Electric heating device

Abstract

An electric heating device (2) comprising an electronics housing (9) forming a partition (8) that separates a connection chamber (6) from a heating chamber (4) for transferring heat to a medium to be heated, and a flow housing (38) that delimits the heating chamber (4), wherein at least one PTC heating device (14) is formed which is thermally connected to the heating chamber (4) and which is electrically connected in the connection chamber (6), wherein a control device (20) with at least one power switch (22) is formed in the connection chamber (6), characterized in that the power switch (22) rests on a channel base (32) formed outside the heating chamber (4) by the partition (8), which together with a channel top (36) forms a channel (34) through which the medium flows, spatially separated from the heating chamber (4), and which is fluidically connected to the heating chamber (4).wherein the channel top (36) and the electronics housing (9) are separate components that are fluid-tightly connected to each other.

Description

[0001] The present invention relates to an electric heating device comprising at least one PTC heating device and a control device with at least one power switch. The electric heating device is used in particular in motor vehicles, especially partially or fully electrically powered motor vehicles.

[0002] Such an electrical heating device is known, for example, from EP 1 872 986 A1, US 10 576 805 B2, DE 20 2019 005 221 U1 or DE 11 2014 002 402 T5. Such an electrical heating device has at least one PTC heating device comprising an electrically contactable PTC element. For contacting, the PTC element has, for example, two poles, which are formed, for example, by corresponding contact plates that rest against the PTC element and, together with corresponding insulation layers that electrically insulate the contact, form the PTC heating device. For operation, a voltage, for example 48 volts or more, is applied to the two poles of the PTC heating device. A power current of, for example, 100 amperes or more then flows through the PTC heating device. The power current is switched via a circuit breaker which is provided in the electric heating device as part of a control device.Switching large currents generates a lot of waste heat at the circuit breaker, which must be dissipated.

[0003] To dissipate heat, it is known, for example, from DE 10 2020 117 366 A1, to place the circuit breaker against a heat sink with a heat sink via a spring element. The spring element must be made of a spring material with good thermal conductivity, such as copper beryllium. The heat sink is located in a terminal chamber, so that the heat sink radiates the waste heat into the terminal chamber. This solution is complex in design, and the waste heat from the circuit breaker is also radiated unused into the terminal chamber. If the waste heat is too high, for example, when high power currents are switched via the circuit breaker, this can lead to overheating of the terminal chamber.

[0004] The present invention is based on the problem of providing a solution that enables more efficient dissipation of the waste heat of the circuit breaker with a simpler structure.

[0005] To solve this problem, an electrical heating device is proposed comprising an electronics housing which forms a partition wall separating a connection chamber from a heating chamber for dissipating heat to a medium to be heated, and a flow housing which delimits the heating chamber. At least one PTC heating device is formed which is thermally conductively connected to the heating chamber and which is electrically connected in the connection chamber. A control device with at least one circuit breaker is formed in the connection chamber. The circuit breaker rests on a channel base formed by the partition wall outside the heating chamber, which, together with a channel upper part, forms a channel through which the medium can flow, which is spatially separate from the heating chamber and which is fluidly connected to the heating chamber. The channel upper part and the electronics housing are separate components which are fluid-tightly connected to one another.The channel floor usually extends parallel to the partition wall.

[0006] Preferably, at least one heating device housing projects from the partition wall in the direction of the heating chamber, forming a receiving pocket in which at least one PTC heating device is supported in an insulated manner.

[0007] The electric heating device according to the present invention is preferably used in a motor vehicle, preferably a partially or fully electrically powered motor vehicle. The PTC heating device comprises at least one PTC element, which has conductor tracks electrically connected to it and electrically connected in the connection chamber. The conductor tracks serve to supply current to the PTC element with different polarities. Thus, the power current for operating the PTC element is fed to the PTC element via the connection chamber. The at least one PTC element and the conductor tracks are supported in an insulated manner in the receiving pocket. The insulating support can be provided, for example, by insulating plates that lie flat against the outer surface of the conductor tracks. The conductor tracks are preferably designed as contact plates.

[0008] For the PTC heating device to operate efficiently, it is necessary to dissipate the heat generated by the PTC element as effectively as possible to both sides of the main side surfaces of the PTC element. The PTC element is preferably cuboid-shaped. The main side surfaces are those side surfaces of the cuboid with the largest areal extent. These main side surfaces are preferably connected to one another by a peripheral edge of the PTC element, which usually has edge surfaces extending at right angles to the main side surfaces. The area of ​​each main side surface is preferably at least a factor of 5 larger than the area of ​​one of the edge surfaces. The heating device housing preferably forms a type of heating fin that protrudes into the heating chamber.

