JP5847135B2 - Motor drive device - Google Patents

Description

  The present invention relates to a motor driving device having an oscillating object therein, and more particularly to a motor driving device having a heat sink for reducing noise while maintaining heat dissipation performance from heat-generating components.

In recent years, with the hybridization of automobiles, etc., the quietness inside the automobile has been improved. When an electric motor is used as a drive source for an automobile, noise transmitted to the interior of the vehicle is significantly less than when an internal combustion engine is used. However, the passenger may recognize the noise from the motor control device mounted on the vehicle due to a decrease in the total amount of noise transmitted into the vehicle.
The motor drive is generally attached to the automobile frame. The vibration of the motor drive device is transmitted to the frame or other members constituting the automobile, and is transmitted to the passenger as noise. That is, the motor drive device becomes a vibration source and transmits sound into the vehicle.

  The vibration source in the motor drive device is due to a smoothing capacitor disposed in the motor drive device. A smoothing capacitor suppresses a surge generated by switching a semiconductor module for driving a motor repeatedly on and off. A smoothing capacitor corresponding to a high voltage and a high current is required in order to increase the output of the motor drive device as the output of the motor increases.

Conventionally, there exists a thing regarding the motor drive device which has a reactor as an example of the noise reduction of the circuit element of a motor drive device. This motor drive device is based on water cooling and aims to reduce noise due to reactor vibration without reducing the heat dissipation performance of the reactor.
This is a method in which the bottom surface of the reactor is brought into contact with water-cooling liquid flowing in an opening provided in the heat sink, and a cooling fin is attached to the bottom of the reactor to reduce the vibration of the reactor with the liquid (Patent Document). 1).

In this technique, in order not to transmit the vibration of the reactor to the heat sink, the contact area between the reactor and the heat sink is reduced, and the vibration transmission efficiency is reduced, thereby reducing the noise caused by the operation of the reactor. Furthermore, since it is directly brought into contact with the cooling water, the reactor can be sufficiently cooled.
Alternatively, there is a method in which a heat sink as a separate member is inserted between the reactor and the heat sink to reduce the vibration transmission efficiency to the main body heat sink.

  Further, in the semiconductor device having the cooling fins mounted on the semiconductor module, the cooling fins include first cooling fins provided at both ends and a plurality of second cooling fins arranged in parallel between the first cooling fins. The first cooling fin is known to be thicker than the second cooling fin to prevent deformation of the cooling fin during processing and assembly (see Patent Document 2). ).

Japanese Patent Laying-Open No. 2005-286020 (FIGS. 6 and 7) Japanese Patent Laid-Open No. 61-35526 (FIG. 4)

However, in the motor driving device by air cooling, vibration cannot be reduced by bringing a vibrating object (in the present invention, not a reactor but a smoothing capacitor) into contact with the liquid. Further, in order to reduce the vibration transmission efficiency, when a separate member is inserted between the vibrating object and the heat sink, the number of parts increases, thereby increasing the cost and increasing the number of parts assembly steps.
When the heat sink is air-cooled, the vibration of the vibrating object is transmitted to the heat sink, causing a problem that the fin of the heat sink vibrates and generates noise. In addition, since there is a heating element such as a semiconductor module inside the motor drive device, it is necessary to maintain the heat dissipation performance.

Also, as a cooling device for a semiconductor device itself, although it is known to increase the strength by making the cooling fins at both ends thicker than other cooling fins, the motor drive device having a vibrating object inside generates heat. It is necessary to reduce noise while maintaining the heat dissipation performance from the parts.
In this respect, since the conventional one does not have a vibrating object inside, no problem regarding noise and measures for reducing the noise are taken.

  The present invention has been made to solve the above problems, and has a heat sink capable of reducing noise while maintaining heat dissipation performance by changing the fin shape of the heat sink without increasing the number of parts. It is an object of the present invention to provide a motor drive device.

The motor drive device according to the present invention radiates heat generated from a semiconductor module that repeatedly switches on and off current or voltage, a smoothing capacitor that smoothes a surge generated by switching of the semiconductor module, A heat sink for fixing the smoothing capacitor, a cover for covering the semiconductor module and the smoothing capacitor, and a cover attached to the heat sink are provided, and the smoothing capacitor vibrates the electrode by taking in and out charges, and the vibration is transmitted to the heat sink. fixed as, the heat sink has a plurality of fins of the plurality of fins, with the fins at both ends to increase the inner thickness of the fin by riff fin than, the chamfered portion at the base portion of the fin at both ends Is provided .

