Abstrict Provided is a heat sensitive flow meter for measuring a flow rate
of a fluid passing through a flow passage provided in an internal
combustion engine, including: a filter (7) (constituted of a fixed
resister (3) and a capacitor (4)) for inputting a flow rate signal
Vin outputted from a flow rate measurement unit installed within
the flow passage to subject the flow rate signal to a predetermined
filter processing; and a selection unit (8) (constituted of a fixed
resister (2), an operational amplifier (5), and a diode (6)) for
comparing the flow rate signal Vin outputted from the flow rate
detection unit and a filter signal Vf passed through the filter
(7) to select the signal having a higher voltage as a new flow rate
signal.
Claims 1. A heat sensitive flow meter for measuring a flow rate of a fluid
passing through a pipe provided in an internal combustion engine,
comprising: a filter for inputting a flow rate signal outputted
from a flow rate detector installed within the pipe and subjecting
the flow rate signal to a filter processing; and a selector for
comparing the flow rate signal outputted from the flow rate detector
and a filter signal outputted from the filter to select the signal
having a higher voltage from the flow rate signal and the filter
signal as a new flow rate signal.
2. A heat sensitive flow meter according to claim 1 wherein the
filter is comprised of a low-pass filter, and the filter processing
is a processing for delaying the flow rate signal with a predetermined
time constant.
3. A heat sensitive flow meter according to claim 1 wherein the
filter is comprised of a high-pass filter, and the filter processing
is a processing for advancing the flow rate signal with a predetermined
time constant.
4. A heat sensitive flow meter according to claim 1 wherein the
filter processing executed by the filter is a processing for arithmetically
operating a value lower than a mean value of the flow rate signal
by a predetermined value to output the resultant value.
5. In a heat sensitive flow meter for measuring a flow rate of
a fluid passing through a pipe provided in an internal combustion
engine, the improvement comprising: comparing a flow rate signal
outputted from a flow rate detection means installed within the
suction pipe and a filter signal obtained by subjecting the flow
rate signal to filter processing using a previously set filter functions,
and selecting the signal having a higher voltage from the flow rate
signal and the filter signal as a new flow rate signal.
6. A heat sensitive flow meter according to claim 5 wherein the
filter processing is a processing for delaying the flow rate signal
with a predetermined time constant.
7. A heat sensitive flow meter according to claim 5 wherein the
filter processing is a processing for advancing the flow rate signal
with a predetermined time constant.
8. A heat sensitive flow meter according to claim 5 wherein the
filter processing is a processing for arithmetically operating a
value lower than a mean value of the flow rate signal by a predetermined
value to output the resultant value.
9. In a heat sensitive flow meter for measuring a flow rate of
a fluid passing through a pipe provided in an internal combustion
engine, the improvement comprising: receiving data on a throttle
aperture of the internal combustion engine and data on the number
of revolutions of the internal combustion engine, and judging whether
or not the throttle aperture is equal to or larger than a set value
for the throttle aperture previously set in correspondence to the
number of revolutions; and when the throttle aperture is equal to
or larger than the set value, judging whether or not a value of
a flow rate signal outputted from the flow rate detection means
installed within the pipe is equal to or smaller than a set value
for a flow rate signal previously set, and selecting the set value
as a new flow rate signal when the value of the flow rate signal
is equal to or smaller than the set value.
10. In a heat sensitive flow meter for measuring a flow rate of
a fluid passing through a pipe provided in an internal combustion
engine, the improvement comprising: receiving data on a pressure
within the pipe and data on the number of revolutions of the internal
combustion engine to judge whether or not the pressure is equal
to or larger than a set value for the pressure previously set in
correspondence to the number of revolutions; and when the pressure
is equal to or larger than the set value, judging whether or not
a value of a flow rate signal outputted from a flow rate detection
means installed within the pipe is equal to or smaller than a set
value for the flow rate signal previously set, and selecting the
set value as a new flow rate signal when the value of the flow rate
signal is equal to or smaller than the set value.
11. A fuel controller for carrying out fuel control using the heat
sensitive flow meter as claimed in claim 1.
Description BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a heat sensitive flow meter
and a fuel controller using the same.
[0003] 2. Related Background Art
[0004] In general, in a heat sensitive flow meter for measuring
a flow rate of a fluid such as intake air of an internal combustion
engine of an automobile or the like, it is known that a magnitude
of an output signal of the flow meter does not show a proportional
relationship (linear model) to the flow rate, but shows a non-linear
relationship in which a rate of increase in the magnitude of the
output signal of the flow meter is more slowly changed as the flow
rate is further increased. At this time, it is known that in a case
where in the heat sensitive flow meter, a response of the flow meter
is delayed due to an influence of a large heat capacity of a flow
rate detection unit, or an influence of a low-pass filter (hereinafter
referred to as "LPF" for short) installed in an interface
between the flow meter and a fuel controller, when an intake gas
pulsation of an engine is generated, a mean flow rate calculated
by the flow meter become less than an actual mean flow rate in cooperation
with the above-mentioned non-linearlity of the output signal to
the flow rate calculated from the flow meter.
[0005] For this reason, there is proposed a technique providing
a delay means for, when a signal obtained from a flow rate detection
unit is delayed, delaying an output signal in a direction of a decrease
of a flow rate after discriminating the direction of decrease from
the direction of increase of a flow rate (refer to JP 62-36522 B
for example).
