JP2006057539A - Air flow rate measuring device and internal combustion engine control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply both an air flow rate detection signal having quick response and an air flow detection signal having poor follow-up from an air flow measuring device to an engine control unit. <P>SOLUTION: The air flow rate measuring device 161 comprises a heating resistor for measuring an air flow rate. It has at least two output terminals for the air flow rate detection signals having difference response times for detection values. The output terminals include an output terminal having a smoothing filter circuit 200 laid on the output side of the heating resistor and an output terminal having no smoothing filter circuit laid thereon. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heating resistor type air flow rate measuring device and an internal combustion engine control system used for measuring an air flow rate taken into an internal combustion engine for an automobile.

  A control system used for conventional internal combustion engine control, for example, as shown in (Patent Document 1), directly inputs an air flow rate detection signal from a heating resistor type air flow rate measuring device to an ECU (engine control unit). Thus, processing such as air flow rate conversion is performed.

JP-A-6-288275

  In the heating resistor type air flow rate measuring device, air flow turbulence is easy to detect in the air flow rate detection of the response value of the detection value of the heating resistor, and the output noise increases and causes the detection value to vary.

  On the contrary, in the air flow rate detection in which the response time of the detection value of the heating resistor is slow, the followability of the detection sensitivity to the transient flow is deteriorated. For this reason, in order to use it for fuel control of an internal combustion engine, either air flow detection including output noise or air flow detection with poor followability must be sacrificed.

  In view of the above problems, the present invention is capable of providing both an air flow rate detection signal having a quick response including output noise and an air flow rate detection signal having poor followability from the air flow rate measuring device to the engine control unit. Objective.

  The present invention is characterized in that at least two air flow rate detection signal output terminals having different response times of detection values are provided in an air flow rate measuring device provided with a heating resistor for air flow rate measurement.

  More specifically, the present invention outputs two systems of air flow rate detection signals, a high-speed response output as an air flow rate detection signal from the heating resistor type air flow rate measuring device and a smooth output smoothed by a filter circuit or the like. The output value of the air flow detection signal required on the engine control unit side was selected and used. When the air flow is almost in a steady state and an average value of the flow rate is mainly required, the smoothness output value is used to increase the average value calculation accuracy. In addition, when a transient flow rate is required, the transient flow rate is accurately obtained using a high-speed response output. The determination of whether or not the flow rate is transient can be made by the engine control unit by using, for example, a throttle opening signal.

  According to the present invention, an accurate intake air flow rate detection signal can be obtained regardless of whether the air flow in the intake pipe is in a steady state or a transient state. For this reason, the measurement of the flow rate of intake air used for fuel control of the internal combustion engine is performed with higher accuracy than before, and the exhaust gas exhausted from the internal combustion engine can be cleaned.

  As described above, the present invention obtains two flow rate detection signals having different response times from one flow rate detection signal with a simple configuration in which a filter circuit is interposed on the output side of the heating resistor or not. Is possible. By selecting and using these two flow rate signals, the fuel control of the internal combustion engine can be performed accurately and satisfactorily.

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

  First, the outline of the heating resistor type air flow measuring device will be described.

  FIG. 4 is a schematic circuit diagram of a heating resistor type air flow rate measuring device. The driving circuit of the heating resistor type air flow rate measuring device is roughly composed of a bridge circuit and a feedback circuit.

  The bridge circuit includes a heating resistor RH for measuring the intake air flow rate, and temperature sensitive resistors RC and R10, R11 for compensating the intake air temperature.

  The feedback circuit has an operational amplifier OP1. Output that outputs an output signal corresponding to the air flow rate by supplying a heating current Ih to the heating resistor RH so as to maintain a constant temperature difference between the heating resistor RH and the temperature sensitive resistor RC while applying feedback using the operational amplifier OP1. It has a terminal (Vout1). This output terminal (Vout1) is provided with another output terminal (Vout2) with a filter circuit 200 interposed.

  The filter circuit 200 has a function as a smoothing circuit that smoothes the output value output from the output terminal of Vout2. Vbatt is a power input terminal, and GND is a ground terminal.

  The heating current Ih flowing through the heating resistor RH varies depending on the air flow rate (air flow velocity) flowing there. That is, when the flow velocity is fast (the air flow rate is large), a large amount of heat is taken from the heating resistor RH, so that a large heating current Ih is passed. On the other hand, when the flow velocity is slow (the air flow rate is small), the amount of heat taken away from the heating resistor Rh is small, so that the heating current can be reduced.

