JP5364059B2 - Thermal flow meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal type flowmeter capable of improving measurement accuracy of a flow rate of a fluid while miniaturizing the flowmeter. <P>SOLUTION: The thermal type flowmeter 10 including a sensor passage S to which a heat wire for measuring a flow rate of a fluid to be measured is laid and a first bypass passage B1 and a second bypass passage B2 from the sensor passage S further includes: a measurement chip 60, a sensor substrate 50; and a passage block 40 for branching the first bypass passage B1 and the second bypass passage B2 form the sensor passage S. The sensor substrate 50 is vertically arranged in a space formed by a body 20 for storing the passage block 40 and the sensor substrate 50 and a cover 30 for covering an aperture of the body 20, a gateway of the fluid to be measured is arranged on the same surface as the body 20, and a rib 70 projected into the first bypass passage B1 is formed on the body 20. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a thermal flow meter that measures the flow rate of a fluid using a hot wire. More specifically, the present invention relates to a thermal type flow meter that can improve the measurement accuracy of a fluid flow rate while reducing the size.

  Conventionally, vacuum suction is used for handling during semiconductor chip mounting, and confirmation of the suction has been performed by a pressure sensor. However, in recent years, semiconductor chips have become smaller and with pressure sensors, there is almost no pressure difference between adsorption and non-adsorption, so adsorption confirmation cannot be performed. Adsorption confirmation using a flow sensor instead of a pressure sensor Has come to be done.

  Here, the flow rate sensor used for the suction confirmation needs to be small because it is installed on the movable head of the chip mounter, and to have excellent responsiveness because the suction confirmation must be completed in a short time. One example of such a small and fast response flow rate sensor is disclosed in Patent Document 1. The flow sensor of Patent Document 1 aims at miniaturization and speeding up of responsiveness by laminating thin plates and forming a flow path therein.

Japanese Patent No. 3637050

  However, the flow rate sensor of Patent Document 1 has a smaller flow path by downsizing, and therefore there is a possibility that the flow rate of the fluid flowing in the flow path formed in the body is not stable. If the flow rate of the fluid flowing in the flow path is not stable, the measurement signal output from the flow sensor becomes unstable, the variation of the measurement signal value between products increases, or the measurement signal value depending on the usage environment It becomes easy to be affected. Therefore, there is a possibility that the measurement accuracy of the flow rate of the fluid may be lowered.

Therefore, in order to stabilize the flow rate of the fluid flowing in the flow path, it is conceivable to rectify by providing a straight pipe part in the flow path or by providing a rectifying grid in the flow path. However, the flow sensor has a large outer shape. turn into.
In addition, since the fluid inlet and outlet are communicated with the flow path space through elbow portions bent at 90 degrees, there is a concern that the pressure loss of the fluid may increase.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a thermal type flow meter that can improve the measurement accuracy of the flow rate of the fluid while reducing the size. .

One aspect of the present invention made to solve the above-described problem is a thermal flow rate comprising a sensor flow channel provided with a hot wire for measuring the flow rate of the fluid to be measured, and a bypass flow channel for the sensor flow channel. A measuring chip provided with the heat wire, a substrate on which the measuring chip is mounted and an electric circuit electrically connected to the measuring chip, a sensor flow path, and a bypass flow path The flow path block includes a plurality of rectifying plates, and is formed of a body that houses the flow path block and the substrate, and a cover that closes the opening of the body. They are arranged vertically with respect to the substrate bottom surface of the body in a fixed state to the body in the space, and the rectifying plate is arranged vertically to the bottom surface of the body, of the fluid to be measured Inlet is disposed on the bottom surface of the body, the ribs projecting into the bypass passage in the body is provided, and wherein.

  According to this aspect, since the rib protruding into the bypass channel is provided on the body, the flow direction can be changed by correcting the flow of the fluid to be measured, and a pressure difference can be intentionally provided at a necessary portion. it can. Therefore, it is possible to flow a measured fluid with a stable flow rate through the sensor flow path. Therefore, a stable flow rate can be measured by the measurement chip, and the measurement accuracy of the flow rate of the fluid to be measured can be improved.

  Further, it is only necessary to provide a rib, and it is not necessary to provide a straight pipe portion or a rectifying grid in the flow path, so that the thermal flow meter can be reduced in size.

  In the above aspect, the flow path block includes a flow straightening plate in which a flow straightening portion for adjusting the flow of the fluid to be measured flowing into the sensor flow path is provided with a boundary portion interposed therebetween, and the rib includes the boundary portion and It is preferable to be provided in a gap formed between the body and the body.

  According to this aspect, since the rib is provided in the gap formed between the boundary portion and the body, a pressure difference is generated between the inlet and the outlet of the flow path block, and the sensor flow path is generated from the inlet of the flow path block. The fluid to be measured can be flowed to the outlet of the flow path block via the. Therefore, the fluid under measurement having a stable flow rate can flow through the sensor flow path more reliably. Therefore, a stable flow rate can be measured with the measuring chip more reliably, and the measurement accuracy of the flow rate of the fluid to be measured can be improved more reliably.

