Method for manufacturing molding, and method for manufacturing assembly for medical use

Abstract

To prevent a groove formed on an outer peripheral surface of a protrusion from becoming an undercut.SOLUTION: A method for manufacturing a molding 30 provided with a protrusion 32 and grooves 34 having a depth of 30 μm or more and 70 μm or less formed on an outer peripheral surface of the protrusion includes steps of: moving a movable side mold 362 toward a stationary side mold 361 so that a mold cavity 363 is defined between the stationary side mold and the movable side mold; injecting a molten thermoplastic resin into the mold cavity; performing primary cooling so that the thermoplastic resin solidifies; moving the movable side mold away from the stationary side mold; performing secondary cooling for cooling the protrusion; and releasing the molding from the movable side mold.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a molded article having a groove, and a method for manufacturing a medical assembly. [Background technology]

[0002] Patent Document 1 discloses a blood pump including a pump housing and an impeller disposed inside the pump housing. The pump housing is a molded product made of a resin material that is transparent to visible light wavelengths. The impeller is disposed in the pump housing in a rotatable state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-213605 A Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing a blood pump, which is an example of a medical assembly, a method of manufacturing the pump housing of the blood pump by assembling multiple components is considered. In this case, each component can be formed by injection molding. When forming a component having a groove, for example, a dynamic pressure groove for realizing a dynamic pressure bearing, the dynamic pressure groove may become undercut when the molded product is released from the die. [Means for solving the problem]

[0005] A manufacturing method of a molded product according to one embodiment of the present invention is a manufacturing method of a molded product having a convex portion and a groove having a depth of 30 μm or more and 70 μm or less formed on the outer peripheral surface of the convex portion, comprising the steps of: moving the movable side mold toward the fixed side mold so that a molding cavity is defined between the fixed side mold and the movable side mold; injecting molten thermoplastic resin into the molding cavity; performing primary cooling so that the thermoplastic resin solidifies; moving the movable side mold away from the fixed side mold; performing secondary cooling to cool the convex portion; and releasing the molded product from the movable side mold.

[0006] In addition, a manufacturing method for a medical assembly according to one embodiment of the present invention includes manufacturing a molded product by the above-described manufacturing method, preparing a member to be mated with the molded product, heating a first mating portion of the member to expand it, mating the first mating portion with a second mating portion of the molded product, cooling the first mating portion, and welding the first mating portion to the second mating portion.

[0007] This makes it possible to prevent the grooves formed on the outer circumferential surface of the protrusion from becoming undercuts. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view of a blood pump. [Diagram 2] FIG. 2 is a schematic exploded perspective view of a pump housing. [Diagram 3] FIG. 1 is a schematic plan view of a blood pump. [Figure 4] 1 is a schematic cross-sectional view of a blood pump according to a first embodiment. [Diagram 5] FIG. [Figure 6] Schematic cross-sectional view of a molded product. [Figure 7] FIG. 2 is an illustration of an injection mold in a closed state. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] 4 is a flowchart showing a molding process. [Figure 11]FIG. 6 is a schematic cross-sectional view of a blood pump according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of components described in the following embodiments can be set arbitrarily and can be changed according to the configuration of the device to which the present invention is applied or various conditions. Furthermore, unless otherwise specified, the scope of the present invention is not limited to the embodiments specifically described below. In this specification, when the inlet port side is defined as the upper direction, the opposite side corresponds to the lower direction.

[0010] [First embodiment] A blood pump 100, which is an example of a medical assembly shown in Fig. 1, is a single-use centrifugal pump used in an extracorporeal circulation circuit and is driven by a drive unit (not shown). The medical assembly is an article formed by assembling a plurality of members. Other examples of medical assemblies include an oxygenator, a heat exchanger, an arterial filter, and a blood storage tank reservoir. In the following, the blood pump 100 will be described as an example of a medical assembly.

[0011] As an example, the extracorporeal circulation circuit in which the blood pump 100 is used includes a flow sensor, a blood reservoir, an artificial lung, and the like. A blood removal circuit, a suction circuit, a negative pressure suction auxiliary circuit, and a fluid replacement filling circuit are connected to the upstream side of the blood reservoir. A blood sending circuit provided with an arterial filter is connected to the downstream side of the artificial lung. A gas supply circuit for sending gas for oxygen exchange is connected to the artificial lung. Furthermore, the artificial lung and the blood reservoir are connected by a blood collection circuit provided with a stopcock. The blood sending circuit is connected via the blood removal circuit and the recirculation circuit, but the recirculation circuit is closed during extracorporeal circulation. When starting extracorporeal circulation, blood is injected into the blood reservoir, and the blood stored in the blood reservoir is led to the blood pump 100.

[0012] The blood pump 100 includes a pump housing 10 and an impeller 50 (FIG. 5) housed inside the pump housing 10. The pump housing 10 is configured by assembling a top case 20, which is an example of a first member, and a base case 30, which is an example of a second member. An inlet port 21 of the blood pump 100 is formed in the top case 20 and is connected to the downstream side of a blood storage tank. Furthermore, an outlet port 22 of the blood pump 100 is formed in the top case 20 and is connected to the upstream side of an oxygenator.

[0013] The top case 20 and the base case 30 are formed from a transparent thermoplastic resin, for example, polycarbonate that is transparent to the wavelength region of laser light. As an example, the absorptance of laser light in the near-infrared region of the transparent thermoplastic resin used in this embodiment is 60 percent or less. In addition, the absorptance of laser light in the near-infrared region of the thermoplastic resin according to another example is 40 percent or less, or 30 percent or less and 20 percent or more. Alternatively, the top case 20 located on the outside may be formed from a transparent thermoplastic resin, and at least the welded portion of the base case 30 located on the inside may be formed from an opaque thermoplastic resin.

