Electrical equipment

Abstract

To prevent occurrence of cracks in an electric device.SOLUTION: An electric device includes: a case in which an electric circuit is stored; a cover which closes an opening surface of the case; a nut holder which holds a nut part with which a bolt for fixing the case to an external attachment object threadedly engages; and a fitting groove which is provided between an outer wall and an inner wall of the case and in which the nut holder is fitted.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrical device.

Background Art

[0002] Conventionally, electrical devices such as cameras are known. Patent Documents 1 and 2 disclose a fixing structure of a nut to which a bolt for fixing an electrical device is screwed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] A nut is fixed to an electrical device, and the electrical device is fixed to an attachment target by screwing a bolt into the nut. It is assumed that unnecessary external forces act on the thus-fixed electrical device due to natural wind or impact applied to the attachment target. If an external force acts on the bolt fixing the electrical device, there is a risk of cracking in the electrical device.

[0005] One aspect of the disclosed technology aims to prevent cracking in an electrical device.

Means for Solving the Problems

[0006] One aspect of the disclosed technology is exemplified by an electrical device as follows. A case for housing an electric circuit, A cover for closing the opening surface of the case, A nut holder that holds a nut portion into which a bolt for fixing the case to an external attachment target is screwed, A fitting groove is provided between the outer wall and the inner wall of the case, into which the nut holder is fitted, Electrical equipment equipped with the necessary features. [Effects of the Invention]

[0007] According to the disclosed technology, it is possible to prevent cracks from forming in electrical equipment. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is an exploded perspective view of an electrical device according to an embodiment. [Figure 2] Figure 2 is a magnified perspective view showing the area around the mating groove of the rear case. [Figure 3] Figure 3(A) is a perspective view showing the nut holder in an extruded state, and Figure 3(B) is a perspective view showing a magnified view of the area around the mating groove. [Figure 4] Figure 4 is a cross-sectional view of an electrical device when cut along the central axis of the nut. [Figure 5] Figure 5 shows the stress distribution in the cross-section of the rear case in this embodiment. [Figure 6] Figure 6 shows the stress distribution in the cross-section of the nut holder in this embodiment. [Figure 7] Figure 7 shows the stress distribution on the outer wall surface of the rear case in this embodiment. [Figure 8] Figure 8 shows the stress distribution in the cross-section of the rear case in the comparative example. [Figure 9] Figure 9 shows the stress distribution on the outer wall surface of the rear case in the comparative example. [Figure 10] Figure 10 is a perspective view of a modified nut holder for electrical equipment. [Figure 11] Figure 11 shows the stress distribution in the cross-section of the rear case in the modified example. [Figure 12] Figure 12 shows the stress distribution in the cross-section of the nut holder in a modified example. [Figure 13]FIG. 13 is a diagram showing the stress distribution on the outer wall surface of the rear case in the modified example.

Embodiments for Carrying Out the Invention

[0009] <Embodiment> The configurations of the embodiments shown below are examples, and the disclosed technology is not limited to the configurations of the embodiments.

[0010] The electric device according to the embodiment includes, for example, the following configurations. That is, the electric device includes a case for housing an electric circuit, a cover for closing the opening surface of the case, a nut holder for holding a nut portion into which a bolt for fixing the case to an external attachment target is screwed, and a fitting groove provided between the outer wall and the inner wall of the case and into which the nut holder is fitted.

[0011] According to the above electric device, it is possible to prevent cracks from occurring in the case. Further, the electric device can maintain the internal waterproofness by preventing cracks from occurring in the case. The electric device can be installed outdoors and can be applied to a camera or the like.

[0012] Hereinafter, the details of the above electric device will be described. FIG. 1 is an exploded perspective view of the electric device according to the embodiment. The electric device 1 according to the present embodiment is an AI (Artificial Intelligence) - equipped AI camera. The AI camera detects the outside world by analyzing still images and moving images acquired by a lens with AI. The AI camera can perform wireless communication corresponding to mobile communication standards such as 4G (4th Generation) and 5G (5th Generation). Note that the electric device 1 is not limited to an AI camera. The electric device 1 may be a network camera without AI or other electronic devices.

