JPS6220901A - Valve positioner - Google Patents

Abstract

PURPOSE:To improve the extent of responsiveness, by connecting a valve driving pressure chamber directly to a pneumatic source and the atmosphere when the absolute value of deviation is larger than the specified value, and leading a pulse width modulated pneumatic signal into this valve driving pressure chamber when the deviation absolute valve is almost zero. CONSTITUTION:A large capacity feed valve 16 and a large capacity exhuast valve 18 both are connected to a driving pressure chamber 101 of a pneumatic control valve 10, while a three-way selector valve 14 is also connected to the chamber via an on-off selector valve 42. When the absolute value of deviation between input signal and a valve displacement in the pneumatic control valve 10 is larger than the specified value, the valve driving pressure chamber 101 is connected directly to a pneumatic source and the atmosphere via these large capacity feed and exhaust valves 16 and 18. And, when the deviation absolute value is almost zero, a pulse width modulated pneumatic signal is led into the valve driving pressure chamber 101 by the three-way selector valve 14. With this constitution, the valve is drivable at high speed so that the extent of responsiveness is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a valve positioner used in a pneumatic control valve.

[Conventional technology]

Conventional general valve positioners apply the deviation between the input signal and the valve displacement amount to the nozzle flapper as a mechanical displacement amount, and after extracting the nozzle back pressure of the nozzle flapper as a pneumatic signal, The pilot relay is configured to amplify the pressure and supply it to the air motor of the control valve.

[Problem that the invention seeks to solve]

However, with such conventional valve positioners, it is difficult to respond at high speed when the deviation between the input signal and the amount of displacement of the valve is large. In particular, if the capacity of the air motor is large, it may be necessary to add a booster relay to the air circuit to amplify the capacity of the air pressure signal to support high-speed response.

Further, as described above, the conventional valve positioner It nozzle, 7-y collar and pilot relay are used, but this nozzle, 7-y collar and pilot relay consume air even in a balanced state.

Specifically, in a valve positioner using a semi-bleed type pilot relay or a bleed type pilot relay, air consumption is 5 to 15 Nt/min in the nozzle portion and a portion of the pilot relay.

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.

[Means for solving problems]

In order to solve these problems, the present invention pulse-width modulates a valve drive signal that indicates the deviation between the input signal and the valve opening, converts it into a pneumatic pressure signal, and drives the valve with this pneumatic pressure signal. In addition to means for communicating the driving pressure chamber of the valve with an air pressure source or the atmosphere when the absolute value of the deviation indicated by the valve driving signal is larger than a predetermined value, and means for communicating the driving pressure chamber of the valve with an air pressure source or the atmosphere when the absolute value of the valve driving signal is close to zero. A means for converting the pulse width modulated valve driving signal into a pneumatic signal and a means for sealing communication with the driving pressure chamber are provided.

[Effect]

If there is a large deviation (absolute value) between the input signal and the amount of valve displacement, the drive pressure chamber is directly connected to an air pressure source or the atmosphere, and its pressure changes to @, the amount of valve displacement. change significantly. Responds quickly to large input signal changes. On the other hand, in a balanced needle where the absolute value of the valve drive signal is close to zero, the pressure within the drive pressure chamber is sealed and air consumption becomes zero.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the valve positioner 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 9, and the bent end of this air g12 is connected to an on/off switching valve 42, which will be described later.
? It is connected to the three-way selector valve 14 through the valve, and also to the large-capacity air supply valve 16 and the large-capacity exhaust valve 18 .

The three-way switching valve 14 is connected, in addition to the air line 12, to an air line 20 communicating with an air pressure source at a pressure P1 and an air line 22 communicating with the atmosphere at a pressure P0. The connection between the air pipe 20 and the air pipe 12 and the connection between the air pipe 22 and the air pipe 12 are switched in response to a signal sent from the pulse width modulator 24 via the gate circuit 44. In other words, the signal is “
When the level is "H", the opening of the air pipe 22 is closed and the air pipe 20 and the air pipe 12 are communicated with each other, and when the level is "L", the opening of the air pipe 20 is closed and the air pipe 22 is communicated with the air v12.

The large-capacity air supply valve 16 is an on/off switching valve that connects and disconnects the air pipe 20 and the air pipe 12 based on a signal from the comparator 26, and the large-capacity exhaust valve 18 receives a signal from the comparator 28. This is an on/off switching valve that connects and disconnects the air pipe 22 and the air pipe 12.

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 potentiometer, or the like.

The input module 32 receives 4 inputs from the input terminal 34.
The input signal of ~20 mA 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 comparison section 36.

