JP2008252975A - Power conversion device and cooling structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion device and cooling structure which perform cooling so that semiconductor elements are aligned in the same temperatures while effectively cooling a switching element so that a temperature of the switching element does not exceed a limit. <P>SOLUTION: The device includes the switching element 7, and a cooling medium passage 5 which is positioned along the switching element, and makes a cooling medium for cooling the switching element flow. The cooling medium passage has a flow-in part 32 formed at a wall face at the opposite side of the switching element so as to make the cooling medium flow from the outside toward a corresponding region of the switching element. <P>COPYRIGHT: (C)2009,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 is increasing rapidly because the mileage per unit fuel is higher than that of engine vehicles. Since a large amount of power is supplied to a motor for 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, to cool a power semiconductor device, a meandering coolant passage is formed of copper, a thin plate of molybdenum (coefficient of thermal expansion close to that of a semiconductor) is pasted thereon, and a semiconductor element is disposed on the molybdenum thin plate. A flat liquid cooling structure is disclosed (Patent Document 1). According to this liquid cooling structure, heat generated in the semiconductor element can be efficiently released to the outside through copper or molybdenum having high thermal conductivity. In addition, trouble caused by a difference in thermal expansion between the semiconductor element and its mounting surface is also suppressed.
Japanese Patent Laid-Open No. 11-121668

  However, in the above liquid cooling structure, the cooling liquid meanders, so that a temperature difference occurs between the inlet side and the outlet side of the cooling liquid passage. That is, since the temperature of the coolant gradually increases due to the heat radiated from the semiconductor element, the temperature of the coolant differs between the vicinity of the inlet and the vicinity of the outlet. For this reason, the on-resistance values of the plurality of semiconductor elements differ between the semiconductor element at the position corresponding to the vicinity of the entrance and the semiconductor element at the position corresponding to the vicinity of the exit. As a result, the operation becomes electrically unbalanced, and the lifetime of the semiconductor element is also biased depending on the arrangement position.

  In addition, switching elements used in power conversion devices for automobile motors are miniaturized as performance improves year by year, and a large current concentrates on the miniaturized elements, so that heat generation also protrudes locally. 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 above-described conventional cooling structure identifies the location where the switching element is disposed and the non-arranged location where the switching element is not disposed, and continuously cools the adjacent disposed location and the non-arranged location in the same manner. is doing. 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.

  The present invention is a heat generation structure in which switching elements, which are extremely large heat generation points, are discretely arranged, and can be efficiently cooled while suppressing pressure loss so that the temperature of the switching elements does not exceed the limit. An object of the present invention is to provide a cooling structure and a power conversion device using the same, which can perform cooling so that the temperatures of the semiconductor elements are uniform when a plurality of semiconductor elements are arranged.

  The power conversion device according to the present invention includes a switching element that performs a switching operation, and a cooling medium path that is positioned along the switching element and allows a cooling medium that cools the switching element to flow. The cooling medium path has an inflow portion for allowing the cooling medium to flow from the outside toward the corresponding region of the switching element on the opposite wall surface of the switching element.

  According to the above configuration, the cooling medium is directly fed into the corresponding region of the switching element from the outside, and is cooled so as to collide with the wall surface of the corresponding region. For this reason, since the cooling medium whose temperature has not risen hits the switching element corresponding region, the thermal resistance is greatly reduced, the heat dissipation is greatly improved, and a strong cooling effect can be obtained. Since the cooling is aimed at the switching element corresponding region and individually and locally strongly cools, the temperature rise of the switching element can be surely suppressed.

  In addition, since the cooled refrigerant flows directly into the corresponding region from the outside without performing heat exchange in the cooling medium path, the temperature difference between the switching elements is reduced, and the temperatures of the switching elements are easily aligned. . For this reason, the ON resistance values of a plurality of semiconductor elements are aligned and electrically balanced, and the lifetimes of the semiconductor elements are aligned regardless of the position.

  Note that the corresponding region of the switching element is a wall surface of the cooling medium path on the switching element side when one switching element is a target, and is an area overlapping the switching element when seen in a plan view. Further, when several units each having a group of switching elements are arranged, the corresponding region may be considered by regarding the unit of a plurality of groups of switching elements as a single switching element. However, even in the latter case, a corresponding region may be defined for each switching element. Further, the positioning along the switching element may include a mounting board on which the switching element is mounted, or may be a form in which a heat sink or a housing wall is further interposed under the mounting board. The cooling medium path may be structured in a housing.

