JPH0445686B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical signal-to-pneumatic conversion unit that converts an electrical signal into fluid pressure, particularly air pressure, and more particularly relates to an electrical signal-to-pneumatic conversion unit that converts an electrical signal into fluid pressure, particularly air pressure.
The present invention relates to an electrical signal-to-pneumatic pressure conversion unit configured so that the ratio of output air pressure to nozzle back pressure, that is, the pressure gain, can be extremely large.

Conventionally, torque motors have been incorporated into devices widely used to convert electrical signals into pneumatic pressure. That is, according to this torque motor, a current is supplied to the coil that constitutes the motor, a rotational force corresponding to this current is obtained to displace the flapper, and this changes the nozzle back pressure to displace the diaphragm. The output air pressure is controlled by opening and closing the fluid passage through a valve body attached to this diaphragm.

According to such conventional technology, a relatively large torque motor must be built into the main body of the electrical signal-to-pneumatic converter, which inevitably increases the size of the device as a whole. Moreover,
The movable coil of the torque motor incorporated in this way is supported by a thin leaf spring so that it can respond even to weak signals. Therefore, even if a minute vibration is caused, this leaf spring moves together. Vary the nozzle back pressure. For this reason, there is a problem that the output pressure fluctuates and precise electrical signal-pneumatic pressure conversion cannot be achieved.
As a result, the disadvantage of being weak against mechanical vibrations has been exposed. In addition, in the device according to the prior art,
The gain of output air pressure with respect to nozzle back pressure is low,
In addition, it has been pointed out that the system is susceptible to the effects of the tension of the diaphragm, and as a result, it is difficult to convert electrical signals to pneumatic pressure with high accuracy. Furthermore, due to the structure, the exhaust flow rate cannot be increased, so when the pressure on the load side suddenly increases significantly, the exhaust gas cannot follow it.

The present invention has been made to overcome such inconveniences, and the flapper is composed of an electrostrictive element, and the nozzle back pressure acts on one of the two diaphragms arranged in parallel. On the other hand, supply air pressure is applied between the two diaphragms, and output air pressure is applied to the other diaphragm, and the effective area of each diaphragm is It is an object of the present invention to provide an electrical signal-pneumatic pressure conversion unit which can select a difference as large as possible, thereby achieving a large gain in output air pressure with respect to nozzle back pressure, and which can also be made smaller and lighter.

In order to achieve the above object, the present invention includes a nozzle flapper mechanism that changes nozzle back pressure according to the amount of displacement of the flapper, and an air supply port that connects a supply port and an output port by a diaphragm that responds to the nozzle back pressure. In the electrical signal-pneumatic pressure conversion unit including a non-bleed type pilot valve section that controls the output air pressure by controlling the opening and closing of a provided inner valve, the flapper is composed of an electrostrictive element that is displaced in response to changes in the electrical signal. , the diaphragm is composed of two diaphragms with different sizes and areas, one diaphragm has a through hole for the nozzle facing, and a passage for introducing supply air pressure is facing between the two diaphragms, and the other diaphragm A passage for introducing the output air pressure is faced, the passage for introducing the output air pressure is branched and communicated with a pressure sensor installed inside the unit main body, and the output of the pressure sensor is used to control the electrostrictive element. It is characterized by

In the electrical signal-to-air pressure conversion unit configured as described above, the nozzle back pressure changes by displacing the flapper made of an electrostrictive element toward the nozzle, and under the action of this nozzle back pressure, one diaphragm is displaced.

By the displacement of the diaphragm, a passage for introducing supply air pressure and a passage for introducing output air pressure are opened, and a part of the supply air pressure becomes output air pressure and is supplied to the passage for introducing output air pressure and the pressure sensor.

When this output air pressure reaches an air pressure corresponding to the nozzle back pressure, the passage for introducing the supply air pressure and the passage for introducing the output air pressure are closed under the action of the other diaphragm that is displaced by the output air pressure. .