[0013] As shown in Figure 1, the electrical device 1 comprises a rear case 2 (an example of a "case" in this disclosure) and a front case 3 (an example of a "cover" in this disclosure). The rear case 2 is a shallow, substantially rectangular box shape, with an outer wall 2A and an inner wall 2B on its side. The rear case 2 is made of, for example, resin. Examples of materials for forming the rear case 2 include polycarbonate (PC) and ABS resin. The rear case 2 houses an electrical circuit 4 inside the inner wall 2B. The electrical circuit 4 is a circuit that includes electronic components necessary for an AI camera, such as an image sensor and integrated circuits.

[0014] The front case 3 is attached to the rear case 2, thereby closing the opening of the rear case 2. The front case 3 is made of, for example, resin. Examples of materials for forming the front case 3 include polycarbonate (PC) and ABS resin. The front case 3 is attached to the front case 3 by screws 11 and screws not shown. The screws 11 are screwed into screw holes (screw holes 13 shown in Figures 2 and 3(B) described later) formed in the rear case 2 through through holes 12 formed in the front case 3. In addition, heat dissipation fins 10 made of metal such as aluminum are arranged on the top surface of the front case 3. The electrical equipment 1 houses the electrical circuit 4 in a sealed state inside by attaching the rear case 2 to the front case 3. The electrical equipment 1 can be installed outdoors because it can protect the electrical circuit 4 by preventing outside air containing water and moisture from entering the interior.

[0015] Furthermore, the electrical device 1 includes a nut holder 6 with a nut portion 6A into which a bolt (not shown) for fixing the rear case 2 to an external mounting object is screwed, and a nut holder 6 that can be fitted into It is equipped with a fitting groove 5. The mounting targets for the electrical equipment 1 are, for example, camera tripods installed outdoors, columns, building ceilings, etc.

[0016] Here, the mating groove 5 and nut holder 6 will be explained in more detail using Figures 2 and 3, with reference to Figure 1. Figure 2 is a perspective view showing an enlarged view of the area around the mating groove 5 of the rear case 2. Figure 3(A) is a perspective view showing the nut holder 6 extracted, and Figure 3(B) is a perspective view showing an enlarged view of the area around the mating groove 5 when the nut holder 6 has been removed from the mating groove 5.

[0017] The mating groove 5 is formed in the center of the long side of the rear case 2. In the center of the long side, the inner wall 2B is shifted inward, forming a rectangular gap between the outer wall 2A and the inner wall 2B. This gap is the mating groove 5. The nut holder 6 can be mated into the mating groove 5 provided between the outer wall 2A and the inner wall 2B. The nut holder 6 is fixed to the rear case 2 by being mated into the mating groove 5. The nut holder 6 is made of resin and has a vertically elongated, thin rectangular parallelepiped shape overall. The dimensions of the nut holder 6 are a height of 18 mm, a width of 16 mm, and a thickness of 5.5 mm. The nut holder 6 is integrally formed with a metal nut portion 6A by insert molding and holds the nut portion 6A. The nut portion 6A is located on the lower center side of the nut holder 6, and a bolt for fixing the electrical equipment 1 to the mounting object is screwed into it.

[0018] As shown in Figures 2 and 3(B), the outer wall 2A of the rear case 2 is provided with a circular through-hole 2C at the position where the mating groove 5 is formed. The through-hole 2C is formed in a position that overlaps with the nut portion 6A when the nut holder 6 is fitted into the mating groove 5. In the electrical device 1, the bolt is screwed into the nut portion 6A through the through-hole 2C.

