EP4792424A1

EP4792424A1 - Electric machine

Info

Publication number: EP4792424A1
Application number: EP24877237.8A
Authority: EP
Inventors: Praveen Mathesan; Farook ABDULLAH; Sanjay RAVICHANDRAN; Arumugapandian DURAIPANDI; Antonyvinoth RAJA
Original assignee: Valeo Electrification SAS
Current assignee: Valeo Electrification SAS
Priority date: 2023-10-10
Filing date: 2024-10-10
Publication date: 2026-08-19
Also published as: CN122029731A; WO2025079643A1

Abstract

ELECTRIC MACHINE　An electric machine 100 for a motor vehicle includes an electric motor 130 which is adapted to drive a machine 110. The electric machine 100 also includes an inverter 120 held in an inverter housing 120a, wherein the inverter 120 is adapted to process and regulate electrical power being supplied to the electric motor 130 from an external power source. The inverter 120 further comprises a printed circuit board 124 and multiple power transistors 126 for converting a High Voltage (HV) Direct Current (DC) to a three-phase Alternating Current (AC) that drives the electric motor 130. In addition the inverter 120 comprises a frame element 128 secured to a bottom wall 123 between the printed circuit board 124 and the bottom wall 123, wherein the frame element 128 is formed with multiple integrated urging portions 128d adapted to urge the power transistors 126 with respect to the bottom wall 123.　(Figure to Abstract: FIG. 1)

Description

ELECTRIC MACHINE

Field of Invention

　　　The present invention relates to an electric machine. More particularly, the present invention relates to an assembly of power transistors of an inverter of the electric machine.

Background of the Invention

　　　Generally, an electric machine for example, an electric driven compressor includes a compressor unit, an electric motor and an inverter. The electric motor drives the compressor unit. The inverter regulates and supplies electrical power to the electric motor. The inverter is received and held inside an inverter housing. The inverter includes a printed circuit board and various heat generating electronic components such as power transistors (for example, IGBT/MOSFET). Generally, electric power is supplied from an external power source to the printed circuit board via an electrical connector mounted on a wall of the inverter housing. The electrical connector is electrically coupled to the printed circuit board. A three-phase bridge circuit consisting of the six power transistors converts a High Voltage (HV) Direct Current (DC) to a three-phase Alternating Current (AC) that drives the electric motor.
　　　The power transistors are heated during operation thereof.
　　　The heat generated during operation of the power transistors may cause damage to the power transistors due to fusing of critical elements of the power transistors, breakage or failure of the power transistors due to reduced mechanical strength of critical elements thereof at elevated temperatures. It is required to dissipate heat from the power transistors for preventing breakage or failure of the power transistors and ensuring efficient performance of the power transistors. The power transistors are urged against a bottom wall of the inverter housing for heat dissipation from the power transistors. The bottom wall being in contact with refrigerant received in the motor accommodating space of the motor housing on other side thereof acts as a heat sink for heat dissipation from the power transistors.
　　　For proper heat dissipation from the power transistors, the power transistors are required to be positioned abutting the bottom wall and in sufficient contact with the bottom wall. Conventionally, metallic leaf spring elements are used for urging the power transistors against the bottom wall. Generally, two or more leaf springs are used for urging the six power transistors against the bottom wall. Each of the leaf spring is secured to the bottom wall by a screw so as to urge the corresponding power transistors disposed between the leaf springs and the bottom wall against the bottom wall.
　　　However such an arrangement for urging the power transistors against the bottom wall requires at least two metallic leaf springs to be secured on the bottom wall. Therefore, the mounting of the leaf springs during the assembly is inconvenient and time consuming. Furthermore, such arrangement of the leaf springs fail to securely hold the power transistors and the power transistors may get dislocated due to power transistors slipping out of grip of the leaf springs.
　　　Accordingly, there is a need for an improved arrangement of power transistors arranged within a front head of an inverter that can achieve proper heat dissipation there from. More particularly, there is a need for an improved arrangement for simultaneously urging multiple power transistors against the bottom wall of the inverter housing for heat dissipation from the power transistors.

