Two-speed direct-current motor with high-speed rotation switch activated by a vehicle sensed parameter signal

A two-speed direct-current electric motor with a high-speed rotation switch activated by a vehicular sensed parameter signal. The motor includes a motor shaft supported by at least one bearing for rotation, at least two sets of windings supported by the shaft, a contactor arrangement supported by the shaft to electrically couple the windings in first and second configurations based upon a sensed parameter signal having at least a first and a second state, and a commutator arrangement coupled to the contactor arrangement to apply electrical energy to the windings. The motor rotates at a first speed when the windings are coupled in the first configuration and rotates at a second speed when the windings are coupled in the second configuration. The high-speed rotation switch is coupled directly to a sensed parameter signal and is integral to the electric motor.

FIELD OF THE INVENTION 
The present invention relates to controlling a direct-current (DC) electric 
motor such as the motor which drives a fan for cooling a vehicle air 
conditioning condenser. In particular, the present invention relates to 
changing the speed of the motor based upon a sensed vehicle parameter such 
as the pressure or temperature of the condenser, wherein the motor speed 
is changed by reconfiguring the motor windings during operation. 
BACKGROUND OF THE INVENTION 
Vehicular air conditioning systems typically employ an air-cooled condenser 
for cooling and condensing the air conditioning refrigerant. An electric 
fan is used to enhance the flow of air across the condenser. Various 
methods for controlling the fan speed are known in the art. For example, 
U.S. Pat. No. 4,590,772 discloses a vehicular air conditioning system 
capable of adjusting draft volume across the radiator and condenser in 
response to air conditioner operating conditions. U.S. Pat. No. 5,285,650 
discloses a controller which automatically turns off a condenser electric 
fan as the speed of the associated automobile surpasses a critical speed, 
or turns on the fan as the speed of the automobile drops below the 
critical speed. These references require relatively complicated control 
circuits and cabling external to the condenser fan motor. 
Condenser fan speed controllers have also been used in refrigeration 
systems. For example, U.S. Pat. No. 3,122,895 discloses a condenser fan 
controller for a refrigeration system wherein a clutch disconnects the fan 
propeller shaft from a motor driven shaft when the condenser pressure 
drops below a certain value. U.S. Pat. No. 3,293,876 discloses a 
refrigeration system including control arrangement for regulating power 
input to the fan drive motor of an air-cooled condenser in response to the 
refrigeration load. U.S. Pat. No. 3,613,391 discloses a 
pressure-responsive motor speed control for maintaining minimum condenser 
pressure in a refrigeration system under varying ambient temperature and 
refrigeration load conditions. 
Another type of fan speed controller used in vehicular air conditioning 
systems includes an automobile computer programmed to trigger a separate 
relay. The relay controls the flow of energy to a two-speed electric motor 
equipped with two brush sets and two commutator sets for low and 
high-speed rotation. The controller employs power resistors and regulators 
for varying motor speed. This design, however, has several disadvantages. 
First, the design is prone to failures leading to ineffective or unsafe 
conditions. For example, a computer failure may prevent the computer from 
commanding the relay to configure the fan for high-speed rotation at high 
condenser pressure or temperature. Also, controller reliability is lower 
due to the extra cabling and connections required between the car 
computer, relay and fan motor. Furthermore, the design is inefficient due 
to energy losses incurred by the power resistors and regulators. Finally, 
the design's two brush sets and two commutator sets increase the physical 
dimensions and weight of the motor. 
Alternating-current motors in which the windings can be reconfigured by 
switches to vary the speed of rotation have been used. For example, U.S. 
Pat. No. 841,609 discloses a multi-speed alternating-current motor 
provided with windings which can be connected in various configurations. 
This alternating-current motor, however, cannot be used in direct-current 
applications such as vehicular air-conditioning systems. 
Accordingly, it would be desirable to provide a safe and effective way to 
control the speed of a direct-current electric motor. It would also be 
useful to provide a direct-current electric motor with an integral (i.e., 
built-in) speed rotation switch directly activated by a vehicle sensed 
parameter signal, and a two-speed direct-current electric motor with a 
high-speed rotation switch which changes the motor speed by reconfiguring 
the motor windings during operation. It would also be desirable to provide 
a two-speed direct-current electric motor which drives a fan for cooling a 
vehicle air conditioning condenser based upon a sensed vehicle parameter 
such as the condenser pressure or temperature. 
