JP2019180839A - Method for manufacturing medical coil, medical coil, method for manufacturing endoscope treatment tool and endoscope treatment tool - Google Patents

Abstract

To provide a method for manufacturing a medical coil with a stable rotation transmission property.SOLUTION: A method for manufacturing a medical coil includes: a heat treatment step S20 of heating a model coil formed of a metal element wire at a temperature equal to or lower than 500°C; a measurement step S30 of measuring compressive residual stress of the model coil after the heat treatment step; and a selection step S40 of selecting only a model coil with a value of the compressive residual stress which is equal to or higher than a specified value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a medical coil and a method for manufacturing an endoscope treatment tool. The present invention also relates to a medical coil and an endoscope treatment tool manufactured by these manufacturing methods.

  Conventionally, a medical coil is used for each part of an endoscope or an endoscope treatment tool. When a medical coil is used as a member that transmits an operation, there is a case where a rotation transmission property that efficiently transmits a rotation operation input on the proximal end side to the distal end side is required.

  Patent Document 1 proposes to perform heat treatment at the same time as twisting in a method for processing a metal element wire in order to improve rotation transmission of a medical coil.

Japanese Patent No. 40986613

In the technique described in Patent Document 1, rotation transmission is improved by combining stress load by twisting and residual stress removal by heat treatment. However, in reality, even if heat treatment is performed on a plurality of coils under the same conditions, variations in rotation transmission occur.
The inventors obtained new knowledge about the relationship between the rotation transmission property and the residual stress of the coil, and based on this, the present invention was completed.

It is an object of the present invention to provide a medical coil having a stable rotation transmission property and a method for manufacturing the medical coil.
Another object of the present invention is to provide a medical treatment instrument that exhibits stable rotation transmission and a method for manufacturing the same.

  The first aspect of the present invention includes a heat treatment step of heating a coil formed of a metal wire at a temperature of 500 ° C. or less, a measurement step of measuring the compressive residual stress of the coil after the heat treatment step, and a value of the compressive residual stress. Is a method for manufacturing a medical coil comprising a selection step of selecting only coils having a predetermined value or more.

  The second aspect of the present invention is a medical coil manufactured by the method for manufacturing a medical coil of the present invention and having a compressive residual stress value of 300 megapascals or more.

  According to a third aspect of the present invention, there is provided an endoscopic treatment tool including the method for manufacturing a medical coil according to the present invention and an assembling step of attaching the original coil selected in the selection step to a component of the endoscopic treatment tool. It is a manufacturing method.

  According to a fourth aspect of the present invention, there is provided an endoscopic treatment tool manufactured by the method for manufacturing an endoscopic treatment tool according to the present invention, wherein the value of the compressive residual stress of the attached original coil is 300 megapascals or more. It is.

  ADVANTAGE OF THE INVENTION According to this invention, the medical coil which has the stable rotation transmission property can be provided efficiently.

It is a flowchart which shows the flow of the manufacturing method of the medical coil which concerns on one Embodiment of this invention. It is a figure which shows an example of the measuring point of a prototype. It is the elements on larger scale of the prototype of a multi-row winding. It is a figure which shows an example of the treatment tool for endoscopes using the medical coil. It is a figure which shows one process of the assembly | attachment process in the manufacturing method of the treatment tool for endoscopes. It is a figure which shows one process of the same assembly | attachment process. It is a figure which shows one process of the same assembly | attachment process. It is a figure which shows one process of the same assembly | attachment process. It is a schematic diagram which shows the evaluation system of rotation transmissibility. It is a graph which shows the correspondence of the rotation angle of the rear end in an Example, and the rotation angle of a front-end | tip.

An embodiment of the present invention will be described with reference to FIGS. First, a method for manufacturing a medical coil according to the present embodiment (hereinafter simply referred to as “manufacturing method”) will be described.
FIG. 1 is a flowchart showing the flow of the manufacturing method of the present embodiment. The manufacturing method includes a heat treatment step S20, a measurement step S30, and a selection step S40.

