JP5542614B2 - Flow measuring device - Google Patents

Description

  The present invention relates to a flow meter, and more particularly, to a flow rate measuring apparatus suitable for configuring an intake system of an automobile engine and detecting and controlling the intake air amount thereof.

  As a flow measurement device that measures the air flow rate, the heating resistor is controlled by heating and the flow rate is measured by the amount of heat released from the heating resistor, or the temperature sensitive resistor is placed near the heating resistor by controlling the heating resistor. A device that measures the flow rate according to the temperature change is known.

  The flow rate measuring device is attached to a part of the intake duct of the vehicle and has a role of measuring the intake air flow rate. Usually, an air filter is provided in the intake duct, and dust contained in the air flowing into the intake duct is removed by the air filter. However, depending on the size of the dust, some may pass through the air filter, and dust may enter the intake duct due to a mounting failure after replacing the air filter. The dust that has entered the intake duct is accelerated to several tens of m / s together with the fluid when the amount of depression of the accelerator is increased, and may reach the sub-passage of the flow rate measuring device. The flow rate measuring element arranged in the sub-passage has a very thin portion, and there is a possibility that the dust may be destroyed by colliding with dust. Further, if dust that has entered the intake duct adheres to the flow rate measuring element of the flow rate measuring device, the heat radiation characteristic of the flow rate measuring element may change to cause a change in output characteristic.

  As a structure that protects the flow rate measuring element from dust entering the intake duct and prevents deterioration over time due to contamination, the thermal resistor is placed in the direction of fluid flow so that the flow rate detection unit is on the lower surface side. A heat-sensitive flow rate measuring device arranged at an angle of ˜60 degrees is known (see Patent Document 1). Further, there is known a flow rate measuring device in which a flow rate measuring element is mounted while being inclined by an angle α with respect to the axial direction of the flow path so that the anti-sensing portion faces upstream (see Patent Document 2).

Japanese Utility Model Publication No. 6-020974 JP 2003-262144 A

  However, although the above-described technique has an effect of protecting the flow measuring element from dust or the like for a steady flow with a constant fluid flow speed, the flow speed of the fluid such as a pulsating flow becomes slow or fast. For the unsteady flow, there is a problem that the direction of movement of the dust changes irregularly depending on the force received from the fluid and the dust reaches the sensing portion.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable flow rate measuring device that is excellent in dust resistance even in an unsteady flow field such as a pulsating flow, is less likely to cause a characteristic error.

  In order to achieve the above object, a flow rate measuring device according to the present invention includes a sub-passage that is disposed in a main passage through which a fluid flows and takes a part of the fluid, and a heating resistor pattern that is disposed in the sub-passage. A first fluid passage section comprising a surface on which the flow rate measuring element is mounted and a passage forming surface of the sub-passage. And a second fluid passage portion comprising a surface opposite to the surface on which the flow rate measuring element is mounted and a passage forming surface of the sub-passage, wherein the flow rate measuring element The passage forming surface of the first fluid passage portion facing the upstream side of the fluid flow has an inclined surface that directs the fluid flow to the flow rate measuring element, and the inclined surface is It is composed of two or more surfaces with different orientations.

  According to the present invention, after the dust is rebounded by the inclined surface provided on the opposite surface upstream of the heating resistor pattern of the heating resistor pattern side fluid passage portion, the heating resistor rides on the fluid flow. The flow toward the pattern can be suppressed. For this reason, it is possible to suppress damage or contamination of the fluid measuring element composed of the heating resistor pattern, and it is excellent in dust resistance even in an unsteady flow field such as pulsating flow, and it is difficult to cause characteristic errors and is reliable. A high flow measuring device can be provided.

1 is a longitudinal sectional view of a flow rate measuring device according to an embodiment of the present invention. The AA cross-sectional enlarged view of Fig.1 (a). The BB cross-sectional enlarged view of FIG.1 (b). The particle distribution map by the CAE analysis implemented in order to confirm the form of a dust track | truck, when the velocity at which intake air flows is a constant flow. The particle distribution map by the CAE analysis implemented in order to confirm the form of the track of the dust by one Embodiment by this invention, when the velocity which the intake air flows is an unsteady flow. The longitudinal cross-sectional view of the flow volume measuring apparatus which is other embodiment of this invention. The AA cross-sectional enlarged view of Fig.4 (a). The BB cross-sectional enlarged view of FIG.4 (b). The longitudinal cross-sectional view of the flow volume measuring apparatus which is other embodiment of this invention. The AA cross-sectional enlarged view of Fig.5 (a). The BB cross-sectional enlarged view of FIG.5 (b). CC sectional enlarged view of FIG.5 (b). The longitudinal cross-sectional view of the flow volume measuring apparatus which is other embodiment of this invention. The AA cross-sectional enlarged view of Fig.6 (a). BB cross-sectional enlarged view of FIG.6 (b). CC sectional enlarged view of FIG.6 (b). The longitudinal cross-sectional view of the flow volume measuring apparatus which is other embodiment of this invention. AA cross-sectional enlarged view of Fig.7 (a). BB cross-sectional enlarged view of FIG.7 (b). CC sectional expanded view of FIG.7 (b). The figure which shows the specific structural example of the internal combustion engine of an electronic fuel injection system using the flow measuring device of invention.

  The following embodiments of the present invention relate to a flow rate measuring device used for measuring the flow rate of air sucked into an internal combustion engine for automobiles, and foreign matters such as dust flowing in the intake duct mixed with the sucked air. Thus, it is possible to prevent the flow measuring element from being damaged by the above and provide a structure capable of performing stable flow measurement. In the following description, foreign substances such as dust are simply referred to as dust.

  Examples of the present invention will be described below.

  FIG. 1 is a view showing a flow rate measuring device according to an embodiment of the present invention. Specifically, FIG. 1 (a) is a front view of the flow rate measuring device, and FIG. FIG. 1C is an enlarged cross-sectional view taken along the line BB. The components of the present embodiment will be described with reference to FIG.

  As shown in FIG. 1A, a connector 2 having a connector terminal 1 for electrically connecting an electronic circuit 5 and an external device, and a flow rate measuring device are fixed to a body 15 which is a fluid conduit constituting member. The module support part 3 for this purpose and the housing frame part 4 that holds the electronic circuit 5 are integrally formed by plastic molding. The connector terminal 1 is electrically connected to a bonding pad 11 formed at the end of the electronic circuit 5 and a bonding wire 12. The electronic circuit 5 is configured as a circuit board in which circuit elements are arranged on a substrate that is a flat plate member and connected by wiring.

  Further, a bypass mold portion 7 in which a sub passage 8 is formed is coupled to the housing frame portion 4. The flow rate measuring element 6 is disposed in the sub passage 8 while being mounted on the electronic circuit 5. The housing frame portion 4 and the bypass mold portion 7 are inserted into the body 15 through a rectangular hole formed in the body 15 constituting the fluid conduit, and are fastened and fixed to the body 15 by the fixing screw 10. Thereby, a part of the intake air 29 to the engine flowing through the intake passage 9 is diverted to the sub-passage 8. The flow rate of the divided intake air 29 is detected by the flow rate measuring element 6 to detect the total flow rate of the air sucked into the engine.

  As shown in FIG. 1B, the flow rate measuring element 6 includes a substrate that is a flat plate member and a resistor pattern 6a such as a heating resistor formed on the substrate by a thin film forming process. The substrate surface of the flow rate measuring element 6 is fixed to the electronic circuit 5 so as to be substantially parallel to the substrate surface of the electronic circuit 5. The electronic circuit 5 is included in the housing frame 4 and is fixed so as to be parallel to the direction of the flow of the fluid 30 flowing in the sub-passage 8. In the present embodiment, the fluid 30 is intake air 29 flowing through the body taken into the sub passage 8.

  At this time, the surface 5a provided with the heating resistor pattern in the electronic circuit 5 is disposed along the flow of the fluid 30 in the sub-passage 8, and the heating resistor pattern constituting surface 5a and the sub-passage in the electronic circuit 5 are arranged. A heating resistor pattern side fluid passage portion 8a through which a fluid flows is formed between the passage forming surface 8d of FIG. 8 and the surface 5b opposite to the heating resistor pattern constituting surface 5a in the electronic circuit 5 and the sub passage 8 A rear-side fluid passage portion 8b is formed between the passage formation surface 8c. That is, the fluid 30 is configured to flow on both surfaces 5 a and 5 b of the electronic circuit 5.

