Brush arrangement used in a vehicle to lead away currents

Abstract

The invention relates to a brush arrangement (10) comprising an elongate housing (12). A contact brush (11) is arranged inside the elongate housing (12) to be movable along an axial extension (A) thereof. Further, a fixation body (13) is fixedly arranged inside the elongate housing (12), and a spring (14) is arranged between the fixation body (13) and the contact brush (11), the spring (14) being configured to push the contact brush (11) towards an open end (16) of the elongate housing (12) such that an outer end (15) of the contact brush (11) extends outside said open end (16) when the spring is unstrained. The fixation body (13) is plastically form fitted inside the elongate housing (12). The invention also relates to a method of producing such a brush arrangement (10).

Description

The invention relates to a brush arrangement and to a method of producing such a brush arrangement. Specifically, the invention relates to a brush arrangement to be used in a vehicle for leading currents to or from a moving object.BACKGROUNDIn the technical field of automotive vehicles, as in many other technical fields involving electrics, unwanted electric currents fields need to be handled in order to avoid unwanted electrical potentials or ether problems that may arise from occurring currents.For arrangements involving moving parts it is common practice to use a spring-loaded brush to lead away unwanted currents and / or to connect the moving part to ground. The spring is used to make sure that the brush will be in electric contact with the moving part, such as a rotor of a motor, without creating any notable friction losses due to the contact between spring-loaded brush and the moving part.Due to constrains in available the space inside a vehicle it is desirable to provide a spring loaded brush assembly inside a rod that is only marginally larger in diameter than the widest point the brush.The size relation between the rod and the brush makes it difficult to attach the brush in an electrically conductive and structurally robust manner, especially since there is little room for screws or other types of fasteners.In the prior art it is known to provide an elastic element arranged inside the rod housing to which the brush is connected via a spring. The idea is to push the flexible element to a desired position inside the rod housing at which position it is intended to stay fixed means of the friction acting between the brush and the rod housing.A problem with such an arrangement is that it may be difficult to correctly position the elastic element and that it be repositioned over time.It would be advantageous to achieve a brush arrangement overcoming, or at least alleviating, at least one or some of the drawbacks of the prior art.It is an object of the invention to provide an arrangement and method of integrating a spring loaded brush assembly in a rod housing that is applicable to embodiments where the rod housing is only marginally larger in diameter than the brush.This object is achieved in accordance with a first aspect the invention by means of a brush arrangement comprising:- an elongate housing having an axial extension,- a contact brush arranged inside the elongate housing to be movable along the axial extension,- a fixation body fixedly arranged inside the elongate housing, and- a spring arranged between the fixation body and the contact brush, the spring being configured to push the contact brush towards an open end of the elongate housing such that an outer end of the contact brush extends outside said open end when the spring is unstrained. The fixation body is plastically form fitted inside the elongate housing to be .The proposed brush arrangement makes it possible to insert a fixation body that initially has a clearance with respect to the rod housing and may be effortlessly inserted, typically by pushing the brush such that spring force will be enough to move the fixation body into position.In embodiments of the brush arrangement, the elongate housing comprises a radial hole providing an opening through a longitudinal wall of the elongate housing extending at least partially orthogonally to the axial extension of the elongate housing, and wherein the fixation body is form fitted at this radial hole.The radial hole is useful both in that it allows for inspection of a correct positioning of the fixation body and in that allows for insertion of a pressure tool for providing a force to the fixation body so to plastically deform it in a manner that locks the position of the fixation body inside the elongate housing.In embodiments of the brush arrangement, a void is provided in the longitudinal wall of the elongate housing on the opposite side of the radial hole, and wherein an outwardly deformed portion of the fixation body extends into this void.The void is beneficial in that it will provide a predefined counter contour to an outwardly deformed portion of the fixation body to thereby contribute to lock the position of the fixation body.In embodiments of the brush arrangement, the fixation body is made of a soft metal configured to plastically deform when subjected to a pressure.In embodiments of the brush arrangement, the elongate housing has a hollow inside extending in the axial direction from the open end and past the fixation body.The hollow inside is useful in that allows for easy positioning of the fixation body into the hollow inside of the elongate housing.In embodiments of the brush arrangement, a conductor is provided between the fixation body and the contact brush.A conductor may be used to conduct currents from the contact brush to the fixation body. However, as an alternative, the currents could also be conducted by the spring.In embodiments of the brush arrangement, the hollow inside at the open end of the elongate housing has a non-circular cross section corresponding to a non-circular crosssectional shape of the contact brush, such that rotation of the contact brush is inhibited in said