Circuit breaker

Abstract

To reduce impact at the time of current limiting interruption in a circuit breaker.SOLUTION: The air damper 23 includes a cylinder 31, a piston rod 32, and a position adjustment spring 33. The cylinder 31 has a tubular shape with a closed proximal end and an open distal end. The piston rod 32 has a base end side fitted into the cylinder 31 in a state of being movable forward and backward in the axial direction, and a tip end facing the movable contactor 22. The position adjustment spring 33 is accommodated on the proximal end side of the cylinder 31 and advances the piston rod 32 toward the distal end side.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a circuit breaker. [Background technology]

[0002] Patent Document 1 discloses a circuit breaker that cuts off a circuit when an overcurrent flows due to an overload or short circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-218765 Summary of the Invention [Problem to be solved by the invention]

[0004] When current-limiting circuit breaker is activated in the event of a short circuit, the moving contact jumps up and hits the housing, which affects the durability of the housing. An object of the present invention is to reduce the shock at the time of current-limiting interruption in a circuit breaker. [Means for solving the problem]

[0005] A circuit breaker according to one aspect of the present invention includes a movable contact and an air damper. The movable contact is rotatable between a closed position and an open position. The air damper is provided in a housing and comes into contact with the movable contact to reduce impact when the movable contact opens due to current-limiting interruption. The air damper includes a cylinder, a piston rod, and a position adjustment spring. The cylinder is tubular with a closed base end and an open tip. The piston rod is fitted into the cylinder at its base end while being movable back and forth in the axial direction, and its tip faces the movable contact. The position adjustment spring is housed in the base end of the cylinder and moves the piston rod forward toward the tip. [Effects of the Invention]

[0006] According to the present invention, the movable contact that is opened by current-limiting interruption abuts against the air damper, thereby reducing the impact. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 illustrates a circuit breaker. [Figure 2] FIG. 2 is a cross-sectional view of a closed circuit breaker. [Figure 3] FIG. 2 is a diagram showing an exploded view of the air damper. [Figure 4] FIG. 10 shows an expanded air damper. [Figure 5] FIG. 10 shows a compressed air damper. [Figure 6] FIG. 10 is a view showing an air damper fixed to the middle cover. [Figure 7] FIG. 1 is a cross-sectional view of a circuit breaker that has been opened by current-limiting interruption. [Figure 8] FIG. 10 is a view showing a movable contactor abutting against an air damper. [Figure 9] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are schematic and may differ from the actual product. Furthermore, the following embodiments exemplify devices and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope described in the claims.

[0009] <<Embodiment>> "composition" 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. FIG. 1 is a diagram illustrating a circuit breaker 11. As shown in FIG. Here, the circuit breaker 11 is shown as seen from one side in the vertical direction, one side in the width direction, and from the front in the depth direction. The circuit breaker 11 is also called a no-fuse breaker, and when it detects an abnormal overcurrent due to an overload or short circuit, it automatically cuts off the circuit to protect against damage caused by the overcurrent. One side in the vertical direction is the power supply side, and the other is the load side. The circuit breaker 11 has a case 12 and a middle cover 13 as a resin housing.

[0010] FIG. 2 is a cross-sectional view of the circuit breaker 11 in a closed state. The figure shows a cross section taken along the vertical and depth directions, passing through the center of the third pole, which is located on one side of the width direction, of the three poles aligned in the width direction on the power supply side of a closed circuit breaker 11. The circuit breaker 11 includes a fixed contact 21, a movable contact 22, and an air damper 23. The fixed contactor 21 is a strip-shaped conductor, and an electrical circuit is connected to the outer end in the vertical direction via an aluminum terminal plate, and a fixed contact 26 is formed on the surface facing the front in the depth direction at the inner end in the vertical direction.

