Enclosures and Electrical Equipment

Abstract

To provide an enclosure and an electric device capable of suppressing noise generated from the enclosure itself.SOLUTION: A housing 50 for holding an electric circuit portion that performs pulse width modulation control inside includes a body portion 201 and a plurality of convex portions 202. A plurality of convex portions 202 are formed on the surface of the body portion 201. Intervals P1 and P2 between a pair of adjacent convex portions 202 in the plurality of convex portions 202 are less than 0.5 times the wavelength λ1 of the sound wave having the same frequency as the carrier frequency in pulse width modulation control.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a housing and an electrical device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known an electric device in which a board on which electronic components are mounted is disposed inside a housing (see, for example, Japanese Patent Application Laid-Open No. 2005-304162). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-304162 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned electrical equipment, sound-absorbing materials made of foamed resin are arranged on the inner surface of the housing to prevent the operating noise of the internal electronic components from leaking to the outside. However, the above-mentioned electrical equipment has a problem in that vibrations from the electronic components are transmitted to the housing, and as a result, the noise generated by the housing itself cannot be sufficiently suppressed.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a housing and an electrical device that are capable of suppressing noise generated from the housing itself. [Means for solving the problem]

[0006] The housing according to the present disclosure is a housing for holding an electric circuit section that performs pulse width modulation control therein, and includes a main body and a plurality of protrusions. The plurality of protrusions are formed on a surface of the main body. The interval between adjacent pairs of protrusions in the plurality of protrusions is less than 0.5 times the wavelength of a sound wave having the same frequency as the carrier frequency in the pulse width modulation control.

[0007] The electrical device according to the present disclosure includes the above-mentioned housing and an electrical circuit section. The electrical circuit section is disposed inside the housing and performs pulse width modulation control.

[0008] The housing according to the present disclosure is a housing that holds an electric circuit section that performs pulse width modulation control therein, and includes a main body section and a plurality of protrusions. The plurality of protrusions are formed on a surface of the main body section. The interval between adjacent pairs of protrusions in the plurality of protrusions is less than 0.5 times the wavelength of a sound wave having a frequency of 10 kHz. Effect of the Invention

[0009] Based on the above, it is possible to obtain a housing and an electric device capable of suppressing noise generated from the housing itself. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic perspective view of an electrical device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. [Diagram 3] 2 is a schematic perspective view of a housing that constitutes the electrical device shown in FIG. 1. [Figure 4] 4 is a schematic perspective view showing the rear side of the housing shown in FIG. 3. FIG. [Diagram 5] 2 is a schematic diagram for explaining the configuration of a housing that constitutes the electrical device shown in FIG. 1. [Figure 6] 2 is a schematic diagram for explaining a vibrating body of a housing constituting the electric device shown in FIG. 1. FIG. [Figure 7] 2 is a schematic diagram for explaining a vibrating body of a housing constituting the electric device shown in FIG. 1. FIG. [Figure 8] 2 is a schematic cross-sectional view illustrating the configuration of a protrusion in a housing that constitutes the electrical device shown in FIG. 1. [Figure 9] 2 is a schematic cross-sectional view illustrating the configuration of a protrusion in a housing that constitutes the electrical device shown in FIG. 1. [Figure 10] 2 is a schematic diagram for explaining a vibrating body of a housing constituting the electric device shown in FIG. 1. FIG. [Figure 11] 2 is a schematic perspective view illustrating the configuration of a protrusion of a housing that constitutes the electrical device shown in FIG. 1. FIG. [Figure 12] 1. FIG. 4 is a schematic perspective view illustrating a modified example of a protrusion of a housing constituting the electrical device shown in FIG. [Figure 13] 1. FIG. 4 is a schematic perspective view illustrating a modified example of a protrusion of a housing constituting the electrical device shown in FIG. [Figure 14] 1. FIG. 4 is a schematic perspective view illustrating a modified example of a protrusion of a housing constituting the electrical device shown in FIG. [Figure 15] FIG. 11 is a schematic perspective view of an electrical device according to a second embodiment. [Figure 16] 16 is a schematic diagram for explaining the configuration of a housing of the electrical device shown in FIG. 15. FIG. [Figure 17] 16 is a schematic diagram for explaining the configuration of a housing of the electrical device shown in FIG. 15. FIG. [Figure 18] FIG. 11 is a schematic perspective view of an electric device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the details of the embodiments of the present disclosure will be described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description thereof will not be repeated.

[0012] Embodiment 1 <Configuration of electrical equipment and case> FIG. 1 is a schematic perspective view of an electric device according to a first embodiment. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a schematic perspective view of a housing constituting the electric device shown in FIG. 1. FIG. 4 is a schematic perspective view showing the rear side of the housing shown in FIG. 3. FIG. 5 is a schematic view for explaining the configuration of a housing constituting the electric device shown in FIG. 1. FIGS. 6, 7, and 10 are schematic views for explaining a vibrating body of a housing constituting the electric device shown in FIG. 1. FIGS. 8 and 9 are schematic cross-sectional views for explaining the configuration of a convex portion in a housing constituting the electric device shown in FIG. 1. FIG. 11 is a schematic perspective view for explaining the configuration of a convex portion of a housing constituting the electric device shown in FIG. 1.

