Flowmeter

Abstract

This flowmeter comprises: a flow path forming member that forms a flow path through which a fluid flows; a temperature controller for heating or cooling the fluid flowing through the flow path; a temperature sensor that detects parameters related to temperatures at two different points in the flow path forming member; and an information processing unit that calculates the flow rate of the fluid on the basis of an output signal from the temperature sensor. The flow path forming member is formed of a ceramic material having formed therein a housing recess in which the temperature controller or the temperature sensor is installed.

Description

flow meter

[0001] This invention relates to a flow meter that utilizes the principle of heat exchange.

[0002] Conventionally, flow meters using the principle of heat exchange are known, such as the one described in Patent Document 1. This device is configured to cool a portion of the piping through which the fluid flows using a cooling device such as a Peltier element, and to calculate the flow rate of the fluid flowing through the piping based on the temperature change occurring inside the piping detected by a temperature sensor.

[0003] International Publication WO2008 / 090839

[0004] Incidentally, in recent years, the use of corrosive fluids in semiconductor manufacturing processes has been increasing. In the flow meters mentioned above, the piping is made of metal pipes such as stainless steel, and when corrosive fluids are passed through them, the pipes corrode, causing contamination and potentially adversely affecting the manufacturing process.

[0005] This invention has been made in view of these problems, and its main objective is to provide a flow meter that does not cause contamination even when corrosive fluids are flowed through it.

[0006] In other words, the flow meter of the present invention comprises a flow path forming member that forms a flow path through which a fluid flows, a temperature controller for heating or cooling the fluid flowing through the flow path, a temperature sensor for detecting temperature parameters at two different points on the flow path forming member, and an information processing unit for calculating the flow rate of the fluid based on the output signal of the temperature sensor, wherein the flow path forming member is made of a ceramic material having a housing recess formed therein in which the temperature controller or the temperature sensor is installed.

[0007] With this design, the entire wetted portion of the flow path can be constructed from a corrosion-resistant ceramic material, preventing contamination due to corrosion even when corrosive fluids are flowed through it. This allows for the measurement of fluid flow rates without adverse effects in semiconductor manufacturing processes that use corrosive fluids. Furthermore, by shaping the flow path forming member to include a recess for installing a temperature controller or temperature sensor, it is possible to increase sensitivity by reducing the wall thickness of the flow path near the location where the temperature controller or temperature sensor is installed, even while using a low-strength ceramic material, while increasing the thickness of areas other than the recess to provide overall strength. Note that "parameters related to the temperatures of two different points in the flow path forming member" refers to, for example, the temperatures of two points, the temperature difference between the two points, or equivalent values.

[0008] The flow path comprises a temperature-controlled region that is heated or cooled by the temperature controller, and a non-temperature-controlled region set upstream of the temperature-controlled region, and is formed such that the flow path diameter in the temperature-controlled region is smaller than the flow path diameter in the non-temperature-controlled region. In this way, the heat capacity of the fluid is increased by making the flow path diameter of the non-temperature-controlled region larger than that of the temperature-controlled region, the thermal influence of the temperature controller in the non-temperature-controlled region can be relatively reduced, and the temperature in the non-temperature-controlled region can be accurately detected as a reference temperature.

[0009] A specific configuration of the block-shaped flow path forming member is one in which a first housing recess for the temperature controller and a second housing recess for the temperature sensor are formed on its surface. In this way, by installing the temperature controller and the temperature sensor in different housing recesses, the temperature controller and the temperature sensor can be positioned at appropriate locations in relation to the distance to the flow path.

[0010] Furthermore, in the flow meter, it is preferable that the first and second housing recesses are formed such that the distance from the flow path to the temperature sensor is shorter than the distance from the flow path to the temperature controller. In this way, the wall thickness on the side of the second housing recess where the temperature sensor is installed is relatively reduced to increase the sensitivity of the sensor, while the wall thickness on the side of the first housing recess where the temperature controller is installed is relatively increased to provide strength. Since ceramic materials have excellent thermal conductivity, it is not necessary to make the wall thickness on the side where the temperature controller is installed excessively small, making this configuration possible.

[0011] Specific embodiments of the flow meter of the present invention include a cooling element which is a temperature controller, a first temperature sensor for detecting the temperature of the temperature-controlled region, a second temperature sensor for detecting the temperature of the temperature controller, a third temperature sensor for detecting the temperature of the non-temperature-controlled region, and an information processing unit which controls the temperature controller so that the difference between the temperature detected by the second temperature sensor and the temperature detected by the third temperature sensor becomes a predetermined value, and calculates the flow rate flowing through the flow path based on the difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor.

