Fluid servo valve and fluid servo device

Abstract

To provide a fluid servo valve which can linearize control pressure characteristics on a valve driving current even when a movable plate is spaced away from an electric magnet which exerts magnetic attraction action.SOLUTION: A fluid servo valve includes: a supply nozzle 11 which communicates with a supply side passage 12 and in which a fluid is discharged from a tip part; an exhaust nozzle 21 which communicates with an exhaust side passage 22 and in which the fluid is suctioned from a tip part; a movable plate 3 provided between the tip parts of the supply nozzle 11 and the exhaust nozzle 21; and an electric magnet 4 which deforms at least a part of the movable plate 3 and displaces the movable plate 3 between the supply nozzle 11 and the exhaust nozzle 22. An effective cross sectional area of the supply nozzle 11 is different from an effective cross sectional area of the exhaust nozzle 21.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fluid servo valve that controls the pressure or flow rate of a fluid by displacing a movable plate between a pair of nozzles, and a fluid servo device equipped with the fluid servo valve. [Background technology]

[0002] For example, active vibration isolation tables using pneumatic actuators are used for micro-vibration control of ultra-precision equipment, etc. In such active vibration isolation tables, the position, speed, and acceleration of a stage on which the ultra-precision equipment, etc. is placed are detected by various sensors, and the internal pressure of the pneumatic actuator is controlled based on the output signals of each sensor.

[0003] To control the internal pressure of the pneumatic actuator, the flow rate of compressed air is adjusted by changing the valve drive current applied to the electromagnet of the fluid servo valve and displacing the position of the movable plate between the pair of nozzles.

[0004] In the fluid servo valve used in the above-mentioned active vibration isolation table, it is required that the generated flow rate or pressure has a linear proportional relationship with respect to a wide range of valve drive current.

[0005] This is because, if the fluid servo valve has a nonlinear characteristic of the flow rate or pressure with respect to the valve drive current, the gain margin must be set excessively, and the original performance of the active vibration isolation table cannot be fully demonstrated. In addition, when the stage of the active vibration isolation table is feedforward controlled based on the acceleration signal, if a generated pressure similar to the valve drive current cannot be obtained from the fluid servo valve due to nonlinearity, it becomes difficult to faithfully apply a generated force in the opposite phase to offset the disturbance. In order to be able to offset disturbances with various characteristics, it is preferable that the region in which the characteristics of the generated pressure (generated force) with respect to the current value or voltage value can maintain linearity is as wide as possible, centered on the operating point of the valve drive current.

[0006] The applicant has already proposed a fluid servo valve in which the control pressure or control flow rate with respect to the valve drive current has better linearity than before (see Patent Document 1). This fluid servo valve includes a supply nozzle that supplies a fluid, an exhaust nozzle that is arranged coaxially opposite the supply nozzle, a disk that is a movable plate arranged between the supply nozzle and the exhaust nozzle and has a thickness equal to or less than a predetermined value, and an electromagnet that is arranged on the exhaust nozzle side and attracts the disk. Furthermore, this fluid servo valve is configured so that a magnetic saturation phenomenon of magnetic flux occurs in the disk within the application range of the valve drive current.

[0007] In other words, in the past, when the valve drive current value was larger than a certain value, the displacement of the movable plate changed exponentially and steeply with respect to the change in current.In contrast, the fluid servo valve already proposed utilizes the magnetic saturation phenomenon, making it possible to linearize the displacement characteristics (pressure or flow rate characteristics) of the movable plate with respect to the valve drive current even in the current value range described above, as shown in the graph of Figure 16.

[0008] By the way, the inventors of the present application have studied in detail the fluid servo valve that has already been proposed, and have found that although such a fluid servo valve has improved linearity compared to the conventional one, the effect is limited to a maximum valve drive current of I max In this case, I>I max Note that the range is limited to / 2. In other words, since this servo valve is able to linearize the displacement characteristics of the movable body relative to the valve drive current when the movable plate is approaching the side where the electromagnet is located, the inventors of the present application have noticed that if a method can be found to linearize the control pressure / flow rate characteristics even when the movable plate is away from the electromagnet, the performance of the fluid servo valve can be further improved. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2016-148373 A Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a fluid servo valve that can linearize the control pressure characteristics relative to the valve drive current even when the movable plate is separated from the electromagnet that exerts the magnetic attraction effect, and a fluid servo device equipped with such a fluid servo valve. [Means for solving the problem]

[0011] That is, the fluid servo valve of the present invention comprises a supply nozzle connected to a supply side flow path and ejecting a fluid from its tip, an exhaust nozzle connected to an exhaust side flow path and sucking in a fluid from its tip, a movable plate provided between the respective tips of the supply nozzle and the exhaust nozzle, and an electromagnet that deforms at least a portion of the movable plate and displaces it between the supply nozzle and the exhaust nozzle, and is characterized in that the effective cross-sectional area of ​​the supply nozzle and the effective cross-sectional area of ​​the exhaust nozzle are different.

[0012] In this manner, the effective cross-sectional area of ​​the supply nozzle and the effective cross-sectional area of ​​the exhaust nozzle are different, so that the movable plate is separated from the electromagnet, and therefore it is possible to linearize the control pressure characteristics and flow rate characteristics with respect to the valve drive current, even in the range where the magnetic attraction effect on the movable plate suddenly becomes small.

[0013] That is, in a region where the valve displacement characteristics relative to the valve drive current applied to the electromagnet become nonlinear, the effect of the nonlinearity of the valve displacement characteristics can be "offset" by making the flow characteristics of the supply nozzle and the exhaust nozzle asymmetric.

