Cooling oil direct current concentrated power module immersion heat dissipation structure

Abstract

The application discloses a cooling oil direct current converging type power module immersion heat dissipation structure, which comprises a shell, the shell comprising a bottom wall, a top wall, a first side wall, a second side wall, a third side wall and a fourth side wall and a cavity surrounded thereby, the first side wall being provided with an oil inlet hole, and the second side wall being provided with an oil outlet hole; a liquid cooling radiator being arranged at the bottom of the cavity, the liquid cooling radiator being provided with a substrate, the substrate being provided with power semiconductor chips and a flow guide structure; the bottom surface of the power semiconductor chips being connected with the top surface of the substrate, the top surface and the side surface of the power semiconductor chips being exposed to the cavity; the flow guide structure being arranged on both sides of the power semiconductor chips and being used for converging the cooling oil to the side surface and the top surface of the power semiconductor chips and dissipating heat from the top surface and the side surface of the power semiconductor chips. The application can dissipate heat from the bottom surface, the top surface and the side surface of the power semiconductor chips and improve heat dissipation efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power module heat dissipation technology, more particularly, to a cooling oil direct current convergent power module immersion heat dissipation structure. BACKGROUND

[0002] With the continuous improvement of power module power density, efficient cooling technology has become the key to its design and development. In view of the heat dissipation problem of power module, at present, domestic and foreign scholars and manufacturers adopt single-sided and double-sided cooling technology. Among them, single-sided cooling connects the bottom surface of the power semiconductor chip with the air-cooled or liquid-cooled heat sink through high thermal conductivity medium, so that the heat emitted by the chip is conducted to the heat sink from the bottom surface; when using double-sided heat dissipation structure, in addition to the bottom surface, the electrode on the top surface of the chip is also connected with the heat sink through high thermal conductivity medium, at this time, the heat emitted by the chip can be dissipated from the bottom surface and the top surface at the same time.

[0003] However, single-sided and double-sided heat dissipation structures each have their own shortcomings: (1) for single-sided cooling, its advantage lies in simple structure, but only the bottom surface of the power semiconductor chip can be cooled, and the heat dissipation efficiency is low. (2) Double-sided cooling can realize the simultaneous heat dissipation of the bottom surface and the top surface of the power semiconductor chip, but on the one hand, it causes the total weight of the heat sink to rise, which is not conducive to the improvement of power density, and on the other hand, the electrode area on the top surface of the chip is relatively small, and its heat transfer efficiency is relatively low, which is difficult to meet the actual heat dissipation demand of high power density module. SUMMARY

[0004] The purpose of the present application is to provide a cooling oil direct current convergent power module immersion heat dissipation structure, which can realize the heat dissipation of the bottom surface, top surface and side surface of the power semiconductor chip and improve the heat dissipation efficiency.

[0005] To achieve the above purpose, the present application provides a cooling oil direct current convergent power module immersion heat dissipation structure, comprising:

[0006] A housing, the housing comprises a bottom wall, a top wall, a first side wall, a second side wall, a third side wall and a fourth side wall and a cavity surrounded thereby, the first side wall and the second side wall are two opposite side walls extending along the width direction of the housing, the third side wall and the fourth side wall are two opposite side walls extending along the length direction of the housing, the first side wall is provided with an oil inlet hole, and the second side wall is provided with an oil outlet hole;

[0007] The bottom of the cavity is provided with a liquid-cooled heat sink, the liquid-cooled heat sink is provided with a substrate, the substrate is provided with a power semiconductor chip and a flow guide structure;

[0008] The bottom surface of the liquid cooling radiator is connected with the bottom wall, and the two sides of the liquid cooling radiator are respectively attached to the third side wall and the fourth side wall, the liquid cooling radiator has a flow channel arranged along the length direction of the shell, and is used for heat dissipation of the bottom surface of the power semiconductor chip; the two ends of the liquid cooling radiator are respectively spaced from the first side wall and the second side wall;

[0009] The bottom surface of the power semiconductor chip is connected with the top surface of the substrate, and the top surface and the side surface of the power semiconductor chip are exposed in the cavity; the flow guide structure is located on the two sides of the power semiconductor chip, and is used for converging the cooling oil to the side surface and the top surface of the power semiconductor chip to dissipate heat of the top surface and the side surface of the power semiconductor chip.

