JP3782650B2 - Air flow measurement device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air flow measurement device that constitutes an intake system of an internal combustion engine and measures the intake air flow rate thereof, and more particularly to a heating resistance type air flow measurement device that is suitable for measuring the air flow rate taken into an automobile engine. About.
[0002]
[Prior art]
Conventional air flow meters areHei 4-75385As shown in the gazetteThe sub-channel has a structure where both ends of the main channel are supported in a bridge shapeIt was.
[0003]
[Problems to be solved by the invention]
However, the patent gazette Four − 75385 No. 1 does not disclose the mounting method of the main flow path, the sub flow path, and the circuit portion, and the sub flow path has a structure in which the main flow path is supported at both ends in a bridge shape. Regardless of the size, the standardized module was not applicable to various internal combustion engines. In addition, since the structure of the sub-flow channel is complicated, there is a concern about deterioration of measurement accuracy, and it is necessary to combine several parts to form, so that it is not suitable for practical use because of high cost.
An object of the present invention is to provide an air flow rate measuring apparatus having a sub-flow path that is small and has good mounting properties to a main flow path.
[0004]
[Means for Solving the Problems]
  The object is that a circuit housing incorporating an electronic circuit, a sub-channel constituent member in which a sub-channel is configured, and a detection element disposed in the sub-channel are configured integrally, and the sub-channel configuration The member is inserted from an insertion hole provided in a wall constituting the main flow path, and the sub flow pathButIn the main channelCantilever the secondary flow path component so that it is positionedIn the air flow rate measuring device to be installed, the sub-flow channel includes an opening surface that opens toward the upstream side of the main flow channel, and a first flow that guides the air that has passed through the opening surface toward the insertion hole. And a second flow path for guiding the air that has passed through the first flow path in a direction opposite to the direction.The sub-flow path component is made of plastic and is integrally assembled with a plastic holder on the circuit housing side, and the plastic holder is a metal base member on the opposite side of the sub-flow path component And a terminal to which the detection element is fixed penetrates the inside of the holder and the detection element is integrated with the sub-flow path component so that the circuit housing is The plastic holder is fixed to the metal base member on the opposite side of the plastic holder, and the plastic holder is formed by insert-molding the metal base member at the time of molding the holder. The sub-flow path component member that is integrated and cantilevered in the sub-flow path is the plastic holder and the The metal base member is supported by a wall constituting the main flow path via a base member made of a metal, the metal base member has a screw insertion hole, and the metal base member is formed on the wall constituting the main flow path. Fixed with screwsThis is achieved by an air flow measuring device.
  In addition, the object is that a circuit housing incorporating an electronic circuit, a sub-channel constituent member in which a sub-channel is configured, and a detection element disposed in the sub-channel are integrally configured, and the sub-stream The sub-flow path is inserted through an insertion hole provided in a wall constituting the main flow path.ButIn the main channelCantilever the secondary flow path component so that it is positionedAn air flow rate measuring device to be installed, wherein the sub-flow path includes an inlet opening surface that receives dynamic pressure from the flow of the main flow path, and a first air that guides the air that has passed through the inlet opening face toward the insertion hole. A flow path, a second flow path for guiding the air that has passed through the first flow path in a direction opposite to the direction, and an outlet portion through which the air that has passed through the second flow path exits the main flow path. A portion of the air flowing through the main flow path passes through the sub-flow path due to a pressure difference between the inlet opening surface and the outlet portion.The sub flow path component is made of plastic, and is integrally assembled with a plastic holder on the circuit housing side, and the plastic holder is made of metal on the opposite side of the sub flow path component. The circuit housing is integrated with the sub-flow path component so that a terminal fixed to the base member and the detection element is fixed penetrates the holder and the detection element is positioned in the sub-flow path. Is fixed to the metal base member on the opposite side of the plastic holder, and the plastic holder is formed by insert-molding the metal base member when the holder is molded. The sub-flow path component that is integrated with the member and cantilevered in the sub-flow path is a plastic holder. And the metal base member are supported by a wall constituting the main flow path, the metal base member has a screw insertion hole, and the metal base member constitutes the main flow path Fixed to the wall with screwsThis is achieved by an air flow measuring device.
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments will be briefly described below, and will be described in detail later with reference to the drawings.
  In order to reduce the system cost of the internal combustion engine, the cost of the heating resistance type air flow rate measuring device is reduced and the number of parts of the system is reduced by integrating with other intake system parts. First, by making a module in which the circuit part and the sub-flow part are integrated, a relatively high-cost flow meter body is formed with a main flow path that is a simple pipe line, a hole provided in the wall surface of the main flow path, and a fixed surface of the circuit. Constructed to enable significant cost reduction. In addition, the shape of the parts that make up the secondary flow path is simplified and miniaturized, making it easy to integrate with the circuit part, and integrating the parts that connect the circuit part and the secondary flow path part to reduce the cost of the air flow measurement device. Reduction achieved. In addition, since the shape of the flow meter body has been simplified, it is possible to form the flow meter body integrally with other intake system components without creating a separate member, thereby reducing the number of system components. Also, a standardized module can be applied even if the position where the main channel is set or the size of the main channel changes.
