JP3405849B2 - Thermal flow sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal type flow velocity sensor for detecting a flow velocity of a fluid, and more particularly to a thermal type flow velocity sensor having a wind velocity detecting element and a temperature compensating element,
The present invention also relates to a thermal type flow velocity sensor that includes a flow velocity detection element and a temperature compensation element to detect the flow velocity of a fluid.

[0002]

2. Description of the Related Art In order to improve comfort in a building, a lot of measurement information for grasping the environment inside the building is required. The most important content of this measurement information is related to temperature, but airflow control is currently emphasized in order to improve the comfort of the human thermal environment. In order to control the air flow in the building, a thermal air velocity sensor that measures the air volume in the air duct is used.

The thermal type wind velocity sensor is a sensor for measuring the heat loss, that is, the wind velocity, by changing the electric resistance of the wire when the electric heating wire is placed in the air flow because the amount of heat taken by the gas is related to the flow velocity. . Here, the operation principle of the thermal wind sensor will be described with reference to FIG. This thermal wind speed sensor measures a resistance change due to cooling of the wind speed detecting element 12 by a Wheatstone bridge composed of a temperature compensating element 14 and resistors R1 and R2. First, the wind speed detection element 1
Apply current to 2 and heat. The resistance value of the heated wind speed detecting element 12 tends to decrease when the wind hits and cools, but the unbalanced voltage of the Wheatstone bridge is returned to the Wheatstone bridge through the operational amplifier 50. The electric current is supplied by the amount of heat taken by the wind, and the temperature is always kept constant. Here, the voltage deviation applied to the wind speed detection element 12 is taken out as a wind speed signal by the voltmeter 52. Then, by inserting a temperature compensating element 14 on one side of the Wheatstone bridge, the temperature change of the wind hitting the wind speed detecting element 12 is compensated, and in this thermal wind speed sensor, a change in the wind temperature is detected. Even so, the compensated signal can be taken out. Since the wind speed detecting element 12 is heated to a temperature higher by about 25 to 30 degrees than the wind temperature, the wind speed detecting element 12 is used in the thermal wind speed sensor so that this heat is not transmitted to the temperature compensating element 14.
The temperature compensation element 14 and the temperature compensation element 14 are separated from each other.

[0004]

As described above, in the thermal wind speed sensor that employs the structure in which the wind speed detecting element and the temperature compensating element are separated, the mounting direction is specified. That is, if the wind speed detecting element is arranged on the windward side of the temperature compensating element, the wind speed detecting element blocks the wind to the temperature compensating element, and conversely, the temperature compensating element winds the wind of the wind speed detecting element. If arranged above, the temperature compensating element will block the wind to the wind speed detecting element. Therefore, the thermal wind velocity sensor needs to be attached to the wind velocity detecting element and the temperature compensating element so that wind blows from the front, and it is necessary to pay close attention to the attaching direction.

Further, in the thermal type wind velocity sensor, the element shape is downsized and the lead wire of the element is thinned in order to improve the responsiveness. Therefore, when the element is exposed, a failure is likely to occur, and thus a protector formed of wire mesh or the like is attached. Here, when the thermal air velocity sensor is arranged in the air duct, dust or the like is clogged in the stitches of the protector, and the accuracy of the thermal air velocity sensor decreases. Therefore, it is necessary to periodically remove the thermal wind speed sensor and clean the clogged protector, but when mounting the thermal wind speed sensor in the air duct after cleaning, if the mounting direction is inappropriate, Since it has directivity, the accuracy has deteriorated.
On the other hand, there has been proposed a device in which the directivity of the wind speed detecting element is made small. However, when the support member for supporting the wind speed detecting element is arranged so as to block the wind to the temperature compensating element, the wind temperature suddenly changes. The responsiveness when doing was poor.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an omnidirectional thermal flow sensor having a robust and simple structure.