[0009] PTC elements are typically sintered ceramic blocks, which are typically metallized on their main side surfaces to conduct the power current into the PTC element. These ceramic components are brittle and prone to breakage. The same applies to the insulating layer, provided it is made of a ceramic plate. The use of an aluminum oxide plate is quite common for insulating the PTC element against the inner surface of the heater housing. To increase electrical safety, corresponding insulating layers are typically provided on both sides. There are suggestions to additionally cover these ceramic plates with an electrically insulating foil to maintain a certain degree of electrical insulation from the metallic heater housing in the event of a breakage of the ceramic plate.

[0010] Due to electromobility, electric heaters are increasingly operated at higher voltages of 48 volts and above. Sometimes these electric heaters operate at a power current of 100 amps or more. Electrical safety and dielectric strength measures must be adapted accordingly.

[0011] A semiconductor element, preferably an insulated-gate bipolar transistor (IGBT), is embodied as the power switch. Preferably, at least two power switches are formed on the circuit board. The at least one power switch is electrically connected to the circuit board.

[0012] Due to the high power currents that the circuit breaker must switch, waste heat is generated at the circuit breaker that must be dissipated to prevent overheating of the circuit breaker and / or damage to the circuit board to which the circuit breaker is connected and / or other semiconductor elements on the circuit board. For this purpose, the circuit breaker lies against the channel, separated by the partition wall forming the channel base. A medium flows through the channel and is heated during operation by the electrical heating device. This medium can be either liquid or gaseous. The medium is preferably a liquid, in particular comprising water. During operation, the medium flows through the channel and is heated by the waste heat from the circuit breaker, which is conducted through the partition wall, which is preferably made of a metal. As a result, only a small number of heat transfers occur.The channel base, especially when made of metal, is a good thermal conductor. This reduces the equipment required to dissipate the waste heat from at least one circuit breaker compared to prior art measures. At the same time, heat dissipation is efficient, as the waste heat from the circuit breaker is used to heat the medium and does not heat the air space in the connection chamber.

[0013] In particular, the term channel base is understood to mean that in the area of ​​the contact with the circuit breaker - if necessary with an intermediate layer of electrically insulating film - it is flat and has no structures. This enables a simple design of the electric heating device. The channel is formed outside the heating chamber, so that a compact design of the electric heating device is possible. The fluid which flows through the channel and the heating chamber during operation serves to dissipate the waste heat from the circuit breaker and to absorb the heat generated by the at least one PTC heating device. Bypass channels are preferably formed via which medium is guided past the at least one PTC heating device, in particular past at least one heating device housing, in order to absorb the heat generated by the PTC heating device, preferably in the corresponding heating device housing.

[0014] The channel is spatially separated from the heating chamber and is usually spatially separated from the bypass channels and / or is designed with a significantly smaller effective cross-section than the bypass channel(s) to increase the flow velocity. Heat transfer is thus increased due to the flow conditions in the channel compared to the bypass channel. Like the heating chamber, the channel can be delimited on one side by the partition wall. To form the channel, the partition wall can bulge towards the connection chamber and thus protrude towards the connection chamber relative to the section of the partition wall delimiting the heating chamber. A housing element completing the channel on the opposite side can also have a curvature in order to form a channel with a round or rectangular cross-sectional area. This further housing element is preferably formed by a section of the flow housing.The channel can be arranged parallel to the heating chamber and extend parallel to the channel over at least half, preferably at least two-thirds, of the extent of the heating chamber.

[0015] According to a preferred embodiment of the present invention, the upper channel section is part of the flow housing. This further simplifies the design of the electric heating device. According to a preferred embodiment of the invention, the channel is fluidically connected to the heating chamber; in particular, the electric heating device has a preferred flow direction in which the channel is formed upstream of the heating chamber. The separate design of the heating chamber and channel enables a compact design of the heating chamber.

[0016] According to a preferred embodiment of the invention, the channel bottom is laterally delimited by bulges in the partition wall, and the channel top is laterally delimited by bulges in the flow housing, which abut each other in a sealing manner. This enables a simple construction of the channel through corresponding communicating bulges in the partition wall and in the flow housing, which abut each other in a sealing manner and are preferably integrally connected. Particularly preferably, both the partition wall and the flow housing are formed from metal, and the bulges are pressed against each other in a sealing manner, compress a sealing material located between them, or are welded.

