JPH11351931A - Heating resistor type air flow air measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply an air flow rate measuring device that can be used easily by supplying a small air sub-path. SOLUTION: In an air sub-path 11, a temperature sensing resistor 8 is arranged at the upstream of the heating resistor and at a position being offset for the heating resistor in a direction that is vertical to the flow direction of a main air path, and the shape of the air sub-path 11 is in structure where the thermally sensitive resistor 8 from the downstream of the temperature sensing resistor 8 to the upstream of the heating resistor is contracted only on one side wall surface in a direction where the temperature sensing resistor 8 from the downstream of the temperature sensing resistor 8 to the upstream of the heating resistor is offset.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air flow measuring device for measuring an intake air flow of an internal combustion engine, and more particularly to a heating resistor type air flow measuring device for measuring an air flow taken into an automobile engine.

[0002]

2. Description of the Related Art As a prior art, there is an air flow measuring device in which a temperature-sensitive resistor provided in a sub-air passage is disposed upstream of a heating resistor as disclosed in Japanese Patent Application Laid-Open No. 8-304136.
As a sub air passage shape, a shape for reducing a measurement error mainly caused by intake pulsation by a curved sub air passage as disclosed in Japanese Patent Application Laid-Open No. 6-194199 is known as a known technique.

[0003]

In the auxiliary air passage structure as disclosed in Japanese Patent Application Laid-Open No. 6-194199, the heating resistor is disposed upstream of the temperature-sensitive resistor, so that the heat-generating resistor prevents air disturbance caused by the temperature-sensitive resistor. The structure was difficult to receive. Also, the positional relationship between the heating resistor and the temperature-sensitive resistor is such that the temperature-sensitive resistor is less susceptible to the influence of heat generated by the heating resistor. The sub-passage structure has a positional relationship such that there is no change in the thermal effect.

However, when the shape of the auxiliary passage is reduced, the structure of the auxiliary passage becomes difficult. Further, there is a sub air passage structure in which a temperature sensitive resistor is disposed upstream of a heating resistor as disclosed in Japanese Patent Application Laid-Open No. 8-304136. However, by reducing the shape of the sub air passage, the design margin of the sub air passage structure is reduced,
The turbulence of air generated by the temperature-sensitive resistor affects the heating resistor,
As a result, the output noise characteristics cannot be maintained sufficiently.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an air flow measuring device capable of sufficiently maintaining initial characteristics due to manufacturing variations and output noise characteristics even when the shape of the auxiliary passage is reduced.

[0006]

In order to solve the above-mentioned problems, in the auxiliary air passage, a temperature-sensitive resistor is provided upstream of the front thermal resistor and in a direction perpendicular to the flow direction of the main air passage. The resistor is arranged at a position offset from the heating resistor, and the shape of the sub air passage is such that only one side wall surface in the direction in which the temperature sensing resistor is offset from the downstream of the heating resistor to the upstream of the heating resistor is contracted. Structure.

Thus, even if the shape of the auxiliary air passage is reduced, only one wall surface on the side of the temperature-sensitive resistor is contracted, so that a sufficient offset distance between the temperature-sensitive resistor and the heating resistor can be secured. Further, it is possible to further reduce the output noise due to the influence of air turbulence on the heating resistor caused by the separation vortex generated behind the temperature sensing resistor. In addition, by making the contraction wall of the sub air passage have a smooth arc shape, for example, that does not disturb the air flow, the flow velocity distribution of the heat generating resistor can be made uniform.

[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. 4 is a schematic configuration circuit diagram of a heating resistor type air flow measuring device. The driving circuit 9 of the heating resistor type air flow measuring device is roughly composed of a bridge circuit and a feedback circuit. Heating resistor 4RH for measuring intake air flow rate, temperature sensitive resistor 5RC and R10, R1 for compensating intake air temperature
1 and a feedback circuit using an operational amplifier OP1 so as to maintain a constant temperature difference between the heating resistor 4RH and the temperature-sensitive resistor 5RC.
The heating current Ih flows through H, and an output signal V2 corresponding to the air flow rate is output.

That is, when the flow velocity is high, the heating resistor 4R
Since a large amount of heat is taken from H, a large amount of the heating current Ih flows. On the other hand, when the flow velocity is low, the heating resistor Rh
Since the amount of heat taken away from the heater is small, the heating current can be reduced. Heating resistor type air flow measuring devices are widely used as flow meters for internal combustion engines because they can directly measure the mass flow rate of air and respond quickly to the flow of air.