[0013] As shown in FIG. 1 to FIG. 5, the electric device 1 includes a housing 50 and an electric circuit section 60. The housing 50 includes an upper case cover 2 and a lower case cover 3. The upper case cover 2 has a box shape. The lower case cover 3 has a flat plate shape. The upper case cover 2 has a flange section 4 formed so as to surround an opening. A plurality of bolt holes 5 are formed in the flange section 4. Bolt holes (not shown) are also formed in the outer periphery of the lower case cover 3. The upper case cover 2 and the lower case cover 3 are arranged so as to overlap each other such that the bolt holes 5 in the flange section 4 of the upper case cover 2 and the bolt holes in the outer periphery of the lower case cover 3 overlap each other. The upper case cover 2 and the lower case cover 3 are fixed to each other by fastening the bolts through the bolt holes. The position of the lower case cover 3 relative to the upper case cover 2 is precisely determined, for example, by passing a knock pin through a positioning hole 6 formed in the flange section 4. A recess for inserting the knock pin is formed in the outer periphery of the lower case cover 3 at a position overlapping with the positioning hole 6.

[0014] The upper case cover 2 has a main body 201 and a plurality of protruding portions 202. The plurality of protruding portions 202 are formed on a surface 13 of the main body 201. The plurality of protruding portions 202 are provided to reduce radiation sound from the housing 50. The intervals P1, P2 between a pair of adjacent protruding portions 202 in the plurality of protruding portions 202 are less than 0.5 times the wavelength of a sound wave having the same frequency as the carrier frequency in the pulse width modulation control. The upper case cover 2 constituting the housing 50 will be described in detail later.

[0015] As shown in FIG. 2, an electric circuit section 60 is housed inside the housing 50. The electric circuit section 60 performs pulse width modulation control. The electric circuit section 60 mainly includes an inverter 8, a converter 9, a water jacket 10, and a capacitor 11 which is a smoothing capacitor. Inside the housing 50, the electric circuit section 60 has the converter 9, the water jacket 10, the inverter 8, and the capacitor 11 stacked in this order from the lower case cover 3 side. The inverter 8 controls, for example, an electric drive motor or a power generation motor. The converter 9 steps up or steps down the power supply voltage. The water jacket 10 cools the components that constitute the power module, such as the inverter 8 and the converter 9. The water jacket 10 includes a refrigerant flow path through which a cooling medium such as water flows. The water jacket 10 has, for example, a flat plate shape. The capacitor 11 smoothes the pulsating component of the voltage.

[0016] The inverter 8 and the converter 9 generate heat and therefore require heat dissipation. As shown in FIG. 2, the inverter 8 and the converter 9 are arranged to sandwich the water jacket 10 from above and below. The inverter 8 and the converter 9 are in contact with the water jacket 10. The water jacket 10 is fixed onto a boss 12 installed on the lower case cover 3. An inlet pipe is connected to the refrigerant flow path of the water jacket 10 from outside the housing 50. A cooling medium is circulated and supplied to the refrigerant flow path via the inlet pipe.

[0017] As shown in Figures 3 and 4, a plurality of protrusions 202 are formed on the surface 13 of the top surface of the upper case cover 2. The upper case cover 2 is manufactured by a die casting method. The plurality of protrusions 202 aligned and arranged on the surface 13 of the upper case cover 2 are integrally molded with the main body 201 of the upper case cover 2. The protrusions 202 have, for example, a quadrangular prism shape. Note that, although the protrusions 202 are provided on the surface 13 on the outer periphery of the upper case cover 2 in this embodiment, the same effect can be obtained by providing the protrusions 202 on the inner periphery 14, which is the back surface.

[0018] Here, the carrier frequency, which is the main frequency component of the electromagnetic noise of the inverter 8, is f1. The wavelength λ1 of the sound (radiated sound) radiated from the housing 50 excited by the electromagnetic noise of the carrier frequency f1 is expressed as λ1=v1 / f1 using the sound speed v1 in air as a medium. In this case, the distance between adjacent protrusions 202 in the longitudinal direction is P1, and the distance between adjacent protrusions 202 in the lateral direction is P2. In the housing 50 according to this embodiment, the multiple protrusions 202 are arranged so that the distance P1 and the distance P2 are shorter than 0.5 times the wavelength λ1 of the radiated sound (P1, P2<0.5×λ1). Note that the above-mentioned distances P1 and P2 refer to the distance between the centers of adjacent protrusions 202 in a plan view (when viewed from a direction perpendicular to the surface 13).