Summary of the Invention

　　　The present invention discloses an electric machine, particularly, an electric driven compressor for a motor vehicle. The electric driven compressor includes a compressor unit, an electric motor and an inverter. The electric motor is received in a motor housing and is adapted to drive the compressor unit. The inverter is held in an inverter housing and is adapted to process and regulate electrical power being supplied to the electric motor from an external power source. The inverter further comprises a printed circuit board and multiple power transistors (also referred to as semiconductors or IGBTs or MOSFETs) for converting a High Voltage (HV) Direct Current (DC) to a three-phase Alternating Current (AC) that drives the electric motor. In addition the inverter comprises a frame element secured to a front head (acting as heat sink) of the inverter housing between the printed circuit board and the bottom wall. The frame element is formed with multiple urging portions integrated therewith and adapted to urge the power transistors with respect to the bottom wall. Preferably, the frame element is made of plastic material.
　　　In accordance with an embodiment of the present invention, the frame element is adapted to simultaneously urge multiple power transistors disposed in an array with respect to the bottom wall against the bottom wall.
　　　In an embodiment, the frame element comprises multiple holding portions, wherein at least one pair of holding portions are oppositely disposed and extending from the frame element towards the bottom wall. The holding portions are adapted to hold corresponding power transistor and restrain relative axial movement of power transistor with respect to the frame element.
　　　In an embodiment, the frame element is formed with positioning pins which are received in the holes formed on the corresponding power transistors and the positioning pins are adapted to position the power transistors with respect to the bottom wall and to prevent relative lateral movement of the power transistors with respect to the frame element.
　　　In an embodiment, the frame element includes guiding holes for receiving lead frames emanating from the corresponding power transistor and extending towards the printed circuit board to guide the lead frames to corresponding apertures formed on the printed circuit board.
　　　Generally, the guiding holes corresponding to power transistors arranged opposite to each other are arranged in adjacent rows, wherein at least one of ribs and cavities are formed between guiding holes arranged in the first and second adjacent rows.
　　　Generally, the urging portions extending from the frame element are aligned with respect to the corresponding power transistors and adapted to urge the power transistors against the bottom wall when the frame element is secured to the bottom wall.
　　　In accordance with an embodiment of the present invention, the urging portion is adapted to exert an urging pressure in the range of 46N to 70N.
　　　In accordance with another embodiment of the present invention, the urging portion is a free-ended elongated finger extending from and overhanging from at least a portion of periphery of an aperture formed on the frame element. Preferably, the free-ended elongate finger comprises a substantial flat portion.
　　　In accordance with another embodiment of the present invention, the free ended elongated finger is bent towards the bottom wall along the plane of the frame element.
　　　In an embodiment, the frame element comprises metallic bushes over-moulded with respect to the frame element and adapted to receive mounting elements for mounting the frame element to the bottom wall. The mounting elements are preferably bolts.
　　　In accordance with another embodiment of the present invention, a thermal pad is disposed between the power transistors and the bottom wall.
　　　Another aspect of the present invention relates to the assembly of said electric machine, wherein the frame element is secured to the bottom wall of the front head of the inverter housing by a plurality of mounting elements. The frame element is formed with multiple integrated urging portions adapted to simultaneously urge the power transistors against the bottom wall, wherein the power transistors are snap-fitted to the frame element and secured by holding portions and positioning pins which restrains relative axial and prevents lateral movement of the power transistors with respect to the frame element respectively. The urging portions integrally formed with the frame element ensures sufficient urging force is applied on the power transistors to urge the power transistors with respect to the front head when the frame element is secured to the bottom wall. The lead frames emanating from the power transistors are guided through the guide holes to the corresponding apertures formed on the printed circuit board. To improve thermal conductivity the thermal pad is disposed between the power transistors and the bottom wall.

　　　Other characteristics, details and advantages of the invention may be inferred from the description of the invention hereunder. A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying figures, wherein:

FIG. 1 illustrates a schematic diagram of assembly of an electric machine in accordance with an embodiment of the present invention.

FIG. 2a illustrates an enlarged cross-sectional view depicting the assembly of an inverter of FIG. 1.

FIG. 2b illustrates an enlarged cross-sectional view A-A of FIG. 2a.

FIG. 3 shows an assembled view of the electric machine according to an embodiment of the present invention.

FIG. 4 illustrates an exploded view depicting the electric machine of FIG. 3.

