JP2007327790A - Heat generation resistor type flow measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a flow measuring error generated in a heat generation resistor type flow measuring instrument by generation of a pulsation phenomenon in travel of a vehicle. <P>SOLUTION: This heat generation resistor type flow measuring instrument of the present invention having a sub-passage having at least one sub-passage bypass part in a midway with one part of a fluid flowing in a main passage, which flows in from a sub-passage inlet part and flowing out to a sub-passage outlet part, and a measuring element for measuring a suction flow rate arranged in the sub-passage, includes a through hole located between the sub-passage inlet part and the measuring element, provided on a wall face constituting the sub-passage, and penetrated through the sub-passage and the main passage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating resistor type flow rate measuring device for measuring a flow rate of air. In particular, the present invention relates to various sensors used for air-fuel ratio control of internal combustion engines and the like, as well as general fluid flow measurement sensors and control systems therefor.

  The heating resistor type flow measurement device utilizes the fact that the amount of heat taken away by the heating resistor has a relationship that increases monotonously with the inflow flow rate, and can directly measure the mass flow rate. It is widely used as a flow meter.

  A heating resistor type flow rate measuring device for an automobile is mounted on a part of an intake duct of a vehicle and has a role of measuring an intake air flow rate. In a gasoline engine, intake air normally flows in the intake duct in conjunction with the accelerator and is carried to the engine cylinder.

  At this time, when the inlet valve of the engine cylinder opens and closes, a large fluctuation or pulsation occurs in the flow, resulting in a measurement error in the heating resistor type flow rate measuring device. However, the measurement error reduction structure using the auxiliary passage is sufficient for practical use. Yes.

  However, it has the advantages of good fuel efficiency and low CO2 emissions, and the technology for injecting high-pressure fuel in the form of a mist and burning it efficiently (common rail) has improved exhaust gas purification and further improved fuel efficiency. For example, in a diesel engine that is increasing in use, there is a concern about the measurement error of the heating resistor type flow rate measuring device.

  This is because in a diesel engine, fuel is burned by utilizing spontaneous ignition, and therefore the pressure in the engine cylinder becomes high and is more susceptible to pulsation than a gasoline engine.

  As a structure for reducing an error due to pulsation of the heating resistor type flow rate measuring device, Patent Document 1 includes an inflow opening, an inflow path, and a sensor, an outflow path, and an outflow path opening in the inflow path. A structure having one or more openings provided in a turning passage between them is described.

Japanese translation of PCT publication No. 2003-502682

  The reason why a measurement error occurs in the heating resistor type flow measuring device when the pulsating flow is generated will be described.

  When a pulsating flow is generated, a positive error that counts backflow as forward flow occurs in a heating resistor type flow rate measuring device having a bypass path provided inside the body that is a part of the intake duct.

  In addition, a pressure fluctuation with a delay occurs in the sub-passage with respect to the pressure fluctuation at the sub-passage inlet and the sub-passage outlet, thereby increasing the average flow velocity and causing an error. These errors prevent accurate flow measurement and accurate fuel control.

  Therefore, it has been known that the pulsation effect can be reduced by providing drain holes and through holes in the sub-passage. However, if the flow rate (flow velocity) changes suddenly, depending on the position and size, air may flow from these holes. May flow out, the flow rate (flow velocity) flowing through the measuring element cannot be secured, and the output value of the heating resistor type flow rate measuring device may drop to the negative side, which may deteriorate the responsiveness.

  An object of the present invention is to reduce flow measurement errors during pulsation while ensuring this responsiveness.

  The present invention provides a sub-passage having at least one sub-passage detour part in the middle of a part of the fluid flowing in the main passage flowing in from the sub-passage inlet part and flowing to the sub-passage outlet part. In the heating resistor type flow measuring device having a measuring element for measuring the intake flow rate, the auxiliary passage and the main passage are provided between the auxiliary passage inlet and the measuring element, and are provided on a wall surface forming the auxiliary passage. A through-hole penetrating the passage is provided.

  According to the present invention, it is possible to reduce flow measurement errors during pulsation.

