JP4027470B2 - Mass flow controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mass flow controller such as a mass flow controller for controlling a fluid flow rate and a mass flow meter for measuring a fluid flow rate, and more particularly, a mass for measuring a mass flow rate by a thermal method using a sensor element such as a self-heating resistor. The present invention relates to a flow control device.
[0002]
[Prior art]
A mass flow controller such as the mass flow controller is widely used in various fields for semiconductor manufacturing apparatuses and the like. FIG. 6 schematically shows a conventional mass flow controller. In this figure, 1 is a main body block, 2 and 3 are fluid introduction joints and fluid lead-out joints connected to both ends of the main body block 1. . 4 is a fluid flow path formed between the fluid inlet 2a and the fluid outlet 3a, and is provided with a sensor unit 5 for measuring the fluid flow rate and a control valve unit 6 for controlling the flow rate.
[0003]
The sensor unit 5 is provided between a measurement flow channel inlet 7 and a measurement flow channel outlet 8 opened so as to face the fluid flow channel 4, and is provided on the upper surface of the main body block 1 via a seal mechanism 9. Self-heating resistors (two thermal mass flow sensor elements) are formed in a flat sensor flow path portion 11a on the upper portion of the sensor tube 11 made of, for example, a thin capillary tube (capillary) formed in an inverted U shape so as to pass through Hereinafter, the sensor elements 12 and 13 are simply wound around, and the sensor elements 12 and 13 are connected to a bridge circuit (not shown). Reference numeral 14 denotes a heat insulating cover that covers the sensor tube 11 and the sensor elements 12 and 13.
[0004]
Reference numeral 15 denotes a bypass portion formed in the fluid flow path 4 in parallel with the sensor portion 5, and a laminar flow element 16 having a constant flow ratio characteristic is provided.
[0005]
The control valve unit 6 is configured as follows. That is, a valve block 20 including a valve port 17, a valve body 18 that opens and closes the valve port 17, and a diaphragm 19 provided around the lower end of the valve port 17 is provided in the fluid flow path 4 on the downstream side of the bypass unit 15. ing. Above the valve block 20, a piezo stack 21 as a valve actuator that presses and drives the valve body 18 downward is provided in a state of being accommodated in a cylindrical valve case 22 erected on the valve block 20. It has been. Reference numeral 23 denotes a metal sphere for transmitting the output of the piezo stack 21 to the valve body 18.
[0006]
In the mass flow controller configured as described above, for example, the gas G flowing from the fluid inlet 2 a is divided into the sensor unit 5 and the bypass unit 15. The sensor unit 5 captures a temperature change proportional to the mass flow rate of the gas G and converts it into an electrical signal by a bridge circuit. This signal is output through an amplifier circuit (not shown) and a correction circuit (not shown). The signal is input to a proportional control circuit (not shown). The proportional control circuit receives a flow rate setting signal from the outside, compares the flow rate output signal with the flow rate setting signal, and sends the difference signal to a valve drive circuit (not shown). With this control signal, the control valve section 6 operates so that the difference signal becomes zero, and the flow rate is always controlled to be set.
[0007]
By the way, the mass flow controller having the above configuration is a sensor in which two sensor elements 12 and 13 are wound as shown in FIG. 7 due to the downsizing of the semiconductor manufacturing apparatus and the configuration of the piping system or the installation space. It may be necessary to install the sensor unit 5 in a vertical posture so that the flow path part 11a (part parallel to the bypass part 15) is vertical. Installation of the mass flow controller in this way is called Z-direction installation.
[0008]
And
(1) A mass flow controller is installed in the Z direction.
(2) A gas having a large molecular weight is flowed.
(3) The primary pressure of the gas is high.
When these conditions overlap, the zero point of the mass flow controller changes. This phenomenon is generally called a thermal siphon phenomenon.
[0009]
The cause of the occurrence of the thermal siphon phenomenon will be described with reference to FIG. 7. The gas G heated by the sensor elements 12 and 13 rises in the direction of the arrow A in the sensor flow path portion 11 a of the sensor tube 11, A gas circulation flow is generated in which the gas is cooled by the bypass portion 15 and descends in the direction of arrow B and returns to the sensor elements 12 and 13 again. Therefore, when the mass flow controller is mounted so that the gas inlet 2a of the mass flow controller is located downward, the gas G flows in the forward direction in the sensor tube 11 and a positive output is generated. When the mouth 2a is at the upper side, a negative output is generated.
[0010]
The thermal siphon phenomenon occurs only when the mass flow controller is installed in the Z direction, and does not occur when the mass flow controller is installed in any other state (posture).
[0011]
As a technique to avoid the thermal siphon phenomenon as described above,
a. The inner diameter of the sensor tube 11 is reduced.
b. The flow path in the sensor unit 5 is changed.
Etc. have been tried.
