WO2021116647A1

WO2021116647A1 - Inverter

Info

Publication number: WO2021116647A1
Application number: PCT/GB2020/052560
Authority: WO
Inventors: Robert ABEBE; Ben Lewis; David Walker
Original assignee: Dyson Technology Limited
Priority date: 2019-12-13
Filing date: 2020-10-14
Publication date: 2021-06-17
Also published as: CN114788433A; GB2590386A; GB201918384D0; GB2590386B

Abstract

An inverter (108) includes a housing portion (110). A coolant inlet (118) and a cooling 5 channel (122) are formed in, and extend along, the housing portion (110). The cooling channel (122) is arranged to receive, in use, coolant from the coolant inlet (118). A power module (124) caps the cooling channel (122) to define a cooling chamber (126) through which the coolant flows, in use, to cool the power module (124). A coolant outlet (146) is formed in the housing portion (110), the coolant outlet (146) being arranged to receive, in use, coolant from the cooling chamber (126). The coolant outlet (146) is configured and arranged to have lower resistance to coolant flow than the coolant inlet (118). For example, the coolant outlet (146) may be shorter than the coolant inlet (118).

Description

INVERTER

Field of the Invention

The present invention relates to an inverter that is cooled by a coolant.

Background of the Invention

Electric and hybrid electric vehicles are becoming increasingly common. Such vehicles comprise some form of electric motor, which may be driven by an inverter. The inverter includes circuitry including switching components, such as silicon carbide FETs, which can generate significant heat. Excess heat can cause damage, including sudden failure or long term degradation of switching components.

It would be desirable to improve inverter cooling.

Summary of the Invention

According to an aspect of the invention, there is provided an inverter comprising: a housing portion; a coolant inlet formed in, and extending along, the housing portion; a cooling channel formed in, and extending along, the housing portion, the cooling channel being arranged to receive, in use, coolant from the coolant inlet; a power module capping the cooling channel to define a cooling chamber through which the coolant flows, in use, to cool the power module; and a coolant outlet formed in the housing portion, the coolant outlet being arranged to receive, in use, coolant from the cooling channel; wherein the coolant outlet is configured and arranged to have lower resistance to coolant flow than the coolant inlet. The coolant outlet having a lower resistance to coolant flow than the coolant inlet may result in a lower pressure drop across the outlet than the inlet, which may improve fluid flow characteristics.

The coolant outlet may be shorter than the coolant inlet, a minimum cross-sectional area of the coolant outlet may be greater than a minimum cross-sectional area of the coolant inlet, an average cross-sectional area of the coolant outlet may be greater than an average cross-sectional area of the coolant inlet, and/or the coolant inlet may include one or more turbulence-producing features that increase coolant flow resistance. Any or all of these factors may be selected based on specific implementation requirements.

The housing portion may comprise a base and at least one wall, the base and at least one wall defining an interior space.

At least a portion of the coolant inlet may extend, viewed in a direction orthogonal to the base, at a non-zero angle relative to a direction of coolant flow through the cooling chamber. This non-zero angle may provide for more flexible positioning of the coolant inlet, as well as optionally allowing for a longer coolant inlet, which may improve fluid flow characteristics.

The direction orthogonal to the base may comprise a direction parallel to the at least one wall, for example a direction parallel to a direction in which the at least one wall extends outwardly from the base.

The coolant inlet may comprise at least one curved portion. The curved portion may allow for a smooth change of direction for coolant flowing through the coolant inlet while optionally allowing for a longer coolant inlet.

The coolant inlet may increase in width within the curved portion, in a downstream direction. This may reduce the average flow rate of fluid within the coolant inlet along its length, potentially allowing for a more even distribution of fluid into the cooling chamber. A radius of the curved portion may decrease in a downstream direction.

The coolant inlet may comprise at least first and second curved portions, wherein the first curved portion curves in an opposite direction to the second curved portion. This may provide for more flexible positioning of the coolant inlet, as well as optionally allowing for a longer coolant inlet, which may improve fluid flow characteristics.