At this time, since the output air pressure read by the pressure sensor is used to control the electrostrictive element, the output air pressure can be controlled with high accuracy.

Furthermore, since the supply air pressure is supplied between the two diaphragms, it is possible to obtain a large gain in the output air pressure with respect to the nozzle back pressure.

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 indicates the main body of the electrical signal-to-pneumatic conversion unit according to the present invention, and this main body 10 has a nozzle flapper mechanism 12 provided in the upper part of the interior thereof, and a pilot valve part 14 provided in the lower part of the interior thereof. include.

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 (described later) via a passage 17, and a plate whose base end is locked to the conversion unit main body 10 by a screw 20. It consists of a flapper 22 shaped like the above. Said flapper 2
2 is formed of a so-called electrostrictive element consisting of two piezoelectric ceramics 24, 24 provided with electrodes (not shown) and an intermediate electrode plate 26 sandwiched between these piezoelectric ceramics 24, 24. , lead wires 28, 2 connected to the piezoelectric ceramics 24, 24, respectively.
The configuration is such that a predetermined voltage is applied via the terminal 8.

On the other hand, the pilot valve section 14 includes two diaphragms 30 and 32 arranged in parallel in the vertical direction, and an exhaust valve 3 interlocked with these diaphragms 30 and 32.
4 and an inner valve 36. As can be easily understood from the figure, in this case, the upper diaphragm 30 is selected to have a larger effective operating area than the lower diaphragm 32.

The inner valve 36 is screwed to the lower end of a diaphragm disk 33 that holds the diaphragms 30 and 32 apart by a predetermined distance, and can slide airtight inside an annular body 40 having a seal ring 38. A downwardly directed bullet-shaped valve body 42 is formed at the tip of the inner valve 36 , and the valve body 42 is configured to sit on a valve seat 44 of the exhaust valve 34 . That is, an annular groove 50 is defined in the support body 48 that is screwed into the main body 10 via the seal ring 46, and an exhaust port 52 is formed through the central axis of the support body 48.
is formed. The exhaust valve 34 is slidable in the vertical direction in the figure through the exhaust port 52 via a seal ring 54. Substantially, the exhaust valve 34
has a flange 56 at its upper end, and a rubber packing 58 is fitted onto this flange 56.
Therefore, when the coil spring 60 mounted so as to revolve inside the concave groove 50 resiliently abuts on the flange 56, the rubber gasket 58 is moved against the main body 1.
It will be easily understood that the annular wall portion 62 is pressed into contact with the annular wall portion 62 protruding inside the 0.

On the other hand, a supply port 66 is defined on one side of the conversion unit main body 10.
Passages 68a, 68b, 68c, 68d from the middle of
and 68e communicate with each other so that the nozzle back pressure chamber 16
It extends to In addition, at that time, the supply port 66
A fixed orifice 70 is interposed in a passage 68d located downstream of the passage 68d, and a passage 68f branches from the passage 68d and communicates with a supply pressure chamber 72 defined between the diaphragms 30 and 32. Therefore, it becomes possible to introduce supply pressure into the supply pressure chamber 72 through the passage 68f. When the nozzle back pressure increases, the valve body 42 is displaced downward to connect the supply port 66 and the output port 78, and when the nozzle back pressure is decreased, the valve body 42 is displaced upward to connect the exhaust port 5.
It is necessary to exhaust the output pressure from 2. For this reason,
By introducing supply pressure into the supply pressure chamber 72 defined between the two diaphragms 30 and 32, it is necessary to generate a force that always holds the valve body 42 in an upward direction. It is. Further, an output pressure chamber 74 is defined below the diaphragm 32 and is configured to communicate with an output port 78 via a passage 76 .

In this case, the inner valve 36 is arranged so as to close the passage 80 connecting the supply port 66 and the output port 78 when the three pressures, that is, the nozzle back pressure, the supply pressure, and the output pressure are balanced, and as described above, At that time, the valve body 42 constituting the inner valve 36 engages with the valve seat 44 formed on the exhaust valve 34, and since the wall portion 62 comes into close contact with the rubber packing 58, this valve seat 44 via output port 78,
It is configured to close the exhaust port 52. Therefore, it is easily understood that this pilot valve section 14 is a non-bleed type in which exhaust is not performed during equilibrium.

