Turbocharged engine with vacuum bleed valve

A turbocharged internal combustion engine has a carburetor fuel metering control rod, an ignition timing control member, an exhaust gas recirculation control pintle, and an induction air temperature control damper operated in a response to vacuum signals created by the pressure in the induction passage between the throttle and the turbocharger compressor and a valve which bleeds the vacuum signals to atmospheric pressure when the compressor discharge pressure rises above a selected value to establish a rich air-fuel mixture, retard ignition timing, inhibit exhaust gas recirculation and provide cool induction air flow for maximum power operation.

This invention relates to a turbocharged internal combustion engine having 
a control device operated in response to a vacuum signal created by the 
pressure in the induction passage between the throttle and the 
turbocharger compressor. 
A naturally aspirated internal combustion engine is conventionally equipped 
with a fuel metering control rod, an ignition timing control member, an 
exhaust gas recirculation control pintle, and an induction air temperature 
control damper which are positioned by vacuum units responsive to vacuum 
signals created by the subatmospheric pressure in the induction passage 
downstream of the throttle. When maximum power is demanded from such an 
engine, that induction passage pressure approaches atmospheric pressure 
and the fuel metering control rod is then positioned to establish a rich 
air-fuel mixture, the ignition timing control member to retard the timing, 
the exhaust gas recirculation control pintle to inhibit recirculation and 
the induction temperature control damper to provide cool air flow. 
When maximum power is demanded from a turbocharged engine, however, the 
pressure in the induction passage between the throttle and the 
turbocharger compressor decreases instead of approaching atmospheric 
pressure. Thus if conventional naturally aspirated engine controls were 
used on a turbocharged engine, the vacuum signals created by such pressure 
would establish a lean air-fuel mixture instead of a rich mixture, advance 
instead of retarding ignition timing, permit instead of inhibiting 
recirculation of exhaust gases, and provide warm instead of cool induction 
air flow during maximum power demands, and in certain applications one or 
more of these conditions may be unsatisfactory. 
This invention allows conventional naturally aspirated engine controls to 
be used on a turbocharged engine by providing a bleed valve which responds 
to the power demand placed on the engine-- represented by the pressure in 
the induction passage downstream of the compressor-- and which causes one 
or more of the aforementioned engine control vacuum signals to approach 
atmospheric pressure during maximum power demands to thereby establish a 
rich air-fuel mixture, retard ignition timing, inhibit recirculation of 
exhaust gases and/or provide cool induction air flow.

Referring first to FIG. 1, an internal combustion engine 10 includes an 
induction passage 12 which extends through an air cleaner snorkel 13, air 
cleaner 14, a carburetor 16, a carburetor discharge plenum 18, a 
turbocharger compressor 20 and an intake manifold 22. Snorkel 13 has a 
cool air inlet 24 for receiving air at the ambient atmospheric temperature 
and a warm air inlet 26 for receiving air heated by, for example, the 
engine exhaust system. Carburetor 16 includes a fuel inlet 28 which opens 
into induction passage 12 and a throttle 30 for controlling air flow 
through induction passage 12. 
Engine 10 also includes an exhaust passage 32 with a turbine 34 driven by 
exhaust gas flow therethrough to drive compressor 20 and thus increase air 
flow through induction passage 12 to engine 10. 
A fuel metering control rod 36 disposed in fuel inlet 28 is carried on a 
vacuum piston 38 and is biased by a spring 40 to a projected position 
permitting increased fuel flow through inlet 28 to establish a rich 
air-fuel mixture. Piston 38 is subjected to the subatmospheric pressure 
(vacuum signal) in induction passage 12 between the throttle 30 and 
compressor 20 through vacuum lines 42, 44 and 46 and upon a decrease in 
such pressure (an increase in vacuum signal), moves metering rod 36 to a 
retracted position in which it restricts fuel flow through inlet 28 to 
establish a lean air-fuel mixture. 
Engine 10 also includes a distributor 48 having an ignition timing control 
member 50. Control member 50 is carried on a vacuum diaphragm 52 and is 
biased by a spring 54 to a projected position in which the ignition timing 
is retarded. Diaphragm 52 is subjected to the subatmospheric pressure 
(vacuum signal) in induction passage 12 between throttle 30 and compressor 
20 through vacuum lines 56, 44 and 46 and upon a decrease in such pressure 
(an increase in vacuum signal), moves control member 50 to a retracted 
position in which the ignition timing is advanced. 
Each of the items mentioned heretofore may be of conventional construction 
well-known to those skilled in the art and thus need not be described to 
any further extent. 
Engine 10 also has an exhaust gas recirculation passage 58 extending from 
exhaust system 32 to induction passage 12 between throttle 30 and 
compressor 20. An exhaust gas recirculation control pintle 60 disposed in 
passage 58 is carried by a vacuum diaphragm 62 and is biased by a spring 
64 toward the projected position shown in which it inhibits recirculation 
of exhaust gases through passage 58. Diaphragm 62 is subjected to the 
vacuum signal created at a port 66 opening into induction passage 12 
adjacent throttle 30 through vacuum lines 68, 70 and 72 and thus senses 
the substantially atmospheric pressure upstream of throttle 30 when 
throttle 30 is closed as shown and the subatmospheric pressure created in 
induction passage 12 between throttle 30 and compressor 20 when throttle 
30 is open. Thus during open throttle operation, diaphragm 62 moves pintle 
60 to a retracted position in which it permits flow of exhaust gases 
through passage 58. In this embodiment, pintle 60, diaphragm 62 and spring 
64 are incorporated in an exhaust gas recirculation valve assembly 74 
which further controls the vacuum signal applied to diaphragm 62 so that 
the flow of exhaust gases through passage 58 varies with the pressure in 
exhaust system 32 and thus is proportional to the flow through induction 
passage 12. Such valve assemblies are well-known to those skilled in the 
art and operate in the manner described in U.S. Pat. No. 3,834,366 issued 
Sept. 10, 1974 in the name of W. L. Kingsbury, although they may differ in 
certain details of construction from the specific embodiments disclosed 
therein. Moreover, in some applications other types of vacuum operated 
exhaust gas recirculation control valve assemblies may be used, and thus 
the specific structure of valve assembly 74 need not be described in 
greater detail. 
If desired, engine 10 may include a thermal vacuum switch 76 which passes 
the vacuum signal from vacuum line 70 to vacuum line 72 during engine 
operation at normal temperatures but which obstructs the vacuum signal and 
instead applies atmospheric pressure to diaphragm 62 at low engine 
temperatures. Thus during engine operation at low temperatures, spring 64 
would move pintle 60 to the projected position to inhibit recirculation of 
exhaust gases. 
An induction air temperature control damper 78 disposed in snorkel 13 is 
connected to a vacuum diaphragm 80 and is biased by a spring 82 to the 
projected position shown, inhibiting warm air flow through warm air inlet 
26 and permitting cool air flow through cool air inlet 24. Diaphragm 80 is 
subjected to the subatmospheric pressure in induction passage 12 between 
throttle 30 and compressor 20 through vacuum lines 84 and 86, a thermal 
sensor 88 disposed in air cleaner 14, and a vacuum line 90. When the 
induction air flow temperature is below a selected value, sensor 88 passes 
the subatmospheric pressure (vacuum signal) to diaphragm 80 which then 
retracts damper 78 to inhibit cool air flow through cool air inlet 24 and 
permit warm air flow through warm air inlet 26, but when the induction air 
flow temperature is above the selected value, sensor 88 opens an air bleed 
which causes the vacuum signal to approach atmospheric pressure and spring 
82 to move the damper toward the projected position shown. The components 
of air cleaner 14 operate generally as described in U.S. Pat. No. 
3,444,847 issued May 20, 1969 in the name of J. B. King, and while the 
details of construction may differ in certain respects from those shown in 
that patent, various embodiments are well-known to those skilled in the 
art; thus air cleaner 14 need not be described in greater detail. 
As throttle 30 is opened to increase the power demand on the engine it 
would be desired to have spring 40 lift vacuum piston 38 and fuel metering 
control rod 36 to a projected position permitting increased fuel flow 
through fuel inlet 28 to provide a rich air-fuel mixture. In general, it 
also would be desired to have spring 54 move diaphragm 52 and ignition 
timing control member 50 to the projected position in which the ignition 
timing is retarded, to have spring 64 move diaphragm 62 and exhaust gas 
recirculation control pintle 60 to the projected position in which 
recirculation of exhaust gases through passage 58 is inhibited, and/or to 
have spring 82 move diaphragm 80 and control damper 78 to the projected 
position in which it inhibits warm air flow through warm air inlet 26 and 
permits cool air flow through cool air inlet 24. However, if throttle 30 
is opened to increase the power demand on the engine, compressor 20 causes 
a decrease, rather than an increase, in the pressure in induction passage 
12 between throttle 30 and compressor 20. Thus in the absence of the bleed 
valve provided by this invention, fuel metering control rod 36, ignition 
timing control member 50, exhaust gas recirculation control pintle 60, and 
induction air temperature control damper 78 all would be held in the 
retracted rather than the projected positions. 
This invention provides a bleed valve 92 which interconnects vacuum line 44 
with vacuum line 46, vacuum line 68 with vacuum line 70, and vacuum line 
84 with vacuum line 86. As shown in FIG. 2, bleed valve 92 has a fitting 
94 for connection to vacuum line 44, a fitting 96 for connection to vacuum 
line 46, and an arcuate chamber 98 for interconnecting fittings 94 and 96 
and thus vacuum lines 44 and 46. Bleed valve 92 also has a fitting 100 for 
vacuum line 68, a fitting 102 for vacuum line 70, and an arcuate chamber 
104 for interconnecting fittings 100 and 102 and thus vacuum lines 68 and 
70. Bleed valve 92 further has a fitting 106 for vacuum line 86, a fitting 
108 for vacuum line 84, and an arcuate chamber 110 for interconnecting 
fittings 106 and 108 and thus vacuum lines 84 and 86. 
Bleed valve 92 also includes a fitting 112 for connection through a line 
114 to a source of clean air such as a port 116 in induction passage 12 
upstream of fuel inlet 28. Bleed valve 92 further includes a fitting 118 
for connection through a line 120 to sense the compressor discharge 
pressure in intake manifold 22. 
As shown in FIG. 3, bleed valve 92 includes an upper portion 122 in which 
fittings 94, 96, 100, 102, 106 and 108 are formed, an intermediate portion 
124 in which fitting 112 is formed, and a cupper lower portion 126 which 
carries fitting 118. Lower portion 126 is formed from sheet metal to 
extend about the sides of portions 124 and 122 and is crimped over the top 
of portion 122, as shown in FIG. 2, to secure the various portions 
together. Thus arcuate chambers 98, 104 and 110 are actually formed by 
recesses in upper portion 122 which are closed by intermediate portion 
124. 
A diaphragm 128 disposed between intermediate portion 124 and lower portion 
126 forms a clean air chamber 130 between intermediate member 124 and 
diaphragm 128 and a compressor discharge pressure chamber 132 between 
diaphragm 128 and lower portion 126. Fitting 112 opens into clean air 
chamber 130, and fitting 118 opens into compressor discharge pressure 
chamber 132. 
Fitting 96 opens into arcuate chamber 98 through a bore 134 surrounded by a 
valve seat 136, and clean air chamber 130 opens into arcuate chamber 98 
through a bore 138 surrounded by a valve seat 140. A valve stem 142 is 
guided in bores 134 and 138, while grooves 144 and 146 in bores 134 and 
138 permit flow about valve stem 142. Valve stem 142 carries a 
double-faced valve member 148 and is biased by a spring 150 and a carrier 
plate 152 to engage valve member 148 against valve seat 140; in this 
position the vacuum signal is transmitted from vacuum line 46 through 
fitting 96 and arcuate chamber 98 to fitting 94 and vacuum line 44. 
When the compressor discharge pressure in intake manifold 22 rises above a 
selected value indicative of high engine power demands, a value of 2"-4" 
Hg above atmospheric pressure for example, diaphragm 128 overcomes the 
bias of spring 150 and pushes valve stem 142 upwardly to engage valve 
member 148 with valve seat 136. The atmospheric pressure in clean air 
chamber 130 is then applied through arcuate chamber 98 and fitting 94 to 
vacuum line 44, and spring 40 lifts piston 38 and fuel metering control 
rod 36 to the projected position permitting increased fuel flow through 
fuel inlet 28 to establish a rich air-fuel mixture. Simultaneously, spring 
54 moves diaphragm 52 and ignition timing control member 50 to the 
projected position to retard ignition timing. 
Arcuate chambers 104 and 110 have an identical construction and contain 
identical double-faced valve members so that when the compressor discharge 
pressure in intake manifold 22 rises above a selected value, spring 64 
moves diaphragm 62 and exhaust gas recirculation control pintle 60 to the 
projected position for inhibiting recirculation of exhaust gases and at 
the same time spring 82 moves diaphragm 80 and induction air control 
damper 78 to the projected position for providing cool induction air flow. 
Accordingly, it will be appreciated that this invention provides a bleed 
valve which responds to the high compressor discharge pressure generated 
during maximum engine power demand and which causes one or more of the 
engine control vacuum signals to approach atmospheric pressure 
notwithstanding the fact that the induction passage pressure which creates 
those signals is very low under such conditions. Thus one or more of the 
engine controls may be moved to its projected position for maximum power 
operation.