JP2021144002A - Flow measurement device - Google Patents

Abstract

To provide a new and compact flow measurement device which has a simple configuration and high sensitivity in measurement of a flow rate of fluid.SOLUTION: A flow measurement device includes: a main channel in which fluid circulates; and a diversion channel which diverges from and rejoins the main channel so that the fluid for measurement circulates. In the diversion channel, a high-flow channel has a high-flow measurement chip for measuring a flow rate of the high-flow fluid, and a low-flow channel has a wider channel section compared to the high-flow channel and a low-flow measurement chip for measuring a flow rate of the lower-flow fluid than in the high-flow measurement chip. The two channels are parallelly provided therein.SELECTED DRAWING: Figure 8

Description

The present invention relates to a flow rate measuring device.

Conventionally, a main flow path, a branch flow rate communicating with the main flow path through a pair of diversion holes, a flow sensor for detecting the flow rate of the fluid flowing through the branch flow path, and a fluid flow rate and the main flow path detected by the flow sensor. In order to set the flow rate of the fluid flowing through the main flow path, the flow rate of the fluid flowing through the main flow path is determined based on the flow rate and the flow rate detected by the flow rate sensor and the flow rate dividing member arranged in the branch flow path. A diversion type flow meter including a calculation circuit for calculating has been proposed (for example, Patent Document 1).

In addition, a pipe that is provided in series on the downstream side of the large flow rate measurement flow path and the small flow rate measurement flow path that has a smaller cross-sectional area than the large flow rate measurement flow path. The large flow rate measurement flow path and the small flow rate measurement flow rate are each provided with a plurality of flow rate sensors. In the region, a flow meter that calculates the flow rate based on the output of the flow velocity sensor in the large flow rate measurement flow path has also been proposed (for example, Patent Document 2).

JP-A-2010-151785 Japanese Unexamined Patent Publication No. 09-068448

The flow meter as described above is required to have a small and simple system and to be able to measure the flow rate in a wide range from a high flow rate fluid to a low flow rate fluid.

In order to miniaturize and simplify the system, there is known a technique of applying a bypass structure having a main flow path and a branch flow path that branches from the main flow path and rejoins the main flow path to a flow meter.

However, when measuring a high flow rate fluid, especially in a thermal flow sensor, the linearity between the flow rate and the sensor output may deteriorate, and when measuring a low flow rate fluid, the bypass structure is flowed. When applied to a meter, the pressure loss becomes small, it is difficult for the flow to be diverted to the divergence channel, and sensitivity may not be ensured.

Therefore, the branch flow rate is further branched, and a configuration in which a high flow rate flow rate and a low flow rate flow rate having a wider cross-sectional area than the high flow rate flow rate are arranged in parallel is applied to the flow meter. The purpose is to realize a flow meter with a wide measurement range by providing dedicated flow paths for each of the high flow rate region and the low flow rate region.

Further, in the present invention, in addition to the miniaturization and simplification of the system and the realization of the measurement of the flow rate of the fluid in a wide range, the type of the fluid is specified by applying the flow rate for measuring the gas type in the branch flow path. The ultimate purpose is to provide a three-chip flow rate measuring device having a good correlation between the physical property values such as the thermal conductivity of the specified fluid and the flow rate.

Here, the flow meter in the present invention has a high flow rate measuring chip arranged in a high flow rate flow path, a low flow rate measuring chip arranged in a low flow rate flow rate, and a gas type measurement flow path in the branch flow rate. It may be a three-chip flow rate measuring device including three types of measuring chips of the gas type measuring chip arranged in.

The present invention for solving the above problems
A flow rate measuring device including a main flow path through which a fluid flows and a branch flow path that branches from the main flow path and rejoins the main flow path to flow a fluid for measurement.
In the branch flow rate, the high flow rate flow rate in which the high flow rate measuring chip for measuring the flow rate of the high flow rate fluid is arranged and the flow rate cross-sectional area are wider than those of the high flow rate flow rate, and the high flow rate It is characterized in that a low flow rate flow path in which a low flow rate measurement chip for measuring the flow rate of a fluid having a lower flow rate than the measurement chip is arranged is formed in parallel.
It is a flow measuring device.
According to the present invention, by forming two flow paths, a main flow path and a branch flow rate, in one device, it is possible to miniaturize and simplify the system, and in the branch flow rate, a high flow rate region and a low flow rate region. By providing each of the above with a dedicated flow path, it is possible to realize a flow rate measuring device having a wide measurement range.

Further, in the present invention, the flow rate measuring device may be used in which the high flow rate flow path and the low flow rate flow rate are formed by branching the branch flow path in the middle. According to this, it is possible to output the measured value of the flow rate of the fluid diverted from the main flow path to the branch flow rate by the high flow rate measurement chip or the low flow rate measurement chip in the branch flow rate.

Further, in the present invention, the branch flow rate has two independent flow paths, and the high flow rate flow rate and the low flow rate flow rate are independent of each other and branched from the main flow rate. It may be a flow rate measuring device. According to this, it is possible to adjust the divergence ratio from the main flow path directly to the high flow rate flow rate and the low flow rate flow rate, and it is easy to realize laminar flow in the divergence flow rate.