[0006] In JP 62-36522 B, an increase and a decrease in flow velocity
are discriminated with a diode, causing a response to be more lagged
when the flow velocity is decreased than when the flow velocity
is increased.
[0007] That is to say, in one embodiment described in JP 62-36522
B, there is adopted a configuration that when a flow velocity is
increased, a signal is transmitted without delaying a response,
while when a flow velocity is decreased, a response is delayed on
the basis of a time constant determined by a capacity of a capacitor
and a resistance value of a resistor.
[0008] In addition, in another embodiment described in JP 62-36522
a signal transmission path when a flow velocity is increased and
a signal transmission path when a flow velocity is decreased are
changed over to each other in order to change a resistance constant
thereby changing a time constant.
[0009] Since in the technique disclosed in JP 62-36522 B, the response
is caused to be more lagged when the flow velocity is decreased
when the flow velocity is increased, for example, there is encountered
a problem that sufficient effects can not be obtained in a pulsation
signal on which higher harmonics are superimposed.
SUMMARY OF THE INVENTION
[0010] In the light of the foregoing, the present invention has
been made in order to solve the above-mentioned problem associated
with the prior art, and it is, therefore, an object of the present
invention to provide a heat sensitive flow meter which is capable
of, when an intake air pulsation of an engine is generated, reducing
an error appearing between a mean flow rate calculated from a flow
meter and an actual mean flow rate, and a fuel controller using
the same.
[0011] With the above object(s) in view, a heat sensitive flow
meter according to the present invention for measuring a flow rate
of a fluid passing through a suction pipe provided in an internal
combustion engine, includes: a filter means for inputting a flow
rate signal outputted from a flow rate detection means installed
within the suction pipe and subjecting the flow rate signal to a
filter processing; and a selection means for comparing the flow
rate signal outputted from the flow rate detection means and a filter
signal outputted from the filter means to select the signal having
a higher voltage from the flow rate signal and the filter signal
as a new flow rate signal.
[0012] In the present invention, the flow rate signal outputted
from the flow rate detection unit and the filter signal outputted
from the filter unit are compared with each other in order to select
the signal having a larger amplitude as a new flow rate signal.
Hence, it is possible to suppress a phenomenon of output reduction
of the flow meter occurring due to an influence of an engine pulsation
or the like to further increase the amplitude of the output signal,
and it is also possible to further reduce an error appearing between
an amount of actual intake air of an engine and an output signal
of the flow meter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a circuit diagram showing a configuration of a
heat sensitive flow meter according to Embodiment 1 of the present
invention;
[0014] FIG. 2 is a waveform chart useful in explaining signal waveforms
in the heat sensitive flow meter according to Embodiment 1 of the
present invention;
[0015] FIG. 3 is a circuit diagram showing a configuration of a
heat sensitive flow meter according to Embodiment 2 of the present
invention;
[0016] FIG. 4 is a waveform chart useful in explaining signal waveforms
in the heat sensitive flow meter according to the Embodiment 2 of
the present invention;
[0017] FIG. 5 is a circuit diagram showing a configuration of a
heat sensitive flow meter according to Embodiment 3 of the present
invention;
[0018] FIG. 6 is a waveform chart useful in explaining signal waveforms
in the heat sensitive flow meter according to the Embodiment 3 of
the present invention;
[0019] FIG. 7 is a circuit diagram showing a modification of the
configuration of the heat sensitive flow meter according to Embodiment
3 of the present invention;
[0020] FIG. 8 is a circuit diagram showing another modification
of the configuration of the heat sensitive flow meter according
to Embodiment 3 of the present invention;
[0021] FIG. 9 is a flow chart showing a flow of processings in
a heat sensitive flow meter according to Embodiment 4 of the present
invention;
[0022] FIG. 10 is a flow chart showing a modification of the flow
of the processings in the heat sensitive flow meter according to
Embodiment 4 of the present invention;
[0023] FIG. 11 is a flow chart showing another modification of
the flow of the processings in the heat sensitive flow meter according
to Embodiment 4 of the present invention;
[0024] FIG. 12 is a flow chart showing a flow of processings in
a heat sensitive flow meter according to Embodiment 5 of the present
invention; and
[0025] FIG. 13 is a schematic view showing one example of a construction
of an internal combustion engine to which the heat sensitive flow
meter according to the present invention is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
[0026] Embodiment 1 of the present invention will hereinafter be
described with reference to FIG. 1. A flow meter of the present
invention is a heat sensitive flow meter for detecting a flow rate
of a fluid using a heat sensitive resistor. That is to say, the
flow meter is constructed such that a flow rate detection unit is
installed within a flow tube provided in an internal combustion
engine of an automobile or the like in order to detect a flow rate
or a flow velocity of a fluid passing through the flow tube on the
basis of a phenomenon of heat transfer from a heating element of
the flow rate detection unit, measuring a flow rate of a fluid such
as an amount of intake air, to a fluid as an object of measurement.