[0014] Even if a control flow path or the like is formed for supplying a fluid to a controlled object, the configuration on the supply nozzle side can be easily miniaturized, and even if the movable plate is located away from the electromagnet, the linearity of the fluid flow rate or pressure relative to the valve drive current applied to the electromagnet can be improved by providing the electromagnet on the exhaust nozzle side of the movable plate and making the effective cross-sectional area of ​​the supply nozzle larger than the effective cross-sectional area of ​​the exhaust nozzle.

[0015] If the inner diameter of the tip of the supply nozzle is larger than the inner diameter of the tip of the exhaust nozzle, the effective cross-sectional area of ​​the supply nozzle located farther from the electromagnet can be made larger than the effective cross-sectional area of ​​the exhaust nozzle while keeping the outer diameter dimensions of each nozzle the same.

[0016] If a restriction is provided in the exhaust side flow passage, even if the supply nozzle and the exhaust nozzle are of the same type, the effective cross-sectional area of ​​the exhaust nozzle can be made small and the effective cross-sectional area of ​​the supply nozzle can be made relatively large.

[0017] As a specific example of a configuration that can improve the linearity of the flow rate or pressure with respect to the valve drive current even when the movable plate is on the supply nozzle side, even when the movable plate is displaced to the supply nozzle side, the effective cross-sectional area of ​​the supply nozzle can be set to A in , the effective cross-sectional area of ​​the exhaust nozzle is A out In this case, 1.8≦A in / A out ≦4.9.

[0018] In a more preferable embodiment in which a control pressure that is faithfully proportional to a minute amplitude input is obtained, the effective cross-sectional area of ​​the supply nozzle is set to A in , the effective cross-sectional area of ​​the exhaust nozzle is A out In this case, 2.5≦A in / A out ≦4.0.

[0019] For example, in order to achieve a fail-safe by preventing fluid from being supplied from the supply nozzle if electricity cannot be applied to the electromagnet due to a malfunction or power outage, the movable plate needs to be provided with a displacement portion that is displaced between the tips of the supply nozzle and the exhaust nozzle by the suction force of the electromagnet, and a fixed portion whose position is fixed relative to the supply nozzle and the exhaust nozzle, and the tip of the supply nozzle is positioned to protrude a predetermined amount toward the exhaust nozzle beyond the fixed portion.

[0020] In order to realize an appropriate fail-safe according to the magnitude of the force applied to the movable plate by the pressure difference, the effective cross-sectional area of ​​the supply nozzle is set to A in , the effective cross-sectional area of ​​the exhaust nozzle is A out In this case, A in / A out The larger the protrusion amount is set, the larger the protrusion amount is set.

[0021] A in / A out If the rigidity of the movable plate is set to be greater as the pressure difference increases, the movable plate can be prevented from yielding or being damaged even if the force due to the pressure difference applied to the movable plate increases.

[0022] As a specific example of a configuration that realizes a fail-safe in which the supply of fluid from the supply nozzle is automatically cut off in the event of a power outage while realizing linearity of the flow rate or pressure with respect to the valve drive current, when the protrusion amount is X0 and the rigidity of the movable plate is k, the following can be used: in / A out In the range of ≦3.0, 28 μm ≦ X0 ≦ 56 μm, 2.75 × 10 4 N / m≦k≦3.30×10 4 Examples include those set to N / m.

[0023] In order to maintain the linearity of the flow rate or pressure relative to the valve drive current applied to the electromagnet and to obtain good linearity over almost the entire range not only when the movable plate is on the supply nozzle side but also when it is on the exhaust nozzle side, it is sufficient that, in a closed-loop magnetic circuit formed so that the magnetic flux generated by the electromagnet passes at least through the movable plate, the magnetic characteristics of a magnetic material component that forms the closed-loop magnetic circuit have a linear region in which the characteristics of the magnetic flux density relative to the magnetizing force are roughly proportional, and a magnetic saturation region, which is a region in which the inclination angle of the magnetic flux density relative to the magnetizing force changes slightly compared to the linear region, and that the magnetic flux density of the magnetic flux flowing through the magnetic material component falls within the magnetic saturation region when the current passed through the electromagnet is increased within the displacement range of the movable plate.

[0024] For example, in order to easily utilize the magnetic saturation phenomenon by adjusting the shape and dimensions of components, the magnetic flux density of the magnetic flux in the movable plate may be configured to fall within the magnetic saturation region.

[0025] A fluid servo device comprising a fluid servo valve according to the present invention, a pneumatic actuator connected to the fluid servo valve, a sensor for detecting the displacement or vibration state of a controlled object, and a controller for controlling the fluid servo valve based on the output of the sensor, enables the fluid servo valve to achieve linear flow rate or pressure for a wide range of valve drive current, thereby (1) obtaining a wide control range centered on the operating point, (2) generating a highly accurate feedforward signal that cancels disturbances, thereby achieving highly accurate vibration suppression control, and (3) reducing the amplitude dependency of the gain-phase characteristics near the operating point. Effect of the Invention