  The output from the output terminal of Vout2 through which the filter circuit 200 is interposed indicates the detection value of the smoothed air flow rate detection signal. On the other hand, the output from the output terminal of Vout1 in which the filter circuit 200 is not interposed indicates the detection value of the true air flow detection signal that is not smoothed.

  Thus, two flow rate detection signals having different detection values can be obtained from one flow rate detection signal with a simple configuration in which a filter circuit is interposed on the output side of the heating resistor or not.

  FIG. 5 is a cross-sectional view showing an example of a heating resistance type air flow measuring device. FIG. 6 is an external view of the heating resistance type air flow rate measuring device as viewed from the upstream (left side in FIG. 5).

  The heating resistor type air flow rate measuring device has the following components. A circuit board 2 constituting a drive circuit, a housing member 1 incorporating the circuit board 2, a sub air passage constituting member 10 formed by a non-conductive member, and the like.

  In the sub air passage constituting member 10, a heating resistor 3 for detecting the air flow rate and a temperature sensitive resistor 4 for compensating the intake air temperature are circuitized via a support 5 constituted by a conductive member. Arranged so as to be electrically connected to the substrate 2, a housing, a circuit board, a sub air passage, a heating resistor, a temperature sensitive resistor, etc. are configured as an integrated module of the heating resistor type air flow measuring device. Yes.

  A hole 25 is formed in the wall surface of the main air constituting member 20 constituting the intake pipe. Through this hole 25, the auxiliary air passage portion of the heating resistor type air flow measuring device 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. Has been.

  Here, the main air passage portion into which the sub air passage is inserted is a substantially cylindrical tube, and the effective cross-sectional area through which the air flows in the main air passage is substantially the same at the location of the entrance and exit of the sub air passage. Moreover, the sealing material 6 is attached between the sub air passage structural member 10 and the main air passage structural member, and airtightness is maintained.

  Next, the main features of the present invention will be described in more detail.

  The responsiveness of the heating resistor type air flow measuring device, which is the main feature of the present invention, will be described with reference to FIG.

  In FIG. 7, the horizontal axis represents time, and the vertical axis represents the air flow rate. A thin line indicates the true air flow rate, and the flow rate is changed stepwise by “flow rate switching” in the drawing.

  In the case of the “fast response heating resistor responsiveness” shown in this figure, a waveform having good followability with respect to the true air flow rate and less response delay is shown. On the other hand, an output having a filter circuit interposed on the output side of the high-speed response heating resistor is the output of the “filtered heating resistor” shown in the figure. In this case, the response waveform increases in response delay according to the filter constant.

  That is, an air flow rate detection signal having a detection value with a different response time (fast / slow) with respect to a change in air flow rate is taken out by interposing or not interposing a smoothing filter circuit on the output side of the heating resistor. be able to.

  FIG. 8 shows a detection signal waveform of a heating resistor type air flow measuring device used in an actual engine. As is clear from this figure, in the case of “fast response heating resistor responsiveness”, the output voltage of the detected flow rate fluctuates greatly, and it is very difficult to calculate the average flow rate. On the other hand, in the case of the “heat generating resistor after filtering”, the fluctuation of the output voltage of the detected flow rate becomes half or less, and the calculation of the average flow rate becomes very easy.

  As described above, the heating resistor type air flow rate measuring device outputs a fast response output with a fast response time and an output with a slow response time. These two air flow detection signals are selected on the engine control unit side and the necessary air flow detection signals are used. That is, when the air flow is almost in a steady state and the average value of the flow rate is mainly required, the average value calculation accuracy is increased by using the smooth output value. In addition, when a transient flow rate is required, the transient flow rate is accurately obtained using a high-speed response output. The determination of whether or not the flow rate is transient can be made by the engine control unit by using, for example, a throttle opening signal.

  FIG. 1 is a diagram showing components of an intake pipe in an internal combustion engine.

  It demonstrates from the upstream side into which air flows. The 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. A body member 160 to which a heating resistor type air flow measuring device 161 is attached is provided downstream of the air cleaner. And the intake manifold 155 and the body member 160 are connected by the intake duct 158, and the whole intake pipe is comprised.

