JPH08159840A - Air filter integration type flow detection device - Google Patents

Abstract

PURPOSE: To stabilize output voltage over the whole area of a detection flow rate range, and detect a flow rate with extremely excellent accuracy by using a filter formed into a corrugated shape and a straightening wire mesh. CONSTITUTION: A straightening portion 20 spreading upward and a square box-shaped air filter containing portion 18 are nuitedly set on a cylindrical flow detection portion 21 equipped with a flow sensor 4. A straightening wire mesh 19 is fitted on the bottom portion of the straightening portion 20, and corrugated seatings 16 are set on two confronting inside faces of the air filter containing portion 18 so as to face each other. A corrugated air filter pressers 12 are set on a top cover 14 so as to face the corrugated seatings 16 so that the filter 3 formed into corrugated shape can be sandwiched and fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot wire type flow rate detecting device for detecting the amount of air mainly based on a change in resistance value of a hot wire exposed in a flow path, and an air filter used in the device. The present invention relates to an air filter integrated flow rate detection device that has low flow resistance and can be easily attached and detached when the air filter is replaced.

[0002]

2. Description of the Related Art Generally, as one of flow rate detecting means, a so-called air flow rate (hereinafter, simply referred to as a flow rate) is detected by a change in resistance value of a self-heated heat wire which is exposed to a fluid flow path. A hot-wire type flow rate detecting device is widely known, and the applicant of the present application has applied for a device having a structure as shown in FIG. 4 as a device for detecting the flow rate of a blower using this flow rate detecting device (special feature: No. 5-315940).

The conventional flow rate detecting device 1 shown in FIG.
The flow rate detecting portion is formed in a cylindrical shape, and a flat air filter 3 having substantially the same area as the flow rate detecting portion is attached to the inflow side end portion 2 at the tip end of the flow rate detecting portion. The hot wire type flow sensor 4 was attached to the central portion, and the outflow side end portion 5 had a shape in which the flow passage forming portion was tapered (about 15 °).

The hot-wire type flow rate sensor 4 comprises a flow rate detecting element 6 and an air temperature detecting element 7. The HIC (hybrid IC) 8 and the flow rate detecting element 6 form a bridge circuit and detect the air temperature. The element 7 corrects the temperature and outputs an electrical signal corresponding to the air flow rate. In the figure, 9 is a blower, 10 is an electronic control unit, and 11 is an external signal.

On the other hand, with respect to the inner diameter of the flow rate detecting portion, in order to increase the change of the output voltage with respect to the flow rate, it is necessary to increase the flow velocity value passing through the flow rate detecting portion, and the inner diameter of the flow rate detecting portion is made as small as possible. Although it is desirable to do so, in the hot-wire type flow rate detection device, the delicate movement of the air around the hot-wire affects the change in the self-heated resistance, and the output voltage slightly fluctuates, causing an error in the flow rate detection. There is a problem,
It is necessary to properly match the Reynolds number relationship to the flow rate range to be detected. In consideration of these contradictory conditions, the size of the inner diameter of the flow rate detecting portion is determined, and the area of the air filter is adjusted to this inner diameter.

[0006]

However, in the air filter in such a conventional flow rate detecting device, due to the design restriction of the inner diameter of the flow rate detecting portion, the flow rate is considered in consideration of the laminar flow of the air flow. The area is almost the same as the inner diameter of the detection part,
Moreover, since it has a flat shape, there is a problem that the filtration area is small and the life of the air filter is short.

To solve this problem, it is possible to increase the area of the air filter by increasing the inner diameter of the flow rate detecting portion and increasing the diameter of the air filter mounting portion only. However, the mechanical strength of the air filter, for example, if the air filter is inadvertently pressed down by the hand, the air filter may fall off or bend, and the size of the flat filter may be limited to achieve a flat shape. If so, the design life value cannot be satisfied.

As a method of satisfying this, there is a method of fixing the air filter with an outer frame (not shown) made of metal. However, the manufacturing cost and the number of parts increase, and the air filter portion and the flow rate are increased. Due to the large difference in the flow area of the detection unit, it is considered that the delicate movement of the air around the heat wire affects the output voltage. In addition, the balance between the size of the flow rate detection unit and the size of the air filter storage unit is poor, resulting in a disadvantageous shape against vibration.
Inevitably, the size of the inner diameter of the flow rate detection unit must be set to a size suitable for holding the air filter storage unit, which causes a problem that the change in the output voltage becomes small.

Further, the output voltage in the conventional flow rate detecting device has a problem that a slight variation of the output voltage occurs in a high flow rate region in the flow rate detecting range, which causes a flow rate detecting error.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rectifying section 20 and a box-shaped air filter accommodating section 18 above a flow rate detecting section, and an air filter formed in a corrugated shape. By storing the filter 3 and providing the rectifying wire net 19 in the rectifying section 20, the change in the output voltage with respect to the flow rate is maximized and the output signal is stabilized to eliminate the flow rate detection error. Another object of the present invention is to provide a flow rate detecting device which can extend the life of the air filter and can be attached / detached at the time of replacement with one touch.

