Field of the Invention
This invention relates to exhaust gas recirculation
(EGR) valves for internal combustion engines, and is
particularly directed to a novel construction for
improving the accuracy and response of the valve to
electric control signals and for improving the ability of
the valve to withstand intrusion of foreign substances,
especially muddy water, into the interior mechanism of
the valve via an ambient air cooling space.
Background and Summary of the Invention
Controlled engine exhaust gas recirculation is a
commonly used technique for reducing oxides of nitrogen
in products of combustion that are exhausted from an
internal combustion engine to atmosphere. A typical EGR
system comprises an EGR valve that is controlled in
accordance with engine operating conditions to regulate
the amount of engine exhaust gas that is recirculated to
the induction fuel-air flow entering the engine for
combustion so as to limit the combustion temperature and
hence reduce the formation of oxides of nitrogen.
Since they are typically engine-mounted, EGR valves
are subject to a harsh operating environment that
includes wide temperature extremes and vibrations.
Exhaust emission requirements impose more stringent
demands for improved control of such valves. Use of an
electric actuator is one means for obtaining improved
control, but in order to commercially successful, such an
actuator must be able to operate properly in such extreme
environments for an extended period of usage. Moreover,
in mass-production automotive vehicle applications,
component cost-effectiveness is also essential. An EGR
valve electric actuator that possesses more accurate and quicker
response results in improved driveability and fuel economy for a
vehicle having an internal combustion engine that is equipped
with an EGR system. It also provides better control over tailpipe
emissions.
An example of a known solenoid activated exhaust gas
recirculating valve is disclosed in PCT application number WO-A-95/19497.
The valve includes a valve body having a gas inlet and
a gas outlet connected by a passageway. A flow control member is
supported in the valve body and regulates the flow through the
passageway. An electronically actuated field-generating solenoid
moves a magnetic drive member to control the flow. The solenoid
and a sensor for monitoring the position of the drive member are
supported in a plastics moulded housing which partially
encapsulates a pole piece that forms a magnetic circuit in
combination with the drive member.
The present invention relates to a new and unique
construction for certain component parts of such a valve that
enables accuracy and response to be improved and also provides
better resistance to the intrusion of muddy water into the internal
valve mechanism via an ambient air cooling space.
Generally speaking, the invention relates to improvements in
an area of the valve that contains a lower stator member that
forms part of the magnetic circuit and a bearing member that
guides the valve pintle. The organisation and arrangement of
these two, and some related parts improves part-to-part
concentricity and also is useful in resisting intrusion of muddy
water into the interior operating mechanism.
The problem of muddy water intrusion arises because of the
desirability of providing air ambient circulation through a portion
of the valve. The pintle head and associated valve seat are in the
hot exhaust path through the valve and are exposed to very high
temperatures. The electric actuator is operatively connected to
the pintle, but is slightly farther away from the engine. It is
desirable to provide for air circulation through the valve housing
between the actuator and the parts that are closer to the engine.
However, since it is engine-mounted, the valve will be subject to
the outside environment, and one of the hazards is muddy water
intrusion due to road splash, etc.
Various features, advantages, and benefits of the invention
for achieving the desired objectives will be seen in the ensuing
description and claims that are accompanied by drawings. The
drawings disclose a presently preferred embodiment of the
invention according
to the best mode contemplated at this time for carrying
out the invention.
Brief Description of the Drawings
Figs. 1, 2, 3, and 4 are respective top plan, front
elevation, left side elevation, and bottom views of an
electric EGR valve (EEGR valve) embodying principles of the
invention.
Fig. 5 is an enlarged view, partly in cross section,
of the EEGR valve of Figs. 1-4.
Fig. 6 is a top plan view of one of the parts of the
EEGR valve shown by itself on an enlarged scale, namely a
valve seat.
Fig. 7 is a cross sectional view taken in the
direction of arrows 7-7 in Fig. 6.
Fig. 8 is an enlarged view in circle 8 of Fig. 7.
Fig. 9 is an elevational view of another of the parts
of the EEGR valve shown by itself on a slightly enlarged
scale, namely a pintle valve element.
Fig. 10 is a top view of Fig. 9.
Fig. 11 is a fragmentary cross sectional view taken in
the direction of arrows 11-11 in Fig. 10 on a larger scale.
Fig. 12 is a full bottom view of Fig. 11 on the same
scale.
Fig. 13 is a top plan view of another of the parts of
the EEGR valve shown by itself on an enlarged scale, namely
a bearing member.
Fig. 14 is a cross sectional view as taken in the
direction of arrows 14-14 in Fig. 13.
Fig. 15 is an enlarged view in circle 15 of Fig. 14.
Fig. 16 is a top plan view of still another of the
parts of the EEGR valve shown by itself on a slightly
enlarged scale, namely a lower stator member.