[0011] The movable contact 22 is a rod-shaped conductor supported to be rotatable between a closed position and an open position. When viewed from one side of the width direction, the clockwise direction is the closed direction and the counterclockwise direction is the open direction. A movable contact 27 is formed on the tip of the surface of the movable contact 22 facing the closed direction. When the movable contact 22 is in the closed position, the movable contact 27 comes into contact with the fixed contact 26, resulting in a closed state. When the movable contact 22 is in the open position, the movable contact 27 separates from the fixed contact 26, resulting in an open state. When a short circuit occurs, the movable contact 22 opens by jumping up due to electromagnetic repulsion, resulting in a current-limiting interruption. The electromagnetic repulsion is generated by the current concentration and diffusion at the contact points between the contacts, and the current flowing in opposite directions generates an electromagnetic repulsion that moves them away from each other. The air damper 23 is provided on the middle cover 13, and when the movable contact 22 opens due to current-limiting interruption, it comes into contact with the movable contact 22 to reduce the impact. The air damper 23 may be provided on at least one of the three poles.

[0012] FIG. 3 is an exploded view of the air damper 23. As shown in FIG. For the sake of convenience, the three mutually orthogonal directions of the air damper 23 are referred to as the axial, x, and y directions. The x direction is parallel to the plane of the vertical and depth directions, and the y direction is parallel to the width direction. Here, the exploded air damper 23 is shown as viewed from the axial tip end, one side in the x direction, and one side in the y direction. The air damper 23 includes a cylinder 31, a piston rod 32, a position adjustment spring 33, and a packing 34. All parts of the air damper 23 except for the packing 34, i.e., the cylinder 31, piston rod 32, and position adjustment spring 33, are made of metal.

[0013] FIG. 4 is a diagram showing the air damper 23 in an expanded state. In the figure, (a) shows the state of the extended air damper 23 as viewed from the axial tip side, one side in the x direction, and one side in the y direction, while (b) shows the state of the extended air damper 23 as viewed from one side in the y direction, in a cross section passing through the center in the y direction and along the x direction and axial direction. The cylinder 31 is formed in a cylindrical shape with a closed base end and an open tip end, and includes a cylindrical portion 41, an engagement portion 42, and an opening 43. The packing 34 attached to the piston rod 32 is slidable on an inner peripheral surface 46 of the cylindrical portion 41. An annular recessed groove 47 into which the position adjustment spring 33 fits is formed on the inner base end surface of the cylindrical portion 41. The engagement portion 42 is formed on the tip side of the cylindrical portion 41, and has an outer diameter larger than that of the cylindrical portion 41. The opening 43 is a circular hole that penetrates in the axial direction on the tip side of the engagement portion 42, and has an inner diameter smaller than the inner diameter of the cylindrical portion 41.

[0014] The piston rod 32 is cylindrical, and its outer diameter is smaller than the inner diameter of the opening 43. A gasket 34 is fitted in a cylindrical groove formed on the base end side of the outer peripheral surface of the piston rod 32. The piston rod 32 is formed with a through-hole 51 (communication passage) and a communication groove 52. The through-hole 51 penetrates the center of the piston rod 32 from the base end to the tip end when viewed from the axial direction. The communication groove 52 is formed on the tip surface of the piston rod 32, passes through the through-hole 51, and extends in a straight line along the y direction to the outer peripheral surface on the radially outer side. The piston rod 32 has an outer diameter larger than the width dimension of the movable contact 22, and the communication groove 52 extends in a direction perpendicular to the extension direction of the movable contact 22 (FIG. 8).

[0015] The position adjustment spring 33 is a compression coil spring that is housed on the base end side of the cylinder 31 and moves the piston rod 32 forward toward the tip side. The position adjustment spring 33 is set to a spring constant that is sufficient to expand when no load is applied, and move the piston rod 32 to the tip side of the cylinder 31. Therefore, the position adjustment spring 33 does not have the function of reducing the impact on the movable contact 22 by means of a repulsive force. The packing 34 is an O-ring with a rectangular cross section, and is attached to the outer peripheral surface of the piston rod 32 to seal the gap between the piston rod 32 and the inner peripheral surface 46 of the cylindrical portion 41 in the circumferential direction. Therefore, the packing 34 regulates the radial position of the piston rod 32. The cylinder 31 has an opening 43 with an inner diameter smaller than the inner diameter of the inner peripheral surface 46. Therefore, the packing 34 catches on the opening 43, thereby regulating the forward position of the piston rod 32 toward the tip side.