  In particular, by providing a through-hole in the portion where the flow velocity increases on the same surface as the sub-passage outlet between the sub-passage inlet and the measuring element, excessive air flow from the through-hole to the main passage is suppressed during response. On the other hand, at the time of pulsating forward flow, it has the effect of increasing the outflow of air from the through hole to the main passage. As a result, the flow velocity inside the sub passage is suppressed and the average flow velocity can be lowered, that is, responsiveness is ensured. However, the flow measurement error during pulsation can be reduced.

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

  1 and 2 show a first embodiment for carrying out the present invention.

  1 and 2, the flow rate measuring device is disposed in a main passage 1 of a body 2 that is a part of an intake duct through which air as a fluid flows.

  The flow rate measuring device includes a sub-passage 3 through which a part of the fluid flows, a sub-passage inlet part 10 through which a part of the fluid flows in, a sub-passage outlet part 4 through which the fluid flowing through the sub-passage 3 flows out, and a sub-passage inlet A sub-passage bypass unit 11 provided in the middle of the part 10 and the sub-passage exit unit 4, and a measuring element 5 disposed between the sub-passage bypass unit 11 and the sub-passage exit unit 4.

  The measuring element 5 disposed in the sub-passage 3 and the temperature sensitive resistor 6 for compensating the temperature of the intake air in the sub-passage 3 are electrically connected to an electronic circuit 7 for outputting a flow rate signal to the outside. Has been.

  The electronic circuit 7 is stored in a cover 8 and a housing 9. Further, a drain hole 12 for preventing a water pool in the sub-passage 3 is disposed between the sub-passage entrance 10 and the sub-passage bypass part 11.

  A through-hole 13 that penetrates the sub-passage 3 and the main passage 1 is provided between the sub-passage entrance 10 and the measuring element 5 in the wall surface that forms the sub-passage 3. The through hole 13 is provided so as to be located in the sub-passage detour part 11.

  The through hole 13 is provided in the vicinity including the center of the sub-passage bypass portion 11.

  The sub-passage bypass unit 11 is a passage narrowed so as to increase the fluid flow rate. The sub-passage bypassing part 11 is a part where the flow velocity of the fluid is fast.

  The auxiliary passage detour part 11 is curved so as to draw an arc. The fluid flowing through the sub-passage bypassing portion 11 has a high flow velocity and has a centrifugal action with a flow that draws an arc. Dust contained in the fluid receives centrifugal force and flows along the outer peripheral side wall surface of the sub-passage 3. For this reason, there is little dust adhering to the measurement element 5, and the detection of the measurement element 5 is performed accurately.

  The through hole 13 is formed so that the opening facing the main passage 1 is opened in the same direction as the sub passage outlet 4.

  The sub passage outlet 4 is formed so as to be divided into left and right as shown in FIG. The opening direction of the sub-passage outlet portion 4 and the opening direction of the sub-passage inlet portion 10 are arranged so as to intersect at a substantially right angle.

  Now, at the time of the pulsation described above, the flow of fluid between the sub-passage 3 and the main passage 1 is promoted by the through-hole 13 provided in the fast flow rate portion (the sub-passage bypassing portion 11), whereby the measuring element The increase in the flow velocity in the vicinity of 5 is suppressed, and the measurement error of the flow rate measuring device can be reduced.

  Since the increase in the flow velocity is suppressed on the upstream side of the measurement element 5, the measurement error of the flow rate measuring device can be reduced. Even if the increase in the flow velocity is suppressed on the downstream side of the measuring element 5, it does not contribute to the reduction of the measurement error.

  Moreover, by providing the through-hole 13 in the portion where the flow velocity is fast (the sub-passage bypassing portion 11), the increase in the flow velocity is effectively suppressed and the measurement error is reduced.

  In order to confirm the effect of the first example, CAE analysis was performed for each of the presence and absence of the through hole 13. FIG. 3 is a cross-sectional view taken along the line AA in which the vicinity of the center of the measuring element 5 in FIG. 2 is cut. FIG. 4 shows the CAE analysis results.

