WO2019087572A1 - Current detection coil - Google Patents

Abstract

This current detection coil (toroidal coil) 10 is provided with: a belt-shaped core part 30 having a uniform thickness or cross-sectional area; and a coil part 32 mounted on the core part 30. A winding portion of the coil part 32 is divided into: a first end section winding portion 32a formed by winding a coil conductor CW at a constant pitch on an end section 30a of one side (the left side in the drawing) of the core part 30; a second end section winding portion 32c formed by winding the coil conductor CW at a constant pitch on an end section of the other side (the right side in the drawing) of the core part 30; and an intermediate section winding portion 32b formed by winding the coil conductor CW at a constant pitch on an intermediate section 30b sandwiched between both the end sections 30a, 30c of the core part 30.

Description

Current detection coil

The present invention relates to a current detection coil which detects a current flowing in a conductor in a contactless manner using the principle of electromagnetic induction.

This type of current detection coil is generally referred to as a toroidal coil or Rogowski coil. As shown in FIG. 12, when current i flows through conductor 100, a loop of magnetic flux M is generated around this conductor 100 at a density based on Ampere's law, and coil 102 is disposed near this conductor 100, An induced electromotive force v is generated in the coil 102 in proportion to the time rate of change of the current i. The toroidal coil utilizes the principle of this electromagnetic induction, and as shown in FIG. 13, the coil 102 is formed in a toroidal shape and disposed around the conductor 100 so as to surround it. Then, when current i flows through conductor 100, magnetic flux M generated around it flows electromagnetically most efficiently with coil 102, and a current detection coil with good measurement sensitivity is obtained.

A typical toroidal coil 106, as shown in FIG. 14, includes a forwardly extending portion 108 extending in a toroidal shape, and a line extending along the coil portion 108 in a reverse direction from the end 108e (turnback point) of the forward portion 108 And a return path portion 110 extending in a shape (or toroidal shape). Here, for the magnetic flux m from the outside passing through the toroidal loop of the toroidal coil 106, the return path section 110 generates an induced electromotive force in the opposite direction by the electromagnetic coupling equivalent to the forward path section 108, and the external magnetic flux It works to cancel the current detection noise caused by m. The current detection signal representing the waveform of the current i from the output terminal of the integration circuit 116 is connected to the input terminal of the integration circuit 116 through the lead end 108s of the forward path section 108 and the end 110e of the return path 110 via the pair of lead wires 112 and 114 S _i is to be obtained.

As shown in FIG. 15, when measuring the welding current in, for example, a resistance welding machine, toroidal coil 106 comprises a welding power supply unit 120 including a welding transformer (not shown), a pair of welding electrodes 122 and 124, and a pressing mechanism. It is removably mounted on a feed conductor 100 which is bridged between a welding head 126 comprising a (not shown). At the time of resistance welding, welding power source unit 120 includes conductor 100 and welding electrodes 122, 124 in a state where welding head 126 applies a constant pressure with welding material (not shown) interposed between welding electrodes 122, 124. A constant welding current i is applied to the material to be welded through. By this welding energization, the vicinity of the welding point of the material to be welded is melted by Joule heat, and the melted portion solidifies after the completion of the energization to form a welded joint. Welding current i flowing through conductor 100 during welding is detected through toroidal coil 106, and current detection signal S _i output from integration circuit 116 (FIG. 14) is used for feedback control of welding current, monitoring of welding quality, etc. Be done.

US Patent Application Publication 2013/0257412 International Publication No. 2009/001581

As understood from FIG. 15, there are variations in how the toroidal coil 106 is hooked (relative positional relationship) to the conductor 100 through which the detected current flows. As shown in FIG. 16, when the toroidal coil 106 has a toroidal shape, one coil end at which the start end 108s of the forward path 108 and the end 110e of the return path 110 are located, the end 108b of the forward path 108 and the start 110s of the return path A gap (discontinuity) G on the toroidal loop is unavoidably formed between the other end of the coil where it is located. Variations in the relative positional relationship between the gap G and the conductor 100 cause a large error in the current detection sensitivity of the toroidal coil 106, and it is a problem that the current detection accuracy is greatly affected.

That is, even the same current value of the detected current i, 16, compared to the case in a position where the conductor 100 is separated from the gap G as [P _1] or [P _2], the [P _3] As described above, when the conductor 100 is at a position close to the gap G, the current measurement value indicated by the current detection signal S _i greatly decreases. This is because when the conductor 100 is at a position close to the gap G, a high density magnetic flux distributed in the vicinity of the conductor 100 does not interlink with the coil portion 108 in the gap G. This is because the current detection sensitivity of the toroidal coil 106 is weakened.