[0005]
In order to reduce the size and weight, the sub-flow path can be simplified without sacrificing its function, the total length of the sub-flow path can be maintained by the curved flow path, and the right-angle bend of the sub-flow path of the temperature sensing resistor The length of the secondary flow path in the main flow direction is reduced by, for example, arranging the second passage perpendicular to the main flow direction of the secondary flow path into a cross-sectional shape that is longer in the direction perpendicular to the main flow direction than the main flow direction. The second passage that is perpendicular to the direction is kept short to reduce the size and weight of the members that make up the sub-channel, and the proportion of the sub-channel components in the main channel is reduced. As a structure that does not increase the cross-sectional area of the main flow path by making it difficult to occur, the main flow path can be reduced in size and weight. In addition, the hole in the wall surface of the main channel for inserting the sub channel can be made into a circular shape with a small diameter without increasing the ratio of the width and length of the members constituting the sub channel. Can be made easier to cope with downsizing of the circuit.
[0006]
As countermeasures for environmental changes, measures are taken to cope with changes in the air flow in the main flow path depending on the position of the intake system and to changes in temperature depending on the position where the air flow measuring device is placed. For measurement errors caused by pulsating flow in the main flow path, the sub-flow path is an L-shaped curved flow path, and the ratio of the length of the first and second passages parallel to the main flow direction is optimal. For the occurrence of backflow, the outlet opening surface of the sub-flow path is formed in a plane parallel to the main flow direction, and an eave-like projection is provided upstream of the outlet portion. To prevent measurement errors due to main flow drift, the inlet opening surface of the sub-flow channel is shaped like a saucer, an inclined surface is provided upstream of the outlet, and the arrangement of the outlets of the sub-flow channels in the main flow channel is optimized. For turbulent flow and swirling flow in the main flow path, the total length of the sub flow path is made sufficiently long so that the cross-sectional area of the second passage can be made larger than the cross-sectional area of the first passage. An inclined surface with walls is provided. For temperature changes, a temperature-sensitive resistor that measures the temperature of the intake air is fixed near the inner corner of the right-angle bend of the secondary flow path at a position away from the base member, and the heating resistor is the temperature-sensitive resistor. It is fixed at a position closer to the base member. Further, in order to prevent the measurement accuracy from deteriorating due to the fixed position of the heating resistor, the interval between the heating resistors is optimized from the saucer-shaped bottom surface of the inlet opening of the sub-flow channel and the corner formed by the first passage.
[0007]
For variations in the mounting of the module to the main flow path, the main flow direction with the inlet opening surface of the sub-flow path such as a rectangular or trapezoidal cross-section is parallel to the base member of the sub-flow path portion of the member constituting the sub-flow path A shape that provides a plane that is perpendicular to the main flow direction and a plane that is parallel to the main flow direction, and that the outlet opening surface of the secondary flow path is formed in a plane parallel to the main flow direction, and the outlet direction of the inlet opening surface is dug It corresponds by doing.
[0008]
For improved handling, the circuit part and the sub-flow channel part are integrated modules, the insertion hole of the main flow channel is sized to be covered by the base member, and it is inserted by an O-ring, packing gasket, etc. By making it possible to prevent air leakage from the hole, forming a groove for mounting the O-ring to achieve modularization with the O-ring, and fixing the module to the main flow path in a removable manner It corresponds.
[0009]
The module can be handled as a single product by combining the circuit unit and the sub-flow channel unit into a module that has most of the functions of a heating resistance type air flow measuring device. As a result, a company that organizes the internal combustion engine, for example, an automobile manufacturer, can obtain an inexpensive heating resistance type air flow measuring device, and can freely layout the intake system.
[0010]
The module protects the electronic circuit by the circuit housing and the cover, and the heating resistor and the temperature sensitive resistor are protected by the sub-flow path constituting member, thereby preventing an accident due to handling.
[0011]
By making the sub-flow path an L-shaped curved flow path, the total length of the sub-flow path can be set sufficiently long, so that the air in the vicinity of the heating resistor due to the disturbance of the air flow in the main flow path at the outlet of the sub-flow path The impact on the flow is reduced. In addition, the structure in which inclined surfaces with walls on both sides are provided upstream of the outlet of the sub-flow path, and the flow of the main flow path at the sub-flow path outlet section has a stable and stable flow with strong inertial force. The turbulence itself is reduced. The inlet opening surface of the secondary channel is opened in a plane perpendicular to the flow direction of the main channel, and the outlet opening surface is opened in a plane parallel to the main flow direction. This is because the pressure difference between the inlet and outlet is increased by pulling, the flow velocity of the air flowing into the auxiliary flow path is increased, and the flow in the auxiliary flow path is stabilized. Furthermore, the reason why the cross-sectional shape of the second passage of the sub-flow path is wide is that the sub-flow path is bent at a right angle by ensuring the cross-sectional area while keeping the length of the sub-flow path component member in the main flow direction short. This is to compensate for the decrease in the flow area of the second passage due to the separation of the generated flow, to prevent the flow velocity of the air flowing into the sub-flow path from decreasing, and to stabilize the flow in the vicinity of the heating resistor. Thus, by stabilizing the flow in the sub-flow channel, particularly in the vicinity of the heating resistor, there is an effect of reducing the output noise of the air flow rate measuring device and improving the measurement accuracy. In addition, the L-shaped sub-channel has a negative error caused by the nonlinearity of the heat dissipation characteristics of the heating resistor when the pulsating flow is generated in the main channel and the response delay, and the relative length of the main channel between the inlet and outlet of the sub-channel. By increasing the length of the secondary flow path and giving the inertial effect to the flow in the manufacturing flow path, the output during pulsation is changed positively to offset the negative error, and the output error due to pulsation is reduced. effective. The length of the second passage is doubled with respect to the length of the first passage of the sub-flow passage, which is optimal for canceling out the minus error in the degree of inertia effect in the L-shaped sub-flow passage. It is a length ratio. Furthermore, since the outlet opening surface of the sub-flow channel is provided on a surface parallel to the base member and the sub-flow channel component member is fixed to the circuit side, the sub-flow channel is fixed to the wall surface of the main flow channel by fixing the circuit portion. Even if the size of the main flow path is different because it is fixed to the main flow path and is cantilevered, the center of the main flow path and the sub flow path It is possible to apply a standardized module without changing the position of the doorway.