On the other hand, a pressure sensor 82 is disposed inside the main body 10, and this pressure sensor 82 receives an output pressure signal from the output port 78 via a passage 83. Although not shown, the pressure sensor 82 includes a semiconductor diaphragm therein, and this semiconductor diaphragm achieves the function of converting the output pressure signal into a voltage signal.

That is, as shown in FIG. 2, when the output pressure from the pilot valve section 14 is detected as an electrical signal by the pressure sensor 82, this detection signal is
The signal is fed back to the controller 86 via the amplifier circuit 84, and the controller 86 compares the detection signal with the input signal. The voltage signal related to the deviation after the comparison is amplified by the amplifier circuit 88 and applied to the flapper 22 according to the deviation, and as a result, the nozzle back pressure in the nozzle back pressure chamber 16 changes. The change in nozzle backpressure causes displacement of the diaphragms 30,32.

On the other hand, the output pressure from the pilot valve section 14 is also applied to the output pressure chamber 74 via the passage 76. That is, the pressure that tends to lower the diaphragm 30 due to a change in nozzle back pressure, for example, will oppose the feedback pressure applied to the output pressure chamber 74. Therefore, the change in the nozzle back pressure is added to the feedback pressure acting as a negative element, and the exhaust valve 34 is displaced by the substantial difference. As a result, the output pressure from the output port 78 constitutes a feedback system for the diaphragm 32, and a minor loop for this feedback is formed in the pilot valve section 14.

In other words, even if an input signal is applied to the nozzle flapper mechanism 12 with a sudden change and the output side is about to change suddenly, the branched pressure from the output port 78 is outputted via the passage 76. Because of the supply to pressure chamber 74, rapid changes in diaphragms 30, 32 in response to the input signal will be prevented within a short period of time.
Therefore, stable output pressure can be obtained.

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

First, according to the findings of the present inventors, it is possible to obtain a large pressure gain with respect to the nozzle back pressure in the following manner. That is, the relationship between the output pressure and the nozzle back pressure is expressed as the ratio of the effective areas of the two diaphragms, that is, the effective area of the diaphragm 30/the effective area of the diaphragm 32. Therefore, in order to increase the pressure gain of the output pressure with respect to the nozzle back pressure, it is sufficient to select a large effective area difference between the two diaphragms.

Therefore, when the voltage applied to the flapper 22 made of an electrostrictive element increases while the system is in equilibrium as shown in FIG. 1, the free end of the flapper 22 is displaced in the direction of closing the nozzle 18. This results in
Since the amount of air ejected from the nozzle 18 decreases, the pressure in the nozzle back pressure chamber 16 (nozzle back pressure) increases, and this pressure acts on the upper surface of the upper diaphragm 30. That is, it acts as pressure to lower the upper diaphragm 30.

As a result, the equilibrium state of the system is disrupted, the upper diaphragm 30 and the lower diaphragm 32 are integrally displaced downward, and with this downward action, the valve body 42 of the inner valve 36 resists the elastic force of the spring 60. The exhaust valve 34 is then lowered. Therefore, the rubber gasket 58 is separated from the wall portion 62 to open a passage 80 that communicates the supply port 66 and the output port 78.
Eventually, a portion of the supply pressure from the supply port 66 becomes output pressure and is supplied to the output port 78. This output air is supplied to the load side (not shown) and performs the intended function.

At this time, in this embodiment, as described above, the ring body 40 on which the inner valve 36 slides is hermetically sealed by the seal ring 38, while the output pressure is applied to the lower diaphragm 32 via the passage 76. It is composed of Furthermore, the supply pressure from the supply port 66 is supplied to the nozzle back pressure chamber 16 via passages 68a to 68e. Therefore, as described above, if the effective area difference between the two diaphragms 30 and 32 is selected to be large, it is possible to obtain a large pressure gain between the nozzle back pressure and the output pressure, and the nozzle back pressure changes slightly. The output pressure will change significantly just by doing so.