[0012] Preferably, the flow meter has the first temperature sensor and the third temperature sensor installed in the second housing recess, and the second temperature sensor is installed in the first housing recess together with the temperature controller. In this way, by installing the second temperature sensor near the temperature controller, the temperature of the temperature controller can be detected more accurately.

[0013] Furthermore, it is preferable that the flow meter is installed on the bottom surface of the first housing recess via a low thermal conductivity material with a lower thermal conductivity than the flow path forming member. For example, if the flow path forming member is made of a ceramic material with high thermal conductivity such as silicon carbide, and both the temperature controller and the second temperature sensor are in contact with the flow path forming member, there is a risk that the temperature of the temperature controller may not be accurately measured because excessive heat is lost from the temperature controller by the flow path forming member. By installing the temperature controller and the second temperature sensor on the bottom surface of the first housing recess via a low thermal conductivity material with a lower thermal conductivity than the flow path forming member, it is possible to prevent excessive heat loss from the temperature controller and measure its temperature more accurately.

[0014] Preferably, the flow meter includes a Peltier element as the cooling element, which has a heat-absorbing surface on one side and a heat-dissipating surface on the other, and a heat sink provided in contact with the heat-dissipating surface of the Peltier element, and the bottom of the first housing recess has a first bottom surface in contact with the heat-absorbing surface of the Peltier element and a second bottom surface in contact with the surface of the heat sink. In this way, heat from the heat sink can be transferred to the non-temperature-controlled region via the second bottom surface, preventing the fluid flowing through the non-temperature-controlled region for measuring the reference temperature from being cooled by the Peltier element.

[0015] One embodiment of the flow meter that demonstrates the effects of the present invention is one in which the flow path forming member is entirely made of silicon carbide. By making the flow path forming member out of silicon carbide, contamination does not occur even when corrosive fluids such as acids or bases (e.g., acetic acid) are flowed through it.

[0016] According to the present invention, it is possible to provide a flow meter that does not cause contamination even when corrosive fluids are flowed through it.

[0017] A schematic diagram showing the overall configuration of a flow meter according to one embodiment of the present invention. A schematic cross-sectional view along line A-A' showing the overall configuration of the flow meter of the same embodiment. An enlarged cross-sectional view of section X in Figure 2. A diagram illustrating the arrangement of each temperature sensor in the flow meter of the same embodiment. A cross-sectional view illustrating the configuration near the temperature control region in a flow meter of another embodiment.

[0018] A flow meter 100 according to one embodiment of the present invention will be described below with reference to the drawings.

[0019] The flow meter 100 of this embodiment uses the principle of heat exchange and is a thermal type that measures the flow rate of a fluid based on the temperature change caused by cooling the flow path P through which the fluid flows. Specifically, as shown in Figures 1 and 2, the flow meter 100 comprises a flow path P through which the fluid flows, a temperature controller 5 which is a cooling element that cools a part of the flow path P, a first temperature sensor 1 that detects the temperature of the temperature-controlled region P1 of the flow path P cooled by the temperature controller 5, a second temperature sensor 2 that detects the temperature of the temperature controller 5, a third temperature sensor 3 that detects the temperature of a non-temperature-controlled region P2 set upstream of the temperature-controlled region P1 in the flow path P, a fourth temperature sensor 4 that detects the ambient temperature of the environment in which the temperature controller 5 is installed, and an information processing unit (not shown) that receives detection signals from the four temperature sensors, controls the temperature controller 5, and calculates the flow rate of the fluid flowing through the flow path P. "Cooling the flow path P" means cooling the fluid flowing through the flow path P. The flow meter 100 converts the difference (temperature difference) of the measured values ​​of each temperature sensor 1 and 2 into a flow rate.

[0020] However, in the flow meter 100 of this embodiment, the flow path P is formed by through holes formed in a block-shaped flow path forming member 8 made of ceramic material. In this embodiment, the flow path forming member 8 has a roughly rectangular parallelepiped shape and is entirely made of SiC (silicon carbide). The flow path forming member 8 may be made of other ceramic materials.

