GB2091947A

GB2091947A - Cooling external-rotor motors

Info

Publication number: GB2091947A
Application number: GB8200500A
Authority: GB
Original assignee: Wilhelm Gebhardt GmbH
Current assignee: Wilhelm Gebhardt GmbH
Priority date: 1981-01-24
Filing date: 1982-01-08
Publication date: 1982-08-04
Also published as: DE3102333C2; SE8200345L; SE454634B; FR2498838B3; GB2091947B; FR2498838A1; DE3102333A1

Abstract

For cooling external-rotor motors as used for driving fans and blowers, an air current (17) is produced along a hollow inside a fixed post (3) inside the stator (2) of the motor so that heat is taken up by the air current from the inside of the stator and transported to the end (6) of the hollow post (3). At this end of the motor there is a plate (7), normal to the post (3) of the motor and designed for producing a radial air current in a space (9), i.e. because of the suction effect of the main outside air current (16) produced by the blower. The radial air current supports the flow of air in the hollow post (3), and heat is thereby removed from the stator. Heat pipes may also be used to remove heat from the stator. <IMAGE>

Description

SPECIFICATION External rotor motors The present invention is with respect to external rotor motors and, more specially, to ways of cooling such motors as used for driving a blower or fan and having an external rotor and an inner fixed part or stator made up of a stack of laminations and supporting copper windings. The invention is furthermore with respect to a motor cooled in this way and to a set of parts for producing an external rotor motor which is, more specially, cooled using the method of the invention. Lastly, the invention is with respect to an external motor, produced using the set of parts named.

In external rotor motors of the sort in question, cooling is a specially important question.

As a rule only the outer part of the external rotor is acted upon by the cooling medium and cooled, while the heat produced in the winding is mostly transmitted by conduction or convection to the rotor before it may be transported away by the cooling medium current. In many cases, such a cooling system does not give the desired effect and, for this reason, in specially complex designs, the rotor is open so that cooling medium may be let into it, for example by using holes for the cooling air so that the air may make its way round the heads of the windings. In such a design, however, the motor comes into a very much lower safety class, the space within the motor may be fouled and it may even be possible for the uncovered windings to be damaged.

For this reason, one purpose of the invention is that of designing an external rotor motor with a high cooling effect so that, in other words, the power may be increased without coming into a lower safety class.

For this purpose, in the present invention, in the new method of cooling, inside the stator a first generally axial current transporting heat from inside the stator is produced running towards at least one of its ends and at said end or the said ends, a second current, flowing past the motor (more specially a forced air current) is used for transporting away the heat transported by the first current, more specially in a radial or generally radial direction. In this respect it is possible for example the first axial or generally axial current to be produced by an ejector effect at the axial end in question or by a heat pipe effect or, lastly, by producing a forced cooling circuit inside the rotor.

An external rotor motor cooled with the new process is characterized in that a post used for turningly supporting the rotor in relation to the stator is made hollow and that a disk-like structure is placed at one open axial end of the post, the structure stretching out radially on all sides from the shaft, it covering the end plate while walling in an inbetween space, stretching in an outward direction. It is, however, for example, possible to have such a motor design that the post used for turningly supporting the rotor in relation to the stator is hollow and is open at at least one axial end and in that the hollow of the post has a heat pipe, slipped into the hollow from the open axial end, one axial end of the heat part being designed running out of the post so as to be acted upon by the incoming air current, for example an air current produced by the blower or fan.Lastly, the design may be made such that for producing a forced coolant circuit inside the motor on the inside of the end plate-like part, turning with the rotor, there are generally radial inwardly running fins turning with the rotor.

With these measures, forming part of the invention, it is now possible to make certain of a cooling of the motor with the desired effect, and even of the windings within it, without the motor being put in a lower safety class and, in fact, such a motor may now be fully safeguarded to keep out dust and against fouling.

In the case of external rotor motors of the prior art there is a further shortcoming in design that, more specially when used for driving fan or blower impellers, production has so far not been able to be rationalized.