[0010] Optionally, the flow guide structure comprises a first bus plate and a second bus plate arranged on the substrate along the longitudinal direction, the first bus plate is located on one side close to the third side wall, the second bus plate is located on one side close to the fourth side wall, and the power semiconductor chip is located between the first bus plate and the second bus plate.

[0011] The projection of the first bus plate and the second bus plate on the substrate is two arcs extending along the length direction of the shell and being axially symmetrically distributed, and along the direction from the first side wall to the second side wall, the distance between the first bus plate and the second bus plate gradually decreases from one end of the power semiconductor chip to the other end of the power semiconductor chip; the first bus plate is provided with a plurality of first flow guide pieces towards one side surface of the power semiconductor chip, the plurality of first flow guide pieces are spaced apart along the length direction of the shell, the first flow guide piece extends along the longitudinal direction from the top of the first bus plate to the top of the first bus plate, one end of the first flow guide piece is connected with the first bus plate, and the other end of the first flow guide piece is inclined towards the downstream direction of the cooling oil flow.

[0012] The second bus plate is provided with a plurality of second flow guide pieces towards one side surface of the power semiconductor chip, the plurality of second flow guide pieces are spaced apart along the length direction of the shell, the second flow guide piece extends along the longitudinal direction from the top of the second bus plate to the top of the second bus plate, one end of the second flow guide piece is connected with the second bus plate, and the other end of the second flow guide piece is inclined towards the downstream direction of the cooling oil flow.

[0013] Optionally, the included angle between the first flow guide piece and the first bus plate ranges from 30° to 60°, and the included angle between the second flow guide piece and the second bus plate is equal to the included angle between the first flow guide piece and the first bus plate.

[0014] Optionally, the first drain sheet and the second drain sheet are arranged one by one opposite to each other, and the distance between the first drain sheet and the power semiconductor chip is equal to the distance between the second drain sheet and the power semiconductor chip.

[0015] Optionally, the height of the first bus plate and the second bus plate is greater than the thickness of the power semiconductor chip, and the length of the first bus plate and the second bus plate is greater than the length of the power semiconductor chip.

[0016] Optionally, the top of the first bus plate and the second bus plate has a gap with the top wall, or the first bus plate and the second bus plate are connected with the top wall.

[0017] Optionally, the substrate is a DBC substrate, and the DBC substrate comprises a lower copper layer, a ceramic layer and an upper copper layer stacked from bottom to top.

[0018] The lower copper layer of the DBC substrate is connected with the top surface of the liquid cooling radiator through a connecting layer.

[0019] The bottom surface of the power semiconductor chip is welded to the upper copper layer of the DBC substrate through a solder layer.

[0020] The bottom of the first bus plate and the second bus plate is welded to the upper copper layer of the DBC substrate.

[0021] Optionally, the connecting layer is silicone grease, adhesive or solder layer.

[0022] Optionally, the oil inlet hole is arranged at the center of the first side wall, and the oil outlet hole is arranged at the center of the second side wall.

[0023] The beneficial effects of the present application are that the cooling oil direct current convergent power module immersion heat dissipation structure is provided with a liquid cooling radiator, a substrate and power semiconductor chips arranged in the cavity of the shell from bottom to top, and an oil inlet hole and an oil outlet hole are arranged on the two end side walls of the shell, after the cooling oil enters the shell, a part of the cooling oil flows into the radiator at the bottom to dissipate heat from the bottom surface of the power semiconductor chips, and the other part converges to the periphery of the power semiconductor chips through the flow guide structure to dissipate heat from the top surface and the side surface of the power semiconductor chips, the heat dissipation structure can realize the heat dissipation of the bottom surface, the top surface and the side surface of the power semiconductor chips at the same time, and the area utilization rate of the top surface is high, and the heat dissipation efficiency can be effectively improved; meanwhile, the flow guide structure is additionally arranged on the two sides of the power semiconductor chips, the cooling oil is guided to the top surface and the side surface of the power semiconductor chips through the flow guide structure, and the heat dissipation effect of the semiconductor chips is enhanced; secondly, the cooling flow path in the liquid cooling radiator is connected in parallel with the cooling oil path around the chips, the total amount of the flowing cooling oil is divided, a part of the total amount participates in the heat dissipation of the radiator (the bottom surface of the power semiconductor chips), and the other part flows through the top surface / side surface of the chips to realize heat dissipation, so that the high heat dissipation efficiency is ensured while the overall small flow resistance is maintained.

