JPH0632596Y2 - Differential pressure detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a differential pressure detector, and more particularly to a differential pressure detector for detecting a static pressure difference between two compartments.

(Prior Art) Conventionally, in an air conditioning / ventilation system or a clean room system, various differential pressure detectors have been used to control the room pressure.

As such a differential pressure detector, one using a diaphragm or one using a float has been conventionally used.

(Problems to be Solved by the Invention) Since the conventional differential pressure detectors each use a displacement member such as a diaphragm or a float that is displaced according to the differential pressure, a range of a small static pressure difference, for example, The accuracy was extremely poor at about 1 to 2 mmAq (water column). Moreover, when a diaphragm or the like is used, a temperature change or a temporal change is large due to a change in the coefficient of linear expansion, and therefore a complicated correction circuit is required. Therefore, the conventional differential pressure detector is also expensive.

Therefore, the main purpose of this invention is to provide a more accurate differential pressure detector.

Another object of this invention is that temperature changes and changes over time are small,
Therefore, it is an object to provide an inexpensive differential pressure detector as a whole.

(Means for Solving the Problems) Briefly stated, the present invention provides a communication part that connects two compartments, a post provided in the communication part, and a communication part that is provided to detect a Karman vortex generated by the post. An ultrasonic transmitter that is provided, an ultrasonic receiver that receives an ultrasonic signal from the ultrasonic transmitter, and a flow velocity detection means that receives a signal from the ultrasonic receiver and outputs a signal that represents the flow velocity in the communication section,
A differential pressure detector in which the output of the flow velocity detecting means is used as a signal related to the static pressure difference between the two sections.

(Operation) In the communication part, Karman vortices are generated downstream of the post according to the magnitude of the static pressure difference between the two sections. The ultrasonic signal from the ultrasonic transmitter undergoes phase modulation in the generation cycle of the Karman vortex. Therefore, the flow velocity detection means outputs an electric signal representing the flow velocity in the communication section based on the output signal of the ultrasonic receiver. This electrical signal is used, for example, by the pressure control means as a signal relating to the static pressure difference between the two compartments.

(Effect of the Invention) According to the present invention, the output of the ultrasonic Karman vortex velocimeter is used as a signal related to the static pressure difference between the two sections, so that a minute differential pressure such as 1 mmAq or less can be accurately detected. it can. Therefore, the accuracy is improved as compared with the conventional differential pressure detector using a diaphragm or a float.

In addition, since the ultrasonic Karman vortex velocimeter does not include a displacement member, it is less susceptible to changes in the coefficient of linear expansion and the like, so changes in temperature and changes over time are small, and thus no special correction circuit is required. Therefore, according to this invention, a cheaper and more accurate differential pressure detector as a whole can be obtained.

Furthermore, Karman vortex velocimeters other than the ultrasonic type are not suitable as differential pressure detectors because they cannot determine whether they are positive or negative.
If you use an ultrasonic Karman vortex meter like this,
Since the positive / negative of the differential pressure can be determined, the differential pressure can be accurately detected.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments below with reference to the drawings.

(Embodiment) FIG. 1 is an illustrative view showing one embodiment of the present invention. The differential pressure detector 10 of the present invention detects the static pressure difference that occurs between the two compartments 12 and 14. Therefore, a communication part 16 is formed between the compartments 12 and 14 so that both ends thereof communicate with the corresponding compartments. Compartments 12 and 14 may each be indoors or conduits. It is also possible that one of the compartments 12 and 14 is atmospheric. Further, the communication part 16 is formed of a pipe line in this embodiment, but may be formed as a through hole in the partition wall forming the partition 12 or 14.

A post 18 such as a column or a prism is provided in the communication section 16 as described above. A Karman vortex 20 is generated downstream of the post 18 by the post 18. In order to detect the Karman vortex 20, an ultrasonic transmitter 22 and an ultrasonic receiver 24 are provided with the communication section 16 in between. The ultrasonic transmitter 22 is driven by the signal from the flow velocity detection circuit 26, and the signal from the ultrasonic receiver 24 is also provided to this flow velocity detection circuit 26. As the flow velocity detection circuit 26, various known circuits can be used,
An example of such a circuit is disclosed, for example, in Japanese Patent Publication No.
No. 333, Japanese Patent Publication No. 61-566, Japanese Patent Application Laid-Open No. 60-22625 and the like. Therefore, a specific and detailed description of the flow velocity detection circuit 26 will be omitted here.

However, it goes without saying that a circuit configuration other than those disclosed in these publications may be used as the flow velocity detection circuit 26.

In any case, from the flow velocity detection circuit 26, the communication unit 16
An electrical signal A representing the flow velocity at is obtained. That is,
If the section 12 has a static pressure P1 and the section 14 has a static pressure P2, a static pressure difference ΔP (= P1−P2) between the two sections 12 and 14 is generated in the communication portion 16. Therefore, as shown in FIG. 2, the flow velocity detection circuit 26 outputs an electric signal representing the static pressure difference ΔP, for example, a DC voltage signal.

According to experiments by the inventors, a graph as shown in FIG. 3 was obtained. As shown in FIG. 3, from the flow velocity detection circuit 26 in the embodiment of FIG. 1, although there is some error range or variation, the communication portion 1 has a small static pressure difference.
An output A having a curve very close to the curve representing the air volume at 6 is obtained. Therefore, this output A is used as a signal or data related to the static pressure difference, and
2 or 14 may be controlled.

