JP2000314646A - Heating resistance type flow measurement device - Google Patents

Abstract

(57) [Summary] [Problem] To improve the accuracy of air temperature measurement by a temperature-sensitive resistor and to achieve high-precision measurement of fluid flow rate even in a sub-passage where the flow path configuration is complicated for the purpose of improving performance such as intake pulsation countermeasures To obtain an exothermic resistance type flow measurement device that can perform the measurement. A wall surface in the direction of the tip of a terminal member that supports a heating resistor is inclined to a position where the temperature-sensitive resistor becomes a shadow of the wall surface, and the wall surface in the direction of the tip of the terminal member that supports the heating resistor is substantially inclined. A Y-shaped ventilation groove is provided. Further, a ventilation hole for guiding an air flow is provided upstream of the temperature-sensitive resistor. The improvement of the air flow velocity flowing through the sub passage and the cooling of the temperature sensitive resistor can be compatible,
It is possible to accurately measure the intake air flow rate even in a high temperature environment inside the engine room. It is also effective in reducing output noise and expanding the measurement flow rate range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring a flow rate of a fluid, and more particularly to an air flow rate measuring device for measuring an air flow rate flowing through an intake air passage of an internal combustion engine and a control system therefor.

[0002]

2. Description of the Related Art A structure in which a sub-passage is integrated with a part of a circuit module and all functions necessary for a heating resistance type air flow measuring device are provided in a single module is known from Japanese Patent Application Laid-Open No. Hei 8-5427. However, a method and structure for promoting the cooling of the temperature-sensitive resistor and improving the temperature measurement accuracy for the purpose of improving the measurement accuracy of the air flow rate are not sufficiently considered.

[0003]

SUMMARY OF THE INVENTION The present invention can be applied to a sub-passage having a complicated passage structure for improving various performances, such as countermeasures against pulsation from the engine and reduction of output noise caused by turbulence in the air flow. Another object of the present invention is to provide a heating resistance type flow rate measuring device capable of measuring the air flow rate with high accuracy while achieving both the improvement of the air flow velocity flowing inside the sub passage and the improvement of the measurement accuracy of the air temperature by the temperature sensitive resistor.

[0004]

Means for Solving the Problems To solve the above problems, the following measures have been taken.

[0005] (1) The wall surface in the direction of the tip of the terminal member supporting the heating resistor is inclined to a position where the temperature-sensitive resistor becomes a shadow of the wall when viewed from the upstream direction. A ventilation groove is provided near the corner of the road and immediately before the temperature-sensitive resistor, near the center of the wall surface, that is, in a substantially Y-shape.

(2) A ventilation hole for guiding an air flow is provided on the inclined surface upstream of the temperature-sensitive resistor.

[0007]

FIG. 1A is a front view showing an embodiment of the present invention, FIG. 1B is a side sectional view taken along the line AA of FIG.
FIG. 3 is a horizontal cross-sectional view taken along line BB of the sub passage portion indicated by reference numeral 5 in FIG.

A heating resistor 1 for detecting the flow rate of the fluid and a temperature-sensitive resistor 2 for detecting the temperature of the intake air and performing temperature compensation are fixed to a terminal member 3 and electrically connected to an electronic circuit 4. I have. The sub-passage 5 having a passage configuration for bypassing the flow of air is used by being fixed to the case member 6 which also holds the terminal member 3 and protects the electronic circuit 4.

Here, the positional relationship between the heating resistor 1 and the temperature-sensitive resistor 2 will be described.

The temperature-sensitive resistor 2 is used at a temperature substantially equal to the air temperature, while the heat-generating resistor 1 is used in a state where the temperature of the temperature-sensitive resistor 2 is increased by several hundred degrees. Therefore, in order to avoid the influence of heat flow from the heat generating resistor 1 arranged on the upstream side, the temperature sensitive resistor 2 is arranged to be offset. Further, in order to accurately measure the intake air temperature in the temperature-sensitive resistor 2, the installation position of the temperature-sensitive resistor 2 is set as far as possible from the case member 6.
This is because the case member 6 and its protective cover 7 are exposed to a high-temperature environment outside the intake duct, that is, directly in the engine room, when the air flow measuring device is incorporated into the vehicle, and the heat is transmitted to the terminal member 3. This is because the heat is transmitted to the temperature-sensitive resistor 2 through the resistor. Therefore, the temperature sensitive resistor 2 is disposed at the tip of the terminal member 3 as much as possible, and is insulated by separating from the heated case member 6 and the like, so as to reduce a temperature measurement error due to heat conduction. For the above reasons, the temperature-sensitive resistor 2 is placed at the tip of the terminal member 3, and the heat-generating resistor 1 and the temperature-sensitive resistor 2 are arranged offset.