Fig. 17 is a cross sectional view as taken in the
direction of arrows 17-17 in Fig. 16.
Fig. 18 is a top plan view of yet another part of the
EEGR valve shown by itself, namely an upper stator member.
Fig. 19 is a cross sectional view as taken in the
direction of arrows 19-19 in Fig. 18.
Fig. 20 is an enlarged view in circle 20 of Fig. 19.
Fig. 21 is a top plan view of another of the parts of
the EEGR valve shown by itself on a slightly enlarged
scale, namely a spring washer.
Fig. 22 is a cross sectional view as taken in the
direction of arrows 22-22 in Fig. 21 on a slightly larger
scale.
Fig. 23 is a top plan view of still another of the
parts of the EEGR valve shown by itself on a larger scale
than in Fig. 5, namely a spring washer.
Fig. 24 is a front elevational view of Fig. 23.
Fig. 25 is a top plan view of yet another part of the
EEGR valve shown by itself in a condition prior to assembly
to the EEGR valve, namely a clinch ring.
Fig. 26 is a cross sectional view as taken in the
direction of arrows 26-26 in Fig. 25.
Fig. 27 is an enlarged fragmentary view in circle 27
of Fig. 25.
Fig. 28 is a fragmentary cross sectional view as taken
in the direction of arrows 28-28 in Fig. 27.
Fig. 29 is a top plan view of still another of the
parts of the EEGR valve shown by itself on a slightly
enlarged scale, namely a bobbin.
Fig. 30 is a front elevational view of Fig. 29.
Fig. 31 is a bottom plan view of Fig. 30.
Fig. 32 is a fragmentary cross sectional view as taken
in the direction of arrows 32-32 in Fig. 30.
Fig. 33 is a cross sectional view as taken in the
direction of arrows 33-33 in Fig. 29.
Fig. 34 is a fragmentary view, on an enlarged scale,
as taken in the direction of arrows 34-34 in Fig. 29.
Fig. 35 is an enlarged cross sectional view as taken
in the direction of arrows 35-35 in Fig. 30.
Fig. 36 is a full left side view of Fig. 35.
Fig. 37 is a front elevational view of yet another
part of the EEGR valve shown by itself on a larger scale
than in Fig. 5, namely an electrical terminal.
Fig. 38 is a top plan view of Fig. 37.
Fig. 39 is a right side elevational view of Fig. 37.
Fig. 40 is a left side elevational view of Fig. 37.
Fig. 41 is a bottom plan view of yet another part of
the EEGR valve, namely a sensor cap.
Fig. 42 is a fragmentary cross sectional view, on an
enlarged scale, as taken in the direction of arrows 42-42
in Fig. 41.
Fig. 43 is a fragmentary cross sectional view, on an
enlarged scale, as taken in the direction of arrows 43-43
in Fig. 42.
Figs. 44, 45, and 46 are views of another form of
clinch ring corresponding to the views of Figs. 25, 27, and
28 respectively.
Description of the Preferred Embodiment
Figs. 1-4 illustrate the exterior appearance of an
electric EGR valve (EEGR valve) 60 embodying principles of
the present invention. EEGR valve 60 comprises a metal
base 62, a generally cylindrical metal shell 64 disposed on
top of base 62, and a non-metallic cap 66 forming a closure
for the otherwise open top of shell 64.
Base 62 comprises a flange 68 having a flat bottom
surface adapted to be disposed against a surface of an
exhaust manifold of an internal combustion engine,
typically sandwiching a suitably shaped gasket (not shown)
between itself and the manifold. Flange 68 comprises two
through-holes 70 that provide for the separable attachment
of EEGR valve 60 to an exhaust manifold. For example, the
manifold may contain a pair of threaded studs which pass
through through-holes 70 and onto the free ends of which
lock washers are first placed, followed by nuts that are
threaded onto the studs and tightened to force flange 68
toward the manifold, thereby creating a leak-proof joint
between valve 60 and the manifold.
Reference numeral 72 designates a main longitudinal
axis of EEGR valve 60. Base 62 further comprises four
through-holes that are parallel to axis 72 and are centered
on a common imaginary circle at 90 degree intervals about
axis 72. Four fasteners 74 fasten base 62 and shell 64
tightly together via the four through-holes in base 62 and
four holes in a bottom wall of shell 64 that register with
the four through-holes in base 62. Each fastener comprises
a bolt, a lock washer, and a nut. The head of each bolt is
received in a suitable recess in flange 68 while a
corresponding lock washer is disposed onto the free end of
the respective bolt shank that extends through the
respective hole in shell 64, and the corresponding nut is
threaded onto the threaded end of the bolt shank and
tightened.
