US20130323096A1

US20130323096A1 - Diagonal fan

Info

Publication number: US20130323096A1
Application number: US14/000,603
Authority: US
Inventors: Martin Mueller; Arno Karwath; Harald Schmid; Tobias Maier; Gerald Hogg; Michael Schmitz; Bjorn Winter
Original assignee: Ebm Papst St Georgen GmbH and Co KG
Current assignee: Ebm Papst St Georgen GmbH and Co KG
Priority date: 2011-03-26
Filing date: 2012-03-20
Publication date: 2013-12-05
Also published as: DE202012013646U1; EP2691655B1; EP2691655A1; CN103597215B; CN103597215A; DE102012005829A1; WO2012130405A1

Abstract

A diagonal ventilating fan (30) has a fan housing (36) and a fan wheel (80), rotatable around a rotation axis, that has associated with it an electric motor (73) to drive it, the fan wheel (80) extending in the direction of the rotation axis between an air inlet side and an air outlet side of the diagonal ventilating fan (30) and serving, as it rotates, to convey air in a main delivery direction from the air inlet side to the air outlet side. The fan wheel (80) has a preferred rotation direction so that, during operation, its blades (82) each have a front side and a back side, and a negative-pressure zone (110) occurs, during operation, adjacent each respective back side of a blade (82). An auxiliary cooling air blower (76) connects to the respective zones (110) to provide an improved flow of cooling air for the electric motor (73).

Description

CROSS-REFERENCES

This application is a section 371 of PCT/EP2012/01217, filed 2012 Mar. 20 and published 2012 Oct. 4 as WO 2012-130405-A1, and further claims priority from application DE 10 2011 016 145.7, filed 2011 Mar. 26.

FIELD OF THE INVENTION

The invention relates to a diagonal ventilating fan having a fan housing and having a fan wheel rotatable around a rotation axis, said wheel having an electric motor associated with it, in order to drive it.

BACKGROUND

A diagonal ventilating fan of this kind is known from DE 4 127 134 A1 and corresponding U.S. Pat. No. 5,695,318, HARMSEN. The fan wheel therein is in the shape of a truncated cone, on whose conical surface the fan blades are arranged. It has, in its interior, a hollow-cylindrical portion, and pressed thereinto is the cup-shaped magnetic yoke of the external rotor of an EC motor (EC=electronically commutated; other expressions are: brushless motor, collectorless motor). The internal stator of this EC motor is mounted on the outer side of a bearing tube, in whose inner side two ball bearings for journaling the external rotor are located.
The disadvantage that results with this type of configuration of a diagonal ventilating fan is that the EC motor is poorly cooled, so that it can deliver only a low performance level, since it would overheat at higher performance levels.
This is an essential difference with respect to an axial ventilating fan in which, because of the cylindrical shape of the fan wheel, the EC motor is better cooled by the air flow generated by the fan. It could be said that a diagonal ventilating fan is “cooling-impaired,” which necessarily reduces its performance.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to make available a novel diagonal ventilating fan with improved motor-cooling airflow.
According to the invention, this object is achieved by providing an auxiliary cooling air blower, and by shaping the fan and its blades to create a respective low-pressure zone on a backside of each fan blade, with a respective connecting airflow channel from an outlet of the auxiliary blower to the respective low-pressure zone. In this context, the negative pressure in a negative-pressure zone on the back side of at least one fan blade therefore becomes effective at the auxiliary cooling air blower and intensifies the latter's effect. It is particularly advantageous here that, although the pressure in the negative-pressure zones behind the fan blades is not uninfluenced by the back pressure that acts on the fan, the direction of the pressure gradient at the negative-pressure zones nevertheless does not change in the working range of the fan, while the magnitude of the pressure difference there depends on the back pressure.
The location of the negative-pressure zone also shifts as a function of the back pressure, but its core continues to exist, regardless of the back pressure, so that with this negative pressure, enhanced by the effect of the auxiliary cooling air blower, it is possible to generate, through the electric motor, a cooling air flow whose direction does not change over the entire working range of the diagonal ventilating fan, and which thus produces effective cooling over the entire working range.

BRIEF FIGURE DESCRIPTION

Further details and advantageous refinements of the invention are evident from the exemplifying embodiments that are described below and depicted in the drawings.