[0014] The top case 20 shown in FIG. 2 has a substantially cylindrical internal space formed therein so as to be covered by the base case 30. The top case 20 has an annular thin portion 24 (FIG. 4) as an example of a first fitting portion. The thin portion 24 defines an opening 23 of the top case 20. The base case 30 has a substantially cylindrical protrusion 32 formed to form a recess that opens downward. The protrusion 32 is inserted into the internal space of the base case 30. A central protrusion 33 is formed in the center of the top surface of the protrusion 32. Furthermore, a plurality of substantially spiral dynamic pressure grooves 34 that realize a dynamic pressure bearing are formed on the outer circumferential surface of the protrusion 32.

[0015] A peripheral recess 35 having a substantially doughnut shape is formed around the protrusion 32. Furthermore, the base case 30 has a raised portion 36 as an example of a second fitting portion. The raised portion 36 is raised from the peripheral recess 35 between the outer peripheral edge of the base case 30 and the peripheral recess 35. Furthermore, the raised portion 36 faces the thin portion 24 after being fitted together. That is, the outer surface of the raised portion 36 faces the inner surface of the thin portion 24 of the top case 20 when the top case 20 and the base case 30 are fitted together. In other words, the outer peripheral surface of the raised portion 36 in the radial direction of the base case 30 faces the inner peripheral surface of the thin portion 24 of the top case 20 in the radial direction.

[0016] Fig. 3 is a schematic plan view of the blood pump 100 as viewed from the inlet port 21 side. As shown in Fig. 3, the base case 30 has a substantially circular outer shape as viewed from the inlet port 21 side. The inlet port 21 is formed so as to protrude from the top surface of the pump housing 10. The outlet port 22 is formed so as to protrude from the outer circumferential surface of the pump housing 10.

[0017] Fig. 4 is a schematic cross-sectional view showing a cross section taken along the dashed line in Fig. 3 which passes through the center of the blood pump 100. For ease of explanation, the impeller 50 housed inside the pump housing 10 is shown by a dashed line in Fig. 4. Fig. 5 is a schematic cross-sectional view showing a cross section passing through the center of the impeller 50. The cross section shown in Fig. 5 corresponds to the cross section shown in Fig. 4, and the IV-IV cross section is a cross section passing through the center of the impeller 50.

[0018] As shown in FIG. 5, a central recess 51 that opens downward is formed in the center of the lower part of the impeller 50. A donut-shaped sealed space 52 that is liquid-tightly sealed is formed outside the central recess 51. A plurality of magnetic elements 53 are housed inside the sealed space 52 at predetermined intervals in the circumferential direction. As an example, a plurality of magnetic elements 53 are housed inside the sealed space 52. The magnetic elements 53 are, for example, permanent magnets. Alternatively, the magnetic elements 53 may be formed of iron pieces, and a drive unit (described later) may have a permanent magnet or an electromagnet that has a magnetic force that attracts the iron pieces.

[0019] The impeller 50 has a plurality of blades (not shown) for pushing out blood. An introduction flow passage 54 through which blood flows is formed in the center of the impeller 50 along the rotation axis CL of the impeller 50. The plurality of blades are disposed in a space between a pair of end plates 55A and 55B extending in a direction intersecting the rotation axis CL of the impeller 50, and extend in the radial direction of the impeller 50. A through hole 56 communicating with the introduction flow passage 54 is formed in the center of the impeller 50 coaxially with the rotation axis CL. The through hole 56 communicates with the inlet port 21 via the introduction flow passage 54. The introduction flow passage 54 communicates with a flow passage 11 (FIG. 4) inside the pump housing 10, which will be described later, via a plurality of flow passages 57 formed in the space between the end plates 55A and 55B. A plurality of dynamic pressure grooves curved in an arc shape are formed on the impeller top surface 58 of the impeller 50. Furthermore, a plurality of dynamic pressure grooves curved in an arc shape are also formed in the impeller bottom surface 59 of the impeller 50. Moreover, a plurality of dynamic pressure grooves curved in an arc shape are formed in the upper surface 51A of the central recess 51. These dynamic pressure grooves extend from the peripheral edge portion of the impeller 50 toward the rotation axis CL of the impeller 50, for example.

[0020] The introduction flow passage 54 is formed coaxially with the rotation axis CL of the impeller 50. Blood flowing in from the inlet port 21 is introduced into a flow passage 57 between the end plates 55A and 55B of the impeller 50 via the introduction flow passage 54. The blades are provided to separate each flow passage 57. As the impeller 50 rotates about the rotation axis CL, the blood introduced into the flow passage 57 is transported to the outer periphery of the impeller 50 by centrifugal force. The transported blood flows through the flow passage 11 along the inner circumferential surface of the pump housing 10 and is successively sent out from the outlet port 22.

[0021] As shown in Fig. 4, the base case 30 is disposed on the bottom side of the pump housing 10. The base case 30 and the top case 20 covering the base case 30 are joined in a liquid-tight manner. A donut-shaped flow path 11 is formed between the base case 30 and the top case 20 so as to surround the periphery of the impeller 50. The flow path 11 is connected to an outlet port 22. A central protrusion 33 protruding from a top surface of a protrusion 32 formed in the center of the base case 30 has a substantially conical shape.

[0022] The inlet port 21 is formed to extend coaxially with the rotation axis CL of the impeller 50. The inlet port 21 is connected to a tube (not shown) that forms part of the upstream flow path of the blood pump 100. The tip opening of the inlet port 21 functions as a blood suction port. The outlet port 22 is formed to extend in a direction substantially tangential to the rotation direction of the impeller 50. The outlet port 22 is connected to a tube (not shown) that forms part of the downstream flow path of the blood pump 100. The tip opening of the outlet port 22 functions as a blood discharge port.

[0023] The protrusion 32 is inserted into the inside of the central recess 51 of the impeller 50. An internal space is formed in the protrusion 32, forming a recess that opens downward. A driving section (not shown) of a driving unit is disposed in the internal space of the protrusion 32. The driving unit rotates the impeller 50 via the magnetic element 53. As an example, the driving unit has a motor. The driving section is attached to an output shaft connected to the motor and rotates together with the output shaft. The driving section also has driving magnetic elements, the same number as the magnetic elements 53 of the impeller 50, disposed at regular intervals in the circumferential direction. The driving magnetic elements are oriented in such a way that they are attracted to the magnetic elements 53. As a result, the driving section attracts the magnetic elements 53 by magnetic force. When the motor is driven and the output shaft rotates, the driving section fixed to the output shaft rotates. When the driving section rotates, the impeller 50 rotates together with the magnetic elements 53.

