Accommodation housing of electric circuit

Abstract

To provide an accommodation housing of an electric circuit, capable of preventing deterioration of a film surface secondary vibration.SOLUTION: A cover in an accommodation housing of an electric circuit, includes: a first region part 22a in contact with a case; a second region part 22b arranged on an inner peripheral side than the first region part in the case where it is viewed from an attachment direction D of the cover; a third region part 22c connecting the first and second region parts; and a reinforcement part 23 that is extended on the third region part, and is connected to the second region part. In the second region part, a mass per unit area is larger than that of the third region part. In the third region part, a fourth region part 22d and a fifth region part 22e that is adjacent to the second region part on the inner peripheral side than the fourth region are provided. The reinforcement part includes a notch 23a at a position excluding a tip end part in an extension direction. In the fifth region part, an angel Θ that is larger than 45 degrees with respect to the second region part on a cross section is formed so that the mass per unit area becomes larger toward the inner peripheral side in the case where it is viewed from a direction where the cover is attached, or a ratio of a curvature radius to a height of the second region part is larger than 1.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a housing for an electric circuit. [Background technology]

[0002] Drive units for electric vehicles are required to be smaller, lighter, and quieter for comfort. Accordingly, the housings of each part of the drive unit tend to be thinner, and because inverter covers are flat members, they tend to vibrate more than the housings of motors and reducers.

[0003] As a measure to suppress sound radiation from a housing due to the propagation of vibration, for example, Patent Document 1 discloses a configuration having a case for housing electronic components and a cover for covering the opening of the case, the cover having a weight portion near the center and a rib connected to the weight portion, with notches provided in the rib to increase the rigidity other than the weight portion and also to reduce the rigidity near the weight portion by concentrating the antinode of the primary vibration of the membrane surface of the cover at the center of the weight portion, thereby enhancing the vibration reduction effect of the weight portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-190563 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in Patent Document 1, the secondary vibration of the membrane surface is aggravated by the concentration of stress at the intersection of the second and third regions, and the rigidity balance of the cover is lost. In view of this, the present invention aims to provide a housing for an electric circuit that prevents the deterioration of the secondary vibration of the membrane surface. [Means for solving the problem]

[0006] The housing for an electric circuit has a case that houses an electric circuit and a cover that covers an opening of the case, the cover has a first region in contact with the case, a second region that is located on the inner side of the first region in a plan view, a third region that connects the first region and the second region, and a reinforcing portion that extends on the third region and is connected to the second region, the second region has a mass per unit area greater than that of the third region when viewed from the direction in which the cover is attached to the case, the third region has a fourth region and a fifth region that is adjacent to the second region on the inner side of the fourth region, the reinforcing portion has a notch at a position excluding a tip portion in the extension direction, and the fifth region forms an angle greater than 45 degrees with respect to the second region on a cross section so that the mass per unit area increases toward the inner side when viewed from the direction in which the cover is attached to the case, or the ratio of the radius of curvature to the height of the second region is greater than 1. Effect of the Invention

[0007] According to the present invention, it is possible to provide a housing for an electric circuit that prevents deterioration of secondary vibration of the membrane surface. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an overall perspective view of a drive unit according to a first embodiment of the present invention; [Diagram 2] Cross section AA of Figure 1 [Diagram 3] FIG. 1 is a diagram illustrating a primary vibration of a membrane surface of a cover according to a first embodiment of the present invention. [Figure 4] Cross section B-B of Figure 3 [Diagram 5] FIG. 11 is a diagram illustrating a secondary vibration of a membrane surface of a cover according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a diagram for explaining the weight-to-weight effect of the inclination angle and the secondary vibration reduction of the membrane surface according to the second embodiment of the present invention. [Figure 7] FIG. 11 is a plan view of a cover according to a second embodiment of the present invention; [Figure 8] Cross section CC of Figure 7 [Figure 9] FIG. 11 is a diagram for explaining the ratio of the radius of curvature r and the weight-to-weight effect on the reduction of secondary vibration of the membrane surface according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications have been made for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0010] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0011] (Overall configuration from the first embodiment) (Fig. 1, Fig. 2) The drive unit 1 is used as a drive source for electrically powered vehicles such as electric cars and hybrid vehicles, and is mounted on the vehicle. The drive unit 1 includes an inverter 2, a motor 3, and a reduction gear 4. The motor 3 and the reduction gear 4 are connected to each other. A drive shaft (not shown) that drives tires (not shown) is connected to an end of an output shaft 41 of the drive unit 1.