  The cooling medium path may have radial fins extending radially from the center of the corresponding region of the switching element on the inner surface on the switching element side. With this configuration, it is possible to smoothly flow the cooling medium directed from the inflow portion toward the switching element corresponding region radially outward from the center of the switching element corresponding region. For this reason, the heat dissipation effect of the radial fins arranged in the switching element corresponding region can be obtained for each switching element corresponding region. As a result, the powerful heat dissipation can be further improved.

  In addition, a plurality of the above switching elements may be mounted on the mounting board, the cooling medium path may be located along the mounting board, and the cooling medium path may have a configuration having an inflow portion for each corresponding region of the switching element. it can. According to this configuration, the plurality of switching elements are directly cooled by the cooling medium from the inflow portion for each corresponding region. For this reason, since the temperature of the cooling medium in each inflow portion can be made the same while locally obtaining a strong cooling effect for each switching element corresponding region, it is easy to make the temperatures of the respective switching elements uniform. As a result, the on-resistance values of the switching elements can be made uniform, the electrical balance can be maintained, and the element lifetime can be made uniform regardless of the position. Note that “positioning along the mounting substrate” includes a form in which a heat sink or the like is interposed under the mounting substrate. The cooling medium path may be built in the housing of the switching element module.

  The cooling medium path may have a structure in which the inflow part or the outflow part from which the refrigerant flowing in from the inflow part flows out is embedded in a wall forming the cooling medium path. With this configuration, predetermined cooling can be realized without impairing space utilization efficiency, and a flat portion can be widened on the outer surface of the bottom of the cooling medium path, so that other devices such as converter semiconductor elements for air conditioners are arranged. And it becomes easy to cool. In other words, the power conversion device for an automobile motor is often placed in a stack with other device modules. In this case, the pipe connected to the inflow portion or the outflow portion is disposed in a direction intersecting the mounting substrate. Then, although space utilization efficiency may be impaired, at least one of the inflow portion and the outflow portion that flows out the refrigerant flowing in from the inflow portion as described above is embedded in the wall forming the cooling medium path. High space utilization efficiency can be ensured by the structure.

  In the cooling medium path, another element different from the switching element may be arranged on the flat portion of the outer surface on the opposite side of the switching element. With this configuration, elements other than the power conversion switching elements can be arranged and cooled on the outer surface on the opposite side, the cooling device can be used effectively, and the space utilization efficiency can be increased.

  The cooling structure of the present invention includes a cooling medium path that is positioned along a flat plate-like component to be cooled and that flows a cooling medium that cools the component to be cooled. The cooling medium path has an inflow portion for allowing the cooling medium to flow from the outside toward the corresponding region of the component to be cooled on the wall surface on the opposite side of the component to be cooled.

  According to the above configuration, the cooling medium is directly fed into the corresponding region of the component to be cooled from the outside, and is cooled so as to collide with the corresponding region wall surface. For this reason, since the cooling medium that does not undergo heat exchange in the cooling medium path hits the corresponding region, the thermal resistance is greatly reduced, the heat dissipation is greatly improved, and a strong cooling effect can be obtained. Since the cooling is aimed at the corresponding region of the component to be cooled and is individually and locally strongly cooled, the component to be cooled can be reliably cooled. In addition, since the refrigerant flows into the corresponding region of the component to be cooled while being cooled without undergoing heat exchange in the cooling medium path, the performance of the component to be cooled can be made uniform.

  Note that the corresponding region of the component to be cooled is a wall surface region of the cooling medium path on the component to be cooled side that overlaps the component to be cooled in plan view when one component to be cooled is targeted. Further, when a structure in which several units of a plurality of parts to be cooled are arranged is targeted, a plurality of the parts to be cooled are regarded as one part to be cooled and the corresponding region. There are also cases where However, even in the latter case, the corresponding area may be determined for each piece of component to be cooled. In addition, the positioning along the component to be cooled includes a mounting substrate on which the mounting substrate is mounted, and includes a form in which a heat sink and a housing wall are further interposed under the mounting substrate. The cooling medium path may be structured in a housing including a heat sink.

