EP4736577A1 - An electric fluid heater - Google Patents

Abstract

An electric fluid heater (100) includes a housing (10), a printed circuit board (20), a heating element (30), a power transistor assembly (40), a thermal pad (50) and a spring (60). The printed circuit board (20) with apertures (20a) formed thereon is mounted spaced from a base portion (10a) of the housing (10). The power transistor assembly (40) includes a holder (42) and power transistors (44) with lead frames (44a) to be received and held in the apertures (20a) of the printed circuit board (20). The power transistor assembly (40) includes a positioning means (46) to position the power transistor assembly (40) either parallel or orthogonal with respect to the base portion (10a). The power transistor assembly (40) is moved substantially orthogonal to and towards the printed circuit board (20) to enable the lead frames (44a) to be received and secured in the apertures (20a).

Description

DESCRIPTION

Title : AN ELECTRIC FLUID HEATER

[1] The present invention relates to a heat exchanger, particularly, the present invention relates to an electric fluid heater for a vehicle.

[2] An electric fluid heater includes a housing, a printed circuit board, at least one heating element, a power transistor assembly, at least one thermal pad, at least one spring element and bolts for mounting the spring element to the housing. The heating element is controlled by the printed circuit board. The power transistor controls current supply to the printed circuit board, particularly converts high voltage (HV) direct current (DC) to a three- phase alternating current (AC) for operation of the electrical heating coils. The power transistor received inside a power transistor holder includes a plurality of lead frames emanating therefrom and extending outside the power transistor holder. The lead frames are received and held in apertures formed on the printed circuit board and are securely connected to the printed circuit board by soldering. The power transistor inherently gets heated during operation thereof. The spring element is mounted on one wall of the housing with the power transistor disposed between the wall of the housing and the spring element. With such configuration, the spring element urges the power transistors of the power transistor assembly towards the wall of the housing with the thermal pad disposed between the power transistor and the wall of the housing. Such arrangement enables improved thermal contact between the power transistor and the wall of the housing, thereby resulting in and cooling of the power transistor by the fluid flowing inside the housing on other side of the wall that acts as a cooling surface.

[3] The lead frames of the power transistor are required to be properly positioned inside the housing and aligned to the apertures of the printed circuit board, any misalignment of the lead frames with respect to the apertures may cause improper soldering and soldering defects. For achieving proper alignment between the lead frames of the power transistor and the apertures of the printed circuit board, the power transistor assembly is required to properly positioned with respect to the housing within limited space inside the housing.

[4] None of the prior art addresses the problem of improper soldering between the printed circuit board and the lead frames of the power transistor due to improper positioning of the power transistor assembly with respect to the housing. [5] Accordingly, there is a need for an electric fluid heater that ensures proper positioning of the power transistor assembly with respect to the housing to achieve proper soldering between the PCB and the lead frames of the power transistor.

[6] An object of the present invention is to provide an electric fluid heater that obviates the drawbacks associated with convention electric coolant heater, particularly, problems due to improper positioning of the power transistor assembly inside limited space in a housing of the electric fluid heater.

[7] Primary object of the present invention is to provide an electric fluid heater that prevents defects in soldering between lead frames emanating from power transistor and printed circuit board due to misalignment between the lead frames and apertures formed on printed circuit board to prevent problems arising due to the soldering defects.

[8] An electric fluid heater for an automotive vehicle is disclosed in accordance with an embodiment of the present invention. The electric fluid heater includes a housing, a printed circuit board, at least one heating element, at least one power transistor assembly, at least one thermal pad and at least one spring element. The housing includes a base portion, side walls and removable covers assembled to form an enclosure to define an interior of the housing. The housing further includes an inlet and an outlet for ingress and egress of fluid with respect to the interior the housing. The printed circuit board is mounted spaced from the base portion of the housing that is in contact with a fluid being heated. The at least one heating element is controlled by the printed circuit board and is received inside the housing. The at least one power transistor assembly includes at least one power transistor holder and at least one power transistor received and securely held inside the at least one power transistor holder. Each power transistor includes a plurality of lead frames emanating therefrom to extend outside the power transistor holder and received and held in apertures formed on the printed circuit board. The least one thermal pad is disposed along at least one of the base portion and the side walls and between the power transistor assembly and the housing. The at least one spring element is mounted on the housing to urge the power transistors against the thermal pad to enable cooling of the at least one power transistor by the fluid circulating inside the housing. The power transistor assembly includes a positioning means to position the power transistor assembly either parallel or orthogonal with respect to the base portion. The power transistor assembly is moved with respect to the housing to enable the lead frames to be received and secured in the apertures.