[0012] The inverter 2 is connected to the motor 3. The motor 3 has a rotor 31 and a stator 32 in a motor housing 30. The motor 3 vibrates due to an electromagnetic excitation force generated in the gap between the rotor 31 and the stator 32 when driven, and therefore serves as a vibration source for the drive unit 1.

[0013] The reducer 4 converts the rotation speed and torque of the motor 3 and transmits them to the drive shaft. The inverter 2 converts DC power from a battery or the like (not shown) into AC power and supplies it to the motor 3, controlling the power supply to the motor 3. The drive unit 1 generates a drive torque or a braking torque for the motor 3 according to a command obtained from the inverter 2.

[0014] The inverter 2 includes a circuit board 20, which is an electric circuit for controlling power, and a case 21 for housing the circuit board 20. The circuit board 20 has various electronic components (not shown) mounted thereon. The case 21 has, for example, an opening for housing the circuit board 20 therein, and a housing space 21a for housing the circuit board 20 through the opening. The case 21 is also provided with a detachable cover 22 for closing the opening of the case 21.

[0015] The case 21 has a bottom portion 21b attached to the motor housing 30, a side wall portion 21c rising from the outer circumferential edge portion of the bottom portion 21b, and an annular flange portion 21d that functions as an attachment portion for attaching the cover 22. The case 21 is fastened to the motor housing 30 with bolts. The outer circumferential portion of the cover 22 is fastened to the flange portion 21d of the case 21 with bolts.

[0016] Vibrations occurring when the drive unit 1 is driven are transmitted to the motor housing 30, the gear case 40, and the case 21 and cover 22 of the inverter 2. Specifically, vibrations caused by the electromagnetic excitation force generated between the stator 32 and the rotor 31 and the gear meshing excitation force are transmitted to the motor housing 30 and the gear case 40, and then transmitted to the case 21 and cover 22 of the inverter 2 via the connection between the motor housing 30 and the inverter 2.

[0017] Since the cover 22 is generally a flat plate-shaped member, it has lower rigidity and is more susceptible to vibration than other members such as the motor housing 30 and the gear case 40. In particular, the lower the vibration mode, the greater the vibration tends to be, and the greater the radiated sound caused by the vibration of the cover 22 tends to be.

[0018] (Figs. 3 to 5) The cover 22 has a basic structure of a plate-like portion that closes the opening of the case 21. The cover 22 has an annular first region 22a that contacts the flange portion 21d (FIG. 2) of the case 21, a second region 22b that is a weight portion located on the inner periphery side of the first region 22a in a plan view, and a third region 22c that is provided between the first region 22a and the second region 22b and connects the first region 22a and the second region 22b. The cover 22 is formed by integrally molding the first region 22a, the second region 22b, and the third region 22c.

[0019] The third region 22c has a fourth region 22d and a fifth region 22e that is adjacent to the second region 22b on the inner circumferential side of the fourth region 22d.

[0020] The first area 22a constitutes the outer periphery of the cover 22. The surface of the first area 22a on the lower side in FIG. 4 comes into contact with the flange portion 21d of the case 21. The first area 22a is fastened to the flange portion 21d of the case 21 by bolts, thereby increasing the rigidity.

[0021] The second region 22b has a mass (weight) per unit area that is relatively larger than that of the third region 22c when viewed from an attachment direction D in which the cover 22 is attached to the case 21. As shown in Fig. 4, the second region 22b is thicker than the third region 22c and protrudes more toward the outside of the cover 22 than the third region 22c in cross section.

[0022] The second area 22b is located approximately at the center of the cover 22 when viewed from the attachment direction D of the cover 22 to the case 21. As shown by the movement 5a of the membrane surface primary vibration of the cover 22, the antinode (the position of maximum amplitude) of the membrane surface primary vibration is included within the range of the second area 22b. In other words, the membrane surface primary vibration of the cover 22 is a vibration mode in which the antinode is located approximately at the center of the cover 22 when viewed from the attachment direction D of the cover 22 to the case 21. The second area 22b is molded integrally with the third area 22c.

[0023] On the third region 22c, ribs 23 for increasing the rigidity of the third region 22c extend from the four corners of the case 21 so as to be connected to the second region 22b. The ribs 23 are reinforcing parts provided on the outer surface side of the third region 22c. As shown in FIG. 3, four ribs 23 are provided on the outer surface side in the cross section of the third region 22c, and are molded from the second region 22b toward the bolts provided at the four corners of the first region 22a. The ribs 23 are molded integrally with the second region 22b and the third region 22c, for example.

