Apparatus and method for electronically controlled hydraulic actuator

An electronically controlled hydraulic unit (10) for use in an anti-lock braking system in an automobile and a method of assembling a coil mounting subassembly are disclosed. The coil mounting assembly includes a wiring or printed circuit board (48, 148, 248) on which toroidal coils (16) are mounted with traces leading to pin terminals (46, 146, 246) to attach this wiring or printed circuit board subassembly to an electronic control board (56). Coils are soldered to this board in a conventional offline soldering operation. The coil wiring or printed circuit board is mounted to a peripheral housing frame (34, 134) and a peripheral seal (42, 142) is located between the wiring or printed circuit board and the housing frame. The printed circuit board serves as a sealing bulkhead when mounted between the electronic control board and a hydraulic pump subassembly.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the fabrication of a sealed and shielded 
hydraulic pump assembly for use in a system such as an anti-lock braking 
system on an automobile. Hydraulic valves or actuators are controlled by 
an electronic control unit which applies electric current to solenoid 
coils surrounding the valves to actuate the valves. The assembly is sealed 
and a seal is established between a hydraulic subassembly and the 
electronic control subassembly. 
2. Description of the Prior Art 
The hydraulic unit for anti-lock braking systems on automobiles includes a 
hydraulic pump and an electrical control unit. The hydraulic pump or valve 
actuator unit of these devices includes a number of valves or domes in the 
form of cylindrical members or fingers. The valve element in these 
cylindrical members is actuated by the magnetic force induced by the 
current flowing in a toroidal solenoid coil in which the cylindrical 
member fits. Standard units can have six to ten valve actuators. 
Commercially available systems employ an assembly consisting of two 
separate components. A hydraulic control unit containing the valves and 
coils for activating the valves are housed in one unit. An electronic 
control unit is located in a separate unit and connected to the hydraulic 
control unit by electrical cable. 
Other prior art systems have been designed in which the hydraulic control 
unit and the electronic control unit are housed as part of the same 
assembly. In these single assembly configurations, the hydraulic control 
unit or subassembly must be isolated from the electronic control unit or 
subassembly. The two subassemblies must be hydraulically isolated. These 
single assembly prior art devices have solenoid coils located in a coil 
chamber located between the unit containing the hydraulic valves and the 
electronic control unit which applies a current to the appropriate coil to 
activate the corresponding valve. These coils have a winding mounted on a 
bobbin which is in turn encased in a metallic coil housing. Coil leads 
extend from the lower coil housing. A number of these individual coils are 
mounted in a coil chamber housing consisting of a plastic housing having 
pillars extending upward from the lower surface of the coil housing to 
define individual, substantially cylindrical, cavities into which 
individual coils are inserted. A gasket is positioned between the 
individual coil housing and the floor of the coil chamber housing to 
provide a resilient spring force between the coil and the floor. 
After the coils are inserted in the coil chamber housing, the coil leads 
extend through openings in the floor of the coil chamber housing where 
they can be connected to the electronic control unit. This connection can 
be established by soldering the coil leads to a lead frame molded in the 
housing. Alternatively they can be soldered directly to a printed circuit 
board which comprises the main substrate for the electronic control 
subassembly, or they can be soldered to a separate printed circuit board 
which is heat staked on the exterior of the floor of the coil chamber 
housing. 
Several different versions of these assemblies, each containing a different 
number of coils, are commonly used. The same coil chamber housing is 
typically used for multiple configurations to eliminate the cost of 
multiple molds. In order to maintain the integrity of the floor of the 
coil chamber housing, which serves as a sealing bulkhead, these holes must 
be filled by a separate manufacturing operation, adding additional cost to 
the product. One method of filling these holes is to pot the lower portion 
of the inner chamber of the coil chamber housing. 
After assembling the coils in the coil chamber housing, this subassembly 
can be tested for electrical continuity and integrity or this test can be 
done after interconnection of the coil to the electronic control unit. In 
either case, any defect in the coils or the coil subassembly will be 
difficult or impossible to repair, thus adding cost to the final product. 
