JP7615924B2 - Thermal overload relay - Google Patents

Description

This invention relates to a thermal overload relay.

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. As shown in Patent Document 1, when the bimetal of a thermal overload relay heats up and bends, it presses a shifter to activate a reversing mechanism and enters a tripped state.

JP 2014-107023 A

Thermal overload relays are available in 1E (single element) type, which protects against overload, and 2E (two element) type, which protects against overload and phase loss. The 1E type generally has a two-element structure with bimetals on two phases, U and W, while the 2E type has a three-element structure with bimetals on three phases, U, V, and W. In other words, the two-element structure has fewer elements than the three-element structure, so the displacement of the shifter is smaller.
SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to amplify the amount of displacement of a shifter and transmit it to a reversing mechanism in a two-element thermal overload relay for protecting against overload.

The thermal overload relay according to one aspect of the present invention is a two-element thermal overload relay that provides protection from overload and includes a bimetal that bends when heated, a shifter that is pushed and displaced by the bimetal when the bimetal bends, a lever that is rotatably supported by a support shaft and that is pushed and rotated by the shifter when the shifter is displaced, and a reversing mechanism that reverses the contacts when the lever is pushed from a position radially outward of the position where the lever is pushed by the shifter when the lever rotates.

According to the present invention, when the bimetal is bent, it pushes the reversing mechanism from a position on the lever that is radially outward of the position where the lever is pushed by the shifter, so that the amount of displacement of the shifter can be amplified and transmitted to the reversing mechanism.

FIG. 1 is a diagram showing a thermal overload relay. FIG. FIG. FIG. FIG. FIG. 5A to 5C are diagrams illustrating the operation of a shifter and a lever. FIG.

The following describes an embodiment of the present invention based on the drawings. Note that each drawing is schematic and may differ from the actual product. Furthermore, the following embodiment illustrates an apparatus and method for embodying the technical concept of the present invention, and does not specify the configuration as 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.

One embodiment
"composition"
In the following description, the three mutually orthogonal directions will be referred to as a vertical direction, a width direction, and a depth direction for the sake of convenience.
FIG. 1 is a diagram showing a thermal overload relay.
The thermal overload relay 11, also called a thermal relay, trips when an overcurrent continues to flow and protects the main circuit from overload by shutting off an electromagnetic contactor (not shown). There are two types of thermal overload relay 11: 1E (single element) type that protects from overload and 2E (two element) type that protects from overload and phase loss. Here, we will use the 1E type. The figure shows the inside of the case 12 of the thermal overload relay 11 as seen from the other vertical side with the cover (not shown) removed.

The case 12 is provided inside with a bimetal 21, a shifter 22, a lever 23, a reversing mechanism 24, and a reset rod 25. The thermal overload relay 11 has a two-element structure with the bimetal 21 for the U and W two phases.
The bimetal 21 extends in the depth direction and is formed in a plate shape along the vertical and depth directions, with the front side in the depth direction being a fixed end and the back side being a free end. The front side in the depth direction of the bimetal 21 is connected to a main terminal, and the back side in the depth direction is joined to one end of the heater 26. The heater 26 is wound around the bimetal 21, and the other end is joined to a connection terminal 27 on the front side in the depth direction. The connection terminal 27 is connected to an electromagnetic contactor (not shown). The bimetal 21 is normally straight, but when an overload condition occurs, the free end side bends to the other side in the width direction and pushes the shifter 22.

The shifter 22 is an insulator, formed in a flat plate shape aligned in the width direction and the length direction, and supported by the case 12 in a state in which it can advance and retreat in the width direction. The shifter 22 engages with the free end of the bimetal 21, and is normally located on one side in the width direction, but when an overload occurs, the bimetal 21 bends and the shifter 22 is displaced to the other side in the width direction. The shifter 22 is formed by coating the surface of a base material with a solid lubricant to reduce the friction coefficient of the surface.
The lever 23 is integrally molded from an electrically insulating resin, extends vertically, and amplifies the amount of displacement of the shifter 22 when an overload state is detected, and transmits the amplified displacement to the reversing mechanism 24 .

The reversing mechanism 24 is a mechanism that reverses the contacts when an overload is detected, i.e., closes the a-contact and opens the b-contact, and includes a compensating bimetal 31, a release lever 32, a tension spring 33, a movable plate 34, a leaf spring 35, and an interlocking plate 36. The reversing mechanism 24 is not a main component of the embodiment, so only an outline will be given.
The compensating bimetal 31 extends in the depth direction and is formed in a flat plate shape aligned in the depth direction and 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 and engaging with the lever 23.
The release lever 32 extends in the depth direction, is formed in the shape of a plate aligned in the depth direction and the vertical direction, is rotatably supported by a support shaft aligned in the vertical direction, and its rear side in the depth direction is in contact with the tension spring 33.
The tension spring 33 pulls the movable plate 34 toward the rear in the depth direction.

