Electric motor

Abstract

An electric motor (1) comprising a housing and a rotor (18) mounted in the housing via a fixed / loose bearing, wherein a deep groove ball bearing (8) with an inner ring and an outer ring (9) is provided as the fixed bearing, and the outer ring (9) of the fixed bearing is elastically clamped in the housing by means of an annular spring steel disc (5), wherein the housing is a deep-drawn steel housing (10) or a deep-drawn steel housing pot, the spring steel disc (5) is hardened, the hardness of the spring steel disc (5) is greater than the hardness of the deep-drawn steel housing (10), and the spring steel disc (5) has the shape of a clamping disc, which has a closed ring in the region radially outside the outer ring (9) with radially inwardly directed spring arms (2), which act on the outer ring (9) in such a way that each spring arm (2) acts on the outer ring (9) with an axial and a radial force component,wherein the steel housing (10) has a plurality of cascade-like recesses (11, 12, 13), wherein a first recess (11) is radially delimited by a first cylinder shell (21) and serves to receive the spring steel disc (5), wherein a second recess (12), radially delimited by a second cylinder shell (22), the inner diameter of which is smaller than the inner diameter of the first recess (11), serves to receive the deep groove ball bearing (8), wherein a third recess (13) is radially delimited by a third cylinder shell (23) and the inner diameter of which is smaller than the inner diameter of the second cylinder shell (22), and wherein the outer ring (9) of the deep groove ball bearing (8) has an axially greater dimension than the depth of the second recess (12).

Description

[0001] The invention relates to an electric motor with a housing and a rotor which is mounted in the housing via a fixed / loose bearing, wherein a deep groove ball bearing with an inner ring and an outer ring is provided as the fixed bearing, the outer ring of the fixed bearing being elastically clamped in the housing by means of a spring steel disc.

[0002] The shape of the spring steel disc according to the invention is known per se; such components are regularly used, especially in spherical bearings. A key difference from the generic type of the invention is that in spherical bearings, the shaft does not exert any axial moment on the bearing. In contrast, with an inner ring of a deep groove ball bearing that is tightly pressed onto the shaft, a large axial load can be transferred to the bearing, particularly under vibration and shock loads.

[0003] From WO 94 / 03 961 A1 an electric motor with a deep-drawn, pot-shaped motor housing for driving an assembly that can be flanged to the front of the motor housing, in particular a hydraulic pump of an anti-lock braking device, is known, with the features: a) an axially outwardly projecting bearing neck is formed without machining into the pot base of the motor housing, b) the bearing neck is provided radially on the inside with a non-machined bearing receptacle for the rotor shaft of the electric motor, c) the bearing neck is provided radially on the outside with a non-machined fastening receptacle for the assembly.

[0004] From GB 2 178 804 A, an engine end cap 1 is known, comprising a pendulum tube bearing 2 with partially conical end surfaces 2a, 2b. One end 2b of the bearing 2 is supported by a single receiving and retaining plate 4. The plate 4 is held in position by a plurality of radially outwardly directed legs 4b in engagement with the wall 1c of the chamber 3.

[0005] US 3,359,021 A discloses a retaining ring assembly comprising a housing with a bore, a machine part arranged in the bore, and a self-locking retaining ring which is aged with the bore surface at its outer edge and abuts a radial surface of the machine part at its inner edge, whereby an artificial shoulder is provided in the bore for axially positioning the machine part therein. The retaining ring comprises an annular, initially planar, closed ring body with an unstressed outer diameter that is larger by a predetermined amount than that of the bore, but which is in a radially limited and thus loaded state within the bore and has the frustoconical arrangement of a Belleville spring washer with an outer diameter corresponding to that of the bore and a cone angle that is such thatthat the tangent of the angle is smaller than the coefficient of friction between the outer edge of the ring and the housing bore surface, the ring body being secured within the bore solely by friction exerted by its outer edge on the bore surface, which tends to cause the ring body to return to its original planar shape and increases as the ring tends to deflect under a load exerted by the machine part in the same direction as its return tendency. The self-locking retaining ring with prongs is limited to assemblies in which the metal of the housing in whose bore the ring is to be mounted is relatively soft compared to the metal from which the ring is formed, otherwise the free ends of the prongs cannot bite into and secure the housing bore surface as intended. The housing in whose bore the ring is mounted,has a hardness close to that of metal, e.g. made of metal with the hardened metal of the ring itself.