[0019] The shorter the interval between the multiple protrusions 202, the higher the spatial resolution with which the mass distribution of the housing 50 (upper case cover 2) can be changed. As a result, the degree of freedom in designing the vibration shape of the housing 50 is improved. In the housing 50, if the protrusions 202 are arranged at intervals shorter than at least 1 / 2 the wavelength λ1 of the radiated sound, the housing 50 can be designed so that the wavelength of the bending wave on the top surface (surface 13) of the upper case cover 2 is shorter than the wavelength of the radiated sound, with the height (protruding height from the surface 13) of each protrusion 202 as a control factor. In this embodiment, the interval P1 between the protrusions 202 adjacent to each other in the longitudinal direction (X-axis direction in FIG. 5) of the surface 13 of the upper case cover 2 is equal to the interval P2 between the protrusions 202 adjacent to each other in the lateral direction (Y-axis direction in FIG. 5). That is, as shown in FIG. 5, all the protrusions 202 are arranged at equal intervals. The multiple protrusions 202 are arranged in a matrix on the surface 13 of the upper case cover 2. The intervals P1, P2 between a pair of adjacent protrusions 202 in the plurality of protrusions 202 may all be the same or may locally differ.

[0020] Here, a frequency range from several kHz to tens of kHz is often used as the carrier frequency. The carrier frequency varies depending on the specifications of the product in which the inverter is installed. Therefore, in order to be able to handle the wavelengths of all carrier frequency components, the intervals P1 and P2 of the convex parts 202 should be set for the maximum value f1max of the range of carrier frequencies to be considered. When the carrier frequency is maximum, the wavelength of the corresponding radiated sound is minimum. In other words, if the wavelength at this time is λ1min (=v1 / f1max), the convex parts 202 should be arranged so that the interval is shorter than 1 / 2 of λ1min (P<0.5×λ1min).

[0021] It is preferable to set the maximum value f1max of the carrier frequency to 10kHz, which is the upper limit frequency of the human audible range. However, in this case, the number of the protrusions 202 covering the entire surface 13 of the housing 50 increases as the interval between the protrusions 202 decreases. When the number of the protrusions 202 increases in this way, the mass of the housing 50 increases. Therefore, it is not desirable to set the intervals P1 and P2 between the multiple protrusions 202 to be shorter than the wavelength of the radiated sound corresponding to the 10kHz component. Therefore, in the electric circuit section 60 including the inverter 8 with a limited carrier frequency, the interval P is set based on the carrier frequency. Also, in the case of modulating the carrier frequency with a variable voltage variable frequency inverter (VVVF) such as that used in a railway motor, the interval P is set based on the maximum value of the variable range of the carrier frequency.

[0022] FIG. 6 shows the vibration shape of a flat plate as a main body 201 including a surface 13 when the heights of a plurality of convex portions 202 in a housing 50 are set to the same uniform height. In FIG. 6, a cross-sectional schematic diagram for explaining the vibration shape in a cross section of a line segment AA of the schematic plan view is shown below the schematic plan view showing a part of the surface 13. Also, in FIG. 6, a cross-sectional schematic diagram for explaining the vibration shape in a cross section of a line segment BB of the schematic plan view is shown to the left of the schematic plan view showing a part of the surface 13. In the schematic plan view of FIG. 6, the nodes of the vibration mode of the flat plate including the surface 13 are shown by solid thin lines. Also, for a small portion 15 surrounded by solid thin lines, the phase of the vibration displacement with respect to the neutral position C of the flat plate is shown by + and - symbols.

[0023] Here, the vibration mode means the form of vibration in a structure, i.e., the distribution of vibration amplitude. The cross section along line AA shows a longitudinal cross section of the plate including surface 13. The cross section along line BB shows a lateral cross section of the plate. The cross section along line AA shows the wavelength λ2X of the bending wave in the longitudinal direction of the plate. The cross section along line BB shows the wavelength λ2Y of the bending wave in the lateral direction of the plate. When both of the wavelengths λ2X and λ2Y are longer than the wavelength λ1 of the sound wave radiated from the plate, sound waves are radiated from almost the entire surface of surface 13 of the plate, and are recognized as noise.

[0024] FIG. 7 shows a case where the vibration shape of the flat plate as the main body 201 including the surface 13 is changed by changing the height of the multiple convex parts 202. FIG. 7 shows a schematic plan view of a part of the surface 13, a schematic cross-sectional view at the line AA cross section, and a schematic cross-sectional view at the line BB cross section, basically similar to FIG. 6 described above. When the wavelength λ2X of the bending wave in the longitudinal direction of the flat plate and the wavelength λ2Y of the bending wave in the lateral direction are shorter than the wavelength λ1 of the sound wave radiated from the flat plate, the medium pushed out by the vibration from the small part 15 surrounded by the solid thin line flows into the adjacent small part 16. At this time, the adjacent positive and negative breathing spheres cancel each other out, so the sound radiated from the surface 13 of the flat plate becomes smaller. That is, it is possible to reduce noise radiation from the housing 50 that houses the electric circuit part 60, particularly noise generated by the vibration of the housing 50 itself.

