JP4707412B2 - Gas flow measuring device - Google Patents

Description

  The present invention relates to a heating resistor type gas flow measuring device for measuring a gas flow rate.

  Heat flow is controlled by the thermal resistor and the flow rate is measured by the temperature change of the temperature sensitive resistor placed near the heating resistor. Heating resistance type gas flow rate measuring devices such as those that do are known.

  In this heating resistance type gas flow measuring device, the flow measuring element including the heating resistor and the electronic circuit components that drive the flow measuring device are mounted on a support base made of an electrically insulating material having a high thermal conductivity such as ceramic. ing.

  In recent years, the gas flow measuring device has been downsized for the purpose of reducing the cost of the gas flow measuring device and reducing the number of components, and the gas flow measuring device and the electronic circuit component have been mounted at positions close to each other. .

  For this reason, heat is easily transmitted to the gas flow rate measuring element due to self-heating of the electronic circuit parts, and this heat causes a measurement error.

  In addition, when the heating resistor type gas flow measuring device is used by being mounted on a device that generates high heat such as an intake system of an automobile engine, it may be mounted in various directions depending on the layout of the intake system. Depending on the heat transfer from the engine or the like, the measurement error may be different.

  In order to solve this difference in measurement error, a technology is adopted in which a metal plate is attached to a circuit board on which electronic circuit components such as temperature measuring elements are mounted, and the metal plate is exposed to a fluid passage as a heat sink to release heat to the outside. Is described in Patent Document 1.

Japanese Patent Laid-Open No. 11-14423

  By the way, when measuring the amount of intake air of an automobile engine, for example, a heating resistor, a temperature sensing resistor, and a temperature measuring element are arranged not near the gas inlet in the spiral sub-passage but near the gas outlet. .

  For this reason, the temperature measuring element has a structure surrounded by a structure, and the heat generated from the power transistor, which is an electronic circuit component, can be radiated by the metal plate, but the heat transmitted to the metal plate is , It was transmitted to the temperature measuring element, causing a measurement error.

  An object of the present invention is to realize a gas flow rate measuring device capable of suppressing heat transfer from a circuit element or the like to a temperature measuring element and reducing measurement errors.

  In order to achieve the above object, the present invention is configured as follows.

(1) A sub-passage that takes in part of the gas flowing in the gas passage, a flow rate measuring element that is arranged in the sub-passage and measures the flow rate of the gas, and a gas passage that measures the temperature of the gas. In a gas flow rate measuring device having a temperature measuring element, an electronic circuit that drives the flow rate measuring element and the temperature measuring element, and a housing member that protects the electronic circuit,
A metal base member that dissipates heat of the electronic circuit; the housing member has a thermal conductivity lower than that of the metal base member; and the sub-passage is formed by the housing member and the metal base member. A vent hole is formed in both side walls of the sub passage forming portion of the housing member, and the temperature measuring element is disposed between the vent holes.

  (2) Preferably, in (1) above, the size of the vent is larger than that of the temperature measuring element.

(3) A sub-passage that takes in part of the gas flowing in the gas passage, a flow rate measuring element that is disposed in the sub-passage and measures the flow rate of the gas, and is disposed in the sub-passage to measure the temperature of the gas. A gas flow rate measuring device having a temperature measuring element, an electronic circuit that drives the flow measuring element and the temperature measuring element, and a housing member that protects the electronic circuit, and includes a metal base member that dissipates heat from the electronic circuit. The sub-passage is formed by the housing member and the metal base member, one of the vent holes is formed in the housing member, and the other vent hole is formed in the metal base member . The temperature measuring element is disposed between them .
(4) Preferably, in (3) above, the size of the vent is larger than that of the temperature measuring element.

(5) Preferably, in the above ( 3 ), the housing member is made of resin.

(6) Preferably, in the above ( 1 ), ( 3 ), and (5), the distance between the temperature measuring element and the metal base member constituting the sub-passage is about 6 mm.

(7) Preferably, in ( 3 ) or (5), a heat insulating layer is formed by a groove or a through hole in the vicinity of the air hole of the metal base member.

