control unit

Abstract

Control device with a housing (102) in which an electronic unit to be cooled is provided, wherein in the housing (102) at least one space (130) is further provided which is at least partially filled with a phase change material (132).

Description

The invention relates to a control device, in particular a control device for a motor vehicle.Prior ArtControl units are electronic modules which are used in particular at locations at which devices or sequences are controlled and / or regulated. Control units are used for controlling machines, installations and other technical processes. Control devices are widely used in motor vehicles.Control units used in motor vehicles are also referred to as automotive control units. Automotive control units which are set up for automated or highly automated driving can be divided into three classes with regard to their cooling. Devices with low waste heat, i.e. less than 30 W in the control device, can be cooled passively via fins depending on the installation location. Reference is made to FIG. 1. Appliances with higher waste heat are cooled via external or internal fans which are guided via cooling fins. From a waste heat of about 100 W, water-cooled systems are also used. Reference is made in this connection to FIG. 2.Systems with external water cooling are in particular in focus for the highly automated driving functions, since these generally require higher computing power and thus also more system waste heat arises. As an additional requirement for these highly automated systems, safety systems must also be taken into account which are used to exclude fault cases or to delay them sufficiently in time, i.e. the critical temperature of the SoC (system on chip) is not exceeded within a set period of time.A typical fault case for such a system is the failure of the cooling water flow, for example, due to a blocking of the coolant pump. For the respective application in automated driving, suitable measures should ensure that the vehicle can be brought into a safe driving state by the vehicle software on an SoC in a certain period of time, i.e. within a few seconds up to half an hour. Therefore, the SoC of the ADAS unit (ADAS: Automated Driving and Steering) cannot be switched off or clocked at a lower rate in this time period, since full functionality is required here until standstill.One measure is the incorporation of materials with a high heat capacity, such as metals. However, both the space and the weight for a control unit (ECU: electronic control unit) are limited. A further possibility is a redundant cooling path either via a separate pump or via active air cooling. However, both are associated with considerable outlay and costs. In addition, these active air cooling systems represent new possible sources of error due to the rare operation, which must likewise be countered constructively.Disclosure of the InventionAgainst this background, a control device having the features of claim 1 is presented. Embodiments are evident from the dependent claims, the description and the drawings.The control device presented has a housing in which an electronic unit to be cooled is provided. The housing can have a control device front side and a control device rear side. In the housing, at least one space is furthermore provided, which is at least partially, in the embodiment completely, filled with a phase change material (PCM).Phase change material (PCM: phase change material) is what are known as latent heat accumulators, which can store a high proportion of heat and cold energy over a long time and can release it again without loss. Reversible thermodynamic changes in state of a storage medium are utilized in this case, for example during the phase transition from solid to liquid.The use of PCM in the automotive sector has hitherto been restricted to use in battery thermal management for electric vehicles.An SoC (system-on-chip) is an integrated circuit in which a plurality of functions of a programmable electronic system are realized. In a SoC, all functions are integrated on a semiconductor substrate. A system is understood here to mean a combination of different elements which together provide a specific functionality.In one embodiment, a cost-effective solution for a temporarily limited heat sink within an ADAS control unit is presented, which can absorb a defined amount of heat for a specific time. Ideally, the process is reversible, so that no replacement of the control unit has to take place after a coolant fault situation. In addition, no further actuator system should be provided, such as, for example. This can be used as a further possible source of faults.In one embodiment, a PCM material is embedded within a water-cooled ADAS control unit in sufficient quantity so that the temporarily limited amount of heat can be buffered by the phase transition.The control device presented has, at least in some of the embodiments, a number of advantages:It is possible to buffer a limited amount of heat without external actuators in such a way that it remains completely operable over the entire use time of the SoC of the ADAS functions.For this solution, no redundant external pumps or redundant heat transport systems, such as additional fans in addition to water cooling, need to be installed.PCMs offer 10 to 100 times higher heat storage quantities in a predefined temperature range compared to typical construction materials such as, for example. Metals.PCMs can be shaped very flexibly and can fill a wide range of the cavities of the control unit.The heat absorption and thus the phase conversion of typical PCMs, such as, for example. Paraffin is reversible. This means that, after such a fault, the control unit is not absolutely necessary to be replaced and this can be used further.Further advantages and embodiments of the invention will become apparent from the description and the appended drawings.It is understood that the features mentioned above and those still to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the present invention.Brief Description of the DrawingsFIG. 1 shows a schematic illustration of a control device with a passively cooled housing according to the prior art. FIG. 2 shows a schematic illustration of a control device with a water-cooled housing according to the prior art. FIG. 3 shows a schematic illustration of an embodiment of the control unit presented. FIG. 4 shows a schematic illustration of a further embodiment of the control unit presented. FIG. 5 shows a graph of temperature profiles through blocks made of different materials. FIG. 6 shows a further embodiment of the presented control device. FIG. 7 shows yet another embodiment of the presented control device.Embodiments of the InventionThe invention is schematically illustrated in the drawings on the basis of embodiments and is described in detail below with reference to the drawings.FIG. 1 shows a control device according to the prior art, which is denoted overall by the reference numeral 10. This control device 10 has a passively cooled housing 12 with a control device front side 14 and a control device rear side 16. For cooling, the control device front side 14 has cooling fins 18. The control device 10 shown generates only a small amount of waste heat, typically less than 30 W, so that passive cooling with the cooling fins 18 is sufficient.FIG. 2 shows a control device 50 with a water-cooled housing 52 according to the prior art. The housing 52 has a control device front side 54 and a control device rear side 56. On the control device front side 54, cooling fins 58 are in turn formed, which provide passive cooling. In the control device 50 or in the housing 52, a printed circuit board 60 and a SoC 62 arranged thereon are provided. Furthermore, a cooling channel 70 is provided in the housing 52 above the SoC 62, in which a cooling liquid 72 is guided.The control device 50 shown typically generates waste heat of about 100 W, so that the cooling liquid 72 and thus water cooling is used for sufficient cooling. It is also to be noted that the external terminals are not shown in FIG. 2. The control device 50 is typically connected to an external cooling circuit.FIG. 3 shows an embodiment of the presented control device, which is denoted overall by the reference numeral 100. The control device 100 has a housing 102, which in turn comprises a control