JP2001099688A - Heating resistance type apparatus for measuring air flow rate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating resistance type apparatus for measuring air flow rate which can reduce costs and has a superior fitness in an internal combustion engine. SOLUTION: A sub air path is integrally formed to part of a module, so that the module singly provides all necessary functions for the heating resistance type apparatus for measuring air flow rate. The module of the apparatus of one kind can be set to every engine. Costs can be reduced including a system cost of an internal combustion engine. Moreover, the module can be set to, e.g. an air cleaner or the like of a suction system. A heating resistance type air flowmeter of a superior fitness can be provided accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air flow measuring device for measuring an intake air flow rate of an intake system of an internal combustion engine and particularly suitable for measuring an air flow rate taken into an automobile engine. The present invention relates to a heating resistance type air flow measuring device.

[0002]

2. Description of the Related Art An air flow meter described in Japanese Patent Application Laid-Open No. 4-75385 is a known example closest to the present invention. However, Japanese Patent Application Laid-Open No. 4-75385 does not disclose a method for mounting and fixing the main flow path, the sub flow path, and the circuit portion. Therefore, the first object of the present invention is to integrate the circuit section and the sub flow path section into an integrated module, and to have a structure in which a standardized module can be applied to various internal combustion engines regardless of the size of the main flow path. Not. In addition, the structure of the sub flow path becomes complicated, and there is a concern that the measurement accuracy may be degraded. Further, since it is necessary to form several parts by combining them, the cost increases, and the like, so that they are not suitable for practical use. Furthermore, the structure does not sufficiently take into account the response to environmental changes due to the main flow path being arranged at a different position in the intake system, and the response to the mounting variation between the module and the main flow path.

[0003]

SUMMARY OF THE INVENTION According to the present invention, a circuit section and an auxiliary flow path section are integrated in order to reduce the system cost of an internal combustion engine, which is the greatest problem of a heating resistance type air flow measuring apparatus. The module has most of the functions of a heating resistance type air flow measurement device so that the module can be handled as a single product. Further, in order to make this practically practical, the size and weight are reduced, the measurement accuracy is degraded due to environmental changes and mounting variations, and the handling is further improved.

[0004]

In order to reduce the system cost of an internal combustion engine, the cost of a heating resistance type air flow measuring device is reduced and the number of components of the system is reduced by integration with other intake system components. I have. First, by using a module in which the circuit section and the sub-flow path section are integrated, a relatively expensive flowmeter body can be mounted on the main flow path, which is a simple conduit, and with holes provided in the wall of the main flow path and the fixing surface of the circuit. With this configuration, significant cost reductions have been made possible. In addition, the shape of the components constituting the sub flow path is simplified and reduced in size, the integration with the circuit section is facilitated, and the components connecting the circuit section and the sub flow path section are integrated to reduce the cost of the air flow measurement device. Reduction achieved. Furthermore, since the shape of the flowmeter body has been simplified, the flowmeter body can be formed integrally with other intake system components without being formed as a separate member, thereby reducing the number of system components. Further, even if the position where the main flow path is set or the size of the main flow path changes, a standardized module can be applied.

In order to reduce the size and weight, the sub flow path is simplified without impairing its function, the shape of the sub flow path is maintained, the entire length of the sub flow path is maintained by a curved flow path, and the sub flow path of the temperature-sensitive resistor is formed at a right angle. The length in the main flow direction of the sub flow path is reduced by disposing the second flow path perpendicular to the main flow direction of the sub flow path in a cross-sectional shape longer in the direction perpendicular to the main flow direction than in the main flow direction. The second passage perpendicular to the main flow direction of the passage is also kept short to reduce the size and weight of the member constituting the sub flow passage, reduce the proportion of the sub flow passage constituting member in the main flow passage, and reduce the shape of the sub flow passage. By making the pressure loss less likely to occur, it is possible to reduce the size and weight of the main flow path as a structure that does not increase the cross-sectional area of the main flow path. Also, the hole in the main flow path wall surface for inserting the sub flow path can be formed into a circular shape having a small diameter without increasing the ratio of the width to the length of the member forming the sub flow path. Simplifies the formation of the circuit and can be adapted to miniaturization of the circuit.

In order to cope with environmental changes, it is necessary to cope with changes in the flow of air in the main flow path depending on the position of the intake system and to cope with temperature changes depending on the position of the air flow measuring device. . 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 passage parallel to the main flow direction and the length of the second passage perpendicular to the main flow direction is optimized. To prevent backflow, the outlet opening surface of the sub flow path is formed in a plane parallel to the main flow direction, and an eave-shaped projection is provided upstream of the outlet portion. With respect to the measurement error due to the drift of the main flow path, the inlet opening surface of the sub flow path is formed as a saucer, an inclined surface is provided upstream of the outlet, and the arrangement of the entrance and exit of the sub flow path in the main flow path is optimized. With respect to the turbulent flow and swirling flow of 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 flow path can be made larger than the cross sectional area of the first flow path. There is an inclined surface with a wall. 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 sub flow path at a position away from the base member, and the heating resistor is a 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 fixing position of the heating resistor, the interval between the heating resistor and the corner formed by the first passage and the bottom surface of the receiving passage is optimized.

[0007] Regarding the variation in the mounting of the module to the main flow path, the outer shape of the cross-section parallel to the base member of the sub-flow path portion of the sub-flow path member is defined by the rectangular or trapezoidal shape of the entrance opening surface of the sub-flow path. A shape perpendicular to the main flow direction and a shape parallel to the main flow direction are provided. The exit opening surface of the sub flow path is formed in a plane parallel to the main flow direction, and the exit direction of the entrance opening surface is dug. This is supported by the shape of a saucer.

