JPH0629796B2 - Fluid resistance type temperature measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fluid resistance type temperature measuring device that measures, for example, the temperature in a furnace or the temperature of a molten metal by utilizing the state change of a fluid. .

(Prior art and its problems) Conventionally, thermocouples or resistance thermometers are generally used for measuring the temperature of molten metal or high temperature parts such as in a furnace. However, these thermometers are, in principle, limited in the material of the temperature sensing part that is exposed to high temperatures, so it is difficult to take measures against oxidation and other causes that shorten the life, and are not suitable for long-term use. there were.

Therefore, a fluid resistance type temperature measuring device has been developed which has an advantage that the material of the sensor which is the temperature sensing portion is not restricted by the principle of measurement and can be freely selected from the viewpoint of life. This fluid resistance type temperature measuring device utilizes the temperature dependence of the viscosity coefficient of gas.
The temperature sensor is a probe 1 having a capillary tube 2 which is a throttle as shown in FIG. 11, and a working fluid is added to the probe 1 as shown by arrows a and b in FIG. 12 or FIG.
(For example, Ar gas) is caused to flow, and the temperature is obtained from the change in pressure loss when the gas (working fluid) passes through the capillary tube 2.

This fluid resistance type temperature measuring device is specifically constructed as shown in FIG. This temperature measuring device is provided with a pressure control device 3 from a working fluid supply source 31 of a working fluid such as Ar gas.
2, the pressure is kept constant via the sensitivity adjusting valve 33 and the supply valve 34.
The pressure loss ΔP of the capillary 2 in the probe 1 corresponding to the temperature of the atmosphere to be measured and the pressure loss of the trim valve 35, that is, the secondary side of the trim valve 35 and the capillary 2.
The pressure difference ΔPc from the secondary side is amplified by the fluid element 36, exchanged into an electric signal by the pressure sensor 37, and output.

Electrically speaking, the configuration of this method is a kind of Wheatstone bridge, and a slight change in pressure loss in the sensitivity adjustment valve 33, the supply valve 34, or the trim valve 35 causes
The pressure signal from the fluidic element 36 is greatly affected. Therefore, the change in the state of the working fluid due to the ambient temperature changes the pressure loss in each of the valves 33, 34, and 35, and apparently changes in the pressure loss ΔP in the capillary tube 2 of the probe 1, that is, as the change in the temperature measured by the probe 1. As will be appreciated, this type of measuring device has the drawback of being susceptible to ambient temperature.

Further, in the fluid resistance type thermometer, when the probe 1 which is a temperature sensitive sensor is cracked or punctured, a working fluid leaks (arrow c) as shown in FIG. , b) or the atmosphere intrudes into the probe 1 (arrow e), the signal output from the pressure sensor 37 continues to be output in a state that does not correctly correspond to the measured temperature.

The breakage of the probe of the fluid resistance type temperature measuring device corresponds to a break in the thermocouple. However, when the thermocouple is broken, no signal is output, whereas in the fluid resistance temperature measuring device, an erroneous signal continues to be output as described above. Therefore, it is difficult to detect breakage of the probe 1, and for example, when the temperature is controlled by measuring the temperature with the fluid resistance temperature measuring device, the temperature is controlled to a value different from the set value. This is a serious drawback of fluid resistance temperature measuring devices.

In addition, when the outer cylinder of the probe is damaged, the atmosphere to be measured is contaminated with the working fluid (arrow d in FIG. 15), or the pressure and component ratio of the atmosphere to be measured are changed (15th arrow).
It also had the drawbacks shown in the arrows d and e).

However, the conventional fluid resistance type temperature measuring device has no means for detecting the damage of the probe having such a large influence. This point was the biggest obstacle to the practical application of the fluid resistance type temperature measuring device.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems,
It is an object of the present invention to provide a fluid resistance type temperature measuring device capable of performing high temperature measurement without being affected by changes in environmental temperature and working fluid temperature and preventing erroneous measurement by detecting damage to a probe.