The motor drive device according to the present invention also dissipates heat generated from a semiconductor module that repeatedly switches on and off current or voltage, a smoothing capacitor that smoothes a surge generated by switching of the semiconductor module, and heat generated from the semiconductor module. And a heat sink for fixing the smoothing capacitor, a cover for covering the semiconductor module and the smoothing capacitor, and a cover attached to the heat sink. The smoothing capacitor vibrates the electrode by taking in and out charges, and the vibration is applied to the heat sink. The heat sink has a plurality of fins, and among the plurality of fins, the fins on both ends have a fin height higher than the fins on the inner side of the fins, and the fins on both ends have fin base portions. A chamfered portion is provided .

The motor drive device according to the present invention also dissipates heat generated from a semiconductor module that repeatedly switches on and off current or voltage, a smoothing capacitor that smoothes a surge generated by switching of the semiconductor module, and heat generated from the semiconductor module. and, a heat sink to fix the smoothing capacitor, to cover the semiconductor module and the smoothing capacitor, and a cover attached to the heat sink, the smoothing capacitor be one electrode is vibrated by input record out of charge, the vibration heatsink fixed to be transferred to the heat sink has a plurality of fins, the fins of the heat sink, the air flow direction, the most wider across the fins, together with the other of the width of the fin is narrow Kunar so Chamfered parts are provided at the base of fins at both ends It is intended.

The smoothing capacitor inside the motor drive device vibrates due to the insertion and removal of electric charges, and this vibration is transmitted to the heat sink that fixes the smoothing capacitor. .
However, according to the present invention, the thickness of the fins at both ends of the heat sink is made thicker than the thickness of the other fins, the height of the fins at both ends of the heat sink is made higher than the height of the other fins, or the fins at both ends of the heat sink It is possible to reduce the noise of the entire unit by shifting the natural frequency of both ends and the inner fins to increase the rigidity by making the width of the fin wider than that of the other fins.

Moreover, since only the thickness, height, and width of the fins at both ends are increased, noise can be reduced while maintaining heat dissipation performance.
Therefore, by changing the fin shape of the heat sink without increasing the number of components, it is possible to provide a motor drive device having a heat sink that can reduce noise while maintaining heat dissipation performance.

1 is a perspective view of a motor drive device according to Embodiment 1 of the present invention. It is sectional drawing of the motor drive device by Embodiment 1 of this invention. It is an image figure about the flow of the wave of the sound wave which arises from the fin of a heat sink. It is sectional drawing of the motor drive device by Embodiment 2 of this invention. It is sectional drawing of the motor drive device by Embodiment 3 of this invention. It is sectional drawing of the motor drive device by Embodiment 4 of this invention. It is sectional drawing and the bottom view of the motor drive device by Embodiment 5 of this invention. It is sectional drawing and the bottom view of the motor drive device by Embodiment 6 of this invention. It is the front view and bottom view of the motor drive device by Embodiment 7 of this invention. It is sectional drawing of the motor drive device by Embodiment 8 of this invention. It is sectional drawing and detail drawing of the motor drive device by Embodiment 9 of this invention.

Embodiment 1 FIG.
Hereinafter, a motor drive apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a perspective view of a motor drive device according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view of the motor drive device according to Embodiment 1 of the present invention.
As shown in FIGS. 1 and 2, the motor drive device includes a semiconductor module 2 that repeatedly switches on and off a large current or a large voltage, and a smoothing capacitor 3 that smoothes a surge generated by the switching of the semiconductor module 2. A heat sink 4 that radiates heat generated from the semiconductor module 2 and fixes the smoothing capacitor 3, and a cover 1 that covers the semiconductor module 2 and the smoothing capacitor 3 and is attached to the heat sink 4.

Next, the main operation of the motor drive device will be briefly described.
First, a motor (not shown) connected to the outside of the motor drive device is driven by electric power generated by an on / off switching operation of the semiconductor module 2 that controls a large current and a large voltage. The switching operation of the semiconductor module 2 needs to be smoothed by the smoothing capacitor 3 in order to generate a large current and large voltage surge. In the smoothing capacitor 3, large current and large voltage charges are taken in and out, so that the internal electrodes vibrate. In this respect, the smoothing capacitor 3 constitutes a vibrating object.

