U.S. patent application number 09/739961 was filed with the patent office on 2001-08-23 for electronic control unit having connector positioned between two circuit substrates.
Invention is credited to Sanada, Kazuya, Yagura, Toshiaki.
Application Number | 20010015887 09/739961 |
Document ID | / |
Family ID | 26585908 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015887 |
Kind Code |
A1 |
Sanada, Kazuya ; et
al. |
August 23, 2001 |
Electronic control unit having connector positioned between two
circuit substrates
Abstract
The electronic control unit controls operation of actuators
connected thereto based on sensor signals fed thereto and processed
therein. The unit includes a control circuit substrate carrying
control elements such as a microcomputer and a driving circuit
substrate carrying driving elements such as power transistors. The
driving circuit substrate handling power and the control circuit
substrate handling only signals are separately positioned in a
metal casing with a separating space therebetween to suppress heat
transfer from the driving circuit substrate to the control circuit
substrate. A connector electrically connecting the unit to outside
sensors and actuators is positioned in the separating space to
utilize the separating space also as a space for containing the
connector.
Inventors: |
Sanada, Kazuya;
(Kariya-city, JP) ; Yagura, Toshiaki; (Nukata-gun,
JP) |
Correspondence
Address: |
LAW OFFICE OF DAVID G POSZ
2000 L STREET, N.W.
SUITE 200
WASHINGTON
DC
20036
US
|
Family ID: |
26585908 |
Appl. No.: |
09/739961 |
Filed: |
December 20, 2000 |
Current U.S.
Class: |
361/704 |
Current CPC
Class: |
H05K 5/0082 20130101;
H05K 7/209 20130101; H05K 7/20854 20130101; H05K 1/144 20130101;
Y10T 29/4913 20150115 |
Class at
Publication: |
361/704 |
International
Class: |
H05K 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2000 |
JP |
2000-45907 |
Mar 15, 2000 |
JP |
2000-72356 |
Claims
What is claimed is:
1. An electronic control unit comprising: a casing including a heat
dissipation plate; a driving circuit substrate having driving
elements mounted thereon for supplying electric power in a
controlled manner to actuators connected to the electronic control
unit, the driving circuit substrate being mounted on the heat
dissipation plate; a control circuit substrate having control
elements mounted thereon for controlling operation of the driving
elements based on signals fed from sensors connected to the
electronic control unit, the control circuit substrate being
contained in the casing apart from the driving circuit substrate
with a separating space; and a connector for electrically
connecting the actuators and sensors to the electronic control
unit, wherein: the connector is contained in the casing so that at
least a part of the connector is positioned within the separating
space.
2. The electronic control unit as in claim 1, wherein: the
separating space is formed between the driving circuit substrate
and the control circuit substrate disposed in parallel to each
other, and the connector is positioned as a whole within the
separating space.
3. The electronic control unit as in claim 1, wherein: the driving
circuit substrate and the control circuit substrate are
electrically connected to each other through flexible wires.
4. The electronic control unit as in claim 3, wherein: the flexible
wires are integrally formed as a single flexible
printed-circuit-sheet.
5. The electronic control unit as in claim 4, wherein: the
connector is mounted on, and electrically connected to the control
circuit substrate by a plurality of connector pins; and the
flexible printed-circuit-sheet is electrically connected to the
driving circuit substrate at one end thereof and to the control
circuit substrate at the other end, the other end being positioned
at a vicinity of the connector pins connected to the control
circuit substrate.
6. The electronic control unit as in claim 4, wherein: the flexible
printed-circuit-sheet is electrically connected to the driving
circuit substrate at one end thereof and to the control circuit
substrate at the other end; and the connector is mounted on the
casing and electrically connected to the flexible
printed-circuit-sheet at a position between both ends of the
flexible printed-circuit-sheet.
7. A method of manufacturing the electronic control unit defined in
claim 5, the method comprising: electrically connecting both ends
of the flexible printed-circuit-sheet to the driving circuit
substrate and to the control circuit substrate, respectively; and
then mounting the connector on and electrically connecting to the
control substrate.
8. A method of manufacturing the electronic control unit defined in
claim 6, the method comprising: electrically connecting the
connector to the flexible printed-circuit-sheet; electrically
connecting both ends of the flexible printed-circuit-sheet to the
driving circuit substrate and to the control circuit substrate,
respectively; and then mounting the connector on the casing.