(Structure of the Invention) In order to achieve the above object, the present invention provides a probe in which an inner cylinder having a narrowed portion at the tip is inserted into an outer cylinder whose one end is sealed, and a pressure control connected to the probe. Device and a mass flow control device, a working fluid supply pipe, a differential pressure gauge for detecting a pressure loss in the throttle portion, a temperature calculation means for calculating a temperature based on a signal from the differential pressure gauge, and a damage to the probe. And a probe breakage detecting means for detecting

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a fluid resistance type temperature measuring device according to the present invention, in which a probe 1 which is a temperature sensitive sensor has a capillary tube 2 which is one form of a narrowed portion and a working fluid which has passed through the capillary tube 2 of the probe 1. It is composed of an inner cylinder 4 forming a working fluid discharge flow path 3 for discharging to the outside, and an outer cylinder 6 forming a working fluid supply flow path 5 for guiding the working fluid to the capillary tube 2. As an example, a furnace wall It was attached to No. 7 and the temperature inside the furnace was measured. The working fluid supply port 8 of the probe 1 is connected to the working fluid supply pipe 1 from the working fluid supply source 9 for supplying the high-pressure working fluid, and the supply pipe 10 is connected to the pressure reducing valve 11, the pressure control device 12, and the mass. Flow controller 13
Are provided in series.

As shown in FIG. 2, the mass flow controller 13 measures the mass flow rate of the working fluid that is being supplied every moment as shown in FIG.
4, and the valve opening adjuster 15 compares it with the set mass flow rate value, and based on the result, controls the opening degree of the valve 16 to maintain a constant mass flow rate.

Further, by providing a pressure detection pipe 19 at the inlet portion 17 of the working fluid supply flow path 5 and the outlet portion 18 of the working fluid discharge flow path 3, and connecting both pressure detection pipes 19 to the differential pressure gauge 20, Pressure loss ΔP in the capillary tube 2 in the probe 1
Is detected directly. Further, the differential pressure gauge 20 is connected with a temperature calculation means 21 for calculating the temperature based on the output signal of the differential pressure gauge and a probe breakage detection means 23a, and the temperature calculation means 21 is connected with a temperature indicator 22. There is. Then, the temperature calculation means 21 converts the pressure loss ΔP into a temperature based on the relationship between the pressure and the temperature which will be described in detail below, and the temperature indicator 22 displays the measured temperature, that is, the temperature inside the furnace.

On the other hand, the probe breakage detecting means 23a is different from the differentiating circuit 2
4. The comparison calculation processing circuit 25a and the alarm means 26 are connected in this order, and the differential pressure gauge 20 is connected to the differentiating circuit 24. Then, the differential circuit 24 uses the differential pressure gauge 20.
The signal of pressure loss ΔP from
The fluctuation speed of P is calculated, this fluctuation speed is compared with the set reference fluctuation speed by the comparison calculation processing circuit 25a, and if there is an abnormality in the fluctuation speed of the pressure loss ΔP, an abnormal signal is issued and an alarm is issued by the alarm means 26. It is designed to emit.

Next, a temperature measuring method using the apparatus having the above-mentioned configuration will be described.

First, a high-pressure working fluid from the working fluid supply source 9, for example, A
Supply gas. The working fluid supplied to the pressure reducing valve 11,
The pressure is reduced to a predetermined pressure by the pressure control valve 12, and further controlled to maintain this pressure. In this state, the mass flow controller 13 supplies the constant mass flow rate Q to the working fluid supply channel 5 of the probe 1. It

The working fluid supplied to the working fluid supply channel 5 at a constant mass flow rate Q is discharged into the atmosphere from the outlet 18 through the capillary tube 2. At this time, since a pressure loss ΔP is generated in the portion of the capillary tube 2, this pressure loss ΔP is directly detected by the differential pressure gauge 20 and the temperature calculation means 21 is based on this detected value.
Calculate the temperature at.

