SE1151045A1 - Pulley for generating cooling air flow to a machine - Google Patents

Abstract

A pulley (2) comprises a hub (4) and an outer jacket, where the pulley is designed for pre-assembly at a machine to be cooled by a lude generated by the pulley. For this purpose, the hub (4) is formed with axially through hub openings (14) provided with co-opening loosely breaking edges (16) adapted to generate a single-axial first loosening (17) when the pulley (2) rotates. In addition, the outer casing has continuous casing openings (18) with a set of second lu-breaking edges (20) adapted to generate a radially second lu-tube (21) substantially inwardly upon rotation of the pulley (2). (Fig. 1)

Description

The object of the present invention is to optimize and improve the cooling of machines where a pulley is coupled to a shaft of the machine regardless of the diameter of the pulley and while maintaining the strength of the pulley.

Summary of the Invention The above objects are achieved by the invention as defined by the independent claim. Preferred embodiments are defined by the dependent claims.

Through the design of the pulley according to the present invention, the pulley can be used to provide an improved air fate to cool underlying components. First, the air is sucked into the pulley substantially in a radial direction, and then it is blown backwards, substantially in an axial direction, towards the machine and towards the components of the machine.

The outer jacket of the pulley is designed, by means of jacket openings, so that it radially sucks in air to the hub.

The invention is based on the inventors' insight that when using a pulley when it is mounted on a rotating shaft and a belt abuts against the mantle surface, about 50% of the pulley surface of the pulley is often free from the belt. This allows a cooling air gap to pass radially through the jacket openings towards the center of the hub. The openings can be designed to suit a specific direction of rotation or to suck in air regardless of the direction of rotation.

The pulley hub is provided with a number of hub openings which act as an axial shaft that blows the air sucked radially through the pulley further back and behind the pulley and towards and into the machine to be cooled. 10 15 20 25 30 3 The solution enables an adjustment of the diameter of the pulley so that it becomes possible to use exactly the gear required without being hindered by the risk of blocking the cooling air flow. This gives the designers great opportunities to optimize the design.

Additional features and advantages will be apparent from the accompanying description which exemplifies a number of different embodiments of the invention. The description is made with reference to the attached schematic drawings. The exemplary embodiments described below are not to be construed as limiting the scope of the invention.

Short drawing description Pig. 1 shows a perspective view of a pulley according to a principal embodiment of the invention.

Pig. 2 shows a view along the axis of rotation of the pulley according to an embodiment of the invention.

Pig. 3 shows a view along a cross section of the pulley showing the air flow in the pulley according to the invention.

Pig. 4 and Pig. 5 shows views along the axis of rotation of the pulley according to two alternative embodiments of the invention.

Pig. 6a and Pig. 6b shows perspective views of the pulley according to a further embodiment of the invention.

Figures 7-9 show side views of the pulley according to the invention which illustrate different embodiments of the jacket openings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In the accompanying figures showing different embodiments, the same or similar parts are shown with the same reference numerals where possible. In Figures 2, 4 and 5, the direction of rotation of the pulley has been indicated by an arrow marked "R". Fig. 1 is a perspective view schematically showing a pulley 2 which is adapted to be mounted on a rotatable shaft 3 from a machine 5 (see Fig. 3). The shaft 3 defines a longitudinal axis of rotation which corresponds to a axis of rotation (A) of the pulley 2.

The machine 5 consists primarily of an electric machine such as a generator or an electric motor which generates heat during its operation and therefore needs to be cooled. The machine can, for example, be arranged at an internal combustion engine in a vehicle, for example a truck, car or bus, a ship or be arranged on a machine in the manufacturing industry. The machine 5 can be driven by an external drive source or constitute a drive source for another machine. The pulley 2 is then included in a belt transmission for being driven by the machine 5 or for driving the machine 5, which belt transmission may comprise further machines.