[0012]
However, even with the above method a, the thermal siphon phenomenon cannot be completely prevented, and there is a problem that clogging is likely to occur when the sensor tube 11 is thinned. In addition, when the method b is used, it is necessary to modify the sensor elements 12 and 13 themselves, and the flow characteristics such as the conversion factor (C.F.) are changed, which increases the cost. Time is needed.
[0013]
In addition, the above-mentioned subject has arisen similarly also in the mass flow meter comprised by removing the control valve part 6 from the structure of a mass flow controller.
[0014]
The present invention has been made in consideration of the above-mentioned matters, and its purpose is to prevent the occurrence of a thermal siphon phenomenon caused by the mounting posture, and to accurately control the mass flow rate of the fluid regardless of the mounting posture. The object is to provide a mass flow controller capable of detection.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a bypass unit for bypassing a fluid and a sensor unit for measuring a fluid flow rate are provided in parallel between a fluid inlet and a fluid outlet formed in the main body block. In the mass flow control device provided, the upper end is connected to the upstream opening of the sensor tube held by the sensor unit and the lower end is connected to the upstream opening on the main body block side between the sensor unit and the main body block. Direction flow path and a flow path that is parallel to the flow path provided with the sensor element in the sensor unit , the upper end is connected to the downstream side of the sensor unit, and the lower end is connected to the downstream side of the main body block side provided with a heater for heating the parallel flow path to the same extent as the amount of heat generated in the sensor unit is provided, further, the parallel flow path and a flow path which the sensor element is provided in the sensor unit The gas flow generated by be fit is arranged so as to cancel the gas flow generated by the heater, and forms a straight channel parallel flow path and the heater in one of the block body, the body of the block body It is detachably interposed between the block and the sensor unit.
[0016]
In the mass flow control device having the above configuration, it is possible to prevent the occurrence of the thermal siphon phenomenon regardless of the mounting posture, and therefore, the zero point fluctuation due to the thermal siphon phenomenon does not occur. Regardless of the method, the mass flow rate can be accurately detected.
[0017]
And in the said mass flow control apparatus, it is not necessary to change or modify the structure of sensor part itself, and there exists an advantage that the conventional sensor part can be used as it is.
[0018]
Further, since the mechanism for canceling the thermal siphon phenomenon can be detachably attached to the mass flow control device, the mechanism need only be attached only when the mass flow control device is attached in the Z-direction posture.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the invention will be described with reference to the drawings. In the following drawings, the same reference numerals as those shown in FIGS. 6 and 7 are the same.
[0020]
1 to 3 show one embodiment of the present invention. 1 and 2, in 24 block body is freely interposed removably sandwiched state between the body block 1 and the sensor block 10 (hereinafter, referred to as flow Michibu lock), the flow Michibu lock 24 For example, like the main body block 1, it consists of stainless steel.
[0021]
Said flow Michibu lock 24, as shown in FIG. 2, therein, the upper end is contiguous with the upstream side of the opening 11b of the sensor tube 11 held on the sensor block 10, the lower end of the body block 1 side upstream opening 7 is formed, and a linear flow path 25 in the vertical direction that is continuous with 7 and a bent flow path 26 that is connected with the opening 11 c on the downstream side of the sensor tube 11 and with the downstream opening 8 on the main body block 1 side at the lower end. A heater 27 is provided.
[0022]
As shown in FIG. 3, the bent channel 26 is continuous with the opening 11 c, a channel 26 a parallel to the linear channel 25, and a downstream side of the channel 26 a 90 toward the linear channel 25. The flow path 26b formed to be bent and parallel to the sensor flow path portion 11a provided with the sensor elements 12 and 13 of the sensor tube 11, and the downstream side of the flow path 26b is bent 90 ° downward. A flow path 26c formed so as to be parallel to the straight flow path 25, and a downstream side of the flow path 26c bend 90 ° in a direction away from the straight flow path 25 so as to be parallel to the flow path 26b. The formed flow path 26d and a flow path 26e which is bent 90 ° downward on the downstream side of the flow path 26d and is parallel to the linear flow path 25 and connected to the opening 8 are formed.
[0023]
The heater 27 is provided, for example, so as to be screwed into a hole 28 provided along the parallel flow path 26 b close to the sensor flow path portion 11 a of the bent flow path 26. The heater 27 is turned on and off by a control device (not shown) so as to adjust the amount of heat generated so as to heat the parallel flow path 26b to the same extent as the amount of heat generated by the sensor elements 12 and 13.
[0024]
Then, the flow Michibu lock 24 is provided in a state of being sandwiched inches and the body block 1 and the sensor block 10, the seal member 29 is interposed between them 1,10 and.
[0025]
When the mass flow controller having the above configuration is installed in the Z-direction posture, that is, when the sensor unit 5 is installed in a vertical posture so that the sensor flow path portion 11a of the sensor tube 11 is vertical, The heater 27 is caused to generate heat. Due to the heat generated by the heater 27, a rising gas flow C is generated as shown by the phantom line C in FIG. For this reason, the rising gas flow A generated by being warmed by the sensor elements 12 and 13 is canceled out by the rising gas flow C generated by the heater heating, and does not reach the bypass portion 15, so that gas circulation does not occur. . That is, the heater 27 may generate heat so as to generate the rising gas flow C necessary for canceling the rising gas flow A.
