Patent Application
20160186763
The invention relates to a centrifugal fan, in particular a gas fan that transports fuel and air and that comprises a fan housing with a fan wheel arranged in it and with a through opening for running a drive shaft through it, which drive shaft is to be connected to the fan wheel.
Such a centrifugal fans are known from the prior art, for example, from DE 102 04 037 B4. The construction known from this patent has frequently proved itself in practice. Nevertheless, it is desirable to reduce the number of parts and to minimize the construction space required for the structural components arranged on the fan housing. It is especially interesting in a fan construction with laterally arranged electromotor to keep the axial extension along the drive shaft as small as possible.
Given this background the invention has the problem of making available a more compact centrifugal fan or gas fan with an electromotor arranged on its side which fan requires fewer structural fixing components and is more economical. Another aspect is to be able to carry out a tightness check of the centrifugal or gas fan in an easier and more comprehensive manner.
Furthermore, it should be ensured that the gas fan in accordance with the invention can be mounted in easy and automated manner. For the operation of the fan it is to be ensured that the shaft and the fan wheel arranged on it do not oscillate in the axial direction. Furthermore, there is the problem for the fan of the invention of ensuring an improved protection against moisture and a lower thermal stressing of electronic structural control components.
These problems are solved by a pre-fixing centrifugal blower according to claim 1 and the following subclaims. Every fan which transports a mixture of fuel and air to a burner is to be understood as a gas fan.
It is provided according to the invention that the centrifugal fan comprises a fan housing with a fan wheel arranged in it and a through opening for running through a drive shaft of an electromotor to be connected to the fan wheel, wherein the electromotor is arranged on the outside of the gas fan housing and held by a motor mounting. A part of the motor mounting extends through the through opening into the interior of the fan housing. The motor mounting lies in the mounted state of the fan on an elastomeric element arranged on the through opening between the fan housing and the motor mounting and is fixed by the elastomeric element on the fan housing.
This construction makes it possible to position the motor mounting with the electromotor arranged on it with a lesser interval than previously on the fan housing or the side wall of the fan housing. No additional fastening means for fixing or decoupling oscillations of the motor mounting need to be provided on the fan housing. In the prior art the motor mounting was always fixed with screws on the fan housing, which are now obsolete due to the fastening by the elastomeric element. The axial length or the height of the motor mounting with the electromotor integrated in it or fastened on it is reduced further by the extension of a part of the motor mounting through the through opening into the interior of the fan housing. The area between the outer surface of the fan housing and the surface of the motor mounting facing the fan housing is limited to a minimum according to the invention, wherein the axial size of the area is determined by the elastomeric element on which the fan housing and the motor mounting rest. The fixing of the motor mounting on the elastomeric element takes place via a safety ring that engages into the motor mounting or via an undercut integrated in the motor mounting. In the case of a solution with a safety ring as well as in a solution with an undercut they are engaged with the elastomeric element in the mounted state and prevent a loosening of the motor mounting from the elastomeric element and therefore from the fan housing. The screwing of the motor mounting to the fan housing, which is necessary in the prior art, is no longer necessary. The associated elimination of at least three screws per fan reduces the expense.
Furthermore, it is advantageous according to the invention that the fan housing used in accordance with the invention has no undercuts for fastening structural components to them so that it can be produced and removed from the mold with a simple open-close tool.
In an advantageous embodiment the elastomeric element is simultaneously constructed as a seal of the motor mounting opposite an edge of the through opening and is arranged directly between the fan housing and the motor mounting. As a result of the sealing function of the elastomeric element between the motor mounting and the fan housing, the only leakage passage that needs to be checked for tightness is the passage from the fan wheel via the support of the drive shaft to the outside. Therefore, an embodiment of the invention provides that a sealing test edge running circumferentially on the outside is provided on the motor mounting. The sealing test edge is constructed in such a manner that a sealing bell can be placed over the motor mounting in such a manner that the remaining leakage path is sealed. Therefore, in the case of a tightness check it can also be checked, in contrast to previously used pre-mixing gas fans whether the fan housing wall including the elastic element to which the motor mounting and therefore indirectly also the electromotor are fastened are also tight.