[0019] Furthermore, as shown in Figure 3(B), multiple rail sections 5A extending in the vertical direction are formed on the side surface within the mating groove 5. The downward direction in this vertical direction coincides with the direction in which the nut holder 6 is fitted into the mating groove 5. The rail sections 5A guide the nut holder 6 downward when it is fitted into the mating groove 5, and after the nut holder 6 is mated into the mating groove 5, they prevent the nut holder 6 from rattling within the mating groove 5.

[0020] Furthermore, a rectangular parallelepiped projection 5B is formed on the bottom surface of the mating groove 5, protruding upward. An insertion hole (not shown) is formed on the bottom surface of the nut holder 6 into which the projection 5B is inserted when mating with the mating groove 5, and the projection 5B is fitted into this insertion hole. The projection 5B prevents the nut holder 6 from rattling within the mating groove 5.

[0021] Furthermore, as shown in Figures 1 to 3(B), the electrical device 1 is equipped with a water-sealing section 7 positioned on the edge of the inner wall 2B facing the front case 3. The water-sealing section 7 is, for example, a water-sealing tape with adhesive surfaces formed on both sides. The water-sealing section 7 is positioned continuously around the edge of the inner wall 2B of the rear case 2, fixing the front case 3 to the rear case 2 while sealing the gap between the rear case 2 and the front case 3 to prevent moisture from entering the inside of the inner wall 2B. As shown in Figures 2 and 3(B), the water-sealing section 7 is also positioned inside the mating groove 5.

[0022] Furthermore, as shown in Figure 3(A), the nut holder 6 has a sheet-like elastic body 6B positioned on one end face (upper end face) of the front case 3. The front case 3 is fixed to the rear case 2 by a screw 11 (see Figure 1) that is screwed into a screw hole 13 provided near the mating groove 5 of the rear case 2, while applying pressure to the elastic body 6B. The elastic body 6B is formed of, for example, rubber or gel.

[0023] Next, using Figure 4, we will examine the forces acting on the rear case 2 and nut holder 6 of the electrical equipment 1. Let me explain. Figure 4 is a cross-sectional view of the electrical device 1 when cut along the central axis of the nut portion 6A. In Figure 4, the forces acting on the rear case 2 and the nut holder 6 are represented by white arrows. Assume that a force F1 (tensile force) acts in the direction of the central axis of the nut portion 6A, loosening the bolt screwed into the nut portion 6A. Forces F2 and F4 act on the nut holder 6 in the direction of the outer wall 2A, and forces F3 as a reaction to force F2 and force F5 as a reaction to force F4 act on the outer wall 2A in the direction of the nut holder 6. Force F1 is an example of an external force acting on the electrical device 1. Also in Figure 4, force F6 is the pressure that the front case 3 applies to the elastic body 6B, and force F7 is the reaction to force F6.

[0024] In this embodiment, a simulation was performed assuming that a force F1 acts on the electrical device 1, and the stress distribution acting on the rear case 2 and nut holder 6 was calculated. In this simulation, the force F1 was set to 1000 N. It can be said that the smaller the stress acting on the outer wall 2A, the lower the possibility of cracks occurring in the outer wall 2A.

[0025] Figures 5 to 7 show the stress distribution when a simulation was performed on the electrical equipment 1 according to this embodiment. The legend shown in Figures 5 to 7 indicates the stress value, and the unit is MPa. In this embodiment, the rear case 2, front case 3, and nut holder 6 are made of resin. In the simulation of this embodiment, the rear case 2, front case 3, and nut holder 6 are made of polycarbonate, with a Young's modulus of 2300 MPa, a Poisson's ratio of 0.33, and a density of 1.19 g / cm³. 3 The nut portion 6A is made of stainless steel (SUS304), with a Young's modulus of 197 GPa, a Poisson's ratio of 0.3, and a density of 7.93 g / cm³. 3 )

