COOLING DEVICE FOR A MOTOR VEHICLE
The invention relates to a cooling device (1) for a motor vehicle with a combustion engine (2) comprising a coolant radiator (5) through which air can flow, an axial blower (3) which is arranged behind the coolant radiator (5) in the airflow direction (L), [and] a shroud (6), arranged between the coolant radiator (5) and the axial blower (3), with a shroud ring (7) in which the axial blower (3, 3b) is arranged so it can turn. It is proposed to widen the shroud ring (7) on the air outflow side radially into a flow guidance device (8).
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The invention relates to a cooling device for a motor vehicle according to the preamble of claim 1.
Known from the applicant's DE 33 04 297 C2 is a cooling device for motor vehicles with an axial blower, which is engine-mounted and can be driven by the combustion engine of the motor vehicle. The axial blower sucks in air through a coolant radiator, to the back side of which is attached a radiator shroud for channeling the air flow. The axial blower has an axial blade attachment with an external guide ring (shell), which projects against the flow direction beyond the front edges of the blade, and extends into an engine-mounted inlet nozzle. As a result of this combination of an inlet nozzle and a projecting guide ring, an annular gap with a 180° direction change is created that produces a strongly throttled gap air flow. The guide ring is radially enlarged in its downstream area, and it can also additionally have a diffuser part. Because of a strong throttling, the axial blower has a semiaxial flow, which is supported, or reinforced, by the enlarged area of the guide ring and diffuser part. As a result of the incorporation of the axial blower in the vicinity of the motor, recirculation of the exiting air flow can occur in the known arrangement, i.e., a renewed aspiration through the radiator can occur that detrimentally affects the cooling capacity.
Known from DE 42 22 264 A1 is a cooling device for a motor vehicle that has an electrofan, i.e., a fan that is driven by an electromotor. In this known construction design, the electromotor and the axial blower (axial fan) are attached by braces, a shroud ring, and a radiator shroud on the radiator side. The shroud ring has a cylindrical part in which the axial blower rotates, and a diffuse, flaring surface which is connected to the cylindrical part downstream of it. Other data regarding the design, the dimensions, and the purpose of the diffuse flaring surface are included in the patent. In accordance with the representation provided in the drawing, the person skilled in the art will therefore start with a conventional diffuser with a flare angle of approximately 7° relative the axial direction. This means that the outflow of the air behind the axial blower is oriented axially, i.e., no deflection occurred, only a deceleration of the flow.
The problem of the present invention is to improve the blower characteristics of a cooling device of the type described in the introduction, and also to prevent the recirculation of the air flow exiting from the fan.
This problem is solved by the characteristics of Claim 1. According to the invention, the shroud ring widens radially on the side of the outflow into a funnel-shaped flow guidance device. The flow exiting from the fan, which is a semiaxial or semiradial flow (flow with an axial and with a radial component), is further deflected by the flow guidance device outward, i.e., in the radial direction. This prevents the outflow behind the fan from frontally hitting the engine block and other units behind the fan, and collecting there. As a result of the radial deflection of the flow, a recirculation, i.e., a reentry of the air flow into the radiator, is also prevented, which improves the cooling capacity.
Advantageous embodiments of the invention can be obtained from the dependent claims. The radial widening of the flow guidance device is characterized by a flare angle which is at least 55°, preferably 60° and more, with respect to the axial direction. The radial expansion can occur in one step, by means of a conical surface with a flare angle, or in at least two steps, by at least two successive connected conical surfaces with increasing flare angles or in the shape of a flare or bell. As a result, a relatively strong expansion occurs, which reinforces the semiradial flow in the fan further in the radial direction. Thus a relatively strong deflection is achieved in a relatively short axial installation space. The flare angle α can also be designed to be variable over the circumference, if the outflow conditions behind the fan vary, for example, because of secondary units arranged on the combustion engine.
The flow guidance device is advantageously characterized by a maximum external diameter on the downstream end that is at least 1.1 times, preferably 1.15 times, that of the fan diameter. As a result, a maximum deflection of the outflow can be achieved in the installation space available in the vehicle.
The fan blades can either turn within the cylindrical area of the shroud ring, or they can have a blade overhang on the downstream side that extends into the widened area of the flow guidance device. As a result, the advantage is achieved that the semiaxial flow into the externally located blade areas or blade tip areas is improved, and it contacts directly—without separation—the internal wall of the flow guidance device; the flow is stabilized.
To further improve the fan characteristics, a known inlet nozzle is provided on the double shroud ring that works in cooperation with a guide ring or shell that is attached to the blade tip. As a result, an annular gap and consequently a gap flow with a 180° direction change is produced. The gap flow in the annular gap is directed against the main axial flow in the fan, and it sucks air out of the outflow area. In this context, it is also advantageous that, as a result of the aspiration caused by the gap flow, a greater deceleration is achieved in the outflow area (the effect of boundary layer aspiration).
