JPH1038653A - Flow velocity detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the presence/absence of a fault in a flow velocity sensor detectable during flow velocity measurement by stopping the heating of a heater element and checking the output value of a sensor detecting circuit. SOLUTION: A flow velocity sensor 20 detects the heat transfer caused by a fluid moving on a heater element 4. When the inspection of the sensor 20 is requested, a sensor checking mechanism 50 stops the heating of the element 4 by turning on a switch. When the element 4 is cooled to the ambient temperature in the non-heating state of the element 4 after several milliseconds, the mechanism 50 reads the output value of a temperature amplifier circuit 40 and returns the element 4 to the original state by turning off the switch. When the element 4 is not heated, the output value of the circuit 40 indicates 0V, because no current difference occurs between temperature measuring resistance elements 5 and 6 irrespective of the presence/absence of the flow of the fluid. Therefore, the output of the sensor 20 can be discriminated as abnormal when the output value of the circuit 40 does not indicate 0V and normal when the output value indicates 0V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the use of a flow rate sensor comprising a heater element and a temperature-measuring resistance element for changing a resistance value by heat transfer caused by a fluid moving on the heater element. The present invention relates to a flow velocity detecting device for detecting a flow velocity, and more particularly to a flow velocity detecting device which can detect whether or not a flow velocity sensor and its driving circuit are out of order during measurement of a flow velocity.

[0002] A flow rate sensor for measuring the flow rate of a fluid requires extremely high reliability when used in a combustion control system or the like. From now on, while measuring the flow velocity,
The construction of a configuration capable of detecting whether or not the flow velocity sensor has failed is called for.

[0003]

2. Description of the Related Art The present applicant discloses in Japanese Patent Application No. 3-106528 a heater element and a temperature-measuring resistance element whose resistance value is changed by heat transfer caused by a fluid moving on the heater element. As a flow rate sensor to be performed, a flow rate sensor having a micro-machined diaphragm that realizes high-accuracy and high-speed response has been disclosed.

FIG. 15A is a perspective view of an example of a flow rate sensor having the microfabricated diaphragm, and FIG.
FIG. In this drawing, reference numeral 1 denotes a semiconductor substrate made of, for example, single-crystal silicon and having a thickness of about 1.7 mm square and a thickness of about 0.7 mm. Is formed, and the upper portion of the gap 2 is spatially isolated from the semiconductor substrate 1, and as a result, a diaphragm 3 thermally insulated from the semiconductor substrate 1 is formed. A thin-film heater element 4 and a pair of thin-film temperature measuring resistance elements 5 and 6 sandwiching the heater element 4 are formed on the surface of the diaphragm portion 3. Is formed with a thin-film ambient temperature measuring resistance element 7 on the surface thereof.

The diaphragm 3 is made of an insulating material such as silicon nitride, silicon oxide, polyimide or the like and is formed to a thickness of, for example, about 1 μm. The loss due to heat conduction from the end is extremely small. Insulation has been achieved. The heater element 4, the resistance temperature measurement elements 5, 6 and the ambient temperature resistance resistance element 7 are made of a thin film of platinum, nickel, iron / nickel alloy, thermistor material, etc. The temperature-measuring resistance element 7 has a characteristic that a resistance value changes according to a temperature change.

FIG. 16 shows a temperature distribution of the flow rate sensor having the microfabricated diaphragm. The control circuit that controls the heating process of the heater element 4 heats the heater element 4 so that the temperature of the heater element 4 becomes a temperature having a certain temperature difference th from the ambient temperature detected by the ambient temperature measuring resistance element 7. At this time, if the fluid does not flow, the temperatures t1, t2 of the temperature measuring resistance elements 5, 6 become substantially equal as shown in this figure.

For example, when the fluid moves from the temperature measuring resistance element 5 to the direction in which the temperature measuring resistance element 6 is disposed, the temperature measuring resistance element 5 on the upstream side is cooled to Δt1
Only the temperature drops, and the temperature measuring resistance element 6 on the downstream side
Heated by the heat transfer, the temperature rises by Δt2. As a result, a temperature difference occurs between the temperature measuring resistance element 5 and the temperature measuring resistance element 6, and in response thereto, a Wheatstone bridge circuit or the like incorporating the temperature measuring resistance elements 5, 6 is generated due to the temperature difference. By converting the resistance change into a voltage, a voltage corresponding to the flow velocity of the fluid is output.

