Converter with cooling channel and coolant

Abstract

The invention relates to a converter (7) for converting a fed-in current type into another current type, comprising at least one power module (1) and at least one heat sink (3), the power module (1) and the heat sink (3) being thermally and operatively connected to one another, the heat sink (3) being introduced at least partially into a cooling channel (9), the coolant flowing through the cooling channel (9) can at least partially flow through the cooling body (3) and the power module (1) can discharge waste heat to the coolant via the cooling body (3). According to the invention, a heat transfer with improved waste heat from a power module into a coolant is disclosed, in which an inner wall section (23) of the cooling channel (9) has spring-like projecting elements (20) which lie opposite a pressure-bearing surface (19) of the cooling body (3) which lie opposite the power module (1), the projecting elements (20) acting against the pressure-bearing surface (19) of the cooling body (3) by means of a restoring force (21), the contact surface (24) of the power module (1) and the cooling body (3) can be increased.

Description

Technical Field

[0001] The present invention relates to a converter for converting a type of current fed into another type of current, the converter having at least one power module and at least one cooling body, wherein the power module and the cooling body are thermally effectively connected to each other, wherein the cooling body is at least partially introduced into a cooling channel, so that a coolant flowing through the cooling channel can flow through the cooling body at least in sections and the power module can discharge waste heat to the coolant via the cooling body. Background Art

[0002] Converters are generally used to convert a current type, which may be direct current or alternating current, into the other current type. In this respect, converters are differentiated according to the type of conversion, i.e. the input current type and the output current type: rectifiers convert alternating current into direct current, inverters convert direct current into alternating current, and frequency converters convert alternating current into alternating current with a different frequency and / or amplitude.

[0003] Methods known in practice for this purpose include clocked control of at least one power module, wherein the power module generally has semiconductor switches (MOSFET, IGBT, etc.). When the semiconductor switches are clocked, waste heat is generated as power loss due to the switching losses and conduction losses that occur in this process, which must be removed from the power module in order to protect the power module, otherwise the power module could be damaged or destroyed. In this regard, for the purpose of transferring the waste heat, a special cooling body is fastened at least in sections to the waste heat surface of the power module provided for this purpose, so that the waste heat can be effectively transferred from the power module to the coolant flowing through the cooling channel.

[0004] A power module with reduced thermal resistance and overall size is known from document US 7 547 966 B2. The document relates to an insulating substrate having an electronic metal layer arranged thereon, which is connected to two surfaces of the semiconductor, for example by soldering. A metal layer is arranged on the back side of the insulating substrate, which is connected to a cooling body by brazing. The heat dissipating side of the cooling body is covered with a housing to form a cooling channel through which a coolant can flow in order to conduct away the waste heat transferred from the semiconductor to the cooling body. According to the document, screws that connect the housing to the cooling body in a force-fitting manner can be used to fix and firmly connect the structure.

[0005] However, this common approach has the disadvantage that mechanical forces acting on the cooling body are caused by the force-fitting connection between the housing and the cooling body, resulting in the cooling body being easily deformed. This does not have a negative effect on the ability of the cooling body to discharge waste heat. However, the slightest deformation of the cooling body affects the contact surface between the back side of the substrate and the metal layer on the cooling body. In this regard, the contact surface is important for the heat transfer of waste heat, because the smaller the contact surface, the less waste heat can be transferred from the semiconductor to the cooling body. Summary of the invention

[0006] According to the present invention, a converter with improved heat transfer from the power module to the waste heat in the coolant according to claim 1 is disclosed, characterized in that the inner wall section of the cooling channel has a spring-like protruding element, which is opposite to the pressure-bearing surface of the cooling body opposite to the power module, wherein the protruding element acts against the pressure-bearing surface of the cooling body by means of a reset force, so that the contact surface between the power module and the cooling body can be increased. The power module usually includes a wiring of multiple semiconductor switches, which is suitable for realizing timing for converting the type of current fed into another type of current. The wiring can be, for example, a half-bridge circuit or a full-bridge circuit, wherein the semiconductor switch is usually a MOSFET or IGBT of a common semiconductor material such as, for example, silicon.

[0007] The waste heat generated by the clock control is conducted within the power module to at least one waste heat surface, wherein a heat sink can be fastened to the waste heat surface from the outside so that the waste heat can be transferred from the power module into the heat sink. In this respect, a contact surface between the power module and the heat sink that is effective for heat transfer is produced at the contact points of the heat sink and the waste heat surface of the power module. All types of bending, bulging or deformation reduce the contact surface, so that according to the invention it is advantageous that such deformations of the heat sink are compensated and reduced by the restoring forces of the protruding elements, wherein the number of contact points and the contact surface are increased overall. A more uniform and simultaneously high surface pressure is also achieved by the protruding elements, so that in principle all contact surfaces are in contact with one another and the heat transfer resistance to the waste heat generated is as low as possible.