[0026] Figure 5 shows the stress distribution in the cross-section of the rear case 2. When a tensile force F1 acts in the direction of loosening the bolt, the nut holder 6 abuts against the rear case 2, and a force F4, as shown in Figure 4, acts on the rear case 2. As a result, as shown in Figure 5, a maximum stress of 32.8 MPa acts on the bottom side surface of the mating groove 5 of the rear case 2. Figure 6 shows the stress distribution in the cross-section of the nut holder 6. In the nut holder 6, the maximum stress (force F4 shown in Figure 4) acts on the lower side of the outer wall 2A, and the stress value is 30.8 MPa. Figure 7 shows the stress distribution on the surface of the outer wall 2A of the rear case 2. On the surface of the outer wall 2A, the maximum stress acts on the lower side of the through hole 2C, and the stress value is 31.1 MPa. As shown in Figures 6 and 7, the maximum stress value acting on the nut holder 6 (30.8 MPa) is smaller than the maximum stress value acting on the surface of the rear case 2 (31.1 MPa).

[0027] In this embodiment, even if a tensile force F1 acts on a bolt, the electrical device 1 distributes the stress from force F1 to forces F2-F5, thus preventing the stress from concentrating on the outer wall 2A.

[0028] Next, a similar simulation was performed on the electrical equipment related to the comparative example, and the stress distribution was calculated. Figures 8 and 9 show the stress distribution when the simulation was performed on the electrical equipment related to the comparative example. The legend shown in Figures 8 and 9 indicates the stress value, and the unit is MPa. The electrical equipment related to the comparative example does not have a mating groove 5 and a nut holder 6, and a metal nut part 60A is press-fitted into a through hole formed in the outer wall 2A. The electrical equipment related to the comparative example has the same configuration as the electrical equipment 1 according to this embodiment, except that the mating groove 5, nut holder 6, and elastic body 6B are not provided. In addition, in the simulation of the comparative example, the forming material, Young's modulus, Poisson's ratio, and density of the rear case 2 and front case 3 were set in the same way as in the simulation of the above embodiment. Also, the forming material, Young's modulus, Poisson's ratio, and density of the nut part 60A were set in the same way as the nut part 6A of the above embodiment.

[0029] Figure 8 shows the stress distribution in the cross-section of the rear case 2. Comparing Figure 5 and Figure 8, this The electrical equipment 1 according to this embodiment experiences less stress on the rear case 2 than the electrical equipment according to the comparative example. In the electrical equipment according to the comparative example, the maximum stress value acting on the rear case 2 is 38.8 MPa. Figure 9 shows the stress distribution on the surface of the outer wall 2A of the rear case 2. On the surface of the outer wall 2A, the maximum stress acts around the through hole 2C, and the stress value is 38.8 MPa. Comparing Figure 7 and Figure 9, the electrical equipment 1 according to this embodiment experiences less stress on the surface of the outer wall 2A than the electrical equipment according to the comparative example, and the area over which the maximum stress acts is also smaller.

[0030] In the comparative example of electrical equipment, when a relatively large tensile force is applied to the bolt screwed into the nut portion 60A, there is a high probability that a crack will occur at the boundary between the outer wall 2A and the nut portion 60A. Furthermore, as the crack expands, the fixing strength of the nut portion 60A decreases, and eventually the nut portion 60A is pulled out of the rear case 2, leading to the destruction of the electrical equipment. In addition, the waterproofing of the electrical equipment is also compromised due to the expansion of the crack in the rear case 2. Moreover, the aesthetic appearance of the electrical equipment is also compromised by the crack that has appeared on its exterior. Thus, as in the comparative example, when the nut portion 60A is press-fitted into the rear case 2, the stress acting on the rear case 2 and changes over time cause cracks to occur in the outer wall 2A, which reduces the fixing strength by the nut and compromises the waterproofing.