[0008] The flow rate sensor having the micro-fabricated diaphragm configured as described above detects the flow rate using the very thin diaphragm section 3 which is thermally insulated, and therefore has high sensitivity, high response speed, and low power consumption. It has the characteristic that the flow velocity can be measured with electric power.

[0009]

In the prior art, when such a flow rate sensor having a microfabricated diaphragm is used, it does not have a function of detecting a failure.

However, since the diaphragm portion 3 of the flow sensor having the microfabricated diaphragm has a very small thickness, the thermal characteristics change due to the adhesion of dust and the like, and the output characteristics are different from those at the beginning. Or damage due to improper handling or exposure to excessive wind speeds. Further, the heater element 4, the temperature measuring resistance elements 5, 6 and the ambient temperature
Is made of a thin film having a fine pattern, and may be burned out when an excessive current or an excessive voltage is applied. In addition, since the electrode portion is exposed for electrical wiring, a short circuit occurs between the electrodes due to the adhesion and deposition of conductive foreign matter, and the heater element 4, the temperature measuring resistance elements 5, 6 and the There is a risk that the temperature measurement resistance element 7 will not function.

[0011] From now on, in order to put a flow sensor having a microfabricated diaphragm configuration into practical use, it is necessary to construct a configuration capable of detecting whether the flow sensor is normal or not.

In particular, when used in industrial combustion control applications requiring high safety, the flow rate sensor must be provided with a diagnosis function to prevent erroneous combustion control due to erroneous detection signals. Becomes indispensable. However, in the prior art, since there is no such technical means, the normal / abnormal diagnosis of the flow rate sensor cannot be performed, and this has a disadvantage that the reliability of the entire combustion control is reduced. .

The present invention has been made in view of such circumstances, and includes a heater element and a temperature measuring resistance element that changes a resistance value by heat transfer caused by a fluid moving on the heater element. When adopting a configuration that detects the flow velocity of a fluid using a flow velocity sensor, a new flow velocity that can detect whether the flow velocity sensor or its drive circuit has failed during measurement of the flow velocity It is intended to provide a detection device.

[0014]

In order to achieve this object, a flow rate detecting device according to the present invention has a heater element as a circuit element, a heater heating circuit for heating the heater element, and a resistance element corresponding to the temperature. A temperature detecting resistance element for changing the value as a circuit element, and a sensor detecting circuit for detecting heat transfer caused by a fluid moving on the heater element. Switch means for controlling the supply / interruption of the drive signal to be supplied, control means for interrupting the drive signal supplied to the heater heating circuit by controlling the switch means, and response to the control operation of the control means. A configuration is provided that includes a determination unit that determines whether the device is normal or abnormal based on the output value of the sensor detection circuit that is output.

[0015] In the flow velocity detecting device of the present invention configured as described above, during normal operation, the control means controls the switch means to supply a drive signal to the heater heating circuit to heat the heater element. In response, the sensor detection circuit outputs an output signal corresponding to the flow rate of the fluid.

In the inspection operation, the control means stops the heating of the heater element by controlling the switch means to cut off the supply of the drive signal to the heater heating circuit,
In response, the sensor detection circuit outputs an output signal that is output when no fluid is flowing.

In response to the control operation of the control means, the determination means checks whether or not the output value of the sensor detection circuit output at the time of the inspection operation indicates a value when no fluid is flowing. Then, it is determined whether or not the device is normal.

As described above, according to the flow rate detecting device of the present invention, it is possible to detect whether a failure has occurred in the heater element or the temperature measuring resistance element used for the flow rate measurement during the measurement of the flow rate. In addition, since it is possible to detect whether or not a failure has occurred in the heater heating circuit or the sensor detection circuit, it can be applied to a place requiring high reliability such as a combustion control system.

In this configuration, when power is supplied, the control means controls the switch means to the cut-off mode in accordance with a sequence operation by using the power as a trigger, and is in a state of normal operation. In some cases, processing is performed to set the supply mode. In this case, it is preferable to employ a configuration in which a determination unit is provided on a device that receives an output signal of the flow velocity detection device.

