JP5548355B2 - Thermal gas flow meter - Google Patents

Description

  The present invention relates to a thermal gas flowmeter that measures a fluid to be measured using a heating resistor and a resistance temperature detector.

  2. Description of the Related Art A thermal gas flow meter that measures the flow rate of exhaust gas flowing through an automobile engine system is known that has a flow sensor (sensor element) with a cantilever support structure based on a wound element. (For example, refer to Patent Document 1). In this flow sensor, three resistors are wound around an alumina pipe serving as a holder in the order of a first heating resistor, a resistance temperature detector, and a second heating resistor from the tip of the element. Six grooves along the longitudinal direction are formed on the outer periphery of the alumina pipe in the circumferential direction, and a support is inserted in each groove. Two supports are assigned to each of the three resistors. Of the two supports, one support is connected to the winding start portion of each resistor by welding or the like, and the other support is connected to the winding end portion of each resistor by welding or the like. The support is made of an electric conductor and serves as a lead conductor for each resistor.

  The flow rate measurement circuit connected to the flow rate sensor has a three-circuit configuration in which the temperature control circuit of the first heating resistor, the temperature control circuit of the second heating resistor, and the temperature measurement circuit of the resistance thermometer are independent, The flow rate is detected by the current flowing through the heating resistor.

JP 2008-32501 A (paragraph 0042, FIG. 19, FIG. 21)

  In the technique disclosed in Patent Document 1, each winding of the first heating resistor, the resistance temperature detector, and the second heating resistor is independent, and one winding is provided at each winding start and end of winding. A lead conductor is provided. Therefore, it has been necessary to provide as many lead conductors as the number of resistors. The lead conductor is related to the heat capacity of the flow sensor. When the number of lead conductors increases, the amount of heat released from the lead conductor increases, and the heat capacity tends to increase.

  An object of the present invention is to provide a thermal gas flow meter capable of reducing power consumption by reducing the heat capacity of a flow sensor having a plurality of resistors including a heating resistor.

To achieve the above object, a thermal gas flowmeter of the present invention, with a flow rate sensor including a resistor antibody constructed by winding a continuous conductor wire to said holding member and the holding member thermal gas flow in total, as before Symbol resistor, on the holding member, the first heating resistor in one direction, constitutes in the order of RTD and the second heating resistor, and the winding start point of said conductor line, said first 1 Constructed by connecting a lead conductor to a dividing point between the heating resistor and the temperature measuring resistor, a dividing point between the temperature measuring resistor and the second heating resistor, and a winding end point It is.

  The thermal gas flowmeter of the present invention has a winding that constitutes a plurality of resistors, winding a continuous conductor wire, and electrically connecting a lead conductor to a dividing point of a winding portion of an adjacent resistor. By configuring, the tact time can be shortened.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a flow sensor 10 of a thermal gas flow meter of the present invention, FIG. 1 (A) is a winding structure of a resistor, and FIG. 1 (B) is a diagram showing electrical connection of the resistor.

  In FIG. 1, the flow rate sensor 10 includes windings of a first heating resistor 100, a resistance temperature detector 200, and a second heating resistor 300 arranged on an alumina pipe 11, and the winding starts from a winding start point 12 to a winding end point. It is continuous to 15. Such a winding may use a wire having the same material and wire diameter from the winding start point 12 to the winding end point 15, or the first heating resistor 100, the resistance temperature detector 200, and the second heating resistor. What changed material and a wire diameter for every body 300 may be finished into one continuous wire. However, as a material, a platinum wire is generally used as will be described later.

  At this time, the resistors are arranged in the order of the first heating resistor 100, the resistance temperature detector 200, and the second heating resistor 300 from the front end side of the flow sensor 10.

  One end of the lead conductor 16 is connected to the winding start point 12 of the first heating resistor 100, and the other end of the lead conductor 16 is a terminal 20. One end of the lead conductor 17 is connected to the dividing point 13 between the first heating resistor 100 and the resistance temperature detector 200, and the other end is a terminal 21. One end of the lead conductor 18 is connected to the dividing point 14 between the resistance temperature detector 200 and the second heating resistor 300, and the other end is a terminal 22. One end of the lead conductor 19 is connected to the winding end point 15 of the second heating resistor, and the other end is a terminal 23.