9. The electronic control unit as in claim 4, wherein: the flexible
printed-circuit-sheet includes a mounting portion for mounting
electrical components thereon and connecting portions formed at
both sides of the mounting portion for connecting the mounting
portion to the driving circuit substrate and to the control circuit
substrate.
10. The electronic control unit as in claim 9, wherein: the
connector is supported by the casing and electrically connected to
the mounting portion of the flexible printed-circuit-sheet.
11. The electronic control unit as in claim 10, wherein:
noise-absorbing elements are mounted and electrically connected to
the mounting portion of the flexible printed-circuit-sheet.
12. The electronic control unit as in claim 10, wherein: a
lead-inserting element is inserted into the mounting portion and
electrically connected thereto.
13. The electronic control unit as in claim 10, wherein: the
mounting portion is made of a hard printed-board, and the
connecting portion is made of a flexible printed-sheet.
14. The electronic control unit as in claim 10, wherein: the
connector includes a holder portion for mechanically supporting the
electrical components mounted on the mounting portion.
15. The electronic control unit as in claim 10, wherein: the
connector is electrically connected to the mounting portion by a
plurality of connector pins, and electrical components are mounted
on the mounting portion at positions outside an area where the
connector pins are located.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims benefit of
priority of Japanese Patent Applications No. 2000-45907 filed on
Feb. 23, 2000 and No. 2000-72356 filed on Mar. 15, 2000, the
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an electronic control unit
for controlling operation of actuators and to a method of
manufacturing the same.
[0004] 2. Description of Related Art
[0005] Electronic control units for use in various controls, such
as automotive engine control and transmission control, are
generally known. The electronic control unit controls operation of
actuators such as electromagnetic solenoids by supplying power
thereto based on signals fed to and processed in the electronic
control unit. Recent electronic controls for an automotive vehicle
are becoming more sophisticated and multi-functional. Electric
power to be controlled by driving elements in the electronic
control unit is also becoming high. An amount of heat generated in
the driving elements such as power transistors or power ICs
contained in the electronic control unit becomes high. Such heat is
transferred to control elements such as microcomputers contained in
the same electronic control unit.
[0006] An example of conventional electronic control units is shown
in FIG. 1. A circuit substrate 40 on which a driving element 5 and
a control element 3 are mounted is contained in a casing 7. A
connector 2 for electrically connecting the electronic control unit
to outside sensors and actuators is also mounted in the casing.
Heat generated in the driving element 5 such as a power transistor
is transferred to the control element 3 such as a microcomputer,
thereby heating the control element 3. If the control element 3 is
excessively heated, its operation stability cannot be maintained.
It could be possible to enlarge the circuit substrate 40 to
suppress the heat transfer from the driving element 5 to the
control element 3. However, it is not preferable, or may not be
possible, to enlarge the size of the electronic control unit from
viewpoints of a mounting space and a cost of the electronic control
unit.
SUMMARY OF THE INVENTION
[0007] The present invention has been made in view of the
above-mentioned problem, and an object of the present invention is
to provide an improved electronic control unit, in which the heat
transfer from the driving elements to the control elements is
suppressed without enlarging the size of the electronic control
unit.
[0008] The electronic control unit according to the present
invention is composed of a metal casing, a driving circuit
substrate, a control circuit substrate, a flexible printed-circuit
sheet connecting both substrates, and a connector for connecting
the electronic control unit to outside actuators and sensors. The
control circuit substrate includes control elements such as a
microcomputer for processing signals fed from the outside sensors
and for supplying control signals to the driving circuit substrate.
The driving circuit substrate includes driving elements such as
power transistors for supplying electric power to the outside
actuators based on the control signals fed from the control circuit
substrate.
[0009] The metal casing has a heat dissipation plate on which the
driving circuit substrate generating a large amount of heat is
mounted. The control circuit substrate that generates substantially
no heat is contained in the casing apart from the driving circuit
substrate. A separating space for suppressing heat transfer from
the driving circuit substrate to the control circuit substrate is
formed between both substrates. The connector is positioned in the
separating space. Thus, the separating space in the casing is also
utilized as a space for containing the connector. Both substrates
are electrically connected by a flexible printed-circuit-sheet
which absorbs vibration energy to protect electrical connections.
The flexible printed-circuit-sheet is connected to the control
circuit substrate at a vicinity of connector pins connecting the
connector to the control circuit substrate to reduce electrical
resistance in the circuit.