The pulley 2 comprises a hub 4 and an outer jacket having an outer jacket surface 6 with two edges 8, 10, the hub having a substantially circular extent in a radially directed plane perpendicular to said axis of rotation (A) and provided with a through opening 12 for mounting on the shaft 3 with the hub facing the machine 5.

The outer sheath has a predetermined width between the two edges 8, 10 and where the sheath surface 6 along one edge 10 passes to the hub 4. The outer sheath is adapted for co-operation with a strap which abuts against parts, about 50%, of the outer mantelytan 6.

The outer jacket surface 6 is for this purpose designed with a design suitable for cooperation with the belt, which can be a single groove or a number of grooves parallel to each other intended for a so-called poly-v-belt. The outer jacket surface can also have a smooth design for cooperation with a flat belt.

The pulley 2 is exposed to great stresses, which affects the choice of material and design.

The pulley 2 is, for example, made of steel, but other metals and metal alloys are of course possible. Other materials such as carbon fiber and various plastic materials may also be considered. Likewise, the hub and jacket can be made of different materials.

In applications for internal combustion engines and vehicles where the machine consists of a generator driven by the internal combustion engine, the diameter of the pulley 2 is, for example, in the range 72- 10 15 20 25 30 5 150 mm and the pulley has a width of 30-70 mm between the edges 8, 10. The weight is under one kg.

The hub 4 has at least two continuous hub openings 14 provided with a set of first air-breaking edges 16 adapted to generate a first air gap on rotation of the pulley 2, which in Fig. 3 is shown by arrows 17, substantially along the pivot axis (A) and directed towards the machine The air-breaking edges 16 have a substantially radial extent on the hub 4. According to one embodiment, the number of hub openings 14 is four, which is illustrated in Figures 2, 6a and 6b. The hub openings 14 are symmetrically arranged so that the center of gravity of the hub 4 coincides in the center of the hub, i.e. at the point of the axis of rotation A. The number of hub openings 14 can of course be significantly fl greater than four and the considerations made when choosing the number include that the pulley meets the requirements for strength and stability, which means that the total area of the hub openings 14 should not exceed 50% of the total area of the hub.

The hub openings 14 have a substantially rhombic or triangular shape as shown in the figures. Other shapes are possible, for example more rounded shapes.

The first air-breaking edges 16 have, according to one embodiment, an oblique bevel of the edges facing the direction of rotation R. These are shown, for example, in Fig. 6a. According to another embodiment, the hub openings can be provided with beveled air-breaking edges 16 on both sides of the opening so that an air flow is achieved independent of the direction of rotation of the pulley 2.

The purpose of the hub openings 14 is thus to generate a first air gap, which is shown in Fig. 3 by arrows 17, directed substantially axially along the axis of rotation A, for cooling the machine and components in the machine.

To further improve the cooling, the outer jacket has at least two continuous jacket openings 18 with a set of second air-breaking edges 20 adapted to generate a second air gap when the pulley 2 is rotated, as shown in the figures by arrows 21, see for example Figures 2-4, substantially directed radially inwards towards the axis A and parallel to the plane of the hub 4. 10 15 20 25 30 As mentioned above, the belt abuts against approximately half of the mantle surface 6, which means that half of the mantle surface 6 is exposed and accessible to the surrounding air. If only two jacket openings 18 are provided, at least one jacket opening 18 will contribute to generating the second air gap 21.

The jacket openings 18 are evenly distributed over the outer jacket so that the pulley 2 has the necessary stability. The number of jacket openings 18 is, according to one embodiment, four, as shown in Figures 4-6. It is possible to arrange considerably more jacket openings, in the order of 10-20 pieces, provided that the abutment of the belt against the pulley does not deviate too much from the semicircular shape, which is most optimal with regard to power transmission and wear. This can also be expressed as the total area for all casing openings occupying a maximum of a predetermined part of the outer casing surface, where this predetermined part is 75%.