In order to improve the handleability, the circuit section and the sub-flow path section are formed as an integrated module, the insertion hole of the main flow path is sized to be covered by a base member, and an O-ring, packing gasket, etc. Thereby, it is possible to prevent air leakage from the insertion hole portion, to form a groove for mounting an O-ring to achieve modularization with an O-ring, and to detachably fix the module to the main flow path. To respond.

The module and the sub-flow path are integrated into a module, and the module is provided with most of the functions of a heating resistance type air flow measuring device, so that the module can be handled as a single product. As a result, a company that integrates internal combustion engines, for example, a car maker, can obtain an inexpensive heating resistance type air flow measurement device, and a free layout of the intake system becomes possible.

In the module, the electronic circuit is protected 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.

Since the length of the sub-flow path can be set sufficiently long by forming the sub-flow path as an L-shaped curved flow path, the heating resistor due to the turbulence of the air flow in the main flow path at the outlet of the sub-flow path can be set. The effect on the flow of air in the vicinity has been reduced. In addition, the structure in which the inclined surface having walls on both sides is provided on the upstream side of the outlet of the sub flow passage, the flow of the main flow passage at the outlet of the sub flow passage has a stable flow with a strong directional inertia force, and the flow of the main flow passage. The turbulence itself is reduced. The inlet opening of the sub flow path is opened in a plane perpendicular to the flow direction of the main flow path, and the outlet opening face is opened in a plane parallel to the main flow direction. This is to increase the pressure difference between the inlet and outlet by pulling, to increase the flow velocity of the air flowing into the sub flow path, and to stabilize the flow in the sub flow path. Furthermore, the reason why the cross-sectional shape of the second passage of the sub-flow passage is widened is that the sub-flow passage is bent at a right angle while securing a cross-sectional area while keeping the length of the sub-flow passage constituent member in the main flow direction short. This is for compensating for the decrease in the flow area of the second passage due to the separation of the generated flow, preventing the flow velocity of the air flowing into the sub flow passage from decreasing, and stabilizing the flow near the heating resistor. As described above, by stabilizing the flow in the sub flow path, particularly in the vicinity of the heating resistor, there is an effect that the output noise of the air flow measurement device is reduced and the measurement accuracy is improved. In addition, the L-shaped sub-flow path reduces the negative error caused by the non-linearity of the heat radiation characteristic of the heating resistor and the response delay when a pulsating flow occurs in the main flow path, and the relative length of the main flow path between the entrance and exit of the sub-flow path. On the other hand, by increasing the length of the sub flow path and giving an inertial effect to the flow in the flow path, the output during pulsation is positively changed to offset the negative error, thereby reducing the output error due to pulsation. effective. The reason why the length of the second passage is twice as long as the length of the first passage of the sub-flow passage is that the degree of the inertial effect in the L-shaped sub-flow passage is optimal for canceling the minus error. It is a length ratio. Furthermore, since the outlet opening surface of the sub-flow path is provided on a surface parallel to the base member and the sub-flow path constituting member has a cantilever structure fixed to the circuit side, the circuit section is fixed to the wall surface of the main flow path. The flow path is also fixed to the main flow path, and even when the size of the main flow path is different because of the cantilever, the distance between the center of the main flow path and the circuit part mounting surface is kept constant, so that the center of the main flow path and the sub flow path are It is possible to apply a standardized module without changing the position of the doorway.

The reason why the heating resistor is disposed in the first passage and the temperature-sensitive resistor is disposed in the right-angle bend portion is to enable the length of the first passage to be kept short, so that both resistors are close to each other. In this case, thermal flow interference due to disposition is prevented, and the measurement error is reduced by disposing the heating resistor in the first passage, which facilitates stabilization of the flow. If the length of the first passage can be shortened to shorten the main flow and the changed length of the sub flow path component, the length of the sub flow path component may be reduced by increasing the pressure loss of the air flow meter. Even if it is small enough not to become smaller, it can be within twice, so that the insertion hole for inserting the sub flow path provided on the wall of the main flow path can be made relatively small circular, so that the insertion hole can be easily formed, It is possible to prevent the road from becoming complicated and large. Further, since the insertion hole can be sized so as to be covered by the base member, a margin for further miniaturization of the circuit portion can be secured, and the O-ring and the O-ring are provided between the bottom surface of the base member and the circuit portion fixing surface of the outer wall of the main flow path. Sealing with a packing, gasket, or the like can prevent air leakage inside and outside the main flow path from the insertion hole, and can prevent measurement errors due to air leakage. Further, since the insertion hole is formed in a circular shape, a diameter seal using an O-ring is also possible.

With the base member as a reference, the terminal is held in a holder and fixed so as to penetrate the base member, and an electronic circuit and a circuit housing are fixed on the upper surface of the base member.
Cover the upper surface of the circuit housing with the cover, fix the heating resistor and the temperature-sensitive resistor on the terminal or holder on the lower surface of the base member, and insert the holder and terminal into the holes provided in the sub-flow path component, The method of fixing the sub-flow path constituting member to the holder or the base member so that the body and the temperature-sensitive resistor are located in the sub-flow path is easy to manufacture and can reduce the production cost. Further, 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, the components can be fixed without any additional components for fixing such as insert molding, bonding, welding and the like. Further, a groove can be formed on the joint surface between the sub-flow path component member and the holder or the base member, and the groove is formed in the groove.
By installing the ring, a module can be obtained that integrates the O-ring for sealing the insertion hole without fear of falling off.
A module with improved handling properties can be obtained.