This configuration has the advantage that it is not necessary to provide a control line for controlling the switch means between the flow velocity detecting device and the device for receiving the output signal of the flow velocity detecting device. There is an advantage that the flow velocity detecting device of the present invention can be directly attached in place of the flow velocity detecting device provided.

Further, in the flow velocity detecting device of the present invention, a heater element is provided as a circuit element, and a heater heating circuit for heating the heater element and a temperature measuring resistance element for changing a resistance value according to the temperature are provided as circuit elements. Have
And a sensor detection circuit for detecting heat transfer caused by a fluid moving on the heater element. The circuit configuration of the heater heating circuit is provided in the heater heating circuit and conducts and non-conducts. 1 to change
One or more switch means, a control means for changing the heat generation temperature of the heater element by controlling the switch means, and an output value of a sensor detection circuit output in response to a control operation of the control means, And a determining means for determining whether the device is normal or abnormal.

In the flow velocity detecting device of the present invention configured as described above, during normal operation, the control means controls the switch means to make the circuit configuration of the heater heating circuit normal, thereby allowing the heater element to operate normally. Upon heating to the temperature, the sensor detection circuit outputs an output signal corresponding to the flow velocity of the fluid.

During the inspection operation, the control means controls the switch means to change the circuit configuration of the heater heating circuit from the normal one, thereby heating the heater element to a temperature different from the normal one. In response, the sensor detection circuit outputs an output signal having an output value specified at the normal temperature and an output value specified from the normal temperature and the changed temperature.

In response to the control operation of the control means, the judging means determines whether or not the apparatus is based on the output value of the sensor detection circuit output before the inspection operation and the output value of the sensor detection circuit output during the inspection operation. It is determined whether or not it is normal.

As described above, according to the flow velocity detecting device of the present invention, it is possible to detect whether or not a failure has occurred in the heater element or the temperature measuring resistance element used for the flow velocity measurement during the measurement of the flow velocity. In addition, since it is possible to detect whether or not a failure has occurred in the heater heating circuit or the sensor detection circuit, it can be applied to a place requiring high reliability such as a combustion control system.

When adopting this configuration, when the power is supplied, the control means controls the switch means to a mode different from that of the normal operation in accordance with the sequence operation by using the trigger as a trigger, and then performs the normal operation. In some cases, the mode may be set to the time mode. At this time, it is preferable to adopt a configuration in which the device that receives the output signal of the flow velocity detecting device includes a determination unit.

This configuration has the advantage that it is not necessary to provide a control line for controlling the switch means between the flow velocity detecting device and the device for receiving the output signal of the flow velocity detecting device. There is an advantage that the flow velocity detecting device of the present invention can be directly attached in place of the flow velocity detecting device provided.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail according to embodiments. FIG. 1 illustrates a device configuration of a flow velocity detecting device 10 having the present invention.

As shown in this figure, the flow velocity detecting device 10 of the present invention has a heater element 4 / temperature measuring resistance element 5,6 / ambient temperature temperature measuring resistance element which is constituted by the micro-machined diaphragm structure shown in FIG. And a heater element 4 and an ambient temperature resistance element 7 as circuit elements.
A heat generation control circuit 30 for controlling the heating process of FIG. 1, a temperature difference amplifying circuit 40 constituted by the circuit shown in FIG. 2 and generating a voltage corresponding to the resistance value of the resistance temperature measuring elements 5 and 6, for example, a microprocessor The heater element 4 /
A sensor check mechanism 50 for detecting a failure or the like of the temperature measuring resistance elements 5, 6 / ambient temperature temperature measuring resistance element 7 is provided.

Here, a symbol 41 shown in FIG. 2 is a differential amplifier.
Is 0 when the heater element 4 is not heated.
It is adjusted to output a voltage of V.