[0012]
The reason why the heating resistor is arranged in the first passage and the temperature sensitive resistor is arranged at the right-angled bent portion is to make it possible to keep the length of the first passage short, so that both resistors are arranged close to each other. Therefore, the heat generation resistor is arranged in the first passage which can easily stabilize the flow, thereby reducing measurement errors. If the length of the first passage is shortened to shorten the main flow and the changed length of the auxiliary flow path component, the length of the auxiliary flow path component may increase the pressure loss of the air flow meter. Since the insertion hole for inserting the sub flow path provided on the wall surface of the main flow path can be made into a relatively small circle, the formation of the insertion hole is facilitated. Complicated and large road formation can be prevented. Further, since the insertion hole can be sized to be covered by the base member, a margin for further miniaturization of the circuit portion can be secured, and an O-ring, between the bottom surface of the base member and the circuit portion fixing surface of the outer wall of the main channel, Sealing with packing, gasket, etc., can prevent air leakage inside and outside the main flow path from the insertion hole, and measurement errors due to air leakage can be prevented. Further, since the insertion hole is circular, a diameter seal by an O-ring is possible.
[0013]
Using the base member as a reference, the terminal is held by the holder and fixed so as to penetrate the base member, the electronic circuit and the circuit housing are fixed to the upper surface of the base member, the upper surface of the circuit housing is covered with a cover, Fix the heating resistor and temperature sensitive resistor to the terminal or holder on the lower surface, and insert the holder and terminal into the hole provided in the sub flow path component so that the heat generating resistor and temperature sensitive resistor are in the sub flow path. The method of fixing the sub-flow path constituting member to the holder or the base member so as to be positioned is easy to manufacture and can reduce the production cost. Furthermore, since the base member and the circuit housing, and the base member and the holder can be integrated, the number of parts can be reduced and the cost can be further reduced. In addition, each part can be fixed without requiring additional parts for fixing such as insert molding, adhesion, and welding. Furthermore, a groove can be formed in the joint surface between the sub-flow path component member and the holder or the base member, and if an O-ring is attached to the groove, the O-ring for sealing the insertion hole can be removed without worrying about dropping off. An integrated module can be obtained, and a module with improved handling can be obtained.
[0014]
The external shape of the cross section parallel to the base member of the sub flow channel portion of the sub flow channel component is rectangular or trapezoidal, such as a shape perpendicular to the main flow direction with the inlet opening surface of the sub flow channel and a shape parallel to the main flow direction. By doing so, it is possible to reduce measurement errors due to variations in the mounting angle with respect to the module rotation direction when the module is mounted on the main flow path. If the mounting angle of the module is bent with respect to the flow direction of the main flow path, the effective area of the inlet opening surface of the sub flow path (the area projected on the cross section perpendicular to the main flow direction) decreases, and therefore flows into the sub flow path. It acts to reduce the air flow rate and cause a negative output error. On the other hand, the surface parallel to the main flow of the sub-flow path component member reduces the effective area of the main flow path if the mounting angle of the module is bent. Therefore, both effects are offset and measurement errors due to variations in module mounting angles can be reduced. Considering the cross-sectional area of the general main channel and the size of the sub-channel constituent member, the length in the main flow direction of the surface parallel to the main flow direction is about twice the width of the sub-channel inlet opening. The above offset effect is appropriate. The shape of the cross-sectional shape parallel to the base member of the sub-channel portion of the sub-channel constituent member and the shape of the trapezoid or the combination of the trapezoid and the rectangle does not impair the effect of reducing the influence of the mounting angle. This is because the dynamic pressure generated on the upper surface of the auxiliary flow path component is reduced without reducing the cross-sectional area of the two passages, and the pressure loss of the air flow rate measuring device is reduced. Furthermore, the reason why the downstream bottom surface of the sub-flow path component is formed in an arc shape is to reduce the pressure vortex in the downstream and reduce the pressure loss, and the cross section of the second passage can also be enlarged with an arc shape on one side. This is because of this. The reason why the length of the longest diagonal line of the cross-sectional profile of the sub-channel and the diameter of the circular insertion hole provided in the wall surface of the main channel are substantially the same is to keep the insertion hole small.