FIG. 1 is an exploded view of a diagonal ventilating fan,

FIG. 2 shows the diagonal ventilating fan of FIG. 1 in the assembled state, and in longitudinal section,

FIG. 3 schematically depicts the ventilating fan of FIGS. 1 and 2 but without wall portions 50 of FIGS. 1 and 2 which act there as an “air brake,”

FIG. 4 is a depiction to explain the mode of operation of FIGS. 1 to 3 with a free-blowing ventilating fan, the pressure P1 on the inlet side being equal to the pressure P2 on the outlet side;

FIGS. 5 and 6 are depictions analogous to FIGS. 3 and 4, except that the back pressure P2 on the outlet side is greater than the pressure P1 on the inlet side,

FIG. 7 schematically depicts fan flange 44, cylindrical partition wall 48, and wall elements 50 mounted in the region of partition wall 48, which form an “air brake” in the fan, i.e. slow down air movement,

FIG. 8 is a schematic partial depiction, analogous to FIG. 3, of a section through a diagonal ventilating fan having an “air brake,”

FIG. 9 depicts the (pneumatic) circuit for the ventilating elements of the fan according to FIGS. 7 and 8,

FIG. 10 shows details of a variant of the diagonal ventilating fan,

FIG. 11 schematically depicts the fan wheel in the fan according to FIG. 10,

FIG. 12 depicts the (pneumatic) circuit for the ventilating elements of the diagonal ventilating fan according to FIGS. 10 and 11,

FIG. 13 is a highly schematic depiction of a variant of FIG. 10, and

FIG. 14 schematically depicts the fan wheel (without full blades) for the fan according to FIG. 13, to show the low-pressure zone on each blade backside.