FIG. 3 shows an embodiment of the heat generation control circuit 30. The heat generation control circuit 30 of this embodiment is configured by connecting a series connection of a heater element 4 and a fixed resistor R1 and a series connection of an ambient temperature resistance measuring element 7 and a fixed resistor R2 in parallel. Circuit and
An operational amplifier U1 for amplifying a potential difference between two series-connected intermediate points of the Wheatstone bridge circuit, and an operational amplifier U
A transistor Q1 for controlling the amount of current supplied to the Wheatstone bridge circuit in accordance with the output of
There are provided fixed resistors R3, 4 for generating one bias voltage, and a switch 300 provided in parallel with the fixed resistor R3 to short-circuit the emitter and base of the transistor Q1.

According to this configuration, when the switch 300 opens, the heat control circuit 30 shown in FIG. 3 supplies a current to the Wheatstone bridge circuit via the transistor Q 1 and is thermally insulated from the semiconductor substrate 1. The heater element 4 increases the resistance value RH by increasing the temperature. On the other hand, the heater element 4
The semiconductor substrate 1 that is thermally insulated from the semiconductor substrate 1 does not rise in temperature, and the resistance value RR of the ambient temperature measuring resistance element 7 that is in contact with the semiconductor substrate 1 does not change.
Therefore, the heat generation control circuit 30 calculates “RH × R2 = RR
× R1 ”.

As described above, the heat generation control circuit 30 determines that the ratio “RH / RR” of the resistance value RH of the heater element 4 and the resistance value RR of the ambient temperature measuring resistance element 7 is constant.
That is, the heating of the heater element 4 is controlled so that the temperature rise of the heater element 4 with respect to the ambient temperature becomes constant.

On the other hand, when the main switch 300 is closed, the emitter and the base of the transistor Q1 are short-circuited, so that the transistor Q1 is turned off, so that the heater element 4 is not heated.

FIG. 4 shows an embodiment of a processing flow executed by the sensor check mechanism 50 when the heat generation control circuit 30 adopts the configuration shown in FIG. Next, according to this processing flow, the check processing of the flow velocity sensor 20 executed by the present invention will be described.

The sensor check mechanism 50 includes a flow sensor 2
When there is an inspection request of 0, first, as shown in the processing flow of FIG.
Then, the transistor Q1 is turned off, and the heating of the heater element 4 is stopped.

Subsequently, in step 2, by waiting for the specified time to elapse, it waits for the heater element 4 that has been heated to cool down. The heater element 4
The cooling time is extremely short, on the order of several ms, since it is formed on the diaphragm 3 having a thickness of about 1 micron.

After the heater element 4 cools down to the non-heated ambient temperature in accordance with the processing in step 2, the output value of the temperature difference amplifier circuit 40 is read in step 3, and the switch 300 is turned on in step 4 By turning OFF, it returns to the state before the inspection request.

When the heater element 4 is not heated, there is no temperature difference between the two resistance temperature measuring elements 5 and 6 regardless of the flow of the fluid. Of 0V.

From now on, in the following step 5, step 3
It is determined whether the output value of the temperature difference amplifying circuit 40 read in step 2 indicates substantially 0 V, and when it is determined that the output value does not indicate 0 V, the process proceeds to step 6 and a sensor abnormality is output to the outside. When it is determined to indicate 0 V, the process proceeds to step 7 and outputs a normal sensor value to the outside.

Thus, the sensor check mechanism 50
Adopts a configuration in which the heating of the heater element 4 is temporarily stopped, and based on the output value of the temperature difference amplifying circuit 40 at that time, the disconnection of the heater element 4, the malfunction of the heat generation control circuit 30, the temperature difference amplification The operation failure of the circuit 40 is detected.

As described above, the diaphragm portion 3 of the flow rate sensor 20 has a thermally insulated structure and has a very high sensitivity, so that the output fluctuates even with a slight fluctuation of gas. . Although there is a disadvantage that it is difficult to confirm the zero point output, the sensor check mechanism 50
According to the processing described above, the output drift can be checked.

FIG. 5 shows another embodiment of the heat generation control circuit 30. The heat generation control circuit 30 of this embodiment includes an ambient temperature measurement resistance element 7 and a fixed resistance R
2 instead of the series connection of
And a fixed resistor R2, a fixed resistor R2 ', and a fixed resistor R2''connected in series.
A main switch 301 for inputting a potential at a connection point 2 'to the operational amplifier U1, a switch 302 for inputting a potential at a connection point between the ambient temperature resistance measuring element 7 and the fixed resistor R2''to the operational amplifier U1, and a fixed resistor R2' And fixed resistor R2 ''
Switch 3 for inputting the potential of the connection point to the operational amplifier U1
03 is provided. Here, the main switch 301 is configured to close during normal operation.