[0021] The flow path P has a circular cross-section through which a fluid such as liquid or gas flows. In this embodiment, the flow path P is formed linearly along the longitudinal direction of the flow path forming member 8 and opens at both ends of the flow path forming member 8. That is, one end along the longitudinal direction is the upstream side and the other is the downstream side. Both ends of the flow path forming member 8 through which the flow path P opens are connected to piping.

[0022] As described above, the flow path P comprises a temperature-controlled region P1 and a non-temperature-controlled region P2, which are set along the flow direction. Here, the non-temperature-controlled region P2 is set on both sides of the temperature-controlled region P1 (i.e., the upstream and downstream sides) along the flow direction. The flow path P is formed such that the flow path axis X coincides between the temperature-controlled region P1 and the non-temperature-controlled region P2.

[0023] In this embodiment, the temperature-controlled region P1 and the non-temperature-controlled region P2 have different flow path diameters, with the flow path diameter in the temperature-controlled region P1 being smaller than the flow path diameter in the non-temperature-controlled region P2. In other words, when viewed from a direction perpendicular to the flow direction, in the portion of the flow path P that overlaps with the temperature controller 5, some areas are narrower than other areas. The non-temperature-controlled region P2 gradually narrows in diameter at its end and connects to the temperature-controlled region P1.

[0024] In the flow path forming member 8, the temperature controller 5 and the temperature sensors 1, 2, 3, and 4 are installed in the portion of the flow path P where the wall thickness is thin. Specifically, the flow path forming member 8 has a first housing recess 81 in which the temperature controller 5 is installed and a second housing recess 82 in which the temperature sensors 1, 2, 3, and 4 are installed formed on its surface. The first housing recess 81 and the second housing recess 82 are formed on the side surfaces of the flow path forming member 8 along the flow direction, and specifically, they are formed on opposite side surfaces with the flow path P in between.

[0025] In this embodiment, the flow path forming member 8 is provided with joint attachment portions F at both ends along the flow direction, which are attached to the external piping, and accommodating recesses 81 and 82 are formed between the two joint attachment portions F. The joint attachment portions F are connected to the external piping by screws and therefore require a certain degree of strength and thickness, while at the same time it is necessary to reduce the wall thickness in the temperature-controlled region P1 of the flow path P formed between them. For this reason, the flow path forming member 8 has a shape in which accommodating recesses 81 and 82 are provided between the ends of a block-shaped member.

[0026] The first receiving recess 81 has a bottom surface 8s parallel to the flow direction of the flow channel P. The first receiving recess 81 is formed such that, when viewed from the depth direction, its bottom surface 8s overlaps with the entire temperature-controlled region P1 of the flow channel P and at least partially overlaps with the non-temperature-controlled region P2 on the upstream side. The temperature controller 5 is installed in the portion of the bottom surface 8s that overlaps with the temperature-controlled region P1.

[0027] The temperature controller 5 in this embodiment is a Peltier element having a flat plate shape with a heat-absorbing surface on one side and a heat-dissipating surface on the other side (opposite side). The temperature of the heat-absorbing surface of the Peltier element 5 is controlled by controlling the voltage applied to it by a power supply and a wiring board (not shown). The temperature controller 5 is installed so that its heat-absorbing surface is in contact with the bottom surface 8s of the first housing recess 81. A heat sink 6 equipped with multiple heat dissipation fins is provided in contact with the heat-dissipating surface of the temperature controller 5. The heat sink 6 has a larger surface area than the heat-dissipating surface of the temperature controller 5 when viewed from the depth direction.

[0028] The bottom surface 8s of the first housing recess 81 is configured in multiple stages, and has a first bottom surface 8s1 in contact with the heat-absorbing surface of the Peltier element 5, and a second bottom surface 8s2 in contact with the surface of the heat sink 6. The first bottom surface 8s1 is formed to overlap with the temperature-controlled region P1 and not overlap with the non-temperature-controlled region P2 when viewed from the depth direction.

[0029] The second bottom surface 8s2 is formed at a position further away from the flow path axis X than the first bottom surface 8s1, and is formed outside the first bottom surface 8s1 with a gap when viewed from the depth direction. This second bottom surface 8s2 is formed to overlap with the non-temperature-controlled region P2, but not with the temperature-controlled region P1. Specifically, the second bottom surface 8s2 partially overlaps with the upstream non-temperature-controlled region P2 and partially overlaps with the downstream non-temperature-controlled region P2.

