AU774017B2

AU774017B2 - Fixing an electromotor on a printed board

Info

Publication number: AU774017B2
Application number: AU22834/00A
Authority: AU
Inventors: Heinrich-Jochen Blume; Markus Keutz; Klaus Kronenberg; Peter Schmidt; Sabine Vorberg; Thomas Vorberg; Frank Weiand
Original assignee: Mannesmann VDO AG
Current assignee: Continental Automotive GmbH
Priority date: 1998-12-23
Filing date: 1999-12-14
Publication date: 2004-06-10
Anticipated expiration: 2019-12-14
Also published as: JP4980515B2; CN1173448C; CN1331861A; WO2000039910A1; BRMU7903460Y1; ES2238872T3; EP1142082B1; KR100882372B1; BR9916555A; AU2283400A; MY126624A; DE59911668D1; KR20010092760A; EP1142082A1; JP2002534945A

Description

4175 PCT Electric motor intended to be fixed to a printed circuit board Description The invention relates to an electric motor which is intended to be fixed to a printed circuit board and has a rotor and a stator which has a number of coils and stator plates, the stator plates extending from the coils to the rotor.

The prior art discloses electric motors, in particular as meter mechanisms in motor vehicle display instruments, in which the coil ends of the electric motors are electrically conductively connected to pins which, in a push-through mounting operation, are electrically conductively connected to a printed circuit board, for example by flow soldering. In addition, the prior art discloses an electric motor in which the coils can be connected by the ends of their windings to electric conductors of a printed circuit board by soldering, using a surface mounting technique, the winding ends being wrapped around electrically nonconductive, fork-like formations on the coil former of the respective coil. The drawback in this case is the complicated production of the electrical connection between the coil and the printed circuit board.

An object of the invention is therefore to specify an electric motor which can be electrically conductively connected simply to a printed circuit board without push-through mounting.

This object is achieved by the motor having contact springs which are in each case electrically conductively connected to one end of the coils, and by the contact springs being configured in such a way that, after the electric motor has been fixed to the printed circuit board, they are in contact under prestress with electric conductors on the printed circuit board.

4175 PCT 2 As a result of this pressure between the contact springs and electrical conductors of the printed circuit board, given appropriately corrosionresistant material of the surfaces of the contact springs, such as zinc, gold or platinum, an additional soldering operation can be dispensed with.

The configuration of the motor is particularly simple if the contact springs are fixed to the coils.

A casing which has openings for the contact springs, through which the contact springs protrude out of the casing, firstly protects the motor against external influences, additionally simplifies the mounting and permits the direct mounting of the contact springs on the coils.

If the contact springs are configured in such a way that, after the motor has been mounted on the printed circuit board, they are in contact underneath the casing, space on the printed circuit board is additionally saved. In addition, the casing can then be configured such that, after the motor has been mounted on the printed circuit board, the printed circuit board covers the openings completely and therefore the casing is closed. In this way, the mechanical and electrical components of the motor are better protected, in particular against the action of heat, during the subsequent surface mounting, necessary after the mounting of the motor, of other components on the printed circuit board.

By configuring the contact springs in such a way that, after the motor has been mounted on the printed circuit board, they are in contact at the side of the casing, the contact springs can additionally be soldered to conductors of the printed circuit board in surface mounting, if particular requirements are placed on the durability of the electrical connection. In this case, the opening in the casing can be configured such that the casing largely protects the motor, so that the 4175 PCT 3 action of heat from, for example, a reflow soldering operation does not damage the motor.

The motor may be fixed to the printed circuit board particularly simply and quickly by using one or more latching pins. This fixing becomes still more stable if one or more of the latching pins can additionally be spread in each case by a spreading element, which can be inserted into the interior of the respective latching pin.

The durability of the prescribed connection can be increased still further if the spreading element can be latched into the latching element and therefore cannot leave its position, even in the event of all conceivable shaking or vibration.

Simple mounting of the contact springs results if the coils each have a coil former and the contact springs are fixed in or on the coil former. Mounting can be carried out particularly simply if the coil former is configured as an injection molding and the contact springs are encapsulated by injection molding with parts of the coil former.