[0025] The vibration shape of the plate including the surface 13 can be obtained from an equation of motion consisting of the mass matrix, stiffness matrix, and external force of the plate. In other words, the vibration shape of the plate depends on the mass matrix, i.e., the distribution of mass in the plate. In this embodiment, the mass matrix of the plate can be changed by changing the height of each protrusion 202 or changing the arrangement of the protrusions 202. As a result, the vibration mode of the plate can be designed to have an arbitrary shape. As shown in FIG. 7, the height of the protrusions 202 is set so that the wavelength λ2X of the bending wave in the longitudinal direction of the plate and the wavelength λ2Y of the bending wave in the lateral direction of the plate are shorter than the wavelength λ1 of the sound wave emitted from the plate.

[0026] The height of the protrusion 202 can be set to different values ​​depending on the wavelength of the sound radiated from the flat plate constituting the housing 50. The change pattern of the height of the protrusion 202 also differs depending on the position of the protrusion 202 on the housing 50. In other words, the height of the protrusion 202 has different change patterns depending on the fluctuation period of the wavelength of the sound radiated from the flat plate and the position of the protrusion 202 on the housing 50.

[0027] Here, if the height h of the convex portion 202 is much smaller than the thickness t of the main body portion 201 of the housing 50, the contribution of the convex portion 202 to the mass matrix is ​​small. In this case, the vibration shape of the main body portion 201 does not change much whether the convex portion 202 is present or not. On the other hand, as shown in FIG. 8, if the height h of the convex portion 202 is approximately the same as the thickness t of the main body portion 201 or is equal to or greater than the thickness t, the contribution of the convex portion 202 to the mass matrix is ​​large. In this case, the vibration shape of the main body portion 201 changes greatly depending on the presence or absence of the convex portion 202. Therefore, it is preferable that the height h of each convex portion 202 is equal to or greater than the thickness t of the main body portion 201 of the housing 50. For example, it is considered that there is an upper limit to the mass and external dimensions of the housing 50 due to the required specifications of the electrical device 1. While satisfying such constraints, it is preferable to set the height of the convex portion 202 so that the wavelength λ2X and the wavelength λ2Y are shorter than the wavelength λ1 of the sound wave emitted from the housing 50 over as wide a range as possible of the surface 13 of the housing 50.

[0028] It is also possible to derive the shape of the housing 50 such that the wavelengths λ2X and λ2Y are shorter than the wavelength λ1 of the sound waves radiated from the housing 50, using the plate thickness distribution in the housing 50 as a design variable. In this case, there is an additional constraint that the housing 50 needs to have a shape that fits the arrangement of the components of the electric circuit unit 60 stored inside, while ensuring sufficient strength (plate thickness) to protect the electric circuit unit 60. For this reason, the above calculation becomes complicated and the calculation cost increases. Therefore, as shown in this embodiment, it is better to make the main body unit 201 have a certain thickness to some extent, while providing multiple protrusions 202 on the surface of the main body unit 201, so that the vibration shape of the housing 50 can be changed to a shape that is less likely to emit radiated sound while maintaining the original shape of the housing 50, which is advantageous in terms of calculation cost. In addition, by maintaining the shape of the main body unit 201 of the housing 50 without changing it from the conventional design, it is possible to change the shape or arrangement of the protrusions 202 provided on the housing 50 according to the carrier frequency in the electric circuit unit 60, while utilizing the conventional design of the housing 50 for other models. In this case, the design of the housing 50 can be simplified for electrical devices of various configurations, and noise countermeasures can be implemented.

[0029] 9, protrusions 202 of different heights may be arranged on the main body 201 of the housing 50. That is, a first protrusion 202a and a second protrusion 202b are formed on the main body 201 of the housing 50. The first protrusion 202a has a first height h1 from the surface 13. The second protrusion 202b has a second height h2 from the surface 13 that is different from the first height h1. In this way, by arranging protrusions 202 of different heights locally, it is possible to easily adjust the vibration shape in the housing 50.

[0030] FIG. 10 shows the vibration shape of the flat plate as the main body 201 including the surface 13 after optimizing the height of each of the convex parts 202. FIG. 10 shows a schematic plan view of a part of the surface 13, a schematic cross-sectional view at the line AA section, and a schematic cross-sectional view at the line BB section, basically similar to FIG. 6 described above. In FIG. 10, unlike the configuration shown in FIG. 7, the wavelength λ2X of the bending wave in the longitudinal direction of the flat plate is shorter than the wavelength λ1 of the sound wave radiated from the flat plate, and the wavelength λ2Y of the bending wave in the lateral direction of the flat plate is longer than the wavelength λ1 of the sound wave. In such a case, the breathing sphere of the small part 15 and the breathing sphere of the small part 18 adjacent in the lateral direction hardly cancel each other out. On the other hand, the breathing sphere of the small part 15 and the breathing sphere of the small part 17 adjacent in the longitudinal direction cancel each other out. Therefore, even with the configuration as shown in FIG. 10, the sound radiated from the housing 50 can be reduced.