With additional reference to Fig. 5, a suitable gasket
75 is sandwiched between the base and shell. Also, an
annular air space 76 is provided within shell 64
immediately above the shell's bottom wall. This air space
is open to the exterior by means of several through-slots
78 formed in the shell side wall immediately above the
shell's bottom wall. This arrangement provides for ambient
air circulation through EEGR valve 60 between base 62 and
internal parts within shell 64 above the shell's bottom
wall. Such air circulation provides beneficial cooling
that serves to reduce the amount of engine heat that might
otherwise be transferred to internal parts.
Cap 66 is a non-metallic part, preferably fabricated
from suitable polymeric material. In addition to providing
a closure for the otherwise open upper end of shell 64, cap
66 comprises a central cylindrical tower 80 and an
electrical connector shell 82 that projects radially
outwardly from tower 80. Tower 80 has a hollow interior
shaped to house a position sensor that is utilized for
sensing the extent to which EEGR valve 60 is open. Cap 66
further contains several electrical terminals that provide
for such a sensor and an electric actuator to be
operatively connected with an engine electrical control
system, as will hereinafter be described in greater detail.
Ends of these terminals are contained within shell 82 to
form an electrical connector plug that is adapted to mate
with a mating plug (not shown) of an electrical wiring
harness of the engine electrical system. Cap 66 also
comprises a series of integral triangularly shaped walls 84
spaced circumferentially around the cap that provide
improved structural rigidity for tower 80 to a bottom wall
85 of the cap with which the tower is integrally formed.
A clinch ring 86 engages an outer perimeter rim of wall 85
to securely attach cap 66 to shell 64 with radial sealing
of the cap to the shell being provided by an O-ring 87
disposed in a radially outwardly open groove extending
circularly around a portion of bottom wall that is below
and radially inwardly of the wall's outer perimeter rim
that is engaged by clinch ring 86. O-ring 87 provides a
radial seal between the cap and the inside wall of shell 64
proximate the shell's top end.
Attention is now directed to details of the internal
construction of EEGR valve 60 with continued reference to
Fig. 5 and also to a number of subsequent drawing figures
showing individual parts in greater detail.
Base 62 comprises an exhaust gas passageway 88 having
an entrance 90 coaxial with axis 72 and an exit 92 that is
spaced radially from entrance 90. Both entrance 90 and
exit 92 register with respective passages in the engine
exhaust manifold.
A valve seat 94, details of which are shown in Figs.
6, 7, and 8, is disposed in passageway 88 coaxial with
entrance 90. Valve seat 94 has an annular shape comprising
a through-hole having a frusto-conically tapered surface
96a extending from the top face of the valve seat to a
straight circular cylindrical surface 96b extending to a
frusto-conical chamfer 96c at the bottom of the valve seat.
A circular perimeter rim 98 extends around the outside of
valve seat 94 at the top. Immediately below rim 98, the
outer perimeter surface of the valve seat comprises a
straight circular cylindrical surface 100 that is coaxial
with axis 72 and extends to a frusto-conical chamfer 102.
Between surface 100 and chamfer 102 is a frusto-conically
tapered surface 104 that begins at the upper circular edge
of chamfer 102, which is essentially at the same diameter
as surface 100. Surface 104 tapers outwardly toward the
top of the valve seat at an angle designated by the numeral
106 in Fig. 8. It ends at a shoulder 108 that extends
radially back to the lower edge of surface 100. Base 62 is
constructed with a counterbore providing a shoulder 109
onto which rim 98 seats. Moreover, the provision of
tapered surface 104 provides a wedge fit of the valve seat
to base 62 when the valve seat is axially aligned with
entrance 90 and pressed into the base to seat rim 98 on
shoulder 109. Rim 98 is then captured against shoulder 109
by means of staking a portion 110 of base 62 against the
top surface of the rim. It is to be appreciated that Fig.
5 portrays the assembled position of valve seat 94 in base
62 and that the staking portion 110 is created by
displacing material of base 62 after rim 98 has been seated
on shoulder 109. The wedging fit provided by surface 104
being in interference with the wall of entrance 90
immediately below shoulder 109 provides a secure, accurate,
and gas-tight assembly of the valve seat to the base.
Fig. 5 further shows that EEGR valve 60 comprises an
armature-pintle assembly 112 that is coaxial with axis 72
and that comprises a pintle 114 and an armature 116.
Details of pintle 114 are illustrated in Figs. 9-12.