A permanent electrical connection between the coil windings and the contact springs may be produced by the ends of the coil windings being electrically conductively fixed to the contact springs, for example by soldering or welding, and then the contact springs being bent over at these ends in such a way that the coil ends are relieved of load.

A compact design of the electric motor may be achieved by the stator plates forming a stator which, at the center, has an opening to accommodate the rotor, the individual stator plates being arranged around the opening. The motor becomes particularly compact if it has four stator plates and two coils.

If two mutually opposite stator plates are bent over once toward each other in such a way that parts of the stator plates are aligned parallel to each other, between which the first coil is arranged in a 4175 PCT 4 magnetically coupled fashion, and if the two other stator plates have a first bend in the vicinity of the opening and a second bend in the vicinity of the free ends, and if the second coil is magnetically coupled between the free ends, it is possible for the coils to be arranged parallel and at the same height and therefore configured identically.

If the stator plates are magnetically coupled at the opening, they can be produced together in one piece from one plate.

If the stator plates are connected to one other at the opening via a nonmagnetic metal, the motor can be driven particularly easily.

By welding coil cores of the coils to the stator plates, the coils can be coupled magnetically to the stator plates in a rapid, permanent and effective manner.

The invention will be explained in more detail below using the figures for particularly preferred exemplary embodiments. In the figures: figure 1 figure 2 shows the view of a particularly preferred embodiment of a coil of the electric motor according to the invention, shows the view of a second particularly preferred embodiment of a coil of the electric motor according to the invention, shows the perspective view of a particularly preferred exemplary embodiment of the stator plates of the electric motor according to the invention, shows the perspective view and the partial section of a stator, comprising coils from figure 1, which are inserted into stator figure 3 figure 4 4175 PCT 5 plates from figure 3 and interact with a particularly preferred rotor, figure 5 shows a plan view of a particularly preferred lower casing part of an electric motor according to the invention for accommodating the stator and rotor, for example from figure 4, figure 6 shows the view and the partial section of a particularly preferred motor on the partial view of a printed circuit board.

The exemplary embodiment in figure 1 of a particularly preferred coil 1 has a coil winding 2, a coil former 3, two contact springs 4 and a coil core The coil winding 2 is wound on the injection-molded coil former 3, in which parts of the contact springs 4 are encapsulated by injection molding with the material of the coil former 3 and are therefore fixed. Winding ends 6 of the coil winding 2 are in each case electrically conductively connected to one end of a contact spring 4, for example by means of soldering or welding. Following the connection, the corresponding end of the contact spring 4 is bent over upward as illustrated, in order to relieve the load on the end of the coil winding 2. The contact springs 4 are produced from a spring strip material and, approximately at the center, are bent through about 1650, as can be seen from figure 1. At its other end, the contact spring 4 has a contact bump 7, with which contact is intended to be made with an electrical conductor on a printed circuit board. The above-described embodiment is provided in order to make contact underneath the casing when an electric motor with a casing is used.

The coil 8 illustrated in figure 2 differs from the coil 1 illustrated in figure 1 in that its contact spring 9 is bent over only by about 450 approximately 4175 PCT 6 at its center. Otherwise, its other components, the coil winding 2, coil former 3, coil core 5 and winding end 6, coincide with the coil 1 in figure 1. The coil 8 is provided in order to make contact at the side of the casing when an electric motor with a casing is used.

The use of the two above-described coils 1, 8 is also possible in the case of a motor without a casing.

Figure 3 reveals four stator plates 10, 11, 12, 13, which with their one end 10a, lla, 12a, 13a, form an opening 14 to accommodate a rotor and are magnetically coupled at the opening 14. The stator plates 10, 11, 12, 13 are bent in such a way that in each case two stator plates 10, 11 and 12, 13 are each located with one end 10b, llb and 12b, 13b parallel to each other in order to accommodate the coil 1 and 8 illustrated in figure 1 and figure 2, respectively. In order to be given this shape, the stator plates 10, 11 each have a bend 10c, llc, and the stator plates 12, 13 each have two bends 12c, 12d, 13c, 13d.