Furthermore, it is provided in an embodiment of the invention for an especially compact construction that the part of the motor mounting extending into the interior of the fan housing extends into a free space provided on the fan wheel or a hub of the fan wheel. Therefore, it is not necessary to maintain a special interval between the fan wheel and the housing wall in which interval the fixing of the motor mounting is completed but rather the fan wheel can be positioned along the inner wall of the fan housing with only a slight slot dimension in order to avoid flow losses.
It is furthermore provided in order to make available an inexpensive construction of the centrifugal fan that can be mounted from one side that the drive shaft is supported by a ball bearing and a sliding bearing in the one-part motor mounting. The use of a sliding bearing has the advantage that it can be readily mounted and is less expensive. The invention provides that the rotor of the electromotor is arranged between the ball bearing and the sliding bearing and that the ball bearing is located axially on the inner side, i.e., closer to the housing and to the fan wheel. In comparison to the construction known from the prior art the mounting can take place here exclusively from one side so that it can be automated. The motor mounting comprises a holder on which the ball bearing of the drive shaft rests. Such a holder can be constructed as a projection in the motor mounting or as a circumferential edge on which the ball bearing is supported. The mounting into the motor mounting takes place in that at first the ball bearing and then the rotor of the electromotor and finally the sliding bearing are pushed or pressed onto the drive shaft. The holder of the motor mounting offers a stop here for the ball bearing and therefore determines the axial position of the drive shaft. Alternatively, the rotor can be injected onto the shaft.
In an advantageous embodiment the electromotor is constructed as a direct current motor with a rotor arranged on the drive shaft and a stator received in the motor mounting. The rotor of the direct current motor is fastened in an advantageous embodiment on the drive shaft and the position of the rotor opposite the stator is offset by one axial length to the outside, i.e., in the direction away from the fan wheel or the housing. This off-center arrangement of the rotor in comparison to the state or in the zero position serves to utilize a magnetic return force during the application of the current to press or draw the driveshaft with the rotor fastened to it into a predetermined direction. The fan wheel itself produces a force in the same direction during operation that is, however, dependent for its magnitude on the speed. The off-center arrangement of the rotor opposite the stator in the currentless state (zero position) ensures that the shaft with the fan wheel arranged on it does not oscillate in both axial directions during operation but rather a defined axial force is always provided in one direction (in the direction of the central position of the rotor to the stator).
Furthermore, another embodiment of the invention provides that a rectangular guide plate is used to control the electromotor. In comparison to the round guide plates with central recesses for running the drive shaft through that are known from the prior art, rectangular guide plates are advantageous since they ensure significantly less waste of material which reduces the cost. A rectangular guide plate can therefore be provided according to the invention since it can be fastened on the motor mounting radially offset from the drive shaft. In this connection the term radially denotes a lateral arrangement relative to the drive shaft. The fastening of the guide plate on the motor mounting can take place, for example, by a clip connection or by some other catch known from the prior art.
An advantageous embodiment provides that the guide plate is arranged on the motor mounting in a position to the side of or below the electromotor and which is not influenced by a heat flow caused by the operation of the electromotor. The inclusion of the pre-mixing centrifugal or gas fan usually takes place in two alternative positions, vertically or horizontally. This brings it about that the motor mounting and the electromotor fastened to it are arranged horizontally in the one case and vertically in the other case. Since the heat flow constantly takes place substantially vertically upward, the guide plate should be arranged either to the side of the flow in the vertical case or below the electromotor in the horizontal case. Basically, the thermal load in a side arrangement of the guide plate directly following the electromotor axially is more advantageous compared to the previous arrangement known from the prior art since the thermal load is less in any case. Furthermore, it is advantageous that a simple connection to the individual coil bodies of the electromotor via a stamped sheet can be ensured by a side arrangement.