[0017] According to a preferred embodiment of the present invention, the electronics housing forms a receiving space spatially separated from the heating chamber, in which components of the control device are located. This reduces the heat input from the heating chamber into the control device.

[0018] According to a preferred embodiment of the present invention, only one insulation element is formed between the circuit breaker and the channel base. Therefore, apart from the insulation element for electrically insulating the circuit breaker from the channel base, there are no further elements between the channel base and the circuit breaker. The electrical insulation element achieves reliable electrical insulation from the - preferably metallic - channel base, while at the same time increasing the number of heat transfers only to a limited extent, namely by two. Preferably, the circuit breaker rests firmly against the channel base, in particular by clamping the insulation element. This improves heat transfer from the circuit breaker to the channel base and thus to the medium flowing in the channel.

[0019] The electric heating device preferably has an inlet nozzle and an outlet nozzle. With a flow direction from the inlet nozzle to the outlet nozzle, the channel is preferably arranged directly downstream of the inlet nozzle. The flow direction is defined by the formation of inlet nozzles for the inlet of the medium into the heating housing and outlet nozzles for the outlet of the medium from the heating housing. The term "direct arrangement of the channel downstream of the inlet nozzle" is understood in particular to mean that, during operation, the medium flows directly from the inlet nozzle into the channel without first flowing past one or more heating device housings. This has the effect that, during operation, the medium flows through the inlet nozzle into the channel at an inlet temperature and is therefore present at the circuit breaker with the lowest temperature in the flow path.In this way, efficient absorption of the circuit breaker's waste heat in the medium can be achieved even without structures in the channel floor.

[0020] Preferably, the flow housing, together with the heater housings, forms flow-connected bypass channels. During operation, medium is guided past the at least one heater housing through these flow channels, absorbing the heat generated by the at least one PTC heater, which is then conducted by the PTC heater into the heater housing. In this context, it is preferred that the flow channels are formed downstream of the channel. This ensures that cooler medium is used to dissipate the waste heat from the circuit breaker. Furthermore, it is preferred that the outlet connection is formed downstream of the flow channels, so that the medium is guided out of the flow housing downstream of the at least one heater housing.

[0021] With a view to a compact design of the electric heating device, the inlet and outlet nozzles are preferably located laterally next to the heating chamber and / or directly adjacent to one another.

[0022] According to a preferred embodiment of the present invention, the electronics housing and the flow housing are formed from a metallic material. Constructing both the electronics housing and the flow housing from a metal has various advantages. Constructing it from metal, preferably by deep-drawing a metallic sheet, is simple to implement. Alternatively, it is preferably also possible to produce at least one of the elements a) electronics housing and b) flow housing using a die-casting process. Constructing the electronics housing from a metallic material further has the advantage that heat conduction, particularly through the channel base and the at least one heater housing, is improved compared to other materials.

[0023] According to a preferred embodiment of the present invention, at least one of the following housings is formed as a single piece: a) the electronics housing and b) the flow housing. This simplifies the manufacture of the electronics housing and / or the flow housing and the assembly of the electric heating device.

[0024] Preferably, the duct is structure-free in the area of ​​the circuit breaker. This means that the duct floor in this area is flat and has no structures protruding into the duct. The flow-through cross-section of the duct remains constant in this area. This simplifies the design and construction of the electric heating device.

[0025] According to a preferred embodiment of the invention, an inlet nozzle and an outlet nozzle are formed next to the heating chamber. Preferably, the inlet nozzle and outlet nozzle extend parallel to at least one PTC heating device in the heating chamber. The formation of the inlet nozzle and outlet nozzle next to the heating chamber enables a compact design of the electric heating device.

[0026] Further details and advantages of the present invention will become apparent from the following description of an embodiment in conjunction with the drawings, in which: Fig. 1: a perspective, partially sectioned view of an electric heating device; and Fig. 2: a perspective view of the embodiment according to Fig. 1.