SUMMARY OF THE INVENTION 
The present invention relates to a direct-current motor rotatable at first 
and second speeds in response to a sensed parameter signal having at least 
a first and a second state. In one embodiment, the motor includes a motor 
shaft supported by at least one bearing for rotation about a rotational 
axis, at least two sets of windings supported by the shaft for rotation 
about the rotational axis, and a contactor arrangement supported by the 
shaft for rotation about the rotational axis to electrically couple the 
windings in first and second configurations. The contactor is operated 
based upon the sensed parameter signal. The motor also includes a 
commutator arrangement coupled to the contactor arrangement to apply 
electrical energy to the windings. The motor rotates at the first speed 
when the windings are coupled in the first configuration and rotates at 
the second speed when the windings are coupled in the second 
configuration. 
In another embodiment, the motor includes a motor shaft supported by at 
least one bearing for rotation about a rotational axis, an armature 
supported by the shaft for rotation about the rotational axis and wound 
with at least a first and a second set of windings, and an electromagnetic 
relay comprising a stationary relay coil and a plurality of relay 
contacts, the relay coil coupled to the sensed parameter signal and the 
relay contacts supported by the shaft for rotation about the rotational 
axis and in magnetic communication with the relay coil. The relay contacts 
are adapted to electrically couple the windings in at least two 
configurations in response to the sensed parameter signal. The motor also 
includes a commutator arrangement coupled to the relay to apply electrical 
energy to the windings, wherein the motor rotates at the first speed when 
the windings are coupled in the first configuration and rotates at the 
second speed when the windings are coupled in the second configuration. 
In still another embodiment, the motor includes a motor shaft supported by 
at least one bearing for rotation about a rotational axis, an armature 
supported by the shaft for rotation about the rotational axis and 
containing at least one coil pair, and a contactor arrangement supported 
by the shaft for rotation about the rotational axis to electrically couple 
the coil pair in at least two configurations. The coil pair is coupled in 
the first configuration when the sensed parameter signal is in the first 
state and in the second configuration when the sensed parameter signal is 
in the second state. The motor also includes a commutator arrangement 
coupled to the coil pair and the contactor arrangement to apply electrical 
energy to the coil pair, the commutator arrangement having inner and outer 
shells. The motor rotates at the first speed when the coil pair is coupled 
in the first configuration and rotates at the second speed when the coil 
pair is coupled in the second configuration. The motor further includes a 
fixed brush mounted in sliding electrical contact with the outer shell of 
the commutator arrangement to provide electrical energy to the commutator 
arrangement, and a fixed magnet surrounding the coil pair.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a vehicular condenser cooling system 10 includes a 
condenser 12 for cooling and condensing a refrigerant or cooling medium 
(not shown) flowing through condenser 12. A fan 14 is arranged to enhance 
the flow of cooling air across condenser 12. Fan 14 is driven by a 
two-speed direct-current electric motor 16. The draft volume of air 
directed to condenser 12 by fan 14 increases when motor 16 is configured 
to rotate at high-speed, thereby increasing the cooling capacity of 
condenser 12. 
Motor 16 is electrically coupled to a signal from condenser pressure sensor 
18. Sensor 18 is mounted in or near condenser 12 in order to sense the 
pressure of the refrigerant flowing through condenser 12. When condenser 
pressure is high, sensor 18 closes a circuit and applies a voltage to 
motor 16. Although sensor 18 is a condenser pressure sensor in the 
preferred embodiment, the invention can use any sensor capable of 
generating a signal having at least a first and a second state. For 
example, sensor 18 could be a condenser temperature sensor or could be a 
sensor attached to a radiator. As explained in detail below, the speed 
configuration of motor 16 is based upon the state of the sensed parameter 
signal from sensor 18. Motor 16 is configured to rotate at a first speed 
when the sensed parameter signal from sensor 18 is in a first state and is 
configured to rotate at a second speed when the sensed parameter signal 
from sensor 18 is in a second state. Motor 16 receives electrical energy 
from vehicle battery 20. 
Referring to FIG. 2 for a sectional view, motor 16 is enclosed in a casing 
30 having a rear wall 32 and a front wall 34. Front wall 34 is integral 
with the sides of casing 30. A motor mounting bracket 35 is attached to 
casing 30 to mount motor 16 to a support (not shown) within the engine 
compartment of a vehicle. A motor shaft 36 is fit through an aperture 38 
in the front wall 34 of casing 30. Motor shaft 36 is supported by sleeve 
bearing 40 and ball bearing 42 for rotation about a rotational axis 44. 
Bearing 40 includes a ball and socket joint 41 which allows motor shaft 36 
to self-adjust, thereby simplifying manufacture. 