[9] Generally, either one of the base portion and the side walls includes a plurality of screwhubs extending there from towards the respective cover opposite thereto to receive mounting screws passing through either one of the printed circuit board and an auxiliary housing for mounting either one of the printed circuit board and the auxiliary housing to the housing.

[10] Particularly, the first cover covers a first opening of the housing along a printed circuit board side of the housing.

[11] Additionally, a second cover covers a second opening of the housing opposite to the first opening.

[12] Generally, at least one of the base portion and the side walls includes at least one flat platform against which the thermal pads and the corresponding power transistors are urged and against which the thermal pads abuts.

[13] Generally, the printed circuit board is disposed spaced from the base portion of the housing and between the base portion and the cover.

[14] Generally, the positioning means includes engagement elements formed on the power transistor holder that interacts with at least one screw hub formed on housing to position the power transistor assembly with respect to the housing.

[15] Further, the power transistor holder includes reinforcement ribs formed thereon.

[16] Particularly, the power transistor holder includes openings formed with cut-outs, tabs and protrusions along inner sides of the openings to support and securely hold the power transistors within the openings.

[17] Generally, the lead frames are either one of orthogonally bent and straight based on whether plane of the power transistor assembly is parallel to or orthogonal to the printed circuit board respectively.

[18] Further, the power transistor holder includes at least one set of positioning apertures corresponding to each power transistor for passage of lead frames there through.

[19] Specifically, each set of positioning apertures includes a central circular aperture and side oblong apertures, the central circular aperture securely holds a central lead frame to position the power transistor inside the corresponding power transistor holder.

[20] Further, the electric fluid heater includes at least one guiding plate corresponding to the at least one power transistor, the at least one guiding plate is disposed between the power transistor assembly and the printed circuit board and is mounted on the printed circuit board.

[21] Specifically, each guiding plate includes at least one set of guiding holes corresponding to at least one power transistor assembly for aligning and guiding the lead frames to the corresponding apertures formed on the printed circuit board. [22] Particularly, the power transistor assembly, the thermal pad and the spring element are disposed parallel to each other and the printed circuit board.

[23] More specifically, the power transistor assembly is sandwiched between the thermal pad and the spring element.

[24] In one embodiment of the present invention, the lead frames extending parallel to the plane of the power transistor assembly and are bent to be orthogonally connected to the printed circuit board.

[25] Generally, the spring is mounted to the housing by means of bolts. Each bolt includes a threaded shaft portion and a bolt head, the threaded shaft portion engages with the base portion.

[26] A method of assembling the electric fluid heater includes the steps of receiving, positioning and securely holding power transistors in a power transistor holder to form a power transistor assembly. Thereafter the method includes the step of positioning the power transistor assembly either parallel or orthogonal to a base portion of the housing of the electric fluid heater by means of engagement elements formed on the power transistor holder and at least one screw-hub formed on the housing. Subsequently, the method includes the step of moving the power transistor assembly with respect to the housing along a direction orthogonal to the base portion and away from the base portion. Simultaneously the method includes the step of aligning the lead frames emanating from the power transistor with respect to the apertures formed on the printed circuit board along by using a guiding plate. Thereafter, the method includes the step of receiving and securely holding the lead frames in the apertures. Further, the method includes the step of mounting the spring element on a base portion of the housing with the power transistor assembly and the thermal pad sandwiched between the spring element and the base portion. Finally, the method includes the step of soldering the lead frames received in the apertures to the printed circuit board.

