Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-10-30
2001-01-16
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S592100, C029S610100, C029S613000, C338S053000, C338S050000
Reexamination Certificate
active
06173487
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a resistor unit, and more particularly to a resistor unit installed in a speed controller for controlling the speed of a fan motor employed in an automotive air conditioning device, and a method of producing the resistor unit. More specifically, the present invention is concerned with a resistor unit which generally comprises a resistor block including a flat resistor, a flat insulating plate and a flat heat radiation plate which are respectively positioned against one another, a holder block of molded plastic having the resistor block mounted thereon, a plurality of terminals partially embedded in the holder block and connected to given portions of the flat resistor, and coupling means for coupling the resistor block with the holder block.
2. Description of the Prior Art
A blower unit of an automotive air conditioning device has a blower installed therein. The blower has a fan held in a fan scroll and driven by an electric motor. The speed of the motor is controlled by a speed controller. The speed controller has a resistor unit including a plurality of resistors connected in series. By varying the total resistance of the resistor unit, the voltage applied to the electric motor is varied, so that the rotation speed of the fan can be controlled to, for example, a high level, a neutral level or a low level.
For cooling the speed controller, the speed controller is usually placed in an air flow duct of the air conditioning device through which cool air flows. Thus, it is desired to reduce the size of the speed controller as small as possible for obtaining a satisfactory air flow in the air flow duct.
Hitherto, for reducing the size and weight of the speed controller, there has been proposed a compact resistor unit called “flat resistance” which generally comprises a flat insulating base board and a resistor pattern printed on the base board. The compact unit having such a flat resistance type is shown in, for example, Japanese Utility Model First Provisional Publications Nos. 1-125708 & 2-145507.
Furthermore, at present, there has been proposed a very compact light weight resistor unit, which is schematically shown in
FIG. 8
of the accompanying drawings.
As shown in the drawing, the resistor unit comprises a flat resistor
1
, two flat insulating plates
2
a
and
2
b
which are placed in intimate contact against the respective opposite surfaces of the flat resistor
1
, and two flat heat radiation plates
3
a
and
3
b
which are placed in intimate contact against the outer surfaces of the two flat insulating plates
2
a
and
2
b
. With the parts thus united, a resistor proper part
4
is created.
The resistor block
4
is mounted to a terminal-mounted plastic holder block
6
. That is, the holder block
6
has a plurality of terminals
5
of metal mounted thereto. The holder block
6
comprises a rectangular coupler portion
7
and an elongate flange portion
8
on which the terminals
5
are aligned. Each terminal
5
has a lower part embedded in the plastic holder block
6
. A so-called “insert molding technique” is used for producing the terminal-mounted plastic holder block
6
.
The flange portion
8
is integrally formed at both ends thereof with connecting lugs
9
a
and
9
b
through which the resistor block
4
is secured to the holder block
6
with the aid of rivets
10
. That is, each rivet
10
extending between the heat radiation plates
3
a
and
3
b
is tightly received in an opening formed in the connecting lug
9
a
or
9
b
. Although not shown in the drawing, upper portions of the heat radiation plates
3
a
and
3
b
are connected through other rivets. Designated by numeral
11
is a projected portion in which a fuse (not shown) is installed.
However, due to inherent construction, the above-mentioned resistor unit has failed to achieve a satisfied durability against shocks applied thereto. That is, because the connecting lugs
9
a
and
9
b
are constructed of plastic which is poor in durability, it tends to occur that the lugs
9
a
and
9
b
are broken or at least damaged when a strong shock is applied thereto. In fact, such breakage tends to occur when the rivets
10
are brought into engagement with the lugs
9
a
and
9
b
for fixing the resistor block
4
to the holder block
6
. Such breakage becomes much severe when the plastic lugs
9
a
and
9
b
are deteriorated due to long usage of the resistor unit. Furthermore, the plastic lugs
9
a
and
9
b
have poor dimensional stability, which tends to induce a loose assembly of the resistor unit.
Furthermore, hitherto, the arrangement of a fuse for such resistor unit has been given little consideration. In fact, in a conventional arrangement of a fuse, there is a possibility that a burnt out part of the fuse causes a short-circuit of two parts. That is, when the fuse is actually operated, the burnt out part of the fuse tends to dangle from a proper position, thereby increasing the possibility of such undesired short-circuit. In fact, the burnt out part of fuse tends to induce various problems in the circuit.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a resistor unit of an automotive air conditioning device, which is free of the above-mentioned drawbacks.
It is a main object of the present invention to provide a resistor unit of an automotive air conditioning device, which has a satisfactory durability against shocks applied thereto.
It is another object of the present invention to provide a resistor unit of an automotive air conditioning device, which is equipped with a fuse holding structure by which operation of a fuse is assured.
It is still another object of the present invention to provide a resistor unit of an automotive air conditioning device, which is equipped with a fuse holding structure by which a fuse is tightly held in a fuse receiving portion of the resistor unit.
It is a further object of the present invention to provide a method of producing the resistor unit.
According to a first aspect of the present invention, there is provided a resistor unit which comprises a resistor block including a flat resistor, a flat insulating plate and a flat heat radiation plate which are respectively positioned against one another; a holder block of molded plastic on which the resistor block is mounted; a plurality of terminals of metal partially embedded in the holder block, the terminals being connected to given portions of the flat resistor; connecting lugs partially embedded in the holder block; and securing means for securing the resistor block to the connecting lugs, wherein the connecting lugs are constructed of metal.
According to a second aspect of the present invention, there is provided a resistor unit which comprises a resistor block including a flat resistor, a flat insulating plate and a flat heat radiation plate which are respectively positioned against one another; a holder block of molded plastic on which the resistor block is mounted; a plurality of terminals of metal partially embedded in the holder block, the terminals being connected to given portions of the flat resistor; a fuse connected to selected two of the terminals; means for defining in the selected two terminals respective recesses which are positioned below the fuse, the recesses being so sized and shaped so as not to establish an electric connection or short-circuit between the selected two terminals by the fuse once the fuse is actually operated; and means for coupling the resistor block with the holder block.
According to a third aspect of the present invention, there is provided a resistor unit which comprises a resistor proper part including a flat resistor, a flat insulating plate and a flat heat radiation plate which are respectively positioned against one another; two projections formed on separated resistor pattern parts of the flat resistor; a fuse connected to the projections to extend therebetween, the fuse and the two projections thus constituting a raised structure whi
Ishii Takashi
Murata Hiroyuki
Yamamoto Shuko
Calsonic Corporation
Foley & Lardner
Smith Sean
Young Lee
LandOfFree
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