External rotor motors, as used more specially for driving fan or blower impellers, may be put into two general design groups, that is to say the "flange-mounting" design, as more generally used for blowers or fans with input at one end in which the rotor has a turning shaft running into the stator bush supporting the stator laminations with the winding and supported in ball bearings, a flange on the stator bush being used for fixing to a support wall, and on the other hand the "post-mounting" motor more specially for blowers or fans with air inlet on their two sides, in the case of which the rotor has two end plates and is placed all the way round the stator, like a housing, the stator laminations with the winding being supported on a fixed post, having fixing ends or pins running out from the two axial ends of the motor and used for supporting the structure on a support.

The known designs these two groups of motors do not have any common parts, that is to say parts of the same form so that producing such motors is not able to be rationalized on a sound footing, this more specially being a shortcoming as well when the second form of design (the "post-mounting" system) is to be made in much smaller numbers and marketed, so that this form of motor may not be produced at a low price. This shortcoming as well is to be taken care of by the present invention; that is to say further purpose of the invention is that of designing an external rotor motor which may be produced in the two different forms with the same general structure so that at least some parts may be used for the two forms.

For this purpose, as part of the invention, a set of parts for producing an external rotor motor of the sort noted is put forward which is characterized in that the parts of the motor are: a rotor with two end plates at its two axial ends and bearing systems in this respect, for use with the end plates, such bearing systems being for example ball bearing systems when put together, a stator having the rotor round it and placed between the end plates, a fixed post running through the middle of the motor, used with the bearing systems and having a length generally equal to the distance between the bearing system used with the end plates in the put-together condition of the motor, a further fixed post for running through the middle of the motor and for use as a fixing part and whose length is so much greater than the distance between the bearing systems, used with the end plates (in the put-together condition of the motor) that its ends come out to the two sides of the motor as outwardly running parts, used as fixing pins for the motor, and with a support flange, designed to be joined with the stator, for fixing the motor on a support wall, and, if necessary, and more specially, fixing parts of a known sort for fixing a fan or blower impeller to the rotor. It is now possible with the main parts as named for a flange-mounting external rotor motor to be produced which is characterized in that the fixed post has, at its two axial ends, generally opposite to the end plates, the bearing systems for supporting the rotor, for example ball bearing systems, it supporting in its middle part the stator which is keyed thereon and in that, at its one axial end, it is fixedly joined with the fixing flange, which is, for example disk-or plate-like.By making the right selection of the main parts as named, it is furthermore, however, possible for a post-mounting external rotor motor to be produced which is characterized in that the fixed post, in its two axial end parts, is used for supporting, on the side in each case turning towards the motor, the bearing systems for the rotor, for example ball bearing systems and it is designed running out past these bearing systems so that the motor may be fixed on a fixing pin, a stator being supported and locked on the shaft in its middle part.

With the help of the measures named, it is now possible for a new simpler, uniform design to be used which makes possible lowprice production while at the same time taking care of special needs. It will be clear to the reader that there will be useful effects with respect to stockholding parts and furthermore, with respect to putting the parts together and everything will be made more generally straightforward.

The external rotor motors in question are, more specially designed for driving blower or fan impellers, the rotors, at the same time, forming the middle part of the impeller so that, in this case, they are right within the air current produced by the blower or fan and, for this reason, better cooled than normal motors placed without the air current. For this reason, such external rotor motors (more specially when used for driving fan or blower impellers) may, at the same time, be used in connection with a cooling system forming part of the present invention.In this respect, it is for example useful for the hollow space (which, in a set of parts of the invention as used for producing external rotor motors of the post-mounting and furthermore the flangemounting sorts, furthermore may be used for taking up electrical wire parts) in the fixed post to be used for cooling the stator in the method of cooling as noted of the present invention and with the help, as well, of the further measures so far noted.

Some working examples of the invention will be seen in the figures accompanying the specification.

Figures 1 and 2 are two working examples of an external rotor motor of the present invention, which has been produced using a set of parts of the present invention, that is to say on the one hand a flange-mounting external rotor motor (Fig. 1) and a post-mounting external rotor motor (Fig. 2), each being seen in a side view and in axial section.