hollow insideAccording to a second aspect the invention relates to method of producing a brush arrangement.The method comprises the following steps:- providing an elongate housing that comprises a radial through hole through a longitudinal wall of the elongate housing, at least partially orthogonally to an axial extension of the elongate housing,- positioning a fixation body and a contact brush inside the elongate housing at a distance in the axial extension from each other, a spring being arranged between the fixation body and the contact brush to allow the contact brush to move along the axial extension with respect to fixation body,- fixing the fixation body inside the elongate housing by applying a pressure through the radial through hole towards the fixation body to deform the fixation body to become form fitted with respect to the elongate housing.Other embodiments and advantages will be apparent from the detailed description and the appended drawings. It is understood that all the various embodiments of the brush arrangement as disclosed herein also applies for a vehicle comprising such a brush arrangement.BRIEF DESCRIPTION OF THE DRAWINGSBelow, specific embodiments of the invention will be described with reference to the appended drawings, of which:Fig. 1 is a side view of a brush arrangement,Fig. 2 is a longitudinal sectional view of a brush holder,Fig. 3 is an exploded view of a brush and connector,Fig. 4 is a cut view of a front portion of an empty housing of the brush arrangement,Fig. 5 is a partly cut view of a front portion of the housing the brush arranged inside it.DETAILED DESCRIPTION OF THE SHOWN EMBODIMENTSAspects of the present invention will now be described more fully. Similar reference numerals refer to similar elements throughout the specification. Well-known functions or constructions will not necessarily be described in detail for brevity and / or clarity reasons.In Fig. 1 a brush arrangement is shown in a side view.The brush arrangement 10 comprises an elongate housing 12, also knows as a brush holder, which has an axial extension A. The elongate housing 12 comprises an attachment portion 24 at a rear end 28 of the elongate housing 12 and a front portion 27 with an open end 16, opposite to the attachment portion 24.A contact brush 11, of which only an outer end is visible in Fig. 1, is arranged inside the elongate housing 12. The contact brush 11 is arranged to be movable along the axial extension A inside the elongate housing 12. Also visible in Fig. 1 is a radial hole 17 providing an opening through a longitudinal wall 19 of the elongate housing 12.The brush arrangement 10 is arranged to lead away unwanted currents and / or to connect a moving part to ground by allowing the contact brush 11 to be in contact with the moving object, such as a rotor, and to ultimately lead the currents via the contact brush 11 and the elongate housing 12 to the attachment portion 24, which is configured to be connected to ground, typically by being attached to a grounded part.In Fig. 2, which is a longitudinal sectional view of a brush arrangement 10 it is visible that the elongate housing 12 has a hollow inside 20 in which the contact brush 11 is movably arranged. In the shown embodiment the elongate housing 12 is hollow along its whole extension, but it may also be solid along a rod portion 25 of the elongate housing 12. It is however hollow at its front portion 27 to house the slidable contact brush 11.A fixation body 13 is fixedly arranged in the hollow inside 20 of the elongate housing 12 and a spring 14 is arranged between the fixation body 13 and the contact brush 11. The spring 14 is configured to push the contact brush 11 towards an open end 16 of the elongate housing 12 such that an outer end 15 of the contact brush 11 extends outside said open end 16 when the spring is unstrained, as is illustrated in Fig. 2.In accordance with the shown embodiments, the fixation body 13 is form fitted inside the elongate housing 12. This fixation by form fitting is typically achieved by applying a force or pressure to the fixation body 13 after it has been correctly positioned inside the housing to deform it such that it will become fixed inside the housing 12. Hence, the form fitting is comprised of altering the shape the fixation body 13 such that at least a portion of the fixation body 13 will be in a moving inhibiting relation with at least a portion of the elongate housing 12.Fig. 3 shows the contact brush 11, the fixation body 13, a connector 23, and a connector attachment 29 in an exploded view. In operation, as is illustrated in Figs. 2 and 5, these parts are assembled to one unit. In the assembled state, the connector 23 is fixed inside the contact brush 11 in an electrically conductive manner to lead currents away from the contact brush 11. Further, the connector 23, which is typically a braid, is in its other end attached to the fixation body 13 to conduct any occurring currents to the fixation body 13. In the shown embodiment the connector 23 is attached by means of a connector attachment 29 arranged on the side of the fixation body 13 that faces away from the contact brush 11 so as to effectively limit the extension that the contact brush 11 may move away from the fixation body 13 during operation.The outer end 15 of the contact brush 11, which is adapted to be in contact with the moving part from which the currents are to be lead away, may comprise a low friction electric conductive material, different from the material in the main core of the contact brush 11.In Fig. 4 the inside of the front portion 27 of the elongate housing 12 is schematically shown in a cut view along a longitudinal section of the elongate housing 12. As is visible in this view the open end 16 of the elongate housing 12 has a hollow portion 20b with a non-circular cross section, which corresponds in shape to the non-circular cross sectional shape of the contact brush 11, such that rotation of the contact brush 11 is inhibited inside said hollow portion 20b. In the shown