  As shown in FIG. 1C, on the passage forming surface 8d, the guide surface 13a, as a guide portion for guiding the fluid 30 from the center of the resistor pattern 6a to the outside, upstream of the resistor pattern 6a. 13b is configured.

  The guide surfaces 13a and 13b are two inclined surfaces in different directions for directing the flow of the fluid 30 to the resistor pattern 6a, and the flow of the fluid 30 is outward from the ridge line 13 at the center of the resistor pattern 6a. It is configured to guide.

  That is, the passage forming surface 8d has inclined surfaces that constitute the guide surfaces 13a and 13b. The guide surfaces 13a and 13b, which are inclined surfaces, are inclined so that the fluid 30 flows outward from the center of the resistor pattern 6a.

  With such a configuration, since the fluid 30 can flow outside the center of the resistor pattern 6a, foreign matters such as dust that flows on the flow of the fluid 30 and mixes with the intake air 29 and flows in the intake duct are heated. It is possible to suppress the flow toward the body pattern 6a, and it is possible to suppress breakage or contamination of the fluid measuring element 6 constituted by the heating resistor pattern 6a.

  The passage forming surface 8c of the back side fluid passage portion 8b opposite to the passage forming surface 8d on which the guide surfaces 13a and 13b are configured has a throttle shape.

  Here, in order to confirm the effect of the embodiment shown in FIG. 1, the form of tracks such as dust on the flow rate measuring element 6 will be described with reference to FIGS.

  FIG. 2 shows the tracks of the dust 14 at regular intervals by CAE analysis when the velocity of the intake air 29 flowing through the auxiliary passage 8 is a constant flow. At time T <b> 1, the dust 14 that has entered the sub-passage 8 has a structure in which the sub-passage 8 has a curve, and thus becomes a track toward the outer peripheral side due to inertial force. At time T2, the dust 14 passes through the back surface of the electronic circuit 5, and flows at the downstream side at time T3. Thus, in the case of a steady flow, the track through which the dust 14 passes is constant, and the electronic circuit 5 is arranged so as not to be exposed to the track, so that it passes through the back surface of the electronic circuit 5 without going to the flow measuring element 6. Can be confirmed.

  Here, the back surface of the electronic circuit 5 is a surface 5b opposite to the heating resistor pattern constituting surface 5a in the electronic circuit 5, and is referred to as a back surface (back surface side). On the other hand, the heating resistor pattern constituting surface 5a in the electronic circuit 5 is referred to as the surface of the electronic circuit 5 or the flow measuring element constituting surface (surface side). The upstream side surface 5 c of the electronic circuit 5 is a surface located on the upstream side in the fluid flow direction among the surfaces along the thickness direction of the circuit board constituting the electronic circuit 5. On the other hand, the downstream side surface 5d exists on the downstream side.

  Next, the result in the case of the auxiliary passage 8 of one embodiment of the present invention is shown in FIG. FIG. 3 shows an unsteady state in which the velocity of the intake air 29 flowing through the auxiliary passage 8 formed with the guide surfaces 13a and 13b on the upstream side of the resistor pattern 6a provided on the passage formation surface 8d becomes slower or faster. The trace of the dust 14 for every fixed time by the CAE analysis in the case of a flow is shown.

  As shown in FIG. 3, the dust 14 that has entered the sub-passage 8 has a structure in which the sub-passage 8 has a bend until reaching the electronic circuit 5. However, the dust 14 colliding with the upstream side surface 5c perpendicular to the flow of the electronic circuit 5 is largely rebounded in the direction opposite to the flow at time T1 in FIG. 3 (a), and reversed at time T2 in FIG. 3 (b). The dust 14 is pushed back by the flow toward the surface of the electronic circuit 5. Further, at time T3 in FIG. 3 (c), a part of the dust 14 goes to the surface of the electronic circuit 5, but the dust 14 collides with the guide surfaces 13a and 13b by providing the guide portion on the passage forming surface 8d. It is confirmed that the resistor pattern 6a is guided outward from the center. In addition, it is confirmed that the resistor pattern 6a is guided from the center to the outside from the dust track shown in FIG. Thus, in the case of an unsteady flow, the track through which the dust 14 passes is irregular, but it is possible to guide the dust in a direction away from the center line of the flow rate measuring element 6 only by providing the guide surfaces 13a and 13b. The collision with the flow rate measuring element 6 can be suppressed.