  The terminals 20 to 23 are connected to a control circuit and operate as a thermal gas flow meter having the flow sensor 10.

  The winding mounting body (holding body) for winding the resistors 100, 200, 300 uses the alumina pipe 11 that is an insulator, and the resistors 100, 200, 300 and the lead conductors 16 to 18 are heat resistant. It is fixed to the alumina pipe 11 by a high glass coating.

  The lead conductors 16 to 19 are connected to the control circuit easily by being drawn out in one direction and supported on one side so as to pass through the inside or the surface of the resistors 100 to 300. You can do it.

  FIG. 2 is a diagram showing a manufacturing process of the flow sensor 10 shown in FIG.

  In FIG. 2, in the first step S <b> 1, an operation of connecting the winding start point 12 of the first heating resistor 100 to the lead conductor 16 is performed.

  In the next step S2, the first heating resistor 100, the resistance temperature detector 200, and the second heating resistor 300 are wound around the alumina pipe 11 by a continuous winding operation.

  In step S3, an operation of connecting to the lead conductor 19 is performed at the end point of the winding work completed in step S2, that is, at the winding end point 15 of the second heating resistor 300.

  In step S4, after the connection operation in step S3, an operation for cutting the winding in the vicinity of the connection portion between the lead conductor 19 and the second heating resistor 300 is performed.

  In step S5, the lead conductors 17 and 18 are respectively connected to the dividing point 13 of the first heating resistor 100 and the resistance temperature detector 200, and in step S6 to the dividing point 14 of the resistance temperature detector 200 and the second heating resistor 300, respectively. After connecting, the manufacturing process of the flow sensor 10 is completed.

  In the flow sensor manufacturing process of FIG. 2, the winding work can be performed continuously with the first heating resistor 100, the resistance temperature detector 200, and the second heating resistor 300. It is possible to finish the manufacturing process after four times of joining work with the lead conductors 16 to 19, and the tact time can be shortened.

  In FIG. 2, the winding start of the winding is the first heating resistor 100, but the winding start of the winding is the second heating resistor 300, and the temperature measuring resistor 200 and the first heating resistor 100 are wound in this order. Even if the work is performed, the tact time can be shortened as in the case where the winding start of the first heating resistor 100 is used.

  The winding mounting body around which the first heating resistor 100, the second heating resistor 300, and the resistance temperature detector 200 are wound is described as an alumina pipe. However, other materials can be used as long as they are electrically insulating. , The effect is equivalent.

  The winding material of the first heating resistor 100, the second heating resistor 300, and the temperature measuring resistor 200 is generally a platinum wire, but is a material having a function as a heating resistor. If there is, it is not limited to platinum wire.

  Next, a control method of the flow sensor of FIG. 1 will be described.

  As shown in the winding structure of FIG. 1, a resistance temperature detector 200 is arranged between the first heating resistor 100 and the second heating resistor 300, and depending on the temperature detected by the resistance temperature detector 200, The temperature of the second heating resistor 300 is controlled to separate the amount of heat generated by the first heating resistor 100 from the heat transfer to the lead conductors 16 and 17. That is, by arbitrarily controlling the heat transfer amount of the first heating resistor 100 and the second heating resistor 300 and making the gas flow rate detection unrelated to the contamination of the lead conductors 16 and 17, the flow rate detection accuracy can be improved. It is possible.

The temperature relationship between the first heating resistor 100 and the second heating resistor 300 is as follows:
It is desirable that the temperature of the first heating resistor 100 <the temperature of the second heating resistor 300.

  FIG. 3 is a diagram showing a state in which the flow rate sensor 10 is arranged in the gas flow path 400 in order to measure the flow rate of the gas 410 to be measured flowing through the gas flow path 400. The flow rate sensor 10 is connected to a control circuit 500 disposed outside the gas flow path 400 through lead conductors 16 to 19.

