JPS6136501A - Valve positioner - Google Patents

Abstract

PURPOSE:To allow a pneumatic type adjusting valve to react with high speed by connecting the driving pressure chamber of the pneumatic type adjusting valve to an air pressure source or the atmosphere through a large-capacity air feeding valve, three-way selector valve driven through pulse-width modulation, and a large-capacity exhaust valve. CONSTITUTION:The driving-pressure chamber 101 of a pneumatic type adjusting valve 10 is connected to an air pressure source or the atmosphere through a three-way selector valve 14 driven by the pulse-width modulation signal. A large- capacity air feeding valve 16 and a large-capacity exhaust valve 18 are connected in parallel to the three-way selector valve 14, and the penumatic type adjusting valve 10 is driven by the air pressure signal pulse-modulated. When the deviation between an input signal and the displacement amount of the valve is large, the driving pressure chamber 101 of the pneumatic adjusting valve 10 is allowed to communicate to the air pressure source or the atmosphere through the large-capacity air feeding valve 16 and the large-capacity exhaust valve 18. Therefore, even if the deviation between the input signal and the displacement amount of the valve is large, the pneumatic adjusting valve 10 can react with high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a valve position used in a pneumatic control valve.

[Prior art]

A typical conventional valve position is to apply the (-) difference between the input signal and the amount of displacement of the valve to the nozzle/flapper as the amount of mechanical displacement, take out the nozzle back pressure of this nozzle/flapper as a pneumatic signal, and then It is configured to amplify the pressure with a pilot relay and supply it to the air motor of the control valve.

However, with such conventional valve positioners, it is difficult to respond at high speed when there is a large deviation between the input (No. 3) and the displacement of the valve.Especially when the capacity of the air motor is large, the air It was necessary to add a separate booster relay to the circuit to amplify the capacity of the pneumatic signal to support high-speed response.

Furthermore, as mentioned above, conventional valve positioners use nozzles, flappers, and pilot relays.
This nozzle flapper and pilot relay consume air even in a balanced state.

Specifically, in a valve positive system using a semi-bleed type pilot relay or a bleed type pilot relay, 5 to 15 NJ/mi-
air consumption.

Non-bleed pilot relays have traditionally been used as pilot relays that minimize air consumption in an equilibrium state, but air consumption is not zero, and air consumption at the nozzle is unavoidable. Type pilot relays have the disadvantage of poor response, so they are not used much in practice.

[Summary of the invention]

The present invention has been made in view of the above problems, and its purpose is to operate the control valve at high speed without using a booster relay even when the deviation between the input signal and the displacement amount of the valve is large. An object of the present invention is to provide a valve positioner that can respond to the following conditions.

Another object of the present invention is to provide a valve position valve that consumes zero air in an equilibrium state.

In order to achieve this object, the present invention pulse-width modulates a valve drive signal indicating the deviation between the input signal and the amount of displacement of the valve, and then converts it into a pneumatic pressure signal.
In addition to driving the control valve, when the deviation indicated by the valve drive signal is large, the driving pressure chamber of the pneumatic control valve is communicated with an air pressure source or the atmosphere, and when the deviation is close to zero, the valve positioner is A means for sealing the pressure within the drive pressure chamber is added.

Hereinafter, the present invention will be described in detail along with examples.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the valve positive screen of the present invention.

The pneumatic control valve 10 includes a driving pressure chamber 101 and a valve 102, and the opening and closing of the valve 102 is controlled by air pressure supplied to the driving pressure chamber 101.

An air pipe 12 is connected to the drive pressure chamber 101, and the other end of this air pipe 12 is connected to a three-way switching valve 14° and a large capacity air supply valve 1.
6 and a large capacity exhaust valve 18.

The three-way switching valve 14 is connected to an air pressure source (Ps) in addition to the air pipe 12.
It is connected to an air pipe 20 communicating with the vent and an air pipe 22 communicating with the atmosphere (Vent). Then, the connection between the air pipe 20 and the air pipe 12 and the connection between the air pipe 22 and the air pipe 1z are switched according to the signal from the pulse width modulator 24.