[0024] The rotation axis CL of the impeller 50 is set coaxially with the output shaft of the motor. In other words, the impeller 50 is disposed in the pump housing 10 in a state in which it can rotate about the rotation axis CL so that the rotation axis CL is positioned coaxially with the output shaft of the motor. Then, when the impeller 50 rotates, blood flows into the inside of the pump housing 10 through the inlet port 21. The blood that has flowed into the pump housing 10 flows into the introduction flow path 54 of the impeller 50. Then, the blood that has flowed into the introduction flow path 54 is caused to flow into the flow path 11 by the rotating multiple blades. Then, the blood that has flowed into the flow path 11 is sent from the flow path 11 to the outside of the blood pump 100 through the outlet port 22.

[0025] The thin portion 24 of the top case 20 is thinner than other portions so as to form a step at the end of the top case 20 on the base case 30 side. When the base case 30 and the top case 20 are fitted together, the inside dimension of the thin portion 24 is approximately equal to the outside dimension of the raised portion 36. The thickness of the raised portion 36 is approximately equal to the width of the step in the radial direction of the top case 20. Furthermore, the height of the raised portion 36 is approximately equal to the height of the step in the direction along the rotation axis CL of the impeller 50. This prevents a step from being formed at the boundary between the thin portion 24 and the raised portion 36 on the inner surface side of the pump housing 10 when the base case 30 and the top case 20 are fitted together.

[0026] [Dynamic pressure bearing] Between the inner surface of the pump housing 10 and the impeller top surface 58 of the impeller 50, a relatively narrow gap is formed for forming a dynamic pressure bearing DB1 that rotatably supports the impeller 50. Also, between the inner surface of the pump housing 10 and the impeller bottom surface 59 of the impeller 50, a relatively narrow gap is formed for forming a dynamic pressure bearing DB2 that rotatably supports the impeller 50. Then, a dynamic pressure groove is formed in the impeller bottom surface 59, and the rotation of the impeller 50 generates dynamic pressure, so that the impeller 50 floats from the dynamic pressure bearing DB2. Furthermore, between the outer peripheral surface of the protrusion 32 and the inner peripheral surface of the central recess 51 of the impeller 50, a relatively narrow gap is formed for forming a dynamic pressure bearing DB3 that rotatably supports the impeller 50. In addition, between the upper surface 51A of the central recess 51 and the protrusion top surface of the protrusion 32, a relatively narrow gap is formed for forming a dynamic pressure bearing DB4 that rotatably supports the impeller 50. It should be noted that through holes 56 in impeller 50 allow blood to move between a flow path 57 between end plates 55A, 55B and hydrodynamic bearings DB2, DB3, DB4.

[0027] When blood is introduced into the pump housing 10, a part of the introduced blood flows into the dynamic pressure bearings DB1, DB2, DB3, and DB4. As a result, the blood introduced into the pump housing 10 flows into the gap between the pump housing 10 and the impeller 50. When the impeller 50 rotates with the blood flowing in, the blood pressure in the dynamic pressure bearings DB1, DB2, DB3, and DB4 increases. As a result, the dynamic pressure bearings DB1, DB2, DB3, and DB4 act as a bearing, and the impeller 50 is rotatably supported. That is, the impeller 50 rotates without contacting the pump housing 10 due to the action of the liquid pressure (dynamic pressure) generated with the rotation of the impeller 50. The bearings DB1, DB2, and DB4 act in the direction of the rotation axis of the impeller 50. That is, the dynamic pressure bearings DB1, DB2, and DB4 function as a type of thrust bearing. The bearings DB3 act in the radial direction of the impeller 50. In other words, the hydrodynamic bearing DB3 functions as a type of radial bearing.

[0028] As a modified example, the dynamic pressure grooves may be formed on the inner surface of the top case 20 facing the impeller top surface 58 of the impeller 50. The dynamic pressure grooves may also be formed on the inner surface of the base case 30 facing the impeller bottom surface 59 of the impeller 50, or on the convex top surface of the convex portion 32 facing the upper surface 51A of the central recess 51. Furthermore, the dynamic pressure grooves may be formed on the inner circumferential surface of the central recess 51 of the impeller 50. A thrust bearing may also be realized by magnetic coupling between the drive unit and the impeller 50. As an example, a magnetic coupling is formed between the magnetic element 53 and the drive magnetic element to restrain the impeller 50 in a direction along the rotation axis CL. This allows the impeller 50 to be supported in a non-contact state with the pump housing 10. Alternatively, a thrust bearing may be realized by arranging a magnetic element that levitates the impeller 50 below the impeller 50.

[0029] [Manufacturing method of assembly] First, the top case 20, the base case 30, and the impeller 50 are prepared. The top case 20 and the base case 30 are formed from a transparent thermoplastic resin. An example of the transparent thermoplastic resin is polycarbonate, and the top case 20 and the base case 30 can be formed by injection molding. Alternatively, the top case 20 may be formed by other methods such as cast molding and 3D printing. The impeller 50 can be formed by a known method.

[0030] 6 is a schematic cross-sectional view showing a cross section passing through the center of the base case 30. As shown in FIG. 6, the base case 30, which is an example of a molded product, has a substantially cylindrical protrusion 32 formed to form a recess that opens downward. A plurality of spiral dynamic pressure grooves 34, which are an example of a groove, are formed on the outer circumferential surface of the protrusion 32. As shown in the enlarged view B surrounded by a dashed line in FIG. 6, the depth DP of the dynamic pressure groove 34 is 30 μm or more and 70 μm or less. In addition, a peripheral recess 35 is formed around the protrusion 32 so as to surround the protrusion 32.

