JPS596429B2 - Time constant conversion device used in pneumatic instruments - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time constant converting device used in a pneumatic meter, which is suitable for changing the time constant of a meter having particularly low rangeability over a short period of time.

For example, if the distance to the controlled object is long and the pipe for transmitting the air signal becomes long, it is necessary to compensate for the delay in signal arrival due to this.

Therefore, conventionally, an air signal transmission compensator having a differential operation function has been used to compensate for the delay due to the length of the piping.

However, in this case, the needle valve used as a time constant changing means requires extremely advanced processing and assembly technology, and the air used must be extremely clean or even the slightest amount of dirt can cause it to go awry. Such inconveniences are likely to occur.

Moreover, since the needle valve adjusts a minute gap, great care must be taken in its operation.

Therefore, the inventor of the present invention previously proposed a time constant conversion device as shown in FIG. 1 to solve the above-mentioned drawbacks.

That is, a cylinder 2 is formed in the upper part of the inside of the casing 1, and a calculation section 3 is provided in the lower part, and a piston 4 that can be raised and lowered is fitted in the cylinder 2, so that the volume of one chamber 5 can be changed. It is like that.

6 is an 0 ring, and 7 is an operating rod. This operating rod can set the piston 4 to a desired position by rotating a knob (not shown), and this position is fixed so as not to be changed only by the pressure inside the cylinder.

8 is a fluid restrictor provided in the branch path 9.

In addition, here, 9 functions as an input hole and 18 functions as an output hole for the chamber 5.

On the other hand, the calculation unit indicated by the reference numeral 3 is composed of a large diaphragm 10, a small diaphragm 11, a connecting rod 12 that connects these two diaphragms, and a nozzle 13 facing the lower side of the small diaphragm 11.
Inside the casing are three chambers 14, 15 and 16.
are separated.

In such an element, the operation rod 7 is now operated to position the piston 4 and determine the volume of the chamber 5 as shown in the figure.

In this state, when external input pin is applied, diaphragm 10
is pushed down, and the nozzle 13 is closed via the connecting rod 12.

As a result, the feeding pressure Ps that was being fed from one port
Since the escape hole is limited, an external output Pout having a size corresponding to the Pin is discharged from the other port 17.

On the other hand, this Pout reaches the chamber 15 through the input hole 9, but since it is communicated with the chamber 5 which has a large capacity in addition to the aperture 8, it takes time for the chamber 15 to be filled with Pout. .

However, the pressure difference between the chambers 15 and 16 eventually decreases, pushing the diaphragm 10 upward.

After a sufficient period of time, each chamber 14, 16, 15 will maintain a constant pressure, and the position of the connecting rod 12 will be balanced.

However, when changing the time constant, the relatively large volume of the cylinder interior 5 is changed by operating the operating rod 7 to change the position of the piston 4, so the machining accuracy is not very high. It is not required, and the degree of contamination caused by the air used does not affect accuracy.

In addition, the operation does not require much precision, and since the volume inside the chamber 5 changes completely in proportion to the amount of elevation and descent of the piston 4, it has the advantage of being easy to operate intuitively.

However, in the above-mentioned device, due to the sag of the diaphragm 10 in the calculation section and the installation reasons, such as the presence of the connecting rod 12, a difference in area tends to occur between the front and back surfaces.
This difference has a disadvantage in that it adversely affects the one-to-one characteristics of input and output.

Furthermore, since the force for pushing up the diaphragm 11 must be entrusted to the supply pressure Ps, if a large amount of supply air cannot be obtained, there is also the inconvenience that a volume booster must be installed in the introduction path for the supply pressure Ps.

The present invention has been made to solve such problems, and details thereof will be explained below with reference to drawings showing one embodiment.

In FIG. 2, this time constant conversion device 20 includes a calculation unit 30.
and a variable capacitance section 50.

The arithmetic unit 30 has an upper plate 31 having one through hole 32 and a lower plate 33 having three through holes 34, 35, 36. A large-diameter bellows 37 is held between them.

An inward protrusion 38 is provided in the axial center of the bellows 37 .

A beam 39 is fitted and fixed to this protrusion 38 from the outside, and one end of this beam 39 is fixed to a pivoting spring 41 implanted in a column 40.