[0031] Here, the shape of the housing 50 may become complicated due to the arrangement of parts such as the inverter 8 constituting the electric circuit unit 60 housed inside the housing 50. The vibration shape of such a housing 50 becomes asymmetric and distorted. Therefore, it may be difficult to change the vibration shape of the housing 50 as shown in FIG. 7 by only changing the height h of the multiple protrusions 202. In such a case, as shown in FIG. 10, the height h of the protrusions 202 may be changed so that the wavelength λ2X of the bending wave is shorter than the wavelength λ1 of the sound wave only in one direction of the flat plate constituting the housing 50. Alternatively, the height of the protrusions 202 may be changed so that the wavelength of the bending wave is shorter than the wavelength λ1 of the sound wave for a part of the flat plate constituting the housing 50. Even in this case, the effect of reducing the radiation sound from the housing 50 can be expected.

[0032] FIG. 11 shows an enlarged view of the convex portion 202 provided on the upper case cover 2 of the housing 50. In this embodiment, the shape of the convex portion 202 is a quadrangular prism as described above. By changing the height h of the convex portion 202, the mass of the convex portion 202 changes, and the mass distribution of the housing 50 in which the convex portion 202 is provided changes. In this embodiment, the upper case cover 2 of the housing 50 and the convex portion 202 are integrally molded using a die by a die casting method. For this reason, it is preferable in terms of manufacturing that the convex portion 202 has a draft angle θ1. By integrally molding the upper case cover 2 and the convex portion 202, the productivity can be improved and the housing 50 can be manufactured at low cost.

[0033] <Action and effect> The housing 50 is for holding therein an electric circuit section 60 that performs pulse width modulation control, and includes a main body section 201 and a plurality of protrusions 202. The plurality of protrusions 202 are formed on the surface of the main body section 201. The intervals P1, P2 between a pair of adjacent protrusions 202 in the plurality of protrusions 202 are less than 0.5 times the wavelength λ1 of a sound wave having the same frequency as the carrier frequency in pulse width modulation control.

[0034] Here, the vibration shape of the housing 50 can be obtained from an equation of motion consisting of the mass matrix, stiffness matrix and external force of the housing 50. That is, the vibration shape of the housing 50 depends on the distribution of mass in the housing 50. In the housing 50 configured as described above, the mass matrix in the housing 50 can be appropriately adjusted by adjusting the shape and / or material of the multiple protrusions 202. As described above, in the housing 50, by setting the intervals P1 and P2 between the multiple protrusions 202, it is possible to control the wavelength of the bending wave of the housing 50 to be shorter than the wavelength of the sound wave having the same frequency as the carrier frequency (radiated sound of the carrier frequency component). That is, the vibration shape of the housing 50 can be set so that the wavelength λ2 of the bending wave in the housing 50 is shorter than the wavelength λ1 of the sound wave (radiated sound of the carrier frequency component) due to the vibration applied from the electric circuit unit 60. As a result, when the housing 50 vibrates, sound cancellation occurs on the adjacent positive and negative vibration surfaces in the housing 50. Therefore, the efficiency of acoustic radiation from the housing 50 decreases, so that the sound radiated from the housing 50 due to vibration of the housing 50 itself can be reduced.

[0035] The electric device 1 including the housing 50 described above can be used in hybrid cars and electric cars, which are attracting attention as environmentally friendly vehicles. Hybrid cars and electric cars are equipped with a power unit, which is an example of the electric device 1, to control the drive of the motor. In general, a pulse width modulation method (PWM) is adopted for controlling motors used in automobiles, factory automation, railroad cars, etc. When a motor is controlled by an inverter using the pulse width modulation method, a carrier frequency component, which is a control frequency of the pulse width modulation method, is included in the output waveform from the electric device. A carrier frequency of several kHz to several tens of kHz is often used. In the electric device, electromagnetic noise caused by such carrier frequency components is likely to be a problem. Therefore, by applying the electric device 1 including the housing 50 configured as described above, the electromagnetic noise can be effectively suppressed.

[0036] In the housing 50, the intervals P1, P2 between the multiple protrusions 202 may be set to 0.5 or more times the wavelength of a sound wave having a frequency of 10 kHz.

[0037] Here, the upper limit frequency of the human audible range is about 10 kHz. Therefore, by setting the lower limit value of the intervals P1, P2 between the multiple protrusions 202 of the housing 50 to 0.5 times the wavelength of a sound wave with a frequency of 10 kHz, it is possible to suppress radiation of sounds in the human audible range (sounds with frequencies up to 10 kHz) from the housing 50. As a result, it is possible to suppress radiation of sounds that are substantially perceptible by humans from the housing 50, thereby obtaining a sufficient effect.