Pintle 114 comprises a shaft having a head 117 at the lower
end and a threaded stud 118 at the upper end. Head 117 is
shaped for cooperation with seat 94 while stud 118 provides
for attachment of the pintle to armature 116. Head 117 has
an outer perimeter that is shaped to comprise a straight
circular cylindrical surface 120 from the lower edge of
which a frusto-conical tapered surface 122 flares radially
outwardly to a further frusto-conical tapered surface 124
of larger taper, but shorter axial dimension, than that of
surface 122. The pintle further comprises a flat bottom
surface 128 that has a generally circular shape but
contains a central blind hole 130. This blind hole
comprises a chamfer 132 extending from surface 128 to a
polygonally shaped surface 134 which in the illustrated
embodiment is a hexagon shape. Immediately inwardly of
surface 134 is a straight circular cylindrical surface 136
of slightly smaller diameter than the maximum diameter
across surface 134. The innermost part of hole 130 is a
conically shaped space 138 extending from surface 136 to a
tip lying on axis 72. As can be seen in Fig. 5, which
represents the closed position of EEGR valve 60, surface
124 seats against chamfer 96c. Preferably the taper of
surface 124 is less than one degree smaller than that of
chamfer 96c.
EEGR valve 60 further comprises a bearing member 140,
details of which appear in Figs. 13-15. Bearing member 140
comprises a circular rim 142 at the bottom. The radially
outer surface of rim 142 comprises a chamfer 144 extending
from the flat bottom surface 145 of the bearing member. At
several circumferentially spaced apart locations, the outer
perimeter of the rim comprises formations 147. Each
formation comprises a frusto-conically tapered surface
section 146 that tapers outwardly from the upper circular
edge of chamfer 144 to a straight, circularly cylindrically
contoured surface section 148. Each surface section 148
extends to the top of rim 142. There are eight such
formations 147 distributed uniformly around the perimeter
of rim 142 in the illustrated embodiment. The formations
are dimensioned for a wedging fit of member 140 to a
partially cylindrical wall surface 149 in base 62 (see Fig.
5). Wall surface 149 is only partially cylindrical because
that portion of passageway 88 that leads to exit 92
intersects this surface and hence there is no material
available for forming the portion of wall surface 149 at
the mutual intersection. This wedging fit of bearing
member 140 to base 62 serves the purpose of accurately and
securely locating the two parts in assembly.
Immediately below wall portion 149 is a shoulder 150.
The outwardly turned upper rim 152 of a cup shaped metal
shield 154 is captured between rim 142 and shoulder 150
after bearing member 140 has pressed into assembly with
base 62. Shield 154 comprises a central circular clearance
hole 156 for passage of the shaft of pintle 114
therethrough.
Fig. 14 shows that bearing member 140 further
comprises a central through-hole having a cylindrical
portion 156 extending upwardly from the bottom surface of
the bearing member to a frusto-conical surface 158 which in
turn extends to a straight cylindrical surface 160 that
occupies a majority of the overall axial length of the
bearing member. The upper end of surface 160 ends at a
chamfer 162, where the bearing member top surface 164 has
a slight crown. The outside diameter of bearing member 140
above rim 142 comprises a ridge 166 that has a circular
shape. Above ridge 166 and continuing to top surface 164
are a series of circumferentially spaced apart flutes 168
that cooperatively define a series of parallel ribs 170
extending axially from ridge 166. The plan shape of these
ribs 170 can be seen in Fig. 13 which shows six such ribs
by way of example. The radially outer surfaces of these
ribs lie on a common circle that is concentric with axis 72
and provide for accurately centering a lower stator member
174 (Fig. 5) in the assembled EEGR valve 60. Fig. 13 also
shows that rim 142 has a semi-circular notch 172 disposed
between two immediately adjacent formations 147 in the
outer surface of the rim.
Details of lower stator member 174 appear in Figs. 16
and 17. Member 174 comprises a circular flange 176
immediately below which is a smaller diameter cylindrical
wall 178 and immediately above which is a tapered
cylindrical wall 180. A central through-hole of member 174
extends upwardly from an inwardly tapered surface 182 to a
straight cylindrical section 184. The latter expands to a
larger diameter cylindrical surface 186 that extends to a
still larger diameter cylindrical surface 188. The upper
edge surface 190 of wall 180 is relatively pointed and
although it does have a finite radial thickness, that
thickness is considerably smaller than the radial thickness
192 at the base of wall 180. The relatively pointed
tapering of wall 180 is for the purpose of enhancing the
magnetic circuit characteristics of the magnetic circuit of
EEGR valve 60, to be hereinafter described in detail.
