FR2643759A3 - DC motor whose bearing flange is composed of a good heat-conducting material - Google Patents

Abstract

a) DC motor whose bearing flange is composed of a good heat-conducting material . b) In a DC motor, in particular a small motor with closed construction, with a view to limiting the thermal loading of the commutator brushes 22, the brush-holders have a large surface area and are inset into a bearing flange 20 composed of a good heat-conducting material, by interposing, without producing a hollow space, a thin heat-conducting insulating layer. The brush-holders 23 almost completely surround the commutator brushes 22 placed inside, with a small degree of play, so that here also heat transfer is very good. c) The invention relates to a DC motor whose bearing flange is composed of a good heat-conducting material.

Description

"DC motor with a bearing flange made of a material which is a good conductor of heat".

 The invention relates to a DC motor, in particular a small motor of closed construction, comprising a stator carrying the excitation poles, a rotor carrying an armature winding and kept rotating in a bearing flange and carrying a connected collector. armature winding, and comprising collector brushes movably guided axially in a brush holder extending radially or axially with respect to the switch, and pressing frontally on the collector, under the action of a brush pressure spring , the brush holders made of an electrically conductive material being fixed in an electrically insulated manner and each being connected to an electrical connection line.

 In known direct current motors, the tubular brush holders receiving the collector or carbon brushes are fixed in isolation on a brush holder maintained on its side on the bearing flange or at another location of the motor housing. It has been found that, in the case of a closed embodiment of these small motors, for which the interior of the motor is practically encapsulated, or in the case of motors having no particular internal ventilation, stress occurs. high thermal performance of the collector brushes, due to the fact that the brush holders are exclusively cooled by the hot interior air - of the motor. To date, it has been taken into account that additional ventilation, for example by separate fans, would blow up the low build volumes that small motors tend to.

 The problem is solved by a DC motor according to the invention, characterized in that the brush holders surround almost completely and with little play each of the collector brushes placed inside and are embedded in the flange of bearing composed of a material which is a good conductor of heat, by inserting a thin thermally conductive insulating layer without forming hollow spaces. This construction has the advantage that due to the integration of the brush holders in the bearing flange composed of a material which is a good conductor of heat and due to the almost complete and narrow wrapping of the brushes - of the collector by the brush holder, the temperature demand of the switch brushes drops drastically, because the heat is evacuated very quickly by the collector brushes due to the large surface area of the heat transmitting faces and as a result of the short paths of heat transmission r outward.

 The necessary electrical insulation of the brush holders from the bearing flange is provided by a thermally conductive insulating layer, as thin as possible. The various materials coming into question for this layer are for example polyester, polyimide, polyamide, rubber, mica, aluminum oxide, composite materials, textiles or impregnated fiber mattresses, mica, glass fibers in silicone, resin prepregs. All materials must be thin in order to guarantee a contact without gaps, leaving no hollow space or air inclusions, both vis-à-vis the bearing flange and also vis-à-vis the brush holders. The materials can be used as parts of pressure cut sheets, if necessary self-adhesive on one side.

 The DC motor according to the invention is distinguished by a simple construction.

The life of the collector brushes is extended by the reduction of thermal stress, as well as the permissible power density for predetermined environmental conditions, thus resulting in an increase in efficiency.

 According to another characteristic of the invention, the bearing flange has two axially projecting parallel ribs, intended for the embedding of a brush holder, ribs between which the brush holder with the insulating layer is pinched over its entire length. by pressing its third side wall covered with an insulating layer, on the bearing flange zone framed by the ribs.

 According to another characteristic of the invention, the depth of the ribs, observed in the axial direction of the rotor, is slightly greater than the width of the brush holder, measured in the same direction, and in that the free ends of the ribs are clamped between the ribs for fixing and applying the brush holder, after its introduction.

 According to another characteristic of the invention, this brush holder has a longitudinal slot in its free lateral wall opposite the rib bottom and in that the brush pressure spring is produced in the form of a spiral spring whose turns spring are located outside the brush holder and which penetrates by its two branches through the longitudinal slot, the branches resting at their end, on the one hand at the bottom of the brush holder and on the other hand on the face front of the collector brush facing towards it.

 According to another characteristic of the invention, the brush holder carries a fastener, preferably consisting of a single piece, used for fixing the brush strand and projecting from the free side wall of the brush holder which is opposite the bottom rib.

 According to another characteristic of the invention, the bearing flange is made of aluminum, according to an extrusion process, with ribs formed in one piece.

