JP7841746B2 - Manufacturing method for noise suppression components - Google Patents

Description

This disclosure relates to a method for manufacturing noise suppression components.

In noise suppression members equipped with a magnetic core, a technique is known in which the magnetic core is molded using a resin molding member (see, for example, Patent Document 1). In such noise suppression members, a ferrite sintered body may be used as the magnetic core.

Japanese Patent Publication No. 2020-005043

As mentioned above, when resin-molding a ferrite sintered body, the wall thickness corresponding to the distance between the inner and outer circumferences of the magnetic core is generally set to approximately 5 mm or more. However, when resin molding is added to both the inner and outer circumferences of a magnetic core using such a ferrite sintered body, the overall noise suppression component becomes considerably bulkier. Therefore, such noise suppression components may be difficult to install in thin devices or in confined spaces.

Therefore, the inventors of this case are considering reducing the thickness of the magnetic core to less than 5 mm. However, when the thickness of the magnetic core is less than 5 mm, the pressure acting on the magnetic core when molten resin is injected into the mold in which the magnetic core is placed can cause cracks or other damage to the magnetic core. If the magnetic core is damaged, its performance as a noise suppression component may deteriorate.

In one aspect of this disclosure, it is desirable to provide a manufacturing method that enables the production of noise suppression components that can be installed in thin devices or confined spaces, and that can suppress damage to the magnetic core during manufacturing.

The structure of this disclosure is described below.
(1) One aspect of the present disclosure is a method for manufacturing a noise suppression member, the noise suppression member comprising a magnetic core and a molded member. The magnetic core is made of a sintered body of a magnetic material and is shaped to allow a conductor to be placed at a position penetrating the inner circumference. The molded member is made of a resin material and is configured to mold the magnetic core. The magnetic core has a thin-walled portion with a wall thickness of 1.5 mm to 4.0 mm, corresponding to the dimension between the inner circumference and the outer circumference. The molded member is a single-piece molded product in which a portion that molds the inner circumference of the thin-walled portion and a portion that molds the outer circumference of the thin-walled portion are integrally molded from a resin material. When molding the molded member, before injecting the resin material into the mold, a retaining pin is brought into contact with the magnetic core placed in the mold to hold the magnetic core in the mold. When injecting resin material into the mold, retaining pins that are in contact with the thin-walled portion are moved to a position away from the thin-walled portion within a period during which the filling volume ratio E = (1 - (D - C) / D) × 100, which can be calculated based on the filling volume C, which is the volume of resin material filled into the mold, and the volume D of the molded member, satisfies the value 60 ≤ E ≤ 90.

The noise suppression member manufacturing method configured in this way allows for the production of the noise suppression member described above. In particular, in this manufacturing method, when injecting the resin material into the mold, at least the retaining pins located in contact with the thin-walled portion are retracted to a position away from the thin-walled portion within a period during which the filling volume ratio E satisfies 60 ≤ E ≤ 90. Therefore, compared to the case where the filling of the resin material to the inner circumference of the thin-walled portion is completed without retracting the retaining pins, the occurrence of cracks in the magnetic core at the thin-walled portion can be suppressed.

Furthermore, the method for manufacturing the noise suppression member described herein may also include the following configurations.
(2) In one aspect of the present disclosure, when injecting resin material into the mold, retaining pins that are in contact with the thin-walled portion may be retracted to a position away from the thin-walled portion during a period in which the filling volume ratio E satisfies 60 ≤ E ≤ 80.

(3) In one aspect of this disclosure, the filling volume C = A × B × t may be calculated based on the area A of the cross-sectional area perpendicular to the axial direction of the screw of the injection molding machine, the injection speed B corresponding to the axial movement speed of the screw, and the injection time t corresponding to the axial movement time of the screw.

(4) In one aspect of this disclosure, the retaining pin may be configured to contact a surface on the outer circumference of the thin-walled portion that is perpendicular to the thickness direction of the thin-walled portion when it contacts the thin-walled portion.

