodiment; FIG. [Figure 10] 10A and 10B are enlarged side views illustrating the states of the bimetal upper before and after rotation in a comparative example; [Figure 11] FIG. 10 is an explanatory diagram showing the load characteristics of the bimetal upper of the thermal tripping device of the circuit breaker according to the first embodiment in comparison with those of a comparative example. [Figure 12] FIG. 10 is an enlarged perspective view showing the configuration of a main part of a thermal tripping device for a circuit breaker according to a second embodiment. [Figure 13] FIG. 10 is a schematic diagram showing the structure of a spring pin of a thermal tripping device according to a second embodiment; [Figure 14] FIG. 10 is an explanatory diagram showing the load characteristics of the bimetal upper of the thermal tripping device of the circuit breaker according to the second embodiment in comparison with those of the first embodiment. [Figure 15]FIG. 10 is an enlarged side view showing the configuration of a thermal tripping device for a circuit breaker according to a third embodiment. [Figure 16] FIG. 10 is an explanatory diagram showing the load characteristics of the bimetal upper of the thermal tripping device of the circuit breaker according to the third embodiment in comparison with those of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a circuit breaker according to an embodiment will be described in detail with reference to the drawings.

[0011] Embodiment 1 FIG. 1 is a front view showing the configuration of a circuit breaker according to the first embodiment. FIG. 2 is a cross-sectional view showing the configuration of the circuit breaker according to the first embodiment. FIG. 1 shows the state of the circuit breaker when it is not interrupting. FIG. 2 is a cross-sectional view taken along line II-II shown in FIG. 1. The schematic structure of a circuit breaker 100 according to the first embodiment will be described with reference to FIGS. 1 and 2. The circuit breaker 100 includes a housing 1 having a base 2 and a cover 3. The base 2 and the cover 3 are formed of an insulating material.

[0012] Circuit breaking units for multiple phases, the number of which corresponds to the number of poles, are arranged in parallel on the base 2. In the case of Figure 1, three (three) circuit breaking units for three phases are arranged. A switching mechanism section 20 having a well-known toggle link mechanism is arranged above the central circuit breaking unit. A cover 3 covers the circuit breaking units for each phase on the base 2 and the switching mechanism section 20. An operating handle 21 of the switching mechanism section 20 protrudes from the cover 3. The circuit breaking units for each phase have the same configuration, and a crossbar 10 is arranged on the base 2 so as to cross the circuit breaking units for each phase and be perpendicular to them.

[0013] The circuit breaker unit for each phase has a power supply side terminal 7, a fixed contact 4, a movable contact 5, a movable contactor 6, a trip device 30, and a load side terminal 8. The power supply side terminal 7 is provided on the base 2. The fixed contact 4 is provided at a location extending from the power supply side terminal 7. The movable contact 5 makes contact with and separates from the fixed contact 4. The movable contactor 6 has the movable contact 5 provided at one end and is held rotatably by a crossbar 10. The trip device 30 is connected to the movable contactor 6 via a movable contactor holder 9. The load side terminal 8 is connected to the trip device 30 and is provided on the base 2.

[0014] The fixed contact 4 and the movable contact 5 constitute a make-and-break contact that opens and closes the electric circuit. When the movable contact 5 comes into contact with the fixed contact 4, the electric circuit between the power supply terminal 7 and the load terminal 8 is turned on. When the movable contact 5 separates from the fixed contact 4, the electric circuit between the power supply terminal 7 and the load terminal 8 is turned off.

[0015] The crossbar 10 is disposed at the bottom of the base 2 and extends perpendicular to the plane of the paper in FIG. 2. The crossbar 10 is rotated about its axis by the switching mechanism 20. Each movable contactor 6 in the circuit breaking unit of each phase is attached to the crossbar 10. When the crossbar 10 rotates about its axis, each movable contactor 6 in the circuit breaking unit of each phase rotates simultaneously, and the rotation of the movable contactor 6 causes the movable contact 5 to contact and separate from the fixed contact 4.