Valve 60 further comprises an upper stator member 194
that is cooperatively associated with lower stator member
174 in the magnetic circuit. Details of upper stator
member 194 appear in Figs. 18-20. Member 194 comprises a
straight cylindrical side wall 196 having a flange 198
extending around its outside proximate its upper end. The
outer surface of flange 198 is constructed to have a
wedging press fit to the inside wall of shell 64 and
comprises a straight cylindrical section 200 extending
upwardly from its lower face to an outwardly tapered
surface 202. Surface 202 terminates at a shoulder 204 that
extends radially inwardly back to a cylindrical surface 206
that extends to the upper face of the flange. In the
assembled valve 60, member 194 is pressed into the shell 64
to seat flange 198 on an internal shoulder 64b (Fig. 5) of
shell 64. The upper stator member further comprises a
straight cylindrical through-hole 212 extending from a
small chamfer 211 at the bottom of side wall 196 to a
larger chamfer 210 at a raised ridge 208 at the top end of
the member. A slot 214 is provided in a portion of flange
198 and ridge 208 to provide a clearance for an electrical
connection between cap 66 and a bobbin assembly 222 (see
Fig. 5) that is disposed within shell 64 in cooperative
association with the two stator members. Additionally,
flange 198 comprises a through-hole 216 diametrically
opposite slot 214 and two smaller through- holes 218, 220 at
90 degrees from hole 216.
Fig. 5 shows solenoid coil assembly 222 disposed
within shell 64 between stator members 174 and 194.
Solenoid coil assembly 222 comprises a non-metallic bobbin
224 having a straight cylindrical tubular core 226 coaxial
with axis 72, and upper and lower flanges 228 and 230 at
the opposite axial ends of core 226. A length of magnet
wire is wound on core 226 between flanges 228, 230 to form
an electromagnet coil 232.
Detail of bobbin 224 appears in Figs. 29-36 in a
condition prior to winding of coil 232. The bobbin is
preferably an injection-molded plastic that possesses
dimensional stability over a range of temperature extremes
that are typically encountered in automotive engine usage.
Lower flange 230 has a circular shape whose outer
perimeter is interrupted at one location by a small
inwardly extending slot 234. Upper flange 228 also has a
circular shape, but its outer perimeter is interrupted by
two closely adjacent slots 236 and 238 that have somewhat
different shapes. Slot 236 is basically U-shaped. One
side of slot 238 is slightly more than a half-U-shape while
the other side 239 runs along a straight line extending
from a point of tangency 240 with the first side at about
55 degrees to a radial 241 to where it meets the circular
outer perimeter of the flange. The lower face of flange
228 comprises an indentation 242 that is seen in Fig. 32 to
be somewhat triangularly shaped. Indentation 242 comprises
an edge surface 244 that extends from a point of tangency
246 with the O.D. of core 226 to a location on the
perimeter of flange 228 that is between slots 238 and 236.
Edge surface 244 makes an angle 250 with radial 241 that is
approximately 35 degrees.
The upper face of flange 228 contains two upstanding
cylindrical posts 252 and 254 that are diametrically
opposite each other and equidistant from axis 72 and whose
upper ends are tapered. At 90 degrees to both posts 252,
254 is a further upright post 256 having a generally
rectangular shape with a radially outwardly projecting
overhang 258 at its top that is also slightly wider in the
circumferential sense about axis 72.
Generally diametrically opposite post 256 on the upper
face of flange 228 are a pair of upright, side-by-side,
walled sockets 260 and 262. Each socket is adapted for
receiving a respective electrical terminal like the one
depicted in Figs. 37-40 (to be described in detail later)
and to provide for the electrical connection of a
respective terminal with a respective end segment of the
magnet wire forming coil 232. Fig. 5 shows one such
terminal 264 received in a respective one of the sockets.
Each socket has a generally rectangular wall that is open
at the top for insertion of a terminal. The opposed
radially inner and radially outer portions of each socket
wall contain straight narrow slots 266 and 268 respectively
that are in parallel and mutual alignment across the
respective socket. The slots are open at the top where
they have a lead that facilitates the passage of respective
segments of the coil magnet wire into the slots, as will be
explained in greater detail later on. A respective grooved
ramp 270 and 272 slopes upwardly from a respective slot
236, 238 to the bottom of the radially outer slot 268 of a
respective socket 260, 262. A respective short grooved
track 274 and 276 is provided on the radially inner wall of
the respective socket 260, 262 slightly above the upper
face of flange 228, each track 274, 276 having a groove
that extends from the bottom of the radially inner slot 266
of the respective socket 260, 262 toward the open center of
the bobbin as viewed in plan.
Figs. 37-40 illustrate an electric terminal 264 prior
to its insertion into a respective one of the sockets 260,
262. Terminal 264 is fabricated as a single piece from
flat strip stock to comprise a generally U-shaped body
having a base 388 whose opposite ends join with flat sides
390 and 392 respectively along 90 degree radii, as shown by
Fig. 37. Each side contains a centrally located axial slot
394 that is open at base 388 and extends upwardly therefrom
for about one-half the overall axial length of the side.
At base 388, a slot 394 comprises an entrance lead 396 that
extends to a straight section 398 which in turn extends via
a tapered section 400 to a narrower straight section 402.