The sub passage 5 is in the main flow direction 8 (the air flow direction).
The total length of the air passage forming the sub-passage 5 is longer than the distance between the inlet opening 9 and the outlet opening 10 of the sub-passage 5 as seen in FIG. The effect of pulsating flow from the engine has been minimized by increasing the inertia. If the flow path structure of the sub-passage 5 is complicated in this way, the flow velocity inside the sub-passage 5 will be reduced. In particular, a heating resistor 1 for detecting a flow rate of a fluid
The reduced flow velocity of the section makes it impossible to obtain important performance as an air flow measuring device. Therefore, the heating resistor 1 is inclined using the constituent members of the sub-passage 5 so as to be the narrowest portion of the flow path. As a result, the same effect as narrowing the flow path can be obtained, and the flow velocity in one portion of the heating resistor can be improved. However, as described above, the temperature-sensitive resistor 2 disposed downstream of the heating resistor 1 is at the tip of the terminal member 3, and
The layout will be hidden by the structure of the aperture section.

Therefore, a ventilation groove 11 is provided in the corner of the flow path near the heating resistor 1 and near the center immediately before the temperature sensing resistor 2, that is, in a substantially Y-shape. By providing the ventilation groove 11, the air flow can be directly guided toward the temperature-sensitive resistor 2, and the cooling effect can reduce the influence of the heat conduction described above.

By providing such a ventilation groove 11, there is a fear that the flow velocity of the heating resistor 1 part may be greatly reduced.
Since the flow path having no circular cross section has a flow velocity component of the secondary flow, the flow velocity is low in a portion corresponding to a corner (corner) viewed in the cross section of the flow path, and the ventilation groove 11 is provided in that portion. In addition, a decrease in flow velocity can be minimized.

If a step is formed immediately downstream of the heating resistor 1 to guide the airflow to the temperature-sensitive resistor 2, an unstable flow is caused by the influence of the separation flow, which causes output noise. However, since there is air flowing through the ventilation groove 11 in the separation region that should occur at the downstream of the step portion, no separation flow is generated, and separation can be delayed to the downstream of the bypass portion. Therefore, rectification around the heating resistor 1 is also effective, and both cooling of the temperature-sensitive resistor 2 and reduction of output noise can be achieved.

Furthermore, by narrowing the flow passage, the flow passage internal pressure increases near the heating resistor 1 in a high flow rate region, and the ventilation groove 11
The proportion of air flowing into the tank increases. For this reason, the flow velocity seen in the entire sub-passage 5 decreases, and conversely, in the low flow rate range, the flow path internal pressure does not change so much, so that little air flows into the ventilation groove 11 due to the flow velocity component of the secondary flow. No noticeable drop in flow velocity occurs. That is, the installation of the ventilation groove 11 can maintain a relatively high flow rate in a low flow rate area and can reduce the flow rate in a high flow rate area, so that the measurement flow rate range can be expanded.

FIG. 3A is a front view showing another embodiment of the present invention, and FIG. 3B is a cross-sectional side view taken along the line CC of FIG.

As described above, if the heating resistor 1 is inclined by using the constituent members of the sub-passage 5 so that the portion of the heating resistor becomes the narrowest portion of the flow path, the flow velocity can be improved, while the temperature-sensitive resistor 2 can be improved. Are hidden in this structure.

Therefore, a ventilation hole 12 communicating from the inclined surface near the entrance opening 9 of the sub passage 5 toward the temperature sensitive resistor 2 is provided. With this configuration, the air flowing through the ventilation holes 12 directly cools the temperature-sensitive resistor 2 while minimizing a decrease in the flow velocity in the sub-passage 5, so that the air flow rate can be accurately detected.

Finally, FIG. 4 shows an embodiment in which the product of the present invention is applied to an electronic fuel injection type internal combustion engine.

The intake air 52 sucked from the air cleaner 51 passes through an intake duct 53, a throttle body 54, and an intake manifold 56 having an injector 55 to which fuel is supplied, and is sucked into an engine cylinder 57. On the other hand, gas 58 generated in the engine cylinder is discharged through an exhaust manifold 59.

The air flow signal and pressure signal output from the drive circuit module 60 of the heating resistance type air flow measuring device, the intake air temperature signal from the intake temperature sensor 61, the throttle valve angle signal output from the throttle angle sensor 62, The control unit 65 that inputs these, such as the oxygen concentration signal output from the oxygen concentration meter 63 provided in the exhaust manifold 59 and the engine rotation speed signal output from the engine rotation speed meter 64, sequentially calculates these signals. The optimum fuel injection amount and the opening degree of the idle air control valve are obtained, and the injector 55 and the idle control valve 66 are controlled using the values.