[0007]

In order to achieve the above object, in claim 1, a wind speed detecting element for detecting a wind speed, a temperature compensating element for detecting a wind temperature, a wind speed detecting element and a temperature compensating element. the thermal flow sensor comprising a support member for supporting said wind sensing element is wound a heating metal resistance wire on the outer circumference of the rod-like member, the outer circumference sensitive metal resistance of the temperature compensation element is a ring-shaped member The present invention is characterized in that a wire is wound, the supporting member is formed of a heat insulating material in a rod shape, and the tip supports the wind speed detecting element and the outer periphery supports the temperature compensating element. .

Further, in claim 2, in claim 1,
The support member has a first cylindrical portion having an outer diameter smaller than the inner diameter of the ring-shaped member of the temperature compensation element, and a second cylinder portion having an outer diameter larger than the outer diameter of the ring-shaped member of the temperature compensation element. And the temperature compensation element is placed on a step between the first cylindrical portion and the second cylindrical portion.

According to claim 3, in claim 2,
The protective member for the wind speed detecting element and the temperature compensating element is formed in a cylindrical shape having an inner diameter substantially equal to the outer diameter of the second cylindrical portion of the supporting member and having a through hole formed in the outer periphery thereof, The gist is that the support member is fitted into the outer periphery of the second cylindrical portion.

In order to achieve the above object, in claim 4, a flow velocity detecting element for detecting the flow velocity of the fluid, a temperature compensating element for detecting the temperature of the fluid, a flow velocity detecting element and a temperature compensating element are supported. In a thermal type flow velocity sensor including a support member, the flow velocity detecting element is formed by winding a heating metal resistance wire around the outer periphery of a rod-shaped member, and the temperature compensating element is configured by winding a temperature-sensitive metal resistance wire around the outer periphery of a ring-shaped member. The gist of the present invention is that the support member is formed by rotating the support member, and the support member is formed of a heat insulating material in the shape of a rod, and supports the flow velocity detecting element at the tip and the temperature compensating element at the outer periphery.

[0011]

In the thermal type flow velocity sensor according to the first aspect, the wind velocity detecting element is supported at the tip of the supporting member, and the temperature compensating element is supported at the outer circumference, so that the wind is equally distributed from any direction around the axis. Since it hits, the directivity of the thermal type flow velocity sensor can be eliminated. Further, since the wind speed detecting element and the temperature compensating element are integrally supported by one supporting member, the thermal type flow velocity sensor can be configured easily and robustly.

In the thermal type flow velocity sensor of the second aspect, the temperature compensating element is mounted on the step portion between the first cylindrical portion and the second cylindrical portion of the supporting member, so that the temperature compensating element is attached. Is easy.

According to another aspect of the thermal type flow velocity sensor of the present invention, the outer diameter of the second cylindrical portion of the support member and the inner diameter of the protective member are made substantially equal to each other, and the protective member is attached to the second cylindrical portion of the support member. Since it is inserted, the protection member can be easily attached to the thermal type flow velocity sensor. Further, the one protection member can protect the wind speed detecting element and the temperature compensating element.

In the thermal type flow velocity sensor of the fourth aspect, since the flow velocity detecting element is supported on the tip of the supporting member and the temperature compensating element is supported on the outer periphery, the fluid is equally distributed from any direction around the axis. Since it hits, the directivity of the thermal type flow velocity sensor can be eliminated. Further, since the flow velocity detecting element and the temperature compensating element are integrally supported by one supporting member, the thermal type flow velocity sensor can be configured easily and robustly.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B show a thermal type flow velocity sensor according to an embodiment of the present invention. FIG. 1A shows a state before assembly and FIG. 1B shows a state after assembly. The thermal type flow velocity sensor includes a wind speed detecting element 12, a temperature compensating element 14, and a support member 16 that coaxially supports the wind speed detecting element 12 and the temperature compensating element 14. Wind speed detection element 12
Is formed by spirally winding a platinum resistance wire 17 around the periphery of a rod material 11 made of ceramics or glass having excellent environment resistance. The platinum resistance wire 17 is formed with a glass overcoat (not shown). The platinum resistance wire 17 is protected and fixed. On the other hand, the temperature compensating element 14 is formed by spirally winding a platinum resistance wire 18 around the outer circumference of a ring-shaped bobbin 13 made of ceramics or glass. The platinum resistance wire 18 also has a glass overcoat (not shown). ) Is performed, and the platinum resistance wire 18 is protected and fixed. The bobbin 13 of the temperature compensating element 14 has an inner diameter of k.
1 and the outer shape is formed as k2.