The material is slit, as shown at 404 in Figs. 39 and 40,
adjacent each side of section 398. The outer edges of
sides 390, 392 contain pointed retention barbs 406. A
somewhat T-shaped tab 408 inclines downwardly and inwardly
from the central portion of the top edge of side 392,
stopping short of the opposite side 390 to provide an
insertion space 410 for a mating terminal (not shown). The
wings 412 of the T-shape are curled back toward, but stop
short of, side 392.
The method of fabricating the solenoid coil assembly
will now be briefly explained. Magnet wire is tightly
wrapped around post 256 below overhang 258. It is then
brought across the bobbin to run in and along the groove of
track 274, thence pass through slot 266 of socket 260 and
across the socket's interior to exit the socket by passing
through slot 268. From slot 268 the magnet wire runs in
and along the groove of ramped track 270 to enter slot 236
where it loops around the edge of the slot to the bottom
face of flange 228. The magnet wire extends within recess
242 from the edge of slot 236 to tangency with core 226
where it begins to form convolutions around the core
between the bobbin flanges to ultimately create the
electromagnet coil 232. By "precision winding" of the coil,
maximum convolutions are placed in minimum space, and they
are accurately located so that the electromagnetic
characteristics of the coil are accurately defined.
Magnet wire extends from the final convolution of the
coil to slot 238 where the magnet wire loops around the
edge of the slot to the upper face of flange 228. The
magnet wire extends from slot 238 to run in and along the
groove in ramped track 272 and thence enter socket 262 by
passing through slot 268 of that socket. The magnet wire
passes across the interior of the socket, exiting via slot
266 to run in and along the groove in track 276. Upon
leaving track 276, the magnet wire extends across the
bobbin to an end segment of the magnet wire that is
wrapped, or tied, securely around post 256.
At all times during the running of the magnet wire on
the bobbin, it is kept tensioned so that not only are the
coil convolutions tensioned, but also the segments that
extend from the coil to post 256.
Terminals 264 are then assembled by aligning each with
the open end of a respective socket 260, 262 and forcefully
inserting them into the sockets. As a terminal is being
inserted into a socket, the portion of the magnet wire
spanning the interior of the socket enters slots 394.
Leads 396 facilitate entry into the narrow portions of the
slots. When the terminal has been fully inserted, the
magnet wire is lodged in section 402 in electric contact
with the terminal. Each slot is dimensioned in relation to
the diameter of the magnet wire to scrape away the thin
insulation covering the magnet wire so that the electric
contact is thereby established. Barbs 406 embed slightly
into the wall of the socket to securely retain the terminal
in the socket. The tensioned magnet wire running across
the interior of each socket is also wedged in the terminal
slots so that the magnet wire is maintained in tension.
The process is completed by severing, or shearing,
both tracks 274, 276 at the location where they join their
respective sockets, severing the magnet wire in the
process, and by shearing post 256 from flange 228 at the
base of the post.
Cap 66 is also an injection-molded plastic part, and
its details can be seen in Figs. 3, 5, and 41-43.
Surrounded by shell 82 are end portions of five electrical
terminals 290, 292, 294, 296, and 298. Terminals 290, 292,
294 provide for electrical connection of the sensor within
tower 80 to the engine electrical system, while terminals
296, 298 provide for electrical connection of coil 232 with
the system. Each terminal 296, 298 is a blade-type that a
flat end portion within shell 82 and an opposite end
portion adapted for mating connection with a respective
terminal 264 in a respective socket 260, 262. Each
terminal 296, 298 has an intermediate 90 degree bend so
that the opposite end portions are at a right angle to each
other, with the end that mates with a terminal 264 having
its length parallel to axis 72 and its width perpendicular
to its length as viewed in Fig. 42. That Fig. further
shows that this end of each terminal 296, 298 comprises a
respective forked blade 300, 302 both of which are disposed
within a surrounding shell 304 of the cap. Fig. 43 shows
that each forked blade has a reduced thickness from that of
the portion that is embedded within the plastic of cap 66.
This allows the forked blades to be deflected in
cantilever-like fashion, as shown in Fig. 5, when mated
with a respective terminal 264. Shell 304 is shaped for
fitting to sockets 260, 262, as also shown in Fig. 5.
Figs. 25-28 show the shape of clinch ring 86 prior to
its being formed to the shape shown in Fig. 5. It
comprises a cylindrical side wall 306 and an upper circular
flange 308 projecting radially inward from the upper end of
the side wall. Fig. 26 shows that flange 308 is at
slightly less than a right angle to side wall 306. The
radially inner edge of flange 308 also contains integral
downward turned pointed barbs 310, the illustrated
embodiment having four such barbs at ninety degree
intervals around the ring by way of example. These barbs
will bite slightly into the polymeric material of the outer
perimeter rim of wall 85 of cap 66 in the finished valve 60
to aid in resisting rotational displacement of the cap
relative to shell 64. Two barbs point in one
circumferential sense while the remaining two point in the
opposite circumferential sense.
After the cap has been placed onto the top of shell
64, the clinch ring is placed over the abutting perimeter
rims of the cap and shell, and the lower portion of side
wall 306 is turned inwardly to the position shown by Fig.
5. The initial shape of clinch ring 86 provides for a
final shape that applies an axial holding force that
effectively immovably clamps the two parts 64, 66 together,
so that neither axial nor circumferential movement between
them can occur.
Fig. 44-46 show an alternate form of clinch ring which
is like the one of Figs. 25-28, but for the shape and
location of barbs 310. In this alternate embodiment, the
barbs are lanced from material of the upper flange that is
spaced inwardly from the flange inner edge. Each barb
points circumferentially as viewed in plan, two in one
sense, two in the opposite sense, and is symmetrical about
its pointed tip.
Returning once more to Fig. 5, one can see that upper
stator member 194 and solenoid coil assembly 222 have been
joined to form an assembly. The joining is done by placing
upper stator member 194 onto the top of bobbin 224 such
that posts 252, 254, while still in the condition shown in
Figs. 29 and 30 but after coil 232 has been wound on core
226 and electric terminals 264 inserted into their sockets,
pass through the holes 218, 220 in flange 198 of the upper
stator member. The tapered ends of the posts are then
deformed to create heads 314 that cooperate with upper
bobbin flange 228 to capture the stator flange 198 between
themselves. It should be noted that Fig. 5 shows one post
and its head 314 ninety degrees out of position
circumferentially, for illustrative clarity only.
Fig. 5 shows a spring wave washer 320 disposed between
lower bobbin flange 230 and flange 176 of lower stator
member 174. Details of spring wave washer 320 are shown in
Figs. 21-22. Wave spring washer 320 serves to assure that
upper bobbin flange 228 is maintained against upper stator
flange 198 should there be any looseness in the bobbin
flange attachment to the upper stator flange provided by
posts 252, 254 and their heads 314. Under extremely harsh
operating conditions, the polymeric material of the bobbin
and its two integral posts with their formed heads might
experience expansion and/or creep that would cause
looseness, but this is prevented by the action of wave
spring washer 320 keeping the upper bobbin flange against
the upper stator flange. The spring characteristic of wave
washer 320 can also keep the rim of flange 176 forcefully
seated against an internal shoulder 64a of shell 64,
although the press-fit of the lower stator member to
bearing member 140 should not result in axial separation of
the rim of flange 176 from shoulder 64a.
The upper stator/solenoid coil assembly is accurately
and securely located within shell 64 by virtue of the
previously described press fitting of flange 198 to the
side wall of shell 64 at shoulder 64b. The upper and
lower stator members are accurately axially positioned
relative to one another by accurately controlling the axial
distance between the two shoulders 64a and 64b in shell 64.
Since both shoulders are in a single part, tighter
tolerancing of that axial distance is made possible.
Greater control of the concentricity of the two stator
members is also made possible by shell 64. By controlling
the concentricity of the hole in the bottom wall of shell
64 into which ridge 166 of bearing member 140 is pressed,
to the concentricity of shoulder 64b, the bearing member's
concentricity is controlled, and through the press fit of
lower stator member 174 to the bearing member, the
concentricity of the lower stator member is controlled.
Consequently, concentricity of the lower stator member to
the upper stator member is controlled through shell 64 and
bearing member 140. Shoulder 64a is made sufficiently wide
not to interfere with this control.
The accurate relative positioning of the two stator
members is important in achieving the desired air gap in
the magnetic circuit that is provided by the two stator
members and shell 64, all of which are ferromagnetic. The
air gap is designated 322 is present between the respective
walls 180 and 196 of the respective stator members.
A portion of armature 116 axially spans air gap 322,
radially inward of walls 180 and 196. A non-magnetic
sleeve 326 is disposed in cooperative association with the
two stator parts and armature-pintle assembly 112. Part
326 has a straight cylindrical wall 328 extending from an
outwardly curved lip 330 to keep armature 116 separated
from the two stator members. Part 326 also has a lower end
wall 332 that is shaped for seating on lower stator member
174 and for providing a spring seat 334 for a helical coil
spring 336. Wall 332 also has a central hole to allow the
shaft of pintle 114 to pass through.
Armature 116 is ferromagnetic and comprises a
cylindrical wall 340 coaxial with axis 72 and a transverse
internal wall 342 across the interior of wall 340 at about
the middle of the length of wall 340. Wall 342 has a
central hole that provides for the upper end of pintle 114
to be attached to the armature by the fastening means that
includes a calibration nut 346, a shim 348, a wave spring
washer 350. Wall 342 also has three smaller bleed holes
352 spaced outwardly from, and uniformly around its central
hole.