However, there is a disadvantage in responding at high speed. The reason is that the heating resistor, which is a sensor, is very small and detects point flow, so it reacts sensitively to turbulent air flow, and the output noise characteristics of the heating resistor type air flow measurement device deteriorates. Is to put it.

Next, an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing an example of a heating resistor type air flow measuring device, and FIG. 2 is an external view seen from the upstream (left side) thereof. As a component of the heating resistor type air flow measuring device, a circuit board 9 constituting a drive circuit is built in, and a housing member 12 having a sub air passage 2 integrated therewith and a cover member for preventing a part of the board installation portion and the sub air passage are provided. In the auxiliary air passage 2, a heating resistor 4 for detecting an air flow rate and a temperature-sensitive resistor 5 for compensating an intake air temperature are provided via a support 6 made of a conductive member. And a housing, a circuit board, an auxiliary air passage, a heating resistor, a temperature-sensitive resistor, etc., which are integrated into a module 7 of a heating resistor type air flow measuring device. Is configured as

Further, since the sub air passage having a substantially U-shaped cross section is formed by combining the housing member 12 and the cover member 10, the auxiliary air passage has a rectangular passage cross section, and the support member 6 is formed from one side thereof. It is a structure that is arranged. Further, the auxiliary air passage 2 has a substantially U-shaped passage structure in order to prevent a measurement error due to pulsation and to improve the mountability of the heating resistor type air flow measuring device and to make the whole module compact. An insertion hole 11 is formed in the wall surface 3 of the main air component constituting the main air passage 1, and the heating resistor type air flow measuring device is inserted from the outside through the hole 11 to form a main air passage configuration. The wall surface 3 of the member and the housing member 12 are fixed with screws 13 or the like so as to maintain mechanical strength.

FIG. 3 is a diagram showing a BB cross section of FIG.
The temperature-sensitive resistor 5 disposed in the sub air passage 2 is disposed upstream with respect to the installation position of the heating resistor 4 as shown in the drawing, and is perpendicular to the flow direction of the main air passage. The heating resistor 4 is arranged at a position offset from the heating resistor 4. As shown in the figure, the inner wall surface of the sub air passage 2 on the side where the temperature-sensitive resistor 5 is offset has a sectional area gradually reduced between the temperature-sensitive resistor 5 and the heating resistor 4. The inner wall surface formed of the cover member 10 on the opposite side has a substantially flat shape.

With the above structure, the temperature-sensitive resistor 5
Even when the heater is arranged upstream of the heating resistor 4, the flow near the heating resistor 4 can be rectified, so that the output noise characteristics and the deterioration of the initial characteristics due to variations between samples in manufacturing can be prevented. Becomes As a result, it is possible to provide a heating resistor type air flow device which is more compact than the conventional one and has excellent mountability.

[0016]

According to the present invention, it is possible to maintain the performance of the initial characteristics and the output noise characteristics due to manufacturing variations, which is a problem when making the shape of the auxiliary air passage small, and to supply a heating type air flow measuring device which is easy to use. it can.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an air flow measuring device according to an embodiment of the present invention.

FIG. 2 is a front view of the upstream appearance of an air flow measuring device according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a circuit diagram showing the operation principle of a heating resistor type air flow measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Main air passage, 2 ... Sub air passage, 3 ... Wall surface of main air passage constituent member, 4 ... Heating resistor, 5 ... Temperature sensitive resistor, 6 ... Supporting part, 7 ... Module, 8 ... Shrink wall, 9 ... Drive circuit, 1
0: cover, 11: insertion hole, 12: housing member, 1
3 ... screw, 14 ... main air flow direction.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinya Igarashi 2477 Takaba, Hitachinaka-shi, Ibaraki Prefecture Within Hitachi Car Engineering Co., Ltd.

Claims (1)

[Claims] At least one bent portion is disposed in a main air passage of an internal combustion engine for measuring an intake air flow rate, and a cross section perpendicular to a flow direction of the main air passage is formed in a square shape. In a heating resistor type air flow measuring device provided with a heating resistor for detecting the amount of air and a temperature sensing resistor for temperature compensation inside the sub air passage, the temperature sensing resistor is located upstream of the heating resistor. And, with respect to the flow direction of the main air passage, the temperature-sensitive resistor is disposed at a position offset with respect to the heating resistor in a direction perpendicular to the flow direction of the main air passage. A heating resistor type air flow measuring device characterized in that the temperature sensitive resistor is reduced in flow only on one side wall surface in the offset direction.