SUMMARY OF THE INVENTION 
This invention relates to an improved hydraulic pump assembly which can be 
part of an anti-lock braking system in an automobile. This assembly 
includes a hydraulic valve subassembly, an electronic control subassembly 
and a coil mounting subassembly. The coil mounting subassembly comprises a 
wiring board, such as a printed circuit board, to which a number of 
individual coils are soldered. The wiring or printed circuit board is then 
mounted in a peripheral frame with a peripheral seal engaging both the 
frame and the wiring or printed circuit board. The wiring or printed 
circuit board will then serve as a sealing bulkhead or wall when the 
hydraulic valve subassembly is mounted on one end of the peripheral frame 
and the electronic control subassembly is mounted to the other end of the 
peripheral frame. The wiring or printed circuit board and the peripheral 
frame, which is otherwise open on both the top and bottom will then 
effectively seal the electronic control subassembly from the hydraulic 
valve subassembly. 
The wiring or printed circuit board can also be double sided with one side 
having a substantially continuous conductive layer which can serve as an 
EMI/RFI shield. In combination with an external cover, the shield provided 
by this printed circuit board can reduce the susceptibility of the 
electronic control unit to external radiation or reduce the radiation 
emitted by the electronic control unit. This shield can be used in 
conjunction with the sealed unit or separately. 
The method of fabricating this unit includes the steps of first soldering 
all of the coils to the coil printed circuit board. Different wiring or 
printed circuit boards dependent upon the desired coil population can be 
used eliminating the need to fill unused openings in the member forming 
the sealing bulkhead. Prior to further assembly operations, this coil 
wiring or printed circuit board subassembly can be tested. The coil wiring 
or printed circuit board can then be assembled to a peripheral mounting 
frame with a peripheral seal being formed. Alternatively the board may be 
sealed on either the upper or the lower face. This peripheral frame and 
the coil wiring or printed circuit board now form a coil and sealing 
subassembly to which the hydraulic subassembly and the electronic control 
subassembly can be mounted on opposite ends of the peripheral frame with 
the coil wiring or printed circuit board now forming a sealing bulkhead 
between them. 
A paramount object of this invention is to reduce the cost of the entire 
electronically controlled hydraulic pump assembly. This invention achieves 
that object by reducing the cost of components, by eliminating assembly 
operations and by reducing costs associated with defective components or 
subassemblies. A key feature of this invention is that the coil 
subassembly is adapted for offline assembly. The coils can be attached to 
the printed circuit board by conventional soldering processes such as 
through hole soldering or reflow soldering. This subassembly can then be 
tested prior to its use with other subassemblies and prior to other 
assembly operations. Rework is now possible and will be less expensive. 
Furthermore this offline assembly operation is conventional in nature. 
Other components are not unnecessarily exposed to wave or reflow soldering 
operations. Thus the plastic housing is not exposed to he high 
temperatures associated with soldering operations and less expensive 
materials can be employed. 
By initially mounting the coils to the printed circuit board, the mounting 
frame now becomes a simpler pan. This reduces the complexity and therefore 
cost of the mold as well as reducing mold cycle time. A simpler part also 
requires less material resulting in an additional cost saving. 
Manufacturing steps required by the use of a common part can also be 
eliminated. No longer is a potting operation necessary to fill unused 
opening in the floor of the housing. The tooling costs required to produce 
different boards for each coil population are insignificant when compared 
to mold tool costs to make different molded parts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The electronically controlled hydraulic unit 10 shown in FIG. 1 is intended 
for use in an anti-lock braking system in an automobile. As shown in FIG. 