DETAILED DESCRIPTION

FIG. 1 shows, at the bottom, base 32 of a diagonal ventilating fan 30. Said base has externally a ring 34 that is implemented for connection to an annular fan housing 36 that tapers from the bottom upward in FIG. 2 and widens again at upper rim 38. Ring 34 and fan housing 36 are connected in suitable fashion, e.g. by threading. The main flow direction of the air in fan housing 36 is indicated in FIG. 2 by arrows 40.
Connected to ring 34 by aerodynamically configured spokes 42 is a flange 44 (FIG. 2) that has at its periphery an elevated rim 46. A ring wall 48 is provided on flange 44 inside rim 46 and at a distance from it. Provided between said ring wall and said rim 46 are radially extending wall portions 50 that project preferably in an axial direction beyond ring wall 48. Wall portions 50 serve as an “air brake,” and have the function of improving the cooling of the diagonal ventilating fan, as will be explained below, with reference to simplified depictions.
Arranged inside ring wall 48 is a circuit board 56 on which are arranged electronic components 58 (FIG. 1) for commutation, and optionally for further functions, of ventilating fan 30.
Flange 44 transitions, at its center, into a bearing tube 60 on which is arranged a lamination stack 62 of an internal stator 64, whose electrical terminals 66 (FIG.) are, as depicted, connected to circuit board 56. Internal stator 64 is surrounded by an external rotor 68. The latter has a cup-like magnetic yoke 70 in which a ring magnet 72 is mounted. External rotor 68 and internal stator 64 are parts of an electric motor 73.
Internal stator 64 that is depicted has multiple salient poles 74, and interacts with corresponding poles of ring magnet 72.
Located on the upper side (FIG. 2) of external rotor 68 is a so-called “air disk” 76. It is implemented preferably in the form of a radial blower that draws in air through holes 78 in magnetic yoke 70 and transports it from there radially outward. Air disk 76 serves to draw air through internal stator 64 and thereby cool it. Air disk 76 can therefore also correctly be referred to as an auxiliary cooling air blower. Air disk 76 is made, for the most part, of plastic and is mounted on yoke 70 in a suitable manner, e.g. by ultrasonic welding, adhesive bonding, etc.
Magnetic yoke 70 is surrounded by an impeller or fan wheel 80. Provided thereon in this variant are nine fan blades 82. Here these are curved and twisted. The rotation direction is indicated at 84, i.e. clockwise when viewed from above.
As FIG. 2 in particular shows, fan wheel 80 is arranged at a radial distance from motor 64, 70, so that electric motor 73 is in practice thermally insulated and is very poorly cooled. A certain improvement results from auxiliary cooling air blower 76, but not over the entire working speed range of ventilating fan 30.
A further improvement is obtained by the fact that respective holes 90 are provided in fan wheel 80 adjacent the respective back sides of fan blades 82. These holes are respectively located in the region of a negative-pressure zone 110 that forms behind fan blades 82 as they rotate, so that air is drawn outward through holes 90 and through fan wheel 80, thus further improving the cooling of stator 64. It proves to be particularly advantageous here that the direction of the air flow through holes 90 does not change during operation, even though the intensity of that air flow can vary, as a function of various operating conditions.
The cooling of motor 73 is also improved as a result of wall portions 50.
FIG. 3 and FIG. 4 show the conditions in a diagonal ventilating fan in which, unlike what is depicted in FIGS. 1 and 2, no wall elements 50 are provided on wall ring 48.
In this case, wall ring 94 of fan wheel 80 acts like a radial ventilating fan. Because wall ring 94 has a considerably greater diameter than wall ring 48, an air flow 96 is generated which is considerably stronger than that of auxiliary cooling air blower 76, so that air flow 96 is drawn through auxiliary blower 76 oppositely to the latter's delivery direction, i.e. in reversed fashion.
When the dynamic pressure P2 at the outlet side of fan 30 rises, as shown in FIG. 5 and FIG. 6, this effect is increasingly compensated for until flow direction 98 reverses (see FIGS. 5 and 6). The reversing point is in the working range of the fan, e.g. at approximately 350 Pa.
At and in the vicinity of the reversing point, no cooling air flows through motor 73, so that the latter is not cooled and thereby becomes overloaded, and possibly destroyed.
FIG. 7 through FIG. 9 show a diagonal ventilating fan 30 that is equipped at its inlet with an air brake 50.
Provided here on flange 44 is annular wall 48, which is located opposite annular wall 94 that is connected to fan wheel 80 and rotates with it. These two parts 48, 94 are safety elements that prevent foreign objects from penetrating into the interior of ventilating fan 30, or prevent anyone from inserting, for example, a screwdriver into the interior of the fan and causing damage there.
In instances in which no such protection is required, wall elements 48, 94 can possibly be omitted or made smaller, specifically in accordance with the strength requirements of the relevant fan wheel or other part.
Outer ring wall 94 acts during operation like a radial ventilating fan, as already explained, and this effect is diminished by wall elements 50; this is indicated in FIG. 9 by the symbol “50.”
In motor 73 according to FIGS. 7 to 9, it is therefore practically only auxiliary blower 76 or holes 90 (FIG. 2) in fan wheel 80 that are effective, so that air flow 93 has approximately the shape depicted in FIG. 8.
Here as well, however, the reversal of the flow direction of the cooling air described in the context of FIGS. 3 to 6 occurs when the pressure P2 changes. According to the Applicant's measurements, this is the case at pressures between 50 and 170 Pa, whereas with FIGS. 3 to 6 the reversing point is at roughly 350 Pa.
A reversal of the flow direction means, however, that no cooling air is flowing through electric motor 73 at the reversing point, so that said motor is not being cooled and rapidly overheats; in other words, such approaches require that the fan be operated at a low maximum performance level.
FIGS. 10 to 12 show a preferred embodiment of the invention. This is based on the effect that a negative-pressure zone 110 occurs, during operation, on a back side of a fan blade 82; this is schematically depicted in FIG. 11 only for one of blades 82, in order to keep the drawing clear.
Negative-pressure zone 110 is generated by the fact that the relevant fan blade 82 moves through an air zone in which there is little fluctuation in pressure, so that the negative pressure P3 in negative-pressure zone 110 also exhibits little fluctuation and, most of all, is continuously lower than the pressure P1 on the suction side of fan 30, even though the magnitude of the pressure difference can change somewhat, depending on operating conditions. The shape of the negative-pressure zone also changes during operation as a function of rotation speed, back pressure P2, etc., but within relatively narrow limits, so that one can create an orifice 90, for example, in the core zone of negative-pressure zone 110, in order to tap this negative pressure P3 (see FIG. 11).