The movable plate 34 is a flat plate extending in the depth direction and the vertical direction, and the front side in the depth direction can be displaced in the width direction with the back side in the depth direction as a fulcrum. The upright position of the movable plate 34 is the dead center, 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 tensile force of the tension spring 33. Normally, the movable plate 34 tilts to one side in the width direction, but when an overload condition occurs, it tilts to the other side in the width direction by being pushed by the release lever 32 via the compensation bimetal 31. The back 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 the front side in the depth direction.

The leaf spring 35 is a flat plate extending in the depth direction and aligned in the depth direction and vertical direction, with its rear side in the depth direction connected to the other auxiliary terminal and a fixed contact formed on its front side in the depth direction facing the movable plate 34. Under normal circumstances, the movable contact of the movable plate 34 is separated from the fixed contact of the leaf spring 35, but when an overload condition 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 condition is established when the a-contact is closed.
The interlocking plate 36 is formed in a plate shape 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 the movable plate 34. The interlocking plate 36 rotates in conjunction with the movable plate 34, thereby opening and closing the contacts on the back side of the interlocking plate 36 (not shown in the figure). That is, under normal circumstances, the movable contact is in contact with the fixed contact, but when an overload condition occurs, the interlocking plate 36 rotates and the movable contact moves away from the fixed contact. These fixed contacts and movable contacts constitute a b-contact, and a tripping condition occurs when the b-contact opens.

The reset rod 25 is an operating element for recovering from a tripped state, and is formed in a generally cylindrical shape with the depth direction as its axial direction, and 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 in a state in which it can be displaced in the depth direction and rotated around its axis, and is biased toward the front side in the depth direction by a leaf spring 47 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 in which the front side in the depth direction protrudes further than the case 12. The manual reset position is a position where the reset rod 25 is merely pushed from the initial position toward the rear side in the depth direction. The automatic reset position is a position where the position in the depth direction is maintained by being pushed from the initial position toward the rear side in the depth direction and being rotated approximately 90 degrees clockwise as viewed from the front side in the depth direction.

When the reset rod 25 is pushed toward the rear in the depth direction while in a 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 if the overload state is eliminated, the a contact opens again and the b contact closes. On the other hand, when the reset rod 25 is pushed toward the rear in the depth direction while in a tripped state and rotated 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 when the overload state is eliminated, the a contact automatically opens again and the b contact closes.

Next, the structures of the shifter 22 and the lever 23 will be described.
FIG. 2 is a diagram showing a shifter and a lever.
Here, the case 12 is shown as viewed from the other side in the vertical direction, one side in the width direction, and the far side in the depth direction.
FIG. 3 is a diagram showing the case.
Here, the case 12 is shown as viewed from the other side in the vertical direction, one side in the width direction, and the far side in the depth direction. On the inside of the case 12, partition walls 41 to 43 and a girder plate 44 are formed.

The partitions 41 to 43 are arranged in order from one side to the other in the width direction, extend in the depth direction, and are formed in a plate shape along the depth direction and the vertical direction. The U-phase bimetal 21 and connection terminal 27 are arranged on one side of the partition 41 in the width direction. The V-phase connection terminal 27 is arranged between the partitions 41 and 42. The W-phase bimetal 21 and connection terminal 27 are arranged between the partitions 42 and 43. The reversing mechanism 24 is arranged on the other side of the partition 43 in the width direction. On the other vertical side of the end face on the back side in the depth direction, the partitions 41 to 43 have a substantially cylindrical protrusion 45 that is convex toward the back side in the depth direction, and the three protrusions 45 are aligned in a straight line along the width direction. Only the protrusion 45 of the partition 42 has a head on the back side in the depth direction that is raised to the other side in the width direction.

The partitions 41 to 43 have a generally cylindrical projection 45 formed on one vertical side of the end face on the far side in the depth direction, which protrudes toward the far side in the depth direction. Similarly, only the projection 45 of the partition 42 has a head portion on the far side in the depth direction that protrudes toward the other side in the width direction. The projection 45 provided on one vertical side is fitted with a shifter when a 1E type or 2E type three-element structure having a bimetal for the V phase is adopted. Therefore, the case 12 is common to the 1E type and 2E type three-element structures.
The girder plate 44 is disposed on the far side in the depth direction, extends in the width direction, and is formed in a plate shape along the width direction and the vertical direction. The girder plate 44 has a groove 46 formed on the other edge in the vertical direction on the other side in the width direction from the partition wall 43, which is recessed toward one side in the vertical direction and has a substantially U-shape when viewed from the depth direction.