Motor 16 has an armature 46 supported by motor shaft 36 for rotation about 
rotational axis 44. Armature 46 includes an armature core 48 wound with at 
least two sets of windings 50 occupying a similar location. A winding set 
may be referred to as a coil, and two winding sets may be referred to as a 
coil pair. The coils in a coil pair may have a similar or different number 
of turns (e.g., 10 turns) or use a similar or different gauge of wire 
(e.g., 18 gauge). A complete winding may contain any number of coil pairs 
(e.g., 20 coil pairs). Armature core 48 is made of a metal such as iron or 
steel. 
Motor shaft 36 also supports a contactor arrangement 52 for rotation about 
rotational axis 44. Contactor arrangement 52 is press-fit onto motor shaft 
36 and is secured to a commutator arrangement 54 along a flat surface 56. 
Commutator arrangement 54 is a dual shell commutator having two 
concentrically molded shells 58 and 60 concluded in reverse hooks. In a 
preferred embodiment, shown in the top cross section of FIG. 3, outer 
commutator shell 58 is divided into ten commutating bars 62 while inner 
commutator shell 60 contains twenty inner bars 64. Outer bars 62 have a 
sliding surface and are used for commutation, hence the name commutating 
bars, whereas inner bars 64 are used only for interconnecting coils 50. 
Returning to FIG. 2, coils 50 are wound such that one end of a coil is 
connected to an outer commutating bar 62 and the other end is connected to 
an inner bar 64. The connections between commutator arrangement 54 and 
armature coils 50 result in the reversal of electrical current applied to 
coils 50 when armature 46 rotates. As explained in detail below in 
reference to FIGS. 3-5, contactor arrangement 52 interacts with commutator 
arrangement 54 to electrically couple the two winding sets 50 in a first 
and a second configuration based upon a sensed parameter signal from 
sensor 18, thereby forming a high speed rotation switch. 
A stationary brush card 66 mounted to the motor casing 30 provides support 
for a fixed brush 68. Brush 68 is preferably a high-speed crescent brush, 
such as that disclosed in U.S. Pat. No. 5,434,463, which makes sliding 
electrical contact with the outer shell 58 of commutator arrangement 54 to 
supply electrical current from battery 20 (FIG. 1) to the commutator 
arrangement. 
Winding sets 50 are surrounded by permanent magnets 70 fixed to the motor 
casing 30. A motor 16 may have, for example, four magnets 70. Electric 
current from battery 20 flows through brush 68 into commutator arrangement 
54 and then through winding sets 50 where it interacts with magnetic 
fields of fixed magnets 70 to produce torque which causes motor shaft 36 
to rotate about rotational axis 44. 
Motor 16 also includes a stationary electromagnet 72 secured to brush card 
66. As explained in detail below in reference to FIGS. 4 and 5, 
electromagnet 72 is coupled to the sensed parameter signal from sensor 18 
and is in magnetic communication with contactor arrangement 52 such that 
the sensed parameter signal is capable of energizing electromagnet 72 and 
causing contactor arrangement 52 to change the configuration of motor 16 
from low-speed to high-speed rotation in response to high condenser 
pressure. Motor 16 also includes a choke 74. 
Turning to FIG. 4, contactor arrangement 52 includes a two-part housing 100 
having a cup 102 and a lid 104. Housing 100 is sealed to increase the 
reliability of contactor arrangement 52 by preventing contamination by 
dust, dirt, water, oil, grease or other contaminants typically present in 
a vehicle engine environment. Housing 100 of contactor arrangement 52 is 
press-fit or keyed onto motor shaft 36 and secured (e.g., glued, screwed, 
riveted) to the flat surface 56 of commutator arrangement 54. Within 
housing 100 is a disk 106 in sliding engagement with the tubular part of 
cup 102 and maintained generally parallel with lid 104, whereby disk 106 
can move in a direction parallel to motor shaft 36. Disk 106 can be 
slidably coupled to housing 100 using grooves in disk 106 and 
corresponding ribs on housing 100 to prevent rotation and maintain 
alignment of disk 106 within housing 100. Both housing 100 and disk 106 
can be made of plastic, and are preferably made of polyester so that no 
lubrication is necessary. A spring 108, located within housing 100 of 
contactor arrangement 52, is coupled to disk 106 and biases disk 106 
against lid 104. FIG. 4 shows disk 106 biased in the low-speed 
configuration of motor 16 while FIG. 5 shows disk 106 moved into the 
high-speed configuration of motor 16 by a mechanism described in detail 
below. 