[0006] From US 2 504 776 A, a support structure is known, comprising a bearing having an inner ring and an outer ring with rolling bearing elements therebetween, a bearing housing arranged around the bearing, and an elastic cap element mounted in the housing over the outer ring; the cap element has an annular ring portion engaging an end wall of the outer ring, a plurality of elastic spring fingers extending axially from the outer periphery of the ring portion over the outer ring and arranged in engagement with a circumferential surface of the housing and the outer surface of the outer ring to provide radial pressure on the outer ring, and a plurality of other elastic spring fingers on the outer periphery of the ring portion between the first spring fingers arranged in engagement with an axial end wall of the housing to generate axial pressure on the outer ring.

[0007] US 2015 / 0 188 383 A1 discloses an internal rotor motor comprising a shaft, a rotor, a stator, an upper bearing, a lower bearing, a motor housing having an opening at an upper portion, a housing cover that holds the upper bearing and covers the opening of the motor housing, and a lower damping element. The motor housing may include a cylindrical portion, a lower wall portion extending inward from the cylindrical portion, and a lower hub portion formed in the shape of a lower cylinder projecting downward from a lower portion of the lower wall portion. The lower bearing is disposed inside the lower hub portion, and the lower damping element is disposed outside the lower hub portion.The lower hub section is provided with a lower hub recess, and the lower damping element is provided with a concave or convex anti-rotation section. The housing cover is made of metal, and the upper hub section holds the upper bearing directly inside it in the radial direction. The upper bearing is inserted into the inner peripheral surface of the cylindrical portion of the upper hub section.

[0008] GB 870 168 A discloses a fastener for securing a pin in a socket in a component, comprising a tubular body with outwardly extending spring teeth at one end for engaging the socket wall and inwardly extending spring teeth at the other end for engaging the pin. The teeth are bent toward the other end, and the teeth are bent toward one end.

[0009] US 6,145,199 A discloses a bearing system for mounting a rotating shaft, comprising a bearing assembly and a bearing mounting structure. The bearing assembly has an inner ring contacting the rotating shaft, an outer ring, and the bearing elements arranged therebetween. The outer ring has an outer surface with an outer dimension. The bearing mounting structure has a region in which it can be attached to an external structure in which the bearing system is to function. An inner surface of the bearing mounting structure defines a bearing cavity in which the bearing assembly is to be arranged. The inner surface engages the outer surface of the outer ring. The holding force exerted by the inner surface on the outer surface is determined by the design of the inner surface of the bearing mounting structure that defines the bearing cavity. The inner surface has cutouts that extend axially (with respect to the shaft) along the inner surface.In addition, the inner surface is pre-angled slightly inward toward the shaft before installation of the bearing assembly. During installation of the bearing assembly, the inner surface deflects outward as the spring action provides the required holding force due to the pre-angle. The amount of holding force for a given material of known thickness depends on the geometry of the cutouts on the inner surface and the pre-angle. Since the holding force associated with the spring action is a function of known variables, a bearing mounting structure can be designed for a specific holding force by selecting the variables to generate the holding force.

[0010] From DE 21 04 452 A an arrangement for holding a bearing, in particular a ball bearing ring, on a bearing part by means of elastic parts in an electric motor is known, wherein the bearing part has an undercut projecting beyond the contour of the bearing in the support area of ​​the bearing and in this undercut the elastic parts are held at least partially against the bearing under pressure.

[0011] AT 389 573 B discloses a device for compensating the radial play of a rolling bearing in a bearing bore by means of a disk mounted in front of the rolling bearing on the end face, with a projection axially formed on its circumference, projecting into the radial play space and adapted to this in the sense of a certain radial pressure, wherein in an axially preloaded rolling bearing a disk is provided with an axially formed edge in the form of a wedge directed towards the outer circumferential surface (outer ring) of the rolling bearing and the wedge is pressed into the play space between the rolling bearing and the bearing bore by the axial preload force of a spring element in the sense of compensating for the respective radial play.

[0012] DE 198 05 844 A1 discloses an electric motor with at least one roller bearing, in particular a ball bearing, whose first bearing ring, in particular the inner bearing ring, facing the motor shaft is firmly connected to the shaft, wherein the unit comprising the roller bearing and the motor shaft is locked to the motor housing via the second (in particular outer) bearing ring.

