Two-layer coil structure

Abstract

To provide a two-layer coil structure having high torsional rigidity and suppressing an occurrence of kink due to rotational resistance.SOLUTION: A torque coil (a two-layer coil structure) is so configured that a winding direction of an inner coil 11 and a winding direction of an outer coil 12 are opposite to each other, and when the torque coil is twisted in a circumferential direction thereof and in a direction of expanding a diameter of the inner coil 11, a variation in the diameter of the outer coil 12 becomes larger than a variation in the diameter of the inner coil 11. When the length of 1596 mm is defined as one unit in each of the inner coil 11 and the outer coil 12, a variation d1 in the diameter of the inner coil 11 when the inner coil 11 is twisted 360° in a circumferential direction thereof and in the direction of expanding the diameter of the inner coil 11 and a variation d2 in the diameter of the outer coil 12 when the outer coil 12 is twisted 360° in a circumferential direction thereof and in a direction of contracting the diameter of the outer coil 12 with respect to the length of the one unit, satisfy the following relation: -4.5<d1 / d2<-1.6.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a two-layer coil structure. [Background technology]

[0002] Conventionally, multilayer coil structures known as torque coils or drive shafts are known, which are disposed inside medical catheters and the like and used to transmit the rotational motion of a proximal operating unit to a distal end. For example, Patent Document 1 discloses a drive shaft 10 configured with a multilayered, tightly-coupled coil made of a metal wire such as stainless steel, which is rotatably incorporated inside a catheter sheath 2 of an ultrasound catheter 1. Furthermore, Patent Document 2 discloses a hollow drive shaft 16 disposed inside a catheter sheath 18 of an acoustic imaging (ultrasound imaging) catheter 10, which has an inner coil 40 and an outer coil 42 formed by winding nitinol. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-062072 [Patent Document 2] Special Publication No. 09-504214 Summary of the Invention [Problem to be solved by the invention]

[0004] Such a two-layer coil structure is driven to rotate by a drive source such as a motor connected to the proximal side, but if the two-layer coil structure gets stuck inside the catheter during catheter operation, for example, and the rotational resistance to the coil portion increases, there is a problem that kinking is likely to occur in the coil portion. A two-layer coil structure that has kinked may not be able to transmit rotation properly, and the occurrence of kinking may also cause the lead wire running inside the two-layer coil structure to break, causing the catheter itself to stop functioning.

[0005] The present invention has been made in view of such points, and an object thereof is to provide a two-layer coil structure having high torsional rigidity and suppressing the generation of kinks due to rotational resistance.

Means for Solving the Problems

[0006] To achieve the above object, the present invention provides a two-layer coil structure including an inner coil formed by spirally winding a metal wire, and an outer coil disposed in close contact with the outer periphery of the inner coil and formed by spirally winding a metal wire. The winding direction of the inner coil and the winding direction of the outer coil are opposite to each other. When the two-layer coil structure is twisted in its circumferential direction and in the direction in which the diameter of the inner coil expands, the amount of change in the diameter of the inner coil is smaller than the amount of change in the diameter of the outer coil. In each of the inner coil and the outer coil, a length of 1596 mm is taken as one unit. For the length of one unit, the amount of change in the diameter d1 of the inner coil when the inner coil is twisted by 360° in its circumferential direction and in the direction in which the diameter of the inner coil expands, and the amount of change in the diameter d2 of the outer coil when the outer coil is twisted by 360° in its circumferential direction and in the direction in which the diameter of the outer coil contracts satisfy the relationship of -4.5 < d1 / d2 < -1.6 (Invention 1).