A flapper 42 as a movable part for detecting displacement of the bellows 37 is fixed to the other end of the beam 39.

An air injection nozzle 43 is disposed below this flapper 42, and this nozzle 43 communicates with one through hole 34 formed in the lower plate 33.

A partition member 44 is fixedly engaged with the protrusion 38 of the bellows 37 in the middle part of the bellows 37, dividing the space inside the bellows 37 into upper and lower halves, and forming a first pressure chamber 45 and a second pressure chamber 4.
The first pressure chamber 45 communicates with the through hole 32 of the upper plate 31, and the second pressure chamber 46 communicates with the through hole 36 of the lower plate 33.

Furthermore, by interposing a small-diameter bellows 48 between the partition member 44 and the seat 47 screwed onto the lower plate 33, a third pressure chamber 49 is formed within the second pressure chamber 46. This chamber 49 communicates with the through hole 35 .

The variable capacity section 50 includes a cylinder 52 in the cylinder case 51 so that the capacity of the internal space can be changed from the outside.
is slidably inserted.

53 is a lid with a screw hole, 54 is its fixing screw, 55
is a threaded rod for sliding the piston 52, and 56 is its lock nut.

A flat head 57 is formed at the inner end of the sliding threaded rod 55, and this head 57 is buried in a recess provided in the piston 52 and fixed with a plate 58, but is rotatable. ing.

A hole 60 is formed in the cylinder 51 to communicate the internal chamber 59 with the outside.

Regarding the air circuit of the calculation section 30 and the variable capacity section 50, a pipe 61 is connected to the through hole 32 of the upper plate 31, and the input signal pressure Pi is introduced to the first pressure chamber 45 through the pipe 61. It will be destroyed.

A pipe 62 is connected to the through hole 34 , and the pipe 62 supplies pressure Ps to the nozzle 43 via a throttle 63 .

A piping 64 is connected to the through hole 35, and a piping 65 is connected to the piping 64, and these piping 64 for output extraction,
65 leads out the output Po from the third pressure chamber 49.

The piping 62 and the piping 64 are connected by a piping 66, and a pilot relay 67 as an amplifier is inserted in the piping 66.

A pipe 68 is connected to the through hole 36 that communicates with the second pressure chamber 45b, and pressure Pd is guided to the second pressure chamber 46.

A throttle 70 is inserted into a pipe 69 that connects this pipe 68 and the pipe 64.

Further, the above-mentioned 68 and the through hole 60 of the cylinder case 51 are connected by a pipe 71.

Next, the operation of this embodiment configured as above will be explained.

First, the input pressure Pi enters the first pressure chamber 45 above the bellows 37 through the through hole 32 and displaces the beam 39 up and down using the spring 41 as a fulcrum.

This displacement of the beam 39 is detected by the nozzle 43,
Change that back pressure.

This back pressure is amplified by the pilot relay 67, and its output enters the small-diameter bellows 48. At the same time, a delay element is set according to the purpose, that is, if the time constant is T, the chamber 59
The pressure is returned to the second pressure chamber 46 of the large-diameter bellows 37 as a delayed pressure Pd through the throttle 70, which serves as a delay element with a time constant T2CR determined by the capacitance C and the resistance R of the throttle 70.

Therefore, initially P. \Pd, but after a certain period of time, the pressures inside and outside the bellows 37 become Po2Pd and become equal.

The time difference during this time can be calculated using the general formula Td=
It is determined by Kd-T (Kd is a differential gain), and in the present invention is determined by manipulating the cylinder internal capacity C, and this directly becomes the compensation time when transmitting the air signal.

For example, when the step human power Pi is given, the output Po
The characteristic is known as the characteristic of general proportional differential operation.

However, when this is used as a transmission compensation device, the proportionality constant Kd can be correctly given as 1 in the present invention.

That is, in response to the step input Pi, the graph shows a rise of Kd·Pi and then approaches Pi with the customization of P i (Kd-1)expd (-it), as shown in FIG. 3.

d Note that it is clear from both equations that the curve of y(t) is determined by the π stone, that is, the time constant T (time until the curve reaches 63.2% of the final output).

Next, an embodiment of the diaphragm indicated by reference numeral 70 in FIG. 2 will be shown as shown in FIGS. 4A and 4B.

