JPH05196485A - Air flow rate measuring device - Google Patents

Abstract

PURPOSE:To enhance the reliability of a heating resistor type air flow rate measuring device during mass production and to produce a product of high accuracy. CONSTITUTION:In a structure wherein an orifice part 7 arranged in a die cast body 1 by processing said body, a heating resistor 4 is arranged in the orifice part 7 and pressure sensors are further arranged on the upstream and downstream sides of an air passage. By this constitution, the self-diagnosis of the heating resistor 4 at the time of contamination or disconnection is made possible and, further, two-system measurement or allotment measurement at a low or high speed is made possible and, by the combination with the heating resistor, the reliability as an air flow rate measuring device is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving body such as an automobile, and more particularly to an air flow rate measuring device suitable for engine control, in which a heating resistor and a pressure sensor are hybridized. The present invention relates to such a configuration and its method.

[0002]

2. Description of the Related Art As a conventional technique, there is a heating resistance type air flow rate measuring device represented by JP-A-59-206714. This is a method in which an electric current is caused to flow through a heating resistor such as a winding or plate made of a material such as Pt in the air flow path, and the amount of heat removed from the heating resistor due to passage of air is converted and calculated as an air flow rate. Is.

On the other hand, there is a speed density type air flow rate measuring device using a pressure sensor disclosed in Japanese Patent Laid-Open No. 3-168349. This is to measure the air flow rate by utilizing the pressure difference in the flow path.

In addition to this, there is a Karman vortex system, etc., and each company currently adopts a system adapted to its own company.

As in the present invention, a system in which the heating resistor system is combined with another system has not been found so far.

[0006]

In the above-mentioned prior art, each of the systems has been put into practical use and the object has been achieved for the time being, but it is basically improved in order to achieve higher accuracy.

In the heating resistor system, the resistor is broken,
There was no method such as self-diagnosis when the performance deteriorates due to dirt or a method of correcting these.

Further, the low speed and high speed flow rates are covered by the same method over the entire area, and the reliability is determined by the selection of this system.

As in the present invention, this is made possible by disposing a pressure sensor in addition to the heating resistor. However, it has not been possible to combine different systems as described above, and it is possible to combine them with high accuracy. The flow rate can be detected.

[0010]

To achieve the above object, a system is possible by incorporating a semiconductor pressure sensor which is currently mass-produced.

By checking and correcting both flow rates, it is possible to combine two systems or self-diagnosis.

[0012]

The function of the air flow measuring device for engine control is to convert the current value, which changes depending on the amount of heat generated by the heat generating resistor into the air flow rate, by the flow velocity of the air flowing into the heat generating resistor incorporated in the die-cast body. By arranging a pressure sensor and combining the speed density method for taking out the differential pressure and converting it into an air flow rate, self-diagnosis and two-system control can be performed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

The body 1 is formed by processing die casting or plastic. A bypass 3 is provided in a part of the main path 2 therein, and the bypass 3 is a venturi-shaped orifice portion 7.

The heating resistor 4 is disposed in the orifice portion 7, and the temperature sensitive resistor 6 for detecting the air temperature is similarly disposed downstream thereof.

As described above, the heating resistor 4 detects the change in the air flow rate with high accuracy as the change in the heating current through the circuit module 5.

In addition to these, an upper pressure introducing portion 10 and a lower pressure introducing portion 11 are provided as air inlets in the upper and lower portions of the orifice portion 7, and an upper pressure sensor 8 and a lower pressure sensor 9 are provided in communication with them. To do. By making the system capable of calculating the differential pressure ΔP by this, the speed density method is established, and the measurement of two systems is possible. As a result, the system self-diagnosis can be performed by comparing and discriminating when the heating resistor 4 deteriorates in performance due to dirt or when measurement becomes unstable due to disconnection.

Further, these can also share the measurement, and most of them are measured by using the system using the heating resistor 4, and the flow rate on the low speed side including the idle is measured by the upper pressure sensor. 8 and the lower pressure sensor 9 can be used for measurement and control by a speed density method.

In addition, it can be said that both measuring systems are operated by two systems, one of them is constantly operated by a monitor system, and the system is switched in an emergency (measurement is impossible due to disconnection or the like).

In the bypass system shown in FIG. 1, the arrangement of the pressure sensor and the like is not clear, but FIG. 2 shows the plane (a) and cross section (b) of the circuit module 5 to show its position. As shown in FIG. 2 (a), the upper pressure sensor 8 and the lower pressure sensor 9 are arranged one above the other, through the circuit of the hybrid IC 12, and through the connector terminal 14, the connector section 13 is connected to an external circuit. ing. The cross section shown in FIG. 2B shows the relationship between the lower (upper) pressure sensor 9 and the lower pressure introducing portion 11, and this lower pressure introducing portion 11 is related to A of the body 1. At the same time, the arrangement positions of the heating resistor 4 and the temperature sensitive resistor 6 are also shown.