(8) Preferably, in ( 1 ) above, a heat insulating layer is formed by a groove or a through hole in the vicinity of the vent hole in the sub-passage forming portion of the housing member.

  (9) In the operation control system of the internal combustion engine, fuel control is performed using the gas flow rate measuring devices according to the above (1) to (8).

  According to the present invention, it is possible to realize a gas flow rate measuring device that can suppress the transfer of heat from a circuit element or the like to a temperature measuring element and reduce measurement errors.

  Moreover, by providing a groove or a through hole between the vent hole opened to reduce the thermal effect of the temperature measuring element and the metal base, heat conduction can be suppressed, and further measurement errors can be reduced. .

  Further, the temperature measuring element can be accommodated in the sub passage, and the air flow measuring device can be downsized.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following examples, the present invention is applied to a thermal flow rate measuring device.

(First embodiment)
FIG. 1 is an external perspective view of a gas flow rate measuring apparatus according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view when the gas flow rate measuring apparatus according to the first embodiment is arranged in an air passage. 3 is a side view of one side of the gas flow rate measuring apparatus according to the first embodiment, and FIG. 4 is a side view of the other side of the gas flow rate measuring apparatus according to the first embodiment.

  1 to 4, the thermal flow rate measuring device 1 is an assembly of a housing member 10 and a cover member 11 formed by resin formation and a metal base member 8, and is formed in the main pipe 3 as shown in FIG. 2. Inserted into the insertion hole 4 and attached so that the lower part (the part where the temperature measuring element 9, the heating resistor 17 and the temperature sensitive resistor 18 are arranged) is located in the main passage 2 formed by the main pipe 3. It is done.

  A sub air passage 5 is formed in a lower portion where the thermal flow measuring device 1 is located in the main passage 2, and a temperature measuring element 9, a heating resistor 17 and a temperature sensitive resistor 18 are formed in the sub air passage 5. Has been placed.

  A heating resistor 17 that measures the air flow rate, a temperature sensing resistor 18 that detects the temperature of the intake air 16 and guarantees the temperature, and a temperature that measures the temperature of the intake air 16 separately from the temperature sensing resistor 18 A measuring element 9 is connected to the housing member 10 via a metal column 12.

  Then, the electronic circuit board 7 is stacked on the metal base member 8, and a part of the metal base member 8 is a sub air passage 5 that forms a bypass passage.

  The housing member 10 is made of plastic, and includes a metal support 12 for holding the temperature measuring element 9, the heating resistor 17, and the temperature sensitive resistor 18 by welding or the like, the electronic circuit board 7, a power source and a signal output. The metal terminal 13 for use is insert-formed.

  The electronic circuit board 7 is made of a plate-shaped alumina ceramic that can withstand high temperatures in consideration of being installed in an engine room of an automobile. Then, a thick film semiconductor or thick film resistor paste is printed on the surface of the alumina ceramic, and then a conductor and a resistor pattern are formed by firing. The power transistor 15 is mounted on the conductor pattern with solder or the like.

  Further, the electronic circuit board 7 is surrounded by the housing member 10 over almost the entire circumference of the side surface of the electronic circuit board 7 so as to be bonded and fixed to the metal base member 8 and protected by the housing member 10. Further, the metal base member 8 is integrated with the housing member 10 by adhesive fixing or insert molding to the housing member 10.

  The electronic circuit board 7 is adjusted in characteristics as necessary, and the plate-like cover member 11 is fixed to the housing member 10 by adhesion or the like, so that the electronic circuit board 7 is hermetically protected. The electronic circuit board 7, the auxiliary air passage 5, the heating resistor 17 for detecting the temperature of the intake air 16, the temperature sensitive resistor 18 and the temperature measuring element 9 incorporated in the housing member 10 are introduced into the internal combustion engine. Arranged inside the intake pipe through which the main air 2 flows.

  In configuring the thermal flow measuring device 1, it is desirable that all electronic circuit components other than the temperature measuring element 9, the heating resistor 17 and the temperature sensitive resistor 18 are mounted on the same circuit board. This is because the number of parts can be deleted, the cost can be reduced by reducing the number of mounting processes, and the product can be downsized.