[27] Other characteristics, details and advantages of the invention can 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:

[28] FIG. 1 illustrates an isometric view of an electric fluid heater in accordance with an embodiment of the present invention. [29] FIG. 2 illustrates the electric fluid heater without a first cover to depict the internal details thereof, also is depicted an enlarged view depicting a section of the interior of the electric fluid heater;

[30] FIG. 3 illustrates an exploded view of the electric fluid heater of FIG. 1;

[31] FIG. 4 illustrates an isometric view of the housing of the electric fluid heater of FIG. 1 ;

[32] FIG. 5 illustrates a schematic representation of a power transistor assembly and a thermal pad disposed between a flat platform and a printed circuit board;

[33] FIG. 6 illustrates an isometric view of a power transistor holder of the power transistor assembly of FIG. 5;

[34] FIG. 7 illustrates another view of the power transistor holder of FIG.6;

[35] FIG. 8 illustrates an isometric view of a power transistor of the power transistor assembly of FIG. 5;

[36] FIG.9 illustrates an isometric view of a guiding plate in accordance with an embodiment of the present invention;

[37] FIG. 10 illustrates an isometric view of an electric fluid heater in accordance with another embodiment of the present invention;

[38] FIG. 11 illustrates an exploded view of the electric fluid heater of FIG. 10;

[39] FIG. 12 illustrates the exploded view depicting elements of a power transistor assemblies and other elements such as spring, bolts and corresponding thermal pads, guiding plates and printed circuit board of the electric fluid heater; and

[40] FIG. 13 illustrates a block diagram depicting various steps involved in a method for assembling an electric fluid heater.

[41] It must be noted that the 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.

[42] The present disclosure envisages an electric fluid heater, particularly, an electric coolant heater, wherein various elements of the electric fluid heater, such as for example, a printed circuit board, at least one heater element, at least one power transistor assembly, at least one thermal pad and at least one spring are packaged in a limited space inside a housing. The housing includes base portion, side walls and removable covers that together form an enclosure to define an interior of the housing. Generally, the base portion divide the interior of the housing into a first portion and a second portion, wherein fluid to be heated, particularly, coolant is heated by an electrical heating coil in the first portion of the housing. The power transistor assembly is disposed in the second portion between the base portion and the printed circuit board disposed in the second portion. The power transistor converts high voltage (HV) direct current (DC) to a three- phase alternating current (AC) for operation of the electrical heating coils. The spring urges a power transistor of the power transistor assembly against flat platform formed on the base portion that acts cooling surface for effective heat dissipation from the power transistor that gets heated during operation thereof. The printed circuit board controls operation of the electrical heating coils by controlling the current flow thereto. The power transistor assembly of the electric fluid heater includes power transistors with lead frames emanating therefrom. The lead frames are secured to the printed board by soldering. The electric fluid heater of the present invention includes various provisions such as positioning means for positioning the power transistor within corresponding power transistor holder and means for positioning the power transistor assembly within the housing. The electric fluid heater further includes guiding plate for guiding the lead frames emanating from the power transistor to apertures formed on the printed circuit board to ensure proper soldering and avoid soldering defects. Although the present invention explained with example of an electric fluid heater in the forthcoming description and the accompanying drawings, wherein it is required to position a power transistor in limited space within a housing and with respect to a printed circuit board to properly align lead frames emanating from the power transistor with respect to apertures formed on the printed circuit board to achieve proper soldering and avoid soldering defects, however, the present invention is also applicable in any other applications wherein an electric component is required to be positioned in a limited space and is required to be aligned with respect to a printed circuit board while being urged against any flat surface of the housing.

[43] FIG. 1 illustrates an isometric view of an electric fluid heater 100 for an automotive vehicle in accordance with an embodiment of the present invention. FIG. 2 illustrates the electric fluid heater 100 without a first cover 10c to depict the internal details thereof, also, is depicted an enlarged view depicting a section of the interior of the electric fluid heater 100 depicting a spring 60 urging a power transistor 44 against a base portion 10a of the housing 10 for heat dissipation for the power transistor 44. FIG. 3 illustrates an exploded view of the electric fluid heater 100.