The large capacity air supply valve 16 receives the signal from the comparator 26.

The large-capacity exhaust valve 18 is an on/off switching valve that connects and disconnects the air pipe 20 and the air pipe 12. It is an off switching valve.

The valve lift detector 30 detects the position of the valve 102 and outputs a voltage value v1 according to the position, and can be configured with a rotary encoder, a drop meter, or the like.

The input module 32 is input from the input terminal 34
The input signal of ~20-A is converted into a voltage value v2, and this voltage value v2 is compared with the voltage value v1 from the valve lift detector 30 in the comparator 36.

The deviation between the voltage value v1 and the voltage value v2 represents the difference between the valve position indicated by the input signal and the actual valve position, and is used as a valve drive signal by the pulse width modulator 24. Input to comparator 26 and comparator 28.

As shown in the characteristic diagram of FIG.
(The valve drive signal C is pulse width modulated only when 11 is satisfied. The duty ratio when ε--61 is set to zero, the duty ratio when ξ-61 is set to 'IJ, (When formula 11 is satisfied, the relationship between 1 and the duty ratio is linear.

The waveform diagram in FIG. 3 shows the output waveform of the pulse width modulator 24 when the duty ratio is C-61, that is, 0.7 J, and 70% of the repetition period T is @H''.
Level, the remaining 30% is m L 1 lebel.

When the valve drive signal field satisfies 1-61 (2), the output of the pulse width modulator 24 becomes "L" level in binary decoding, and the valve drive signal 6 becomes e>δ. ! ...0), the output of the pulse width modulator 24 is "H" in the binary signal.
“It becomes a level.

The three-way switching valve 14 closes the opening of the air pipe 22 to connect the air pipe 20 and the air pipe 12 when the signal from the pulse width modulator 24 is at the "H" level, and closes the opening of the air pipe 22 to connect the air pipe 20 and the air pipe 12 when the signal is at the @L" level. The opening of the air pipe 20 is closed to establish communication between the air pipe 22 and the air pipe 12.

As shown in the characteristic diagram of FIG. 2 (CB), the comparator 26 outputs a binary output signal of When the output signal reaches the "L" level and satisfies the condition C δ2 . . . 1 (5), the binary output signal becomes the "L" level.

When the signal from the comparator 26 is at "H" level, the large-capacity air supply valve 16 opens the opening of the air pipe 20.
and the air pipe 12 are connected, the air pressure source (Ps) and the drive pressure chamber 101 of the pneumatic control valve 10 are connected, and the comparator 26
When the signal from the air pipe 20 is at the "L° level," the opening of the air pipe 20 is closed and the connection between the air pipe 20 and the air pipe 12 is severed.

In addition, as shown in the characteristic diagram of FIG. 2(C), the comparator 28 detects 2 When the value output signal is at the "H" level and the following is satisfied, the binary output signal is at the @L" level.

The signal from the comparator 28 of the Daigonj1m air valve 18 is “H”
At the level, the opening of the air pipe 22 is opened and the air pipe 22 and the air pipe 12 are connected, and the drive pressure chamber 101 of the pneumatic control valve IO communicates with the atmosphere (Vent), and the air pressure from the comparator 28 is When the signal is at the "L" level, the opening of the air pipe 22 is closed and the connection between the air pipe 22 and the air pipe 12 is severed.

Next, the operation of this embodiment will be explained.

The value of the valve drive signal - from the comparator 36 is 61 (Q<m
If l<61), the pulse width modulator 24 performs a pulse width modulation operation, and at the same time, the outputs of the comparators 26 and 28 both go to the 4L'' level.

That is, the large capacity air supply valve 16 and the large capacity exhaust valve 18 are both in a non-communicating state, and the drive pressure chamber 101 is communicated with the air pressure source (Ps) and the atmosphere (Vent) only through the three-way switching valve 14. .