Further, in the present invention, the branch flow rate is further formed with a gas type measurement flow path in which a gas type measurement chip for specifying the type of fluid flowing in the branch flow path is arranged, and is used for gas type measurement. The flow path may be a flow rate measuring device characterized in that the high flow rate flow path and the low flow rate flow path are formed so as to communicate with each other. According to this, by specifying the type of fluid flowing in the shunt flow path, it is possible to grasp the correlation between the physical property value such as the thermal conductivity of the specified fluid and the flow rate.

Further, in the present invention, the gas type measurement flow path is formed so that the high flow rate flow rate and the low flow rate flow rate communicate with each other in the middle of each flow rate. It may be used as a flow rate measuring device. According to this, it is possible to measure the flow rate of the fluid after specifying the type of the fluid.

Further, in the present invention, a comparison unit for comparing the measured value by the low flow rate measuring chip with a predetermined threshold value is further provided, and when the comparison unit determines that the measured value is equal to or higher than the threshold value, the high value is obtained. A flow rate measuring device characterized in that a measured value by a flow rate measuring chip is output, and when the comparison unit determines that the measured value is less than the threshold value, the measured value by the low flow rate measuring chip is output. May be. According to this, it is possible to obtain a more accurate output value by outputting the flow rate of the fluid from the high flow rate measuring chip or the low flow rate measuring chip with reference to the threshold value.

Further, in the present invention, the flow rate measuring device may be characterized in that the ratio of the flow path cross-sectional area of the high flow rate flow path and the low flow rate flow path is 1: 3. According to this, it is possible to measure the flow rate in a wide range from the high flow rate fluid to the low flow rate fluid.

In the flow rate measuring device, miniaturization and simplification are achieved by forming a bypass structure in which a branch flow path is added to the main flow path through which the fluid flows, and the branch flow rate is further branched to form a high flow rate flow path and a low flow rate flow path. It will be possible to provide a new technology that enables the measurement of flow rate in a wide range.

It is an exploded perspective view which shows an example of the flow rate measuring apparatus which concerns on embodiment. It is a perspective view which shows an example of the flow rate measuring apparatus. It is a top view which shows the subchannel part. It is a perspective view which shows an example of a sensor element. It is sectional drawing for demonstrating the mechanism of a sensor element. It is a top view which shows the schematic structure of the flow rate detection part. It is a top view which shows the schematic structure of the physical characteristic value detection part. It is a schematic plan view which shows the schematic structure of a branch flow path. It is a block diagram which shows the functional structure at the time of flow rate measurement. It is a flow showing from the measurement of the flow rate value to the output. It is a graph which shows the relationship between the measured value of the flow rate and the output value in a high flow rate measuring chip or a low flow rate measuring chip with reference to a threshold value. Schematic configuration of a high-flow rate branch, a low-flow rate branch, and a gas type measurement branch, and the high-flow and low-flow rate branches are independent of each other. It is a schematic plan view which shows.

[Application example]
In this application example, a case where the bypass structure is applied to the 3-chip flow rate measuring device will be described. The three-chip flow rate measuring device according to this application example has a bypass structure through which a fluid flows, and the bypass structure has two flow paths, a main flow path and a branch flow path that branches from the main flow path and rejoins the main flow path. .. Further, the branch flow path is branched into two flow paths having different flow path cross-sectional areas.

Two flow paths with different flow path cross-sectional areas are formed in parallel in the branch flow rate, and a high flow rate measuring chip for measuring the flow rate of a high flow rate fluid is arranged in the high flow rate flow rate, and the flow rate is high. A low flow rate measuring chip for measuring the flow rate of a low flow rate fluid is arranged in a low flow rate flow path having a wider flow path cross-sectional area than the flow rate flow path.

Further, a gas type measurement flow path is formed in the branch flow path, and the type of fluid is specified by a gas type measurement chip arranged in the gas type measurement flow path. Here, even under the same conditions, the physical property values differ depending on the type of fluid, so it is indispensable to specify the type of fluid. The gas type measurement flow path is formed so that the high flow rate flow rate and the low flow rate flow rate communicate with each other in the middle of each flow rate.

After specifying the type of fluid with the gas type measurement chip, the flow rate of the fluid is measured from the low flow rate measurement chip. The 3-chip flow rate measuring device is provided with a comparison unit that compares the flow rate measurement value of the low flow rate measurement chip with a predetermined threshold, and when the comparison unit determines that the flow rate measurement value is equal to or higher than the threshold value, high flow rate measurement is performed. The measured value by the chip is output, and when it is determined that the flow rate measured value is less than the threshold value, the measured value by the low flow rate measuring chip is output.

[Example 1]
Hereinafter, the three-chip flow rate measuring device according to the embodiment of the present invention will be described with reference to the drawings. In the following embodiments, an example in which the present invention is applied to a 3-chip flow rate measuring device will be described, but the present invention may be applied to another flow rate measuring device such as a 2-chip flow measuring device. The embodiment shown below is an example of a three-chip flow rate measuring device, and the three-chip flow measuring device according to the present invention is not limited to the following configuration.