  The horizontal axis of the graph shown in FIG. 4 shows the diameter of the through-hole 13 shown in FIG. 3, and the vertical axis shows the flow velocity A during the steady flow analysis at the point P shown in FIG. The average flow velocity B at the time is calculated, and the pulsation error calculated by Equation 1 is shown.

  From the graph shown in FIG. 4, it can be confirmed that the provision of the through-hole 13 has the effect of greatly reducing the pulsation error.

  Moreover, it has been confirmed by experiments that the size of the through-hole 13 is required to be 1.5 mm or more in consideration of drainage and prevention of dust clogging, and the minimum diameter is desirably 1.5 mm or more.

  The maximum diameter is desirably 4.5 mm or less because the pulsation error increases rapidly when the diameter exceeds 4.5 mm from the graph shown in FIG.

  That is, it can be confirmed that the size of the through hole 13 has an effect of reducing the pulsation error in the range of 1.5 to 4.5 mm in diameter.

  Furthermore, CAE analysis is also conducted for responsiveness, and it is confirmed that there is no problem.

  Next, a second embodiment will be described with reference to FIG.

  Similar to the first embodiment, the sub-passage 3 and the main passage 1 pass through between the sub-passage inlet 10 and the measuring element 5, and the portion of the wall where the sub-passage 3 has a high fluid flow velocity ( A through hole 13 that opens in the same direction as the outlet part 4 of the sub-passage 3 is arranged in the passage detour part 11), and further, the outlet part 4 of the sub-passage 3 and In this structure, a through hole 13A that opens in the same direction is arranged.

  In order to confirm the effect of this example as well, the same CAE analysis as in the first example was performed. FIG. 6 shows the CAE analysis results.

  From the graph shown in FIG. 6, it can be confirmed that even if a plurality of through holes 13 are provided, the same effect as in the first embodiment is obtained.

  Further, for example, even if any of the through holes 13 is blocked by water droplet adhesion, freezing, oil, dust, or the like, the measurement error of the flow rate measuring device is not greatly deteriorated, and the highly reliable heating resistance A body flow measuring device can be realized.

  Next, a third embodiment will be described with reference to FIG.

  As in the first embodiment, the sub-passage 3 and the main passage 1 are passed between the sub-passage inlet 10 and the measuring element 5, and the portion of the wall surface constituting the sub-passage 3 has a high fluid flow velocity. The through-hole 13 extended along the stream line of the air opened in the same direction as the sub-passage outlet part 4 of the sub-passage 3 is arranged, and the length is 1.5 to 4.5 mm. If it is within the range, the same effect as the first embodiment is obtained.

  Furthermore, since the through-hole 13 has a shape extending along the air flow line, dust and water droplets mixed in the sub-passage 3 are easily discharged from the through-hole 13 to the main passage 1 and become clogged with dust. There is also an effect of reducing deterioration of water drainage due to water droplet adhesion.

  FIG. 8 is a diagram showing an embodiment of a control system for an internal combustion engine using the heating resistor type flow rate measuring device described above.

  In FIG. 8, an air cleaner 100, a body 2, an intake duct 103, a throttle angle sensor 111, an idle air control valve 102, and a throttle body 104 are integrated with an intake manifold 106 to form an intake passage.

  The intake air 101 to the engine is a passage or sub-passage 3 in the middle of flowing through the intake passage, and the flow rate is detected by the module 110 of the heating resistor type flow measuring device according to the present embodiment.

  Then, the detected flow rate signal is taken into the control unit 114 in the form of a signal such as voltage and frequency, and the injector 105, the engine rotation speed meter 113, the engine cylinder 107, the exhaust manifold 109, the exhaust gas 108, and the oxygen concentration meter. 112 is used to control the fuel unit structure and the subsystem composed of 112.

  By applying the heating resistor type flow rate measuring device according to the present invention to the control of the fuel part structure and the subsystem, an accurate air flow rate can be measured by reducing the influence of pulsation, and the engine control accuracy is improved.

  The present invention relates to a flow meter having a sub passage, and is particularly suitable for a heating resistor type flow rate measuring device used in an internal combustion engine.

