JPS6120721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an actuator having an electropneumatic positioner for actuating a diaphragm valve.
In particular, it relates to explosion-proof and safe actuators.

[Conventional technology]

In the past, most of the mainstream actuators were operated by pneumatic signals, that is, air signals. However, this type of actuator has drawbacks such as a delay in the transmission time of control signals, so it is hardly used at present.

As an alternative to this actuator, actuators currently used in general industrial plants are mainly operated by electrical signals. Power methods include pneumatic, hydraulic, and electric motors. Among these, in chemical plants where explosion-proof safety measures are most required, 90%
More than % are pneumatic types operated by electrical signals.

Here, a general example of a pneumatic actuator operated by an electric signal is shown in FIG. 1st
In the figure, the excitation coil 2 of the force motor 1 is supplied with an electric signal as an operation signal (for example, DC 4 to 20
[mA]) A is given. The lever 3 moves in response to this electric signal A, and the amount of air discharged from the nozzle 5 is adjusted by a flapper 4 attached to the lever 3.

On the other hand, the pilot valve 6 is supplied with compressed air (for example,
A pressure of 1.4 [Kg/cm ² ]) B is supplied. This supplied compressed air B is adjusted by the flapper 4 and the nozzle 5 to provide an operating pressure corresponding to the electrical signal A (for example, 0.2~
1 [Kg/cm ² ]) of compressed air C is added to the diaphragm 8 of the diaphragm valve 7. This operating pressure opens and closes the valve 10 via the main shaft 9. A feedback link mechanism 11 for adjusting the stroke of the valve 10 is connected to the main shaft 9, including a stroke adjustment pin 12, a restoring lever 13,
The valve opening degree is determined by the balance between the stroke amount fed back via the restoring spring 14 and the command amount from the force motor 1.

For the above actuators, force motor 1
The plant contains electrical systems such as the electrical system, and exposing this to the plant atmosphere must be avoided for explosion-proof measures. Therefore, in the past, the diaphragm valve and actuator shown in Figure 1 were housed in their entirety in a casing to isolate them from the outside air, and the inside was purified with still air, or they were buried underground and only the exhaust pipe was removed. Measures were taken to ensure safety, such as bringing it above the ground.

[Problem that the invention seeks to solve]

However, in order to take essential safety measures in terms of explosion protection, it is necessary to reduce the number of electrical systems that can cause explosions.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an actuator that is essentially safe in terms of explosion protection and is less susceptible to external disturbances.

[Means for solving problems]

The present invention provides an actuator that includes a pilot valve that controls the pressure of compressed air and a force motor that drives the pilot valve, which includes: a drive circuit that supplies power to an excitation coil of the force motor to drive the force motor; an optical fiber that transmits light energy with low internal energy density to drive the excitation coil, and a photoelectric converter that converts the light energy into electrical energy and outputs it to the drive circuit. And the photoelectric converter is housed in a storage container and is isolated from the external atmosphere.

[Effect]

In the present invention, energy for driving the force motor is supplied by a low-energy optical signal, and safety is ensured by lowering the energy density in the optical energy transmission system.

[Example] The present invention will be described in detail below based on an illustrative example. First, a case will be considered in which the force motor 1 of the actuator is driven by optical energy.

As an example, the commonly used caliber 50
[cm] and a fluid pressure of 10 [Kg/cm ² ]. Consider the case of a pneumatic diaphragm valve operated by an electrical signal.

The force F generated on the main shaft 9 when the valve 10 is operated is expressed as F=πD ² /4·P [Kg] (1). Here, D: diaphragm diameter [cm], P: contact pressure [Kg/cm ² ]. Now, D=
40 [cm] (When smoothly controlling a valve with a diameter of 50 [cm] and a fluid pressure of 10 [Kg/cm ² ], a diaphragm with a diameter of D = 40 [cm] is generally used.), P = 0.2 ~
1 [Kg/cm ² ], the force F is F=π×40 ² /4 (0.2 to 1) = 251.2 to 1256 [Kg].

The power W [w] supplied to the force motor is expressed as W=I ² R [w] (2). Here, I is the current value [A] to be supplied by the coil 2, and R is the general value of the winding resistance of the coil 2 [Ω]. Now, I=0.004~0.02
[A], R = 250 [Ω], the electric power W is as follows: W = (0.004) ² × 250 to (0.02) ² × 250 = 0.004 to 0.1 [W].

Therefore, as can be seen from the above example, the above valve can be operated if the power after photoelectric conversion is 0.004 to 0.1 [W] as an operation signal to the actuator.

On the other hand, consider a case where the energy for operating the valve is entirely dependent on optical energy. In this case, a considerable amount of energy is required. When transmitting such a huge amount of energy, if the transmission cable is damaged, for example in a flammable atmosphere, a serious disaster may occur, so it is not an explosion-proof safety measure. I don't get it.

However, as mentioned above, if the energy is small, it is extremely advantageous in terms of explosion protection, and also has the advantage that it is not affected by disturbances such as electromagnetic noise.

Next, a specific example will be explained. FIG. 2 is a sectional view showing an embodiment of the actuator according to the present invention. Note that in FIG. 2, parts that overlap with those in FIG.

The coil 2 of the force motor 1 is driven by power supplied from a drive circuit 15 through a power line 16 . The drive circuit 15 is supplied with power by converting optical energy transmitted through the optical fiber 17 into electrical energy by a photoelectric converter 18 . Further, an optical control signal D for drive control is given to the drive circuit 15 through an optical fiber 23, and the operating pressure C of the pilot valve 6 is controlled by this control signal D. The above coil 2 is placed in the pressure vessel 19, the power line 16 is placed in the piping 20, and the drive circuit 15 is placed in the pressure vessel 2.
1 and the photoelectric converter 18 are respectively housed in a pressure vessel 22 and isolated from the outside air.
In other words, the entire power system is cut off from the outside air.

Optical fiber 17 is designed to transmit optical energy at a low energy density during its transmission path. That is, as shown in FIGS. 3 and 4, the optical fiber is formed of a plurality of fibers with the individual fibers spaced apart from each other. The reason for forming it in this way is as follows.

In other words, generally the light emitted from the end of an optical fiber (one fiber) diverges radially (the fifth
figure). Here, 24 indicates a core, and 25 indicates a glad. However, when these fibers are brought into close contact with each other to form a bundle (Figure 6), even if the energy of each individual fiber is small, the energy concentrates when the fibers are close to the ends, causing the object irradiated with light to overheat. There is enough fear. Therefore, if the individual fibers are spaced apart from each other, their radiant energy will be divergent (FIG. 7).

Thus, the optical fiber 17 is
Separate the individual fibers with a spacing material (e.g., plastic, rubber, heat-resistant fiber, etc.) 2 as shown.
6, the energy density within the optical fiber 17 is lowered by arranging them at appropriate intervals. Incidentally, FIG. 4 shows an example in which even if the optical fibers 17 are in close contact with each other partially, it is fine as long as the entire optical fiber 17 is not in close contact with each other.

Note that the pressure vessels 19, 21, 22 and the piping 20 are constructed using non-magnetic materials (for example, austenitic stainless steel, titanium, etc.). Furthermore, instead of the pressure vessel 19 covering the coil 2, the entire coil 2 may be molded with epoxy resin and integrally molded to achieve isolation from the outside air.

Next, in the example shown in FIG. 8, the force motor 1 in the actuator shown in FIG. 2 is replaced with an electric piston 27, and the pressure vessels 19, 21, 22,
The inside of the pipe 20 is connected to a compressed air supply pipe 28 to the pilot valve 6 through a pipe 29. By doing so, the coil 2, drive circuit 15, photoelectric converter 17, etc. are sealed in the same atmosphere as the supply pipe 28.

〔Effect of the invention〕

As described above, according to the present invention, the energy for operating the actuator is optical energy and air pressure, and since the optical energy is transmitted with low energy, there is no danger even if an accident such as cable breakage occurs. Therefore, it is essentially safe in terms of explosion protection. Additionally, the optical signal is not affected by electromagnetic noise that is common in plants.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional electro-pneumatic actuator, FIG. 2 is a sectional view showing an embodiment of an actuator according to the present invention, and FIGS.
The figure is a sectional view showing the structure of the optical fiber, FIGS. 5 to 7 are explanatory views showing the state of light divergence of the optical fiber, and FIG. 8 is a sectional view showing another embodiment. 1...Force motor, 6...Pilot valve,
16...Drive circuit, 17...Optical fiber, 18...
...Photoelectric conversion device, 19...Pressure vessel, 20...Piping, 21...Pressure vessel, 22...Pressure vessel, C...
...supply compressed air, D...light control signal.

Claims (1)

[Claims] 1. A pilot valve that controls the pressure of compressed air;
An actuator equipped with a force motor that drives the pilot valve includes a drive circuit that supplies power to an excitation coil of the force motor to drive the force motor, and a drive circuit that supplies power to an excitation coil of the force motor to drive the force motor, and a drive circuit that supplies light energy for driving the force motor in a state with a low internal energy density. It includes an optical fiber for transmission, and a photoelectric converter that converts the optical energy into electrical energy and outputs it to the drive circuit, and the excitation coil, drive circuit, and photoelectric converter are housed in a storage container and are isolated from the external atmosphere. An actuator characterized in that it is blocked. 2. The actuator according to claim 1, wherein the storage container communicates with a pipe for supplying compressed air to the pilot valve, and compressed air is added to the storage container. 3. The actuator according to claim 1 or 2, wherein the optical fibers have a reduced internal energy density by spacing each fiber of the plurality of fibers. 4. The actuator according to claim 1, 2, or 3, wherein the drive circuit is controlled by an optical signal.