U.S. patent application number 11/453385 was filed with the patent office on 2006-11-23 for carbon brush and method and material for the production thereof.
Invention is credited to Gerhard Bachauer, Christian Bottger.
Application Number | 20060260436 11/453385 |
Document ID | / |
Family ID | 34683604 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060260436 |
Kind Code |
A1 |
Bachauer; Gerhard ; et
al. |
November 23, 2006 |
Carbon brush and method and material for the production thereof
Abstract
Carbon brush comprising a base body produced from carbon
material by pressing and optionally sintering and a layer of a
metallic material applied to an outer surface of the base body by
pressing and possibly sintering, the metal layer being connectable
to a metallic carrier by welding or soldering.
Inventors: |
Bachauer; Gerhard; (Bad
Ischl, AT) ; Bottger; Christian; (Gravenwiesbach,
DE) |
Correspondence
Address: |
ALIX YALE & RISTAS LLP
750 MAIN STREET
SUITE 1400
HARTFORD
CT
06103
US
|
Family ID: |
34683604 |
Appl. No.: |
11/453385 |
Filed: |
June 15, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/EP04/14235 |
Dec 14, 2004 |
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11453385 |
Jun 15, 2006 |
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Current U.S.
Class: |
75/231 ;
419/6 |
Current CPC
Class: |
H01R 39/39 20130101;
H01R 39/20 20130101 |
Class at
Publication: |
075/231 ;
419/006 |
International
Class: |
B22F 7/06 20060101
B22F007/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2003 |
DE |
103 59 896.0 |
Claims
1. Carbon brush comprising a base body produced from carbon
material and a metal layer which is applied to an outer surface of
the base body and can be connected by welding or soldering to a
metal carrier, the metal layer being a layer made from metal powder
by pressing and optionally sintering and undetachably bonded to the
base body by pressing and optionally sintering, characterized in
that the metal layer contains a base metal (A) and at least one
further metal (B) of higher ductility and lower melting point than
the base metal (A), the further metal (B) being present at least
predominantly as a metal phase which is separate from the base
metal (A) and is intimately bonded to the base metal (A) by
pressing and optionally sintering but predominantly does not form
an alloy therewith.
2. Carbon brush according to claim 1, characterized in that the
further metal (B) is so chosen that at sintering temperature in the
liquid phase it wets the base metal (A) but does not diffuse into
said base metal, or only slightly.
3. Carbon brush according to claim 1, characterized in that the
further metal (B) is composed of tin, indium or bismuth or an alloy
thereof.
4. Carbon brush according to claim 1, characterized in that the
further metal (B) has a melting point of not more than 400.degree.
C. and a breakage elongation of not less than 5%.
5. Carbon brush according to claim 1, characterized in that the
further metal (B) is present in a proportion between 1.5 and 15% by
weight of the metal layer.
6. Carbon brush according to claim 1, characterized in that the
metal layer additionally contains an additive (C) of non-metallic,
organic and/or inorganic material.
7. Carbon brush according to claim 6, characterized in that the
non-metallic additive (C) contains stearates, graphite, talcum, SiC
or Al.sub.2O.sub.3.
8. Carbon brush according to claim 1, characterized in that the
metal layer thereof is connected to a carrier of metal by welding
or soldering.
9. Carbon brush according to claim 8, characterized in that the
carrier is a leaf spring.
10. Material for producing a weldable and/or solderable layer of a
carbon brush comprising a powder mixture which contains a
pulverulent main metal (A), in particular copper or copper alloy,
and a pulverulent additive metal (B) of greater ductility and lower
melting point than the main metal, the main metal (A) being copper
or a copper alloy and the additive metal (B) being tin, indium or
bismuth or an alloy thereof.
11. Material according to claim 10, characterized in that it
contains a pulverulent additive (C) of non-metallic, organic and/or
inorganic material.
12. Material according to claim 10, characterized in that the
additive metal (B) is present in a proportion of 1.5 to 15% by
volume of the powder mixture.
13. Method for producing a carbon brush comprising a base body of
carbon material and a metal layer undetachably bonded thereto,
comprising the steps: a) producing the base body by pressing and
sintering of a pulverulent carbon-containing material; b)
simultaneously with or following step a): producing the metal layer
by pressing and sintering a pulverulent metallic material, the
metal layer being bonded undetachably to the base body by pressing
and sintering; c) the pulverulent metallic material contains a
mixture of a pulverulent base metal A and at least one pulverulent
further metal B of greater ductility and lower melting point than
the base metal A; and d) the further metal B and the sintering
temperature are so selected that during the sintering the further
metal in the liquid phase wets the base metal A but does not, or
only slightly, diffuse into the latter, whereby the further metal B
is present at least predominantly as a metal phase separate from
the base metal A and predominantly not alloyed therewith.
14. Method according to claim 13, characterized in that the main
metal A comprises copper or copper alloy and the further metal B
comprises tin, indium or bismuth or an alloy thereof.