<Device configuration>
FIG. 1 is an exploded perspective view showing an example of a flow rate measuring device 1 which is a premise of the present embodiment, and FIG. 2 is a perspective view showing an example of a flow rate measuring device 1.

The flow rate measuring device 1 is incorporated in, for example, a gas meter, a combustion device, an internal combustion engine such as an automobile, a fuel cell, other industrial devices such as medical care, or an embedded device, and measures the flow rate of gas passing through a flow path. The broken line arrows in FIGS. 1 and 2 exemplify the direction in which the fluid flows.

As shown in FIG. 2, in the present embodiment, the flow rate measuring device 1 is provided inside the branch flow path 3 branched from the main flow path 2. Further, the flow rate measuring device 1 includes a flow rate detecting unit 11 and a physical characteristic value detecting unit 12. The flow rate detection unit 11 and the physical characteristic value detection unit 12 are thermal flow sensors including a heating unit formed by a microheater and a temperature detection unit formed by a thermopile.

As shown in FIGS. 1 and 2, the flow rate measuring device 1 according to the present embodiment includes a main flow path 2, a branch flow path 3, a seal 4, a circuit board 5, and a cover 6.

The main flow path 2 is a tubular member penetrating in the longitudinal direction. On the inner peripheral surface of the main flow path 2, an inflow port (first inflow port) 34A is formed on the upstream side and an outflow port (first outflow port) 35A is formed on the downstream side with respect to the flow direction of the fluid to be measured. Has been done. For example, the axial length of the main flow path 2 is about 50 mm, the diameter of the inner peripheral surface (inner diameter of the main flow path 2) is about 20 mm, and the outer diameter of the main flow path 2 is about 24 mm. Not limited to the example.

The branch flow path 3 is provided on the main flow path 2, and is constructed as a bypass structure that branches from the main flow path 2 and rejoins the main flow path 2. One end of the branch flow path 3 communicates with the inflow port 34A, and the other end communicates with the outflow port 35A. In the flow rate measuring device 1, the branch flow path 3 is composed of an inflow flow path 34, a physical property value detection flow path 32, a flow rate detection flow rate 33, and an outflow flow path 35.

The inflow flow path 34 is a flow path for allowing the fluid to be measured flowing through the main flow path 2 to flow into the flow rate detection flow path 32 and the flow rate detection flow path 33. The inflow flow path 34 is formed so as to penetrate the branch flow path 3 in a direction perpendicular to the main flow path 2, one end communicating with the inflow port 34A, and the other end opening at the upper surface of the main flow path 2 to have physical characteristics. It communicates with the value detection flow path 32 and the flow rate detection flow path 33. As a result, a part of the fluid to be measured flowing through the main flow path 2 can be divided into the physical characteristic value detection flow path 32 and the flow rate detection flow path 33 via the inflow flow path 34.

The physical property value detection flow path 32 is a flow path having a substantially U-shaped vertical cross section, which is formed on the upper surface of the branch flow path 3 and extends in a direction parallel to the main flow path 2. The physical characteristic value detecting unit 12 for detecting the physical characteristic value of the fluid to be measured is arranged in a portion extending in the longitudinal direction (direction parallel to the main flow path 2) of the physical characteristic value detecting flow path 32.

One end of the physical property value detection flow path 32 communicates with the inflow port 34A via the inflow flow path 34, and the other end communicates with the outflow port 35A via the outflow flow path 35.

The flow rate detection flow path 33 is a flow path having a substantially U-shaped vertical cross section, which is formed on the upper surface of the branch flow path 3 and extends in a direction parallel to the main flow path 2. The flow rate detection flow path 33 is a flow rate detection flow path 33 in which a flow rate detection unit 11 for detecting the flow rate of the fluid to be measured is arranged in a portion extending in the longitudinal direction (direction parallel to the main flow rate 2). have.

One end of the flow rate detection flow path 33 communicates with the inflow port 34A via the inflow flow path 34, and the other end communicates with the outflow port 35A via the outflow flow path 35. The physical characteristic value detection unit 12 and the flow rate detection unit 11 are arranged in the physical characteristic value detection flow path 32 or the flow rate detection flow path 33 in a state of being mounted on the circuit board 5.

The outflow flow path 35 is a flow path for causing the fluid to be measured that has passed through the physical property value detection flow path 32 and the flow rate detection flow path 33 to flow out to the main flow path 2. The outflow flow path 35 is formed so as to penetrate the branch flow path 3 in a direction perpendicular to the main flow path 2, one end communicating with the outflow port 35A, and the other end opening at the upper surface of the main flow path 2. It communicates with the physical property value detection flow path 32 and the flow rate detection flow path 33. As a result, the fluid to be measured that has passed through the physical property value detection flow path 32 and the flow rate detection flow path 33 can flow out to the main flow path 2 via the outflow flow path 35.