Therefore, a method for obtaining the furnace temperature T in the probe 1 from the pressure loss ΔP will be described.

The working fluid supplied from the working fluid supply port 8 to the probe 1 is heated from the atmosphere inside the furnace via the outer cylinder 6 of the probe 1 while flowing through the working fluid supply passage 5, and the temperature rises to the furnace temperature T. , To the capillary tube 2.

Since the Hagen-Boiseuille flow can be generally assumed for the flow in the capillary tube 2, the pressure loss generated in the capillary tube 2 is expressed by the following equation.

However, l and d represent the length and inner diameter of the capillary, respectively, and μ (T) and ρ (T) represent the viscosity coefficient and density of the working fluid at the furnace temperature T. Further, Q indicates the mass flow rate of the working fluid, which is a constant because the mass flow rate controller 13 controls the mass flow rate to be constant here.

Strictly speaking, the length 1 or the inner diameter d of the capillary tube 2 is also affected by the temperature. In consideration of this, the kinematic viscosity ν (T) of the working fluid is ν (T) = μ (T) / ρ (T), and therefore the equation (1) can be rewritten as follows.

Therefore, it can be seen that ΔP is a function of the furnace temperature T.

In general, the temperature dependence of l and d is often smaller than that of ν (T), so Can be expressed as From this equation (3), it can be said that the pressure loss ΔP generated in the capillary tube 2 is proportional to the kinematic viscosity ν (T) of the working fluid when passing through the capillary tube 2. Working fluid kinematic viscosity ν
Since (T) is a temperature function, the pressure loss ΔP is a function of the temperature of the working fluid when passing through the capillary 2, that is, the temperature T in the furnace.

Therefore, in either case of the equations (2) and (3), the furnace temperature T can be known by measuring the pressure loss ΔP generated in the capillary tube 2. In many cases, the temperature dependence of l and d (that is, the thermal expansion of the probe 1) depends on the kinematic viscosity ν
Since it is lower than the temperature dependence of (T), it can be considered that it is generally expressed by the equation (3).

As described above, the pressure loss ΔP in the capillary tube 2 depends only on the temperature of the working fluid passing therethrough.
Therefore, it is not affected by the temperature history of the working fluid before entering the capillary tube 2, the material environmental temperature of the probe 1, the atmospheric pressure, and the like.

Next, as a specific example of the probe 1, as shown in FIG. 1, the inner diameter d of the capillary tube 2 is 0.76 mm (at 0 ° C.) and the length l is 13 mm.
Consider a case where tungsten (at 0 ° C.) and a coefficient of thermal expansion of 20 × 10 ⁻⁶ / ° C. is used and the working fluid is Ar gas. The relationship between the pressure loss ΔP and the temperature T at this time is Ar
FIG. 3 shows the flow rate of the gas (working fluid) as a parameter. The pressure loss ΔP generated in the capillary tube 2 increases monotonically with increasing temperature.

Further, it can be seen from FIG. 3 that the larger the mass flow rate Q flowing through the capillary tube 2, the larger the value of the pressure loss ΔP and the stronger the temperature dependence. From this alone, it can be considered that the measurement accuracy or the temperature resolution of the thermometer is improved as the mass flow rate Q is increased. However, the following problems become more prominent as the flow rate increases.

First, the first problem is that heat transfer in the probe 1 cannot follow and the difference between the working fluid and the temperature inside the furnace becomes large, so that the temperature inside the furnace cannot be accurately displayed. Especially, the temperature inside the furnace changes rapidly. The longer the delay, the greater.

The second problem is that, compared with the pressure loss ΔP in the capillary 2, the probe tip or the working fluid inlet 17 of the probe 1
That is, the ratio of the magnitude of the pressure loss in the curved portion, the throttle portion, etc. becomes relatively large, and as a result, the temperature dependence of the pressure loss ΔP in the capillary tube 2 becomes relatively small.

The third problem is the tip of the probe 1, or the probe 1.
The pressure loss ΔP fluctuates because the flow becomes unstable at the bent portion and the throttle portion such as the working fluid inlet portion 17.

