JPS61157912A - Mass flow controller - Google Patents

Abstract

PURPOSE:To control arbitrarily the flow of a gas with a simple operation by amplifying a sensor signal based on correction data corresponding to the type of the gas and controlling mass flow according to results available from comparing the output with a set value. CONSTITUTION:After the gas flows an inlet part 2, it is divided into a bypass part 4 and a sensor pipe 5. When the gas passes through the sensor pipe 5, resistance exothermic bodies 6a and 6b is deprived of their heat. At this time, a bridge circuit 7 takes out a temperature difference because of the further temperature drop of the exothermic body 6A than that 6B as a resistance change, and outputs it to an amplifying means 10. On the basis of the correction data corresponding to the type of the gas given from an operating part 19, the means 10 amplifies and outputs the temperature difference. Since a signal corresponding to the mass flow detected in the vicinity of the sensor pipe 5 reflects the mass flow of the entire gas, a valve 16 is controlled through a comparator circuit 12 so that the amplified signal can be equal to a set signal, whereby the mass flow can be appropriately controlled.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an improvement of a mass flow control device of the type that obtains flow rate data by amplifying a signal extracted by a thermal sensor. In a flow rate control device, the temperature signal taken out by a thermal sensor is amplified by an amplifier designed to have an amplification factor specifically for a specific gas to obtain flow rate data for that gas. Ta. Using such a thermal sensor, an output proportional to the 5!L flow rate of the gas (generally several c c 15) 4 + c e/min flowing inside the sensor tube can be obtained, but between different gases, Because the density and specific heat of the gases are different, there is a difference in the output obtained even though the quality of the gas flowing inside the sensor tube is the same.Therefore, in general, N is used as the standard and the output is different. The mass flow rate of a certain gas required to obtain the same output as that obtained by flowing N! is expressed as a ratio to N!)
- A curve factor (CF) and ~2 constants are used. For example, Le's CF is 1.44. This means that when we are getting an output of l at N, this N
This means that the same output of 1 cannot be obtained unless 1.44 times the 51 quantity flow rate of . Therefore, correct flow data cannot be obtained unless an amplifier is used that has a gain of 1.44 times the temperature signal picked up by the thermal sensor. [Problems to be Solved by the Invention] Therefore, during production, it is necessary to adjust the amplification factor of the amplifier according to one gas, which is troublesome and increases the number of man-hours. Additionally, mass flow control devices including amplifiers thus tuned can now be used only for specific gases. Therefore, when a user wants to control the flow rate of several types of gases, there is a drawback that a number of mass flow rate control devices are required depending on the gas flow rate to be controlled. The present invention was made in view of the shortcomings of conventional mass flow rate control devices, and its purpose is to provide a mass flow rate control device that can control the flow rate of any gas with simple operations. Chiru. [Means for solving the problem] Therefore, in the present invention, the temperature signal of the gas in the flow path is
a thermal sensor provided to output the temperature signal; and an amplification means for amplifying and outputting the temperature signal taken out by the thermal sensor based on correction data given corresponding to the type of gas, and an output from the amplification means. The valve drive signal based on the comparison result is used to control the gas mass flow rate by controlling the pulp opening rate. [Function] The temperature signal taken out by the armored sensor installed to extract the temperature signal of the gas in the flow path must be corrected by OF in order to be converted into gas mass flow rate data as described above. Must be. The amplification means amplifies and outputs the temperature signal with a corresponding amplification factor based on correction data given corresponding to the type of gas. For example, the amplifying means 10 is given correction data L44 during ordinary flow rate control, and amplifies and outputs the temperature signal to become flow rate data that is 144 times that during N flow rate control. Therefore, the temperature signal for each gas is output after being appropriately corrected.

【Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the invention. In the mass flow controller shown in the figure, 2 indicates a gas inlet section, and 3 indicates a gas outlet section. When the gas enters the inlet s2, it is branched into the bypass section 4 and the sensor pipe 5. The sensor ys includes a pair of resistance heating elements (thermal sensors) 6A and 6B on the upstream and downstream sides of the gas flow.
is wound. Six resistance heating elements, 6B, are connected to the bridge circuit 7. When the gas passes through the sensor tube 5, the resistance heating element 6A,
6B is deprived of heat. At this time, the temperature of the six resistance heating elements becomes lower than that of the resistance heating element 6B, and the resulting temperature difference is extracted as a resistance value change in the bridge circuit 7. Based on this change in resistance value, the mass flow of the gas flowing through the sensor tube 5 can be detected.Since the dividing ratio between the sensor tube 5 and the bypass section 4 is predetermined, the mass flow of the gas flowing through the sensor tube 5 can be detected. This is the value determined by Seishiryusha based on the IR flow rate of the entire flowing gas. Specifically, when a resistance change occurs in the bridge circuit 7, a signal corresponding to the resistance change (a temperature signal since the a resistance change depends on a temperature difference) is output to the amplifying means 1G. The amplifying means 10 amplifies and outputs the applied signal based on correction data corresponding to the type of gas applied from the operating section 19 including a BCD switch. Here, one embodiment of the amplification means IO is shown in FIG. In the figure, numeral 20 is an amplifier, and an operational amplifier 21, an input resistor 22, and a recessive resistor 23 constitute an inverting amplifier. The input of this amplifier 20 is also provided to the bridge circuit 7 via an input terminal 24, and its output is outputted from an output Q gate 101 via a variable gain amplification section 100. The variable gain amplifier Zoo includes an operational amplifier 102, a feedback resistor 103, and an input resistor 04, which constitute an amplifier. The input resistor section 104 is provided with a semiconductor switch SL that selects whether or not to incorporate the resistor 105 into the input resistor. Can be switched. In parallel with the resistor 105, the first 2R of the four stages
-R ladder resistor 106 can be connected. The semiconductor switch is switched by a BCD switch that controls the digits of 'a o-'. In the same figure (1
), (2), (4), and (8) indicate BCD switch. In addition, the resistor 105 and the first 2R-R ladder resistor 1
06 and K are connected to the second 2R-R of the four stages through the resistor 107.
Ladder resistors 108 can be connected in parallel. Semiconductor switches 86 to S are switched to BCD switches that control the 1cr' digit. Further, a resistor 105 and a first 2R-R ladder resistor 106
A third 2R-R ladder resistor 11 is connected to the resistor 107 and the second 2R-R ladder resistor 108 via a resistor 109.
0 can be connected. semiconductor switch 5
Ie-S1s is switched by a BCD switch that controls the digits of the IC. Moreover, between the resistor 107 and the ground,
Resistors 111 . . . are connected between the resistor 109 and the ground, respectively.
The variable gain amplifier section 100 having such a configuration is an inverting amplifier], and its input resistance is B.
It is changed by the CD switch, and its gain changes. Note that each resistance value is shown in parentheses in the figure. A perspective view of the external appearance of the mass flow control device 1 having such a configuration is shown in FIG. In the figure, the operating section 19 has a 1.1O-
A BCD switch 151 of 1, 1O-', 104 and a corresponding 4-digit display 152 are provided. Therefore,
For example, when controlling the flow rate of He, operate the BCD switch 151 and display the CF of crow on the 5 display 152.
44o25 to be shown. Then, due to this, the semiconductor switch 5t-sts is appropriately switched, and the gain of the inverting amplifier of the variable gain amplifier section 1000 becomes 1440.
Then, the output of the amplifier 20 is multiplied by 144 and outputted. Returning to FIG. 1 again, the explanation will be given. Reference numeral 8 indicates a metal mesh interposed in the bypass section 4, and the mesh 8 maintains a predetermined division ratio of gas flowing through the bypass section 4 and the sensor tube 5. Further, 9 is a casing of the sensor section, and this casing 9 prevents the resistance heating elements 6 and 6B from being influenced from the outside, thereby making it possible to detect the mass flow rate with high accuracy. The output signal of the bridge circuit 7 is amplified by the amplifying means 10 described above, and is output from the sensor output terminal 11 to an external display device (not shown), etc., and is also output to the comparison circuit 12. A setting signal corresponding to a predetermined value of a desired quality i flow rate is applied to the comparison circuit 12 from the outside via a setting signal input terminal 13. Comparison circuit 12
compares the output signal of the amplifying means 10 and the setting signal,
A signal corresponding to the difference is output. This signal is applied to a pulp drive circuit 14)C, and the pulp drive circuit 14 applies a drive voltage to the pulp heater 15 based on the above signal. 16