[0031] In this embodiment, the electrical equipment 1 experiences less stress under tensile force than the comparative example, thus preventing cracks from forming in the outer wall 2A. The electrical equipment 1 reduces the stress generated in the nut holder 6 that holds the nut portion 6A by distributing it to forces F2 and F4, thereby reducing the stress acting on the outer wall 2A and preventing cracks from forming in the outer wall 2A. Furthermore, even if a crack were to form at the boundary between the nut holder 6 and the nut portion 6A, the crack would not be visible from the outside of the rear case 2, thus preserving the aesthetic appearance of the electrical equipment 1. Moreover, since the mating groove 5 is installed outside the watertight section 7, even if a crack forms in the nut holder 6, the watertightness to the inside of the inner wall 2B of the electrical equipment 1 is maintained by the watertight section 7. Therefore, the electrical equipment 1 can protect the electrical circuit 4 from water and moisture-laden outside air.

[0032] The electrical device 1 according to this embodiment reduces the stress acting on the outer wall 2A by distributing the stress when a tensile force F1 is applied, thereby preventing cracks from forming in the outer wall 2A. As a result, the electrical device 1 can improve the fracture resistance of the nut portion 6A and the waterproofing to the inside of the inner wall 2B while maintaining airtightness by the rear case 2. The electrical device 1 according to this embodiment prevents crack formation that may occur from the nut portion 6A due to external forces acting on the bolt, thereby ensuring the fracture resistance and waterproofing of the nut holder 6 while also preventing damage to the aesthetics.

[0033] Incidentally, the tripod screw member disclosed in the aforementioned Patent Document 1 ensures strength by fitting a cylindrical hub with a tripod screw as its axis into a hole provided in the bottom plate of the cabinet and fixing the hub to the cabinet with a screw. However, because the cylindrical hub and the screw are arranged coaxially, the load on the hub is concentrated in one place. For this reason, the tripod screw member disclosed in Patent Document 1 cannot distribute stress against external forces. Furthermore, in the clip disclosed in the aforementioned Patent Document 2, a clip equipped with a nut housing is passed through a fixing hole in the panel, and a bolt is screwed into the nut. In Patent Document 2, the panel is sandwiched between the bolt and the nut when the bolt is fastened, and this clip does not have a structure that reduces the load on the nut housing. In contrast, the electrical equipment 1 according to this embodiment can distribute the load on the nut portion 6A, thus preventing cracks from forming in the outer wall 2A.

[0034] <Variation> Next, an electrical device 1 according to a modified example of this embodiment will be described. The electrical device 1 according to this modified example is characterized in that the nut holder 6 has a flange portion. Hereinafter, see Figure 10. The nut holder 6 in this modified example will be described using the provided diagram. Figure 10 is a perspective view of the nut holder 6. The nut holder 6 is provided on one end face of the front case 3 and has flange portions 6C protruding on both sides. The direction of extension of the flange portions 6C is the same as the direction of the long side of the rear case 2 shown in Figure 1. A through hole 6D is formed in the flange portion 6C. The through hole 6D is formed to overlap with the through hole 12 (see Figure 1) and the screw hole 13 (see Figure 3(B)) when the nut holder 6 is fitted into the mating groove 5. The screw 11 (see Figure 1) is screwed into the screw hole 13 via the through holes 12 and 6D. The electrical equipment 1 according to this modified example includes a screw 11 that fixes the front case 3 to the rear case 2 and also fixes the flange portion 6C to the rear case 2. As a result, the electrical device 1 according to this modified example can prevent rattling when the nut holder 6 is fitted into the mating groove 5. The dimensions of the nut holder 6 in this modified example are the same as those of the nut holder 6 in the above embodiment, except for the flange portion 6C. Furthermore, the nut holder 6 in this modified example does not have an elastic body 6B.

[0035] Next, in this modified example, a simulation is performed assuming that a force F1 acts on the electrical device 1, and the stress distribution acting on the rear case 2 and nut holder 6 is calculated. In this simulation as well, the force F1 was set to 1000 N. Figures 11 to 13 show the stress distribution when the electrical device 1 according to this modified example was simulated. The legend shown in Figures 11 to 13 indicates the stress value, and the unit is MPa. The forming material, Young's modulus, Poisson's ratio, and density of the rear case 2, front case 3, nut holder 6, and nut portion 6A were set in the same way as in the above embodiment.