[0030] The second housing recess 82 has a bottom surface 8t parallel to the flow direction of the flow channel P. The second housing recess 82 is formed such that, when viewed from the depth direction, its bottom surface 8t overlaps with the entire temperature-controlled region P1 of the flow channel P and at least partially overlaps with the non-temperature-controlled region P2 on the upstream side. At least the first temperature sensor 1 is installed in the portion of the bottom surface 8t that overlaps with the temperature-controlled region P1. In this embodiment, all of the first temperature sensors 1 to the fourth temperature sensors 4 are housed in the second housing recess 82. Each temperature sensor 1, 2, 3, 4 can be, for example, a linear thermistor, a platinum thermometer, a resistance temperature element, a winding, a thermocouple, etc., but a resistance temperature element is preferred for improving measurement accuracy.

[0031] The bottom surface 8t of the second receiving recess 82 is configured in multiple stages, and when viewed from the depth direction, it has a first bottom surface 8t1 formed to overlap with the temperature-controlled region P1 of the flow path P, and a second bottom surface 8t2 formed outside the first bottom surface 8t1 and to overlap with the upstream non-temperature-controlled region P2. The second bottom surface 8t2 is formed at a position further away from the flow path axis X than the first bottom surface 8t1.

[0032] In this embodiment, the first temperature sensor 1 and the second temperature sensor 2 are installed in contact with the first bottom surface 8t1, and the third temperature sensor 3 and the fourth temperature sensor 4 are installed in contact with the second bottom surface 8t2. The first temperature sensor 1 and the second temperature sensor 2 are connected to a common wiring board C1, and the third temperature sensor 3 and the fourth temperature sensor 4 are connected to a common wiring board C2. The temperature detection signals from each of the temperature sensors 1, 2, 3, and 4 are output to the information processing unit via the wiring boards C1 and C2.

[0033] Further, as shown in FIG. 3, the flow path forming member 8 is formed such that the wall thickness of the flow path P on the second accommodation recess 82 side is smaller than the wall thickness of the flow path P on the first accommodation recess 81 side. Specifically, the wall thickness of the flow path P in the temperature control region P1 is greater on the first accommodation recess 81 side than on the second accommodation recess 82 side. The wall thickness of the flow path P means the distance between the wall surface of the flow path P and the bottom surfaces 8s, 8t of the respective accommodation recesses 81, 82. By forming the first accommodation recess 81 and the second accommodation recess 82 in this manner, in the temperature control region P1, the distance from the flow path P to the first temperature sensor 1 is shorter than the distance from the flow path P to the temperature controller 5.

[0034] Next, the specific arrangement of each of the temperature sensors 1, 2, 3, 4 will be described with reference to FIG. 4 which shows the arrangement of each temperature sensor 1, 2, 3, 4 viewed from the depth direction.

[0035] The first temperature sensor 1 only needs to be arranged at a position where it can detect the temperature of the temperature control region P1 in the flow path P, and is preferably arranged at a position where the temperature change is the greatest due to cooling by the temperature controller 5. In the present embodiment, when viewed from the depth direction, the first temperature sensor 1 is arranged on the flow path axis X near the downstream end in the temperature control region P1 at a position overlapping the heat absorption surface of the temperature controller 5.

[0036] The second temperature sensor 2 only needs to be arranged at a position overlapping the heat absorption surface of the temperature controller 5 when viewed from the depth direction. In the present embodiment, when viewed from the depth direction, the second temperature sensor 2 overlaps the heat absorption surface of the temperature controller 5 and is arranged at the position farthest from the flow path axis X. Further, in the flow direction, the second temperature sensor 2 is desirably arranged near the upstream end in the temperature control region P1.

[0037] When viewed from the depth direction, the third temperature sensor 3 is desirably arranged at a position that is less susceptible to thermal influence from the temperature controller 5 in the non-temperature control region P2 on the upstream side. Specifically, the third temperature sensor 3 is arranged on the flow path axis X in the non-temperature control region P2 at a position overlapping the second bottom surface 8s2 of the first accommodation recess 81.

[0038] The fourth temperature sensor 4 only needs to be arranged at a position where it can detect the ambient temperature, and is arranged at a position distant from the temperature controller 5 and the flow path P.

