JPH06110557A - Mass flow controller - Google Patents

Abstract

PURPOSE:To facilitate package and to improve reliability by mutually communicating required information between a device main body and an instrument part without interposing any exclusive communication cable. CONSTITUTION:In order to set the fluid flow rate of a main body 20 of the device, a flow rate set value is inputted by an input setter 17 and modulated by a modulation circuit 50 and afterwards, a radio wave is transmitted through an antenna 51. This radio wave is inputted through an antenna 30 of the device main body 20 to a reception circuit 26, demodulated by a demodulation circuit 27, fetched into a valve control part 7 later, D/A-converted and turned to a flow rate setting signal (b). On the other hand, information to be detected in the main body 20, for example, a flow rate detecting signal (a) obtained in the valve control part 7, is sent to a modulation circuit 25 and modulated and afterwards, a radio wave is oscillated through the antenna 30. This radio wave is inputted through the antenna 51 of the instrument part 40 to a reception circuit 41. Afterwards, this radio wave is inputted through the antenna 51 of the instrument part 40 to the reception circuit 41 and demodulated by a demodulation circuit 42, and a detected flow rate value is displayed on an instrument 18 after the D/A conversion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flow controller for controlling the flow rate of fluid such as gas or liquid.

[0002]

2. Description of the Related Art For example, when various gases used for manufacturing semiconductors are supplied to a semiconductor manufacturing apparatus, a mass flow controller (hereinafter referred to as MFC) is provided in each of the supply flow paths to adjust the gas flow rate. is doing.

FIG. 2 is a block diagram schematically showing the structure of a conventional MFC. In FIG. 2, reference numeral 1 denotes a main body device of a mass flow controller. In the main body 1 of the device, a fluid F such as gas is indicated by an arrow, for example. A fluid flow path 2 that flows in the direction is formed. Reference numerals 3 and 4 denote inlets and outlets of the fluid F, which are connected to pipes (not shown). Reference numeral 5 denotes a flow rate sensor portion provided so as to face the fluid flow path 2, and although not shown in detail, for example, a pair of heat-sensitive resistors are appropriately used as a flow rate sensor in a measurement flow path connected in parallel to the fluid flow path 2. It is configured by winding at intervals.

Reference numeral 6 is a control valve provided so as to face the fluid flow passage 2 on the downstream side of the flow rate sensor portion, and although not shown in detail, for example, the opening degree of the orifice formed in the fluid flow passage 2 is piezo-stacked. It is configured so that it can be arbitrarily adjusted from a closed state to an open state by a valve element driven by an actuator such as.

Reference numeral 7 denotes a valve control unit, which is composed of, for example, a one-chip microcomputer, is provided in the apparatus main body 1 together with the flow rate sensor unit 5 and the control valve 6, and is configured as follows, for example. That is, 8 is a bridge circuit in which the flow rate sensor is a part of the constituent members, and is configured to output an electrical flow rate detection signal a corresponding to the instantaneous flow rate Q of the fluid F flowing in the fluid flow path 2. There is. Reference numeral 9 denotes a comparison (error detection) unit, which detects a flow rate detection signal a and a signal cable 10 and an input / output from an instrument unit 15 (described later) which is separate from the apparatus main body 1.
The output terminal portion 11 is opened and compared with a flow rate setting signal b provided thereto, and a difference signal ε (= b−a) thereof is output.

Reference numeral 12 is an arithmetic control unit for performing, for example, PID control, which uses the difference signal ε from the comparison unit 9 and preset control constants for P, I, D, etc., for example, as shown below. By the following equation, V = ε · P + I∫ε · dt + Ddε / dt is calculated, and the control information V obtained thereby is output. That is, the difference signal ε
However, if ε <0, the signal V for driving the control valve 6 in the closing direction is given, and if ε> 0, the signal V for driving the control valve 6 in the opening direction is given by the valve driving unit 13 (described later).
Is output to.

Reference numeral 13 is a valve drive unit, which is the arithmetic control unit 1
The valve drive signal W is applied to the control valve 6 based on the control information V from 2 to drive the control valve 6. Reference numeral 14 is a power cable for supplying electric power from the instrument unit 15 to the apparatus main body 1, and the input / output terminal unit 1
Connected to 1.

Reference numeral 15 is an instrument portion, inside which a circuit and a memory for signal processing are provided, while the surface thereof is
A power supply on / off switch 16, a dial 17 for setting the flow rate setting signal b, and the like, and a display section 18 for displaying the values of various detection signals obtained in the apparatus body 1 including the flow rate detection signal are formed. .