In the prior art, both ends of the toroidal coil are closed and held in order to reduce the error in which the current detection sensitivity is significantly lowered when the conductor 100 is at a position close to the gap G as described above to improve current detection accuracy. Although the structure, material, and the like of the connector have been elaborated (Patent Documents 1 and 2), the effect of improving the current detection accuracy is limited in proportion to the complication of the connector and the cost increase.

The present invention solves the above-described problems, and provides a current detection coil that achieves a significant improvement in current detection accuracy by devising the winding structure of the coil portion.

The current detection coil according to the present invention has a core portion capable of taking a toroidal shape so as to surround a conductor through which a current to be detected flows, and a coil portion mounted on the core portion, and the coil portion A first end section winding section formed by winding a coil wire in one end section of the core section, and a second end section formed by winding a coil lead in the other end section of the core section An end section winding section, and an intermediate section winding section formed by winding a coil wire in an intermediate section sandwiched between the first and second end sections of the core section; The winding density of the second end section winding portion is higher than the winding density of the intermediate section winding portion.

In the above configuration, since the winding density of the first and second end section winding portions is higher than the winding density of the intermediate section winding portion, the conductor through which the current to be measured flows is the toroidal of the current detection coil. In the loop, near or far from the gap between the coil ends, the electromagnetic coupling between the conductor and each section winding portion is substantially equal, and the overall mutual inductance of the coil portion Is stable, the error in current detection sensitivity due to the relative positional relationship between the conductor and the gap can be effectively reduced.

In a preferred aspect of the invention, each of the first and second end section windings has more winding layers than the middle section winding. Preferably, in the forward section or the reverse section of the coil section, the first and second end section winding sections have a plurality of winding layers, and the middle section winding section has a single winding layer.

In a particularly preferred embodiment of the present invention, the first end section winding portion starts winding the coil wire from the vicinity of the tip of one end section of the core in the forward direction toward the other end section side. The coil wire is wound at a fixed pitch, folded around the boundary with the middle section winding part, wound in a reverse direction at a fixed pitch, folded around the end of one end section, It has a portion formed by winding the coil conductor at a constant pitch again in the forward direction to the vicinity of the boundary with the winding portion. The middle section winding portion has a portion in which the coil wire is wound at a constant pitch in the forward direction through the middle portion of the core portion. Then, in the other end section of the core portion, the second end section winding portion winds the coil conductor at a constant pitch in the forward direction from the vicinity of the boundary with the intermediate section in the other end section, and turns around the tip of the other end section In the reverse direction, the coil conductor is wound at a constant pitch, folded around the boundary with the intermediate section, and wound in the forward direction to the vicinity of the tip of the other end section.

According to the current detection coil of the present invention, it is possible to effectively reduce the error in the current detection sensitivity caused by the variation in the arrangement position in the coil of the conductor through which the current to be detected flows, and to realize significant improvement of the current detection accuracy .

It is a perspective view which shows the external appearance structure of the current detection coil (toroidal coil) in one Embodiment of this invention. It is a figure which unfolds and shows the principal part of the above-mentioned toroidal coil. It is a figure which shows the cross-section of the outward winding part of the intermediate section of the said toroidal coil. It is a figure which shows the cross-section of the forward winding part of each end area of the said toroidal coil. It is a figure showing the whole cross section structure of the middle section of the above-mentioned toroidal coil. It is a figure which shows the whole cross-section of the end area of the said toroidal coil. It is a figure which shows the creation process of the outward winding part of the 1st end area winding part of the coil part in the said toroidal coil. It is a figure which shows the preparation process of the outward winding part of the intermediate section winding part of the said coil part. It is a figure which shows the preparation process of the outward winding part of the 2nd end section winding part of the said coil part. It is a figure which shows the longitudinal cross-section structure of the outward winding part of the 2nd end area of the said toroidal coil, and an intermediate area, and a return way winding part. It is a figure which shows the longitudinal cross-section structure of the outward winding part of the 1st end area of the said toroidal coil, and an intermediate area, and a return way winding part. It is a figure which shows typically one structural example of the connector which can be used for the said toroidal coil. It is a figure which shows typically another structural example of the connector which can be used for the said toroidal coil. Fig. 6 shows an experimental model for measuring the error of the current detection sensitivity depending on the relative position of the mounted conductor with respect to the toroidal coil. It is a graph which shows the characteristic of the range error of the detection current value obtained from the toroidal coil of a comparative example in the said experimental model. It is a graph which shows the characteristic of the range error of the detection current value obtained from the toroidal coil of embodiment in the said experimental model. It is a figure which shows one modification of the manufacturing process of the end area winding part in the coil part of the toroidal coil of embodiment. It is a figure which shows the cross-sectional structure of the intermediate section of the colloidal coil which has the return path part of one modification. It is a figure which shows the cross-sectional structure of the end area of the toroidal coil which has a return path part of the said modification. It is a figure which shows the principle of the current detection coil (toroidal coil) which detects the electric current which flows through a conductor contactlessly. It is a figure which shows the principle of a toroidal coil. It is a figure which shows the structure of the conventional typical toroidal coil. It is a figure which shows the use form of the toroidal coil in a resistance welding machine. It is a figure for demonstrating the dispersion | variation in the electric current detection sensitivity depending on how the toroidal coil is hooked with respect to the conductor through which a to-be-measured electric current flows.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