On the other hand, the supporting member 16 is made of a resin having a high heat insulating property such as polyacetal, and the temperature compensating element 1 is used.
The outer diameter smaller than the inner diameter k1 of the bobbin 13 of 4 (outer diameter k
3) the first cylindrical portion 16b and the outer shape k2 of the bobbin 13
A second cylindrical portion 16d having an outer diameter k4 larger than
A step portion 16c having a substantially horizontal upper end surface is formed between the first cylindrical portion 16b and the second cylindrical portion 16d. A hole 16a for inserting the wind speed detecting element 12 is formed at the upper end of the first cylindrical portion 16b.

To assemble the thermal type flow velocity sensor 10, as shown in FIG. 1B, the hole 16a at the upper end of the support member 16 is formed.
The wind speed detecting element 12 is fitted into the casing and fixed with an Epokin bond 19a. The temperature compensating element 14 is inserted into the first cylindrical portion 16b of the supporting member 16 and abutted against the step portion 16c. Fix at. The lead wire of the wind speed detecting element 12 (not shown) is provided in the first cylindrical portion 16
Wiring is provided between b and the bobbin 13 of the temperature compensating element 14. In addition, instead of wiring this lead wire inside the bobbin 13, a through hole (not shown) is provided in the support member 16,
It is also possible to arrange it in this through hole.

Next, the protector of the thermal type flow velocity sensor according to this embodiment will be described with reference to FIG. The protector 20 is formed in a hollow cylindrical shape using a resin having excellent heat insulating properties such as polyacetal, and has an inner diameter k5 of which the supporting member 1 is formed.
It is formed to be slightly larger than the outer shape k4 of the second cylindrical portion 16d of No. 6. The upper end 20a of the protector 20 is shaped like a lid. Then, the outer circumference 20b has a diameter of 2
A through hole 22 of mm is formed. The protector 20 is attached to the thermal type flow velocity sensor 10 by attaching the protector 20 to the thermal type flow sensor 10.
Is applied to the thermal type flow sensor 10. As described above, the inner diameter k5 of the protector 20 is equal to the support member 1
The protector 20 can be easily attached to and detached from the thermal type flow sensor 10 because it is formed to be slightly larger than the outer shape k4 of the second cylindrical portion 16d of No. 6. The vent hole 22 of the protector 20 is provided on the side of the wind speed detecting element 12 and the temperature compensating element 14 to ventilate both elements.

Here, the circuit configuration of the thermal type flow velocity sensor 10 shown in FIG. 1 will be described with reference to FIG. The detection circuit of the thermal type flow velocity sensor 10 detects a resistance change due to cooling of the wind speed detecting element 12 and the temperature compensating element 14 and the resistors R1 and R2.
It is measured by the Wheatstone bridge. First, an electric current is passed through the wind speed detecting element 12 to heat it to a temperature 30 ° C. higher than the air temperature. When the wind speed detecting element 12 that has generated heat is cooled by the wind, the resistance value tends to decrease, but the unbalanced voltage of the Wheatstone bridge is fed back to the Wheatstone bridge through the operational amplifier 50. Electric current is supplied for the amount of heat taken by the wind, and the air temperature is always + 30 °
Kept at C. Here, the voltage deviation applied to the wind speed detection element 12 is taken out as a wind speed signal by the voltmeter 52. By inserting the temperature compensating element 14 on one side of the Wheatstone bridge, the wind velocity signal compensated for the change of the wind temperature can be taken out.

