JP5183402B2 - Heating resistor type air flow measuring device - Google Patents

Description

  The present invention relates to a heating resistor type air flow rate measuring device suitable for intake air flow rate measurement of an internal combustion engine.

  A heating resistor type air flow rate measuring device is known as a flow rate measuring technique for an internal combustion engine. This utilizes the fact that the amount of heat taken away by the heating resistor has a correlation with the inflow flow rate, and can directly measure the mass flow rate required for engine combustion control. It is widely used as a total (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-14423

  The heating resistor type air flow measuring device is small and excellent in responsiveness, and has the advantage of being able to measure mass air flow, and is widely used as an air flow meter for internal combustion engines for automobiles and the like. When used in an internal combustion engine, the intake air becomes a pulsating flow with the opening and closing of the intake valve, and sometimes a pulsating flow with backflow. For this reason, it is necessary to reduce the influence of the pulsating flow by installing a heating resistor, which is a flow rate detecting element, in the auxiliary air passage.

  When the heating resistor is installed in the sub air passage, a heating resistor support member made of metal for electrically connecting the driving circuit of the heating resistor type air flow measuring device and the heating resistor is required. This heating resistor support member is generally integrally formed with a resin member that constitutes a part of the sub air passage.

  When a metal heating resistor support member is integrally molded, it is common to divide it with a mold and mold it. This mold division part can be molded without any problems at the beginning, but when it is used for a long period of time, the mold division is not successful and a thin burr may occur. When this burr occurs, the air flow near the heating resistor is disturbed. That is, the measurement value of the heating resistor varies depending on the presence or absence of burrs and the size of burrs. This variation directly affects the measurement variation of the air flow rate, and thus adversely affects highly accurate fuel injection control in the vehicle.

  An object of the present invention is to provide a heating resistor type air flow rate measuring device capable of highly accurate flow rate measurement.

  In general, it is necessary to flatten the parting line in order to suppress the above-mentioned variation, and to frequently perform maintenance of the mold so as not to generate burrs. On the other hand, in the present invention, on the contrary, by using this parting, a step is intentionally created and the air is disturbed initially, so that even if burrs occur, the effect is reduced. Invented to do. According to the results of the study by the authors, by providing an initial step of about 0.3 mm in the parting line part, there is no significant difference in the measured value of the air flow measured by the heating resistor with or without burr. It was confirmed.

  At present, attention is focused on the global environment such as global warming. For this reason, a low fuel consumption vehicle is desired. On the other hand, car users need not only the means of carrying cars and people but also the power of the engine to enjoy driving the car itself. In order to achieve both, high-precision fuel control of the engine is indispensable, and the present invention enables high-precision air flow measurement for this high-precision fuel control.

  Embodiments of the present invention will be described in detail with reference to the following drawings.

  First, the principle of operation of a heating resistor type air flow measuring device using a heating resistor will be described as an example of an intake air measuring device.

  FIG. 10 is a schematic circuit diagram of the heating resistor type air flow measuring device. The drive circuit 1 of the heating resistor type air flow measuring device is roughly divided into a bridge circuit and a feedback circuit. The heating resistor RH for measuring the intake air flow rate and the temperature sensitive resistors RC and R10, R11 for compensating the intake air temperature are combined to form a bridge circuit, and the feedback is made using the operational amplifier OP1 to sense the heating resistor RH. A heating current Ih is supplied to the heating resistor RH so as to maintain a constant temperature difference between the temperature resistors RC, and an output signal V2 corresponding to the air flow rate is output. That is, when the flow rate is high, a large amount of heat is taken from the heating resistor RH, so that a large amount of heating current Ih is passed. On the other hand, when the flow rate is low, the amount of heat taken away from the heating resistor Rh is small, so that the heating current can be reduced.

  FIG. 8 is a cross-sectional view showing an example of a heating resistance type air flow meter, and FIG. 9 is an external view as viewed from the upstream side (left side).

  Components of the heating resistor type air flow rate measuring device include a housing member 1 containing a circuit board 2 constituting a driving circuit, a sub air passage constituent member 10 formed by a non-conductive member, and the like. 10, a heating resistor 3 for detecting the air flow rate 3 and a temperature sensitive resistor 4 for compensating the intake air temperature are electrically connected to the circuit board 2 via a support 5 made of a conductive member. The housing, the circuit board, the auxiliary air passage, the heating resistor, the temperature sensing resistor, and the like are arranged as an integrated module of the heating resistor type air flow measuring device. Further, a sub air passage insertion hole 25 is formed in the wall surface of the main air passage constituting member 20 constituting the intake pipe serving as the main air passage 22, and a heating resistor type air flow measuring device is formed from the sub air passage insertion hole 25. The auxiliary air passage 14 is inserted from the outside, and the wall surface of the auxiliary air passage constituting member and the housing member 1 are fixed with screws 7 or the like so as to maintain the mechanical strength. Moreover, the sealing material 6 is attached between the sub air passage constituting member 10 and the main air passage constituting member 20 to maintain the airtightness between the inside and outside of the intake pipe.