[0016] The switching mechanism 20 is composed of a known toggle link mechanism, and is equipped with a known trip bar 22 driven by a tripping device 30, and a trip bar stopper (not shown) that locks the trip bar 22 at the maximum trip position. In addition, an arc extinguishing chamber 11 is disposed adjacent to the movable contact 6, and extinguishes an arc that occurs between the movable contact 5 and the fixed contact 4 when the switching mechanism 20 is in operation.

[0017] Fig. 3 is an enlarged side view showing the configuration of the trip device 30 of the circuit breaker 100 according to the first embodiment. As shown in Fig. 3, the trip device 30 is made up of an electromagnetic trip device 40 and a thermal trip device 50. The electromagnetic trip device 40 includes a fixed core 41, a movable core 42, a return spring 43, and a shaft 44. The return spring 43 biases the movable core 42. The shaft 44 supports the movable core 42. The movable core 42 is attracted to the fixed core 41 during instantaneous interruption and drives the trip bar 22.

[0018] FIG. 4 is an enlarged perspective view showing the configuration of the thermal tripping device 50 of the circuit breaker 100 according to the first embodiment. FIG. 5 is an enlarged perspective view showing the main parts of the thermal tripping device 50 of the circuit breaker 100 according to the first embodiment, viewed from a different angle. As shown in FIGS. 3 to 5, the thermal tripping device 50 includes a bimetal 51, a bimetal upper base 52, a rotating shaft 53, a bimetal upper 54, and a bimetal upper spring 56. The lower end of the bimetal 51 is fixedly connected to the armature holder 9, as shown in FIGS. 2 and 4. The tip (upper end) of the bimetal 51 is fixed to the bimetal upper base 52. The rotating shaft 53 is journaled on the bimetal upper base 52. The bimetal upper base 52 includes a support portion 52a for supporting the bimetal upper spring 56 and a bimetal upper stopper 52b that functions as a stopper for the bimetal upper 54.

[0019] The bimetal upper 54 is rotatably supported on the bimetal upper base 52 by the rotary shaft 53. As shown in Fig. 4, the bimetal upper 54 is L-shaped and has a rotary shaft support portion 54b located on the lower side that supports the rotary shaft 53, a screw support portion 54c located on the upper side for threading an adjustment screw 57, and an engagement portion 54a located on the upper side with which the biasing portion 56a of the arm of the bimetal upper spring 56 engages. The adjustment screw 57 is a screw for adjusting the overcurrent characteristics.

[0020] The bimetal upper spring 56 is formed of a torsion coil spring and includes a coil portion 56b and two arms extending from the coil portion 56b. The bimetal upper spring 56 is held in the bimetal upper base 52 by inserting the coil portion 56b of the bimetal upper spring 56 into the support portion 52a of the bimetal upper base 52. For this reason, the coil portion 56b of the bimetal upper spring 56 will hereinafter be referred to as the holding portion 56b of the bimetal upper spring 56. Furthermore, one arm of the bimetal upper spring 56 engages with the engaging portion 54a of the bimetal upper 54 to apply a movable load to the bimetal upper 54. As the bimetal upper 54 rotates, the position on the arm that abuts against the engaging portion 54a of the bimetal upper 54 changes, but the portion on the arm that abuts against the engaging portion 54a of the bimetal upper 54 will be referred to as the biasing portion 56a of the bimetal upper spring 56. The bimetal upper spring 56 biases the bimetal upper 54 toward the trip bar 22 via the biasing portion 56a.

[0021] An electric connection member 58 is fixed to the upper end of the bimetal 51 by a rivet 60. The bimetal 51 is connected to the load terminal 8 via the electric connection member 58 and a flexible conductor 59, allowing current to flow through the electrical path. Note that although an example is shown in FIGS. 3 to 5 in which the bimetal upper base 52 is formed integrally with the electric connection member 58, the bimetal upper base 52 and the electric connection member 58 may be separate bodies and fixed together by welding or the like.

[0022] The bimetal upper 54 is constantly biased in the direction of the trip bar 22 by the bimetal upper spring 56 while in contact with the bimetal upper stopper 52b provided on the bimetal upper base 52, and the spring load of the bimetal upper 54 is set to be greater than the trip load at the contact position of the trip bar 22.

