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Patent Abstract
A vent solenoid valve for use in an automotive emission system.
The vent valve includes a housing having a canister port and an
atmospheric port. The housing includes a bobbin having a coil for
generating a magnetic field wherein the bobbin includes an internal
channel. A stator is located in an upper portion of the channel
and a stop element is located near a lower portion of the channel.
The vent valve further includes an armature having a permanent magnet
and a valve element, wherein the magnet is located in the channel
and is moveable therein to enable movement of the valve element
between a closed position wherein the canister port is isolated
from the atmospheric port and an open position for enabling fluid
communication between the canister port and the atmospheric port.
When the coil is energized with a predetermined polarity, the valve
element moves to the open position and is kept in the open position
by magnetic attraction between the magnet and the stator. Further,
when the coil is energized with a reverse polarity, the first magnetic
attraction is overcome to move the valve element to the closed position
wherein the valve element is kept in the closed position by a second
magnetic attraction between the magnet and the stop.
Patent Claims
What is claimed is:
1. A solenoid, comprising: a bobbin having a coil for generating
a magnetic field, said bobbin including an internal channel; a stator
located within said channel; and an armature having a permanent
magnet, wherein said permanent magnet is located in said channel
to enable movement of said armature between first and second positions
relative to said stator and wherein said armature is kept in said
first position by magnetic attraction between said magnet and said
stator.
2. The solenoid according to claim 1 further including a stop element
which is spaced apart from said stator and wherein said armature
is moveable between said stator and said stop element.
3. The solenoid according to claim 2 wherein said armature is kept
in said second position by magnetic attraction between said magnet
and said stop element.
4. The solenoid according to claim 3 wherein said armature is moved
to said first position by energizing said coil to overcome the magnetic
attraction between said magnet and said stop element to move said
armature to said first position.
5. The solenoid according to claim 1 wherein said armature is moved
to said second position by energizing said coil to overcome the
magnetic attraction between said magnet and said stator to move
said armature to said second position.
6. The solenoid according to claim 1 further including a switch
for determining a position of said armature.
7. The solenoid according to claim 6 wherein said switch is a reed
switch.
8. A method for operating a valve, comprising the steps of: generating
a magnetic field for overcoming a first magnetic attraction and
for moving a valve from a first position to a second position; providing
a permanent magnet for magnetically attracting said valve to a housing
to form a second magnetic attraction for maintaining said valve
in said second position; and reversing said magnetic field to overcome
said second magnetic attraction and for moving said valve to said
first position wherein said permanent magnet magnetically attracts
said valve to said housing to form said first magnetic attraction,
wherein said first magnetic attraction maintains said valve in said
first position.
9. The method according to claim 8, wherein said valve includes
said permanent magnet.
10. The method according to claim 8, wherein said first magnetic
attraction is between a stator and said permanent magnet.
11. The method according to claim 8, wherein said second magnetic
attraction is between a stop element and said permanent magnet.
12. The method according to claim 8 further including a switch
for determining a position of said valve.
13. The method according to claim 12 wherein said switch is a reed
switch.
14. The method according to claim 8 wherein said first and second
magnetic fields are de-energized when said first and second magnetic
attractions are formed.
15. A vent solenoid valve for use in an automotive emission system,
comprising: a housing having a canister port and an atmospheric
port; a bobbin having a coil for generating a magnetic field, said
bobbin including an internal channel; a stator located in an upper
portion of said channel; a stop element located near a lower portion
of said channel; an armature having a permanent magnet and a valve
element, wherein said magnet is located in said channel and is moveable
therein to enable movement of said valve element between a closed
position wherein said canister port is isolated from said atmospheric
port and an open position for enabling fluid communication between
said canister port and said atmospheric port and wherein when said
coil is energized with a predetermined polarity, said valve element
moves to said open position and is kept in said open position by
a first magnetic attraction between said magnet and said stator
and when said coil is energized with a reverse polarity, said first
magnetic attraction is overcome to move said valve element to said
closed position and wherein said valve element is kept in said closed
position by a second magnetic attraction between said magnet and
said stop.
16. The vent solenoid according to claim 15, wherein said coil
is not energized when said valve element is kept in said open and
closed positions by said first and second magnetic attractions,
respectively.
17. The vent solenoid valve according to claim 15, wherein said
stator and said stop element are fabricated from a ferromagnetic
material.
18. The vent solenoid valve according to claim 15 further including
a switch for determining a position of said valve element.
19. The vent solenoid valve according to claim 15 wherein said
switch is a reed switch.