Figure 3 is an axial section and side view of the rotor of the designs to be seen in Figs. 1 and 2.

Figure 4 is an axial section of an external rotor motor of the invention, cooled using the method of the invention.

Figures 5 to 9 are axial sections of further forms of the system of Fig. 4.

The account of the different working examples of the invention will be started with Fig.

4 before details are given of the other designs of the present invention.

In Fig. 4 the reader will see an external rotor motor having a rotor 1 and a stator 2 together with a fixed post 3 which is used for supporting the rotor 1 so that it may be turned in relation to stator 2 and is hollow at 4. In the middle or on the one end the post is shut off by wall 5 while the other end is is open at 6, to the left of which there is a disklike structure 7, designed stretching out radially on all sides from the post and covering the end plate 8 with a space 9 between it and the end plate. The disk-like structure 7 is symmetrical with respect to post 3 and in radial cross-section it has the form of an umbrella covering over the end of the motor, it outer edge part being skirted back towards the motor at 10.Generally speaking, the hollow post 3 is shut off at the middle 5 and a cylindrical sleeve 11 open at its two axial ends is placed in the hollow of the post 3 from the open axial end 6, sleeve 11 having a smaller diameter than hollow 4 and having between it and the inner face 1 2 of the post (round the hollow) a ring-like space 13, sleeve 11 stretching axially to a point short of the wall 5 forming the end of the hollow so that there is an inbetween space 1 4. The disk-like structure 7 is placed to the left of the open axial end of the sleeve 12, the ring-like space 1 3 being joined up between the sleeve and the inner face 1 2 (round the hollow) with the inbetween space 9 between the disk-like structure 7 and the end plate 8, the post at the open axial end 6, stretching as far as the bearing points 1 5 (for example in the form of ball bearings) between the stator and the rotor, the sleeve running out at the open axial end, from the hollow 4 and the disk-like structure 7 being made in one piece with this sleeve 11 inasfar as it is formed by turning over the end of the sleeve in question. The medium (air) taken in by the fan or blower in the direction A is made to go over the umbrella-like face of disk-like structure 7 as arrowed at 1 6 so that in space 9 a lower pressure or vacuum is produced by an ejector effect.Transported medium, which at the same time is used as a coolant, makes its way as marked by arrows 1 7 through sleeve 11 and then through the cylindrical ring-space 1 3 between the sleeve and the shaft and then comes back into the main current in space 9 so that heat, taken up by the post from the stator laminations, may be freely transported away.

In the working example of Fig. 5, post 20 is designed stretching at the open axial end 21 out past the bearing point 22 between the stator 23 and the rotor 24 outwardly as a sort of nosepiece, while sleeve 25, 35 goes outwards from hollow 27 at the open left hand end 26. The disk-like structure 28 is, in its middle part, fixed to the outwardly running axial end of the post by skirt 29, the ringspace 30, walled in between the sleeve 25 and the hollow post 20, being joined up with space 31 between the disk-like structure 28 and the end plate 32 by way of radial holes 33 in the wall of post 20. The outwardly running axial end 26 of the sleeve 25 is trumpet-like and outwardly flared, as the reader will see at 34, this flared-out end of sleeve 25 generally stopping any inlet of air into the ring-space 30 round the sleeve, at least generally, from the left.It will be noted that in this case the outwardly running axial end 21 of post 20 or the ends of this post is or are used as a bearing or fixing pin, so that it is a question of the use of the same teaching but, however, in connection with the "post-mounting motor", to be noted in more detail later on, unlike the "flange-mounting motor" as will be in Fig. 4.

In the case of the forms of the invention so far detailed, for cooling the external rotor motor and in this respect more specially for cooling the inner fixed part or stator made up generally of armature laminations and supporting the copper winding, a method is used in which inside the stator a generally axially running (see arrows 1 7 in Fig. 4 and 35, 36 in Fig. 5) current of a medium (in the present case an air current produced by the fan or blower) is produced for transporting heat from the middle part of the stator 2 or 23 towards at least one of its two axial ends, in which respect at the axial end or ends in question, the air current moving over the outer face of the motor (see arrows 1 6 in Fig. 4 and 37 in Fig. 5) is used for transporting away heat, transported to this position, more specifically in a radial or generally radial direction.