[0016] FIG. 5 is a diagram showing the compressed air damper 23. FIG. 1(a) shows the compressed air damper 23 as viewed from the axial tip, one side in the x direction, and one side in the y direction. FIG. 1(b) shows the compressed air damper 23 as viewed from one side in the y direction, in a cross section passing through the center in the y direction and along the x direction and axial direction. When the air damper 23 is pushed from the outside and the piston rod 32 retracts toward the base end, the air inside the cylinder 31 is compressed, thereby slowing down the retraction of the piston rod 32. When the air inside the cylinder 31 is released to the outside through the through-hole 51, the increase in pressure inside the cylinder 31 is damped.

[0017] FIG. 6 is a diagram showing the air damper 23 fixed to the middle cover 13. As shown in FIG. FIG. 1A shows the air damper 23 fixed to the middle cover 13 as viewed from one side in the vertical direction, one side in the width direction, and the rear in the depth direction. FIG. 1B shows a cross section of the air damper 23 fixed to the middle cover 13, taken along the depth direction and the vertical direction and passing through the center of the air damper 23, as viewed from one side in the width direction. The inner circumferential surface of the middle cover 13 is formed with a recess 56 into which the cylinder 31 fits. Only the engaging portion 42 at the tip end of the cylinder 31 fits into the recess 56. For example, the engaging portion 42 is press-fitted into the recess 56, or a female thread formed in the recess 56 is engaged with a male thread formed in the engaging portion 42 to secure the cylinder 31. A gap d is provided between the inner circumferential surface of the recess 56 and the outer circumferential surface of the cylindrical portion 41. The gap d is set in consideration of the expansion of the cylindrical portion 41 when the air in the cylinder 31 is compressed.

[0018] FIG. 7 is a cross-sectional view of the circuit breaker 11 that has been opened by current-limiting interruption. Here, the cross section is shown as viewed from one side in the width direction, passing through the center of the third pole, which is located on one side of the width direction, of the three poles aligned in the width direction on the power source side of the circuit breaker 11 that has been opened by current-limiting interruption. When the moving contact 22 is opened by current-limiting interruption, the air damper 23 comes into contact with the moving contact 22. At this time, the air damper 23 is pushed by the moving contact 22, causing the piston rod 32 to retract toward the base end, and the air inside the cylinder 31 is compressed, generating a reaction force that slows down the retraction of the piston rod 32 and reduces the impact on the moving contact 22.

[0019] FIG. 8 is a view showing the movable contact 22 in contact with the air damper 23. As shown in FIG. 2A shows the movable contact 22 abutting against the air damper 23 as viewed from one side in the vertical direction, one side in the width direction, and the rear in the depth direction. FIG. 2B shows the movable contact 22 abutting against the air damper 23 as viewed from the rear in the depth direction. The piston rod 32 has an outer diameter larger than the width dimension of the movable contact 22, and the communicating groove 52 extends in a direction perpendicular to the direction in which the movable contact 22 extends. This prevents the air damper 23 from being completely sealed, and air inside the cylinder 31 is released to the outside through the through-hole 51 and the communicating groove 52, thereby damping the pressure rise inside the cylinder 31. After the air inside the cylinder 31 is released, the repulsive force due to the compressed air disappears, and the movable contact 22 is not pushed back in the contact closing direction.

[0020] <<Action and Effect>> Next, the main effects of the embodiment will be described. The circuit breaker 11 includes a movable contact 22 and an air damper 23. The movable contact 22 is rotatable between a closed position and an open position. The air damper 23 is provided on the middle cover 13 and contacts the movable contact 22 to reduce impact when the movable contact 22 is opened due to current-limiting interruption. The air damper 23 includes a cylinder 31, a piston rod 32, and a position adjustment spring 33. The cylinder 31 is cylindrical with a closed base end and an open tip end. The piston rod 32 is axially movable forward and backward, with the base end engaged with the cylinder 31 and the tip facing the movable contact 22. The position adjustment spring 33 is housed in the base end of the cylinder 31 and moves the piston rod 32 forward toward the tip end. As a result, the movable contact 22, which is opened due to current-limiting interruption, contacts the air damper 23, thereby reducing impact.