The outer shape of the cross section parallel to the base member of the sub flow path portion of the sub flow path component member is defined as a rectangular or trapezoidal shape having a surface perpendicular to the main flow direction having an inlet opening surface of the sub flow path and a surface parallel to the main flow direction. By adopting a certain shape, it is possible to reduce a measurement error due to a variation 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 a cross section perpendicular to the main flow direction) decreases, so that it flows into the sub flow path. It acts to reduce the air flow and cause a negative output error. On the other hand, if the mounting angle of the module is bent, the area of the sub flow path component that is parallel to the main flow will decrease the effective area of the main flow path. Therefore, the two effects cancel each other out, and a measurement error due to a variation in module mounting angle can be reduced. Considering the general cross-sectional area of the main flow path and the size of the sub-flow path constituent members, the length in the main flow direction of a plane parallel to the main flow direction with respect to the width of the sub-flow path inlet opening is about twice as large. The above-mentioned offset effect becomes appropriate. The outer shape of the cross-section parallel to the base member of the sub-flow path portion of the sub-flow path component member and the shape in which the trapezoid or the trapezoid and the rectangle are combined do not impair the effect of reducing the effect of the mounting angle, and
This is because the dynamic pressure generated on the upper surface of the sub-flow path component is reduced without reducing the cross-sectional area of the second passage, and the pressure loss of the air flow measuring device is reduced. Further, the downstream bottom surface of the sub-flow path component is formed in an arc shape in order to reduce the downstream separation vortex and reduce pressure loss, and it is also possible to enlarge the cross section of the second passage so that one side is formed in an arc shape. That's why. The length of the longest diagonal of the cross-sectional shape of the sub-flow path and the diameter of the circular insertion hole provided in the wall of the main flow path are substantially the same,
This is for keeping the insertion hole small.

The shape of the saucer in which the exit direction of the inlet opening face of the sub flow path is dug down is to take air into the sub flow path from a wide area of the main flow path, and a drift occurs in the main flow path. The first object is to reduce the measurement error at the time of occurrence. The effect of reducing the measurement error at the time of the drift is also present on the inclined surface upstream of the sub flow path outlet. If the flow velocity at the outlet upstream increases due to the drift, the separation area generated downstream of the inclined surface expands, the suction effect at the sub flow path outlet increases, and the air flow rate flowing into the sub flow path increases. When the flow rate becomes slower, the separation area at the outlet becomes smaller and the air flow rate flowing into the sub flow path decreases, so that the position that cancels out the effect of the flow rate of the sub flow path flow rate due to the change of the upstream flow velocity at the inlet opening surface of the sub flow path If an entrance is provided in the relationship, measurement errors due to drift can be reduced.
This operation is most effective because the first passage is provided at a position eccentric from the center of the main flow passage, the pan-shaped portion is expanded to include the vicinity of the center of the main flow passage, and the outlet of the sub flow passage is connected to the main flow passage. This is when it is provided at the opposite part of the entrance with respect to the center. In addition, the tray-shaped inlet opening has an effect of reducing measurement errors due to variations in inclination in the upstream and downstream directions due to the inclined insertion holes in the circuit fixing surface and the main channel wall surface. When the exit direction of the sub flow path is inclined in the upstream direction of the main flow path, the exit opening surface is inclined in a direction that can be seen from the upstream side of the main flow path, so that a slight dynamic pressure is generated in the exit opening surface, or a negative pressure is generated. Due to the decrease, the pressure difference between the inlet and outlet of the sub flow path is reduced, and the flow rate of air flowing into the sub flow path is reduced, thereby acting to cause a negative measurement error. On the other hand, the pan-shaped opening surface is inclined in the direction in which the first passage is located downstream, so that the flow near the center of the main flow passage is more easily guided to the sub flow passage, and the separation area generated in the first passage is increased, thereby generating heat. In order to increase the flow velocity near the resistor, it acts so as to cause a measurement error on the plus side.
Since these two actions cancel each other, a measurement error due to the variation in inclination of the sub-flow path constituting member can be reduced. On the other hand, if the outlet is inclined so that the outlet is located on the downstream side, the negative pressure is increased at the outlet, and the inlet is inclined in a direction in which air is hardly taken into the sub-flow passage, and the separation area in the first passage is reduced. Are offset by each other, and the measurement error can be reduced.

The temperature-sensitive resistor is fixed at a position farther from the base member than the center line of the first passage. The temperature-sensitive resistor is located near the inner corner where the flow velocity is the fastest in the right-angle bend, and the intake air temperature is fixed. In a temperature environment where there is a difference between the intake air temperature and the ambient temperature of the air flow measurement device, heat conduction through terminals and holders can improve the detection accuracy of ambient air. This has the 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 from the holder to the terminal. If the temperature-sensitive resistor erroneously measures higher than the intake air temperature, a positive-side flow rate measurement error occurs. On the other hand, the heating resistor acts to cause a negative flow rate measurement error because the amount of heat radiation due to heat conduction to the terminal and the boulder decreases in an environment with a high ambient temperature. Therefore, if the degree of influence on both resistors is made equal, a measurement error in an environment where the intake air temperature and the ambient temperature are different can be reduced.
Actually, the influence of heat conduction and the influence of heat transfer to the air are different due to the difference in temperature between the two resistors, so simply the heat resistance of the terminal and holder of the heating resistor and the temperature sensitive resistor are simply made equal. However, it is not sufficient, so that the thermal resistance of the heat-sensitive resistor side should be increased and the thermal resistance of the heat-generating resistor side should be smaller than that of the temperature-sensitive resistor. By fixing the temperature-sensitive resistor at a position distant from the base member and fixing the heating resistor closer to the base member than the temperature-sensitive resistor, the two resistors for reducing the measurement error in the above temperature environment are used. A proper thermal balance of the body can be easily obtained.

It is necessary to arrange the heating resistor in the first passage in the main flow in the first passage, that is, in a stable flow having a high flow velocity. Therefore, when arranging the heating resistor in consideration of the temperature environment as described above, it is necessary to consider not only the positional relationship with the temperature-sensitive resistor but also the position in the first passage. In the case of a simple circular pipe passage, the main flow is near the center thereof, but factors determining the position of the main flow in the first passage in the right-angled curved passage having a saucer-shaped opening surface are as follows. The action of moving the main flow toward the base member rather than the center of the pipeline by the separation flow generated by the first corner formed by the first passage, and the flow velocity near the inner corner (second corner) at the right-angled bend is increased. This has the effect of moving the mainstream in a direction away from the base member rather than the center of the pipeline. That is, the positional relationship between the first corner and the second corner affects the position of the main flow in the first passage, and the inner wall farthest from the base member of the first passage, which is the wall connecting the two corners, and the heating resistor By appropriately setting the distance between the first and second passages, the heating resistor can be arranged in the main stream of the first passage. In a general size of the sub-flow path, a portion separated from the inner wall of the first passage farthest from the base member in the direction of the base member by 1/2 to 1 times the interval between the first corner and the second corner. This is the range of the main flow of the first passage.

The reason why the cross section of the first passage is formed by combining a semicircle and a rectangle is that the heating resistor is placed in the main flow of the first passage while the positional relationship between the heating resistor and the temperature sensitive resistor is appropriate. This is one way to place it. That is, the position of the heating resistor is optimized based on the relationship with the temperature-sensitive resistor,
In order to move the position of the main flow of the passage to the vicinity of the heating resistor, the shape of the first passage inner wall farthest from the base member having the first corner and the second corner is freely set. .

As described above, the configuration of the sub-flow path portion of the present invention has many functions against environmental changes, mounting variations, and mounting properties. There is no need to combine them, and they maintain a simple shape that can be formed as one plastic molded product. Therefore, the cost of the module itself can be reduced. In addition, other intake system components can be simplified because the shape of the main flow path can be simplified, the module has a function and structure that can be handled as one product, and it can respond to environmental changes and mounting variations. In addition, since the main flow path can be integrated, and the module can be standardized, the system cost of the internal combustion engine can be reduced. Further, since the module can be fixed to the main flow path only by attaching the circuit portion to the outer wall of the main flow path, the module has good mounting properties and can be easily fixed detachably. If detachable fixing is used, it is possible to easily cope with a failure in the market by replacing only the module part.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a cross-sectional view of one embodiment of the present invention, and FIG. 2 is an external view as viewed from the upstream side (left side).

An electronic circuit 8 and a circuit housing 9 are fixed on 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, and the upper surface of the circuit housing 9 is covered with a cover. Covered by 10. The terminal 13 that is electrically connected to the electronic circuit 8 is drawn 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 sub flow path 3 includes an inlet opening surface 301 that opens in a plane perpendicular to the base member 7, a first passage 302 extending parallel to the base member from the inlet opening surface, and a first passage 302 extending in a direction perpendicular to the base member. A second passage 304 having about twice the length, an outlet opening surface 305 opening in a plane perpendicular to the base member, and a first passage 302 and a second passage 304
Is an L-shaped flow path constituted by a right-angled bent portion 303 corresponding to the intersection of the heat generating resistor 1 and the first passage 30.
2, the sub-flow path constituent member 4 is fixed to the base member 7 so that the temperature-sensitive resistor 2 is located in the right-angled bent portion 303. Thus, a module in which the circuit section and the sub-flow path section of the heating resistance type air flow measuring device are integrated is configured.

On the other hand, a flow meter body 6 constituting the main flow path 5
An insertion hole 14 for inserting the sub-flow path constituting member 4 and an attachment fixing surface 15 for attaching the base member 7 are provided on the wall surface. The flowmeter body 6 is provided with the first
The sub flow path component member 4 is inserted into the main flow path 5 through the insertion hole 14 so that the passage 302 is parallel to the flow direction 17 of the main flow path 5, and the mounting fixing surface 15 is so formed that the periphery of the insertion hole 14 is sealed. The base member 7 is fixed to the outer wall of the main flow channel by screws 18 with a rubber packing 16 interposed between the bottom surfaces of the base member 7.

FIG. 3 is a cross-sectional view of an embodiment in which a configuration for reducing the deterioration of measurement accuracy under various environments and a method of fixing the sub-flow path constituent member and the base member are further reduced. FIG. 4 is an external view of the apparatus viewed from the upstream side (left side).
Shown in

The terminal 13 is integrated with the holder 19 so that the terminal 13 passes through 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 will be described.
3 and the base member 7 are made of metal, and the holder 19 is made of plastic. When the holder 19 is formed, the terminal 13 and the base member 7 are insert-molded to integrate the three members, and the terminal 13 and the holder 19 are formed by insert molding. A method of fixing to the base member 7 by bonding or the like, or shown as a separate member in FIG.
The terminal 13 is inserted by molding the terminal 13 into one plastic molded product by using 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 is a molding method. The electronic circuit 8 is fixed to the upper surface of the base member 7 or the holder 19, and has the terminal 13 and a conductive member 22 such as a wire.
Are electrically connected via In addition, the circuit housing 9
Is 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.

On the other hand, the heating resistor 1 and the temperature-sensitive resistor 2 are electrically connected and fixed to the terminal 13 at the opposite end of the electronic circuit 8. In this embodiment, the temperature-sensitive resistor 2 is
The heating resistor 1 is fixed at a position closer to the base member 7 than the temperature-sensitive resistor 2 in the first passage 302 of the sub-flow path 3 within the right-angled bent portion 303 of the sub-flow passage 3. The configuration is such that the measurement error can be reduced even in an environment where the temperature changes drastically.

As in the first embodiment, the sub-flow path constituting member 4 includes an inlet opening 301, a first passage 302, a right angle bend 303, a second passage 304, and an outlet opening 305. In addition to the U-shaped flow path, a saucer-shaped inlet 30 dug out leaving a wall around the purpose of guiding air taken into the sub-flow path 3 over a wide range, particularly near the center of the main flow path 5.
6. An inclined surface 307 having walls on both sides for the purpose of stabilizing the flow at the outlet portion, and the tip of the inclined surface is connected to the outlet opening surface 3
Exit eaves 308 that traveled downward from 05, and a joint surface 402 between the holder 401 and the hole 401 into which the holder 19 is inserted.
Is provided. Further, the first passage 302 of the sub flow path 3
Sets the fixed position of the heating resistor 1 to the first position with priority given to temperature effects.
As a direction approaching the base member 7 from the center of the passage 302, in order to bring the range in which the flow velocity is relatively fast and the flow is stable in a cross section perpendicular to the flow of the first passage 302 to the fixing portion of the heating resistor 1. And an inner wall of the first passage 302 connecting the bottom with the bottom of the saucer-shaped inlet 306, the corner formed by the first passage 302, and the inside corner of the right-angled bent portion 303. The distance between the heating resistor 1 and the heating resistor 1 is set to 1/2 to 1 (the same interval). Further, a meat stealing hole 403 parallel to the second passage 304 is provided.
The thickness of the sub-flow path constituting member 4 is made uniform to prevent a change in shape due to sink in plastic molding, and the material cost and weight are reduced.

The sub-flow path constituting member 4 has a holder insertion hole 4
01 and the holder 1 at the joint surface 402.
9 and fixed. Here, a groove 404 is formed by the step provided on the holder 19 and the joint surface 402 of the sub-flow path component. The groove 404 is a mounting groove for the O-ring 20, and has a configuration in which the O-ring 20 seals the insertion hole 14 on the wall of the main flow path. As described above, a module is formed in which the circuit section, the sub-flow path section, and the O-ring for insertion hole sealing are integrated.

By fixing this to the flow meter body 6 in the same manner as in the first embodiment, a heating resistance type air flow 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 the present 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 a rectifying grid 21 is provided on the inlet face of the main flow path 5 of the flowmeter body 6. Is shown, and the measurement accuracy is further improved.

FIG. 5 is a transverse sectional view of a module in which the circuit section and the sub-flow path section of the heating resistance type air flow measuring apparatus shown in the second embodiment are integrated, and FIG. FIG.

The external shape of the cross-section parallel to the base member 7 of the sub-flow path constituting member 4 is such that the insertion portion of the holder 19 is circular and the sub-flow path portion has a length perpendicular to the flow direction of the first passage. In this case, the length of the side parallel to the flow direction of the first passage is made to be a rectangle of 1-2 times. Also, the outer shape of the part of the holder 19 to be inserted into the insertion hole 14 on the main flow path wall surface is circular,
Since the diameter is made substantially equal to the length of the diagonal line of the rectangular cross section of the sub-flow channel portion, the insertion hole provided in the main flow channel wall surface can be made a relatively small circle. Further, the opening width of the inlet opening surface 301 of the sub-flow passage perpendicular to the flow direction of the second passage 304 is about の of the length of the side parallel to the first passage 302 of the rectangular cross section of the sub-flow passage portion. And the second passage 304
Has a rectangular shape having a longer vertical side than a side parallel to the first passage 302.

7 and 8 are external views as viewed from below in FIG. 5, similarly to FIG. FIG. 7 is a cross-sectional view of a portion of the holder 19 inserted into the insertion hole 14 on the wall of the main flow path parallel to the base member 7 having a circular shape having the same diameter as that of FIG. 6, the outer shape of the cross section parallel to the base member 7 of the sub flow path portion of the sub flow path component 4 is formed by combining a trapezoid and a rectangle. FIG. 8 is a view in which the downstream bottom surface of the second passage and the downstream bottom surface of the cross-sectional shape of the sub-flow passage portion are arc-shaped.

FIG. 9 shows a throttle body 24 having a valve 23 for controlling the intake air amount of the engine.
1 shows a heating resistance type air flow measuring device comprising the module shown in FIG. The flow measuring unit is arranged upstream of the valve, and the flow of air flows from left to right in the figure. A throttle body integrated heating resistance air flow meter with a sub air passage is already commercialized, but the sub air passage member is formed integrally with the throttle body, or a housing member that covers the module circuit is provided. It is formed integrally with the throttle body, which considerably complicates the structure of the throttle body. 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. Further, in an intake system without a throttle valve (for example, a diesel vehicle), the module can be directly mounted on the intake manifold.

FIG. 10 shows an embodiment in which the module shown in FIG. 5 is attached to a part of an air cleaner disposed in an engine room. The air cleaner is a filter for removing dust in the air by 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. This is a structure in which the member 29 is inserted and fixed. As a matter of course, the flow of air 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, a part of the duct 28 has an insertion hole 14 for inserting the sub air passage of the heating resistance type air flow measuring device, and this is mechanically connected to the duct 28 and the module by using a screw or the like. Fix it. This makes it possible to form the main air passage by using a part of an air cleaner such as the duct 28 instead of the body forming the main air passage described above. An air flow measuring device can be provided.

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 similarly to FIG. In FIG. 10, the module part 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.
FIG. 1 shows an example in which a duct 31 is provided inside the downstream case member 27, and an insertion hole 14 is provided in a part of the duct 31 to mount a module. In the figure, the tip portion of the duct 31 is formed in a bell mouth shape in order to rectify the flow of air. By inserting the module of the heating resistance type air flow measuring device inside the air cleaner as in this structure, the length of the portion corresponding to the duct 28 shown in FIG. 10 can be shortened, so that the intake system can be made more compact. It is. Note that the duct 28 shown in FIG.
Although the duct 31 shown in FIG. 1 is described as being integrated with the case member 27 on the downstream side of the air cleaner, it may be manufactured separately and fixed so as to maintain the mechanical strength afterwards.

FIG. 12 is a cross-sectional view of a heating resistance type air flow measuring apparatus showing another embodiment, and FIG. 13 is a view seen from the upstream side (left side). The difference from FIGS. 3 and 4 is that the inner diameter of the body 32 constituting the main air passage is increased. If it is simply considered that the inside diameter of the body is increased, the first passage 302 in which the heating resistor 1 for measuring the flow rate is arranged and the inlet opening surface 302 of the auxiliary air passage are biased near the body wall surface. In this case, if the air flow in the body 32 has a drift due to the upstream shape (air cleaner and duct shape) of the body 32, the drift is generated near the wall surface by the heating resistance type air flow measurement device due to the drift. An error will occur. Normally, the flow velocity distribution flowing in the pipe shows a distribution close to a parabola such that the flow velocity is the highest in the central part of the pipe and becomes slower as approaching the wall. That is, the flow velocity is faster than the average flow velocity at the center in the pipe and slows down on the wall surface, and it is desired to measure the average value of the flow velocity at a position shifted from the center. For this reason, in the product of the present invention, the value of the average flow velocity is taken into the sub air passage by shifting the entrance and exit of the sub air passage from the center of the pipe. This is a pressure difference, and it is necessary for both the entrance and exit to shift from the center of the pipe). However, for most of the drift, the position where the flow velocity is the fastest is shifted from the center position, and one of them shows a value of a fast flow velocity with respect to the center, and the other shows a value of a slow flow velocity. For this reason, if the inlet opening surface 301 of the sub air passage is located at the position of the fast flow velocity distribution, a measurement error on the plus side is generated from the average flow velocity.

As described above, even when the inner diameter of the body 32 is increased, the mounting surface 33 for mounting the base member 7 on the body 32 is dug down from the outer diameter of the body 32 as shown in the figure in order to suppress the measurement error due to the drift. The inner wall of the body 32 is shaped so as to have a different diameter at the module mounting portion,
The distance between the center of the inner diameter of the body 32 and the entrance is substantially the same. In this case, since the inner wall of the body 32 becomes convex at the module mounting portion, the upper and lower portions of the portion may be gently inclined as shown in FIGS. 34 and 35 so as to minimize the disturbance of the air flow. desired.

Finally, FIG. 14 shows an embodiment in which the product of the present invention is applied to an internal combustion engine of the electronic fuel injection system.

The intake air 101 sucked from the air cleaner 100 is supplied to the body 10 of the heating resistance type air flow measuring device.
2. The air is sucked into an engine cylinder 107 via a manifold 106 having an intake duct 103, a throttle body 104, and an injector 105 to which fuel is supplied. On the other hand, gas 108 generated in the engine cylinder is discharged through an exhaust manifold 109.

Circuit module 1 of heating resistance type air flow meter
10, a throttle valve opening signal output from a throttle angle sensor 111, an oxygen concentration signal output from an oximeter 112 provided in an exhaust manifold 109, and an engine speed meter 11.
The control unit 114, which receives the rotational speed signal output from the control unit 3, calculates the optimum fuel injection amount and the idle air control valve opening by calculating these signals, and determines the values by the injector 105 and the idle air control valve 115. Control.

[0041]

The module can be treated as a single product by providing the module with most of the functions as a heating resistance type air flow measuring device. For example, the module can be attached to a part of an air cleaner or a part of an intake duct. By installing the module, the function as a heating resistance type air flow measuring device can be sufficiently performed. Further, since one type of module can be used for each engine, matching and the like become easy, and the system cost of the internal combustion engine is reduced. It becomes possible.

Also, in a conventional heating resistance type air flow measurement requiring a body constituting a main air passage, the body occupying a large weight can be formed into a simple cylindrical shape among the costs. In addition, as described above, by providing one type of module with a function as a heating resistance type air flow measurement device, standardization of the heating resistance type air flow measurement device according to the displacement of the mounted engine only by the main diameter of the body. With these effects, the cost can be reduced by about 10 to 20% as compared with a conventional heating resistance type air flow measuring device having a body having an integral sub air passage.

Further, in the market, even if any abnormality occurs in the heating resistance type air flow measuring device, only the module itself needs to be replaced, so that the handling of the heating resistance type air flow measuring device in the market can be improved. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a heating resistance type air flow measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram of FIG. 1 viewed from an upstream side of an air flow.

FIG. 3 is a cross-sectional view of a heating resistance type air flow measuring device showing an embodiment for improving measurement accuracy.

FIG. 4 is a view of FIG. 3 viewed from an upstream side of an air flow.

FIG. 5 is a diagram of a single module of FIG. 3;

FIG. 6 is a view of FIG. 5 as viewed from an outlet direction of a sub air passage.

7 is an embodiment in which the shape of the upstream side of the sub air passage is changed from FIG.

8 is an embodiment in which the shape of the upstream side of the sub air passage is changed from FIG.

FIG. 9 is a cross-sectional view of a throttle body-integrated heating resistance type air flow measuring device showing an 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 measuring device showing an embodiment of the present invention.

FIG. 12 is a cross-sectional view of a heating resistance type air flow measuring device when an inner diameter of a body is increased, showing one embodiment of the present invention.

FIG. 13 is a view of FIG. 12 as viewed from the upstream side of the flow of air.

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 ... Heating resistor, 2 ... Temperature sensitive resistor, 3 ... Sub flow path, 4 ... Sub flow path constituent member, 5 ... Main flow path, 6 ... Flow meter body, 7 ... Base member, 8 ... Electronic circuit, 9 ... Circuit housing, 10 ...
Cover, 11 connector, 13 terminal, 14 insertion hole, 15 mounting surface, 16 rubber packing, 17
Flow direction, 18: screw, 19: holder, 20: O-ring, 21: rectifying 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 ... Intake duct, 31 ... Duct, 32 ... Body, 33 ... Mounting surface, 100 ... Air cleaner, 101 ... Intake air, 102 ...
Heating resistance type air flow measuring device, 103 ... intake duct, 10
5: 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-angled bent portion, 304: second passage, 3
05: outlet opening surface, 306: saucer-shaped inlet, 307: inclined surface, 308: outlet eave, 401: holder insertion hole, 402:
Joining surface, 403: hole for digging meat, 404: groove.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01F 1/68 101B (72) Inventor Chihiro Kobayashi 2520 Takada, Katsuta-shi, Ibaraki Prefecture Hitachi, Ltd. Automotive Equipment Within the business division (72) Inventor Hiroshi Hirayama 2477 Kashima Yatsu, Kata-shi, Ibaraki Pref.Hitachi Automotive Engineering Co., Ltd. Engineering Co., Ltd. (72) Inventor Nobukatsu Arai 502, Kandachi-cho, Tsuchiura-city, Ibaraki Pref.

Claims (36)

[Claims] 1. A main flow path constituting an intake passage of an internal combustion engine,
In a heating resistance type air flow measuring device including a sub flow path having a heating resistor and a temperature-sensitive resistor therein, and an electronic circuit electrically connected to the heating resistor and the temperature-sensitive resistor, The member constituting the sub-flow path is fixed to a base of the electronic circuit, and an outlet portion of the sub-flow path is formed on a surface parallel to the base. measuring device. 2. A main flow path constituting an intake passage of an internal combustion engine;
In a heating resistance type air flow measuring device having a sub flow path having a heating resistor and a temperature sensing resistor therein, and an electronic circuit electrically connected to the heating resistor and the temperature sensing resistor, a plate-like base is provided. The electronic circuit and a circuit housing that internally protects the electronic circuit are fixed to one side of the member, and the heating resistor and the temperature-sensitive resistor are fixed to the opposite side of the electronic circuit fixing surface of the base member, and are perpendicular to the base member. A first passage that is a flow path formed in parallel with the base member from an inlet opening surface that opens on a flat surface, and is formed perpendicular to the base member that continues to an outlet opening surface that opens on a surface parallel to the base member. An L-shaped sub-flow path composed of a second passage, which is a flow path, is fixed so that the heating resistor and the temperature-sensitive resistor are located in the sub-flow path, and a circuit section and a sub-flow path section are formed. Integrated module, provided on the wall of the main flow path A heating resistance type air flow measuring device, wherein the sub flow path portion is inserted into a main flow path through a hole, and the base member or the circuit housing is fixed to an outer wall surface of the main flow path. 3. The method according to claim 2, wherein the first flow path of the sub flow path is provided.
The heating resistance type air flow measuring device, wherein the length of the second passage is approximately twice as long as the length of the passage. 4. The sub-channel according to claim 2, wherein the sub-channel portion of the sub-channel has a cross-sectional shape parallel to the base member with respect to a width perpendicular to a flow direction of the main channel. ,
A heating resistance type air flow measuring device, wherein a length parallel to a flow direction of a main flow path is in a range of 1 to 2 times. 5. The sub-flow passage according to claim 2, wherein the heating resistor is located in a first passage of the sub-flow passage, and the temperature-sensitive resistor is located at an intersection of the first passage and the second passage. A heating resistance type air flow measuring device, which is located at a certain right angle bend. 6. The flow path of the main flow path according to claim 2, wherein a sectional shape of the second flow path of the sub flow path parallel to the base member has a length parallel to a flow direction of the main flow path. A heating resistance type air flow measuring device, characterized in that the length perpendicular to the direction is longer. 7. The heating resistance type according to claim 2, wherein a hole provided in a wall surface of said main flow passage for inserting a sub flow passage portion is covered by said base member. Air flow measurement device. 8. A heating resistance type air flow measuring device according to claim 2, wherein the module in which the circuit section and the sub-flow path section are integrated is detachably attached to the main flow path. apparatus. 9. The base member according to claim 2, wherein the terminal for electrically connecting the heating resistor and the temperature-sensitive resistor to the electronic circuit is held by a holder made of an insulating material. The heating resistor and the temperature-sensitive resistor are fixed to the terminal or the holder, and the holder and the terminal are inserted into insertion holes provided in a member constituting the sub flow path. Wherein a member constituting the sub flow passage is fixed to the base member or the holder so that the heating resistor and the temperature sensitive resistor are located in the sub flow passage, and a heating resistance air flow rate is provided. measuring device. 10. The heating resistance type air flow measuring device according to claim 9, wherein said holder is a plastic molded product integrated with said base member. 11. A heating resistance type air flow measuring device according to claim 2, wherein said base member is formed in a box shape and also serves as said circuit housing. 12. A member according to claim 2, wherein the member forming the sub-flow path is a plastic molded product, and is fixed to the holder or the base member by adhesion or welding. Heating resistance type air flow measurement device. 13. A groove according to claim 2, wherein a groove formed by combining the holder or the base member and a member constituting the sub-flow path is provided at a joint portion between the holder and the base member and the member constituting the sub-flow path. A heating resistance type air flow measuring device, characterized in that an O-ring is mounted on the device. 14. An insertion hole provided in a wall surface of the main flow path according to any one of claims 2 to 13, and is inserted into the insertion hole of the holder, the sub flow path constituent member or the base member. A heating resistance type air flow measuring device, wherein a portion between a circular outer wall and an inner wall of the insertion hole is sealed by an O-ring. 15. The heat generation apparatus according to claim 2, wherein a space between said base member or said holder and an outer wall surface of said main flow path is sealed with an O-ring, packing or gasket. Resistance type air flow measurement device. 16. The heating resistance type according to claim 2, wherein an outer shape of a cross section of said sub flow path component member parallel to said base member is substantially rectangular. Air flow measurement device. 17. The external shape of a cross section of the sub flow passage portion parallel to the base member may be a trapezoid in which a side having an inlet opening surface of the sub flow passage is a short side, or a trapezoid and a rectangle. A heating resistance type air flow measuring device having a combined shape. 18. A heating resistance type air flow measuring device according to claim 16, wherein a bottom surface of the cross-sectional shape of said sub-flow passage portion on the downstream side of said main flow passage is formed in an arc shape. 19. The method according to claim 16, wherein the insertion hole provided in the wall surface of the main flow path has a circular shape having an inner diameter substantially equal to a length of a longest diagonal of a cross-sectional shape of the sub flow path. Characteristic heating resistance type air flow measurement device. 20. The apparatus according to claim 16, wherein a distance from the inlet opening of the cross-sectional shape of the sub-flow passage portion to the downstream bottom surface of the main flow passage is equal to an inlet opening width of the sub-flow passage. A heating resistance type air flow measuring device characterized in that the length is approximately doubled. 21. The sub-flow passage according to claim 2, wherein the inlet opening surface of the sub-flow passage is formed in a saucer shape dug out leaving a wall around the extension extending toward the outlet direction of the sub-flow passage. A heating resistance type air flow measuring device characterized in that: 22. The method according to claim 21, wherein the first flow path of the sub flow path is provided.
The passage is set at a position closer to the base member than the center line of the main flow passage, and a saucer-shaped dug portion of the inlet opening surface of the sub flow passage is formed in a range including the center line of the main flow passage. A heating resistance type air flow measuring device characterized by the following. 23. An apparatus according to claim 2, wherein an inclined surface having walls on both sides is formed integrally with said sub-flow path member at an upstream portion of said main flow path at an outlet of said sub-flow path. A heating resistance type air flow measuring device, characterized in that: 24. An apparatus according to claim 2, wherein an eaves-shaped projection is formed integrally with said sub-flow path constituting member at an outlet of said sub-flow path at an upstream portion of said main flow path. Characteristic heating resistance type air flow measurement device. 25. The temperature-sensitive resistor according to claim 2, wherein the temperature-sensitive resistor is fixed at a position farther from the base member than a center axis of the first passage of the sub-flow passage. Heat generation resistance type air flow measurement device. 26. A heating resistance type air flow measuring device according to claim 2, wherein said heating resistor is fixed at a position closer to said base member than said temperature sensitive resistor. apparatus. 27. An apparatus according to claim 21, wherein a distance between said heat generating resistor and a wall surface of said first passage of said auxiliary passage farthest from said base member is equal to a distance between a bottom surface of said pan-shaped opening. 1/2 of the distance between the corner formed by the first passage and the inner corner of the right-angled bend of the sub flow path
1. A heating resistance type air flow measuring device, wherein the range is 1. 28. The method according to claim 27, wherein the first of the sub-flow paths is
The shape of the cross section of the passage perpendicular to the flow direction is a shape combining a semicircle and a rectangle in which a portion close to the base member is semicircular and a portion away from the base member is rectangular. Characteristic heating resistance type air flow measurement device. 29. A heating resistance type air flow measuring device according to claim 1, wherein said main flow passage is formed integrally with a housing of the air cleaner. 30. A heating resistance type air flow measuring apparatus according to claim 1, wherein the main flow path is formed integrally with the throttle body. 31. A heating resistance type air flow measuring device according to claim 1, wherein the main flow path is formed integrally with an intake manifold component of the engine. 32. In any one of claims 1 to 31, even if the size of the main flow path changes, the position of the inlet / outlet of the sub flow path in the main flow path is constant with respect to the center of the main flow path. A heating resistance type air flow measuring device, wherein the length of the center of the main flow path and the fixed surface of the base member or the housing are constant regardless of the size of the main flow path. 33. A heating resistance type air flow measuring device comprising: a main flow passage constituting an intake passage of an internal combustion engine; and a sub flow passage having a heating resistor and a temperature-sensitive resistor therein. Is composed of an axial flow path and a radial flow path of the main flow path, and a cross-sectional shape of the axial flow path is a shape obtained by combining a semicircle and a rectangle. . 34. A heating resistance type air flow measuring apparatus according to claim 33, wherein a member constituting said sub flow path is fixed to a base of an electronic circuit to which said heating resistor is electrically connected. apparatus. 35. The heating resistor air flow measuring device according to claim 34, wherein the outlet of the sub-flow path is formed on a plane parallel to the base. 36. A control system for an internal combustion engine, wherein the control of the internal combustion engine is performed using the heating resistance type air flow device according to any one of claims 1 to 35.