In this way, the fluid to be measured that has flowed in from the same inflow port 34A is divided into the physical characteristic value detection flow path 32 and the flow rate detection flow path 33, so that the physical property value detection unit 12 and the flow rate detection unit 11 have a temperature. It is possible to detect the physical characteristic value or the flow rate based on the fluid to be measured under the same conditions such as density and density. Therefore, the measurement accuracy of the flow rate measuring device 1 can be improved.

In the flow rate measuring device 1, the circuit board 5 is arranged after the seal 4 is fitted into the branch flow path 3, and the circuit board 5 is further fixed to the branch flow path 3 by the cover 6 to form the inside of the branch flow path 3. Airtightness is ensured.

FIG. 3 is a plan view showing a branch flow path 3 in the flow rate measuring device 1 which is a premise of this embodiment as shown in FIG. As shown in FIG. 3, in the physical property value detection flow path 32, one end of a substantially U-shape communicates with the inflow flow path 34, and the other end communicates with the outflow flow path 35. Similarly, in the flow rate detection flow path 33, one end of a substantially U-shape communicates with the inflow flow path 34, and the other end communicates with the outflow flow path 35.

Further, both ends of the physical property value detection flow path 32 and the flow rate detection flow path 33 are also in communication with each other, and the physical property value detection flow path 32 and the flow rate detection flow path 33 are rectangular on the upper surface of the branch flow path 3. It constitutes a shaped flow path.

In the flow rate measuring device 1, the portion of the physical property value detecting flow path 32 including the physical property value detecting unit 12 and the portion of the flow rate detecting flow path 33 including the flow rate detecting unit 11 are both perpendicular to the upper surface of the branch flow path 3. The shape when viewed from the direction (normal direction) is square, and each is formed at a position symmetrical with respect to the straight line connecting the inflow flow path 34 and the outflow flow path 35.

Further, arrows P and Q represent the flow rates of the fluid to be measured that are divided into the physical property value detection flow path 32 and the flow rate detection flow path 33. In the present embodiment, the physical property value detection flow path 32 is such that the fluid to be measured at the flow rate P is diverted into the flow rate detection flow path 32 and the measurement target fluid at the flow rate Q flows through the flow rate detection flow path 33. And the width of the flow rate detection flow path 33 is set.

The values of the flow rate P and the flow rate Q vary depending on the flow rate of the fluid to be measured flowing through the main flow path 2, but in the normal usage mode, the flow rate P is a value within the detection range of the physical property value detection unit 12. The flow rate Q is a value within the detection range of the flow rate detection unit 11, and the flow rate 3 for detecting the physical property value.
The widths of 2 and the flow rate detection flow path 33 are set respectively. The widths of the physical property value detection flow path 32 and the flow rate detection flow path 33 are examples, and are not limited to the example of FIG.

In this way, in the flow rate measuring device 1, it is possible to individually control the flow rate of the fluid to be measured, which is divided into the physical property value detecting flow path 32 and the flow rate detecting flow path 33, by adjusting the widths of each. be. Therefore, the flow rate of the fluid to be measured flowing through the physical property value detection flow path 32 is controlled according to the detection range of the physical property value detection unit 12, and flows through the flow rate detection flow path 33 according to the detection range of the flow rate detection unit 11. The flow rate of the fluid to be measured can be controlled.

Therefore, the physical characteristic value detecting unit 12 can detect the physical characteristic value of the fluid to be measured at the optimum flow rate according to the unique detection range, so that the detection accuracy of the physical characteristic value detecting unit 12 can be improved.

Similarly, since the flow rate detection unit 11 can detect the flow rate of the fluid to be measured at the optimum flow rate according to the unique detection range, the detection accuracy of the flow rate detection unit 11 can be improved.

The physical property value detection flow path 32 and the flow rate detection flow path 33 are not limited to a substantially U-shaped structure. That is, the physical property value detection flow path 32 and the flow rate detection flow path 33 are set to a width in which the flow rate of the fluid to be measured passing through the physical property value detection flow path 32 and the flow rate detection flow path 33 can be controlled. For example, other shapes may be adopted.

Further, in the present embodiment, the shape of the portion including the physical characteristic value detection unit 12 in the physical characteristic value detection flow path 32 and the portion including the flow rate detection unit 11 in the flow rate detection flow path 33 are square, but the present invention has a square shape. Not limited to this. The shape of the physical property value detection flow path 32 and the flow rate detection flow path 33 may be such that the physical property value detection unit 12 or the flow rate detection unit 11 can be arranged, and the physical property value detection unit 12 and the flow rate detection unit 11 are arranged. Determined according to the shape.

Therefore, for example, when the size of the physical property value detection unit 12 is smaller than the width of the physical characteristic value detection flow path 32, the width of the portion of the physical property value detection flow path 32 including the physical characteristic value detection unit 12 is set as the physical characteristic value. It may match the width of the detection unit 12. In this case, the portion extending in the longitudinal direction of the physical property value detecting flow path 32 is formed in a linear shape. The same applies to the flow rate detection flow path 33.