However, in that case, for example, as shown in FIG. 3, the curve of the output A is almost a straight line in the range of the static pressure difference of 1 to 6 mmAq.
Can be used as it is as a voltage proportional to the static pressure difference. However, below 1 mmAq,
Since the curve is large, it is difficult to use the output A as it is. Therefore, it is conceivable to use means for linearly approximating the output A.

Therefore, in the embodiment of FIG. 1, as an example of such a linear approximation means, the square root of the output A of the flow velocity detection circuit 26 is received. The converter 28 is used. An example of such a square root converter 28 is an integrated circuit "NJM" as shown in FIG.
4200 ″ or the like can be used. In the square root converter 28, the output A of the flow velocity detecting circuit 26 as shown in FIG. 2 can be expressed by a linear type or proportional type as shown in FIG. Convert to B.

That is, as shown in FIG. 4, the square root converter 28 is
The output A from the flow velocity detector 26 is received at the input terminal 28a, converted into a square root by the circuit portion 28b and its related circuit, and the output B is output from the output terminal 28c. More specifically, if the current flowing from the input terminal 28a through the resistor R ₁ is I ₁ , the current flowing from the reference voltage V _R through the resistor R ₂ is I _2, and the current flowing through the resistor R ₄ is I ₄ , then the integrated circuit Circuit part 28
From b, the current I ₃ = I ₁ I ₂ / I ₄ is output. This current is applied to the operational amplifier, and therefore, the voltage of the input A is V
_{Letting X} be the output B of the voltage V ₀ .

Thus, the output A is square-root converted to obtain the voltage output B by passing through the square-root converter 28.

However, it is of course possible to perform square root conversion using a digital arithmetic circuit without using the analog circuit shown in FIG.

Thus, using the square root converter 28, its output can be used as a signal or data having a magnitude proportional to the static pressure difference between the two sections 12 and 14 as shown in FIG. become.

FIG. 6 is a block diagram showing an application example of the present invention.
The example of FIG. 5 is a system for controlling the static pressure in the chamber 100 to a positive (+) pressure, and can be used as, for example, a clean room control system.

The chamber 100 includes an air supply fan 102 and an exhaust fan 10
4 are connected by ducts 106 and 108, respectively. Then, a communication portion 16 is formed between the duct 100 from the chamber 100 to the exhaust fan 104 and the atmosphere, and a flow in the direction of the atmosphere is detected in the communication portion 16 so as to detect the flow toward the atmosphere. A differential pressure detector 10 using a Karman vortex velocimeter as shown in the embodiment is provided.

Then, the fan capacity control device 110 is provided so as to receive the output B of the differential pressure detector 10 or its data. The fan capacity control device 110 allows the exhaust fan 1 to operate in response to a signal or data from the differential pressure detector 10.
Control the displacement of 04. That is, the capacity of the exhaust fan 104 is controlled by the fan capacity control device 110 according to the output B of the differential pressure detector 10 (this may be the output A) or its data. This fan capacity control device 11
Zero may directly control the rotation speed of the exhaust fan 104, that is, the frequency of the inverter, or may control the opening degree of the inlet vane. Further, instead of controlling the exhaust fan 104, the exhaust damper or the air supply fan 102 may be controlled.

In the example of FIG. 6, since the communication portion 16 that communicates with the atmosphere is formed in the middle of the duct 108, the outflow of air into the atmosphere and the inflow of air from the atmosphere occur, but the air volume is small and the air conditioning There is no effect on the temperature control of ventilation or the air cleanliness of the room, and there is almost no increase in power accompanying it.

In the embodiment of FIG. 6, the case where the inside of the chamber 100 is set to the positive (+) pressure has been described. However, it is of course possible to control the inside of the chamber 100 to a negative (-) pressure. In this case, the flow velocity in the direction opposite to that shown in FIG. 6 may be detected. For example, the ultrasonic transmitter 22 and the ultrasonic receiver 24 (FIG. 1) may be provided on the downstream side of the Karman vortex generating post 18. It may be arranged in the.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a graph showing the output of the flow velocity detection circuit of the embodiment shown in FIG. FIG. 3 is a graph showing the experimental results. FIG. 4 is a circuit diagram showing in detail an example of the square root converter of the embodiment shown in FIG. FIG. 5 is a graph showing the output of the square root converter in the embodiment of FIG. FIG. 6 is a block diagram showing an application example of the present invention. In the figure, 12 and 14 are compartments, 16 is a communication part, 2
6 is a flow velocity detection circuit, and 28 is a square root converter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-61-77718 (JP, A) Actually opened 61-52224 (JP, U) Actually opened 61-146723 (JP, U)

Claims (5)

[Scope of utility model registration request] 1. A differential pressure detector for detecting a static pressure difference between two compartments, the communicating section communicating the two compartments, a post provided in the communicating section, and a post generated by the post. An ultrasonic transmitter provided in the communication unit for detecting a Karman vortex, an ultrasonic receiver that receives an ultrasonic signal from the ultrasonic transmitter, and a communication unit that receives a signal from the ultrasonic receiver. A differential pressure detector comprising: a flow velocity detecting means for outputting a signal representing a flow velocity, wherein the output of the flow velocity detecting means is used as a signal relating to the static pressure difference. 2. The differential pressure detector according to claim 1, further comprising approximation means for approximating the output signal of the flow velocity detection means by a straight line. 3. The differential pressure detector according to claim 2, wherein the approximating means includes a square root converter. 4. The differential pressure detector according to claim 1, wherein the output of the flow velocity detecting means is given to control means for controlling the pressure of at least one of the two sections. 5. The output of the approximating means is provided to control means for controlling the pressure in at least one of the two compartments.
The differential pressure detector according to claim 2 or 3 of the utility model registration claim.