[0013] From US 2005 / 0 041 897 A1, a bearing assembly is known, comprising: a spherical plain bearing with a centering bore, the centering bore having a central axis defining mutually perpendicular axial and radial directions, the bearing having an outer surface with a pair of end surfaces at axially opposite ends of the bearing and a convex surface between the pair of end surfaces, the convex surface extending around the bearing axis; a bearing support having a bearing support surface, the bearing support surface engaging the convex bearing surface; and a projection on the bearing, the projection engaging the outer surface of the bearing. The outer peripheral portion of the bearing holder is formed with a plurality of arcuate flanges. The arcuate flanges protrude at an angle from the annular portion.The width of the ring section and the angled orientation of the arcuate flanges allow the distal edges of the flanges to dig into the shoulder surface of the cylindrical wall of the end plate when the retainer is mounted to the end plate. This securely holds the bearing retainer in position.

[0014] DE 10 2013 209 202 A1 discloses a drive unit comprising an electric drive motor, the motor shaft of which is rotatably received in a first bearing and a second bearing, and the drive unit also comprises a clamping ring which is arranged in a housing and axially supports the second bearing of the motor shaft, wherein the clamping ring is received in an axially displaceable manner in a receiving space in the housing, and that a circumferential surface of the clamping ring has a clamping section which rests against an inner wall of the receiving space in the housing and is designed to be elastic, so that a clamping force emanating from the clamping ring is transmitted via the second bearing to the motor shaft and from the motor shaft to the first bearing.

[0015] The object of the invention is to securely and permanently mount a deep groove ball bearing in a deep-drawn steel housing using simple means, with as few process steps as possible and a minimum number of components. This object is achieved according to the invention by the features of claim 1.

[0016] It is proposed that the housing be a deep-drawn steel housing (10) or a deep-drawn steel housing pot, that the spring steel disc (5) be hardened, that the hardness of the spring steel disc (5) be greater than the hardness of the deep-drawn steel housing (10), and that the spring steel disc (5) be in the form of a clamping ring which, in the region radially outside the outer ring (9), has a closed ring with radially inward-directed spring arms (2) which act on the outer ring (9) in such a way that each spring arm (2) acts on the outer ring (9) with an axial and a radial force component. Due to the different degrees of hardness of the joining partners, the spring steel disc (5) can claw into the deep-drawn steel housing (10) when a force is applied opposite to the joining direction, thus finding a secure hold. The outer ring (9) of the deep groove ball bearing (8) is mounted in the steel housing (10) for axial movement and is held only by the spring steel disc (5).When a force is applied opposite to the joining direction, an axial and radial force component acts on the spring arms (2), causing them to deflect more or less depending on the magnitude of the force, slightly increasing the distance between adjacent ends of the spring arms (2). In a closed ring, this effect would lead to fracture of the hardened component. Since the force-locking connection shown has proven sufficiently strong, no additional securing elements or forming processes are required. This provides a very simple and effective fastening of the deep groove ball bearing (8).

[0017] The steel housing (10) has several cascade-like recesses (11, 12, 13). A first recess (11) is radially delimited by a first cylindrical shell (21) and serves to accommodate the spring steel disc (5). This recess (11) is dimensioned in diameter such that it is sufficient to accommodate the spring steel disc (5). A second recess (12), radially delimited by a second cylindrical shell (22), whose inner diameter is smaller than the inner diameter of the first recess (11), serves to accommodate the deep groove ball bearing (8). The diameter of the second recess (12) differs from the diameter of the first recess (11) such that the spring arms (2) extend radially significantly into the region of the second recess (12), so that the outer ring (9) of the deep groove ball bearing (8) can be held in the axial direction by the spring arms (2).A third recess (13) is radially delimited by a third cylinder shell (23), and its inner diameter is smaller than the inner diameter of the second cylinder shell (22). This recess (13) is designed to securely mount a cover cap (16). A cover cap (16) may be required if a housing opening is required to allow access for an assembly tool for pressing the inner ring onto a motor shaft.

[0018] It is particularly important that the outer ring (9) of the deep groove ball bearing (8) has a greater axial dimension than the depth of the second recess (12). Only then is a clearance-free seating of the outer ring (9) in the second recess (12) possible.

[0019] Further developments of the invention are presented in the subclaims. It is particularly advantageous if the steel housing (10) is tin-plated. The zinc layer, which is very thin after deep-drawing, nevertheless significantly increases the holding force of the spring steel disc (5) in the steel housing (10).