20. An evaporative emission control system, wherein said system
is in fluid communication with a fuel tank that generates fuel vapors,
comprising: a vapor collection canister in fluid communication with
said fuel tank for absorbing fuel vapors in said system; a vent
valve in fluid communication with said canister for enabling venting
of said canister to atmosphere, wherein said vent valve comprises:
a housing having a canister port and an atmospheric port; a bobbin
having a coil for generating a magnetic field, said bobbin including
an internal channel; a stator located in an upper portion of said
channel; a stop element located near a lower portion of said channel;
an armature having a permanent magnet and a valve element, wherein
said magnet is located in said channel and is moveable therein to
enable movement of said valve element between a closed position
wherein said canister port is isolated from said atmospheric port
and an open position for enabling fluid communication between said
canister port and said atmospheric port and wherein when said coil
is energized with a predetermined polarity, said valve element moves
to said open position and is kept in said open position by a first
magnetic attraction between said magnet and said stator and when
said coil is energized with a reverse polarity, said first magnetic
attraction is overcome to move said valve element to said closed
position and wherein said valve element is kept in said closed position
by a second magnetic attraction between said magnet and said stop;
a leak detection monitor for determining whether there are leaks
in said system which are greater than a predetermined level; a canister
purge valve for purging said canister; and an electronic engine
control unit for controlling opening and closing of said vent valve
and said canister purge valve to enable purging of said canister
and performance of an on board diagnostic procedure, wherein said
engine control unit includes drivers for energizing said pick and
release coils.
Patent Description
CROSS REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/407,762 (Attorney Docket No. 2002 P 14197 US)
filed on Aug. 30, 2002 in the name of Kirk Ivens and Russell Miles
Modien and entitled SELF LATCHING CANISTER VENT SOLENOID USING PERMANENT
MAGNETS, which is incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to evaporative emission control systems
for internal combustion engines, and more particularly, to a canister
vent solenoid valve which utilizes a permanent magnet for maintaining
valve position.
BACKGROUND OF THE INVENTION
[0003] Motor vehicles having an internal combustion engine typically
include an evaporative emission control system for reducing fuel
vapor emissions. Such systems include a vapor collection canister
which serves to absorb fuel vapors that are generated within a fuel
system. The canister includes a vent solenoid valve which is opened
under the appropriate conditions so as to place the canister in
fluid communication with atmospheric air. This enables vacuum generated
by the engine to draw in atmospheric air through the canister and
then draw out the fuel vapors from the canister as part of a process
for purging the canister.
[0004] Alternatively, the vent solenoid valve is closed to isolate
the canister from atmospheric air. This enables the performance
of a selected on board diagnostic procedure for detecting whether
there is a fuel vapor leak in the system that is above a predetermined
level. The vent solenoid valve includes a solenoid for moving a
valve element between the open and closed positions. In a conventional
vent solenoid valve, the solenoid is energized in order to move
the valve element to the closed position. Further, the solenoid
must continue to be energized for the valve element to remain in
the closed position. A spring is utilized to return the valve to
the open position when power to the solenoid is removed.
[0005] However, the use of such vent solenoid valves increases
the amount of components needed and thus ultimately increases costs.
Further, many engines are becoming smaller in capacity, resulting
in smaller capacity alternators and thus less electrical power which
is available for energizing such solenoids.
SUMMARY OF THE INVENTION
[0006] The invention is directed to a vent solenoid valve for use
in an automotive emission system. The vent valve includes a housing
having a canister port and an atmospheric port. The housing includes
a bobbin having a coil for generating a magnetic field wherein the
bobbin includes an internal channel. A stator is located in an upper
portion of the channel and a stop element is located near a lower
portion of the channel. The vent valve further includes an armature
having a permanent magnet and a valve element, wherein the magnet
is located in the channel and is moveable therein to enable movement
of the valve element between a closed position wherein the canister
port is isolated from the atmospheric port and an open position
for enabling fluid communication between the canister port and the
atmospheric port. When the coil is energized with a predetermined
polarity, the valve element moves to the open position and is kept
in the open position by a first magnetic attraction between the
magnet and the stator. Further, when the coil is energized with
a reverse polarity, the first magnetic attraction is overcome to
move the valve element to the closed position wherein the valve
element is kept in the closed position by a second magnetic attraction
between the magnet and the stop.
[0007] The features of the invention believed to be novel are set
forth with particularity in the appended claims. The invention itself,
however, both as to organization and method of operation, may be
best understood by reference to the following description taken
in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a cross sectional view of vent solenoid valve
in accordance with the present invention.