[0010] The connector may be mounted on the control circuit
substrate and electrically connected thereto. In this case,
preferably, both substrates are first connected by the flexible
printed-circuit-sheet, and then the connector is mounted on the
control circuit substrate to simplify the manufacturing
process.
[0011] Alternatively, the connector may be mounted on the casing
and electrically connected to the flexible printed-circuit-sheet.
In this case, preferably, the connector is electrically connected
to the flexible printed-circuit-sheet, and then the flexible sheet
is electrically connected to both substrates. After that, the
connector is mounted on the casing. Elements for absorbing noise
coming into the electronic control unit may be surface-mounted on
the flexible sheet. Components having inserting leads may also be
mounted on the flexible sheet, removing such components from the
control circuit board. If no such component is mounted on the
control circuit substrate, electrical connections on the control
circuit substrate can be carried out only by reflow-soldering.
Further, a portion of the flexible sheet on which electric
components are mounted may be made of a hard printed-board to
secure stable electrical connections against vibration. Components
mounted on the flexible sheet may be supported by a holder formed
integrally with the connector to secure a higher mechanical
strength.
[0012] According to the present invention, the driving circuit
substrate and the control circuit substrate are positioned in the
casing with a separating space therebetween, and the connector is
disposed within the separating space. In other words, the
separating space for suppressing the heat transfer is also utilized
as a space for containing the connector therein. Accordingly, the
heat transfer is effectively suppressed without enlarging the size
of the electronic control unit.
[0013] Other objects and features of the present invention will
become more readily apparent from a better understanding of the
preferred embodiments described below with reference to the
following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a cross-sectional view showing a conventional
electronic control unit;
[0015] FIG. 2A is a cross-sectional view showing an electronic
control unit as a comparative example to embodiments of the present
invention;
[0016] FIG. 2B is a plan view of the electronic control unit shown
in FIG. 2A with its upper case removed;
[0017] FIG. 3A is a cross-sectional view showing an electronic
control unit as a first embodiment of the present invention;
[0018] FIG. 3B is a cross-sectional view showing one stage of
assembling the electronic control unit shown in FIG. 3A;
[0019] FIG. 3C is a perspective view showing the same assembling
stage as shown in FIG. 3B;
[0020] FIG. 4A is a cross-sectional view showing one stage of
assembling an electronic control unit as a second embodiment of the
present invention;
[0021] FIG. 4B is a cross-sectional view showing the next
assembling stage following the stage shown in FIG. 4A;
[0022] FIG. 4C is a perspective view showing the same assembling
stage as shown in FIG. 4A;
[0023] FIG. 5A is a cross-sectional view showing an electronic
control unit as a third embodiment of the present invention;
[0024] FIG. 5B is a cross-sectional view showing one stage of
assembling the electronic control unit shown in FIG. 5A;
[0025] FIG. 5C is a cross-sectional view showing the next
assembling stage following the stage shown in FIG. 5B;
[0026] FIG. 5D is a perspective view showing the same assembling
stage as shown in FIG. 5B;
[0027] FIG. 6A is a cross-sectional view showing an electronic
control unit as a fourth embodiment of the present invention;
[0028] FIG. 6B is a cross-sectional view showing the electronic
control unit shown in FIG. 6A, viewed from a connector side;
[0029] FIG. 6C is a cross-sectional view showing one stage of
assembling the electronic control unit shown in FIG. 6A;
[0030] FIG. 6D is a cross-sectional view showing the next
assembling stage following the stage shown in FIG. 6C;
[0031] FIG. 7A is a cross-sectional view showing an electronic
control unit as a fifth embodiment of the present invention;
[0032] FIG. 7B is a cross-sectional view showing the electronic
control unit shown in FIG. 7A, viewed from a connector side;
[0033] FIG. 8A is a cross-sectional view showing an electronic
control unit as a sixth embodiment of the present invention;
[0034] FIG. 8B is a cross-sectional view showing the electronic
control unit shown in FIG. 8A, viewed from a connector side;
[0035] FIG. 9A is a cross-sectional view showing an electronic
control unit as a seventh embodiment of the present invention;
[0036] FIG. 9B is a cross-sectional view showing the electronic
control unit shown in FIG. 9A, viewed from a connector side;
and
[0037] FIG. 10 is a cross-sectional view showing an example of
modified forms of the embodiments shown above.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] One solution for suppressing heat transfer from driving
elements to control elements contained in the same casing is to
divide the circuit substrate 40 shown in FIG. 1 into a substrate
carrying only the control elements thereon and another substrate
carrying the driving elements thereon.