[0039] Next, a flow rate calculation method by the information processing unit will be briefly described. The information processing unit calculates the flow rate based on the detection temperatures of the four temperature sensors 1, 2, 3, and 4 described above, and is a general-purpose or dedicated computer equipped with a CPU, a memory, an input / output interface, an AD converter, and the like. The information processing unit, by causing the CPU, peripheral devices, and the like to cooperate in accordance with a predetermined program stored in a predetermined area of a memory, functions as at least: a temperature adjustment control unit that controls the temperature adjuster 5; a storage unit that stores temperature-flow rate relationship data indicating a relationship between a temperature difference and a flow rate; and a flow rate calculation unit that calculates a flow rate based on outputs from each temperature sensor and the temperature difference-flow rate relationship data.

[0040] Next, the operation of the information processing unit according to the present embodiment will be briefly described. The detection temperature T of the second temperature sensor 2 ２ and the detection temperature T of the third temperature sensor 3 ３ difference (T ３ - T ２ ) controls the temperature adjuster 5 such that the difference becomes a predetermined value, and the detection temperature T of the second temperature sensor 2 ２ and the detection temperature T of the first temperature sensor 1 １ difference (T １ - T ２ ), the flow rate of the fluid flowing through the flow path P is calculated based on the difference. Further, the information processing unit of the present embodiment uses the detection temperature T of the fourth temperature sensor 4 ４ to correct the temperature control of the temperature adjuster 5 based on a difference between an ambient temperature and a temperature of the fluid. Specifically, the information processing unit uses the detection temperature T of the fourth temperature sensor 4 ４ and the detection temperature T of the third temperature sensor 3 ３ temperature difference (T ４ - T ３ ) is added to the temperature control value of the Peltier element 5, and the temperature of the Peltier element 5 is controlled so as to follow a temperature change of the fluid. A specific calculation method is known and therefore will be omitted here.

[0041] According to the flow meter 100 of the present embodiment configured as described above, the entire wetted portion of the flow path P can be formed of a corrosion-resistant ceramic material. Therefore, even when a corrosive fluid is passed therethrough, contamination due to corrosion does not occur. This makes it possible to measure the flow rate of the fluid without adverse effects in a semiconductor manufacturing process that uses a corrosive fluid. In the present embodiment, the entire wetted portion is formed of a SiC material, so that contamination does not occur even when an acid or base fluid is passed as the corrosive fluid. Further, by forming the flow path forming member 8 into a block shape (mass), a through-hole serving as the flow path P can be formed even while using a ceramic material with low strength.

[0042] Further, since the wall thickness of the flow path P in the temperature control region P1 is made smaller on the second accommodation recess 82 side than on the first accommodation recess 81 side, the wall thickness on the second accommodation recess 82 side where the temperature sensors 1 and 2 are installed is relatively reduced to increase the sensitivity of the sensors. On the other hand, the wall thickness on the first accommodation recess 81 side where the temperature controller 5 is installed can be relatively increased to provide strength.

[0043] Further, the heat capacity of the fluid is increased by increasing the flow path diameter of the non-temperature-controlled region P2 compared to the temperature-controlled region P1, and furthermore, the surface of the heat sink 6 is in contact with the second bottom surface 8s2 of the first accommodation recess 81, so that the thermal influence of the temperature controller 5 in the non-temperature-controlled region P2 can be reduced. Accordingly, the temperature of the non-temperature-controlled region P2, which is the reference temperature, can be accurately detected by the third temperature sensor 3.

[0044] The present invention is not limited to the above embodiment. For example, in the flow meter 100 of the above embodiment, the wall thickness of the flow path P in the temperature control region P1 is smaller on the second accommodation recess 82 side than on the first accommodation recess 81 side, but the present invention is not limited thereto. In other embodiments, the wall thickness of the flow path P in the temperature control region P1 may be the same on the first accommodation recess 81 side and the second accommodation recess 82 side, or may be larger on the second accommodation recess 82 side than on the first accommodation recess 81 side.

[0045] Furthermore, in the above embodiment, all of the first temperature sensors 1 to the fourth temperature sensors 4 were installed in the second housing recess 82, but this is not limited to this. In other embodiments, some of the first temperature sensors 1 to the fourth temperature sensors 4 may be installed in the second housing recess 82, and it is preferable that the second temperature sensor 2 is installed in the first housing recess 81 together with the temperature controller 5. The fourth temperature sensor 4 may also be connected together with the first temperature sensor 1 to the wiring board C1 on the first bottom surface 8t1 side. Furthermore, the flow meter 100 in other embodiments may not be equipped with the fourth temperature sensor 4. The multiple temperature sensors should be arranged so as to be able to detect parameters related to the temperature of at least two different points in the flow path forming member 8 (the temperature of each point, or the temperature difference).