Figure 1A is a perspective view of the noise suppression member of the first embodiment, viewed from the upper right front. Figure 1B is a perspective view of the noise suppression member of the first embodiment, viewed from the upper right rear. Figure 1C is a perspective view showing the internal structure of the noise suppression member of the first embodiment. Figure 1D is a perspective view showing an excerpt of a part of the internal structure of the noise suppression member of the first embodiment. Figure 2A is a plan view of the noise suppression member of the first embodiment. Figure 2B is a front view of the noise suppression member of the first embodiment. Figure 2C is a right side view of the noise suppression member of the first embodiment. Figure 2D is a rear view of the noise suppression member of the first embodiment. Figure 2E is a bottom view of the noise suppression member of the first embodiment. Figure 3A is a perspective view of the noise suppression member of the second embodiment, viewed from the upper right front. Figure 3B is a perspective view of the noise suppression member of the second embodiment, viewed from the upper left rear. Figure 3C is a perspective view showing the internal structure of the noise suppression member of the second embodiment. Figure 3D is a perspective view showing the noise suppression member of the second embodiment in use. Figure 4A is a plan view of the noise suppression member of the second embodiment. Figure 4B is a left side view of the noise suppression member of the second embodiment. Figure 4C is a front view of the noise suppression member of the second embodiment. Figure 4D is a right side view of the noise suppression member of the second embodiment. Figure 4E is a bottom view of the noise suppression member of the second embodiment.

Next, the manufacturing method of the noise suppression member described above will be explained with reference to exemplary embodiments.
(1) First Embodiment The first embodiment will be described below. As shown in Figures 1A, 1B, 1C, and 1D, the noise suppression member 1 comprises a magnetic core 3, a collar 5, a molded member 7, and a conductor 9. In the following description, in order to briefly explain the relative positions and orientations of each part of the noise suppression member 1, the directions front, back, left, right, up, and down indicated in the figures will be used for the explanation. These directions are defined as follows: front is the direction towards which the part shown in the front view of the noise suppression member 1 (see Figure 2B) is directed; rear is the direction towards which the part shown in the rear view (see Figure 2D) is directed; left is the direction towards which the part shown in the left side view (not shown; the left side view is shown identically to the right side view); right is the direction towards which the part shown in the right side view (see Figure 2C) is directed; up is the direction towards which the part shown in the top view (see Figure 2A) is directed; and down is the direction towards which the part shown in the bottom view (see Figure 2E) is directed.

The magnetic core 3 is constructed from a sintered magnetic material (in this embodiment, a sintered ferrite). The magnetic core 3 is shaped to allow the conductor 9 to be positioned through its inner circumference. In this embodiment, the magnetic core 3 is constructed as a flattened cylindrical shape with an oval cross-section perpendicular to the axial direction, and its axial direction is oriented in the front-to-back direction as shown in the figure. Therefore, the conductor 9, which extends in the front-to-back direction as shown in the figure, can be positioned to penetrate the inner circumference.

The magnetic core 3 has a thin-walled portion 3A with a wall thickness of 1.5 mm to 4.0 mm, corresponding to the distance between the inner and outer circumferences of the magnetic core 3. In this embodiment, the magnetic core 3 has a wall thickness of 4.0 mm around its entire circumference. That is, in this embodiment, the entire magnetic core 3 is the thin-walled portion 3A.

Collar 5 is formed from a metal material (e.g., stainless steel). Collar 5 is a cylindrical member, and when, for example, the noise suppression member 1 is fixed to a predetermined mounting position with bolts, the shaft of the bolt passes through the inner circumference of collar 5.

The conductor 9 is a plate-shaped conductor (busbar) made of copper alloy. A projection 13 is provided near the center of the conductor 9 in its longitudinal direction (front-to-back direction in the diagram), projecting in the width direction (left-to-right direction in the diagram). This projection 13 suppresses the displacement of the conductor 9 in the front-to-back direction relative to the molded member 7.

The molded member 7 is formed from a resin material (e.g., polyamide) and is configured to mold the magnetic core 3, collar 5, and conductor 9. The molded member 7 is a single-piece molded product in which the portion molding the inner circumference of the thin-walled portion 3A and the portion molding the outer circumference of the thin-walled portion 3A are integrally molded from the resin material.

