JPH0440006Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a zero point and span adjustment mechanism in a positioner.

[Prior Art] Generally, positioners are used to control the operations of control valves, fluid pressure actuators, and the like.

FIG. 4 shows an example of a positioner with a control valve 1 as a control section, and this positioner has the following:
The control valve 1 includes a nozzle flapper mechanism 5 having a flapper 2, a nozzle 3 opening opposite the flapper 2, and an input bellows 4 that expands and contracts depending on the magnitude of an input signal. It is configured as a diaphragm type driven by an amplified output signal from the nozzle flapper mechanism 5.

A valve lever 9 is attached to the stem 8 of the control valve 1, and the tip of the valve lever 9 is attached to the elongated hole 12 of the cam lever 11, which swings together with the stem 8 about a support shaft 10.
The cam 13 is inserted into the support shaft 10 and fixed to the support shaft 10.
A roller provided at the swinging end of a swingably supported feedback lever 15a is in contact with the roller.

The coiled feedback spring 16 is
One end is fixed to the flapper 2 so as not to rotate, and the other end passes through a feedback lever 15b that is swingably supported, and a zero point adjustment screw 18 is screwed to the other end.
b comes into contact with the span adjustment piece 19, which is movable by a moving mechanism (not shown), and swings together.

Although not shown, the feedback lever is configured with one lever, and a span adjustment piece is screwed onto a zero point adjustment screw, and the adjustment piece is rotated to the other end of the feedback spring 16. Possibly locking versions are also known.

In the positioner shown in Fig. 4, when the control section is in an equilibrium state, when the input signal increases, the flapper 2 swings in the direction of the arrow and the nozzle 3 is closed, so that the increased back pressure of the nozzle is transferred to the pilot. The signal is amplified by the valve 7 and input to the diaphragm motor 6, whereby the valve lever 9 rotates the cam lever 11 and the cam 13 coaxial therewith clockwise.

The cam 13 rotates clockwise to rotate the support shaft 10.
Since the feedback levers 15a and 15b have a cam surface that increases the distance from the feedback spring 16, the feedback levers 15a and 15b rotate counterclockwise.
When the flapper 2 is rotated in the direction in which the nozzle 3 opens through , a new equilibrium state is reached and the control section becomes stable. The control operation of the positioner is the same even when the feedback lever is composed of one lever.

These positioners are equipped with a zero point adjustment mechanism and a span adjustment mechanism in order to maintain a certain relationship between the input signal and the displacement of the control section depending on the purpose of use. The adjustment to move straight line A-B in parallel as shown in Figure 5 as CD is called zero point adjustment, and the adjustment to change the inclination angle of straight line A-B as shown in A-D is called span adjustment. I'm here.

The positioner shown in FIG.
The same applies when the zero point adjustment mechanism is configured and the zero point adjustment is performed by changing the tension of the feedback spring 16 by rotating the zero point adjustment screw 18, and the feedback lever consists of one lever.

The span adjustment piece 19 constitutes a span adjustment mechanism, and the positioner shown in FIG.
Span adjustment is performed by changing the lever ratio of 5a and 15b.

On the other hand, a positioner in which a span adjustment piece is screwed onto a zero point adjustment screw adjusts the span by changing the number of turns of the feedback spring by rotating the span adjustment piece.

However, since these positioners lack consideration for adjustment operations, they have the following problems.

That is, the positioner shown in FIG. 4 requires two levers 15a and 15b, which not only complicates the feedback mechanism, but also makes the adjustment cumbersome because adjustment operations are performed at two separate locations and from different directions. It is.

In addition, positioners in which the span adjustment piece is screwed onto the zero point adjustment screw have the advantage of being able to use the zero point adjustment screw for span adjustment, but not only do they have to be done in two separate places, but they also have to rotate the span adjustment piece. Since touching the feedback spring is unavoidable at times, the feedback spring moves, and this movement is sensed by the nozzle flapper mechanism, causing the control section to vibrate, making span adjustment difficult.

