JPH0416643B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electric signal-pneumatic conversion unit that converts an electric signal into fluid pressure, particularly air pressure, and more specifically, the nozzle flapper as the conversion element is electrostrictive. The present invention relates to an electric signal to pneumatic conversion unit composed of elements.

[Prior Art] Conventionally, torque motors have been widely used as devices for converting electrical signals into pneumatic pressure. That is, according to this torque motor, current is supplied to the coils constituting the motor, and by converting the rotational force corresponding to the current value into displacement, it is converted into air pressure via the nozzle flapper, pilot valve, etc. In this case, the torque motor usually has 4mA or
A direct current of 20mA is used.

When using such a torque motor to configure a control device such as an electric-pneumatic converter, the larger the force generated by the torque motor, the stronger it will be against the effects of mechanical vibration, etc. A product with stable performance can be obtained.

However, recently, there has been a demand for smaller control equipment, so how to make the torque motor as small as possible has become an important issue. In other words, the smaller the torque motor is, the smaller the force generated in response to the current value will be, so it will inevitably become more susceptible to the mechanical vibrations mentioned above, and depending on the usage conditions of the control equipment, the torque Using a motor itself is technically impossible. On the other hand, in recent years, electrostrictive elements have been adopted as elements for converting electrical signals into air pressure from a completely different angle than before, with the aim of improving vibration resistance and impact resistance, and making them smaller and lighter. I reached the point where

[Problem to be solved by the invention] As described above, the vibration resistance and impact resistance are significantly improved by using an electrostrictive element, but it is still not possible to commercialize it as an electric signal to pneumatic converter by combining it with a pilot valve. Problems remain.

In other words, in general, an electrostrictive element has a small displacement in response to a change in voltage, and in order to obtain a relatively large displacement, the applied voltage change must also be large, which simplifies the electrical circuit. It is also unfavorable from the point of view. Moreover, if the displacement is large, it is undesirable from the viewpoint of performance and the life of the element, and becomes impractical. Therefore, it is necessary to make some improvements on the pilot valve side so that a large change in output pressure can be obtained even if the amount of displacement of the electrostrictive element is small.

The present invention has been proposed in consideration of these circumstances, and has improved vibration resistance by effectively combining electrostrictive electronics and a non-bleed pilot valve that consumes less air even when used at high pressure. It is an object of the present invention to provide an electrical signal-to-pneumatic conversion unit which can be easily reduced in size and weight by improving impact resistance and has high precision.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a nozzle flapper mechanism that changes the nozzle back pressure according to the amount of displacement of the nozzle flapper, and a diaphragm that responds to the nozzle back pressure to control the supply port and the output. An electrical signal-pneumatic conversion unit that includes a non-bleed type pilot valve section that controls the output air pressure by opening and closing an inner valve provided at an air supply port connected to a port, and the nozzle flapper responds to changes in the electrical signal. The upper and lower diaphragms define a supply pressure chamber, a nozzle back pressure chamber is defined above the upper diaphragm, and a nozzle back pressure chamber is defined below the lower diaphragm. It is characterized by defining an atmospheric pressure chamber.

[Function] When a voltage is applied to the electrostrictive element, the nozzle back pressure changes. This change in nozzle back pressure displaces the pilot valve, allowing fluid to flow toward the output port. Since the lower diaphragm is in contact with the atmospheric pressure side, the output pressure is not transmitted to the lower diaphragm, and the pressure gain between the nozzle back pressure and the output pressure is extremely large.

[Embodiments] Next, preferred embodiments of the electrical signal-pneumatic conversion unit according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 denotes an electrical signal to pneumatic conversion unit main body, which is comprised of a nozzle flapper mechanism 12 provided at the upper part of the interior and a pilot valve section 14 provided at the lower part of the interior.

The nozzle flapper mechanism 12 includes a nozzle 18 of a predetermined diameter that communicates with a nozzle back pressure chamber 16 of a pilot valve section 14, which will be described later, and a base. It consists of a plate-shaped flapper 22 whose end portion is fixed to the conversion unit main body 10 with screws 20. As shown in FIG. 2, the flapper 22 has two piezoelectric ceramics 24, 24 each having an electrode on its upper and lower surfaces, and
The lead wires 2 are formed of a so-called electrostrictive element consisting of an intermediate electrode plate 26 sandwiched between the lead wires 2 and
A predetermined voltage is applied via terminals 8 and 28.