Since the three-way switching valve 14 is currently driven by a pulse width modulation signal with a duty ratio of 0.7, the driving pressure chamber lO1
The air pipe 12 communicating with the air pipe 20, that is, the air pressure source (Ps) for 70% of the repetition period T,
0% of the time, the air pipe 22 is communicated with the atmosphere (Vent).

Therefore, air from the air pressure source (Ps) is gradually supplied to the driving pressure chamber 101, and the valve 102 is gradually displaced accordingly.

Assuming that the signal input to the input terminal 34 is constant, the valve drive signal 1 gradually approaches zero due to the displacement of the valve 102, and when it becomes 1-0, the output signal of the pulse width modulator 24 becomes The equity ratio is 0.5.

The pneumatic control valve lO is set to valve 1 at the supplied air pressure at this time.
Since the displacement of valve 102 is adjusted to stop, the driving of valve 102 will stop unless the input signal changes thereafter.

Next, consider a case where the signal input to the input terminal 34 increases rapidly.

Due to the increase in the input signal level, the valve drive signal 6 becomes [ε
〉δ2], the comparator 28 still outputs a “L” level signal to keep the large capacity exhaust valve 18 in a disconnected state, but the output of the comparator 26 becomes “H” level. , the large capacity air supply valve 16 is brought into communication.

Further, the pulse width modulator 24 completely stops the pulse width modulation operation and outputs an "H" level signal, thereby causing the three-way switching valve 14 to constantly communicate the air pipe 12 and the air pipe 20.

Therefore, the driving pressure chamber 101 is connected to the air pressure source (Ps) through two valves, the three-way switching valve 14 and the large capacity air supply valve 16.
As a result, the pressure supplied to the drive pressure chamber 101 rises rapidly, and the valve 102 is largely displaced. In other words, it responds quickly to a large increase in input.

Due to the displacement of the valve 102, the εΦ value becomes smaller [-
61≦6≦61], the process returns to the pulse width modulation operation described above.

On the other hand, when the signal input to the input terminal 34 suddenly decreases, that is, when it becomes [Saku-62], the output of the pulse width modulator 24 and the output of the comparator 26 become "L" level comparator. The output of 28 becomes "H" level. As a result, the three-way switching valve 14 brings the air pipe 12 and the air pipe 22 into communication, puts the large-capacity air supply valve 16 into a non-communicating state, and puts the large-capacity air supply valve 18 into a communication state.

Therefore, the driving pressure chamber 101 is connected to the atmosphere (Yent
), the pressure supplied to the driving pressure chamber 101 suddenly drops, and the valve 102 widens (displaces) in the opposite direction to when the customer value increases.

Due to the displacement of the valve 102, the value of C increases [-
61≦C≦61], the process returns to the pulse width modulation operation, as in the above case.

FIG. 4 is a block diagram showing another embodiment of the valve body insulator of the present invention.

In this figure, the same or corresponding parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

As shown in the characteristic diagram of FIG.
It outputs "L" level only when δ1<-60<0.0<δ0×δ1), and otherwise outputs "H" level.

The output of comparator 40 is provided to on/off switching valve 42 and gate circuit 44.

The on/off switching valve 42 is a three-way switching valve 14. Air pipe 121 communicating with large capacity air supply valve 16 and large capacity exhaust valve 18
and the air pipe 122 that communicates with the drive pressure chamber 101, and when the output of the comparator 40 is at the "L" level, it is in a non-communicating state to seal the pressure inside the drive pressure chamber 101, and the comparator 40 When the output is at "H" level, the communication state is established.

The gate circuit 44 includes the pulse width modulator 24 and the three-way switching valve 1.
When the output of the comparator 40 is at the L level, the output signal is at the L2 level, and when the output of the comparator 40 is at the H level, the output signal of the pulse width modulator 24 is is output as is.

Therefore, the output of the gate circuit 44 is as shown in FIG. When −δ0×6〈δ0〕, it becomes II level, and when ■[ε〉δ1), it becomes “H” level, and ■(−
61≦ε≦−δO1δ0≦6≦61) (7) In some cases, pulse width modulation operation is performed.