FIG. 4 is a perspective view showing an example of a sensor element used in the flow rate detection unit and the physical characteristic value detection unit. Further, FIG. 5 is a cross-sectional view for explaining the mechanism of the sensor element. The sensor element 100 includes a microheater (heating unit) 101 and a thermopile (temperature detection unit) 102 symmetrically provided with the microheater 101 interposed therebetween. Insulating thin films are formed above and below these, and are provided on a silicon substrate. The microheater 101 is, for example, a resistor made of polysilicon.

Further, the silicon substrate below the microheater 101 and the thermopile 102 is provided with a cavity area 103 which is a recess. The cavity area 103 is surrounded by a frame 104 made of polysilicon. Since the heat generated from the microheater 101 is discharged to the cavity area 103, the diffusion of the heat generated into the silicon substrate is suppressed.

Further, since the frame 104 has a large heat capacity and is difficult to heat, the temperature of the cold contact on the frame 104 hardly rises, and the temperature difference from the hot contact can be detected more accurately.

FIG. 5 schematically shows the temperature distribution when the microheater 101 generates heat by the broken line ellipse. The thicker the broken line, the higher the temperature. When there is no air flow, the temperature distribution on both sides of the microheater 101 becomes almost uniform as shown in the upper part (1) of FIG. On the other hand, for example, when air flows in the direction indicated by the broken line arrow in the lower part (2) of FIG. 5, the temperature is higher on the leeward side than on the leeward side of the microheater 101 because the surrounding air moves. .. The sensor element outputs a value indicating the flow rate by utilizing such a bias of the heater heat distribution.

なお、Ｔ_ｈはマイクロヒータ１０１の温度、Ｔ_ａはサーモパイル１０２の外側に設けられる周囲温度センサが測定した温度、Ｖ_ｆは流速の平均値、Ａとｂは所定の定数である。 The output voltage ΔV of the sensor element is represented by, for example, the following equation (1).

Incidentally, T _h is the temperature of the micro-heater 101, T _a is the temperature at which ambient temperature sensor provided outside of the thermopile 102 is measured, V _f is the mean value of the flow velocity, A and b are predetermined constants.

<Flow rate detection unit and physical property value detection unit>
FIG. 6 is a plan view showing a schematic configuration of the flow rate detection unit 11 shown in FIG. 1, and FIG. 7 is a plan view showing a schematic configuration of the physical characteristic value detection unit 12 shown in FIG. In the flow rate measuring device 1, the width of the flow path extending in the longitudinal direction is different between the physical property value detection flow path 32 and the flow rate detection flow path 33, and the physical property value detection flow path 32 detects the physical property value. The width of the portion including the portion 12 is narrower than the width of the portion including the flow rate detection unit 11 in the flow rate detection flow path 33. As a result, the flow rate measuring device 1 individually controls the flow rates of the fluids to be measured that are divided into the physical property value detecting flow path 32 and the flow rate detecting flow path 33.

As shown in FIG. 6, the flow rate detection unit 11 includes a first thermopile (first temperature detection unit in the flow rate detection unit) 111 and a second thermopile (second temperature detection unit in the flow rate detection unit) 112 that detect the temperature of the fluid to be measured. And a microheater 113 for heating the fluid to be measured. The microheater 113, the first temperature detection unit 111 in the flow rate detection unit, and the second temperature detection unit 112 in the flow rate detection unit are arranged side by side in the flow rate detection unit 11 along the flow direction P of the fluid to be measured. ..

Further, the shapes of the microheater 113, the first temperature detection unit 111 in the flow rate detection unit, and the second temperature detection unit 112 in the flow rate detection unit are substantially rectangular in a plan view, and their longitudinal directions are the flow directions P of the fluid to be measured. Orthogonal to.

In the first temperature detection unit 111 in the flow rate detection unit and the second temperature detection unit 112 in the flow rate detection unit, the first temperature detection unit 111 in the flow rate detection unit is arranged on the upstream side of the microheater 113, and the second temperature in the flow rate detection unit is on the downstream side. The detection unit 112 is arranged to detect the temperature at symmetrical positions with the microheater 113 in between.

In the flow rate measuring device 1, sensors having substantially the same structure are used in the physical property value detecting unit 12 and the flow rate detecting unit 11, and the sensors are arranged at different angles of 90 degrees with respect to the flow direction of the fluid to be measured. .. As a result, the sensor having the same structure can function as the physical characteristic value detecting unit 12 or the flow rate detecting unit 11, so that the manufacturing cost of the flow rate measuring device 1 can be reduced.

On the other hand, as shown in FIG. 7, the physical property value detection unit 12 has a first thermopile (first temperature detection unit in the physical property value detection unit) 121 and a second thermopile (second in the physical characteristic value detection unit) that detect the temperature of the fluid to be measured. A temperature detection unit) 122 and a microheater (heating unit in the physical property value detection unit) 123 for heating the fluid to be measured are provided. The heating unit 123 in the physical characteristic value detection unit and the first in the physical characteristic value detection unit
The temperature detection unit 121 and the second temperature detection unit 122 in the physical property value detection unit are arranged side by side in the physical property value detection unit 12 in a direction orthogonal to the flow direction Q of the fluid to be measured.