[Configuration of current detection coil (toroidal coil) in the embodiment]
The overall configuration of the current detection coil according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4A and 4B.

As shown in FIG. 1, the current detection coil 10 in this embodiment is disposed so as to surround a conductor (not shown) through which a current to be detected flows, and has its toroidal shape (donut shape) when both ends are closed. It is supposed to be taken. The current detection coil (hereinafter referred to as "toroidal coil") 10 is covered with a heat shrinkable tube 12 for insulation and protection having a uniform thickness over the entire surface, and the inner side of this heat shrinkable tube 12 And a substantial portion that performs the current detection function. A connector (not shown) for holding the toroidal shape is attached to both ends of the toroidal coil 10, and the both ends are held by the connector.

The toroidal coil 10 is physically divided into three sections in the length direction or toroidal loop direction, that is, a first coil end section 14, a coil intermediate section 16 and a second coil end section 18. As shown, the first and second coil end sections 14, 18 are much thicker than the coil intermediate section 16. This is due to the difference in coil winding structure as described later. A pair of lead wires 20, 22 drawn from the first coil end section 14 are for connecting both ends of the current detection coil 10 to an external circuit such as an input terminal of the integration circuit 116 (FIG. 14). .

The configuration of the contents of the toroidal coil 10 is shown in FIG. As illustrated, the toroidal coil 10 has a belt-like core 30 having a uniform thickness or cross-sectional area, and a coil 32 (32a, 32b, 32c) mounted on the core 30 from end to end. And).

Although any nonmagnetic material may be used as the material of the core portion 30, for example, a resin having excellent flexibility such as a fluorine resin can be suitably used. As a material of the coil portion 32, any lead wire or wire excellent in flexibility may be used, but for example, an enameled wire made of polyurethane, polyethylene or the like as an insulating film can be suitably used.

Here, the coil section 32 is a first end section formed by winding the coil wire CW at a constant pitch in the end section 30a of one of the core sections 30 (left side in the figure) over substantially the entire length of the core section 30. A second end section winding section 32c formed by winding a coil wire CW at a constant pitch in an end section of the winding section 32a and the other (right side in the drawing) of the core section 30, and both ends of the core section 30 An intermediate section winding portion 32b is formed by winding the coil conductor CW at a constant pitch in the intermediate section 30b sandwiched between the sections 30a and 30c.

In this embodiment, each of the winding portions 32a, 32b, 32c of the coil portion 32 has a forward winding portion and a return winding portion. Here, the forward winding section is set in the forward section of the coil section 32 in which the coil section 32 extends from one end (left end in FIG. 2) of the core section 30 to the other end (right end in FIG. 2) It is a winding part. The return winding portion is a winding portion in which the coil portion 32 is set in the return path section of the coil portion 32 from the other end (right end in FIG. 2) of the core portion 30 to one end (left end in FIG. 2) It is. In FIG. 2, in order to facilitate the illustration, only the forward winding portion of each of the winding portions 32a, 32b and 32c is shown, and the return winding portion is omitted.

The starting end of the coil portion 32 is also the starting end of the forward winding portion of the first end section winding portion 32a, and is connected to one of the lead wires 20 (FIG. 1). The end of the coil portion 32 is also the end of the return winding portion of the first end section winding portion 32a, and is connected to the other lead wire 22 (FIG. 1).

In the toroidal coil 10, focusing on the forward path section of the coil section 32, the coil conductor CW which constitutes the three section winding sections 32c, 32b and 32c of the coil section 32 is a continuous lead (enamel wire) However, while the winding of the intermediate section winding portion 32b is a single layer, the windings of the first and second end section winding portions 32a and 32c are configured in multiple layers. For this reason, the first and second coil end sections 14 and 18 are thicker than the coil intermediate section 16.