The coolant inlet may comprise a plenum. The use of a plenum may allow for more even distribution of coolant into the cooling chamber.

The coolant inlet may comprise a laterally-extending slot defining an exit from the plenum into the cooling chamber. For example, a cross-section of the slot, taken in a direction parallel to the direction of coolant flow through the cooling chamber and normal to the base, may include opposed parallel sides. The use of such a slot may allow for more even distribution of coolant into the cooling chamber.

The slot may be at an oblique angle to the base, and may be arranged such that, in use, the slot directs the coolant into the cooling chamber such that it impinges on at least a portion of the power module at an oblique angle. This may provide for improved cooling of the power module.

The coolant inlet may be formed in the base at a different depth to the coolant channel. The slot may extend from the coolant inlet at a first depth in the base to the coolant channel at a second, different, depth in the base. The slot may extend diagonally through the base, for example at an oblique angle relative to exterior and interior surfaces of the base.

The oblique angle may be between 30° and 50°. In some embodiments, the oblique angle may be about 41°. These angles have been found to be a good compromise between cooling performance and wear characteristics. The power module may comprise a plurality of pins, ribs, and/or other turbulence generating and/or surface area increasing structures extending into the cooling chamber, to enhance cooling of the power module by the coolant, in use. The slot may be arranged such that, in use, the slot directs the coolant into the cooling chamber such that it impinges on the plurality of pins, ribs, and/or other turbulence-generating and/or surface area increasing structures.

At least a portion of the coolant outlet may extend, viewed in a direction orthogonal to the base, at a non-zero angle relative to the direction of coolant flow through the cooling chamber. This non-zero angle may provide for more flexible positioning of the coolant outlet, as well as optionally allowing for a longer coolant outlet, which may improve fluid flow characteristics.

The coolant outlet may comprise at least one curved portion. The curved portion may allow for a smooth change of direction for coolant flowing through the coolant outlet.

The coolant outlet may decrease in width within the curved portion of the coolant outlet, in a downstream direction. This may increase a velocity of coolant flowing through the coolant outlet, which may improve fluid flow characteristics.

A radius of the curved portion of the outlet may increase in a downstream direction.

The coolant outlet may comprise at least first and second curved portions, wherein the first curved portion curves in an opposite direction to the second curved portion. This may provide for more flexible positioning of the coolant outlet, as well as optionally allowing for a longer coolant outlet, which may improve fluid flow characteristics.

The non-zero angle may be 80 to 100°, and the portion of the coolant inlet and/or outlet may be a straight portion at or adjacent a beginning of the coolant inlet and/or an end of the coolant outlet. In some embodiments, the non-zero angle may be 90°. This may provide for more flexible positioning of the coolant inlet and/or outlet, as well as optionally allowing for a longer coolant inlet and/or outlet, which may improve fluid flow characteristics.

According to another aspect of the invention, there is provided an electric drive unit comprising: a gearbox; an electric machine mounted to the gearbox; and an inverter according to the preceding aspect, mounted to the gearbox and connected to provide drive current to the electric machine.

According to yet another aspect of the invention, there is provided a vehicle comprising: an inverter according to the first aspect; or an electric drive unit according to the preceding aspect.

In order that the present invention may be more readily understood, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a partially see-through side view of a vehicle comprising a front- mounted electric drive unit (EDU) and a further rear-mounted EDU;

Figure 2 is a perspective view of the front-mounted EDU of Figure 1;

Figure 3 is a side elevation of a housing portion of the inverter from the EDU of Figures 1 and 2;

Figure 4 is a perspective view of the opposite side of the housing portion of Figure

3; Figures 5 and 6 are an opposite side elevation of the housing portion of Figures 3 and 4, with the power modules removed for clarity in Figure 6;

Figures 7 and 8 are a vertical section taken along line VII- VII in Figure 3, with the power modules removed for clarity in Figure 8;

Figure 9 is a plan view of turbulence generating features in the form of pins;

Figure 10 is a plan view of turbulence generating features in the form of vanes; and

Figure 11 is a plan view of turbulence generating features in the forms of ribs.