In figure 4, in each case one coil 1 is arranged between two ends 10b, llb and 12b, 13b of the stator plates 10, 11, 12, 13. It is preferable for the coil cores 5, which are not visible in figure 4 to be welded to the stator plates 10, 11, 12, 13 in the region of the ends 10b, llb, 12b, 13b. This has the effect of a stable, rapid connection and, at the same time, good onward conduction of the magnetic flux.

However, the connection between the. stator plates 11, 12, 13 and the coils 1 can also be carried out by means of other connection techniques, such as screwing or riveting.

It is also possible to see in figure 4 a rotor, comprising a diametrically magnetized disk 15, which is largely arranged in the opening 14 and is connected firmly to a shaft 16 so as to rotate with it.

Preferably arranged on the shaft 16 is a worm (not illustrated), which interacts with a worm wheel 17 4175 PCT 7 illustrated in figure 6. The mounting of the shaft 16 is not illustrated in figure 4 either. If current is applied to the two coils 1, they produce a magnetic flux, which is conducted via the stator plates 10, 11, 12, 13 and exerts a force on the diametrically magnetized disk 15. It is thus possible for the electric motor to be operated as a stepping motor, for example, if the coils are energized with DC one after another or else simultaneously. It is also possible, by driving the two coils 1 with sinusoidal currents offset by 900, to operate the motor as a synchronous motor, in which the rotational speed of the shaft 16 corresponds to the frequency of the sinusoidal currents.

In figure 5, a lower casing part 18 has two flat hollows 19, 20, four openings in the form of longitudinal slots 21, shaft bearings 22, 23, a wormwheel shaft bearing 24, latching pins 25 with spreading elements 26 and a latching clip 27. The flat hollows 19, 20 are configured in such a way that the stator plate 11 can rest in the hollow 19 and the stator plate 13 can rest in the hollow 20, and therefore the stator, comprising stator plates 10, 11, 12, 13 and coils 1, can assume a predetermined position in the lower casing part 18. In this case, the contact springs 4 then protrude out of the lower casing part through the longitudinal slots 21. The shaft 16 from figure 4 can be mounted in the shaft bearings 22, 23 and then assumes the correct position in the stator described in figures 3 and 4. The spreading elements 26 are connected to the latching pin 25 via webs 26a.

In figure 6, a stator has been inserted into a casing, comprising lower casing part 18 and upper casing part 30. The stator differs from the stator described in figures 3 and 4 only in that the stator plates 10, 11, 12, 13 are not magnetically coupled in the region of the opening 14, but are connected to one another via a ring 29 of nonmagnetic metal, for example brass. This connection can comprise, for example, 4175 PCT 8 projection-welding the stator plates 10, 11, 12, 13 to the ring 29. The diametrically magnetized disk 15 is connected, via the shaft 16 (not illustrated in figure 6) and the worm arranged on the shaft 16 and likewise not illustrated in figure 6, to the worm wheel 17, which in the axial direction is connected on both sides to a worm-wheel shaft 31. The worm-wheel shaft 31 is mounted in the lower casing part 18 in the worm-wheel shaft bearing 24 (see figure 5) and in the upper casing part 30 in a bearing (not illustrated). The upper casing part 30 is seated on the lower casing part 18 and is firmly held by latching clips, of which the latching clip 27 is illustrated in figure 6. The latching pins 25 have a rotationally symmetrical shape and are connected to the remaining lower casing part 18 via webs 25a. The latching pins 25 are divided up into arms 25b by slots 25c running axially. The slots and the tapering ends 25d make it possible to push the latching pins 25 through round holes 32 in the printed circuit board 28, the diameter of the round holes 32 being smaller than the diameter of the latching pin in the unloaded state illustrated in figure 6. As a result of the elasticity of the latching pin 25, or as a result of inserting the spreading element 26 into the latching pin 25, the latching pin assumes its original shape, so that the motor is fixed to the printed circuit board 28. The webs 26a (see figure 5) of the spreading element 26 are designed such that they break in the event of pressure on the spreading elements 26 from above. The spreading element 26 can then be inserted into the latching pin 25 by means of further pressure from above on the spreading element 26. In this way, the motor is pressed with the underside of its lower casing part 18 onto the printed circuit board 28. At the same time, the contact springs 4 (not illustrated in figure 6) are pressed onto the printed circuit board 30 and electrically connected to electric conductors 33 located on the printed circuit board 28.