[0027] The Fig. 1 and Fig. 2 show an example of an electric heating device 2 in various views. These figures are described jointly below unless explicit reference is made to one of the figures. Fig. Figure 1 shows the electric heating device 2, which has a heating chamber 4 and a connection chamber 6, which are separated from each other by a partition 8. The partition 8 is part of an electronics housing 9. Heating device housings 10 protrude from the partition 8, forming receiving pockets 12 for PTC heating devices 14. A PTC heating device 14 is known, for example from DE 10 2020 208 643 A1. The PTC heating device 14 comprises a PTC element (not shown here), which is electrically contacted in the connection chamber 6. For contacting, the PTC element has contact plates or the like, which have contact tongues 16 that protrude into the connection chamber 6. For the sake of clarity, not all contact tongues 16 are shown. Fig. 1. Each PTC heating device 14 has two contact blades 16 for applying a voltage to them. In the connection chamber 6, the contact blades 16 are directly connected to a circuit board 18 of a control device 20 of the electric heating device 2, as in this example, or are connected via a contacting unit or wiring module, for example, which is then in turn connected to the circuit board 18.

[0028] The control device 20 controls the at least one PTC heating device 14. For this purpose, the control device 20 switches power current, which then flows through the PTC heating device 14. For this purpose, at least one power switch 22, preferably an insulated-gate bipolar transistor (IGBT), is formed on the circuit board 18 of the control device 20. The nominal voltage of the PTC heating device 14 is typically 48 volts in today's applications, particularly in partially or fully electric motor vehicles, and power currents of 100 amperes and more are possible. As a result, the power switch 22 generates considerable waste heat, which must be dissipated to prevent overheating of the power switch 22 and, if applicable, other elements of the control device 20.

[0029] The circuit breaker 22 has a first side 24 facing the printed circuit board 18 and is connected via electrical connecting elements 26 to conductor tracks (not shown) on or in the printed circuit board 18. With a second side 28 opposite the first side 24, the circuit breaker 22 rests, electrically insulated by an insulating element 30, against a part of the partition 8, which in this area is formed, in particular deep-drawn, as a channel bottom 32. The channel bottom 32, the circuit breaker 22, the insulating element 30, and the printed circuit board 18 are dimensioned and positioned such that the circuit breaker 22 presses the insulating element 30 against the channel bottom 32. The channel bottom 32 forms a lower part of a channel 34, the upper part 36 of which is part of a flow housing 38. The channel bottom 32 and the channel top 36 do not have any built-in components or the like; rather, they form a smooth channel 34 whose cross-section is constant in the area of ​​the circuit breaker 22.The channel 34 is unstructured in the area of ​​the circuit breaker 22. The channel 34 is bounded laterally by bulges 46 of the partition wall 8 and by bulges 48 of the flow housing 38. These bulges 46, 48 extend parallel to one another and abut one another. The bulges 46, 48 are preferably integrally connected to one another.

[0030] In the present example, both the electronics housing 9 and the flow housing 38 are made of metal, in particular by deep drawing from a sheet metal. In addition to the channel upper part 36, the flow housing 38 also forms, together with the heater housings 10, flow channels 40 around the heater housings 10. For the sake of clarity, only some of the flow channels 40 are provided with reference numerals. The flow housing 38 forms a flow path 39 of the heating chamber 4, which in this example is composed of the channel 34 and the flow channels 40.

[0031] Fig. 2 shows a perspective view of the electric heating device 2. The flow housing 38 has an inlet nozzle 42 through which, during operation, the medium, in particular a liquid medium comprising water, initially flows directly into the channel 34 and downstream of the channel 34 through the flow channels 40 until it leaves the flow housing 38 again through an outlet nozzle 44. The inlet nozzle 42 and outlet nozzle 44 are formed next to the heating chamber 4 and extend parallel to the PTC heating devices 14 in the heating chamber 4. The inlet and outlet nozzles 42; 44 are located laterally next to the heating chamber 4, directly adjacent to one another, such that the hoses supplying or discharging the medium to be heated can still be easily connected to the nozzles 42; 44.

[0032] Channel 34 is located directly downstream of inlet port 42. During operation, medium is supplied via inlet port 42 at an inlet temperature. When flowing out of outlet port 44, the medium has a higher outlet temperature. Thus, during operation, medium initially flows through channel 34 at a relatively low temperature, so that the waste heat from circuit breaker 22 is initially used to heat the medium. After flowing through channel 34, the medium then flows at an elevated temperature through bypass channels 40 to absorb and dissipate the heat generated by PTC heating devices 14. The medium then flows out via outlet port 44. In the present example, flow path 39 is defined by inlet port 42 and outlet port 44 and extends from inlet port 42 to outlet port 44 via channel 34 and bypass channels 40.