  FIG. 1 is a cross-sectional view of a heating resistor type air flow measuring device showing an embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view when FIG. 1 is viewed from the upstream side. The intake pipe constituting member 105 constituting a part of the intake air passage 103 that is the main air passage has a hole (insertion hole) into which the heating resistor type air flow measuring device 200 is assembled, and the housing member 212 is a screw 211 or the like. Is fixed to the intake pipe constituting member 105. The housing member 212 of the heating resistor type air flow measuring device 200 has a connector terminal 201 for interfacing with an external electric signal, a heating resistor 205, and a terminal member 207 to which the temperature sensitive resistor 206 is fixed, such as a resin material. Is integrally molded. In addition, a drive circuit board 202 of the heating resistor type air flow measuring device 200 is provided inside the housing member 212 and is configured to be protected and fixed by the base member 210 and the cover member. Further, the drive circuit board 202 and the connector terminal 201 and the terminal member 207 are electrically connected via connection members 203 and 208 such as aluminum wires.

  The heating resistor 205 and the temperature sensitive resistor 206 for measuring the air flow 100 are installed in the auxiliary air passage 106 constituted by the auxiliary air passage constituting member 204, and the air flow in the auxiliary air passage 106 is measured. By measuring 101, the entire air flow 100 is representatively measured.

  A terminal member 207, which is a support member that also serves as a terminal of the heating resistor 205 and the temperature-sensitive resistor 206, protrudes from the surface of the housing member 212 facing the sub air passage 106. Two terminal members 207 are provided for each of the heating resistor 205 and the temperature sensitive resistor 206. A step 212 a is formed in the housing member 212 at the base of each terminal member 207.

  Next, the details of a portion of the cross section AA of FIG. 1 will be described with reference to FIG. The sub air passage 106 includes a housing member 212, a sub air passage constituting member 204, and a base member 210. Terminal members 207 (207a, 207b, 207c, 207d) are integrally formed in the housing member 212 at four locations. A heating resistor 205 is attached to the terminal members 207a and 207b, and a temperature sensitive resistor 206 is attached to the terminal members 207c and 207d.

  Although this terminal member 207 is configured by a plane, since it has a complicated and complicated shape, the mold configuration at the time of molding is divided into the upper and lower surfaces in the figure. FIG. 6 and FIG. 7 show this mold configuration.

  In order to hold down the terminal 207, the metal mold 400 and the metal mold 401 are partially divided into comb shapes. For this reason, a parting line (die division) as indicated by 410 occurs on the wall surface of the housing member 212. This parting is configured substantially perpendicular to the flow in the auxiliary air passage when the auxiliary air passage 106 is formed.

  Normally, the parting line 410 is designed to match the mold 400 and the mold 401 so that the burr (convex amount) is minimized. However, due to changes over time and the like, gaps are gradually generated in fitting the molds, and the height of burrs is gradually increased. As the height increases, the flow in the sub air passage slightly changes, and the measured flow rate of the heating resistor changes.

  As a result of examining the influence of the heating resistor due to the height of this burr by the authors' experiment, the result as shown in FIG. 3 was obtained. 2 shows the air flow rate on the horizontal axis, the left side of the drawing shows a small air flow rate, and the air flow rate increases toward the right side. The vertical axis indicates the value of output noise indicating the degree of air flow disturbance measured by the heating resistor. The larger the output noise value, the more disturbed the flow of the measurement unit is. When the burr height is zero, the output noise value decreases. However, when the burr height is 0.2 mm, the output noise increases at a specific flow rate. As the value is further increased, the output noise becomes smaller and approaches the value of zero burr height. In other words, the height of the burr increases at a specific height, and the effect decreases when the height increases to some extent.

  The reason is as shown in FIG. If there is a burr 300 in the auxiliary air passage, a separation region 301 in which a separation vortex of the air flow is generated downstream is generated. If the height of the burr 300 is low, the separation vortex repeatedly generates and disappears, so that the air flow becomes unstable and the value of the output noise measured by the heating resistor increases. On the other hand, if the height of the burr 300 is sufficiently high, a separation region will be sufficiently developed downstream of the burr, and the air flow will be throttled as shown at 302 in that place. When the air flow is throttled, the air flow velocity partially increases, and the flow at that location is stabilized. That is, if the heating resistor 205 is installed at this narrowed place, the value of the output noise becomes small.

