JPH06174514A - Flow rate measuring device - Google Patents

Abstract

PURPOSE:To improve measurement reliability and to reduce the dimensions of a main channel by providing a space part with a large channel area at the main channel and then providing the entrance of a bypass channel. CONSTITUTION:A space part 12 with a larger channel area than that of a main channel 13 is provided at the downstream of the main channel 13 and a main channel 14 is connected to the downstream of the space part 12. Liquid flowing in the direction of an arrow 6 enters the space part 12 and partially flows to a bypass channel 2. After flow velocity is measured by a thermal sensor 5 in the channel 2, a fluid flows from an exit 4 to the main channel 14 and then merges. The flow rate of the fluid flowing into the main channels 13 and 14 is obtained from the flow rate in the channel 2 which is measured by the sensor 5. Since the channel area of the space part 12 is larger than a main channel 13, the flow velocity decreases and at the same time pressure increases. Since the channel area is smaller than the space part 12 at the main channel 14, the flow velocity increases and at the same time pressure decreases. Therefore, the pressure in the space part 12 becomes higher than that of the main channel 14 and the flow in the channel 2 is constantly directed from the entrance 3 to the exit 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus suitable for measuring a flow rate of a fluid and a method of using the apparatus.

[0002]

2. Description of the Related Art In a flow rate measuring device for measuring a flow rate in a main flow path by measuring a flow velocity in a bypass flow path, when a flow vibration source (for example, a cylinder of an automobile engine) exists downstream of a flow rate measuring section, a reverse flow is temporarily generated. It is necessary to prevent fluctuations in the measured flow rate due to the flow of water. In the conventional flow rate measuring device, as described in JP-A-62-54126, a main flow path is provided with a bypass flow path for flow velocity measurement, a main flow path is provided with a bypass flow path inlet, and a venturi portion is provided downstream thereof. Provided, the bypass flow path outlet is provided in the venturi part, and the structure is such that the fluid after flow velocity measurement merges with the main flow in the venturi part. By making the inlet pressure larger than the bypass outlet pressure, the flow in the bypass flow passage is made smooth and the back flow in the bypass flow passage due to the temporary back flow of the main flow is prevented.

Further, in the conventional apparatus, as described in Japanese Patent Laid-Open No. 56-14915, the influence of the backfire of the internal combustion engine on the heat ray for air temperature measurement provided upstream of the bypass passage inlet of the main passage is affected. Some have a buffer chamber to alleviate.

[0004]

In the prior art disclosed in Japanese Unexamined Patent Publication No. 62-54126, there is a problem that the performance of an internal combustion engine or the like cannot be improved because pressure loss occurs in the venturi portion and the fluid supply amount decreases. there were.

Further, in the prior art disclosed in Japanese Patent Laid-Open No. 56-14915, in addition to the above-mentioned problems, the reverse flow of the bypass flow passage cannot be prevented during the temporary reverse flow of the main flow, and the characteristic of the flow velocity detecting member is There was a problem that the reliability of flow measurement of turbulent main flow was reduced.

An object of the present invention is to measure a flow rate in a fluid flow rate measuring device without increasing a pressure loss in a main flow path and prevent a temporary backflow to a bypass flow path.

[0007]

In order to achieve the above object, the present invention provides a means for detecting the flow velocity of a fluid in a bypass flow passage in which a part of the flow from the main flow passage is separated to flow in the main flow passage. In a bypass type flow rate measuring device that detects the flow rate of a fluid, the main flow passage is provided with a space portion having a flow passage area larger than that of the main flow passage, and the flow passage area of the main flow passage downstream of the space portion is set to the flow passage area of the space portion. Further, the space is provided with an inlet of the bypass flow passage, and the main flow passage downstream of the space is provided with a confluence portion of the bypass flow passage to the main flow passage.