Furthermore, it is advantageous that in an embodiment of the invention a motor protection cap with a circumferential edge is provided that covers at least the electromotor, the guide plate and the motor mounting and rests with the circumferential edge on the fan housing. This eliminates the slot between the motor protection cap and the fan housing wall which was previously provided in the prior art and prevents a penetration of moisture or other contaminating particles between the fan housing wall and the motor protection cap. Therefore, the electromotor is better protected. A direct contact is made possible by the fact that the motor protection cap is fastened directly on the fan housing and not, as in the state of the art, on the motor mounting. The motor mounting was constantly influenced by the vibrations of the electromotor which were transferred onto the motor protection cap and therefore made a slot necessary between the fan housing wall and the motor protection cap. This disadvantage is overcome with the direct connection of the motor protection cap to the fan housing.
Another embodiment provides that air conduction conduits are injected into the motor protection cap produced with the injection molding method and ensure a better removal of the heat generated by the motor. In order to further the removal of heat, a cooling wing is customarily provided on the drive shaft whose flow cooperates with the air conduction conduits.
All the above-cited features can be combined in all variants in as far as this is technically possible.
Other advantageous further developments of the invention are characterized in the subclaims and are presented in detail in the following together with a description of the preferred embodiment of the invention using the figures. In the figures:
The figures are of an exemplary, schematic nature and the same reference numerals refer to the same parts in all views.
The direct resting of the motor mounting 7 directly on the elastomeric element 9 brings about in addition to the seal a decoupling of the oscillations of the motor mounting 7 with the electromotor 6 arranged on it. The motor mounting 7 moves closer to the fan housing 2 in contrast to explanations from the prior art so that the entire structural space required is reduced in the axial direction of the drive shaft 5. The part 8 of the motor mounting 7 which extends into the interior of the fan housing 2 ends in a free space 12 provided in the area of the hub of the fan wheel 3. This also makes possible a more compact construction of the motor mounting 7 to the fan wheel 3.
The drive shaft 5 is supported twice by a ball bearing 13 and a sliding bearing 14. The ball bearing 13 rests on a holder 15 of the motor mounting 7, which holder 15 is constructed as a circumferential edge in the embodiment shown. The mounting of the structural components of the bearing and of the electromotor 6 takes place on the drive shaft 5 exclusively from one side, from above in the embodiment shown. At first, the ball bearing 13 is pressed onto the drive shaft 5, then the rotor 16 of the electromotor 6 and finally the sliding bearing 14 is placed on. The rotor 16 can also be injected onto the drive shaft 5. The support of the drive shaft 5 takes place from two sides, wherein the ball bearing 13 lies axially inward, i.e. closer to the fan wheel 3 and the sliding bearing 14 is located axially outward, i.e. further removed from the fan wheel 3.
The electromotor 6 is a direct current motor in the embodiment according to
A rectangular guide plate 18 is schematically shown on a holder 28 on the motor mounting 7. The guide plate 18 is offset radially to the side by the length X2 relative to the drive shaft 5. Radially offset signifies in this connection nothing more than a lateral arrangement of the guide plate 18 relative to the motor mounting 7 and to the electromotor 6 fastened on it. Furthermore, the arrangement of the guide plate 18 is selected in such a manner that when the gas fan 1 is being used in the vertical position (
The design of the invention is not limited to the previously indicated preferred exemplary embodiments but rather a plurality of variants is conceivable which make use of the solution shown even in the case of embodiments which are basically differently designed. For example, the fan housing can form a base in the area of the through opening on which the elastomeric element and the motor mounting rest.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 108 368.4 | Aug 2013 | DE | national |
| 10 2013 109 401.5 | Aug 2013 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/055997 | 3/25/2014 | WO | 00 |
