Patent Application
20120255827
1. Field of the Invention
The invention relates to a drive system of an engine cooling system in a motor vehicle, the cooling system including a radiator, an internal combustion engine and a fan, which is driven by a driveshaft of the internal combustion engine, which cools the engine cooling medium, and which is arranged between the radiator and the internal combustion engine. The drive system has a viscous coupling and a vibration damper which are both arranged between the internal combustion engine and the fan, that is to say the viscous coupling and vibration damper are directly or indirectly operatively connected to the internal combustion engine and to the fan. The vibration damper serves to ensure damping and/or decoupling of the vibrations acting between the driveshaft-side output of the internal combustion engine and the fan.
2. Description of the Related Art
DE 2007001921 U1 discloses a drive system for the engine cooling system for heavy motor vehicles, which drive system has a rotary vibration damper arranged on the driveshaft between a viscous coupling and an engine which drives the driveshaft. The rotary vibration damper restricts the wear of the components of the drive system, of the bearing arrangement of the fan and of the gearing to a level arising solely from normal frictional wear.
An object of the present invention is to provide a drive system of the engine cooling system for motor vehicles such that a reduction in the engine-induced noise emissions of fans can be realized in a simple and inexpensive manner. Furthermore, it is an object of the invention, despite the implementation of means for reducing the engine-induced noise emissions, to ensure the provision of a drive system which is as compact as possible with regard to the axial structural length of the arrangement.
The object of the present invention is achieved in that a vibration damper is arranged between the fan and a viscous coupling and decouples vibrations acting between the fan and the viscous coupling.
According to an embodiment of the present invention, the vibration damper is arranged between the fan and the viscous coupling and, at this location, dampens the vibrations acting between the fan and the viscous coupling. The arrangement of the vibration damper in the connecting region of the fan and the viscous coupling allows the vibration damper to be designed so as to be optimized with regard to its requirements for strength and durability, and to minimize costs. A first connecting side of the vibration damper comprises only the fan. Accordingly, the strength demanded of the vibration damper is correspondingly low because, at one end side, the only torque-influencing mass acting is that of the fan itself. In the prior art, the damping element is arranged between the viscous coupling and the driveshaft which drives said viscous coupling. As such, the vibration damper must furthermore accommodate forces resulting from the rotating mass of the viscous coupling, of parts of the driveshaft, and if appropriate of further components arranged between the driveshaft and the fan. Since the vibration damper according to the invention is “relieved of load” with regard to the lower forces to be accommodated, the vibration damper can be designed in a more targeted manner for the vibration-damping function. The vibration damper with its elastic element acts primarily as a body-borne sound vibration damper, such that the transmission of body-borne sound between the engine and the fan is eliminated or at least considerably reduced. This is associated with a reduction in noise emissions by the fan.
The viscous coupling is preferably regulated in a temperature-dependent fashion and can be varied in terms of its action for example by a bimetal or an electrical/electronic input variable. Below a certain temperature threshold, the viscous coupling is open, and the maximum rotational speed of the fan is thereby limited. For example, in response to an increase in the temperature, the bimetal regulates the action of the viscous coupling and couples the latter into a second state in which the fan rotational speed then corresponds at most to the corresponding speed transformation of the engine rotational speed. Instead of a bimetal or other thermal element, the regulation may also be realized by electrical or electronic actuation of the viscous coupling. As a result of the temporary decoupling and the associated decrease in rotational speed of the fan, the energy expenditure with regard to the rotational movement of the fan is reduced.
In a preferred embodiment, the vibration damper is designed as a connecting element connecting the fan and viscous coupling. Accordingly, the vibration damper not only performs its vibration damping function but also acts as a connector between the fan and the viscous coupling. This configuration has the advantage that the vibration damper may be designed for example as a cohesively connected or detachably fastened constituent part of the fan and/or a cohesively connected or detachable constituent part of the viscous coupling. The mounting of the vibration damper on the rest of the drive system is simplified, in particular, if the vibration damper is a detachable or cohesively connected constituent part of the fan. Provision may also be made for an existing drive system to be retrofitted by exchanging a conventional fan with a fan according to the invention which is provided with a vibration damper.
Geometric changes to the fan/viscous coupling interface arising from the provision of a vibration damper may advantageously be eliminated or minimized by designing the fan such that the fan-vibration damper assembly has flange points (interfaces) to the viscous coupling which are similar or identical to those of a conventional fan.
Here, it is advantageous for the vibration damper to have parallel rigid and elastic layers arranged one after the other in the axial direction.
If permitted by the installation space in the axial direction, provision may alternatively be made for an existing fan to be equipped through the interposition of a vibration damper according to the invention which corresponds both to the fan interface and also to the viscous coupling connecting point.