Fig. 3 is a view along a cross section of the pulley 2 which schematically shows the air flow in a pulley according to the invention. The figure shows in particular how the air flow, when it is sucked in through the jacket openings 18 has a substantially radial direction, see reference 21, to then fold off and be sucked in and pass through the hub openings 14, see reference 17, and further along the shaft 3 towards and into the machine.

The other air-breaking edges 20 at the jacket openings 18 have a substantially axial extension parallel to the axis A, and preferably have an oblique bevel of edge edges facing the direction of rotation R. The oblique bevel is shown in Fig. 4 and Fig. 5.

The jacket openings 18 can, according to one embodiment, be provided with bevelled air-breaking edges 20 on both sides of the opening 18 so that an air gap is achieved independent of the direction of rotation of the pulley 2.

The jacket openings 18 may have different shapes and have a width which preferably extends over the greater part of the width of the jacket surface 6 between its edges 8, 10. The jacket may also comprise two or two openings located next to each other or offset relative to each other where each such opening has a width which is substantially less than the width of the mantle surface 10, for example in the range one tenth to half of the width of the mantle surface. The different jacket openings 18 can thus be displaced both axially and circumferentially relative to each other. Such a design with a plurality of jacket openings 18 can give a more even radial fate through the jacket compared to a design with a smaller number of jacket openings. The air flow through the jacket openings 18 is effected by the force acting on the air-breaking edges, but this is supported to some extent by the pumping action obtained when the belt approaches the jacket openings to finally completely block a jacket opening. However, this pumping action becomes pulsating and largely depends on the design and number of jacket openings 18.

Figures 7-9 are radial side views of the pulley 2 which illustrate different designs of the jacket openings 18. In these figures the hub and the machine are placed to the right, i.e. the axial air fate is to the right.

Figure 7 shows an embodiment where the jacket openings 18 are rectangular and where the other air-breaking edges 20 are substantially straight and parallel to the axis of rotation A.

Fig. 8 shows an embodiment where the jacket openings 18 have the shape of a parallelogram where the other air-breaking edges 20 are substantially straight and parallel to each other.

But the edges 20 have a direction which differs a predetermined angle in relation to the axis of rotation A. The angle may be in the range 10 ° -50 °.

Fig. 9 shows an embodiment in which the jacket openings 18 are defined by edges which have a curved shape in whole or in part. According to this embodiment, the other air-breaking edges 20 have a predetermined curve shape which substantially corresponds to a part of a circle.

With reference to Fig. 4 and Fig. 5 which are views along the axis of rotation A of the pulley 2, two further embodiments will now be described. In order to further improve the second air gap 21 radially inwards, according to these embodiments, one or more lamellae 22 have been arranged adjacent to the jacket openings 18. The lamellae 22 are walls which run along all or part of the air-breaking edges of the jacket openings 18 and are 15 Are substantially perpendicular to the plane of the hub 2 if they are arranged in connection with jacket openings of the type illustrated in Fig. 7, i.e. where the edges are parallel to the axis of rotation A. If, on the other hand, the jacket openings form an angle, or are curved, the slats will follow the edge of the opening and thus form an oblique angle in relation to the plane of the hub. Ifig. Fig. 4 shows four slats 22 which are straight, while in Fig. 5 the slats 22 have a curved shape to improve the air flow inwards. The slats 22 are preferably arranged in connection with the jacket openings, but further slats (not shown in the figures) can be arranged in suitable positions in order to further improve the air flow.

In addition to improving airflow, the slats also help to provide stability to the pulley.