[0023] Here, the rotating shaft 53 is provided on the opposite side of the bimetal upper 54 from the retaining portion 56b of the bimetal upper spring 56, and the distance between the retaining portion 56b of the bimetal upper spring 56 and the biasing portion 56a of the bimetal upper spring 56 is configured to be longer after the bimetal upper 54 rotates than before the bimetal upper 54 rotates. This point will be described in detail later.

[0024] Next, the interruption operation of the circuit breaker 100 will be described. FIG. 6 is a cross-sectional view showing the state of the circuit breaker 100 according to the first embodiment during interruption. When an overcurrent exceeding a certain current value flows through the bimetal 51, the bimetal 51 generates heat, which causes the bimetal 51 to bend and deform. Because the adjustment screw 57 is fixed to the bimetal 51 via the bimetal upper 54 and the bimetal upper base 52, when the bimetal 51 bends, the adjustment screw 57 pushes the trip bar 22. This drives the switching mechanism 20, causing the movable contact 6 to rotate. When the movable contact 6 rotates, the movable contact 5 separates from the fixed contact 4, completing the current interruption operation of the circuit breaker 100. Note that FIG. 6 shows the state at the moment when the thermal trip device 50 is activated, and in this state, the movable contact 5 is still in contact with the fixed contact 4.

[0025] When the adjustment screw 57 presses the trip bar 22, the bimetal upper 54 is constantly biased toward the trip bar 22 by the bimetal upper spring 56 while in contact with the bimetal upper stopper 52b provided on the bimetal upper base 52. In this case, the spring load of the bimetal upper 54 is set to be greater than the tripping load at the contact position of the trip bar 22, so the bimetal upper 54 can push in the trip bar 22 without rotating.

[0026] Fig. 7 is an enlarged side view showing a state in which the thermal tripping device 50 of the circuit breaker 100 according to the first embodiment has pushed the trip bar 22 to the maximum trip position. Fig. 8 is an enlarged side view showing a state in which the bimetal 51 has further bent and the bimetal upper 54 has rotated from the state shown in Fig. 7 in the thermal tripping device 50 of the circuit breaker 100 according to the first embodiment. Fig. 7 shows a state in which the trip bar 22 has been pushed to the maximum trip position where the trip bar 22 is locked by a trip bar stopper (not shown).

[0027] Because the tripping load of the trip bar 22 is set smaller than the initial load of the bimetal upper spring 56, the bimetal upper 54 does not rotate until the trip bar 22 reaches the maximum lock position where it abuts against the trip bar stopper, as shown in Figure 7. If the curvature of the bimetal 51 increases further after the trip bar 22 reaches the maximum lock position, the bimetal upper 54 begins to rotate, and the biasing force of the bimetal upper spring 56 begins to increase, as shown in Figure 8.

[0028] FIG. 9 is an enlarged side view illustrating the state before and after rotation of the bimetal upper 54 in the thermal tripping device 50 of the circuit breaker 100 according to the first embodiment. FIG. 10 is an enlarged side view illustrating the state before and after rotation of the bimetal upper 54 in a comparative example. FIG. 10 shows the configuration of a tripping device 90 corresponding to the configuration shown in Patent Document 1. In the comparative example shown in FIG. 10, the rotating shaft 53 according to the first embodiment is replaced with a rotating shaft 53c according to Patent Document 1, and the other components and their reference numerals are the same as those in the first embodiment for convenience of comparison. The rotating shaft 53c is positioned on an extension line of the bimetal upper 54 in the longitudinal direction. In FIGS. 9 and 10, the initial position of the adjusting screw 57 is indicated by a solid line, and the position after rotation of the adjusting screw 57 is indicated by a two-dot chain line.