As was the case with the designs of Figs. 4 and 5, in the design of Fig. 6 as well, in which the same cooling system is used, a generally axial current is produced by an ejector effect at the left hand end and in this case post 41 is open at its two axial ends and it has a hollow 40, its stretching as far as the bearing point between the stator 43 and the rotor 44. The disk-like structure 45 is shut off in the middle part 46 and is place like a cap over the open axial end 47 of the post 41 so as to be walling in a space 48 between it and the motor, hollow 40 within post 41 being joined up with the inbetween space 48. In this case as well, for producing the ejector effect at the open end of the post, used is made of the air current (produced by the fan or blower) moving up towards the left hand end of the motor as marked by arrows 48'.

This air current is furthermore used for transporting away the heat transported to this point from the right along the hollow of post 41.

This form of the invention is more specially used, the main current of air is mixed with dust so that, if it were to get into the hollow inside the post, the cooling effect would be decreased.

However, the generally axial current in the system of the invention may be produced as well by a "heat pipe" effect as will be seen from Figs. 7 and 8 with a heat pipe 55 of known design. In Fig. 7 the post 52 for turningly supporting the rotor 51 in relation to the stator 50 is made hollow at 53. At least at end 54 of the hollow a space 53 is left open and heat pipe 55 is slipped or forced into it from the open end, the left hand end 56 of the pipe running out of the post 52 so as to be acted upon by the incoming forced air current as marked by arrow 57 and produced by a blower powered by the motor. For stepping up the heat exchange rate, the outwardly running end 56 of heat pipe 55 has axiallyradially running cooling fins 58 spaced round its outside.The post 52, in this case, goes as far as the side facing the cooling air current 57, at the bearing 59 between the stator 50 and the rotor 51. In this working example, the heat pipe is fluid-tightly shut off at the two ends and which in the inside of it has a lining of porous material, whose pores are joined together in all directions, the material being for example a sintered metal, a metal or textile felt-like or knitted material or a number of layers of fine-mesh netting structures, the pipe being filled with an amount of a working liquid whose properties are exactly in line with the special heat transport function in a given case, the liquid and its vapor being in phase equilibrium at the working temperature of the working material.If one end of the pipe, which, as in the case of the working example figured, is best designed as a piece of finned pipe, is acted upon by a cooling air current, at this part a part of the liquid working material, which is in equilibrium with its vapor, will be condensed, the liquid then making its way to the other end of the pipe acted upon by the heat inside the motor, so that it will be evaporated at this position, it producing a cooling effect because of its heat of evaporation. The temperature level of the working material, thatis to say the condensation and evaporation temperatures, in this case may take on such values every time that the equilibrium between heat uptake and the giving up of heat is kept to in the system. The liquid is then mainly in the pores of the capillary lining while the vapor will be in the space kept free in the middle of the heat pipe.The nature of working liquid and the amount used will be dependent on the use in question.

The same teaching is generally used in the working example to be seen in Fig. 8 in which the post 62 is used for supporting the rotor 61 turningly on the stator 60 and is made hollow at 63 and at least a part of the hollow 63 of the post 62 is shut off at the two ends marked at 64 and 64 in the figu re and in this respect is used as a heat pipe, it being filled with cooling liquid or refrigerant for this purpose. The end part 66 of the part of the post is to the left of the bearing point 67 between the stator 60 and the rotor 61 so as to be in the air moving towards the motor as marked by arrows 68, heat transport being undertaken by the liquid referigerant in the hollow part 63, which is circulated as marked by arrows 69 and which is cooled down again by the forced air current 68 moved by the blower or the like.

In Fig. 9, a further example will be seen of the use of the system of the invention, although, however, the generally axial current used for heat transport is kept inside the rotor.