Detailed Description of the Invention

Referring to the drawings, and Figures 1 and 2 in particular, there is shown an electric vehicle 100 having a front-mounted electric drive unit 102. The electric drive unit 102 comprises a gearbox 104. An electric machine 106 is mounted to a first lateral side of the gearbox 104, and an inverter 108 is mounted to a second lateral side of the gearbox 104 opposite the first lateral side. The electric vehicle 100 and electric drive unit 102 are merely examples used to show a particular implementation of the inverter 108.

The inverter 108 contains circuitry including switching components (described below) that provide drive current to the electric machine 106. The switching components generate significant heat and must be cooled. One way of cooling such components involves using a coolant, which may, for example, be cooled by the vehicle’s HVAC system. The cooled coolant is supplied to the inverter 108, and passed over cooling structures that are in thermal communication with the switching components. The coolant takes heat from the cooling structures, and then passes from the inverter 108 to the HVAC system for cooling. The inverter 108 includes a housing portion 110, which in the illustrated embodiment forms part of an external housing of the electric drive unit 102. As best shown in Figures 2-6, the housing portion 110 includes a base 112 and a wall 114. In the illustrated embodiment, the base 112 is generally planar and approximately square in plan. The wall 114 extends normally from the edges of the square, such that the base 112 and wall 114 define an interior space 116. The interior space 116 is closed by a surface (not shown) of the gearbox 104 when the housing portion 110 is attached to the electric drive unit 102.

It will be appreciated that the inverter 108 may take any other form, including being mounted separately from the electric drive unit 102 and the gearbox 104, and that the base 112 and wall 114 may take other shapes and configurations to suit the particular implementation.

A coolant inlet 118 is formed in, and extends along, the base 112. In the illustrated embodiment, the coolant inlet 118 extends from an inlet connector 120 adjacent a corner of the housing portion 110. The details of the coolant inlet 118 will be described in more detail below.

A cooling channel 122 is formed in, and extends along, the base 112. The cooling channel 122 is arranged to receive, in use, coolant from the coolant inlet 118, as will be described in more detail below. The coolant, in use, flows in the direction indicated by arrow 132 (see Figure 6).

As best shown in Figures 5 and 7, a power module 124 caps the cooling channel 122 to define a cooling chamber 126 through which the coolant flows, in use, to cool the power module 124. The power module 124 includes switching components such as silicon carbide FETs (not shown) mounted to a power module base 125. The power module base 125 covers the cooling chamber 126 and is sealed around its edges with a gasket or sealant to prevent leakage of the coolant, in use, into the interior space 116 of the housing portion 110 It will be appreciated that the inverter 108 includes many other components, which have been omitted for clarity.

Projections in the form of pins 127 extend from the power module base 125 into the cooling chamber. The pins 127 are formed from a thermally conductive material such as a metal. The pins 127 may form part of the power module base 125, or may be attached to the power module base 125 in any suitable manner. As described below, the pins 127 increase cooling of the power module 124 due to increased surface area and turbulence.

In other embodiments, the projections may take any other suitable form, including one or more ribs, lands, projections, vanes, or any combination thereof. The projections may extend the full width and/or length of the power module 124, or may cover only a portion of the power module 124. Similarly, the projections may extend the full depth of the cooling chamber 126, only partly through the cooling chamber, or some combination thereof.

The switching components are controlled to output drive current, which is supplied to the electric machine 106 in order to cause the vehicle 102 move. DC power is input to the inverter via a power connector 128 (see Figure 3) to which a power cable (not shown) is connected. Control signals from a vehicle management system (not shown) are input to the inverter 108 via a data connector 130 to which a data cable (not shown) is connected.

It will be appreciated that the inverter 108 includes many other components, which have been omitted for clarity.

In the illustrated embodiment, at least a portion of the coolant inlet 118 extends, viewed in a direction orthogonal to the base 112, at a non-zero angle relative to the direction 132 of coolant flow through the cooling chamber 126.