FIG. 5 shows a frame element according to another embodiment of the present invention.

FIG. 6 illustrates bottom view of the frame element of FIG. 5.

Detailed Description of the Invention

　　　 It must be noted that the accompanying figures disclose the invention in a detailed enough way to be implemented, said figures helping to better define the invention if needs be. The invention should however not be limited to the embodiment disclosed in the description.
　　　The present invention envisages an electric machine, particularly, an electric driven compressor 100. Referring to FIG. 1, the electric driven compressor 100 is illustrated. The electric driven compressor 100 comprises a compressor unit 110, an electric motor 130 and an inverter 120.
　　　The compressor unit 110 is received in an enclosure defined by a compressor housing 110a. The compressor housing 110a is an open ended housing that includes a bottom wall and peripheral wall. The compressor unit 110 compresses a fluid, particularly, a refrigerant flowing through an air-conditioning loop of a vehicle air-conditioning system. The compressor unit 110 is generally a scroll type compressor. However, the present invention is not limited to any particular configuration of the compressor unit 110. The compressor housing 110a protects the compressor unit 110 against harmful external environment conditions.
　　　The electric motor 130 is received and held in a motor housing 130a. The electric motor 130 drives the compressor unit 110. In accordance with an embodiment, the motor housing 130a is also an open ended housing that includes a bottom wall and peripheral wall disposed along a periphery of the bottom wall.
　　　The inverter 120 is received and held in an inverter housing 120a. The inverter housing 120a is of larger radial dimension compared to the motor housing 130a and at least a portion of the inverter housing 120a extends beyond the motor housing 130a to provide space for mounting of at least one electrical connector (not shown) to the inverter housing 120a. The inverter housing 120a comprises a front head 122 (acting as a heat sink) and a cover 121. The front head 122 is an open ended housing that includes a bottom wall 123 and a peripheral wall 123a disposed along a periphery of the bottom wall 123. The front head 122 and the cover 121 are assembled together to define an enclosure that receives components, particularly electronic components such as for example a printed circuit board 124 to safeguard the electronic components from harmful external environment. The cover 121 is removable with respect to the front head 122 for accessing the components received in the front head 122 for service and maintenance.
　　　The motor housing 130a is open ended separate housing arranged between the compressor housing 110a and the inverter housing 120a. In one arrangement an open end of the motor housing 130a is abutting the bottom wall 123 or closed end of the inverter housing 120a and the bottom wall 123 or closed end of the motor housing 130a is abutting open end of the compressor housing 110a to define separate enclosures for receiving the electric motor 130 and the compressor unit 110.
　　　Alternatively, the closed ends or bottom walls of the motor housing 130a and the inverter housing 120a are abutting each other and the open ends of the motor housing 130a and the compressor housing 110a are abutting each other to define a common enclosure for the electric motor 130 and the compressor unit 110.
　　　 In accordance with yet another embodiment, the motor housing 130a and the front head 122 of the inverter housing 120a are formed integrally with two open ends opposite to each other and a common wall between the front head 122 and the motor housing 130a. The first open end is closed by the open end of the compressor housing 110a to define a common enclosure for the electric motor 130 and the compressor unit 110. The second open end is closed by the cover 121 to define the enclosure for receiving the inverter 120.
　　　However, the present invention is not limited to any particular configuration and arrangement of the compressor housing 110a, the motor housing 130a and the inverter housing 120a as far as the compressor housing 110a, the motor housing 130a and the inverter housing 120a are capable of enclosing the compressor unit 110, the electric motor 130 and the inverter 120 to protect these against harmful external environment conditions.