That is, the air filter integrated flow rate detecting device of the present invention is provided with the hot-wire type flow rate sensor 4 at a substantially central portion of the flow rate detecting section 21 formed in a cylindrical shape.
A rectifying part 20 having an expanded shape and a box-shaped air filter accommodating part 18 are integrally provided above the rectifying part 20, a rectifying wire net 19 is attached to the bottom part of the rectifying part 20, and the air-filter accommodating part 18 is opposed to the box-shaped air filter accommodating part 18. The undulating bases 16 are provided on the two inner side surfaces facing each other, and on the other hand, the upper and lower lids 14 having the plurality of ventilation holes 15 fitted in the air filter housing 18 are provided with two opposite sides. A corrugated air filter holder 12 is provided at the end corresponding to the corrugated pedestal 16, the corrugated air filter 3 is placed on the corrugated portion of the pedestal 16, and the upper lid 14 is fitted into the storage portion 18. It is characterized in that the outer peripheral portion of the air filter 3 is sandwiched and fixed by the air filter retainer 12.

In a second aspect of the present invention, the straightening wire net 19 is a square wire net and the flow rate detection range is 0 to 2.
When the wire diameter of the straightening wire mesh is d and the pitch of the wire mesh is t with respect to 00l / min (average flow velocity 0 to 3.3 m / s), d / t
= About 0.5-0.7, The air filter integrated type flow rate detection device according to claim 1, wherein.

[0013]

According to the present invention, the air filter 3 has a corrugated shape to increase the surface of the air filter to prolong the service life. Further, the rectifying wire net 19 provided in the rectifying section 20 allows the turbulent flow of the entire flow path. Since the pulsating flow is alleviated and the air flow rectified by the rectifying wire mesh flows around the heat wire, the output voltage of the heat wire type flow sensor becomes a stable output, and the accurate flow rate can be detected.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of an air filter integrated flow rate detection device of the present invention, and FIG. 2 is a semi-longitudinal side view of the same device. The air filter integrated flow rate detection device of the present invention is provided with an outflow portion 22 as an outflow side end portion 5 at the lower side, a hot wire type flow rate sensor 4 is provided in a central flow rate detection portion 21, and an upper portion of the flow rate detection portion 21. An air filter accommodating portion 18 that constitutes the inflow side end portion 2 is integrally provided with resin via a rectifying portion 20. In the case of this embodiment, the outflow portion 22
Has a smaller diameter than the flow rate detection unit 21 according to the size of the device to be connected (blower in the present invention), but on the contrary, when the inner diameter is increased or the inner diameter of the outflow unit 22 is changed to the flow rate detection unit 2.
Even if it is the same as the inner diameter of 1, there is no problem.

Further, a straightening wire net for stabilizing the flow of fluid is fixed to the bottom of the straightening part 20 by heat staking. The straightening wire net 19 is a square wire net, and its effect will be described in detail later.

The air filter accommodating portion 18 is formed in a box shape, and a corrugated pedestal 16 for mounting an air filter 3, which will be described later, is mounted on two inner side surfaces of the air filter accommodating portion 18 which face each other. It is set up opposite. Also,
The other inner surface is provided with a notch 17 for fitting a protrusion 13 on the outer surface of the upper lid 14 which will be described later.

The inverted lid-like upper lid 14 has a plurality of ventilation holes 15 in the upper portion thereof, and the air filter holder 12 formed in a wavy shape corresponding to the wavy pedestal 16 at two opposite side end portions. Is provided. In addition, a protrusion 13 that fits into the notch 17 is provided on the outer peripheral portion of the air filter retainer 12.
Is provided. The upper lid 14 may be integrated with the air filter housing portion 18 by resin molding via the hinge 23, or the hinge 23 may be removed to form a separate body.

The air filter 3 is formed by bending a non-woven fabric into a corrugated shape. The air filter 3 is placed on the corrugated portion of the pedestal 16 and the upper lid 14 is fitted into the accommodating portion 18 to hold the air filter 12 in place. The outer peripheral portion of the air filter 3 can be clamped and fixed.

The flow rate detecting element 6 of the hot wire type flow sensor 4
Is exposed to the inner surface of the flow rate detection unit 21 in a self-heated state, and a so-called constant temperature type flow rate detection that forms a bridge circuit by the resistance value at the set heating temperature configured inside the HIC 8 is used. The voltage applied to the bridge, that is, the output voltage, is correlated with the flow rate. In addition, the air temperature detecting element 7 has a resistance value that changes depending on the ambient temperature, and corrects the temperature of the output voltage. Although the HIC connected to the hot wire type flow sensor 4 is externally attached, the flow sensor unit and the HIC may be integrally formed.

Next, regarding the effect of the rectifying wire net 19 used in the apparatus of the present invention, various flow rectifying grids are used and the flow rate detection range is 0 to 200 l / min. As a result of confirming the rectification effect on the turbulent flow region above / min, the characteristics shown in Table 1 were obtained.