Pig. 6a and Fig. 6b are perspective views of the pulley 2 illustrating a further embodiment of the invention. Fig. 6a shows the pulley 2 where, among other things, the inside of the hub 4 is shown, i.e. side facing the inside of the pulley. To improve the abutment of the belt against the pulley, the outer jacket surface 6 is provided with a number of longitudinal grooves 22 in the circumferential direction of the pulley for co-operation with a belt formed with corresponding elevations. Such a pulley is usually referred to as a poly-v pulley and the belt for a poly -v-rem. These grooves 22 are shown in Figures 6a and 6b. Fig. 6a also shows the air-breaking edge 20 which is bevelled. Fig. 6b shows a perspective view of the pulley 2 where the outside of the hub 4 is shown, i.e. side facing the machine to which the pulley is intended to be mounted.

The invention is not limited to the preferred embodiments described above. Various alternatives, modifications and equivalents can be used. It has been described above that the hub of the pulley is provided with a radial plane, which must be arranged closest to the machine in question. This is advantageous because it enables air to not only flow in from the jacket openings but also to flow in axially towards the plane in order to be passed on to the machine together with the air flow from the jacket openings.

In alternative embodiments, this plane may be arranged in another axial plane relative to the mantle surface. It is also possible to arrange your radial planes in your different axial positions.

For example, both axial ends of the pulley may be formed with radial planes in accordance with what has been described, so that the pulley takes the form of a cylindrical cage. The first plane then functions completely in accordance with what has been described above, while openings in the second plane contribute with an axial flow of air into the space between the two planes, from where it is then passed on to the machine together with air flow from the jacket openings by means of the openings in the first plane. Such a pulley can be given a stable construction even if the jacket openings are designed relatively large.

In the embodiments described, the jacket openings 18 have been designed as more or less large openings where the belt had no abutment surface. In an alternative embodiment, for example where the pulley is intended for cooperation with a poly-v-belt, the pulley is formed with a number of mutually parallel grooves extending in the circumferential direction. In such an application it is possible to design the recesses as openings only in the respective bottoms of the grooves while the tops of the grooves remain intact. In such an embodiment, the belt can have a continuous, albeit limited, abutment against the pulley even where it is designed in some places with casing openings. This entails a more even load on both the belt and the pulley and also that the recesses do not significantly reduce the pulley's ability to transmit large torques.

Claims (9)

10 15 20 25 30 10 Patent claims A pulley (2) comprising a hub (4) configured to attach the pulley to a rotated shaft of a machine (5) and an outer shell formed with an outer shell surface (6) for co-operation with a belt, the hub (4) is formed with at least two continuous hub openings (14) provided with a set of first air-breaking edges (16) adapted to generate a first air gap (17) substantially axially in the direction of the machine (5) when the pulley (2) is rotated, characterized in that the outer jacket has at least two continuous jacket openings (18) with a set of second air-breaking edges (20) adapted to generate a second air gap (21) substantially inwards in the direction of the pivot axis (A) of the pulley when rotating the pulley (2). The pulley according to claim 1, wherein said second air-breaking edges (20) have an oblique bevel of the edges facing the direction of rotation (R) of the pulley. The pulley according to any one of claims 1-2, wherein the pulley (2) consists of a poly-v-pulley and that the outer jacket surface (6) is thus provided with a number of longitudinal grooves (22). The pulley according to any one of claims 1-3, wherein said second air-breaking edges (20) are substantially straight and parallel to the axis of rotation (A) of the pulley (2). The pulley according to any one of claims 1-3, wherein said second air-breaking edges (20) are substantially straight and have a direction which differs a predetermined angle with respect to the axis of rotation (A) of the pulley (2). The pulley according to any one of claims 1-3, wherein said second air-breaking edges (20) have a predetermined curve shape. The pulley according to any one of claims 1-6, wherein one or more lamellae (22) are arranged in connection with said jacket openings (18) for directing said second air inwardly. ll A pulley according to any one of claims 1-7, wherein said first air-breaking edges (16) have an oblique bevel of the edges facing the direction of rotation (R) of the pulley (2). A pulley according to any one of claims 1-8, wherein it is mounted on a rotating shaft (3) of an electric machine (5), such as a generator or an electric motor.