[0024] Further, the flow guide structure of the present application includes a pair of flow convergence plates, each of the flow convergence plates is provided with a plurality of flow guide pieces on the side facing the power semiconductor chips, the two flow convergence plates project two axisymmetric arcs on the substrate, and the distance between the two flow convergence plates gradually narrows along the flow direction of the cooling oil, the structure design can converge the cooling oil to the periphery of the power semiconductor chips and increase the flow speed of the cooling oil around the chips, meanwhile, the plurality of flow guide pieces are inclined at a certain angle towards the downstream of the flow direction of the cooling oil, the structure can make the cooling oil flowing between the two flow convergence plates further converge to the area where the chips are located, and further strengthen the flow speed of the cooling oil on the top surface and the side surface of the chips, so as to strengthen the heat dissipation effect of the top surface and the side surface of the chips, in addition, the inclined flow guide pieces can prevent the reverse flow of the cooling oil, so as to strengthen the circulating flow effect of the cooling oil in the shell.

[0025] The system of the present application has other characteristics and advantages, which will be apparent from or set forth in the accompanying drawings and the subsequent detailed description, which together serve to explain certain principles of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views.

[0027] Figure 1 and Figure 2respectively are a longitudinal sectional view and a top view of a chip top surface of a cooling oil direct current convergent power module immersion heat dissipation structure according to the present embodiment 1. DETAILED DESCRIPTION

[0028] The present application will be described in more detail by referring to the attached drawings. Although the preferred embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0029] Embodiment 1

[0030] As Figure 1 shown, the present embodiment provides a cooling oil direct current convergent power module immersion heat dissipation structure, comprising:

[0031] a housing 1, the housing 1 comprises a bottom wall 101, a top wall 102, a first side wall 103, a second side wall 104, a third side wall 105 and a fourth side wall 106 and a cavity surrounded thereby, the first side wall 103 and the second side wall 104 are two opposite side walls extending along the width direction of the housing 1, the third side wall 105 and the fourth side wall 106 are two opposite side walls extending along the length direction of the housing 1, the first side wall is provided with an oil inlet hole 10, and the second side wall is provided with an oil outlet hole 11; the bottom of the cavity is provided with a liquid cooling radiator 2, the liquid cooling radiator 2 is provided with a substrate, the substrate is provided with a power semiconductor chip 9 and a flow guide structure 12;

[0032] the bottom surface of the liquid cooling radiator 2 is connected with the bottom wall 101, the two sides of the liquid cooling radiator 2 are respectively attached with the third side wall 105 and the fourth side wall 106, and the liquid cooling radiator 2 has a flow channel arranged along the length direction of the housing 1 for dissipating heat from the bottom surface of the power semiconductor chip 9; the two ends of the liquid cooling radiator 2 are respectively spaced apart from the first side wall 103 and the second side wall 104;

[0033] the bottom surface of the power semiconductor chip 9 is connected with the top surface of the substrate, and the top surface and the side surface of the power semiconductor chip 9 are exposed in the cavity; the flow guide structure 12 is located on both sides of the power semiconductor chip 9 for converging cooling oil to the side surface and the top surface of the power semiconductor chip 9 to dissipate heat from the top surface and the side surface of the power semiconductor chip 9.

[0034] In this embodiment, the substrate is a DBC substrate (Direct Copper Bond), which comprises a lower copper layer 4, a ceramic layer 5 and an upper copper layer 6 stacked from bottom to top; the lower copper layer 4 of the DBC substrate is connected to the top surface of the liquid cooling radiator 2 through a connecting layer 3; the bottom surface of the power semiconductor chip 9 is welded to the upper copper layer 6 of the DBC substrate through a solder layer 8; the bottom of the first bus plate 12a and the second bus plate 12b is welded to the upper copper layer 6 of the DBC substrate. Among them, the connecting layer 3 is silicone grease, adhesive or solder layer 8.