　　　FIG. 2a illustrates an enlarged cross-sectional view depicting the assembly of the inverter 120. The inverter 120 further comprises a printed circuit board 124 and multiple power transistors 126 (also referred to as semiconductors or IGBTs or MOSFETs) for converting a High Voltage (HV) Direct Current (DC) to a three-phase Alternating Current (AC) that drives the electric motor 130. In addition the inverter 120 comprises a frame element 128 secured to a bottom wall 123 of a front head 122 of the inverter housing 120a between the printed circuit board 124 and the bottom wall 123. In the assembled state, the frame element 128 is secured to the bottom wall 123 by a plurality of mounting elements 140. The frame element 128 is formed with multiple urging portions 128d integrally formed there with and adapted to simultaneously urge the power transistors 126 disposed in an array against the bottom wall 123. The urging portions 128d ensures exerting sufficient urging force on the power transistors to urge the power transistors against the bottom wall 123. The frame element 128 further includes positioning pins 128b orthogonally extending from the frame element 128 and received in holes 126b formed on the corresponding power transistors 126 to position the power transistors 126 with respect to the bottom wall 123 and prevent relative lateral movement of the power transistors 126 with respect to the frame element 128. The frame element 128 further comprises guiding holes 128c for receiving lead frames 126c emanating from the corresponding power transistor 126 and extending towards the printed circuit board 124 to guide the lead frames 126c to corresponding apertures 124a formed on the printed circuit board 124.
　　　FIG. 2b illustrates an enlarged cross-sectional view of the inverter along section line A-A illustrated in FIG. 2a. The frame element 128 comprises at least one urging portion 128d and at least one pair of holding portion 128a, at least one positioning pin 128b and a set of guiding holes 128c corresponding to each power transistor 126 to be urged by the urging portion 128d. Generally, holding portions 128a of the multiple holding portions are disposed opposite to each other and extend from the frame element 128 towards the bottom wall 123. The holding portions 128a are adapted to hold corresponding power transistors 126 and restrains relative axial movement of the power transistors 126 with respect to the frame element 128.
　　　FIG. 3 and 4 illustrates an isometric view and an exploded view of the electric driven compressor 100 in accordance with an embodiment of the present invention respectively. The power transistors 126 are urged against the bottom wall 123 by the corresponding urging portions128d. More specifically, the power transistors 126 are positioned and held by corresponding pair of holding portions 128a and positioning pins 128b and urged against the bottom wall 123 by the urging portions 128d. The lead frames 126c emanating from the corresponding power transistors 126 are guided through the corresponding guide holes 128c to the corresponding apertures 124a formed on the printed circuit board 124 (not shown). Further, the frame element 128 is secured to the bottom wall 123 of the front head 122 of the inverter housing 120a by a plurality of mounting elements 140. To improve thermal conductivity a thermal pad 150 is disposed between the power transistors 126 and the bottom wall 123.
　　　In accordance with one embodiment, the frame element 128 is having a planar structure with at least one raised portion as shown in FIG 5 and 6. Preferably, the frame element 128 is made of plastic material. Preferably, the frame element 128 comprises a centrally disposed first portion 128.1 and a pair of side portions 128.2 on both sides of the first portion 128.1. The centrally disposed first portion 128.1 extends along a first plane and the side portions 128.2 coplanar with respect to each other extend along a second plane different from and parallel to the first plane. Generally, the side portions 128.2 are relatively closer to the bottom wall compared to the first portion 128.1 in the assembled configuration of the frame element 128 on the front head 122. Since the holding portions 128a, positioning pins 128b, the guiding holes 128c and the urging portion 128d are all integrally formed with the frame element 128, these are of plastic material. The frame element 128 further comprises metallic bushes 128e over-moulded with respect to the frame element 128 and adapted receive mounting elements 140 for mounting the frame element 128 to the front head 122, particularly, to the bottom wall 123. The guiding holes 128c are disposed on the first portion 128.1. The urging portions 128d, the holding portions 128a and the positioning pins are disposed on the side portions 128.2. Such stepped configuration of the side portions 128.2 of the frame element 128 and the urging portions 128d configured on the side portions 128.2 provides improved urging of the power transistors 126 against the bottom wall 123 when the frame element 128 is mounted to the front head 122.
　　　The frame element 128 is mounted to the front head 122 by means of mounting elements 140, preferably bolts. The bottom wall 123 of the front head 122 comprises columns with mounting holes 122a formed thereon for mounting the frame element 128 to the front head 122. Particularly, mounting bolts 140 pass through aligned holes 128f formed on the frame element 128 and the mounting holes 122a formed on the columns of the front head 122 to mount the frame element 128 to the bottom wall 123 of the front head 122. When the frame element 128 and the printed circuit board 124 is mounted to the front head 122, the frame element 128 is disposed parallel to the bottom wall 123 and between the printed circuit board 124 and the bottom wall 123. The frame element 128 is urged against the bottom wall 123 of the front head 122, thereby causing the urging portions 128d to urge the power transistors 126 disposed there-between towards the bottom wall 123 as the frame element 128 is mounted on the bottom wall 123.