[0031] Furthermore, between the outer peripheral edge of the base case 30 and the peripheral recess 35, a raised portion 36 is raised from the peripheral recess 35. The height H of the raised portion 36, which corresponds to the depth of the peripheral recess 35, is set to a height that allows the base case 30 to be released from the mold even if it shrinks inward due to secondary cooling, which will be described later. Furthermore, the height H is set to a length that ensures an area to be welded to the thin portion 24. As an example, the height H is 1.1 mm or more and 1.3 mm or less. Furthermore, the inner side surface of the raised portion 36, which is the edge of the peripheral recess 35, is slightly inclined toward the outside.

[0032] Here, when the base case 30 is molded by a normal method, the dynamic pressure grooves 34 become undercut when the base case 30 is released from the movable mold. Therefore, the dynamic pressure grooves 34 get caught in the mold during release. To address this, the movable mold can be configured to be separable or the movable mold can be rotated to achieve release. However, when the movable mold is configured to be separable, a parting line overlapping with the dynamic pressure grooves 34 is generated. Furthermore, when the movable mold is rotated, the dynamic pressure grooves 34 may be rubbed against the mold and scratched. Therefore, the parting line or scratch may hinder the configuration of the dynamic pressure bearing, and problems such as eccentricity of the rotating impeller 50 may occur. Furthermore, when the movable mold is configured to be separable or when the movable mold is rotated, the cost of mold production increases.

[0033] Therefore, in this embodiment, the molded product is released by performing secondary cooling to cool the protruding portion 32 as follows. That is, the protruding portion 32 is contracted by secondary cooling to separate the surface of the dynamic pressure groove 34 from the movable mold. As a result, the dynamic pressure groove 34 does not become an undercut, and the molded product can be released by simply moving it linearly away from the mold. Hereinafter, with reference to Figs. 7 to 10, a molding method according to this embodiment will be described as a manufacturing method for the base case 30, which is an example of a molded product. Figs. 7 to 9 are explanatory diagrams for explaining the operation of the fixed mold 361 and the movable mold 362. Fig. 10 is a flowchart showing the molding process.

[0034] [Molding process] Specifically, injection molding of the base case 30, which is an example of a molded product, is performed as follows using an injection molding die 300 including a fixed die 361 and a movable die 362. The fixed die 361 has a core 364 for forming a recess in the protrusion 32. Furthermore, the fixed die 361 has a pin gate 366. In the example of FIG. 7, the fixed die 361 has three pin gates including a pin gate not shown. Furthermore, the movable die 362 has a stripper 365 for releasing the base case 30 from the movable die 362.

[0035] First, as shown in FIG. 7, the movable mold 362 is moved toward the fixed mold 361 so that a molding cavity 363 is defined between the fixed mold 361 (cavity mold) and the movable mold 362 (core mold) to close the injection molding mold 300 (S110 in FIG. 10). Next, molten thermoplastic resin is injected into the molding cavity 363 through the pin gate 366 (S111 in FIG. 10). As an example, the injection time is 2 seconds. Then, primary cooling is performed so that the thermoplastic resin solidifies (S112 in FIG. 10). In the primary cooling, as an example, the mold temperature, which is the cooling temperature, is lowered to 75° C. or more and 90° C. or less to cool the base case 30. The cooling time is 25 seconds or more and 30 seconds or less.

[0036] 8, the movable die 362 is moved away from the fixed die 361, and the injection molding die 300 is opened (S113 in FIG. 10). When the injection molding die 300 is opened, the runner 367 is cut off from the base case 30. In addition, before the secondary cooling, the core 364 is extracted from the convex portion 32 of the base case 30 (S114 in FIG. 10). That is, when the movable die 362 is moved away from the fixed die 361, the core 364 is extracted from the convex portion 32 of the base case 30. Then, the secondary cooling is performed with the core 364 extracted (S115 in FIG. 10). The base case 30, which is a molded product, is cooled and contracted by the secondary cooling process. The core 364 can be extracted simultaneously with the movement of the movable die 362 or before or after the movement.

[0037] In this way, the core 364 is extracted from the protrusion 32 before the secondary cooling. Therefore, the outer peripheral surface of the protrusion 32, which shrinks due to the secondary cooling, shrinks toward the center of the recess in the protrusion 32. That is, the outer peripheral surface of the protrusion 32 is not hindered by the core 364 and displaces inward toward the central axis of the base case 30. As a result, the dynamic pressure groove 34 is displaced in a direction away from the movable side mold 362. Then, a gap is generated between the dynamic pressure groove 34 and the movable side mold 362. As a result, the base case 30 can be released from the movable side mold 362 simply by moving the base case 30 in a direction away from the movable side mold 362. Alternatively, if the shrinkage of the protrusion 32 is sufficient and can be realized, the core 364 may be extracted simultaneously with the secondary cooling or after the secondary cooling.

[0038] The secondary cooling is intended to cause the protrusions 32 to shrink by cooling. Therefore, the cooling time of the secondary cooling is shorter than that of the primary cooling. As an example, the cooling time of the secondary cooling is 6 seconds or more and 10 seconds or less. Furthermore, the cooling temperature of the secondary cooling is lower than that of the primary cooling. As an example, the mold temperature, which is the cooling temperature of the secondary cooling, is 75°C or less. Furthermore, during the secondary cooling, a low-temperature fluid (e.g., cooled gas) may be sprayed onto the protrusions 32. The temperature of the low-temperature fluid at this time is, as an example, 75°C or less.

[0039] Thereafter, as shown in Fig. 9, the base case 30 is released from the movable mold 362 (S116 in Fig. 10). Specifically, during release, the stripper 365 holding the base case 30 is moved away from the movable mold 362. That is, the stripper 365 lifts the shrunken base case 30 from the movable mold 362. This causes the base case 30 to be released. The top case 20 is also injection molded in the same manner, except for the secondary cooling process.