First, in step S10, a metal wire is wound in a coil shape to produce a medical coil prototype (prototype coil). As the material of the metal wire, various known materials can be used, but in view of applications, stainless steel, titanium and the like are preferable, and austenitic stainless steel is more preferable.
The shape of the metal wire is not particularly limited, and a round wire having a circular cross section or a rectangular flat wire can be used.
There is no particular limitation on the number of metal wires used for forming the prototype. Therefore, it may be either a single-strand coil wound with one metal strand or a multi-strand coil wound with a plurality of metal strands.
There is no particular limitation on the winding method of the metal wire. Therefore, the prototype may be a closely wound coil in which adjacent loops are in close contact, or there may be a gap between the loops.

  Next, the prototype is heated in the heat treatment step of step S20. The heating temperature and the heating time may be appropriately set in consideration of the material of the metal strand, the cross-sectional dimension, and the like. For example, when the metal strand is austenitic stainless steel, the heating temperature is preferably 200 ° C. or higher and 500 ° C. or lower, and more preferably 300 ° C. or higher and 400 ° C. or lower. The time for holding the heating temperature (holding time) is preferably from 5 minutes to 180 minutes, more preferably from 10 minutes to 60 minutes. When the holding time is less than 5 minutes, the whole prototype cannot be heated uniformly, which is not preferable. If the holding time exceeds 180 minutes, it is not preferable in terms of the process.

  Next, in the measurement process of step S30, the residual stress of the metal strand forming the prototype is measured. When creating a prototype using a metal strand, an external force pulling in the winding direction acts on the metal strand, so that a compressive residual stress mainly occurs in the winding direction on the metal strand.

Although there is no restriction | limiting in particular in the specific measurement direction in a measurement process, X-ray diffraction method is preferable from a viewpoint which can measure the residual stress of the trace area | region of a metal strand.
When the measurement process is executed by the X-ray diffraction method, the beam diameter is set to be equal to or smaller than the dimension in the cross-sectional direction of the metal strand, and the X-ray is irradiated along the winding direction of the metal strand.
Since many medical coils are long (approximately 1000 mm or more in length), it is preferable to employ an arithmetic average value of measurement values measured at a plurality of points as a measurement value in the measurement process. For example, as shown in FIG. 2, the measurement may be performed at a total of three points, that is, a central portion M1 in the longitudinal direction of the prototype coil 100 and positions M2 and M3 separated by a predetermined distance D on both sides in the longitudinal direction. At this time, since the measurement values of the both ends 100a and 100b in the longitudinal direction of the prototype coil are difficult to stabilize due to the fact that the operator often grips them during the assembly work, 250 mm from the ends 100a and 100b When the total length of the prototype coil is 1000 mm or more in a range that is at least twice as wide as the width, it is preferable to set the measurement points within a range excluding 25% of the total length from the end portions 100a and 100b.

  When the prototype is a multi-strip coil, it is preferable to perform measurement with a metal strand excluding metal strands located on both sides in the longitudinal direction of the prototype among a plurality of metal strands arranged in the longitudinal direction of the prototype. . Since the metal wires located on both sides in the longitudinal direction of the prototype are located at the longitudinal ends of the medical coil to be formed, residual stress acts due to external forces acting differently from other metal strands when creating the prototype. It varies. Furthermore, in multi-strand winding, as shown in the enlarged view of FIG. 3, a minute pitch P may occur between one turn of the plurality of metal wires W1 to W5. Therefore, it is preferable to exclude the metal wires W1 and W5 located on both sides in the longitudinal direction from the measurement target. When the number of metal strands is an odd number, it is preferable to measure the central metal strand (metal strand W3 in FIG. 3). When the number of metal strands is an even number, only one of the two metal strands closest to the center may be measured, or the average value of the measured values of the two metal strands may be adopted. Also good.