[0024] The rib 23 has notches 23a at positions excluding the four corners of the third region 22c, which is the tip end in the extension direction. The notches 23a are formed from any position on the rib 23 along the extension direction to a position reaching the second region 22b.

[0025] The shape of rib 23, such as its length, width (thickness), height, etc., and the shape of notch 23a, taking into consideration its position, length, depth, etc., are set so that the position of the antinode of the primary vibration of the membrane surface of cover 22 is within the range of second area portion 22b.

[0026] The shapes of the rib 23 and the notch 23a are set so as to prevent the natural frequency of the membrane primary vibration of the cover 22 from being in the region of the natural frequency of other members such as the case 21, or in the frequency region where the sensitivity of human hearing is high (for example, in the range from 1 kHz to 4 kHz). In other words, by adjusting various parameters of the rib 23 and the notch 23a, the position of the antinode of the membrane primary vibration of the cover 22 can be adjusted, and the natural frequency of the membrane primary vibration of the cover 22 can be set to a frequency region within a predetermined range.

[0027] The fifth region 22e forms an arbitrary inclination angle θ on the cross section so that the mass per unit area increases toward the inner periphery when viewed from the mounting direction D of the cover 22 to the case 21. The fifth region 22e connects the second region 22b and the fourth region 22d.

[0028] 5, when viewed from the mounting direction D, the membrane secondary vibration that vibrates like the membrane secondary vibration movement 5b has a vibration node (a position where the amplitude is 0) at approximately the left-right or top-bottom center of the second area 22b in a plan view. In other words, the center portion between the boundary between the fourth area 22d and the first area 22a and the node position becomes the antinode of the membrane secondary vibration. The membrane secondary vibration is a vibration mode that vibrates in antiphase with the node as a boundary.

[0029] By providing the fifth region 22e around the second region 22b, stress is not concentrated near the antinode of the membrane surface secondary vibration, so that the deterioration of the membrane surface secondary vibration can be prevented. In addition, by providing the fifth region 22e, the balance of the rigidity of the cover 22 does not change with respect to the membrane surface primary vibration, so that the antinode of the membrane surface primary vibration can be maintained at approximately the center of the second region 22b. Therefore, the membrane surface primary vibration can be reduced while suppressing the deterioration of the membrane surface secondary vibration.

[0030] (Figure 6) The inclination angle θ of the fifth region 22e (FIG. 5) that is effective in reducing the secondary vibration of the membrane surface will be described. Note that the horizontal axis of FIG. 6 indicates the inclination angle θ of the fifth region 22e, and the vertical axis indicates the weight-to-effect ratio for reducing the secondary vibration of the membrane surface. Note that the base showing the amount of reduction on the vertical axis is a shape that does not include the fifth region 22e.

[0031] As the inclination angle θ is increased, the weight-to-benefit ratio of the reduction in the secondary vibration of the membrane increases when the angle exceeds 45 degrees, and the weight-to-benefit ratio converges at an inclination angle of about 60 degrees. This is because, from a state in which force is concentrated near the antinode of the secondary vibration of the membrane (the intersection of the second region 22b and the fourth region 22d), as the inclination angle θ is increased, the concentration of force is gradually released and the inclination angle converges at 60 degrees. Therefore, the inclination angle θ may be set to an angle greater than 45 degrees, for example. Furthermore, by setting the inclination angle θ to 60 degrees or more, the weight-to-benefit ratio of the reduction in the secondary vibration of the membrane becomes maximum.

[0032] Second embodiment (Fig. 7, Fig. 8) The fifth region 22e does not need to form an inclination angle θ as described above, but as long as it has a radius of curvature r whose ratio to the height h of the second region 22b is greater than 1, as shown in FIG. 8, the same effect can be obtained.

[0033] (Fig. 9) The radius of curvature r of the fifth region 22e, which is effective in reducing the secondary vibration of the membrane surface shown in Fig. 8, will be described. The horizontal axis of Fig. 9 is the ratio (r / h) of the radius of curvature r of the fifth region 22e to the height h of the second region 22b, and the vertical axis is the weight-to-effect of reducing the secondary vibration of the membrane surface. Note that the base showing the amount of reduction on the vertical axis is a shape that does not include the fifth region 22e.

