JPH01282427A - Flow rate controller - Google Patents

Abstract

PURPOSE:To enable normal control of a flow rate, by a method wherein a temperature of a fluid flowing through a pipe body is converted into a change in temperature of a heat resistor mounted on the pipe body and the heat resistor is heated to measure a gradient of temperature while a quantity of heat is measured as flowing to the fluid from a heat source. CONSTITUTION:A difference is temperature near a pipe body 1 of a heat resistor 3 and near a heater 2 is obtained between temperature sensors 9 and 10. Based on the resulting measurement data, a quantity of heat flowing to a fluid from the heater 2 is calculated and a flow rate of the fluid is computed to be shown on a flow rate display section 14 with due consideration given to correction by a specific heat of the fluid and a heat conductivity of the pipe body 1. To cause a fluidization of heat near the pipe body 1 from the heater 2 of the resistor 3, temperature in a contact surface between the resistor 3 and the pipe body 1 must be higher that the temperature of the fluid. Temperature information of the temperature sensor 8 is inputted into a heater control section 4 and a heating temperature of the heater 2 is kept higher than the temperature of the fluid. Then, a valve control section 11 compares a flow rate data from a flow rate computing section 7 with a set flow rate value predetermined at a flow rate setting section 13. This enables control 12 of a flow rate to attain a set flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flow rate control device for fluid transported within a tube.

[Conventional technology]

BACKGROUND ART Conventionally, liquid flow rate control devices have been known that control the flow rate by adjusting the opening degree of a needle valve based on the flow rate measured by a flow meter. As this flowmeter, a mechanical type such as a tapered tube float type or a rotary impeller type is used. Further, there is a device called a mass flow device as a gas flow rate control device. Mass flow is the third
As shown in FIG.
There are two types: one in which a heater 34 and a temperature sensor 31'l temperature sensor 35 and 36 are arranged in the main line 31 as shown in FIG. 3(b). In either type, 31 on the upstream and downstream sides of the heater 34
'l C sensor 35 and 36 respectively measure the gas temperature a+
q is determined, and based on the measured value, the gas flow rate is calculated by the calculation control unit 38 based on the calorific value of the heater 34 and the specific heat of the gas, and the valve driver 40 is operated to control the opening degree of the flow rate control valve 41. be.

[Problem to be solved by the invention]

By the way, the above-described conventional liquid flow rate control device has disadvantages in that measurement accuracy is poor and changes over time are severe because the measurement value of the flowmeter and the valve operation are not in a closed loop. Furthermore, since the flow meter itself forms a part of the flow path and is also a quantity display section, it is necessary to attach it to the front of the device, which makes the piping complicated and long, which causes problems in terms of piping.

On the other hand, in mass flow, when a bypass line is provided, the bypass line has a small diameter and is easily clogged with foreign matter. Since this disturbs the gas flow, the measurement accuracy of the flow rate deteriorates, making it impossible to control the gas flow rate normally. Furthermore, since some of the heater and sensor come into contact with the gas, there is a drawback that it cannot be used with strongly reactive gases.

An object of the present invention is to provide a flow rate control device that solves the above problems.

[Differences between the invention and the prior art]

In contrast to the conventional flow rate control device described above, the present invention converts the temperature of the fluid flowing inside a tube into a temperature change in a thermal resistor attached to the tube, and heats the thermal resistor to reduce the temperature gradient. ?
1l11, and the amount of heat flowing from the heat source to the fluid is 4111
The difference is that it is defined.

(Problem f! - Means for Solving) In order to achieve the above object, the present invention provides a flow rate control valve provided in a pipe body for transporting fluid, a thermal resistor attached to a part of the pipe body, and a heat resistor attached to a part of the pipe body. A heater that heats the resistor, a temperature sensor that measures the temperature gradient that occurs in the thermal resistor near the tube body and near the heater, respectively, and a tube temperature on the upstream/stream side of the installation position of the thermal resistor. a temperature sensor that measures temperature, a calculation section that calculates the flow rate of the fluid flowing in the pipe from the temperature measurement data obtained by each sensor and the known specific heat of the fluid, and a calculation section that calculates the flow rate of the fluid flowing in the pipe based on the calculation data obtained by the calculation section. and a valve control section that controls the opening degree of the valve.

(Example) Next, the present invention will be explained with reference to the drawings.

(Embodiment 1) FIG. 1 is a structural diagram showing a first embodiment of the flow rate control device d of the present invention.

The flow control device of the present invention includes a flow control valve 12 provided in the middle of a pipe 1 for transporting fluid, a thermal resistor 3 attached in contact with a part of the outer surface of the pipe 1, and a A heater 2 that heats the resistor 3 and a heater control section 4 that controls the amount of heat generated by the heater 2.