As shown in Figures 2C, 2D, and 2E, the molded member 7 has a left positioning recess 21, a right positioning recess 22, a first lower positioning recess 23, a second lower positioning recess 24, a third lower positioning recess 25, a fourth lower positioning recess 26, a first rear positioning recess 27, and a second rear positioning recess 28 formed therein.

The left positioning recess 21, the right positioning recess 22, the first lower positioning recess 23, the second lower positioning recess 24, the third lower positioning recess 25, the fourth lower positioning recess 26, the first rear positioning recess 27, and the second rear positioning recess 28 are locations where a holding portion (not shown) that holds the magnetic core 3 in a predetermined position within the mold (not shown) during the molding of the molded member 7 using the mold (not shown) was in contact with the magnetic core 3.

The holding portions that contact the magnetic core 3 in the left positioning recess 21 and the right positioning recess 22 position the magnetic core 3 in the left-right direction. The holding portions that contact the magnetic core 3 in the first rear positioning recess 27 and the second rear positioning recess 28 position the magnetic core 3 in the front-rear direction.

In this embodiment, the flow path of the resin material within the mold is configured to proceed from the front to the rear of the magnetic core 3. Therefore, the magnetic core 3 is pushed backward by the resin material, and when the holding portions in the first rear positioning recess 27 and the second rear positioning recess 28 contact the magnetic core 3, the front-to-back position of the magnetic core 3 can be positioned.

The retaining portions that contact the magnetic core 3 in the first lower positioning recess 23, the second lower positioning recess 24, the third lower positioning recess 25, and the fourth lower positioning recess 26 work in cooperation with retaining pins (not shown) that contact the upper surface of the magnetic core 3 to position the magnetic core 3 in the vertical direction. The retaining pins that contact the upper surface of the magnetic core 3 are configured to move up and down within the mold at the locations indicated by dashed lines in Figures 1A, 1B, and 2A.

Therefore, when the retaining pin contacts the thin-walled portion 3A, it contacts a surface on the outer circumference of the thin-walled portion 3A that is perpendicular to the thickness direction of the thin-walled portion 3A. When molding the molded member 7, before injecting the resin material into the mold, the retaining pin is moved downward to contact the magnetic core 3 positioned inside the mold. This holds the magnetic core 3 within the mold in a position fixed in the vertical direction.

When injecting resin material into the mold, after injecting the resin material, and before the resin material has completely filled the inner circumference of the thin-walled portion 3A, the retaining pin is moved upward and retracted to a position away from the thin-walled portion 3A. More specifically, the process of injecting resin material into the mold includes an injection process in which a predetermined amount of resin material is injected into the mold, and a holding pressure process in which pressure is applied to the resin material in the mold after the injection process is completed.

In this embodiment, during the injection process, the resin material is injected via speed control, and the screw of the injection molding machine is driven at a preset speed. As a result, an amount of resin material corresponding to the screw drive amount is injected. In this embodiment, the injection process takes approximately 0.24 seconds. Once the screw reaches a predetermined switching position, the control switches from speed control to pressure control, and the process transitions to the holding pressure process. In the holding pressure process, a preset pressure is applied to the resin material in the mold, and this state is maintained. In this embodiment, the holding pressure process takes approximately 2 seconds.

Of the processes described above, the retaining pin is retracted upward during the injection process. The specific means for retracting the retaining pin are arbitrary; for example, power can be transmitted from a power source such as a cylinder to actively operate the retaining pin. The timing of moving the retaining pin upward is crucial; if it is too early, it may cause misalignment of the magnetic core 3, while if it is too late, it may cause cracks in the magnetic core 3.

Therefore, based on the volume of molten resin filled into the mold (referred to as the filling volume C in this specification) and the volume D of the mold member 7, the filling volume ratio E = (1 - (D - C) / D) × 100 was calculated, and the relationship between the filling volume ratio E and the timing of moving the retaining pin upward was verified. The filling volume C can be calculated as filling volume C = A × B × t based on the area A of the cross-section perpendicular to the axial direction of the screw of the injection molding machine, the injection speed B corresponding to the axial movement speed of the screw, and the injection time t corresponding to the axial movement time of the screw.

