JPH1123334A - Heating resistor type apparatus for measuring air flow rate and method and apparatus for correcting measurement error thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct measurement errors to a temperature change in a wide range by measuring a temperature of sucked air, and correcting a flow rate dependency of an output temperature characteristic with the use of a temperature signal to offset errors. SOLUTION: A suction air temperature Ta is measured by a suction air temperature sensor 157 set at an intake duct 158 and sent to an engine control unit(ECU) 100. A flow rate of the suction air flowing in an intake pipe is measured by a heat- generating resistance body 3. An output of the heat-generating resistance body is sent as a voltage V0 to the ECU 100 from a module 161. At this time, a V0D converted to a digital signal at an A/D converter 170 is converted to the air flow rate by a converter circuit 171 and integrated at an integrator 172. Then, a revolution number Ne of an engine is taken into the ECU 100 and an air flow rate Qa per one cylinder is calculated at an operator 173. A measurement error of an air flow rate-measuring apparatus due to a temperature change is corrected in a processing apparatus 174 with the use of the air flow rate Qa and suction air temperature Ta, whereby an injector jet signal tp is output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating resistor type air flow rate measuring device for measuring the flow rate of air taken into an internal combustion engine for an automobile, and a method and apparatus for correcting the measurement error.

[0002]

2. Description of the Related Art From the viewpoint of environmental protection and resource saving, a more precise combustion control is required for an automobile engine, and an air flow meter capable of detecting an intake air flow rate with high accuracy is desired. For this reason, control systems employing a heating resistor type air flow measuring device capable of directly measuring the mass flow rate of air have become mainstream. Japanese Patent Application Laid-Open No. 60-100218 discloses a heating resistor type air flow measuring device closest to the present invention. This prior art is an invention which describes correction of temperature characteristics of a heating resistor type air flow measuring device.

[0003]

In the above-mentioned prior art, the correction is performed only by changing a constant voltage corresponding to the intake air temperature to the flow rate signal regardless of the measured air flow rate. However, in practice, the output signal corresponding to the air flow rate changes depending on the temperature of the air flowing through the heating resistor. This is due to the following causes.

The heating resistor type air flow measuring device is constituted by a bridge circuit as shown in FIG. 6, and an output voltage Vout is expressed by the following equation (1).

Vout = √ (A + B√ (Q)) Equation 1 Here, the constants A and B are constant with respect to the flow rate Q but have temperature characteristics. This is mainly because the thermal conductivity of air has a temperature characteristic in A and B. This is because A and B include changes in physical properties of air, such as thermal conductivity or kinematic viscosity coefficient. Therefore, the differential coefficient dV / dT of the output of the bridge circuit with respect to the temperature T has a flow rate dependency. Further, the influence of heat conduction from the heating resistor to a member holding the heating resistor is one of the factors depending on the flow rate. For this reason, there is a problem that the above conventional technique cannot be corrected over a wide flow rate and a wide temperature range.

SUMMARY OF THE INVENTION An object of the present invention is to improve the temperature characteristics of a heating resistor type air flow measuring device under a wide flow rate range and a wide temperature range.

[0007]

In order to cope with the above problem, the temperature of the intake air in the intake pipe is measured, and the temperature signal is used to obtain the output temperature characteristic of the heating resistor type air flow measuring device by a microcomputer or the like. This is achieved by providing a correction to offset the error to the flow dependence.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the following drawings.

First, the operating principle of the heating resistor type air flow measuring device will be described. FIG. 5 is a schematic configuration circuit diagram of a heating resistor type air flow measuring device. The driving circuit 91 of the heating resistor type air flow measuring device is roughly composed of a bridge circuit and a feedback circuit. Heating resistor 3RH for measuring the intake air flow rate, temperature-sensitive resistor 4RC and R10, R for compensating the intake air temperature
A bridge circuit is formed at 11 and the heating resistor 3R is maintained so as to maintain a constant temperature difference between the heating resistor 3RH and the temperature-sensitive resistor 4RC while applying feedback using the operational amplifier OP1.
The heating signal Ih is passed through H and the output signal V corresponding to the air flow rate
2 is output. In other words, when the flow velocity is high, the heating resistor 3
Since a large amount of heat is taken from the RH, a large amount of the heating current Ih flows. On the other hand, when the flow velocity is low, the amount of heat taken away from the heating resistor Rh is small, so that the heating current is small.