[0008] According to the present invention, the pressure surface of the heat sink is located on the side of the heat sink opposite to the waste heat surface, and in this regard the protruding element is oriented and fastened to the inner wall section of the cooling channel so that the protruding element protrudes from the inner wall section in the direction of the cooling channel and the restoring force of the protruding element acts as vertically as possible on the pressure surface of the heat sink and can press the heat sink against the waste heat surface of the power module.

[0009] The projection element can be designed in different ways; for example, a coil spring or a helical spring can be suitable as the projection element, wherein a disc spring can also be used as an alternative, provided that the spring or the projection element can exert a restoring force that is large enough to keep the contact surface between the waste heat surface and the heat sink sufficiently large during the service life of the converter. The strength of the force and its central position of action on the heat sink make it possible to press the waste heat surface of the power module more evenly. This results in a uniform surface pressure.

[0010] Alternatively, it is also conceivable to place the projection element exactly above the switching element of the power module so that the greatest contact pressure of the projection element is present exactly where the most waste heat is generated. Alternatively, a plurality of projection elements may also be defined. Alternatively, instead of a round projection element, a projection element of an annular, square or similar design may also be provided.

[0011] Optionally, a heat-conducting paste is used between the waste heat surface and the cooling body for improved heat transfer. The heat-conducting paste additionally increases the contact surface due to its viscosity, because it is pressed into multiple intermediate spaces, gaps and uneven parts of the waste heat surface and the cooling body by the pressure of the cooling body against the waste heat surface. Although the heat-conducting paste should have the highest possible thermal conductivity, it is always less thermally conductive than a metallic waste heat surface or a metallic cooling body. Therefore, it is particularly advantageous according to the invention for an improved thermally effective connection between the power module and the cooling body that the restoring force of the protruding element acting on the pressure surface of the cooling body can keep the thickness of the heat-conducting paste as small as possible.

[0012] In the case of the converter according to the invention, a thermally conductive paste can optionally be used, which is particularly effective above certain temperatures and certain pressures, because it can be further compressed above certain values ​​- for example, the thickness of this thermally conductive paste then decreases from 100 μm to 40 μm at an ambient temperature of more than 80° C.

[0013] According to a particularly cost-effective embodiment of the converter according to the invention, it can be provided that the spring-like protruding element of the inner wall section is designed as a recess of the cooling channel that faces the pressure surface of the heat sink. The protruding element can then be produced by a recess introduced into the cooling channel from the outside, which is curved in the cooling channel in the direction of the pressure surface of the heat sink. This is inexpensive in terms of production technology, cost-effective and allows for a protruding element of simple design.

[0014] The elastic and restoring effect of the protruding element designed in this way can be achieved by a suitable choice of material for the area surrounding the recess or the entire cooling channel. For this purpose, it is particularly suitable to manufacture the cooling channel from a spring steel with high strength or elasticity, so that the recess or the protruding element that is curved in the direction of the pressure-bearing surface of the heat sink can exert a sufficiently high restoring force.

[0015] In order to be able to cool the power module particularly effectively, it can be provided according to an advantageous design of the converter according to the invention that two heat sinks are fastened to two opposite sides of the power module, wherein the restoring force acts from the protruding elements on the pressure-bearing surfaces of the heat sinks. This can achieve an improved, double cooling effect of the power module, so that other power parameters of the converter according to the invention can be matched. For example, on the one hand, the electrical power of the converter can be increased according to this design; on the other hand, the average temperature load of the power module during the service life of the converter can also be subsequently reduced in order to extend the service life again.

[0016] According to an advantageous design of the converter according to the invention, it can be proposed that the first cooling body is at least partially introduced into the inlet section of the cooling channel and the second cooling body is at least partially introduced into the outlet section of the cooling channel, so that the coolant can flow through the two cooling bodies in succession. The longer the coolant can flow through the cooling body, the more waste heat can be transferred to the coolant. Since the structural dimensions of the power module are usually preset by the purchased power module in practice, the cooling body cannot be of any size in these cases. On the other hand, it is more cost-effective to increase the maximum temperature of the coolant. In this regard, it is advantageous according to this design that the power module is cooled twice by the same coolant flow, because this can improve the heat transfer of the waste heat of the power module in the same coolant flow.