FIG. 4 is a diagram showing a shifter.
The shifter 22 is a substantially rectangular flat plate with a long side in the width direction and a short side in the vertical direction. The shifter 22 has a long hole 51 extending in the width direction and into which the protrusion 45 of the partition 41 fits on one side in the width direction. The shifter 22 has a long hole 52 extending in the width direction and into which the protrusion 45 of the partition 42 and the protrusion 45 of the partition 43 fit on the other side in the width direction. The long hole 52 has a different vertical size on one side in the width direction and the other side in the width direction, and the one side in the width direction is larger than the head of the protrusion 45 of the partition 42, and the other side in the width direction is smaller than the head of the protrusion 45 of the partition 42. The shifter 22 is displaceable along the width direction by fitting the long hole 51 into the protrusion 45 of the partition 41 and fitting the long hole 52 into the protrusion 45 of the partition 42 and the protrusion 45 of the partition 43. When the protrusion 45 of the partition 42 is on one side of the elongated hole 52 in the width direction, the shifter 22 can be removed. When the protrusion 45 of the partition 42 is on the other side of the elongated hole 52 in the width direction, the head of the protrusion 45 prevents the shifter 22 from being removed.

The shifter 22 has engagement pieces 53 to 55 formed on one side in the vertical direction. The engagement piece 53 is disposed on one side in the width direction from the partition wall 41, and protrudes from one side in the vertical direction toward one side in the width direction. The free end of the bimetal 21 in the U phase engages with the tip of the engagement piece 53 that faces one side in the width direction. The engagement piece 54 is disposed between the partition wall 41 and the partition wall 42, and protrudes from one side in the vertical direction toward one side in the width direction. The engagement piece 55 is disposed on the other side in the width direction from the partition wall 43, and protrudes from one side in the vertical direction toward both one and the other sides in the width direction. The free end of the bimetal 21 in the W phase engages with the tip of the engagement piece 53 that faces one side in the width direction, and the lever 23 engages with the tip 56 that faces the other side in the width direction.
When the 1E type of three-element structure is adopted, the free end of the bimetal in the V phase engages with the tip of the engagement piece 54 that faces one side in the width direction. Therefore, the shifter 22 is common to the 1E type of three-element structure.

FIG. 5 is a perspective view showing the lever.
(a) in the figure shows the lever 23 as viewed from the other side in the vertical direction, one side in the width direction, and the rear side in the depth direction, and (b) in the figure shows the lever 23 as viewed from one side in the vertical direction, the other side in the width direction, and the front side in the depth direction.
FIG. 6 is a perspective view showing the lever.
(a) in the figure shows the lever 23 when viewed from the back side in the depth direction with hidden lines displayed, (b) in the figure shows the lever 23 when viewed from the other side in the width direction, and (c) in the figure shows the A-A cross section of (b).

A pair of opposing plates 61 and 62 are formed on one side of the lever 23 in the vertical direction. The opposing plates 61 and 62 are formed in the shape of flat plates along the vertical and width directions, face each other while being spaced apart in the depth direction, and are connected by a cylindrical support shaft 63 extending in the depth direction. The distance between the opposing plates 61 and 62 is slightly larger than the thickness of the girder plate 44, and the diameter of the support shaft 63 is slightly smaller than the groove 46. With the opposing plates 61 and 62 sandwiching the girder plate 44, the support shaft 63 fits into the groove 46, so that the lever 23 is rotatably supported by the support shaft 63 with respect to the case 12. The lever 23 has an end surface 64 facing one side in the width direction formed over approximately half of the other side in the vertical direction. The end surface 64 is a flat surface along the vertical and depth directions, and engages with the tip 56 of the engagement piece 53 in the shifter 22. The lever 23 has an end face 65 facing the other side in the width direction formed on the other side in the vertical direction. The end face 65 is a curved surface along the depth direction that is convex toward the other side in the width direction, and engages with the free end of the compensation bimetal 31 in the reversing mechanism 24. As shown in FIG. 6, when viewed from the depth direction, a straight line L1 indicated by a dotted line connecting the center of the support shaft 63 and the position of the end face 65 that bulges most toward the other side in the width direction extends along the vertical direction.

