Cooling device for a motor vehicle engine

Abstract

Cooling device for a motor vehicle engine with an air guide device that directs air to the engine in such a way that the engine experiences a cooling effect through the airflow (9, 9'), wherein at least a portion of the air is conveyed through the air guide device by means of a blower (4), wherein the air guide device is provided with at least one air inlet opening (2, 2') and one air outlet opening (8, 8'), characterized in that at least one further air inlet opening (7, 7') is provided and the air guide device is designed to function as a jet pump (6), for which purpose the portion of air (3c, 3c') conveyed by means of the blower (4) enters the air guide device through the air inlet opening (2, 2') as a motive medium and draws in a suction medium (3b, 3b') through the further air inlet opening (7, 7'), after which the motive and suction medium are discharged as cooling air via the Air outlet opening (8,8') to reach the unit.,

Description

[0001] The invention relates to a cooling device for a motor vehicle assembly, in particular a disc brake, with an air guiding device for guiding cooling air according to the preamble of claim 1.

[0002] It is already known to supply air to the brake discs in vehicles with disc brakes for cooling purposes. To avoid high brake disc temperatures, the brake discs are also internally cooled, i.e., cooling air is directed through essentially radially directed cavities in the brake disc. It is also important to ensure that sufficient air is directed to the brake disc, as the majority of the energy converted during braking is dissipated via convection in the brake disc. In response to this problem, the state of the art includes a multitude of improvements in brake disc cooling. For example, it is also known to completely permeate brake discs with holes and grooves so that the airflow can cover a larger surface area.

[0003] However, despite all the measures taken to cool the brake disc with airflow, it is still conceivable that, for example, when braking slowly downhill, the airflow may be too low, allowing the service brake to reach undesirable operating temperatures. Therefore, air guiding devices have also become known for supplying cooling air to the brake discs. In these devices, an air flow entering the inlet cross-section of a guide duct is fed to a forced-air heat exchanger, followed by a partial air flow to an associated braking device. The cooling air supplied to the braking device is branched off from the exhaust air flow of the heat exchanger. DE 10 2008 039 728 A1 describes such an air guiding device for wheel brake cooling in a motor vehicle.

[0004] DE 10 2012 010 502 A1 relates to an air ducting device for a motor vehicle. DE 42 33 276 A1 relates to a cooling air duct for a vehicle brake. DE 38 38 798 A1 relates to an injector for combined use on machines.

[0005] The object of the invention is therefore to provide a cooling device for an assembly of a motor vehicle, in particular for a disc brake, in which the air cooling is further improved for certain operating conditions.

[0006] This object is achieved by the features of claim 1. Further embodiments of the invention are described in the dependent claims.

[0007] According to the invention, a cooling device for an assembly of a motor vehicle with an air guiding device which guides air to the assembly in such a way that the latter experiences a cooling effect due to the air flow, wherein at least temporarily a portion of the air is conveyed through the air guiding device by means of a fan and the air guiding device is provided with at least one air inlet opening and one air outlet opening, characterized in that at least one further air inlet opening is provided and the air guiding device is designed such that it has the function of a jet pump, for which purpose the portion of the air which is conveyed by means of the fan passes through the air inlet opening into the air guiding device as a driving medium and sucks in a suction medium via the further air inlet opening and then the driving and suction medium pass through the air outlet opening to the assembly as cooling air.

[0008] This has the advantage that efficient and robust engine cooling is possible with an existing radiator fan, even at low vehicle speeds. In addition, the exhaust air flow from the heat exchanger also conveys cooling air at ambient temperature, and subsequent cooling with mixed air is particularly efficient. Furthermore, engine cooling with cooling air at ambient temperature always occurs, even when the radiator fan is not operating, if, as provided in an advantageous embodiment of the invention, the additional air inlet opening is directed in the forward direction of travel at a location on the vehicle exposed to the airstream.

[0009] Such a unit cooling device is preferably used to cool a wheel brake, in particular a disc brake, and in this case, in particular to cool the brake disc. In addition to the effect of the airstream, an existing heat exchanger fan of an internal combustion engine heat exchanger can be used as a fan to generate the propellant gas flow, and the air inlet opening can therefore be connected downstream to the internal combustion engine heat exchanger with heat exchanger fan. The air outlet opening is then preferably located in a wheel house, facing the center of the vehicle, with the mixed air flowing into the interior of the wheel toward the brake disc and / or the brake caliper of the disc brake, which, according to the state of the art, is usually located on the inside of the wheel.

[0010] For example, depending on the speed of the motor vehicle, it is conceivable in preferred embodiments of the invention to utilize controlled air guide flaps in the air guiding device to reverse the flow of propellant and carrier gas for a defined design or operating strategy. This further optimizes the cooling effect.

[0011] A preferred embodiment of the invention is described in the following description with the accompanying drawings. They show: Fig. 1: a schematically drawn arrangement of a cooling device according to the invention for a disc brake, as an aggregate of a motor vehicle, in a plan view of a front area of ​​the motor vehicle without the bonnet and Fig. 2: the detail 6 of the air guiding device marked by a circle from Fig. 1, with jet pump action according to the invention, in a schematically drawn embodiment.