  For the three windings of the first heating resistor 100, the second heating resistor 300, and the resistance temperature detector 200, there are four lead conductors 16-19, and the control circuit 500 is provided on the lead conductors 16-19. It is necessary to perform temperature control and temperature measurement of the first heating resistor 100 and the second heating resistor 300 and temperature measurement of the temperature measuring resistor 200 by the four terminals 20 to 23 that are provided.

  FIG. 4 is a diagram showing circuit connections of the control circuit 500.

  The temperature setting circuit 510 has a voltage drop 511 of the first heating resistor 100, a voltage drop 512 of the first heating resistor 100 and the temperature measuring resistor 200, with reference to the winding start side of the first heating resistor 100. The temperature is calculated by taking in the voltage drop 513 among the first heating resistor 100, the resistance temperature detector 200, and the second heating resistor 300, and the heating control circuit 520 of the first heating resistor 100 and the second heating resistor. Temperature set values 514 and 515 are output to the 300 heating control circuit 530.

  The heating control circuit 520 energizes the first heating resistor 100 with the heating current 521, the heating control circuit 530 energizes the second heating resistor 300 with the heating current 531, and sets the first heating resistor 100 to the temperature setting value 514. (2) The heating resistor 300 is controlled to have the temperature set value 515.

  The temperature measuring resistor 200 is supplied with a temperature measuring current 541 from the constant current circuit 540 to a series circuit in which the first heating resistor 100, the temperature measuring resistor 200, and the second heating resistor 300 are connected in series. Energize.

  The temperature measuring current 541 interrupts energization of the heating currents 521 and 531 of the first heating resistor 100 and the second heating resistor 300, and energizes a constant current from the constant current circuit 540 that is not influenced by the resistance value of the resistor.

  Accordingly, the temperature of the first heating resistor 100 is the value of the voltage drop 511, the temperature of the resistance temperature detector 200 is the value of the voltage difference between the voltage drops 512 and 511 (512-511), and the temperature of the second heating resistor 300 is The temperature can be calculated from the value of the voltage difference (513-512) between the voltage drops 513 and 512.

  FIG. 5 shows the temperature change of the first heating resistor 100 and the second heating resistor 300 with respect to the flow rate of the measured gas 410, and FIG. 6 shows the flow of the control method.

  FIG. 5 shows an example in which the temperature of the heating resistor is controlled so that “the set temperature T1 of the first heating resistor 100 <the set temperature T3 of the second heating resistor 300”. A temperature change of the second heating resistor 300 in the case where the set temperature T1 is controlled almost equally according to the flow rate of 410 is shown.

  That is, at the high flow rate, the temperature drop of the lead conductors 16 and 17 becomes large and the contamination cannot evaporate. Therefore, the temperature T3 of the second heating resistor is increased, and the second heat generation at the low flow rate is higher than that at the high flow rate. The temperature T3 of the resistor is controlled to be low.

  As a result, the amount of heat generated by the first heating resistor 100 and the heat transfer to the lead conductor can be separated, and the detection of the gas flow rate can be made independent of the contamination of the lead conductor.

  FIG. 6 is a diagram illustrating an example of a specific control flow of temperature control of the second heating resistor 300.

  First, in step S10, the voltage drops 511, 512, and 513 shown in FIG. 4 are read. In step S11, the resistance value of the first heating resistor 100 and the resistance value of the resistance temperature detector 200 are calculated from the voltage drop. The temperature T1 of the first heating resistor 100 and the temperature T2 of the resistance temperature detector 200 are calculated using the temperature coefficient of each resistor.

  Next, in step S12, the temperature determination “T1 ≦ T2” of the calculated temperatures T1 and T2 is executed. If NO, the heating current 531 of the second heating resistor 300 is increased in step S13, and step S12 is performed. Steps S10 to S13 are repeatedly executed until the temperature determination “T1 ≦ T2” becomes YES.