[Problems to be Solved by the Invention] In the present invention, the zero point adjustment screw of the positioner and the span adjustment screw, which has a span adjustment piece fixed to one end, are screwed together and arranged concentrically. The problem to be solved is to facilitate the span adjustment operation and the assembly of the adjustment mechanism to the positioner.

[Means for Solving the Problems] The zero point and span adjustment mechanism in the positioner of the present invention drives the control section by the output signal from the nozzle flapper mechanism that swings in response to the input signal, and also controls the above-mentioned adjustment by the feedback mechanism. A positioner that displaces a control unit in proportion to the input signal, and adjusts the zero point and span by changing the tension and number of turns of a coiled feedback spring using a zero point adjustment screw and a span adjustment piece in the feedback mechanism. In the zero point and span adjustment mechanism in the positioner, the zero point adjustment screw and the span adjustment screw to which the span adjustment piece is fixed are screwed together and arranged concentrically, and the zero point adjustment screw is connected to the zero point adjustment mechanism in the feedback mechanism. The feedback spring is swingably attached to the feedback lever, one end of the feedback spring is unrotatably locked to the nozzle flapper mechanism, and a span adjustment piece is rotatably locked to the other end. This solves the problem mentioned above.

[Operation] When an input signal is applied, the control section is driven by an output signal from the nozzle flapper mechanism which swings in response to the application, and the feedback mechanism displaces the control section in proportion to the input signal.

When the zero point adjustment screw is rotated, the span adjustment screw moves back and forth without rotating relative to the feedback lever, so zero point adjustment can be performed by changing the tension of the feedback spring.

When the span adjustment screw is rotated, the span adjustment piece rotates together with the span adjustment screw and moves forward and backward relative to the feedback spring, so the span can be adjusted by changing the number of turns of the feedback spring.

Furthermore, since the zero point adjustment screw is swingably provided on the feedback lever, the zero point and span can be adjusted without difficulty.

Furthermore, by threading these adjustment screws together and arranging them concentrically, zero point and span adjustments can be made at the same location and from the same direction, making adjustment operations easy. Since it can be integrated into the positioner, it is easy to assemble the adjustment device to the positioner.

[Embodiment] Figures 1 to 3 show an embodiment of the present invention in which the control unit is a control valve 21, and this positioner includes a flapper 22, a nozzle 23 opening opposite the flapper 22, and an input signal. The control valve 2 is equipped with a nozzle flapper mechanism 25 having an input bellows 24 that expands and contracts depending on the size of the control valve 2.
1 is configured as a diaphragm type in which a diaphragm motor 26 is driven by an output signal from a nozzle flapper mechanism 25 amplified by a pilot valve 27. However, the control unit of the present invention
The control valve is not limited to a diaphragm type control valve, and may be a control valve other than a diaphragm type or a fluid pressure actuator such as a fluid pressure cylinder.

A valve lever 29 that is driven integrally with the stem 28 of the control valve 21 is attached, and the tip of the lever 29 is inserted into the elongated hole 32 of a cam lever 31 that swings together with the stem 28 about a support shaft 30. It is slidably inserted and the support shaft 30
A roller provided at the swinging end of a swingably supported feedback lever 35 is in contact with the cam 33 fixed to the cam 33 . Further, the cam 33 has a cam surface whose distance from the support shaft 30 increases as it rotates clockwise in FIG.

As shown in FIGS. 2 and 3, the feedback lever 35 has a through hole formed in the middle thereof.
A hollow zero-point adjusting screw 38 is rotatably inserted into the bearing 37, and the inner threaded surface of the hollow zero point adjusting screw 38 includes a bearing 37 that is swingably supported by a pair of pins 36, 36. An adjustment screw 39 is screwed onto the span adjustment screw 39, and a span adjustment piece 40 is fixed to the tip of the span adjustment screw 39. on the other hand,
A coiled feedback spring 41 disposed on an extension of the span adjustment screw 29 has one end fixed to the flapper 22 by a hook so as not to rotate, and the span adjustment piece rotatable at the other end. (See Figure 2).