For producing this cooling circuit inside the motor on the inside face of the end plate-like part 71, turning with the rotor 70, there are radial or generally radial fins 72 turning with the rotor. The post 73 is, at least in the part between the two axial ends 71 and 74 of the motor housing, hollow at 75, the hollow being shut off by end walls 76 and 77.At its inner part or edge facing the stator 76, rotor 70 has axially running spaces 77 running through it which are open at their two ends and which are best equally spaced round the rotor, the holes opening into the axial space 78 or 79 between the stator 76 and the rotor 70 on the one side and the end plate-like end parts 71, 74 of the housing on the other side, each being joined up with the hollow space 75 of the post 73 by way of radial holes 80 so that an inside, unbroken circuit is produced as marked by arrows 81, 82, 83 and 84. As noted earlier, hollow space 75 of post 73 is shut off in each case at bearing points 85 and 86 between the stator and the rotor, the radial holes 80 being positioned in this case, as seen from the middle, a small distance short of the end walls 76 and 77, such holes being best generally opposite to the axial end in each case of the winding head 87.In the working example to be seen, post 73 has its two axial ends running as far as a position past the bearing points 85 and 86 between the stator and the rotor, the post running outwardly somewhat. The outwardly running parts 88 and 89 are designed as bearing or supporting parts in Fig. 8 as well. On the other hand, in Fig. 7, the post has its two axial ends stretching as far as the bearing points between the stator and the rotor. In this system of the invention, the general teaching is that the outer face of the rotor is most strongly cooled and the heat produced in the stator is furthermore quickly transmitted to the rotor. This is effected by having cooling fins causing a current circuit, the refrigerant or cooling material (air) moving over the holes and over the hollow space for giving up heat to the well-cooled rotor faces.In the case of this design, the best possible motion of air over the winding head is produced as well. A further increase in efficiency may be produced if, furthermore, heat pipes are placed in the post as well for so taking up and directly transporting away a part of the heat.

A further purpose of the invention is the rationalization of production and taking steps for making assembly cheaper and warehousing simpler so that the "flange-mounting" motor has, as far as possible, the same structure as the "post-mounting" motor, the stator laminations being in both cases turningly supported on a fixed hollow post, while the rotor is turningly supported on a post.The stator lamination stack may have the same size, but for the breadth of the stack possibly being different, which, in any case, is necessary for designing one power and type series, while the rotor stack has the same size as well, For effecting this purpose of the invention, the use of a set of parts for producing an external rotor motor is put forward having the parts: a rotor-90 (length a,) in Fig. 1 and 91 (length a2) in Fig. 2-with two end plates at its two axial ends-92 and 93 in Fig. 1, 94 and 95 in Fig. 2-with their bearing parts, placed in the end plates and having the form for example of ball bearing systems 96, 96a, 96b and 96c, a stator (97 in Fig. 1, 98 in Fig. 2) having the rotor round it when the motor is put together and placed between the end plates 92, 93 or 94, 95, and the fixed post running through the middle of the motor and used as a bearing part. In the further design of Fig. 1, the length of the post 99 is generally equal to the distance between the bearing systems such as ball bearing 96 or 96a, used with the end plates, while in the design of Fig. 2 the post, which in this case is not only used as a bearing part, but furthermore as a fixing part, is longer.The length of the post 100 of Fig. 2 is somewhat greater and the distance between the bearing systems 96b and 96c of the end plates 94 and 95 in the put-together condition of the motor that their ends take the form of parts 101, 102 running out from the two sides of the motor and which may be used as fixing pins or posts for the motor. For the system of Fig. 1 there is furthermore a support flange 103, which may be joined up with the stator, and which is used for fixing the motor to a support wall.