device front side 104 and a control device rear side 106. Cooling fins 108 are formed on the control device front side 104, which provide passive cooling. In the control device 100 or in the housing 102, a printed circuit board 110 and a SoC 112 arranged thereon are provided. Furthermore, a cooling channel 120 is provided in the housing 102 above the SoC 112, in which cooling channel a cooling liquid 122 is guided.Furthermore, in the controller 100, two spaces 130 are provided on both sides of the SoC 112 which are filled with a phase change material (PCM) 132 at least partially or completely. Since the PCMs can become liquid during their use, they are generally encapsulated, in particular microencapsulated. It is also to be noted that the external terminals are not shown in FIG. 3. The control device 100 is typically connected to an external cooling circuit.FIG. 3 illustrates the incorporation of PCMs 132 into the water cooled controller 100 with the PCMs 132 mounted laterally adjacent the SoC 112. The PCMs 132 absorb the non-removable waste heat of the control unit 100, in particular in the event of a fault, for a fault which is in particular limited in time and calculated previously. Further, the PCMs 132 are selected such that the phase transition point is outside the operating points of the liquid cooling. Therefore, at a maximum operating point of 50° C. in the cooling liquid, a PCM 132 with a phase transition temperature of 60° C. is conceivable.The spaces 130 and thus the PCM 132 should be arranged in such a way that the highest possible heat flow is conducted into the PCM in the case of a stationary cooling liquid. This can be done by direct mechanical contact between PCM and cooling channel in the direct vicinity of the SoC, as shown in FIG. 3. Here, the heat no longer flows through the liquid, which may be still, but through the metal of the cooling channel 120 into the PCM 132 due to the lower heat flow. One possibility for further increasing this heat flow is illustrated in FIG. 4.FIG. 4 shows an embodiment of the presented control device, which is designated overall by the reference numeral 150. The control device 150 has a housing 152 which in turn comprises a control device front side 154 and a control device rear side 156. Cooling fins 158 are formed on the control device front side 154, which provide passive cooling. In the control device 150 or in the housing 152, a printed circuit board 160 and a SoC 162 arranged thereon are provided. Furthermore, a cooling channel 170 is provided in the housing 152 above the SoC 162, in which cooling channel a cooling liquid 172 is guided.In addition, in the controller 150, two spaces 180 are provided on both sides of the SoC 162 that are at least partially or completely filled with a phase change material (PCM) 182. It is also to be noted that in FIG. 4, the external terminals are not illustrated. The control device 150 is typically connected to an external cooling circuit. This also applies to the further embodiments of FIGS. 6 and 7.As shown in FIG. 4, small metallic fins 184 extend into the PCM 182, thereby substantially increasing the transfer of heat into the spaces 180 filled with the PCM 182. In this case, attention must be paid to the metal-to-PCM ratio. This construction results above all due to the low thermal conductivity of typical PCMs, such as, for example. Paraffin. These cooling ribs 184 can also be provided in the embodiments of FIGS. 6 and 7.In FIG. 5, the mode of operation of the PCM in comparison with a heat sink is shown. FIG. 5 shows a graph 200 on whose abscissa 202 time [s] is plotted and on whose ordinate 204 temperature [° C.] is plotted. A first curve 210 shows the temperature profile for a copper block with 4567 g and a second curve 212 shows the temperature profile for a PCM block with 410 g.As shown in Figure 5, an identical heat flux is passed through cubes of PCM or copper of equal size but not of equal weight. The PCM in this simulation has a phase transition temperature of about 70° C. Thus, the phase transition temperature of the material is seen to be about 70° C., at which the PCM maintains the temperature almost constant for a very long time. It is also evident that, with an identical volume and a cooling time limited over time, significant weight savings are possible by using PCM.The PCM can be installed in the control device wherever such a high heat flow occurs in the event of a fault that the critical temperatures in the SoC as an example of the electronic unit are not exceeded. This is different depending on the design of the control unit, but some predicted installation locations can be identified across different variants.FIG. 6 shows an embodiment of the presented control device, which is designated overall by the reference numeral 250. The control device 250 has a housing 252 which in turn comprises a control device front side 254 and a control device rear side 156. Cooling fins 258 are formed on the control device front side 254, which provide passive cooling. In the control device 250 or in the housing 252, a first printed circuit board 260 and a SoC 262 arranged thereon are provided. Furthermore, a cooling channel 270 is provided in the housing 252 above the SoC 262, in which cooling channel a cooling liquid 272 is guided and from which cooling ribs 276 project into the cooling liquid 272. Furthermore, a second printed circuit board 280 is arranged in the housing 252 on the control device front side 254.The illustration further shows three spaces 290 filled with PCM 292. Of these, two are disposed on both sides of the SoC 262 and one above the cooling passage 270. The control device 250 thus has the cooling channel 270 with the PCM 292 located above it. The cooling liquid 272 heats the top of the cooling channel 270 by its own convection, and thus the PCM 292.A basic variant is to install the PCM directly above the SoC. This is advantageous above all for horizontally installed control units, since the warm cooling liquid rising by natural convection heats the upper side of the cooling channel 270 and thus the control unit 250. Depending on the thermal conductivity of the material of the cooling channel 270 and the material thickness, a corresponding PCM quantity can be placed there.The internal cooling ribs 276 can additionally ensure that the heat transfer is particularly efficient here and that the lowest possible thermal resistance to the opposite side is produced.An alternative design is a vertical installation of control unit and printed circuit board, as is shown in FIG. 7.FIG. 7 shows a further embodiment of the presented control device, which is denoted overall by the reference numeral 300. The control device 300 has a housing 302 which comprises a control device front side 304 and a control device rear side 306. Cooling fins 308 are formed on the control device front side 304, which provide passive cooling. In the control device 300 or in the housing 302, a first printed circuit board 310 and a SoC 312 arranged thereon are provided. Furthermore, a cooling channel 320 is provided in the housing 302 above the SoC 312, in which cooling channel a cooling liquid 322 is guided and from which cooling ribs 326 project into the cooling liquid 322. Furthermore, a second printed circuit board 330 is arranged in the housing 302 on the control device front side 304.The illustration further shows three spaces 340 filled with PCM 342. Of these, two are disposed on both sides of the SoC 312 and one above the cooling passage 320.In this case, the heat flow (arrow 400) is upward within the cooling channel 320 so that the PCMs 342 should be mounted above on both sides of the cooling channel 320. Below the heat source, the SoC 312, however, no larger heat flow is to be expected.Depending on the orientation of the control unit and the installation location of the components to be heat-removed, different installation variants for the PCM result. The variants shown represent only a portion of the possible installation possibilities. Common to all is the operating principle of using PCM for buffering a limited amount of heat, in particular in the emergency mode of the control unit.The proposed approach is particularly appropriate in the case of water-cooled control units and, in particular, in the case of control units in which there are enhanced safety requirements in the event of a fault.