[0026] Thus, with the fluid servo valve according to the present invention, the linearity of the flow rate or pressure of the fluid relative to the valve drive current can be improved even in an area where the movable plate is away from the electromagnet. As a result, good linearity can be achieved over the entire range of the valve drive current. Furthermore, a fluid servo device using such a fluid servo valve with good linearity can achieve a wide control range and highly accurate FF control. Furthermore, it is possible to obtain a characteristic in which the transfer characteristic (gain-phase characteristic) of the output relative to the input is independent of the magnitude of the input amplitude. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic exploded perspective view of a fluid servo valve according to a first embodiment of the present invention. [Diagram 2] 1A and 1B are a schematic vertical sectional view and a partially enlarged view of a fluid servo valve according to a first embodiment. [Diagram 3] FIG. 2 is a schematic partial enlarged view showing a closed loop magnetic circuit of the fluid servo valve in the first embodiment. [Figure 4] 5 is a schematic diagram showing the positional relationship between each nozzle and a movable plate of the fluid servo valve in the first embodiment. [Diagram 5] 5 is a graph showing an analysis result of input voltage-output voltage characteristics versus effective cross-sectional area ratio of each nozzle of the fluid servo valve in the first embodiment. [Figure 6] A graph highlighting a portion of the analysis results in Figure 5. [Figure 7] 5 is a graph showing an analysis result of the relationship between an input voltage waveform and an output pressure waveform to the fluid servo valve in the first embodiment. [Figure 8] 5 is an analysis result showing an optimal operating range of the fluid servo valve in the first embodiment. [Figure 9] FIG. 5 is a schematic cross-sectional view of a fluid servo valve according to a second embodiment of the present invention. [Figure 10] FIG. 4 is a schematic diagram showing the position of a movable plate when measuring the effective cross-sectional area of ​​each nozzle. [Figure 11] FIG. 4 is a schematic diagram showing a configuration for measuring the effective cross-sectional area of ​​each nozzle. [Figure 12]FIG. 11 is a schematic vertical cross-sectional view of a fluid servo valve according to a third embodiment. [Figure 13] FIG. 13 is a schematic vertical cross-sectional view showing a first modified example of the fluid servo valve in the third embodiment. [Figure 14] FIG. 13 is a schematic vertical cross-sectional view showing a second modified example of the fluid servo valve in the third embodiment. [Figure 15] FIG. 13 is a schematic diagram showing a fluid servo device according to a fourth embodiment. [Figure 16] 4 is a schematic graph showing the characteristics of a conventional fluid servo valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] A fluid servo valve 100 according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

[0029] <Configuration of the fluid servo valve 100> This fluid servo valve 100 is used to control the flow rate of compressed air in order to control the internal pressure of a pneumatic actuator provided on an active vibration isolation table, for example. As shown in the exploded perspective view of Fig. 1, the fluid servo valve 100 is provided with a supply-side valve body formed in a roughly rectangular parallelepiped shape and having a supply-side flow path 12 for supplying compressed air into the inside of the fluid servo valve 100, an exhaust-side valve body 2 formed in a roughly two-stage cylindrical shape and having an exhaust-side flow path 22 for exhausting a portion of the supplied compressed air to the outside, and a movable plate 3 sandwiched between the supply-side valve body 1 and the exhaust-side valve body 2.

[0030] 2, the supply-side valve body 1 is provided with a supply-side flow passage 12 which is a through hole formed along the central axis, and a control flow passage 13 which is a through hole offset a predetermined distance radially outward from the central axis and runs parallel to the supply-side flow passage 12. A roughly thin disk-shaped recess is formed on the inner surface of the supply-side valve body 1, forming a supply-side gap 14 between the supply-side flow passage 12 and the movable plate 3. A supply nozzle 11 is provided on the side of the supply-side flow passage 12 facing the movable plate 3.

[0031] On the other hand, the exhaust side valve body is provided with an exhaust side flow passage 22 which is a through hole formed along the central axis. An exhaust nozzle 21 is provided on the inner surface of the exhaust side valve body 2 in the exhaust side flow passage 22 so as to face the movable plate 3. That is, the supply nozzle 11 and the exhaust nozzle 21 are arranged side by side on the same axis, and the center of the movable plate 3 is disposed between the tips of the nozzles. The exhaust side valve body 2 is also made up of an electromagnet 4 which is roughly cylindrical and has the exhaust nozzle 21 and exhaust side flow passage 22 formed on its central axis, and a roughly cylindrical outer cover 2C which houses the electromagnet 4 inside and is fixed to the supply side valve body 1 to hold the movable plate 3 in between.

[0032] 2, the inner diameter of the tip of supply nozzle 11 is larger than the inner diameter of exhaust nozzle 21. In other words, the effective cross-sectional area of ​​supply nozzle 11, which is disposed on the opposite side of electromagnet 4 with respect to movable plate 3, is configured to be larger than the effective cross-sectional area of ​​exhaust nozzle 21, which is disposed on the same side of movable plate 3 as electromagnet 4. In this way, supply nozzle 11 and exhaust nozzle 21 are configured so that their characteristics are asymmetric with respect to the midpoint of each nozzle.

[0033] 3, the electromagnet 4 includes a coil bobbin 41, a coil 42 wound around the coil bobbin 41, and a yoke 43 that forms a closed-loop magnetic circuit MC of magnetic flux generated when a valve drive current is applied to the coil 42. The coil bobbin 41 is made of a non-magnetic material, and the yoke 43 is made of a magnetic material.

[0034] The yoke 43 is generally cylindrical and comprises a central shaft portion 44 on whose outer peripheral surface the coil bobbin 41 is fitted, a bottom surface portion 45 which spreads radially outward from the base end side of the central shaft portion 44 and is shaped like a thin disk and is fixed to the outer cover by bolts, a generally thin-walled cylindrical outer peripheral portion 46 which extends axially from the outer periphery of the bottom surface portion 45, and a generally thin-walled two-stage cylindrical top surface portion 47 which spreads radially inward from the tip side of the outer peripheral portion 46. The exhaust side gap 23 is formed between the top surface portion 47 and the movable plate 3.