[0012] In Fig. 1 symbolically depicts two front wheels 1, 1' of a motor vehicle with disc brakes that are not visible because they are located within a wheel rim and have a ventilated brake disc ring. For cooling purposes, an air guiding device is arranged for each front wheel 1, 1', which guides air at least to the brake disc ring so that the latter is cooled by an air flow. The disc brakes are each located on an inner side of the invisible wheel rims, and the air flow of a headwind against a front 3 of the motor vehicle, symbolically represented by arrows 3a, 3b, 3b', is guided by the two air guiding devices, one on each side of the motor vehicle, from its surroundings into the respective wheel interior to a brake disc and / or a brake caliper.For this purpose, each air guiding device has an air inlet opening 2, 2', which is acted upon by a heat exchanger fan 4 of an internal combustion engine heat exchanger 5, since each air inlet opening 2, 2' is located downstream of the cooling air flow for the internal combustion engine heat exchanger 5 behind the heat exchanger fan 4. A further air inlet opening 7, 7' of the air guiding device is located at a point on the motor vehicle exposed to the airstream (arrow 3b, 3b'), directed in the forward direction of travel, and an air outlet opening 8, 8' of the air guiding device is located in the respective wheel house (not shown), installed in such a way that the air flow flowing through the respective air guiding device (arrows 9, 9') acts on the respective disc brake.

[0013] Within each air guiding device, the air inlet openings 2, 2' are connected to the further air inlet openings 7, 7' by means of an air duct 10, 10', which leads into a further air duct 11, 11' with the respective air outlet opening 8, 8', in such a way that the air flow leaving the respective air guiding device (arrows 9, 9') is combined from the airstream component (arrows 3b, 3b') and the heat exchanger fan component, symbolically represented by arrows 3c, 3c'. In this way, on each side of the vehicle, an exclusively airstream-induced airflow with an additional fan-generated airflow is created to cool each front disc brake, as shown in Fig. 2 as a detail to reference number 6 at the position symbolized by the circle in Fig.1. Here, at the junction of the respective air shaft 10, 10' with the respective further air shaft 11, 11', the air guiding device is designed such that it has the function of a jet pump 6, for which purpose the respective partial quantity of the air flow (arrows 3c, 3c'), which is conveyed by means of the blower 4, passes through this as a driving medium after the respective air inlet opening 2, 2' into a driving nozzle 14 of the respective jet pump 6 of the air guiding device and as a suction medium via the respective further air shaft 11, 11' sucks in the air flow flowing through this (arrows 3b, 3b') and accelerates it, after which the driving and suction medium mix in a collecting nozzle 12 and, after flowing through a diffuser 13, reach the respective disc brake (not shown) as cooling air via the air outlet opening 8, 8'.

[0014] The propellant medium (air flow arrows 3c, 3c') exits the propellant nozzle 14 at the highest possible speed. This creates a dynamic pressure drop according to Bernoulli's law. For this reason, the pressure in the air flow is lower than normal pressure. To maximize speed, the propellant nozzle 14 is advantageously designed as a state-of-the-art Laval nozzle, and the propellant jet (air flow arrows 3c, 3c') exits at supersonic speed. In the collecting nozzle 12, the propellant jet (air flow arrows 3c, 3c') strikes the suction medium (air flow arrows 3b, 3b') located there, which is usually at normal pressure. After exiting the propellant nozzle 14, the propellant jet (air flow arrows 3c, 3c') initially behaves like a free jet. Internal friction and turbulence create shear stress in the boundary layer between the fast driving medium (air flow arrows 3c, 3c') and the much slower suction medium (air flow arrows 3b, 3b').This tension causes a momentum transfer, i.e. the suction medium (air flow arrows 3b, 3b') is accelerated and entrained. Mixing occurs according to the principle of momentum conservation. The widening of the propulsion jet (air flow arrows 3c, 3c') and the suction of suction medium (air flow arrows 3b, 3b') slows down the propulsion jet (air flow arrows 3c, 3c'), i.e. dynamic pressure is converted into static pressure. As the suction medium (air flow arrows 3b, 3b') is accelerated in the mixing chamber, according to Bernoulli there is also a pressure drop for the suction medium (air flow arrows 3b, 3b'), i.e. a suction effect which conveys further suction medium (air flow arrows 3b, 3b') via the further air shaft 11, 11'.

[0015] Such brake cooling, as described above, also allows the design criteria regarding maximum brake disc temperature to be met even with higher demands on the braking system and / or limited installation space dictated by the wheel size, without changing the brake dimensions. Or, with the same braking performance and the same vehicle weight, the brake dimensions can be reduced, which then results in weight and cost advantages.

Claims

[1] Cooling device for a unit of a motor vehicle with an air guiding device which guides air to the unit in such a way that the unit experiences a cooling effect through the air flow (9, 9'), wherein at least temporarily a portion of the air is conveyed through the air guiding device by means of a fan (4), wherein the air guiding device is provided with at least one air inlet opening (2, 2') and one air outlet opening (8, 8'), characterized bythat at least one further air inlet opening (7, 7') is provided and the air guiding device is designed such that it has the function of a jet pump (6), for which purpose the partial quantity of air (3c, 3c') which is conveyed by means of the blower (4) passes through the latter as a driving medium via the air inlet opening (2, 2') into the air guiding device and sucks in a suction medium (3b, 3b') via the further air inlet opening (7, 7'), after which the driving and suction medium pass to the unit as cooling air via the air outlet opening (8, 8'). [2] Cooling device according to claim 1, characterized by that the further air inlet opening (7, 7') is directed in the forward direction of travel at a point of the motor vehicle exposed to the wind. [3] Cooling device according to claim 1 or 2, characterized by that the air inlet opening (2, 2') is acted upon by a heat exchanger fan (4) of an internal combustion engine heat exchanger (5). [4] Cooling device according to one of claims 1 to 3, characterized by that the air outlet opening (8, 8') is located in a wheel house. [5] Cooling device according to one of claims 1 to 4, characterized by that the unit is a wheel brake. [6] Cooling device according to claim 5, characterized by that the wheel brake is a disc brake located on an inner side of the wheel, wherein the air flow (9, 9') of the cooling air is directed into the wheel interior towards the brake disc and / or the brake calliper.

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