[0022]

[Effects of the Invention] Even if the flow path configuration of the sub-passage used in the heating resistance type flow rate measuring device is complicated for the purpose of high performance such as countermeasures against pulsation from the engine, the improvement of the flow velocity and the cooling of the temperature-sensitive resistor can be achieved. Both are compatible, and the intake air flow rate can be measured accurately even in a high temperature environment inside the engine room.

In addition, the air flows into the separation region which should occur at the step due to the effect of the ventilation groove, and the separation can be delayed to the downstream of the bypass portion. For this reason, it is effective for rectification around the heating resistor, and is highly effective for reducing output noise. Furthermore, by narrowing the flow path, near the heating resistor, the internal pressure of the flow path increases in a high flow rate region, and the proportion of air flowing into the ventilation groove increases. For this reason, the flow velocity observed in the entire sub-passage decreases, and conversely, in the low flow rate region, the flow passage internal pressure does not change so much. No decrease in flow velocity occurs. In other words, the installation of the ventilation groove can maintain a relatively high flow velocity in a low flow rate area and can reduce the flow velocity in a high flow rate area.

[Brief description of the drawings]

FIG. 1A is a front view showing one embodiment of the present invention,
(B) is AA side sectional drawing of (a).

FIG. 2 is a BB horizontal sectional view of a sub-passage portion indicated by reference numeral 5 in FIG.

FIG. 3 (a) is a front view showing another embodiment of the present invention,
(B) is CC side sectional drawing of (a).

FIG. 4 is a front view showing an embodiment in which the product of the present invention is applied to an internal combustion engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating resistor, 2 ... Temperature sensitive resistor, 3 ... Terminal member, 4 ... Electronic circuit, 5 ... Sub passage, 6 ... Case member, 7 ...
Protective cover, 8: main flow direction, 9: inlet opening, 10: outlet opening, 11: ventilation groove, 12: ventilation hole, 51: air cleaner, 52: intake air, 53: intake duct, 54: throttle body, 55 ... Injector, 56 ... Intake manifold, 57 ... Engine cylinder, 58 ... Gas, 59
... exhaust manifold, 60 ... drive circuit module, 61
... intake air temperature sensor, 62 ... throttle angle sensor, 63 ...
Oxygen concentration meter, 64: tachometer, 65: control unit, 66: idle air control valve.

Claims (2)

[Claims] 1. A heating resistor for detecting a flow rate of a fluid, a temperature sensing resistor for temperature compensation thereof, an electronic circuit for outputting a signal corresponding to the flow rate of the fluid, the heating resistor and a temperature sensing element. A terminal member for supporting a resistor and electrically connecting to the electronic circuit, and a circuit module integrating a case member for protecting the electronic circuit inside, a sub-passage having at least one bent portion, A heating resistor type in which the heating resistor and the temperature-sensitive resistor are fixed so as to be located inside thereof, and the temperature-sensitive resistor is attached to the heating resistor at a position further away from the circuit module. In the flow rate measuring device, the flow path forming the sub-passage at the installation position of the heating resistor is the narrowest portion, so that the wall surface in the distal direction of the terminal member that supports the heating resistor is located upstream. Seen from the direction The temperature-sensitive resistor is tilted to a position where it becomes a shadow of the wall surface, and near the heating resistor on the wall surface, near the corner of the flow path, and immediately before the temperature-sensitive resistor, near the center of the wall surface, that is, a substantially Y-shaped ventilation groove. A heating resistance type flow rate measuring device characterized by comprising: 2. A heating resistor for detecting a flow rate of a fluid, a temperature sensing resistor for temperature compensation thereof, an electronic circuit for outputting a signal corresponding to the flow rate of the fluid, the heating resistor and a temperature sensing element. A terminal member for supporting a resistor and electrically connecting to the electronic circuit, and a circuit module integrating a case member for protecting the electronic circuit inside, a sub-passage having at least one bent portion, A heating resistor type in which the heating resistor and the temperature-sensitive resistor are fixed so as to be located inside thereof, and the temperature-sensitive resistor is attached to the heating resistor at a position further away from the circuit module. In the flow rate measuring device, the flow path forming the sub-passage at the installation position of the heating resistor is the narrowest portion, so that the wall surface in the distal direction of the terminal member that supports the heating resistor is located upstream. Seen from the direction Is inclined to a position where the temperature sensitive resistor is in the shadow of the wall, the heat generating resistance flow rate measuring apparatus characterized in that a ventilating hole for guiding the air flow upstream of the temperature sensitive resistor on the inclined surface.