[0039] One example of such arrangements is shown in FIGS. 2A and
2B.
[0040] FIG. 2A is a cross-sectional view and FIG. 2B is a plan view
with an upper case removed. A control circuit substrate 10 carrying
the control element 3 is supported in the middle portion of the
casing 7, while a driving circuit substrate 20 carrying the driving
elements 5 is mounted on bottom heat dissipation plate of the
casing 7. Both substrates are electrically connected by a flexible
printed-circuit-sheet 4. A connector 2 for electrically connecting
the electronic control unit to outside sensors and actuators is
mounted on and electrically connected to the control circuit
substrate 10.
[0041] Since the driving circuit substrate 20 is positioned apart
from the control circuit substrate 10 with a certain space
therebetween, the heat transfer from the substrate 20 to the
substrate 10 can be suppressed. If it is possible to make the space
between two substrates 10, 20 sufficiently large, the heat transfer
would be sufficiently suppressed. However, it is desirable to make
this space smaller to make an entire control unit size smaller. The
height of the upper half space in the casing 7 cannot be shortened
because there is positioned the connector 2.
[0042] A first embodiment of the present invention shown in FIG. 3A
is designed to further improve the example shown in FIGS. 2A and
2B. The first embodiment of the present invention will be described
in detail with reference to FIGS. 3A-3C.
[0043] First, referring to FIG. 3A, the structure of an electronic
control unit 1 will be described. The electronic control unit 1 is
used for controlling operation of various actuators of an
automotive engine 100, such as ignition plugs and electromagnetic
solenoids. The electronic control unit 1 is electrically connected
to the actuators and sensors through a cable 102. The electronic
control unit 1 is composed of a casing 7, a control circuit
substrate 10 carrying control elements 3 thereon, a driving circuit
substrate 20 carrying driving elements 5 thereon, and a connector 2
coupled to the cable 102. Both substrates 10 and 20 are
electrically connected through a flexible printed-circuit-sheet
4.
[0044] The casing 7 is composed of an upper case 7a and a lower
case 7b, and both cases 7a, 7b are connected by screws 8. The
control circuit substrate 10 is mounted in the casing 7, being
inserted between the upper case 7a and the lower case 7b. The
driving circuit substrate 20 is mounted on an inner wall 7d of an
upper wall 7c of the casing 7. The connector 2 is inserted through
a side opening 7e of the upper case 7a so that its portion 2a is
positioned inside the casing 7, and is mounted on the substrate 10.
The connector 2 is positioned in a space between a surface A (the
inner surface 7d of the upper wall 7c) and a surface B (the upper
surface of the substrate 10), preferably in the space between a
surface C (the lower surface of the substrate 20) and the surface
B. A plurality of connector pins 6 extending from the connector 2
are inserted into the control circuit substrate 10 and electrically
connected thereto.
[0045] The control elements 3 consist of an one-chip microcomputer
to which signals from various sensors are fed. The signals fed to
the microcomputer are processed to form control signals to be
supplied to the driving elements 5. The control elements 3 also
perform communication with various electronic components mounted on
the automobile through the cable 102. The control circuit substrate
10 on which the control elements 3 are mounted is made of a resin
board such as an epoxy-impregnated glass-cloth, and control
circuits are formed thereon. Electronic components (not shown)
other than the control elements 3 are also mounted on both sides of
the control circuit substrate 10.
[0046] The connector 2 is mounted on the control circuit substrate
10, and the connector pins 6 are electrically connected to the
control circuit substrate 10. As shown in FIG. 3A, the connector
pins 6 are connected to the control circuit substrate 10 at its
left side end, and one end of the flexible printed-circuit sheet 4
is electrically connected to the control circuit substrate 10 by
soldering at a vicinity of the position where the connector pins 6
are connected. The other end of the flexible printed-circuit sheet
4 is electrically connected to the driving circuit substrate 20.
The flexible printed-circuit sheet 4 is bent and connected to both
substrates 10, 20 with a proper allowance as shown in FIG. 3A, so
that it absorbs vibration transferred from the engine and does not
contacts the upper wall 7c.