[0040] In the injection molding of the base case 30, the base case 30 is formed so that the dynamic pressure grooves 34 have a predetermined depth, for example, a depth of 30 μm to 70 μm. By forming the dynamic pressure grooves 34 to a depth of 30 μm or more, it is possible to suppress the pressure between the inner peripheral surface of the central recess 51 of the impeller 50 and the outer peripheral surface of the protrusion 32 of the base case 30 from decreasing below a desired value. This suppresses the eccentricity of the rotating impeller 50, and prevents contact between the base case 30 and the impeller 50. In addition, by forming the dynamic pressure grooves 34 to a depth of 70 μm or less, it is possible to suppress hemolysis. Furthermore, since the dynamic pressure grooves 34 are only slightly deep, the dynamic pressure grooves 34 that have contracted due to secondary cooling can be separated from the movable side mold 362.

[0041] As shown in FIG. 6, the base case 30 has a raised portion 36 between the convex portion 32 and the outer peripheral edge. The height of the raised portion 36 is set to a height that allows the base case 30 to be released from the movable mold 362 even if the base case 30 shrinks due to secondary cooling. Specifically, the height of the raised portion 36 is 1.1 mm or more and 1.3 mm or less. This can reduce the contact area between the raised portion 36 displaced inward due to shrinkage and the movable mold 362 when the base case 30 shrinks. This can prevent the raised portion 36 from becoming an undercut. Furthermore, the inner side surface of the raised portion 36, which is the edge of the peripheral recess 35, is slightly inclined toward the outside. This can further prevent the raised portion 36 from getting caught by the movable mold 362 during release.

[0042] [Assembly process] The impeller 50 is placed before fitting the thin portion 24 of the top case 20 and the raised portion 36 of the base case 30 together so that the impeller 50 is accommodated in the space defined by the top case 20 and the base case 30. Specifically, after preparing the top case 20, the base case 30, and the impeller 50, the impeller 50 is placed on the base case 30 so that the convex portion 32 of the base case 30 is inserted into the central concave portion 51 of the impeller 50. The placement of the impeller 50 may be performed after or simultaneously with the heating process of the thin portion 24. For example, the impeller 50 may be placed inside the top case 20 in a heated and expanded state. In this case, the base case 30 is fitted into the held top case 20 so that the convex portion 32 of the base case 30 is inserted into the central concave portion 51 of the impeller 50.

[0043] Next, in the heating process, the thin-walled portion 24 of the top case 20 is heated and expanded. Before heating, the inside dimension of the thin-walled portion 24 is smaller than the outside dimension of the raised portion 36. That is, when the inside diameter of the thin-walled portion 24 in the radial direction of the top case 20 is ID and the outside diameter of the raised portion 36 in the radial direction of the base case 30 is OD, the relationship OD>ID is established. Therefore, in the heating process, the thin-walled portion 24 is heated and expanded, so that the inside dimension of the thin-walled portion 24 is made larger than the outside dimension of the raised portion 36. The outside dimension of the raised portion 36 is set to be smaller than the inside dimension of the thin-walled portion 24 that expands when heated. In other words, the inside dimension of the thin-walled portion 24 is set to be larger than the outside dimension of the raised portion 36 when the size of the expansion when heated is added.

[0044] Specifically, in the heating step, the thin-walled portion 24 is heated to expand. To this end, the top case 20 is placed in a high-temperature bath and heated for 15 to 30 minutes in an air atmosphere at 40° C. to 60° C. Thereafter, the top case 20 is removed from the high-temperature bath and fitted to the base case 30 in a held state in an air atmosphere at room temperature. Alternatively, the base case 30 may be fitted to the top case 20 in a held state. The thin-walled portion 24 may also be heated by bringing a heating device (e.g., a heater) into contact with the thin-walled portion 24 or by spraying a high-temperature fluid (e.g., a heated gas) onto the thin-walled portion 24.

[0045] When fitting the thin portion 24 and the raised portion 36, the lower end of the thin portion 24 is abutted against the base case 30. Specifically, the lower end of the thin portion 24 is abutted against the plane between the raised portion 36 and the periphery of the base case 30. This allows the thin portion 24 to be positioned in the height direction. Therefore, it is possible to prevent the welding positions of the thin portion 24 and the raised portion 36 from being misaligned. On the other hand, when fitting by press-fitting, the top case 20 and the base case 30 are fitted together with the thin portion 24 and the raised portion 36 in contact with each other. Therefore, resistance is generated during fitting, and the top case 20 may be fixed in an inclined state. Furthermore, the thin portion 24 and the raised portion 36 may be deformed or damaged during press-fitting.

[0046] Next, in the cooling step, the thin-walled portion 24 is cooled. To this end, the top case 20 and the base case 30 are cooled for 10 to 20 seconds in an air atmosphere at room temperature. This causes the thin-walled portion 24 to shrink, and the thin-walled portion 24 and the raised portion 36 are fixed together. Furthermore, the shrunken thin-walled portion 24 presses the raised portion 36 inward, so that the thin-walled portion 24 and the raised portion 36 come into close contact with each other. Alternatively, the thin-walled portion 24 may be cooled by spraying a low-temperature fluid (e.g., a cooled gas) onto the thin-walled portion 24.

[0047] [Welding process] Next, in a welding process, the thin-walled portion 24 and the raised portion 36 are welded together. If the thin-walled portion 24 and the raised portion 36 are not in close contact with each other, the efficiency of heat conduction of the heated thermoplastic resin decreases, and the strength of the joint decreases. In this regard, with the assembly fitted together as described above, the contracted thin-walled portion 24 presses the raised portion 36 inward. Therefore, the thin-walled portion 24 and the raised portion 36 are in close contact with each other, and the decrease in the strength of the joint can be suppressed. Furthermore, the joint by welding is more suitable for medical assemblies than the joint by adhesive, which may be thermally altered or may affect the human body.

[0048] In the welding process, the thin portion 24 and the raised portion 36 are welded to each other by irradiating a laser onto the interface between the thin portion 24 and the raised portion 36. Alternatively, the top case 20 and the base case 30 may be welded to each other by a method other than laser welding, such as ultrasonic welding or high-frequency welding. In this case, at least one of the top case 20 and the base case 30 may be formed from an opaque thermoplastic resin. However, in a medical assembly, the use of a transparent resin has the advantage that the inside of the assembly can be viewed.