[0034] The weight-to-benefit ratio increases when the ratio of the radius of curvature r of the fifth region 22e to the height h of the second region 22b exceeds 1, and the effect is maximized and converges when the ratio of the radius of curvature r is 2.3. The mechanism is the same as in the first embodiment. Therefore, the weight-to-benefit ratio in reducing the secondary membrane vibration is maximized by making the radius of curvature r of the fifth region 22e in the second embodiment, for example, 2.3 times larger than the height h of the second region 22b.

[0035] In the present invention, the rib 23 may be provided anywhere in the third region 22c, and the number and shape of the ribs are not limited. The second region 22b and the fifth region 22e may be provided not only on the outside of the space formed by the cover 22 and the case 21, but also on the inside. The fifth region 22e may be provided from the top surface of the second region 22b instead of the side surface, or from the side surface of the second region 22b midway in the height direction. The fifth region 22e may extend over the entire outer periphery of the second region 22b or may be a part of it. The object having this configuration may be not only the drive unit constituted by the inverter, motor, and reducer exemplified in this embodiment, but also, for example, a housing structure for an electric circuit in another device such as a motor generator.

[0036] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0037] (1) The housing for the electric circuit includes a case 21 that houses the electric circuit and a cover 22 that closes an opening of the case 21. The cover 22 includes a first region 22a that contacts the case 21, a second region 22b that is disposed on the inner periphery side of the first region 22a in a plan view, a third region 22c that connects the first region 22a and the second region 22b, and a reinforcing portion 23 that extends on the third region 22c and is connected to the second region 22b. When viewed from a direction in which the cover 22 is attached to the case 21, the second region 22b has a mass per unit area larger than that of the third region. The third region 22c is larger than the third region 22c, and the third region 22c has a fourth region 22d and a fifth region 22e adjacent to the second region 22b on the inner circumferential side of the fourth region 22d, and the reinforcing portion 23 has a notch 23a at a position in the extension direction excluding the tip portion, and the fifth region 22e forms an angle of more than 45 degrees with respect to the second region 22b on the cross section, or the ratio of the radius of curvature to the height of the second region 22b is more than 1, so that the mass per unit area increases toward the inner circumferential side when viewed from the direction in which the cover 22 is attached to the case 21. In this way, it is possible to provide a housing for an electric circuit that prevents the deterioration of the secondary vibration of the membrane surface.

[0038] (2) The fifth region 22e forms an angle of more than 60 degrees with respect to the second region 22b on the cross section, or the ratio of the radius of curvature to the height of the second region 22b is more than 2.3. By doing so, the weight-to-effect ratio for reducing the secondary vibration of the membrane surface is maximized.

[0039] The present invention is not limited to the above-described embodiment, and various modifications and other configurations can be combined without departing from the spirit of the present invention. Furthermore, the present invention is not limited to those having all of the configurations described in the above-described embodiment, and includes those in which some of the configurations are omitted. [Explanation of symbols]

[0040] 1 Drive unit 2 Inverter 3 Motor 4 Reducer 5a Primary vibration of membrane 5b Secondary vibration of membrane 20 Circuit Board 21 cases 21a Containment Space 21b bottom 21c Side wall part 21d Flange part 22 Cover 22a 1st area part 22b 2nd area part 22c 3rd area part 22d 4th area part 22e 5th area 23 Ribs 23a Notch 30 Motor housing 31 Rotor 32 Stator 40 Gear Case 41 Output shaft

Claims

1. The device has a case that houses an electric circuit and a cover that closes an opening of the case, the cover has a first region in contact with the case, a second region disposed on the inner circumferential side of the first region in a plane, a third region connecting the first region and the second region, and a reinforcing portion extending on the third region and connected to the second region; the second region has a mass per unit area greater than that of the third region when viewed from a direction in which the cover is attached to the case; The third region includes a fourth region and a fifth region adjacent to the second region on the inner circumferential side of the fourth region, The reinforcing portion has a notch at a position other than a tip portion in an extension direction, When viewed from a direction in which the cover is attached to the case, the fifth region forms an angle of greater than 45 degrees with respect to the second region on a cross section so that a mass per unit area increases toward an inner periphery side, or a ratio of a radius of curvature to a height of the second region is greater than 1. An enclosure that contains electrical circuits.

2. 2. The electric circuit housing according to claim 1, The fifth region forms an angle of greater than 60 degrees with respect to the second region on a cross section, or the ratio of the radius of curvature to the height of the second region is greater than 2.

3. An enclosure that contains electrical circuits.

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