  In the above aspect, the flow path block includes at least a first rectifying plate and a second rectifying plate as the rectifying plate, and the area of the rectifying portion of the first rectifying plate is the rectifying portion of the second rectifying plate. It is preferable that it is smaller than the area.

  According to this aspect, even if turbulent flow of the fluid to be measured occurs in the bypass flow path, a stable flow rate can be measured by the measuring chip without being affected by the turbulent flow. Therefore, the measurement accuracy of the flow rate of the fluid to be measured can be improved, the degree of freedom in designing the shape of the body forming the bypass channel is increased, and the thermal flow meter can be more reliably downsized. .

  In the above aspect, with respect to the inflow direction of the fluid to be measured from the inlet of the fluid to be measured into the body, the width of the rectifying portion of the first rectifying plate is larger than the width of the rectifying portion of the second rectifying plate. Is preferably small.

  According to this aspect, the measurement tip is less susceptible to the influence of the high pressure in the bypass flow path that can occur on the depth side in the inflow direction of the measured fluid from the inlet of the measured fluid into the body. A stable flow rate can be measured. Therefore, the measurement accuracy of the flow rate of the fluid to be measured can be further improved.

  According to the thermal type flow meter of the present invention, it is possible to improve the measurement accuracy of the flow rate of the fluid while reducing the size.

It is a disassembled perspective view of a thermal type flow meter. It is a bottom view which shows the bottom face of a body. It is a figure for demonstrating the lamination order of the thin plate which comprises a flow-path block. It is a top view which shows a 1st spacer. It is a top view which shows a 1st mesh board. It is an enlarged view of the mesh part of a 1st mesh board. It is a top view which shows a 2nd mesh board. It is a top view which shows a 3rd mesh board. It is a top view which shows a 2nd spacer. It is a figure which shows the flow-path structure in a thermal type flow meter. It is a top view which shows the surface of a sensor board | substrate. It is a top view which shows the surface of a printed circuit board. It is a top view which shows a measurement chip | tip. It is a circuit diagram which shows the structure of a constant temperature difference circuit. It is a circuit diagram which shows the structure of an output circuit. It is a perspective view which shows schematic structure of a cover. It is a front view of a body. It is an analysis result of pressure distribution. It is an analysis result of pressure distribution. It is an analysis result of pressure distribution. It is an analysis result of pressure distribution. It is a figure which shows the evaluation result of a flow volume and a midpoint potential. It is a figure which shows the evaluation result of a flow volume and a midpoint potential.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments in which a thermal flow meter of the invention is embodied will be described in detail with reference to the drawings. First, the entire thermal flow meter is described, and then the flow rate stabilization in the flow path space is described.

[Overall description of thermal flow meter]
FIG. 1 is an exploded perspective view of the thermal flow meter 10. As shown in FIG. 1, the thermal flow meter 10 includes a body 20, a cover 30, a flow path block 40, a sensor substrate 50, and the like. The sensor substrate 50 is fixed in the body 20 with the flow path block 40 attached to the body 20.

  On one side of the body 20 (on the left side in FIG. 1), a flow path space 21 that houses the flow path block 40 is formed. The channel space 21 is open on the front side in the figure, and a gasket mounting groove 22 for mounting the sensor gasket 51 is formed on the opening end face. Further, on the surface 21b opposite to the opening surface of the channel space 21 (the back side surface in FIG. 1), the channel block 40 is prevented from being in close contact with the surface 21b (gap 21s (see FIG. 10)). ) Is provided. By this step 24, the flow path block 40 is accommodated in the flow path space 21 with a gap 21s between the surface block 21b. The gap 21s forms a part of the first bypass flow path B1 as will be described later (see FIG. 10). Further, as will be described in detail later, a rib 70 is provided on the surface 21b.

  The fluid inlet 11 and the fluid outlet 12 are opened on the lower surface of the flow path space 21. That is, the fluid inlet 11 and the fluid outlet 12 are provided on the bottom surface of the body 20 as shown in FIG. FIG. 2 is a bottom view showing the bottom surface of the body 20. The fluid inlet 11 and the fluid outlet 12 are formed at the end of the body 20 (the back side end in FIG. 1) that is offset from the center line C in the depth direction of the body 20. A gasket mounting groove 14 for mounting the gasket 13 is provided around the fluid inlet 11 and the fluid outlet 12.

  As shown in FIG. 2, engagement holes 25 a, 25 b and 25 c for assembling the cover 30 are provided on the bottom surface of the body 20. Similarly, as shown in FIG. 1, engagement holes 25 d and 25 e are also provided on the upper surface of the body 20. In addition, connection portions 27 a and 27 b for connecting to connection devices such as the piping block 90 are provided at both ends of the body 20.

  As shown in FIG. 1, the flow path block 40 is configured by laminating a plurality of types of thin plates. In the present embodiment, the flow path block 40 is configured by laminating a total of nine thin plates of five types. Specifically, from the back in FIG. 1 toward the front (toward the sensor substrate 50), as shown in FIG. 3, the first spacer 41, the first mesh plate 42, the first spacer 41, the second mesh plate. 43, the 1st spacer 41, the 2nd mesh board 43, the 1st spacer 41, the 3rd mesh board 44, and the 2nd spacer 45 are laminated | stacked and adhered in order. 3 is a diagram for explaining the stacking order of the thin plates constituting the flow path block 40. FIG. The first mesh plate 42, the second mesh plate 43, and the third mesh plate 44 are examples of the “rectifying plate” of the present invention, and the first mesh plate 42 is an example of the “first straightening plate” of the present invention. The second mesh plate 43 is an example of the “second rectifying plate” in the present invention.