[0036] Figure 11 shows the stress distribution in the cross-section of the rear case 2. When a tensile force F1 acts in the direction of loosening the bolt, the nut holder 6 rotates with the through hole 6D as the pivot point, and the nut holder 6 abuts against the bottom side surface of the mating groove 5, causing the force F4 shown in Figure 4 to act on the rear case 2. The rear case 2 experiences a maximum stress of 30.4 MPa at the bottom side surface of the mating groove 5. Figure 12 shows the stress distribution in the cross-section of the nut holder 6. In the nut holder 6, the maximum stress (force F4 shown in Figure 4) acts on the lower side of the outer wall 2A, and its stress value is 28.4 MPa. Figure 13 shows the stress distribution on the surface of the outer wall 2A of the rear case 2. On the surface of the outer wall 2A, the maximum stress acts on the lower side of the through hole 2C, and its stress value is 29.5 MPa. As shown in Figures 12 and 13, the maximum stress value acting on the nut holder 6 (28.4 MPa) is smaller than the maximum stress value acting on the surface of the rear case 2 (29.5 MPa).

[0037] In this modified example, even if a tensile force F1 acts on the bolt, the stress from force F1 is distributed to forces F2 to F5, thus preventing the stress from concentrating on the outer wall 2A.

[0038] Comparing Figure 13, which shows the stress distribution in this modified example, with Figure 9, which shows the stress distribution in the comparative example described above, the electrical equipment 1 in this modified example has less stress acting on the surface of the outer wall 2A than the electrical equipment in the comparative example, and the area over which the maximum stress acts is also smaller. Because the electrical equipment 1 in this modified example has less stress under tensile force than the comparative example, it can prevent cracks from forming in the outer wall 2A.

[0039] <Other variations> The above embodiments and modifications can be combined in various ways. Furthermore, while the rear case 2, front case 3, and nut holder 6 are made of resin in the above embodiments, the present invention is not limited to this. For example, the rear case 2, front case 3, and nut holder 6 may be made of metal such as aluminum, or the rear case 2 and front case 3 may be made of resin and the nut holder 6 may be made of stainless steel (SUS304) similar to the nut portion 6A. This is also possible. The stainless steel nut holder 6 may be integrally formed with the nut portion 6A. Furthermore, by unifying the forming materials of the rear case 2, front case 3, and nut holder 6, the coefficient of linear expansion of each of these components can be made the same, and the rate at which each component expands in the event of a temperature change at the installation location of the electrical equipment 1 can be made uniform. [Explanation of symbols]

[0040] 1. Electrical equipment 2. Rear Case 2A...Outer wall 2B·Inner wall 2C...Through hole 3. Front Case 4. Electrical circuits 5...Mating groove 5A Rail section 5B·Protrusion 6. Nut holder 6A, 60A... Nut section 6B · Elastic body 6C Flange section 6D·Through hole 7. Water-stopping section 10 Fins 11. Screw 12. Through hole 13. Screw holes

Claims

1. A case for housing electrical circuits, A cover that closes the opening surface of the aforementioned case, A nut holder that holds a nut portion into which a bolt for fixing the case to an external mounting object is screwed, A fitting groove is provided between the outer wall and the inner wall of the case, into which the nut holder is fitted, Equipped with, The case, the cover, and the nut holder are made of resin. The nut holder has an elastic body positioned on one end face of the cover side, The cover is fixed to the case by screws while applying pressure to the elastic body. Electrical equipment.

2. It includes a water-stopping portion positioned at the edge of the inner wall facing the cover, The electrical equipment according to claim 1.

3. The nut holder is provided on one end face of the cover and has flange portions protruding on both sides. The cover is fixed to the case and the flange portion is fixed to the case with screws. The electrical equipment according to claim 1 or 2.

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