1, the hydraulic actuator unit, subassembly or pump 12 is shown partially 
removed to expose the interior of the unit. More specifically the 
orientation of FIG. 1 is intended to show the valve actuators 14 on the 
hydraulic unit 12 and the solenoid coils 16. The pump 12 and the valve 
subassembly containing valves 14 are part of the same hydraulic actuator 
subassembly. The valve actuators 14 are referred to as domes and comprise 
generally cylindrical members. When the unit is properly assembled, these 
valve actuators extend through the center of the toroidal coils 16 so that 
the magnetic field induced by the application of an electrical current to 
the coils 16 causes the valve located in the corresponding valve actuator 
member 14 to move between a seated and an unseated position. Bosses 18 
which receive conventional fastening members, not shown are shown on the 
exterior of the body of the assembly. For example bolts extending upward 
through bosses 18 could be used to attach the hydraulic subassembly 10 in 
position. Other conventional fastening means, such as clamps, or other 
similar devices known to one skilled in the art could also be employed. 
The hydraulic unit 10 also includes an input output connector 20 located on 
the exterior of the coil chamber in which the coils 16 are located. This 
electrical connector 20 provides for the input and output of both 
electrical power and signal currents to the device. A second connector in 
the form of header 22 mates with connector 24 to deliver power over 
external cable 26 to the hydraulic pump 12. 
FIG. 2 is a top plan view of the peripheral coil mounting housing frame 34 
of the first embodiment of this invention. Signal terminals or pins 30 and 
power pins 32 in connectors 20 and 22 are visible in this view. These pins 
can be stitched in the plastic coil mounting housing 34 in a conventional 
manner. The coil mounting housing 34 has continuous peripheral sidewalls 
36 extending upward from the base of the housing 34 to form a coil chamber 
in which a plurality of coils 16 can be located. The sidewalls are shown 
more clearly in FIG. 3. The pin header connectors 20 and 22 are located on 
an extension of the base 38 of the coil mounting housing 34. The coil 
mounting housing 34 also contains a sealing rim 40 consisting of an 
upwardly facing surface surrounding the central area in which the coils 
will be positioned. In the embodiment of FIG. 2, this sealing rim 
comprises an upwardly facing surface which extends completely around the 
inner periphery of the sidewalls 36. 
The exploded section view of FIG. 3 shows the components of the coil 
mounting subassembly 28, the electronic control unit control board 56 and 
the lower cover 58. The coil mounting subassembly 28 comprises the coils 
16 mounted to coil printed circuit board 48, which is mounted in the coil 
mounting housing 34 formed by sidewalls 36, and a resilient seal 42 which 
maintains sealing integrity between the coil printed circuit board 48 and 
the coil housing 34. In this embodiment a plurality of electrical contact 
terminals in the form of pins 46 are also mounted on the coil printed 
circuit board 48. These pins are shown in a conventional single row 
configuration. 
Each of the coils 16 has two coil leads 50 extending from the bottom. These 
coil leads are bent to provide resiliency so that the solder joint will 
not be stressed when a compressive load is applied to the coil in the 
direction parallel to the axis of the coil. Although not shown, these 
coils are otherwise conventional in construction. A winding on a bobbin is 
housed in a metallic coil enclosure with the coil leads extending axially 
from the bottom of the bobbin. A coil seal or gasket 52 is positioned 
between each coil 16 and the printed circuit board 48. In the embodiment 
shown herein this gasket is secured to the outer periphery of a coil 
mounting seat 51 which includes a snap in hold down feature 54 extending 
from the center of the gasket. This hold down feature extends through a 
hole in the coil printed circuit board and secures the coil to the printed 
circuit board. This coil seat can be secured to the printed circuit board 
and the coil can be subsequently snapped into engagement with this seat 
51. Alternatively the hold down seat can be insert molded to the coil 16 
and its outer metal coil housing and the hold down feature 54 can be used 
to secure the coil 16 to the printed circuit board 48. When the gasket or 
seal 52 is compressed a seal is formed prohibiting the passage of fluids 
through the printed circuit board hole in which the hold down is located. 
In addition to providing sealing integrity, this seal or gasket 52 also 
imparts resilience to the coils so that when a downward load toward the 
coil printed circuit board is applied to the coil, the seal or gasket 
resists that force and urges the coil upward . This significance of this 
resilience will be subsequently described. It should be understood that 
the seal or gasket 52 can also be mounted to the coil 16 by insert molding 
the seal to the exterior of the coil body. 