Shim 348 is circular in shape having flat, mutually
parallel end wall surfaces between which extends a straight
circular through-hole that is coaxial with axis 72. The
shim's O.D. is tapered, as shown. Shim 348 serves three
purposes: 1) to provide for passage of the upper end
portion of pintle 114; 2) to provide a locator for the
upper end of spring 336 to be substantially centered for
bearing against the lower surface of wall 342; and 3) to
set a desired axial positioning of armature 116 relative to
air gap 322.
Detail of wave spring washer 350 is shown in Figs. 23
and 24 in its uncompressed shape. It has the annular shape
of a typical wave spring washer, but with three tabs 360
equally spaced about its inner perimeter that are
dimensioned for a very slight interference fit with a
portion of calibration nut 346 to allow it to be retained
on the nut for assembly convenience when attaching the
pintle to the armature.
The O.D. of calibration nut 346 comprises straight
cylindrical end portions between which is a larger
polygonally shaped portion (i.e. a hex). The lower end
portion of the nut has an O.D. that provides some radial
clearance to the central hole in wall 342. It is onto the
lower end portion that wave spring washer 350 is assembled,
prior to calibration nut 346 being threaded onto threaded
stud 118 of the pintle. When calibration nut 346 is
threaded onto threaded stud 118, wave spring washer 350 is
axially compressed between the lower shoulder of the nut's
hex and the upper surface of wall 342 surrounding the
central hole therein. The nut is tightened to a condition
where a shoulder on pintle 114 just below stud 118 engages
shim 348 to force the flat upper end surface of shim 348 to
bear with a certain force against the flat lower surface of
wall 342. The calibration nut does not abut the shim.
Wave spring washer 350 is, at that time, not fully axially
compressed, and this type of joint allows armature 116 to
position itself within sleeve 326 to better align to the
guidance of the pintle that is established by bearing
member 140. Hysteresis is minimized by minimizing any side
loads transmitted from the pintle to the armature, or from
the armature to the pintle, as the valve operates, and the
disclosed means for attachment of the pintle to the
armature is highly effective for this purpose.
Armature 116 is accurately axially positioned
relative to air gap 322 by controlling the axial
dimension of shim 348. The axial distance between the
air gap and the valve seat is measured. The axial
distance along the pintle between the location where
valve head 117 seats on the valve seat and the location
where the shoulder of the pintle bears against the shim
is measured. Based on these two measurements, the axial
dimension of the shim can be chosen such that the
armature, when fastened to the pintle and disposed
against the pintle shoulder, will be in a desired axial
position to the air gap.
The position sensor that is housed within tower 80
of cap 66 comprises a plunger 414 that is self-biased
against the flat upper end surface of nut 346. The
sensor is accurately calibrated to the axial position of
the armature-pintle assembly by setting the axial
location of the flat upper end surface of calibration nut
346. The axial dimension of the calibration nut is at
least a certain minimum. The flat upper surface is
ground, as required, to achieve a desired location that
will cause plunger 414 to assume a desired calibration
position when abutting the upper end of the calibration
nut.
The inventive features that are the subject of this
disclosure relate to provision of concentricity of lower
stator member 174 to bearing member 140 by the
aforementioned press-fit, and to the shaping of the lower
stator member 174 to resist muddy water intrusion. Because
flutes 168 provide for communication between air space 76
and section 186 of the through-hole in lower stator member
174, muddy water that enters the air space via through-slots
78 can possibly intrude into section 186. Since a
portion of pintle shaft 114 passes through section 186, it
is possible that muddy water can reach the pintle shaft.
However, by the same token, the flutes also provide a path
for drainage. Additionally, the frusto-conical shaped
section 182 of the lower stator member tends to deflect
muddy water away.
Cylindrical wall 178 ends at a lower edge surface 400.
Muddy water that intrudes through through-slots 78 tends to
deposit on the inside of the bottom wall of shell 64 below
the lower edges of through-slots 78. If the lower edge
surface 400 were to be situated below the lower edges of
through-slots 78, negative pressure in section 186 (caused
by leakage of vacuum through the very small sliding
clearance between the pintle shaft and member 140) could
draw the muddy water into section 186 where it might
intrude into the sliding clearance. Edge surface 400 is
therefore situated above the lower edges of through slots
178. Consequently, as muddy water, or drops, fall from the
lower surface of lower stator member 174, or run downwardly
along the outside of cylindrical wall 178, they will tend
to fall toward the shell's bottom wall, rather than being
sucked into section 186 via flutes 168. Because surface
182 tapers downwardly and outwardly away from straight
section 184 to the inner edge of lower edge surface 400, it
helps to guide water away from section 186.
While the foregoing has described a preferred
embodiment of the present invention, it is to be
appreciated that the inventive principles may be practiced
in any form that falls within the scope of the following
claims.