JPH0358047B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air flow rate detection device for detecting an air flow rate within a predetermined air passage.

Conventionally, as this type of air flow rate detection device,
For example, a hot wire that is heated by electricity is arranged in a predetermined air passage, and the heating current is supplied to the hot wire to compensate for the temperature drop as the hot wire is cooled by the circulating air in the air passage. Control the increase/decrease to
It is well known that the temperature of the heating wire is always maintained at a predetermined value, and the mass flow rate of the circulating air in the passage is detected by the increase/decrease change in the output voltage caused by the increase/decrease in the heating current. (For example, see Japanese Patent Application Laid-Open No. 57-35128, etc.).

However, in the above-mentioned conventional device, the output voltage generated by the heating current is proportional to the fourth root of the air flow rate (see Figure 2 of the above-mentioned publication). The disadvantage is that detection accuracy deteriorates in a large range.

Therefore, instead of relying on the conventional method of detecting the mass flow rate of the flow rate air in the air passage, a method has been proposed in which the air flow rate can be detected accurately over a wide range by detecting the flow velocity of the circulating air. There is. That is, in this method, a Karman vortex generation column is arranged in a predetermined air passage, and the number (frequency) of Karman vortices generated by this vortex generation column is directly proportional to the air flow velocity in the passage. The air flow velocity is detected by measuring the generation frequency of the vortex as a change in heat amount using a heat wire sensor such as the one described above, and the air flow rate is detected as a result.
(See Publication No. 148722, etc.) However, this proposal relies on the detection of air flow velocity, so if the air flow velocity is constant, it will always remain constant even if the air flow rate actually increases or decreases due to changes in air density. The disadvantage is that it is detected as a flow rate of . That is, the generation frequency of the Karman vortex is proportional to the air flow velocity, but there is a drawback that it does not change with respect to changes in air density.

The present invention has been made in view of these points, and in addition to the above-mentioned proposed configuration, it includes the use of a heat quantity change detection sensor such as a hot wire as the original mass flow sensor.
That is, by utilizing the fact that the amplitude value of the output of the heat quantity change detection sensor changes in magnitude depending on the density change of the circulating air, the generation frequency of the measured Karman vortex is corrected based on the change in the amplitude value. By doing so, it is an object of the present invention to enable the air flow rate in a predetermined air passage to be detected easily and accurately over a wide range.

In order to achieve this purpose, the present invention uses a Karman vortex generation column disposed in an air passage, and a heat amount that detects the Karman vortex generated by the Karman vortex generation column as a change in heat amount, as shown in FIG. a change detection sensor; a memory storing in advance an air density correction value set corresponding to the amplitude value of the output of the heat amount change detection sensor; It consists of a calculation circuit that calculates and outputs an air flow signal based on a correction value corresponding to the amplitude value of the output read from the memory, and calculates and outputs an air flow signal based on the Karman vortex generation frequency measured by the heat amount change detection sensor and the correction value of the heat amount change detection sensor. Based on the air density correction value read from the memory in accordance with the amplitude value of the output, an air flow rate signal corresponding to the air flow rate is output from the arithmetic circuit.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment in which the present invention is applied to the detection of air flow rate for controlling a fuel injection type fuel supply device of an engine, in which 1 is an engine, and 2 is slidably arranged in a cylinder 1a. installed piston,
3 is an intake passage communicating with the cylinder 1a via the intake port 4; 5 is an intake valve disposed in the intake port 4; and 6 is a throttle valve disposed in the intake passage 3 to control the air flow into the cylinder 1a. , 7 is a fuel injection valve disposed downstream of the throttle valve 6 in the intake passage 3, and 8 is an air cleaner.