  Here, the power transistor 15 disposed on the electronic circuit board 7 generates self-heating during current amplification. For this reason, when the power transistor 15 and other electronic circuit elements are mounted on the same substrate, the electronic circuit elements around the power transistor 15 may be affected by heat.

  When the power transistor 15 is mounted on the electronic circuit board 7, the heat of the electronic circuit board 7 caused by the self-heating of the power transistor 15 is conducted to the metal base member 8 fixed to the electronic circuit board 7 by adhesion or the like. To do. Since the metal base member 8 has high thermal conductivity, the temperature rises as a whole.

  Here, the temperature measuring element 9 is disposed in the sub air passage 5, and in the periphery thereof, one side wall (side wall of the sub air passage 5) is configured by the metal base member 8, and the other side wall is The housing member 10 is used.

  Therefore, when the heat of the power transistor 15 is conducted to the metal base member 8, the heat of the metal base member 8 is transferred to the internal air of the sub air passage 5.

  For this reason, in the case where the configuration of the present invention is not employed, the temperature measuring element 9 that detects the temperature of the intake air 16 is affected by the heat caused by the self-heating of the power transistor 15 and generates an error in the detected temperature. There is a possibility that.

  Under an extremely low flow rate of no wind and intake air 16 of about 0.5 m / s, the metal base member 8 radiates heat during natural convection, and the temperature measuring element 9, the heating resistor 17, and the temperature sensitive resistor. 18 is affected by heat. On the contrary, when the intake air 16 is at a high flow rate, the heat due to the temperature rise of the metal base member 8 is almost taken away by the air and cooled, so that the temperature of the sub air passage 5 becomes equal to the temperature of the intake air 16.

  That is, the temperature of the metal base member 8 depends on the flow velocity of the intake air 16, but the temperature detection error also depends on this flow velocity.

  Therefore, in the first embodiment of the present invention, the position where the temperature measuring element 9 is attached is the resin member 19 in which the metal base member 8 is cut and integrated with the housing member 10, and the housing member 10. The sub-air passage member 21 is a part of which the sub-air passage 5 is formed.

  Further, a vent hole 14 larger than the temperature measuring element 9 is formed in the resin member 19 and the sub air passage member 21 (both side walls (19, 21) forming the sub path), and the temperature measuring element is interposed between the vent holes 14. 9 is attached. The metal base member 8 is disposed on the downstream side of the temperature measuring element 9, and in the case of forward flow, the air flow passes through the metal base member 8 after passing through the temperature measuring element 9.

  For this reason, although heat from the power transistor 15 disposed on the electronic circuit board 7 is transferred from the electronic circuit board 7 to the metal base member 8, the heat transfer rate from the metal base member 8 to the resin member 19 is low. It is difficult to transmit to the measuring element 9.

  Further, the position where the temperature measuring element 9 is disposed has a cooling effect because the two large vent holes 14 are formed to face each other.

  Thereby, the temperature rise of the temperature measuring element 9 due to the heat of the metal base member 8 is suppressed.

  5 and 6 are diagrams illustrating an example of a temperature distribution of a CAE calculation result performed in order to confirm the effect of the first embodiment of the present invention. The scales in FIGS. 5 and 6 indicate temperature.

  FIG. 5 is a view showing a comparative example with respect to the first embodiment of the present invention, in which almost the entire one side surface of the auxiliary ventilation passage 5 is constituted by the metal base member 8, and the temperature measuring element 9 is the auxiliary air passage 5. This is a temperature distribution of the temperature measuring element 9 when it is arranged in the downstream portion of the temperature sensor and does not have the vent hole 14.

  On the other hand, FIG. 6 is a first embodiment of the present invention, and is a temperature distribution diagram when the distance L between the metal base member 8 and the temperature measuring element 9 is 6 mm or more.

  As can be seen by comparing the case of the example shown in FIG. 5 with the case of the first embodiment of the present invention shown in FIG. 6, the first embodiment of the present invention is the temperature transmitted through the metal base 8. The thermal influence on the measuring element 9 can be reduced.