In the subsequent selection process of step S40, only a prototype whose compressive residual stress value is equal to or greater than a predetermined value is selected as a non-defective product that satisfies the standard, and the rest is discarded as a defective product that does not satisfy the standard.
Conventionally, as described in Patent Document 1, it has been considered that removal of residual stress as much as possible by a heat treatment process leads to improvement of rotation transmission. However, according to the inventors' investigation, in a medical coil that is used in a long and meandering state, it is preferable that the residual compressive stress remains to some extent rather than completely remove the residual stress. It was found that the transmission was good. That is, by selecting only a prototype having a compressive residual stress value equal to or greater than a predetermined value and performing subsequent steps as necessary, a medical coil that exhibits stable rotation transmission can be manufactured.
The increase in the compressive residual stress after the heat treatment is considered to be due to the relaxation of the tensile residual stress outside the coil before the compressive residual stress by the heat treatment process. If the compressive residual stress is high, the crystal density of the metal wire increases, and it is considered that the fact that it works favorably in the transmission of rotation contributes to the improvement of the rotation transmission.
The predetermined value in the selection step can be appropriately set in consideration of the material of the metal element wire, the yield rate (yield), and the like, but at least 300 megapascals (MPa) or more and 600 MPa. When a metal strand is austenitic stainless steel, 350 MPa or more and 500 MPa or less are preferable. The metal wire before becoming the prototype coil usually has a tensile residual stress, and compressive residual stress is generated when becoming the prototype coil, but the compressive residual stress value does not become 300 MPa or more before the heat treatment.

  When a desired process such as a finishing process is performed as necessary after step S40, the prototype is completed and becomes the medical coil of the present embodiment, and the manufacturing method of the present embodiment ends. Since the medical coil of this embodiment manufactured by the manufacturing method of this embodiment has passed through measurement process S30 and selection process S40, it has a compressive residual stress of 300 MPa or more.

  The completed medical coil can be used as a part of an endoscope treatment tool. Even if the medical coil of this embodiment is long, a rotation operation applied at one end is suitably transmitted to the other end while suppressing a time lag. Further, even in a curved or meandering state, the rotation transmission property is suitably maintained. Therefore, even if it passes through the channel of the endoscope that is curved or meandering in the patient's body, the rotation operation at hand can be suitably transmitted to the distal end portion to be treated.

An example of an endoscope treatment tool including the medical coil of the present embodiment is shown in FIG. A high-frequency snare (endoscopic treatment tool) 1 shown in FIG. 4 includes a snare loop 10 for performing treatment such as polypectomy, an operation wire 20 connected to the snare loop 10, and a sheath through which the operation wire 20 is passed. 30 and an operation unit 40 attached to the proximal end side of the sheath 30. The operation unit 40 includes a main body 41 and a slider 42 attached to the main body 41. The rear end of the operation wire protruding from the sheath 30 is connected to the slider 42 inside the main body 41.
The medical wire 21 of the present embodiment constitutes a part of the operation wire 20 and imparts high rotation transmission to the operation wire 20.

An example of the assembly procedure (assembly process) of the medical wire 21 in the method for manufacturing the high-frequency snare 1 of the present embodiment is shown.
First, as shown in FIG. 5, the snare loop 10 and the core wire 22 of the operation wire 20 are connected. The connecting step may be omitted by forming the snare loop and the core wire 22 with the same wire.

  Next, as shown in FIG. 6, the core wire 22 to which the snare loop 10 is connected is passed through the medical wire 21. Subsequently, the end portion of the core wire 22 protruding from the rear end of the medical wire 21 is fixed to the connector 23 connected to the slider 42 by brazing or the like, as shown in FIG. Finally, as shown in FIG. 8, when the rear end of the medical wire 21 is fixed to the connector 23 by brazing or the like, and the front end of the medical wire 21 is connected to the core wire 22 or the snare loop 10, it is connected to the snare loop 10. The completed operation wire 20 is completed. Thereafter, the high-frequency snare 1 of the present embodiment can be manufactured by assembling in the same procedure as a known high-frequency snare.