[0035] More specifically, the central shaft portion 44 is hollow cylindrical, and the internal cavity forms the exhaust side flow path 22. The aforementioned exhaust nozzle 21 is formed at the tip of the central shaft portion 44. Furthermore, the first magnetic pole 48 is formed by an annular protrusion with three notches formed so as to surround the periphery of the exhaust nozzle 21. In addition, the top surface portion 47 has a second magnetic pole 49 formed by an annular protrusion protruding from the center so as to be close to the movable plate 3 side. That is, a closed loop magnetic circuit MC is formed so that the magnetic flux generated by the coil 42 circulates through the path of "inside the central shaft portion 44 → first magnetic pole 48 → exhaust side gap portion 23 → movable plate 3 → exhaust side gap portion 23 → second magnetic pole 49 → top surface portion 47 → outer periphery portion 46 → bottom surface portion 45 → central shaft portion 44". In addition, the movable plate 3 is configured such that the magnetic flux density of the magnetic flux within the movable plate 3 causes magnetic saturation depending on the material, thickness, shape, and the like of the movable plate 3.

[0036] More specifically, the magnetic characteristics of the magnetic material parts forming the closed loop magnetic circuit MC have a linear region where the magnetic flux density characteristic is approximately proportional to the magnetizing force, and a magnetic saturation region where the inclination angle of the magnetic flux density to the magnetizing force changes smaller than that in the linear region. The thickness and shape of the movable plate 3 forming a part of the closed loop magnetic circuit MC are set so that the magnetic flux density characteristic to the magnetizing force in the movable plate 3 falls within the above-mentioned magnetic saturation region when the valve drive current is within a predetermined range. When the movable plate 3 is closer to the electromagnet 4 side than a predetermined position between the supply nozzle 11 and the exhaust nozzle 21, magnetic saturation is caused in the movable plate 3 so that the displacement of the movable plate 3 changes approximately proportionally to the change in the valve drive current.

[0037] 1 and 2, the movable plate 3 is a thin, circular disk that is configured to be displaced between the tips of the supply nozzle 11 and the exhaust nozzle 21 by the magnetic attraction force of the electromagnet 4. More specifically, the outer edge of the movable plate 3 is sandwiched and fixed between the supply side valve body 1 and the exhaust side valve body 2, and the movable plate 3 is configured so that the maximum displacement occurs in the center due to elastic deformation of the unfixed portion.

[0038] That is, a displacement portion 31 which is the center of the movable plate 3 is the location which is most displaced by the magnetic attraction force of the electromagnet 4. The outer edge portion of the movable plate 3 is a fixed portion 32 whose position is fixed with respect to the supply nozzle 11 and the exhaust nozzle 21. Specifically, the fixed portion 32 is a portion which is pressed and held between the supply side valve body 1 and the exhaust side valve body 2, and is a portion which is supported by the movable plate 3 at its fixed end.

[0039] 1, four fluid circulation holes 33 are formed in the face plate portion of the movable plate 3 to pass compressed air, which is a fluid, from the supply-side gap 14 to the exhaust-side gap 23, and each fluid circulation hole 33 is arranged in a spiral shape about the center of the movable plate 3. The fluid circulation holes 33 are formed so that the slit width becomes smaller as they move from the outer edge side to the center side. The spiral shape of the fluid circulation holes 33 allows the axial spring rigidity of the movable plate 3 to be set as desired.

[0040] 2 and 4, when no valve drive current is applied to the electromagnet 4, the displacement portion 31 of the movable plate 3 is in contact with the tip of the supply nozzle 11, blocking its opening. Note that for ease of understanding, the radial length of the movable plate 3 is exaggerated in FIG. 4. As shown in the schematic diagram of FIG. 4, the tip of the supply nozzle 11 protrudes toward the exhaust nozzle 21 by a predetermined protrusion amount relative to the fixed portion 32 of the movable plate 3. Therefore, when no magnetic attraction force is acting on the movable plate 3, the movable plate 3 is slightly deformed such that the displacement portion 31 protrudes toward the exhaust nozzle 21 relative to the fixed portion 32 of the movable plate 3.

[0041] In the fluid servo valve 100 thus configured, compressed air supplied from the supply nozzle 11 flows into the supply-side gap 14, and a portion of the compressed air flows out from the control flow path 13 to the pneumatic actuator. The remainder of the compressed air that flows into the supply-side gap 14 flows into the exhaust-side gap 23 through the fluid communication holes 33 of the movable plate 3. The compressed air in the exhaust-side gap 23 is sucked in through the exhaust nozzle 21 and exhausted to the outside through the exhaust-side flow path 22. The position of the movable plate 3 between the supply nozzle 11 and the exhaust nozzle 21 is controlled by the magnetic attraction force of the electromagnet 4, thereby controlling the flow rate of compressed air supplied from the control flow path 13 to the pneumatic actuator.

[0042] The position of the movable plate 3 is determined by the point where the attractive force of the electromagnet and the restoring force of the spring of the movable plate are in balance. in and the flow rate Q flowing out from the control chamber (exhaust side gap 23) to the exhaust nozzle 21. out So that Q in =Q out The pressure at which Q is obtained is the control pressure Pa output from the control flow passage 13. At this time, the larger the opening area of ​​the supply nozzle 11 is and the smaller the opening area of ​​the exhaust nozzle 21 is, the greater the pressure Q is. in =Q out The control pressure Pa that satisfies the above condition becomes a large value.

[0043] In the fluid servo valve 100 of the first embodiment, in the region where the valve displacement characteristic with respect to the valve drive current becomes nonlinear, the flow characteristics of the supply nozzle 11 and the exhaust nozzle 21 are asymmetric, thereby "offsetting" the effect of the nonlinearity of the valve displacement characteristic. For example, even when the movable plate 3 is in a position away from the electromagnet 4, that is, when the movable plate 3 is close to the supply nozzle 11, the control pressure Pa maintains a large value. Due to this asymmetric nozzle effect, max Even in the region of 0.1 V to 1.2 V, the nonlinearity of the control pressure characteristic with respect to the current of the conventional valve can be eliminated.

[0044] <Analysis and experiment results>​ Next, the analysis results for the fluid servo valve 100 of this embodiment will be described with reference to the graph in Fig. 5. In the following description, the operating point is, for example, a value set to the median current value or voltage value in the application range of the valve drive current or valve drive voltage applied to the fluid servo valve 100. The operating point may be set to a value shifted from the median value.

[0045] The graph in FIG. 5 shows the opening area A of the exhaust nozzle 21. out On the other hand, the opening area A of the supply nozzle 11 in Change it to A. in / A out The control pressure (pressure of the fluid flowing out of the control flow path 13) relative to the voltage (valve drive current) applied to the electromagnet 4 was calculated using A as a parameter. in It was found that the following parameters also needed to be changed at the same time according to the magnitude of (1) Protrusion amount of supply nozzle 11 (X0 in FIG. 4) (2) Rigidity of the movable plate 3

[0046] The characteristic curve diagram shown in Fig. 5 was obtained by taking into consideration the above (1) and (2). The reason for this is that, as described above, it is necessary to set the positions of the supply nozzle and the movable plate 3 so that the supply nozzle 11 is blocked by the movable plate 3 when the valve drive current value I = 0 (voltage V = 0). In other words, when the voltage V applied to the electromagnet 4 is 0, the movable plate 3 is pressed against the supply nozzle 11 in a state where it is slightly deformed, as shown in Fig. 4. This is a safety function (fail-safe function) that blocks the inflow of high-pressure air to the pneumatic actuator (not shown) in the event that active control becomes impossible due to a power outage.

[0047] A in When the force acting on the movable plate 3 at the tip surface of the supply nozzle 11 becomes large, the force (= A in × pressure difference) also increases. inIn response to the magnitude of the error, it is necessary to readjust (1) and (2) above. Examples of setting parameters to realize such a fail-safe function are as follows:

[0048] [Table 1]

[0049] That is, the nozzle opening area ratio A in / A out As the amount of protrusion is increased, the rigidity of the movable plate 3 is increased. in / A out In the range of ≦3.0, 28 μm ≦ X0 ≦ 56 μm, 2.75 × 10 4 N / m≦k≦3.30×10 4 Just set it to N / m.

[0050] The graph in Figure 6 shows A in / A out = 1.5, and A in / A out For the case of =4.0, the control pressure characteristic with respect to voltage is extracted from the graph in Figure 5. By drawing an envelope curve (shown by a two-dot chain line) on each characteristic curve (shown by a solid line), the following can be seen. (1) In low pressure regions where the control pressure is close to atmospheric pressure, and in high pressure regions where the control pressure is close to the supply pressure, the control pressure characteristics with respect to voltage are nonlinear. (2) In the intermediate control pressure region, the control pressure characteristic with respect to voltage is linear over a wide range. (3) That is, when a voltage V is applied, the characteristic curve first enters the nonlinear region, then enters the linear region, and then enters the nonlinear region again. (4) A in / A out When the voltage is changed, the control pressure characteristic shifts parallel to the X-axis (voltage). The profile of each characteristic curve is almost the same.

[0051] The graph in Fig. 7 shows a model of the waveform of the control pressure, which is the output signal when the valve drive voltage is input as an input signal to the fluid servo valve 100. in / A out = 1.5 In this example, the central value of the voltage signal at the operating point G is set to the central value of the maximum voltage (5 V in this embodiment).

[0052] From this analysis result, in / A out = 1.5, the control pressure at the operating point G is in the nonlinear region. Also, depending on the amplitude of the input signal, the output pressure waveform has the following characteristics. That is, (1) In the case of a small amplitude input, the output pressure waveform becomes asymmetric in the vertical direction, i.e., the waveform is accompanied by harmonic distortion. (2) In the case of a large amplitude input, the output pressure waveform has a limiter characteristic, i.e., the waveform saturates, so that there is a limit to the magnitude of the lower limit of the control input.

[0053] FIG. 8 shows the aperture area ratio A of an asymmetric nozzle consisting of a supply nozzle 11 and an exhaust nozzle 21, each of which has a different effective cross-sectional area, found in the above-mentioned research. in / A out 13 is a graph showing how to determine an optimum value for

[0054] A verification experiment was carried out by mounting the fluid servo valve 100 of the first embodiment on a pneumatic actuator of an active vibration isolation table. As a result, the following became clear. (1) 1.8 in / A out If the range is set to <4.9, a control pressure that is faithfully proportional to the minute amplitude input can be obtained. This is suitable for vibration isolation control that only handles minute vibrations. (2) 2.5 in / A out If the range is set to <4.0, it can also handle large amplitude input. By applying feedforward control, which cancels large load fluctuations with an inverse phase pressure waveform, sufficient results were obtained. ​​In other words, even if the input amplitude is large, the limiter characteristic as shown in FIG. 7 does not appear in the output control pressure waveform.

[0055] <Effects of the fluid servo valve 100> In this way, in the fluid servo valve 100 of the first embodiment, the effective cross-sectional area of ​​the supply nozzle 11 provided on the opposite side of the movable plate 3 from the electromagnet 4 is set to be larger than the effective cross-sectional area of ​​the exhaust nozzle 21 provided on the same side of the movable plate 3 as the electromagnet 4, so that the control pressure characteristic with respect to the valve drive current can be linearized even when the movable plate 3 is at the position farthest from the electromagnet 4, i.e., even in the initial state where the movable plate 3 is separated from the supply nozzle 11.

[0056] Furthermore, since the fluid servo valve 100 of the first embodiment utilizes the magnetic saturation phenomenon of the magnetic flux flowing inside the movable plate 3, the control pressure characteristic with respect to the valve drive current can be linearized even when the movable plate 3 is on the exhaust nozzle 21 side.

[0057] Therefore, the control pressure characteristic with respect to the valve drive current can be linearized over the entire displacement range of the movable plate 3.

[0058] As a result, the flow rate or pressure of the fluid output from the control flow path 13 can be made faithfully proportional to the input valve drive current or voltage, as shown in the analysis results of Figures 7 and 8. For this reason, by using such a fluid servo valve 100 for controlling an active vibration isolation table, for example, highly accurate feedforward control can be realized, and vibrations of a control target such as a mounted object can be accurately controlled.

[0059] In addition, in this fluid servo valve 100, the movable plate 3 is driven only by the magnetic attractive force of the electromagnet 4. Therefore, no permanent magnets are provided in the supply side valve body 1 and the exhaust side valve body. Therefore, the supply side valve body 1, the movable plate 3, and the exhaust side valve body 2 can be assembled by simply arranging them along the central axis and fixing the supply side valve body 1 and the exhaust side valve body with bolts. Therefore, assembly is easier than with a fluid servo valve that uses a permanent magnet and an electromagnet 4 and uses a flapper as the movable plate 3 that oscillates between the supply nozzle 11 and the exhaust nozzle 21 by magnetic attractive force.

[0060] In other words, conventional fluid servo valves using permanent magnets and nozzle flappers require a large number of high-precision parts due to the three-dimensional part arrangement, which increases manufacturing costs and increases the cumulative error in the nozzle flapper part, making it difficult to achieve uniform performance between each fluid servo valve.

[0061] In contrast, in the fluid servo valve 100 of the first embodiment, when fixing the exhaust valve body 2 to the supply valve body, it is only necessary to sandwich the movable plate 3 formed as a thin disk between them. Therefore, accumulated errors in assembly of the movable plate 3 are unlikely to occur, and the precision required for each part can be reduced. In addition, since the structure is simple and assembly is easy, it is easy to standardize the performance between the fluid servo valves 100.

[0062] Next, a fluid servo valve 100 in a second embodiment will be described with reference to Fig. 9. Note that the same reference numerals will be used to designate members corresponding to those described in the first embodiment.

[0063] <Configuration of the fluid servo valve 100> The fluid servo valve 100 of the second embodiment differs from the fluid servo valve 100 of the first embodiment in the following respects. That is, the fluid servo valve 100 of the second embodiment differs in that, while the inner diameters of the supply valve and the exhaust valve are set to the same diameter, a throttle 5 is provided in the exhaust-side flow path 22. This throttle 5 is composed of, for example, a blocking plate provided so as to block the exhaust-side flow path 22, and a hole with a diameter smaller than the inner diameter of the tip of the exhaust nozzle 21.

[0064] <Effects of the fluid servo valve 100> That is, in the fluid servo valve 100 of the second embodiment, the configurations of the supply nozzle 11 and the exhaust nozzle 21 are common, while the characteristics of the supply nozzle 11 and the exhaust nozzle 21 can be changed by the restrictor 5 provided in the exhaust-side flow path 22. As a result, in the second embodiment as well, the effective cross-sectional area of ​​the supply nozzle 11 can be set to be larger than the effective cross-sectional area of ​​the exhaust nozzle 21.

[0065] Therefore, even in the fluid servo valve 100 of the second embodiment, the control pressure characteristic can be linearized with respect to the valve drive current over the entire displacement range of the movable plate 3, similar to the first embodiment.

[0066] Also, by changing the diameter of the hole of the orifice 5 provided in the exhaust side flow path 22, it is possible to absorb, for example, manufacturing errors of each nozzle and realize a desired effective cross-sectional area ratio. Also, since fluid servo valves 100 with various characteristics can be realized simply by changing the orifice 5, it is easy to realize product variations while limiting the number of types of parts.

[0067] Here, we will supplement the definition of the effective cross-sectional area (effective flow area) of the nozzle. In either case where no throttle is provided in the exhaust side flow path 22 as in the fluid servo valve 100 of the first embodiment, or where a throttle is provided in the exhaust side flow path 22 as in the fluid servo valve 100 of the second embodiment, the effective cross-sectional areas of the supply nozzle 11 and the exhaust nozzle 21 can be actually measured by the experimental method described below.