[0038] It is technically possible to set the intervals P1, P2 between the multiple protrusions 202 to 0.5 times the wavelength of a sound wave with a frequency exceeding 10 kHz (to make the intervals P1, P2 narrower), but narrowing the intervals P1, P2 would increase the number of multiple protrusions 202. In this case, the mass of the housing 50 would increase. Therefore, by setting a lower limit for the intervals P1, P2 between the multiple protrusions 202 as described above, it is possible to prevent the mass of the housing 50 from increasing excessively.

[0039] In the housing 50, the multiple protrusions 202 may include a first protrusion 202a and a second protrusion 202b. As shown in Fig. 9, the first protrusion 202a may have a first height h1 from the surface 13. The second protrusion 202b may have a second height h2 from the surface 13 that is different from the first height h1.

[0040] In this case, by forming a plurality of protrusions 202 having different heights, the degree of freedom in adjusting the mass matrix in the housing 50 can be increased.

[0041] As shown in FIG. 8, in the housing 50 , the height h from the surface 13 of at least one of the multiple protrusions 202 may be equal to or greater than the thickness t of the housing 50 .

[0042] In this case, it is possible to sufficiently increase the ratio of the mass of the multiple protrusions 202 to the mass of the main body 201 of the housing 50. Therefore, by adjusting the arrangement and size of the multiple protrusions 202, the mass matrix in the housing 50 can be easily adjusted.

[0043] In the above-described housing 50, the plurality of protrusions 202 may be integral with the main body 201. In this case, the housing 50 can be manufactured more easily than when the main body 201 and the plurality of protrusions 202 are separate bodies.

[0044] In the above-described housing 50, the intervals P1, P2 between a pair of adjacent protrusions 202 among the plurality of protrusions 202 may all be the same. In this case, it is possible to obtain a substantially uniform sound reduction effect over the entire housing 50.

[0045] The electric device 1 according to the present disclosure includes the above-mentioned housing 50 and an electric circuit section 60. The electric circuit section 60 is disposed inside the housing 50 and performs pulse width modulation control.

[0046] In this way, sound waves having the same frequency as the carrier frequency in the pulse width modulation control of the electric circuit section 60 can be prevented from being emitted from the housing 50 as noise.

[0047] In the above electric device 1, the electric circuit section 60 may include any one selected from the group consisting of an inverter 8, a converter 9, and a capacitor 11.

[0048] Here, the electric circuit section 60 including the above-mentioned inverter 8 and the like may be applied to, for example, the drive control of the motor of an electric vehicle or a hybrid vehicle. In such applications, noise caused by the carrier frequency is likely to be a problem. Therefore, the electric device 1 including the housing 50 according to this embodiment can suppress the noise, and is therefore particularly effective in the above-mentioned applications.

[0049] The housing 50 according to the present disclosure holds an electric circuit section 60 that performs pulse width modulation control therein, and includes a main body section 201 and a plurality of protruding sections 202. The plurality of protruding sections 202 are formed on the surface of the main body section 201. The intervals P1, P2 between a pair of adjacent protruding sections 202 in the plurality of protruding sections 202 are less than 0.5 times the wavelength of a sound wave having a frequency of 10 kHz.

[0050] In this way, radiation of the entire frequency band that humans can practically perceive from the housing 50 can be suppressed. Furthermore, radiation of sounds in a range that exceeds the upper limit frequency (10 kHz) of the human audible range from the housing 50 can also be suppressed.

[0051] <Modification> 12 to 14 are schematic perspective views for explaining modified examples of the convex portion 202 of the housing 50 constituting the electric device 1 shown in FIG. 1. As shown in FIG. 12 to FIG. 14, the shape of the convex portion 202 can be any shape. Specifically, as shown in FIG. 12, the shape of the convex portion 202 can be a cylinder. As shown in FIG. 13, the shape of the convex portion 202 can be a cone. As shown in FIG. 14, the shape of the convex portion 202 can be a hemisphere. The shape of the convex portion 202 can be any other shape, such as a cylinder, a pyramid, or a polygonal column. Even in this case, the same effect as the electric device 1 shown in FIG. 1 to FIG. 11 can be obtained.