[0027] Before giving a description with reference to FIG. 1 first
of all, a description is given with respect to one example of the
whole construction of an internal combustion engine to which the
heat sensitive flow meter according to the present invention is
applied with reference to FIG. 13. As shown in FIG. 13 an engine
101 is provided with an air cleaner 102 for cleaning air which is
sucked by the engine 101 through a suction pipe 104 as will be
described later, for intaking air, and an air flow sensor 103 for
measuring an amount of intake air passed through the air cleaner
102. The air flow sensor 103 is a flow rate detection unit in a
heat sensitive rate meter of the present invention. The suction
pipe 104 is provided with a throttle valve 105. The throttle valve
105 serves to adjust an amount of intake air to control an output
of the engine 101. The throttle valve 105 is provided with a throttle
aperture sensor 112 for detecting a throttle aperture. In addition,
a branched intake manifold 109 is provided downstream with respect
to the throttle valve 105. The intake manifold 109 is provided with
an injector 106. The injector 106 serves to supply fuel corresponding
to an amount of intake air. In addition, the suction valve 104 is
also provided with a pressure sensor 115 for detecting an intake
manifold pressure within the intake manifold 109. In addition, a
sparking plug 111 for generating a spark with which a mixed gas
within a combustion chamber is burnt, and a sparking coil 110 for
supplying a high voltage energy to the sparking plug 111 are provided
in the upper portion of the engine 101. Also, an exhaust pipe 107
for discharging therethrough a burnt exhaust gas is provided on
a side opposite to the suction pipe 104. The exhaust pipe 107 is
provided with an oxygen (O.sub.2) sensor 108 for detecting an amount
of remaining oxygen within the exhaust gas. A sensor plate 121 for
detecting a crank angle is provided in a lower portion of the engine
101. The sensor plate 121 is provided with a projection (not shown)
in its predetermined position, and is mounted to a crank shaft to
be rotated in a body with the crank shaft. The sensor plate 121
is provided with a rotation sensor 122. The rotation sensor 122
serves to detect a position of the crank shaft to detect the number
of revolutions of the engine. That is to say, the rotation sensor
122 is adapted to generate a signal at the time when the projection
(not shown) of the sensor plate 121 has crossed the rotation sensor
122 to thereby detect the number of revolutions of the engine. Actuators
(valve timing adjustment units) 113 are provided in an outlet portion
of the suction pipe 104 and an inlet portion of the exhaust pipe
107 respectively. The actuators 113 serve to change a relative
angle of a cam shaft with respect to the crank shaft. An oil control
valve (hereinafter referred to as an "OCV" for short)
114 serves to adjust a supply oil pressure to the cam phase actuator
113 to control a relative angle (cam phase) of the cam shaft with
respect to the crank shaft. In addition, an oil pump 118 generates
an oil pressure at which the cam phase actuator 113 is driven and
also sends labricating oil in mechanism elements of the engine 101
to corresponding portions under pressure. Also, an oil passing tube
for the oil concerned is provided with an oil pressure sensor 119
for detecting the oil pressure concerned, and an oil temperature
sensor 120 for detecting an oil temperature. An ECU 117 receives
input detection values from the various kinds of sensors to carry
out control on the basis of the detection values. The internal combustion
engine has been described above. Now, a description is returned
back to a circuit diagram of FIG. 1.
[0028] FIG. 1 is one example of a circuit diagram showing a configuration
of a heat sensitive flow meter according to Embodiment 1 of the
present invention. An illustrated circuit 1 is connected to a general
heat sensitive flow meter (hereinafter referred to as a "flow
rate detection unit", and its illustration is omitted here)
shown in JP 62-36522 B or the like. Then, the circuit 1 shown in
FIG. 1 constitutes, together with the flow rate detection unit,
a heat sensitive flow meter of the present invention. Note that,
in other embodiments described later as well, the flow rate detection
unit will not be illustrated, and only a circuit portion according
to the present invention will be described. As shown in FIG. 1
in the circuit 1 according to the present invention, a fixed resistor
2 and other portion are connected in parallel with each other. Here,
other portion means a circuit including a fixed resistor 3 a capacitor
4 an operational amplifier 5 and a diode 6. Note that, the circuit
1 shown in FIG. 1 of the present invention receives as its input
a voltage value Vin of a flow rate signal outputted from the flow
rate detection unit concerned (hereinafter referred to as a "flow
rate signal Vin" for short) to output an output signal Vout.
At that, the fixed resistor 3 and the capacitor 4 constitute a low-pass
filter (LPF) 7 (hereinafter referred to as a "filter 7"
for short) for delaying the flow rate signal by a predetermined
time constant.
[0029] Accordingly, as shown in the figure, the flow rate signal
Vin obtained from the flow rate detection unit branches into two
systems of a signal passing through the fixed resistor 2 and a signal
passing through the circuit constituted by the filter 7 (constituted
by the fixed resistor 3 and the capacitor 4), the operational amplifier
5 and the diode 6. At this time, when an electrostatic capacity
of the capacitor 4 is assigned C, and a resistance value of the
fixed resistor 3 is assigned R1 a signal Vf which has passed through
the filter 7 becomes a signal which is obtained by delaying the
flow rate signal Vin by a time constant .tau.=C.times.R1. Though
the flow rate signal Vin and the signal Vf are equal in frequency
to each other, an amplitude of the signal Vf is smaller than that
of the flow rate signal Vin (refer to FIG. 2).
[0030] After the signal Vf has passed through an ideal diode constituted
by the operational amplifier 5 and the diode 6 the signal Vf meets
the flow rate signal Vin which has passed through the fixed resistor
2. Hence, for the output signal Vout, the signal having a higher
voltage of the flow rate signal Vin and the signal Vf is selected
on the basis of an operation of the operational amplifier 5 the
diode 6 and the fixed resistor 2.
[0031] In such a manner, in this embodiment, the filter 7 (constituted
by the capacitor 4 and the fixed resistor 3) constitutes a filter
unit for receiving as its input the flow rate signal Vin outputted
from the flow rate detection unit to subject the flow rate signal
Vin to a predetermined processing. Also, the operational amplifier
5 the diode 6 and the fixed resistor 2 constitute a selection unit
8 for comparing voltages (or flow rate voltages) of the flow rate
signal Vin and the signal Vf passed through the filter 7 to select
the signal having the higher voltage value as a new flow rate signal.
[0032] FIG. 2 shows signal waveforms of the flow rate signal Vin,
the output signal Vf and the signal Vout in which a fine line represents
the signal Vin, a broken line represents the signal Vf, and a heavy
line represents the output signal Vout. As apparent from this figure
as well, for the output signal Vout, the signal having the higher
voltage value of the signal Vin and the signal Vf is selected. More
specifically, while the voltage of the flow rate signal is increased,
the flow rate signal Vin is continuously selected as the output
signal Vout. While the voltage of the flow rate signal is decreased,
the signal Vin is continuously selected as the signal Vout until
a time point when the signal Vf and the signal Vin cross each other.
Also, the signal Vf is continuously selected as the signal Vout
at and after that time point.
[0033] As described above, according to the present invention,
apart of the flow rate signal outputted from the flow rate detection
unit is made to pass through the filter 7 and the signal having
the higher voltage, in the signal waveforms before and after passing
through the filter 7 of the two signals is used as a new flow rate
signal Vout. Hence, a phenomenon of reduction in an amplitude of
an output signal of a flow meter occurring due to an influence of
an engine pulsation or the like can be suppressed to increase the
amplitude of the output signal, and it is possible to reduce an
error appearing between an actual amount of intake air of the engine
and data on the output signal of the flow meter. Note that, in case
of the configuration of Embodiment 1 since the circuit 1 is constituted
by the fixed resistors 2 and 3 the capacitor 4 the operational
amplifier 5 and the diode 6 the circuit 1 can be configured at
a relatively low cost.
Embodiment 2
[0034] A configuration of a heat sensitive flow meter according
to Embodiment 2 of the present invention is shown in FIG. 3. FIG.
3 is one example of a circuit diagram embodying the present invention.
As shown in the figure, in this embodiment, a filter 10 and a fixed
resistor 12 are connected in parallel with an operational amplifier
15 and a diode 16. The filter 10 is a high-pass filter (HPF) constituted
by an operational amplifier 17 a fixed resistor 13 and a capacitor
14. While in the above-mentioned Embodiment 1 for a filter configuration,
the LPF is adopted, in this embodiment, as shown in FIG. 3 the
HPF is adopted. Note that, the circuit of FIG. 3 receives as its
input the flow rate signal Vin outputted from the flow rate detection
unit to output the output signal Vout.
[0035] In this embodiment, as shown in the figure, the flow rate
signal Vin obtained from the flow rate detection unit branches into
two systems of a signal passing through the filter 10 (constituted
by the operational amplifier 17 the fixed resistor 13 and the
capacitor 14) and the fixed resistor 12 and a signal passing through
an ideal diode constituted by the operational amplifier 15 and the
diode 16. At this time, when an electrostatic capacity of the capacitor
14 is assigned C, and a resistance value of the fixed resistor 13
is assigned R1 a signal Vf which has passed through the filter
10 becomes a signal which is obtained by advancing the flow rate
signal Vin by a time constant .tau.=C.times.R1. Though the flow
rate signal Vin and the signal Vf are equal in frequency to each
other, an amplitude of the signal Vf is larger than that of the
flow rate signal Vin (refer to FIG. 4).
[0036] After passing through the fixed resistor 12 the signal
Vf meets the flow rate signal Vin which has passed through an ideal
diode constituted by the operational amplifier 15 and the diode
16. Hence, for the output signal Vout, the signal having a higher
voltage of the flow rate signal Vin and the signal Vf is selected
on the basis of an operation of the fixed resistor 12 the operational
amplifier 15 and the diode 16. In such a manner, in this embodiment,
the filter 10 constitutes a filter unit for receiving as its input
the flow rate signal Vin outputted from the flow rate detection
unit to subject the flow rate signal Vin to a predetermined processing.
Also, the fixed resistor 12 the operational amplifier 15 and the
diode 16 constitute a selection unit 11 for comparing voltages (or
flow rate voltages) of the flow rate signal Vin and the signal Vf
passed through the filter 10 to select the signal having the higher
voltage value as a new flow rate signal.
[0037] FIG. 4 shows signal waveforms of the flow rate signal Vin,
the output signal Vf, and the signal Vout in which a fine line represents
the signal Vin, a broken line represents the signal Vf, and a heavy
line represents the output signal Vout. As apparent from this figure
as well, for the output signal Vout, the signal having the higher
voltage value of the signal Vin and the signal Vf is selected. More
specifically, while the voltage of the flow rate signal is increased,
the signal Vf is continuously selected as the output signal Vout
from a time point when the signal Vf and the signal Vin cross each
other until the signal Vf reaches its peak value. While the voltage
of the flow rate signal is decreased, the signal Vf is continuously
selected as the signal Vout until a time point when the signal Vf
and the signal Vin cross each other. Also, the signal Vin is continuously
selected as the signal Vout until a time point when the signal Vf
and the signal Vin cross each other.
[0038] In this way, in Embodiment 2 a signal having a higher voltage
between the flow rate signal Vin and the signal Vf is selected as
a signal Vout in the same manner as in Embodiment 1.
[0039] As described above, according to the present invention,
a part of the flow rate signal outputted from the flow rate detection
unit is made to pass through the filter 10 and the signal having
the higher voltage, in the signal waveforms before and after passing
through the filter 10 of the two signals is used as a new flow
rate signal Vout. Hence, a phenomenon of reduction of an amplitude
of an output signal of a flow meter occurring due to an influence
of an engine pulsation or the like can be suppressed to increase
the amplitude of the output signal, and it is possible to reduce
an error appearing between an amount of actual intake air of the
engine and data of the output signal of the flow meter. Further,
according to this embodiment, a delayed flow rate signal is advanced,
so that there is an effect such that superficial responsibility
is enhanced.
Embodiment 3
[0040] FIG. 5 is one example of a circuit diagram showing a configuration
of a heat sensitive flow meter according to Embodiment 3 of the
present invention. As shown in the figure, a circuit including a
filter 20 an operational amplifier 27 and a diode 26 is connected
in parallel with a fixed resistor 22. The filter 20 is constituted
by a fixed resistor 23 a capacitor 24 an operational amplifier
25 and a battery 28. Note that, the circuit of the present invention
receives as its input the flow rate signal Vin outputted from the
flow rate detection unit to output the output signal Vout.
[0041] Consequently, as shown in the figure, the flow rate signal
Vin obtained from the flow rate detection unit branches into two
systems of a signal passing through the fixed resistor 2 and a signal
passing through the circuit constituted by the filter 20 (constituted
by the fixed resistor 23 the capacitor 24 the operational amplifier
25 and the battery 28), the operational amplifier 27 and the diode
26. At this time, when an electrostatic capacity of the capacitor
24 is assigned C, and a resistance value of the fixed resistor 23
is assigned R1 a signal Vave which has passed through the filter
constituted by the capacitor 24 and the fixed resistor 23 becomes
a signal which is obtained by delaying the flow rate signal Vin
by a time constant .tau.=C.times.R1. After the signal Vave has passed
through the operational amplifier 25 a predetermined voltage Vc1
is subtracted from the voltage of the signal Vave in the battery
28. Then, the signal Vave passes through an ideal diode constituted
by the operational amplifier 27 and the diode 26 and then meets
the flow rate signal Vin which has passed through the fixed resistor
22.
[0042] In such a manner, with the configuration of FIG. 5 a value
lower than the mean value Vave of the flow rate signal by the predetermined
value Vc1 previously set is clipped, whereby when a signal having
a pulsation amplitude becomes a signal having a voltage value exceeding
the clip value, an apparent mean flow rate can be increased. In
such a manner, in this embodiment, the filter 20 constitutes a filter
unit for receiving as its input the flow rate signal Vin outputted
from the flow rate detection unit to subject the flow rate signal
Vin concerned to the predetermined processing (the processing for
arithmetically operating the value lower than the mean value of
the flow rate signal by the predetermined value). Also, the fixed
resistor 22 the operational amplifier 27 and the diode 26 constitute
selection unit for comparing the voltage values (or the flow rate
values) of the flow rate signal Vin and the signal Vf passed through
the filter unit and selecting the signal having the larger value
as a new flow rate signal.
[0043] FIG. 6 shows signal waveforms of the flow rate signal Vin,
the mean value signal Vave, and the output signal Vout in which
a fine line represents the signal Vin, a broken line represents
the signal Vave of the flow rate signal, and a heavy line represents
the signal Vout. As apparent from the figure as well, for the output
signal Vout, a value lower than the mean value Vave by the predetermined
value Vc1 is set as a limit value. At the time when the amplitude
of the flow rate signal has become equal to or lower than the set
value concerned, the output signal Vout at this time point is set
as the signal (Vave-Vc1). That is to say, the signal having the
higher voltage of the flow rate signal Vin and the signal (Vave-Vc1)
is selected as the output signal Vout.
[0044] In addition, the configuration of this embodiment may be
simplified as shown in FIG. 7. In a configuration of FIG. 7 a diode
29 is provided instead of the operational amplifier 25 the battery
28 the operational amplifier 27 and the diode 26 in the configuration
of FIG. 5. The mean value Vave of the flow rate signal is obtained
through the fixed resistor 23 and the capacitor 24 and the signal
(Vave-Vc1) is obtained on the basis of a function of the diode 29.
As a result, it is possible to obtain the signal waveforms of the
flow rate signal Vin, the mean value signal Vave and the output
signal Vout similar to those shown in FIG. 6. Note that, in this
case, the filter 20 including the fixed resistor 23 and the capacitor
24 constitute the filter unit, and the fixed resistor 22 and the
diode 29 constitute a selection unit 21.
[0045] In addition, if the circuit is configured as shown in FIG.
8 a value lower than the mean value of the flow rate signal by
a predetermined ratio previously set can be clipped from the mean
value of the flow rate signal. That is to say, in the configuration
of FIG. 8 two fixed resistors 21a and 21b are provided instead
of the battery 28 in the configuration of FIG. 5. A desired predetermined
ratio (R3/R4) can be obtained depending on how to set resistance
values R3 and R4 of the two fixed resistors 21a and 21b. Note that,
in this case, the filter 20 including the fixed resistor 23 the
capacitor 24 the operational amplifier 25 the fixed resistor 21a
and the fixed resistor 21b constitute the filter unit, and the fixed
resistor 22 the operational amplifier 27 and the diode 26 constitute
the selection unit 21.
[0046] In such a manner, in the configuration of FIG. 8 a value
of (Vave.times.(R3/R4)) lower than the mean value Vave of the flow
rate signal by a predetermined ratio previously set is clipped,
whereby at the time when a signal having a pulsation amplitude has
become a signal having an amplitude exceeding the clip value, an
apparent mean flow rate can be increased. That is to say, the signal
having the higher voltage of the flow rate signal Vin and the signal
(Vave-Vave.times.(R3/R4)) is selected.
[0047] As described above, according to the present invention,
a part of the flow rate signal outputted from the flow rate detection
unit is made to pass through the filter 20 and the signal having
the higher voltage, in the signal waveforms before and after passing
through the filter 20 of the two signals is used as a new flow
rate signal Vout. Hence, a phenomenon of reduction of an amplitude
of an output signal of a flow meter occurring due to an influence
of an engine pulsation or the like can be suppressed to increase
the amplitude of the output signal, and it is possible to reduce
an error appearing between an amount of actual intake air of the
engine and data of the output signal of the flow meter. Further,
according to Embodiment 3 signal correction is performed only when
the pulsation amplitude is large. Thus, there is an effect that
characteristics of the flow meter achieved in prior art can be utilized.
Embodiment 4
[0048] In the above-mentioned Embodiments 1 to 3 the description
has been given with respect to the example in which the phenomenon
of reduction of the amplitude of the output signal from the flow
meter occurring due to the influence of the engine pulsation or
the like is suppressed to increase the amplitude of the output signal
on the basis of the circuit configuration. However, in this embodiment,
a description will now be given with respect to an example of executing
the same processing with a processing using software. FIGS. 9 10
and 11 are flow charts each showing a flow of a software processing
in this embodiment.
[0049] The processing shown in FIG. 9 is such that a signal inputted
from the flow rate detection unit to a fuel controller is processed
using software. In FIG. 9 Vi is a flow rate signal outputted from
the flow rate detection unit, Qi is a flow rate conversion signal
which is obtained by flow rate-converting the flow rate signal Qi,
and Qf is a filter signal which is obtained by filter-processing
the flow rate conversion signal Qi.
[0050] In the processings of FIG. 9 first of all, in Step S, the
flow rate signal Vi detected by the flow rate detection unit is
inputted. Next, in Step S2 the inputted flow rate signal Vi is
converted into the flow rate conversion signal Qi as a signal exhibiting
a flow rate of a fluid. Next, in Step S3 the flow rate conversion
signal Qi is subjected to a predetermined filter processing to obtain
the filter signal Qf (=f(Qi)) where f is a filter function). Note
that, the filter processing concerned is a software processing for
obtaining the results corresponding to the results of the processing
in the filter 1 or the filter 10 shown in the above-mentioned Embodiment
1 or 2 respectively. That is to say, the signal Qi is delayed or
put forward with a predetermined time constant to obtain the signal
waveform which is identical in frequency to the signal Qi, but different
in amplitude from the signal Qi. Next, in Step S4 the amplitudes
of the flow rate conversion signal Qi and the filter signal Qf are
compared with each other. When it is judged as a result of the comparison
in Step S4 that the amplitude of the flow rate conversion signal
Qi is larger than that of the filter signal Qf, the process proceeds
to Step S5 and no processing is then especially executed (Qi=Qi).
On the other hand, when it is judged as a result of the comparison
in Step S4 that the amplitude of the flow rate conversion signal
Qi is smaller than that of the filter signal Qf, the process proceeds
to Step S6 and a value of the signal Qf is then substituted for
the value of the signal Qi (Qi=Qf). As a result, in Step S7 the
signal having the larger amplitude of the signal Qi and the signal
Qf is used as a new signal Qi as a flow rate conversion signal Qi
for fuel control. In such a manner, in FIG. 9 the processings of
Steps S1 to S3 constitute the filter unit for receiving as its input
the flow rate signal Vin outputted from the flow rate detection
unit to subject the flow rate signal Vin to the predetermined processing.
Also, the processings of Steps S4 to S7 constitute the selection
unit for comparing any ones of the voltage values and the flow rate
values of the flow rate signal and the signal passed through the
filter unit to select the signal having the larger value as a new
flow rate signal.
[0051] Note that, as shown in FIG. 10 the flow rate signal Vi
before the flow rate conversion may be subjected to the filter processing
in order to select the signal having the larger value before and
after the filter processing.
[0052] In the processings of FIG. 10 first of all, in Step S11
the flow rate signal Vi detected by the flow rate detection unit
is inputted. Next, in Step S12 the flow rate signal Vi is subjected
to a predetermined filter processing to obtain the filter signal
Vf (=f(Vi)) where f is a filter function). Note that, the filter
processing concerned is a software processing for obtaining the
results corresponding to the results of the processing in the filter
1 or the filter 10 shown in the above-mentioned Embodiment 1 or
2 respectively (that is, signal waveform of the signal Vf shown
in shown in FIGS. 2 and 4). Next, in Step S13 the amplitudes of
the flow rate signal Vi and the filter signal Vf are compared with
each other. When it is judged as a result of the comparison in Step
S13 that the amplitude of the flow rate signal Vi is larger than
that of the filter signal Vf, the process proceeds to Step S14 and
no processing is then especially executed (Vi=Vi). On the other
hand, when it is judged as a result of the comparison in Step S13
that the amplitude of the flow rate signal Vi is smaller than that
of the filter signal Vf, the process proceeds to Step S15 and a
value of the signal Vf is then substituted for the value of the
signal Vi (Vi=Vf). Next, in Step S16 the signal having the larger
amplitude of the signal Vi and the signal Vf is used as a new signal
Vi as a flow rate signal Vi for fuel control. Next, in Step S17
the flow rate of the new flow rate signal Vi is converted into a
flow rate conversion signal Qi. Then, the signal having a higher
voltage is selected from the signal Vi and the signal Vf as the
flow rate signal Vi for fuel control. In such a manner, in FIG.
10 the processings of Steps S11 to S12 constitute the filter unit
for receiving as its input the flow rate signal Vi outputted from
the flow rate detection unit to subject the flow rate signal Vi
to the predetermined processing. Also, the processings of Steps
S13 to S17 constitute the selection unit for comparing any ones
of the voltage values and the flow rate values of the flow rate
signal Vi and the signal Vf passed through the filter unit to select
the signal having the larger value as a new flow rate signal.
[0053] Note that, as shown in FIG. 11 the value of the flow rate
conversion signal may be compared with a value that is lower than
the mean flow rate Qave by the flow rate Qc1 previously set to clip
the flow rate signal Q1 with the signal (Qave-Qcl) when the voltage
value of the signal Qi is equal to or lower than that of the signal
(Qave-Qc1). At that, as a result, the same effects as those of the
above-mentioned Embodiment 3 can be obtained.
[0054] In the processings shown in FIG. 11 first of all, in Step
S21 the flow rate signal Vi detected by the flow rate detection
unit is inputted. Next, in Step S22 the inputted flow rate signal
Vi is converted into the flow rate conversion signal Qi exhibiting
the flow rate. Next, in Step S23 the amplitude of the flow rate
conversion signal Qi is compared with a value lower than the mean
flow rate Qave by the flow rate Qc1 previously set. Note that, the
mean flow rate Qave will be previously arithmetically operated to
be prepared for the next processings in Step S27 which will be described
later. When it is judged as a result of the comparison in Step S23
that the amplitude of the flow rate conversion signal Qi is larger
than that value, the process proceeds to Step S24 and no processing
is especially executed (Qi=Qi). On the other hand, when it is judged
as a result of the comparison in Step S23 that the amplitude of
the flow rate conversion signal Qi is smaller than that value, the
process proceeds to Step S25 and a value of (Qmin=Qave-Qcl) is
substituted for the value of Qi (Qi=Qmin). As a result, in Step
S26 the signal having the larger value of the signal Qi and the
signal Qmin is used as a new signal Qi as a flow rate conversion
signal Qi for fuel control. Next, the mean flow rare Qave is arithmetically
operated for the next processings using the present measurement
results and the past measurement results. In such a manner, in FIG.
11 the processings for obtaining the signal (Qave-Qc1) in Steps
S21 and S22 and Step S23 constitute the filter unit for receiving
as its input the flow rate signal Vin outputted from the flow rate
detection unit to subject the flow rate signal Vin to the predetermined
processing. Also, the processings from the amplitude comparison
processing in Step S23 to Step S27 constitute the selection unit
for comparing the voltage values (and any ones of the voltage values
and the flow rate values) of the flow rate signal Vin and the signal
Vf that is passed through the filter 7.
[0055] As described above, according to this embodiment, similarly
to the above-mentioned Embodiments 1 to 3 the flow rate signal
outputted from the flow rate detection unit is subjected to the
predetermined software processing, and the signal having the higher
voltage in the signal waveforms before and after the software processing
is used as a new flow rate signal Vout. As a result, the phenomenon
of reduction of the amplitude of the output signal from the flow
meter occurring because of the influence of the engine pulsation
or the like can be suppressed to increase the amplitude of the output
signal, and it is possible to reduce an error appearing between
an amount of actual intake air of the engine and the output signal
of the flow meter. In addition, according to this embodiment, since
the process is carried out by executing the software processing,
the flow meter becomes inexpensive.
Embodiment 5
[0056] In this embodiment as well, similarly to the above-mentioned
Embodiment 4 an example of processings using software will herein
below be described. FIG. 12 is a flow chart showing a flow of software
processings in this embodiment. In general, the aperture of the
throttle valve 105 (hereinafter referred to as "the throttle
aperture" for short) for adjusting an amount of intake air
to the engine 101 is controlled by driving a throttle actuator (not
shown) provided for the throttle valve 105 in accordance with the
control made by the ECU 117 as a controller provided in the internal
combustion engine on the basis of the number of revolutions of the
engine 101. Thus, in this embodiment, a set value for the throttle
aperture is set every number of revolutions of the engine. When
the throttle aperture has become equal to or larger than the set
value that is previously set every number of revolutions of the
engine, equal to or smaller than the flow rate previously set is
clipped.
[0057] In the processings shown in FIG. 12 first of all, in Step
S31 the flow rate signal Vi detected by the flow rate detection
unit is inputted. Next, in Step S32 the inputted flow rate signal
Vi is converted into the flow rate conversion signal Qi exhibiting
a flow rate. Next, in Step S33 a throttle aperture Vtps detected
by the throttle aperture sensor 112 is compared with a predetermined
set value Vtpsmin. Note that, the predetermined set value Vtpsmin
is a set value for a throttle aperture signal which is previously
set in correspondence to the number of revolutions of the engine.
For example, a data table is generated to store the set values for
the throttle aperture signal in a memory of the ECU in correspondence
to the number of revolutions of the engine. Note that, the number
of revolutions of the engine, as described with reference to FIG.
13 is detected by the rotation sensor 122. When it is judged as
a result of the comparison in Step S33 that the throttle aperture
Vtps is larger than the predetermined set value Vtpsmin, the process
proceeds to Step S34. On the other hand, when it is judged as a
result of the comparison in Step S33 that the throttle aperture
Vtps is smaller than the predetermined set value Vtpsmin, the process
proceeds to Step S38 and no processing is especially executed (Qi=Qi),
and then the process proceeds to Step S37. In Step S34 the amplitude
of the flow rate conversion signal Qi obtained in Step S32 is compared
with a predetermined value Qmin. The predetermined value Qmin is
suitably set to a suitable value with the method in the above-mentioned
Embodiment 4 as one example. When it is judged as a result of the
comparison in Step S34 that the amplitude of the flow rate conversion
signal Qi is larger than the predetermined set value Qmin, the process
proceeds to Step S35 and no processing is especially executed (Qi=Qi).
On the other hand, when it is judged as a result of the comparison
in Step S34 that the amplitude of the flow rate conversion signal
Qi is smaller than the predetermined set value Qmin, the process
proceeds to Step S36 and the predetermined set value Qmin is substituted
for the value of the flow rate conversion signal Qi (Qi=Qmin). Accordingly,
when in Step S37 the throttle aperture has become equal to or larger
than a predetermined value for the flow rate conversion signal Qi
for fuel control, the signal having the larger value of the signal
Qi and the signal Qmin is used as a new signal Qi. As a result,
when the throttle aperture has become equal to or larger than the
set value for the throttle aperture which is previously set every
number of revolutions of the engine, it is possible to clip equal
to or smaller than the flow rate previously set.
[0058] Note that, in this embodiment, Step S33 constitutes a judgement
step of inputting a value of the throttle aperture and a value of
the number of revolutions of the engine to judge whether or not
the throttle aperture is equal to or larger than the set value for
the throttle aperture which is previously set in correspondence
to the number of revolutions. Also, Steps S34 to S37 constitute
a selection step of, when the throttle aperture is equal to or larger
than the set value, judging whether or not the amplitude of the
flow rate signal outputted from the flow rate detection unit installed
within the suction pipe is equal to or smaller than a set value
for the flow rate signal previously set to select the set value
as a new flow rate signal if the amplitude of the flow rate signal
is judged to be equal to or smaller than the set value.
[0059] As described above, according to this embodiment, similarly
to the above-mentioned Embodiment 4 the flow rate signal outputted
from the flow rate detection unit is subjected to the predetermined
software processing, and the signal having the higher voltage in
the signal waveforms before and after the software processing is
used as a new flow rate signal Vout. As a result, the phenomenon
of reduction of the amplitude of the output signal from the flow
meter occurring because of the influence of the engine pulsation
or the like can be suppressed to increase the amplitude of the output
signal. It is also possible to reduce an error appearing between
an amount of actual intake air of the engine and the output signal
of the flow meter. In addition, according to this embodiment, since
the process is carried out by executing the software processing,
similarly to the Embodiment 4 the flow meter becomes inexpensive.
Moreover, in this embodiment, since the clip value can be set every
number of revolutions of the engine, a degree of freedom of the
engine is increased. Furthermore, since a region in which no error
of the flow meter appears due to the engine pulsation can be set
with the throttle aperture, it is possible to maintain the fuel
accuracy achieved in prior art.
[0060] Note that, in this embodiment, the description has been
given with respect to the example in which when the throttle aperture
becomes equal to or larger than the throttle aperture that is previously
set every number of revolutions, equal to or smaller than the predetermined
flow rate is clipped. However, the present invention is not intended
to be limited to that example, and an intake manifold pressure may
be used. In general, a pressure within the intake manifold 109
serving as a suction pressure in the suction pipe 104 provided downstream
with respect to the throttle valve 105 (hereinafter referred to
as "an intake manifold pressure" for short) is controlled
by adjusting the throttle aperture with the ECU 117 on the basis
of the number of revolutions of the engine. For this reason, as
a modification of this embodiment, a set value for the intake manifold
pressure is previously set every number of revolutions of the engine.
Then, when the intake manifold pressure detected by the pressure
sensor 115 provided in the intake manifold 109 has become equal
to or larger than the set value for the intake manifold pressure
previously set every number of revolutions, equal to or smaller
than a predetermined flow rate is clipped. The same effects can
be obtained in this case as well.
[0061] In addition, when the heat sensitive flow meter described
in the above-mentioned Embodiments 1 to 5 is used in a fuel controller
for an internal combustion engine of an automobile or the like,
since an error appearing between a flow rate of actual intake air
of the engine and an output signal of the flow meter is less, the
fuel control can be carried out with high accuracy. |