[0029] 9, in the first embodiment, the rotation shaft 53 of the bimetal upper 54 is provided on the opposite side of the retaining portion 56b of the bimetal upper spring 56, with the screw support portion 54c, which is an upper portion of the bimetal upper 54, sandwiched between them, at least before the bimetal upper 54 rotates. Comparing the distance L1 between the retaining portion 56b of the bimetal upper spring 56 and the biasing portion 56a of the bimetal upper spring 56 before the bimetal upper 54 rotates with the distance L2 between the retaining portion 56b of the bimetal upper spring 56 and the biasing portion 56a of the bimetal upper spring 56 after the bimetal upper 54 rotates, L1 <L2となっている。

[0030] 10, when the distance L3 between the retaining portion 56b of the bimetal upper spring 56 and the biasing portion 56a of the bimetal upper spring 56 before the bimetal upper 54 rotates is compared with the distance L4 between the retaining portion 56b of the bimetal upper spring 56 and the biasing portion 56a of the bimetal upper spring 56 after the bimetal upper 54 rotates, L4 > L3. However, when Fig. 9 is compared with Fig. 10, (L2 / L1) > (L4 / L3), so the distance ratio L2 / L1 in the first embodiment is greater than the distance ratio L4 / L3 in the comparative example, and the distance L2 between the retaining portion 56b of the bimetal upper spring 56b and the biasing portion 56a after the bimetal upper 54 rotates is longer than the distance L4 in the comparative example. That is, according to the first embodiment, bimetal upper 54 is L-shaped and rotating shaft 53 is provided on the opposite side of bimetal upper 54 from retaining portion 56b, so the radius of rotation of bimetal upper 54 is larger than in the comparative example, and distance L2 between retaining portion 56b and biasing portion 56a when bimetal upper 54 rotates is longer than in the comparative example. Therefore, even if bimetal upper 54 rotates and bimetal upper spring 56 bends, the increase in load by bimetal upper spring 56 is more gradual in the first embodiment than in the comparative example.

[0031] FIG. 11 is an explanatory diagram showing the load characteristics of the bimetal upper of the thermal trip device 50 of the circuit breaker 100 according to the first embodiment in comparison with those of a comparative example. In FIG. 11, the horizontal axis represents the bending stroke of the bimetal 51, and the vertical axis represents the biasing force of the bimetal upper spring 56 converted into a moment at the bimetal upper 54 to explain the load acting on the bimetal 51. In FIG. 11, P1 corresponds to the position where the adjustment screw 57 abuts against the trip bar 22, P2 corresponds to the position where the trip bar 22 starts its tripping operation, and P3 corresponds to the position where the trip bar 22 is locked at the maximum trip position. Mc represents the allowable moment of the bimetal 51. La represents the load characteristics of the first embodiment, and Lb represents the load characteristics of the comparative example.

[0032] The biasing force of the bimetal upper spring 56 remains at the initial load M1 limited by the bimetal upper stopper 52b until the trip bar 22 is locked at the maximum trip position indicated by P3. This is because the tripping load of the trip bar 22 is set smaller than the initial load M1 of the bimetal upper spring 56, and the bimetal upper 54 does not rotate during this period. Furthermore, as the curvature of the bimetal 51 increases, the bimetal upper 54 begins to rotate, and the biasing force of the bimetal upper spring 56 begins to increase, as shown in FIG. 8. After the load of the bimetal upper spring 56 begins to increase, in the case of the comparative example, the rate of increase is large, as indicated by Lb, and the moment in the bimetal upper 54 exceeds the allowable moment (load) Mc of the bimetal 51, which may cause permanent deformation of the bimetal 51. In contrast, in the first embodiment, even if the bimetal upper 54 rotates and the bimetal upper spring 56 bends, the load on the bimetal upper spring 56 increases more slowly than in the comparative example, as shown by La. As a result, in the first embodiment, the moment on the bimetal upper 54 does not exceed the allowable moment (load) Mc of the bimetal 51.