Claims

Control device having a housing (102, 152, 252, 302) in which an electronic unit to be cooled is provided, wherein at least one space (130, 180, 290, 340) which is at least partially filled with a phase change material (132, 182, 292, 342) is furthermore provided in the housing (102, 152, 252, 302).Control device according to Claim 1, in which at least one cooling duct (120, 170, 270, 320) for conducting a cooling medium is provided in the housing (102, 152, 252, 302).Control device according to Claim 2, in which a cooling liquid (122, 172, 272, 322) is used as the cooling medium.The controller of claim 2 or 3, wherein there is direct contact between at least one space (130, 180, 290, 340) of the at least one space (130, 180, 290, 340) and at least one cooling channel (120, 170, 270, 320) of the at least one cooling channel (120, 170, 270, 320).The controller of claim 4, wherein the at least one cooling channel (120, 170, 270, 320) carries cooling fins (276, 326) that protrude into the at least one space (130, 180, 290, 340).Control device according to one of Claims 3 to 5, in which the phase-change material (132, 182, 292, 342) of at least one space (130, 180, 290, 340) is selected in such a way that the phase transition point lies outside the operating points of the liquid cooling system directed through the cooling duct (120, 170, 270, 320) and the cooling liquid (122, 172, 272, 322).Control device according to one of Claims 1 to 5, in which at least one space (130, 180, 290, 340) of the at least one space (130, 180, 290, 340) is arranged in the region of the electronic unit.Control device according to Claim 6, in which a space (130, 180, 290, 340) is arranged in each case on both sides of the electronic unit.Control device according to one of Claims 1 to 7, in which the electronic unit is designed as a system-on-chip (SoC) (112, 162, 262, 312).Control device according to one of Claims 1 to 9, in which at least one space (130, 180, 290, 340) is embodied in an encapsulated manner by the at least one space (130, 180, 290, 340).Control device according to one of Claims 1 to 10, in which at least one space (130, 180, 290, 340) of the at least one space (130, 180, 290, 340) is installed at a location at which such a high heat flow occurs in the event of a fault that the critical temperatures in an SoC (112, 162, 262, 312) are not exceeded in the process.

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