According to this configuration, the heat generation control circuit 30 shown in FIG.
When only the main switch 301 performs the closing operation, “R
H × R2 = (RR + R2 ′ + R2 ″) × R1 ”, and when only the switch 302 is closed,“ RH × (R2 + R2 ′ + R2 ″) = RR × R1 ”
, And when only the switch 303 is closed, “RH × (R2 + R2 ′) = (RR + R
2 ″) × R1 ”.

That is, when only the main switch 301 performs the closing operation, RH is stabilized at the highest resistance value. Therefore, the heater element 4 is heated to the highest temperature. When only the switch 302 performs the closing operation, RH is maintained. Is stable at the lowest resistance value, so that the heater element 4 is heated to the lowest temperature, and when only the switch 303 is closed, RH is stable at the middle resistance value, and thus the heater element 4 is stable. Is heated to an intermediate temperature.

When the flow velocity sensor 20 is operating normally, a proportional relationship is established between the heating temperature of the heater element 4 and the output value of the temperature difference amplifying circuit 40. For example, the temperature difference amplification circuit 40
It outputs the largest voltage when only the main switch 301 is closed, outputs the smallest voltage when only the switch 302 is closed, and outputs an intermediate voltage when only the switch 303 is closed. Become.

FIG. 6 shows an embodiment of a processing flow executed by the sensor check mechanism 50 when the heat generation control circuit 30 adopts the configuration shown in FIG. Next, according to this processing flow, the check processing of the flow velocity sensor 20 executed by the present invention will be described.

When there is a request for inspection of the flow rate sensor 20 when the flow rate does not change during normal operation, as shown in the processing flow of FIG. First, in step 1, the output value of the temperature difference amplifier circuit 40 is read. As described above, during the normal operation, only the main switch 301 is ON, and the output value at this time indicates a regular value corresponding to the flow velocity.

Subsequently, at step 2, "1" is set to the variable i, and at step 3, only the switch indicated by the variable i is turned on. It is defined that the value "1" of the variable i indicates the switch 300. Therefore, in step 3, control is first performed so that only the switch 300 is turned on. That is, control is performed so that heating of the heater element 4 is stopped.

Subsequently, in step 4, waiting for the specified time to elapse, the temperature of the heater element 4 is stabilized, and then in step 5, the temperature difference amplifying circuit 40
Read the output value of. In a normal state, as described above, this output value indicates 0V.

Subsequently, in step 6, the value of the variable i is incremented by one. In the following step 7, it is determined whether or not the value of the variable i has reached "4". When the determination is made, the process from step 3 to step 6 is repeated by returning to step 3.

According to this repetitive processing, the switch 30
By turning ON only the switch 302 indicated by the value “2” of the variable i after turning ON only 0, the heater element 4 is heated to the lowest temperature, and the output of the temperature difference amplifier circuit 40 at that time is heated. Read the value, followed by the variable i
By turning on only the switch 303 indicated by the value “3”, the heater element 4 is heated to an intermediate temperature, and the output value of the temperature difference amplifier circuit 40 at that time is read.

When it is determined in step 7 that the value of the variable i has reached "4", the process proceeds to step 8, in which only the main switch 301 is turned on to return to the state during normal operation.

Subsequently, in step 9, it is determined whether or not the output value read in step 1 indicates 0 V, and the output value read in step 5 is proportional to the heating temperature of the heater element 4. The flow rate sensor 20, the heat generation control circuit 30, and the temperature difference amplifying circuit 40 are detected as to whether the flow rate sensor 20 is normal or not. Output.

In this manner, the sensor check mechanism 50
As shown in FIG. 7, the temperature difference amplifying circuit 40 employs a configuration in which the heating of the heater element 4 is temporarily stopped and the heating of the heater element 4 is temporarily changed from a normal one. From the output value of the heater element 4, a malfunction of the heat control circuit 30 and a malfunction of the temperature difference amplifying circuit 40 are detected.