[0033] When an excessive current such as a short-circuit current flows, the magnetic force generated in the fixed core 41 of the electromagnetic tripping device 40 of the tripping device 30 attracts the movable core 42 to the fixed core 41, and the movable core 42 rotates around the shaft 44 as the axis of rotation against the biasing force of the return spring 43. This rotation causes the movable core 42 to push the trip bar 22, which drives the opening / closing mechanism 20 and rotates the movable contactor 6. The rotation of the movable contactor 6 separates the movable contactor 5 from the fixed contactor 4, breaking the excessive current and completing the tripping operation.

[0034] However, even when an excessive current such as a short-circuit current flows, the bimetal 51 bends, and the bending stroke is greater than the stroke at which the trip bar 22 abuts against the trip bar stopper of the opening / closing mechanism 20. This causes the bimetal upper 54 to rotate. A load greater than the spring load characteristics of the bimetal upper spring 56 is applied to the bimetal upper 54, causing the bimetal upper spring 56 to bend and rotate. This rotation of the bimetal upper 54 prevents the bimetal 51 from being subjected to a load greater than the spring load characteristics of the bimetal upper spring 56.

[0035] As described above, according to the first embodiment, the distance between the retaining portion 56b of the bimetal upper spring 56 and the biasing portion 56a of the bimetal upper spring 56 relative to the bimetal upper 54 is longer after the bimetal upper 54 rotates than before the bimetal upper 54 rotates, and the rotation shaft 53 of the bimetal upper 54 is provided on the opposite side of the bimetal upper 54 from the retaining portion 56b of the bimetal upper spring 56. Therefore, even if the bimetal upper 54 rotates and the bimetal upper spring 56 bends, the load on the bimetal upper spring 56 increases gradually, reducing the stress applied to the bimetal 51 and preventing permanent deformation of the bimetal 51. In this way, the first embodiment can efficiently suppress permanent deformation of the bimetal. Furthermore, a circuit breaker can be obtained that allows stable tripping with no change in tripping time before and after breaking.

[0036] Embodiment 2 Fig. 12 is an enlarged perspective view showing the configuration of the main part of the thermal tripping device 50 of the circuit breaker 100 according to the second embodiment. Fig. 13 is a schematic diagram showing the structure of the spring pin of the thermal tripping device 50 according to the second embodiment. Fig. 14 is an explanatory diagram showing the load characteristics of the bimetal upper 54 of the thermal tripping device 50 of the circuit breaker 100 according to the second embodiment in comparison with those of the first embodiment. In Fig. 14, the load characteristic Lc of the second embodiment is added to Fig. 11.

[0037] In the second embodiment, the adjustment screw 57 in the first embodiment is replaced with a spring pin 57a. The other configurations are the same as those in the first embodiment, and redundant explanations will be omitted. The spring pin 57a ​​includes a main body portion 57a1, a compression spring 57a2, and an abutment portion 57a3. The main body portion 57a1 has a hollow portion in which the compression spring 57a2 is provided. The abutment portion 57a3 is biased by the compression spring 57a2 to protrude from the main body portion 57a1 and abut against the trip bar 22.

[0038] According to the second embodiment, the bimetal upper spring 56 and the compression spring 57a2 are mechanically arranged in series. In other words, the bimetal upper 54 is biased by a spring so that the contact portion that contacts the trip bar 22 can move. Therefore, as shown by the load characteristic Lc in FIG. 14 , in a region where the stroke of the trip bar 22 is greater than the lock position P3, the increase in the moment of the bimetal upper 54 is more gradual than the load characteristic La of the first embodiment. Therefore, even if the bimetal upper 54 rotates and the bimetal upper spring 56 bends, the increase in the load of the bimetal upper spring 56 is gradual, and permanent deformation of the bimetal 51 can be prevented.

[0039] Embodiment 3 Fig. 15 is an enlarged side view showing the configuration of the thermal tripping device 50 of the circuit breaker 100 according to the third embodiment. Fig. 16 is an explanatory diagram showing the load characteristics of the bimetal upper 54 of the thermal tripping device 50 of the circuit breaker 100 according to the third embodiment in comparison with those of the first embodiment. In Fig. 16, position P4 and the load characteristic Ld of the third embodiment are added to Fig. 11. Position P4 corresponds to the position where the biasing portion 56a of the bimetal upper spring 56 reaches the bent portion 56c.

