Abstrict An object of the present invention is to provide a hot-electrical-resistance
type gas flow meter wherein a deterioration of a gas-cooled hot-electrical-resistance
is prevented at the maximum flow rate, a decrease of sensitivity
is prevented at the minimum flow rate and a wide dynamic range is
achieve, and a structural feature of such gas flow meter is that
the gas flow meter includes auxiliary path flow resistance changing
means for changing a flow resistance of the auxiliary path so that
the larger the flow rate of the flow is, the larger the flow resistance
of the auxiliary path is.
Claims What is claimed is:
1. An electrical-resistance type air flow meter for measuring a
flow of air passing therethrough, comprising:
a primary flow path for passing a substantial part of said flow
of air;
a first auxiliary flow path for passing another part said flow
of air;
an electrical resistance device which is disposed in said first
auxiliary flow path within said another part of said flow of air;
and
flow resistance changing means for increasing the passage resistance
of the first auxiliary flow path according to an increase in the
flow rate of said flow of air, including a second auxiliary flow
path extending in parallel to said first auxiliary flow path for
receiving a still further part of said flow of air.
2. An electrical-resistance type air flow meter according to claim
1 wherein said flow resistance changing means further includes
a member which is moved in accordance with a variation in flow rate
of the flow of air by air flowing into said second auxiliary flow
path so that, when the flow rate of the flow is increased, the passage
resistance of the first auxiliary flow path is increased.
3. An electrical-resistance type air flow meter according to claim
2 wherein the movable member is an elastic plate disposed over
an end of said second auxiliary flow path, one end of which elastic
plate is fixed and another end of which is subjected to dynamic
pressure from air flowing into said second auxiliary flow path so
as to be moved elastically in said first auxiliary flow path.
4. An electrical-resistance type air flow meter comprising:
a body;
a primary flow path formed in the body and constituting an intake
air passage;
an electrical resistance device for measuring intake air flow;
an auxiliary flow path formed in the body and having mounted therein
said electrical resistance device; and
variable means for changing the path resistance of said auxiliary
flow path in accordance with an amount of the intake air flow, including
another auxiliary flow path extending substantially in parallel
to said axial flow path and communicating at its outlet end with
said auxiliary flow path.
5. A flow meter according to claim 4
wherein said auxiliary flow path includes an axial flow path extending
in a direction of said primary flow path and a radial flow path
extending in a radial direction of said primary flow path.
6. A flow meter according to claim 4 wherein said variable means
further includes a flexible plate at an outlet opening of said another
auxiliary flow path, said flexible plate changing a cross-sectional
area of said radial flow path in accordance with a dynamic pressure
of air flowing into said another auxiliary flow path.
7. A flow meter according to claim 4
wherein said auxiliary flow path includes an axial flow path extending
in an axial direction of said primary flow path and an annular flow
path which crosses a downstream side of said axial flow path and
extends along an inner periphery of the body.
8. A flow meter according to claim 7 wherein said another auxiliary
flow path has an outlet end which communicates with said annular
flow path.
9. An electrical-resistance type air flow meter comprising:
a body;
a primary flow path formed in the body for constituting an intake
air passage;
an electrical resistance device for measuring intake air;
an auxiliary flow path formed in the body and having mounted therein
said electrical resistance device; and
variable means for changing a path resistance of said auxiliary
flow path including, an additional auxiliary flow path formed in
the body in parallel to said auxiliary flow path and means responsive
to air flowing into said additional auxiliary flow path for controlling
the passage area of said auxiliary flow path.
10. A flow meter according to claim 9
wherein said controlling means of said variable means is arranged
at a downstream side of said electrical resistance device.
11. An internal combustion engine comprising:
a hot-electrical-resistance type air flow meter having a body,
a primary flow path formed in the body for constituting an intake
air passage to conduct a portion of a flow of air, an electrical
resistance device for measuring intake air, an auxiliary flow path
formed in the body to conduct another portion of the flow of air
and having mounted therein said electrical resistance device;
variable means for changing the path resistance of said auxiliary
flow path to said another portion of the flow of air in accordance
with an amount of the flow of air, including a second auxiliary
flow path operating to change said passage resistance of the first
auxiliary flow path by passing a still further part of said flow
of air to an end of the second auxiliary flow path which joins the
first auxiliary flow path downstream of said electrical resistance
device;
speed measuring means for measuring a rotational speed of the engine;
an injection device for injecting fuel into the intake air; and
control means for calculating a suitable amount of fuel injected
by said injection device from the measured rotational speed of the
engine and from the measured flow rate of the intake air and for
controlling said injection device to inject a suitable amount of
fuel.