[0020] Advantageously, the spring steel disc (5) rests axially against a stop (6) when assembled. The axial position of the stop (6) is crucial for the preload with which the spring arms (2) act on the outer ring (9). This allows for a definable force within calculable tolerance limits, also due to the dimensional tolerances of the joining partners.

[0021] The spring steel disc (5) is provided with a conical clamping area (4) with which it grips the inner wall of the first cylinder jacket (21) of the steel housing (10) when mounted. Due to geometric principles, the hold of the spring steel disc (5) in the steel housing (10) increases when a force is applied opposite to the joining direction, because in the illustrated situation, the conical clamping area (4) is forced radially outward, thereby further increasing the frictional connection.

[0022] It is expressly claimed that the deep groove ball bearing (8) is held exclusively by the force-locking connection of the spring steel disc (5) with the steel housing (10) in order to meet the object of the invention.

[0023] Another important advantage of the invention is that the deep groove ball bearing (8) is elastically held by the spring arms (2). This allows radial loads to be absorbed without causing permanent deformation.

[0024] Last but not least, it is useful that a force directed axially from the outer ring (9) of the deep groove ball bearing (8) onto the spring arms (2) in the disassembly direction increases the force acting radially from the clamping area (4) onto the first cylinder jacket (21).

[0025] It has been shown that the spring arms (2) of the spring steel disc (5) should be inclined by 25° to 35° relative to the disc plane in the unassembled state, that the clamping area (4) of the spring steel disc (5) should be inclined by 35° to 45° relative to the disc plane in the unassembled state and that the outer diameter of the clamping area (4) of the spring steel disc (5) in the unassembled state should be 2% to 4% larger than the inner diameter of the first cylinder jacket (21) in order to achieve an optimal holding force of the spring steel disc (5) and an optimal elastic mounting of the deep groove ball bearing (8).

[0026] The invention also encompasses housings having more than the stated number of recesses (11, 12, 13). In this case, the "first recess" would mean the recess in which the spring steel disc (5) is received.

[0027] An embodiment of the invention is explained in more detail below using an example. Shown are: Fig. 1 a sectional view of a deep-drawn steel housing pot, Fig. 2 a spring steel disc in a plan view, in section and three-dimensional, Fig. 3 a partial sectional view of an installed deep groove ball bearing and Fig. 4 an assembly drawing of an electric motor.

[0028] Fig. 1 shows a sectional view of a deep-drawn steel housing 10, with a first recess 11 for receiving a spring steel disc 5, a second recess 12 for receiving a deep groove ball bearing 8, and a third recess 13 for forming a stop 6 for the deep groove ball bearing 8. A housing opening 7 is provided for a counterholder of a press-in device. The first recess 11 is bounded radially inward by a first cylinder shell 21, and the second recess 12 by a second cylinder shell 22.

[0029] Fig. Figure 2 shows the spring steel disc 5 in a top view, a section view, and a three-dimensional view. The spring steel disc 5 is circular in its basic shape and has three sections in the radial direction. An outer clamping area 4 is chamfered in the shape of a cone. A central stop ring area 3 is aligned perpendicular to a motor shaft when assembled. Inner spring arms 2, as a whole, form partial surfaces of a conical surface. The spring arms 2 are separated from one another by slot-like recesses 14. The recesses 14 extend into the stop ring area 3.

[0030] Fig. Figure 3 shows an assembly drawing with the steel housing 10, the deep groove ball bearing 8, and the spring steel disk 5. As can be clearly seen, the deep groove ball bearing 8 protrudes from the second recess 12, so that the spring steel disk 5 rests with its spring arms 2 on an edge of an outer ring 9 of the deep groove ball bearing 8 and can exert a radial and an axial force component on the outer ring 9. The spring steel disk 5 is accommodated in a first recess 11, and the deep groove ball bearing 8 is accommodated in a second recess 12. The spring steel disk 5 is firmly clamped to the first cylinder jacket 21 with its clamping area 4. To make this possible, the spring steel disk 5 is hardened, so that its material is harder than the steel housing 10. With its stop ring area 3, the spring steel disk 5 rests against the stop 6 of the steel housing 10.