Further, the shapes of the heating unit 123 in the physical characteristic value detection unit, the first temperature detection unit 121 in the physical characteristic value detection unit, and the second temperature detection unit 122 in the physical characteristic value detection unit are substantially rectangular in a plan view, and the longitudinal directions of each are measured. It is along the flow direction Q of the target fluid.

Further, the first temperature detection unit 121 in the physical property value detection unit and the second temperature detection unit 122 in the physical property value detection unit are arranged symmetrically with the heating unit 123 in the physical characteristic value detection unit interposed therebetween, and the heating unit 123 in the physical characteristic value detection unit. Detects the temperature at symmetrical positions on both sides of. Therefore, the measured values of the first temperature detection unit 121 in the physical property value detection unit and the second temperature detection unit 122 in the physical characteristic value detection unit are substantially the same, and one of the values may be adopted, or the average of both may be adopted. The value may be calculated.

Here, since the temperature distribution is biased to the downstream side due to the flow of the fluid to be measured, the change in the temperature distribution in the direction orthogonal to the flow direction is smaller than the change in the temperature distribution in the flow direction of the fluid to be measured. Therefore, the first temperature detection unit 121 in the physical property value detection unit, the heating unit 123 in the physical property value detection unit, and the second temperature detection unit 122 in the physical property value detection unit are in this order in a direction orthogonal to the flow direction of the fluid to be measured. By arranging them side by side, it is possible to reduce changes in the output characteristics of the first temperature detection unit 121 in the physical property value detection unit and the second temperature detection unit 122 in the physical property value detection unit due to changes in the temperature distribution.

Therefore, the influence of the change in the temperature distribution due to the flow of the fluid to be measured can be reduced, and the detection accuracy by the physical property value detecting unit 12 can be improved.

Further, since the longitudinal direction of the heating unit 123 in the physical property value detection unit is arranged along the flow direction of the fluid to be measured, the heating unit 123 in the physical property value detection unit has a wide range of the fluid to be measured over the flow direction of the fluid to be measured. Can be heated. Therefore, even if the temperature distribution is biased to the downstream side due to the flow of the fluid to be measured, the output characteristics of the first temperature detection unit 121 in the physical property value detection unit and the second temperature detection unit 122 in the physical property value detection unit can be changed. Can be reduced.

Therefore, the influence of the change in the temperature distribution due to the flow of the fluid to be measured can be reduced, the influence of the change in the temperature distribution due to the flow of the fluid to be measured can be reduced, and the detection accuracy by the physical property value detecting unit 12 can be improved. ..

Further, since the longitudinal directions of the first temperature detection unit 121 in the physical property value detection unit and the second temperature detection unit 122 in the physical characteristic value detection unit are arranged along the flow direction of the fluid to be measured, the first temperature detection in the physical characteristic value detection unit is performed. The unit 121 and the second temperature detection unit 122 in the physical characteristic value detection unit can detect the temperature in a wide range over the flow direction of the fluid to be measured. Therefore, even when the temperature distribution is biased to the downstream side due to the flow of the fluid to be measured, the change in the output characteristics of the first temperature detection unit 121 in the physical property value detection unit and the second temperature detection unit 122 in the physical property value detection unit is reduced. can do.

Therefore, the influence of the change in the temperature distribution due to the flow of the fluid to be measured can be reduced, and the detection accuracy by the physical property value detecting unit 12 can be improved.

Next, the flow rate measuring device according to this embodiment will be described including the features of the branch flow path 3. In the thermal flow rate measuring device 1, a bypass structure in which the branch flow rate 3 is added to the main flow path 2 is constructed, so that the high flow rate fluid is excessively divided with respect to the branch flow rate 3 and the low flow rate fluid. Is difficult to measure the flow rate because it is difficult to divide the flow into the branch flow path 3. Therefore, in this embodiment, aiming at widening the measurement range of the flow rate, instead of measuring the flow rate at one place of the flow rate detection unit 11 in the branch flow rate 3, the flow rate is divided into a high flow rate region and a low flow rate region, respectively. It was decided to have a dedicated flow path and measure the flow rate in each flow path.

Further, in this embodiment, in order to grasp the correlation between the physical property value such as the thermal conductivity of the fluid flowing in the shunt flow path and the flow rate, it was decided to adopt a system for specifying the type of fluid. In the following description, the high flow rate measurement chip 7, the low flow rate measurement chip 8, and the gas type measurement chip 9 are sensors equivalent to the flow rate detection unit 11 and the physical property value detection unit 12 in the above description. ..

<Functional configuration>
FIG. 8 is a schematic plan view showing a schematic configuration of the branch flow path 3. The branch flow path 3 is connected to the main flow path 2 based on the inflow port 34A and the outflow port 35A. The branch flow path 3 is further branched, and the flow rate cross-sectional area is wider than that of the high flow rate flow rate 71 in which the high flow rate measuring chip 7 for measuring the flow rate of the high flow rate fluid is arranged and the high flow rate flow rate 71. The low flow rate measuring chip 8 for measuring the flow rate of the fluid having a lower flow rate than the high flow rate measuring chip 7 is arranged in parallel with the low flow rate flow rate 81. Here, the ratio of the flow path cross-sectional areas of the high flow rate flow path 71 and the low flow rate flow path 81 may be, for example, 1: 3.