The check processing of the sensor check mechanism 50 must be performed when the flow velocity of the fluid is constant in principle. This constant flow velocity state can be detected, for example, by monitoring the movement of the output value of the temperature difference amplifying circuit 40 or monitoring the movement of a fluid flow control valve provided outside.

It should be noted that the heater element 4 and the temperature-measuring resistance elements 5 and 6 are made of a diaphragm 3 having a thickness of about 1 micron.
Since the response time is extremely fast, the check processing can be executed in an extremely short time. As a result, even when the flow rate is not constant, the flow rate sensor 20, the heat generation control circuit 30, and the temperature difference amplification circuit 40 can be checked with considerably high accuracy.

FIG. 8 shows another embodiment of the heat generation control circuit 30. In the embodiment of FIG. 5, the heat generation control circuit 30 of this embodiment includes a fixed resistor R2, a fixed resistor R2 ′, and a fixed resistor R2.
By adopting a configuration in which 2 '' is connected in series, a configuration in which the heating temperature of the heater element 4 is changed is adopted, while connecting them in parallel and connecting a fixed resistor R2 and a fixed resistor R2 'in parallel. And a switch 305 that realizes a parallel connection of the fixed resistor R2, the fixed resistor R2 ′, and the fixed resistor R2 ″.

By turning on the switch 304 in accordance with this configuration, the combined resistance R2c of the fixed resistance R2 and the fixed resistance R2 'having a smaller value than the fixed resistance R2 is made effective instead of the fixed resistance R2. As a result, “RH × R2
According to the relational expression of c = RR × R1, the heater element 4 is heated to a temperature higher than that in the normal operation by stabilizing the RH at the point where the resistance shows a higher resistance value than in the normal operation.

The switches 304 and 30
By turning on 5, the combined resistor R2d of the fixed resistor R2, the fixed resistor R2 ′, and the fixed resistor R2 ″ having a value smaller than the combined resistor R2c is effective instead of the fixed resistor R2. Thereby, “RH × R2d = RR × R
In accordance with the relational expression of "1", the heater element 4 is heated to a higher temperature by stabilizing the RH at a point where the RH shows a higher resistance value.

According to the embodiment of FIG. 8, there is an advantage that a switch equivalent to the main switch 301 required in the embodiment of FIG. 5 is not required.
Since the / switch 305 enters the Wheatstone bridge circuit, there is a disadvantage that it is affected by its ON resistance.

The heat generation control circuit 30 shown in FIGS. 5 and 8 uses the ambient temperature resistance element 7 to control the heating temperature of the heater element 4 to a value higher than the ambient temperature by a specified temperature. Although the present invention is adopted, the present invention does not assume such a configuration, and can be applied as it is even when the ambient temperature measuring resistance element 7 is not used.

That is, for example, as shown in FIG.
When employing a configuration in which the heater element 4 is heated at a constant voltage by using the output voltage of the operational amplifier U1 that short-circuits the input terminal and the output terminal, the input voltage to the + input terminal of the operational amplifier U1 is changed using a switch. By doing
The present invention can be realized by changing the voltage applied to the heater element 4. The switch 306 shown in the figure functions as a switch for stopping the heating of the heater element 4.

For example, as shown in FIG. 10, the heater element 4 is fixed by using an operational amplifier U1 for short-circuiting the input terminal and the output terminal and a transistor Q1 controlled by the output voltage of the operational amplifier U1. When employing a configuration in which heating is performed with a current, the present invention can be realized by changing the applied current to the heater element 4 by changing the input voltage to the + input terminal of the operational amplifier U1 using a switch. The switch 307 shown in the figure functions as a switch for stopping the heating of the heater element 4.

FIG. 11 shows another device configuration of the flow velocity detecting device 10 provided with the present invention. In this device configuration, the sensor check mechanism 50 is not developed inside the flow velocity detecting device 10 but is developed into a main body device 100 such as a combustion control device to which the flow velocity detecting device 10 is connected.
In order to realize this configuration, a configuration in which a timer mechanism 60 including a hardware circuit, a microprocessor, and the like is provided inside the flow velocity detecting device 10 is adopted.

According to this device configuration, the flow velocity detecting device 1
The signal lines between 0 and the main unit 100 are characterized in that they are a power supply line, a ground line, and an output signal line of the temperature difference amplifying circuit 40, as in the case of the flow velocity detector not having the present invention. From this, the flow velocity detecting device 10 of the present invention can be directly attached instead of the already mounted flow velocity detecting apparatus.

FIG. 12 shows an embodiment of a processing flow executed by the timer mechanism 60, and FIG. 13 shows an embodiment of a processing flow executed by the sensor check mechanism 50 when this configuration is followed. Here, in this processing flow, it is assumed that the heat generation control circuit 30 has the configuration shown in FIG.

Next, the check processing of the flow velocity sensor 20 executed by the present invention will be described according to these processing flows. When the power supply is started from the main device 100, the timer mechanism 60, as shown in the processing flow of FIG.
First, in Step 1, only the switch 300 is turned on for a specified time, then, in Step 2, only the switch 302 is turned on for a specified time, and then, in Step 3, only the switch 303 is turned on for a specified time. Then, only the main switch 301 is turned on, and the process is terminated.

According to the processing of the timer mechanism 60, FIG.
As shown in FIG. 4, since the heater element 4 is not heated during the specified time from the start of power-on, a voltage of 0 V is output from the temperature difference amplifying circuit 40. When the heater element 4 is heated at the lowest temperature, a small voltage is output from the temperature difference amplifier circuit 40. Subsequently, the heater element 4 is heated at an intermediate temperature for a specified time, so that the temperature difference is increased. An intermediate voltage is output from the amplifier circuit 40, and subsequently, the heater element 4 is set to be heated at the highest normal temperature, so that a normal large voltage is output from the temperature difference amplifier circuit 40. Will be.

In response to the processing of the timer mechanism 60, when the main body device 100 starts supplying power to the flow velocity detecting device 10, the sensor checking mechanism 50 firstly performs step 1 as shown in the processing flow of FIG. When the specified time elapses after the power is turned on and the elapse of the specified time is confirmed, the process proceeds to step 2 where the output value of the temperature difference amplifier circuit 40 is read and the area A shown in FIG.
(The area where only 00 is ON) is read.

Subsequently, in step 3, after waiting for the specified time to elapse, and confirming the elapse, the process proceeds to step 4, in which the output value of the temperature difference amplifying circuit 40 is read.
The output value of the area B (the area where only the switch 302 is ON) shown in FIG. 14 is read.

Subsequently, in step 5, after waiting for the specified time to elapse, and confirming the elapse, the process proceeds to step 6, where the output value of the temperature difference amplifying circuit 40 is read.
The output value of the area C (the area where only the switch 303 is ON) shown in FIG. 14 is read.

Subsequently, in step 7, after waiting for the specified time to elapse, and confirming the elapse, the process proceeds to step 8, in which the output value of the temperature difference amplifying circuit 40 is read, and
Region D shown in FIG. 14 (only main switch 301 is ON)
Read the output value of the

Subsequently, in step 9, it is determined whether or not the output value read in step 2 indicates 0 V, and the output value read in step 4 / step 6 / step 8 is the heating temperature of the heater element 4. By evaluating whether it shows a proportional relationship according to,
Flow velocity sensor 20, heat generation control circuit 30, temperature difference amplification circuit 4
0 is normal or not, and the following step 10
Output the detection result.

As described above, in the case of following the apparatus configuration shown in FIG.
By changing the heating temperature of the heater element 4 with time when the power is turned on without receiving a control signal from the controller, the temperature required for checking the flow velocity sensor 20, the heat generation control circuit 30, and the temperature difference amplification circuit 40 is obtained. By adopting a configuration in which the output value of the difference amplifying circuit 40 is output in time series, the sensor check mechanism 50 deployed in the main body device 100 executes a check process using the time series data, so that the flow rate detection device 10 A configuration is adopted in which the check processing is realized without requesting a new signal line between the device and the main unit 100.

Note that this check processing is also performed in principle.
This must be performed when the flow velocity of the fluid is constant, but the heater element 4 and the temperature measuring resistance elements 5, 6 are formed on the diaphragm portion 3 having a thickness of about 1 micron, so that an extremely fast response is exhibited. Therefore, it can be executed in a very short time. From now on, even if it is executed when the flow velocity is not constant, the flow velocity sensor
The check of 0, the heat generation control circuit 30 and the temperature difference amplification circuit 40 can be executed.