　　　The holding portions 128a extend from the frame element towards the bottom wall 123. At least two holding portions 128a are arranged along opposite sides of the power transistor 126 urged by the urging portion 128d. Each holding portion 128a extending from the frame element 128 comprises a fixed end and a free end opposite to the fixed end. The fixed end is integrally formed with and extends from the frame element 128. The holding portion 128a comprises a latching member 128a.1 formed at the free end thereof adapted to engage with engaging member 126a in the form of a lip formed on a corresponding side of the power transistor 126. The latching members 128.1 of the opposite holding portions 128a engage with the engaging members 126a extending along the opposite sides of the power transistor 126 to securely hold the power transistor 126. Generally, the engaging members 126a are formed above the base of the power transistor 126 such that the power transistor 126 extends beyond the holding portions 128a when held by the holding element 128a. With such configuration, the power transistor 126 can be urged against the bottom wall by the corresponding urging portion 128d. More specifically, the opposite holding members 128a securely hold the corresponding power transistor 126 and retains relative axial movement of power transistor 126 with respect to the frame element 128 along a direction orthogonal to the bottom wall. The holding portions 128a holds the respective power transistors 126 aligned with corresponding urging portions 128d to be urged by the corresponding urging portions 128d when the frame element 128 is mounted on the front head 122. Further, the opposite holding portions 128a securely holds the corresponding power transistor 126 and prevents relative angular movement of power transistor 126 with respect to the frame element 128.
　　　The positioning pins 128b extend orthogonally from the frame element 128 towards the bottom wall 123 in the assembled configuration of the frame element 128 with respect to the front head 122. Each positioning pin 128b adapted to register with a complementary hole 126b formed in a corresponding power transistor 126 to arrest movement thereof in at least one degree of freedom. The positioning pins 128b received in respective holes 126b formed on the corresponding power transistors 126 are adapted to position the power transistors 126 with respect to the urging portions 128d and the bottom wall 123 and prevent relative sliding movement of the power transistors 126 with respect to the frame element 128.
　　　The set of guiding holes 128c for a corresponding power transistor receives lead frames 126c emanating from the power transistor 126 and extending towards the printed circuit board 124 to guide the lead frames 126c to corresponding apertures 124a formed on the printed circuit board 124.
　　　Preferably, the frame element 128 comprises a plurality of urging portions 128d corresponding to plurality power transistors 126 arranged in an array. More specifically, at least one urging portion 128d interacts with one power transistor 126 of the plurality of power transistors to urge the power transistor 126 against a bottom wall 123 of the front head 122 as the frame element 128 is mounted on the front head 122. The urging portions 128d are configured on the frame element 128 based on the arrangement of the power transistors 126 to be held, positioned and urged against the bottom wall 123 for heat dissipation from the power transistors 126. In one embodiment, the urging portions 128d are configured on the frame element 128 in parallel rows to interact with corresponding power transistors 126 arranged in parallel rows. However, the present invention is not related to any particular configuration and place.
　　　In accordance with an embodiment of the present invention, the urging portion 128d is a free-ended elongated finger overhanging from at least a portion of periphery of an aperture 128d.1 formed on the frame element 128. Advantageously, the free-ended elongate finger comprises a substantial flat portion. In addition, the free ended elongated finger is bent towards the bottom wall 123 along the plane of the frame element 128.
　　　In accordance with another embodiment of the present invention, the urging portion 128d is adapted to exert an urging pressure in the range of 46N to 70N. However, the present invention is not limited to any particular value of urging pressure to exert on the power transistors 126.
　　　With such configuration of the frame element 128 formed with multiple urging portions 128d, the frame element 128 is adapted to simultaneously hold, position and urge multiple power transistors 126 arranged in an array with respect the bottom wall 123.