The deviation ε 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 the valve drive signal by the pulse width modulator 24. Comparator 26. Input to comparator 28 and comparator 40.

As shown in the characteristic diagram of FIG.
---- Pulse width modulate the valve drive signal I only when (1) is satisfied. ε=-δ
The duty ratio when l is zero, the duty ratio when ε=δ1 is rlJ, and the relationship between ε and the duty ratio when equation (1) is satisfied is linear.

The waveform diagram in FIG. 3 shows the output waveform of the Norse width modulator 24 when ε=εl, that is, when the density ratio is rO, 7J. 70% of repetition period T2>E
The remaining 30% of the “H” level is Z>E “L” level.

Valve drive signal ε is C〈-δ1...(2
), the output of the pulse width modulator 24 is the "L" level in the binary signal9, and the valve drive signal C is C>δ1...(3
), the output of the pulse width modulator 24 becomes an "H" level in a binary signal.

As shown in the characteristic diagram of FIG. 2(B), the comparator 26 is configured such that the valve drive signal C satisfies the following condition: ε≧δ2 (where δ2>δ1) (4
), when the binary output signal is “H” level, e〈δ2 @・・・(5
), the binary output signal becomes "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.
0 and the air pipe 12 are connected, the air pressure source (P8) and the drive pressure chamber 101 of the pneumatic control valve 10 are connected, and the comparator 2
When the signal from 6 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.
), the binary output signal becomes ``H'' level, I〉-δ2''...
When (7) is satisfied, the binary output signal becomes "L" level.

When the signal from the comparator 28 is at the "H" level, the large capacity exhaust valve 18 opens the opening of the air pipe 22.
2 and the air pipe 12 are connected, and the driving pressure chamber 101 of the pneumatic control valve 10 and the atmosphere (P) communicate with each other, and when the signal from the comparator 28 is at "L" level, the opening of the air pipe 22 is connected. is closed and the connection between the air pipe 22 and the air pipe 12 is severed.

As shown in the characteristic diagram of FIG. 4, the comparator 40 has an input valve drive signal C that It outputs a "L" level only when satisfying <δ0<81), and outputs an "H" level in other cases.

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

The on/off switching valve 42 includes an air pipe 121 communicating with the three-way switching valve 14 and an air pipe 122 communicating with the drive pressure chamber 101.
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 when the output of the comparator 40 is at the 'H' level, it is in a communicating state. becomes.

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 "L" level, and when the output of the comparator 40 is at the "H" level, the output signal is at the "H" level. 24 output signals are output as they are.

Therefore, the output of the gate circuit 44 is as shown in diagram M5.

■ [5 Kuichi δ1. “L” when −δO<l<aO)
When the level is ①(g>δl), the level becomes “H”.

■ [-δl≦C≦-δ0. When δ0≦C≦δl], pulse width modulation operation is performed.

Next, the operation of this embodiment will be explained.

If the value of the valve drive signal C from the comparator 36 is 11 (δ0 (11 (Jl)), for example, as shown in FIG. At the same time, the outputs of the comparators 26 and 28 are both at the "LI+" level, and the output of the comparator 40 is at the "H" level.

Therefore, the large capacity air intake valve 16 and the large capacity exhaust valve 18
The drive pressure chamber 101 and the air pressure source CPM) and the atmosphere (Po) are connected to the three-way switching valve 1.
4.

Since the three-way switching valve 14 is currently driven by a pulse width modulation signal with a duty ratio of 0.7, the drive pressure chamber 10
The air pipe 12 communicating with the air pipe 12 is communicated with the air pipe 20, that is, the air pressure source (P,) for 70% of the repetition period T,
The air pipe 22 is connected to the atmosphere (PO) for about 30 minutes.

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

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

Due to an increase in the input signal level, the valve drive signal ε becomes [C
≧δ2], the ratio Ii ¥528 is still “
Although the large-capacity exhaust valve 18 is maintained in a non-communicating state by outputting a signal at the "L" level, the output of the comparator 26 remains at the "H" level, and the large-capacity air supply: ll'f'16 is maintained. Make it connected.

Further, the pulse width modulator 24 stops the pulse width adjustment 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 drive pressure chamber 101 is connected to the air pressure source (pm
), the pressure supplied to the drive pressure chamber 101 rises, 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 value of ε becomes smaller [−
δl≦l≦δ1], the pulse width adjustment operation returns to the above-mentioned pulse width.

Conversely, when the signal input to the input terminal 34 suddenly decreases, that is, when [C≦-δ2], the output of the pulse width modulator 24 and the output of the comparator 26 are set to "L" level. The output of the device 28 becomes "H" level.As a result, the three-way switching valve 14 puts the air pipes 12 and 22 into communication, puts the large-capacity air supply valve 16 into a non-communicating state, and puts the large-capacity exhaust valve 18 into the communication state. Make it connected.

