JP2007250673A - Power converter and cooling structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter where cooling is performed so that a temperature of an element does not exceed a limit in a heat generation structure in which a switching element in a large heat generation part is arranged. <P>SOLUTION: The power converter is provided with a plurality of switching elements 7 performing a switching operation, a switching element cooler where a cooling medium cooling the switching element flows, and at least one rotation body 11 which is positioned in a passage 5 of the cooling medium of the switching element cooler and can be rotated around a pivot 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power conversion device and a cooling structure, and more particularly to a power conversion device and a cooling structure for an automobile motor.

Engines have been overwhelmingly used in automobiles, but electric cars and hybrid cars have attracted attention, especially against the backdrop of soaring fossil fuels and the suppression of CO ₂ emissions to prevent global warming. The number of hybrid vehicles has increased dramatically since the mileage per unit fuel is higher than that of engine vehicles. Since a large amount of electric power is supplied to a motor of an automobile such as a hybrid vehicle, the power conversion device also handles a large amount of power, and it is necessary to reduce power loss of the power conversion device itself and perform efficient power conversion. For this reason, a semiconductor device that operates as a switch that repeatedly turns on and off power, that is, a switching element is used in the power conversion device. Since the switching element has zero voltage in the on state and zero current in the off state, the power consumption is zero if there is no time lag between the on / off voltage and current. However, since a time lag actually occurs, the power consumption of the switching element is not zero, and heat is generated as a loss. In a power conversion device for driving a motor and regenerating power mounted in an electric vehicle such as a hybrid vehicle or a fuel cell vehicle, the above-described thermal problem has become serious as the battery has a large capacity and high-speed switching.

The temperature rise of the semiconductor element is not limited to power converters for automobile motors, and has been a problem for a long time, and many efforts have been made. For example, a structure in which a baffle plate for generating turbulent flow is attached so that the airflow does not pass straight through the gap between the fins in order to improve the heat dissipation of the parallel fins used for heat dissipation of the semiconductor device, Or the structure of the cylindrical fin of a staggered arrangement is disclosed (patent document 1). According to this structure, a turbulent flow is generated by the baffle plate or the staggered columnar fins attached obliquely, and the heat dissipation effect can be enhanced.
JP 2001-345585 A

  However, the switching element used in the power conversion device for an automobile motor is miniaturized as the performance improves year by year, and a large current concentrates on the miniaturized element. Take. For this reason, the conventional cooling structure as described above cannot take an appropriate measure. That is, in a heat generation structure in which very large heat generation points (switching elements) are discretely and locally arranged, the structure is not effectively cooled so that the temperature of the switching elements does not exceed the limit. In other words, the higher-order conventional cooling structure identifies the switching element placement location and the non-placement location where the switching element is not placed in the same manner, and makes adjacent switching element placement locations and non-placement locations continuously the same. It is cooling. For this reason, the cooling technology has not yet sufficiently coped with the heat generation characteristic peculiar to the switching element in the power conversion device for an automobile motor.

  INDUSTRIAL APPLICABILITY The present invention relates to a power conversion device capable of efficiently cooling a heating structure in which a switching element, which is a very large heating point, is arranged, so that the temperature of the switching element does not exceed the limit, and is used therein. An object is to provide a cooling structure.

  The power conversion device of the present invention is located in the cooling medium flow path of the switching element cooling section, the switching element cooling section in which a plurality of switching elements that perform the switching operation, the cooling medium that cools the switching elements flows, and the switching element cooling section. And at least one rotating body rotatable about an axis.

  With the above configuration, the rotating body rotates according to the flow rate of the cooling medium, the cooling medium is dispersed by centrifugal force, and a turbulent flow state is generated, so that the heat dissipation effect can be improved. As a result, the temperature rise of the switching element can be suppressed, the on-resistance of the switching element can be reduced, and the loss of the power conversion device can be reduced.

  Said rotary body can be arrange | positioned for every corresponding | compatible area | region of a switching element. Here, the corresponding region of the switching element refers to a region of the cooling medium path that overlaps with the switching element in plan view when one switching element is targeted. However, when a group of a plurality of switching elements are targeted, the area corresponding to the place where the group of switching elements is arranged is indicated. With the above configuration, since the rotating body is arranged for each switching element corresponding region, aiming at the switching element, the rotating body causes dispersion of the cooling medium and generation of a vortex (occurrence of a turbulent flow state), It is possible to efficiently suppress the temperature rise of the individual switching elements arranged discretely.