The present invention has been described with reference to the illustrated embodiments.
The present invention is not limited to this. For example, in the embodiment, the heater element 4 and the temperature-measuring resistance elements 5, 6
Although the flow rate sensor 20 formed on the thin diaphragm portion 3 formed on the semiconductor substrate 1 is assumed, the application of the present invention is not limited to the flow rate sensor 20 having this configuration.

[0078]

As described above, according to the present invention,
When adopting a configuration in which a flow rate of a fluid is detected using a flow rate sensor composed of a heater element and a temperature measuring resistance element that changes a resistance value by heat transfer caused by a fluid moving on the heater element. ,
During the measurement of the flow velocity, it becomes possible to detect whether or not the flow velocity sensor is out of order, and it is also possible to detect whether or not the drive circuit of the flow velocity sensor is out of order.

The flow velocity sensor can be used to control the flow velocity of a fluid even in a system that requires high reliability despite being used in a poor environment such as a combustion control system. Measurement can be performed with high accuracy and high speed response.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus of the present invention.

FIG. 2 is an explanatory diagram of a temperature difference amplifier circuit.

FIG. 3 is an embodiment of a heat generation control circuit.

FIG. 4 is an embodiment of a processing flow executed by a sensor check mechanism.

FIG. 5 is another embodiment of the heat generation control circuit.

FIG. 6 is an embodiment of a processing flow executed by a sensor check mechanism.

FIG. 7 is an operation explanatory diagram of the embodiment.

FIG. 8 is another embodiment of the heat generation control circuit.

FIG. 9 is another embodiment of the heat generation control circuit.

FIG. 10 is another embodiment of the heat generation control circuit.

FIG. 11 is a diagram showing another device configuration of the present invention.

FIG. 12 is an example of a processing flow executed by a timer mechanism.

FIG. 13 is an embodiment of a processing flow executed by a sensor check mechanism.

FIG. 14 is an operation explanatory diagram of the embodiment.

FIG. 15 is an explanatory diagram of a flow rate sensor having a microfabricated diaphragm.

FIG. 16 is an explanatory diagram of a flow rate sensor having a microfabricated diaphragm.

[Explanation of symbols]

 Reference Signs List 4 heater element 5 RTD element 6 RTD element 7 Ambient temperature RTD element 10 Flow velocity detector 20 Flow velocity sensor 30 Heat generation control circuit 40 Temperature difference amplification circuit 50 Sensor check mechanism

Claims (3)

[Claims] 1. A heater heating circuit having a heater element as a circuit element and heating the heater element;
A flow rate detection device comprising: a temperature measurement resistance element that changes a resistance value according to a temperature as a circuit element; and a sensor detection circuit that detects heat transfer caused by a fluid moving on the heater element. Switch means for controlling supply / interruption of a drive signal supplied to the heating circuit; control means for interrupting the drive signal supplied to the heater heating circuit by controlling the switch means; and control of the control means A flow rate detection device comprising: a determination unit configured to determine whether the device is normal or abnormal from an output value of the sensor detection circuit output in response to an operation. 2. A heater heating circuit having a heater element as a circuit element and heating the heater element;
A flow rate detection device comprising: a temperature measurement resistance element that changes a resistance value according to a temperature as a circuit element; and a sensor detection circuit that detects heat transfer caused by a fluid moving on the heater element. One or a plurality of switch means provided in the heating circuit to change the circuit configuration of the heater heating circuit by conducting / non-conducting operation; and controlling the switch means to change the heat generation temperature of the heater element. A flow velocity detection device comprising: a control unit; and a determination unit that determines whether the device is normal or abnormal based on an output value of the sensor detection circuit output in response to a control operation of the control unit. 3. The flow velocity detecting device according to claim 1, wherein when the power is supplied, the control means controls the switch means in accordance with a sequence operation by using the power supply as a trigger, and then controls the switch means normally. A flow velocity detecting device, characterized in that processing is performed to set the state at the time of operation.