[0052] Embodiment 2 <Configuration of electrical equipment and case> FIG. 15 is a perspective schematic diagram of the electric device 1 according to the second embodiment. FIG. 16 and FIG. 17 are schematic diagrams for explaining the configuration of the housing 50 of the electric device 1 shown in FIG. 15. The electric device 1 shown in FIG. 15 to FIG. 17 basically has the same configuration as the electric device 1 shown in FIG. 1 to FIG. 5, but the configuration of the housing 50 is different from that of the electric device 1 shown in FIG. 1 to FIG. 5. Specifically, in the housing 50 of the electric device 1 according to the present embodiment, a plurality of holes 20 for fixing the convex portion 202 are formed on the surface 13 (top surface) of the main body portion 201 of the upper case cover 2. That is, the main body portion 201 and the plurality of convex portions 202 are separate bodies in the upper case cover 2. The holes 20 are, for example, screw holes. The holes 20 may be bolt holes. The configuration of the holes 20 can be selected according to the specifications of the housing 50.

[0053] 17 , the convex portion 202 includes a protruding portion 21 that serves as an added mass, and an insertion portion 22. The insertion portion 22 is inserted into and fixed to the hole 20. The insertion portion 22 is, for example, a male screw. The insertion portion 22 is inserted into and fixed to the hole 20, whereby the convex portion 202 is attached to the main body portion 201.

[0054] 15 to 17, in the present embodiment, upper case cover 2 of housing 50 has convex portion 202, which is a separate part, fixed to main body portion 201. It is preferable to prepare a plurality of types of convex portion 202 having different sizes of protruding portion 21 (for example, height h of convex portion 202 shown in FIG. 8).

[0055] Here, consider a case where the main body 201 is a common part, and the configuration of the electric circuit unit 60 housed inside the housing 50 is changed to realize a plurality of types of products. In this case, it is necessary to change the mass distribution of the plurality of protruding parts 202 arranged on the main body 201 of the upper case cover 2 according to the carrier frequency of the inverter 8 of the electric circuit unit 60. In such a case, if the main body 201 and the protruding parts 202 are integrally molded as in the housing 50 of the electric device 1 according to the first embodiment, it is necessary to prepare a mold for the upper case cover 2 in which the main body 201 and the protruding parts 202 are integrated for each product. As a result, the cost of manufacturing the electric device 1 increases.

[0056] However, in the electric device 1 according to the present embodiment, the size of the convex portion 202 fixed to the main body portion 201 and the fixed position of the convex portion 202 on the main body portion 201 can be changed according to the carrier frequency of the electric circuit portion 60. In other words, the main body portion 201 and the convex portion 202 can be used as common parts for electric circuit portions 60 with different specifications.

[0057] <Action and effect> In the above-mentioned housing 50, the plurality of protruding parts 202 may be separate from the main body part 201. In this case, the main body part 201 and the protruding part 202 are commonly applied to the electric circuit part 60 that performs pulse width modulation control with different carrier frequencies, and the arrangement of the plurality of protruding parts 202 in the main body part 201 is changed, thereby realizing the housing 50 that accommodates the electric circuit part 60 with different specifications. The above-mentioned protruding part 202 may be prepared by making the configuration of the insertion part 22, which is a part that connects to the main body part 201, common to the protruding part 202, and by preparing a plurality of types of protruding parts 202 with different masses and shapes of the protruding part 21. As a result, when manufacturing a wide variety of electric devices 1, it is possible to suppress capital investment and reduce the manufacturing cost of the electric devices 1 compared to the case where a mold for manufacturing the housing 50 is individually prepared for each type.

[0058] Embodiment 3 <Configuration of electrical equipment and case> FIG. 18 is a perspective schematic diagram of an electric device according to a third embodiment. The electric device 1 shown in FIG. 18 basically has the same configuration as the electric device 1 shown in FIGS. 1 to 5, but the configuration of the housing 50 is different from that of the electric device 1 shown in FIGS. 1 to 5. Specifically, the housing 50 of the electric device 1 according to this embodiment has a more complicated shape than the housing 50 in the electric device 1 shown in FIGS. 1 to 5, and the multiple protrusions 202 formed on the upper case cover 2 are formed at an unequal pitch. That is, the interval P1 between the protrusions 202c and 202d in the first pair of adjacent pairs is different from the interval P1' between the protrusions 202d and 202e in the second pair of adjacent pairs.

[0059] As shown in FIG. 18, when the shape of the upper case cover 2 is complicated and the rigidity of the upper case cover 2 varies locally, the vibration shape of the upper case cover 2 becomes asymmetric and distorted. For the housing 50 (upper case cover 2) having such a vibration shape, the convex parts 202 are arranged so that the wavelength λ2X (see FIG. 7) of the bending wave in the longitudinal direction of the flat plate constituting the housing 50 and the wavelength λ2Y (see FIG. 7) of the bending wave in the lateral direction of the flat plate are shorter than the wavelength λ1 of the sound wave emitted from the flat plate. In this case, as shown in FIG. 18, a portion where the convex parts 202 are densely distributed and a portion where the convex parts 202 are sparsely distributed are formed. In other words, the intervals P1, P1' between adjacent convex parts 202 are not necessarily the same. The intervals P1, P1' between adjacent convex parts 202 in the plurality of convex parts 202 can be determined using a conventionally known method such as simulation.