Reference numeral 9 denotes a Karman vortex generating column disposed upstream of the throttle valve 6 in the intake passage 3, and as shown in FIG. Karman vortices 10, 10, . . . are generated in two regular rows at the upper and lower ends of the vortex generating column 9, alternating up and down. A cavity 13 is provided in the vortex generating column 9, and the cavity 11 communicates with the intake passage 3 through a communication passage 12 that communicates the upper and lower ends of the vortex generating column 9. Place 1
1 includes a heat amount change detection sensor 1 consisting of a thermistor that is constantly heated by a heating current of a predetermined current value.
3 are arranged. Therefore, when the Karman vortices 10, 10, etc. are generated alternately at the upper and lower ends of the vortex generating column 9, pressure fluctuations occur at the upper and lower ends of the vortex generating column 9, and this causes the circulating air in the intake passage 3 to flow through the communication path. 12 from the top to the bottom or from the bottom to the top, the heat quantity change detection sensor 13 is cooled and each Karman vortex 10, 10 is cooled.
... is detected as a change in heat quantity, and as a result, the terminal voltage (output voltage) of the detection sensor 13 is periodically changed at the generation frequency of the Karman vortices 10, 10, as shown by the solid line in FIG. ing. The heat amount change detection sensor 13 is connected to a fuel injection control circuit 14.

The fuel injection control circuit 14 includes a waveform shaping circuit 15 that shapes the output signal from the heat quantity change detection sensor 13 into a pulse wave, and a constant pulse width signal of the same number as the frequency of the pulse wave of the shaping circuit 15. Constant pulse width signal generation circuit 1 that generates pulses
6, an amplitude detection circuit 17 that generates a voltage signal having a magnitude corresponding to the amplitude value of the output signal of the heat quantity change detection sensor 13, and an amplitude detection circuit 17 that generates a voltage signal of a magnitude corresponding to the amplitude value of the output signal of the heat quantity change detection sensor 13; A memory 18 that stores in advance air density correction values (correction coefficients) as shown in FIG. 4, which are set corresponding to the values.
and the number of constant pulse width signals included in the control pulse of the constant pulse width signal generation circuit 16 is added to the memory 1 read out based on the voltage signal of the amplitude detection circuit 17.
an arithmetic circuit 19 that outputs a control pulse (air flow rate signal) consisting of the corrected number of constant pulse width signals by multiplying the correction value in 8; and an amplification circuit 20 that amplifies the air flow signal of the arithmetic circuit 19. By outputting the air flow signal amplified by the amplification circuit 20 to the fuel injection valve 7, fuel corresponding to the air flow signal value is injected from the fuel injection valve 7.

Next, to explain the operation of the above embodiment,
When a predetermined flow rate of air flows through the intake passage 3, Karman vortices 10, 10, . For this reason, pressure fluctuations occur at the upper and lower ends of the vortex generating column 9, and the circulating air in the intake passage 3 alternately moves from the top to the bottom or from the bottom to the top in the communication passage 12 of the vortex generation column 9. The flow and heat quantity change detection sensor 13 is periodically cooled by this circulating air, and its output signal changes periodically with the generation frequency of the Karman vortices 10, 10, as shown by the solid line in FIG. This output signal is waveform-shaped into a pulse wave of the same frequency by the waveform shaping circuit 15 of the fuel injection control circuit 14, and then controlled by the constant pulse width signal generation circuit 16 using constant pulse width signals of the same number as the frequency of the pulse wave. converted into pulses.

At the same time, the output signal of the heat quantity change detection sensor 13 is output to the amplitude detection circuit 17, where it is converted into a voltage signal of a magnitude corresponding to the amplitude value, and the air density is corrected according to this voltage signal. The value is read from memory 18 and output to arithmetic circuit 19 . Then, in the arithmetic circuit 19, the number of constant pulse width signals constituting the control pulse of the constant pulse width signal generation circuit 16 is multiplied by the air density correction value from the memory 18, and the air flow rate signal is is output. This air flow rate signal is amplified by the amplifier circuit 20 and then output to the fuel injection valve 7, and as a result, fuel corresponding to the intake flow rate of the intake passage 3 is injected from the fuel injection valve 7.