In FIG. 12, the outlet of auxiliary cooling air blower 76 is connected, via a conduit 114 in the interior of fan wheel 80, to one or more such orifices 90. For this purpose, the space between magnetic yoke 70 and ring wall 94 is sealed off by an annular disk 116 that is also depicted in FIG. 2. This annular disk 116 thus divides the interior of fan wheel 80 into an upper space 118 in which negative pressure P3 exists, and a lower space 120 in which dynamic pressure P2 exists. The pressure difference between these two spaces produces the cooling air flow through stator 62 of electric motor 73. Outer rim 121 of the housing for auxiliary blower 76 abuts here sealingly against fan wheel 80, in order to seal space 118 against pressure P1.
The result is as schematically depicted in FIG. 12. Radial blower 94 is rendered largely ineffective by wall elements (panels) 50, as already described.
Cooling air 126 (FIG. 10) then flows through stator 62 of ECM 73 and travels to auxiliary blower 76 which, like diagonal ventilating fan 30, is driven by ECM 73.
From the outlet of auxiliary blower 76, cooling air 126 travels via conduit 114 to orifice 90, and through the latter is aspirated outward and discharged with the air flow of diagonal ventilating fan 30.
It is advantageous here in particular that no reversal of the flow direction of the cooling air takes place during operation, since air is constantly being aspirated outward into orifices 90 during operation.
FIG. 13 and FIG. 14 show a variant of FIGS. 10 to 12. As in FIG. 11, during operation a negative-pressure zone 110 occurs on the back side of blades 82, this zone being depicted, for reasons of clarity, for only one of blades 82. In zone 110, a negative pressure P3 occurs that is consistently lower than pressure P1 on the inlet side of fan 30, as has been described in detail in the context of FIGS. 10 and 11. In contrast to FIGS. 1, 2, 10, and 11, however, no orifices 90 are provided.
Instead, as shown in FIG. 13, respective connecting members in the form of suction tubes 130′ are provided adjacently to the outlet of auxiliary cooling air blower 76, connecting said outlet to respective negative-pressure zones 110. Fan wheel 80 of FIG. 1 can have, for example, nine blades 82, and the outlet of auxiliary cooling air blower 76 would consequently be connected via nine suction tubes 130′ preferably to all nine negative-pressure zones 110, so that what exists at the outlet of auxiliary blower 76 is the pressure P3 of negative-pressure zones 110, which is lower than the pressure P1 at the inlet.
Because the pressure difference between pressures P1 and P3 consistently exists during operation, auxiliary blower 76 therefore consistently operates with a lower pressure at its outlet, as depicted in FIG. 12; in FIG. 12, suction tubes 130′ of FIG. 13 are effective instead of internal connection 114 of FIG. 10.
The version according to FIGS. 10 to 12 is of simpler construction, since the sealing of suction tubes 130′ in the context of FIGS. 13 and 14 requires corresponding measures.
A flange 130 of a so-called “circular blank” 132 is mounted in fan wheel 80. This blank is in the shape of, for example, a cylindrical tube, usually made of sheet steel, and flange 130 of said blank protrudes slightly outward radially.
Magnetic yoke 70 of rotor 68 is pressed into the inner side of this circular blank 132. The torque of rotor 68 is thereby transferred to fan wheel 80.
As depicted, flange 130 is preferably equipped with holes so that it can be effectively anchored in fan wheel 80 when the latter is injection molded.
FIGS. 1 to 14 show a diagonal ventilating fan that comprises:
a fan housing 36; a fan wheel 80, rotatable around a rotation axis 168, that has associated with it an electric motor 73 to drive it, fan wheel 80 extending in the direction of the rotation axis between an air inlet side and an air outlet side of diagonal ventilating fan 30 and serving, as it rotates, to convey air in a main delivery direction from the air inlet side to the air outlet side; fan blades 82 provided on the outer side of fan wheel 80 which have, with reference to rotation direction 84 of fan wheel 80 during operation, a front side and a back side, such that a negative-pressure zone 110 occurs respectively on fan wheel 80 in the region of the back side of a blade 82 during operation; an auxiliary cooling air blower 76 which is designed to transport cooling air on the inner side of the fan wheel 80 from the air outlet side toward the air inlet side, and by that air flow, to cool the electric motor 73 of the diagonal ventilating fan 30; and at least one fluid connection 114; 118; 130′ from the outlet of auxiliary cooling air blower 76 to at least one of the negative-pressure zones 110 in order to assist a flow 126; 126′, occurring from the air outlet side of diagonal ventilating fan 30 toward the latter's air inlet side, of the cooling air for electric motor 73.
Fan wheel 80 preferably comprises, on the air outlet side of diagonal ventilating fan 30, a first annular portion 94 that interacts with a second annular portion 48, located opposite it, of a stationary part 44 of diagonal ventilating fan 30, said second annular portion 48 being located oppositely to first annular portion 94, air-directing elements 50 being provided on this second portion 48, said air-directing elements 50 acting, during operation, as a brake for the air that is entrained by a rotation of first portion 94 being provided on this second portion 48.
Fluid connection 114, 118 preferably extends from the outlet of auxiliary cooling air blower 76, through the inner side of fan wheel 80 and through at least one opening 90 provided in fan wheel 80, to a negative-pressure zone 110 of fan wheel 80.
Auxiliary cooling air blower 76 preferably comprises a connecting member 130′ that extends over the outer side of fan wheel 80 as far as a negative-pressure zone 110 occurring at the fan wheel during operation, so that the pressure of that negative-pressure zone 110 becomes effective at the outlet of auxiliary blower 76. The inner side of fan wheel 80 is preferably divided into a first space 120 in which substantially the pressure P2 at the air outlet of the diagonal ventilating fan exists during operation, and a second space 118 that is connected via at least one opening 90 of fan wheel 80 to the latter's outer side. At least one opening 90 is preferably arranged in a suction pressure zone 110 on the back side of a fan blade 82, the “back side” referring to rotation direction 84 of fan wheel 80. A separating member 116, which extends between the inner side of fan wheel 80 and rotor 76 of electric drive motor 73, is preferably provided here between first space 120 and second space 118. Electric motor 73 is preferably implemented in this context as an electronically commutated external-rotor motor.
The air guidance system in fan wheel 80 is preferably sealed against leaks, and openings 90 on the back side of fan blades 82 are at a greater radial distance from the rotation axis of ventilating fan 30 than are the inlet openings.
Many variants and modifications are of course possible within the scope of the invention. Features of the individual exemplifying embodiments can also be combined with one another. In many cases, for example, it may be sufficient to use air brake 50 according to FIG. 1 in conjunction with the extraction system at locations 90, i.e. without auxiliary blower 76, although the solution using auxiliary blower 76 is preferred because the additional costs for part 76 are extremely low, and produce an improvement in the cooling of electric motor 73.