A temperature measurement unit 6 that measures the temperature gradient of the thermal resistor 3, a flow rate calculation unit 7 that calculates the flow rate of the fluid in the tube body 1 based on the measurement data of the temperature gradient, and a flow rate calculation unit 7 that calculates the opening degree of the flow rate control valve 12. It has a valve control section 11 for adjusting, and a flow rate setting section 13 for setting the flow rate of the fluid flowing inside the pipe body 1. Heater 2
The thermal resistor 3 is covered with a heat insulating material 5 to prevent heat exchange with the outside air, and the thermal resistor 3 exchanges heat with the fluid only through the contact surface with the tube body 1. In order to determine this heat flow rate ii+11, in this embodiment, the temperature sensor 8 is attached to the outer surface of the tube upstream from the position, and the temperature sensor 8 is attached to a part of the heat resistor 3 near the tube. A temperature sensor 10 is attached to a part of the thermal resistor 3 near the temperature sensor 9 and the heater 2, respectively.

The temperature difference between the vicinity of the tube of the thermal resistor 3 and the vicinity of the heater is obtained between the temperature sensors 9 and 10. Based on this measurement data,
The amount of heat flowing from the heater 2 to the fluid is calculated, and the flow rate of the fluid is calculated by taking into account correction based on the specific heat of the fluid and the thermal conductivity of the tube body 1.

The calculated flow rate is displayed on the flow rate display section 14. Here, in order to cause heat to flow from the vicinity of the heater of the thermal resistor 3 to the vicinity of the tube body, the temperature at the contact surface between the thermal resistor 3 and the tube body 1 must be higher than the temperature of the fluid. Must be. 8
The +11 temperature sensor 8 measures the temperature of the fluid upstream from the thermal resistor 3, inputs the temperature information to the heater control unit 4, controls the amount of heat generated by the heater 2, and constantly controls the temperature of the fluid generated by the heater 2. Temperature higher than temperature 1: It is maintained. The valve control unit 11 compares the flow rate set value predetermined in the flow rate setting unit 13 with the flow rate data from the flow rate calculation unit 7, and based on the data, adjusts the opening degree of the flow rate control valve 12 so that the set flow rate is achieved. The flow rate is controlled by adjusting the flow rate.

(Embodiment 2) FIG. 2 is a structural diagram showing a second embodiment of the present invention. The device configuration is the same as in the first embodiment.

In this embodiment, an annular heat resistor 3 having an inner diameter equal to the inner diameter of the tube 1 is attached in the middle of the tube 1. Therefore, the inner circumferential surface of the thermal resistor 3 is exposed to the inner surface of the tube body 1. Further, the thermal resistor 3 is formed thin in parts other than the heater vicinity and the tube body vicinity to increase thermal resistance.

This increases the temperature gradient of the thermal resistor 3 and increases the sensitivity of the flow control device. Also.

By exposing a part of the thermal resistor 3 inside the tube body, the efficiency of heat exchange with the fluid is improved, and in particular, since the thermal resistor 3 is in direct contact with the fluid, the correction term related to the tube body part is removed. can.

Furthermore, by increasing the thickness of the heat insulating material 5, errors related to heat scattering can be eliminated, and a highly accurate flow rate control device can be realized.

〔Effect of the invention〕

As explained above, according to the present invention, since sensitive parts such as heaters and sensors are not brought into direct contact with the fluid, it is possible to control the flow rate of substances with strong reactivity, and the change over time is small. Also, since the only part that comes in contact with liquid is the inside diameter of the tube, there is no possibility of clogging with foreign matter and normal flow control can be achieved. Another advantage is that there is no leakage even when used in areas subject to ultra-high vacuum.

[Brief explanation of the drawing]

Fig. 1 is a structural diagram showing a first embodiment of the present invention, Fig. 2 is a structural diagram showing a second embodiment of the invention, Fig. 3(a),
(b) is a structural diagram showing a conventional example.

Claims (1)

[Claims] (1) A flow rate control valve provided on a pipe for transporting fluid, a thermal resistor attached to a part of the pipe, a heater for heating the heat resistor, and a flow rate control valve provided in the pipe body and near the heater, respectively. A temperature sensor that measures the temperature gradient that occurs in the thermal resistor, a temperature sensor that measures the temperature of the pipe body upstream from the mounting position of the thermal resistor, and temperature measurement data obtained from each sensor and known data. A flow rate control device comprising: a calculation unit that calculates the flow rate of fluid flowing in a pipe from the specific heat of the fluid; and a valve control unit that controls the opening degree of the valve based on calculation data obtained by the calculation unit. .