  Here, individual thin plates will be described. First, the first spacer 41 will be described with reference to FIG. FIG. 4 is a plan view showing the first spacer 41. As shown in FIG. 4, the first spacer 41 is etched so as to leave the positioning portion 41a, the outer peripheral portion 41b, and the boundary portion 41c. As shown in FIG. 4, the first spacer 41 has a substantially T shape, and a positioning portion 41 a is formed on the upper portion, and a pair of openings 41 o symmetrically in FIG. 4 with respect to the boundary portion 41 c. , 41o are formed. The positioning part 41 a is a part for positioning in the flow path space 21, and its outer peripheral end is in close contact with the inner wall of the flow path space 21.

  Next, the 1st mesh board 42 is demonstrated using FIG.5 and FIG.6. FIG. 5 is a plan view showing the first mesh plate 42. FIG. 6 is an enlarged view of the mesh portion 42 m of the first mesh plate 42. As shown in FIG. 5, the first mesh plate 42 has a substantially T-shape, a positioning portion 42 a is formed on the upper portion, and a pair of mesh portions symmetrically in FIG. 5 about the boundary portion 42 c. 42m and 42m are formed. The positioning part 42 a is a part for positioning in the flow path space 21, and the outer peripheral end thereof is in close contact with the inner wall of the flow path space 21. On the other hand, as shown in FIG. 6, the mesh part 42m is formed so that the distances between the centers of the holes constituting the mesh are all equal. That is, the holes are formed so that the centers of the holes are the vertices of the equilateral triangle. The mesh portion 42m is a rectifying portion that adjusts the flow of the fluid to be measured.

  Further, in the depth direction of the body 20, as shown in FIG. 5, the width δ1 of the mesh portion 42m of the first mesh plate 42 is equal to the width δ2 (see FIG. 7) of the mesh portion 43m of the second mesh plate 43 described later. It is smaller than the width δ3 (see FIG. 8) of the mesh portion 44m of the 3-mesh plate 44. Thereby, the area of the mesh part 42m of the 1st mesh board 42 is smaller than the area of the mesh part 43m of the 2nd mesh board 43 mentioned later, or the area of the mesh part 44m of the 3rd mesh board 44. FIG. And the parts 42d and 42e are formed in the position of the up-down direction of FIG. 5 with respect to the mesh part 42m. Details of the portions 42d and 42e will be described later.

  Next, the second mesh plate 43 will be described with reference to FIG. FIG. 7 is a plan view showing the second mesh plate 43. As shown in FIG. 7, the second mesh plate 43 has a substantially T-shape. A positioning part 43a is formed on the upper part, and a pair of mesh parts symmetrically in FIG. 7 with respect to the boundary part 43c. 43m and 43m are formed. The positioning part 43 a is a part for positioning in the flow path space 21, and its outer peripheral end is in close contact with the inner wall of the flow path space 21. The mesh portion 43m has the same configuration as the mesh portion 42m of the first mesh plate 42, and is a rectifying portion that regulates the flow of the fluid to be measured.

  Next, the third mesh plate 44 will be described with reference to FIG. FIG. 8 is a plan view showing the third mesh plate 44. As shown in FIG. 8, the third mesh plate 44 has the same shape as the cross-sectional shape of the channel space 21, and a pair of mesh portions 44m, 44m are symmetrically formed in FIG. 8 about the boundary portion 44c. Is formed. The mesh portion 44m has the same configuration as the mesh portion 42m of the first mesh plate 42 and the mesh portion 43m of the second mesh plate 43, and is a rectifying portion that regulates the flow of the fluid to be measured.

  Next, the second spacer 45 will be described with reference to FIG. FIG. 9 is a plan view showing the second spacer 45. As shown in FIG. 9, the second spacer 45 has the same shape as the cross-sectional shape of the flow path space 21, and a pair of openings 45 o and 45 o and a step difference symmetrically in FIG. 9 about the boundary 45 c. Portions 45a and 45a are formed.

  Then, by attaching the flow path block 40 in which the thin plates 41 to 45 are laminated and bonded in order from the left side shown in FIG. 3 to the flow path space 21, as shown in FIG. The first bypass flow path B1 and the second bypass flow path B2 are formed by the path block 40. More specifically, a part of the first bypass flow path B1 is formed by a gap 21s between the surface 21b of the flow path space 21 and the flow path block 40 (boundary portion 41c of the first spacer 41 (see FIG. 4)). A part of the second bypass flow path B2 is formed by the gap between the flow path block 40 (second spacer 45 (see FIG. 9)) and the measurement chip 60. FIG. 10 is a diagram showing a flow path configuration in the thermal flow meter 10.