4175 PCT 9 As an example, a pointer of a display appliance, for example a tachometer or revolution counter or a clock, can be fitted to the worm-wheel shaft 31.

Claims

1. An electric motor which is intended to be fixed to a printed circuit board and has a rotor and a stator which has a number of coils and stator plates, the stator plates extending from the coils to the rotor, characterized in that the motor has contact springs which are in each case electrically conductively connected to a winding end of the coils, in that the contact springs are configured such that after the electric motor has been fixed to the printed circuit board they rest under spring prestress on electric conductors of the printed circuit board in that the electric motor has one or more latching pins, with which it can be latched into recesses in the printed circuit board, and in that the latching pin or pins can be spread in each case by a spreading element, which can be inserted into the interior of the latching pin.

2. The electric motor as claimed in Claim 1, characterized in that the contact springs are fixed to the coils.

3. The electric motor as claimed in Claim 1 or 2, 0:0 characterized in that the electric motor has a casing in 00go which openings are formed, through which the contact 2 springs protrude out of the casing. 25 4. The electric motor as claimed in Claim 3, S°characterized in that the contact springs are configured in such a way that, after the motor has been mounted on the printed circuit board they are in contact at an underneath portion of the casing. 30 5. The electric motor as claimed in Claim 3, characterized in that the contact springs are configured in such a way that, after the motor has been mounted on the printed circuit board, they are in contact at a side of the casing.

6. The electric motor as claimed in any one of Claims 1 to 5, characterized in that the spreading element can be latched into the latching pin. \\melb_files\home$\Leanne\Keep\22834-00.doc 21/04/04 11

7. The electric motor as claimed in any one of the preceding claims, characterized in that the coils have a coil former, and in that the contact springs are fixed in or on the coil former.

8. The electric motor as claimed in Claim 7, characterized in that the coil former is injection molded and the contact springs are encapsulated byinjection molding with parts of the coil former.

9. The electric motor as claimed in Claim 7 or 8, characterized in that that the winding ends of the coil windings are each electrically conductively fixed to one end of a contact spring, and in that the contact springs are bent over at this end. The electric motor as claimed in any one of the preceding claims, characterized in that the stator plates form a stator which, at the center, has an opening to accommodate the rotor, the individual stator plates being arranged around the opening.

11. The electric motor as claimed in Claim characterized in that in each case two opposite stator plates are arranged in relation to each other such that they accommodate a coil.

12. The electric motor as claimed in Claim 11, characterized in that the electric motor has four stator 25 plates and two coils. "13. The electric motor as claimed in Claim 12, characterized in that two mutually opposite stator plates are bent over once toward each other in such a way that parts of the stator plates are aligned parallel to each 30 other, between which the first coil is arranged in a *9*e magnetically coupled fashion. :14. The electric motor as claimed in claim 13, characterized in that the two other mutually opposite stator plates have a first bend in the vicinity of the S 35 opening and a second bend in the vicinity of the free ends, and the second coil is arranged between the free ends in a magnetically coupled fashion. \\melb_files\home\Leanne\Keep\22834-OO.doc 21/04/04 12 The electric motor as claimed in any one of Claims 10 to 14, characterized in that the stator plates are magnetically coupled at the opening.

16. The electric motor as claimed in any one of Claims to 14, characterized in that the stator plates are connected to one another at the opening via a nonmagnetic metal.

17. The electric motor as claimed in one of the preceding claims, characterized in that the coils each have a coil core which is welded to the stator plates.

18. An electric motor substantially as hereinbefore described with reference to the accompanying drawings. Dated this 21st day of April 2004 MANNESMANN VDO AG By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and S 20 Trade Mark Attorneys of Australia \\melbfiles\home$\Leanne\Keep\22834-0Odoc 21/04/04