More specifically, as shown in FIG. 3A, in the forward winding portion of the intermediate section winding portion 32b of the coil portion 32, the core wire 30 is formed on the core portion 30 in a cross section orthogonal to the extending direction of the core portion 30. Has a single-layer winding structure wound around only once. On the other hand, as shown in FIG. 3B, in the forward winding portions of the first and second end section winding portions 32a and 32c of the coil portion 32, the coil wire CW is 2 around the core portion 30 in the cross section. It has a three-layer winding structure which is wound three times via two insulating layers 34 (1) and 34 (2).

As shown in FIGS. 4A and 4B, in each winding portion 32a, 32b, 32c of the coil portion 32, the insulating layer 34 (3) is provided outside or around the forward winding portion (FIGS. 3A and 3B). The return winding portion 36 of the coil portion 32 is provided. The return winding portion 36 has a single-layer winding structure consisting of one coiled wire CW continuous with the forward winding portion, and extends over the three winding portions 32c, 32b, 32a to form a return path portion. Configure. The first coil end section 14, the coil intermediate section 16 and the second coil end section 18 in appearance are connected to the first end section winding section 32a, the middle section winding section 32b and the second section end 18 via the heat shrinkable tube 12. It corresponds to the end section winding part 32c of 2 respectively. The insulating layers 34 (1), 34 (2), 34 (3) may be any flexible resin, and for example, an adhesive vinyl tape can be suitably used.

[Method of Forming Coil Winding in Embodiment]
Next, with reference to FIGS. 5A to 5C, a method of producing the main part of the toroidal coil 10 in this embodiment (in particular, the section winding parts 32a, 32b, 32c of the coil part 32) will be described.

FIG. 5A shows a process of forming the forward winding portion of the first end section winding portion 32 a of the coil portion 32. In the first end section winding portion 32a, winding of the coil conductor CW is started from the starting end point [S] set near the tip (left end in the figure) of one end section 30a of the core 30 The coil wire CW is wound at a constant pitch in the direction (direction of arrow A ₁ ), and the winding operation is once performed at a _first intermediate point [R ₁ ] set near the boundary between the core 30 and the intermediate section 30b. Stop. As a result, as shown in (a) of FIG. 5A, the winding portion of the first layer is formed.

Next, as shown in (b) of FIG. 5A, the first vinyl tape 34 (1) is attached to the outer surface of the winding portion of the first layer. Then, winding a coil conductor CW at a predetermined pitch in the opposite direction (the direction of arrow A ₂₎ from the first intermediate point on the vinyl tape 34 (1) [R _1], wound around the starting point [S] Stop the operation. Thus, as shown in (c) of FIG. 5A, the winding of the second layer is formed.

Next, as shown in (d) of FIG. 5A, the second layer vinyl tape 34 (2) is attached to the outer surface of the winding portion of the second layer. Then, on the second layer vinyl tape 34 (2), the coil conductor CW at a constant pitch again in the forward direction (direction of the arrow A ₃ ) from the vicinity of the start point [S] toward the first intermediate point [R ₁ ] Roll around. Then, as shown in (e) of FIG. 5A, the winding portion of the third layer is formed. Thus, the forward winding portion of the first end section winding portion 32a has a three-layer winding structure having three winding layers.

In the forward winding portion of the intermediate section winding portion 32b, as shown in FIG. 5B, the coil conductor from the vicinity of the first intermediate point [R ₁ ] by extension or continuation from the first end section winding portion 32a. The winding of the CW is started, and the coil conductor CW is wound at a constant pitch in the forward direction (the direction of the arrow B) through the middle section 30b of the core 30 as it is. Then, as shown in (a) of FIG. 5C, when passing through the _second middle point [R ₂ ] set near the boundary with the other (right) end section 30 c of the core 30, the middle section winding The creation of the line portion 32b is completed. Thus, the forward winding portion of the intermediate section winding portion 32b has a single-layer winding structure having one winding layer.

In the forward winding portion of the second end segment winding portion 32c, as shown in (a) of FIG. 5C, from the vicinity of the _second intermediate point [R ₂ ] in the continuation from the intermediate segment winding portion 32b start the winding of the coil conductor CW, winding a coil conductor CW at a constant pitch on the end section 30c in the forward direction (direction of the arrow C ₁₎ of the other core portion 30 (right side), the tip end section 30c Stop the winding operation at the termination point [E] set near (right end). As a result, as shown in (a) of FIG. 5C, the winding portion of the first layer is formed.