As described above, the pressure sensor 82 feeds back the output pressure to the input side as an electrical signal. Therefore, when the output pressure matches the input signal, the inner valve 36 also returns to its original state, closes the valve seat 44, and a new equilibrium state is obtained. On the other hand, when the pressure on the output port 78 side increases, the inner valve 36 rises and the exhaust port 52 is opened. Therefore, the pressure fluid on the output port side is bled from this exhaust port 52.

In the above embodiments, the nozzle flapper mechanism 12 and the pilot valve part 14 are integrated into the unit body 10, but the nozzle flapper mechanism 12 and the pilot valve part 14 are Needless to say, they can be configured to be separated.

As explained above, according to the present invention, the pressure gain can be increased by increasing the effective area difference between the two diaphragms in the pilot valve part, and even a small amount of displacement of the electrostrictive element can cause a large It becomes possible to obtain a change in output pressure. Furthermore, there is an advantage that a highly accurate conversion unit can be provided by reducing the effects of hysteresis characteristics and nonlinearity of the electrostrictive element. Furthermore, since the amount of displacement of the electrostrictive element is 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. Further, according to the present invention, the supply pressure is fed back to the middle of the two diaphragms, and the output pressure is fed back to the bottom side of the diaphragm with a small area, and exhaust is performed from below, so that the pressure is reduced. It becomes possible to further increase the gain and has the advantage of improving the stability of the output.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to the above embodiments, and the present invention unit is used as a pilot relay to control the displacement of a control valve. 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 pneumatic positioner.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an electrical signal-to-pneumatic conversion unit according to the present invention, and FIG. 2 is an explanatory view of a control system used in the unit of the present invention. DESCRIPTION OF SYMBOLS 10...Unit main body, 12...Nozzle flapper mechanism, 14...Pilot valve part, 16...Nozzle back pressure chamber, 18...Nozzle, 22...Flapper, 24...Piezoelectric ceramic, 26...Intermediate electrode plate, 28...Lead wire, 30, 32 ...Diaphragm, 33...Diaphragm disk, 34...Exhaust valve, 36...Inner valve, 38
...Seal ring, 42...Valve body, 44...Valve seat, 46
...Seal ring, 48...Support, 52...Exhaust port, 56...Flange, 58...Rubber packing, 60
... Spring, 66 ... Supply port, 72 ... Supply pressure chamber, 74 ... Output pressure chamber, 78 ... Output port, 82
...Pressure sensor, 84...Amplification circuit, 86...Controller, 88...Amplification circuit.

Claims (1)

[Scope of Claims] 1. A nozzle flapper mechanism that changes nozzle back pressure according to the amount of displacement of the flapper, and an inner valve provided at an air supply port that connects a supply port and an output port with a diaphragm that responds to the nozzle back pressure. In an electrical signal-pneumatic conversion unit that includes a non-bleed type pilot valve that controls output air pressure by opening and closing, the flapper is composed of an electrostrictive element that displaces in response to changes in the electrical signal, and has two diaphragms. It consists of diaphragms of different sizes, with one diaphragm facing the nozzle hole, and
A passage for introducing supply air pressure is made to face between the two diaphragms, and a passage for introducing output air pressure is made to face the other diaphragm, and the passage for introducing the output air pressure is branched to increase the pressure inside the unit body. An electrical signal-pneumatic conversion unit, characterized in that it communicates with a sensor and uses the output of the pressure sensor to control the electrostrictive element. 2. In the unit according to claim 1, the inner valve coupled to the diaphragm engages with the exhaust hole, and the exhaust hole is opened under the action of displacement of the inner valve to bleed the output side pressure fluid. An electric signal to pneumatic conversion unit configured as follows.