  FIG. 4 shows a second embodiment. In contrast to the embodiment shown in FIG. 1, the shape of the guide surfaces 16a, 16b, 16c, and 16d shown in FIG. It can be expected to suppress the rebounding toward the center of the resistor pattern 6a when a collision occurs. It is effective that at least one of the ridge lines is formed at the center of the resistor pattern 6a.

  FIG. 5 shows a third embodiment. In contrast to the embodiment shown in FIG. 1, the guide surfaces 17a and 17b shown in FIG. 5C are formed with concave curved surfaces, and when the dust 14 collides, the resistor pattern 6a is formed. The effect which suppresses bouncing toward the center of can be expected. It is effective that the ridge line is formed at the center of the resistor pattern 6a.

  FIG. 6 shows a fourth embodiment. In contrast to the embodiment shown in FIG. 1, the shape of the passage forming surface is changed in parallel to the resistor pattern 6a joined to the guide surface of the passage forming surfaces 18a, 18b, 18c, 18d shown in FIG. It is formed by two or more surfaces or planes, and the effect of guiding the dust 14 from the center to the outside without separating the flow of the fluid 30 from the resistor pattern 6a can be expected. It is effective that at least one of the ridge lines is formed at the center of the resistor pattern 6a.

  FIG. 7 shows a fifth embodiment. In contrast to the embodiment shown in FIG. 1, the shape of the passage forming surface that changes in parallel to the resistor pattern 6 a joined to the guide surface of the passage forming surfaces 19 a and 19 b shown in FIG. With the formation, the effect of guiding the dust 14 from the center to the outside can be expected without separating the flow of the fluid 30 from the resistor pattern 6a. It is effective that the ridge line is formed at the center of the resistor pattern 6a. Therefore, it is possible to realize a flow rate measuring device that can ensure the reliability of the flow rate measuring element 6 at the time of mounting and the like, and can suppress a change in characteristics at the time of downsizing without increasing costs.

  In the above description, the flow measuring element 6 is arranged in the sub-passage 8 while being mounted on the electronic circuit 5. However, the flow measuring element 6 is directly arranged without being mounted on the electronic circuit 5. There can also be a configuration. In this case, the “back surface” of the electronic circuit 5 corresponds to the substrate surface opposite to the substrate surface on the side where the resistor pattern 6 a is formed on the substrate constituting the flow measuring element 6. Alternatively, a configuration in which the flow rate measuring element 6 is mounted on another support member instead of the electronic circuit 5 and arranged in the sub-passage 8 is also conceivable. In this case, the electronic circuit 5 may be replaced with another support member and the “back surface” of the electronic circuit 5 may be considered.

  FIG. 8 is a diagram showing a specific configuration example of an operation control system for an internal combustion engine of an electronic fuel injection system using the flow rate measuring device 101 of the present invention.

  In FIG. 8, the intake air 29 sucked from the air cleaner 100 is an intake having a body 15 in which a flow measuring device 101 is disposed, an intake duct 103, a throttle body 104, and an injector (fuel injection valve) 105 to which fuel is supplied. It is sucked into the engine cylinder 107 through the manifold 106. The gas 108 generated in the engine cylinder 107 is discharged to the outside through the exhaust manifold 109.

  An air flow rate signal output from the flow rate measuring device 101, an intake air temperature signal, a throttle valve angle signal output from the throttle angle sensor 111, an oxygen concentration signal output from an oxygen concentration meter 112 provided in the exhaust manifold 109, and An engine speed signal or the like output from the engine speed meter 113 is supplied to the control unit 114. The control unit 114 sequentially calculates the supplied signal to obtain an optimal fuel injection amount and an idle air control valve opening, and controls the injector 105 and the idle air control valve 115 using these values. If the flow rate measuring device 101 according to the present invention is used in an internal combustion engine of an electronic fuel injection system, an accurate flow rate can be measured and accurate operation control of the internal combustion engine can be performed.