[44] The electric fluid heater 100 includes a housing 10, a printed circuit board 20, at least one heating element 30, at least one power transistor assembly 40, at least one thermal pad 50 and at least one spring element 60 corresponding to the power transistor assemblies 40. [45] The housing 10 includes the base portion 10a, side walls 10b and removable covers 10c and 10d forming an enclosure defining an interior of the housing 10. More specifically, the housing 10 includes the base portion 10a and a side walls 10b also referred to as peripheral wall 10b disposed along the periphery of the base portion 10a. The base portion 10a divide the interior of the housing 10 into a first portion and a second portion. The housing 10 is open on both sides and is closable by covers 10c and 10d. The first cover 10c covers a first opening 16a of the housing 10 along the printed circuit board side of the housing 10 to define the first portion between the base portion 10a and the first cover 10c. Similarly, a second cover 10d covers a second opening 16b opposite to the first opening 16a to define the second portion between the base portion 10a and the second cover 10d. The base portion 10a includes a first side facing the first cover 10c and a second side facing the second cover 10d. The first side of the base portion 10a includes at least one flat platform 10f extending towards the first cover 10c as illustrated in FIG. 5. The power transistor assembly 40 is disposed in the first portion of the housing 10 between the base portion 10a and the printed circuit board 20. The thermal pads 50 and the corresponding power transistors 44 are urged against the flat platform 10f and the thermal pads 50 abuts against the flat platform 10f when the spring 60 mounted on the first side of the base portion 10a urges the power transistors towards the base portion 10a. The second side of the base portion 10a facing the second cover 10d is configured with channels that receives the fluid to be heated, particularly, coolant and the heating element 30 in the form of at least one electrical heating coil. With such configuration, the base portion 10a is constantly in contact with the coolant flowing in the channels and act as a cooling surface. The electrical heating coils are maintained spaced apart from each other inside the channels. The removable covers 10c and 10d provide access to the at least one power transistor assembly 40 and the heating coils respectively. The housing 10 further includes an inlet 12a and an outlet 12b for ingress and egress of fluid with respect to the interior the housing 10, particularly, the second side of the housing 10. Particularly, the inlet 12a and the outlet 12b are in fluid communication with the channels configured on the base portion 10a on the second side thereof facing the second cover, for ingress and egress of the fluid to be heated with respect to the channels. The housing 10 further includes an electrical connector socket 13 for receiving an electrical connector secured to extreme end of a power cable for supplying electrical power to the electric fluid heater 100. In accordance with another embodiment of the present invention, the housing includes an auxiliary housing 11 extending from one of the side walls 10b of the housing 10 for receiving the at least one power transistor assembly 40 therein. The open end of the auxiliary housing 11 is closed by a cover 10e to protect the delicate electronic components of the power transistor assembly 40 against harsh external environment. [46] The printed circuit board 20 is received in the first portion of the housing 10 and is mounted spaced from the base portion 10a of the housing 10. The printed circuit board 20 is disposed parallel to the base portion 10a of the housing 10. The printed circuit board 20 is disposed between the base portion 10a and the first cover 10c. Generally, the first side of the base portion 10a includes a plurality of screw-hubs 14 that extend there from towards the first cover 10c and receive mounting screws 14a for mounting the printed circuit board 20 inside the housing 10. The printed circuit board 20 further includes apertures 20a formed thereon for receiving lead frames.

[47] The at least one heating element 30 is controlled by the printed circuit board 20 and received inside the channels formed on second side of the base portion 10a facing the second cover 10d. Each channel receives and securely holds at least one electrical heating coils therein. In case multiple electrical heating coils are received and held in the channel, the multiple electrical heating coils are maintained in spaced apart configuration with respect to each other.

[48] The electric fluid heater 100 includes at least one power transistor assembly 40 received in the second portion of the housing 10 between the spring element 60 and the thermal pad 50. In accordance with one embodiment, the power transistor assembly 40 is positioned parallel with respect to the base portion 10a as illustrated in FIG. 2 by means of engagement elements 42a formed on a power transistor holder 42 that interacts with at least one screw-hub 14 extending from the base portion 10a towards the cover 10c. Each power transistor assembly 40 includes at least one power transistor holder 42 as illustrated in Fig. 6 and FIG. 7, and power transistors 44.