  The rotator may have a wing portion extending radially from the support shaft. With this configuration, the flow energy of the cooling medium can be received with high sensitivity, and the cooling medium can be dispersed and the vortex can be generated efficiently.

  The surface of the wing portion may have an oblique intersection surface portion that obliquely intersects the surface on which the switching element is disposed. With this configuration, the oblique crossing surface portion of the rotation band gives the cooling medium a velocity component in the crossing direction toward the element side wall surface on which the switching element is disposed or in the crossing direction away (direction toward the element facing side wall surface). can do. The cooling medium obtains the velocity component in the intersecting direction, prevents the formation of laminar flow (low heat transfer) on the element side wall surface of the cooling medium path, and makes it easy to generate vortex. Since eddy currents frequently occur and leave on the wall surface on the switching element side, the eddy current is excellent in heat transfer and can effectively suppress the temperature rise of the switching element. The oblique crossing surface portion may be any surface as long as it can give the cooling medium a speed component in a direction intersecting the element side wall surface, and may be a flat surface or a curved surface (concave surface, convex surface, etc.).

  The rotating body may have a water wheel structure. With this configuration, it is possible to efficiently utilize the flow energy of the cooling medium, disperse the cooling medium in the switching element corresponding region, and promote the vortex generation, that is, the turbulent flow state. Here, any turbine structure such as a Berton turbine, a Francis turbine, a mixed flow (Delia) turbine, a propeller (Kaplan) turbine, or a tubular (valve) turbine can be used as the turbine structure.

  In addition, the above rotating body can be formed of a resin material. As a result, the rotating body can be reduced in weight and can be easily rotated by the flow of the cooling medium, and as a result, the dispersion of the cooling medium and the promotion of eddy current generation can be ensured. Moreover, corrosion resistance can be improved compared with the case where it is metal. Any resin material may be used, but a lightweight resin is more preferable.

  Further, the rotating body may be formed of a resin material subjected to DLC (Diamond Like Carbon) coating. As a result, the wear resistance can be improved, the coefficient of friction can be further reduced, and as a result, the pressure loss can be reduced.

  Further, another element can be further provided on the outer surface of the cooling medium flow path facing the switching element. With this configuration, the other elements can be arranged on the outer surface on the element facing side to be cooled, and space utilization efficiency can be improved. The other element may be an element having a switching action.

  The cooling structure of the present invention includes a cooling section through which a cooling medium for cooling a component to be cooled flows, and at least one rotating body that is positioned in the flow path of the cooling medium in the cooling section and is rotatable around a support shaft. It is characterized by.

  With the above configuration, the rotating body rotates according to the flow rate of the cooling medium, the cooling medium is dispersed by centrifugal force, and a turbulent flow state is generated, so that the heat dissipation effect can be improved. As a result, the temperature rise of the component to be cooled can be suppressed.

  FIG. 1 is a diagram for explaining a power exchange device according to an embodiment of the present invention. This power conversion device 10 has a U-phase terminal, a V-phase terminal, and a W-phase terminal that are terminals for a motor of a hybrid vehicle, and also has a + terminal and a − terminal that are terminals for a generator. The switching element 7 includes motor switching elements 7a and 7b and a generator switching element 7c. The motor switching element includes an IGBT (Insulated Gate Bipolar Transistor) 7a and a reflux diode 7b. The freewheeling diode is a diode disposed in parallel with a load (not shown) including an inductance, and is used for leveling the load current. In the description of the embodiment of the present invention, although not strictly a switching element, a semiconductor element used in the same circuit as the switching element is also called a switching element. These switching elements 7a, 7b, and 7c are mounted on a mounting board (not shown), and the heat sink 3 is disposed under the mounting board. The switching element 7, the mounting board, and the like are housed in a housing 31. A control signal mounting board (not shown) on which a semiconductor element or the like for controlling the gate signal of the switching element is mounted on the switching element 7 with an insulating plate interposed therebetween is disposed in the casing 31. A cooling medium path (flow path) 5 through which a cooling medium flows is provided under the heat radiating plate 3 so as to be in contact with the heat radiating plate. The cooling medium path 5 may be formed as a part of the casing 31 of the switching element module. An ethylene glycol aqueous solution that is an antifreeze can be used as the cooling medium.

(Embodiment 1)
FIG. 2 is a schematic diagram for explaining the cooling structure of the power conversion device according to the embodiment of the present invention (a back view when the switching element is viewed from the back side). In FIG. 2, the cooling medium flows from the inlet 37 toward the outlet 38 to form a central flow _Fo . The rotating body 11 is disposed directly below the switching element 7. In the rotor 11, is fixed to the wing fixing portion 13, the wing portions 12 extending out radially, with the biasing force of the central flow F _o, rotates about the support shaft 14.

By this rotation, the cooling medium mainly generates an H flow component parallel to the wall surface of the cooling medium passage, but a component that intersects the H flow component at the width end (edge) of the blade portion (an N flow component described later). And a flow with S flow component). The flow of the H flow component is sufficiently generated not only at the central flow portion but also at the end portion E, so that the entire switching element can be cooled. At the end E, the coolant flows in a direction opposite to the flow direction of the central flow _Fo by driving the rotating body 11. The blade portion 12 may have a width (height range) that covers the entire thickness of the cooling medium path 5. For example, when the support shaft 14 is fixed to the element side wall surface of the cooling medium path, switching is performed. It is sufficient to cover the cooling medium path close to the element side.

  FIG. 3 is a diagram illustrating a modification of the power conversion device in FIG. 2. In the case of the power conversion device of FIG. 3, one rotating body 11 is arranged corresponding to the plurality of switching elements 7 a and 7 b. For example, the switching elements 7a and 7b and the rotating body 11 form a crystal group in the crystal, and the switching elements 7a and 7b and the rotating body 11 are repeatedly arranged in the power converter. The switching element corresponding region can be considered as one unit pattern region in a repeated arrangement, such as the crystal group region.

  The wing portion 12 of the rotating body 11 is preferably formed of resin. Especially, it is good to form with a lightweight resin. This is because it easily rotates with the energy of the flow of the cooling medium, and the pressure loss can be reduced. The specific gravity of the resin itself ranges from 0.83 for polymethylpentene to 2.1 for tetrafluororesin, but is about 0.04 for foamed materials, and about 3 for heavy materials such as minerals or metals. can do. Any of these resins may be used, but the specific gravity is preferably 2.0 or less. Moreover, it is good to set it as the material fully equipped with corrosion resistance and heat resistance (a cooling medium may be 150-250 degreeC). Polyimide resin, polyamide resin, polyamide imide resin, polyether imide resin, polyether sulfone resin, polyphenylene sulfide resin and the like having good heat resistance are preferable. However, these resins are made of graphite and silica to improve strength and heat resistance. Alternatively, a resin filled with a filler such as may be used. Other fillers such as graphite and silica, or unfilled resins can be used.

Further, the flow rate of the cooling medium is usually 7 to 8 liters / minute, but it may be more or less. Further, the wing portion may be flat or curved, and in the case of a curved surface, the wing may be curved concavely toward the flow. Pressure loss can also be reduced by mirror finishing the wing portion.

  In particular, the surface layer of the wing portion is preferably DLC (Diamond-like-carbon) coated. This is because the corrosion resistance and wear resistance can be improved by the DLC coating treatment, the friction coefficient can be further reduced, and the pressure loss can be reduced. In the case of a resin to be subjected to DLC coating treatment, the resin is preferably conductive. The DLC coating is formed by an ion plating method that is a plasma process in a high vacuum. First, benzene gas or other hydrocarbon gas is introduced into the vacuum chamber, and hydrocarbon ions and excited radicals are generated in DC arc discharge plasma. The hydrocarbon ions collide with the material to be coated (in this case, the blade portion) biased to a negative DC voltage with energy corresponding to the bias voltage, and are solidified to form a film. Since non-equilibrium plasma is used, the substrate temperature during film formation is usually 200 ° C. or lower. Since the DLC coating film has an amorphous structure, the DLC coating film does not have a crystal grain boundary and has a very smooth surface compared to a hard thin film having a polycrystalline structure. As a result, the friction coefficient with the cooling medium can be reduced, and the pressure loss can be suppressed.

(Embodiment 2)
FIG. 4 is a diagram for explaining a cooling structure of the power conversion device according to Embodiment 2 of the present invention. FIG. 4A is a partial cross-sectional view seen from the central flow side, and FIG. 4B is a plan view. The present embodiment is characterized in that the blade portion 12 is inclined so as to intersect the wall surfaces 5a and 5b of the cooling medium passage. In other words, the wing portion 12 has an oblique intersection surface portion that obliquely intersects the surface on which the switching element is disposed. The rotating body 11 has a support shaft root portion 14b fixed to the element facing side wall surface 5b, and the wing portion 12 is rotatably supported by a bearing portion 14a including a bearing (not shown). In the wing portion W ₁ of the central flow side F _o of the wing portions 12, the front end edge a is farther than the element-side wall surface 5a, it is inclined in a direction such trailing edge b is a position closer than the front end side to the device side wall 5a Yes. Also, the wing parts W _2, in the relationship between the front end and the rear end, has the same inclination as the wing portion W _1.