The sidewalls 36 on the coil mounting housing are shown in section in FIG. 
3. FIG. 2 shows that these sidewalls are continuous to form a frame or 
shroud extending around all four sides of the coil cavity defined by the 
housing 34. This cavity is open on both the top and the bottom of 
sidewalls 36. A sealing rim 40 having an upwardly facing surface extends 
completely around the inner periphery of the upstanding sidewalls 36. The 
opening defined by this sealing rim is smaller than the coil printed 
circuit board 48 so that the coil printed circuit board overlaps the 
sealing rim 40 around its entire peripheral length. A seal 42 is 
positioned on the upper surface of the sealing rim 40 between the sealing 
rim and the coil printed circuit board 48. This seal 42 may be a resilient 
member or it may be a viscous sealing material deposited on the sealing 
rim Conventional materials are available to form a suitable seal of this 
type when placed under compression. In this configuration, the coil wiring 
board subassembly, comprising a plurality of coils 16 soldered to the coil 
printed circuit board 48, is mounted in the coil housing 34 by inserting 
the coil wiring board subassembly into the open top of the housing 34. The 
coil printed circuit board 48 can then be seated on the sealing rim with 
the seal 42 maintaining sealing integrity therebetween. One or more 
staking pins 44 extending upwardly from the housing 34 can be bent over to 
hold the coil printed circuit board securely in place. 
FIG. 4 shows coil subassembly secured to the coil housing 34. FIG. 4 also 
shows the assembled configuration of the electronic control printed 
circuit board 56. As depicted herein, this printed circuit board contains 
a number of components, shown here only in representative form. The exact 
configuration of this control board does not form part of the subject 
matter of the invention disclosed herein. This control board subassembly 
includes the hardware of the electronic control subassembly or unit. Note 
that pins 46 can be soldered to control board 56 after assembly of the 
coil board 48 in housing 34. As part of the same operation, the pins in 
the input/output header 20 can also be soldered to control board 56. In 
the position shown the coil printed circuit board 48 now forms a sealing 
bulkhead above the control board 56. As shown in FIG. 4, the tops of coils 
16 extend above the upper edge of the sidewalls 36 of the housing frame 
34. When the hydraulic actuator subassembly is secured the subassembly 
shown in FIG. 4, the lip surrounding the base of the valves engage the 
tops of the metal coil housing of coils 16 forming a tight metal to metal 
interface. The coils are forced down and the resilient coils sealing 
members 52 exert a force urging the metal coil housings of coils 16 upward 
into engagement with valve lips. A continuous magnetic flux path is thus 
formed through the coil housing and the metal valves. 
FIGS. 5 and 6 show both sides of the double sided coil printed circuit 
board 48. FIG. 5 shows the bottom or solder side of the board. Plated 
through holes 62 are provided so that the coils 16 can be soldered to this 
board. Header 64 is a connector with a plurality of terminals or pins 46 
soldered to the printed circuit board 48. These pins can be soldered in 
plated through holes which are obstructed by the presence of the header in 
FIG. 5. Substantially all of the side of the printed circuit board 48 
shown in FIG. 5 has a substantially continuous conductive surface 60 which 
can serve as a shield. In the preferred embodiment, this conductive 
surface 60 comprises a layer of copper deposited on the insulative 
substrate. Portions of this copper layer surrounding the plated through 
holes 62 have been etched to provide an annular insulating area 
surrounding the solder joints connecting the coils 16 and the pins 46 to 
the plated through holes. This conductive layer can serve as a shield 
since it is positioned on one side of the control printed circuit board 
56. This conductive layer could also serve as a ground plane. The 
electronic circuits on this control board can thus be shielded from 
electromagnetic radiation along this side of the assembly. Alternatively 
this shield would also prevent radiation emanating from the electronic 
control circuit from affecting other components. FIG. 6 shows the opposite 
coil mounting or component side of printed circuit board 48. The traces 66 
which would connect the coils 16 to the pins 46 are shown in FIG. 6. In 
the preferred embodiment this printed circuit board would be a 
conventional 0.062 inch thick FR-4 printed circuit board. Alternatively 
thicker boards could be employed. 