[0047] The driving elements 5 mounted on the driving circuit
substrate 20 are so-called switching elements for supplying
electric power to the outside actuators. The electric power is
supplied from an on-board battery (not shown) through the driving
elements based on the control signals fed from the control elements
3. The driving circuit substrate 20 is made of a heat-conductive
ceramic plate on which driving circuits are formed. Components (not
shown) other than the driving elements 5 are also mounted on the
driving circuit substrate 20. The driving circuit substrate is
mounted on the inner surface 7d of the upper wall 7c in close
contact therewith, so that heat generated in the driving elements 5
is easily transferred to the casing 7 and dissipated therefrom. The
casing 7 is made of a metallic material such as cast aluminum, and
its upper wall 7c serves as a heat-dissipation plate.
[0048] A process of assembling the electronic control unit 1 will
be described with reference to FIGS. 3B and 3C. The driving
elements 5 and other components are mounted on and connected to the
driving circuit substrate 20. The driving circuit substrate 20 is
bonded on the inner surface 7d of the upper wall 7c with a
heat-conductive adhesive which is cured by applying heat (e.g.,
150.degree. C.) for a certain time (e.g., 30 minutes). Heat
resistance between the upper wall 7c and the driving circuit
substrate 20 is made as small as possible. On the other hand, the
control elements 3 and other components are mounted on and
connected to the control circuit substrate 10. The connector 2 is
also mounted on and connected to the control circuit substrate
10.
[0049] Then, the upper case 7a carrying the driving circuit
substrate 20 thereon and the control substrate 10 are positioned as
shown in FIG. 3B. The flexible printed-circuit-sheet 4 is placed
over the both substrates 10, 20 through the side opening 7e of the
upper case 7a. Both ends of the flexible printed-circuit-sheet 4
are pressed down on the terminal portions of both circuit
substrates 10, 20 by jigs S. The flexible printed-circuit-sheets 4
is soldered to both substrates 10, 20, at their terminal portions
under heat and pressure. More particularly, solder is attached to
the terminal portions of both substrates 10, 20, and then both ends
of the flexible printed-circuit-sheet 4 are pressed down on the
solder by heated jigs S. Since the connector 2 mounted on the
control circuit substrate 10 prevents the flexible
printed-circuit-sheet 4 from being extended flat, the upper case 7a
and the control circuit substrate 10 are positioned as shown in
FIGS. 3B and 3C (FIG. 3C is a perspective view of FIG. 3B).
[0050] After the flexible printed-circuit-sheet 4 is soldered, the
upper case 7a is flipped over the control circuit substrate 10 so
that the inner surface 7d of the upper case 7a faces the control
circuit substrate 10. Then, the control circuit substrate 10 is
sandwiched between the upper case 7a and the lower case 7b, as
shown in FIG. 3A. Screws 8 are inserted into through-holes 10a
formed on the control circuit substrate 10 and tightly fastened
thereby to form a unitary casing 7.
[0051] The electronic control unit 1 as the first embodiment of the
present invention has the following advantages. Since the connector
2 is positioned in the space between the driving circuit substrate
20 and the control circuit substrate 10, the control substrate 10
can be placed sufficiently apart from the driving circuit 20
thereby to suppress heat transfer from the driving circuit
substrate 20 to the control circuit substrate 10. In other words,
the space for containing the connector 2 in the casing 7, is also
utilized as the space for separating both substrates 10, 20 from
each other. Thus, the harmful heat transfer is effectively
suppressed without enlarging an entire size of the electronic
control unit 1.
[0052] Since both substrates 10, 20 are electrically connected by
the flexible printed-circuit-sheet 4, the electrical connection is
stably secured against vibration transferred to the casing 7.
Vibration caused by engine operation, for example, does not
directly affect the electrical connection because it is absorbed by
the flexibility of the flexible printed-circuit-sheet 4. Since the
soldering of the flexible printed-circuit-sheet 4 to both
substrates 10, 20 can be carried out at the same time, the
manufacturing process of the electronic control unit 1 is
simplified.
[0053] Further, since the flexible printed-circuit-sheet 4 is
soldered to the control circuit substrate 10 at a vicinity of the
connector pins 6, the soldering terminal portions of the control
circuit substrate 10 can be simplified. At the same time,
electrical resistance between the connector pins 6 and the circuit
pattern can be reduced.
[0054] A second embodiment of the present invention will be
described with reference to FIGS. 4A-4C. The structure of the
second embodiment is the same as that of the first embodiment.