[0015]
The outlet shape of the inlet opening surface of the sub-channel is made into a saucer shape so that air is taken into the sub-channel from a wide area of the main channel, and when a drift occurs in the main channel The first object is to reduce measurement errors. The effect of reducing the measurement error at the time of drift is also on the inclined surface upstream of the sub-channel outlet. If the flow velocity upstream of the outlet increases due to the drift, the separation zone that occurs downstream of the inclined surface widens, the suction effect of the sub-channel outlet increases, and the air flow rate flowing into the sub-channel increases. As the flow rate becomes slower, the separation area at the outlet becomes smaller and the flow rate of air flowing into the secondary flow path decreases. If an entrance is installed in the relationship, measurement errors due to drift can be reduced. This action is most effective when the first passage is provided at a position decentered from the center of the main flow path, the saucer-shaped portion is expanded to a range including the vicinity of the center of the main flow path, and the outlet of the sub flow path is connected to the main flow path. It is when it is provided in the opposite part of the entrance with respect to the center. In addition, the saucer-shaped inlet opening has an effect of reducing measurement errors due to variations in inclination in the upstream and downstream directions of the sub-channel constituent member due to the inclination of the insertion hole of the circuit fixing surface and the main channel wall surface. When the outlet direction of the sub-channel is inclined in the upstream direction of the main channel, the outlet opening surface is tilted in a direction that can be seen from the upstream side of the main channel, so that some dynamic pressure is generated on the outlet port surface or negative pressure is generated. Since the pressure decreases, the pressure difference between the inlet and outlet of the secondary flow path becomes small, the flow rate of air flowing into the secondary flow path decreases, and a negative measurement error occurs. On the other hand, the saucer-shaped opening surface is inclined in the direction in which the first passage is downstream, so that the flow in the vicinity of the center of the main flow path can be more easily guided to the sub flow path, and the separation zone generated in the first passage becomes larger and heat is generated. In order to increase the flow velocity in the vicinity of the resistor, it acts to generate a measurement error on the plus side. Since both these actions cancel each other, the measurement error due to the variation in the inclination of the sub-flow passage constituting member can be reduced. On the other hand, if the outlet is tilted so as to be on the downstream side, the outlet portion has a negative pressure, and the inlet portion is inclined in a direction in which it is difficult to take air into the sub-flow path, and the separation area in the first passage is reduced. The measurement errors can be reduced by canceling out the effects of each other.
[0016]
The temperature sensing resistor is fixed at a position away from the base member from the center line of the first passage. The temperature sensing resistor is positioned near the inner corner where the flow velocity is the fastest among the right angle bends, and the detection accuracy of the intake air temperature In a temperature environment where there is a difference between the intake air temperature and the ambient temperature of the air flow measuring device, heat transfer through the terminal or holder, for example, when the ambient temperature is high, This is to provide an effect of reducing the intake air temperature detection error such that the temperature of the temperature sensitive resistor becomes higher than the intake air temperature due to the heat transmitted through the terminal. If the temperature-sensitive resistor is erroneously measured higher than the intake air temperature, a positive flow measurement error occurs. On the other hand, the heating resistor acts to generate a flow measurement error on the minus side because the heat radiation amount due to heat conduction to the terminal and the boulder decreases in an environment where the ambient temperature is high. Therefore, if the influences on both resistors are made equal, measurement errors in an environment where the intake air temperature and the ambient temperature are different can be reduced. Actually, the effect of heat conduction and the effect of heat transfer to the air differ depending on the temperature difference between the two resistors. However, it is not sufficient, and it is preferable to increase the thermal resistance on the temperature-sensitive resistor side and to decrease the thermal resistance on the heat-generating resistor side than on the temperature-sensitive resistor side. Both resistors to reduce the measurement error under the above temperature environment by fixing the temperature sensitive resistor at a position away from the base member and fixing the heating resistor closer to the base member than the temperature sensitive resistor An appropriate thermal balance of the body can be easily obtained.
[0017]
The position of the heating resistor in the first passage needs to be arranged in the main flow in the first passage, that is, in a stable flow with a high flow velocity. Therefore, when arranging the heating resistors in consideration of the temperature environment as described above, not only the positional relationship with the temperature sensitive resistor but also the position in the first passage must be considered. In the case of a simple circular pipe passage, the main flow is near the center, but as a factor for determining the position of the main flow in the first passage in the right-angled bending passage having a saucer-like opening surface, the bottom surface of the saucer-like inlet opening surface The separation flow generated by the first corner formed by the first passage causes the main flow to move in the direction of the base member rather than the pipe center, and the flow velocity near the inner corner (second corner) becomes faster at the right-angled bend. Therefore, there is an action of moving the main flow in a direction away from the base member rather than the center of the pipe line. That is, the positional relationship between the first corner and the second corner affects the position of the mainstream in the first passage, and the inner wall and the heating resistor farthest from the base member of the first passage, which is the wall surface connecting both corners. The heating resistor can be disposed in the main flow of the first passage. In a general size of the secondary flow path, a portion separated from the inner wall farthest from the base member of the first passage in the direction of the base member by 1/2 to 1 times the interval between the first corner and the second corner. It becomes the mainstream range of the first passage.
[0018]
The reason why the sectional shape of the first passage is a combination of a semicircle and a rectangle is to arrange the heating resistor in the main flow of the first passage while making the positional relationship between the heating resistor and the temperature sensitive resistor appropriate. Is one of the means. That is, the position of the heating resistor is optimized from the relationship with the temperature sensitive resistor, and the base member having the first corner and the second corner in order to move the mainstream position of the first passage to the vicinity of the heating resistor. It is made into the shape which can set the position of the 1st channel | path inner wall furthest away from the position freely.
[0019]
As described above, the configuration of the sub-flow channel portion of the present invention has many functions with respect to environmental changes, mounting variations, and wearability. However, the sub-flow channel component member needs to be combined with a plurality of parts. There is no simple shape that can be formed as a single plastic molded product. Therefore, the cost of the module itself can be reduced. In addition, because the shape of the main flow path has been simplified, the module has a function and structure that can be handled as one product, and it can cope with environmental changes and mounting variations, other intake system components In addition, the main flow path can be integrated, and the module can be standardized, so that the system cost of the internal combustion engine can be reduced. Furthermore, since the module can be fixed to the main flow path simply by attaching the circuit portion to the outer wall of the main flow path, the module is easy to mount and can be fixed detachably. If detachable fixing is adopted, it is possible to easily cope with failure in the market by replacing only the module part.
[0020]
nextEmbodiments of the present invention will be described with reference to FIGS.
[0021]
FIG. 1 is a cross-sectional view of an embodiment of the present invention, and FIG. 2 is an external view as viewed from the upstream side (left side).
[0022]
An electronic circuit 8 and a circuit housing 9 are fixed to the upper surface of the base member 7, and a connector 11 for electrically connecting to an external device is integrated with the circuit housing 9. The upper surface of the circuit housing 9 is covered with a cover 10. It has been broken. The terminal 13 that is electrically connected to the electronic circuit 8 is pulled out toward the lower surface of the base member 7, and the heating resistor 1 and the temperature sensitive resistor 2 are electrically connected to the terminal 13 and fixed. The auxiliary flow path 3 includes an inlet opening surface 301 that opens in a plane perpendicular to the base member 7, a first passage 302 that extends parallel to the base member from the inlet opening surface, and a first passage that extends in a direction perpendicular to the base member. L constituted by a second passage 304 having a length of about twice, an outlet opening surface 305 that opens in a plane perpendicular to the base member, and a right-angled bent portion 303 corresponding to the intersection of the first passage 302 and the second passage 304. The sub-flow path constituting member 4 is fixed to the base member 7 so that the heating resistor 1 is located in the first passage 302 and the temperature-sensitive resistor 2 is located in the right-angle bent portion 303. . As described above, a module in which the circuit unit and the sub-flow channel unit of the heating resistance type air flow rate measuring device are integrated is configured.
[0023]
On the other hand, the wall surface of the flow meter body 6 constituting the main flow path 5 is provided with an insertion hole 14 for inserting the sub flow path constituting member 4 and a mounting fixing surface 15 for attaching the base member 7. The sub flow path component member 4 is inserted into the main flow path 5 from the insertion hole 14 so that the first passage 302 of the sub flow path 3 is parallel to the flow direction 17 of the main flow path 5 into the flow meter body 6. The base member 7 is fixed to the outer wall of the main flow path by screws 18 with a rubber packing 16 sandwiched between the mounting fixing surface 15 and the bottom surface of the base member 7 so that the periphery of 14 is sealed.
[0024]
FIG. 3 is a cross-sectional view of the embodiment in which the configuration for reducing the deterioration of measurement accuracy under various environments and the fixing method of the sub-flow channel component member and the base member are embodied in FIG. FIG. 4 shows an external view seen from the side (left side).
[0025]
The terminal 13 is integrated with the holder 19 so that the terminal 13 penetrates the inside of the holder 19, and the base member 7 and the holder 19 are fixed through the hole of the base member 7. Here, various fixing methods of the terminal 13, the holder 19, and the base member 7 are listed. The terminal 13 and the base member 7 are made of metal and the holder 19 is made of plastic. A method of integrating the three members by insert molding, a method of insert-molding the terminal 13 and the holder 19 and fixing them to the base member 7 by adhesion or the like, or a separate member in FIG. A method of insert molding the terminal 13 with the holder 19 as one plastic molded product, and insert molding the terminal 13 with the circuit housing 9, the base member 7 and the holder 19 as one plastic molded product in order to minimize the number of parts. There are ways to do this. The electronic circuit 8 is fixed to the upper surface of the base member 7 or the holder 19 and is electrically connected to the terminal 13 via a conductive member 22 such as a wire. The circuit housing 9 is also fixed to the upper surface of the base member 7, and the upper surface of the circuit housing 9 is covered by fixing the cover 10.
[0026]
On the other hand, the heating resistor 1 and the temperature sensitive resistor 2 are electrically connected and fixed to the opposite end of the electronic circuit 8 of the terminal 13. In this embodiment, the temperature-sensitive resistor 2 is fixed so as to be positioned near the inner corner of the right-angled bending portion 303 of the sub-flow channel 3, and the heating resistor 1 is located in the first passage 302 of the sub-flow channel 3. Thus, the temperature error is fixed so that it is closer to the base member 7 than the temperature sensitive resistor 2, so that the measurement error can be reduced even in an environment where the temperature changes rapidly.
[0027]
Similarly to the first embodiment, the auxiliary flow path component 4 has an L-shaped flow formed by an inlet opening surface 301, a first passage 302, a right angle bend 303, a second passage 304, and an outlet opening surface 305. In addition to the path, the flow of the saucer-shaped inlet 306 and the outlet part that have been dug out leaving a wall in the periphery for the purpose of guiding the air taken into the sub-flow path 3 from a wide range, particularly from the vicinity of the center of the main flow path 5 An inclined surface 307 having walls on both sides for the purpose of stabilization, an outlet rod 308 in which the tip of the inclined surface is made to travel below the outlet opening surface 305, and a hole 401 for inserting the holder 19 and the holder 19 The joint surface 402 is provided. Further, the first passage 302 of the sub-passage 3 has a flow position of the first passage 302 so that the fixing position of the heating resistor 1 is set closer to the base member 7 than the center of the first passage 302 with priority given to the temperature effect. In order to bring the stable range of the heating resistor 1 to the fixing portion of the heating resistor 1 in a vertical section, the flow velocity is relatively fast, and the sectional shape is a combination of a semicircular shape and a rectangular shape. The distance between the inner wall of the first passage 302 that connects the corners formed by the passage 302 and the inner corner of the right-angled bent portion 303 and the heating resistor 1 is set to 1/2 to 1 (the same interval). ing. Further, a meat stealing hole 403 parallel to the second passage 304 is provided to make the auxiliary flow path component member 4 uniform, thereby preventing a shape change due to sink marks of plastic molding, and reducing material costs and weight.
[0028]
The sub-flow path constituting member 4 is inserted and fixed to the holder 19 at the joint surface 402 by inserting the holder 19 into the holder insertion hole 401. Here, the groove portion 404 is formed by the step provided on the holder 19 and the joining surface 402 of the sub-flow channel constituting member. The groove 404 is a mounting groove for the O-ring 20, and the insertion hole 14 on the wall surface of the main flow path is sealed by the O-ring 20. As described above, a module in which the circuit portion, the sub flow channel portion, and the O-ring for sealing the insertion hole are integrated is configured.
[0029]
By fixing this to the flow meter body 6 as in the first embodiment, a heating resistance type air flow rate measuring device is completed. In this embodiment, since the O-ring for sealing the insertion hole is mounted on the module, no rubber packing is required. In this embodiment, the circuit housing 9 is fixed together with the base member 7 with screws 18 to increase the fixing strength of the circuit housing, and the rectifying grid 21 is formed on the inlet face of the main flow path 5 of the flow meter body 6. It shows the one that is equipped with and further improved measurement accuracy.
[0030]
FIG. 5 is a cross-sectional view of a module in which the circuit portion and the sub-flow passage portion of the heating resistance type air flow measuring device shown in the second embodiment are integrated, and FIG. 6 is an external view seen from below (outlet direction). FIG.
[0031]
The external shape of the cross section of the auxiliary flow path component 4 parallel to the base member 7 is such that the insertion portion of the holder 19 is circular and the auxiliary flow path portion is first with respect to the length of the side perpendicular to the flow direction of the first passage. It is a rectangle in which the length of the side parallel to the flow direction of the passage is 1 to 2 times. Further, the outer shape of the portion of the holder 19 that is inserted into the insertion hole 14 of the main channel wall surface is also circular, and the diameter thereof is substantially equal to the length of the diagonal line of the rectangular cross section of the sub-channel unit. The insertion hole can be a relatively small circle. Furthermore, the opening width perpendicular to the flow direction of the second passage 304 of the inlet opening surface 301 of the sub-flow channel is about ½ of the length of the side parallel to the first passage 302 of the rectangular cross section of the sub-flow channel portion. The cross-sectional shape of the second passage 304 is a rectangle whose side is perpendicular to the side parallel to the first passage 302.
[0032]
7 and 8 are external views as seen from the bottom of FIG. 5, as in FIG. 6. 7 shows that the outer shape of the section parallel to the base member 7 at the portion inserted into the insertion hole 14 on the wall surface of the main channel of the holder 19 is a circle having the same diameter as that of FIG. 6, and the shape of the second channel 304 of the sub channel is also shown. 6, the external shape of the cross section parallel to the base member 7 of the sub flow path portion of the sub flow path constituting member 4 is a combination of a trapezoid and a rectangle. In FIG. 8, the downstream bottom surface of the second passage and the downstream bottom surface of the cross-sectional shape of the sub-flow channel portion are arcuate.
[0033]
FIG. 9 shows a heating resistance type air flow measuring device in which the module shown in FIG. 5 is inserted into a throttle body 24 having a valve 23 for controlling the intake air amount of the engine. The flow rate measuring unit is arranged upstream of the valve, and the air flows from the left side to the right side in the figure. Although the throttle body integrated heat resistance type air flow meter having the auxiliary air passage has already been commercialized, the auxiliary air passage member is formed integrally with the throttle body, or the housing member that covers the module circuit is provided. Since it is integrated with the throttle body, the structure of the throttle body is considerably complicated. On the other hand, according to the embodiment of the present invention shown in FIG. 9, since the housing member and the sub air passage member are integrated with the module, the structure of the throttle body can be simplified. In addition, in an intake system (for example, a diesel vehicle) that does not have a throttle valve, the module can be directly mounted on the intake manifold.
[0034]
FIG. 10 shows an embodiment in which the module shown in FIG. 5 is attached to a part of the air cleaner arranged in the engine room. The air cleaner is a filter for removing dust in the air with an upstream case member 26 having an introduction duct 25 for taking in new air, and a downstream case member 27 having a duct 28 for connecting the intake duct 30 and the air cleaner. The member 29 is sandwiched and fixed. Naturally, the air flow flows as shown by the arrows in the figure, and clean air from which dust has been removed by the filter 29 flows through the duct 28. Here, there is an insertion hole 14 for inserting a sub air passage portion of the heating resistance type air flow measuring device in a part of the duct 28, and this is mechanically connected between the duct 28 and the module using screws or the like. Fix it. As a result, the main air passage can be formed by using a part of an air cleaner such as the duct 28 instead of the body constituting the main air passage described above, and an inexpensive heating resistance type with a single module that does not require a body. An air flow measurement device can be provided.
[0035]
The example shown in FIG. 11 basically shows an embodiment in which the module shown in FIG. 5 is attached to a part of the air cleaner as in FIG. In FIG. 10, the module portion of the heating resistance type air flow measuring device is attached to a part of the duct 28 provided outside the downstream case member 27, but in FIG. 11, the duct 31 is provided inside the downstream case member 27. In this example, the insertion hole 14 is provided in a part of the duct 31 and the module is attached. In the figure, the tip portion of the duct 31 has a bell mouth shape to rectify the air flow. Since the length of the portion corresponding to the duct 28 shown in FIG. 10 can be shortened by inserting the module of the heating resistance type air flow measuring device into the air cleaner as in this structure, the intake system can be made compact. It is. The duct 28 shown in FIG. 10 and the duct 31 shown in FIG. 11 are described integrally with the case member 27 on the downstream side of the air cleaner in the drawing, but each may be manufactured separately and fixed to maintain mechanical strength afterwards. It doesn't matter.