Possibly, and preferably, there are fixing parts of a known sort for fixing on a blower or fan impeller, which may be pressed on to the outer face of the rotor, or fixing flanges may be present as may be seen in Fig. 1 at 104 and at 105 in Fig. 2. In the working example of Fig. 1, a view of an external rotor motor of the "flange-mounting type" the fixed post 99 has the bearing systems, for example ball beerings 96 and 96a at its two ends at the end plates 92 and 93, for supporting the rotor 90 and in its middle part the post supportingly takes up the stator 97 fixed thereto, while at its one axial end the post is joined up, for example, with a wheel or platelike fixing flange 103. In this respect, the rotor is turningly supported with the help of the end plates on the fixed post and the lastnamed is fixed by way of fixing flange 103 to a support part.In the case of the design of Fig. 2--in this respect it is a question of a "post-mounting external rotor motor' '-bear- ing systems, as for example ball bearing systems 96b and 96c, are supported on the fixed post 1 00 at its two axial end parts on the side in each case turned towards the motor, while the post is furthermore designed running out past these bearings as fixing pins 101, 102 used for supporting the motor on a support part, the post supporting at its middle part the stator 98, which is keyed thereto. Rotor 91 is in this case turningly supported with the help of end plates 94 and 95 on the fixed post 100, which, by way of its fixing post ends 101, 102 running out axially, is fixed to a support.In Fig. 1 the end plate 93 has a molded-on fixing flange 104 for having the impeller fixed thereto, this end plate may, however, furthermore have the same form as the end plates 92 or 95. At any rate, in the design of the rotor, the starting point may be a structure 110 as to be seen in Fig. 3, on which, on one side, an end plate 111 is fixed, while on the other side, on the fixing ring 11 2 an end plate like the end plate 93 of Fig. 1 and an end plate like the end plate 95 in Fig.

2, may be fixed. For further rationalization it is naturally possible for only one single sort of end plate to be used, it being clear that this will do the work needed.

It will be seen that the fixed post is hollow in the case of all working examples in the figures, this being necessary on the one hand because of the measures taken for cooling the stator in the method of the invention and on the other hand the hollow space may be used for taking up the electrical wires so that it is necessary in this case not only in the case of the flange mounting, but furthermore in the case of the post mounting motor.

It will be seen that the design, which has now been made simpler and more uniform, makes possible low-price production with great flexibility, because the post mounting and the flange mounting motors have generally the same design, the stator lamination stack being seated on the fixed post in the two cases, while the rotor is bearinged on the post so that for the post mounting and the flange mounting motors the same parts, but for the post, are used, which in the two cases in question are made with different lengths and in one case is made with a support post, while for the flange mounting motor a further support flange is necessary.

Claims

1. A method of cooling an external rotor motor, having an external rotor and an inner stator made up generally of a stack of laminations and copper windings, characterized in that inside the stator a first generally axial current of medium transporting heat from an inside part of the stator towards at least one end thereof is produced and in that at the said axial end or the axial ends a second current, moving towards the said end is used for taking up the heat from the motor, transported by the first current.

2. A method as claimed in claim 1, characterized in that the first current is produced by an ejector effect at the one axial end of the motor.

3. A method as claimed in claim 1, characterized in that the first axial current is produced by a heat pipe effect.

4. A method as claimed in claim 1, characterized in that the first generally axial current is produced by a forced coolant circuit within the stator.

4a. An external rotor motor comprising a hollow post for rotatably supporting the rotor in relation to the stator of the motor, means for producing a first generally axial flow of a medium inside the stator for transporting heat from an inner part of the stator towards at least one end thereof, and presenting said one end in the path of flow of a medium for taking up the heat from the motor transported by the first flow.

5. An external rotor motor, characterized by a hollow post placed for turningly supporting the rotor in relation to the stator of the motor, the motor having a disk-like structure at an open axial end of the hollow of the post, the structure stretching out radially on all sides from the post for covering over an end plate of the motor while walling in an outwardly stretching space therebetween.

6. An external rotor motor as claimed in claim 5, characterized in that the hollow post is shut off at one end, in that the hollow of the post has placed in it a generally pipe-like sleeve open at its two ends, the sleeve being of smaller diameter than the hollow in the post for walling in a ring-like space between the sleeve and the inner face of the post so that there is a path running along the inside of the sleeve as far as an end of the sleeve within the post and then back again round the outside of the sleeve and within the post, the disk-like structure being placed at an open axial end of the sleeve, the space between the disk-like structure and the end of the motor being joined up with the space round the sleeve within the post.