[0009] FIG. 2 is an illustrative depiction of an emission control
system which includes the vent solenoid valve.
DETAILED DESCRIPTION OF THE INVENTION
[0010] While this invention is susceptible of embodiment in many
different forms, there is shown in the drawings and will herein
be described in detail specific embodiments, with the understanding
that the present disclosure is to be considered as an example of
the principles of the invention and not intended to limit the invention
to the specific embodiments shown and described. In the description
below, like reference numerals are used to describe the same, similar
or corresponding parts in the several views of FIGS. 1-2.
[0011] Referring to FIG. 1, a cross sectional view of a vent solenoid
valve 10 in accordance with the present invention is shown. The
vent valve 10 includes a generally cylindrically shaped housing
12 having upper 14 and lower 16 walls and left 18 and right 20 side
walls. The housing 12 includes a bobbin 22 having a center member
24 positioned between upper 26 and lower 28 flanges that lie circumferentially
about a center axis 30. A coil 32 is positioned between the upper
26 and lower 28 flanges. The bobbin 22 resides within an enclosure
34 fabricated from a ferromagnetic material such as steel. A connector
36 extends from the housing 12 which serves to transmit electrical
power from a power source to the coil 32 for forming a magnetic
field.
[0012] The center member 24 includes a channel 38 that extends
between the upper 26 and lower 28 flanges and through the enclosure
34. In addition, the housing 12 includes a stator element 40 having
a head portion 42 and a stator shaft 44 that extends into the channel
38 to form a substantially T-shaped configuration. The stator element
40 is affixed to the bobbin 22 and is also fabricated from a ferromagnetic
material.
[0013] An armature 46 is positioned in a cooperative relationship
with the stator element 40 to form a solenoid. The armature 46 includes
a valve shaft 48 located between a valve element 50 and a magnet
element 52. The magnet element 52 includes a permanent magnet 54
and is located in the channel 38 between a lower end 56 of the stator
shaft 44 and a lip or stop 58 that extends from the enclosure 34.
The magnet element 52 may be moved along the center axis 30 within
the channel 38 so as to enable upward and downward movement of the
armature 46 relative to the stator element 40.
[0014] The housing 12 further includes an internal passageway 60
located between the enclosure 34 and the lower wall 16. Canister
port walls 62 extend from the lower wall 16 to form a canister port
64 having a first passageway 66 which is in fluid communication
with a vapor collection canister 84 (FIG. 2). A valve seat 68 for
receiving the valve element 50 is formed at the intersection of
the canister port walls 62 and the lower wall 16. Atmospheric port
walls 70 extend from the right side wall 20 to form an atmospheric
port 72 having a second passageway 74 which is in fluid communication
with atmospheric air through a filter 88 (FIG. 2).
[0015] In FIG. 1, the valve element 50 is shown in a closed position.
In this position, the valve element 50 is in contact with the valve
seat 68 to thus close the canister port 64 and isolate the canister
port 64 from the atmospheric port 72. In addition, the magnet element
52 is located adjacent the stop 58 to enable magnetic attraction
between the magnet element 52 and the stop 58. In accordance with
the present invention, the magnetic attraction keeps the valve element
50 in the closed position. As such, electrical power is not needed
to maintain the valve element 50 in the closed position.
[0016] The valve element 50 is also moveable to an open position.
In the open position, the valve element 50 is located above the
valve seat 68 to enable fluid communication between the canister
port 64, the internal passageway 60 and the atmospheric port 72.
The valve element 50 is moved to the open position by first energizing
the coil 32 with electrical power having a predetermined polarity
sufficient to overcome the magnetic attraction between the magnet
element 52 and the stop 58. The valve element 50 continues to move
upward from the closed position until the magnet element 52 is adjacent
the lower end 56. This results in magnetic attraction between the
magnet element 52 and the lower end 56 which serves to keep the
valve element 50 in the open position. As such, electrical power
is not needed to maintain the valve element 50 in the open position
and may be turned off.
[0017] In order to move the valve element 50 back to the closed
position, the coil 32 is again energized with electrical power,
but with a reversed polarity, which is sufficient to overcome the
magnetic attraction between the magnet element 52 and lower end
56. The valve element 50 continues to move downward until contact
is made between the valve element 50 and the valve seat 68 and the
magnet element 52 is located adjacent the stop 58. This enables
magnetic attraction between the magnet element 52 and the stop 58
which serves to keep the valve element 50 in the closed position
as previously described. As such, electrical power is not needed
to maintain the valve element 50 in the closed position and may
again be turned off.