In this state, when the flow velocity of the circulating air in the intake passage 3 remains constant, for example, when the intake air temperature decreases and the air density increases, the cooling efficiency of the heat amount change detection sensor 13 increases accordingly, and the output signal is As shown by the broken line in Figure 6, the frequency does not change and only the amplitude value increases. As a result, the amplitude detection circuit 1
The voltage signal value of 7 increases, and the air density correction value read out from the memory 18 also increases accordingly. Based on this correction value, the arithmetic circuit 19 calculates the amount of air that has increased in accordance with the increase in air density. Outputs flow rate signal. As a result, an increased amount of fuel is injected from the fuel injection valve 7 in accordance with the increase in air density. Therefore, even if the flow velocity of the circulating air is constant, if the air flow rate changes due to a change in air density, an appropriate amount of fuel corresponding to this air flow rate can be injected from the fuel injection valve 7. Moreover, since the heat quantity change detection sensor 13 is disposed in the space 11 of the Karman vortex generation column 9 and communicates with the intake passage 3 via the communication passage 12, the communication passage 12
By appropriately selecting a small diameter, the mass flow rate can be detected by the heat quantity change detection sensor 13 as a mass flow rate sensor within a range of accuracy, and the air flow rate in the intake passage 3 can be corrected accurately. be able to.

Next, a concrete circuit of the amplitude detection circuit 17 is shown in FIG.

This circuit includes a buffer circuit 17a that receives and buffers the output signal of the heat quantity change detection sensor 13, a rectifier circuit 17b that double-wave rectifies the output of the buffer circuit 17a, and an integration circuit 17c that integrates the output of the rectifier circuit 17b. Therefore, a voltage signal having a magnitude corresponding to the amplitude value of the output of the heat quantity change detection sensor 13 is obtained.

In the above embodiment, the heat amount change detection sensor 13
is placed in the space 11 of the Karman vortex generating column 9 to measure the generation frequency of the Karman vortex. Of course, it is also possible to measure the frequency at which the vortices occur. However, the above embodiment is preferable in that the air flow rate can be corrected more accurately.

Further, in the above embodiment, a case has been described in which the present invention is applied to detecting the air flow rate for controlling a fuel injection type fuel supply device, but the present invention is not limited to this. Of course, the present invention can also be similarly applied to devices in which a predetermined operation is performed while detecting the flow rate. In this case, if the frequency of the output of the heat quantity change detection sensor 13 is once converted into an analog value, either the frequency of the output before conversion or the analog value after conversion is used as the correction value in the memory 18. It may be corrected by

As explained above, according to the air flow rate detection device of the present invention, the generation frequency of the Karman vortex generated by the Karman vortex generation column disposed in the intake passage is measured based on the output of the heat amount change detection sensor, and Since the air flow rate signal is output based on the generation frequency of the Karman vortex and the air density correction value corresponding to the amplitude value of the exit of the heat quantity change detection sensor, the air flow rate in a given air passage can be determined by the flow velocity and the air density correction value. It is possible to easily and accurately detect both the mass flow rate and the air flow rate in various devices, for example, to inject the appropriate amount of fuel according to the air flow rate in a fuel injection type fuel supply device. It is suitable for detection.

[Brief explanation of drawings]

Fig. 1 shows the configuration of the present invention, Figs. 2 to 6 show embodiments of the present invention, and Fig. 2 shows the case where the present invention is applied to detecting the air flow rate in a fuel injection type fuel supply device. 3 is a vertical cross-sectional view of the Karman vortex generation column, FIG. 4 is a diagram showing the contents of memory, FIG. 5 is an electric circuit diagram showing a specific circuit of the amplitude detection circuit, and FIG. The figure is an output waveform diagram of the heat amount change detection sensor. 3... Intake passage (air passage), 9... Karman vortex generation column, 13... Calorific value change detection sensor, 18...
...Memory, 19...Arithmetic circuit.

Claims (1)

[Claims] 1. A Karman vortex generation column disposed in the air passage, a heat quantity change detection sensor that detects the Karman vortex generated by the Karman vortex generation column as a heat quantity change, and a heat quantity change detection sensor that corresponds to the amplitude value of the output of the heat quantity change detection sensor. Based on a memory that stores in advance a correction value for the air density set by An air flow rate detection device comprising a calculation circuit that calculates and outputs an air flow rate signal.