[49] Referring to Fig. 6 and FIG. 7, the power transistor assembly 40, particularly, the power transistor holder 42 includes a positioning means 46 in the form of engagement elements 42a formed on outer sides thereof to position the power transistor holder 42 with respect to the housing 10. Particularly, the positioning means includes engagement elements 42a formed on the power transistor holder 42 that interacts with at least one screw-hub 14 formed on housing 10 to permit movement of the power transistor assembly 40 in the direction A orthogonal to the base portion 10a and the printed circuit board 20 as illustrated in FIG. 2. The power transistor holder 42 further includes openings 42b formed with cut-outs 42c, tabs 42d and protrusions 42e formed along inner sides of the openings 42b to support and securely hold the power transistors 44 within the openings 42b. Particularly, the cut-outs 42c formed on peripheral walls of the power transistor holder 42 supports the power transistors 44 within the openings 42b. Whereas the tabs 42d extending inwardly towards the openings 42b retain the power transistors 44 within the openings 42b and the protrusions formed on inside walls of the power transistor holder 42 protrude inwardly towards the opening 42b to grip the power transistors 42 from sides. The power transistor holder 42 further includes reinforcement ribs 48 formed thereon. With such configuration of the power transistor holder 42, the power transistors 44 are received and securely held in the openings 42b of the corresponding power transistor holder 42. The power transistor holder 42 further includes at least one set of positioning apertures 43 corresponding to each power transistor 44 for passage of lead frames 44a emanating from the power transistor 44 there through. In case the power transistor assembly 40 is arranged parallel to the base portion 10a, the positioning apertures 43 are formed on a portion of the power transistor holder 42 along the plane of the power transistor holder 42. The lead frames 44a emanating from the power transistors 44 are orthogonally bent and extreme ends of the lead frames 44a pass through the positioning apertures 43. More specifically, the number of apertures in each set of positioning apertures corresponds to the number of the lead frames 44a emanating from the corresponding power transistor 44. Each set of positioning apertures 43 includes a central circular aperture 43a and side oblong apertures 43b disposed on sides of the central circular aperture 43a. The central circular aperture 43a securely holds a central lead frame 44a to position the power transistor 44 inside the corresponding power transistor holder 42.

[50] The power transistor 44 converts high voltage (HV) direct current (DC) to a three- phase alternating current (AC) for operation of the electrical heating coils. Referring to the FIG. 8, each power transistor 44 includes the lead frames 44a emanating therefrom that extend outside the power transistor holder 42 and are received and held in the apertures 20a formed on the printed circuit board 20. The lead frames 44a extending parallel to the plane of the power transistor assembly 40 are bent to be orthogonally connected to the printed circuit board 20. Such configuration of power transistor 44 with orthogonally bent lead frames 44a is applicable for configuring connection between the lead frames and the printed circuit board when the power transistor assembly 40 and the printed circuit board 20 disposed parallel with respect to the base portion 10a.

[51] The at least one thermal pad 50 illustrated in FIG. 3 is disposed along the base portion 10a and between the power transistor assembly 40 and the housing 10, particularly, between the power transistors 44 and the flat platform 10f formed on the first side of the base portion 10a. The thermal pad 50 improves surface contact between the power transistors 44 and the flat platform 10f formed on the first side of the base portion 10a that acts as cooling surface, thereby improving heat dissipation from the power transistors 44 that are prone to get heated during operation thereof. [52] The at least one spring element 60 is mounted on the housing 10, particularly, the first side of the base portion 10a to urge the power transistors 44 against the thermal pad 50 to ensure efficient heat dissipation from the power transistors 44. More specifically, the spring element 60 is mounted on the first side of the base portion 10a by means of bolts 70. Each bolt 70 bolt includes a threaded shaft portion 70a and a bolt head 70b, wherein the threaded shaft portion 70a engages with the base portion 10a. At least a portion of the spring element 60 passes through the openings 42b formed on the corresponding power transistor holder 42 and urges the power transistors 44 received in the power transistor holder 43 against the flat platform 10f for cooling of the power transistors 44 by the fluid circulating on the other side of the base portion 10a.