7. An external rotor motor as claimed in claim 5, characterized in that the post is open at its two axial ends, it stretching as far as a bearing point between the stator and the rotor, the disk-like structure is shut off in the middle part of the stator, it being bell-like and placed over one end of the motor walling in a space between the motor and itself, this space being joined with the space in the post so that a forced air current moving towards one end of the motor is responsible for an ejector effect moving air in through one end of the post which is downstream in the direction of the outside air current, through the hollow post and then out into the space between the upstream end of the motor and the disk-like structure.

8. An external rotor motor, characterized by a hollow post placed within the stator and used for supporting bearings for the rotor on it, there being a heat pipe placed within the hollow post, one end of the heat pipe running out from one end of the post to a point where it may be cooled by a current of air moving towards this end of the motor.

9. An external rotor motor as claimed in claim 8, wherein the end of the heat pipe outside the post is finned in an axial direction.

10. An external rotor motor, characterized by a hollow post for supporting bearings for joining the stator and rotor together, one end of the post running out from end of the motor so that it may be acted upon by a current of air, this part of the post and a part of the post within the stator being shut off to take the form of a space for heat transport medium able to be moved from the part of the post within the stator to the outer part of the post for the transport of heat from the inside of the stator to the outer part of the post acted upon by the air current.

11. An external rotor motor, characterized by blades on the inside of the motor for producing a forced current of air within the motor, the blades being on an end plate of the motor and being generally radial.

1 2. A motor as claimed in claim 11, characterized by a post running through the stator and being hollow from at least one end of the motor to the other, the rotor having axial spaces therein opening towards the stator and opening axially at the ends of the stator, said spaces being joined up with spaces at the ends of the stator within the rotor, such lastnamed spaces being furthermore joined up by holes in said post with the space within the post, and running radially past heads of windings within said motor, the hollow within the post being shut off at its two ends for keeping such forced current of air within the motor.

1 3. A set of parts for producing an external rotor motor characterized by a rotor with two end plates at its two ends, bearings for use in said end plates, a stator to be placed in said rotor between the end plates, two posts for supporting said stator in said rotor, the one post having a length generally equal to the distance between the bearings when the motor parts have been put together, the second post for supporting the rotor on the stator running through the stator, the second post being somewhat longer than the rotor, such end parts of said post sticking out from the two ends of the motor and being able to be used for fixing the motor in position as pins, and a fixing flange which may be joined up with the stator for fixing the motor on a support wall.

14. A set of parts as claimed in claim 13, further having parts for fixing a blower impeller on the rotor.

1 5. A motor assembled from the parts listed in claim 12, characterized in that bearings for the rotor are supported on the post, the same furthermore supporting said stator between its ends, said stator being locked on said post, said post further having a support ing flange on it at one end, said flange being designed for supporting, by way of the post, the stator and the rotor being supported by said said post.

1 6. An external rotor motor made from the parts listed in claim 13, characterized in that the hollow support post has an end part running outwards from the motor past the bearing at the end of the rotor and designed for use as a support, the stator being fixed on the post.

1 7. An external rotor motor substantially as described in the specification with reference to and as illustrated in Fig. 4 of the accompanying drawings.

18. An external rotor motor, substantially as described in the specification with reference to and as illustrated in Fig. 5 of the accompanying drawings.

1 9. An external rotor motor, substantially as described in the specification with reference to and as illustrated in Fig. 6 of the accompanying drawings

20. An external rotor motor, substantially as described in the specification with reference to and as illustrated in Fig. 7 of the accompanying drawings.

21. An external rotor motor, substantially as described in the specification with reference to and as illustrated in Fig. 8 of the accompanying drawings.

22. An external rotor motor, substantially as described in the specification with reference to and as illustrated in Fig. 9 of the accompanying drawings.

23. An external rotor motor, substantially as described in the specification with reference to and as illustrated in Figs. 1 and 2 of the accompanying drawings.