However, the assembling process is partly different. That is, the
connector 2 is not yet mounted on the control circuit substrate 10
when the flexible printed-circuit-sheet 4 is soldered to both
substrates 10, 20. As shown in FIGS. 4A and 4C (FIG. 4C is a
perspective view of FIG. 4A), the upper case 7a having the driving
circuit substrate 20 mounted thereon and the control circuit
substrate 10 are placed at a same level L. The flexible
printed-circuit-sheet 4 is extended flat over both substrates 10,
20, and then it is soldered under heat and pressure in the same
manner as in the first embodiment.
[0055] Then, the upper case 7a is flipped over the control circuit
substrate 10 as shown in FIG. 4B. Then, the connector 2 is inserted
through the side opening 7e of the upper case 7a and mounted on and
connected to the control circuit substrate 10. The flexible
printed-circuit-sheet 4 is bent not to contact the connector 2 when
the connector 2 is positioned below the flexible sheet 4. Then, the
lower case 7b is fastened to the upper case 7a, sandwiching the
control circuit substrate 10, in the same manner as in the first
embodiment.
[0056] Since, in the second embodiment, the connector 2 is not on
the way of the flexible sheet 4 in the soldering process, the
flexible sheet 4 can be extended flat over both substrates 10, 20.
Both substrates 10, 20 can be positioned at the same level L to
solder the flexible sheet 4, and therefore, the soldering can be
performed easier.
[0057] A third embodiment of the present invention will be
described with reference to FIGS. 5A-5D. An electronic control unit
51 as the third embodiment is similar to the first embodiment,
except that the connector 2 is replaced with a connector 32 which
is mounted on the flexible printed-circuit-sheet 4, and that the
control circuit substrate 10 is replaced with a control circuit
substrate 30 having a somewhat different shape.
[0058] As shown in FIG. 5A, the connector 32 includes a flange 32b
having a hole 32c. A screw hole 7f is formed through the side wall
of the upper case 7a, and the connector 32 is fixed to the side
wall by a screw 9. The connector 32 is inserted into the casing 7
through the side opening 7e so that it is positioned between the
surfaces A and B, preferably between the surfaces C and B. A
portion 32a of the connector 32 is positioned inside the casing 7.
Connector pins 36 are inserted into a middle portion of the
flexible printed-circuit-sheet 4 and electrically connected
thereto. One end of the flexible sheet 4 is electrically connected
to the driving circuit substrate 20, while the other end is
electrically connected to an end portion of the control circuit
substrate 30. Structures other than the above are the same as those
of the first embodiment.
[0059] Referring to FIGS. 5B-5D, a process of assembling the
electronic control unit S will be described. First, the driving
circuit substrate 20 and the control circuit substrate 30 are
prepared in the same manner as in the foregoing embodiments, but
the connector 32 is not mounted on the control circuit substrate
30. Instead, the connector 32 is electrically connected to the
flexible printed-circuit-sheet 4 at a middle portion thereof. The
driving circuit substrate 20 is mounted on the inner surface 7d of
the upper case 7a.
[0060] Then, as shown in FIG. 5B, the upper case 7a and the control
circuit substrate 30 are positioned in the same horizontal level L.
Then, the flexible sheet 4 carrying the connector 32 thereon is
placed over both substrates 20, 30, and soldered on the terminal
portions of both substrates 20, 30 under heat and pressure. Since
the connector 32 is not an obstacle to stretch the flexible sheet 4
over both substrates 20, 30, the soldering process is easily
carried out by placing both substrates 20, 30 at an even level.
FIG. 5D is a perspective view showing the same stage as shown in
FIG. 5B.
[0061] Then, as shown in FIG. 5C, the connector 32 is mounted on
and fixed to the sidewall of the upper case 7a with the screw 9.
Then, the upper case 7a is flipped over the control circuit
substrate 30, so that the control circuit substrate 30 is
positioned underneath the upper case 7a as shown in FIG. 5A. Then,
the lower case 7b is fixed to the upper case 7a with screws 8
inserted into the through hole 30a formed on the control circuit
substrate 30. The control circuit substrate 30 is sandwiched
between the upper case 7a and the lower case 7b. Thus, the
electronic control unit 51 is completed.