Next, as shown in (b) of FIG. 5C, the first vinyl tape 34 (1) is attached to the outer surface of the winding portion of the first layer. Then, winding a coil conductor CW at a predetermined pitch in the opposite direction (the direction of arrow C ₂₎ from the vicinity of the end point [E] on the vinyl tape 34 (1), second intermediate point [R _2] wound around Stop operation. As a result, as shown in (c) of FIG. 5C, the winding of the second layer is formed.

Next, as shown in (d) of FIG. 5C, a second-layer vinyl tape 34 (2) is attached to the outer surface of the winding portion of the second layer. Then, winding a coil conductor CW at a predetermined pitch in the second intermediate point on the vinyl tape 34 (2) again forward from [R _2] (direction of arrow C _3), past the end point [E] By the way, the winding operation is stopped. At the same time, the entire winding operation or manufacturing process relating to the forward winding portion of the coil portion 32 is completed. As a result, as shown in (e) of FIG. 5C, a winding portion of the third layer is formed in the second end section winding portion 32c. Thus, the forward winding portion of the second end section winding portion 32c has a three-layer winding structure having three winding layers.

As described above, the first end section winding section 32a, the middle section winding section 32b and the second end section winding section 32c in the order of the first end section winding section 32a, the second end section winding section 32c, and the like from the left end to the right end on the core section 30 Windings are created. Next, a common vinyl tape 34 (3) is attached to the outer surface of the forward winding portion of each winding portion 32a, 32b, 32c. Then, as shown in FIGS. 6A and 6B, the coil conductor CW is wound on the vinyl tape 34 (3) from near the end point [E] to near the start point [S] at a constant pitch. As a result, a common return winding portion (return path portion) 36 is created in the order of the second end section winding section 32c, the intermediate section winding section 32b, and the first end section winding section 32a.

6A and 6B, the arrow D indicates the winding advancing direction of the return path winding portion (return path portion) 36. Further, in the forward winding portions of the first and second end section winding portions 32a and 32b, arrows A ₁ and C ₁ indicate the winding advancing direction of the winding portion of the first layer as described above, and the arrows A ₂ and C ₂ indicate the winding advancing direction of the winding portion of the second layer as described above, and arrows A ₃ and C ₃ indicate the winding advancing direction of the winding portion of the third layer as described above. . Further, in the intermediate section winding portion 32b, the arrow B indicates the winding advancing direction of the forward winding portion as described above.

As described above, the operation of winding the coil wire CW at a constant pitch on the core portion 30 can be easily performed using a known coil winding machine. Further, since the coil wire CW is an enameled wire, it is possible to electrically omit the vinyl tapes (insulation layers) 34 (1), 34 (2), 34 (3). In particular, in the forward winding portions of the first and second end section winding portions 32a and 32c, it is also possible to obtain a multilayer winding structure without interposing the vinyl tapes 34 (1) and (2). . However, by interposing vinyl tape 34 (1), 34 (2) between different winding layers, the unevenness of the lower layer winding portion is compensated, and the winding operation of the upper layer side winding portion is stabilized and It can be done with high accuracy. Further, in the coil portion 32, the winding pitch of each winding portion is normally set between all the section winding portions 32a, 32b and 32c, and by opening all the winding layers of the end section winding portions 32a and 32c. The values may be set to the same value, but may be set to individual values for each section or each winding layer as needed.

[Function of Toroidal Coil in Embodiment]
As described above, the toroidal coil 10 in this embodiment is characterized by the configuration of the coil portion 32 (particularly, the winding portion in the forward path section) which is a substantial portion of the current detection function, and the coil portion 32 has a length Divided into three in the first end section winding section 32a, middle section winding section 32b and second end section winding section 32c in the direction, and the forward winding section of each winding section 32a, 32b, 32c The both end section winding portions 32a and 32c have a three-layer winding structure having a relatively high winding density, and the middle section winding portion 32b has a single layer winding structure having a relatively low winding density.

According to this configuration, when the toroidal coil 10 is mounted on the conductor (covered conductor) through which the detected current flows, that is, when the toroidal coil 10 is arranged toroidally around the covered conductor, Even if there are variations in how the toroidal coil is hooked (relative positional relationship) to the mounting conductor, the error in the current detection sensitivity of the toroidal coil can be effectively reduced.

That is, also in the toroidal coil 10 of this embodiment, when the toroidal shape is adopted, a gap on the toroidal loop (hereinafter referred to as "coil gap") is inevitably formed between the both ends thereof. For this reason, when the covered conductor is at a position close to the coil gap inside the toroidal loop, that is, when it is close to the first end section winding section 32a or the second end section winding section 32c, A part of the high-density magnetic flux distributed in the vicinity of the mounted conductor passes through the coil gap without being linked to the coil portion, thereby reducing the mutual inductance between the mounted conductor and the toroidal coil 10. However, in the toroidal coil 10, the first and second end section winding portions 32a and 32c have a winding density several steps or several times higher than that of the intermediate section winding portion 32b, Since the degree of electromagnetic coupling is large, it is possible to effectively compensate for the reduction in mutual inductance due to the variation in the relative positional relationship between the mounted conductor and the coil gap as described above.