[0033] The electronics housing 9 further forms a receiving space 50 for accommodating further elements and components of the control device 20. The receiving space 50 is spatially separated from the heating chamber 4, so that the heat input from the heating chamber 4 into the receiving space 50 is limited. In this case, the receiving space 50 is formed by a deep-drawn pot of the electronics housing 9, wherein the pot protrudes from the connection chamber 6 in the same direction as the flow housing 38.

[0034] The structure shown here, in which a circuit breaker 22 rests directly or only mediated by the insulation element 30 against a flat channel floor 32 of a channel 34 through which a medium can flow, allows for a simple structure and design of the electric heating device 2. In particular, no internal components are necessary in the channel 34, since the waste heat from the circuit breaker 22 is efficiently dissipated via the medium flowing past it. At the same time, a compact design of the electric heating device 2 is possible. List of reference symbols 2 electric heaters 4 heating chamber 6 Connection chamber 8 Partition wall 9 Electronics housing 10 heater housing 12 Recording pocket 14 PTC heating device 16 contact tongue 18 circuit board 20 Control device 22 circuit breakers 24 first page 26 Connecting element 28 second page 30 Insulation element 32 Canal floor 34 channels 36 Channel top 38 flow housing 39 Flow path 40 flow channels 42 inlet nozzles 44 outlet nozzles 46 Bulge of the partition wall 48 Bulge of the flow housing 50 recording room

Claims

[1] Electric heating device (2) comprising an electronics housing (9) which forms a partition wall (8) which separates a connection chamber (6) from a heating chamber (4) for dissipating heat to a medium to be heated, and a flow housing (38) which delimits the heating chamber (4), wherein at least one PTC heating device (14) is formed which is thermally conductively connected to the heating chamber (4) and which is electrically connected in the connection chamber (6), wherein a control device (20) with at least one power switch (22) is formed in the connection chamber (6), characterized byin that the circuit breaker (22) rests on a channel base (32) formed outside the heating chamber (4) by the partition wall (8), which, together with a channel upper part (36), forms a channel (34) through which the medium can flow, which is spatially separated from the heating chamber (4) and which is fluidically connected to the heating chamber (4), wherein the channel upper part (36) and the electronics housing (9) are separate components which are connected to one another in a fluid-tight manner. [2] Electric heating device (2) according to claim 1, characterized by that the channel upper part (36) is part of the flow housing (38). [3] Electric heating device (2) according to one of the preceding claims, characterized by that the channel (34) is formed between an inlet nozzle (42) and the heating chamber (4). [4] Electric heating device (2) according to one of claims 2 or 3, characterized bythat the channel bottom is laterally delimited by bulges (46) of the partition wall (8) and / or the channel upper part (36) is laterally delimited by bulges (48) of the flow housing (38), and that the channel upper part (36) and the flow housing (38) lie sealingly against one another. [5] Electric heating device (2) according to one of the preceding claims, characterized by that the electronics housing (9) forms a receiving space (50) spatially separated from the heating chamber (4), in which components of the control device (20) are formed. [6] Electric heating device (2) according to one of the preceding claims, characterized by that only one insulation element (30) is formed between the circuit breaker (22) and the channel bottom (32). [7] Electric heating device (2) according to one of the preceding claims, characterized bythat at least one heating device housing (10) projects from the partition wall (8) in the direction of the heating chamber (4), which forms a receiving pocket (12) in which at least one PTC heating device (14) is supported in an insulated manner. [8] Electric heating device (2) according to one of the preceding claims, characterized by that the electronics housing (9) and the flow housing (38) are made of a metallic material. [9] Electric heating device (2) according to claim 8, characterized by that at least one of the following housings: a) the electronics housing (9) and b) the flow housing (38) are deep-drawn. [10] Electric heating device (2) according to claim 8 or 9, characterized by that at least one of the following housings: a) the electronics housing (9) and b) the flow housing (38) are die-cast. [11] Electric heating device (2) according to one of the preceding claims, characterized bythat at least one of the following housings is formed in one piece: a) the electronics housing (9) and b) the flow housing (38). [12] Electric heating device (2) according to one of the preceding claims, characterized by that the channel (34) is structure-free. [13] Electric heating device (2) according to one of the preceding claims, characterized by that an inlet nozzle and an outlet nozzle are formed next to the heating chamber.

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