 According to another characteristic of the invention, the bearing flange is manufactured according to a pressure molding process, in a zinc or aluminum alloy, with ribs formed in one piece.

 According to another characteristic of the invention, the brush holder is made of sheet metal and in that the insulating layer consists of an insulating sheet inserted between the brush holder and the bearing flange.

 According to another characteristic of the invention, the insulating sheet consists of silicone rubber.

 According to another characteristic of the invention, the brush holder is made of a sheet coated in an insulating manner on one side.

 According to another characteristic of the invention, the brush holder is prefabricated in a sheet which is folded so that its cross section has a trapezoid shape, the face of the brush holder which has the longitudinal slot forming the base line of the trapezoid and the opposite face corresponding in its dimensions to the distance between the ribs, and in that the brush holder is clamped between the ribs by reducing the width of the slot to the predetermined dimension.

 According to another characteristic of the invention, to clamp the ends of the ribs, a calibration piece is inserted into the brush holder, instead of inserting it into the collector brush.

 According to another characteristic of the invention, the bearing flange is provided, on the inner face carrying the ribs and / or on the outer face opposite the ribs, axially projecting cooling ribs.

 In place of the current helical pressure spring intended to press the collector brushes on the collector, there is used according to another embodiment of the invention for each brush holder, a spiral spring whose spring coils are located at the exterior of the brush holder and the branches of which pass through a longitudinal slot in the free, non-recessed face of the brush holder. One branch is supported on the front face of the collector brush and the other branch is supported on the bottom of the brush holder. By determining the spiral spring accordingly, one can thus achieve a constant pressure of application of the brushes, on the entire movement of the collector brush, because for a smaller brush length and thus for a lower torque of the spiral spring, the axis of the coils of the spring approaches the axis of the brush and thereby the lever arm of the spiral spring is reduced. By reducing the lever arm, the reduction in the torque is again compensated. The poor damping behavior of the spiral spring can be compensated by means of high friction between the collector brush and the brush holder. The brush strand is connected to a spaced attachment on the brush holder, in order to ensure electrical contact.

 In order to achieve embedding with a large surface of the brush holder in the bearing flange, according to a preferred form of the invention, the latter is provided with parallel ribs projecting axially or radially on the inner face of the bearing flange . These ribs are made in one piece with the bearing flange.

The brush holders are thus surrounded over their entire length by the bearing flange, on three sides. The bearing flange is preferably made of extruded aluminum or of an aluminum or zinc alloy, by die-casting. It has good thermal conductivity.

Various other characteristics of the invention will emerge from the detailed description which follows. An embodiment of the invention is shown by way of nonlimiting example in the appended drawings in which - FIG. 1 represents a longitudinal section of a small DC motor, - FIG. 2 is an enlarged representation of the part It of Figure 1, - Figure 3 is a representation identical to Figure 2, with two different brush lengths, - Figure 4 shows a section along the line
IV-IV of Figure 2, - Figure 5 is an exploded representation of Figure 4, without collector brush, or brush pressure spring.

 The small direct current motor of closed construction which is shown in longitudinal section in Figure 1, by way of example of a direct current motor; In a known manner, a stator 10 and a rotor il with armature winding 12. The stator 10 is constituted by a hollow cylindrical casing part 13 which is occupied by magnetic poles formed from segments of permanent magnet 14. Most often, small motors are made with two blades, so that there are two diametrically opposite permanent magnet segments 14 on the housing part 13.

 The rotor It has a rotor shaft 17, kept in rotation in two bearings 15, 16, on which a stack of grooved sheets 18 and a collector are placed locked in rotation in a known manner. The two bearings 15, 16 are each arranged in a bearing flange 20, 21. The two bearing flanges 20, 21 cover the hollow cylindrical casing part 13 on the two front faces. The armature winding 12 is placed in the grooves of the stack of sheets 18 and is connected in a known manner to the lamellae of the collector 19. The electrical supply to the armature winding 12 is effected by a number of brushes. collector rubbing frontally on the periphery of the collector 19 and electrically connected to corresponding connection lines. The number of collector brushes corresponds to the number of magnetic batteries. a single collector brush 22 is visible in FIG. 1.