[0007] According to such an invention (Invention 1), since the winding direction of the inner coil and the winding direction of the outer coil are opposite to each other, when the two-layer coil structure is twisted in its circumferential direction and in the direction in which the diameter of the inner coil expands, while the diameter of the inner coil expands, the diameter of the outer coil will shrink. As a result, the outer coil and the inner coil will press against each other. At this time, if the amount of change in the diameter of the inner coil is smaller than the amount of change in the diameter of the outer coil, the outer coil will strongly tighten the inner coil, and the layers between the outer coil and the inner coil will adhere firmly, so that the torsional rigidity of the two-layer coil structure will increase, and the generation of kinks due to rotational resistance can be suppressed. In particular, with respect to each of the inner coil and the outer coil, taking 1596 mm in length as one unit, when the inner coil is twisted 360° in its circumferential direction and in the direction in which the diameter of the inner coil expands, the amount of change in the diameter of the inner coil is d1, and when the outer coil is twisted 360° in its circumferential direction and in the direction in which the diameter of the outer coil shrinks, the amount of change in the diameter of the outer coil is d2. If the relationship of -4.5 < d1 / d2 < -1.6 is satisfied, the maximum torque force of the two-layer coil structure will be improved, and a two-layer coil structure having more excellent torsional rigidity can be realized.

[0008] In the above invention (Invention 1), it is preferable that the inner coil is formed by spirally winding two or more and 18 or less metal strands (Invention 2).

Effect of the Invention

[0009] ​​​​​​​​​​​​​​​10 is a graph showing the relationship between the ratio of the radial change amount of the inner coil and the outer coil in the torque coils of the example and the comparative example, and the maximum torque force and torsional rigidity of the torque coil. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing the overall structure of a torque coil 10 according to this embodiment, and FIG. 2 is an explanatory diagram showing the structure of a shaft body 1 in the torque coil 10. Note that the present invention is not limited to the embodiment described below, and the embodiment is merely an example described to explain the technical features of the present invention. Furthermore, the shapes and dimensions shown in the drawings are shown merely to facilitate understanding of the contents of the present invention and do not accurately reflect the actual shapes and dimensions.

[0012] In this specification, the term "distal side" refers to the direction along the axial direction of the shaft body 1 constituting the torque coil 10, in which the torque coil 10 advances toward the treatment site. The term "proximal side" refers to the direction along the axial direction of the shaft body 1 constituting the torque coil 10, in the opposite direction to the distal side. Furthermore, the term "distal" refers to the distal end of a given component or component, and the term "proximal end" refers to the proximal end of a given component or component. Furthermore, the term "distal portion" refers to the portion of a given component or component that includes the distal end and extends from the distal end toward the proximal end to the middle of the component, etc., and the term "proximal end" refers to the portion of a given component or component that includes the proximal end and extends from the proximal end toward the distal end to the middle of the component, etc. In addition, in Figures 1 and 2, the left side of the figure represents the "distal side" that is inserted into the body while being inserted into an ultrasound catheter or the like, and the right side represents the "proximal side" that is connected to a driving source such as a motor.

[0013] 1, the torque coil 10 includes a long shaft body 1, a housing 2 attached to the distal end side of the shaft body 1, and a connector 3 attached to the proximal end side of the shaft body 1. As shown in FIG. 2, the shaft body 1 in this embodiment has a hollow two-layer coil structure including an inner coil 11 formed by spirally winding a metal wire 111, and an outer coil 12 arranged in close contact with the outer periphery of the inner coil 11 and formed by spirally winding a metal wire 121.

[0014] A housing 2 is attached to the tip of the shaft body 1 of the torque coil 10. When the torque coil 10 is used in an ultrasound imaging catheter, a transducer (not shown) for ultrasound imaging is built into the housing 2, and the housing 2 is attached to the tip of the shaft body 1 by a known fastening technique such as epoxy resin or adhesive. Depending on the application of the torque coil 10, a coil member made of a different material from the shaft body 1 may be joined instead of the housing 2, or a connecting member for connecting to an object to be operated, such as a medical clip, may be joined, or the tip of the shaft body 1 may be brazed with a brazing material and then machined to form a desired shape.