[0040] In the third embodiment, a bent portion 56c is provided on the tip side of the bimetal upper spring 56 in the first embodiment. In the bimetal upper spring 56 of the third embodiment, the bent portion 56c is provided at the middle position of the part constituting the biasing portion 56a of the bimetal upper spring 56, and the tip side of the bent portion 56c is bent toward the rotary shaft 53.

[0041] As a result, the bimetal upper 54 rotates and the bimetal upper spring 56 bends, and the moment of the bimetal upper 54 increases at the same rate as in the first embodiment until the biasing portion 56a reaches the bent portion 56c. However, after the biasing portion 56a reaches the bent portion 56c, the biasing portion 56a moves over the bent portion 56c. Therefore, after the biasing portion 56a overcomes the bent portion 56c, that is, from position P4 onwards, the increase in the moment of the bimetal upper 54 becomes more gradual than the load characteristic La in the first embodiment, as shown by the load characteristic Ld in FIG.

[0042] According to the third embodiment, a bent portion 56c is provided midway along the portion constituting the biasing portion 56a of the bimetal upper spring 56, and the tip side of the bent portion 56c is bent toward the rotary shaft 53. Therefore, as the bimetal upper 54 rotates and the bimetal upper spring 56 flexes, after the biasing portion 56a reaches the bent portion 56c, the increase in the moment in the bimetal upper 54 becomes gradual, and permanent deformation of the bimetal 51 can be prevented.

[0043] It is possible to combine the embodiments, and to modify or omit the embodiments as appropriate.

[0044] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies, and parts of the configurations may be omitted or modified within the scope of the gist of the present disclosure. [Explanation of symbols]

[0045] 1 housing, 2 base, 3 cover, 4 fixed contact, 5 moving contact, 6 moving contactor, 7 power supply side terminal, 8 load side terminal, 9 moving contact holder, 10 crossbar, 11 arc extinguishing chamber, 20 opening / closing mechanism, 21 operating handle, 22 trip bar, 30, 90 tripping device, 40 electromagnetic tripping device, 41 fixed core, 42 moving core, 43 return spring, 44 shaft, 50 thermal tripping device, 51 bimetal, 52 bimetal upper base, 52a support portion, 52b bimetal upper stopper, 53, 53c rotating shaft, 54 bimetal upper, 54a engagement portion, 54b rotating shaft support portion, 54c screw support portion, 56 bimetal upper spring, 56a biasing portion, 56b holding portion (coil portion), 56c bending portion, 57 Adjustment screw, 57a spring pin, 57a1 main body, 57a3 abutment, 58 current-carrying connection member, 59 flexible conductor, 60 rivet, 100 circuit breaker.

Claims

1. A circuit breaker comprising: a switching mechanism that drives a switching contact that opens and closes an electric circuit; and a thermal trip device that drives a trip bar by a bimetal that bends when an overcurrent occurs in the electric circuit, thereby tripping the switching mechanism, The thermal tripping device is a bimetal upper base fixed to the tip of the bimetal; a bimetal upper rotatably mounted on the bimetal upper base and facing the trip bar with a gap therebetween; a bimetal upper spring that is held by the bimetal upper base and biases the bimetal upper toward the trip bar with a load greater than the tripping load of the opening / closing mechanism, a distance between a holding portion of the bimetal upper spring and a biasing portion of the bimetal upper spring against the bimetal upper is longer after the bimetal upper is rotated than before the bimetal upper is rotated, The rotation axis of the bimetal upper is provided on the opposite side of the bimetal upper from the holding portion of the bimetal upper spring, with the bimetal upper sandwiched between them. A circuit breaker characterized by:

2. The bimetal upper has a contact portion that contacts the trip bar and is biased by a spring so as to be movable.

2. The circuit breaker of claim 1.

3. The biasing portion of the bimetal upper spring has a bent portion bent toward the rotation shaft at its end, and when the bimetal upper spring rotates, the biasing portion moves over the bent portion toward the end.

2. The circuit breaker of claim 1.

Images