Therefore, according to the MFC configured as described above, the flow rate detection signal a from the flow rate sensor section 5 and the flow rate setting signal b are compared in the comparison section 9, and the difference output from the comparison section 9 is compared. The opening degree of the control valve 6 can be controlled based on the control information V obtained by processing the signal ε, whereby the flow rate of the fluid F can be adjusted and the fluid flow rate at that time can be known. You can

In such a configuration, for example, by centrally arranging a plurality of MFC instrument units 15 in a central control unit or the like, it is possible to collectively set and monitor the flow rate for each MFC. That is the advantage.

[0011]

However, in the mass flow controller having the above structure, the apparatus main body 1 and the instrument portion 15 are connected by the signal cable 10.
There is a drawback that the wiring structure becomes complicated. Also,
Since the signal cable 10 needs to be routed around, the mounting is very troublesome, and there is a problem that the cost is increased accordingly.

The present invention has been made in consideration of the above matters, and an object thereof is to provide a highly reliable mass flow system which does not require a signal cable to be routed between the apparatus main body and the instrument unit. To get the controller.

[0013]

In order to achieve the above object, a mass flow controller according to the present invention modulates control information from an instrument unit and then transmits the modulated control information to the apparatus main body, and the result detected by the apparatus main body. Is transmitted to the instrument unit after being modulated, and can be communicated with each other without using a dedicated communication cable.

As the communication method, any one of radio waves, electromagnetic induction, light and ultrasonic waves can be used as the information transmission medium. Further, information may be placed on a carrier wave, the carrier wave may be placed on a power cable, or if the pipe through which the fluid flows is made of metal, the carrier wave may be placed on the metal pipe. When the information is carried on the carrier wave, one of the power supply lines may be shared with the metal pipe.

[0015]

In the mass flow controller having the above-described structure, it is possible to communicate with each other without using a dedicated communication cable. Therefore, it is necessary to circulate the communication cable like the conventional mass flow controller of this type. And a mass flow controller with high reliability can be obtained at low cost.

[0016]

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

FIG. 1 is a block diagram schematically showing the structure of an MFC according to the present invention. In this figure, 20 is a main body of the apparatus and 40 is an instrument unit. Further, in this embodiment, it is assumed that one instrument unit 40 common to the plurality of device main bodies 20 is provided.

The apparatus main body 20 is substantially the same as the apparatus main body 1 shown in FIG. 2 and includes a flow rate sensor section 5, a control valve 6 and a valve control section 7 including a one-chip microcomputer. , The valve control unit 7 is A
It has a D conversion function and a DA conversion function.

The device body 20 is provided with the following members. That is, 21 is an address code, 22 is an encoder, 23 is a radio frequency transmission circuit provided with a crystal oscillator 24, and 25 is a modulation circuit. Also,
26 is a receiving circuit, 27 is a demodulation circuit, 28 is an address selector, 29 is a decoder, and 30 is an antenna.

On the other hand, the instrument section 40 has the following members in addition to the basic functions of the instrument body 15 shown in FIG. That is, 41 is a receiving circuit, 42 is a demodulation circuit, 43 is an address selector, 44 is a decoder, and 45 is a DA conversion circuit. 46 is an address code, 47 is an encoder, 48 is a radio frequency transmission circuit including a crystal oscillator 49, 50 is a modulation circuit, and 51 is an antenna.

In the mass flow controller configured as described above, in order to set the fluid flow rate in the apparatus main body 20, the flow rate set value is input by an input setting device such as a dial. In this case, since a plurality of device main bodies 20 are controlled by one instrument unit 40, in order to specify which device main body 20 the flow rate set value is,
The address code is added to the flow rate setting value signal. In this way, the flow rate setting value signal to which the address code is added is modulated in the modulation circuit 50 and then transmitted as a radio wave via the antenna 51.

The transmitted radio wave is input to the receiving circuit 26 via the antenna 30 of the apparatus body 20. afterwards,
This radio wave is demodulated by the demodulation circuit 27 and then the decoder 2
After being decoded in 9, it is taken in by the valve control unit 7,
DA converted. This DA-converted signal becomes the flow rate setting signal b (see FIG. 2).

On the other hand, various information including the fluid flow rate detected in the apparatus main body 20 is transmitted to the instrument unit 40 side as follows. For example, the flow rate detection signal a (see FIG. 2) obtained by the valve control unit 7 is the encoder 2
At 2, the address code is added and sent to the modulation circuit 25 for modulation, and then radio waves are transmitted through the antenna 30.

The transmitted radio wave is input to the receiving circuit 41 via the antenna 51 of the instrument unit 40. Thereafter, this radio wave is demodulated by the demodulation circuit 42 and then the decoder 44.
After being decoded by, the signal is DA converted by the DA conversion circuit 45 and displayed as a detected flow rate value on the meter 18 such as a meter. In the instrument unit 40, the detected flow rate value may be stored in the memory.