FIG. 6 is a cross-sectional view showing an example of a heating resistance type air flow meter, and FIG. 7 is an external view seen from the upstream (left side).

The components of the heating resistor type air flow measuring device include a housing member 1 containing a circuit board 2 constituting a drive circuit, and a sub air passage component member 10 formed by a non-conductive member. A heat generating resistor 3 for detecting the air flow rate and a temperature sensitive resistor 4 for compensating for the intake air temperature are provided in the passage constituting member 10 with the circuit board 2 via a support 5 made of a conductive member. They are arranged so as to be electrically connected, and are configured as an integrated module of a heating resistor type air flow measuring device, such as a housing, a circuit board, a sub air passage, a heating resistor, and a temperature sensing resistor. A hole 25 is formed in the wall surface of the main air component member 20 that constitutes the intake pipe. The sub air passage portion of the heating resistor type air flow measuring device is inserted through the hole 25 from outside to form a sub air passage. The wall surface of the passage constituting member and the housing member 1 are fixed with screws 7 or the like so as to maintain mechanical strength. Here, the main air passage portion into which the sub air passage is inserted is substantially a cylindrical tube, and the effective sectional area of the main air passage through which the air flows is substantially the same at the location of the entrance and exit of the sub air passage.
In addition, a seal member 6 is attached between the sub air passage component 10 and the main air passage component to maintain airtightness.

Next, the specific contents of the present invention will be described.

FIG. 2 is a diagram showing components of an intake pipe in an internal combustion engine. Description will be made from the upstream side where air flows. An air cleaner is configured such that the air cleaner element 152 is sandwiched between the air cleaner dirty side case 150 and the air cleaner clean side case 151. On the downstream side of the air cleaner, a part of the main air passage is constituted by a body member 160 which is a constituent material of the heating resistor type air flow measuring device, and the intake manifold 15 is provided.
5 and body member 160 are connected by an intake duct 158 to form the entire intake pipe.

Signal processing and control from various sensors and the like in the internal combustion engine are performed by an engine control unit (hereinafter referred to as E).
CU) 100. Therefore, the temperature measurement error correction of the heating resistor type air flow measuring device according to the present invention is also performed inside the ECU 100.

In the ECU 100, an input circuit unit 101, an output circuit unit 102, and a central processing unit (hereinafter, CPU) are provided.
103 and a memory 104. The exchange of information between the components inside the ECU 100 is performed at portions indicated by arrows 105a and 105b.

The intake duct 158 has an intake air temperature sensor 15
7 is attached to measure the intake air temperature Ta, and the flow rate of the intake air flowing through the intake pipe is measured by the heating resistor 3, and each is sent to the ECU 100. At this time, the memory 104
The CPU 103 corrects the measurement error due to the temperature in accordance with the correction value stored therein, calculates the air flow rate signal, and sets the control signal for fuel injection to T based on the obtained result.
It is sent to the injector 154 as p. The calculation steps of the intake air flow rate taken into the internal combustion engine are schematically shown in FIG.

The flow rate of the intake air flowing through the intake pipe is measured by the heating resistor 3 and output from the drive circuit module 161 as an output voltage Vo. When this output voltage Vo is supplied to the ECU 100, it is converted into a digital signal by the analog / digital converter 170 and becomes VoD. Next, this VoD is converted into an air flow rate by the conversion circuit 171 and integrated by the integrator 172 for a time T. Next, the engine speed signal Ne is taken into the ECU 100, and the calculator 173 calculates the air flow rate Qa per cylinder. Using the air flow rate Qa and the intake air temperature signal Ta from the intake air temperature sensor, a correction process for a measurement error due to a temperature change of the heating resistor type air flow rate measurement device is performed in the processing device 174, and the injector 15
It is output as a four injection signal tp.

FIGS. 3 and 4 show the contents of the correction processing.
The correction processing shown in FIG. FIG. 3 is a graph of a measurement error when the temperature of the circuit module of the heating resistor type air flow measuring device is set to 20 ° C. and the intake air temperature is set to 80 ° C., based on the value when the intake air temperature is also set to 20 ° C. It is. The error is positive on the low flow rate and negative on the high flow rate. Therefore, the correction value is set to a minus value on the low flow rate side and a plus value on the high flow rate side so as to cancel the error. FIG. 4 also shows that only the intake air temperature is -30.degree. C. based on the output value of the heating resistor type air flow measuring device when the intake air temperature and the circuit module section are set at 20.degree.
This is a graph of the measurement error when “” is set. A low-flow rate error is on the negative side, and a high-flow rate is a positive error, but correction is made to cancel the error as in FIG.