Next, the operation of this embodiment will be explained.

When the value of the valve drive signal 1 satisfies 8<-60, δ0 * ε, the same operation as in the above-mentioned embodiment is performed, so a description thereof will be omitted.

Therefore, the value of the valve drive signal 6 is -δO Kusaku δ0 The operation when this happens is explained below.

When the value of the valve drive signal a falls within the range [-δQ<a<60], the three-way switching valve 14 stops the pulse width modulation operation and closes the air pipe 20, while the large capacity air supply valve 16 Since the drive signal εΦ value is [1 x δ2], it is in a non-communicating state. Therefore, the air supply path from the air pressure source (Ps) is completely cut off, and air consumption in this state becomes zero.

On the other hand, the on/off switching valve 42 enters a non-communicating state when the value of the valve drive signal ε falls within the range of -δ0, so the air pipe 121 is connected to the atmosphere (Vent) via the three-way switching valve 14. Although it communicates with the drive pressure chamber 10
The air pressure inside the pulp 102 is not exhausted, and the position of the pulp 102 is kept constant.

Note that if the value of the valve drive signal 6 changes due to a new signal input and becomes outside the range of [-δO Kusaku δ0], this sealed state is released.

〔Effect of the invention〕

As explained above, according to the valve control method of the present invention, the valve drive signal indicating the deviation between the input signal and the displacement amount of the valve is pulse width modulated and then converted into a pneumatic pressure signal, and this pneumatic pressure signal is used for pneumatic control. In addition to driving the valve, if the deviation indicated by the valve drive signal is large, the driving pressure chamber of the pneumatic control valve is communicated with the air pressure source or the atmosphere. The control valve can be operated at high speed without using a booster relay.

Further, according to the valve body 5 of the present invention, since it is equipped with a means for sealing the pressure in the drive pressure chamber when the deviation is approximately zero, the air consumption in an equilibrium state can be reduced to zero. This is effective in reducing running costs and can also contribute to energy savings. Furthermore, since air consumption can be reduced, the supply form of supply pressure can be changed from conventional piping to a cylinder method, which is also effective in reducing piping construction costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the valve positioner of the present invention, FIG. 2 is a characteristic diagram of the pulse width modulator and comparator of the embodiment, FIG. 3 is an output waveform diagram of the pulse width modulator, FIG. 4 is a block diagram showing another embodiment of the valve positioner of the present invention, FIG. 5 is a characteristic diagram of the comparator, and FIG. 6 is a characteristic diagram of the gate circuit. 10... Pneumatic control valve, 101... Drive pressure chamber, 1
02...Valve, 12,121,122.20.22
...Air pipe, 14...Three-way switching valve, 16...Large capacity air supply valve, 18...Large capacity exhaust valve, 24...Pulse width modulator, 26.28.40... Comparator, 30...
Valve lift detector, 42...On/off switching valve, 44...
...Gate circuit. Patent applicant Yamatake Honeywell Co., Ltd. Agent Yamakawa Administration (and 2 others) Figure 1! Figure 1 to 2 Figure 3

Claims (2)

[Claims] (1) means for pulse width modulating a valve driving signal indicating the deviation between the input signal and the displacement amount of the pneumatic control valve; and converting the output signal of the pulse width modulation means into a pulse width modulated pneumatic signal. , means for inputting the pneumatic pressure signal into a driving pressure chamber for displacing the valve position of the pneumatic control valve; What is claimed is: 1. A valve positioner comprising means for communicating with a source or the atmosphere. (2) means for pulse-width modulating a valve driving signal indicating the deviation between the input signal and the displacement amount of the pneumatic control valve; and converting the output signal of the pulse-width modulating means into a pulse-width modulated pneumatic signal. , means for inputting the pneumatic pressure signal into a driving pressure chamber for displacing the valve position of the pneumatic control valve; A valve positioner comprising means for communicating with a source or the atmosphere, and means for sealing the pressure within the drive pressure chamber when the absolute value of the valve drive signal is close to zero.