[0021]

[Table 1]

According to an experiment conducted by the present inventor, as shown in Table 1 above, the 100 specified in JIS8801 is particularly used.
A remarkable rectifying effect was observed for the and those of 150 mesh. Here, d / t was calculated for 100 meshes (d = 0.104, t = 0.150) and 150 meshes (d = 0.060, t = 0.19) of the rectifying wire mesh used in the present invention. As a result, in the case of 100 mesh, d / t = 0.693, and in the case of 150 mesh, d / t = 0.550. That is, when the wire diameter of the rectifying wire mesh is d and the pitch of the wire mesh is t with respect to the flow rate detection range of 0 to 200 l / min (average flow velocity of 0 to 3.3 m / s), d / t = about 0.5. It was concluded that it is desirable to use a rectifying wire mesh with a value of ~ 0.7. That is, the rectifying wire net of the present invention can enhance the rectifying effect by reducing the area for one square and realize a laminar flow of air.

For reference, JIS B8330-19
In the blower test and inspection method of 81, the rectifying wire mesh used for the test device is described. The rectifying wire mesh in this case is d: linear shape of the rectifying wire mesh [mm], t: pitch of the rectifying wire mesh [mm]. Therefore, it is desirable that the value of d / t is about 0.13. This is due to the difference in usage environment,
In other words, it can be inferred that the values greatly vary depending on the size of the channel inner diameter, the flow rate value, and the like.

Further, FIG. 3 is a flow sensor output characteristic diagram of the product of the present invention (100 is used as the rectifying wire mesh) and the conventional product shown in FIG. In the product, a large fluctuation is seen in the output voltage, whereas in the product of the present invention, such a phenomenon does not occur at all. That is, in the product of the present invention, after being purified by the air filter 3 formed in a wave shape, the rectifying wire net 19
Since there is no turbulent flow or pulsating flow in the air flow, minute fluctuations in the output voltage are significantly reduced, and the flow rate detection accuracy is extremely good.

[0025]

As described above, according to the present invention, the rectifying wire net 19 stabilizes the output voltage over the entire detected flow rate range, so that the flow rate can be detected extremely accurately.

The inner diameter of the flow passage forming portion (flow passage detecting portion 21) can obtain a laminar flow by the straightening wire net 19 as described above, so that the strength balance with the air filter housing portion 18 is taken into consideration. Not only can it be made as small as possible,
By using the rectifying wire net 19, it is not necessary to use a honeycomb rectifying grid composed of a large number of cells, which has been commonly used in the past, so that the product can be made compact.

Further, by using the upper lid 14 which forms the air filter 3 in a corrugated shape to increase the filtration area and protects the air filter 3, not only the life of the air filter is extended but also the air filter 3 It can be attached and removed at the time of replacement with a single touch.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an air filter integrated flow rate detection device of the present invention.

FIG. 2 is a semi-longitudinal side view of an air filter integrated flow rate detection device of the present invention.

FIG. 3 is a comparison graph of flow sensor output characteristics of the product of the present invention and the conventional product.

FIG. 4 is a block diagram of a centrifugal blower using a conventional flow rate detection device.

[Explanation of symbols]

1 Flow rate detector. 2 Inflow end. Three
Air filter. 4 Flow rate sensor. 5 Outflow end. 6 Flow rate detection element. 7 Air temperature detection element.
8 HIC. 9 Blower. 10 Electronic control unit. 11 External signal. 12 Air filter holder. 13 Protrusion. 14 Top lid.
15 Vents. 16 Wavy pedestal. 17
Notch part. 18 Air filter storage part. 19 Straightening wire mesh. 20 Rectifier. 21 Flow rate detector. Two
2 Outflow section. 23 Hinge.

Claims (2)

[Claims] 1. A hot-wire type flow rate sensor 4 is provided at a substantially central portion of a flow rate detection section 21 formed in a cylindrical shape.
A rectifying part 20 having an expanded shape and a box-shaped air filter accommodating part 18 are integrally provided above the rectifying part 20, a rectifying wire net 19 is attached to the bottom part of the rectifying part 20, and the air-filter accommodating part 18 is opposed to the box-shaped air filter accommodating part 18. The corrugated pedestals 16 are provided so as to face each other on the two inner side surfaces, and on the other hand, there are two opposite sides of the inverted box-shaped upper lid 14 which is provided with a plurality of ventilation holes 15 and which is fitted into the air filter accommodating portion 18. A corrugated air filter holder 12 is provided at the end corresponding to the corrugated pedestal 16, the corrugated air filter 3 is placed on the corrugated portion of the pedestal 16, and the upper lid 14 is fitted into the storage portion 18. An air filter integrated type flow rate detection device, wherein the air filter holder 12 is inserted and the outer peripheral portion of the air filter 3 is clamped and fixed. 2. The rectifying wire net 19 is a square wire net and has a flow rate detection range of 0 to 200 l / min (average flow velocity of 0 to 3.3 m / s).
On the other hand, when the wire diameter of the rectifying wire mesh is d and the pitch of the wire mesh is t, d / t is approximately 0.5 to 0.7, and the air filter integrated flow rate according to claim 1. Detection device.