[0015] A connector 3 for connecting to a drive source 4 such as a motor for rotating the torque coil 10 is attached to the base end of the shaft body 1 of the torque coil 10 using a known fastening technique such as epoxy resin or adhesive.

[0016] The present invention also provides a shaft for a medical device in which a torque coil and a drive source are connected by a connector, and a medical device including such a shaft. The shaft is particularly suitable for medical devices equipped with a motor, and can be used, for example, as a shaft for use in intravascular ultrasound (IVUS) with an ultrasonic transducer at its tip, or as a shaft for an internal retrieval mechanism used to remove material from a patient's internal lumen. The torque coil of the present invention is particularly effective in a shaft for use in intravascular ultrasound (IVUS) that rotates at 1000 rpm or more, more preferably 1500 rpm or more.

[0017] In this embodiment, the outer diameter of the inner coil 11 is set in the range of 0.24 to 0.79 mm, and preferably in the range of 0.3 to 0.5 mm. The inner diameter of the inner coil 11 is set in the range of 0.17 to 0.57 mm, and preferably in the range of 0.2 to 0.4 mm. The axial length of the inner coil 11 is set in the range of 1.0 to 3.0 m. The material of the metal wires 111 forming the inner coil 11 is not particularly limited, but may be, for example, austenitic stainless steel such as SUS304 or SUS316.

[0018] The inner coil 11 is formed by spirally winding a plurality of metal wires 111, and is formed so that there are no gaps between adjacent metal wires 111 in the axial direction of the inner coil 11. In this embodiment, the inner coil 11 is formed by spirally winding 2 to 18 metal wires, and the diameter of each of the metal wires 111 is set to a range of 0.03 to 0.11 mm. It is particularly preferable that the diameter of each of the metal wires 111 is in a range of 0.04 to 0.08 mm. If the inner coil 11 is a single-strand coil, the rotation performance of the torque coil 10 may be reduced.

[0019] In this embodiment, the outer diameter of the outer coil 12 is set in the range of 0.3 to 1.0 mm, and preferably in the range of 0.4 to 0.6 mm. The inner diameter of the outer coil 12 is set in the range of 0.24 to 0.79 mm, and preferably in the range of 0.3 to 0.5 mm. Since the outer coil 12 is disposed in close contact with the outer periphery of the inner coil 11, the inner diameter of the outer coil 12 is set to be approximately equal to the outer diameter of the inner coil 11. The axial length of the outer coil 12 is the same as that of the inner coil 11 and is set in the range of 1.0 to 3.0 m, for example. The material of the metal wires 121 forming the outer coil 12 is not particularly limited, but austenitic stainless steels such as SUS304 and SUS316 are used, for example. The metal wires 111 forming the inner coil 11 and the metal wires 121 forming the outer coil 12 are preferably formed of the same material.

[0020] The outer coil 12 is formed by spirally winding a plurality of metal wires 121, and is formed so that there are no gaps between adjacent metal wires 121 in the axial direction of the outer coil 12. In this embodiment, the outer coil 12 is formed by spirally winding 2 to 18 metal wires, and the diameter of each of the metal wires 121 is set in the range of 0.03 to 0.50 mm. It is particularly preferable that the diameter of each of the metal wires 121 is in the range of 0.03 to 0.08 mm.

[0021] In this embodiment, the metal wires 111 forming the inner coil 11 and the metal wires 121 forming the outer coil 12 are both round wires having an approximately circular cross section, but are not limited to this and may be round wires having an elliptical cross section or flat wires having an approximately rectangular cross section.

[0022] 2, in the shaft body 1, the outer coil 12 is disposed on the outer periphery of the inner coil 11 so that the winding direction of the inner coil 11 and the winding direction of the outer coil 12 are opposite to each other. As a result, when the shaft body 1 is twisted circumferentially in a direction that increases the diameter of the inner coil 11, the diameter of the inner coil 11 increases and the diameter of the outer coil 12 decreases.