When the high-frequency snare 1 is used, the snare loop 10 is rotated around the axis of the operation wire 20 as necessary to adjust the direction of the snare loop 10 so that the snare loop 10 can be easily applied to a treatment target such as a polyp. The adjustment is performed by rotating the entire operation unit 40 around the axis of the operation wire 20. However, since the sheath and the snare loop 10 are not fixed, the rotation operation is transmitted from the operation wire 20 to the snare loop 10.
The operation wire 20 of the high-frequency snare 1 includes the medical wire 21 of the present embodiment. Therefore, even if the endoscope through which the high-frequency snare 1 is passed is meandering in the patient's body, the rotation operation in the operation unit 40 is preferably transmitted to the snare loop, and the orientation of the snare loop 10 can be easily adjusted. Can do.

The manufacturing method of the medical wire of this embodiment is further demonstrated using an Example. The following description of the examples does not limit the scope of rights of the present invention.
(Example 1)
As metal wires, five round wires (diameter 0.3 mm) made of austenitic stainless steel SUS316WPA were prepared. By winding five metal strands arranged in the radial direction around the core metal at the same time, three single-layer five-layer prototype coils (A, B, C) having a total length of 2000 mm were produced. A piano wire SWP-B having a diameter of 1.0 mm was used as the core metal.

Next, a heat treatment step was performed on the prototype A, the prototype B, and the prototype C under the conditions of a heating temperature of 300 to 400 ° C. and a holding time of 30 minutes. The heating rate was 25 ° C./min, and the cooling rate was 0.57 ° C./min (furnace cooling).
Next, the measurement process was performed with respect to the prototypes A to C after the heat treatment. The measurement points were M1 to M3 shown in FIG. 2, and the distance D was 500 mm. The measurement was performed on the metal strand W3 closest to each measurement point, and the arithmetic average value of the obtained measurement values was adopted.
A micro X-ray stress measuring device (trade name: AutoMATE (manufactured by Rigaku Corporation)) was used as a measuring instrument. Using a Cr-Kα X-ray having an output of 40 mA, 40 kV, and a beam diameter of Φ0.3 mm, the compressive residual stress along the winding direction of the metal strand was measured by an X-ray diffraction method. Γ-Fe (220) was used as an unstrained reference sample.
Although details will be described later, prototypes A and B having a residual compression stress value of 300 MPa or more in the measurement process are selected as non-defective products in the selection process, and a prototype C having a residual compression stress value of less than 300 MPa is selected. There wasn't.

(Measurement of rotational transmission)
For prototypes A to C, rotation transmission was measured. FIG. 9 shows an evaluation system for rotation transmission. One end (rear end) of the prototype coil 100 </ b> A was chucked by the rotating device 201, and the prototype coil 100 </ b> A was looped once, and the other end (tip) was inserted into the detector 202. A rotation operation about the axis of the prototype 100A was applied to the rear end of the prototype coil 100A while recording the rotation angle with the rotating device 201. In parallel, the rotation angle of the tip of the prototype 100A was detected by the detector 202. The loop diameter Dm was 200 mm.
Table 1 shows the results of the measurement process and rotation transmission measurement.

  In all the prototypes, the compressive residual stress value after the heat treatment step increased compared to that before the heat treatment step. However, the compressive residual stress after the heat treatment process of each prototype was not the same as shown in Table 1, even though the heat treatment process was performed under the same conditions with the same material. The prototype A and the prototype B had a compressive residual stress of 300 MPa or more, whereas the prototype C had a compressive residual stress of 178 MPa. From this result, it is understood that it is not easy to manufacture a medical coil with stable performance only by adjusting the winding conditions at the time of producing the prototype and the conditions of the heat treatment process. Further, there was almost no difference in appearance between the prototypes, and it was impossible to identify good products by visual observation.

Table 1 shows the value of the rotation start angle as a result of the rotation transmission measurement. This is the value of the rotation angle of the rear end when the front end starts to rotate. In the prototype A and the prototype B, despite the harsh conditions of one rotation loop, the tip started to rotate when the rear end rotated about 1/4 rotation, and good rotation transmission was confirmed. On the other hand, in the original pattern C in which the compressive residual stress was less than 300 MPa, even though the rear end was rotated by 1/3, the front end did not start rotating yet.
According to the manufacturing method of the present embodiment, since the measurement process and the selection process are provided, only non-defective products are reliably selected from the prototypes created under the same conditions, and the rotational transmission of the manufactured medical coil is stabilized. be able to.