  As a result, the temperature T3 of the second heating resistor 300 rises, and the temperature T2 of the resistance temperature detector 200 rises due to the influence.

  If the temperature determination “T1 ≦ T2” in step S12 is YES, a temperature determination “T2 <T2max” of the temperature T2 of the resistance thermometer 200 and the preset upper limit value T2max is executed in step S14. In step S15, the heating current 531 of the second heating resistor 300 is decreased, and steps S10 to S15 are repeatedly executed until the temperature determination “T2 <T2max” in step S14 becomes YES.

  The temperature control of the second heating resistor 300 in FIG. 6 is always controlled to “T1 ≦ T2 <T2max” by repeatedly executing at a constant cycle, so that the temperature gradient of the first heating resistor 100 part is set to a predetermined value. Can be within the range.

  As a control method, in addition to FIG. 6, the lower limit target temperature is set to the temperature T2 of the resistance temperature detector 200, and the relationship of “lower limit target temperature <temperature resistance temperature T2 ≦ first heating resistor temperature T1” is established. It is possible to hold it.

  According to one embodiment of the present invention, the winding cutting process is performed once by continuously winding the windings of the first heating resistor 100, the resistance temperature detector 200, and the second heating resistor 300. In addition, by connecting the lead conductors 16 to 19 to the four winding start points 12, the winding end point 15, and the winding dividing points 13 and 14, the tact time of the manufacturing process of the flow sensor 10 can be shortened. effective.

  In addition, since four of the lead conductors 16 to 19 may be connected to the control circuit 500, the number of connection terminals can be reduced.

  Furthermore, in the temperature measurement of the first heating resistor 100, the temperature measuring resistor 200, and the second heating resistor 300, a constant current circuit for measurement can be shared, and the circuit can be simplified.

  FIG. 7 is a view showing another embodiment of the flow sensor 10, (A) is a view showing a cross section of the alumina pipe 600, (B) is a side view of the flow sensor 10, and (C) and (D) are first views. 1 is a connection diagram of a heating resistor 100, a resistance temperature detector 200, a second heating resistor 300, and a lead conductor, and the same parts as those in FIG.

  As shown in FIG. 7 (A), groove-like recesses 610 to 640 for inserting lead conductors are arranged on the outer peripheral surface of the alumina pipe 600 as a winding mounting body in the circumferential direction so as to follow the longitudinal direction of the alumina pipe 600. A plurality (four) are formed. In each of the recesses 610, 620, 630, and 640, one lead conductor 16, 17, 18, and 19 is inserted. FIG. 7B shows a state in which the lead conductors 18 and 19 are inserted into the recesses 630 and 640.

  As shown in FIG. 7C, the end portions of the lead conductors 18 and 19 are L-shaped from the bottom side of the groove-like recesses 610 to 640 toward the resistor crossing over the groove-like recesses 610 to 640. The end portions 18a and 19a that are in contact with the resistor are formed, and the end portions of the end portions 18a and 19a are connected to the resistor at the dividing point 14 and the winding end point 15, respectively. It has become.

  When the lead conductors 18 and 19 are inserted into the recesses 630 and 640 of the alumina pipe 600, the end portions 18a and 19a of the lead conductor are located below the resistor (the bottom side of the recesses 630 and 640), and the connection is easy. It can be done.

  FIG. 7D shows that the end portions 18b and 19b along the groove direction of the recesses 630 and 640 are further bent on the lead conductors 18 and 19 at the tips of the L-shaped ends 18a and 19a. The example which formed is shown.

  The end portions 18b and 19b have a larger area of the connecting portion to the resistor than the end portions 18a and 19a shown in FIG. That is, the tolerance can be increased in the connection between the resistor and the end portion of the lead conductor as compared with FIG.

  In the second embodiment, since the lead conductors 18 and 19 do not protrude from the alumina pipe 600, the first heating resistor 100, the resistance temperature detector 200, and the first heating resistor 100 can be tightly wound around the alumina pipe 600. There is an effect that stable fixing can be achieved, and an amount of use of the winding material can be reduced.