  There is no problem if the burr can always be managed at zero. However, it is necessary to frequently perform maintenance of the mold, which makes management difficult. For this reason, as shown in FIG. 4, by forming a step 212a that simulates burrs with a mold in the initial stage, it is possible to reduce the degree of influence even if burrs subsequently occur. . As can be seen from FIGS. 5, 6 and 7, the step 212 a is formed along the parting line 410. In this embodiment, the step 212a is provided for each of the terminals 207a, 207b, 207c, and 207d, but may be provided for any one of them. In particular, when the step 212a is provided for the terminal 207a located on the most upstream side, the greatest effect can be obtained.

  Finally, FIG. 11 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 67 sucked from the air cleaner 54 passes through the intake manifold 59 including the body 53 of the heating resistance type air flow rate measuring device 53, the suction duct 55, the throttle body 58, and the injector 60 to which fuel is supplied, to the engine cylinder 62. Inhaled. On the other hand, the gas 63 generated in the engine cylinder is discharged through the exhaust manifold 64.

  The air flow rate signal and pressure signal output from the circuit module 52 of the heating resistance type air flow rate measuring device, the intake air temperature signal from the temperature sensor, the throttle valve angle signal output from the throttle angle sensor 57, and the exhaust manifold 64 are provided. The control unit 66 for inputting the oxygen concentration signal output from the oxygen concentration meter 65 and the engine rotation speed signal output from the engine rotation speed meter 61, etc., sequentially calculates these signals to obtain the optimum fuel injection amount. And the idle air control valve opening is obtained, and the injector 60 and the idle control valve 56 are controlled using the values.

  Engine control for automobiles is the main application, and it can be used for diesel engines and gasoline engines.

It is a block diagram of the air flow rate measuring apparatus which shows one Example of this invention. It is the longitudinal cross-sectional view which looked at FIG. 1 from the air flow upstream. It is a graph which shows the height of a burr | flash, and the value of output noise. It is detail drawing in a subair passage. It is a figure which shows the cross section AA of FIG. It is a figure which shows matching of the metal mold | die of a housing member. It is a figure which shows the state which the metal mold | die of FIG. 5 opened. It is a cross-sectional view of a typical heating resistor type air flow measuring device. It is the figure which looked at FIG. 7 from the upstream. It is a schematic circuit block diagram of a heating resistor type air flow measuring device. 1 is a schematic system configuration diagram of an internal combustion engine using a heating resistor type air flow rate measuring device. It is a figure in the subair passage for explaining the relation between a burr and output noise.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,212 Housing member 2 Circuit board 3 Heating resistor 4 Temperature sensitive resistor 5 Conductive support 6 Sealing material 7 Screw 10 Sub air passage member 14 Sub air passage 20 Main air passage member 22 Main air passage 25 Sub air Passage insertion hole 51 Intake temperature sensor 52 Circuit module 53 Body 54 Air cleaner 55 Intake duct 56 Idle air control valve 57 Throttle angle sensor 58 Throttle body 59 Intake manifold 60 Injector 61 Engine tachometer 62 Engine cylinder 63 Gas 64 Exhaust manifold 65 Oxygen concentration Total 66 Control unit 67 Intake air 100 Main air passage air flow 101 Air flow in sub air passage 102 Air flow in sub air passage (exit)
103 Intake air passage 105 Intake pipe constituent member 106 Sub air passage 200 Heating resistor type air flow measuring device 201 Connector terminal 202 Drive circuit board 203 Connection member 204 Sub air passage constituent member 205 Heat generating resistor 206 Temperature sensing resistor 207 Terminal member 208 Connection member 209 Cover 210 Base member 211 Screw 300 Burr 301 Peeling area 400 Mold 1
401 Mold 2
410 Parting line

Claims (2)

A heating resistor is installed in the sub air passage disposed in the main air passage and measures the flow rate of the air flowing through the main air passage based on the heat radiation to the air flowing through the sub air passage. In the heating resistor type air flow rate measuring device in which the heating resistor is supported in the auxiliary air passage through the supporting member protruding from the inner wall constituting the structure,
Providing a step on the inner wall of the auxiliary air passage near the base of the support member;
The sub air passage is molded by using a plurality of molds so that a metal supporting member protrudes from the inner wall surface by a resin material, and the step is formed by a parting line generated by mold division during molding. A heating resistor type air flow rate measuring device that is formed in a direction perpendicular to the air flow in the auxiliary air passage. 2. A heating resistor type air flow rate measuring device according to claim 1, wherein the height of the step on the inner wall of the sub air passage is approximately 0.3 mm or more.

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