 As shown enlarged in Figure 2, each collector brush 22 is guided axially movably in a brush holder 23 extending radially, the brush holder 23 surrounding almost completely and with very little play the collector brushes 22. The brush holder 23 is made of an electrically conductive material and is for example made of cut and folded sheet metal, as shown in FIG. 5. The longitudinal edges 24, 25 are then located one at opposite to each other, at a distance, so that there is a longitudinal slot 26 running the full length once the brush holder 23 is finished. As can be seen in FIG. 5, the folding of the sheet metal strip in order to obtain the brush holder 23 is first such that the free brush holder 23 has a roughly trapezoid-shaped cross section, the face of the brush holder which contains the longitudinal slot 26 constituting the baseline of t rapeze. The longitudinal slot 26 is first of all larger than that which is determined, but it is however brought to the desired dimension during mounting by elastic compression of the two sides of the branch opposite to each other.

 The brush holder 23 is connected to a connection line, not shown, in order to supply it electrically, and it is fixed in isolation on the bearing flange 20, and this, so as to be embedded by a large surface in the bearing flange 20 or to be surrounded by the latter. The bearing flange 20 is made of a material which is a good conductor of heat, for example extruded aluminum or an alloy of aluminum or zinc die-cast. To maintain it, the brush holder 23 carries on its inner face turned towards the rotor 11 two ribs 27, 28 parallel projecting axially. The free distance between the ribs 27, 28 corresponds to the external width, seen in the peripheral direction of the manifold 19, of the brush holder 23. The ribs 27, - 28 are made in one piece with the bearing flange 20 and are cast at the same time during its manufacture. The brush holder 23 is then pressed over its entire length between the ribs 27, 28, with the interposition of a thin thermally conductive insulating layer, as shown in FIG. 5. The two sides of the branches, one facing the other are then compressed and the two edges 24, 25 move towards each other in order to finally limit the longitudinal slot 26 to its predetermined slot width.

As seen in Figure 5, the insulating layer is introduced in the form of a separate insulating sheet 29. The insulating sheet 29 can for example be made of silicone rubber. It is important that the insulating sheet 29 is very thin, so that on the one hand it presses on the ribs 27, 28 and on the zone 30 of the bearing flange 20 which is delimited by them, and that it presses 'on the other hand on the brush holder 23 without forming an empty space, that is to say without letting air spaces of any kind exist, which would be thermally insulating. The insulating layer can however be produced by the fact that the brush holder 23 is composed of a sheet coated on one face with an insulating layer. The brush holder 23 is completely inserted between the ribs 27, 28, until its side wall opposite to the longitudinal slot presses on its zone 30, by pressing the insulating sheet 29 on the latter. The width of the ribs 27, 28, measured in the axial direction of the rotor 11; what is called the depth of the ribs, is greater than the corresponding depth of the brush holder 23, so that the ends of the rib 27, 28 protrude a little above the free face carrying the longitudinal slot 26, once the brush holder 23 has been completely inserted. By slightly bordering the points of the ribs, as shown in FIG. 4, the brush holder 23 is then held by shape adjustment between the ribs 27, 28, being connected, on a total of three of its faces, so as to conduct the heat well, to the bearing flange itself consisting of a material which is a good conductor of heat.

During the bridging of the points of the ribs, a calibration piece is inserted in the brush holder 23, so as to guarantee that the internal dimension of the brush holder 23 is respected.

 The collector brush 22 inserted in the brush holder 23 and axially movable is fixed with its brush strand 31 located on a clip 32 of the brush holder 23, for example by clamping connection.

The fastener 32 protrudes axially on the face of the brush holder 23 having the longitudinal slot 26. The brush strand 31 is guided through the longitudinal slot 26. A spiral spring 33 is provided for pressing the collector brush 22 on the collector 19, spring whose pack of spring turns 34 is placed outside of the brush holder 23 and whose two branches 35, 36 pass through the longitudinal slot 26, to arrive inside the brush holder 23. The branch of spring 35 is supported on the bottom of the brush holder 23 and the spring branch 36 is supported on the front face of the collector brush 22. The spring branches 35, 36 are for this purpose folded at the end in the form of hook, so that the free ends extend in the direction of the spring axis 37. The end of the spring branch 35 is then placed in a corresponding groove located at the bottom of the brush holder 23 and the end of the spring branch 36 is placed da ns a groove located in the collector brush 22. By an adequate design of the spiral spring 33, a constant brush pressure is reached. over the entire stroke of the collector brush 22-. As can be seen in FIG. 3, the spiral spring 33 sees its torque decrease when the collector brush 22 becomes smaller, owing to the greater spacing of the spiral spring 33. Simultaneously, due to the greater spacing of the spiral spring 33, its axis 37 approaches the axis of the brush. This corresponds to a reduction in the lever arm passing from length 1 to length 1 ', which again results in a increase in force, compensating for the decrease in torque. The brush application force thus remains constant, even when the collector brush 22 becomes shorter due to wear.

