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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates generally to a clothes washing machine having
an electronically controlled motor and, more particularly, to such a
machine for advantageously utilizing heat resulting from motor control
circuit losses, which would otherwise be wasted energy.
There have been a number of proposals to eliminate the mechanical
transmission conventional in clothes washing machines for converting
relatively high speed unidirectional motor rotation to low speed
oscillatory (reversing) motion for agitation. These proposals envision
coupling of a reversible, speed controllable DC motor either directly or
through simple reduction gearing to the washing machine agitator. Through
suitable control of the motor winding energization, desired agitator
motion can be effected.
A number of suitable DC motor control circuits have been proposed employing
various forms of semiconductor switching elements for effecting the
desired control of motor rotational velocity and direction. By way of
example, without in any way intending to limit the scope of the invention,
such semiconductor switching elements include power bi-polar transistors,
power field effect transistors, silicon controlled rectifiers (SCR's),
triacs, and other forms of thyristors. Additionally, many such circuits
employ free-wheeling diodes. Examples of such circuits may be found in the
following U.S. Patents: Elliott et al U.S. Pat. No. 3,152,462; Sones et al
U.S. Pat. No. 3,152,463; Crane et al U.S. Pat. No. 3,369,381; and Lake
U.S. Pat. No. 3,503,228. Further examples may be found in the following
commonly-assigned U.S. patent applications: Ser. No. 109,587 filed Jan. 4,
1980, by Robert P. Alley Ser. No. 109,579, filed Jan. 4, 1980, by Robert
P. Alley and Richard C. Weischedel; and Ser. No. 109,705, filed Jan. 4,
1980, by John F. Park.
In such circuits, the semiconductor motor control elements are generally
operated in a high efficiency switching mode such that minimal losses
occur in the semiconductor switching elements. However, due to the
substantial power switching requirements to control up to a horsepower DC
motor with directional reversals more than once per second, substantial
circuit losses, particularly in the switching transistors, nevertheless
occur. These circuit losses are in the order of 25 to 70 watts.
As is known, such heating of power semiconductors results in a temperature
rise which would rapidly destroy the semiconductors if not somehow
dissipated. For this reason, heat sinks are conventionally provided for
power semiconductors to carry away this excess heat.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to utilize this otherwise
wasted heat resulting from losses in semiconductor switching elements, as
well as other circuit losses, associated with motor power control circuits
in clothes washing machines.
Briefly stated, and in accordance with a general concept of the invention,
it is recognized that such circuit losses can perform the useful function
of heating the wash water. Not only is the heat thus put to an
advantageous use, but the problem of heat sinking the semiconductor
heating elements is lessened. Even with wash water at a temperature which
would be termed "hot", the semiconductor junctions may be operated at an
even higher temperature, thus permitting the flow of heat from the
semiconductor elements, as well as other circuit components, to the wash
water. For example, the wash water may have a temperature as high as
60.degree. C., and the semiconductor elements may have a temperature as
high as 70.degree. C.
It should be noted that the invention is not intended as a substitute for
warm or hot incoming wash water, but rather provides auxiliary warming of
the wash water which, at least, keeps the water from cooling as fast as it
would otherwise during a wash cycle.
Briefly stated, and in accordance with a more particular aspect of the
invention, a laundry machine for washing or cleaning clothes and the like
using liquid, for example, water or other suitable fluid, includes an
agitator, and an electric motor for driving the agitator. The laundry
machine additionally includes motor power control circuitry having
semiconductor devices for controlling energization of the motor, the
circuitry generating heat as a result of circuit losses. In particular
accordance with the invention, the laundry machine includes heat transfer
structure for transferring heat generated by the circuitry to the washing
liquid.
In one form, the laundry machine includes a pump for recirculating washing
liquid, and the heat transfer structure comprises a semiconductor heat
sink included as an element of the pump. More particularly, the heat
transfer structure is in the form of a metallic plate-like element, one
side of which is in contact with the washing liquid.