In the positioner of the above embodiment, the control operation of displacing the control unit in proportion to the fluctuation of the input signal is as follows:
Since it is substantially the same as the known positioner shown in FIG. 4, detailed explanation will be omitted.

Next, the zero point adjustment and span adjustment of the above embodiment will be described.

When the zero point adjustment screw 38 is rotated by the knob 38a, the bearing 37 is moved to the feedback lever 35.
Since it is supported by and does not rotate, the zero point adjustment screw 38
The span adjustment screw 39 screwed into the span adjustment screw 39 moves back and forth without rotating, and the tension of the feedback spring 41 is changed by the movement of the span adjustment piece 40 fixed thereto, so that zero point adjustment can be performed.

On the other hand, when the span adjustment screw 39 is rotated by a suitable rotating instrument, the span adjustment screw 39 moves forward and backward while rotating with respect to the bearing 37 and the zero point adjustment screw 38, and the coiled shape of the span adjustment piece 40 fixed thereto is rotated. Since the number of windings of the feedback spring 41 is changed by moving it forward and backward relative to the feedback spring 41, the span can be adjusted.

In this case, the bearing 3 provided with adjusting screws 38, 39
7 is swingably supported by the feedback lever 35, so these adjustments can be made easily.

The above-mentioned zero point adjustment and span adjustment can not only be performed by rotating the adjustment screws 38 and 39 screwed together concentrically, but also can be adjusted from the same location and from the same direction, making the adjustment operation easy. Since the flapper 22 does not vibrate, the span adjustment is not hindered by the vibratory movement of the control section.

Furthermore, by threading the adjustment screws 38 and 39 together and arranging them concentrically, they can be assembled into the positioner in an integrated state, making it easy to assemble the adjustment mechanism into the positioner.

The control unit controlled by the positioner of the present invention is not limited to a control unit that moves reciprocatingly, but may also be a control unit that rotates, such as a swinging actuator. It is also possible to do this.

[Effect of the invention] The zero point and span adjustment mechanism in the positioner of the present invention has the zero point adjustment screw and the span adjustment screw screwed together and arranged concentrically, so that both adjustments can be made at the same location and in the same direction. The zero point and span can be adjusted by rotating each adjustment screw, so the adjustment operation is easy.
Further, since both adjustment screws can be integrated into the positioner, the adjustment mechanism can be easily assembled.

Furthermore, since the zero point adjustment screw is rotatably provided on the feedback lever, the zero point and span can be adjusted without difficulty.

[Brief explanation of the drawing]

Fig. 1 is a schematic block diagram of an embodiment of the present invention, Figs. 2 and 3 are enlarged views of the main parts of the same, Fig. 4 is a schematic block diagram of an example of a conventional positioner, and Fig. 5 is a zero point adjustment and It is an explanatory view of span adjustment. 21...Control valve, 25...Nozzle flapper mechanism, 35...Feedback lever,
38...Zero point adjustment screw, 39...Span adjustment screw, 40...Span adjustment piece, 41...Feedback spring.

Claims (1)

[Claims for Utility Model Registration] A positioner that drives a control section by an output signal from a nozzle flapper mechanism that swings in response to an input signal, and also displaces the control section in proportion to the input signal using a feedback mechanism. It's hot,
In the zero point and span adjustment mechanism of the positioner, the zero point adjustment screw and the span adjustment piece in the above-mentioned feedback mechanism perform zero point adjustment and span adjustment by changing the tension and number of turns of a coiled feedback spring. , the span adjustment piece and the fixed span adjustment screw are screwed together and arranged concentrically, the zero point adjustment screw is swingably attached to the feedback lever of the feedback mechanism, and the feedback spring is attached to the feedback spring. one end is unrotatably locked to the nozzle flapper mechanism, and the other end is rotatably locked to a span adjustment piece;
A zero point and span adjustment mechanism in a positioner characterized by: