JP2003042823A - Air flow rate-measuring instrument and air cleaner for composing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air flow rate-measuring instrument for maintaining appropriate flow rate measurement accuracy while restraining the increase in costs by integrating a bypass channel in an air cleaner, and to provide the air cleaner for composing the air flow rate-measuring instrument. SOLUTION: A flow rate-measuring body 15 having a bypass channel 18 is integrated with an air cleaner outlet duct 3a of an air cleaner cap 3 that is set to a different shape for each car type for formation, thus eliminating the need for the conventional, independent flow-rate measuring body 15 as a component, reducing the number of components and restraining the increase in costs to the minimum, and at the same time nearly eliminating the variation in the mounting position in the flow rate-measuring body 15 and the air cleaner outlet duct 3a, and hence appropriately maintaining the air flow rate measurement accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air flow rate measuring device for measuring an air flow rate in an air passage by measuring an air flow rate flowing in a bypass passage arranged in the air passage.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine (hereinafter referred to as an engine), an air flow rate measuring device of this type distributes an air cleaner for removing dust contained in intake air and the intake air to each cylinder of the engine. It is installed in the middle of the intake pipe that connects the intake manifold and the intake manifold, and is used to measure the intake air flow rate.
There is one as shown in Japanese Patent No. 87991. This is because the flow measurement pipe that protrudes toward the center of the intake pipe of the engine is assembled, and the space inside the flow measurement pipe is divided into an upstream side and a downstream side by a partition wall except for the upper part. And an inverted U-shaped bypass flow path is formed. Then, a part of the air flowing in the intake pipe is made to flow into the bypass flow passage from an inlet provided at the intake pipe central portion on the upstream side surface of the flow measurement pipe and opening toward the upstream side, and this flow measurement pipe It is designed to flow out from an outlet formed on the downstream side of the. Then, a flow rate measuring element (heat generating element) and a temperature sensitive element are installed in this bypass flow path, and the bypass flow rate and eventually the intake air flow rate are determined based on the electric power supplied to the flow rate measuring element and the temperature detected by the temperature sensitive element. It is something to measure.

By the way, since each cylinder of the engine intermittently sucks air in a predetermined order, pulsation occurs in the air flow in the intake pipe. When the air flow has pulsation, it is difficult to measure the air flow rate with high accuracy. However, in the above-described air flow rate measuring device, the bypass flow path is formed in an inverted U shape, so that the entire length of the bypass flow path is increased. To increase the inertia of the air in the bypass flow passage, thereby reducing the pulsation of the bypass flow due to the pulsation of the air flow in the intake pipe, and preventing the deterioration of the flow rate measurement accuracy due to the pulsation. .

[0004]

The magnitude of the air flow pulsation in the intake pipe depends on the shape of the air cleaner, that is, the positional relationship between the air inlet and outlet of the air cleaner, the internal volume of the air cleaner case, and the filter element which is the filter body. It varies depending on the shape of the. The shape of the air cleaner is
Since it is set according to the space on the vehicle in which it is installed, it differs for each vehicle type. Therefore, the magnitude of the air flow pulsation in the intake pipe also differs depending on the vehicle type.

On the other hand, when the magnitude of the air flow pulsation in the intake pipe changes, the total length of the bypass flow passage that effectively reduces the pulsation in the bypass flow passage of the air flow rate measuring device also changes. Therefore, in order to measure the air flow rate in the intake pipe with high accuracy, it is necessary to set the total length of the bypass flow path of the air flow measurement device to an optimum value for each vehicle type to which it is applied. The number of types increases and the cost increases.

Further, when the above-described air flow rate measuring device is attached to the intake pipe, the positional relationship between the air flow rate measuring device and the bypass flow passage and the intake pipe vary. there is a possibility.

The present invention has been made in order to solve the above problems, and an object thereof is to integrally form a bypass flow passage in an air cleaner, thereby maintaining good flow rate measurement accuracy while suppressing cost increase. An object is to provide an air flow rate measuring device and an air cleaner constituting the same.

[0008]

In order to achieve the above object, the present invention employs the following technical means.

In the air flow measuring device according to the first aspect of the present invention, the air passage in which the bypass passage is installed is the outlet passage of the air cleaner, and the bypass passage is integrally formed with this outlet passage. As a result, by integrally forming the bypass flow passage when forming the air cleaner case having different specifications for each vehicle type, it is possible to eliminate the need for many types of conventional bypass flow passages and reduce the cost of the air flow measuring device.

In the air flow rate measuring device according to the second aspect of the present invention, the bypass passage and the air cleaner as well as the outlet passage are integrally formed of resin. As a result, the bypass passage can be easily integrated with the air cleaner.

An air cleaner according to a third aspect of the present invention has a structure in which a bypass flow passage of an air flow rate measuring device is integrally formed in an outlet passage on the downstream side of a filter body. This eliminates the need for a separate bypass flow path, which can reduce the cost of the air flow rate measuring device.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings by taking an air flow rate measuring device mounted on an engine and used for measuring an intake air flow rate as an example.

FIG. 1 is a partial sectional view of an air flow measuring device 1 according to an embodiment of the present invention, which is an enlarged sectional view of a portion I in FIG.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an overall sectional view of the air flow measuring device 1 according to one embodiment of the present invention.

As shown in FIG. 3, the air flow measuring device 1 comprises an air cleaner section 2, a circuit module 14, and a flow measuring body 15.

The air cleaner portion 2 accommodates a filter element 5 which is a filter body for collecting dust in the air in an air cleaner case 4 forming an air flow path, and an air cleaner cap 3 is provided downstream of the air cleaner case 4. It is assembled. Dust in the air is collected and removed while the air sucked from the air cleaner inlet portion 4a formed in the air cleaner case 4 passes through the filter element 5. An air cleaner outlet duct 3a, which is an outlet passage of the air cleaner, is integrally formed on the downstream side of the air cleaner cap 3.

The flow rate measuring body 15 is arranged in the air passage 3b, and is made of a resin material, and the air cleaner cap 3, the air cleaner outlet duct 3a, and the air passage 3b are used.
Is integrally formed with the air cleaner outlet duct 3a to extend from the wall surface of the air cleaner outlet duct 3a to the vicinity of the central axis C of the air cleaner outlet duct 3a. As shown in FIG. 1, the flow rate measuring body 15 includes two pipes extending in the radial direction of the air cleaner outlet duct 3a.
By arranging along the air flow direction of a and joining with the joining wall 17, an inverted U-shaped bypass passage 18 in which two adjacent parallel passages 18a and 18c are connected by a bent portion 18b is formed. There is.

On the upstream side surface of the flow rate measuring body 15, an inflow port 19 for letting a part of the air (main flow) flowing in the air cleaner outlet duct 3a into the bypass flow passage 18 is provided with a central axis C of the air cleaner outlet duct 3a. Is formed so as to be adjacent to.

On the other hand, a venturi pipe portion 16 is integrally formed at the lower end of the flow rate measuring body 15 in parallel with the main flow direction, and an inlet 21 of the venturi pipe portion 16 and an inlet 19 of the bypass passage 18 are mutually air cleaner outlets. They are close to each other with the central axis C of the duct 3a interposed therebetween. An outlet 22 of the bypass flow passage 18 is formed on the downstream side peripheral wall of the Venturi pipe portion 16,
In the downstream side of the Venturi pipe section 16, that is, near the throat, the flow of the bypass flow path 18 (bypass flow) is the Venturi pipe section 1.
It merges with the flow in 6 (Venturi flow).

Further, on the downstream side peripheral wall of the venturi pipe portion 16, at a portion where the bypass flow from the bypass flow passage 18 joins, a flow passage expanding portion 23 (Fig. 1) is formed so as to extend in the circumferential direction. Then, by forming the upstream end surface of the flow passage expanding portion 23 into a slope shape, the guide portion 24 that guides the bypass flow toward the downstream side of the Venturi pipe portion 16 is provided at the outlet 22 of the bypass flow passage 18. Has been formed.

The venturi pipe portion 16 is formed so that the outer diameter becomes larger toward the downstream side, and an air flow path between the outer peripheral surface of the venturi pipe portion 16 and the inner peripheral surface of the air cleaner outlet duct 3a is formed in the venturi pipe portion 16. It becomes narrower on the downstream side of. As a result, the air flow (main flow) in the air cleaner outlet duct 3a becomes faster toward the downstream side of the venturi pipe portion 16, and the main flow increases the suction force (negative pressure) acting on the outlet of the venturi pipe portion 16, The flow velocity of the air in the Venturi pipe section 16 is increased.

On the other hand, at the upper end opening of the flow rate measuring body 15,
Mounting hole 1 for fitting with the fitting protrusion 36 of the circuit module 14
2 is formed and the circuit module 14 is attached.

A flow rate measuring element 29 (heat generating element) and a temperature sensitive element 30 are attached to the lower surface of the circuit module 14 at predetermined intervals by supporting members 31 and 32, respectively.
The flow rate measuring element 29 and the temperature sensitive element 30 are installed in the upstream side flow passage 18 a of the bypass flow passage 18. Further, since the temperature sensitive element 30 measures the temperature of the air contacting the flow rate measuring element 29, it is preferable to install the temperature sensitive element 30 near the flow rate measuring element 29 within a range not affected by heat radiation of the flow rate measuring element 29.

A circuit board 33 for controlling energization of the flow rate measuring element 29 and the temperature sensitive element 30 is provided inside the circuit module 14, and a wire harness (not shown) is provided on a side portion of the circuit module 14. Connector 3 for connecting
4 is integrally molded. An intake air temperature sensor 35 is insert-molded on the lower surface side of the circuit module 14 so as to project downward, and the intake air temperature sensor 35 (see FIG. 2) is located on the side of the flow rate measuring body 15 and is located at the air cleaner outlet. The temperature of the air flowing in the duct 3a (intake air temperature) is detected. The fitting protrusion 36 on the lower surface of the circuit module 14
An annular groove 36a is provided in the inner peripheral portion of the mounting hole 12, and an O-ring 37 attached to the annular groove 36a seals the inner peripheral portion of the mounting hole 12. Then, the screw 39 is inserted through the screw insertion hole of the fixed piece portion 38 formed on the side portion of the circuit module 14, and the mounting flange 40 formed on the air cleaner outlet duct 3a.
The circuit module 14 is assembled into the mounting hole 12 of the air cleaner outlet duct 3a by tightening the screw hole.

Next, the operation of the air flow rate measuring device 1 configured as described above and the air flow in each part of the air flow rate measuring device 1 will be described.

Part of the air flowing in the air cleaner outlet duct 3a flows into the bypass passage 18 and the venturi pipe portion 16 separately. The air (bypass flow) that has flown into the bypass flow passage 18 merges with the air flow (venturi flow) in the venturi pipe portion 16 on the downstream side of the venturi pipe portion 16 where the flow velocity of the air increases. At this merging portion, a suction force (negative pressure) acts on the outlet 22 of the bypass flow passage 18 by the Venturi flow to increase the flow velocity of the bypass flow.
Then, the bypass flow rate and thus the intake air flow rate are measured based on the electric power supplied to the flow rate measuring element 29 exposed to the bypass flow and the temperature detected by the temperature sensing element 30. That is, the current (heat generation temperature) of the flow rate measuring element 29 is measured by the temperature sensing element 3
The temperature difference from the detected temperature of 0 (intake air temperature) is controlled to be constant, and the intake air flow rate is measured by the current value of the flow rate measuring element 29 at that time.

In order to improve the accuracy of measuring the air flow rate, in the flow rate measuring body 15, the total length of the bypass flow path 18 is set so that the measurement error when the air flow in the bypass flow path 18 is pulsating is minimized. It is set.

The optimum value of the total length of the bypass flow passage 18 differs depending on the shapes of the air cleaner case 4 and the air cleaner cap 3, that is, each vehicle type to be mounted. Therefore, in the conventional air flow rate measuring device, in order to minimize the measurement error during pulsation, the bypass flow path 18, that is, the flow rate measuring body 15 needs to be manufactured by setting the specifications for each vehicle type.
The types of the flow rate measuring body 15 and the air flow rate measuring device increase, and the cost increases.

In the embodiment of the present invention, the flow rate measuring body 15 is connected to the air cleaner outlet duct 3a of the air cleaner cap 3.
Was formed by integral molding. This integral molding of the flow rate measuring body 15 can be performed by a relatively easy means of partially changing the molding die of the air cleaner cap 3, and the air cleaner cap 3 is originally set in shape for each vehicle type. Therefore, even if the flow rate measuring body 15 is additionally formed by integral molding, the number of types of the air cleaner cap 3 does not increase. As a result, it is possible to reduce the number of parts and suppress an increase in cost by eliminating the need for many types of flow rate measuring bodies 15 as conventional independent parts. Further, by integrally forming the flow rate measuring body 15 in the air cleaner outlet duct 3a, it is possible to improve the positional accuracy of the flow rate measuring body 15 and the air cleaner outlet duct 3a and maintain the air flow rate measuring accuracy in good condition.

Next, a method of assembling the air flow rate measuring device 1 according to the embodiment of the present invention will be described.

By this point, the circuit module 1
4 includes a flow rate measuring element 29 (heating element) and a temperature sensing element 30.
Are assembled, and the electrical connection among these elements 29, 30, the intake air temperature sensor 35, the circuit board 33, and the connector 34 is completed.

First, the filter element 5 is attached to the air cleaner case 4, and then the air cleaner cap 3 is attached to complete the air cleaner portion 2.

Next, the circuit module 14 is attached to the air cleaner outlet duct 3a of the air cleaner cap 3. At this time, the fitting convex portion 36 of the circuit module 14 is fitted into the mounting hole 12 of the air cleaner outlet duct 3a, and the screw 39 is inserted into the screw insertion hole of the fixing piece portion 38 formed on the side portion of the circuit module 14. Air cleaner outlet duct 3a
Tighten it into the screw hole of the mounting flange 40 formed in the above.

With the above, the assembly of the air flow rate measuring device 1 according to one embodiment of the present invention is completed.

In the air flow rate measuring device 1 according to the embodiment of the present invention described above, the flow rate measuring body 15 having the bypass passage 18 is formed integrally with the air cleaner outlet duct 3a of the air cleaner portion 2. That is,
A part of the molding die of the air cleaner cap 3 which is originally set to have a different shape for each vehicle type is used to change the flow rate measuring member 15
Is integrally formed with the air cleaner outlet duct 3a of the air cleaner portion 2. As a result, it is possible to reduce the number of parts and suppress an increase in cost by eliminating the need for multiple types of flow rate measuring bodies 15 that are conventional independent parts.

Further, in the conventional air flow rate measuring device, the mounting positions of the flow rate measuring body 15 and the intake pipe may vary, which may affect the air flow rate measuring accuracy. However, in the embodiment of the present invention, By integrally forming the flow rate measuring body 15 with the air cleaner outlet duct 3a,
It is possible to improve the positional accuracy between the flow rate measuring body 15 and the air cleaner outlet duct 3a and maintain the air flow rate measuring accuracy in good condition.

FIG. 4 shows a modification of the air flow rate measuring device 1 according to one embodiment of the present invention. In this modification, a part of the flow rate measuring body 15 is provided on the circuit module 14 side.
That is, the wall portion 3 forming the upstream flow passage 18a of the bypass flow passage 18 near the flow rate measuring element 29 and the temperature sensing element 30.
6a and 36b are integrally formed on the fitting convex portion 36 of the circuit module 14 or provided as separate parts by adhesion or welding. Thereby, the flow rate measuring element 29 and the temperature sensing element 30.
And the positional relationship accuracy between the upstream flow path 18a and
The air flow rate measurement accuracy can be maintained even better. In this case, if the wall portions 36a and 36b are set to be the common portion of the flow rate measuring bodies 15 whose shape is set for each vehicle type, it is possible to cope with the increase in the type of the circuit module 14. You can

[Brief description of drawings]

FIG. 1 is an air flow measuring device 1 according to an embodiment of the present invention.
4 is a partial cross-sectional view of FIG. 3, and is an enlarged cross-sectional view of I part in FIG. 3.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an air flow measuring device 1 according to an embodiment of the present invention.
FIG.

FIG. 4 is an air flow measuring device 1 according to an embodiment of the present invention.
It is a fragmentary sectional view showing a modification of.

[Explanation of symbols]

1 Air flow measuring device 2 Air cleaner part (air cleaner) 3 Air cleaner cap 3a Air cleaner outlet duct (outlet passage) 3b air passage 4 Air cleaner case 4a Air cleaner inlet 5 Filter element (filter body) 12 mounting holes 14 circuit modules 15 Flow rate measuring body 16 Venturi pipe section 17 joint wall 18 Bypass channel 18a upstream flow path 18b Downstream flow path 18c bend 19 Inflow hole 21 Inflow hole 22 Outflow hole 23 Channel expansion part 24 Guide 29 Flow rate measuring element 30 temperature sensitive element 31, 32 Support member 33 circuit board 34 connector 35 Intake temperature sensor 36 Fitting convex part 36a, 36b wall 37 O-ring 38 Fixed piece 39 screws 40 mounting flange C center line

Claims (3)

[Claims] 1. A bypass flow path which is disposed in the air passage and which allows a part of the air flowing through the air flow path to flow in, a flow rate measuring element installed in the bypass flow channel, and an electrical flow of the flow rate measuring element. In an air flow rate measuring device including a control circuit unit that is connected and outputs a flow rate detection signal, the air passage is configured as an outlet passage of an air cleaner, and the bypass passage is integrally formed with the outlet passage. Air flow measuring device. 2. The air flow measuring device according to claim 1, wherein the bypass flow passage and the outlet passage are integrally molded of resin. 3. A filter constituting a part of the air flow rate measuring device according to claim 1 or 2 and provided in the middle of the air flow path for collecting dust contained in the inflowing air. An air cleaner, wherein the bypass passage is integrally formed in the outlet passage on the downstream side of the filter body.