The coolant inlet 118 may include at least one curved portion. For example, the coolant inlet may include at least first and second curved portions, wherein the first curved portion curves in an opposite direction to the second curved portion. As best shown in Figure 3, in the illustrated embodiment, the coolant inlet 118 forms a complex curve extending from the inlet connector 120 to the cooling channel 122.

The complex curve is indicated by a line 134 shown in Figure 3 that approximates the centre of the coolant inlet 118 along its length. The angle of the coolant inlet 118 relative to the direction 132 of coolant flow through the cooling chamber 126 may be determined by taking a tangent to the line 134 at any point between the inlet connector 120 and the cooling channel 122. It will be seen that this tangent is non-zero for all points along the coolant inlet 118, except for right at downstream end adjacent the cooling channel 122.

In the illustrated embodiment, the coolant inlet 118 includes a straight portion 136 extending downstream from the inlet connector 120. Such a straight portion may extend at any angle relative to the direction 132 of coolant flow through the cooling chamber 126. For example, the angle may be between 80° and 100°. In the illustrated embodiment, the angle is 90°.

Viewed in a direction orthogonal to the base, the coolant inlet 118 increases in width within the curved portion, in a downstream direction. In addition, a radius of the curved portion may decrease in a downstream direction. For example, the curved portion at the downstream end of the coolant inlet 118 has a tightening curve as a result of a decreasing radius of curvature.

As best shown in Figures 7 and 8, the coolant inlet comprises a plenum 138 adjacent its downstream end. The plenum 138 is a region of increased cross-sectional area. In the illustrated embodiment, the plenum 138 is disposed beneath a plane of the cooling chamber 126.

The coolant inlet 118 may optionally comprise at least one turbulence generating feature for generating turbulence in the coolant as it flows through the coolant inlet 118 in use. Such coolant features may be positioned anywhere along the length of the coolant inlet 118.

In general, placing such features closer to the downstream end of the coolant inlet 118 tends to be more effective, because any turbulence generated has less time to dampen before the coolant reaches the cooling chamber 126. However, this may need to be balanced against the speed at which coolant flows at different points in the coolant inlet 118, and the available space.

For example, coolant flow is at its fastest at the upstream end of the coolant inlet 118 in the illustrated embodiment, because this region has the smallest cross-sectional area. Higher speed coolant flow may help with the production of turbulence, but the narrow cross-sectional area may leave less space to introduce turbulence generating features, and less space for turbulent fluid flow characteristics to develop. The skilled person will choose the appropriate position for the turbulence generating features, taking into account all of these factors.

As best shown in Figures 3, 7, 8 and 9, in the illustrated embodiment, the turbulence generating features comprise a plurality of pins 144 that extend into the coolant inlet 118. The pins 144, in this case, extend into the plenum 38. In use, the pins 144 disrupt the flow of coolant through the plenum, breaking up the laminar flow by causing eddies and other forms of turbulence. The location of the pins 144 is selected to provide a suitable balance between turbulence generation and flow resistance. The disrupted flow of the coolant may improve cooling of the power module 124, as described in more detail below.

Figure 9 shows an example of how the pins 144 may be distributed within the plenum 138 and coolant inlet 138.

In other embodiments, the turbulence generating features may comprise any other type of feature that causes the required turbulence in the coolant flow. For example, the turbulence generating features may comprise one or more ribs, lands, projections, vanes, recesses, or any combination thereof. Typically, such turbulence generating features are disposed on an inner surface of the coolant inlet, but may also be suspended in the coolant flow by a cantilever or other member extending from outside the coolant inlet 118.

Figure 10 shows an alternative example, in which the turbulence generating features take the form of vanes 156 that extend into the fluid flow within the plenum 138. In addition to causing turbulence, the vanes 156 also act to help change the direction of the coolant as it passes.

Figure 11 shows yet another alternative example, in which the turbulence generating features take the form of ribs 158 formed on the internal surface of the plenum 138 and coolant inlet 118. In this case, the ribs extend roughly normal to the general direction of fluid flow. In order to reduce resistance, the ribs 158 extend only partly into the plenum 138 and coolant inlet 118. The ribs 158 therefore generate turbulence most strongly near the internal surface of the plenum 138 and coolant inlet 118.