[0035] As shown in Figure 2 In this embodiment, the flow guide structure 12 comprises a first bus plate 12a and a second bus plate 12b arranged on the substrate in the longitudinal direction, the first bus plate 12a is located near one side of the third side wall 105, the second bus plate 12b is located near one side of the fourth side wall 106, and the power semiconductor chip 9 is located between the first bus plate 12a and the second bus plate 12b;

[0036] The projection of the first bus plate 12a and the second bus plate 12b on the substrate is two arcs extending along the length direction of the shell 1 and axially symmetrically distributed, and along the flow direction of the cooling oil 7 (i.e. from the first side wall 103 to the second side wall 104 direction), the distance between the first bus plate 12a and the second bus plate 12b gradually decreases from one end of the power semiconductor chip 9 to the other end of the power semiconductor chip 9;

[0037] The first bus plate 12a is provided with a plurality of first flow guide pieces 12c on one side surface facing the power semiconductor chip 9, a plurality of the first flow guide pieces 12c are spaced apart along the length direction of the shell 1, the first flow guide piece 12c extends in the longitudinal direction from the top of the first bus plate 12a to the top of the first bus plate 12a, one end of the first flow guide piece 12c is connected to the first bus plate 12a, and the other end of the first flow guide piece 12c is inclined towards the downstream direction of the cooling oil 7;

[0038] The second bus plate 12b is provided with a plurality of second flow guide pieces 12d on one side surface facing the power semiconductor chip 9, a plurality of the second flow guide pieces 12d are spaced apart along the length direction of the shell 1, the second flow guide piece 12d extends in the longitudinal direction from the top of the first bus plate to the top of the second bus plate 12b, one end of the second flow guide piece 12d is connected to the second bus plate 12b, and the other end of the second flow guide piece 12d is inclined towards the downstream direction of the flow of the cooling oil 7.

[0039] Preferably, the included angle between the first flow guide sheet 12c and the first flow collecting plate 12a (the included angle a in the figure) ranges from 30° to 60°, and the included angle between the second flow guide sheet 12d and the second flow collecting plate 12b is equal to the included angle between the first flow guide sheet 12c and the first flow collecting plate 12a.

[0040] In the embodiment, the first flow guide sheets 12c and the second flow guide sheets 12d are arranged opposite to each other one by one, and the distance between the first flow guide sheet 12c and the power semiconductor chip 9 is equal to the distance between the second flow guide sheet 12d and the power semiconductor chip 9.

[0041] Further, in the embodiment, the height of the first flow collecting plate 12a and the second flow collecting plate 12b is greater than the thickness of the power semiconductor chip 9, and the length of the first flow collecting plate 12a and the second flow collecting plate 12b is greater than the length of the power semiconductor chip 9. The top of the first flow collecting plate 12a and the second flow collecting plate 12b has a gap with the top wall 102.

[0042] Specifically, the flow guide structure 12 of the embodiment can collect part of the cooling oil 7 entering the cavity to the periphery of the power semiconductor chip 9 and increase the flow rate of the cooling oil 7 around the chip; at the same time, the plurality of flow guide sheets are inclined at a certain angle towards the downstream of the flow direction of the cooling oil 7, and the plurality of flow guide sheets can further collect the cooling oil 7 flowing between the two flow collecting plates to the area where the chip is located, further strengthening the flow rate of the cooling oil 7 on the four sides and the top of the chip, thereby strengthening the heat dissipation effect on the top and sides of the chip. In addition, the flow guide sheets inclined towards the downstream direction of the cooling oil 7 can also prevent the cooling oil from flowing in the opposite direction, and strengthen the circulating flow effect of the cooling oil in the housing 1. In addition, since the plurality of first flow guide sheets 12c and the plurality of second flow guide sheets 12d are arranged opposite to each other one by one and the distance between the first flow guide sheet 12c and the second flow guide sheet 12d and the power semiconductor chip 9 is equal, the flow and flow rate of the cooling oil 7 flowing through both sides of the power semiconductor chip 9 are the same, avoiding the generation of vortex or turbulent flow, and improving the circulating effect and heat dissipation effect of the cooling oil 7. Secondly, the height of the first flow collecting plate 12a and the second flow collecting plate 12b is greater than the thickness of the power semiconductor chip 9, and the length of the first flow collecting plate 12a and the second flow collecting plate 12b is greater than the length of the power semiconductor chip 9, which can ensure that the top and sides of the power semiconductor chip 9 are completely located in the flow guide structure, and ensure that there is enough cooling oil flowing through the top and sides of the chip.