The high flow rate channel 71 and the low flow rate channel 81 merge on the upstream side of the confluence point where the branch channel 3 rejoins the main flow rate 2. Further, in the branch flow path 3, a gas type measurement flow path 91 in which a gas type measurement chip 9 for specifying the type of fluid flowing in the branch flow path 3 is arranged is provided as a high flow rate flow rate flow rate 71 and a low flow rate flow rate flow rate. It is formed so as to communicate the road 81. Here, in this embodiment, a three-chip flow rate measuring device including three types of measuring chips, a high flow rate measuring chip 7, a low flow rate measuring chip 8, and a gas type measuring chip 9, is exemplified in the branch flow path 3. doing.

FIG. 9 is a block diagram showing a functional configuration at the time of flow rate measurement. The flow rate measuring device 1 includes a MicroControl Unit (MCU) 13 and an Analog-to-Digital Converter (ADC) 14. The first temperature detection unit 111 in the flow rate detection unit, the second temperature detection unit 112 in the flow rate detection unit, the microheater 113, and the first temperature detection unit 121 in the physical characteristic value detection unit shown in FIG. The second temperature detection unit 122 in the physical property value detection unit and the heating unit 123 in the physical property value detection unit are not shown.

The flow rate detection unit 11 detects a value indicating the flow rate of the fluid to be measured based on the temperature detection signals output from the first temperature detection unit 111 in the flow rate detection unit and the second temperature detection unit 112 in the flow rate detection unit.

Specifically, the flow rate detection unit 11 calculates the difference between the temperature detection signal output from the first temperature detection unit 111 in the flow rate detection unit and the temperature detection signal output from the second temperature detection unit 112 in the flow rate detection unit. , Obtain a value indicating the flow rate of the fluid to be measured based on the difference. Then, the flow rate detection unit 11 outputs a value indicating the flow rate to the MCU 13 via the ADC 14.

The physical characteristic value detection unit 12 obtains the average value of the temperature detection signals output from the first temperature detection unit 121 in the physical characteristic value detection unit and the second temperature detection unit 122 in the physical characteristic value detection unit.

Further, the heating unit 123 in the physical characteristic value detection unit shown in FIG. 7 changes the temperature according to, for example, control by the control unit 13. As a result, the first temperature detection unit 121 in the physical property value detection unit and the second temperature detection unit 122 in the physical characteristic value detection unit can obtain the output value before and after the temperature change of the heating unit 123 in the physical characteristic value detection unit. The physical characteristic value detection unit 12 outputs the output value acquired to the MCU 13 via the ADC 14.

Here, the flow rate detecting unit 11 detects the flow rate from the high flow rate measuring chip 7 and the low flow rate measuring chip 8, and the physical characteristic value detecting unit 12 detects the physical characteristic value from the gas type measuring chip 9.

FIG. 10 is a flow showing from the measurement of the flow rate value to the output. The fluid to be measured is subjected to gas type detection measurement (S101) by the gas type measurement chip 9, low flow rate measurement (S102) by the low flow rate measurement chip 8, and then high flow rate measurement (S103) by the high flow rate measurement chip 7. Will be implemented.

The branch flow path 3 has a comparison unit for comparing the value measured by the low flow rate measuring chip 8 with a predetermined threshold value, and in the comparison unit, the output from the low flow rate measuring chip 8 is equal to or more than the threshold value or less than the threshold value. (S104) is carried out. Here, if the output is determined to be equal to or higher than the threshold value, the flow rate value is calculated (S105) from the high flow rate measuring chip 7, and if it is determined to be less than the threshold value, the flow rate value is calculated from the low flow rate measuring chip 8. (S106) is carried out.

FIG. 11 is a graph showing the relationship between the measured value of the flow rate and the output value of the high flow rate measuring chip 7 or the low flow rate measuring chip 8 based on the threshold value. As shown in FIG. 11, regarding the relationship between the measured value of the flow rate and the output value, if the measured value by the low flow rate measuring chip 8 is equal to or more than the threshold value, the linearity is good in the output by the high flow rate measuring chip 7, and if it is less than the threshold value. Good linearity at the output of the low flow rate measuring chip 8. From the above, by applying the switching of the output chip according to the threshold value, more accurate flow rate measurement becomes possible in the branch flow path 3.