[0017] In order to reduce the structural size of the converter, it can be proposed according to an advantageous design of the converter according to the invention that at least one power module and at least one cooling body are jointly at least partially introduced into the cooling channel, so that both the power module and the cooling body can be flowed through by the coolant. Power modules that are cast by resin and thus coolant-tight are available. According to the design of the power module, the power module can be introduced directly into the cooling channel together with at least one cooling body and its waste heat surface in a space-saving manner. According to this design, the power module can be better cooled directly by the coolant or indirectly via the cooling body, thereby improving the performance of the power module and the converter can be constructed in a space-saving manner.

[0018] In order to be able to manufacture the converter according to the invention cost-effectively, it can be provided according to an advantageous design that the cooling channel is at least partially made of plastic material. Plastic material is generally more advantageous and lighter than metal and the cooling channel is easier to manufacture from plastic material. Although the cooling channel is partially made of plastic material, the technical robustness of the converter according to the invention can still be improved in the following case: According to a particularly advantageous design of the converter according to the invention, it is provided that the cooling channel is made of metal at least in the area surrounding the inner wall section with the spring-like protruding element. This particularly concerns the area around the power module, because the power module causes high electromagnetic interference emissions in a clock-related manner and the metal section or inner wall section of the cooling channel in the area of ​​the power module can act as an electromagnetic shield. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Below, a schematic diagram of a converter according to the present invention is shown as an example. The accompanying drawings show:

[0020] Figure 1 A perspective view showing a power module;

[0021] Figure 2 A cross-sectional view showing the converter along the flow direction of the coolant;

[0022] Figure 3 A cross-sectional view showing the converter transverse to the flow direction of the coolant; and

[0023] Figure 4 A perspective overview of a converter with three power modules is shown. DETAILED DESCRIPTION

[0024] exist Figure 1 , a three-dimensional view of a power module 1 is shown, which contains two silicon carbide MOSFETs as semiconductor switches in a half-bridge circuit. The two semiconductor switches are fixed to a carrier plate, which is thermally operatively connected to a waste heat surface 2 outside the power module 1 and to which a heat sink 3 can be fixed.

[0025] For electrical wiring, two DC terminals 4 and one AC terminal 5 are led out of the power module 1, which are led to corresponding contact points of the semiconductor switch within the power module 1. For the control of the semiconductor switch and possible measurement value detection, a plurality of auxiliary contacts 6 are also led out of the power module 1.

[0026] exist Figure 2 7 shows a sectional view of a converter 7, wherein two partially visible power modules 1 are provided along the flow direction 8 of the coolant. Figure 3 In FIG. 8 , a cross-sectional view of the converter 7 is shown correspondingly to the flow direction 8 of the coolant, and in FIG. Figure 4 , a perspective overview of a converter 7 is shown, which has all three power modules 1 .

[0027] The power modules 1 each have two waste heat surfaces 2, which are located on two opposite sides of the power module 1 and to which a heat sink 3 is fastened, respectively, wherein a thermal conductive paste is applied between the heat sink 3 and the waste heat surfaces 2 to improve heat transfer of the waste heat 2 from the power module 1 into the heat sink 3.

[0028] According to this design, the two cooling bodies 3 of each power module 1 are introduced into the cooling channel 9, wherein the cooling bodies 3 are pressed against the power module 1 by a plastic part 10 made of plastic material, and the plastic part 10 is used as a frame of the power module 1 as a whole, and positions and aligns the power module, as well as keeps it fixed.

[0029] The structure of the plastic part 10 is designed such that, on the one hand, it forms the lower bottom of the cooling channel 9, into which the heat sink 3 is introduced via a cooling channel opening 11 into the cooling channel 9, and, on the other hand, it has two cooling channel connections 12 for the coolant flowing in and out. The coolant can be introduced into the cooling channel 9 through one cooling channel connection 12, flow along the inlet section 13 and the outlet section 13 of the cooling channel 9, and flow out of the cooling channel 9 through the other cooling channel connection 12.

[0030] Along the inlet section 13, the coolant can flow through all the first cooling bodies 3 of the power module 1, and along the outlet section 14, the coolant can flow through all the second cooling bodies 3 of the power module 1, wherein the order of flowing through all the cooling bodies 3 as a whole ensures that all the power modules 1 are cooled approximately equally well. Because when the temperature of the coolant is at its lowest, the first cooling body 3 of the first power module 1 is flowed through by the coolant, but the situation is the opposite for the second cooling body 3 of the first power module 1; accordingly, the two cooling bodies 3 of the last power module 1 are flowed through by the coolant with approximately the same temperature in the cooling sequence. In this regard, the power modules 1 have approximately the same core temperature with respect to each other due to the two cooling bodies 3 and the cooling sequence on the two opposite sides of the power module 1. The cooling channel 9 is closed and sealed from the top by two stamped metal plates 15 made of spring steel, which are fastened to the plastic part 10 by means of screws 16.