[0060] <Action and effect> In the housing 50, in the plurality of protrusions 202, the interval P1 between the protrusions 202c, 202d in a first pair of adjacent pairs may be different from the interval P1' between the protrusions 202d, 202e in a second pair of adjacent pairs.

[0061] In this case, even if the shape of the housing 50 is complex and the rigidity of the housing 50 varies locally, the radiation of noise caused by the vibration of the housing 50 itself can be suppressed by changing the spacing P1, P1' between locally adjacent convex portions 202.

[0062] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. Unless inconsistent, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0063] 1 Electrical equipment, 2 Upper case cover, 3 Lower case cover, 4 Flange portion, 5 Bolt hole, 6 Positioning hole, 8 Inverter, 9 Converter, 10 Water jacket, 11 Capacitor, 12 Boss, 13 Surface, 14 Inner surface, 15, 16, 17, 18 Small portion, 20 Hole, 21 Protrusion, 22 Insertion portion, 50 Housing, 60 Electrical circuit portion, 201 Main body portion, 202, 202c, 202d, 202e Convex portion, 202a First convex portion, 202b Second convex portion.

Claims

1. A housing for holding an electric circuit section for performing pulse width modulation control therein, A main body portion, A plurality of protrusions are formed on a surface of the main body, The interval between adjacent pairs of protrusions in the plurality of protrusions is less than 0.5 times the wavelength of a sound wave having the same frequency as a carrier frequency in the pulse width modulation control, A housing, wherein the spacing varies locally depending on the stiffness of the body portion.

2. A housing for holding an electric circuit section that performs pulse width modulation control, A main body portion, A plurality of protrusions are formed on a surface of the main body, The interval between adjacent pairs of protrusions in the plurality of protrusions is less than 0.5 times the wavelength of a sound wave having the same frequency as a carrier frequency in the pulse width modulation control, The plurality of protrusions are arranged in a matrix pattern, A housing in which the interval between adjacent protrusions in one direction is different from the interval between adjacent protrusions in a direction perpendicular to the one direction.

3. A housing for holding an electric circuit section that performs pulse width modulation control, A main body portion, A plurality of protrusions are formed on a surface of the main body, The interval between adjacent pairs of protrusions in the plurality of protrusions is less than 0.5 times the wavelength of a sound wave having the same frequency as a carrier frequency in the pulse width modulation control, The plurality of protrusions are arranged in a matrix pattern, A housing, wherein a surface of the main body portion is formed with a first portion in which a plurality of the convex portions are distributed, and a second portion in which the plurality of the convex portions are distributed more sparsely than the distribution of the convex portions in the first portion.

4. A housing for holding an electric circuit section that performs pulse width modulation control, A main body portion, A plurality of protrusions are formed on a surface of the main body, The interval between adjacent pairs of protrusions in the plurality of protrusions is less than 0.5 times the wavelength of a sound wave having the same frequency as a carrier frequency in the pulse width modulation control, The plurality of protrusions are arranged in a matrix pattern, The plurality of protrusions include a first protrusion having a first height from the surface; a second convex portion having a second height from the surface that is different from the first height.

5. A housing for holding an electric circuit section that performs pulse width modulation control, A main body portion, A plurality of protrusions are formed on a surface of the main body, The interval between adjacent pairs of protrusions in the plurality of protrusions is less than 0.5 times the wavelength of a sound wave having the same frequency as a carrier frequency in the pulse width modulation control, A housing, wherein the spacing between the protrusions in a first set of adjacent sets of the plurality of protrusions is different from the spacing between the protrusions in a second set of adjacent sets.

6. The housing according to claim 1 , wherein the interval between the plurality of protrusions is equal to or greater than 0.5 times the wavelength of a sound wave having a frequency of 10 kHz.

7. A housing described in any one of claims 1 to 5, wherein the height of the convex portion from the surface is greater than or equal to the thickness of the main body portion.

8. The housing according to claim 1 , wherein a height of at least one of the plurality of protrusions from the surface is equal to or greater than a thickness of the housing.

9. The housing according to claim 1 , wherein the plurality of protrusions are integral with the main body.

10. The housing according to claim 1 , wherein the plurality of protrusions are separate from the main body.

11. The housing according to claim 2 , wherein the intervals between adjacent pairs of protrusions in the plurality of protrusions are all the same.

12. A housing as described in claim 11, wherein the spacing between a pair of adjacent protrusions in the plurality of protrusions in the direction perpendicular to the one direction is all the same.

13. A housing according to any one of claims 1 to 5; an electric circuit section that is disposed inside the housing and performs the pulse width modulation control.

14. The electric device according to claim 13 , wherein the electric circuit section includes any one selected from the group consisting of an inverter, a converter, and a capacitor.

15. A housing as described in any one of claims 1 to 5, which holds the electrical circuit unit that performs the pulse width modulation control inside.

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