[0049] In the case of laser welding, the top case 20 and the base case 30 are formed of the same thermoplastic resin that transmits laser light. Alternatively, the transmittance of the laser light of the top case 20 and the base case 30 may be different. Then, in the direction shown by the arrow D in FIG. 4 perpendicular to the rotation axis CL of the impeller 50, a laser is irradiated from the outer surface side of the thin portion 24 with a focus set on the interface between the thin portion 24 and the raised portion 36. For example, the laser is a laser in the near-infrared region, for example, a laser in a wavelength region of 800 nm to 2500 nm, and preferably a laser with a central wavelength of 1940 nm. Alternatively, the laser may be irradiated from an oblique direction intersecting the rotation axis CL with a focus set on the interface between the thin portion 24 and the raised portion 36.

[0050] When the laser is applied, heat is generated on at least one of the inner peripheral surface of the thin portion 24 and the outer peripheral surface of the raised portion 36 at the interface between the top case 20 and the base case 30, and the thermoplastic resin melts. Then, the heat is conducted to the other of the inner peripheral surface of the thin portion 24 and the outer peripheral surface of the raised portion 36, and the other thermoplastic resin also melts. Then, when the application is stopped and the heat generation subsides, the melted thermoplastic resin resolidifies. As a result, the inner peripheral surface of the thin portion 24 and the outer peripheral surface of the raised portion 36 are welded together, and the thin portion 24 and the raised portion 36 are joined liquid-tightly. Alternatively, the laser may be applied to the interface between the top surface of the raised portion 36 and the surface of the top case 20 facing the top surface.

[0051] Then, while the laser is being irradiated, the blood pump 100 is rotated at a constant speed around the rotation axis CL. This allows the outer periphery of the blood pump 100 to be scanned with the laser, and the entire circumference of the blood pump 100 to be welded. Alternatively, the laser emission part may rotate around the blood pump 100 to weld the entire circumference of the blood pump 100. The laser may be irradiated intermittently or continuously. However, by irradiating continuously, it is possible to suppress distortion of the shape of the welded portion. This allows the top case 20 and the base case 30 to be more reliably joined liquid-tightly.

[0052] Furthermore, when irradiating the laser, the laser is irradiated to the interface between the thin portion 24 and the raised portion 36 so as to avoid the space defined by the top case 20 and the base case 30. That is, the laser may be irradiated so as to avoid the space in which the impeller 50 is housed. Specifically, in the example of FIG. 4, the laser is irradiated at a height lower than the bottom of the peripheral recess 35. This makes it possible to prevent the impeller 50 from being irradiated with the laser that has passed through the top case 20 and the base case 30. However, if the irradiation of the laser does not pose a problem, the laser may be irradiated to the space defined by the top case 20 and the base case 30.

[0053] According to the manufacturing method of the molded product according to the first embodiment described above, it is possible to prevent the grooves 34 formed on the outer peripheral surface of the protrusions 32 from becoming undercut. That is, the protrusions 32 are contracted by secondary cooling, and the surface of the dynamic pressure grooves 34 can be separated from the movable die 362. As a result, the dynamic pressure grooves 34 do not become undercut, and the molded product can be released from the die simply by moving it linearly away from the die.

[0054] In addition, according to the above-described manufacturing method of the medical assembly, the components constituting the medical assembly can be stably joined together. Furthermore, since there is no need for press-fitting, it is possible to suppress design constraints on each component to be fitted. That is, one of the two components to be fitted is heated and expanded, and the two components are fitted together in the expanded state and cooled. As a result, the contracted one component presses the other component, and the two components can easily be brought into close contact with each other. Therefore, the two components can be stably welded together without press-fitting, and the welded portion can also provide sealing properties. Furthermore, although a press-fitting device is required for press-fitting, the components can be fitted together by simply heating them, so there is no need to use a press-fitting device.

[0055] [Second embodiment] The second embodiment will be described with reference to FIG. 11. In the second embodiment, the positions at which the thin portion 224 and the raised portion 236 are formed are different from those of the first embodiment. In the second embodiment, the base case 230 is molded in the same manner as in the first embodiment, but the height of the raised portion 236 is higher than that of the first embodiment. In addition, the raised portion 236, which is an example of the first fitting portion, and the thin portion 224, which is an example of the second fitting portion, both have an annular shape. However, the second embodiment differs from the first embodiment in that the inner dimension of the raised portion 236 is smaller than the outer dimension of the thin portion 224 before heating. In the description of the second embodiment, differences from the first embodiment will be described, and the same reference numbers will be assigned to components that have already been described, and their description will be omitted. Except as otherwise described, components assigned the same reference numbers perform substantially the same operations and functions, and their effects are also substantially the same.

[0056] FIG. 11 is a schematic cross-sectional view showing a cross section passing through the center of the blood pump 200. For convenience of explanation, the impeller 50 housed inside the pump housing 210 is shown by a dashed line in FIG. 11. In FIG. 11, a base case 230, which is an example of a first member, and a top case 220, which is an example of a second member, are joined in a liquid-tight manner. The top case 220 has a substantially cylindrical internal space that is covered by the base case 230. The top case 220 has an annular thin portion 224 as an example of a second fitting portion. The base case 230 has a substantially cylindrical protrusion 232 that is formed to form a recess that opens downward. The protrusion 232 is inserted into the internal space of the base case 230.

[0057] Moreover, a substantially doughnut-shaped peripheral recess 235 is formed around the protrusion 232 so as to surround the protrusion 232. Furthermore, the base case 230 has a raised portion 236 as an example of a first fitting portion. The raised portion 236 is raised from the outer peripheral edge portion between the outer peripheral edge portion of the base case 230 and the peripheral recess 235. Moreover, the inner surface of the raised portion 236 faces the outer surface of the thin portion 224 of the top case 220 when the top case 220 and the base case 230 are fitted together. That is, the inner peripheral surface of the raised portion 236 in the radial direction of the base case 230 faces the outer peripheral surface of the thin portion 224 of the top case 220 in the radial direction.