[0023] Here, the torque coil 10 is configured so that, when the shaft body 1 is twisted in its circumferential direction in a direction in which the diameter of the inner coil 11 increases, the amount of change in the diameter of the outer coil 12 is larger than the amount of change in the diameter of the inner coil 11. Specifically, as shown in Fig. 2, the winding angle α of the inner coil 11 in the longitudinal cross-sectional direction and the winding angle β of the outer coil 12 in the longitudinal cross-sectional direction are made different from each other, and the winding angle α of the inner coil 11 in the longitudinal cross-sectional direction is set to be larger than the winding angle β of the outer coil 12 in the longitudinal cross-sectional direction. In this way, the winding angle α of the inner coil 11 is larger than the winding angle β of the outer coil 12 (i.e., the twist angle of the inner coil 11 is steeper than the twist angle of the outer coil 12), so that, as described above, when the shaft body 1 is twisted in its circumferential direction in a direction in which the diameter of the inner coil 11 increases, the amount of change in the diameter of the outer coil 12 is larger than the amount of change in the diameter of the inner coil 11.

[0024] The relationship between the winding angle α of the inner coil 11 in the longitudinal cross-sectional direction and the winding angle β of the outer coil 12 in the longitudinal cross-sectional direction is determined by the combination of the wire diameters and the number of threads of the metal wires 111, 121 that form the inner coil 11 and the outer coil 12, respectively. For example, if the diameter of the wires that form the coils is fixed, the winding angle in the longitudinal cross-sectional direction of the coil decreases as the number of threads in the coil increases, and vice versa. Furthermore, if the number of threads in the coils is fixed, the winding angle in the longitudinal cross-sectional direction of the coil decreases as the diameter of the wires that form the coil increases, and vice versa.

[0025] According to the torque coil 10 described above, the winding direction of the inner coil 11 and the winding direction of the outer coil 12 are opposite to each other, and therefore, when the torque coil 10 is twisted circumferentially in a direction that increases the diameter of the inner coil 11, the diameter of the inner coil 11 increases while the diameter of the outer coil 12 decreases, resulting in the outer coil 12 and the inner coil 11 being pressed against each other. At this time, if the amount of change in the diameter of the outer coil 12 is greater than the amount of change in the diameter of the inner coil 11, the outer coil 12 tightly clamps the inner coil 11, and the layers of the outer coil 12 and the inner coil 11 adhere firmly to each other, thereby increasing the torsional rigidity of the torque coil 10 and suppressing the occurrence of kinking due to rotational resistance.

[0026] The torque coil (two-layer coil structure) according to the present invention has been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiment and various modifications are possible. For example, the shape, length, diameter, etc. of the inner coil 11 and the outer coil 12 constituting the torque coil 1 may be designed appropriately depending on the purpose of use, the position of use, etc. Furthermore, a lead wire or the like may be inserted inside the shaft main body 1, and the shaft main body 1 may be provided with members other than the inner coil 11 and the outer coil 12, such as a reinforcing body or an X-ray opaque marker. [Example]

[0027] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0028] In order to verify that the torque coil according to the present invention has excellent torsional rigidity, multiple test torque coils were fabricated, each including an inner coil that is a multi-filament coil formed by helically winding multiple metal wires, and an outer coil that is also a multi-filament coil formed by helically winding multiple metal wires and is disposed in close contact with the outer periphery of the inner coil, and the maximum torque force and torsional rigidity were measured using a motor and a torque sensor.

[0029] Multiple test torque coils were fabricated by changing the wire diameter and number of strands in the inner and outer coils. All test torque coils were fabricated with an inner diameter of 0.32 mm and a length of 1606 mm. The structures of the inner and outer coils of the fabricated test torque coils are shown in Table 1.

[0030] [Table 1]

[0031] In Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, the number of strands in the inner coil and outer coil is fixed at 8, and the wire diameter of the inner coil and outer coil is varied. On the other hand, in Examples 4 to 7 and Comparative Examples 4 to 7 in Table 1, the wire diameter of the inner coil and outer coil is fixed at 0.06 mm, and the number of strands in the inner coil and outer coil is varied. Note that the pitch in Table 1 refers to the length of one period in the axial direction of the coil in which the strands are wound.

[0032] Next, assuming that one end of the fabricated test torque coils of the examples and comparative examples was fixed and the other end was twisted 360°, calculations were performed to calculate the amount of change d1 in the diameter of the inner coil when the inner coil, having a length of 1596 mm, was twisted 360° in its circumferential direction in a direction in which the diameter of the inner coil increases, and the amount of change d2 in the diameter of the outer coil when the outer coil, having a length of 1596 mm, was twisted 360° in its circumferential direction in a direction in which the diameter of the outer coil decreases. The calculation results are shown in Table 2.

[0033] Although the length of the test torque coil that was actually fabricated was 1606 mm, the theoretical amount of change in diameter d1 of the inner coil and the amount of change in diameter d2 of the outer coil were calculated on the assumption that the length of each coil was 1596 mm. This is because, as will be described later, when measuring the maximum torque force and torsional rigidity of the test torque coils of the fabricated Examples and Comparative Examples, both ends of the test torque coil are attached to a motor and a torque sensor, and 5 mm of each end is chucked to connectors for attaching to the motor and the torque sensor, so the length of the test torque coil that is the subject of measurement of the maximum torque force and torsional rigidity becomes 1596 mm.

[0034] [Table 2]

[0035] The theoretical change in diameter d1 of the inner coil and the change in diameter d2 of the outer coil for each example and comparative example shown in Table 2, and the ratio (d1 / d2) of the change in diameter d1 of the inner coil and the change in diameter d2 of the outer coil were calculated as follows: (1) The PCD of each of the inner coil and the outer coil was determined. Here, PCD is the diameter of an imaginary circle that is centered at the center of the coil when viewed in cross section and passes through the radial center of each wire that forms the coil, and is a value calculated by adding the inner diameter of the coil to the radial length of the wire. (2) For each of the inner and outer coils, the circumference of a circle with the PCD as its diameter was calculated as "PCD x π". (3) For each of the inner coil and the outer coil, the degree of twist was calculated by dividing the twist angle (360° in this example) by the number of pitches. The number of pitches was calculated by dividing the length of the coil by the length of one pitch. The length of one pitch was calculated by measuring 10 pitches and averaging the measurements. (4) For the inner coil, the circumference of a circle whose diameter is the PCD after twisting in the radial expansion direction was calculated using the formula "PCDπ + ({twisting degree / 360°} × PCDπ)", and the PCD after twisting in the radial expansion direction was calculated by dividing the circumference by π. (5) For the outer coil, the circumference of a circle whose diameter is the PCD after twisting in the diameter-reducing direction was calculated by "PCDπ - ({twisting degree / 360°} × PCDπ)", and the PCD after twisting in the diameter-reducing direction was calculated by dividing the circumference by π. (6) The “change in diameter of the inner coil d1” was calculated by subtracting the “PCD of the inner coil before twisting” from the “PCD after twisting the inner coil in the radially expanding direction,” while the “change in diameter of the outer coil d2” was calculated by subtracting the “PCD of the outer coil before twisting” from the “PCD after twisting the outer coil in the radially contracting direction.” (7) Using these, the ratio (d1 / d2) of the change in diameter of the inner coil d1 to the change in diameter of the outer coil d2 was calculated. In this embodiment, the twist angle was set to 360°, but if the length of the inner coil and outer coil is shorter than 1596 mm, the above d1 / d2 can be calculated by setting the twist angle to "360[°] x {(length of the inner coil and outer coil [mm]) / 1596[mm]}".