[0043] The liquid cooling radiator 2 of the cooling oil direct current convergent power module immersion heat dissipation structure is installed on the inner bottom surface of the shell 1, the lower copper layer 4 of the DBC substrate is connected with the liquid cooling radiator 2 through the connecting layer 3 (which can be silicone grease, adhesive or welding layer 8), and the power semiconductor chip 9 is welded on the upper copper layer 6 of the DBC substrate through the welding layer 8. Due to the existence of the ceramic layer 5 of the DBC substrate, the power semiconductor chip 9 is electrically insulated from the liquid cooling radiator 2. The central part of the first side wall 103 at one end of the shell 1 is provided with an oil inlet hole 10, and the central part of the second side wall 104 at the other end of the shell 1 is provided with an oil outlet hole 11.

[0044] In the embodiment, the circulation process of the cooling oil 7 in the shell 1 is as follows: the cooling oil 7 flows into the shell from the oil inlet hole 10, and then the cooling oil 7 is divided into two parts. One part flows into the liquid cooling radiator 2 to achieve high-efficiency heat dissipation of the bottom surface of the power semiconductor chip 9. The other part flows out of the liquid cooling radiator 2 and converges around the power semiconductor chip 9 through the flow guide structure 12 to achieve high-efficiency heat dissipation of the top surface and the side surface of the power semiconductor chip 9. The two parts of the cooling oil are aggregated near the oil outlet hole 11 and flow out of the shell 1 from the oil outlet hole 11. Due to the cooling oil direct current convergent power module immersion heat dissipation structure, the bottom surface, the top surface and the side surface of the power semiconductor chip can be cooled at the same time, the cooling efficiency is high, and the total flow resistance is low because the two parts of the cooling oil circuit are connected in parallel.

[0045] The heat dissipation structure of the embodiment can simultaneously achieve heat dissipation of the bottom surface, the top surface and the side surface of the power semiconductor chip 9, and the area utilization rate of the top surface is high, which can effectively improve the heat dissipation efficiency. At the same time, the flow guide structure 12 added on both sides of the power semiconductor chip 9 guides the cooling oil 7 to the top surface and the side surface of the power semiconductor chip 9, which effectively enhances the heat dissipation effect of the power semiconductor chip 9. Secondly, the heat dissipation structure connects the cooling flow path in the liquid cooling radiator 2 and the cooling oil 7 path around the chip in parallel, the total cooling oil amount is divided, a part participates in the heat dissipation of the liquid cooling radiator 2 (the bottom surface of the power semiconductor chip 9), and the other part flows through the top surface and the side surface of the power semiconductor chip 9 to achieve heat dissipation, so that the high heat dissipation efficiency is ensured while the overall small flow resistance is maintained.

[0046] In other embodiments, the first and second flow plates 12a and 12b can also be connected with the top wall 102, the first flow plate 12a is attached to the third side wall 105 near one end of the second side wall 103, and the second flow plate 12b is attached to the fourth side wall 106 near one end of the second side wall 104. In this case, the cooling oil 7 in the upper channel can be completely converged to the top surface and the side surface of the power semiconductor chip 9 through the flow guide structure 12, thereby further enhancing the cooling effect.

[0047] Having described various embodiments of the application, it is to be understood that the above description is meant to be illustrative only, and that many modifications and variations of the embodiments are possible without departing from the scope and spirit of the described embodiments. Many modifications and variations of the described embodiments are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the described embodiments can be practiced otherwise than as specifically described.