[0062] Since, in this third embodiment, the connector 32 is not
mounted on the control circuit substrate 30 but is mounted on the
sidewall of the upper case 7a and electrically connected to the
middle portion of the flexible sheet 4, the height of the casing 7
can be made further smaller than that of the first embodiment. The
inner space of the casing 7 where the connector 32 is located is
utilized as the space separating both substrates 10, 30 in the same
manner as in the first embodiment, the heat transfer from the
driving circuit substrate 20 to the control circuit substrate 30 is
effectively suppressed without enlarging the size of the casing 7.
Since the connector 32 is electrically connected to the middle
portion of the flexible sheet 4, it is not necessary to form
driving current paths on the control circuit substrate 30. In
addition, the driving current paths from the driving circuit
substrate 20 to the connector 32 are shorter than those in the
first embodiment. Therefore, heat generated in the driving current
paths is further suppressed.
[0063] With reference to FIGS. 6A-6D, a fourth embodiment of the
present invention will be described. The electronic control unit 51
as the fourth embodiment is similar to the third embodiment, except
that noise-absorbing elements 13 are additionally mounted on the
flexible printed-circuit-sheet 4, and that an element 14 having
inserting leads 14a is additionally mounted on the control circuit
substrate 30.
[0064] To suppress or absorb noises entering into the electronic
control unit 51 through the cable 102 and the connectors 32, it is
often required to dispose noise-absorbing elements both on the
driving circuit substrate 20 and on the control circuit substrate
30. The noise-absorbing elements have to be properly selected
according to situations where the electronic control unit is used.
If such noise absorbing elements are mounted on the substrates 20,
30, both substrates cannot be standardized because the
noise-absorbing elements have to be changed according to the
situations. Therefore, in this fourth embodiment, such
noise-absorbing elements 13 are mounted on the flexible sheet 4,
thereby to simplify and standardize both substrates 20, 30 and to
reduce the manufacturing cost of the electronic control unit
51.
[0065] First, referring to FIG. 6A showing a cross25 sectional view
of the electronic control unit 51 and FIG. 6B showing the same
viewed from the side where the connector 32 is mounted, the fourth
embodiment will be described. Since the most structures are the
same as those of the third embodiment, only the structure peculiar
to this embodiment will be described below.
[0066] The flexible printed-circuit-sheet 4 is composed of a
mounting portion on which the connector pins 36 and the
noise-absorbing elements 13 and connecting portions formed at both
sides of the mounting portion. The connecting portions are
electrically connected to both substrates 20, 30, respectively, in
the same manner as in the third embodiment. As shown in FIG. 6B,
the mounting portion includes an area P where the connector pins 36
are inserted and an outer area where the noise-absorbing elements
13 are surface-mounted (mounted on the surface without inserting
leads). The element 14 having inserting leads is mounted on and
connected to the control circuit substrate 30 by inserting its
leads.
[0067] A process of assembling the electronic control unit 51 will
be briefly described with reference to FIGS. 6C and 6D. The driving
circuit substrate 20 is mounted on the inner surface 7d of the
upper case 7a in the same manner as in the foregoing embodiments.
The control elements 3 are surface-mounted on the control circuit
substrate 30, and the element 14 is also mounted on the same
substrate 30 by inserting its leads 14a. The connector pins 36 are
inserted into and soldered on the mounting portion of the flexible
sheet 4, and the noise-absorbing elements 13 are surface-mounted
thereon.
[0068] Then, as shown in FIG. 6C, the upper case 7a having the
driving circuit substrate 20 thereon and the control circuit
substrate 30 having components mounted thereon are positioned at an
even level L. The flexible printed-circuit-sheet 4 having the
connector 32 and the noise-absorbing elements connected thereto is
placed over both substrates 20, 30. The flexible sheet 4 is
electrically connected to the terminal portions of both substrates
20, 30 under heat and pressure in the same manner as in the
foregoing embodiments. Then, as shown in FIG. 6D, the connector 32
is turned by 90 degrees and mechanically fixed to the side wall of
the upper case 7a with screws 9. Then, the upper case 7a is flipped
over the control circuit substrate 30 to place the substrate 30
underneath the upper case 7a. Then, the upper case 7a and the lower
case 7b are mechanically connected by screws 8, sandwiching the
control circuit substrate 30 between the upper case 7a and the
lower case 7b. Thus, the electronic control unit 51 is
completed.
[0069] The same advantages as those of the third embodiment are
obtained in this embodiment, too. In addition, since the
noise-absorbing elements 13 are mounted on the flexible
printed-circuit-sheet 4, noises entering into the electronic
control unit 51 are absorbed by those elements without mounting
respective noise-absorbing elements on both substrates 20, 30.