Next, the measurement results of the influence of the heat of the wind speed detecting element 10 on the temperature compensating element 14 will be described with reference to FIG. Here, in the thermal type flow velocity sensor 10 used for this measurement, the wind velocity detecting element 12 has an outer diameter of 1.6 mm and a length of 15 mm, and the bobbin 13 of the temperature compensating element 14 has an outer diameter. 4 mm, inner diameter 3 mm, and height 3 mm. Then, the first cylindrical portion 16b of the support member 16
Is the height (ie top 16a ′ to step 16 shown in FIG. 3).
(distance to c) 8 mm. As a result, the lower end (left end in the drawing) of the wind speed detecting element 12 and the upper end (right end in the drawing) of the temperature compensating element 14 are separated by 5 mm. Figure 3
As can be seen from the above, even if the wind speed detecting element 12 and the temperature compensating element 14 are integrally attached to the supporting member 16, the wind speed detecting element 12 and the temperature compensating element 14 are separated from each other by a distance of 5 mm. The heat of the wind speed detecting element 12 does not affect the temperature compensating element 14 in the state where the temperature of 12 is increased to + 30 ° C.

Next, the experimental results on the thermal response of the thermal type flow velocity sensor 10 will be described with reference to FIG. Here, with the wind speed kept constant, the air temperature was changed from 10 ° C to 30 °.
The output of the thermal type flow velocity sensor 10 when the temperature was raised to C was measured. Note that FIG. 4A shows a state in which the protector 20 is attached to the thermal type flow velocity sensor 10 and the temperature compensating element 14 is blown by the through hole 22 of the protector 20.
Shows a state in which a cover is attached to the temperature compensating element 14 to prevent wind from hitting. In the figure, the vertical axis represents output and air temperature, and the horizontal axis represents time. Wind temperature from 10 ° C to 3
When the temperature is raised to 0 ° C., the output is not much reduced in FIG. 4A showing the present embodiment, whereas the output is greatly reduced in the state shown in FIG. 4B. As can be seen from the results of this experiment, by providing the protector 20 with the through hole 22 and sufficiently blowing the temperature compensating element 14, the deterioration of the responsiveness to the temperature change can be suppressed. Therefore, in the thermal type flow velocity sensor 10, the omnidirectional protector 2
By attaching 0, the temperature compensating element 14 is sufficiently blown with wind from any direction around the axis, so that the responsiveness to a temperature change can be made constant.

Further, the result of measuring the output when the thermal type flow velocity sensor 10 of this embodiment is rotated around the axis by 360 ° under a constant wind speed will be described with reference to FIG. In the figure, the vertical axis shows the output and the horizontal axis shows the angle around the axis.
The solid line E shows the output of the thermal type flow velocity sensor 10, the dotted line F shows the value of plus 2% of the output of the thermal type flow velocity sensor 10, and the dotted line G shows the value of 2% of the output of the thermal type flow velocity sensor 10. Is represented. In the thermal type flow velocity sensor 10 of the present embodiment, as shown in FIG.
Since the wind velocity detecting element 12 is supported on the tip of the supporting member 16 and the temperature compensating element 14 is supported on the outer periphery of the first cylindrical portion 16c as shown in FIG. Will be hit. Therefore, as is clear from FIG. 5, the pointing accuracy within ± 2% of the full scale, that is, high omnidirectionality is achieved.

Next, the result of a comparative test of the output when the protector 20 is attached to the thermal type flow velocity sensor 10 of this embodiment and the output when the protector 20 is not attached will be described with reference to FIG. FIG. 6A shows the case where the protector 20 is attached, and FIG. 6B shows the case where the protector 20 is not attached. It can be seen from FIG. 6 that by attaching the protector 20, the wind hitting the thermal type flow velocity sensor is rectified and the output is stabilized.