Even when the covered conductor is close to the intermediate section winding portion 32b inside the toroidal loop, a part of the magnetic flux generated around the covered conductor does not link with the coil portion. Pass through the coil gap. However, because the magnetic flux through the coil gap is far from the mounted conductor and the magnetic flux density or magnetic field strength is much lower, the reduction in mutual inductance is not as great as in the first and second end section windings 32a, 32c. On the other hand, since the winding density of the intermediate section winding portion 32b is relatively low, the high density magnetic flux distributed in the vicinity of the conductor to be covered is electromagnetically linked even if the intermediate section winding portion 32b is interlinked. The connectivity is not as great as the first and second end section windings 32a, 32c.

As described above, in the toroidal coil 10, regardless of where the covered conductor is located inside the toroidal loop, the electromagnetic between the covered conductor and each of the section winding parts 32a, 32b and 32c. The coupling properties are substantially even, and the overall mutual inductance of the coil portion 32 is stable. Thereby, even if there is variation in the relative positional relationship between the mounted conductor and the toroidal coil 10 (particularly, the coil gap), the error of the current detection sensitivity of the toroidal coil 10 can be effectively reduced.

Further, in the toroidal coil 10 of this embodiment, not only each winding portion in the forward path section of the coil section 32 but also the return path section 36 in the return path section has the form of a coil. The magnetic field lines generated around the mounted conductor when the current to be detected flows flows into both the winding portion in the forward path section and the winding portion of the return path portion 36 in the return path section, and the forward path and the return path An induced electromotive force occurs in both of the sections. Thereby, the current detection sensitivity can be further improved.

In addition, in this embodiment, in each winding portion 32a, 32b, 32c of the coil portion 32, the winding portion advancing in the forward direction and the winding portion advancing in the reverse direction are balanced with each other. That is, in the first and second end section winding portions 32a and 32c, the forward winding portion of the second layer winding forward in the direction opposite to the forward winding portion of the first layer and the third layer, and It is balanced with the single layer return winding section. Also in the intermediate section winding portion 32b, the forward winding portion of the single layer winding in the forward direction is balanced with the return winding portion of the single layer winding in the reverse direction. By this, the current detection noise which may be generated in the toroidal loop due to the external magnetic flux m (FIG. 14) passing through the toroidal loop of the toroidal coil 10 can be sufficiently cancelled.

Furthermore, in the toroidal coil 10 of this embodiment, since the coil portion 32 itself has a function of effectively reducing the error of the current detection sensitivity, when the toroidal shape is adopted, the function of the connector for holding both ends thereof is taken. There is no need to ask for and any connector can be used. For example, as shown in FIG. 7A, the connector 40 can be used without any problem even if the both ends of the toroidal coil 10 are butted in the circumferential direction of the toroidal loop. Of course, as shown in FIG. 7B, a connector 40 in which both ends of the toroidal coil 10 are butted in the radial direction of the toroidal loop can be used without any problem.

In the connector 40 shown in FIGS. 7A and 7B, the connector members 40a and 40b are fixed to both ends of the toroidal coil 10, and both connector members are detachably coupled by screws or the like. Alternatively, the whole or the main body of the connector 40 may be coupled to one end of the toroidal coil 10, and the other end of the toroidal coil 10 may be detachably inserted and fixed to the connector 40 as a free end. is there.

The inventor of the present invention prototypes the toroidal coil 10 of this embodiment according to the production method as described above, and as a comparative example to the toroidal coil 10, one end of the core portion 30 of the same material and the same size (FIG. A toroidal coil 10A in which a winding structure formed by winding the coil conducting wire CW at a constant pitch in the forward direction from the left end) to the other end (right end) was used as a winding portion in the forward path section of the coil portion. The toroidal coil 10A of this comparative example has a cross-sectional structure similar to that shown in FIG. 4A throughout its entire length.

Then, as shown in FIG. 8, the inventor has made eight representative points [A], [B], [C], [D] for each of the toroidal coil 10 of the embodiment and the toroidal coil 10A of the comparative example. Selectively arrange the coated conductor 100 of the resistance welding machine in the vicinity of [E], [F], [G] and [H] (in FIG. 8, [A], [D] and [H]). When the alternating current is supplied to the mounted conductor 100 under a constant condition (10 kA, 50 Hz, 7 cycles), it is obtained from the integrating circuit 116 (FIG. 14). An experiment was conducted to acquire the range error of the detected current value at each measurement point from the detected current detection signal S _i .