[0018] Accordingly, the coil 32 is only energized to overcome the
magnetic attraction between the magnet element 52 and either the
stop 58 or lower end 56 and to move the valve element 50 to either
the open or closed position. Further, the magnet element 52 serves
to keep the valve element 50 in either the open or closed position.
Once the valve element 50 is in either position, power to the coil
32 may be removed, resulting in less power usage than in conventional
vent valves. In addition, the present invention also eliminates
the need for a return spring to move the valve element 50 to its
original position as in a conventional vent valve.
[0019] A switch may be used to provide feedback information regarding
the position of the valve element to an engine electronic control
unit (ECU) 80. By way of example, a mechanical switch may be used
that is actuated through contact with the armature 46 when the valve
element 50 is in either the open or closed position, as desired.
Actuation of the switch then enables the ECU 80 to determine the
position of the valve element 50.
[0020] Alternatively, a switch that does not require actual contact
for actuation may be used such as a magnetic reed switch. Referring
to FIG. 1, an illustrative depiction of a magnetic reed switch 76
is shown. The switch 76 includes two magnetizable contacts 78 located
in a glass tube or other container 81 filled with a protective gas.
The switch 76 is located adjacent the housing 12 such that when
the valve element 50 is in the open position, the magnet element
52 is sufficiently close to the contacts 78 to cause the contacts
78 to become magnetized and attracted to each other. This closes
the switch 76 and enables the ECU 80 to determine the position of
the valve element 50. When the magnet element 52 is moved away from
the contacts 78, the contacts 78 demagnetize and separate, thus
opening the switch 76. It is noted that the location of the switch
76 shown in FIG. 1 is for illustrative purposes only and that the
switch 76 may be located such that the switch 76 is closed when
the valve element 50 is in the closed position.
[0021] Referring to FIG. 2, the vent valve 10 in accordance with
the present invention is shown in an emission control system 82.
The system 82 includes a leak detection monitor 85 which is used
as part of a selected on board diagnostic procedure for determining
whether there is a fuel vapor leak in the system 82 that is above
a predetermined level.
[0022] The canister 84 is in fluid communication with a fuel tank
86 and includes carbon or other similar material which serves to
absorb fuel vapors that are generated within the fuel tank 86 and
in the emission control system 82. The canister 84 includes the
vent valve 10 which is opened under the appropriate conditions so
as to place the canister 84 in fluid communication with atmospheric
air through the filter 88 as described in relation to FIG. 1. Alternatively,
the vent valve 10 is closed as previously described to isolate the
canister 84 from atmospheric air so as to enable performance of
the on board diagnostic procedure.
[0023] A canister purge valve 90 is located between the canister
84 and an engine intake manifold 92 of an internal combustion engine
94. The canister purge valve 90 may be opened to place the canister
84 in fluid communication with the intake manifold 92. Alternatively,
the canister purge valve 90 may be closed to isolate the canister
84 from the intake manifold 92. The opening and closing of both
the canister purge valve 90 and the vent valve 10 is controlled
by the ECU 80.
[0024] Under the appropriate conditions, the canister 84 is purged
so that fuel vapors collected within the canister 84 do not undesirably
escape into the atmosphere. This is done by opening the canister
purge valve 90 and the vent valve 10, thus enabling vacuum which
is present at the intake manifold 92 to draw in atmospheric air
through the canister 84 and then draw out the fuel vapors from the
canister 84. The purged fuel vapors are then used in the normal
combustion process. The ECU 80 determines when purging is to occur
based on received signals indicative of various engine parameters.
Further, the ECU 80 may be programmed to allow purging of the canister
84 at differential rates depending upon the prevailing engine operating
conditions. As such, greater amounts of purging may be permitted
at certain times while at other times lesser amounts may be allowed.
[0025] While the invention has been described in conjunction with
specific embodiments, it is evident that many alternatives, modifications,
permutations and variations will become apparent to those skilled
in the art in light of the foregoing description. In particular,
it noted that more than one magnet may be used. Further, the entire
enclosure 34 may be substituted with a separate stop element located
near the bottom of the channel 38. In addition, the vent valve 10
may be configured such that the magnet element 52 magnetically attracts
a top portion of the enclosure 34 rather than the lower end 56 to
move the valve element 50 to the open position. Accordingly, it
is intended that the present invention embrace all such alternatives,
modifications and variations as fall within the scope of the appended
claims. |