15. Carbon brush according to claim 2, characterized in that the
further metal (B) is composed of tin, indium or bismuth or an alloy
thereof.
16. Carbon brush according to claim 2, characterized in that the
further metal (B) is present in a proportion between 1.5 and 15% by
weight of the metal layer.
17. Carbon brush according to claim 3, characterized in that the
further metal (B) is present in a proportion between 1.5 and 15% by
weight of the metal layer.
18. Carbon brush according to claim 4, characterized in that the
further metal (B) is present in a proportion between 1.5 and 15% by
weight of the metal layer.
19. Carbon brush according to claim 2, characterized in that the
metal layer additionally contains an additive (C) of non-metallic,
organic and/or inorganic material.
20. Material according to claim 11, characterized in that the
additive metal (B) is present in a proportion of 1.5 to 15% by
volume of the powder mixture.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of PCT Patent Application
No. PCT/EP04/014235 filed on Dec. 14, 2004.
BACKGROUND OF THE INVENTION
[0002] Carbon brushes for electric motors or generators must be
secured to a support which ensures the necessary application
pressure on the commutator or the like and permits the follow-up
movement corresponding to the wear of the carbon brush. A carrier
for the carbon brush which is particularly suitable because of its
simplicity, cheapness and low weight is a leaf spring which in
addition to the function of supporting and guiding can also perform
the function of current transmission. However, the problem arises
of securing the carbon brush to the leaf spring in such a manner
that on the one hand the necessary mechanical strength in long-term
operation and on the other the transmission of large currents is
ensured.
[0003] From DE 102 07 406 A1 a carbon brush is secured to a leaf
spring serving as carrier by welding or soldering and for this
purpose is tin-plated, nickel-plated or coated with metal in
another manner at the surface to be joined to the carrier.
[0004] From DE 40 40 002 A1 a carbon brush is known for a fuel pump
motor which is soldered to a leaf spring serving as carrier and for
this purpose has a solderable layer which consists of a copper
layer and a tin layer applied thereto. However, with such
metallizations, as a rule metal layers applied by electroplating,
it is difficult to obtain a solder or weld connection between the
carbon brush and leaf spring which has a mechanical, thermal and
electrical load capacity adequate for long-term operation. In
particular, the stress compensation between the carbon brush and
the leaf spring involves problems due to the difference in modulus
of elasticity and thermal coefficient of expansion.
[0005] From DE 2444957 A1 it is known to produce a carbon brush
provided with a solderable or weldable metallic layer by jointly
compressing a layer of pulverulent carbon-containing material and a
layer of metal powder and then conducting a heat treatment. The
metal powder consists of copper.
[0006] From U.S. Pat. No. 3,601,645 it is known to produce an
electrical contact brush having a base body consisting of metal and
carbon material and a metal layer undetachably connected to said
base body by pressing and sintering a pulverulent metal-carbon
material for the base body and a metal powder, wherein the metallic
layer can consist of copper, iron or an alloy.
[0007] From DE 32 17 217 C2 it is known to produce a contact brush
by pressing a bundle of metal-coated carbon fibres, wherein the
metal coating of the carbon fibres can consist inter alia of
copper, aluminium, tin, iron or an alloy thereof.
SUMMARY OF THE INVENTION
[0008] The invention is based on the problem of providing a carbon
brush and a method and a material for the production thereof which
permits a simple bonding to a leaf spring which can bear high
mechanical and electrical loads.
BRIEF DESCRIPTION OF THE DRAWING
[0009] The FIGURE is a schematic view of a carbon brush welded to a
leaf spring.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] The invention will be explained hereinafter in detail with
reference to an example of embodiment.
[0011] It is commercially of interest to weld carbon brushes to
leaf springs because this enables a bond to be obtained through
which high currents of more than 15 .ANG. can be transmitted. This
would enable this cheaper design to be used also for motor types
which because of the high demands regarding the current strength in
the blocking test or also in continuous operation hitherto could
not be produced using this concept. Motors of this type, in which
the carbon brush with small dimensions must transmit high currents,
are for example actuators in motor vehicles, for example drive
mechanisms for window lifters, seat adjustments, sunshine roofs,
mirror adjustments and the like.
[0012] According to the invention a carbon brush is provided which
apart from the usual one-layer or multi-layer base body of pressed
and sintered carbon material has at least one outer layer of
metallic material which ensures the weldability or solderability of
the carbon brush, this metallic layer likewise being made by
pressing and sintering and connected to the base body.
[0013] For welding or soldering a carbon brush a suitable welding
method (for example ultrasonic welding, laser welding or the like)
or soldering method must be applied and furthermore to produce the
carbon brushes having a weldable metallic layer a material must be
available which on the one hand in the powder-metallurgical
processing bonds well to the carbon material of the base body of
the carbon brush and on the other hand can be readily welded or
soldered with the method chosen. It has been found that pure copper
and its alloys as well as iron or steel are not suitable because
their coefficient of thermal expansion and modulus of elasticity
are not compatible with those of the carbon material of the base
body of the carbon brush in the sintering method. Materials which
are similar to the carbon material of the base body of the carbon
brush cannot be employed either because due to the graphite
component contained therein they cannot be welded.