The filling volume fraction E is a value that changes from 0% to 100% as time elapses from the start to the completion of injection. When the filling volume fraction E is Ex%, the filling volume Cx is Cx = D × (Ex/100). Therefore, the injection time tx at which the filling volume Cx = D × (Ex/100) is tx = Cx / (A × B), which simplifies to tx = D × (Ex/100) / (A × B).

In the following verification experiment, the injection times tx corresponding to the filling volume fraction E being Ex = 50%, 60%, 70%, 80%, 90%, and 100% were calculated based on the above relationship: tx = D × (Ex/100) / (A × B). Then, when molding the mold member 7, the retaining pin was moved upward at the timing of each injection time tx, creating six test specimens corresponding to Ex = 50%, 60%, 70%, 80%, 90%, and 100%.

For these six test specimens, the following were evaluated: (A) cracking and displacement of the magnetic core 3, (B) resin appearance of the molded member 7, and (C) resin strength of the molded member 7. For (A) above, part or all of the molded member 7 was peeled off and the cracking and displacement of the magnetic core 3 was visually checked. If there were no cracks or displacement, it was evaluated as "A," and if there were cracks or displacement, it was evaluated as "C." For (B) above, the appearance of the molded member 7 was visually checked and evaluated as "A" if there were no pin marks or weld marks, "B" if there were weld marks, and "C" if there were pin marks. For (C) above, the test specimens were subjected to a temperature change of -40°C/125°C using a thermal shock tester, and the appearance of the molded member 7 after 1000 hours was visually checked and evaluated as "A" if there was no change, "B" if thin lines were observed, and "C" if cracks occurred in the resin. Based on the above, the overall evaluation was determined as follows: if all three evaluation items received an "A" rating, the overall evaluation was "A"; if there were no "C" ratings but at least one "B" rating, the overall evaluation was "B"; and if even one "C" rating was received, the overall evaluation was "C". The evaluation results are shown in [Table 1].

In the above [Table 1], when the retaining pin was moved with a filling volume ratio E = 50%, a slight displacement occurred in the magnetic core 3, resulting in an evaluation of "C" and an overall evaluation of "C". When the retaining pin was moved with a filling volume ratio E = 60% to 80%, all three evaluation items were "A", resulting in an overall evaluation of "A". When the retaining pin was moved with a filling volume ratio E = 90%, weld marks occurred on the surface of the molded member 7, and thin lines were observed after the thermal shock test, resulting in "B" for two evaluation items and an overall evaluation of "B". If weld marks etc. do not pose a practical problem, there are no performance issues even with a test specimen that receives an overall evaluation of "B", but if appearance is also important, it is preferable to move the retaining pin with a filling volume ratio E = 60% to 80%. When the retaining pin was moved with a filling volume ratio E = 100%, cracks occurred in the magnetic core 3. Furthermore, pin marks remained on the surface of molded component 7, and crack formation was observed after the thermal shock test. Therefore, each item received a "C" rating, resulting in an overall "C" rating.

Based on the above evaluation results, it is preferable to retract the retaining pins, which are in contact with the thin-walled portion 3A, to a position away from the thin-walled portion 3A during the period in which the above-mentioned filling volume ratio E satisfies 60 ≤ E ≤ 90. Furthermore, if the appearance of the molded member 7 is also important, it is preferable to retract the retaining pins to a position away from the thin-walled portion 3A during the period in which the above-mentioned filling volume ratio E satisfies 60 ≤ E ≤ 80.

As explained above, by retracting the retaining pin at the timing described above, crack formation can be suppressed even in magnetic cores 3 with extremely thin wall thicknesses of 0.15 mm to 0.4 mm in the thin-walled portion 3A. Therefore, the noise suppression effect of the noise suppression member 1 can be fully demonstrated. Furthermore, suppressing the occurrence of such cracks reduces the number of defective products, thereby improving the productivity of the noise suppression member 1.