[53] The electric fluid heater 100 further includes at least one guiding plate 80 corresponding to the power transistor assembly 40. The at least one guiding plate 80 is disposed between the power transistor assembly 40 and the printed circuit board 20. The at least one guiding plate 80 is mounted on the printed circuit board 20 and aligns and guides the lead frames 44a emanating from the power transistor 44 to the respective apertures 20a formed on the printed circuit board 20 as the power transistor assembly is moved away from the base portion 10a and towards the printed circuit board 20. Each guiding plate 80 includes at least one set of guiding holes 82 corresponding to each power transistor assembly 40 for aligning and guiding the lead frames 44a with respect to the apertures 20a formed on the printed circuit board 20. The set of guiding holes 82 formed on the guiding plate 80 are aligned with respect to the set of positioning apertures 43 formed on the power transistor holder 42.

[54] With such configuration and arrangement of the printed circuit board 20, the power transistor assembly 40, the thermal pad 50 and the spring element 60 inside the housing

10, the power transistor assembly 40, the thermal pad 50 and the spring element 60 are disposed parallel to each other and the printed circuit board 20. Particularly, the power transistor assembly 40 is sandwiched between the thermal pad 50 and the spring element 60.

[55] In accordance with another embodiment of the present invention as illustrated in FIG.

11, the power transistor assembly 40 is so arranged within the housing 10 that the plane of the power transistor assembly 40 is orthogonal with respect to the printed circuit board 20. More specifically, one of the side walls 10b of the housing 10 orthogonal to the base portion 10a includes an auxiliary housing 11 extending therefrom. The auxiliary housing

11 receives the at least one power transistor assembly 40 therein and the open end of the auxiliary housing 11 is closed by a cover 10e to protect the delicate electronic components of the power transistor assembly 40 against harsh external environment. More specifically, the power transistors 44 of the power transistor assembly are urged against the side wall 10b for cooling thereof by means of the spring 60 mounted on the side wall 10b. The positioning means 46 in the form of engagement elements 42a formed on the power transistor holder 42 interact I engage with the screw hubs 14 extending from the side wall 10b to position the power transistor assembly 40 orthogonal with respect to the base portion 10a. The screw-hubs 14 extend from the side wall 10b towards the respective cover 10e opposite thereto to receive mounting screws passing through the auxiliary housing 11 for mounting the auxiliary housing 11 to the housing 10. In case the power transistor assembly 40 is disposed orthogonally with respect to the printed circuit board 20, the lead frames 44a emanating from the power transistor 44 are straight. The straight lead frames 44a are aligned with respect to the apertures 20a formed on the printed circuit board 20 by means of the positioning apertures formed on a top wall of the power transistor holder 42 and guiding holes 82 formed on the guiding plate 80 and inserted into the apertures 20a formed on the printed circuit board 20 when the power transistor assembly 40 is moved towards the printed circuit board 20. The set of guiding holes 82 formed on the guiding plate 80 are aligned with respect to the set of positioning apertures formed on the top side of the power transistor holder 42 to allow passage of the straight lead frames 44a there through and guide the straight lead frames 44a to the apertures 20a formed on the printed circuit board 20. The straight lead frames 44a are connected to the printed circuit board 20 by soldering, after the straight lead frames 44a are securely held in the apertures 20a formed on the printed circuit board 20.

[56] Also, is disclosed a method 200 of assembling the electric fluid heater 100 in accordance with an embodiment of the present invention. FIG. 13 illustrates a block diagram depicting the various steps of the method 200 for assembling the electric fluid heater 100. Particularly, the method 200 includes the step of receiving, positioning and securely holding power transistors 44 in a power transistor holder 42 to configure a power transistor assembly 40 and positioning the power transistor assembly 40 either parallel or orthogonal to a base portion of housing of the electric fluid heater 100 by means of engagement elements 42a formed on the power transistor holder and at least one screw hub formed on the housing 10 and thereafter moving the power transistor assembly with respect to the housing along a direction A orthogonal to the base portion and away from the base portion to insert the lead frames emanating from power transistors of the power transistor assembly into apertures formed on the printed circuit board. Such method enables packaging of the various elements of the electric fluid heater in limited space inside the housing and aligning of the lead frames emanating from the power transistor to the apertures formed on the printed circuit board to prevent joining defects when the lead frames are joined, particularly, soldered to the printed circuit board. Although, the various steps of the method 200 are depicted by blocks in the flow diagram and any number of steps described as method blocks can be combined in any order or can be performed in parallel to employ the method 200, or an alternative method. Additionally, individual blocks may be deleted from the flow chart depicting the method without departing from the scope and ambit of the present invention. The method 200 is to be understood with reference to the following description along with the Fig. 10.