The skilled person will appreciate that the particular shape, size, and arrangement of the or each turbulence generating features may be selected to suit the particular cooling needs of needs of inverter. Different types of features may be combined in particular embodiments.

In yet other embodiments, there are no turbulence generating features in the coolant inlet 118.

The coolant inlet 118 also comprises a laterally-extending region immediately upstream of the cooling chamber 126 and downstream of the plenum 138. In the illustrated embodiment, the region takes the form of a slot 140 that extends a full width of cooling channel 126. The slot 140 is at an oblique angle Q to the base 112, and arranged such that, in use, the slot 140 directs the coolant into the cooling chamber 126 such that substantially all of the coolant from the region impinges on a subset of the projections at the oblique angle Q. The oblique angle Q may be between 30° and 50°. In the illustrated embodiment, the oblique angle Q is about 41°.

Figures 7 and 8 show a cross-section through the housing portion 110, taken in a direction parallel to the direction 132 of coolant flow through the cooling chamber 126 and normal to the base 112. In this cross-section, the slot 140 includes opposed parallel sides 142. The region between the parallel sides 142 has a smaller cross-sectional area than the plenum 138 immediately upstream in the coolant inlet 118. This accelerates coolant flow, in use, to improve impingement cooling.

The inverter 108 includes a coolant outlet 146 downstream of the cooling chamber 126. In the illustrated embodiment, the coolant outlet 146 is shorter than the coolant inlet 118. At least a portion of the coolant outlet 146 extends, viewed in a direction orthogonal to the base, at a non-zero angle relative to the direction 132 of coolant flow through the cooling chamber 126.

The coolant outlet 146 comprises at least one curved portion. For example, the coolant outlet 146 may include at least first and second curved portions, wherein the first curved portion curves in an opposite direction to the second curved portion. As best shown in Figure 3, in the illustrated embodiment, the coolant outlet 146 forms a complex curve extending from an outlet of the cooling chamber 126 to an outlet connector 148.

The complex curve is indicated by a line 150 that approximates the centre of the coolant outlet 146 along its length. The angle of the coolant outlet 146 relative to the direction 132 of coolant flow through the cooling chamber 126 may be determined by taking a tangent to the line 150 at any point between the cooling chamber 126 and the outlet connector 148. It will be seen that this tangent is non-zero for all points along the coolant outlet 146, except for right at downstream end adjacent the outlet connector 148.

In the illustrated embodiment, the coolant outlet 146 includes a straight portion 152 adjacent the outlet connector 148. Such a straight portion may extend at any angle relative to the direction 132 of coolant flow through the cooling chamber 126. For example, the angle may be between 80° and 100°. In the illustrated embodiment, the angle is 90°.

Viewed in a direction orthogonal to the base, the coolant outlet 146 decreases in width within the curved portion, in a downstream direction. In addition, a radius of the curved portion may decrease in a downstream direction. For example, the curved portion at the upstream end of the coolant outlet 146 has a curve with a decreasing radius of curvature.

The coolant outlet 146 may be configured and arranged to have lower resistance to coolant flow than the coolant inlet 118. This outcome may be achieved in any of a number of ways, which may also be combined in certain embodiments. For example, in the illustrated embodiment, the coolant inlet 118 is significantly longer than the coolant outlet 146. In conjunction with the optional turbulence generating pins 144, the extra length of the coolant inlet 118 gives it a higher resistance to coolant flow than the coolant outlet 146.

Other differences that can be used, alone or in combination, to change a resistance of the coolant inlet 118 or coolant outlet 146 include, for example, cross-sectional area (e.g., minimum, maximum, average), turbulence generating structures, and more (or more extreme) curves. By balancing the contributions of any of these factors, the resistance of the coolant inlet 118 can be made higher than that of the coolant outlet 146.

Although the illustrated vehicle 100 is a car, the invention may find application in other types of vehicles, such as trucks and vans.