  Further, the opening 41o of the first spacer 41, the mesh part 42m of the first mesh plate 42, the mesh part 43m of the second mesh plate 43, the mesh part 44m of the third mesh plate 44, and the opening 45o of the second spacer 45 Thus, the communication channels 15 and 16 are formed. The communication channel 15 communicates the fluid inlet 11, the first bypass channel B1, the second bypass channel B2, and the sensor channel S, and the communication channel 16 is connected to the fluid outlet 12 and the first bypass channel. The path B1, the second bypass flow path B2, and the sensor flow path S are communicated.

  In the communication channels 15 and 16, a total of four mesh portions are arranged, one mesh portion 42m, two mesh portions 43m, and one mesh portion 44m. Thereby, every time the fluid to be measured passes through the mesh portions 42m, 43m and 44m, the disturbance of the flow of the fluid to be measured decreases. Therefore, the fluid to be measured whose flow has been adjusted can be poured into the sensor flow path S. In addition, the number of each of the 1st mesh board 42, the 2nd mesh board 43, and the 3rd mesh board 44 is not limited like a present Example, It can change. Therefore, for example, two or more mesh portions 42m may be provided.

  The sensor substrate 50 disposed via the sensor gasket 51 with respect to the flow path block 40 outputs the measured flow rate as an electrical signal. Therefore, as shown in FIG. 11, the measurement chip 60 is mounted on the sensor substrate 50 near the center of the right half in the figure on the surface side (the mounting surface side to the body 20) of the printed circuit board 52 serving as a base. Yes. FIG. 11 is a plan view showing the surface of the sensor substrate 50.

  And the groove | channel 53 is processed as shown in FIG. 12 in the part in which the measurement chip | tip 60 of the printed circuit board 52 is mounted. FIG. 12 is a plan view showing the surface of the printed circuit board 52. Circuit electrodes 54, 55, 56, 57, 58, 59 are provided on both sides of the groove 53. These electrodes 54 to 59 are electrically connected to a constant temperature difference circuit and an output circuit, which will be described later, through pattern wiring formed in the printed circuit board 52.

  Here, the measurement chip 60 will be described with reference to FIG. FIG. 13 is a plan view showing the measurement chip 60. As shown in FIG. 13, the measurement chip 60 is obtained by performing a semiconductor micromachining processing technique on the silicon chip 62. At this time, a groove 63 is processed at the center of the chip and a resistor (heat wire) is used. ) Electrodes 64, 65, 66, 67, 68, 69 are provided at both ends of the chip.

  At this time, the upstream temperature detection resistor R <b> 1 extends from the resistor electrodes 65 and 67 and is laid over the groove 63. Further, the downstream temperature detection resistor R <b> 2 extends from the resistor electrodes 67 and 69 and is laid over the groove 63. Furthermore, the heating resistor Rh extends from the resistor electrodes 66 and 68 and is laid over the groove 63 between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2. In the measurement chip 60, the fluid temperature detection resistor Rt extends from the resistor electrodes 64 and 66 on the upstream side in the forward direction of the sensor flow path S.

  Then, the resistor electrodes 64, 65, 66, 67, 68, 69 of the measuring chip 60 are joined to the circuit electrodes 54, 55, 56, 57, 58, 59 of the sensor substrate 50 respectively by solder reflow or The measurement chip 60 is mounted on the sensor substrate 50 by bonding with a conductive adhesive or the like. Therefore, when the measurement chip 60 is mounted on the sensor substrate 50, the fluid temperature detection resistor Rt, the upstream temperature detection resistor R1, the downstream temperature detection resistor R2, and the heating resistor Rh provided on the measurement chip 60 are: Electricity is supplied to the constant temperature difference circuit of FIG. 14 and the output circuit of FIG. 15 provided on the sensor substrate 50 via the resistor electrodes 64 to 69 of the measurement chip 60 and the circuit electrodes 54 to 59 of the sensor substrate 50. Connected.

  Here, the constant temperature difference circuit shown in FIG. 14 is a circuit for controlling the heating resistor Rh to have a certain temperature difference from the fluid temperature detected by the fluid temperature detection resistor Rt. The output circuit shown in FIG. 15 is a circuit for outputting a voltage value corresponding to the temperature difference between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2. In this output circuit, the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2 are connected in series, and a constant voltage Vc is applied. The midpoint potential Vout between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2 is output as a measurement signal.

  Further, when the measurement chip 60 is mounted on the sensor substrate 50, the groove 63 of the measurement chip 60 overlaps with the groove 53 of the sensor substrate 50. Therefore, when the sensor substrate 50 on which the measurement chip 60 is mounted is fixed to the body 20, the groove 63 of the measurement chip 60 is provided between the sensor substrate 50 and the measurement chip 60 in the flow path space 21, as shown in FIG. In addition, an elongated sensor flow path S including the groove 53 of the sensor substrate 50 is formed. Therefore, in the sensor flow path S, the fluid temperature detection resistor Rt, the upstream temperature detection resistor R1, the downstream temperature detection resistor R2, and the heating resistor Rh are provided so as to cross the bridge.