[0008]

When the fluid flowing through the main flow passage flows into the space having a larger flow passage area than the main flow passage, the flow velocity decreases and the pressure increases. Furthermore, since the flow passage area of the main flow passage downstream from the space portion is smaller than that of the space portion, the flow velocity of the fluid increases and the pressure decreases. As a result, the pressure in the space always becomes higher than the pressure in the downstream of the main flow path. In this flow path, a bypass flow path having a device for detecting the flow velocity is provided, a bypass flow path inlet is provided in the space part, an outlet of the bypass flow path is provided downstream of the space part of the main flow path, and the bypass flow becomes the main flow. The structure is such that it merges.

As a result, the bypass flow passage outlet pressure becomes lower than the bypass flow passage inlet pressure even when the fluid temporarily flows back in the main flow passage, so that the back flow in the bypass flow passage can be prevented and the characteristics of the flow velocity detecting member can be prevented. Is not affected by the turbulence of the main flow, improving the reliability of flow rate measurement.

Further, as compared with the conventional device, the flow passage area of the main flow passage is not reduced, and the pressure loss of the main flow passage can be reduced. As a result, the size of the main flow path can be reduced, so that the economical efficiency of the present flow rate measuring device and the system to which the present device is applied is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a vertical sectional view of a flow rate measuring device according to the present invention. In the figure, the flow of fluid is indicated by arrows.

The main flow path 13 for the fluid is constituted by the flow path structure wall 1. Downstream of the main flow path 13, the flow path area is
A larger space 12 is provided, and the main flow path 14 is connected downstream of the space 12. In this flow measuring device,
The bypass flow path 2 that connects the space 12 and the main flow path 14 is provided, and the thermal flow velocity sensor 5 is provided in the bypass flow path 2. The fluid flowing in the main flow path 13 in the direction of the arrow 6 enters the space 12 and a part of the fluid flows from the bypass flow path inlet 3 to the bypass flow path 2
Flow into. After measuring the flow velocity with the thermal sensor 5 in the bypass flow passage 2, the fluid in the bypass flow passage 2 flows from the bypass flow passage outlet 4 to the main flow passage 14, and joins with the fluid in the main flow passage 14. From the flow velocity of the fluid in the bypass passage 2 measured by the thermal sensor 5, the flow rate of the fluid flowing in the main passage 13 and the main passage 14 can be obtained.

The flow path area of the space 12 is the main flow path 13
Since it is larger, the flow velocity decreases and the pressure increases. Since the flow passage area of the main flow passage 14 is smaller than that of the space portion 12, the flow velocity increases and the pressure decreases. Therefore, the pressure in the space portion 12 is higher than the pressure in the main passage 14, and the flow in the bypass passage 2 always flows from the bypass passage inlet 3 to the bypass passage outlet 4.

If there is a vibration source of pressure such as an internal combustion engine downstream of the main flow path 14, a temporary backflow of the flow indicated by the arrow 7 may occur. Also in this case, since the pressure in the space 12 is high, backflow is unlikely to occur in the bypass flow passage 2,
It is possible to prevent a characteristic change of the thermal sensor 5 due to a temporary backflow in the main flow path 14.

Also, when the flow repeats the forward flow indicated by the arrow 6 and the reverse flow indicated by the arrow 7, the flow passage area of the space 12 is large, the flow velocity of the reverse flow is reduced, and the bypass flow passage 2 is affected. In addition to being alleviated, backflow to the main flow path 13 is also prevented.

As a result, the influence of the backflow in the main flow passage 14 on the characteristics of the thermal sensor 5 in the bypass flow passage 2 is eliminated, the flow velocity measurement accuracy of the thermal sensor 5 is improved, and the insides of the main flow passages 13 and 14 are improved. The accuracy of flow rate measurement of flowing fluid and the reliability of measurement are improved. Further, since the flow passage area of the space portion 12 is larger than the flow passage areas of the main flow passage 13 and the main flow passage 14, the pressures of the main flow passage 13 and the main flow passage 14 are larger than those of the conventional main flow passage having a venturi. Loss is reduced.