As described above, the noise suppression member 1 has a thin-walled portion 3A with a wall thickness of 1.5 mm to 4.0 mm, corresponding to the distance between the inner and outer circumferences of the magnetic core 3. Therefore, compared to conventional products, which generally have a wall thickness of approximately 5 mm or more, the noise suppression member 1 can be made thinner. Consequently, such a noise suppression member 1 can be installed on thin devices and in confined spaces where conventional products were difficult to install.

(2) Second Embodiment Next, a second embodiment will be described. Since the second embodiment is only a modification of the configuration illustrated in the first embodiment, the differences from the first embodiment will be described in detail, and the parts that are the same as the first embodiment will not be described in detail.

As shown in Figures 3A, 3B, and 3C, the noise suppression member 31 comprises a magnetic core 33, a collar 35, and a molded member 37. The molded member 37 has a through-hole 41 (see Figure 4C) that penetrates in the front-to-back direction. A conductor 39 (for example, the flat cable shown in Figure 3D) is passed through this through-hole 41, thereby positioning the conductor 39 to penetrate the inner circumference of the magnetic core 33.

The magnetic core 33, collar 35, and mold member 37 differ in their detailed shapes and dimensions from those of the first embodiment, but their constituent materials and functions are the same as those of the first embodiment. In particular, the magnetic core 33 has a thin-walled portion 33A with a thickness of 1.5 mm to 4.0 mm around its entire circumference, and this point is also the same as in the first embodiment.

As shown in Figures 4A, 4B, 4D, and 4E, the molded member 37 has a left positioning recess 51, a right positioning hole 52, a first lower positioning recess 53, a second lower positioning recess 54, a first rear positioning recess 55, and a second rear positioning recess 56 formed thereon. The left positioning recess 51, right positioning hole 52, first lower positioning recess 53, second lower positioning recess 54, first rear positioning recess 55, and second rear positioning recess 56 are the locations where a holding portion (not shown) that holds the magnetic core 33 in a predetermined position within the mold (not shown) during the molding of the molded member 37 using the mold (not shown) was in contact with the magnetic core 33.

The retaining portion that contacts the magnetic core 33 in the left positioning recess 51 and the right positioning hole 52 positions the magnetic core 33 in the left-right direction. The retaining portion that contacts the magnetic core 33 in the first rear positioning recess 55 and the second rear positioning recess 56 positions the magnetic core 33 in the front-rear direction. In this embodiment, the flow path of the resin material within the mold is configured to proceed from the front to the rear of the magnetic core 33. Therefore, the magnetic core 33 is pushed backward by the resin material, and when the retaining portion contacts the magnetic core 33 in the first rear positioning recess 55 and the second rear positioning recess 56, the front-rear position of the magnetic core 33 can be positioned.

The retaining portions that contact the magnetic core 33 in the first lower positioning recess 53 and the second lower positioning recess 54 work in cooperation with retaining pins (not shown) that contact the upper surface of the magnetic core 33 to position the magnetic core 33 in the vertical direction. The retaining pins that contact the upper surface of the magnetic core 33 are configured to move up and down within the mold at the locations indicated by dashed lines in Figures 3A, 3B, and 4A. Therefore, when the retaining pins contact the thin-walled portion 3A, they contact a surface on the outer circumference of the thin-walled portion 3A that is perpendicular to the thickness direction of the thin-walled portion 3A. When molding the molded member 37, before injecting the resin material into the mold, the retaining pins are moved downward to contact the magnetic core 33 placed inside the mold. As a result, the magnetic core 33 is held within the mold in a vertically positioned state.

By adopting this configuration, the molded member 37 can be formed using the same process as in the first embodiment. Furthermore, by retracting the retaining pin at the same timing as in the first embodiment, crack formation can be suppressed even with a magnetic core 33 having an extremely thin wall thickness of 0.15 mm to 0.4 mm in the thin-walled portion 33A. Therefore, the noise suppression effect of the noise suppression member 31 can be fully demonstrated. Moreover, suppressing the occurrence of cracks as described above reduces the production of defective products, thereby improving the productivity of the noise suppression member 31.

The noise suppression member 31, configured as described above, has a thin-walled portion 33A with a wall thickness of 1.5 mm to 4.0 mm, corresponding to the distance between the inner and outer circumferences of the magnetic core 33. Therefore, compared to conventional products, which generally have a wall thickness of approximately 5 mm or more, the noise suppression member 31 can be made thinner. Consequently, such a noise suppression member 31 can be installed on thin devices or in confined spaces where conventional products were difficult to install.