  The sensor substrate 50 on which the measurement chip 60 is mounted in this manner is fixed within the body 20 by the body 20 and screws 71 (see FIG. 1). That is, as shown in FIG. 1, the sensor substrate 50 is fixed to the body 20 with the screws 71, and the sensor substrate 50 is arranged upright (vertically). As a result, the thermal flow meter 10 is reduced in size in the depth direction, that is, reduced in thickness, without being limited by the size of the sensor substrate 50. Specifically, the depth dimension is about 30% smaller than that of a conventional flow meter. And with this miniaturization, the weight of the thermal flow meter 10 is also reduced, so that weight reduction is also achieved.

  Further, it is not necessary to fix the sensor substrate 50 to the body 20 with a mold resin or the like. Therefore, since the space for fixing the sensor substrate 50 can be reduced, the thermal flow meter 10 can be reduced in size. And since the weight of the thermal type flow meter 10 also decreases with this miniaturization, the weight reduction of the thermal type flow meter 10 can be achieved.

  The sensor substrate 50 is located on the opposite side (front side) to the fluid inlet 11 and the fluid outlet 12 with respect to the center line C in the depth direction of the body 20. Accordingly, the flow path block 40 is disposed between the fluid inlet 11 and the fluid outlet 12 and the sensor substrate 50. With such an arrangement configuration, the flow path block 40 can be efficiently arranged in a limited space. This also makes the thermal flow meter 10 thinner and lighter.

  FIG. 16 is a perspective view illustrating a schematic configuration of the cover 30. Three engagement protrusions 31a, 31b, and 31c are formed on the bottom surface (left side in FIG. 16) of the cover 30, and engagement protrusions 31d and 31e are formed on the top surface (right side in FIG. 16) of the cover 30. Yes. These engagement protrusions 31a, 31b, 31c, 31d, and 31e are engaged with engagement holes 25a, 25b, 25c, 25d, and 25e formed in the body 20, respectively, when the cover 30 is attached to the body 20. It is like that.

  Then, the effect | action of the thermal type flow meter 10 which has an above-described structure is demonstrated. In the thermal flow meter 10, in the case of a forward flow, the fluid to be measured that has flowed into the flow path space 21 from the piping block 90 via the fluid inlet 11 is a flow path mounted in the flow path space 21. The block 40 divides the flow into the sensor flow path S and the flow into the first bypass flow path B1 or the second bypass flow path B2. Then, the fluids to be measured that have flowed out from the sensor flow path S, the first bypass flow path B1, and the second bypass flow path B2 merge and flow out to the piping block 90 via the fluid outlet 12.

On the other hand, in the case of the flow in the reverse direction, the fluid to be measured that has flowed into the flow path space 21 from the piping block 90 via the fluid outlet 12 is caused by the flow path block 40 mounted in the flow path space 21.
The flow is divided into a flow into the sensor flow path S and a flow into the first bypass flow path B1 and the second bypass flow path B2. Then, the fluids to be measured that have flowed out from the sensor flow path S, the first bypass flow path B1 and the second bypass flow path B2 merge and flow out to the piping block 90 via the fluid inlet 11.

  Here, even if the fluid to be measured flows in either the forward direction or the reverse direction, the fluid to be measured flowing into the sensor flow path S is the mesh part 42m (see FIG. 5) and the mesh part 43m in the flow path block 40. (See FIG. 7), after passing through the mesh portion 44m (see FIG. 8), it flows into the sensor flow path S. Therefore, the fluid to be measured in a state where the flow is very arranged flows through the sensor flow path S. Then, the fluid to be measured flowing through the sensor flow path S removes heat from the heating resistor Rh bridged in the sensor flow path S.

  Then, the constant temperature difference circuit shown in FIG. 14 provided on the sensor substrate 50 is controlled so that the fluid temperature detection resistor Rt and the heating resistor Rh have a constant temperature difference. Further, by the output circuit shown in FIG. 15 provided on the sensor substrate 50, the midpoint potential Vout between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2 connected in series and applied with the constant voltage Vc is measured. Is output as At this time, when the fluid to be measured is a forward flow, the temperature (resistance value) of the upstream temperature detection resistor R1 decreases and the temperature (resistance value) of the downstream temperature detection resistor R2 increases. The point potential Vout increases. On the other hand, when the fluid to be measured flows in the reverse direction, the temperature (resistance value) of the upstream temperature detection resistor R1 increases and the temperature (resistance value) of the downstream temperature detection resistor R2 decreases. The potential Vout decreases. For this reason, the flow direction of the fluid to be measured can be detected.

[Explanation on stabilization of flow rate in channel space]
Next, stabilization of the flow rate in the flow path space 21 will be described. In this embodiment, a device for stabilizing the flow of the fluid to be measured in the flow path space 21 of the thermal flow meter 10 is provided.

  FIG. 17 is a front view of the body 20. As shown in FIGS. 10 and 17, in this embodiment, a rib 70 protruding into the first bypass channel B1 (gap 21s) is provided on the surface 21b of the body 20. As shown in FIG. 17, the rib 70 is formed in an elongated shape in the vertical direction of the drawing, and the cross section is formed in a half of an ellipse or a semicircle as shown in FIG. As shown in FIG. 10, the rib 70 is located at a substantially central position of the boundary portions 41 c to 45 c of the flow path block 40 in the direction in which the fluid inlet 11 and the fluid outlet 12 are arranged (the horizontal direction in FIG. 10). Is provided. Further, the height H of the rib 70 is set to a size that does not affect the pressure loss of the fluid to be measured flowing in the flow path space 21. In the present embodiment, as an example, the height of the first bypass flow path B 1 (gap 21 s) is high. About 40% of h. The rib 70 is integrally formed with the body 20.