[Example 2]
Next, Example 2 of the present invention will be described. The difference between the present embodiment and the first embodiment is that the two flow paths of the branch flow paths are independent of each other. FIG. 12 shows, as an example of modifying the shape of the branch flow path, the high flow rate branch flow path 72, the low flow rate branch flow path 82, and the gas type measurement branch flow path 92 branched from the main flow path 2 with respect to the above-mentioned branch flow path 3. It is a schematic plan view which shows the schematic structure of the branching flow path which has

By applying the high flow rate dividing flow path 72 branched from the main flow rate 2 and the low flow rate dividing flow path 82, the distribution ratio from the main flow path 2 to the high flow rate dividing flow path 72 and the low flow rate dividing flow path 82 can be determined directly. It becomes possible to adjust. Further, since the high flow rate branching channel 72 and the low flow rate dividing channel 82 are independent of each other, the probability of turbulent flow occurring near the inflow port and the outflow port is low, and the fluid flow is increased by realizing the laminar flow. It becomes possible to stabilize.

In this embodiment, the measured value of the flow rate in the high flow rate measuring chip 7 or the low flow rate measuring chip 8 based on the functional configuration at the time of flow rate measurement, the flow from the measurement of the flow rate value to the output, and the threshold value. The relationship between the output values is as shown in FIGS. 9, 10 and 11 as in the first embodiment.

In the above embodiment, the flow meter according to the present invention is applied to the three-chip flow rate measuring device, but the flow meter according to the present invention does not necessarily have the gas type measurement chip 9.

In addition, in order to make it possible to compare the constituent requirements of the present invention with the configurations of the examples, the constituent requirements of the present invention are described below with reference numerals in the drawings.
<Invention 1>
A flow rate measuring device (1) including a main flow path (2) through which a fluid flows and a branch flow path (3) that branches from the main flow path and rejoins the main flow path to flow a fluid for measurement. ,
In the branch flow rate, the high flow rate flow rate (71) in which the high flow rate measuring chip (7) for measuring the flow rate of the high flow rate fluid is arranged, and the flow path cross-sectional area as compared with the high flow rate flow rate. The low flow rate measuring chip (8) is arranged in parallel with the low flow rate measuring chip (81) for measuring the flow rate of the fluid having a lower flow rate than the high flow rate measuring chip. ,
Flow rate measuring device (1).

1: Flow rate measuring device 100: Sensor element 101: Microheater 102: Thermopile 103: Cavity area 104: Frame 11: Flow rate detection unit 111: First temperature detection unit in the flow rate detection unit 112: Second temperature detection unit in the flow rate detection unit 113: Microheater 12: Physical characteristic value detection unit 121: First temperature detection unit in the physical characteristic value detection unit 122: Second temperature detection unit in the physical characteristic value detection unit 123: Heating unit in the physical characteristic value detection unit 13: Micro Controller Unit
14: Analog-to-Digital Converter
2: Main flow path 3: Branch flow path 32: Physical property value detection flow path 33: Flow rate detection flow rate 34: Inflow flow rate 34A: Inflow port 35: Outflow flow path 35A: Outlet 4: Seal 5: Circuit board 6: Cover 7: High flow rate measuring chip 71: High flow rate flow rate 72: High flow rate distribution channel 8: Low flow rate measurement chip 81: Low flow rate measurement chip 82: Low flow rate distribution channel 9: Gas type measurement chip 91: Gas type measurement flow path 92: Gas type measurement branch flow rate

Claims (7)

A flow rate measuring device including a main flow path through which a fluid flows and a branch flow path that branches from the main flow path and rejoins the main flow path to flow a fluid for measurement.
In the branch flow rate, the high flow rate flow rate in which the high flow rate measuring chip for measuring the flow rate of the high flow rate fluid is arranged and the flow rate cross-sectional area are wider than those of the high flow rate flow rate, and the high flow rate It is characterized in that a low flow rate flow path in which a low flow rate measurement chip for measuring the flow rate of a fluid having a lower flow rate than the measurement chip is arranged is formed in parallel.
Flow measuring device. By branching the branch flow path in the middle, the high flow rate flow rate and the low flow rate flow rate are formed.
The flow rate measuring device according to claim 1. The branch channel has two independent channels and has two independent channels.
The high flow rate flow rate and the low flow rate flow rate are flow paths branched from the main flow rate independently of each other.
The flow rate measuring device according to claim 1. In the branch flow path, a gas type measurement flow path in which a gas type measurement chip for specifying the type of fluid flowing in the branch flow path is arranged is further formed.
The gas type measurement flow path is formed so as to communicate the high flow rate flow rate and the low flow rate flow rate.
The flow rate measuring device according to claim 2 or 3. The gas type measurement flow path is characterized in that the high flow rate flow rate and the low flow rate flow rate are formed so as to communicate with each other in the middle of each flow rate.
The flow rate measuring device according to claim 4. A comparison unit for comparing the value measured by the low flow rate measuring chip with a predetermined threshold value is further provided.
When the comparison unit determines that the measured value is equal to or higher than the threshold value, the measured value by the high flow rate measuring chip is output.
When the comparison unit determines that the measured value is less than the threshold value, the measured value by the low flow rate measuring chip is output.
The flow rate measuring device according to any one of claims 1 to 5. The ratio of the flow path cross-sectional area of the high flow rate channel to the low flow rate channel is 1: 3.
The flow rate measuring device according to any one of claims 1 to 6.

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