[0021] When the piston rod 32 is pushed by the open movable contact 22 and moves back toward the base end, the air damper 23 compresses the air inside the cylinder 31, thereby slowing down the movement of the piston rod 32. This reduces the impact of the open movable contact 22 due to current-limiting interruption. The air damper 23 includes a packing 34. The packing 34 is attached to the outer peripheral surface of the piston rod 32 and seals the gap between the outer peripheral surface of the piston rod 32 and the inner peripheral surface 46 of the cylinder 31 in the circumferential direction. This prevents air from leaking between the outer peripheral surface of the piston rod 32 and the inner peripheral surface 46 of the cylinder 31, thereby achieving the desired state in which air is compressed inside the cylinder 31. It also prevents rattling of the piston rod 32 in the radial direction. The packing 34 restricts the forward position of the piston rod 32 toward the tip side, thereby preventing the piston rod 32 from falling off the cylinder 31 and keeping the piston rod 32 in an appropriate position.

[0022] The cylinder 31 includes a cylindrical portion 41 and an opening 43. The packing 34 can slide on the inner circumferential surface of the cylindrical portion 41. The opening 43 is formed at the tip of the cylindrical portion 41, and has an inner diameter smaller than the inner diameter of the cylindrical portion 41. This allows the packing 34 to reliably restrict the forward position of the piston rod 32 toward the tip side. A through-hole 51 is formed in the piston rod 32, penetrating from the base end to the tip. This prevents the inside of the cylinder 31 from being completely sealed, and damps the pressure rise inside the cylinder 31 when air is released to the outside from the through-hole 51. This prevents the movable contact 22 from bouncing back in the closing direction in reaction to the collision, and effectively absorbs the impact. After the air inside the cylinder 31 is released, the repulsive force caused by the compressed air disappears, so the movable contact 22 is not unnecessarily pushed back in the closing direction.

[0023] A communication groove 52 extending from the through hole 51 to the outer peripheral surface on the radially outer side is formed in the piston rod 32 at the tip thereof facing the movable contact 22. This allows air inside the cylinder 31 to be released even when the movable contact 22 is in contact with the tip of the piston rod 32. The outer diameter of the piston rod 32 is larger than the width of the movable contact 22. The communication groove 52 extends in a direction perpendicular to the direction in which the movable contact 22 extends. This ensures that air inside the cylinder 31 is allowed to be released even when the movable contact 22 is in contact with the tip of the piston rod 32. The air damper 23 attenuates the pressure rise inside the cylinder 31 by releasing the air inside the cylinder 31 to the outside through the through-hole 51 and the communication groove 52. This prevents the movable contact 22 from bouncing back in the closing direction in reaction to the collision, and effectively absorbs the impact.

[0024] The position adjustment spring 33 does not reduce the impact on the movable contact 22 by using a repulsive force, but has a spring constant set so that it expands when no load is applied, and moves the piston rod 32 to the tip side of the cylinder 31. As a result, after the air inside the cylinder 31 is released, the repulsive force of the position adjustment spring 33 does not unnecessarily push the movable contact 22 back in the contact closing direction. The middle cover 13 is formed with a recess 56 into which the cylinder 31 fits. A gap d is provided between the inner peripheral surface of the recess 56 and the outer peripheral surface of the cylinder 31. This allows the cylindrical portion 41 to expand when the air inside the cylinder 31 is compressed, and prevents the middle cover 13 from deforming or cracking. Only the engagement portion 42 on the tip side of the cylinder 31 fits into the recess 56. This allows the cylinder 31 to be fixed to the middle cover 13.

[0025] Next, a comparative example will be described. The comparative example is similar to the above-described embodiment except that the air damper 23 is omitted, so the same reference numerals are used for the common components and detailed description thereof will be omitted. FIG. 9 is a diagram showing a comparative example. This figure shows a cross section of a circuit breaker 61 of the comparative example that has been opened by current-limiting interruption, taken along the vertical and depth directions and passing through the center of the third pole, which is located on one side of the width direction, of the three poles aligned in the width direction. During current-limiting interruption during a short circuit, the movable contact 22 jumps up and hits the middle cover 13, which affects the durability of the middle cover 13.