[0031] Fig.Figure 4 shows an assembly drawing of an electric motor 1 with the deep groove ball bearing 8 acting as a fixed bearing, which is fastened to the spring steel disk 5, and with a second ball bearing acting as a loose bearing 15. A cover cap 16 is also shown, which is fastened in the recess 14. The electric motor 1 shown in the application example is an electronically commutated DC motor, which has a rotor 18 equipped with permanent magnets 27, a stator 19 wound with a winding 24, and a housing consisting of a bearing shield 20 and the steel housing 10. The rotor 18 consists of a smooth shaft 25, a rotor core 26, the permanent magnets 27, and a sensor pole wheel 28, which is held on a carrier 33 that is pressed axially into recesses 34 of the rotor core 26. Also shown are a stator core 29, a gear pump 30, a circuit board 31, a sensor 17 and a connector 32. List of reference symbols 1 electric motor 2 spring arms 3 Stop ring area 4 clamping area 5 spring steel disc 6 stop 7 Housing opening 8 deep groove ball bearings 9 Outer ring 10 steel cases 11 first deepening 12 second deepening 13 third recess 14 Free space 15 loose bearings 16 Cover cap 17 Sensor 18 Rotor 19 Stator 20 bearing plate 21 first cylinder jacket 22 second cylinder jacket 23 third cylinder jacket 24 windings 25 Wave 26 rotor lamination package 27 Permanent magnet 28 encoder pole wheel 29 Stator laminated core 30 Gear pump 31 circuit board 32 plugs 33 carriers 34 recesses

Claims

[1] An electric motor (1) comprising a housing and a rotor (18) mounted in the housing via a fixed / loose bearing, wherein a deep groove ball bearing (8) with an inner ring and an outer ring (9) is provided as the fixed bearing, and the outer ring (9) of the fixed bearing is elastically clamped in the housing by means of an annular spring steel disc (5), wherein the housing is a deep-drawn steel housing (10) or a deep-drawn steel housing pot, the spring steel disc (5) is hardened, the hardness of the spring steel disc (5) is greater than the hardness of the deep-drawn steel housing (10), and the spring steel disc (5) has the shape of a clamping disc, which has a closed ring in the region radially outside the outer ring (9) with radially inwardly directed spring arms (2), which act on the outer ring (9) in such a way that each spring arm (2) acts on the outer ring (9) with an axial and a radial force component,wherein the steel housing (10) has a plurality of cascade-like recesses (11, 12, 13), wherein a first recess (11) is radially delimited by a first cylinder shell (21) and serves to receive the spring steel disc (5), wherein a second recess (12), radially delimited by a second cylinder shell (22), the inner diameter of which is smaller than the inner diameter of the first recess (11), serves to receive the deep groove ball bearing (8), wherein a third recess (13) is radially delimited by a third cylinder shell (23) and the inner diameter of which is smaller than the inner diameter of the second cylinder shell (22), and wherein the outer ring (9) of the deep groove ball bearing (8) has an axially greater dimension than the depth of the second recess (12). [2] Electric motor (1) according to claim 1, characterized by that the steel housing (10) is galvanized. [3] Electric motor (1) according to claim 1 or 2, characterized bythat the spring steel disc (5) in the assembled state rests against a stop (6) in the axial direction. [4] Electric motor (1) according to claim 1 or 2, characterized by that the spring steel disc (5) has a conical-shell-shaped clamping area (4) with which the spring steel disc (5) in the mounted state grips the inner wall of the first cylinder shell (21) of the steel housing (10). [5] Electric motor (1) according to at least one of the preceding claims, characterized by that the deep groove ball bearing (8) is held exclusively by the force-locking connection of the spring steel disc (5) with the steel housing (10). [6] Electric motor (1) according to at least one of the preceding claims, characterized by that the deep groove ball bearing (8) is held elastically by the spring arms (2). [7] Electric motor (1) according to at least one of the preceding claims, characterized bythat a force directed axially from the outer ring (9) of the deep groove ball bearing (8) onto the spring arms (2) in the disassembly direction increases the force acting radially from the clamping area (4) onto the first cylinder jacket (21). [8] Electric motor (1) according to at least one of the preceding claims, characterized by that the spring arms (2) of the spring steel disc (5) are inclined by 25° to 35° relative to the disc plane when unassembled. [9] Electric motor (1) according to at least one of the preceding claims, characterized by that the clamping area (4) of the spring steel disc (5) is inclined by 35° to 45° relative to the disc plane when unassembled. [10] Electric motor (1) according to at least one of the preceding claims, characterized by that the outer diameter of the clamping area (4) of the spring steel disc (5) in the unassembled state is 2% to 4% larger than the inner diameter of the first cylinder jacket (21).

Images