Claims

1. A diagonal ventilating fan that comprises:

a fan housing (36);

a fan wheel (80), rotatable in a preferred direction about a rotation axis, that has associated with it an electric motor (73) to drive it, the fan wheel (80) extending, along the direction of the rotation axis, between an air inlet side and an air outlet side of the diagonal ventilating fan (30) and serving, as the fan wheel rotates, to convey air in a main delivery direction from the air inlet side to the air outlet side;

fan blades (82), provided on the outer side of the fan wheel (80) which each have, with reference to said rotation direction (84) of the fan wheel (80) during operation, a front side and a back side, such that, during operation, a respective negative-pressure zone (110) arises adjacent the back side of each blade (82);

an auxiliary cooling air blower (76) which is configured to transport cooling air on an inner side of the fan wheel (80) from the air outlet side toward the air inlet side, and by that air flow, to cool the electric motor (73) of the diagonal ventilating fan (30); and

at least one fluid connection (114; 118; 130′) from the outlet of the auxiliary cooling air blower (76) to at least one of the negative-pressure zones (110) in order to assist a flow (126; 126′) of motor-cooling air, occurring from the air outlet side of the diagonal ventilating fan (30) toward the air inlet side thereof.

2. The diagonal ventilating fan according to claim 1, in which

the fan wheel (80) comprises, on the air outlet side of the diagonal ventilating fan (30), a first annular portion (94) that interacts with a second annular portion (48), located opposite it, of a stationary part (44) of the diagonal ventilating fan (30), said second annular portion (48) being located oppositely to the first annular portion (94),

air-directing elements (50) being provided on this second portion (48), said air-directing elements (50) acting, during operation, as a brake for air that is entrained by a rotation of said first portion (94).

3. The diagonal ventilating fan according to claim 1 wherein

the fluid connection (114, 118) extends from the outlet of the auxiliary cooling air blower (76), through the inner side of the fan wheel (80) and through at least one opening (90) provided in the fan wheel (80), to a negative-pressure zone (110) arising adjacent the fan wheel (80).

4. The diagonal ventilating fan according to claim 1, wherein

the auxiliary cooling air blower (76) comprises a connecting member (130) that extends over the outer side of fan wheel (80) as far as a negative-pressure zone (110) occurring at the fan wheel during operation, so that the pressure of that negative-pressure zone (110) becomes effective at an outlet of the auxiliary blower (76).

5. The diagonal ventilating fan according to claim 3, wherein the inner side of the fan wheel (80) is divided into

a first space (120) in which, during operation, substantially the pressure (P2) at the air outlet of the diagonal ventilating fan pertains, and

a second space (118) that is connected via at least one opening (90) of the fan wheel (80) to the outer side of the fan wheel.

6. The diagonal ventilating fan according to claim 5, wherein

at least one opening (90) is arranged in a zone (110) of reduced pressure arising on the back side of a fan blade (82), said back side being defined with reference to the rotation direction (84) of the fan wheel (80).

7. The diagonal ventilating fan according to claim 5 wherein

a separating member (116), which extends between the inner side of the fan wheel (80) and the rotor (76) of the electric drive motor (73), is provided between the first space (120) and the second space (118).

8. The diagonal ventilating fan according to claim 7, in which the electric motor (73) is implemented as an electronically commutated external-rotor motor.

9. The diagonal ventilating fan according to claim 1, wherein

an air guidance system defined in the fan wheel (80) is sealed against leaks, and the openings (90) on the back side of the fan blades (82) are at a greater radial distance from the rotation axis of the ventilating fan (30) than are the inlet openings.