  In the present embodiment, as shown in FIG. 5, the longitudinal width δ1 of the mesh portion 42m of the first mesh plate 42 is equal to the longitudinal width δ2 of the mesh portion 43m of the second mesh plate 43 (see FIG. 5). 7) or the width δ3 in the longitudinal direction of the mesh portion 44m of the third mesh plate 44 (see FIG. 8). Thereby, the area of the mesh part 42 m of the first mesh plate 42 is smaller than the area of the mesh part 43 m of the second mesh plate 43 and the area of the mesh part 44 m of the third mesh plate 44. The widths δ1 to δ3 are the widths in the depth direction of the body 20 when the mesh plates are attached to the body 20, that is, the inflow direction of the fluid to be measured from the fluid inlet 11 into the flow path space 21 of the body 20. Width. As described above, the first mesh plate 42 is not provided with the mesh portion 42m in the depth-side portion 42d and the near-side portion 42e of the body 20 when the first mesh plate 42 is attached to the body 20, and the portions 42d and 42e. Then, the fluid to be measured is shut off.

In the thermal type flow meter 10 having such a structure, when the fluid to be measured flows into the flow path space 21 from the fluid inlet 11, the flow path block 40 flows into the sensor flow path S, and the first bypass flow The flow is diverted to the flow into the path B1 or the second bypass flow path B2. Then, the fluids to be measured that have flowed out from the sensor flow path S, the first bypass flow path B1, and the second bypass flow path B2 merge and flow out to the piping block 90 via the fluid outlet 12.
At this time, in the present embodiment, the first bypass channel B1 (gap 21s) located between the inlet portion 72 of the communication channel 15 and the outlet portion 78 of the communication channel 16 formed by the channel block 40 is ribbed. Since 70 is provided, the flow direction of the fluid to be measured changes compared to the case where the rib 70 is not provided.

  Thereby, between the inlet part 72 (refer FIG. 10) of the communication flow path 15, and the inlet part 74 (refer FIG. 10) of the sensor flow path S, the inlet part 74 and outlet part 76 (refer FIG. 10) of the sensor flow path S ) Between the outlet portion 76 of the sensor flow path S and the outlet portion 78 (see FIG. 10) of the communication flow path 16, the pressure distribution is such that a large pressure difference is intentionally generated. be able to. With such a pressure distribution, the fluid to be measured easily flows smoothly from the fluid inlet 11 to the fluid outlet 12 via the communication channel 15, the sensor channel S, and the communication channel 16. Note that the pressure distribution is the same even if the flow rate of the fluid to be measured changes. Therefore, the flow rate of the fluid to be measured in the sensor flow path S is stable, and the stable flow rate can be measured by the measurement chip 60. Therefore, the measurement accuracy of the flow rate of the fluid to be measured can be improved. Further, it is only necessary to provide the rib 70, and it is not necessary to provide a straight pipe portion or a rectifying grid in the flow path space 21, so that the thermal flow meter 10 can be downsized.

Further, the width δ1 of the mesh portion 42m of the first mesh plate 42 is made smaller than the longitudinal width δ2 of the mesh portion 43m of the second mesh plate 43 and the longitudinal width δ3 of the mesh portion 44m of the third mesh plate 44. In the portions 42d and 42e, the fluid to be measured is blocked.
As a result, the fluid under measurement having a flow rate corresponding to the pressure difference of each part can be caused to flow through the sensor passage S without being affected by the flow of the fluid under measurement in the first bypass passage B1. Therefore, even if the first bypass flow path B1 has a shape in which turbulent flow is likely to occur, the fluid to be measured can flow through the sensor flow path S at a stable flow rate. Therefore, a stable flow rate can be measured with the measuring chip 60 more reliably, and the measurement accuracy of the flow rate of the fluid to be measured can be improved. Moreover, since the freedom degree of design of the body 20 increases and the thin thermal flow meter 10 can be manufactured, the thermal flow meter 10 can be reduced in size.

  Furthermore, the influence of the high pressure in the first bypass flow path B1 that can occur on the depth side in the flow direction of the fluid to be measured from the fluid inlet 11 into the flow path space 21 of the body 20 (the depth direction of the body 20). Therefore, the fluid to be measured can flow through the sensor flow path S at a stable flow rate. Therefore, it is possible to more reliably measure a stable flow rate with the measurement chip 60, and to further improve the measurement accuracy of the flow rate of the fluid to be measured.

  In the present embodiment, the portion 42d and the portion 42e are provided. However, the present invention is not limited to this, and it is possible to provide only one of the portion 42d and the portion 42e.