Further, since the connector pins 36 are connected to the flexible
sheet 4 in the area P while the noise-absorbing elements 13 are
mounted on the area outside the area P, the process of mounting
those components on the flexible sheets is easily carried out.
[0070] Referring to FIGS. 7A and 7B, a fifth embodiment of the
present invention will be described. This embodiment is almost the
same as the fourth embodiment, except that the element 14 having
inserting leads 14a is mounted on and connected to the flexible
printed-circuit-sheet 4. In other words, the element 14 mounted on
the control circuit substrate 30 in the fourth embodiment is moved
to the flexible sheet 4.
[0071] As shown in FIG. 7B, the element 14 having inserting leads
14a is positioned at the center of the mounting area of the
flexible sheet 4 where the connector pins 36 are connected. The
inserting leads 14a are inserted into the flexible sheet 4 in the
same direction as the connector pins 36 are inserted. Accordingly,
the connector pins 36 and the element 14 can be soldered at the
same time by flow-soldering. The control circuit substrate 30 in
this embodiment only carries surface-mounting elements including
the control element 3. Therefore, those surface-mounting elements
can be soldered only by reflow-soldering. If lead-inserting
elements were also included on the same substrate, flow-soldering
would be required in addition to the reflow-soldering.
[0072] Since, in the fifth embodiment, the lead-inserting element
14 is removed from the control circuit substrate 30,. the soldering
process for the substrate 30 is simplified. Since the element 14 is
mounted on the flexible printed-circuit-sheet 4 at a position
between connecting pins 36, the space on the flexible sheet 4 is
effectively utilized.
[0073] A sixth embodiment of the present invention will be
described with reference to FIGS. 8A and 8B. In this embodiment,
the lead-inserting element 14 mounted on the flexible
printed-circuit-sheet 4 is supported by a holder portion 32d
integrally formed with the connector 32. Other structures are the
same as those of the fifth embodiment. The holder portion 32d is
made of the same resin material as the connector 32 and is shaped
in a cylinder which holds the outer periphery of the element
14.
[0074] There is a possibility that the electrical connection of the
lead-inserting element 14 carried by the flexible sheet 4 would be
loosened if the casing 7 is excessively vibrated. For avoiding such
a possibility, the holding portion 32d is formed to support the
lead-inserting element 14 connected to the flexible
printed-circuit-sheet 4.
[0075] A seventh embodiment of the present invention will be
described with reference to FIGS. 9A and 9B. In this embodiment,
the flexible printed-circuit-sheet 4 used in the foregoing
embodiments is divided into two portions, a hard printed-board 60
and flexible printed-sheets 64. The mounting portion for mounting
components including the noise-absorbing elements 13 and the
lead-inserting element 14 is replaced with the hard printed-board
60. The connecting portions for connecting the flexible
printed-circuit-sheet 4 to both substrates 20, 30 are replaced with
the flexible printed-sheets 64. Other structures are the same as
those of the fifth embodiment.
[0076] The hard printed-board 60 is made of a hard resin material
such as glass-epoxy and is shaped into a rectangular shape. The
hard printed-board 60 is mechanically supported by the connector
pins 36 soldered thereon. The flexible printed-sheets 64 made of a
flexible resin material electrically connect the hard printed-board
60 to both substrates 20, 30.
[0077] Since, in this embodiment, the components such as the
noise-absorbing elements 13 and the lead-inserting element 14 are
mounted on and electrically connected to the hard printed-board 60,
the electrical connections of those components are more stable
against vibration.
[0078] The present invention is not limited to the foregoing
embodiments, but those embodiments may be variously modified. For
example, as shown in FIG. 10, the lead-inserting element 14 which
is mounted in the center portion of the flexible
printed-circuit-sheet 4 in the fourth embodiment may be moved to an
outside of the area P where the connector pins 36 are connected.
Alternatively, those components such as the noise-absorbing
elements 13 and the lead-inserting element 14 may be placed both in
the area P and the outside thereof. Though the electronic control
unit according to the present invention is explained to be used in
the automobile engine control, it may be used for other
purposes.
[0079] While the present invention has been shown and described
with reference to the foregoing preferred embodiments, it will be
apparent to those skilled in the art that changes in form and
detail may be made therein without departing from the scope of the
invention as defined in the appended claims.
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