[0058] Between the base case 230 and the top case 220, a doughnut-shaped flow passage 11 is formed so as to surround the periphery of the impeller 50. The outlet port 222 is connected to the flow passage 11. The inlet port 221 is formed so as to extend coaxially with the rotation axis CL of the impeller 50. The outlet port 222 is formed so as to extend in a direction generally tangential to the rotation direction of the impeller 50. The protruding portion 232 of the base case 230 is inserted into the inside of the central recess 51 of the impeller 50. An internal space is formed in the protruding portion 232, forming a recess that opens downward. The central protruding portion 233 protruding from the top surface of the protruding portion 232 of the base case 230 has a generally conical shape.

[0059] A drive section (not shown) of the drive unit is disposed in the internal space of the protrusion 232. When the impeller 50 rotates, blood flows into the inside of the pump housing 210 through the inlet port 221. The blood that has flowed into the pump housing 210 flows into the introduction flow path 54 of the impeller 50. The blood that has flowed into the introduction flow path 54 is then caused to flow into the flow path 11 by the rotating multiple blades. The blood that has flowed into the flow path 11 is then sent from the flow path 11 to the outside of the blood pump 200 through the outlet port 222.

[0060] Between the inner surface of the pump housing 210 and the impeller top surface 58 of the impeller 50, a relatively narrow gap is formed for forming a dynamic pressure bearing DB1 that rotatably supports the impeller 50. Also, between the inner surface of the pump housing 210 and the impeller bottom surface 59 of the impeller 50, a relatively narrow gap is formed for forming a dynamic pressure bearing DB2 that rotatably supports the impeller 50. Furthermore, between the outer peripheral surface of the protruding portion 232 and the inner peripheral surface of the central recessed portion 51 of the impeller 50, a relatively narrow gap is formed for forming a dynamic pressure bearing DB3 that rotatably supports the impeller 50. In addition, between the upper surface 51A of the central recessed portion 51 and the protruding portion top surface of the protruding portion 232, a relatively narrow gap is formed for forming a dynamic pressure bearing DB4 that rotatably supports the impeller 50.

[0061] When blood is introduced into pump housing 210, some of the introduced blood flows into dynamic pressure bearings DB1, DB2, DB3, and DB4. As a result, the blood introduced into pump housing 210 flows into the gap between pump housing 210 and impeller 50. When impeller 50 rotates with blood flowing in, the blood pressure rises in dynamic pressure bearings DB1, DB2, DB3, and DB4. As a result, a bearing effect is generated in dynamic pressure bearings DB1, DB2, DB3, and DB4, and impeller 50 is rotatably supported.

[0062] In the second embodiment, before heating, when comparing the outer dimension of the thin portion 224 and the inner dimension of the raised portion 236, the inner dimension of the raised portion 236 is smaller than the outer dimension of the thin portion 224. That is, when the outer diameter of the thin portion 224 in the radial direction of the top case 220 is OD and the inner diameter of the raised portion 236 in the radial direction of the base case 230 is ID, the relationship of OD>ID is established. Therefore, in the heating process, the raised portion 236 of the base case 230 is heated and expanded. The outer dimension of the thin portion 224 is set to be smaller than the inner dimension of the raised portion 236 expanded by heating. In other words, the inner dimension of the raised portion 236 is set to be larger than the outer dimension of the thin portion 224 when the size of expansion by heating is added.

[0063] [Manufacturing method of assembly] First, the top case 220, the base case 230, and the impeller 50 are prepared. The top case 220 and the base case 230 are formed from a transparent thermoplastic resin. An example of the transparent thermoplastic resin is polycarbonate, and the top case 220 and the base case 230 can be formed by injection molding.

[0064] The injection molding of the base case 230 is performed in the same manner as in the first embodiment. That is, the injection mold 300 is closed so that the molding cavity 363 is defined between the fixed mold 361 and the movable mold 362. Next, molten thermoplastic resin is injected into the molding cavity 363 through the pin gate 366. Next, primary cooling is performed so that the thermoplastic resin solidifies. Then, the movable mold 362 is moved away from the fixed mold 361 to open the injection mold 300. Also, before secondary cooling, the core 364 is extracted from the protrusion 232 of the base case 230. Then, secondary cooling is performed with the core 364 extracted. Then, the base case 230 is released from the movable mold 362. The top case 220 is also injection molded in the same manner except for the secondary cooling process. In this manner, the top case 220 and the base case 230 are prepared.

[0065] Then, before fitting together the thin portion 224 of the top case 220 and the raised portion 236 of the base case 230, the impeller 50 is positioned so that the impeller 50 is accommodated within the space defined by the top case 220 and the base case 230. Specifically, after preparing the top case 220, the base case 230, and the impeller 50, the top case 220 is turned upside down, and the impeller 50 is inserted into the inside of the top case 220 with the inlet port 221 facing downward.

[0066] Next, in a heating step, the raised portion 236 of the base case 230 is heated and expanded. Thereafter, the base case 230 is fitted to the top case 220 in a held state in an air atmosphere at room temperature. Alternatively, the top case 220 may be fitted to the base case 230 in a held state. The raised portion 236 may also be heated by bringing a heating device into contact with the raised portion 236 or by spraying a high-temperature fluid onto the raised portion 236.

[0067] When fitting the top case 220 and the base case 230 together, the top surface of the raised portion 236 is abutted against the top case 220. Specifically, the top surface of the raised portion 236 is abutted against the plane between the thin portion 224 and the periphery of the top case 220. This allows the raised portion 236 to be positioned in the height direction. Therefore, it is possible to prevent the welding position from shifting.

[0068] Subsequently, in the cooling step, the raised portion 236 is cooled. To this end, the top case 220 and the base case 230 are cooled under an air atmosphere at room temperature. As a result, the raised portion 236 contracts, and the thin-walled portion 224 and the raised portion 236 are fixed together. Furthermore, the contracted raised portion 236 presses the thin-walled portion 224 inward, so that the thin-walled portion 224 and the raised portion 236 come into close contact with each other. Alternatively, the raised portion 236 may be cooled by spraying a low-temperature fluid onto the raised portion 236. Note that the impeller 50 may be disposed after or simultaneously with the heating step of the raised portion 236. For example, the impeller 50 may be placed on the base case 230 in a heated and expanded state. In this case, the convex portion 232 of the base case 230 is inserted into the central concave portion 51 of the impeller 50. Then, the top case 220 is fitted to the held base case 230.