Further, the result of an experiment conducted on the directivity when the size of the wind speed detecting element 12 is changed with the size of the through hole 22 of the protector 20 fixed at a diameter of 2 mm is shown in FIG.
Will be described with reference to. In FIG. 7, the vertical axis indicates the pointing accuracy, the bar C indicates the state in which the protector 20 is not attached to the wind speed detection element 12 of each size, and the bar D indicates the state in which the protector 20 is attached. The wind speed detecting element 12 shown in the figure has a diameter (φ) of 1.2 mm and a length (l).
In the case of 8 mm, the air is rectified by the honeycomb-shaped through holes 22 of the protector 20, and the case without the protector 20 (C in the figure) is more omnidirectional than the one with the protector 20 (D in the figure). Is over. When the wind velocity detecting element 12 has a diameter (φ) of 1.6 mm and a length (l) of 10 mm, the case with the protector 20 (D in the figure) is more than the case without the protector 20 (C in the figure). The omnidirectional accuracy is slightly better. Similarly, when the wind velocity detecting element 12 has a diameter (φ) of 1.6 mm and a length (l) of 15 mm, the case with the protector 20 (D in the figure) and the case without the protector 20 (C in the figure)
The omni-directional accuracy is better than that. As can be seen from FIG. 7, the aperture ratio of the through hole 22 of the omnidirectional protector 20,
Depending on the correlation with the size of the wind speed detecting element 12, improvement of the rectification effect and omnidirectionality may be expected. At least the through hole 22 of the protector 20 has a diameter of 2 mm and the wind speed detecting element 12 has a diameter of 1.2 mm. When the length is 8 mm, the one without the protector 20 (C in the drawing) is more omnidirectional than the one with the protector 20 (D in the drawing). In addition,
In order to increase the omnidirectionality, it is necessary to make the wind speed detecting element 12 large to some extent, but if it is too large, the responsiveness will decrease.

As described above, in this embodiment, since the temperature compensating element 14 is placed on the step portion 16c between the first cylindrical portion 16b and the second cylindrical portion 16d of the supporting member 16, The temperature compensating element 14 can be easily attached. Further, since the outer diameter of the second cylindrical portion 16d of the support member 16 and the inner diameter of the protector 20 are made substantially equal to each other so that the protector 20 is fitted into the second cylindrical portion 16d of the support member 16, The protector 20 can be easily attached to and detached from the thermal type flow sensor 10. For this reason,
Even if the protector 20 is clogged during use of the thermal type flow velocity sensor 10, the thermal type flow velocity sensor 10 causes the protector 2 to move.
It can be easily cleaned by removing 0. Further, the wind velocity detecting element 12 and the temperature compensating element 14 are provided on one supporting member 16.
Since and are supported coaxially, the wind speed detection element 12 and the temperature compensation element 14 can be protected by the single protector 20 having a simple cylindrical shape.

In the embodiment described above, the support member 16
Although the support member 16 is formed in a cylindrical shape, the support member 16 may be formed in a prismatic shape, for example. Further, in this embodiment, the platinum wire is used as the heat-generating metal resistance wire of the wind speed detecting element 12 and the thermal type flow velocity sensor, but other metal wire, for example, tungsten wire may be used instead of the platinum wire. Further, in the above-described embodiment, the protector 20 is used as the thermal type flow sensor 10.
Although the configuration in which the protector 20 is fitted and fixed is illustrated, it is also possible to form a screw on the protector and the thermal flow sensor and fix the protector 20 with the screw. Furthermore, although the example in which the support member 16 is formed of resin has been described, the support member can be formed of various materials as long as the material has sufficient heat insulation.

Further, in the above-mentioned embodiment, the thermal type flow velocity sensor is composed of the wind velocity detecting element 12 and the temperature compensating element 14 to detect the wind velocity. In the present invention, instead of this, a flow velocity detecting element for detecting the flow velocity of the fluid is formed in the same structure as the wind velocity detecting element 12 described above, and a temperature compensating element for measuring / compensating the temperature of the fluid is used. The flow velocity detecting element and the temperature compensating element may be coaxially supported by the support member 16 so that the flow velocity of a liquid such as warm water can be measured.