[0014] According to the invention it has been found that a metallic
material in the form of a powder mixture of a base metal component
A, a ductile and low-melting metal component B and possibly further
additives C meets both requirements at the same time, that is the
good bonding by pressing and sintering with the functional carbon
material of the base body of the carbon brush on the one hand and
the good weldability or solderability on the other hand.
[0015] According to the invention component A constitutes the major
part, preferably more than 80% of the material and preferably
comprises copper or a copper alloy with for example Sn, Zn, Ni or
Ag. It is preferably in powder form having a mean diameter D.sub.50
of 15 to 25 .mu.m.
[0016] Component B is an additional metal which has a higher
ductility and lower melting point than the component A. Preferably,
the melting point is 400.degree. C. or less and the breaking
elongation 5% or more. The component B consists preferably of Sn or
an alloy of Sn with for example Cu, Ag, Sb. Zn, Ga, In, Bi or Pb.
The metal component B may also consist of In and/or Bi or an alloy
with In or Bi. Its proportion in the total powder mixture of the
material is preferably 1.5 to 15% by weight. The additional metal B
is present preferably in a mean grain size of D.sub.50 of 15 to 35
.mu.m.
[0017] In addition, the material may preferably contain one or more
non-metallic organic and/or inorganic additives C in powder form.
Possible additives of this type are for example stearates,
graphite, talcum, SiC or A1.sub.2O.sub.3. Their mean grain size
D.sub.50 is preferably not more than 20 .mu.m.
[0018] A preferred example of the composition of the material is
(figures in percent by weight): [0019] A: 92% Cu (D.sub.50 15-25
.mu.m) [0020] B: 7.5% Sn (D.sub.50 15-55 .mu.m) [0021] C: 0.5%
graphite (D.sub.50 .ltoreq.20 .mu.m)
[0022] The material indicated can be excellently processed
powder-metallurgically by pressing and sintering and bonds
excellently to the functional layer (base body) of the carbon brush
to form a metal layer having excellent welding and soldering
properties. It has been found that in the pressing and sintering
the low-melting and ductile metal B wets the base metal A but does
not diffuse into the latter, or only to a slight extent.
[0023] It is thereby ensured that the predominant or at least an
adequate part of the metal B is not alloyed to the metal A after
the sintering but is present in pure form and thus the desired
ductility of the metal layer is achieved. Due to the ductility of
the material a stress compensation is achieved between the base
body 1 of the carbon brush and the weldable metal layer 2 on the
one hand and the leaf spring welded to the metal layer 2 on the
other hand.
[0024] In other words, in the sintered metal layer 2 made by
pressing and sintering the base metal A and at least the
predominant part of the other metal B form two separate metal
phases which although being intimately connected to each other by
the pressing and sintering are not, however, substantially alloyed
with each other.
[0025] The heat treatment, that is the sintering of the metal
layer, is carried out at a temperature which is lower than the
melting point of the base metal A but higher than the melting point
of the further metal B. This is thus preferably a liquid sintering
in which the further metal B is present in the liquid phase but the
base metal A in the solid pulverulent phase. If the base metal A is
copper and the further metal B tin, the sintering temperature is
advantageously in the range from 300 to 700.degree. C., preferably
in the range from 400 to 500.degree. C.
[0026] The non-metallic organic or inorganic additive C is not
wetted by the metal B in the sintering process and thereby prevents
any undesirably great diffusion of the metal B into the base metal
A.
[0027] The attached drawing illustrates schematically a carbon
brush according to the invention welded to a leaf spring.
[0028] The carbon brush comprises a base body 1 made in the usual
manner in one or more layers from a conventional carbon material
for carbon brushes, in particular a graphite mixture containing
additives, by pressing and heat treatment (sintering). The
excellently weldable or solderable metal layer 2, which is made
from the aforementioned pulverulent material according to the
invention likewise by pressing and possibly sintering, is
undetachably connected or bonded to the base body 1. The base body
1 and weldable metal layer 2 may be simultaneously made and bonded
together by pressing and sintering or the base body 1 may be
prefabricated and the weldable metal layer 2 subsequently formed
thereon by pressing and sintering.
[0029] The easily weldable metal layer 2 enables the entire carbon
brush to be secured to a leaf spring 3 by welding, for example by
weld spots 4 or for instance by a continuous weld seam.
[0030] The thickness of the sintered metal layer 2 depends on the
requirements of the welding or soldering technique selected for
connecting to the leaf spring 3. The thickness of the metal layer 2
preferably lies in the range from 0.2 to 5 mm. For a soldering
connection to the leaf spring 2 as a rule a thickness of the metal
layer 2 of less than 1 mm, in particular in the range from 0.2 to
0.5 mm, should suffice. For a weld joint as a rule a thickness of
at least 1 mm, for example in the range from 2 to 4 mm, would be
advantageous.
* * * * *