Although the invention has been described with reference to specific examples, it will be appreciated that the invention may be embodied in many other forms that fall within the scope of the appended claims.

Claims

1. An inverter compri sing : a housing portion; a coolant inlet formed in, and extending along, the housing portion; a cooling channel formed in, and extending along, the housing portion, the cooling channel being arranged to receive, in use, coolant from the coolant inlet; a power module capping the cooling channel to define a cooling chamber through which the coolant flows, in use, to cool the power module; and a coolant outlet formed in the housing portion, the coolant outlet being arranged to receive, in use, coolant from the cooling chamber; wherein the coolant outlet is configured and arranged to have lower resistance to coolant flow than the coolant inlet; and wherein a minimum cross-sectional area of the coolant outlet is greater than a minimum cross-sectional area of the coolant inlet.

2. The inverter of claim 1 , wherein the coolant outlet is shorter than the coolant inlet.

3. The inverter of claim 1 or claim 2, wherein an average cross-sectional area of the coolant outlet is greater than an average cross-sectional area of the coolant inlet.

4. The inverter of any preceding claim, wherein the coolant inlet includes one or more turbulence-producing features that increase coolant flow resistance.

5. The inverter of any preceding claim, wherein housing portion comprises a base and at least one wall, the base and at least one wall defining an interior space.

6. The inverter of claim 5, wherein at least a portion of the coolant inlet extends, viewed in a direction orthogonal to the base, at a non-zero angle relative to a direction of coolant flow through the cooling chamber.

7. The inverter of claim 6, wherein the non-zero angle is 80° to 100°, and the portion of the coolant inlet is a straight portion at or adjacent a beginning of the coolant inlet.

8. The inverter of any of claims 5 to 7, wherein, viewed in a direction orthogonal to the base, the coolant inlet comprises at least one curved portion.

9. The inverter of claim 8, wherein, viewed in a direction orthogonal to the base, the coolant inlet increases in width within the curved portion, in a downstream direction.

10. The inverter of claim 8 or claim 9, wherein a radius of the curved portion decreases in a downstream direction.

11. The inverter of any of claims 5 to 7, wherein, viewed in a direction orthogonal to the base, the coolant inlet comprises at least first and second curved portions, wherein the first curved portion curves in an opposite direction to the second curved portion.

12. The inverter of any of claims 5 to 11, wherein the coolant inlet comprises a plenum.

13. The inverter of claim 12, wherein the coolant inlet comprises a slot defining an exit from the plenum into the cooling chamber.

14. The inverter of claim 13, wherein a cross-section of the slot, taken in a direction parallel to the direction of coolant flow through the cooling chamber and normal to the base, includes opposed parallel sides.

15. The inverter of claim 13 or claim 14, wherein the slot is at an oblique angle to the base, and is arranged such that, in use, the slot directs the coolant into the cooling chamber such that it impinges on at least a portion of the power module at an oblique angle.

16. The inverter of any of claims 5 to 15, wherein at least a portion of the coolant outlet extends, viewed in a direction orthogonal to the base, at a non-zero angle relative to the direction of coolant flow through the cooling chamber.

17. The inverter of claim 16, wherein the non-zero angle is 80° to 100°, and the portion of the coolant outlet is a straight portion at or adjacent an end of the coolant outlet.

18. The inverter of any of claims 5 to 17, wherein, viewed in a direction orthogonal to the base, the coolant outlet comprises at least one curved portion.

19. The inverter of claim 18, wherein, viewed in a direction orthogonal to the base, the coolant outlet decreases in width within the curved portion of the coolant outlet, in a downstream direction.

20. The inverter of claim 18 or claim 19, wherein a radius of the curved portion of the outlet increases in a downstream direction.

21. The inverter of any preceding claim, wherein, viewed in a direction orthogonal to the base, the coolant outlet comprises at least first and second curved portions, wherein the first curved portion curves in an opposite direction to the second curved portion.

22. An electric drive unit comprising: a gearbox; an electric machine mounted to the gearbox; and the inverter of any preceding claim, mounted to the gearbox and connected to provide drive current to the electric machine.