Preferably, the metallic plate-like element is aluminum, and carries a
non-metallic layer of high thermal conductivity and high electrical
resistivity, for example, alumina (Al.sub.2 O.sub.3) or beryllia (B.sub.e
O), and metallic conductors, for example, copper, are direct bonded to the
non-metallic layer. The semiconductor devices are in turn direct bonded to
the copper or metallic conductors. These bonding techniques are more fully
described in the commonly-assigned Burgess et al U.S. Pat. No. 3,744,120
and the commonly-assigned Babcock et al U.S. Pat. No. 3,766,634, the
entire disclosures of which are hereby incorporated by reference.
In one form of the invention, the heat transfer structure forms a base
plate for a self-contained module including the motor power control
circuitry, all being of fairly compact configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
While the novel features of the invention are set forth with particularity
in the appended claims, the invention, both as to organization and
content, will be better understood and appreciated, from the following
detailed description taken in conjunction with the drawings in which:
FIG. 1 is a highly schematic representation of a direct drive clothes
washing machine;
FIG. 2 is an exploded perspective view of the manner in which the
circuitry-containing module of the FIG. 1 washing machine may be arranged
in heat transfer relationship with water in a recirculating pump;
FIG. 3 is a cross-sectional view showing direct bonding techniques
preferred in the practice of the invention; and,
FIG. 4 is a bottom sectional view, taken along line 4--4 of FIG. 2, showing
semiconductor bodies, copper conductors and alumina sheet elements mounted
to the heat sinking base plate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, wherein identical reference numerals denote
similar or corresponding elements throughout the various view, FIG. 1 is a
highly schematic representation of a clothes washing machine 10 having a
conventional agitator 12 and a tub 14 containing wash water 16 and driven
by a bi-directional electronically commutated motor (ECM) 18 capable of
producing relatively slow oscillation of the agitator 12 during a wash
cycle, and relatively high speed unidirectional spinning of the agitator
12 and tub 14 during a spinout cycle. Both types of motions are
implemented by means of appropriate control of the voltage and current
applied to the windings of the motor 18 by an electronic motor power
control circuit generally designated 20.
Also seen in FIG. 1 is a connection mechanism 22 comprising a shifting
device and a relatively simple reduction gearing mechanical transmission.
The connection mechanism 22 has an input shaft 24 driven by the motor 18,
an output shaft 26 for driving the agitator 12, and a connection to the
tub 14. The connection mechanism 22 is operable in an agitate mode to
transmit oscillatory motion of the input shaft 24 to the output shaft 26
to effect agitation and the laundering of clothes within the tub 14. In a
spinout mode, the connection mechanism 22 is operable to transmit
unidirectional rotation of the input shaft 24 to effect conjoint
unidirectional rotation of the agitator 12 and the tub 14. A detailed
description of a suitable connection mechanism 22 may be found in the
commonly-assigned Erdman application Ser. No. 077,656, filed Sept. 21,
1979.
The particular clothes washing machine 10 illustrated in FIG. 1
additionally includes a motor driven pump 28 for recirculating the wash
water 16, for example, to provide continuous filtering of the wash water
16 for removing lint and the like by means of a filter and recirculating
path which are not shown, or to operate an additive dispensing system (not
shown).
With reference now to FIG. 2, it will be seen that the circuitry 20 of FIG.
1 comprises a self contained module 20 mounted in heat transfer
relationship with the pump 28, more particularly, in heat transfer
relationship with the wash water 16 recirculated therethrough.
The module 20 comprises a disc-like aluminum base plate 30 secured to the
underside of the pump 28 by means of a flange 32 of channel configuration,
with the base plate 30 forming an element of the pump 28 having the top
side thereof (in the FIG. 2 orientation) in direct contact with the wash
water 16 which, it will be understood, circulates through the pump 28.
The module 20 additionally includes an outer housing 44, with a number of
electrical connection terminals 36 extending from the bottom thereof and
connected to circuitry therewithin. By way of example, a pair of terminals
38 serve to input 120 volt AC power supplied from a conventional household
branch circuit, four terminals 40 serve to receive input control commands
concerning desired rotational velocity and direction of the motor 18, and
six terminals 42 are for connection to the windings (not shown) of the
motor 18.
An outer housing or drip shield 44 completes the FIG. 2 assembly, so as to
protect the power control module 20 and the electrical connections thereto
from water.