A set of relay contacts or cramps 110 are secured to the bottom of disk 
106, preferably by molding or riveting contacts 110 directly onto disk 
106. Contacts 110 have a first conductive member 112 and a second 
conductive member 114 coupled by a support 116. The first and second 
conductive members 112 and 114 are supported at right angles with respect 
to each other, and are movable between low-speed and high-speed positions 
as disk 106 moves. In the low-speed configuration of motor 16 shown in 
FIG. 4, first conductive member 112 makes no electrical contact between 
commutating bar 62 and inner bar 64 whereas second conductive member 114 
makes electrical contact between bar tabs 118 of adjacent inner bars 64 
(FIGS. 3-4). However, in the high-speed configuration of motor 16 shown in 
FIG. 5, first conductive member 112 makes electrical contact between 
commutating bar 62 and bar tab 118 of inner bar 64 whereas second 
conductive member 114 makes no electrical contact between bar tabs 118 of 
adjacent inner bars 64. The preferred embodiment uses ten copper contacts, 
but the number of contacts can change with the number of windings and 
other conductive materials (e.g., gold) can be used. 
Contactor arrangement 52 includes a ferromagnetic (e.g., iron or steel) 
ring 120 secured to the bottom of disk 106 and aligned with electromagnet 
72 along a direction parallel to the movement of disk 106 and generally 
perpendicular to the longitudinal axis of shaft 36. In the low-speed 
configuration of motor 16 shown in FIG. 4, the sensed parameter signal 
from sensor 18 is in a first state and no voltage is applied to 
electromagnet 72. Since de-energized electromagnet 72 does not generate a 
magnetic field, disk 106 is pressed against lid 104 by the bias of spring 
108 and contacts 110 are in their low-speed positions. However, in the 
high-speed configuration of motor 16 shown in FIG. 5, the sensed parameter 
signal from sensor 18 is in a second state and a voltage from battery 20 
is applied to electromagnet 72. Energized electromagnet 72 generates a 
magnetic field strong enough to attract ring 120 with a force sufficient 
to compress spring 108 and move disk 106 towards electromagnet 72. In this 
configuration, contacts 110 are moved into their high-speed positions. 
In the preferred embodiment, capacitors 122 are connected between adjacent 
inner bars 64 to protect the relay contacts 110 from sparking. 
FIG. 6 shows an electrical schematic diagram of the high-speed rotation 
switch and some of the windings 50 of coils 200 and 202 (for purposes of 
simplification, all of the windings 50 and all of the contacts 110 have 
not been shown). In the low-speed configuration of motor 16, the sensed 
parameter signal from sensor 18 is in a first state and no voltage is 
applied to electromagnet 72. With electromagnet 72 de-energized, first 
conductive member 112 makes no electrical contact between commutating bar 
62 and inner bar 64 whereas second conductive member 114 makes electrical 
contact between adjacent inner bars 64. The first and second set of 
windings 50 are connected in series between adjacent commutating bars 62. 
The electrical path starts at a first commutating bar 62, goes through a 
first coil 200 to an inner bar 64, continues through second conductive 
member 114 to an adjacent inner bar 64, and then goes through a second 
coil 202 to a second commutating bar 62. However, in the high-speed 
configuration of motor 16, the sensed parameter signal from sensor 18 is 
in a second state and a voltage from battery 20 is applied to 
electromagnet 72. Magnetic field 204 switches the position of contacts 110 
such that first conductive member 112 makes electrical contact between 
commutating bar 62 and inner bar 64 whereas second conductive member 114 
makes no electrical contact between adjacent inner bars 64. Only one 
winding set 50 is connected between adjacent commutating bars 62 (i.e., 
winding sets 50 are connected in series). The electrical path starts at a 
first commutating bar 62, goes through first conductive member 112 to an 
inner bar 64, and continues through coil 202 to a second commutating bar 
62. Since the high-speed configuration results in only a single winding 
set 50 being connected in series between commutating bars 62, this winding 
set can be made from a heavier gauge of wire than the other winding set. 
While the embodiments illustrated in the FIGURES and described above are 
presently preferred, it should be understood that these embodiments are 
offered by way of example only. The invention is not intended to be 
limited to any particular embodiment, but is intended to extend to various 
modifications that nevertheless fall within the scope of the appended 
claims. Although the preferred embodiments described above show a 
two-speed condenser motor controlled by a pressure sensor for use in a 
vehicular air conditioning system, the multi-speed motor could be used in 
any other direct-current motor application requiring different rotation 
speeds in response to a control signal. For example, an electric motor 
incorporating the invention could be used in a refrigeration system, or 
the sensed parameter could be a temperature or other sensed parameter 
having different states. Additionally, an electric motor incorporating the 
present invention could also be a direct-current electric motor having 
more than two speeds in response to a control signal having more than two 
states.