That is, one screw 73 among the screws for attaching the lid 53
A bushing 74 is driven into the lower hole, and a throttling screw 75 is screwed into the bushing 74, so that the flow path resistance is determined by the screwing depth, and the amount of air flowing through can be adjusted.

Such a diaphragm requires various measures to prevent it from being easily operated after it is set to a certain aperture value, but according to the present invention, no special measures are required since it is not exposed to the outside.

This throttle improves the space efficiency at the end of the cylinder by providing it in the pilot hole of the screw, but it is not limited to this as long as it is a part that is hidden by the lid.

Note that 72 is a through hole directly connected to the piping 64 shown in FIG. 2, and the throttle 70 in this case is the throttle screw 7 described above.
Consisting of a screw depth of 5.

As explained above, according to the present invention, since the two pressure chambers are formed by one bellows partitioned in the center, the difference in effective area of the surface pressure chambers can be ignored, and the input/output of the time constant conversion device can be ignored. It has the advantage that the one-to-one characteristic of can be obtained without adjustment.

Further, if the supply pressure Ps cannot be sufficiently obtained, if the output of the pilot relay is configured to be given to the internal bellows or delay element, there is no need to use a volume booster.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view illustrating a conventional structure. FIG. 2 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 3 is a diagram showing output characteristics, and FIGS. 4A and 4B are a longitudinal sectional view and a front view of a variable capacitance section. 20... Time constant conversion device, 30... Arithmetic unit, 32.34, 35, 36... Through hole, 37
...Large diameter bellows, 39...Beam,
41... Pivoting spring, 42...
・Flapper, 43... Nozzle, 44...
Partition member, 45...First pressure chamber, 46...
...Second pressure chamber, 48...Small diameter bellows, 49...Third pressure chamber, 50...Variable displacement cylinder, 51...・Cylinder case,
52...Piston, 60...Through hole, 6L62, 64, 65゜66.68, 69.71...
...Piping, 63,70...Aperture, 67...
...Pilot relay, 75...Adjustment screw, Pi...Input pressure signal, Po...
Output pressure, Ps... Supply pressure, Pd...
・Lag pressure.

Claims (1)

[Claims] Eleven large-diameter bellows 37 and a first and second pressure chamber 45, 4 partitioning the axial center of the bellows 37.
a small-diameter bellows 48 having one end connected to the partition member 44 to form a third pressure chamber 49 within the second pressure chamber 46;
an inlet 32 provided in the pressure chamber 45 for introducing the input signal pressure Pi, and a partition member 44 of the large-diameter bellows 37.
an air injection nozzle 43 that detects the displacement of the movable part 42 that moves integrally with the air injection nozzle 43; and an air circuit 34, 35 that distributes the back pressure of this nozzle 43 to the second and third pressure chambers 46, 49.
36, 62, 64, 66° 68.69, and a throttle 70 interposed in series with the air circuit 69 to the second pressure chamber 46;
A variable capacity cylinder 50 is connected to the second pressure chamber 46 through air circuits 36, 60, 68, and 71, and an air circuit 35 for taking out the output Po is connected to the third pressure chamber 49.
, 64.65 A time constant conversion device used in a pneumatic instrument. 2 The throttle 70 is connected to the cylinder case 51 of the cylinder 50.
A time constant conversion device for use in a pneumatic instrument according to claim 1, which is formed by a gap between a screw hole provided in the screw hole and a screw 75 screwed into the screw hole so as to be able to move forward and backward. Thirty-one large-diameter bellows 37 and the axial center of the bellows 37 are partitioned into first and second pressure chambers 45.4.
a small-diameter bellows 48 having one end connected to the partition member 44 to form a third pressure chamber 49 within the second pressure chamber 46;
an air injection nozzle 43 that detects the displacement of the movable part 42 that moves integrally with the partition member 44 of the large-diameter bellows 37; The back pressure of pilot relay 6
7 to said second and third pressure chambers 46.49;
68, 69, a throttle 70 interposed in series with the air circuit 69 to the second pressure chamber 46, and a variable capacity connected to the air circuit 36° 60, 68, 71 to the second pressure chamber 46. A time constant conversion device used in a pneumatic instrument, comprising a shaped cylinder 50 and an air circuit 35, 64, 65 for taking out the output PO connected to the third pressure chamber 49.