  The cooling medium path may have radial fins extending radially from the center of the corresponding region of the component to be cooled on the inner surface of the component to be cooled. With this configuration, it is possible to smoothly flow the cooling medium flowing in from the inflow portion radially outward from the center of the corresponding region of the component to be cooled. For this reason, the heat dissipation effect of the radial fins arranged in the corresponding region of the component to be cooled can be obtained individually and locally for each corresponding region of the component to be cooled. As a result, the powerful heat dissipation can be further improved.

  A plurality of the components to be cooled are mounted on the mounting board, the cooling medium path is located along the mounting board, and the cooling medium path can have an inflow portion for each corresponding region of the cooled component. According to this configuration, the plurality of parts to be cooled are directly cooled by the cooling medium from the inflow portion for each corresponding region. For this reason, since the temperature of the cooling medium in each inflow portion can be made the same while locally obtaining a strong cooling effect for each corresponding region of the component to be cooled, it is easy to equalize the temperature of each component to be cooled. As a result, the ON resistance values of the components to be cooled can be made uniform, the electrical balance can be maintained, and the device life can be made uniform regardless of the position. Note that “positioning along the mounting substrate” includes a form in which a heat sink or the like is interposed under the mounting substrate. The cooling medium path may be built in a casing of a module for a component to be cooled that incorporates a heat sink.

  The cooling medium path may have a structure in which at least one of the inflow part and the outflow part from which the refrigerant flowing in from the inflow part flows out is embedded in the wall forming the cooling medium path. With this configuration, predetermined cooling can be realized without impairing space utilization efficiency, and a flat portion can be widened on the outer surface of the bottom of the cooling medium path, so that other devices such as converter semiconductor elements for air conditioners are arranged. And it becomes easy to cool.

  The cooling medium path may have a flat portion for disposing another element different from the switching element on the outer surface on the opposite side of the component to be cooled. With this configuration, components other than the component to be cooled for power conversion can be arranged and cooled on the outer surface on the opposite side, the cooling device can be used effectively, and the space utilization efficiency can be increased.

  According to the power conversion device and the cooling structure of the present invention, in the heat generation structure in which the switching elements are discretely arranged, the temperature of the switching elements is efficiently cooled while suppressing the pressure loss so as not to exceed the limit. When a plurality of semiconductor elements are arranged, it is possible to perform cooling so that the temperature of each semiconductor element is uniform.

  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 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 5 through which a cooling medium flows is provided below the heat radiating plate 3 so as to be in contact with the heat radiating plate 3. An ethylene glycol aqueous solution that is an antifreeze can be used as the cooling medium. The cooling medium path 5 may be formed as a part of the casing 31 of the switching element module. Next, the power conversion device or the cooling structure according to the embodiment of the present invention will be described according to the first to fourth embodiments.

(Embodiment 1)
2 and 3 are diagrams for explaining a cooling structure according to Embodiment 1 of the present invention. 2 is a longitudinal sectional view, and FIG. 3 is a bottom view as seen from the bottom side of the switching element 7 on the opposite side. The embodiment of the present invention is characterized in that the inflow portion 32 is formed by an inflow pipe through which a refrigerant flows from the outside. The cooling medium path 5 may be built in the casing 31 of the switching element module. By this inflow portion 32, the refrigerant is pushed out to the wall surface on the switching element corresponding region side while being cooled by the cooling device, and collides with the wall surface. Fins 11 extending radially are provided in the switching element corresponding region, and are guided to the fins 11 and flow outward from the switching element corresponding region. The vortex generated one after another with the inflow of the cooling medium flows out one after another with the heat generated in the switching element. The fins 11 are desirably manufactured by integral molding with the heat sink 3. However, the part of the corresponding region of the heat sink is a separate part, and the fin 11 is formed in the separate part by integral molding, and the separate part is fitted into the corresponding part (as a hole) of the heat sink to connect the edges. It may be formed by welding.