Claims

1. A cooling oil DC converging power module immersion heat dissipation structure, characterized in that, include: The housing includes a bottom wall, a top wall, a first side wall, a second side wall, a third side wall, and a fourth side wall, and a cavity formed therein. The first side wall and the second side wall are two opposing side walls extending along the width direction of the housing, and the third side wall and the fourth side wall are two opposing side walls extending along the length direction of the housing. The first side wall is provided with an oil inlet hole, and the second side wall is provided with an oil outlet hole. The bottom of the cavity is provided with a liquid cooling heat sink, and a substrate is provided on the liquid cooling heat sink. A power semiconductor chip and a current-guiding structure are provided on the substrate. The bottom surface of the liquid-cooled heat sink is connected to the bottom wall, and the two sides of the liquid-cooled heat sink are respectively attached to the third side wall and the fourth side wall. The liquid-cooled heat sink has a flow channel arranged along the length of the housing for heat dissipation of the bottom surface of the power semiconductor chip. There is a gap between the two ends of the liquid-cooled heat sink and the first side wall and the second side wall, respectively. The bottom surface of the power semiconductor chip is connected to the top surface of the substrate, and the top and side surfaces of the power semiconductor chip are exposed in the cavity; the drainage structure is located on both sides of the power semiconductor chip and is used to gather cooling oil to the side and top surfaces of the power semiconductor chip to dissipate heat from the top and side surfaces of the power semiconductor chip. The current-guiding structure includes a first busbar and a second busbar disposed longitudinally on the substrate. The first busbar is located on the side closer to the third sidewall, and the second busbar is located on the side closer to the fourth sidewall. The power semiconductor chip is located between the first busbar and the second busbar. The projections of the first busbar and the second busbar on the substrate are two arcs extending along the length of the housing and symmetrically distributed. The distance between the first busbar and the second busbar gradually decreases from one end of the power semiconductor chip to the other end along the direction from the first sidewall to the second sidewall. A plurality of first guide plates are provided on the side surface of the first busbar facing the power semiconductor chip. These first guide plates are spaced apart along the length of the housing. The first guide plates extend longitudinally from the top of the first busbar to the top of the first busbar. One end of each first guide plate is connected to the first busbar, and the other end of each first guide plate is inclined towards the downstream direction of the cooling oil. The second busbar has a plurality of second guide plates on one side surface facing the power semiconductor chip. The plurality of second guide plates are spaced apart along the length direction of the housing. The second guide plates extend longitudinally from the top of the second busbar to the top of the second busbar. One end of the second guide plate is connected to the second busbar, and the other end of the second guide plate is inclined in the downstream direction of the cooling oil flow.

2. The cooling oil DC converging power module immersion heat dissipation structure according to claim 1, characterized in that, The angle between the first drain plate and the first manifold ranges from 30° to 60°, and the angle between the second drain plate and the second manifold is equal to the angle between the first drain plate and the first manifold.

3. The cooling oil DC converging power module immersion heat dissipation structure according to claim 2, characterized in that, Multiple first drain plates and multiple second drain plates are arranged opposite to each other, and the distance between the first drain plate and the power semiconductor chip and the distance between the second drain plate and the power semiconductor chip are equal.

4. The cooling oil DC converging power module immersion heat dissipation structure according to claim 3, characterized in that, The height of the first busbar and the second busbar is greater than the thickness of the power semiconductor chip, and the length of the first busbar and the second busbar is greater than the length of the power semiconductor chip.

5. The cooling oil DC converging power module immersion heat dissipation structure according to claim 4, characterized in that, There is a gap between the top of the first and second busbars and the top wall, or the first and second busbars are connected to the top wall.

6. The cooling oil DC converging power module immersion heat dissipation structure according to claim 1, characterized in that, The substrate is a DBC substrate, which includes a lower copper layer, a ceramic layer and an upper copper layer stacked from bottom to top; The lower copper layer of the DBC substrate is connected to the top surface of the liquid cooler through a bonding layer; The bottom surface of the power semiconductor chip is soldered to the upper copper layer of the DBC substrate via a solder layer; The bottom of the first busbar and the second busbar are soldered to the upper copper layer of the DBC substrate.

7. The cooling oil DC converging power module immersion heat dissipation structure according to claim 6, characterized in that, The connecting layer is silicone grease, adhesive, or solder layer.

8. The cooling oil DC converging power module immersion heat dissipation structure according to claim 1, characterized in that, The oil inlet is located in the center of the first sidewall, and the oil outlet is located in the center of the second sidewall.

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