[0069] Next, in the welding process, the thin portion 224 and the raised portion 236 are welded together. At this time, if the thin portion 224 and the raised portion 236 are not in close contact with each other, the efficiency of heat conduction of the heated thermoplastic resin decreases, and the strength of the joint decreases. In this regard, according to the assembly fitted together as described above, the contracted raised portion 236 presses the thin portion 224 inward. Therefore, the thin portion 224 and the raised portion 236 are in close contact with each other, and the decrease in the strength of the joint can be suppressed. In the welding process, the thin portion 224 and the raised portion 236 are laser welded together by irradiating a laser to the interface between the thin portion 224 and the raised portion 236.

[0070] In the case of laser welding, the top case 220 and the base case 230 are formed of the same thermoplastic resin that transmits laser light. Then, in the direction shown by the arrow D in FIG. 11 perpendicular to the rotation axis CL of the impeller 50, a laser is irradiated from the outer surface side of the raised portion 236, with a focus set on the interface between the thin portion 224 and the raised portion 236. When the laser is irradiated, heat is generated on one of the inner peripheral surface of the raised portion 236 and the outer peripheral surface of the thin portion 224 at the interface between the top case 220 and the base case 230, and the thermoplastic resin melts. After that, the other thermoplastic resin on the inner peripheral surface of the raised portion 236 and the outer peripheral surface of the thin portion 224 also melts. Then, when the irradiation is stopped and the heat generation subsides, the melted thermoplastic resin resolidifies. As a result, the outer peripheral surface of the thin portion 224 and the inner peripheral surface of the raised portion 236 are welded together, and the thin portion 224 and the raised portion 236 are joined together in a liquid-tight manner.

[0071] Then, in the state where the laser is irradiated, the blood pump 200 is rotated at a constant speed around the rotation axis CL. As a result, the outer periphery of the blood pump 200 can be scanned with the laser, and the entire circumference of the blood pump 200 can be welded. Furthermore, when the laser is irradiated, the laser is irradiated to the interface between the thin portion 224 and the raised portion 236 so as to avoid the space defined by the top case 220 and the base case 230. Specifically, in the example of FIG. 11, the laser is irradiated at a height lower than the bottom of the peripheral recess 235. This makes it possible to prevent the impeller 50 from being irradiated with the laser that has passed through the top case 220 and the base case 230. However, if the laser irradiation is not a problem, the laser may be irradiated to the space defined by the top case 20 and the base case 30.

[0072] The above-described second embodiment also prevents the groove 34 formed on the outer peripheral surface of the protrusion 232 from becoming an undercut. The above-described manufacturing method for a medical assembly also allows the members constituting the medical assembly to be stably joined together. Since there is no need for press-fitting, it is possible to prevent each member to be fitted from being subject to design constraints. That is, one of the two members to be fitted is heated and expanded, and the two members are fitted together in the expanded state and cooled. As a result, the contracted one member presses the other member, and the two members can easily be brought into close contact with each other. Therefore, the two members can be stably welded together without press-fitting, and the welded portion can provide sealing properties. Furthermore, although a press-fitting device is required for press-fitting, the members can be fitted together by simply heating them, so there is no need to use a press-fitting device.

[0073] Although the present invention has been described above with reference to each embodiment, the present invention is not limited to the above embodiment. The present invention also includes inventions that have been modified without going against the present invention, and inventions equivalent to the present invention. In addition, each embodiment and each modified form can be appropriately combined without going against the present invention.

[0074] For example, the top case 20, 220 may not have the thin portion 24, 224. Specifically, the thickness of the portion of the top case 20, 220 facing the raised portion 36, 236 may be the same as or thicker than the other portions of the top case 20, 220. However, by providing the thin portion 24, 224 and welding it with a laser that has passed through the thin portion 24, 224, the proportion of laser light absorbed by the resin can be reduced. [Explanation of symbols]

[0075] 20: Top case (component) 24: Thin wall part (first mating part) 30: Base case (molded product) 32: Convex 34: Dynamic pressure groove (groove) 36: Raised part (second mating part) 100: Blood pump (medical assembly) 200: Blood pumps (medical assemblies) 236: Raised part 361: Fixed side mold 362: Movable mold 363: Molding cavity 364: Middle child 365: Stripper

Claims

1. A method for producing a molded product comprising a convex portion and a groove having a depth of 30 μm or more and 70 μm or less formed on an outer peripheral surface of the convex portion, comprising: moving the movable die toward the fixed die such that a molding cavity is defined between the fixed die and the movable die; Injecting molten thermoplastic resin into the mold cavity; A primary cooling is performed so that the thermoplastic resin is solidified. moving the movable die away from the fixed die; performing secondary cooling to cool the protruding portion; The molded product is released from the movable mold.

2. Before the secondary cooling, the core is removed from the protruding portion of the molded product, The method for producing a molded product according to claim 1 , wherein the secondary cooling is carried out in a state in which the core is removed.

3. The method for producing a molded product according to claim 1 or 2, further comprising the step of moving a stripper holding the molded product away from the movable mold when the molded product is released from the movable mold.

4. The method for producing a molded article according to claim 1 , wherein a cooling time of the secondary cooling is shorter than a cooling time of the primary cooling.

5. The molded product has a raised portion between the convex portion and an outer circumferential edge portion, 5. The method for manufacturing a molded product according to claim 1, wherein the height of the raised portion is set to a height that allows the molded product to be released from the movable mold even if the molded product shrinks due to the secondary cooling.

6. A molded product is manufactured by the manufacturing method according to any one of claims 1 to 5, preparing a member to be fitted with the molded article; Heating a first mating portion of the member to expand it; The first fitting portion is fitted to a second fitting portion of the molded product, Cooling the first mating portion; The method of manufacturing a medical assembly further comprises welding the first mating portion and the second mating portion together.

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