[0031] The friction-fitting fastening of the heat sink 3 at the edge region of the power module 1 by means of the plastic part 10 necessarily has the effect that the distance between the heat sink 3 and the waste heat surface 2 is greatest in the central region 17 of the waste heat surface 2. As a result, the waste heat of the power module 1 is dissipated in the worst possible manner precisely in the central region 17 and can be transferred into the heat sink 3, because the power module 1 becomes hottest in the central region 17 due to the placement of the semiconductor switches and generates the most waste heat to be dissipated there.

[0032] According to the present invention, the metal plate 15 of the cooling channel 9 has a recess 18 in the middle area 17 of the power module 1, and the recess forms a protruding element 20 inwardly toward the pressure surface 19 of the heat sink 3, wherein the protruding element 20 has elasticity in the direction of the pressure surface 19 of the heat sink 3 in a spring-like manner due to the material of the metal plate 15, so that the protruding element 20 can act on the pressure surface 19 by means of a restoring force 21 without damaging the power module 1 or the heat sink 3.

[0033] The position of the recess 18 and the screw 16 ensures, on the one hand, that the cooling channel 9 is securely coolant-tight due to the high screw force 22 and, on the other hand, that the protruding element 20 formed by the inner wall section 23 of the metal plate 15 acts on the pressure surface 19 of the heat sink 3 via the recess 18 only with its restoring force 21, so that the contact surface 24 between the heat sink 3 and the power module 1 is as large as possible and the waste heat from the power module 1 can be effectively discharged without damaging the power module 1 or the heat sink 3.

[0034] Reference numerals list

[0035] 1 Power Module

[0036] 2 Waste heat surface

[0037] 3 cooling body

[0038] 4DC terminal

[0039] 5AC terminal

[0040] 6 auxiliary contacts

[0041] 7. Converter

[0042] 8 Flow direction

[0043] 9 Cooling channels

[0044] 10 plastic parts

[0045] 11 Cooling channel opening

[0046] 12 Cooling channel connector

[0047] 13 Entrance Section

[0048] 14Exit section

[0049] 15 Spring steel plate

[0050] 16 screws

[0051] 17 Power module middle area

[0052] 18 recess

[0053] 19 Pressure surface

[0054] 20 protruding elements

[0055] 21Restoration force

[0056] 22 Screw force

[0057] 23 inner wall section

[0058] 24 contact surfaces

Claims

1. A converter (7) for converting a type of current fed into another type of current, the converter comprising at least one power module (1) and at least one cooling body (3), wherein the power module (1) and the cooling body (3) are thermally effectively connected to each other, wherein the cooling body (3) is at least partially introduced into a cooling channel (9), so that a coolant flowing through the cooling channel (9) can flow through the cooling body (3) at least in sections and the power module (1) can discharge waste heat to the coolant via the cooling body (3), It is characterized in that The inner wall section (23) of the cooling channel (9) has a spring-like protruding element (20), which is opposite to the pressure-bearing surface (19) of the cooling body (3) opposite to the power module (1), wherein the protruding element (20) acts against the pressure-bearing surface (19) of the cooling body (3) by means of a restoring force (21), so that the contact surface (24) between the power module (1) and the cooling body (3) can be increased.

2. The converter (7) according to claim 1, It is characterized in that The spring-like protruding element (20) of the inner wall section (23) is designed as a recess (18) of the cooling channel (9) pointing in the direction of the pressure surface (19) of the cooling body (3).

3. The converter (7) according to claim 1 or 2, It is characterized in that Two heat sinks (3) are fastened to two opposite sides of the power module (1), wherein a restoring force (21) of a protruding element (20) acts on a pressure surface (19) of the heat sink (3) in each case.

4. The converter (7) according to claim 3, It is characterized in that The first heat sink (3) is at least partially introduced into an inlet section (13) of the cooling channel (9), and the second heat sink (3) is at least partially introduced into an outlet section (14) of the cooling channel (9), so that the coolant can flow through the two heat sinks (3) successively.

5. The converter (3) according to any one of the preceding claims, It is characterized in that The at least one power module (1) and the at least one cooling body (3) are jointly at least partially introduced into the cooling channel (9), so that the coolant can flow through both the power module (1) and the cooling body (3).

6. Converter (7) according to any one of the preceding claims, It is characterized in that The cooling channel (9) is formed at least in sections from a plastic material.

7. The converter (7) according to any one of the preceding claims, It is characterized in that The cooling channel (9) is composed of metal at least in the region surrounding the inner wall section (23) having the spring-like projection element (20).

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