By reducing the pressure loss, the size of the main flow path can be reduced when the same flow rate is flown into the main flow path.
The present flow rate measuring device and a system such as an internal combustion engine that employs the present flow rate measuring device can be downsized, and the economy of the system is improved.

According to the present embodiment, since the flow rate measurement accuracy is improved in the flow rate measurement apparatus, the reliability of the flow rate measurement is improved and the flow rate measurement apparatus and the system employing the flow rate measurement apparatus can be downsized. Therefore, the economical efficiency of the system is improved.

A second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a vertical sectional view of a flow rate measuring device according to the present invention. In the figure, the flow of fluid is indicated by arrows.

In the flow rate measuring device shown in the first embodiment, the bypass flow passage 2 is provided inside the space 12 and the main flow passage 14 by the bypass flow passage supporting portion 11, and the bypass flow passage inlet 3
Is opened to the space 12, and the bypass flow path outlet 4 is connected to the main flow path 1
Open to 4. In the example shown in FIG. 2, the bypass flow path outlet 4 is open in the direction intersecting with the flow. The fluid flowing in the main flow path 13 and the space 12 has a high flow velocity in the central portion and a low flow velocity in the vicinity of the wall surface. Therefore, by arranging the bypass flow passage 2 including the thermal sensor 5 in the central portion of the space 12 and the main flow passage 14,
The absolute value of the flow velocity in the bypass flow passage 2 increases, and the flow velocity in the bypass flow passage 2 and the flow rate measurement accuracy in the main flow passage 13 and the main flow passage 14 improve.

Further, since the bypass flow path outlet 4 is opened in the direction intersecting with the flow, even if a reverse flow is temporarily generated in the main flow path 14, the flow is generated by the dynamic pressure of the reverse flow. It does not flow directly into the bypass flow passage 2.
As a result, the influence of the backflow on the characteristics of the thermal sensor 5 is mitigated, and the flow velocity in the bypass passage 2 and the flow rate measurement accuracy in the main passage 13 and the main passage 14 are further improved.

According to this embodiment, since the flow rate measuring accuracy is improved in the flow rate measuring device, the reliability of the flow rate measuring is further improved.

[0023]

According to the present invention, the accuracy of flow rate measurement in the flow rate measuring apparatus is improved, the reliability of the flow rate measuring apparatus is improved, and the flow rate measuring apparatus and the system to which the apparatus is applied can be miniaturized. Has the effect of improving the economic efficiency of.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a flow rate measuring device according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a flow rate measuring device according to a second embodiment of the present invention.

[Explanation of symbols]

1 ... Channel structure wall, 2 ... Bypass channel, 3 ... Bypass channel inlet, 4 ... Bypass channel outlet, 5 ... Thermal sensor, 6,
7, 8, 9, 10 ... Arrows, 11 ... Bypass flow path support portion,
12 ... Space part, 13, 14 ... Main flow path.

Claims (4)

[Claims] 1. A bypass type flow rate measuring device for detecting a flow rate of a fluid flowing in the main flow path by providing a means for detecting a flow velocity of the fluid in a bypass flow path in which a part of the flow from the main flow path is separated. In, the flow passage area in the main flow passage of the inlet portion of the bypass flow passage is larger than the area of the main flow passage, and the flow passage area in the main flow passage of the confluence portion of the bypass flow passage to the main flow passage is the bypass. A flow rate measuring device characterized in that it is smaller than a flow passage area in the main flow passage at an inlet portion of the flow passage. 2. The main flow passage according to claim 1, wherein a space portion having a flow passage area larger than that of the main flow passage is provided, and a flow passage area of the main flow passage downstream of the space portion is set to a flow passage area of the space portion. A flow rate measuring device that is smaller, in which an inlet of a bypass flow passage is provided in the space portion, and a confluence portion of the bypass flow passage to the main flow passage is provided in a main flow passage downstream of the space portion. 3. The flow rate measuring device according to claim 1, wherein a thermal sensor is used as the fluid velocity detecting member. 4. A throttle body with an air flow sensor for an automobile, which uses the flow rate measuring device according to claim 1, 2, or 3.