[0036]
FIG. 12 is a cross-sectional view of a heating resistance type air flow measuring device showing another embodiment, and FIG. 13 is a view as seen from the upstream side (left side). The difference from FIGS. 3 to 4 is that the inner diameter of the body 32 constituting the main air passage is increased. If the inner diameter of the body is increased, the first passage 302 and the inlet opening surface 302 in which the heating resistor 1 for measuring the flow rate is arranged in the sub air passage are shifted closer to the body wall surface. In this case, if a drift occurs in the air flow in the body 32 due to the upstream shape (air cleaner and duct shape) of the body 32, the measurement by the heating resistance type air flow measuring device is caused by the drift in a place near the wall surface. An error will occur. Normally, the flow velocity distribution flowing in the pipe shows a distribution close to a parabola so that the center portion of the pipe has the highest flow velocity and becomes slower as it approaches the wall surface. That is, it is desired that the flow velocity is faster than the average flow velocity at the center in the pipe and is slow on the wall surface, and the average value of the flow velocity is measured at a position shifted from the center. For this reason, in the product of the present invention, the inlet / outlet of the auxiliary air passage is shifted from the center of the pipe so that the average flow velocity value is taken into the auxiliary air passage (the flow velocity value flowing in the auxiliary air passage is determined by the inlet / outlet). This is a pressure difference, and it is necessary to shift the inlet and outlet from the center of the pipe). However, in most of the drift, the position where the flow velocity is the fastest is shifted from the center position, and one shows a fast flow velocity value and the other shows a slow flow velocity value. For this reason, if the inlet opening surface 301 of the sub air passage is at a position with a fast flow velocity distribution, a measurement error on the plus side of the average flow velocity occurs, and conversely on the slow position, a measurement error on the minus side occurs.
[0037]
Thus, even when the inner diameter of the body 32 is increased, the mounting surface 33 for attaching the base member 7 to the body 32 is dug down from the outer diameter of the body 32 as shown in FIG. The module mounting portion has a different diameter, and the distance between the center of the inner diameter of the body 32 and the entrance / exit is substantially the same. In this case, since the inner wall of the body 32 becomes convex at the module mounting portion, the upstream and downstream portions of the body 32 may be gently inclined as shown in FIGS. 34 and 35 so as not to disturb the air flow as much as possible. desired.
[0038]
Finally, FIG. 14 shows an embodiment in which the product of the present invention is applied to an electronic fuel injection type internal combustion engine.
[0039]
The intake air 101 sucked from the air cleaner 100 is sucked into the engine cylinder 107 via a manifold 106 including a body 102 of an exothermic resistance type air flow measuring device, an intake duct 103, a throttle body 104, and an injector 105 to which fuel is supplied. Is done. On the other hand, the gas 108 generated in the engine cylinder is discharged through an exhaust manifold 109.
[0040]
An air flow rate signal output from the circuit module 110 of the heating resistance type air flow meter, a throttle valve opening signal output from the throttle angle sensor 111, and an oxygen concentration signal output from the oxygen concentration meter 112 provided in the exhaust manifold 109 And a control unit 114 for inputting a rotational speed signal output from the engine rotational speed meter 113 calculates these signals to obtain an optimal fuel injection amount and an idle air control valve opening, and these values are obtained as the values for the injector 105 and the idle speed. The air control valve 115 is controlled.
[0041]
Heat resistance type air flow measuring deviceThe module can be handled as one product by giving the module most of the functions, for example, by attaching the module to a part of the air cleaner or a part of the intake duct, etc. In addition, since one type of module can be used for each engine, matching and the like are facilitated, and the system cost of the internal combustion engine can be reduced.
[0042]
In addition, in the heating resistance type air flow measurement that requires a body constituting the conventional main air passage, the body that occupies a large weight in the cost can be made into a simple cylindrical shape. In addition, by providing a function as a heating resistance type air flow measurement device in one type of module as described above, the standardization of the heating resistance type air flow measurement device corresponding to the displacement of the mounted engine is achieved only by the main diameter of the body. As a result of these effects, the cost can be reduced by about 10 to 20% compared to a conventional heating resistance type air flow rate measuring device having a body integrated with a sub air passage.
[0043]
Furthermore, even if any abnormality occurs in the heating resistance type air flow measuring device in the market, it is possible to improve the handling of the heating resistance type air flow measuring device in the market because only a single module needs to be replaced. .
【The invention's effect】
According to the present invention, it is possible to realize a sub-flow-type air flow rate measuring apparatus that is small and has good mounting properties to the main flow path.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a heating resistance type air flow measuring device showing an embodiment of the present invention.
FIG. 2 is a diagram of FIG. 1 as viewed from the upstream side of the air flow.
FIG. 3 is a cross-sectional view of a heating resistance type air flow measuring device showing one embodiment for the purpose of improving measurement accuracy.
4 is a view of FIG. 3 as viewed from the upstream side of the air flow. FIG.
FIG. 5 is a diagram of a single module in FIG. 3;
6 is a view of FIG. 5 as viewed from the outlet direction of the auxiliary air passage.
7 shows an embodiment in which the upstream side shape of the sub air passage is changed from FIG.
8 shows an embodiment in which the shape of the upstream side of the auxiliary air passage is changed with respect to FIG.
FIG. 9 is a cross-sectional view of a throttle body integrated heating resistance type air flow rate measuring device showing one embodiment of the present invention.
FIG. 10 is a cross-sectional view of an air cleaner integrated with a heating resistance type air flow measuring device showing an embodiment of the present invention.
FIG. 11 is a cross-sectional view of an air cleaner with a built-in heating resistance type air flow rate measuring device according to an embodiment of the present invention.