[0068] As shown in FIG. 10, the effective cross-sectional area A in When actually measuring, the valve drive voltage is set to a maximum and the exhaust nozzle 21 is closed by the movable plate 3. Based on the supply pressure Ps of the supply nozzle 11 at this time and the actual measured flow rate of the fluid flowing through the control flow passage 13 that is open to the atmosphere, the effective cross-sectional area A in Similarly, the effective cross-sectional area A of the exhaust nozzle 21 is calculated. out When actually measuring, the valve drive voltage is set to zero and the supply nozzle 11 is closed by the movable plate 3. Based on the supply pressure Ps of the control flow passage 13 at this time and the actual measured flow rate of the fluid flowing through the exhaust side flow passage 22, the effective cross-sectional area A out The experimental apparatus shown in FIG. 11 and the formula for calculating the effective sectional area may be, for example, that specified in JIS B 8390.

[0069] The experimental apparatus consists of a pressure measuring mechanism PM equipped with a pressure regulator P1 and a pressure sensor P2 connected to the supply side flow path 12 or the control flow path 13 of the fluid servo valve 100 as shown in Figure 11, and a flow rate measuring mechanism FM connected to the control flow path 13 or the exhaust side flow path 22 of the fluid servo valve 100.

[0070] In the second embodiment described above, only the case where the exhaust side flow passage 22 is provided with a throttle has been described, but the supply side flow passage 12 can also be provided with a throttle in the same manner. in can be calculated using the above-mentioned measurement method.

[0071] Next, a fluid servo valve 100 in a third embodiment will be described with reference to Fig. 12. Note that the same reference numerals will be used to designate members corresponding to those described in the first embodiment.

[0072] The fluid servo valve 100 of the first embodiment is composed of only axisymmetric parts. In contrast, the fluid servo valve 100 of the third embodiment is formed by combining various iron cores such as rectangular pillars, cylinders, horseshoe-shaped and annular cores, rectangular thin plate materials, square blocks, etc., in addition to axisymmetric parts, to form a closed loop magnetic circuit MC and a fluid circuit.

[0073] More specifically, in Fig. 12, the block arranged on the upper side is the supply-side valve body 1 in which the supply-side flow path 12 and the control flow path 13 are formed, and the block arranged on the lower side is the exhaust-side valve body 2. In the third embodiment, the supply-side flow path 12 through which compressed air flows and the exhaust-side flow path 22 are arranged coaxially at the outer edge of each valve body. The movable plate 3 is a rectangular thin plate with one end fixed to the supply-side valve body 1, and its free end side is arranged between the tips of the supply-side nozzle and the exhaust nozzle 21 in a cantilever state. In addition, the exhaust-side valve body 2 is composed of an arm portion 4A provided in the yoke 43 so that its magnetic pole faces the center portion of the movable plate 3, and a core portion 4B fixed to the arm portion 4A and the supply-side valve body 1 with bolts.

[0074] The inner diameter of the supply nozzle 11 is larger than the inner diameter of the exhaust nozzle 21, and the nozzle is configured as an asymmetric nozzle. In addition, the closed loop magnetic circuit MC including the movable plate 3 is configured so that the magnetic flux circulates in the order of the core part 4B, the arm part 4A, inside the movable plate 3, and the core part 4B. The movable plate 3 is configured to have the thinnest thickness among the members constituting the closed loop magnetic circuit MC, and is configured so that the magnetic saturation phenomenon occurs within the displacement range of the movable plate 3.

[0075] Even in the fluid servo valve 100 of the third embodiment, by utilizing the magnetic saturation phenomenon and configuring the supply nozzle 11 and the exhaust nozzle 21 as asymmetric nozzles, the control pressure characteristics with respect to the valve drive current can be linearized over the entire displacement range of the movable plate 3.

[0076] A modification of the third embodiment will be described with reference to FIGS.

[0077] 13 and 14, the coil 42 of the electromagnet 4 may be configured to be exposed to the outside from within the accommodation space formed between the supply side valve body 1 and the exhaust side valve body 2. Also, as shown in Fig. 13, the shape of the core part 4B of the exhaust side valve body 2 may be changed and the fixed end of the movable plate 3 may be fixed to the exhaust side valve body 2 with a bolt. As shown in Fig. 14, a thin part or a notch 34 may be formed in part of the movable plate 3 so that the displacement part 31 is displaced more greatly by the magnetic attraction force of the electromagnet 4.

[0078] A fluid servo device 200 according to a fourth embodiment will be described. As shown in FIG. 15, the fluid servo valve 100 described in each of the above-described embodiments may be used to configure an active vibration isolation table, which is the fluid servo device 200. Specifically, the active vibration isolation table includes a table ST on which an object to be isolated or controlled is placed, a pneumatic actuator AS provided on the leg of the table ST and connected to the fluid servo valve 100, a sensor SN that detects the displacement or vibration state of the table ST, which is the object to be controlled, and a controller CN that controls the fluid servo valve 100 based on the output of the sensor SN. The position, speed, and acceleration of the table ST are detected by a plurality of sensors SN provided on the table ST and the foundation, and the output signals of these sensors are input to the controller CN. The controller CN is a device whose functions are realized by using, for example, a computer, and controls the fluid servo valve 100 by feedforward control so that the influence of disturbances such as vibration of the foundation is canceled based on the output of each input sensor SN. That is, the controller CN controls the pressure or flow rate of compressed air supplied to the pneumatic actuator AS via the control flow path 13 from the fluid servo valve 100 connected to a supply source of compressed air.