embodiment, the hollow portion 20b and the contact brush 11 have mutually corresponding rectangular sectional shapes, but of course other mutually corresponding rotation inhibiting shapes are possible. It suffices that the contact brush 11 comprises one rotation inhibiting element mating with a corresponding element in the inside of the housing 12.In a hollow portion 20a of the rod portion 25 of the elongate housing 12, extending from the attachment portion of the elongate housing, the cross section may be circular. The two hollow portions 20a and 20b are connected to each other at a transition portion 26. The transition portion 26 is, in the shown embodiment, comprised of a circumferential recess that joins the different cross sections of the two hollow portions 20a and 20b in a smooth manner, preferably without sharp edges. The transition portion 26 is positioned between the open end 16 of the housing 12 and a radial hole 17 providing an opening through a longitudinal wall 19 of the elongate housing 12.Preferably, the hollow portion 20b with a rectangular cross section extends long enough to house the whole of the contact brush 11, but short enough to allow the fixation body 13 to be positioned on the opposite side of the transition portion 26, in the hollow portion 20a with a circular cross section.The radial hole 17 through the longitudinal wall 19 extends at least partially orthogonally to the axial extension A of the elongate housing 12. In the shown embodiment and the fixation body 13 may be form fitted at this radial hole 17, by a plastic deformation of the fixation body 13.Specifically, a void 18 is provided in the longitudinal wall 19 of the elongate housing 12 on the opposite side of the radial hole 17, which is configured to receive an outwardly deformed portion 22 of the fixation body 13. In the shown embodiment the void 18 is provided as a through hole which as aligned with the radial hole 17 on the opposite side of the elongate housing 12. However, the void 18 may also be provided as a recess in the hollow portion 20a of the rod portion 25, opposite to the radial hole 17. The void should be configured to receive and house an outwardly deformed portion of the fixation body 13, such that a positive form locking, or form fitting may be achieved between the fixation body 13 and the void 18.In Fig. 5 it is illustrated in a schematic manner how an outwardly deformed portion 22 of the fixation body 13 extends into the void 18.The method of arranging the brush arrangement inside the elongate housing 12 is preferably achieved in by firstly positioning the fixation body 13 and the contact brush 11 inside the elongate housing 12 at a distance in the axial extension A from each other. The distance between the fixation body 13 and the contact brush 11 will be governed by the spring 14 arranged between them.The spring is configured to allow the contact brush 11 to move along the axial extension A with respect to the fixation body 13 but will be configured and positioned such that an outer end 15 of the contact brush 11 extends outside the open end 16 when the spring 14 is unstrained.The fixation body 13 may be positioned into the inside of the elongate housing 12 by pushing it through the open end 16 thereof, wherein the final positioning of the fixation body 13 is achieved by positioning the contact brush 11 such that the spring action of the spring 14 will act on the fixation body 13, which is easily moved inside the housing in its undeformed state.The radial hole 17 may be used to verify that the fixation body 13 is in a correct position inside the elongate housing 12. Also, the fixation body 13 may be provided with a marking that is visible through the radial hole 17 to facilitate correct positioning thereof.Once, the fixation body 13 is in a correct position inside the elongate housing 12 it may be fixed by applying a pressure through the radial through hole 17 towards the fixation body 13 to deform the fixation body 13 to become form fitted with respect to the elongate housing 12.In the shown embodiment the fixation body 13 is made of a soft metal configured to plastically deform when subjected to a force or pressure, wherein the fixation body 13 is configured to be subjected to such a force after having been positioned inside the elongate housing 12.Typically, the applied force will form an inwardly deformed portion 21 on the side from which the force is applied, wherein an outwardly deformed portion 22 will form on the opposite side of the fixation body 13 or where room is present to allow such a deformation. In the shown embodiment outwardly deformed portion 22 will extend into the void 18.A conductor 23 is provided between the fixation body 13 and the contact brush 11 for connecting the contact brush 11 to ground, via the fixation body 13 and the housing 12, the housing 12 being connected to ground. Typically, the conductor 23 is provided in the form of a braid. The conductor 23 should be of such a length that it will not limit the movement of the contact brush 11 away from the fixation body 13. The conductor 23 may be connected to the rear end 28 of the housing 12, either in that it is provided all the way to said rear end 28 or in that it is connected to the housing via the fixation body 13.Hence, in such an embodiment the rod portion 25 of the housing 12, extending from the fixation body 13 to the rear end 28 of the housing 12, should be made of an electrically conductive material.In an alternative embodiment the spring 14 may be provided in an electrically conductive material to provide the electric connection between the contact brush 11 and the fixation body 13. In such an embodiment, where the spring 14 also functions as a connector, a connector in the form of a braid or the like may be excluded.Above, the invention has been described with reference to specific embodiments. The invention is however not limited to these embodiments. It is obvious to a person skilled in the art that other embodiments are possible within the scope of the following claims.