  Further, since the lead conductors 18 and 19 are inserted into the recesses 610 and 620, stable fixing can be achieved. When the flow sensor 10 is coated with glass, the recesses 610 and 620 are also filled with a coating material, whereby the lead conductors The strengths of 18 and 19 can be reinforced, and there is an effect of reinforcing the strength of the entire flow sensor 10 having a cantilever structure.

  The lead conductors 16 and 17 are inserted into the recesses 610 and 620, respectively, and the same connection structure as that shown in FIG. 7C or 7D is adopted. The four lead conductors 16 to 19 are drawn in one direction, and the flow sensor 10 is supported in a cantilever state.

  FIG. 8 is a diagram showing another embodiment of the flow sensor 10. FIG. 9 is a diagram illustrating a current path that is energized from the control circuit of the flow sensor 10 of FIG. 8 and 9, the same parts as those in FIGS. 1 and 4 are denoted by the same reference numerals.

  In this embodiment, as shown in FIG. 8, the lead conductors 16 and 24 are connected to the winding start point 12 of the first heating resistor 100 to provide the terminals 20 and 26, and the winding of the second heating resistor 300 is finished. The lead conductors 19 and 25 are connected to the point 15 and the terminals 23 and 27 are provided.

  In FIG. 9, as in the first embodiment, the energizing current is the heating current 521 from the terminal 20 to the terminal 21 in the first heating resistor 100, and the heating current 531 from the terminal 22 to the terminal 23 in the second heating resistor 300. A temperature measuring current 541 is supplied to the temperature measuring resistor 200 from the terminal 20 to the terminal 23.

  The temperature of each resistor is calculated from the voltage drop by the terminal 26 and the terminal 27 through which no current is passed. That is, the voltage drop 516 is measured for the first heating resistor 100, the voltage drop 517 is measured for the second heating resistor 300, and the voltage drop 518 is measured for the resistance temperature detector 200, and the temperature of each resistor is calculated.

  In FIG. 8, the lead conductor 24 is connected to the first heating resistor 100 at the winding start point 12 like the lead conductor 16, and the lead conductor 25 is connected to the second heating resistor 300 at the winding end point 15 like the lead conductor 19. However, the lead conductor 24 may be shifted from the winding start point 12 that is the connection point between the lead conductor 16 and the first heating resistor 100 and connected to the first heating resistor 100, or the lead conductor. 25 may be shifted from the winding end point 15, which is a connection point between the lead conductor 19 and the second heating resistor 300, and connected to the second heating resistor 300.

  Further, when applied to the winding attachment shown in FIG. 7, the lead conductors 16 and 24 and the lead conductors 19 and 25 are inserted into the same recess so that the respective lead conductors are electrically insulated. .

  Further, the recesses of the winding mounting body shown in FIG. 7 can be individually formed for the lead conductors 24 and 25 to provide six recesses to be electrically insulated.

  In the third embodiment, the voltage drops 516, 517, and 518 are measured by using the lead wires and the lead conductors 24 and 25 connected to the terminals 26 and 27 that are not energized with current. Since the voltage drop and noise components of the lead wire and the lead conductors 16 and 19 connected to 23 are eliminated, the voltage drop at the time of temperature measurement is stabilized, and the temperature calculation accuracy can be improved.

  FIG. 10 is a diagram illustrating another control circuit 500 of the flow sensor 10.

  The circuit 700 inputs the potential of the intermediate point 709 and the potential of 710 of the bridge circuit constituted by the first heating resistor 100, the resistance temperature detector 200, the resistor 701, and the resistor 702 to the + terminal and the − terminal of the operational amplifier 703, respectively. In addition, the transistor 704 connected to the power source 800 is controlled by the output of the operational amplifier 703 to control the temperature of the first heating resistor 100.

  When the first heating resistor 100 is cooled by the gas flow rate, the potential at the positive terminal of the operational amplifier 703 increases, the supply current from the transistor 703 increases, and the temperature of the first heating resistor 100 is increased. The potentials of the + terminal and the − terminal of are kept constant.

  Since the potential at the + terminal of the operational amplifier 703 has a certain relationship with the gas flow rate, the gas flow rate can be measured by measuring the potential at the terminal 705.

  On the other hand, the circuit 800 inputs the potential of the intermediate point 813 and the potential of 814 of the bridge circuit constituted by the second heating resistor 300, the temperature compensation resistor 801, the resistor 802, and the resistor 803 to the + and − terminals of the operational amplifier 804, respectively. In addition, the transistor 805 connected to the power source 800 is controlled by the output of the operational amplifier 804 to control the temperature of the second heating resistor 300.

  The second heating resistor 300 is constantly controlled to a predetermined temperature that is temperature compensated by the temperature compensation resistor 801.

  As described with reference to FIG. 5, the temperature of the second heating resistor 300 is controlled to be higher than that of the first heating resistor so that the heat transfer to the lead conductor is cut off.

  Since the three resistors 100, 200, and 300 of the flow sensor 10 are connected in series, the circuit 700 and the circuit 800 cannot be operated simultaneously.

  Therefore, in the control of the first heating resistor 100, the switch elements 806 and 807 of the circuit 800 are turned off, and in the control of the second heating resistor 300, the switch elements 706 and 707 of the circuit 700 are turned off and switched. Yes.

  Switching between the switch elements 806, 807 and 706, 707 is performed in a time-sharing manner at fixed time intervals, and a value that optimizes flow rate measurement and temperature control is selected for this time interval.

  FIG. 11 is a diagram showing still another control circuit 500 of the flow sensor 10, and the same parts as those in FIG. 10 are denoted by the same reference numerals.

  The difference from FIG. 10 is that the control of the first heating resistor 100 by the circuit 700 is controlled to reach a predetermined temperature by the temperature compensation resistor 708, and the control of the second heating resistor 300 by the circuit 800 is a constant current source. A constant current is applied to the resistance temperature detector 200 in 808 to measure the voltage drop 809, the temperature is calculated by the arithmetic circuit 810, and the resistance value of the resistor 811 is changed based on the result, so that the predetermined temperature is reached. Is controlling.

  In the control of the first heating resistor 100, the switch elements 806, 807, and 812 of the circuit 800 are turned off, and in the control of the second heating resistor 300, the switch elements 706 and 707 of the circuit 700 are turned off and switched. I have to.

  In FIGS. 10 and 11, when heating the heating resistor, a direct current is applied by the emitter follower operation of the transistors 704 and 805, but there is a problem that the power consumption of the transistor increases.

  Therefore, the control circuit can be digitized using an A / D converter or a microcomputer to control the temperature of the heating resistor in the PWM method using the transistors 704 and 805 in the switching operation.

  In the fourth embodiment, the temperature control, temperature measurement, and gas flow rate of the resistor can be controlled in a time-sharing manner in the thermal gas flow meter using the four-terminal flow sensor 10.

  Further, the resistance thermometer 200 is omitted, and the first heating resistor 100 and the second heating resistor 300 are constituted by two resistors, and the temperature of each resistor is individually controlled so that the first heating resistor Even in the control system that suppresses the temperature drop of the lead conductor joined to the body 100, a flow sensor having a configuration in which the windings of the two resistors are continuously wound can be provided.

  Moreover, it can also be applied to a flow sensor having a configuration in which a heating resistor or a resistance temperature detector is divided and three or more windings are wound, and it is possible to obtain the same effect.

  In the technique disclosed in Patent Document 1, each winding of the first heating resistor, the resistance temperature detector, and the second heating resistor is independent, and one winding is provided at each winding start and end of winding. Since the support was provided, it was necessary to join a total of six supports. For this reason, in order to manufacture one resistor, the four steps of the joining process of the part which starts winding to the alumina pipe and the support, the winding process, the joining process of the winding end part and the support, and the cutting process of the winding are performed. Was necessary. These four steps need to be performed three times with three resistors, and the tact time tends to increase and the cost tends to increase. Moreover, six support bodies are required, and the amount of heat radiation at the support section increases, resulting in an increase in heat capacity. For this reason, the power supply tends to increase. On the other hand, according to each embodiment of the present invention, the number of lead conductors (supports) from the resistor can be reduced, and the tact time can be shortened.