The longitudinal cross-sectional view with respect to the flow direction of the heating resistor type | formula flow measuring device which is the 1st Embodiment of this invention. The longitudinal cross-sectional view with respect to the flow direction of the heating resistor type | formula flow measuring device which is the 1st Embodiment of this invention. 1 is a cross-sectional view taken along line AA of a heating resistor type flow rate measuring apparatus according to a first embodiment of the present invention. FIG. The CAE analysis result of the heating resistor type flow measuring device which is the 1st embodiment of the present invention. The longitudinal cross-sectional view with respect to the flow direction of the heating resistor type | formula flow measuring device which is the 2nd Embodiment of this invention. The CAE analysis result of the heating resistor type flow measuring device which is the 2nd embodiment of the present invention. The longitudinal cross-sectional view with respect to the flow direction of the heating resistor type flow measuring device which is the 3rd Embodiment of this invention. The control system figure of the internal combustion engine which performs fuel control using the heating resistor type flow measuring device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Main passage, 2 ... Body, 3 ... Sub passage, 4 ... Sub passage exit part, 5 ... Measuring element, 6 ... Temperature sensitive resistor, 7 ... Electronic circuit, 8 ... Cover, 9 ... Housing, 10 ... Sub passage Inlet portion, 11 ... bypass passage portion, 12 ... drain hole, 13, 13A ... through hole, 14 ... terminal, P ... fluid velocity measurement point during analysis, 100 ... air cleaner, 101 ... intake air, 102 ... idle air Control valve 103 ... Intake duct 104 ... Throttle body 105 ... Injector 106 ... Intake manifold 107 ... Engine cylinder 108 ... Exhaust gas 109 ... Exhaust manifold 110 ... Module 111 ... Throttle angle sensor 112 ... Oxygen Densitometer, 113 ... engine speed meter, 114 ... control unit.

Claims (9)

A part of the fluid flowing in the main passage flows from the inlet portion of the auxiliary passage and flows to the outlet portion of the auxiliary passage, and the intake passage disposed in the auxiliary passage having at least one auxiliary passage detour portion. In a heating resistor type flow measuring device having a measuring element for measuring
A heating resistor type flow rate measurement comprising a through hole between the sub passage entrance and the measuring element and provided in a wall surface constituting the sub passage and penetrating the sub passage and the main passage. apparatus. A sub-passage in which a part of the fluid flowing through the main passage circulates, a sub-passage inlet portion into which the part of the fluid flows, provided in the sub-passage, and the sub-passage provided in the sub-passage. A sub-passage outlet portion through which fluid flows, a sub-passage bypass portion provided in the sub-passage and in the middle of the sub-passage inlet portion and the sub-passage outlet portion, and the sub-passage provided in the sub-passage In the heating resistor type flow rate measuring device having a measuring element for measuring the intake flow rate disposed between the passage detour portion and the sub passage outlet portion,
A heating resistor type flow rate measuring device comprising a through hole penetrating the sub passage and the main passage on the upstream side of the measuring element. In the heating resistor type flow measuring device according to claim 1 or 2,
The heating resistor type flow rate measuring device, wherein the bypass passage detour portion is a flow path that narrows so that the fluid flowing in the bypass passage becomes faster. In the heating resistor type flow measuring device according to any one of claims 1 to 3,
The sub-passage bypassing part is curved so as to draw an arc. In the heating resistor type flow measuring device according to any one of claims 1 to 4,
The heating resistor type flow rate measuring device, wherein the through hole is provided in the vicinity including the center of the bypass passage bypassing portion. In the heating resistor type flow measuring device according to any one of claims 1 to 5,
The heating resistor type flow rate measuring device, wherein the through-hole has an opening facing the main passage in the same direction as the sub-passage outlet. In the heating resistor type flow measuring device according to any one of claims 1 to 6,
The heating resistor type flow rate measuring device, wherein the through hole has a diameter of about 1.5 to 4.5 mm. In the heating resistor type flow measuring device according to any one of claims 1 to 7,
A heating resistor type flow rate measuring apparatus comprising a plurality of the through holes.   8. A control system for an internal combustion engine, wherein fuel control is performed using the heating resistor type flow rate measuring device according to any one of claims 1 to 7.

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