FIG. 12 is a cross-sectional view of a heating resistance type air flow rate measuring device when the body inner diameter is widened, showing an embodiment of the present invention.
FIG. 13 is a view of FIG. 12 as viewed from the upstream side of the air flow.
FIG. 14 is a control system diagram of an internal combustion engine using the product of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Heat generating resistor, 2 ... Temperature sensitive resistor, 3 ... Subchannel, 4 ... Subchannel component, 5 ... Main channel, 6 ... Flowmeter body, 7 ... Base member, 8 ... Electronic circuit, 9 ... Circuit housing, 10 ... cover, 11 ... connector, 13 ... terminal, 14 ... insertion hole, 15 ... mounting fixing surface, 16 ... rubber packing, 17 ... flow direction, 18 ... screw, 19 ... holder, 20 ... O-ring, 21 Rectifier grid, 22 conductive member, 23 valve, 24, 104 throttle body, 25 introduction duct, 26 upstream case member, 27 downstream case member, 28 connection duct, 29 filter, 30 DESCRIPTION OF SYMBOLS ... Intake duct, 31 ... Duct, 32 ... Body, 33 ... Mounting surface, 100 ... Air cleaner, 101 ... Intake air, 102 ... Heat generation resistance type air flow measuring device, 103 ... Intake duct, 105 ... Injector, 106 ... Manifold, 107 ... Engine cylinder, 108 ... Gas, 109 ... Exhaust manifold, 110 ... Circuit module, 111 ... Throttle angle sensor, 112 ... Oxygen concentration meter, 113 ... Tachometer, 114 ... Control unit, 115 ... Idle air control valve , 301 ... inlet opening surface, 302 ... first passage, 303 ... right angle bend, 304 ... second passage, 305 ... outlet opening surface, 306 ... saucer-shaped inlet, 307 ... inclined surface, 308 ... outlet bowl, 401 ... holder Insertion hole, 402 ... joining surface, 403 ... meat stealing hole, 404 ... groove part.

Claims (7)

A circuit housing incorporating an electronic circuit, a sub-channel constituent member in which a sub-channel is configured, and a detection element arranged in the sub-channel are configured integrally.
An air flow rate in which the auxiliary flow path component is inserted from an insertion hole provided in a wall constituting the main flow path, and the auxiliary flow path component is installed in a cantilever manner so that the auxiliary flow path is located in the main flow path A measuring device,
The sub-flow path includes an opening face that opens toward the upstream side of the main flow path, a first flow path that guides air that has passed through the opening face toward the insertion hole, and the first flow path. A second flow path for guiding the passed air in a direction opposite to the direction ,
The sub flow path component is made of plastic, and is assembled integrally with a plastic holder on the circuit housing side,
The plastic holder is fixed to a metal base member on the opposite side of the sub-flow path component member, and a terminal to which the detection element is fixed penetrates the inside of the holder, and the detection element is connected to the sub-flow path Integrated with the sub-flow path component so as to be located inside,
The circuit housing is fixed to the metal base member on the opposite side of the plastic holder;
The plastic holder is integrated with the metal base member by insert molding the metal base member at the time of forming the holder,
A sub-flow path component member installed in a cantilever manner in the sub-flow path is supported by a wall constituting the main flow path via the plastic holder and the metal base member,
The metal base member has a screw insertion hole, and the metal base member is fixed to the wall constituting the main flow path with a screw . In claim 1,
The air flow measuring device according to claim 1, wherein the opening surface is elongated in the insertion direction. In claim 1,
The air flow rate measuring device, wherein the second flow path opens toward a wall constituting the main flow path. A circuit housing incorporating an electronic circuit, a sub-channel constituent member in which a sub-channel is configured, and a detection element arranged in the sub-channel are configured integrally.
An air flow rate in which the auxiliary flow path component is inserted from an insertion hole provided in a wall constituting the main flow path, and the auxiliary flow path component is installed in a cantilever manner so that the auxiliary flow path is located in the main flow path A measuring device,
The sub-channel includes an inlet opening surface that receives dynamic pressure from the flow of the main channel, a first channel that guides the air that has passed through the inlet opening surface toward the insertion hole, and the first channel. A second flow path that guides air that has passed through the second flow path in a direction opposite to the direction, and an outlet portion through which the air that has passed through the second flow path exits the main flow path,
Due to the pressure difference between the inlet opening surface and the outlet portion, a part of the air flowing through the main channel passes through the sub channel ,
The sub flow path component is made of plastic, and is assembled integrally with a plastic holder on the circuit housing side,
The plastic holder is fixed to a metal base member on the opposite side of the sub-flow path component member, and a terminal to which the detection element is fixed penetrates the inside of the holder, and the detection element is connected to the sub-flow path Integrated with the sub-flow path component so as to be located inside,
The circuit housing is fixed to the metal base member on the opposite side of the plastic holder;
The plastic holder, by the insert molding the metallic base member during molding of the holder are integrated with the metallic base member,
A sub-flow path component member installed in a cantilever manner in the sub-flow path is supported by a wall constituting the main flow path via the plastic holder and the metal base member,
The metal base member has a screw insertion hole, and the metal base member is fixed to the wall constituting the main flow path with a screw . In claim 1 or 4,
The air flow rate measuring device according to claim 1, wherein the first flow path includes a surface perpendicular to the flow direction of the main flow path and a surface parallel to the flow direction of the main flow path. In claim 4,
The inlet opening surface is an air flow rate measuring device elongated in the insertion direction. In claim 1 or 4,
An air flow rate measuring apparatus, wherein the detection element is provided in a passage between the first flow path and the second flow path .

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