The semiaxial outflow and the radial deflection of the outflow toward the exterior can be supported by a radially widening shell of the fan, i.e., by a shell which widens like a diffuser. The tendency for the flow to separate is thereby decreased.
According to an advantageous embodiment of the invention, the shroud ring is engine-mounted, i.e., it is fixed to the block of the combustion engine. As a result, relative motions are generated between the shroud and the radiator and between the shroud ring and the shroud, respectively. The relative movements are compensated by flexible or movable sealing means in the form of lips or folded bellows.
The axial blower is also engine-mounted, and it is driven by the combustion engine preferably via a fluid friction clutch. As a result, minimal gaps are formed between the shroud ring and the blower blade tips or the blower shell.
Embodiments of the invention are represented in the drawing and explained in greater detail below. In the drawing
The flow guidance device 8, 8a according to the invention has the effect that the air flow—represented by a dashed flow arrow P—that exits from the fan 3b is deflected outward in the radial direction. As a result, on the one hand, an accumulation of the air flow in front of the engine block 2 is prevented, and on the other hand a recirculation, i.e., a return flow in the direction of the radiator inlet 5, is also prevented.
The injection molded part which consists of the shroud 12, the shroud ring 13, the flow guidance device 14, and the inlet nozzle 15, is connected by braces, which are not shown, to the engine block 2. Therefore there are practically no relative movements at all between the guide ring 17 and the shroud ring 13, so that a minimal annular gap 18 can be achieved. However, an elastic or movable fastening of the shroud 12 to the radiator 5 is required, and it is preferably achieved using an elastic fastening element 12a.
In contrast to the embodiments represented in the drawing, which has a conical or cone-shaped surface 8a of the flow guidance device 8, a bell- or flare-shaped form is also possible and within the scope of the invention.
Claims
1. A cooling device for a motor vehicle with a combustion engine, comprising a coolant radiator through which air can flow, an axial blower which is arranged behind the coolant radiator in the airflow direction (L), a shroud with a shroud ring that is arranged between the coolant radiator and the axial blower, with the axial blower being arranged in the frame ring so that it can turn, wherein the shroud ring is radially widened on the air outflow side into a flow guidance device.
2. The cooling device according to claim 1, wherein the flow guidance device has a surface that forms a flare angle α with the axis (a) of the axial blower, where α≧55°.
3. The cooling device according to claim 2, wherein the flow guidance device has a conical surface.
4. The cooling device according to claim 2, wherein the flare angle α of the flow guidance device, seen over the circumference of the shroud ring, is variable.
5. The cooling device according to claim 1, wherein the axial blower has an external diameter DL, and the flow guidance device has an external diameter DA on the outflow side, where the following relation applies: DA≧1.1 DL.
6. The cooling device according to claim 1, wherein the axial blower has blades that turn within the axial extent of the cylindrical area of the shroud ring.
7. The cooling device according to claim 1, wherein the axial blower has fan blades with a blade overhang (ü) on the outflow side, where the overhang extends in the axial direction of the flow guidance device.
8. The cooling device according to claim 1, wherein, on the side against which the air flows, the shroud ring has an inlet nozzle and the axial blower has a shell, and in that an annular gap with a 180° direction change is formed between the inlet nozzle and the shell.
9. The cooling device according to claim 8, wherein a radially external area of the inlet nozzle transitions into the shroud ring.
10. The cooling device according to claim 8, wherein the shroud, the inlet nozzle, the shroud ring, and the flow guidance device are designed as one piece.
11. The cooling device according to claim 8, wherein the shell has a downstream, diffuser-like widened area.
12. The cooling according to claim 1, wherein at least the shroud ring having the flow guidance device is engine-mounted.
13. The cooling device according to claim 12, further comprising flexible and/or movable sealing means for compensating relative movement between the shroud and the coolant radiator.
14. The cooling device according to claim 1, wherein the axial blower is driven by the combustion engine.
15. The cooling device of claim 2, wherein α≧α°.
16. The cooling device of claim 4, wherein α has values between α1≧55° and α2≦90°.
17. The cooling device of claim 5, wherein DA≧1.5 DL.
18. The cooling device of claim 10, wherein the one piece is injection molded.
19. The cooling device of claim 14, wherein the axial blower is driven by a fluid friction clutch.
Type: Application
Filed: Aug 6, 2007
Publication Date: Feb 14, 2008
Applicant: BEHR GMBH & CO. KG (Stuttgart)
Inventors: Uwe Blass (Moglingen), Ulrich Vollert (Stuttgart)
Application Number: 11/834,064
International Classification: F28D 1/00 (20060101); F28F 13/00 (20060101);