 In order to increase the heat evacuation, the bearing flange 20 is provided externally, that is to say on the face opposite to the ribs 27, 28, of cooling ribs 38 regularly arranged on the periphery of the flange of- bearing 20. Similar cooling ribs can also be provided on the inner face of the bearing flange 20, therefore also on the face carrying the ribs 27, 28. The bearing flange 20 can moreover be provided with housings 40 intended for deworming coils 39, as shown in an offset manner in FIG. 1 for one of them.

Claims (8)

 1 ') DC motor, in particular small motor of closed construction, comprising a stator carrying the excitation poles, a rotor carrying an armature winding and kept rotating in a bearing flange and carrying a collector connected to the winding 'armature, and comprising collector brushes movably guided axially in a brush holder extending radially or axially relative to the switch, and pressing. frontally on the collector, under the action of a brush pressure spring, the brush holders made of an electrically conductive material being fixed in an electrically isolated manner and each being connected to an electrical connection line, characterized in what the brush holders (23) surround almost completely and with very little play each of the collector brushes (22) placed inside and are embedded in the bearing flange (20) made of a good material conductive of heat, and intercalating without constituting hollow spaces, a thin thermally conductive insulating layer (29).  2 ') Motor according to claim 1, characterized in that the bearing flange (20) has two parallel ribs (27, 28) axially projecting, intended for the mounting of a brush holder (23), ribs between which the brush holder (23) with the insulating layer (29) is pinched over its entire length by pressing its third side wall covered with an insulating layer (29), on the bearing flange zone (30) framed by the ribs ( 27, 28).  3 ') Motor according to claim 2, characterized in that the depth of the ribs (27, 28), observed in the axial direction of the rotor (11), is slightly greater than the width of the brush holder (23), measured in the same direction, and in that the free ends of the ribs are clamped between the ribs (27, 28), for the purpose of fixing and tightening the brush holder (23), after its introduction.  4) Motor according to any one of claims 1 to 3, characterized in that the brush holder (23) has a longitudinal slot (26) in its free side wall opposite the bottom of the ribs and in that the brush pressure spring is made in the form of a spiral spring (33) whose spring turns (34) are located outside of the brush holder (23) and which penetrates by its two branches (35, 36) through the slot longitudinal (26), the arms resting at their ends, on the one hand on the bottom of the brush holder (23) and on the other hand on the front face of the collector brush facing towards it.  5) Motor according to any one of claims 1 to 4, characterized in that the brush holder (23) carries a fastener (32), preferably consisting of a single piece, used for fixing the brush strand (31) and projecting from the free side wall of the brush holder (23) which is opposite the bottom of the rib.  6) Motor according to any one of claims 1 to 5, characterized in that the bearing flange (20) is made of aluminum, according to an extrusion process, with ribs formed in one piece (27, 28 ).  7 ") Motor according to any one of claims 1 to 5, characterized in that the bearing flange (20) is manufactured according to a pressure molding process, in a zinc or aluminum alloy, with ribs ( 27, 28) formed in one piece.  8) Motor according to any one of claims 1 to 7, characterized in that the brush holder (23) is made of sheet metal and in that the insulating layer consists of an insulating sheet (29) inserted between the brush holder (23) and the bearing flange (20, 27, 28).  Motor according to claim 8, characterized in that the insulating sheet (29) consists of silicone rubber.  10 ') Motor according to any one of claims 1 to 7, characterized in that the brush holder (23) is made of a sheet coated with insulating material on one side.  11 ') Motor according to any one of claims 8 to 10, characterized in that the brush holder (23) is prefabricated in a sheet which is folded so that its cross section has a trapezoid shape, the face of the brush holder (23) which has the longitudinal slot (26) forming the base line of the trapezoid and the opposite face corresponding in its dimensions to the distance between the ribs (27, 28), and in that the brush holder (23) is clamped between the ribs (27, 28) by reducing the width of the slot to the predetermined dimension.  12 ') Motor according to any one of claims 3 to 11, characterized in that to clamp the ends of the ribs, a calibration piece is inserted into the brush holder (23), instead of inserting it into the brush manifold (22).  13 ') Motor according to any one of claims 1 to 12, characterized in that the bearing flange (20) is provided, on the inner face carrying the ribs (27, 28) and / or on the outer face opposite to ribs (27, 28, of cooling ribs (38) projecting axially.