Claims

1. A brush arrangement (10) comprising:- an elongate housing (12) having an axial extension (A);- a contact brush (11) arranged inside the elongate housing (12) to be movable along the axial extension (A),- a fixation body (13) fixedly arranged inside the elongate housing (12),- a spring (14) arranged between the fixation body (13) and the contact brush (11), the spring (14) being configured to push the contact brush (11) towards an open end (16) of the elongate housing (12) such that an outer end (15) of the contact brush (11) extends outside said open end (16) when the spring is unstrained,wherein the fixation body (13) is plastically form fitted inside the elongate housing (12).

2. The brush arrangement (10) according to claim 1, wherein the elongate housing (12) comprises a radial hole (17) providing an opening through a longitudinal wall (19) of the elongate housing (12) extending at least partially orthogonally to the axial extension (A) of the elongate housing (12), and wherein the fixation body (13) is form fitted at this radial hole (17).

3. The brush arrangement (10) according to claim 2, wherein a void (18) is provided in the longitudinal wall (19) of the elongate housing (12) on the opposite side of the radial hole (17), and wherein an outwardly deformed portion (22) of the fixation body (13) extends into this void (18).

4. The brush arrangement (10) according to claim 1 or 2, wherein the fixation body (13) is made of a soft metal configured to plastically deform when subjected to a pressure.

5. The brush arrangement (10) according to any one of the preceding claims, wherein the elongate housing (12) has a hollow inside (20, 20a, 20b) extending in the axial direction (A) from the open end (16) and past the fixation body (13).

6. The brush arrangement (10) according to claim 5, wherein a conductor (23) is provided between the fixation body (13) and the contact brush (11).

7. The brush arrangement (10) according to any one of the preceding claims, wherein the hollow inside (20b) at the open end (16) of the elongate housing (12) has a noncircular cross section corresponding to a non-circular cross sectional shape of the contact brush (11), such that rotation of the contact brush (11) is inhibited in said hollow inside (20b).

8. Method of producing a brush arrangement (10), comprising the steps of:- providing an elongate housing (12) that comprises a radial through hole (17) through a longitudinal wall (19) of the elongate housing (12), at least partially orthogonally to an axial extension (A) of the elongate housing (12),- positioning a fixation body (13) and a contact brush (11) inside the elongate housing (12) at a distance in the axial extension (A) from each other, a spring (14) being arranged between the fixation body (13) and the contact brush (11) to allow the contact brush (11) to move along the axial extension (A) with respect to fixation body (13),- fixing the fixation body (13) inside the elongate housing (12) by applying a force through the radial through hole (17) towards the fixation body (13) to deform the fixation body (13) to become form fitted with respect to the elongate housing (12).