(3) Other Embodiments Although exemplary embodiments of the method for manufacturing noise suppression members have been described above, the embodiments described above are merely illustrative examples of the present disclosure. That is, the present disclosure is not limited to the exemplary embodiments described above, and can be implemented in various forms without departing from the technical idea of the present disclosure.

For example, in the above embodiment, specific shapes and materials for the magnetic core, conductor, and molded member were given as examples, but the shapes and materials of the magnetic core, conductor, and molded member are not limited to the examples given above.

Furthermore, while specific times for the injection and holding pressure processes were given as examples in the above embodiment, these times can be arbitrarily adjusted considering the shape and dimensions of the molded component, the performance of the injection molding machine, etc.

Furthermore, multiple functions realized by one component as exemplified in the above embodiment may be realized by multiple components. One function realized by one component as exemplified in the above embodiment may be realized by multiple components. Multiple functions realized by multiple components as exemplified in the above embodiment may be realized by one component. One function realized by multiple components as exemplified in the above embodiment may be realized by one component. Some of the configurations exemplified in the above embodiment may be omitted. At least a part of the configuration exemplified in one of the above embodiments may be added to or replaced with the configurations exemplified in the other embodiments.

1, 31…Noise suppression member; 3, 33…Magnetic core; 3A, 33A…Thin-walled section; 5, 35…Collar; 7, 37…Molded member; 9, 39…Conductor; 13…Protrusion; 21, 51…Left positioning recess; 22…Right positioning recess; 22, 52…Right positioning hole; 23, 53…First lower positioning recess; 24, 54…Second lower positioning recess; 25…Third lower positioning recess; 26…Fourth lower positioning recess; 27, 55…First rear positioning recess; 28, 56…Second rear positioning recess; 41…Through hole.

Claims (4)

A method for manufacturing a noise suppression member,
The noise suppression member is
A magnetic core is made of a sintered magnetic material and has a shape that allows a conductor to be placed at a position that penetrates the inner circumference,
A mold member formed from a resin material and configured to mold the magnetic core,
Equipped with,
The magnetic core has a thin-walled portion with a wall thickness of 1.5 mm to 4.0 mm, corresponding to the distance between the inner and outer circumferences.
The molded member is a one-piece molded product in which a portion that molds the inner circumference of the thin-walled portion and a portion that molds the outer circumference of the thin-walled portion are integrally molded from the resin material.
When forming the aforementioned mold member,
Before injecting the resin material into the mold, the retaining pin is brought into contact with the magnetic core placed inside the mold to hold the magnetic core inside the mold.
When injecting the resin material into the mold, the retaining pins that are in contact with the thin-walled portion are retracted to a position away from the thin-walled portion during a period in which the filling volume ratio E = (1 - (D - C) / D) × 100, which can be calculated based on the filling volume C, which is the volume of the resin material filled in the mold, and the volume D of the mold member, satisfies 60 ≤ E ≤ 90.
A method for manufacturing noise suppression components. A method for manufacturing a noise suppression member according to claim 1,
When injecting the resin material into the mold, the retaining pins that are in contact with the thin-walled portion are retracted to a position away from the thin-walled portion during a period in which the filling volume ratio E satisfies 60 ≤ E ≤ 80.
A method for manufacturing noise suppression components. A method for manufacturing a noise suppression member according to claim 1 or claim 2,
Based on the area A of the cross-sectional area perpendicular to the axial direction of the screw of the injection molding machine, the injection speed B corresponding to the axial movement speed of the screw, and the injection time t corresponding to the axial movement time of the screw, the filling volume C = A × B × t is calculated.
A method for manufacturing noise suppression components. A method for manufacturing a noise suppression member according to claim 1 or claim 2,
The retaining pin is configured to contact a surface on the outer circumference of the thin-walled portion that is perpendicular to the thickness direction of the thin-walled portion when it contacts the thin-walled portion.
A method for manufacturing noise suppression components.