  The following effects are obtained by the embodiment described above.

  In the sub-passage arranged in the main passage through which the fluid flows, the fluid flows to the flow measurement element side in the sub-passage on the opposite surface of the circuit board constituting the electronic circuit arranged in parallel with the fluid flow. By providing a guiding part or an inclined surface that guides the dust outside the center of the heating resistor pattern on the upstream side of the flow measurement element, it is possible to suppress the dust collision of the fluid measurement element. It is possible to prevent damage or contamination of the element.

  And it can provide a highly reliable operation control system of an internal-combustion engine by setting it as a flow measuring device which is hard to receive influence of dust also to unsteady flow like pulsation flow.

DESCRIPTION OF SYMBOLS 1 Connector terminal 2 Connector 3 Module support part 4 Housing frame part 5 Electronic circuit (circuit board)
6 Flow measuring element 6a Resistor pattern 7 Bypass mold part 8 Sub passage 9 Intake passage 10 Fixing screw 11 Bonding pad 12 Bonding wire 13 Ridge lines 13a, 13b, 16a to 16d, 17a, 17b Guide surface 14 Dust, dust, etc. 15 Body 18a to 18d, 19a, 19b Passage forming surface 29 Intake air 30 Fluid 100 Air cleaner 101 Flow rate measuring device 103 Intake duct 104 Throttle body 105 Injector 106 Manifold 107 Engine cylinder 108 Gas 109 Exhaust manifold 111 Throttle angle sensor 112 Oxygen meter 113 Engine rotation Speedometer 114 Control unit 115 Idle air control valve

Claims (9)

A sub-passage that is disposed in the main passage through which the fluid flows and takes in a part of the fluid; a flow rate measuring element that is disposed in the sub-passage and has a heating resistor pattern formed thereon; and a support on which the flow rate measuring element is mounted And a first fluid passage portion configured by a surface on which the flow rate measuring element is mounted and a passage forming surface of the sub-passage, and on a side opposite to the surface on which the flow rate measuring element is mounted A flow rate measuring device comprising: a second fluid passage portion configured by a surface and a passage forming surface of the sub passage;
The passage forming surface of the first fluid passage portion facing the upstream side of the fluid flow with respect to the flow measuring element has an inclined surface that directs the fluid flow toward the flow measuring element,
The said inclined surface is comprised from the surface of two or more of different directions, The flow measuring device characterized by the above-mentioned. The flow measurement device according to claim 1,
Two or more surfaces in different directions constituting the inclined surface are flat surfaces or concave curved surfaces. The flow rate measuring device according to claim 1 or 2,
At least one of the ridge lines constituted by two faces in different directions constituting the inclined surface is formed on a center line of the pattern of the heating resistor. The flow rate measuring device according to claim 3,
Two surfaces forming a ridge line on the center line of the heating resistor pattern constituting the inclined surface are directions for guiding dust colliding with the inclined surface in a direction away from the center line of the heating resistor pattern. A flow rate measuring device characterized by that. The flow measurement device according to claim 1,
The passage forming surface of the first fluid passage portion facing the surface on which the pattern of the heating resistor is formed has a facing surface that changes the flow of the fluid in parallel to the pattern of the heating resistor. ,
The flow measuring device according to claim 1, wherein the facing surface is composed of two or more surfaces in different directions. The flow rate measuring device according to claim 5,
The flow rate measuring device according to claim 1, wherein the two or more surfaces in different directions constituting the facing surface are flat surfaces or concave curved surfaces. In the flow measuring device according to claim 5 or 6,
At least one of the ridge lines constituted by two faces in different directions constituting the facing surface is formed on a center line of the pattern of the heating resistor. The flow rate measuring device according to claim 7,
The flow rate measuring device according to claim 1, wherein the facing surface is directed to guide the dust colliding with the inclined surface in a direction away from the center line of the pattern of the heating resistor.   A fuel injection system for an internal combustion engine, comprising the flow rate measuring device according to claim 1.

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