[0028]

As described above, in the thermal type flow velocity sensor of the present invention, the wind velocity detecting element is supported at the tip of the supporting member, and
Since the temperature compensating element is supported on the outer circumference of the first cylindrical portion, the wind is uniformly applied from any direction around the axis, and the directivity can be eliminated. Therefore, for example, when it is attached to the air duct, it can be attached in any direction, which facilitates the work. Further, since the wind speed detecting element and the temperature compensating element are integrally supported by one supporting member, the thermal type flow velocity sensor can be configured easily and robustly.

[Brief description of drawings]

FIG. 1 is a perspective view showing a thermal type flow sensor according to one embodiment of the present invention.

FIG. 2 is a perspective view showing a protector of the thermal type flow velocity sensor shown in FIG.

FIG. 3 is an explanatory diagram showing the thermal response of the thermal type flow velocity sensor shown in FIG.

FIG. 4 is an explanatory diagram showing the responsiveness of the thermal type flow sensor shown in FIG. 1 to a change in wind temperature.

5 is a characteristic diagram showing omnidirectionality of the thermal type flow velocity sensor shown in FIG.

FIG. 6 is a graph showing a rectifying effect by the protector according to the embodiment of the present invention.

FIG. 7 is a graph showing the influence of the presence / absence of a protector and the size of the wind speed detection element according to the embodiment of the present invention.

FIG. 8 is a circuit diagram of a detection circuit using a thermal type flow velocity sensor.

[Explanation of symbols]

10 Thermal flow sensor 11 bars 12 Wind speed detection element 13 bobbins 14 Temperature compensation element 16 Support member 20 protectors

─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP 59-102118 (JP, A) JP 5-142237 (JP, A) JP 5-93706 (JP, A) Actual development 63- 135231 (JP, U) Actual development Sho 61-152920 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01P 5/12 G01F 1/68

Claims (4)

(57) [Claims] 1. A thermal type flow velocity sensor comprising a wind speed detecting element for detecting a wind speed, a temperature compensating element for detecting a wind temperature, and a supporting member for supporting the wind speed detecting element and the temperature compensating element. The element is formed by winding a heating metal resistance wire around the outer periphery of a rod-shaped member, the temperature compensation element is formed by winding a temperature-sensitive metal resistance wire around the outer periphery of a ring-shaped member, and the support member is formed into a rod-shaped heat insulating material. A thermal type flow velocity sensor, which is formed, and which supports the wind speed detecting element at the tip and also supports the temperature compensating element at the outer circumference. 2. The support member includes a first cylindrical portion having an outer diameter smaller than the inner diameter of the ring-shaped member of the temperature compensation element, and an outer diameter larger than the outer diameter of the ring-shaped member of the temperature compensation element. 2. The thermal formula according to claim 1, further comprising: a second cylindrical portion, wherein the temperature compensating element is mounted on a step portion between the first cylindrical portion and the second cylindrical portion. Flow sensor. 3. A protective member for the wind speed detecting element and the temperature compensating element is formed into a cylindrical shape having an inner diameter substantially equal to the outer diameter of the second cylindrical portion of the supporting member and having a through hole formed in the outer periphery thereof. The thermal flow velocity sensor according to claim 2, wherein the thermal flow velocity sensor is formed and fitted to the outer periphery of the second cylindrical portion of the support member. 4. A flow velocity detecting element for detecting the flow velocity of a fluid,
In a thermal type flow velocity sensor comprising a temperature compensation element for detecting the temperature of a fluid and a support member for supporting the flow velocity detection element and the temperature compensation element, the flow velocity detection element has a heating metal resistance wire wound around an outer periphery of a rod-shaped member. The temperature compensating element is formed by winding a temperature-sensitive metal resistance wire around the outer periphery of the ring-shaped member, the support member is formed of a heat insulating material in a rod shape, and the flow velocity detecting element is formed at the tip. A thermal type flow velocity sensor, characterized in that it supports and also supports the temperature compensating element on the outer periphery.