  Since the cooling medium immediately after being cooled as described above flows along the corresponding region wall surface 5a with a high eddy current density, it is possible to aim at the switching element corresponding region and improve the heat dissipation of the region. In addition, since the cooled refrigerant flows from the outside, the temperature difference between the switching elements becomes small, and the temperatures of the switching elements are easily aligned. For this reason, the ON resistance values of a plurality of semiconductor elements are aligned and electrically balanced, and the lifetime of the semiconductor elements is aligned regardless of the arrangement position. Further, as shown in FIG. 2, a flat portion 25 is provided between the pipes connected to the outflow portion 32 on the outer surface of the bottom portion of the cooling medium passage, and another device, for example, a semiconductor element for an air conditioner is disposed here for cooling. Can do.

  Moreover, the overall pressure loss can be suppressed by sufficiently increasing the sum of the caliber areas of all the inflow portions 32 and the sum of the caliber areas of all of the outflow portions 33. Four outflow portions 33 are arranged so as to surround one switching element 7. For this reason, it is possible to smoothly discharge the refrigerant while suppressing pressure loss. Further, since the refrigerant is mainly used for cooling one switching element and reaches the outflow portion 33, the temperature rise can be suppressed low.

(Embodiment 2)
FIG. 4 is a top view for explaining the cooling structure in the second embodiment of the present invention. In this embodiment, two single group of switching elements 7a, 7b is regarded as one switching element, there is a feature at the point set of the switching elements corresponding area A _1. Inlet 33 arranged to be positioned in the center of the switching elements corresponding area A _1. Also, outlet portion 33, so as to surround the periphery of the switching element corresponding region A _1, to four arrangement.

By defining the switching element corresponding area A ₁ (area including two switching elements) as described above and arranging _one inflow portion with respect to the A ₁ , the number of parts and manufacturing man-hours are reduced, and the manufacturing cost is suppressed. can do. In addition, heat dissipation can be maintained at a level comparable to that of the first embodiment.

(Embodiment 3)
5 and 6 are diagrams for explaining a cooling structure according to Embodiment 3 of the present invention. FIG. 5 is a side view, and FIG. 3 is a bottom view as seen from the bottom side of the switching element 7 on the opposite side. The embodiment of the present invention is characterized in that the inflow portion 52 and the outflow portion 53 are provided so as to be embedded in the casing 31 or the heat sink 3.

  In many cases, power conversion devices for motors for automobiles are stacked with other device modules, and in that case, when piping connected to an inflow portion or an outflow portion is disposed in a direction intersecting the mounting substrate. , There is a risk of harming space utilization efficiency. However, as shown in FIGS. 5 and 6, according to the configuration in which the pipe is connected to the side portion of the mounting substrate, predetermined cooling can be realized without impairing the space utilization efficiency. In particular, in the present embodiment, the flat portion 25 can be widened on the outer surface of the bottom of the cooling medium passage, so that it is easy to cool by arranging another device such as a converter semiconductor element for an air conditioner.

(Embodiment 4)
FIG. 7 is a top view seen from the switching element side for explaining the cooling structure in the fourth embodiment of the present invention. In the present embodiment, as in the second embodiment, the two switching elements 7a and 7b are regarded as one switching element, and the switching element corresponding region (range A ₁ to ensure the simplicity of FIG. 7). Is not described), and in the same manner as in the third embodiment, the inflow portion 53 and the outflow portions 53 and 54 are embedded in the housing 31 and the like.

Inlet 33 arranged to be positioned in the center of the switching elements corresponding area A _1. Also, outlet portion 33, so as to surround the periphery of the switching element corresponding region A _1, to four arrangement. For this reason, the heat dissipation can be maintained at a level comparable to that of the first embodiment while reducing the number of parts and the number of manufacturing steps and suppressing the manufacturing cost. Further, with the configuration in which the pipe is connected to the side portion of the mounting substrate, predetermined cooling can be realized without impairing space utilization efficiency.

  Since the cooling medium immediately after being cooled as described above flows along the corresponding region wall surface 5a with a high eddy current density, it is possible to aim at the switching element corresponding region and improve the heat dissipation of the region. In addition, since the cooled refrigerant flows from the outside without undergoing heat exchange in the cooling medium path, the temperature difference between the switching elements is reduced, and the temperatures of the switching elements are easily aligned. For this reason, the ON resistance values of a plurality of semiconductor elements are aligned and electrically balanced, and the lifetime of the semiconductor elements is aligned regardless of the arrangement position.