In a further embodiment, the vibration damper is connected to the fan in a cohesive and/or positively locking manner. In particular, a cohesive connection of the vibration damper to the fan allows provision of an effective fan-vibration damper assembly which simultaneously takes up minimal installation space. The cohesive connection may be realized by an adhesive bond or vulcanization of the vibration damper onto the fan.
In a further embodiment, the vibration damper is formed in the shape of a ring and/or in the manner of a hollow cylinder, wherein in the fully assembled state of the vibration damper, at least regions of the viscous coupling and/or at least regions of the driveshaft which leads to the viscous coupling are surrounded and/or enclosed in the central recess of the vibration damper. Because the vibration damper is formed in the shape of a ring and/or in the manner of a hollow cylinder and the central recess of the vibration damper serves for receiving regions of the viscous coupling, it is possible for damping of the fan wheel to be ensured with compact dimensioning.
The vibration damper has for example a ring width which corresponds at most to the inner radius of the central recess or at most to ¾, ⅗, ½, ⅖ or at most ¼ of the inner radius of the central recess. Here, the ring width is to be understood to be the radial wall thickness of the vibration damper which is formed in the shape of a ring and/or in the manner of a hollow cylinder, i.e., the difference between the inner and outer radii of the circular ring. Such a ring-shaped vibration damper whose central recess is dimensioned to be larger than or equal to the ring width makes it possible to provide a vibration damper which is of adequate strength and which provides adequate damping.
With regard to the dimensions of the fan, the ratio of the radius of the fan to the inner radius of the central recess of the vibration damper (central recess) preferably amounts to at most 25:1. In further embodiment, the ratio is preferably at most 14:1, preferably at most 9.5:1, preferably at most 8.5:1, and particularly preferably at most 7.5:1.
This means that the vibration damper is arranged relatively far from the center proceeding from the fan radius, and therefore adequate space for accommodating further elements of the drive train is available in the central recess of the vibration damper. Simultaneously, the material requirement for the vibration damper to ensure the strength thereof can be kept low. Also, the forces which act at the location far from the center and which are to be accommodated by the damping element are lower than in the case of an arrangement of the vibration damper close to the center.
A further advantageous embodiment is one in which the ring depth of the vibration damper corresponds at most to the ring width, preferably at most to ¾ of the ring width, particularly preferably to at most one half of the ring width of the vibration damper. As a result of the fact that the vibration damper is arranged relatively far from the center as a circular ring, its axial connecting surface has a relatively large surface area, such that to realize the required strength and durability of the vibration damper, only a small ring depth and therefore only a small installation space requirement in the axial direction is required to its further material components/connecting partners which adjoin it in the axial direction.
It is preferable for the vibration damper to be constructed from at least two parts and, here, to comprise at least one rigid connecting element and at least one elastic damping element. Here, the connecting element connects the vibration damper to the viscous coupling, and thereby forms a suitable counterbearing for providing a connection of the vibration damper and the viscous coupling, for example using detachable fastening elements such as screws. The elastic damping element is preferably cohesively connected at one end side to the connecting element and preferably cohesively connected at the other side to the fan, such that the damping element performs the damping function of the vibration damper. In a further preferred embodiment, the damping element is formed in a sandwich-like manner between a first connecting element for connecting the vibration damper to the viscous coupling and a second connecting element for connecting the vibration damper to the fan. Here, the second connecting element can serve as a counterbearing for fastening elements for fastening a fan to the vibration damper.
Alternatively, the elastic damping element is cohesively connected to the fan, such that the second connecting element for connecting the vibration damper to the fan can be omitted.
The structure, which comprises at least two elements, of the vibration damper may furthermore be designed such that the damping element comprises at least two ring segments which are spaced apart from one another, wherein the intermediate space between the ring segments is, at least in regions, free and/or provided with an element which has a different elasticity than the damping element. The free spaces or the intermediate spaces with the element of a different elasticity make it possible to targetedly influence the vibration-damping characteristics of the vibration damper. For example, the vibration damper is provided with at least one damping element region which can be broken out of the vibration damper by predetermined breaking points. It is advantageous here that an adaptation of the damping characteristics can be carried out after the manufacturing of the damping element. It is also possible for both the connecting element and the damping element to be formed as ring segments, which are for example aligned congruently or with an offset with respect to one another.
According to a further aspect of the invention, the connecting element is provided with at least one fixing element receiving bore which adjoins a fixing element receiving recess in the damping element. The fixing element receiving recess is preferably aligned at right angles with respect to the fixing element receiving bore. As fixing element, use is made for example of a screw whose screw shank is passed through the fixing element receiving bore and whose screw head is countersunk and/or can be at least partially received in the fixing element receiving recess at the level of the damping element.