In the above embodiment, the control information from the instrument unit 40 to the device body 20 and the instrument unit 40 from the device body 20.
The information detected by the above is converted into a digital signal, modulated and then transmitted using radio waves. However, the present invention is not limited to this, and various modifications can be carried out. it can.

For example, one apparatus main body 20 and one instrument unit 40 may correspond to each other. Further, the n device main bodies 20 and the n instrument units 40 may be associated with each other.

Then, the control information and the detection information may be transmitted as analog signals. In addition to electromagnetic waves, electromagnetic induction or light may be adopted as the transmission medium that carries the information. When the range in which the device body 20 is provided is limited, it is convenient to use electromagnetic induction or light as the transmission medium.

In addition, ultrasonic waves may be used as a transmission medium, and further, the information may be carried as a carrier wave on a power cable, or if the pipe through which a fluid such as gas or liquid flows is made of metal, it may be carried on the carrier wave. You may In addition,
When the information is carried on the carrier wave, one of the power supply wirings may be shared with the metal pipe.

As the information modulation method, phase modulation (PM), frequency modulation (FM), amplitude modulation (AM),
Either pulse position modulation (PPM) or pulse width modulation (PDM) may be adopted.

In order to send and receive control information from the instrument unit 40 to the device body 20 and detection information from the device body 20 to the instrument unit 40 smoothly and reliably, the following functions A to D are provided. You may make it hold.

A. The apparatus main body 20 and the instrument unit 40 are provided with a memory function for storing information to be transmitted and received information. This is, for example, one device body 2
When configuring a mass flow controller with 0 and one instrument unit 40, it is possible to transmit and receive at the same time by changing the transmission frequency from the device body 20 side and the transmission frequency from the instrument unit 40. In the case where there are a plurality of both 20 and the instrument unit 40, such a method cannot be adopted because many frequencies are required.

Therefore, as described above, when there are a plurality of apparatus main bodies 20 and a plurality of instrument units 40, when a single transmission path is used, it is necessary to perform transmission and reception alternately in time division. Furthermore, in such a case, it is necessary to perform polling in both the apparatus main body 20 and the instrument unit 40.

B. The apparatus main body 20 and the instrument unit 40 are provided with the function of checking whether or not the received information has an error. This is because there are many things such as noise that cause an error during communication in the transmission path, and therefore, error detection is performed using a means such as a parity bit or a checksum.

C. When the received information has an error, the apparatus main body 20 and the instrument unit 40 are provided with a function of correcting the error. When an error is found by the function shown in B, a resend request is issued to the other party and the error is corrected.

D. Communication control function a. Function to detect free / busy of transmission line When trying to send, monitor the transmission line, judge whether communication is in progress, start transmission if not in use,
If it is in use, it waits for it to become available before transmission starts.

B. Function to detect collision Detects a collision by monitoring the transmission path while transmitting and comparing the transmitted data with the monitoring result.

C. Function to recover from collision When a collision is detected, immediately send jamming, notify the other MFC of the occurrence of the collision, and after a certain period of time has passed by a predetermined method, confirm the availability of the transmission path and then perform transmission. Of.

D. Function for simultaneous communication with all parties The address code for the unspecified number may be sent from the sending side and sent out, and the receiving side may fetch it.

As described above, although various embodiments can be considered in the present invention, the types of information transmitted and received are as follows.
Flow rate setting signal, valve forced opening / closing signal, flow rate output signal, various signals indicating the operating state of the apparatus main body 20, valve opening degree,
The temperature of each part in the apparatus main body 20, the voltage of each part, and the like. Also, control data and the like are transmitted and received in the digital control MFC.

[0040]

As described above, according to the present invention,
Necessary information can be communicated between the main unit and the instrument unit without using a dedicated communication cable, so there is no need to circulate the communication cable as with conventional mass flow controllers, and mounting is easy. become. Therefore, a highly reliable mass flow controller can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a mass flow controller according to the present invention.

FIG. 2 is a block diagram showing an example of a conventional mass flow controller.

[Explanation of symbols]

5 ... Flow rate sensor section, 6 ... Control valve, 7 ... Valve control section, 17 ... Setting means, 18 ... Display section, 20 ... Device body,
40 ... Instrument part.

Claims (1)

[Claims] 1. A flow rate sensor section for a flow path of a fluid, a control valve provided on the downstream side or upstream side of the flow rate sensor section, and a flow rate measurement signal and a flow rate setting signal from the flow rate sensor section. Comparing, the device main body having a valve control unit for controlling the opening degree of the control valve based on the comparison result, and the flow rate setting signal setting means together with the flow rate measurement signal is input. In a gas control system comprising an instrument unit having a display unit for displaying, the control information from the instrument unit is modulated and then transmitted to the device body, while the result detected in the device body is modulated, and then the instrument A mass flow controller, which is configured to be able to communicate with each other without a dedicated communication cable.