FIGS. 7 and 8 show an alternative version of assembly in which the printed 
circuit board 148 is mounted to the peripheral housing frame 134 from the 
bottom instead of from the top as in the embodiment of FIGS. 2-6. FIGS. 7 
and 8 show the bottom mounted embodiment in a fashion analogous to the way 
that FIGS. 3 and 4 show the top mounted embodiment. The sealing rim 140 
comprises a downwardly facing annular surface along which a seal 142 is 
located. This seal 142 engages the top surface or component side of the 
coil printed circuit board 148. In the embodiment of FIG. 7, the terminals 
or pins 146 are not initially mounted in a printed circuit board header as 
for the top mounted version. In this embodiment the pins 146 are stitched 
in the housing 134 using a conventional terminal assembly stitching 
machine. Thus the pins are not soldered to the coil printed circuit board 
148 until after this board is mounted on the housing frame 134. This 
embodiment does require staking or mounting pins 144. Other components of 
the second embodiment perform similar functions to the corresponding 
component of the first embodiment. This similarity is represented by using 
a "1" prefix for the corresponding component. For example coil 116 
corresponds to coil 16 of the first embodiment. 
The first and second embodiments of this invention show the use of a 
conventional copper laminate printed circuit board. These printed circuit 
boards comprise only one type of wiring board which can be employed. FIGS. 
9 and 10 show an insert molded wiring board 248 in which a stamped and 
formed lead frame is used. Insert molding in a conventional operation in 
which the lead frame is mounted in a mold and then plastic is injected 
around the lead frame. Portions of the lead frame are then severed to form 
distinct traces which serve the same purpose as traces on conventional 
printed circuit boards. As shown in FIG. 9 these lead frame traces include 
holes 262 through which coil leads 52 can be inserted. Solder pads, which 
are integral portions of the lead frame traces, surround these holes and 
the coil leads can be soldered directly to these pads in a conventional 
fashion. As shown in FIG. 10, the pins 246 are also integral portions of 
the lead frame which have been formed at right angles to the portion of 
the lead frame which forms the traces. Plastic has been insert molded 
around portions of the pin 246 leaving the ends of the pins exposed for 
soldering to the control board. This plastic surrounding pins 246 can 
serve as wiring board separators and it also serves to secure the lead 
frame to the plastic substrate. The insert molded wiring board 248 of the 
type shown in the embodiment of FIGS. 9 and 10 can be substituted directly 
for the printed circuit boards 48 and 148 of the first two embodiments. 
The assembly operations of both embodiments of this invention are 
conventional and these components are reliably manufacturable. The 
components are first soldered to the wiring or printed circuit board using 
conventional soldering operations. For example, the components can be wave 
soldered. If the first embodiment is wave soldered, a secondary operation 
will be necessary to remove solder deposited on the pins 46. This 
operation can be performed with a hot air knife and is a conventional 
operation. Alternatively solder paste can be deposited on printed circuit 
pads adjacent to the plated through holes, and a surface mount operation, 
such as reflow soldering can be used to solder the coils and the pins to 
the printed circuit board. These same conventional offline soldering 
operations can also be employed to solder coils to the insert molded 
wiring board 248 of FIGS. 9 and 10. The seals 24 can be molded elastomer 
seals or a viscous sealant can be deposited along the sealing rim. This 
sealant can also be an adhesive. The materials used for the seal are 
conventional and readily available. The housing frame is an injection 
molded member which can be easily fabricated. No special materials are 
necessary. Pins 46, 146 or 246 can also be soldered to the control boards 
56 and 156 can be soldered using conventional techniques. 
Although three embodiments are depicted herein, it will be appreciated by 
those skilled in the an that numerous other equivalent embodiments can be 
used in the same manner as those depicted herein. These two embodiments 
are intended to be representative only.