Therefore, it is considered that the flow rate of the working fluid has an upper limit value that is restricted by the above problem.

The mass flow rate of the working fluid should be determined from the measurement temperature range, the range of the differential pressure gauge 20, the measurement resolution, etc. within a range of an appropriate flow rate that does not exceed the above upper limit value. The proper flow rate of the working fluid greatly depends on the type of working fluid or the structure, shape, and size of the probe, and should be determined experimentally.

Further, according to this temperature measuring device, only the tip of the probe 1 is exposed to the high temperature portion. From the measurement principle,
Since the material of the probe 1 does not affect the measurement accuracy, any material can be used as long as it can withstand the measurement temperature range. This is one of the advantages over a thermocouple that requires a combination of metals that can withstand the measurement temperature range and generate an electromotive force, for example.

Next, the operation principle of the probe breakage detecting means 23a will be described by taking the case of the above embodiment as an example.

As described above, in this case, the working fluid flows in the direction from the outer cylinder 6 into the inner cylinder 4. The pressure inside the furnace is higher than the pressure inside the probe 1.

Consider a case where the probe 1 shown in FIG. 1 is damaged as shown in FIG. Since the furnace pressure P ₀ is higher than the probe pressure P ₁ , the gas in the furnace atmosphere is indicated by the arrow f.
As described above, it flows into the probe 1 and passes through the capillary tube 2 together with the working fluid. Therefore, the measured pressure loss value ΔP in the differential pressure gauge 20 instantaneously increases at the same time as the probe 1 is damaged, and the measured pressure loss change rate of the measured pressure loss value ΔP in the differential pressure gauge 20 at that time. Is large due to the pressure loss change rate corresponding to the fluctuation of the furnace temperature. That is, even if the temperature in the furnace fluctuates from T ₁ to T ₂ instantaneously, the pressure loss value ΔP ₁₂ generated in the capillary tube 2 of the probe 1 is detected from the temperature T ₁ to the temperature of the outer surface of the outer cylinder of the probe 1. T ₂ become the time required: t ₁ time required for the outer cylinder surface of the probe 1 is temperature T _2: t ₂ working fluid temperature T ₂ becomes the time required: time delay consisting of t ₃ is Occurs. By the way, the time delay t ₁ is greatly influenced by the components of the atmosphere, the pressure, the flow condition, etc., and the time delay t ₃ is greatly influenced by the pressure, the flow condition of the working fluid, etc. Alternatively, it is difficult to understand, but the time delay t ₂ can be estimated by the following equation (4) since the temperature conductivity α and the wall thickness l of the probe 1 are known.

t ₂ = l / 16α (4) Therefore, the pressure loss change rate of the pressure loss value ΔP ₁₂ If the pressure loss value corresponding to the furnace temperature T ₁ is ΔP ₁ and the pressure loss value corresponding to the furnace temperature T ₂ is ΔP ₂ , the following (5)
It can be represented by a formula.

And if the probe 1 is not damaged,
Pressure loss change speed measured by differential pressure gauge 20 Is at least It means that the above speed is not exhibited.

On the other hand, the pressure loss value corresponding to the upper limit temperature Tmax of the temperature measuring range of the fluid resistance type temperature measuring device is ΔPmax and the lower limit temperature Tmin.
Let ΔPmin be the pressure loss value corresponding to Can be expressed by the following equation (6).

Therefore, based on the equation (6) the setting reference change speed, The output signal of the differential pressure gauge 20 is differentiated with respect to time by the differentiating circuit 24, and the measured pressure loss change speed is The measured pressure loss change speed is compared with the set reference change speed in the comparison calculation processing circuit 25a. As a result, the measured pressure loss change speed is the set reference change speed. If it is larger, it is determined that the probe 1 is broken, an abnormal signal is issued, and an alarm is issued by the alarm means. Next, a case where the furnace pressure P ₀ is lower than the pressure P ₁ in the probe 1 as shown in FIG. In this case, at the same time as the damage 27 occurs in the probe 1, a part of the working fluid flowing in the probe 1 flows out into the furnace as indicated by an arrow g. Therefore, the measured pressure loss value ΔP in the differential pressure gauge 20 sharply decreases at the same time when the probe 1 is damaged, and the measured pressure loss change rate at that time is decreased. Is greater than the set reference change speed as described above.