  Signal processing and control from various sensors in the internal combustion engine are performed by an engine control unit (ECU) 100. The ECU 100 includes an input circuit unit 101, an output circuit unit 102, a central processing unit (CPU) 103, and a memory 104. Exchange of information between the internal components of the ECU 100 is performed at the portions indicated by the arrows 105a and 105b. The flow rate of the intake air flowing through the intake pipe is measured by the heating resistor 3, and an intake air temperature signal Ta from an intake air temperature sensor 157 attached to the intake duct 152, a rotation speed signal from a rotation sensor (not shown), etc. It is sent to ECU100. A control signal Tp for fuel injection is output to the injector 154 with respect to the result obtained by performing arithmetic processing based on various sensor signals and the like sent to the ECU.

  FIG. 2 shows a circuit of the heating resistor type air flow measuring device 161 provided with the filter circuit 200 and a circuit of the ECU 100 together. The circuit of this air flow rate measuring device has two output terminals, but does not go through a plurality of output terminals in which a plurality of smoothing filter circuits having different filter constants are arranged in parallel on the output side of the heating resistor and the filter circuit. By providing output terminals together, it is possible to provide three output terminals.

  FIG. 3 shows a circuit of the heating resistor type air flow measuring device 161 not provided with a filter circuit and a circuit of the ECU 100 together. Here, since the filter circuit 200 is provided on the ECU 100 side, the air flow measuring device 161 has one output terminal. Since there is only one output terminal, the cost can be reduced.

  FIG. 9 shows an enlarged view of the terminal holder (connector) 210 of FIG. Since the terminal holder 210 is provided with an output terminal (Vout1), an output terminal (Vout2), a power input terminal (Vbatt), and a ground terminal (GND), the terminal holder can be easily connected.

  Although the filter circuit described in the above embodiment includes a hardware circuit and a software circuit, the cost can be reduced by using the hardware circuit.

The figure which concerns on the Example of this invention and shows the control system of an internal combustion engine. The figure concerning the Example of this invention, and the figure which shows the circuit of the heating flow resistor type air flow measuring device provided with the filter circuit, and the circuit of ECU together. The figure which concerns on the other Example of this invention, and shows the circuit of the heating flow resistor type air flow measuring device which is not provided with a filter circuit, and the circuit of ECU. The figure which concerns on the Example of this invention, and shows the drive circuit of a heating resistor type air flow measuring device. The cross-sectional view of a heating resistor type air flow rate measuring apparatus according to an embodiment of the present invention. The figure which looked at the heating resistor type air flow measuring device from the upstream side. FIG. 6 is a view of the heating resistor type air flow rate measuring device shown in FIG. 5 as viewed from the upstream side according to the embodiment of the present invention. The figure which concerns on the Example of this invention and shows the responsiveness of a heating resistor. The figure which concerns on the Example of this invention and shows the detection signal waveform of a heating resistor when an engine is mounted | worn. FIG.

Explanation of symbols

  3 ... heating resistor, 161 ... air flow rate measuring device, 210 ... terminal holder, Vout1 ... output terminal, Vout2 ... output terminal.

Claims (6)

In the air flow measurement device equipped with a heating resistor for air flow measurement,
An air flow rate measuring apparatus comprising at least two output terminals for air flow rate detection signals having different response times of detection values of the heating resistors with respect to changes in air flow rate. The air flow rate measuring device according to claim 1,
The air flow rate measuring apparatus, wherein the output terminal includes an output terminal having a smoothing filter circuit interposed on an output side of the heating resistor, and an output terminal not having the smoothing filter circuit interposed. The air flow rate measuring device according to claim 1,
The air flow rate measuring apparatus according to claim 1, wherein the output terminal includes a plurality of output terminals in which a plurality of smoothing filter circuits having different filter constants are disposed in parallel on the output side of the heating resistor. In the air flow measuring device according to claim 2 or 3,
An air flow rate measuring apparatus having a power input terminal and a ground terminal in addition to the output terminal, wherein the output terminal, the power input terminal and the ground terminal are collected in a terminal holder. In an internal combustion engine control system having an air flow rate measuring device provided with a heating resistor for air flow rate measurement, and an engine control unit for inputting an air flow rate detection signal of the air flow rate measuring device,
The internal combustion engine control system, wherein the engine control unit performs combustion control of the internal combustion engine based on two air flow rate detection signals output from the air flow rate measuring device. The internal combustion engine control system according to claim 5, wherein
The internal combustion engine control system according to claim 2, wherein the two air flow rate detection signals have different response times of detection values of the heating resistors with respect to changes in the air flow rate.

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