Here, on the toroidal loop of the toroidal coil 10 (10 A), assuming that the position of the coil gap is the reference position [Q] (0 °) and the counterclockwise direction is the positive direction, the representative point [A] is 45 ° Position, [B] at 90 ° position, [C] at 135 ° position, [D] at 180 ° position, [E] at 225 ° position, [F] at 270 ° position, and [G] at 315 ° position is there. [H] is the toroidal center position.

In the toroidal coil 10 of the embodiment, the first coil end section 14 (the first end section winding portion 32a) is provided in the sections [Q] to [A], and the coils [A] to [G] are provided. The intermediate section 16 (intermediate section winding section 32b) is provided, and the second coil end section 18 (second end section winding section 32c) is provided in the sections [G] to [Q]. In this case, the lengths of the first and second end section winding parts 32a and 32c are formed in at least a part of the area within 12.5% of the respective end parts with respect to the entire length of the coil part 32. It is a portion, and the length of the intermediate section winding portion 32 b is a remaining portion area, and is a portion formed over an area of 75% or more with respect to the entire length of the coil portion 32.

FIG. 9A shows the distribution characteristic of the range error of the detected current value obtained from the toroidal coil 10A of the comparative example in the above experiment. As shown in the figure, when the coated conductor 100 is arranged at each of the representative points [B], [C], [D], [E], [F] in the middle section of the toroidal loop, the range error is Although it fell within 0.5%, when the conductor 100 was placed at representative points [A] and [G] close to the coil gap, the range error dropped significantly (more than 2%). Even when the mounted conductor 100 is disposed at the toroidal center [H], the range error is reduced by 1% or more.

The distribution characteristic of the range error obtained from the toroidal coil 10 of the embodiment is shown in FIG. 9B. As shown in the figure, at any position of representative points [A], [B], [C], [D], [E], [F], [G] and toroidal center point [H] on the toroidal loop. Even when the mounted conductor 100 was arranged, the range error was within ± 0.5%. In particular, at representative points [A] and [G] close to the coil gap and the toroidal center point [H], the drop of the range error was less than 0.5%. Thus, according to the toroidal coil 10 of the embodiment, the error in the current detection sensitivity due to the relative positional relationship between the mounted conductor and the coil gap is effectively reduced, and the current detection accuracy is significantly improved. It was confirmed to achieve.

[Other Embodiments or Modifications]
As mentioned above, although the suitable embodiment of the present invention was described, the embodiment mentioned above does not limit the present invention. Those skilled in the art can add various modifications and changes in the specific embodiments without departing from the technical concept and the technical scope of the present invention.

For example, in the above embodiment, in the forward section of the coil section 32, the first and second end section winding sections 32a and 32c have a three-layer winding structure, and the middle section winding section 32b has a single-layer winding. Structure. However, the number of winding layers in each section winding 32a, 32b, 32c may be arbitrarily changed. For example, the first and second end section windings 32a and 32c may have a five-layer winding structure, and the intermediate section winding unit 32b may have a three-layer winding structure. Alternatively, the number of layers of the multilayer winding structure in the first and second end section windings 32a and 32c can be set independently.

Further, in the winding process of each part of the coil portion 32, instead of winding the coil wire CW around the core portion 30, as shown in FIG. 10, the peripheral portion of the core portion 30 is penetrated to sew a thread It is also possible to wind the coil conductor CW as it is attached.

In the toroidal coil 10 of the above embodiment, the core 30 is not limited to a flexible one, and although not shown, a fixed type in which the toroidal shape is always held is also possible. In that case, in order to make it possible to open and close the toroidal coil 10 with respect to the mounted conductor, it is possible to preferably adopt a configuration in which a hinge portion is provided at a central point on the toroidal loop.

In the above embodiment, the lengths of the first and second end section winding portions 32a and 32b are each 12.5% or less with respect to the total length of the coil portion 32, but they are significantly shorter than 12.5%. It is also good. In principle, the preferable range k of the region in which the end section winding portions 32a and 32c are formed is 0% <k ≦ 12.5%, respectively. The range error of the current value detected in the section A to H of the coil section 32 is obtained by increasing the winding density of each end section winding section or increasing the number of winding layers compared to the intermediate section winding section. It is the central technical idea of the present invention that it has been found to be reduced. Although there are elements such as winding material, wire diameter, number of windings, material of core material, etc. in design of toroidal coil, inventors increase winding density or winding layer in end section winding part Focusing on the fact that the range error of the detected current values shown in FIGS. 9A and 9B tends to be reduced even when the area is only one turn, the winding density of the end section winding portion is increased, or By increasing the number of winding layers, and by setting the region k where the end section winding portion is formed in the range of 0% <k ≦ 12.5% at both ends, the range of the section A to H It has been found that it is possible to reduce the error, leading to the present invention.