No particular electrical control circuitry for the motor 18 is described in
detail herein, as the present invention is not concerned with circuit
details. Rather, in accordance with the present invention it is assumed
that the power control circuitry within the module 20 contains various
semiconductor control devices, perferably operated in a switching mode, to
effect the required motions of the motor 18, as described hereinabove. By
way of example, such power control circuits are described in the following
commonly-assigned U.S. patent applications: Ser. No. 109,587, filed Jan.
4, 1989, by Robert P. Alley; Ser. No. 109,579, filed Jan. 4, 1980, by
Robert P. Alley and Richard C. Weischedel; Ser. No. 109,705, filed Jan. 4,
1980, by John F. Park; and Ser. No. 077,656, filed Sept. 21, 1979, by
David M. Erdman.
In FIG. 3, a cross-sectional view shows the preferred technique for
mounting heat generating semiconductor switching elements comprising
circuitry within the module 20 to the aluminum base plate 30. More
particularly, the aluminum base plate 30 carries a non-metallic layer 46
of high thermal conductivity and high electrical resistivity, such as
alumina (Al.sub.2 O.sub.3) or beryllia (B.sub.e O). A metallic conductor
48, for example, copper, is direct bonded to the non-metallic layer 46,
and a representative semiconductor body 50 comprising a controlled
switching element is in turn direct bonded to the copper or metallic layer
48. The direct bonding techniques employed may be those disclosed in the
above-referenced commonly-assigned Burgess et al U.S. Pat. No. 3,744,120,
and Babcock et al U.S. Pat. No. 3,766,634.
To complete the FIG. 3 representative structure, a representative lead 52
is bonded to the semiconductor body 50 using conventional fabrication
technqiues.
It will be understood that the non-metallic layer 46 comprises a sheet of
limited extent suitably bonded to the base plate 30, preferably after the
semiconductor body 50 and the metallic conductor 48 are bonded to the
non-metallic layer 46. This subsequent bonding of the non-metallic layer
46 to the base plate 30 may be accomplished using a high temperature
epoxy, or by providing metallization on the layer 46 and soldering to the
base plate 30.
While the particular embodiment illustrated is one which is presently
preferred, it will be appreciated that other techniques for providing
circuitry in heat transfer relationship with a metallic plate may be
employed. One example is an enamel on steel circuit board with printed
copper conductors on one side, and the other side in contact with the wash
water. It will further be appreciated that the side of the base plate 30
in contact with the water may be either bare or coated with an
electrically insulating layer of the same material as the layer 46. This
is an especially likely configuration in the case of an enamel on steel
circuit board.
With reference now to FIG. 4, there is shown a representation of the manner
in which power switching components of a representative circuit layout are
mounted to the underside of the base plate 30 and, more particularly, to
the alumina 46 layer thereof.
In FIG. 4, conductive circuit pads in the form of copper elements 48 bonded
to the sheet elements of alumina layer 46 as described above with
reference to FIG. 3 comprise printed wiring conductors in accordance with
the particular power control circuitry selected. As is mentioned above,
the precise circuit details comprise no part of the present invention.
Accordingly, the particular layout shown for the copper conductors 48 is
representative only.
Bonded at preselected locations to the copper conductors 48 are
representative semiconductor bodies 50 comprising semiconductor switching
elements such as power switching transistors or power field effect
transistors, or power diodes. Accordingly, it will be appreciated that
during operation of the transistors, the heat dissipated therein is
efficiently transmitted through the copper 48 and the layer 46 to the
alumunium base plate 30, and then to the wash water being recirculated by
the pump 28.
In addition to the semiconductor components such as the bodies 50, it will
be appreciated that other circuit components also generate heat to some
extent, and this heat is likewise conducted through the plate 30 to the
water.
Accordingly, it will be appreciated that the present invention provides
efficient and synergistic use of otherwise wasted heat generated by the
control circuitry in a direct drive clothes wash machine. Not only is the
necessary heat sinking for the semiconductor elements simplified, but
advantageous heating of the wash water results, for more effective washing
operation.
While specific embodiments of the invention have been illustrated and
described herein, it is realized that numerous modifications and changes
will occur to those skilled in the art. It is, therefore, to be understood
that the appended claims are intended to cover all such modifications and
changes as fall within the true spirit and scope of the invention.
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