Electricity: conductors and insulators – Conduits – cables or conductors – Accessories
Reexamination Certificate
2002-08-08
2004-07-06
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Accessories
C174S09400S, C029S860000, C439S874000
Reexamination Certificate
active
06759594
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wheel speed sensor for use in detecting wheel speeds of vehicles such as automobiles and motorcycles. Further, the present invention relates to a terminal to which an electric wire is connected in which a plurality of thin metallic wires are bundled together to constitute a conducting portion and a method for welding the electric wire to the terminal.
2. Description of the Related Art
In general, wheel speed sensors attached to wheels of a vehicle, respectively, to detect wheel speeds of a running vehicle are designed to detect the rotation of rotors which rotate together with axles coupled to the respective wheels. The rotors contain a magnetic material and magnetic sensors such as Hall ICs and MR elements are used to detect the rotation of the rotors.
However, in the event that the magnetic sensors such as Hall ICs are provided directly on the axle portions of the running vehicle, there is a risk that the sensors maybe damaged by flying stones, and moreover, a connecting portion between lead portions and electric wires is liable to be disconnected.
To cope with this problem, it is a conventional common practice in wheel speed sensors to mold a detection element such as a Hall IC by a synthetic resin together with a connecting portion with the cords to improve the durability thereof.
As an example of the resin-sealed wheel speed sensor, a wheel speed sensor disclosed in JP-A-2000-206130 is conventionally known.
The construction of this conventionally known wheel speed sensor will be briefly described with reference to FIG.
11
.
A wheel speed sensor has a detection element
110
such as a Hall IC, electric wires
112
connected to the detection element, an accommodating portion
113
for accommodating the detection element
110
and a lid unit
114
for covering an upper face of the accommodating portion
113
in which the detection element
110
is accommodated.
The electric wires
112
are connected to terminals
111
of the detection element
110
by welding or clamping. Then, the detection element
110
to which the electric wires
112
are so connected is accommodated in the accommodating portion
113
.
The lid unit
114
is attached to the upper face of the accommodating portion
113
in which the detection element
110
is accommodated.
Finally, an assembly into which the detection element
110
, the electric wires
112
, the accommodating portion
113
and the lid unit
114
are assembled is disposed within a mold (comprising a stationary mold half and a movable mold half) (not shown) so that the whole periphery of the assembly is sealed with a synthetic resin, whereby the wheel speed sensor is formed.
As has been described heretofore, in the conventional wheel speed sensor, the electric wires have to be connected to the terminals of the detection element by welding or clamping, the detection element to which the electric wires are connected has to be accommodated in the accommodating portion, and the lid unit has to be mounted on the accommodating portion prior to sealing with the resin, this causing a problem that a number of man hours are required to assemble the respective constituent component parts.
In addition, in this construction in which the detection element is accommodated in the accommodating portion for sealing with the resin after the electric wires have been connected to the terminals of the detection element, stress is applied to the terminals and the electric wires before they are accommodated in the accommodating portion, and this may trigger a risk that the connection between the detection element and the electric wires is disconnected.
In addition, in order to position an assembly to which the electric wires are connected within a mold, positioning projections are provided on an accommodating portion and a lid unit in such a manner as to project therefrom, and positioning portions are formed in the mold.
In resin molding the assembly, the assembly is placed in an opened mold (a stationary mold half) and is positioned by bringing the positioning projections into engagement with the positioning portions on the mold side, and thereafter, the assembly is clamped with the stationary mold half and a movable mold half and is them molded with a resin to form a housing.
In the wheel speed sensor disclosed in the aforesaid JP-A-2000-206130, of the positioning projections provided at a plurality of positions around the periphery of the assembly, firstly, the projections corresponding to the positioning portions on the stationary mold half are brought into engagement with the same positioning portions, and then the positioning projections corresponding to the positioning portions on the movable mold half are brought into engagement with the same positioning projections. Due to this, the posture and position of the assembly within the cavity tend to remain unstable until the assembly is clamped by the mold halves. Since the assembly is placed in the cavity while the electric wires are connected to the assembly with an L-shape, the assembly is liable to be twisted or floated within the cavity. When there is caused a deviation in position of the assembly within the cavity, it is not possible to form a uniform resin sealed portion, whereby the penetration of water or the like into the assembly from an exposed portion thereof is liable to happen.
In addition, in the event that a plurality of positioning portions are attempted to be provided on both the assembly and the mold (the stationary and movable mold halves), a production cost for the assemblage of the component parts is increased, and, time has to be spent in placing the assembly in the mold and therefore the assemblage of the component parts is deteriorated. Moreover, the mold and the wheel speed sensor itself have to be enlarged.
Next, a conventional method for welding an electric wire in which a plurality of thin metallic wires are bundled together to constitute a conducting portion (a signal wire) to another member will be described with reference to
FIGS. 12 and 13
.
FIG. 12
shows an electric wire
210
having a certain thickness being welded to a metallic terminal
211
.
An electrode
212
for use in the welding is constituted by two electrodes; one of them is one electrode
212
a
which contacts a conducting portion
213
of the electric wire
210
and the other is the other electrode
212
b
which contacts the terminal
211
. A recessed groove
214
is formed in the one electrode
212
a
for accommodating therein the conducting portion
213
.
The conducting portion
213
is held in the recessed groove
214
formed in the one electrode
212
a
and is then pressed against the terminal
211
by the one electrode
212
a.
When welding, electric current is allowed to flow from the one electrode
212
a
toward the other electrode
212
b
through the conducting portion
213
and the terminal
211
(as shown by a narrow A in the figure). The conducting portion
213
and the terminal
211
are heated by the current for welding.
Thus, in a case where the electric wire
210
of a predetermined thickness is welded to the terminal
211
, since the conducting portion
213
is accommodated in the recessed groove
214
in the electrode
212
, the conducting portion
213
can be welded to the terminal
211
without getting discrete to the individual thin metallic wires when welding.
FIG. 13
shows an electric wire
215
of a diameter which is smaller than that of the electric wire shown in
FIG. 12
being welded to a terminal
211
. In addition,
FIG. 13
shows that a conducting portion
216
gets discrete to individual thin electric wires
219
.
In this case, too, one electrode
218
a
is disposed on a conducting portion
216
side in which a recessed groove
217
matching the conducting portion
216
in size is formed, while the other electrode
218
b
which is flat is disposed on a terminal
211
side.
Note that in the event that the diameter of the electric wire is small, the individual thin metallic wires
219
,
219
.
Fukazawa Shigeru
Iijima Jun
Ota Kazuhiro
McGuireWoods LLP
Nino Adolfo
Nissin Kogyo Co. Ltd.
Reichard Dean A.
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