Therefore, the drive pressure chamber 101 is in communication with the atmosphere (Pa) through the two valves, the three-way switching valve 14 and the large-capacity exhaust valve 18, and the pressure supplied to the drive pressure chamber 101 suddenly drops, causing g The valve 102 is largely displaced in the opposite direction to when the value of becomes large.

Due to the displacement of the valve 102, the value of ε becomes large [-
When δl≦e≦δl], the pulse width modulation operation is returned to, as in the above case.

Assuming that the signal input to the input terminal 34 is constant, the valve drive signal C gradually approaches zero due to the displacement of the valve 102. Then, the value is (−aO<ξ×δ
O], the three-way switching valve 14 stops the pulse 1 width modulation operation and closes the air pipe 2°. On the other hand, large capacity air supply valve 1
6 is in a non-communicating state because the valve drive signal CQ value is CM<δ2]. Therefore, the air pressure source (P
The air supply route from G) is completely cut off, and air consumption in this state is zero.

On the other hand, the air pipe 121 is connected to the atmosphere (P
However, when the value of the valve drive signal C falls within the range of -δo - δ0, the on/off switching valve 42 becomes disconnected, and the large-capacity exhaust valve 18 Since is −δ2(g, it is in a non-communicating state, so the air in the drive pressure chamber 101 is never exhausted, and the position of the valve 102 is maintained constant.

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

A similar effect can be obtained by changing the insertion position of the off-on switching valve 42 to the three-way switching valve 14. Large capacity air supply valve 16 and large capacity exhaust valve 1
It is also possible to obtain this by connecting the air pipe 12 communicated with the drive pressure chamber 101 to the drive pressure chamber 101, but in that case, the amount of air that the on/off switching valve 42 turns on and off becomes large. , the shape of the valve itself must be enlarged. In addition, large capacity air supply valve 16. There is no problem as long as the switching times of the large-capacity exhaust valve 18 and the on/off switching valve 42 are the same, that is, the time from the application of an electric signal until the air flows, but compared to the former two, the on/off switching valve If the switching time of 42 is slow, this will adversely affect the supply/exhaust characteristics to the drive pressure chamber 101, in other words, the response characteristics of the positioner. In contrast, in this embodiment, the on/off switching valve 42 is inserted between the three-way switching valve 14 and the drive pressure chamber 101, and only the communication between them is sealed. A capacity switching valve can be used, making it possible to reduce the size and quantity, and improve the responsiveness of the positioner.

〔Effect of the invention〕

As explained above, according to the valve positioner 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. In addition to driving the pneumatic control valve, when the deviation indicated by the valve drive Gt is large, the driving pressure chamber of the pneumatic control valve is communicated with the air pressure source or the atmosphere, so when the deviation between the input signal and the displacement amount of the valve is large. Even if the deviation is almost zero, it is possible to not only make the control valve respond quickly without using a booster relay, but also to seal off the communication between the means for outputting the pulse width modulated pneumatic signal and the drive pressure chamber when the deviation is almost zero. Since the air conditioner is equipped with a means for stopping air, the air consumption IT in an equilibrium state can be reduced to zero, which is effective in reducing running costs and can also contribute to energy saving. Furthermore, since air consumption can be reduced, the supply pressure type 7J can be changed from conventional piping to a cylinder method, which is also effective in reducing piping construction costs.

[Brief explanation of drawings]

1st! 1: 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, and FIG. 3 is an output profile diagram of the pulse width modulator. FIG. 4 is a characteristic diagram of another comparator, and FIG. 5 is a characteristic diagram of a gate circuit. 10...Pneumatic control valve, 101.°°@driving pressure chamber, 102...Valve, 12, 121.122°2
0.22...Air pipe, 14...Three-way switching valve, 1
6...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 Kazu Yamakawa A4 (and 2 others) Figure 2 Figure 3! −≦

Claims (1)

[Claims] means for pulse-width modulating a valve driving signal indicating the deviation between the input signal and the amount of displacement of the valve of the pneumatic control valve; converting the output signal of the pulse-width modulating means into a pulse-width-modulated pneumatic signal; means for inputting a signal into a driving pressure chamber for displacing the valve position of the pneumatic control valve; and means for inputting a signal into a driving pressure chamber for displacing the valve position of the pneumatic control valve; means for communicating with the drive pressure chamber; means for converting the output signal of the pulse width modulation means into a pneumatic signal when the absolute value of the valve drive signal is close to zero; and means for sealing communication with the drive pressure chamber. A valve positioner characterized by: