Flow measuring device

Abstract

A flow measuring device has a sensor element for outputting a nonlinear signal according to a flow rate. The device comprises: a first signal processing system for obtaining a first signal by filtering the nonlinear signal output from the sensor element, thereafter correcting a sensitivity of the filtered signal; a second signal processing system for obtaining a second signal by linearizing the nonlinear signal from the sensor element, thereafter filtering the linearized signal and correcting a sensitivity of the filtered signal, and then nonlinearizing the linearized signal with a corrected sensitivity; an amplifier for amplifying a differential signal between the first and second signals; and a correcting section for correcting the nonlinear signal by using the amplified differential signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system configuration diagram of a flow measuring device according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing digital processing for pulsation error correction used in Embodiment 1.

FIG. 3 is a block diagram showing signal processing for the computation of a pulsation error correction amount in Embodiment 1.

FIG. 4( a) is a graph showing the characteristic of a V-Q conversion function and FIG. 4(b) is a graph showing the characteristic of a Q-V conversion function, both the functions being used in Embodiment 1.

FIG. 5 comprises graphs showing the movements of waveforms in pulsation error correction processing in Embodiment 1.

FIG. 6( a) is a graph showing the characteristic of a V-Q conversion function and FIG. 6(b) is a graph showing the characteristic of a Q-V conversion function, both the functions being used in Embodiment 2 of the present invention.

FIG. 7 is a sectional view showing a bypass and a flow rate sensor disposed in an intake passage and used in Embodiment 3 of the present invention.

FIG. 8 is a graph showing the effect of pulsation error correction in Embodiment 3.

FIG. 9 is a sectional view showing a bypass and a flow rate sensor disposed in an intake passage and used in Embodiment 4 of the present invention.

FIG. 10 is a graph showing the effect in Embodiment 4. (Embodiment 4).

FIG. 11 is a block diagram showing signal processing for the computation of a pulsation error correction amount in Embodiment 5 of the present invention.

FIG. 12 is another block diagram showing signal processing for the computation of a pulsation error correction amount in Embodiment 5.

FIG. 13 is a block diagram showing signal processing for the computation of a pulsation error correction amount in Embodiment 6 of the present invention.

FIG. 14 comprises explanatory graphs showing operations in the computation processing of a pulsation characteristic amount in Embodiment 6.

FIG. 15 comprises other explanatory graphs showing operations in the computation processing of a pulsation characteristic amount in Embodiment 6.

FIG. 16 is a block diagram showing signal processing for the computation of a pulsation error correction amount in Embodiment 7 of the present invention.

FIG. 17 comprises explanatory graphs showing the movements of waveforms for pulsation error correction in Embodiment 7.

FIG. 18 is a block diagram showing pulsation error correction processing in a modification of Embodiment 1.

FIG. 19 comprises graphs showing the movements of waveforms for pulsation error correction processing.

FIG. 20 is a graph showing output characteristics of a thermal air flowmeter.

FIG. 21 is a graph showing the relationship among a sensor output, an air flow rate, and a mean flow rate.

Claims

1. A flow measuring device having a sensor element for outputting a nonlinear signal according to a flow rate, comprising: a first signal processing system for obtaining a first signal by filtering the nonlinear signal output from said sensor element, thereafter correcting a sensitivity of the filtered signal;a second signal processing system for obtaining a second signal by linearizing the nonlinear signal from said sensor element, thereafter filtering the linearized signal and correcting a sensitivity of the filtered signal, and then nonlinearizing the linearized signal with a corrected sensitivity;an amplifier for amplifying a differential signal between said first and second signals; anda correcting section for correcting the nonlinear signal by using the amplified differential signal.

2. The flow measuring device according to claim 1, wherein: said first signal processing system is configured by connecting a lowpass filter, a voltage-flow rate converter for performing linearization, and a flow rate-voltage converter for performing nonlinearization to each other, in order of the listed; andsaid second signal processing system is configured by connecting a voltage-flow rate converter for performing linearization, a lowpass filter, and a flow rate-voltage converter for performing nonlinearization to each other, in order of the listed.

3. The flow measuring device according to claim 1, wherein: said first signal processing system is configured by connecting a highpass filter, a voltage-flow rate converter for performing linearization, and a flow rate-voltage converter for performing nonlinearization to each other, in order of the listed; andsaid second signal processing system is configured by connecting a voltage-flow rate converter for performing linearization, a highpass filter, and a flow rate-voltage converter for performing nonlinearization to each other, in order of the listed.

4. A flow measuring device having a sensor element for outputting a nonlinear signal according to a flow rate, comprising: a first filter for filtering a nonlinear signal output from said sensor element;a signal processor for obtaining an absolute value of a differential signal between the filtered signal from said first filter and the nonlinear signal output from said sensor element;a second filter for filtering the absolute value of the differential signal from said signal processor;an amplifier for amplifying the filtered differential signal from said second filter; anda correcting section for correcting the nonlinear signal output from said sensor element by using the amplified differential signal.

5. The flow measuring device according to claim 4, wherein each of said first and second filters comprises a lowpass filter for cutting a high-frequency zone and form a phase lag of a signal.

6. The flow measuring device according to claim 4, wherein each of said first and second filters comprises a highpass filter for cutting a low-frequency zone and form a phase lead of a signal.

7. The flow measuring device according to claim 1, wherein said each filtering is performed with a variable filter capable of changing a frequency band in accordance with a magnitude of an input signal.

8. A flow measuring device having a sensor element for outputting a nonlinear signal according to a flow rate, comprising: a signal processor for correcting a nonlinear signal which is output from said sensor element and that contains an AC component,wherein said signal processor is comprised of:a first signal processing system for obtaining a first signal with a mean value error by nonlinearly integrating the nonlinear signal output from said sensor element;a second signal processing system for obtaining a second signal for linearly integrating the nonlinear signal output from said sensor element whose phase is matched with that of said first signal;an amplifier for amplifying a differential signal between said first and second signals; andan adder-subtracter for adding or subtracting the differential signal amplified by said amplifier to or from the nonlinear signal output from said sensor element.

9. The flow measuring device according to claim 1, wherein: said first and second signal processing systems are operated with time-sharing; andsaid first and second signal processing systems allow the shared use of a section for correcting said sensitivities of said filtered signals respectively, via a changeover switch for selectively connecting said section for correcting said sensitivities to either one of said first and second signal processing systems.

10. The flow measuring device according to claim 2, wherein: said first and second signal processing systems are operated with time-sharing; andsaid voltage-flow rate converters in said first and second signal processing systems are shared with these signal processing signals by a common converter, via a changeover switch for selectively connecting said section for correcting said sensitivities to either one of said first and second signal processing systems.

11. A flow measuring device having a sensor element for outputting a nonlinear signal according to a flow rate, comprising: a signal processor for correcting a nonlinear signal output from said sensor element: whereinsaid signal processor is comprised of:a digital signal processing section for processing the nonlinear signal output from said sensor element at plural steps with time-sharing;a sample hold section for holding a first signal obtained by processing in a first time zone of said time-sharing and a second signal obtained by processing in a second time zone of said time-sharing, respectively;an amplifier for amplifying the differential signal between said first and second signals held in said sample hold section; anda correcting section for correcting the error of said the nonlinear signal from said sensor element by using the amplified differential signal.

12. The flow measuring device according claim 1, wherein: said amplifier is configured to variably set a gain for amplifying said differential signal so that the gain depends on a magnitude of an AC signal component or a magnitude of a variation per time caused by pulsation of a flow rate signal; andsaid gain is variably set with a function or a map.

13. The flow measuring device according to claim 1, wherein: wherein each filtering at said first and second signal processing system is performed with a variable filter capable of changing its frequency band in accordance with a magnitude of an input signal; andsaid amplifier is configured to variably set a gain for amplifying said differential signal in accordance with said frequency band.

14. The flow measuring device according to claim 1, wherein said sensor element is placed in a bypass disposed along a fluid passage for feeding a fluid to be measured.

15. The flow measuring device according to claim 1, wherein said amplifier is configured to variably set a gain for amplifying said differential signal so that said gain can be changed in accordance with information from an external engine controller or the other external controller.