As described above, since the measurement error of the heating resistor type air flow measuring device differs depending on the flow rate and the temperature, for example, the correction of the processing device 174 shown in FIG. 1 requires a map of the suction temperature and the air flow rate shown in FIG. The correction value is created and written in the map, and the air flow rate and the intake air temperature are read and corrected.

Although the above description has been made on the assumption that the correction is performed by the ECU, in recent years, a heating resistor type air flow rate measuring device having an expanded function by installing an intake air temperature sensor has been mass-produced. For example, the effect is also obtained by a structure in which a microcomputer is mounted inside the heating resistor type air flow rate measuring device, the intake air temperature and the air flow rate are measured, and the intake air flow rate signal and the intake temperature signal corrected for the measurement error due to the temperature are sent to the ECU. Is the same.

[0021]

According to the present invention, it is possible to provide a heating resistor type air flow measuring device capable of correcting a measurement error with respect to a suction temperature change over a wide flow range.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating temperature correction according to the present invention.

FIG. 2 is a schematic diagram of components of an internal combustion engine necessary for understanding the present invention.

FIG. 3 is a graph showing a measurement error of the heating resistor type air flow measuring device when the intake air temperature is high.

FIG. 4 is a graph showing a measurement error when the intake air temperature of the heating resistor type air flow measuring device is low.

FIG. 5 is a correction map including temperature and flow rate showing an example of correction according to the present invention.

FIG. 6 is a configuration circuit diagram of a heating resistor type air flow measuring device.

FIG. 7 is a sectional view of a heating resistor type air flow measuring device.

FIG. 8 is a view of FIG. 7 as viewed from the left side (upstream side).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Housing member, 2 ... Circuit board, 3 ... Heating resistor,
DESCRIPTION OF SYMBOLS 4 ... Temperature-sensitive resistor, 5 ... Support, 6 ... Sealing material, 10 ... Sub air passage component, 11 ... Sub air passage inlet, 12 ... Sub air passage outlet, 13 ... Vertical passage, 14 ... Horizontal passage, 20 .. Main air passage constituent member, 22 main air passage, 23 forward air flow, 25 hole, 100 engine control unit, 101 input circuit section, 102 output circuit section, 103
... Central processing unit, 104 ... Memory, 105 ... Information exchange unit, 150 ... Air cleaner dirty side case, 1
51: air cleaner clean side case, 152: air cleaner element, 153: throttle valve, 1
54 ... injector, 155 ... in manifold, 156 ... intake valve, 157 ... intake temperature sensor, 158 ... intake duct, 170 ... analog / digital converter, 171 ... air flow rate conversion circuit, 172 ... integrator, 173 ... calculator, 17
4. Correction processing device.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Takashi Kadohiro 2477 Takaba, Hitachinaka City, Ibaraki Prefecture Inside Hitachi Car Engineering Co., Ltd.

Claims (4)

[Claims] In a method for correcting a measurement error of a heating resistor type air flow rate measuring device for measuring an intake air flow rate based on heat generated by passing a heating current and radiating heat to the intake air, the intake air temperature is measured. And correcting the measurement error in accordance with the flow rate of the intake air and the intake air flow rate. 2. A method for compensating an output signal according to claim 1, wherein a map comprising an air flow rate from a heating resistor type air flow rate measuring device and an intake air temperature is created, and the correction value stored in the map is used to calculate the intake air temperature. A method for correcting a measurement error of a heating resistor type air flow measuring device, wherein a correction of an intake air flow signal is performed for the air flow. 3. A control device for an internal combustion engine provided with a measurement error correction device for performing the correction method according to claim 1 or a correction device therefor. 4. A heating resistor type air flow measuring device for use in an internal combustion engine, wherein the heating current flows to generate heat and measures the intake air flow based on heat radiation to the intake air. A heating resistor type air flow measuring device, comprising: means for measuring a temperature; and means for correcting an average air flow rate according to an intake air temperature.