  The vibration generated inside the motor drive device is transmitted to the cover 1 and the heat sink 4. The vibration transmitted to the heat sink 4 vibrates the fins 41 and 42 of the heat sink 4, and noise is emitted to the outside of the motor drive device. In addition, since the semiconductor module 2 performs a switching operation of a large current and a large voltage, the heat generation is large, and it is necessary to transfer heat to the heat sink 4 to dissipate heat. In this respect, the heat sink 4 is required to reduce noise while maintaining heat dissipation performance.

Here, the following four points are listed as noise reduction methods.
(1) The natural frequency between the fins is shifted.
(2) Increase the fin rigidity.
(3) The generated sound wave is not leaked to the outside or leakage is reduced.
(4) The sound wave amplified between the fins is reduced by making the reflection of the sound wave between the fins indefinite.
Based on these four points, the present invention changes the fin shape of the heat sink 4 to reduce noise while maintaining heat dissipation performance.

  This noise reduction will be described in detail in the cross-sectional view of FIG. Since the smoothing capacitor 3 that is a vibrating object is fixed to the heat sink 4 of the housing, vibration from the smoothing capacitor 3 is transmitted to the heat sink 4. The plurality of fins 41 and 42 of the heat sink 4 vibrate due to the transmitted vibration. Among the plurality of fins of the heat sink 4, the thickness of the fins 41 at both ends is thicker than that of the numerous fins 42 on the inner side, so that the natural frequency changes and the rigidity increases.

Here, the flow of the wave of the sound wave emitted from the fin 42 of the heat sink 4 will be described with reference to FIG.
Usually, the wave 101 of the sound wave generated by the vibration 102 of the fin 42 is as shown in FIG. The sound wave 101 generated by the vibration 102 of the fin 42 is transmitted to the adjacent fin 42b by the wave of air as indicated by the arrow in FIG. 3B, and the natural frequency of the adjacent fin 42b is the same as that of the fin 42. In the same case, it resonates and amplifies the sound wave.

As shown in the fin shape of FIG. 2, the thickness of the fins 41 at both ends is made thicker than that of the large number of fins 42 on the inside, thereby shifting the natural frequency and increasing the rigidity. Furthermore, since the fins 41 at both ends do not resonate, noise is not amplified.
Further, as a characteristic of the sound wave generated from the vibrating fin 42, it is strongly emitted in the lateral direction as shown in FIG. Therefore, it is possible to reduce noise generated as a whole of the motor driving device by increasing the rigidity by providing the thickness of the fins 41 at both ends. Further, since only the thickness of the fins 41 at both ends is increased, the surface area of the heat sink 4 is hardly changed, and noise can be reduced while maintaining the heat dissipation performance.

Embodiment 2. FIG.
Next, a motor drive apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 4 shows a sectional view of a motor drive apparatus according to Embodiment 2 of the present invention.
In the first embodiment shown in FIG. 2, all of the fins 42 inside the fins 41 at both ends of the heat sink 4 have the same thickness. However, in the second embodiment, the thickness of the inner fins 42 is reduced. It is a uniform one.

As shown in FIG. 4, the thickness of each fin of the heat sink 4 is maximized at the fins 41 at both ends, and the thickness of the inner fins 42 is gradually reduced from the end portion toward the center portion so that the thickness is not uniform. It is a thing. Other configurations are the same as those in FIG. 2, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.
As described with reference to FIG. 3, the wave 101 of the sound wave generated by the fin resonates and amplifies noise when the adjacent fins have the same natural frequency. Therefore, by changing the thickness of each of the inner fins 42, the natural frequency is different and resonance between the fins can be prevented.

  Further, by making the fins 41 at both ends the thickest, the rigidity can be increased, and leakage of noise generated by the inner fins 42 can be reduced. By doing in this way, it becomes possible to reduce the noise which arises as a whole unit to the minimum. Further, since the surface area of the fins of the heat sink 4 may be slightly reduced, the position of the heating element (semiconductor module) to be arranged is adjusted, and the thickness of the fin immediately below the heating element is adjusted according to the amount of heat generated by the heating element. Adjust it.

  Furthermore, as shown in FIG. 4, the fin 42 in the center is made the thinnest and becomes thicker toward the outside, so that the rigidity increases as it goes to the outside fin. The vibration of the sound wave thus made is less likely to transmit vibration to the outer fin 41, and noise can be further reduced.

Embodiment 3 FIG.
Next, a motor drive apparatus according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 5 shows a sectional view of a motor drive apparatus according to Embodiment 3 of the present invention.
In the first and second embodiments, the thickness of the fins 41 at both ends of the heat sink 4 is thicker than the thickness of the fins 42 on the inner side, but the invention of the third embodiment is similar to the fin of the heat sink 4. The thicknesses 41 and 42 are all the same, and the height is changed.

As shown in FIG. 5, the natural frequency of the fin is shifted by making the height of the fin 41 at both ends of the heat sink 4 higher than the height of the fin 42 inside. Other configurations are the same as those in FIG. 2, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.
Since the wave 101 of the sound wave generated from the fin is generated as shown in FIG. 3, the adjacent fin resonates and amplifies noise when the adjacent fin has the same natural frequency. Therefore, by increasing the height of the fins 41 at both ends, noise leaking to the outside of the unit can be reduced and shut off. Since the surface area of the fins of the heat sink 4 is almost the same, noise reduction can be achieved while maintaining heat dissipation performance.

Embodiment 4 FIG.
Next, a motor drive apparatus according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 6 shows a cross-sectional view of a motor drive apparatus according to Embodiment 4 of the present invention.
In the third embodiment shown in FIG. 5, all the fins 42 inside the fins 41 at both ends of the heat sink 4 have the same height. However, in the fourth embodiment, the height of the inner fins 42 is not the same. It is a uniform one.

As shown in FIG. 6, among the fins 42 inside the heat sink 4, the fins 42 at the center are made the lowest and increased toward the outside, and the fins 41 at both ends are the highest. Other configurations are the same as those in FIG. 2, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.
In this way, by making the heights of all the fins 41 and 42 non-uniform, the natural frequency of each fin is different, so that adjacent fins do not resonate and the noise of the heat sink 4 as a whole is reduced. can do.

  Further, depending on the fins, the height is lowered and the heat dissipation effect is lowered. Therefore, if the fins directly below the heat generating material are adjusted so as to be higher in consideration of the position of the heat generating material (semiconductor module) fixed to the heat sink 4, the heat dissipation performance is reduced. Will be better. Further, as in the shape of FIG. 6, it is desirable that the fin 42 in the central portion is lowest and higher as it goes outward in consideration of the flow of sound waves generated from the fins. From the viewpoint of thermal design and noise level, it is necessary to optimize the fin shape.

Embodiment 5 FIG.
Next, a motor drive apparatus according to Embodiment 5 of the present invention will be described with reference to FIG. FIG. 7 shows a cross-sectional view and a bottom view of a motor drive device according to Embodiment 5 of the present invention.
In the first to fourth embodiments, the thickness or height of the fins 41 at both ends of the heat sink 4 is made thicker or higher than the fins 42 on the inner side, but in the invention of the fifth embodiment, the heat sink The widths of the fins 41 at the both ends of 4 are the widest, and the widths of the other fins 42 are narrower than the widths of the fins 41 at both ends.

  7A is a cross-sectional view taken along line AA, FIG. 7B is a bottom view, and FIG. 7C is a cross-sectional view taken along line BB. As shown in FIG. The width of the fin 42 having the widest width and the inner fin 42 is narrower in the air flow direction, and the natural frequency of the fin is shifted. That is, when the width of the fins 41 at both ends is t1, and the width of the inner fins 42 is t2, the relationship is t1> t2. Other configurations are the same as those in FIG. 2, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

Since the sound wave is generated in a form that diverges from the fins, the inner fin 42 is made narrower than the width of the fins 41 at both ends in the air flow direction, so that the noise generated by the inner fins 42 can be reduced. It is possible to reduce leakage. By changing the shape of the fins in this way, it is possible to reduce the noise of the entire unit.
In FIG. 7, the inner fins 42 have the same width, but may be non-uniform.

Embodiment 6 FIG.
Next, a motor drive apparatus according to Embodiment 6 of the present invention will be described with reference to FIG. FIG. 8 shows a sectional view and a bottom view of a motor driving apparatus according to Embodiment 6 of the present invention.
8A is a cross-sectional view taken along the line AA, and FIG. 8B is a bottom view. As shown in FIG. 8, chamfered portions 43 are provided at the base portions of the fins 41 at both ends of the heat sink 4. By doing so, the rigidity of the fins 41 at both ends is increased, and the rigidity can be increased by shifting the natural frequency with the inner fins 42. Other configurations are the same as those in FIG. 2, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 8, as described in the first and second embodiments, the fins 41 at both ends are thicker than the fins 42 on the inner side. Thus, the fins 41 on both ends are made higher than the fins 42 on the inner side, or the fins 41 on both ends are made wider than the fins 42 on the inner side as in the fifth embodiment. Is also applicable.

  Thus, since only the shape of the fins 41 at both ends is changed, the surface area of the entire heat sink 4 is hardly changed, and the heat dissipation performance can be maintained. Further, by providing the chamfered portion 43 at the base portion of the fins 41 at both ends, it is possible to reduce noise as a whole unit while maintaining heat dissipation performance.

Embodiment 7 FIG.
Next, a motor drive apparatus according to Embodiment 7 of the present invention will be described with reference to FIG. FIG. 9 shows a front view and a bottom view of a motor drive apparatus according to Embodiment 7 of the present invention.
In the sixth embodiment, the chamfered portions 43 provided at the base portions of the fins 41 at both ends of the heat sink 4 extend over the entire width of the fins 41, but the invention of the seventh embodiment A chamfered portion 43 is provided in a part.

  9A is a front view and FIG. 9B is a bottom view. As shown in FIG. 9, only the portions necessary for the rigidity of the fins 41 are chamfered in the root portions of the fins 41 at both ends of the heat sink 4. A portion 43 (three locations at the center and both ends in the width direction in the figure) is provided, and the other unnecessary portions are provided with a thinning portion 44. Other configurations are the same as those in FIGS. 2 and 8, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

As shown in FIG. 8 of the sixth embodiment, when the chamfered portion 43 is provided from the inlet to the outlet of the fin 41 in the air flow direction, the area of the chamfered portion 43 is increased, and the chamfered portion 43 becomes a flute, Nests (cavities) are likely to be generated, which is a problem in molding. In addition, there is a demerit that the surface area of the heat sink 4 is reduced and the weight is increased.
On the other hand, as shown in FIG. 9, the unnecessary portion of the chamfered portion 43 is used as the thickness removing portion 44, so that noise reduction and weight increase can be prevented.
8 and 9, the chamfered portion 43 is provided only for the fins 41 at both ends. However, depending on the required performance of the heat sink 4, the chamfered portion 43 may be similarly provided on the inner fin 42.

Embodiment 8 FIG.
Next, a motor drive apparatus according to Embodiment 8 of the present invention will be described with reference to FIG. FIG. 10 shows a sectional view of a motor drive apparatus according to Embodiment 8 of the present invention.
As shown in FIG. 10, in the configuration of the first to seventh embodiments, a thick weight portion 45 with a weight attached to a part of the fins 41 and 42 of the heat sink 4 is provided. Further, the position where the weight portion 45 is provided is made different depending on the fins 41 and 42. As a result, the natural frequencies of the fins 41 and 42 can be shifted. Other configurations are the same as those in FIG. 2, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  By providing the weights 45 in the fins 41 and 42 in this way, the natural frequencies of adjacent fins are different, and therefore, resonance of sound waves generated from the fins 41 and 42 can be prevented. Moreover, since the bulge can be provided in the fins 41 and 42 by the weight part 45, the surface area of the heat sink 4 as a whole is increased, and the heat dissipation is improved. Further, the shape as shown in FIG. 10 is difficult in die casting, but can be easily formed by extrusion.

Embodiment 9 FIG.
Next, a motor drive device according to Embodiment 9 of the present invention will be described with reference to FIG. FIG. 11 shows a sectional view and a detailed view of a motor drive apparatus according to Embodiment 9 of the present invention.
11A is a cross-sectional view, and FIG. 11B is an enlarged detailed view of the fins of the broken-line circle shown in FIG. 11A. As shown in FIG. 11, the configurations of the first to seventh embodiments. In FIG. 3, the corrugated portion 46 is provided on the surface of the fins 41 and 42 so as to have a wave in the air flow direction. It is considered that such a wave-like shape is also effective in the surface blast shot blasting. Other configurations are the same as those in FIG. 2, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

When the surface of the fin is a normal plane, the sound wave 101 generated from the adjacent fins is reflected in a certain direction between the fins, thus amplifying the noise. Therefore, as shown in FIG. 11, by providing a wave-like portion 46 shaped so as to wave the surface of the fins 41, 42, the sound wave 101 generated by each fin 41, 42 is not reflected in a certain direction. For this reason, it is possible to reduce amplification between the fins 41 and 42. In addition, since the surface area is larger than that of normal fins, heat dissipation is improved.
Further, instead of providing the corrugated portion 46 shaped like a wave on the surface of the fins 41, 42, irregularities may be provided on the surfaces of the fins 41, 42.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

1: cover, 2: semiconductor module, 3: smoothing capacitor,
4: heat sink, 41: fins at both ends, 42: fins on the inside,
43: Chamfered portion, 44: Dehumidified portion, 45: Weight portion, 46: Wavy portion.

Claims (10)

A semiconductor module that repeatedly switches on and off current or voltage; a smoothing capacitor that smoothes a surge generated by switching of the semiconductor module; a heat sink that dissipates heat generated from the semiconductor module and fixes the smoothing capacitor; And a cover that covers the semiconductor module and the smoothing capacitor and is attached to the heat sink. The smoothing capacitor has an electrode that vibrates when a charge is taken in and out, and is fixed so that the vibration is transmitted to the heat sink. is, the heat sink has a plurality of fins, the plurality of fins, with the fins at both ends to increase the inner thickness of the fin by riff fin than, the chamfered portion at the base portion of the fin at both ends motor driving apparatus, wherein a is provided.   The motor drive device according to claim 1, wherein the fins of the heat sink have the thickest fins at both ends and the thicknesses of the other fins are not uniform. A semiconductor module that repeatedly switches on and off current or voltage; a smoothing capacitor that smoothes a surge generated by switching of the semiconductor module; a heat sink that dissipates heat generated from the semiconductor module and fixes the smoothing capacitor; And a cover that covers the semiconductor module and the smoothing capacitor and is attached to the heat sink. The smoothing capacitor has an electrode that vibrates when a charge is taken in and out, and is fixed so that the vibration is transmitted to the heat sink. The heat sink has a plurality of fins, and among the plurality of fins, the fins at both ends have a fin height higher than the fins on the inner side, and chamfered portions are provided at the root portions of the fins at both ends. The motor drive device characterized by the above-mentioned.   The motor drive device according to claim 3, wherein the fins of the heat sink have the highest fins at both ends, and the other fins have nonuniform heights. A semiconductor module that repeatedly switches on and off current or voltage; a smoothing capacitor that smoothes a surge generated by switching of the semiconductor module; a heat sink that dissipates heat generated from the semiconductor module and fixes the smoothing capacitor; And a cover that covers the semiconductor module and the smoothing capacitor and is attached to the heat sink. The smoothing capacitor has an electrode that vibrates when a charge is taken in and out, and is fixed so that the vibration is transmitted to the heat sink. is, the heat sink has a plurality of fins, the fins of the heat sink, the air flow direction, the most wider across the fins, together with the other of the width of the fin is narrow Kunar so, both ends of the fin provided chamfer of the root portion Motor driving apparatus according to claim and. Chamfered portion provided at the base portion of the fin at both ends of the heat sink, the motor driving apparatus according to any one of claims 1-5, characterized in that provided on the entire base of the fin. Chamfered portion provided at the base portion of the fin at both ends of the heat sink, the motor driving apparatus according to any one of claims 1 5, characterized in that provided on a part of the root portion of the fin.   The motor driving device according to any one of claims 1 to 7, wherein a corrugated portion having a wave shape is provided on a surface of a fin of the heat sink.   The motor drive device according to any one of claims 1 to 7, wherein a thick weight portion that becomes a weight is provided in a part of the fin of the heat sink.   The motor driving device according to any one of claims 1 to 7, wherein unevenness is provided on a surface of the fin of the heat sink.