[Explanation of analysis results]
Next, since the pressure distribution in the flow path space 21 is analyzed in order to confirm the change in the pressure distribution in the flow path space 21 of the body 20 by providing the rib 70, the analysis result will be described. 18 to 21 are analysis results of the pressure distribution. 18 and 19 are analysis diagrams of pressure distribution in the vicinity of the surface 21b (first bypass channel B1) in the channel space 21 as viewed from the front of the body 20, and FIG. 18 shows an analysis result when the rib 70 is not provided. FIG. 19 shows an analysis result when the rib 70 is provided. 20 and 21 are analysis diagrams of pressure distribution in the channel space 21 when the cross section of the thermal flow meter 10 is viewed, and FIG. 20 is an analysis result when the rib 70 is not provided. These are the analysis results when the rib 70 is provided.

  When the rib 70 is not provided, as shown in FIG. 18, the pressure on the back side in the depth direction of the body 20 is increased, while the pressure at the inlet portion 72 of the communication channel 15 is decreased. On the other hand, when the rib 70 is provided, as shown in FIG. 19, the pressure on the back side in the depth direction of the body 20 is slightly low, and the pressure of the inlet portion 72 of the communication channel 15 is high. Yes.

Further, as shown in FIGS. 20 and 21, the pressure difference between the inlet portion 72 of the communication channel 15 and the inlet portion 74 of the sensor channel S, and the difference between the inlet portion 74 and the outlet portion 76 of the sensor channel S, The pressure difference between the outlet portion 76 of the sensor flow path S and the outlet portion 78 of the communication flow path 16 is greater when the rib 70 is provided than when the rib 70 is not provided. .
As described above, by providing the rib 70, the pressure of the inlet portion 72 of the communication flow path 15 is increased, the pressure distribution in the flow path space 21 is changed, and the pressure difference in each part in the flow path space 21 is increased. It was confirmed that

[Explanation of evaluation results]
Next, the evaluation result of the midpoint potential Vout (see FIG. 15) measured with respect to the flow rate of the fluid to be measured at the fluid inlet 11 will be described. 22 and 23 are diagrams showing the measurement result of the midpoint potential Vout with respect to the flow rate of the fluid to be measured. FIG. 22 shows the case where the rib 70 is not provided, and FIG. 23 shows the case where the rib 70 is provided. The plurality of thermal flow meters 10 were evaluated.

  Then, as shown in FIG. 22, when the rib 70 was not provided, the amount of variation in the midpoint potential Vout between the plurality of thermal flow meters 10 increased. On the other hand, as shown in FIG. 23, when the rib 70 is provided, the amount of variation in the midpoint potential Vout between the plurality of thermal flow meters 10 is very small. Thus, it was confirmed that the variation amount of the midpoint potential Vout between the plurality of thermal flow meters 10 can be suppressed by providing the rib 70. Therefore, it was found that by providing the rib 70, variation in measurement accuracy between products of the thermal flow meter 10 can be suppressed.

[Effect of this embodiment]
As described above, according to the thermal flow meter 10 according to the present embodiment, the rib 70 protruding to the first bypass channel B1 is provided on the surface 21b of the body 20, so that the fluid to be measured The flow direction can be changed by correcting the flow, and a pressure difference can be intentionally provided at a necessary portion in the flow path space 21. Therefore, a fluid to be measured having a stable flow rate can flow through the sensor flow path S. Therefore, a stable flow rate can be measured by the measuring chip 60, and the measurement accuracy of the flow rate of the fluid to be measured can be improved.

Further, it is only necessary to provide the rib 70, and it is not necessary to provide a straight pipe portion or a rectifying grid in the flow path space 21, so that the thermal flow meter 10 can be reduced in size.
Furthermore, the height H of the rib 70 is set to a size that does not affect the pressure loss of the fluid to be measured flowing in the flow path space 21. In the present embodiment, as an example, the height of the first bypass flow path B 1 (gap 21 s) is high. About 40% of h. Therefore, the pressure loss of the fluid to be measured can be suppressed.

  Further, by providing the rib 70 in the gap 21s, a pressure difference is generated between the inlet and the outlet of the flow path block 40, and the communication flow path 15, the sensor flow path S, and the communication flow path 16 are connected from the inlet of the flow path block 40. The fluid to be measured can be made to flow to the outlet of the flow path block 40 through. Therefore, the fluid under measurement having a stable flow rate can flow through the sensor flow path S more reliably. Therefore, a stable flow rate can be measured with the measuring chip 60 more reliably, and the measurement accuracy of the flow rate of the fluid to be measured can be improved more reliably.

  The width δ1 of the mesh portion 42m of the first mesh plate 42 is equal to the width δ2 (see FIG. 7) of the mesh portion 43m of the second mesh plate 43 and the width δ3 of the mesh portion 44m of the third mesh plate 44 (see FIG. 8). Smaller than). Thereby, the area of the mesh part 42 m of the first mesh plate 42 is smaller than the area of the mesh part 43 m of the second mesh plate 43 and the area of the mesh part 44 m of the third mesh plate 44. Therefore, the fluid under measurement having a flow rate corresponding to the pressure difference of each part can be flowed through the sensor passage S without being affected by the flow of the fluid under measurement in the first bypass passage B1. Therefore, it is possible to measure the flow rate of the fluid to be measured stably by the measuring chip 60 more reliably, and to improve the measurement accuracy of the flow rate of the fluid to be measured. Moreover, since the freedom degree of the shape design of the body 20 increases and the thin thermal flow meter 10 can be manufactured, the thermal flow meter 10 can be further reduced in size.