List of Reference Numerals

　　　100 : electric machine
　　　110 : compressor unit
　　　110a : compressor housing
　　　120 : inverter
　　　120a : inverter housing
　　　121 : cover
　　　122 : front head
　　　122a : mounting hole
　　　123 : bottom wall of the front head
　　　123a : peripheral wall
　　　124 : printed circuit board
　　　124a : aperture on the printed circuit board
　　　126 : power transistor
　　　126a : engaging member
　　　126b : hole in the power transistor
　　　126c : lead frame from the power transistor
　　　128 : frame element
　　　128.1 : centrally disposed first portion of the frame element
　　　128.2 : pair of side portions 128.2 of the frame element
　　　128a : holding portion
　　　128a.1 : latching member of the holding portion
　　　128b : positioning pin
　　　128c : guiding hole
　　　128d : urging member
　　　128d.1 : aperture in the frame element where the urging member is overhanging
　　　128e : metallic bush
　　　128f : hole in the frame element for over moulding the metallic bush
　　　130 : electric motor
　　　130a : motor housing
　　　140 : mounting bolt
　　　150 : thermal pad

Claims

　　　An electric machine (100) comprising:
　　　　　　● an electric motor (130);
　　　　　　● a machine (110) driven by the electric motor (130);
　　　　　　● an inverter (120) received and held in an inverter housing (120a) and adapted to process and regulate electrical power being supplied to the electric motor (130) from an external power source, wherein the inverter (120) comprising:
　　　　　　　　　o a printed circuit board (124); and
　　　　　　　　　o multiple power transistors (126) for converting a High Voltage (HV) Direct Current (DC) to a three-phase Alternating Current (AC) that drives the electric motor (130),
　　　characterized in that the inverter (120) further comprising a frame element (128) secured to a bottom wall (123) of a front head (122) of the inverter housing (120a) between the printed circuit board (124) and the bottom wall (123), wherein the frame element comprises integrated urging portions (128d) adapted to urge the power transistors (126) to the bottom wall (123).
　　　The electric machine (100) as claimed in the previous claim, wherein the frame element (128) is made of plastic material.
　　　The electric machine (100) as claimed in any of the preceding claims, wherein the frame element (128) is adapted to simultaneously urge the multiple power transistors (126) disposed in an array with respect the bottom wall (123).
　　　The electric machine (100) as claimed in any of the preceding claims, wherein the frame element (128) further comprising at least one pair of oppositely disposed holding portions (128a) extending therefrom towards the bottom wall (123), adapted to hold corresponding power transistor (126) and prevent relative axial movement of power transistor (126) with respect to the frame element (128).
　　　The electric machine (100) as claimed in any of the preceding claims, wherein the frame element (128) further comprising positioning pins (128b) received in holes (126b) formed on the corresponding power transistors (126) and adapted to position the power transistors (126) with respect to the bottom wall (123) and prevent relative lateral movement of the power transistors (126) with respect to the frame elements (128).
　　　The electric machine (100) as claimed in any of the preceding claims, wherein the frame element (128) further comprising guiding holes (128c) for receiving lead frames (126c) emanating from the corresponding power transistor (126) and extending towards the printed circuit board (124) to guide the lead frames (126c) to corresponding apertures (124a) formed on the printed circuit board (124).
　　　The electric machine (100) as claimed in any of the preceding claims, wherein the urging portions (128d) are aligned with respect to the corresponding power transistors (126) and adapted to urge the power transistors (126) against the bottom wall (123) when the frame element (128) is secured to the bottom wall (123).
　　　The electric machine (100) as claimed in any of the preceding claims, wherein the urging portion (128d) is adapted to exert an urging pressure in the range of 46N to 70N.
　　　The electric machine (100) as claimed in the previous claim, wherein the urging portion (128d) is a free-ended elongate finger overhanging from at least a portion of periphery of an aperture (128d.1) formed on the frame element (128).
　　　The electric machine (100) as claimed in the previous claim, wherein the free-ended elongate finger comprises a substantial flat portion.
　　　The electric machine (100) as claimed in the previous claim, wherein the free ended elongate finger is bent towards the bottom wall (123) along the plane of the frame element (128).
　　　The electric machine (100) as claimed in any of the preceding claims further comprises a thermal pad (150) disposed between the power transistors (126) and the bottom wall (123).
　　　The electric machine (100) as claimed in any of the preceding claims, wherein the frame element (128) further comprising metallic bushes (128e) over-moulded with respect to the frame element (128) and adapted receive bolts (140) for mounting the frame element (128) to the bottom wall (123).