[0026]
Therefore, even if the conditions (1) to (3) overlap, the thermal siphon phenomenon does not occur, the zero point of the mass flow controller does not fluctuate, and the gas mass flow rate can be detected accurately. it can.
[0027]
Then, in this embodiment, the mechanism for canceling the thermal siphon effect, since the provided freely flow Michibu lock 24 detachable from the main body block 1 and the sensor block 10, the mass flow controllers Z only when installing in the direction and orientation, the flow Michibu lock 24 need only mount between the body block 1 and the sensor block 10.
[0028]
Then, when the mounting of the flow Michibu lock 24 in the configuration of the sensor unit 5, in particular, the sensor element 12, 13 can be used as a sensor element which is provided in the mass flow controller this type of conventional, There is no change in the flow characteristics such as the conversion factor, and there is no extra cost for modification, which is highly desirable for the user.
[0029]
The present invention is not limited to the above-described embodiment, and can be implemented with various modifications. For example, as a heater for heating the parallel flow path 26b, as shown in FIG. it may be provided at a predetermined point Michibu lock 24 flow heater 31.
[0030]
Further, in the above embodiments, but to form a linear flow path 25 and the bent flow path 26 to flow Michibu lock 24, instead of this, as shown in FIG. 5, the body block 1 The flow passages 25 and 26 are formed of stainless steel pipes in a U-shaped stainless steel block body 32 having contact surfaces 32a and 32b respectively corresponding to the sensor block 10, and the parallel flow of the pipe 26 '. The heater 30 may be wound around the outer periphery of the path 26'b. In FIG. 5, the numbers with “′” indicate members corresponding to the numbers 25 and 26 with no symbols.
[0031]
The operational effects of the embodiment shown in FIGS. 4 and 5 are the same as those of the embodiment shown in FIGS.
[0032]
Needless to say, the present invention is not limited to the mass flow controller described above, and can be similarly applied to a mass flow meter configured by removing the control valve unit 6 from the configuration of the mass flow controller.
[0033]
【The invention's effect】
According to the mass flow control device of the present invention, it is possible to reliably prevent the thermal siphon phenomenon due to the mounting posture and the like, and it is possible to eliminate the zero point shift caused by the thermal siphon phenomenon. Therefore, it is possible to accurately detect the fluid, particularly the gas mass flow rate, regardless of the attitude of the mass flow control device.
[0034]
According to the present invention, it is not necessary to change the configuration of the sensor unit such as the sensor element, and it is only necessary to make a slight improvement to the conventional mass flow rate control device, which gives an extra burden on the user side. There is nothing.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a mass flow control device according to one embodiment of the present invention.
2 is an exploded perspective view showing the mass flow controller to incorporated flow Michibu locking configuration near.
Figure 3 is an enlarged view showing the flow Michibu locking vicinity.
4 is an exploded perspective view showing the configuration of a flow Michibu lock the vicinity of the other embodiments.
[5] In addition, a perspective view showing a configuration of a flow Michibu lock according to another embodiment.
FIG. 6 is a longitudinal sectional view showing a conventional mass flow control device.
FIG. 7 is a diagram for explaining a problem to be solved by the invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Main body block, 2a ... Fluid inlet, 3a ... Fluid outlet, 5 ... Sensor part, 11a ... Sensor flow path part, 12, 13 ... Sensor element, 15 ... Bypass part, 24, 32 ... Block body, 26b ... Parallel flow Road, 26 '... pipe, 27, 31, 33 ... heater.

Claims (2)

In the mass flow control device, a bypass unit for bypassing the fluid and a sensor unit for measuring the flow rate of the fluid are provided in parallel between the fluid inlet and the fluid outlet formed in the main body block. Between the sensor block and the main body block , the upper end is connected to the upstream opening of the sensor tube held by the sensor section, and the lower end is connected to the main body block side upstream opening, includes a channel sensor element is parallel to the flow path provided, the sensor together with the parallel flow path upper end lower end contiguous with the downstream side of the sensor portion is provided with a curved flow path communicating with the downstream side of the main body block side A heater for heating to the same extent as the amount of heat generated in the section is provided, and the flow path in which the sensor element is provided and the parallel flow path are configured to reduce the gas flow generated by being heated in the sensor section It is arranged to cancel the gas flow generated by the motor heat, and a straight channel parallel flow paths and the heater is formed in one of the block body, detachable the block body between the main body block and the sensor unit A mass flow control device characterized by being freely inserted.   The mass flow rate control device according to claim 1, wherein the parallel flow path is formed by a pipe, and a heater is provided on an outer periphery of the pipe.

Images