Action
Next, the main operation of the embodiment will be described.
FIG. 7 is a diagram illustrating the operation of the shifter and the lever.
Here, the case 12 is shown as seen from the rear side in the depth direction. Normally, the shifter 22 is located on one side in the width direction, and the end face 65 of the lever 23 is pressed by the compensating bimetal 31, so that the other side in the vertical direction is located on one side in the width direction.
When an overload condition occurs, the bimetal 21 bends, and at least one of the engagement pieces 53 and 55 of the shifter 22 is pushed and displaced to the other side in the width direction. As a result, the end face 64 of the lever 23 is pushed by the tip 56 of the engagement piece 55 as the shifter 22 is displaced to the other side in the width direction, and the lever 23 rotates counterclockwise as viewed from the back side in the depth direction, and the other side in the vertical direction is displaced to the other side in the width direction. As a result, the free end side of the compensating bimetal 31 is displaced to the other side in the width direction, and the reversing mechanism 24 enters a trip state in which the a contact is closed and the b contact is opened.

When the overload state is eliminated, the bimetal 21 returns to a straight line and the free end returns to one side in the width direction. Furthermore, when the reset rod 25 is in the manual reset position or the automatic reset position, the reversing mechanism 24 returns to the normal state in which the a contact is open and the b contact is closed, and the free end of the compensating bimetal 31 displaces to one side in the width direction. As a result, the end face 65 of the lever 23 is pressed by the compensating bimetal 31, causing it to rotate clockwise when viewed from the back side in the depth direction, and the other side in the vertical direction is displaced to one side in the width direction. As a result, the engagement piece 55 of the shifter 22 is pressed by the end face 64 of the lever 23, causing it to return to one side in the depth direction.

Action
Next, the main operation of the embodiment will be described.
The thermal overload relay 11 with a two-element structure for protection against overload includes a bimetal 21, a shifter 22, a lever 23, and a reversing mechanism 24. The bimetal 21 bends when heated. When the bimetal 21 bends, the shifter 22 is pushed by the bimetal 21 and displaced. The lever 23 is rotatably supported by a support shaft 63, and when the shifter 22 is displaced, the lever 23 is pushed by the shifter 22 and rotates. When the lever 23 rotates, the reversing mechanism 24 is pushed from a position on the lever 23 that is radially outward of the position where the lever 23 is pushed by the shifter 22, thereby reversing the contacts.

As a result, the lever 23 can amplify the displacement of the shifter 22 and transmit it to the reversing mechanism 24. That is, since the two-element structure has fewer elements than the three-element structure, the displacement of the shifter 22 is smaller, but the displacement of the shifter 22 can be compensated for by the amplifying action of the lever 23. Therefore, there is no need to redesign the heater 26 to obtain the same displacement with the two-element structure as with the three-element structure. In addition, there is no need to design the heater 26 separately for the two-element structure and the three-element structure, and it can be made common. This makes it possible to suppress increases in manufacturing costs and to facilitate management of each part in the assembly process. Since the lever 23 has the support shaft 63 molded as an integral part, it suppresses an increase in the number of parts and also improves the ease of assembly work.

The amplification factor of the displacement amount in the shifter 22 is adjusted by adjusting the position of the pivot 63, which is the center of rotation of the lever 23, the position where it is pressed by the shifter 22, and the position where it presses the reversing mechanism 24. For example, the closer the position of the pivot 63 and the position where it is pressed by the shifter 22 are, as viewed from the depth direction, and the farther the position where it is pressed by the shifter 22 and the position where it presses the reversing mechanism 24 are, the greater the amplification factor becomes. In this way, the amplification factor can be arbitrarily adjusted and transmitted to the reversing mechanism 24. Depending on the amplification factor, the displacement amount of the compensation bimetal 31 can be made larger than in the three-element structure, which can suppress malfunctions of the reversing mechanism 24 and improve reliability.

When the bimetal 21 is not curved, that is, in normal operation, the position of the support shaft 63 that is the center of rotation and the position where the reversing mechanism 24 is pressed are aligned in a direction perpendicular to the direction of pressing the reversing mechanism 24, as viewed from the axial direction of the support shaft 63. In other words, as viewed from the depth direction, the angle θ that the straight line L1 that connects the center of the support shaft 63 and the position of the end face 65 that bulges most to the other side in the width direction makes with the vertical direction is made as small as possible. This is because when the lever 23 rotates, the trajectory of the position of the end face 65 that bulges most to the other side in the width direction is displaced more in the width direction as the angle θ that the straight line L1 makes with the vertical direction is smaller. Therefore, the trajectory of the position where the reversing mechanism 24 is pressed is most likely to displace in the width direction, and the amplification factor of the displacement amount in the shifter 22 can be increased.