Therefore, as in the case described above, the output signal of the differential pressure gauge 20 is time-differentiated by the differentiating circuit 24 to measure the pressure loss change pressure fluctuation speed. Is calculated and measured by the comparison calculation processing circuit 25a. And setting reference change speed And compare If it is larger, it is determined that the probe 1 is damaged, an abnormal signal is output, and the alarm means 26 issues an alarm.

Therefore, If is established, an alarm is issued.

Although the differential pressure gauge 20 is connected to the differentiating circuit 24 in the above embodiment, as shown in FIG.
Probe breakage detecting means 23b in which a differentiating circuit 24 is connected to
May be provided. In this case as well, after the measured pressure loss value ΔP is converted into temperature by the temperature calculation means 21, this temperature signal is input to the differentiating circuit 24, and the rate of change of the calculated temperature is input instead of the rate of change of the measured pressure loss value ΔP. Then, the comparison operation processing circuit 25a can detect the probe breakage by comparing the change speed of the calculated temperature with the reference change speed (calculated temperature change speed).

Note that the set reference change rate is not limited to the one based on the present measurement apparatus as described above, and can be appropriately selected, for example, the pressure loss change rate, the temperature change rate, or the temperature change rate corresponding to the heat curve of the processing material. .

FIG. 7 shows an apparatus for automatically stopping the measurement when the breakage of the probe 1 is detected as described above. In addition to the apparatus shown in FIG. Electromagnetic valves 28 and 29 are provided in the gas passages on the discharge side and the discharge side. Then, by the comparison calculation processing circuit 25a,
When the breakage of the probe 1 is detected, the normally open solenoid valves 28 and 29 are closed to form a working fluid so as to prevent the working fluid from flowing into the furnace atmosphere and the furnace atmosphere from flowing out of the furnace. is there.

Furthermore, since the signal output from the comparison calculation processing circuit 25a is an electric signal, this signal can be input to other than the solenoid valves 28 and 29. For example, by inputting it to the control unit of the power source of the heater of the furnace, When the probe 1 is damaged, the solenoid valve 28,
It is possible to apply such as turning off the power source of the heater of the furnace while closing 29.

In each of the above-described embodiments, the device in which the damage of the probe 1 is detected from the pressure loss value ΔP of the probe 1 is shown, but the present invention is not limited to this.
It also includes detection of breakage of the probe 1 from changes in the mass flow rate of the working fluid.

Specifically, as shown in FIG. 8, a mass flowmeter 3 for measuring the mass flow rate of the working fluid on the working fluid discharge side of the probe 1.
0, and a probe breakage detecting means 23c formed by connecting a comparison calculation processing circuit 25b to the mass flow meter 30 and the mass flow meter 14 of the mass flow controller 13.
The same numbers are given to the parts corresponding to each other. Then, the working fluid supply side of the probe 1,
Mass flow rate of working fluid on discharge side, that is, mass flow meter 1
The flow rate signals from 4 and 30 are compared by the comparison calculation processing circuit 25b to detect the breakage of the probe 1. That is, if the probe 1 is normal, both signals will match, but if damaged, both signals should be different. Therefore, when the comparison operation processing circuit 25b detects a mismatch, an abnormal signal is output, and an alarm is issued by the alarm means 26 to inform the surroundings of the damage of the probe 1.

FIG. 9 corresponds to FIG. 7 described above. Further, the apparatus of FIG. 8 is further provided with solenoid valves 28 and 29 in the gas flow passages on the working fluid supply side and the discharge side of the probe 1 so that the probe 1 of FIG. When damage is detected, the solenoid valves 28 and 29 are closed.