[57] The method 200 of assembling the electric fluid heater 100 includes a step 102 of receiving, positioning and securely holding power transistors 44 in a power transistor holder 42 by means of cut - outs 42c, tabs 42d and protrusions 42e formed along inner sides of openings 42b formed on the power transistor holder 42 to form a power transistor assembly 40. Thereafter, the method 200 involves a step 104 of positioning the power transistor assembly 40 either parallel or orthogonal to a base portion 10a of housing of the electric fluid heater 100 by means of engagement element 42a formed on the power transistor holder 42 and at least one screw-hub 14 formed on the housing 10. Thereafter, the method 200 involves the step 106 moving the power transistor assembly 40 with respect to the housing 10 along a direction A substantially orthogonal to the base portion 10a and away from the base portion 10 and towards a printed circuit board 20. Thereafter, the method 200 includes the step 108 of aligning the lead frames 44a emanating from the power transistor 40 with respect to the apertures 20a formed on the printed circuit board 20 by using a guiding plate 80. Thereafter, the method includes the step 110 of receiving and securely holding the lead frames 44a in the apertures 20a. Subsequently, the method includes the step 112 of mounting the spring element 60 on the base portion 10a with the power transistor assembly 40 and the thermal pad 50 sandwiched between the spring element 60 and the base portion 10a of the housing 10. Finally, the method 200 involves the step 114 of soldering the lead frames 44a received in the apertures 20a to the printed circuit board 20.

[58] In any case, the invention cannot and should not be limited to the embodiments specifically described in this document, as other embodiments might exist. The invention shall spread to any equivalent means and any technically operating combination of means.

Claims

[Revendication 1] An electric fluid heater (100) for an automotive vehicle, the electric fluid heater (100) comprising : a housing (10) comprising a base portion (10a), side walls (10b) and removable covers (10c, 10d, 10e) forming an enclosure defining an interior of the housing (10), the housing (10) further comprising an inlet (12a) and an outlet (12b) for ingress and egress of fluid with respect to the interior the housing (10); a printed circuit board (20) mounted spaced from the base portion (10a) of the housing (10) that is in contact with a fluid being heated; at least one heating element (30) controlled by the printed circuit board (20) and received inside the housing (10); at least one power transistor assembly (40), each power transistor assembly (40) comprising : at least one power transistor holder (42); at least one power transistor (44) received and securely held inside the power transistor holder (42), each power transistor (44) comprising lead frames (44a) emanating therefrom to extend outside the power transistor holder (42) and adapted to be received and held in apertures (20a) formed on the printed circuit board (20); at least one thermal pad (50) disposed along at least one of the base portion (10a) and the side walls (10b) and between the power transistor assembly (40) and the housing (10); and at least one spring element (60) adapted to be mounted on the housing (10) to urge the at least one power transistor (44) against the thermal pad (50) to enable cooling of the power transistor (44), characterized in that the power transistor assembly (40) comprises a positioning means (46) adapted to position the power transistor assembly (40) either parallel or orthogonal with respect to the base portion (10a), the power transistor assembly (40) adapted to be moved with respect to the housing (10) to enable the lead frames (44a) to be received and secured in the apertures (20a).

[Revendication 2] The electric fluid heater (100) as claimed in the previous claim, wherein either one of the base portion (10a) and the side walls (10b) comprises a plurality of screw-hubs (14) extending there from towards the respective cover (10c, 10e) opposite thereto and adapted to receive mounting screws passing through the either one of the printed circuit board (20) and an auxiliary housing (11) for mounting either one of the printed circuit board (20) and the auxiliary housing (11) to the housing (10).

[Revendication 3] The electric fluid heater (100) as claimed in the previous claim, wherein the first cover (10c) adapted to cover a first opening (16a) of the housing (10) along a printed circuit board side of the housing (10).

[Revendication 4] The electric fluid heater (100) as claimed in the claim 3, wherein the second cover (10d) adapted to cover a second opening (16b) of the housing (10) opposite to the first opening (16a).