  Further, the fluid to be measured is less susceptible to the influence of high pressure in the first bypass flow path B1 that can occur on the depth side in the flow direction of the fluid to be measured from the fluid inlet 11 into the flow path space 21 of the body 20. The measurement accuracy of the flow rate can be further improved.

  Further, it is only necessary to adjust the width δ1 of the mesh portion 42m of the first mesh plate 42, and it is not necessary to provide a straight pipe portion or a rectifying grid in the flow path space 21, so that a simple structure can be achieved. The size of the flow meter 10 can be further reduced.

  A sensor substrate 50 is vertically arranged in a space formed by the body 20 and the cover 30. Further, the inlets and outlets 11 and 12 for the fluid to be measured are arranged on the same surface of the body 20 so as to be shifted from the center line C in the depth direction of the body 20. The sensor substrate 50 is fixed to the body 20 so that the measurement chip 60 mounted on the sensor substrate 50 is disposed on the opposite side of the center line C from the inlets 11 and 12 of the fluid to be measured. . By these, while being able to arrange | position the flow-path block 40 efficiently in the limited space, without being restrict | limited to the magnitude | size of the sensor board | substrate 50, size reduction in the depth direction of the thermal type flow meter 10, That is, the thickness can be reduced. Further, the thermal flow meter 10 can be reduced in weight.

  In the thermal flow meter 10, the flow path block 21 is attached to the flow path space 21 formed in the body 20 to configure the first bypass flow path B 1 and the second bypass flow path B 2, thereby measuring Since an optimum bypass ratio of the fluid can be set, linear output characteristics can be obtained. The flow path block 40 includes multilayer mesh portions 42m, 43m, and 44m disposed between the first bypass flow path B1 and the second bypass flow path B2 and the sensor flow path S. Thereby, the flow of the fluid to be measured flowing into the sensor flow path S is adjusted. Therefore, a very stable output can be obtained. Further, the measurement chip 60 is provided with an upstream temperature detection resistor R1, a downstream temperature detection resistor R2, a heating resistor Rh, and a fluid temperature detection resistor Rt, and the heating resistor Rh and the fluid temperature detection resistor Rt are provided by an electric circuit. Are controlled to have a constant temperature difference, and the flow rate of the fluid to be measured is measured based on the temperature difference between the upstream temperature detection resistor R1 and the downstream temperature detection resistor R2. Thereby, bidirectional flow rate detection can be performed.

  It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 Thermal type flow meter 11 Fluid inlet 12 Fluid outlet 15 Connecting flow path 16 Connecting flow path 20 Body 21 Flow path space 21b Surface 21s Gap 30 Cover 40 Flow path block 41 First spacer 41c Boundary part 41o Opening part 42 First mesh plate 42c boundary portion 42d portion 42e portion 42m mesh portion 43 second mesh plate 43c boundary portion 43m mesh portion 44 third mesh plate 44c boundary portion 44m mesh portion 45 second spacer 45c boundary portion 45o opening portion 50 sensor substrate 60 measurement chip 70 rib 72 Inlet part of communication channel 74 Inlet part of sensor channel 76 Outlet part of sensor channel 78 Outlet part of communication channel B1 First bypass channel h Height of first bypass channel H Height of rib C Center Line Vout Midpoint potential δ1 to δ3 Width

Claims (4)

In a thermal flow meter comprising a sensor flow path provided with a heat wire for measuring the flow rate of the fluid to be measured, and a bypass flow path for the sensor flow path,
A measuring chip provided with the heat ray;
A substrate on which the measurement chip is mounted and provided with an electric circuit electrically connected to the measurement chip;
A flow path block that branches the sensor flow path and the bypass flow path;
The flow path block includes a plurality of rectifying plates,
The substrate is disposed perpendicular to the bottom surface of the body in a state of being fixed to the body in a space formed by a body that houses the flow path block and the substrate and a cover that closes the opening of the body. And the said baffle plate is arrange | positioned perpendicularly | vertically with respect to the bottom face of the said body,
The inlet / outlet of the fluid to be measured is disposed on the bottom surface of the body,
The body is provided with a rib projecting into the bypass flow path;
Thermal flow meter featuring The thermal flow meter of claim 1,
The flow path block includes a rectifying plate provided with a pair of rectifying portions for adjusting the flow of the fluid to be measured flowing into the sensor flow channel with a boundary portion interposed therebetween,
The rib is provided in a gap formed between the boundary portion and the body;
Thermal flow meter featuring The thermal flow meter of claim 2,
The flow path block includes at least a first rectifying plate and a second rectifying plate as the rectifying plate,
The area of the rectifying portion of the first rectifying plate is smaller than the area of the rectifying portion of the second rectifying plate;
Thermal flow meter featuring The thermal flow meter according to claim 3,
The inflow direction of the fluid to be measured from the inlet of the fluid to be measured into the body, the width of the rectifying portion of the first rectifying plate is smaller than the width of the rectifying portion of the second rectifying plate,
Thermal flow meter featuring