Further, according to the present invention, both the component part for detecting the breakage of the probe 1 from the change of the fluctuation speed of the pressure loss value ΔP or the change speed of the temperature and the constituent part for detecting the breakage of the probe 1 from the disagreement of the mass flow rate are provided. You may have both,
FIG. 10 shows an example thereof, which is provided with a probe breakage detecting means 23d having a structure in which the probe breakage detecting means 23a and the probe breakage detecting means 23c are combined.

Although the working fluid in the probe 1 flows only in the direction from the outer cylinder 6 to the inner cylinder 4 in each of the above embodiments, the present invention is not limited to the inner cylinder 4 as shown in FIG. Including those in which the working fluid is made to flow in the direction from the
In this case as well, damage to the probe 1 is detected in the same manner as described above if there is a pressure abnormality or a mass flow rate abnormality, and a description thereof will be omitted.

(Effects of the Invention) As is apparent from the above description, according to the present invention, a probe in which an inner cylinder having a narrowed portion at its tip is inserted into an outer cylinder whose one end is sealed, and a probe which is connected to the probe for pressure control. Device and a mass flow control device, a working fluid supply pipe, a differential pressure gauge for detecting a pressure loss in the throttle portion, a temperature calculation means for calculating a temperature based on a signal from the differential pressure gauge, and a damage to the probe. And a probe breakage detecting means for detecting

Therefore, with a simple structure, highly reliable temperature measurement can be performed even at a high temperature (1,500 to 3,000 ° C.) without being affected by the ambient temperature and the working fluid temperature.

Further, when the probe is damaged, it can be detected, so that an erroneous measurement can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of a fluid resistance type temperature measuring device according to the present invention, FIG. 2 is a detailed diagram of the mass flow rate control device of FIG. 1, and FIG. 3 is a working fluid of Ar gas and FIG. FIG. 4 is a diagram showing a relationship between pressure loss and temperature when the probe shown in FIG. 4 is used, FIGS. 4 and 5 are partially enlarged views showing a state when the probe is broken, and FIGS. 6 to 10 are other views of the present invention. 11 is a block diagram showing a flow state of a probe and a working fluid, FIG. 14 is a block diagram of a conventional fluid resistance type temperature measuring device, and FIG. 15 is a diagram showing a probe. It is a partial expanded sectional view showing a damaged state. 1 ... Probe, 2 ... Capillary tube, 3 ... Working fluid discharge passage, 4 ... Inner cylinder, 5 ... Working fluid supply passage, 6 ... Outer cylinder, 12 ... Pressure control device, 13 ... Mass flow controller, 19 ... Pressure detection tube, 20 ... Differential pressure gauge, 21 ... Temperature calculation means, 23a, 23b, 23c, 23d ... Probe breakage detection means.

Claims (3)

[Claims] 1. A working fluid supply device comprising a probe having an inner cylinder having a narrowed portion at its tip and an inner cylinder having one end sealed therein, and a probe which is connected to the probe and which is equipped with a pressure controller and a mass flow controller. A pipe, a differential pressure gauge for detecting a pressure loss in the throttle portion, a temperature calculation means for calculating a temperature based on a signal from the differential pressure gauge, and a probe breakage detection means for detecting breakage of the probe. Characteristic fluid resistance type temperature measuring device. 2. The probe breakage detection means includes means for calculating a fluctuation speed of an output signal from the differential pressure gauge, and means for comparing the calculated fluctuation speed with a set reference change speed to determine whether or not the fluctuation is normal. The fluid resistance type temperature measuring device according to claim 1, wherein the fluid resistance type temperature measuring device comprises: 3. The probe breakage detecting means comprises means for comparing the mass flow rate of the working fluid supplied to the probe with the mass flow rate of the working fluid discharged from the probe to determine whether or not it is normal. The fluid resistance type temperature measuring device according to claim 1 or 2, characterized in that there is.