This pulp 16, which represents the i-1 valve, is a normally open type (the valve is in the (open) state when pressure is applied, and the valve is in the CFA state when voltage is applied). When the pulp heater 15 is inserted, the expansion of the metal pin 17 due to the heat generated by the pulp heater 15 causes the spherical valve body 18 fixed to the tip of the metal pin to move up and down, adjusting the orifice relative to the gas passage. According to the configured mass flow rate controller l, the signal corresponding to the jR amount flow rate detected at the sensor tube 50 portion reflects the mass flow rate of the gas body, so the difference between this signal and the set signal is By controlling the pulp 16 so that there is no ]The output temperature signal is amplified by an amplification factor based on CF according to the h class of the gas, so that one mass flow controller can handle any gas. In the same figure,
Reference numeral 201 indicates an input terminal, from which an output signal of the amplifier 20 shown in FIG. 2 is applied. This output signal is digitized by a Φ converter (not shown). 'C is taken in. CPU
A key 203 for selecting the type of gas is connected to the key 202, and the CPU 202 receives and receives gas type data based on the operation of the key 203. CPU 202 has 1 display 2
04 is connected; based on the gas type data, the name of the gas can be displayed, for example, "]". Further, the CPU 202 is connected to the semiconductor switch S shown in FIG. 3 from the boat 205. - Outputs a switching digital signal of StS. CPU20
2 is connected to a storage unit 206 in which a memory table of correction data corresponding to each gas is stored. The correction data in the memory table is set to 5 so that the name of the gas can be extracted as an index, and is a correspondence table of voltages to be corrected corresponding to each voltage. Such a correspondence table is based on the assumption that one gas corresponds to one CF in the amplifying means IO shown in FIG. Tsumashi, C
The table for F is experimentally as shown in Table 1 below. Table 1: Table 1. However, to be precise, sensor sensitivity changes depending on the mass flow rate even for the same gas, so the amplification factor of the variable gain amplifier Zoo is changed depending on the output voltage of the amplifier 20 in Fig. 2. Must be. For example, the CF of a certain gas is Q, 60, and the variable gain amplifier Zoo. Assume that the rate of increase is α60. This is amplifier 2 in Figure 2.
Yes when the output of 0 is xV, 0.6 at (g+l)V
5, Cz+2)V, there is a gas whose amplification factor must be changed, such as 0.655. Therefore, in this example,
Experiment in advance to determine the rate of increase corresponding to voltage changes.
It is stored in a memory table in the storage unit 206. The CPU 202 extracts data on the voltage value to be corrected from the corresponding voltage value in the memory table in response to the digital data based on the signal from the input terminal 201, and based on this data, the CPU 202 outputs data from the semiconductor switch 5t-205 to the voltage value to be corrected.
Outputs a switching digital signal of F%g. As a result, the semiconductor switches S and -Su are switched in the variable gain amplifier Zoo, and the necessary increase a! The flow rate data outputted from the amplifying means 10 is amplified by the linearity characteristic due to the change in voltage. In this embodiment, although not shown, semiconductor switches S, - are sent from the boat 205 so that one CF is simply selected for the gas selected by the key 203, and the CPU 202 makes corrections based on this selection. A switching digital signal of S□ may be output. In this case, if the operator has memorized the CF, there is no need to take the trouble of searching for the CF from a conversion table such as Table 1. For example, one mass flow rate controller can be used to control the flow rate of any gas with simple operations. Therefore, no complicated work is required during production, and the number of work steps can be reduced. Moreover, the user can make adjustments when necessary to obtain a dedicated mass flow controller for the desired gas, which is extremely convenient.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a schematic diagram of main parts of an embodiment of the invention, Fig. 3 is a perspective view of the external appearance of an embodiment of the invention, and Fig. 4 is a schematic diagram of an embodiment of the invention. FIG. 7 is a block diagram of a receiver according to another embodiment of the present invention.

Claims (2)

[Claims] (1) A thermal sensor installed to take out a temperature signal of the gas in the flow path, and an amplification means for amplifying and outputting the temperature signal taken out by the thermal sensor based on correction data given corresponding to the type of gas. and comparing the flow rate data output from the amplifying means with the set flow rate data, and controlling the mass flow rate of the gas by adjusting the opening degree of the valve using a valve drive signal based on the comparison result. A mass flow controller featuring: (2) A patent claim characterized in that the amplifying means has correction data for amplifying each of the plurality of gases so that the signal based on the temperature signal taken out by the thermal sensor becomes a signal with a predetermined value. The mass flow controller according to the range (1).