[0046] In the above embodiment, the first accommodating recess 81 and the second accommodating recess 82 were formed on opposite sides of the flow path forming member 8, with the flow path P in between, but the embodiment is not limited to this. In other embodiments, the first accommodating recess 81 and the second accommodating recess 82 may be formed on adjacent sides of the flow path forming member 8.

[0047] Furthermore, although the second temperature sensor 2 was positioned near the upstream end of the temperature-controlled region P1 in the above embodiment, it is not limited to this. It may be positioned near the part that is first affected by the temperature from the fluid, that is, near the upstream part of the temperature-controlled region P1, or it can be positioned at any position that overlaps with the heat-absorbing surface of the temperature controller 5 in the temperature-controlled region P1.

[0048] Furthermore, in the above embodiment, the flow path diameter of the temperature-controlled region P1 was smaller than the flow path diameter of the non-temperature-controlled region P2, but this is not limited to this. In other embodiments, the flow path diameter of the temperature-controlled region P1 and the flow path diameter of the non-temperature-controlled region P2 may be substantially the same.

[0049] Furthermore, although the flow path forming member 8 was in the shape of a rectangular parallelepiped in the above embodiment, it is not limited to this. Any shape is acceptable as long as it is a block-shaped (lump-shaped) object made of ceramic material.

[0050] Furthermore, although the channel forming member 8 in the above embodiment was entirely made of silicon carbide, it is not limited to this. The channel forming member 8 may be made of any corrosion-resistant ceramic material, such as quartz, alumina, zirconia, or silicon nitride.

[0051] Furthermore, in the above embodiment, a non-temperature-controlled area P2 was provided downstream of the temperature-controlled area P1, but this is not limited to that. The non-temperature-controlled area P2 only needs to be provided at least upstream of the temperature-controlled area P1.

[0052] Furthermore, while the flow meter 100 in the above embodiment was configured to cool the temperature-controlled region P1 using a temperature controller 5, it is not limited to this configuration. In other embodiments of the flow meter 100, the temperature controller 5 may be a heater and configured to heat the temperature-controlled region P1.

[0053] In another embodiment, the flow meter 100 may be equipped with multiple self-heating resistors (e.g., electric heating wires) as temperature controllers, detect the temperature difference between these resistors, and calculate the flow rate based on this temperature difference. In this case, the temperature controller can also function as a temperature sensor.

[0054] In another embodiment, the flow meter 100 may be configured with a heater between the upstream temperature sensor and the downstream temperature sensor. The change in temperature distribution caused by the heater may be detected from the temperature difference between the upstream and downstream temperature sensors, and the flow rate may be calculated from this.

[0055] The disclosures herein also include fluid control equipment comprising a flow meter 100, a fluid control valve provided upstream or downstream of the flow meter, and a valve controller that controls the opening degree of the fluid control valve based on the deviation between a set flow rate and the flow rate of the fluid output by the flow meter 100.

[0056] In the above embodiment, the temperature controller 5 was positioned so that its heat-absorbing surface was in contact with the bottom surface 8s of the first housing recess 81, but it is not limited to this. In other embodiments, as shown in Figure 5, a low thermal conductivity member 7, which has a lower thermal conductivity than the flow channel forming member 8, may be interposed between the temperature controller 5 and the bottom surface 8s of the first housing recess 81. The temperature controller 5 may then be positioned so that its heat-absorbing surface is in contact with the surface of the low thermal conductivity member 7. The low thermal conductivity member 7 is preferably made of, for example, stainless steel or copper and is in the form of a plate or sheet. The temperature controller 5 and the low thermal conductivity member 7 may be joined together with, for example, an adhesive such as thermally conductive silicone. Similarly, the low thermal conductivity member 7 and the flow channel forming member 8 may also be joined together with an adhesive such as thermally conductive silicone.

[0057] As shown in Figure 5, the low thermal conductivity member 7 may be U-shaped when viewed from the flow direction and extend to the bottom surface 8t of the second housing recess 82, surrounding the temperature control region P1. In this embodiment, the flow path forming member 8 has a communication passage 83 that connects the bottom surface 8s of the first housing recess 81 and the bottom surface 8t of the second housing recess 82, and the low thermal conductivity member 7 extends from the first housing recess 81 to the second housing recess 82 through the communication passage 83. In this embodiment, the first temperature sensor 1 may be installed on the surface of the low thermal conductivity member 7 on the side of the second housing recess 82, and the second temperature sensor 2 may be installed on the side of the low thermal conductivity member 7 on the side of the first housing recess 81. The position of the first temperature sensor 1 is not limited to this, and for example, it may be installed on the surface 7u of the low thermal conductivity member 7 that faces the communication passage 83.