In the multilayer winding structure in which the coil wire is folded back at both ends of each section as in the end section windings 32a and 32c in the above embodiment, a region for at least several turns is required in the direction in which the core extends. I assume.

In the toroidal coil 10 of the above embodiment, a configuration in which the winding structure in the forward path section of the coil portion 32 and the winding structure in the return path section are reversed, that is, the configuration corresponding to the return path section 36 is arranged in the forward path section It is also possible to adopt a configuration in which a configuration corresponding to the first end section winding section 32a, the intermediate winding section 32b, and the second end section winding section 32c is disposed in the return section.

Furthermore, in the toroidal coil 10 of the above-described embodiment, the return path portion 36 may not be in the form of a winding, but may be in the form of a line as shown in, for example, FIGS. 11A and 11B. In the modification of FIG. 11A and FIG. 11B, although the coil wire CW which comprises the return path part 36 is arrange | positioned (inserted) inside the core part 30, you may arrange | position around the core part 30. FIG. The cross-sectional shape of the core 30 can be arbitrarily selected. In addition, although the current detection noise caused by the external magnetic flux m (FIG. 14) can not be canceled, a configuration in which the return path portion 36 is omitted is also possible. In that case, the end of the coil portion 32, that is, the end of the second end section winding portion 32c is connected to the lead wire 22.

10 toroidal coil 30 core portion 32 coil portion 32a first end section winding section 32b middle section winding section 32c second end section winding section 34 (1), 34 (2), 34 (3) insulating layer ( Vinyl tape)
36 Return path part 40 connector CW coil wire

Claims (9)

A core portion capable of taking a toroidal shape so as to surround a conductor through which a detected current flows;
And a coil portion attached to the core portion;
The coil portion is formed by winding a coil wire in a first end section winding portion formed by winding a coil wire in one end section of the core portion and the other end portion of the core portion A second end section winding section, and an intermediate section winding section formed by winding a coil wire in an intermediate section sandwiched between the first and second end sections of the core section;
The winding density of the first and second end section winding sections is higher than the winding density of the intermediate section winding section,
Current detection coil. The current detection coil according to claim 1, wherein the first and second end section winding sections each have more winding layers than the intermediate section winding section. The coil portion has a forward path section extending from one end of the core portion to the other end, and a return path section extending from the other end of the core portion to one end.
In one of the forward path section or the return path section, each of the first and second end section winding sections has a plurality of winding layers, and the intermediate section winding section has one winding layer. The current detection coil according to Item 1. The current detection coil according to claim 3, wherein in one of the forward path section or the return path section, the first and second end section winding portions have at least three winding layers. The current detection coil according to claim 3, wherein the coil portion has a winding portion extending at a constant winding density in the other of the forward path section or the return path section. The current detection coil according to claim 3, wherein the coil portion has a path portion extending in a line shape in the entire section in the other of the forward path section or the return path section. The first end section winding portion starts winding the coil conductor from the vicinity of the tip end of one end section of the core portion, and has a constant pitch in the forward direction toward the second end section side. Winding the coil wire at the winding portion, turning around the boundary with the middle section winding portion, winding the coil lead at a constant pitch in the reverse direction, turning around the tip of the one end section, winding the middle section winding It has a portion formed by winding the coil conductor at a constant pitch again in the forward direction to the vicinity of the boundary with the wire portion,
The intermediate section winding portion has a portion in which a coil wire is wound at a constant pitch in the forward direction through the intermediate portion of the core portion,
In the other end section of the core section, the second end section winding section winds a coil wire at a constant pitch in the forward direction from the vicinity of the boundary with the intermediate section in the other end section of the core section, and near the tip of the other end section The coil conductor is wound at a constant pitch in the reverse direction, folded back near the boundary with the intermediate section, and the coil conductor is wound in the forward direction again to the vicinity of the tip of the other end section Have,
The current detection coil according to claim 2. The current detection coil according to claim 2, further comprising an insulating layer between the lower layer winding layer and the upper layer winding layer in the first and second end section winding portions. 2. The current detection coil according to claim 1, wherein the lengths of the first and second end section winding portions are respectively 12.5% or less with respect to the entire length of the coil portion.

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