[0079] With such a fluid servo device 200, the fluid pressure or flow rate output by the fluid servo valve 100 has linearity over a wide range of valve drive current, making it possible to realize highly accurate feedforward control so as to cancel various disturbances to the table ST.

[0080] Other embodiments will be described. The fluid servo valve may have an electromagnet in the supply side valve body. In such a case, the effective cross-sectional area of ​​the exhaust nozzle provided on the opposite side of the electromagnet with respect to the movable plate may be made larger than the effective cross-sectional area of ​​the supply side nozzle. In other words, by making the effective cross-sectional area of ​​the nozzle on the side farther from the electromagnet with respect to the movable plate larger than the effective cross-sectional area of ​​the other nozzle, the control pressure characteristic can be linearized in a state where the movable plate is displaced to a position farther from the electromagnet than the operating point.

[0081] The movable plate is not limited to a thin circular disk or a thin rectangular parallelepiped plate member, and may have various shapes. In addition, the fluid servo valve according to the present invention may be configured so that the magnetic saturation phenomenon does not occur in the closed loop magnetic circuit.

[0082] The effective cross-sectional areas of the supply nozzle and the exhaust nozzle may be made asymmetrical by, for example, narrowing the flow path diameter of the supply flow path or the exhaust flow path to act as a flow path resistance.

[0083] The position of the movable plate when no valve drive current is applied to the electromagnet is not limited to a position that allows it to close the supply nozzle. For example, if a separate fail-safe mechanism is provided, the movable plate may be spaced apart from the tip of the supply nozzle when no valve drive current is applied to the electromagnet.

[0084] The fluid servo valve according to the present invention is not limited to use for controlling pneumatic actuators, but may be used for other purposes requiring control of the pressure or flow rate of fluids.

[0085] The fluid servo device according to the present invention is not limited to an active vibration isolation table, but may be, for example, a passive vibration isolation table in which only feedback control is performed, or other devices.

[0086] In addition, various modifications may be made and parts of each embodiment may be combined together as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0087] 200 Fluid servo device 100 Fluid Servo Valve 11 Supply valve 21 Exhaust valve 3...Movable plate 4. Electromagnet

Claims

1. a supply nozzle that is connected to a supply-side flow path and that ejects a fluid from a tip thereof; an exhaust nozzle that is connected to an exhaust side flow path and that draws in a fluid from a tip thereof; a movable plate provided between the tip ends of the supply nozzle and the exhaust nozzle; an electromagnet that deforms at least a portion of the movable plate and displaces the movable plate between the supply nozzle and the exhaust nozzle; the movable plate is moved by the attractive force of the electromagnet and contacts the tip of the supply nozzle to close the opening of the supply nozzle; an effective cross-sectional area of ​​the supply nozzle and an effective cross-sectional area of ​​the exhaust nozzle are greater than that of the exhaust nozzle; In the fluid supplied from the supply nozzle, a control pressure characteristic of the fluid output from the control flow path with respect to an applied voltage is set to be located in a linear region in which an operating point that is a median value in an applied range of a drive current or a drive voltage is located in an intermediate region, A fluid servo valve, characterized in that an area of ​​said movable plate covering each nozzle tip surface is a flat surface.

2. 2. The fluid servo valve according to claim 1, wherein the electromagnet is provided on the exhaust nozzle side with respect to the movable plate.

3. 3. The fluid servo valve according to claim 2, wherein an inside diameter of the tip of said supply nozzle is larger than an inside diameter of the tip of said exhaust nozzle.

4. 3. The fluid servo valve according to claim 2, wherein a throttle is provided in the exhaust side flow passage.

5. The effective cross-sectional area of ​​the supply nozzle is A in , the effective cross-sectional area of ​​the exhaust nozzle is A out In this case, 1.8≦A in / A out 3. The fluid servo valve of claim 2, configured to satisfy ≦4.

9.

6. The effective cross-sectional area of ​​the supply nozzle is A in , the effective cross-sectional area of ​​the exhaust nozzle is A out In this case, 2.5≦A in / A out 3. The fluid servo valve of claim 2, configured to satisfy ≦4.

0.

7. The movable plate is a displacement portion that is displaced between the tip portions of the supply nozzle and the exhaust nozzle by an attractive force of the electromagnet; a fixed portion whose position is fixed with respect to the supply nozzle and the exhaust nozzle, 3. The fluid servo valve according to claim 2, wherein a tip of the supply nozzle is disposed so as to protrude a predetermined protruding amount toward the exhaust nozzle beyond the fixed portion.

8. In a closed loop magnetic circuit formed so that the magnetic flux generated by the electromagnet passes at least through the movable plate, the magnetic characteristics of the magnetic material components forming the closed loop magnetic circuit have a linear region in which the magnetic flux density characteristic is approximately proportional to the magnetizing force, and a magnetic saturation region in which the gradient angle of the magnetic flux density to the magnetizing force changes smaller than that in the linear region, 2. A fluid servo valve according to claim 1, wherein the magnetic flux density of the magnetic flux flowing through the magnetic material component falls within the magnetic saturation region when the current passing through the electromagnet is increased within the displacement range of the movable plate.

9. 9. The fluid servo valve according to claim 8, wherein the magnetic flux density in the movable plate is configured to fall within the magnetic saturation region.

10. A fluid servo valve according to any one of claims 1 to 9, a pneumatic actuator connected to the fluid servo valve; A sensor for detecting a displacement or vibration state of a controlled object; and a controller for controlling the fluid servo valve based on an output of the sensor.

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