  In the embodiment of the present invention, the measurement of the gas flow rate in the exhaust gas atmosphere of the automobile is described. However, the measurement can be applied to the measurement of the air flow rate and other fluid flow rates.

1 is a structural diagram showing a first embodiment of a flow sensor of a gas flow meter of the present invention. The manufacturing process figure of the flow sensor of this invention. The flow measurement configuration figure of the gas flowmeter of the present invention. The control circuit block diagram of the gas flowmeter of this invention. Explanatory drawing of temperature control of the gas flowmeter of this invention. The temperature control flowchart of the gas flowmeter of this invention. FIG. 3 is a structural diagram showing Example 2 of a flow sensor of a gas flow meter of the present invention. FIG. 6 is a structural diagram showing Example 3 of a flow sensor of a gas flow meter of the present invention. Explanatory drawing of the temperature detection by Example 3 of this invention. The control circuit block diagram by Example 4 of this invention. The other control circuit block diagram by Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flow sensor 11 Alumina pipe 12-15 Joint part 16-19, 24, 25 Lead conductor 18a, 19a, 18b, 19b End part 20-23, 26, 27 of lead conductor 18, 19 Flow sensor terminal 100 1st heating resistance Body 200 RTD 300 Second heating resistor 500 Control circuit 510 Temperature setting circuit 520, 530 Heating control circuit 540 Constant current circuit 610-640 Concave part of alumina pipe 600

Claims (9)

The thermal gas flowmeter having a flow rate sensor including a resistor antibody constructed by winding a continuous conductor wire to said holding member and the holding member,
As before Symbol resistor, on the holding member, the first heating resistor in one direction, constitutes in the order of RTD and the second heating resistor,
The winding start point of the conductor wire, the dividing point of the first heating resistor and the resistance temperature detector, the dividing point of the resistance temperature detector and the second heating resistor, and the winding end point A thermal gas flowmeter characterized by connecting a lead conductor. The thermal gas flow meter according to claim 1,
The thermal gas flowmeter, wherein the lead conductor is drawn in one direction in an extension direction of the arrangement of the first heating resistor, the temperature measuring resistor, and the second heating resistor. The thermal gas flow meter according to claim 1,
The thermal gas flowmeter, wherein the first heating resistor, the temperature measuring resistor, and the second heating resistor are connected in series, and a temperature measuring current is passed through the series connected resistors. The thermal gas flow meter according to claim 3,
The thermal gas flowmeter is characterized in that the temperature measuring current is energized by a single constant current source. The thermal gas flow meter according to claim 1 ,
Before Symbol first heating resistor, thermal gas flowmeter and performing at different times from the energization of the heating current of electrical communication with the heating resistor temperature measuring current of RTD and the second heating resistor . The thermal gas flow meter according to claim 1,
The holding body has an arrangement direction of the first heating resistor, the temperature measuring resistor, and the second heating resistor on a surface around which the first heating resistor, the temperature measuring resistor, and the second heating resistor are wound. A thermal gas flowmeter is characterized in that a recess extending along the line is formed, and the lead conductor is disposed in the recess. The thermal gas flow meter according to claim 6,
The thermal gas flowmeter, wherein the lead conductor disposed in the recess is bent toward the conductor wire at an end connected to the conductor wire. The thermal gas flow meter according to claim 1,
There are two lead conductors connected to the winding start point and the winding end point of the conductor wire, respectively. The thermal gas flow meter according to claim 8,
A temperature measuring current is passed through one of the two lead conductors connected to the winding start point and one of the two lead conductors connected to the winding end point. A temperature measuring current is not passed through the other lead conductor of the two lead conductors connected to the start point and the other lead conductor of the two lead conductors connected to the winding end point. The thermal gas flowmeter according to claim 9.

Images