On the other hand, the pilot valve section 14 consists of two diaphragms 30, 3 arranged vertically in tandem.
2, an exhaust valve 34, an inner valve 36, etc. which are interlocked with these diaphragms 30, 32. The inner valve 36 has an air supply valve section 55 and an exhaust valve section 56, and the inner valve 36 is formed separately from the exhaust valve 34 in the axial direction.

Next, supply pressure (pressurized air) is introduced into the nozzle back pressure chamber 16 defined above the upper diaphragm 30 through passages 40 and 42 communicating with the supply port 38. At this time, a fixed orifice 44 is provided in the downstream passage 40 to regulate the flow rate of the pressurized air.

Further, a supply pressure chamber 46 defined by the upper diaphragm 30 and a lower diaphragm 32 having a slightly smaller effective area than the upper diaphragm 30 is connected to a supply port 3 via the upstream passage 42.
The supply pressure from 8 is introduced directly.

Additionally, an atmospheric pressure chamber 48 is defined below the lower diaphragm 32, into which the atmosphere is directly introduced via a passageway (exhaust port) 50.

The inner valve 36 is arranged so as to close the air supply port 54 connecting the supply port 38 and the output port 52 when the three pressures described above are balanced. Moreover, at this time, the exhaust valve 56 formed integrally with the inner valve 36 engages with an exhaust port 60 formed in the exhaust valve 34, and an exhaust passage 58 leading from the exhaust port 60 to the atmospheric pressure chamber 48. occlude. Therefore, this pilot valve section 14 is constructed of a non-bleed type in which exhaust is not performed during equilibrium.

Furthermore, an O-ring 64 is interposed in the passage 62 in which the exhaust valve 34 slides, and the above-mentioned atmospheric pressure chamber 4
8, the output pressure in the output port 52 is prevented from being fed back to the lower diaphragm 32 etc. in the pneumatic state.

Instead, the output pressure is electrically fed back to the input side via a pressure sensor 66 that converts the pressure into an electrical signal, as shown in FIG.

That is, after the output pressure from the pilot valve section 14 is detected as an electrical signal by the pressure sensor 66, it is sent to the controller 70 via the amplifier circuit 68 as appropriate.
Feedback will be provided to and controller 7
At 0, the signal is compared with the input signal to the electrical signal-pneumatic conversion unit main body 10, and the deviation is amplified by the successive amplifier circuit 72 and converted into a voltage as appropriate, and then applied to the flapper 22. It's becoming like that.

Note that reference numeral 74 in FIG. 1 is a spring that always biases the inner valve 36 in the valve-closing direction.

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

Now, when the system is in equilibrium as shown in Figure 1,
When the voltage applied to the flapper 22 made of an electrostrictive element increases, the free end of the flapper 22 moves toward the nozzle 18.
Displaced in the direction of closing.

As a result, the amount of air ejected from the nozzle 18 decreases, so the pressure in the nozzle back pressure chamber 16 (nozzle back pressure) increases, and this pressure is applied to the upper diaphragm 3.
Acts on the top surface of 0.

As a result, the equilibrium state of the system is disrupted, and as the upper and lower diaphragms 30, 32 descend, the exhaust valve 34 integrated therewith and the inner valve 36 linked to the exhaust valve 34 also descend. The air port 54 is opened and a portion of the supply pressure from the supply port 38 becomes output pressure and is supplied to the output port 52. This output pressure is supplied to the load side (not shown) and performs the intended function.

At this time, in this embodiment, as described above, the passage 62 in which the exhaust valve 34 slides is hermetically sealed by the O-ring 64, and the lower diaphragm 32
Since the lower side is always open to the atmosphere and the output pressure is not fed back to the lower diaphragm 32 in the pneumatic state, the pressure gain of the nozzle back pressure versus the output pressure is very large, and the nozzle back pressure is Even a small change in pressure will result in a large change in output pressure.

In addition, if the inner valve 36 moves downward and the air supply port 54 remains open, in reality, as described above, the output pressure is input as an electrical signal by the pressure sensor 66 (see Fig. 3). Feedback is given to the side. Therefore, when the output pressure matches the input signal, the nozzle back pressure returns to its original state, which causes the inner valve 36 to
The air supply port 54 and the exhaust port 6 are also restored to their original state.
0 together and a new equilibrium state is obtained.

Next, FIGS. 4 to 6 show second to fourth embodiments of the present invention.

In FIG. 4, a bypass passage 76 with a very small passage diameter is formed in the housing of the converter main body 10 so as to bypass the air supply port 54, and a small amount of pressurized air from the supply port 38 is constantly supplied to the output port 52 side. This is an example of supplying

According to this, even in an equilibrium state of the system, as the output pressure increases successively, the exhaust valve 56 and the air supply valve part 55 of the inner valve 36 open slightly to release the excess pressure (in other words, the air supply valve part 55 opens slightly). ), the valve is sensitive to even the slightest change in nozzle back pressure, further increasing valve accuracy. That is, if the bypass passage 76 is not present, the air supply valve portion 55
When the valve is closed, the air supply port 54, etc. has a lining member made of rubber or the like, and the sensitivity is reduced due to strong contact with the seat portion of the air supply port 54, etc., which has a lining member such as rubber, but this is avoided in this embodiment. be done.

FIG. 5 shows an example in which a bypass passage 78 is formed inside the inner valve 36 for the same purpose as in FIG. 4.

FIG. 6 shows an example in which a bypass passage 80 is formed inside the inner valve 36 as in FIG. 5, but it is formed so as to bypass the exhaust port 60 instead of the air supply port 54. In this case, contrary to FIGS. 4 and 5, the inner valve 36 and the like are slightly opened to introduce the supply pressure to the output side so as to compensate for the output pressure which gradually decreases in the equilibrium state. Further, the bypass passage 80 may be formed in the housing so as to communicate the output port 52 and the exhaust port 50.

In each of the above embodiments, the nozzle flapper mechanism 12 and the pilot valve section 14 are integrated into the converter main body 10, but both 12,
Needless to say, it is possible to construct the 14 parts separately.

[Effects of the Invention] As explained above, according to the present invention, since the nozzle flapper is formed of an electrostrictive element,
The conversion unit can be easily made smaller and lighter by improving vibration resistance and impact resistance.

Furthermore, since the output pressure in the pilot valve part is in the pneumatic state and no feedback is applied to the diaphragm, a large change in output pressure can be obtained even with a small amount of displacement of the electrostrictive element, resulting in savings in power consumption. At the same time, it is possible to reduce the influence of the hysteresis characteristics and nonlinearity of the electrostrictive element, thereby providing a highly accurate conversion unit. Furthermore, since the amount of displacement of the electrostrictive electrons can be small, it is also effective in terms of durability of the electrostrictive element itself.

In addition, since the pilot valve part is constructed as a non-bleed type, there is an advantage that air consumption is small even when used at high pressure.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to the above-mentioned embodiments. Of course, various improvements and changes in design are possible without departing from the gist of the present invention, such as suitably applying it as a type positioner.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the first embodiment of the present invention, FIG. 2 is a front view of the main part thereof, FIG. 3 is a block circuit diagram of the feedback control, and FIGS. 4 to 6 are the second embodiment of the present invention. FIG. 7 is a cross-sectional view of each of the to fourth embodiments. 10...Electric signal-pneumatic conversion unit main body,
12... Nozzle flapper mechanism, 14... Pilot valve section, 16... Nozzle back pressure chamber, 18... Nozzle, 20... Screw, 22... Flutter, 24...
Piezoelectric ceramic, 26... Intermediate electrode plate, 28...
Lead wire, 30... Upper diaphragm, 32...
Lower diaphragm, 34...exhaust valve, 36...inner valve, 38...supply port, 40, 42...passage,
44... fixed orifice, 46... supply pressure chamber,
48... Atmospheric pressure chamber, 50... Passage, 52... Output port, 54... Air supply port, 55... Air supply valve section, 5
6... Exhaust valve section, 58... Exhaust passage, 60... Exhaust port, 62... Passage, 64... O-ring, 66...
... Pressure sensor, 68 ... Amplification circuit, 70 ... Controller, 72 ... Amplification circuit, 74 ... Spring, 76, 78, 80 ... Bypass passage.

Claims (1)

[Claims] 1. A nozzle flapper mechanism that changes the nozzle back pressure according to the amount of displacement of the nozzle flapper, and a diaphragm that responds to the nozzle back pressure to control the opening and closing of an inner valve provided at the air supply port that connects the supply port and the output port to adjust the output air pressure. The nozzle flapper is formed of a bimorph type electrostrictive element that is displaced in response to changes in the electrical signal, while the An electrical signal-pneumatic conversion unit characterized in that a supply pressure chamber is defined by two diaphragms, a nozzle back pressure chamber is defined above the upper diaphragm, and an atmospheric pressure chamber is defined below the lower diaphragm.