In this connection, it is particularly advantageous for the geometry and/or the dimensioning of the fixing element receiving recess and the geometry and/or the dimensioning of the fixing element to be received in the fixing element receiving recess to be configured such that, at least in the fully assembled state, the damping element makes contact at least in regions with the fixing element in the region of the fixing element receiving recess.
If a screw is used as the fixing element, a screw head contacts at least in regions the damping element which delimit the fixing element receiving recess. Aside from the maximum space utilization afforded by this measure—as a result of the fact that a maximum surface area is provided for the damping element for contact with further elements and at the same time only a space necessary for receiving the screw heads is required—a further advantage can be seen in the fact that the contact of the screw head against the damping element simultaneously secures the screw so as to prevent it from being unscrewed. In particular, screws on moving parts have a tendency to loosen with progressive operating duration, and therefore such an exertion of load on the screw head by the damping element (for example clamping) can reduce this risk.
In a specific embodiment, a hexagon socket screw is used and a screw head surface thereof makes contact with the inner wall surface or raised regions of the inner wall surface. The damping element therefore both performs a damping function and also performs the function of securing the screw connection.
Furthermore, it is advantageous for the connecting element and the damping element to be arranged parallel and offset relative to one another in the axial direction. It is for example possible for both the connecting element and also the damping element to each be in the form of a circular ring, which circular rings are aligned concentrically and with an axial offset and are connected to one another at the ring surfaces. Here, the connecting and damping elements lie in separate planes which are parallel to and adjoin one another and which extend at right angles to the axial direction.
In a preferred embodiment of the invention, the vibration damper is designed with a ring-shaped and/or hollow cylindrical form, wherein the ratio of fan outer diameter to axial depth (thickness) lies in the range from 7:1 to 15:1, preferably in the range from 8:1 to 10:1.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.
In the drawings, wherein like reference characters denote similar elements throughout the several views:
a is a schematic sectional illustration of the connection of the viscous coupling to the vibration damper in detail, with the viscous coupling and vibration damper spaced apart from one another (in a pre-assembled state);
b is a schematic sectional illustration of the embodiment of
According to
Arranged between the viscous coupling 6 and the internal combustion engine 3 is a vibration damper 7 which dampens and/or decouples vibrations between the driveshaft-side output A of the internal combustion engine 3 and the fan 5.
In a first embodiment of the present invention shown in
In yet a further embodiment shown
Here, the vibration damper 7 is particularly preferably formed in the shape of a ring and/or in the manner of a hollow cylinder, such that at least regions of the viscous coupling 6 and/or at least regions of the drive shaft 4 which leads to the viscous coupling 6 are surrounded by the central recess 8 in the fully assembled state.
In
Details of the connection of the viscous coupling 6 to the fan 5 are illustrated in
In the embodiment of
Preferred dimensions of the fan-vibration damper assembly 5, 7 will be explained on the basis of
It is furthermore advantageous for the ratio of the outer radius 16 of the fan 5 to the inner radius 15 of the vibration damper 7 to be at most 25:1, preferably at most 14:1, preferably at most 9.5:1, preferably at most 8.5:1 or particularly preferably at most 7.5:1.
In a further embodiment, as seen in the juxtaposition of
As can be seen in
In a further embodiment, the vibration damper 7 is of ring-shaped and/or hollow cylindrical form, and here, a ratio of the outer radius 20 of the vibration damper 7 to the axial depth (ring depth 17) of the vibration damper 7 lies in the range from 7:1 to 15:1, preferably in the range from 8:1 to 10:1.
Advantageous absolute dimensions for the vibration damper 7 are as follows:
for the ring width 14: 10 to 80 mm, preferably 20 to 40 mm;
for the inner radius 15: 50 to 150 mm, preferably 70 to 120 mm;
for the outer radius 20: 90 to 200 mm, preferably 90 to 150 mm;
for the ring depth 17: 10 to 50 mm, preferably 10 to 25 mm.
The diameter of the fan 5 may amount to between 150 and 950 mm, preferably between 600 and 950 mm. The advantages of the invention are brought to bear primarily in the case of fan diameters of 600 to 950 mm, because in the case of such diameters a greater fan mass and greater lever forces act on the damping element 13, and the required strength and sound damping characteristics can be ensured by the design according to the invention of the vibration damper 7 together with its damping element 13. Fan diameters of greater than 950 mm are basically also practicable in the design according to the invention.
For the advantageous ratios of the dimensions of the vibration damper 7 and of the fan 5, the following ratio ranges are expedient:
ratio of ring width 14 to inner radius 15: between 1.00 and 0.05;
ratio of radius 16 of the fan 5 to inner radius 15: between 2.5 and 25, preferably between 2.5 and 9.5;
ratio of outer radius 20 to ring depth 17: between 7.0 and 15.0.
Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 016 204.6 | Apr 2011 | DE | national |