[0026] <<Variation>> In the embodiment, a configuration in which the through hole 51 and the communicating groove 52 are formed in the piston rod 32 has been described, but the present invention is not limited to this. The key is to gradually release air when the air damper 23 is compressed, so a communicating passage that communicates from the base end to the tip end of the piston rod 32 as an air escape route is sufficient. Therefore, a groove extending from the base end to the tip end may be formed on the outer circumferential surface of the piston rod 32. Furthermore, the packing 34 may be omitted, and only a small gap may be provided between the inner circumferential surface of the cylinder 31 and the outer circumferential surface of the piston rod 32.

[0027] Although the present invention has been described above with reference to a limited number of embodiments, the scope of the invention is not limited thereto, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art. [Explanation of symbols]

[0028] 11...circuit breaker, 12...case, 13...middle cover, 21...fixed contact, 22...moving contact, 23...air damper, 26...fixed contact, 27...moving contact, 31...cylinder, 32...piston rod, 33...position adjustment spring, 34...packing, 41...cylindrical portion, 42...engaging portion, 43...opening, 46...inner peripheral surface, 47...recess, 51...through hole, 52...communicating groove, 56...recess, 61...circuit breaker

Claims

1. a movable contact that is rotatable between a closed position and an open position; an air damper provided in the housing, which comes into contact with the movable contact to reduce impact when the movable contact is opened by current-limiting interruption; The air damper is a cylindrical cylinder having a closed base end and an open tip end; a piston rod whose base end is fitted into the cylinder in an axially movable state and whose tip faces the movable contact; a position adjustment spring that is housed in the base end side of the cylinder and moves the piston rod forward toward the tip end side.

2. 2. The circuit breaker according to claim 1, wherein the air damper decelerates the retraction of the piston rod by compressing the air in the cylinder when the piston rod is pushed back toward the base end by the open movable contact.

3. The air damper is 2. The circuit breaker according to claim 1, further comprising a packing attached to an outer peripheral surface of the piston rod and sealing the gap between the piston rod and an inner peripheral surface of the cylinder in a circumferential direction.

4. 4. The circuit breaker according to claim 3, wherein the packing restricts the forward position of the piston rod toward the tip end.

5. The cylinder is a cylindrical portion on whose inner circumferential surface the packing is slidable; 5. The circuit breaker according to claim 4, further comprising: an opening formed at a tip of the cylindrical portion, the opening having an inner diameter smaller than the inner diameter of the cylindrical portion.

6. 2. The circuit breaker according to claim 1, wherein the piston rod has a communication passage formed therein, the communication passage extending from the base end to the tip end.

7. the communication passage is a through hole that penetrates the piston rod, 7. The circuit breaker according to claim 6, wherein the piston rod has a communicating groove formed at a tip thereof facing the movable contact, the communicating groove extending from the through hole to an outer peripheral surface on the radially outer side.

8. The piston rod has an outer diameter larger than the width dimension of the movable contact, The circuit breaker according to claim 7, wherein the communication groove extends in a direction perpendicular to the direction in which the movable contact extends.

9. 8. The circuit breaker according to claim 7, wherein the air damper attenuates a pressure increase in the cylinder by releasing air in the cylinder to the outside through the through hole and the communicating groove.

10. 2. The circuit breaker according to claim 1, wherein the position adjustment spring has a spring constant set to extend when no load is applied, so as to move the piston rod to the tip end side of the cylinder, rather than reducing the impact of the movable contact by a repulsive force.

11. The housing is formed with a recess into which the cylinder fits, 2. The circuit breaker according to claim 1, wherein a gap is provided between an inner peripheral surface of the recess and an outer peripheral surface of the cylinder.

12. The circuit breaker according to claim 11, wherein only an engagement portion on a tip side of the cylinder fits into the recess.

Images