[0036] Next, the test torque coils of each Example and Comparative Example were attached to a guidewire transmission characteristic measuring instrument PT-1950GHS (manufactured by Protec Co., Ltd.) equipped with a motor and a torque sensor, and the maximum torque force and torsional rigidity of the test torque coils of each Example and Comparative Example were measured by rotating the coils in the forward direction with the motor to apply a twist. Measurements were performed multiple times for each Example and Comparative Example, and the average values ​​were calculated to obtain the measurement results. The measurement results are shown in Table 3.

[0037] [Table 3]

[0038] Based on the measurement results shown in Table 3, the relationship between the ratio of the radial change amount between the inner coil and the outer coil in the torque coils of Examples 1 to 7 and Comparative Examples 1 to 7, and the maximum torque force and torsional rigidity of the torque coils is graphed in Fig. 3. Fig. 3(a) is a graph for Examples 1 to 3 and Comparative Examples 1 to 3, and Fig. 3(b) is a graph for Examples 4 to 7 and Comparative Examples 4 to 7.

[0039] As is clear from Fig. 3, it can be seen that the torque coils of Examples 1 to 7 have excellent torsional rigidity compared to the torque coils of Comparative Examples 1 to 7. In particular, when the inner coil with a length of 1596 mm is twisted 360° in its circumferential direction and in the direction in which the diameter of the inner coil expands, the change amount d1 of the diameter of the inner coil, and when the outer coil with a length of 1596 mm is twisted 360° in its circumferential direction and in the direction in which the diameter of the outer coil contracts, the change amount d2 of the diameter of the outer coil satisfy the relationship of -4.5 < d1 / d2 < -1.6, it can be seen that the maximum torque force of the torque coil (two-layer coil structure) is improved and the torque coil has more excellent torsional rigidity.

[0040] In particular, it is understood that a torque coil in which the wire diameters of the inner coil and the outer coil are the same and the number of turns of the outer coil is larger than the number of turns of the inner coil, like the torque coils of Examples 4 to 7, exhibits extremely excellent torsional rigidity and the maximum torque force also improves dramatically.

Explanation of Signs

[0041] 10 Torque coil (two-layer coil structure) 1 Shaft body 11 Inner coil 12 Outer coil 2 Housing 3 Connector 4 Motor

Claims

1. an inner coil formed by winding a metal wire in a spiral shape; an outer coil arranged in close contact with the outer periphery of the inner coil and formed by spirally winding a metal wire, The winding direction of the inner coil and the winding direction of the outer coil are opposite to each other, The material forming the inner coil and the outer coil is SUS304 or SUS316 stainless steel, The wire diameter of the metal wires forming the inner coil and the outer coil is in the range of 0.03 to 0.11 mm, the outer diameter of the inner coil is in the range of 0.3 to 0.5 mm; the inner diameter of the inner coil is in the range of 0.2 to 0.4 mm; The outer diameter of the outer coil is in the range of 0.4 to 0.6 mm; The inner diameter of the outer coil is in the range of 0.3 to 0.5 mm; The inner coil and the outer coil are formed by spirally winding 8 to 16 metal wires, The number of threads in the outer coil is greater than the number of threads in the inner coil, when the two-layer coil structure is twisted in its circumferential direction and in a direction in which the diameter of the inner coil increases, the amount of change in the diameter of the inner coil is smaller than the amount of change in the diameter of the outer coil, The length of each of the inner coil and the outer coil is defined as 1596 mm, and the amount of change d in the diameter of the inner coil when the inner coil is twisted 360° in the circumferential direction and in the direction in which the diameter of the inner coil increases is defined as １ and the change in diameter d of the outer coil when the outer coil is twisted 360° in its circumferential direction and in the direction in which the diameter of the outer coil is reduced. ２ However, -4.5<d １ / d ２ <-1.

6.

2. A two-layer coil structure as described in claim 1, wherein the wire diameters of the metal wires forming the inner coil and the outer coil are the same.

3. A two-layer coil structure as described in claim 1 or 2, used in a shaft for a medical device used in intravascular ultrasound that rotates at 1000 rpm or more.

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