[0058] Furthermore, as shown in Figure 5, the low thermal conductivity member 7 positioned in the first accommodating recess 81 may have a non-contact region 7a that does not come into contact with the surface of the flow channel forming member 8. It is preferable that a gap is provided between the non-contact region 7a and the surface of the flow channel forming member 8. It is preferable that the temperature controller 5 is positioned so that a portion of it rests on the non-contact region 7a of the low thermal conductivity member 7, and that the second temperature sensor 2 is positioned so that its entirety rests on the non-contact region 7a of the low thermal conductivity member 7.

[0059] In this configuration, the first temperature sensor 1 and the second temperature sensor 2 measure the temperature of the low-thermal-conductivity member 7, and the temperature controller 5 controls the temperature of the low-thermal-conductivity member 7 based on the measurements taken by the first temperature sensor 1 and the second temperature sensor 2.

[0060] The present invention can be modified in various ways, as long as it does not contradict its spirit.

[0061] According to the present invention, a thermal flow meter can be provided that does not cause contamination even when corrosive fluids are flowed through it.

[0062] 100... Flow meter 1... First temperature sensor 2... Second temperature sensor 3... Third temperature sensor 4... Fourth temperature sensor 5... Temperature controller 8... Flow path forming member P... Flow path P1... Temperature controlled area P2... Non-temperature controlled area

Claims

1. A flow meter comprising: a flow channel forming member that forms a flow channel through which a fluid flows; a temperature controller for heating or cooling the fluid flowing through the flow channel; a temperature sensor for detecting temperature parameters at two different points on the flow channel forming member; and an information processing unit for calculating the flow rate of the fluid based on the output signal of the temperature sensor, wherein the flow channel forming member is made of a ceramic material having a housing recess formed therein for installing the temperature controller or the temperature sensor.

2. The flow meter according to claim 1, wherein the flow path comprises a temperature-controlled region that is heated or cooled by the temperature controller and a non-temperature-controlled region set upstream of the temperature-controlled region, and the flow path diameter in the temperature-controlled region is formed to be smaller than the flow path diameter in the non-temperature-controlled region.

3. The flow meter according to claim 1 or 2, wherein the flow path forming member has a first housing recess for which the temperature controller is installed and a second housing recess for which the temperature sensor is installed formed on its surface.

4. The flow meter according to claim 3, wherein the first and second accommodating recesses are formed such that the distance from the flow path to the temperature sensor is shorter than the distance from the flow path to the temperature controller.

5. A flow meter according to claim 2, or claim 3 or 4, which references claim 2, comprising: a cooling element which is a temperature controller; a first temperature sensor for detecting the temperature of the temperature-controlled region; a second temperature sensor for detecting the temperature of the temperature controller; a third temperature sensor for detecting the temperature of the non-temperature-controlled region; and an information processing unit which controls the temperature controller so that the difference between the temperature detected by the second temperature sensor and the temperature detected by the third temperature sensor becomes a predetermined value, and calculates the flow rate flowing through the flow path based on the difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor.

6. The flow meter according to claim 5, referencing claim 3, wherein the first temperature sensor and the third temperature sensor are installed in the second housing recess, and the second temperature sensor is installed in the first housing recess together with the temperature controller.

7. The flow meter according to claim 5, which references claim 3, wherein the temperature controller and the second temperature sensor are installed on the bottom surface of the first housing recess via a low thermal conductivity member having a lower thermal conductivity than the flow path forming member.

8. The flow meter according to claim 6, referencing claim 3, wherein the cooling element is a Peltier element having a heat-absorbing surface on one side and a heat-dissipating surface on the other side, and further comprises a heat sink provided in contact with the heat-dissipating surface of the Peltier element, and the bottom of the first housing recess has a first bottom surface in contact with the heat-absorbing surface of the Peltier element and a second bottom surface in contact with the surface of the heat sink.

9. The flow meter according to any one of claims 1 to 8, wherein the flow path forming member is entirely made of silicon carbide.

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