When the rotating body 11 rotates in the arrangement shown in FIG. 4B, first, an H flow component is generated, and accordingly, as shown in FIG. 4A, the N flow component toward the element side wall surface 5a. Occurs in both wing portions W ₁ and W ₂ . For this reason, formation of laminar flow with low heat transfer can be prevented on the element side wall surface 5a, and generation and separation of eddy currents on the element side wall surface 5a can be promoted. As a result, the heat transfer is improved and the switching element is improved. Temperature rise can be suppressed. In FIG. 4A, another element (an element having a switching action) 17 may be disposed on the outer surface of the element facing side wall 5b for cooling. This is because the space utilization efficiency can be increased while suppressing the temperature rise of the element 17. Note that the N flow component shows only the velocity component toward the element side wall surface 5a. However, in actuality, in addition to this, an emergency flow such as a flow that wraps around the rotating blade portion or a vortex flow that separates from the flow on the rear side. A complicated flow appears, and the flow including such a complicated flow is represented by “N flow component” and “arrow”. The same applies to the S flow component. The N flow component (S flow component) appearing in the following description represents such an actual complicated flow unless otherwise specified.

FIG. 5 is a diagram showing a modification of the cooling structure of the power conversion device of FIG. FIG. 5A is a partial cross-sectional view seen from the central flow side, and FIG. 5B is a plan view. W _1, W ₂ of the airfoil portion 12 of the rotating body 11 shown in FIG. 5 together than the wing portions 12 shown in FIG. 4, the inclination of the front and rear ends are opposite with respect to the direction of rotation. For this reason, the rotation of the blade portion 12 generates an H flow component and a flow component (S flow component) in the cross direction toward the element facing sidewall surface 5b in both W ₁ and W ₂ of the blade portion 12.

Also by the above S flow component, the formation of a laminar flow along the element side wall surface 5a can be suppressed. On the element side wall surface 5a, vortex flows are generated one after another after the separating vortex flow, heat removal proceeds smoothly, and the temperature rise of the switching element is suppressed.

FIG. 6 is a view showing a modification of the cooling structure shown in FIGS. 4 and 5. FIG. 6A is a partial cross-sectional view seen from the central flow side, and FIG. 6B is a plan view. W _1, W ₂ of the airfoil portion 12 of the rotating body 11 shown in FIG. 6 is a single plate-like vanes are integrally formed. That is, the support shaft is arranged at the center of the inclined plate. For this reason, the inclination of the front end and the rear end is reversed in the rotation direction between W ₁ and W _{2 of} the blade portion 12. Therefore, as shown in FIG. 6, when the by W ₁ produces the N flow component causes a W ₂ in S flow component, also when producing S flow component by W _1, resulting in W ₂ in N current component.

  It is preferable that the support shaft base portion 14b and the bearing portion 14a of the rotating body 11 are made of metal in order to ensure inexpensive and strong durability. Further, when the support shaft base portion 14b is fixed to the element side wall surface 5a, heat generated by the switching element can be transmitted, and it functions as a kind of fin, so it is formed of a metal having high thermal conductivity. It is good to do.

  For this reason, in the element side wall surface 5a immediately below the switching element 7, a flow that fluctuates in a complicated manner occurs within the rotation period of the rotating body. In such a complicated flow, eddy currents are frequently generated and separated on the element side wall surface 5a, and a turbulent state with excellent heat transfer can be realized as in the case described above.

(Embodiment 3)
FIG. 7 is a diagram for explaining a cooling structure of the power conversion device according to Embodiment 3 of the present invention. The second embodiment is an example in which the support shaft root portion 14b is fixed to the element facing side wall surface 5b. However, in the present embodiment, the support shaft root portion 14b is fixed to the element side wall surface 5a. Has characteristics. The inclination of the blade portion is the same as in the case of FIG. 4. As the rotating body 11 rotates, both blade portions generate an N-flow component toward the element side wall surface 5 a together with the H-flow component.

  As shown in FIG. 7, in the case where the support shaft base portion 14b is fixed to the element side wall surface 5a, in addition to the action of the N flow component in the structure shown in FIG. . Further, when the support base portion 14b is made of metal, it is possible to obtain an effect of conducting and dissipating heat from the switching element 7.