FIG. 3 shows the bypass method for both the heat generation resistance method and the speed density method in FIG. 1, but shows the speed density method arranged in the main path 2. The arrangement of the heating resistors 4 and the like arranged in the bypass 3 is the same as that in FIG. 1, and the pressure sensor is shown by the main path. The upper pressure sensor 8'is on the upper side of the body 1 and the lower pressure is on the lower side. The sensor 9'is provided, and the operation and the like are the same as those of the bypass system of FIG.

FIG. 4 shows the upper (lower) pressure introducing portion 10 (11).
The details of the inlet portion A are provided at the time of die-casting the body 1, and the pressure is surely introduced by protruding from the wall surface.

FIG. 5 shows a circuit of the air flow rate measuring device of the present invention. A normal heat generating resistor type drive circuit B and a differential pressure calculation circuit C for processing the differential pressure ΔP from the pressure sensor are provided in the CPU 26. It is configured to be determined by.

The differential pressure ΔP is not linearly related to the air flow rate. A signal from the pressure sensor is converted into a signal having a linear relationship to the air flow rate by the analog calculator 21 and then passed through the filter 22 and the A / D converter 23. The signal processing circuit 24 averages the pulsation, the comparison discrimination circuit 25 discriminates it, and the CPU 26 processes it. These are CPU
Needless to say, it is also possible to make the comparison judgment with the air flow drive circuit B by using an engine control circuit provided with a comparator circuit and an A / D converter.

FIG. 6 shows an example of a speed density system, in which the throttle valve 29 provided in the main path 2 of the body 1 is used as a signal of the throttle sensor 28 together with the signals of the pressure sensors 8 and 9 in the signal processing circuit 24. It is something to process. These inputs a temperature sensor 27 (or may be processed by using a changing value of the temperature sensitive resistor 6) to calculate the mass of air. It goes without saying that the lower pressure sensor may be used by connecting the connecting path S portion by using a differential pressure sensor.

FIG. 7 shows a conventional heating resistor type air flow rate measuring device. FIG. 7A shows a bypass system, in which the air from the flow path of the bypass 3 passes through the heating resistor 4 and the temperature sensitive resistor 6 and enters the engine from the downstream path 20. This is a configuration for detection by the module 5.
In the circuit (b) of FIG. 7, the signals of the heating resistor 4 and the temperature sensitive resistor 6 are supplied to the power transistor 15 and the Zener diode 1.
6, processed by the circuit of the operational amplifier 17, and connected to an external circuit through the analog output terminal 19 and the ground terminal 18.

As described above, by adding a pressure sensor (differential pressure sensor) to the conventional configuration shown in FIG. 7, self-diagnosis, two-system measurement, shared measurement, etc. can be performed.

[0028]

According to the present invention, it is possible to provide a heating resistance type air flow rate measuring apparatus as an air flow rate measuring apparatus for controlling an engine of an automobile or the like, thereby facilitating manufacturing and improving reliability. effective.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a plane and a cross section of a circuit module.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a view showing an enlargement of a pressure inlet portion.

FIG. 5 is a circuit diagram of the present invention.

FIG. 6 is a system diagram of the present invention.

FIG. 7 is a diagram showing a conventional structure and its circuit.

[Explanation of symbols]

1 ... Body, 2 ... Main path, 3 ... Bypass, 4 ... Heating resistor, 5 ... Circuit module, 6 ... Temperature sensitive resistor, 7 ... Orifice part, 8 (8 ') ... Upper pressure sensor, 9 (9') ) ... Lower pressure sensor (differential pressure sensor), 10 (10 ') ... Upper pressure introducing section, 11 (11') ... Lower pressure introducing section, 12 ... Hybrid IC, 13 ... Connector section, 14 ... Connector terminal,
15 ... Power transistor, 16 ... Zener diode, 17 ... Operation amplifier, 18 ... Ground terminal, 19 ... Analog output terminal, 20 ... Downstream path, A ... 10, 10 ', 1
1, 11 'inlet, B ... Air flow drive circuit, C ...
Differential pressure calculation circuit, 21 ... Analog calculation circuit, 22 ... Filter, 23 ... A / D conversion circuit, 24 ... Signal processing circuit, 2
5 ... Comparison discrimination circuit, 26 ... CPU, 27 ... Temperature sensor,
28 ... Throttle sensor, 29 ... Throttle valve, S
... Connection path for differential pressure sensor.

Claims (4)

[Claims] 1. An air flow measuring device using a heating resistor, wherein a pressure sensor is provided in addition to the placement of the heating resistor so that deterioration and disconnection due to dirt on the heating resistor can be self-diagnosed. A characteristic air flow measuring device. 2. The air flow rate measuring device according to claim 1, wherein a pressure sensor is provided side by side to measure an air flow rate of two systems with a heating resistor. 3. The air flow measuring device according to claim 1, wherein a pressure sensor is provided side by side so that one is divided into a low flow amount side and the other is divided into a high flow amount side. .. 4. The air flow rate measuring device according to claim 1, wherein when the heat flow resistance makes it impossible to measure the air flow rate, the air flow rate is measured by switching to a speed density method using a pressure sensor. Air flow measuring device.