  FIG. 10 is a graph showing the relationship between the rotation angle of the rear end and the rotation angle of the front end in the prototype before the heat treatment and each prototype after the heat treatment step. The “angle ideal line” in FIG. 10 is a straight line indicating an ideal state where the rotation angle of the rear end and the rotation angle of the front end always coincide. In a long medical coil with meandering or bending, the relationship between the rotation angle of the rear end and the rotation angle of the tip is unlikely to coincide with the ideal angle line, but the rotation angle of the rear end and the rotation angle of the tip The degree of operability and feeling when the medical coil is applied to the endoscope treatment tool can be estimated to some extent depending on how close the relationship to the ideal angle line is.

As shown in FIG. 10, it can be seen that the prototype before the heat treatment hardly rotates even when the rear end rotates 2.5 times, and the rotation transmission is extremely poor. Although each prototype has improved rotational transmission after the heat treatment than before the heat treatment, it is presumed that the prototype C has no intersection with the angle ideal line and has a poor operational feeling.
In the prototype A and the prototype B, a coincident point with the ideal angle line is seen where the rear end makes one rotation, and it is assumed that the operational feeling is better than the prototype C. In prototype B, the phenomenon of momentarily rotating beyond the rotation angle of the rear end was observed when the tip rotated vigorously, but in prototype A having a compressive residual stress of 350 MPa or more, this phenomenon almost occurred. It was estimated that the operation feeling was better.

(Example 2)
Except for using a SUS316WPA flat wire having a thickness of 0.2 mm and a width of 0.4 mm as the metal strand, each step and rotation transmission measurement were performed in the same manner as in Example 1.
The compressive residual stress was 330 MPa, and the rotation start angle was 100 ° or less. From the graph showing the relationship between the rotation angle of the rear end and the rotation angle of the front end, it was presumed that the operational feeling when applied to the endoscope treatment tool was also good. In the manufacturing method of the present embodiment, the flat wire coil exhibited higher rotation transmission than the round wire coil.

  As mentioned above, although one embodiment of the present invention has been described, the technical scope of the present invention is not limited to the above-described embodiment, and combinations of components or components may be changed without departing from the spirit of the present invention. It is possible to make various changes to or delete them.

  The endoscope treatment tool of the present invention is not limited to the above-described high-frequency snare. That is, the medical coil of the present invention can be applied to any endoscopic treatment tool as long as the distal end portion for performing the treatment is rotated.

1 High-frequency snare (endoscopic instrument)
10 Nozzle 21 Medical coil 100, 100A Prototype coil S20 Heat treatment step S30 Measurement step S40 Selection step W1, W2, W3, W4, W5 Metal strand

Claims (8)

A heat treatment step of heating a prototype coil formed of a metal wire at a temperature of 500 ° C. or less;
A measurement step of measuring the compressive residual stress of the prototype coil after the heat treatment step;
A selection step of selecting only the original coil having a value of the compressive residual stress equal to or greater than a predetermined value;
Comprising
A method for manufacturing a medical coil. The predetermined value is 300 megapascals or more;
The manufacturing method of the medical coil of Claim 1. The measurement step is performed using an X-ray diffraction method.
The manufacturing method of the medical coil of Claim 1. The metal strand is formed of austenitic stainless steel,
The manufacturing method of the medical coil of Claim 1. The metal wire is a flat wire,
The manufacturing method of the medical coil of Claim 1. Manufactured by the method for manufacturing a medical coil according to claim 1,
The value of the compressive residual stress is 300 megapascals or more,
Medical coil. A method for manufacturing the medical coil according to claim 1;
An assembling step of attaching the selected prototype coil to a part of the endoscope treatment tool;
Comprising
A method for manufacturing a treatment instrument for an endoscope. It is manufactured by the manufacturing method of the treatment tool for endoscope according to claim 7,
The value of the compressive residual stress of the attached prototype coil is 300 megapascals or more,
Endoscopic treatment tool.

Images