[Revendication 5] The electric fluid heater (100) as claimed in any of the preceding claims, wherein at least one of the base portion (10a) and side walls (10b) comprises at least one flat platform (10f) against which the thermal pads (50) and the corresponding power transistors (44) are urged and against which the thermal pads (50) abuts.

[Revendication 6] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the printed circuit board (20) is disposed spaced from the base portion (10a) of the housing (10) and between the base portion (10a) and the cover (10c).

[Revendication 7] The electric fluid heater (100) as claimed in the claim 2, wherein the positioning means (46) comprises engagement elements (42a) formed on the power transistor holder (42) that interacts with at least one screw-hub (14) formed on housing (10) to position the power transistor assembly (40) with respect to the housing (10).

[Revendication 8] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the power transistor holder (42) further comprises reinforcement ribs (48) formed thereon.

[Revendication 9] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the power transistor holder (42) further comprises openings (42b) formed with cut - outs (42c), tabs (42d) and protrusions (42e) along inner sides of the openings (42b) adapted to support and securely hold the power transistors (44) within the openings (42b).

[Revendication 10] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the lead frames are either one of orthogonally bent and straight based on whether plane of the power transistor assembly (40) is parallel to or orthogonal to the printed circuit board (20) respectively.

[Revendication 11 ] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the power transistor holder (42) further comprises at least one set of positioning apertures (43) corresponding to each power transistor (44) for passage of the lead frames (44a) there through.

[Revendication 12] The electric fluid heater (100) as claimed in the previous claim, wherein each set of positioning apertures (43) comprises a central circular aperture (43a) and side oblong apertures (43b), the central circular aperture adapted to securely hold a central lead frame (44a) to position the power transistor (44) inside the corresponding power transistor holder (42).

[Revendication 13] The electric fluid heater (100) as claimed in any of the preceding claims further comprises at least one guiding plate (80) corresponding to the at least one power transistor (44), the at least one guiding plate (80) is disposed between the power transistor assembly (40) and the printed circuit board (20) and adapted to be mounted on the printed circuit board (20),

[Revendication 14] The electric fluid heater (100) as claimed in the previous claim, each guiding plate (80) comprises at least one set of guiding holes (82) corresponding to at least one power transistor (44) for aligning and guiding the lead frames (44a) to the corresponding apertures (20a) formed on the printed circuit board (20).

[Revendication 15] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the power transistor assembly (40), the thermal pad (50) and the spring element (60) are disposed parallel to each other and the printed circuit board (20).

[Revendication 16] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the power transistor assembly (40) is sandwiched between the thermal pad (50) and the spring element (60).

[Revendication 17] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the lead frames (44a) extending parallel to the plane of the power transistor assembly (40) are bent to be orthogonally connected to the printed circuit board (20).

[Revendication 18] The electric fluid heater (100) as claimed in any of the preceding claims, wherein the spring (60) is mounted to the housing (10) by means of bolts (70), each bolt (70) comprises a threaded shaft portion (70a) and a bolt head (70b), the threaded shaft portion (70a) adapted to engage with the base portion (10a).

[Revendication 19] A method of assembling the electric fluid heater (100) comprising: a step (102) of receiving, positioning and securely holding power transistors (44) in a power transistor holder (42) to form a power transistor assembly (40); a step (104) of positioning the power transistor assembly (40) either parallel or orthogonal to a base portion (10a) of housing (10) of the electric fluid heater (100) by means of engagement elements (42a) formed on the power transistor holder (42) and at least one screw-hub (14) formed on housing (10); a step (106) of moving the power transistor assembly (40) with respect to the housing (10) along a direction A orthogonal to the base portion (10a) and away from the base portion (10a); a step (108) of aligning the lead frames (44a) emanating from the power transistor (40) with respect to the apertures (20a) formed on a printed circuit board (20) by using a guiding plate (80); a step (110) of receiving and securely holding the lead frames (44a) in the apertures (20a); a step (112) of mounting the spring element (60) on a base portion (10a) of the housing (10) with the power transistor assembly (40) and the thermal pad (50) sandwiched between the spring element (60) and the base portion (10a); and a step (114) soldering the lead frames (44a) received in the apertures (20a) to the printed circuit board (20).