(Embodiment 4)
FIG. 8 is a diagram for explaining a cooling structure of the power conversion device according to the fourth embodiment of the present invention. According to FIG. 8, for example, even when it is appropriate to provide a partition wall and fold the cooling medium path (flow path), the flow path length can be reduced by providing a rotating body without providing the partition wall. The cooling medium flow at the end E can be ensured by shortening the length. As a result, the temperature rise of the switching element can be suppressed, the pressure loss can be reduced, and the power required for driving the cooling medium can be reduced. Although not shown in FIG. 8, the cooling medium flow guide can be arranged particularly on the inlet side so that the cooling medium flow can apply a sufficient rotational force to the rotating body 11.

  FIG. 9 is a diagram showing a cooling medium path (flow path) having a width W divided by a partition wall 29. By narrowing the flow path, variation in heat dissipation due to the position of the flow path width can be reduced, and the amount of cooling medium can be reduced. However, there is a possibility that an increase in pressure loss occurs due to a reduction in the cross-sectional area of the flow path and an increase in the length of the flow path, and an increase in the temperature difference of the cooling medium between the inlet side and the outlet side of the flow path.

  Although the embodiments and examples of the present invention have been described above, the embodiments and examples of the present invention disclosed above are merely examples, and the scope of the present invention is the implementation of these inventions. It is not limited to the form. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  In the power conversion device of the present invention and the cooling structure used there, a switching element, which is a large heating element, is aimed at, and a rotating body is provided so as to improve heat dissipation in the corresponding region, so that vortex generation and separation of the vortex flow are prevented. Since it accelerates | stimulates, the temperature rise of the switching element can be suppressed very effectively, without impairing pressure loss.

It is a figure explaining the power converter device in embodiment of this invention. It is a figure explaining the cooling medium path in the power converter device in Embodiment 1 of this invention. It is a figure which shows the modification of the cooling structure of the power converter device of FIG. It is a figure explaining the cooling-medium path | route in the power converter device in Embodiment 2 of this invention, (a) is the fragmentary sectional view seen from the center flow side, (b) is a top view. It is a figure which shows the modification of the cooling structure of FIG. 4, (a) is the fragmentary sectional view seen from the center flow side, (b) is a top view. It is a figure which shows the modification of the cooling structure of FIG.4 and FIG.5, (a) is a fragmentary sectional view seen from the center flow side, (b) is a top view. It is a figure which shows the cooling structure of the power converter device in Embodiment 3 of this invention. It is a figure which shows the cooling structure of the power converter device in Embodiment 4 of this invention. It is a figure which shows the modification of the cooling structure of FIG.

Explanation of symbols

3 heat sink, 5 cooling medium path (flow path), 5a element side wall surface, 5b element opposing side wall surface, 7 switching element, 7a IGBT (switching element), 7b reflux diode (switching element), 7c switching element, 11 rotator , 12 blade parts, 13 blade fixing parts, 14 support shafts, 14a bearing parts, 14b support shaft root parts, 17 other elements, 29 partition walls, 31 housing, 37 inlet, 38 outlet, F ₀ central flow, E end Part, a, b The width edge part (edge) of a wing | blade part.

Claims (9)

A plurality of switching elements for performing a switching operation;
A switching element cooling unit through which a cooling medium for cooling the switching element flows;
An electric power converter comprising: at least one rotating body that is positioned in a flow path of a cooling medium of the switching element cooling unit and is rotatable around a support shaft.   The power converter according to claim 1, wherein the rotating body is arranged for each corresponding region of the switching element.   The power converter according to claim 1, wherein the rotating body has a blade portion extending radially from the support shaft.   The power conversion device according to claim 3, wherein a surface of the wing portion has an oblique intersection surface portion that obliquely intersects a surface on which the switching element is disposed.   The power converter according to claim 1, wherein the rotating body has a water wheel structure.   The power converter according to claim 1, wherein the rotating body is made of a resin material.   The power converter according to claim 6, wherein the rotating body is made of a resin material subjected to a DLC (Diamond Like Carbon) coating process.   The power conversion device according to claim 1, further comprising another element on an outer surface of the cooling medium flow path facing the switching element. A cooling unit through which a cooling medium for cooling the component to be cooled flows;
A cooling structure comprising: at least one rotating body that is positioned in a flow path of the cooling medium of the cooling unit and is rotatable around a support shaft.

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