  Moreover, the overall pressure loss can be suppressed by sufficiently increasing the sum of the caliber areas of all the inflow portions 32 and the sum of the caliber areas of all of the outflow portions 33. Four outflow portions 33 are arranged so as to surround one switching element 7. For this reason, it is possible to smoothly discharge the refrigerant while suppressing pressure loss. Further, since the refrigerant is mainly used for cooling one switching element and reaches the outflow portion 33, the temperature rise can be suppressed low.

  Although the first to fourth embodiments of the present invention have been illustrated and described, the present invention should not be limited to the exemplification of the first to fourth embodiments. For example, although the inflow part illustrated the shape which does not protrude from a wall surface, the shape which a pipe line protrudes in the cooling medium path from the said wall surface may be sufficient.

  In short, what is necessary is just to aim at a switching element corresponding | compatible area | region and to make a refrigerant | coolant flow in from an inflow part. In other words, in the present invention, the aim is to suppress the temperature rise of the switching element without excessively increasing the size of the cooling structure device by providing an inflow portion aiming at the switching element corresponding region. . For both the switching element corresponding region and the non-corresponding region, the same increase in heat dissipation results in an excessively large device and is incompatible with the present invention. In addition, when a plurality of switching elements are grouped as a unit and a plurality of units of switching elements are arranged, the range of “corresponding region of switching elements” is appropriately expanded so that one unit is The inflow portion can be arranged by being interpreted as a switching element.

  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 and the cooling structure of the present invention, a switching element or a component to be cooled, which is a large heating element, is aimed and an outflow portion is provided so as to enhance heat dissipation in the corresponding region. It is difficult to occur, and the temperature rise of the switching element or the component to be cooled can be efficiently suppressed.

It is a figure which illustrates the power converter device in embodiment of this invention. It is a figure which shows the cooling structure in Embodiment 1 of this invention. It is the bottom view which looked at the cooling structure of FIG. 2 from the downward direction. It is a figure which shows the cooling structure in Embodiment 2 of this invention. It is a figure which shows the cooling structure in Embodiment 3 of this invention. It is the bottom view which looked at the cooling structure of FIG. 5 from the downward direction. It is a figure which shows the cooling structure in Embodiment 4 of this invention.

Explanation of symbols

3 heat sink, 5 cooling medium path (flow path), 7 switching element, 7a IGBT (switching element), 7b reflux diode (switching element), 7c switching element, 10 power converter, 11 fin, 25 bottom of cooling medium path Flat portion of the outer surface of the wall, 31 housing, 32 inflow portion, 33 outflow portion, 52 inflow portion, 52a inflow port, 53 outflow portion (end side), 54 outflow portion (central portion), 31 housing, A ₁ switching Element corresponding area.

Claims (6)

A switching element for performing a switching operation;
A cooling medium path that is positioned along the switching element and that flows a cooling medium that cools the switching element;
The power conversion device according to claim 1, wherein the cooling medium path has an inflow portion for allowing the cooling medium to flow from the outside toward a corresponding region of the switching element on a wall surface on the opposite side of the switching element.   2. The power conversion device according to claim 1, wherein the cooling medium path includes radial fins extending radially from a center of a corresponding region of the switching element on an inner surface on the switching element side.   A plurality of the switching elements are mounted on a mounting board, the cooling medium path is located along the mounting board, and the cooling medium path has the inflow portion for each corresponding region of the switching element. The power conversion device according to claim 1 or 2.   The said cooling medium path has embed | buried the outflow part which flows out the said inflow part or the refrigerant | coolant which flowed in from the inflow part in the wall which forms the said cooling medium path, The Claims 1-3 characterized by the above-mentioned. The power converter in any one.   5. The power conversion device according to claim 1, wherein the cooling medium path includes another element different from the switching element in a flat portion of an outer surface on the opposite side of the switching element. A cooling medium path is provided along a flat plate-shaped component to be cooled, and a cooling medium path for flowing a cooling medium for cooling the component to be cooled is provided.
The cooling structure according to claim 1, wherein the cooling medium path has an inflow portion for allowing the cooling medium to flow from the outside toward a corresponding region of the component to be cooled on a wall surface on the opposite side of the component to be cooled.

Images