Description BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to measuring the flow rate of intake
gas, particularly to a gas-cooled hot-electrical-resistance type
gas flow meter which is mounted in an intake line to measure the
flow rate of the intake gas by detecting a variation in electrical
resistance value of a hot electrical resistance which is cooled
by the intake gas.
In ordinary automobiles, the minimum mass flow rate Qi is 10 to
15 Kg/h during idling of the engine and the maximum mass flow rate
Qm is 500 to 600 Kg/h on a critical rotational speed of the engine
when a displacement of the engine is 4000 c.c.; while the minimum
mass flow rate Qi is 5 to 10 Kg/h on idling of the engine and the
maximum mass flow rate Qm is 300 to 400 Kg/h on the critical rotational
speed of the engine when the displacement of the engine is 2000
c.c.. Therefore, the ratio of the maximum mass flow rate to the
minimum mass flow rate (a dynamic range) Qm/Qi is 60 to 80. In the
future, the maximum mass flow rate will be increased for purposes
of making the rotational speed and output power of the mobile engine
higher, while the minimum mass flow rate will be kept at the present
level, so that the dynamic range will reach 150.
The flow speed of intake air in an intake line, that is, the flow
speed thereof at a gas-cooled hot-electrical-resistance type gas
flow meter depends on the cross-sectional area of the main passage
(the diameter of the intake line) and so forth and is limited within
0.5 m/s to 50 m/s over a whole range of the flow rate at the present
time. The reason for restraining a further increase of the flow
speed is that the higher the flow speed of intake air is, the larger
will be deterioration (change in characteristics) by extremely small
dust which cannot be filtered off by air cleaner, which dust sticks
on the gas-cooled hot-electrical-resistance device with the passage
of time, as explained on page 26 and FIG. 15 in SAE Paper 840137
1984. An increase of the dynamic range, that is, an increase of
the maximum flow rate causes an increase of the maximum flow speed
and accelerates the sticking of the dust on the gas-cooled hot-electrical-resistance.
In a conventional hot-wire type gas flow meter as shown in Publication
of Japanese Patent Application Laid-open No. Shou 54-76182 the
temperature of the hot wire is increased to more than the normal
operational temperature thereof so that the dust on the hot wire
is burned out and the cleanliness of the hot wire is maintained.
But, since the dust includes calcium, the dust sticks securely on
the hot wire even with the temperature increase of the hot wire
and the deterioration of the characteristics thereof is made large.
In another conventional hot-wire type gas flow meter as shown in
Publication of Japanese Patent Application Laid-open No. Shou 59-190624
an obstacle is arranged at an upstream side of the hot wire so that
the dust sticks on the obstacle and the dust is prevented from sticking
on the hot wire. But, since the flow speed of air at the hot wire
is decreased by the obstacle, the sensitivity of the hot wire is
decreased when the flow rate of intake air is low. And, since the
obstacle generates a disturbance or eddy in the intake air, the
output noise of the hot wire is increased.
In another conventional hot-wire type gas flow meter as shown in
Publication of Japanese Patent Application Laid-open No. Shou 55-66716
a straight tube receiving the hot wire is arranged in a main passage.
In this structure, the flow speed in the tube (on the hot wire)
is substantially equal to the flow speed in the main passage surrounding
the tube. Therefore, in order to keep the maximum flow speed within
a desirable degree when the maximum flow rate of intake air is increased,
the cross-sectional area, that is, the diameter of the passage must
be increased with an increase in space receiving a duct system.
And, in this case, since the minimum flow rate of intake air is
not increased, the flow speed is decreased to less than a desirable
degree so that the sensitivity of the hot wire is decreased and
noise protection is needed.
In another conventional hot-wire type gas flow meter as shown in
Publication of Japanese Patent Application Laid-open No. Shou 56-18721
a bypass passage is formed independently from a main passage. In
this case, a flow speed of intake air in the bypass passage is made
different from a flow speed in the main passage by adjusting (increasing)
the flow resistance of the bypass passage. Therefore, when the maximum
flow rate is increased, the maximum flow speed in the bypass passage
can be kept less than a desirable degree without increasing the
size of the body forming the passages. But, in this structure, since
the flow speed in the bypass passage is in proportion to the flow
speed in the main passage, the flow speed in the bypass passage
is decreased to less than a desirable degree when the flow speed
in the main passage is decreased, so that the sensitivity of the
hot wire is decreased and the generated noise (a small disorder
in flow) is large in comparison with the overall flow.
In another conventional hot-wire type gas flow meter as shown in
Publication of Japanese Utility Model Application Laid-open No.
Shou 55-145321 a valve device is arranged in a bypass passage to
control the flow resistance of the bypass passage for changing the
flow rate of intake air. In this structure, the cross-sectional
area of the bypass passage is increased to decrease the flow resistance
characteristic so that the flow speed at a sensor portion (a hot
wire) is increased when the flow rate is increased. This operation
in this structure is opposite to an operation in the present invention.
This operation is effective for compensating a variation in rate
of an output voltage of the sensor to a flow speed at the sensor,
because the output voltage of the sensor is in proportion to a square
root of the flow speed at the sensor and the higher the flow rate
is, the smaller is the rate of the output voltage of the sensor
to the flow speed at the sensor.
In the conventional hot-wire type gas flow meters, a deterioration
of the hot wire cannot be restrained when the maximum flow rate
of intake air to be measured is large, and a suitable flow speed
for preventing a decrease in sensitivity of the hot wire at the
minimum flow rate cannot be obtained.
OBJECT AND SUMMARY OF THE INVENTION
An object of the present invention is to provide a gas-cooled hot-electrical-resistance
type gas flow meter wherein a deterioration of a gas-cooled hot-electrical-resistance
is prevented at the maximum flow rate, a decrease of sensitivity
is prevented at the minimum flow rate and a wide dynamic range (measured
range of flow rate) is achieved.
Another object of the present invention is to provide a high speed
and high output internal combustion engine wherein an optimum rate
of intake air to fuel is achieved both at an idling time of the
engine and at a maximum output time thereof.
According to the present invention, a hot-electrical-resistance
type gas flow meter comprises a primary flow passage through which
a main part of an intake gas passes, an auxiliary flow passage through
which a part of the intake gas passes, and a hot-electrical-resistance
which is received by the auxiliary flow passage and through which
a flow rate of the intake gas is measured by detecting a variation
in electrical resistance value of the hot electrical resistance
which is cooled by the part of the intake gas, wherein the hot-electrical-resistance
type gas flow meter further comprises variable means for changing
the flow resistance of the auxiliary flow passage in accordance
with the flow rate of the intake gas so that the larger the flow
rate of the intake gas is, the larger the flow resistance of the
auxiliary flow passage is.
According to the present invention, an internal combustion engine
comprises the above mentioned gas-cooled hot-electrical-resistance
type gas flow meter, speed measuring means for measuring the rotational
speed of the engine, injection device for injecting fuel into the
intake gas, control means for calculating a suitable amount of fuel
injected by the injection device from the measured rotational speed
of the engine and from the measured flow rate of the intake gas
and for controlling the injection device to inject the suitable
amount of fuel.
Since the hot-electrical-resistance type gas flow meter according
to the present invention comprises the variable means for changing
the flow resistance of the auxiliary flow passage in accordance
with the flow rate of the intake gas so that the larger the flow
rate of the intake gas is, the larger the flow resistance of the
auxiliary flow passage is, the flow rate of the intake gas in the
auxiliary flow passage is in proportion to the flow rate of the
intake gas in the primary flow passage and a dynamic range of the
intake gas in the auxiliary flow passage is smaller than a dynamic
range of the intake gas in the main flow passage. Therefore, the
flow rate of the intake gas in the auxiliary flow passage is kept
small even when the flow rate of the intake gas in the primary flow
passage is large, so that a deterioration of the hot-electrical-resistance
is prevented. Further, the flow rate of the intake gas in the auxiliary
flow passage may be large when the flow rate of the intake gas in
the primary flow passage is small, so that a sensitivity of the
variation in electrical resistance value of the hot electrical resistance
is sufficiently large to maintain a high accuracy of the flow meter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing an internal combustion
engine with a gas-cooled hot-electrical-resistance type gas flow
meter according to the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of the present
invention.
FIG. 3 is a cross-sectional view taken along a line III--III of
FIG. 2.
FIG. 4 is a cross-sectional view taken along a line IV--IV of FIG.
2.
FIG. 5 is a cross-sectional view taken along a line V--V of FIG.
2
FIG. 6 is a cross-sectional view showing another embodiment of
the present invention.
FIG. 7 is a cross-sectional view taken along a line VII--VII of
FIG. 6.
FIG. 8 is a cross-sectional view showing another embodiment of
the present invention on a small flow rate.
FIG. 9 is a cross-sectional view showing the embodiment of FIG.
8 on a large flow rate.
FIG. 10 is a cross-sectional view showing another embodiment of
the present invention on a small flow rate.
FIG. 11 is a cross-sectional view showing the embodiment of FIG.
10 on a large flow rate.
FIG. 12 is a cross-sectional view showing another embodiment of
the present invention.
FIG. 13 is a cross-sectional view showing the other embodiments
of the present invention.
FIGS. 14 and 15 are cross-sectional views showing the other embodiments
of the present invention, respectively.
FIGS. 16 and 17 are a cross-sectional view showing another embodiment
of the present invention.
FIG. 18 is a diagram showing relations between flow speeds at a
sensing portion and measured flow rates, in the prior art and the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 shows an internal combustion engine with an electrically
controlled fuel injection device and a hot-electrical-resistance
type gas flow meter according to the present invention.
Intake air 52 is supplied to the internal combustion engine (cylinder)
50 through an air-filter 53 an intake duct 54 a flow meter (the
gas-cooled hot-electrical-resistance type gas flow meter) 1 and
an intake manifold 51. The flow meter 1 includes a primary path
21 a first auxiliary path 31 and a second auxiliary path 35. A
main part of the intake air 52 flows through the primary path 21
and the other part of the intake air 52 flows through the first
auxiliary path 31 and the second auxiliary path 35. The first auxiliary
path 31 has positioned therein an electrical resistance device 2A
and temperature variation compensating device 2B integrally connected
to a circuit unit 2. The electrical resistance device 2A measures
air flow rate to generate through the circuit unit 2 an output signal
corresponding to the overall whole flow rate of the intake air 52.
At a down-stream side of the electrical resistance device 2A in
the flow meter 1 there is arranged a throttle valve 3 connected
to an accelerator pedal for controlling the flow rate of the intake
air 52 and an idling speed control (ISC) valve 8 for controlling
the flow rate of the intake air 52 when the throttle valve 3 completely
prevents a flow of the intake air 52 (idling time).
Fuel F is injected by a pump 56 from a fuel tank 55 through an
injector 57 into an intake manifold 51 so that the fuel F is supplied
to the internal combustion engine 50 with the intake air. The exhaust
gas is discharged as shown by an arrow E. A control device 60 calculates
a fuel injecting rate and an opening degree of the ISC valve 8 on
the basis of the output signal of the circuit unit 2 a rotational
degree of the throttle valve 3 an output signal of an oxygen density
sensor 58 mounted on the intake manifold 57 and an output signal
of an engine rotational speed sensor 59. And, the control device
60 controls the injector 57 and the ISC valve 8 on the basis of
these calculations.
In FIGS. 2 to 5 a body 20 includes a flow meter body 20A, a throttle
valve body 20B and an ISC valve body 20C. A lattice member (honeycomb)
40 for regulating the flow is arranged at an inlet of the flow meter
body 20A. A block (bridge) 30 forming the first auxiliary path 31
and the second auxiliary path 35 extends from the flow meter body
20A into the primary passage 21 at a downstream side of the lattice
member 40. The first auxiliary path 31 includes an axial path 31B
extending substantially parallel to the primary passage 21. The
sensor circuit unit 2 is fixed to the flow meter body 20A by screws
41a and 41B and a mold portion 2C extends from the sensor circuit
unit 2 into the axial path 31B. The mold portion 2C has a hole whose
diameter is substantially equal to a diameter of the axial path
31B, which forms a part of the axial path 31B, and by which the
electrical resistance device 2A and temperature variation compensating
device 2B are received.
The throttle valve body 20B receives the throttle valve 3 for controlling
the flow rate of intake air, and a valve shaft 4 extends through
the throttle valve body 20B. A lever mechanism 5 for driving the
valve shaft 4 a spring 6 and a throttle position sensor 7 for measuring
a rotational angle of the valve shaft 4 are connected to the shaft
4 at the outside of the throttle valve body 20B. The ISC valve 8
for controlling the flow rate of intake air when the throttle valve
3 blocks the flow of the intake air during idling time of the engine
and air paths 23 24 and 25 for the ISC valve 8 are arranged in
the ISC valve body 20C. Plugs 26 and 27 close ends of the paths
23 and 25 so that the paths 23 and 25 do not communicate with the
outside of the ISC valve body 20C.
The first auxiliary path 31 includes the axial path 31B, whose
inner diameter is smaller, than the inner diameter of the primary
path and has a round shape, and a radial path 31C which extends
perpendicularly from a downstream side of the axial path 31B and
whose cross-sectional shape is square. The radial path 31C is formed
by a groove arranged at a downstream side of the block 30 and by
a cover 32 fixed to the block 30 by screws 33. A lower end portion
32A of the cover 32 has a width smaller than the width of the groove
of the radial path 31C and extends over a flow-out portion 31D of
the auxiliary path. A flow resistance formed by a L-shaped passage
line and friction of the auxiliary path 31 is larger than a flow
resistance of the primary path 21. Since most of an outer wall of
the block 30 is cooled by main flow of the intake air, the temperature
of the path wall of axial path 31B is substantially equal to that
of the intake air so that heat from the outside is cooled by the
intake air to maintain the accuracy of measuring the flow rate.
And since the lower end portion 32A of the cover 32 extends over
the flow-out portion 31D, a reverse flow into the radial path 31C,
for example, a back-fire of the internal combustion engine, is prevented
to protect the hot wire device 2A. And, since the flow resistance
absorbs an oscillating variation in flow rate of the intake air,
the output of the hot wire device 2A is stabilized.
An elliptic recess 34 is formed by an edge 30A slightly projecting
around an inlet opening 31A of the first auxiliary flow path 31
toward an upperstream portion. In this embodiment, the inlet opening
31A of the first auxiliary flow path 31 opens at a bottom of the
recess 34 and at an upper side of FIG. 2 that is, a side wherein
the sensor unit 2 is arranged. A side portion of the recess 34 other
than the inlet opening 31A extends substantially to a center of
the primary path. Since the recess 34 is arranged in this way, an
oscillating variation in flow rate caused by an air-cleaner and
a bent intake duct arranged at an upperstream portion of the path
31 is absorbed to stabilize a division of flow rate to the first
auxiliary path 31.
At least one second auxiliary path 35 with a small diameter has
an inlet opening 35A at an radially inner part of the bottom of
the recess 34 in the primary path 21 and extends substantially parallel
to the axial path 31B of the first auxiliary path 31. An outlet
opening 35B of the second auxiliary path 35 is arranged at the radial
path 35C of the first auxiliary path 31. Flow rates of the first
auxiliary path 31 and the second auxiliary path 35 vary in accordance
with the total flow rate of the intake air. Since the flow in the
second auxiliary path 35 is added into the flow of the first auxiliary
path 31 at the radial path 31C, an effective area of flow of the
first auxiliary path 31 is decreased, that is, the flow resistance
thereof is increased in accordance with an increase of the total
flow rate of the intake air. Therefore, an increasing characteristic
of the flow rate of the first auxiliary path 31 having the hot-electrical-resistance
device 2A and the temperature compensating device 2B is smaller
than that of the total flow rate.
In an embodiment shown in FIGS. 6 and 7 a large thickness portion
230 of a body 220 receives a first auxiliary path 231 including
an axial path 231B extending parallel to a primary path 221 and
a loop-shaped path 231C bypassing the primary path 221 at an outer
periphery thereof. An outlet opening 231D of the first auxiliary
path 231 opens to an inner wall of the primary path 221. A tube
path body 225 at a downstream side is connected to the body 220
through a packing 224. An upperstream end surface of the large thickness
portion 230 of the body 220 forms a plane 230A extending perpendicularly
to the flow. An inlet opening 231A of the first auxiliary path 231
opens to the plane 230A. A circular edge 232 projecting toward an
upperstream portion is arranged between the inlet opening 231A and
the primary path 221. The edge 232 prevents the intake gas remaining
on the plane 230A from flowing out to the primary path 221 so that
a static pressure at the inlet opening 231A is stabilized. Therefore,
a division in flow rate between the first auxiliary path 231 and
the primary path 221 is stabilized against a variation of flow at
the upperstream portion.
At least one second auxiliary path 233 extends substantially parallel
to the axial path 231B of the first auxiliary path 231. An inlet
opening 233A of the second auxiliary path 233 is arranged on the
plane 230A and an outlet opening 233B is arranged inside of the
loop-shaped path (path extending in a direction crossing an axis
of the primary path) 231C of the first auxiliary path 231. Therefore,
the second auxiliary path 233 operates as the auxiliary path 35
above mentioned, and an increasing characteristic of the flow rate
of the first auxiliary path 231 is smaller than that of the total
flow rate.
In an embodiment shown in FIGS. 8 and 9 wherein a modification
of the embodiment shown in FIGS. 2 to 5 is shown, at least one second
auxiliary path 80 extends substantially parallel to the axial path
31B of the first auxiliary path 31. An inlet opening 80A of the
second auxiliary path 80 is arranged at the recess 34 and an outlet
opening 80B is arranged in the radial path 31C of the first auxiliary
path 31. At least one flexible plate or spring plate 81 is arranged
at the outlet opening 80B so that the outlet opening 80B is closed
when the flow rate in the second auxiliary path 80 is small. The
flexible plate 80 is fixed at an end thereof and deforms in the
radial path 31C as shown in FIG. 9 when a pressure difference between
upperstream and downstream sides of the second auxiliary path 80
is large, that is, a flow rate therein is large. Therefore, a cross-sectional
area of the radial path 31C is decreased by the flexible plate 81
and the effective area of flow of the radial path 31C is decreased
by the addition of the flow of the second auxiliary path 80 to that
of the first auxiliary path 31 so that the flow resistance of the
first auxiliary path 31 is increased and the increasing characteristic
of the flow rate of the first auxiliary path 31 is smaller than
that of the total flow rate.
In an embodiment shown in FIGS. 10 and 11 wherein a modification
of the embodiment shown in FIGS. 2 to 5 is shown, at least one step-shaped
hole (second auxiliary path) 93 extends substantially parallel to
the axial path 31B and receives at least one step-shaped piston
90 including a longitudinal end facing to the upperstream side to
be pressed toward the downstream side by the pressure difference
therebetween and at least one spring member 91 pressing the piston
90 toward the upperstream side. An upperstream end of the step-shaped
hole 93 opens to the recess 34 at an inlet thereof, and a stop ring
92 arranged at an inlet opening 90A prevents the piston 90 from
moving out from the step-shaped hole 93. A downstream end of the
step-shaped hole 93 opens to the inside of the radial path 31C so
that another longitudinal end of the piston 90 can move into the
radial path 31C. The piston 90 is moved by a pressure difference
between the longitudinal upperstream side and downstream side ends
thereof against the force of the spring member 91 so that the longitudinal
end of the piston 90 projects into the radial path 31C to decrease
the cross-sectional area of the radial path 31C as shown in FIG.
11 when the flow rate is large. The more the flow rate is large,
the more the piston 90 projects into the radial path 31C so that
the more the flow rate is large, the more the flow resistance in
the auxiliary path 31 is large.
An embodiment shown in FIG. 12 includes a body 101 receiving a
part of an intake path, a sensor unit 102 and a tube member 103
receiving a auxiliary path 105 arranged at a substantially central
portion of a primary path 104. A hot electrical resistance device
102A and a temperature compensating device 102B are arranged in
the auxiliary path 105. A plurality of outlet openings 106A and
106B of the auxiliary path 105 extend radially from an inlet surface
103A having a conical shape. A piston 107 having also a conical
surface 107A is arranged on the inlet surface 103A and is urged
by springs 108 and 109. A downstream end 110 of the piston 107 limits
the movement thereof. When the flow rate or speed in the auxiliary
path 105 is large, an upperstream end of the piston 107 receives
a large pushing force generated by the mass of the intake gas running
onto the upperstream end in the auxiliary path 105 at a large speed
so that the piston 107 moves toward the downstream end and decreases
a clearance H between the conical surfaces to increase the flow
resistance of the auxiliary path 105. When the flow rate in the
auxiliary path 105 is small, the piston is moved toward the upperstream
end by the spring force so that the flow resistance of the auxiliary
path 105 is decreased.
In an embodiment shown in FIG. 13 a bridge 118 extends transversely
in a primary path 112 formed in a body 111 and includes an auxiliary
path 113 having an axial path 113B and a radial path 113C. A piston
115 is supported by a rib member 114 integrally formed with the
body 111 and is arranged at an upperstream side of an inlet portion
of the auxiliary path 113. A spring 116 is arranged between the
rib member 114 and a stopper 117 of the piston 115. An inlet opening
113A of the auxiliary path 113 has a large conical surface, and
a movement of the piston 115 changes the clearance H between the
inlet opening 113A and the piston 115. When the flow rate or speed
in the auxiliary path 113 is large, an upperstream end surface of
the stopper 117 of the piston 115 receives a large pushing force
generated by a mass of the intake gas running onto the upperstream
end surface in the auxiliary path 113 at a large speed so that the
piston 115 moves toward the downstream side and decreases the clearance
H to increase the flow resistance of the auxiliary path 113. When
the flow rate in the auxiliary path 113 is small, the piston 115
is moved toward the upperstream side by the spring force so that
the flow resistance of the auxiliary path 113 is decreased.
In an embodiment shown in FIGS. 14 and 15 wherein a modification
of the embodiment shown in FIGS. 2 to 5 is shown, the second auxiliary
path is deleted. A thermo-responsive deform member 120 for example,
a bimetal or shape memory alloy is arranged on a surface of the
bridge 30 in the radial path 31C. The thermo-responsive deform member
120 deforms in accordance with a variation in temperature thereof
and a constant electric current is supplied to the thermo-responsive
deform member 120 to heat it. When the flow rate in the radial path
31C is small and a cooling for the thermo-responsive deform member
120 is weak, the thermo-responsive deform member 120 keeps a flat
shape so that the flow resistance of the auxiliary path 31 is small.
When the flow rate in the radial path 31C is large and the cooling
for the thermo-responsive deform member 120 is strong to decrease
largely the temperature of the thermo-responsive deform member 120
the thermo-responsive deform member 120 deforms to decrease the
cross-sectional area of the radial path 31C as shown in FIG. 15
so that the flow resistance of the auxiliary path 31 is large.
In an embodiment shown in FIGS. 16 and 17 wherein a modification
of the embodiment shown in FIGS. 2 to 5 is shown, the second auxiliary
path is deleted. At least one thermo-responsive deform ring 130
made of, for example, a shape memory alloy is arranged at the downstream
side of the hot electrical-resistance device 2A and the temperature
compensating device 2B in the axial path 31B. An inner diameter
of a hole of the thermo-responsive deform ring 130 changes in accordance
with a variation in temperature thereof and a constant electric
current is supplied to the thermo-responsive deform member 130 to
heat it. When the flow rate in the axial path 31B is small and the
cooling for the thermo-responsive deform member 130 is weak, the
thermo-responsive deform ring 120 keeps the diameter of the hole
thereof equal to the diameter of the axial path 31B so that the
flow resistance of the auxiliary path 31 is small. When the flow
rate in the axial path 31B is large and the cooling for the thermo-responsive
deform ring 130 is strong to decrease largely the temperature of
the thermo-responsive deform ring 130 the thermo-responsive deform
ring 120 deforms to decrease the diameter of the hole thereof as
shown in FIG. 17 so that the flow resistance of the auxiliary path
31 is large.
In the embodiments using the thermo-responsive deform members 120
or 130 the electric current may be changed to control the movement
of the thermo-responsive deform members 120 or 130 in accordance
with the flow rate in the auxiliary path so that the larger the
flow rate in the auxiliary path is, the larger the flow resistance
of the auxiliary path is.
Any of the above mentioned embodiments may be applied to an internal
combustion engine or fuel injector for the internal combustion engine,
as shown in FIG. 1.
According to the present invention, as shown in FIG. 18 a measurable
range of the flow rate of the intake gas is larger than that of
the prior art when the ranges of flow rate on the hot-electrical-resistance
device and the diameters of the main passages are even therebetween
respectively. The X logarithmic coordinate indicates a total flow
rate Q and the Y logarithmic coordinate indicates a flow speed on
the hot-electrical-resistance device. A dot-line indicates a relation
therebetween according to the prior art, and a solid line indicates
a relation therebetween according to the present invention. The
dynamic range according to the prior art is 60 to 80; on the other
hand, the dynamic range according to the present invention is 120
to 150.
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