  That is, the temperature of the temperature measuring element 9 is 28.25 degrees in the present invention with respect to the intake air temperature of 20 degrees, which is a significant improvement over the comparative example.

  FIG. 7 is a diagram showing a modification of the first embodiment of the present invention. In the example shown in FIG. 7, the groove 20 is formed on the resin member 19 on the side in contact with the metal base member 8, and the heat insulating effect by the air layer (heat insulating layer) corresponding to the groove 20 portion is obtained. This is an example in which the heat transmitted from 8 to the temperature measuring element 9 is further blocked.

  FIG. 8 is a diagram illustrating an example of a temperature distribution of a CAE calculation result performed in order to confirm the temperature rise suppression effect of the example illustrated in FIG.

  As can be seen from a comparison between the example shown in FIG. 8 and the example shown in FIG. 6, it can be understood that the example shown in FIG.

  Although FIG. 7 shows an example in which the groove 20 is formed, a through hole may be used instead of the groove 20.

  In addition, compared with the example of FIG. 5, the temperature rise of the temperature measuring element 9 was reduced by 56% in the example of FIG. Further, in the example of FIG. 8, the temperature rise of the temperature measuring element 9 is reduced by 65% compared to the example of FIG. 5.

(Second Embodiment)
FIG. 9 is a schematic cross-sectional view when the gas flow measuring device according to the second embodiment of the present invention is arranged in the air passage, FIG. 10 is a side view of one side of the gas flow measuring device according to the second embodiment, FIG. 11 is a side view of the other side of the gas flow rate measuring apparatus according to the second embodiment.

  The difference between the second embodiment and the first embodiment is that the auxiliary air passage 5 has a spiral shape in the second embodiment, and the resin member shown in FIG. 19 is not provided, and the temperature measuring element 9 is disposed in the vent hole 14 formed in the metal base member 8. Other configurations are the same as those of the second embodiment and the first embodiment, and the vent hole 14 is formed in the vicinity of the intake air inlet of the sub air passage 5.

  In the second embodiment, the resin member 19 is not interposed between the metal base member 8 and the vent hole 14, but the heat of the metal base member 8 is directly transmitted to the temperature detection element 9. In addition, since the vent hole 14 is formed in the vicinity of the intake air inlet of the sub air passage 5, the temperature rise of the temperature detecting element 9 due to the heat of the metal base member 8 can be suppressed.

  Here, in the vent hole 14 formed in the metal base member 8, the distance between the temperature detecting element 9 and the frame portion of the metal base member 8 forming the vent hole 14 is preferably 6 mm or more.

  In the second embodiment, it is also possible to form the groove 20 or the through hole as in the example shown in FIG.

  FIG. 12 is a diagram showing a specific configuration example of an operation control system of an internal combustion engine of an electronic fuel injection method using the gas flow rate measuring device of the present invention.

  In FIG. 12, the intake air 16 sucked from the air cleaner 100 includes a main pipe 3 in which the gas flow rate measuring device 1 is disposed, an intake duct 103, a throttle body 104, and an injector (fuel injection valve) 105 to which fuel is supplied. The air is sucked into the engine cylinder 107 through the intake 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 gas flow rate measuring device 1, an intake air temperature signal, a throttle valve angle signal output from the throttle angle sensor 111, an oxygen concentration signal output from the oxygen concentration meter 112 provided in the exhaust manifold 109, The engine rotational speed signal output from the engine rotational 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 gas flow rate measuring device 1 according to the present invention is used in an electronic fuel injection type internal combustion engine, an accurate air flow rate can be measured, and an accurate operation control of the internal combustion engine can be performed.

  The present invention can be heat shielded by a simple method of forming a ventilation hole in a member that conducts heat, and can also be applied to a measuring device that includes a temperature measuring element and that requires temperature measurement accuracy.

1 is an external perspective view of a gas flow rate measuring device according to a first embodiment of the present invention. It is sectional drawing at the time of arrange | positioning the gas flow measuring device which is the 1st Embodiment of this invention in an air path. It is a side view of one side of the gas flow measuring device which is the 1st embodiment of the present invention. It is a side view of the other side of the gas flow measuring apparatus which is the 1st Embodiment of this invention. It is a figure which shows the temperature distribution of the CAE calculation result in the comparative example with respect to this invention. It is a figure which shows the temperature distribution of the CAE calculation result in the 1st Embodiment of this invention. It is an external appearance perspective view of the modification in the 1st Embodiment of this invention. It is a figure which shows the temperature distribution of the CAE calculation result in FIG. It is a schematic sectional drawing of the state which attached the gas flow measuring device which is the 2nd Embodiment of this invention to the intake pipe. It is a side view of the one side of the gas flow measuring device which is the 2nd Embodiment of this invention. It is a side view of the other side of the gas flow measuring device which is the 2nd Embodiment of this invention. It is a figure which shows the specific structural example of the internal combustion engine of an electronic fuel injection system using the gas flow measuring device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal flow measuring device 2 Main passage 3 Main pipe 4 Insertion hole 5 Sub air passage 6 Flow measurement sensor element 7 Electronic circuit board 8 Metal base member 9 Temperature measurement element 10 Housing member 11 Cover member 12 Metal support 13 Metal terminal 14 Ventilation hole 15 Power transistor 16 Intake air 17 Heating resistor 18 Temperature sensitive resistor 19 Resin member 20 Groove 21 Sub air passage member 100 Air cleaner 103 Intake duct 104 Throttle body 105 Injector 106 Manifold 107 Engine cylinder 109 Exhaust manifold 111 Throttle angle sensor 112 Oxygen concentration meter 113 Engine speed meter 114 Control unit 115 Idle air control valve

Claims (9)

A sub-passage that takes in part of the gas flowing in the gas passage, a flow rate measuring element that is arranged in the sub-passage and measures the flow rate of the gas, and a temperature measurement element that is arranged in the sub-passage and measures the temperature of the gas And a gas flow rate measuring device having an electronic circuit that drives the flow rate measuring element and the temperature measuring element, and a housing member that protects the electronic circuit.
A metal base member that dissipates heat of the electronic circuit; the housing member has a thermal conductivity lower than that of the metal base member; and the sub-passage is formed by the housing member and the metal base member. A gas flow rate measuring device, wherein vent holes are formed in both side walls of the sub-passage forming portion of the housing member, and the temperature measuring element is disposed between the vent holes. In the gas flow measuring device according to claim 1,
The gas flow rate measuring device according to claim 1, wherein a size of the vent hole is larger than that of the temperature measuring element. A sub-passage that takes in part of the gas flowing in the gas passage, a flow rate measuring element that is arranged in the sub-passage and measures the flow rate of the gas, and a temperature measurement element that is arranged in the sub-passage and measures the temperature of the gas And a gas flow rate measuring device having an electronic circuit that drives the flow rate measuring element and the temperature measuring element, and a housing member that protects the electronic circuit .
A metal base member that dissipates heat of the electronic circuit, wherein the sub-passage is formed by the housing member and the metal base member, one of the vent holes is formed in the housing member, and the other of the vent holes Is formed on the metal base member, and the temperature measuring element is disposed between the vent holes. In the gas flow measuring device according to claim 3,
The gas flow rate measuring device according to claim 1, wherein a size of the vent hole is larger than that of the temperature measuring element. In the gas flow measuring device according to claim 3 ,
The heating resistance type flow rate measuring device, wherein the housing member is made of resin. In the gas flow measuring device according to any one of claims 1, 3, and 5,
A gas flow rate measuring apparatus, wherein a distance between the temperature measuring element and the metal base member constituting the sub-passage is about 6 mm. In the gas flow measuring device according to claim 3 or 5,
A gas flow rate measuring apparatus, wherein a heat insulating layer is formed by a groove or a through hole in the vicinity of the vent hole of the metal base member. In the gas flow measuring device according to claim 1 ,
A gas flow rate measuring device, wherein a heat insulating layer is formed by a groove or a through hole in the vicinity of the vent hole in the sub passage forming portion of the housing member. In an internal combustion engine operation control system,
9. An operation control system for an internal combustion engine, wherein fuel control is performed using the gas flow rate measuring device according to any one of claims 1 to 8.

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