The position of the shifter 22 where it is pressed by the bimetal 21 and the position where it presses the lever 23 are arranged on a straight line along the displacement direction. In this way, the point of force and the point of action are arranged on a straight line, so that when the shifter 22 is pressed by the bimetal 21, it is possible to prevent a clockwise moment from acting on the shifter 22 as viewed from the rear side in the depth direction. Therefore, it is no longer necessary to suppress the moment by weight balance, for example by making the shape of the shifter 22 significantly larger on one side in the vertical direction than the position where it is pressed by the bimetal 21 as viewed from the depth direction, and weight reduction and space saving can be achieved.
The shifter 22 is flat, and the lever 23 has a support shaft 63 extending perpendicular to the surface of the shifter 22 and rotates in the surface direction of the shifter 22. This makes it possible to prevent the thermal overload relay 11 from becoming large in size in the depth direction.

Next, a comparative example will be described.
FIG. 8 is a diagram showing a comparative example.
Here, the case 12 is shown as seen from the rear side in the depth direction. The thermal overload relay 71 includes a shifter 72, and has a different shape from the shifter 22 of the embodiment. In the thermal overload relay 71 of the comparative example, the shifter 72, pushed by the bimetal 21, directly pushes the reversing mechanism 24, thereby tripping the relay. The two-element structure has fewer elements than the three-element structure, so the displacement of the shifter 72 is smaller. To obtain the same displacement amount as the three-element structure with the two-element structure, the design of the heater 26 needs to be reviewed, but conversely, with the three-element structure, the amount of heat generated is large, and the temperature rise of each terminal may exceed the standard range. In other words, the heater 26 must be designed separately for the two-element structure and the three-element structure, and it was not possible to use the heater 26 in common.

In addition, the position where the shifter 72 presses the compensating bimetal 31 is on the other vertical side of the position where it is pressed by the bimetal 21, and the point of force and the point of action are not arranged on a straight line along the width direction. Therefore, when the shifter 72 is pressed by the bimetal 21, a clockwise moment acts on it when viewed from the back side in the depth direction, which becomes a sliding resistance against the protrusion 45. Therefore, the shape of the shifter 72 is greatly expanded on one vertical side of the position where it is pressed by the bimetal 21 when viewed from the depth direction, in order to suppress the moment through weight balance. This has therefore been an obstacle to weight reduction and space saving.

The above description refers to a limited number of embodiments, but the scope of the rights is not limited to these, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art.

Reference Signs List 11...thermal overload relay, 12...case, 21...bimetal, 22...shifter, 23...lever, 24...reversal mechanism, 25...reset rod, 26...heater, 27...connection terminal, 31...compensating bimetal, 32...release lever, 33...tension spring, 34...movable plate, 35...leaf spring, 36...interlocking plate, 41...partition wall, 42...partition wall, 43...partition wall, 44...beam plate, 45...projection, 46...groove, 47...leaf spring, 51...long hole, 52...long hole, 53...engaging piece, 54...engaging piece, 55...engaging piece, 56...tip, 61...opposing plate, 62...opposing plate, 63...support shaft, 64...end surface, 65...end surface, 71...thermal overload relay, 72...shifter

Claims (5)

In a two-element thermal overload relay for protection against overload,
Case and
a bimetal provided inside the case and bending when heated;
a shifter provided inside the case, the shifter being pushed and displaced by the bimetal when the bimetal is bent;
a lever provided inside the case, rotatably supported by a support shaft that fits into a groove in the case , and that is pushed by the shifter and rotates when the shifter is displaced;
a reversing mechanism provided inside the case , which reverses the contacts when the lever is pushed from a position radially outward from the position of the lever pushed by the shifter when the lever rotates. The thermal overload relay of claim 1, characterized in that the amplification factor of the displacement amount in the shifter is adjusted by adjusting the position of the support shaft that serves as the center of rotation, the position where the lever is pressed by the shifter, and the position where the lever presses the reversing mechanism. The thermal overload relay according to claim 1 or 2, characterized in that when the bimetal is not bent, the position of the support shaft that serves as the center of rotation and the position that presses the reversing mechanism are aligned in a direction perpendicular to the direction in which the reversing mechanism is pressed, as viewed from the axial direction of the support shaft. The thermal overload relay according to any one of claims 1 to 3, characterized in that the position where the shifter is pressed by the bimetal and the position where the shifter presses the lever are arranged on a straight line along the displacement direction. The shifter is flat,
5. A thermal overload relay according to claim 1, wherein said lever has a support shaft extending in a direction perpendicular to a surface of said shifter and rotates in the direction of the surface of said shifter.

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