VALVE DEVICE

A valve device may include a housing, an inlet passage into which a fluid is introduced from outside, a first discharging unit disposed at a downstream end of the inlet passage, an outlet passage communicating with the first discharging unit and configured to discharge the fluid outside, a communication chamber communicating with the first discharging unit and including an end communicating with the outlet passage, a valve seat disposed on the first discharging unit, a valve body configured to contact the valve seat and to open and close the first discharging unit, a plunger configured to move the valve body relative to the valve seat, a driving unit fixed to the housing and supporting the plunger in a movable state, and a restricting portion configured to restrict movement of the valve body by being interposed between the plunger and the driving unit when the first discharging unit is open.

REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2022-165622 filed on Oct. 14, 2022, the contents of which are hereby incorporated by reference into the present application.

TECHNICAL FIELD

The description herein discloses an art related to valve devices.

BACKGROUND ART

JP 2008-232352 A (hereinbelow termed Patent Document 1) describes a valve device configured to open and close a fluid channel. The valve device of Patent Document 1 includes a housing constituting the fluid channel, a valve seat disposed in the housing, a valve body configured to contact the valve seat, a plunger fixed to the valve body, and a driving unit fixed to the housing and supporting the plunger in a movable state. In Patent Document 1, the fluid channel is opened and closed by moving the plunger by the driving unit so that the valve body comes into contact with and separates from the valve seat. Further, in Patent Document 1, a cushioning member is disposed between the plunger and the driving unit (at a portion that is immobile relative to the housing) to suppress impact from being applied to the plunger and the driving unit by these members contacting each other. The cushioning member is disposed on the plunger an opposite side from where the plunger is fixed to the valve body.

SUMMARY

In the case of the valve device of Patent Document 1, not only a space for the plunger to move but also a space for arranging the cushioning member need to be secured between the plunger and the driving unit. If the cushioning member is not disposed between the plunger and the driving unit, the space for arranging the cushioning member can be omitted, by which the size reduction of the valve device can be achieved accordingly. However, unless the cushioning member is disposed between the between the plunger and the driving unit, a possibility that the plunger and the driving unit come into contact cannot be eliminated, and a possibility that impact is applied to these members cannot be eliminated. That is, in Patent Document 1, the size reduction of valve components and impact suppression between the plunger and the driving unit are in a tradeoff relationship. The description herein aims to provide an art for reducing a size of a valve device while suppressing an impact between a plunger and a driving unit.

A first aspect of the art disclosed herein is a valve device configured to open and close a fluid channel. The valve device may comprise: a housing; a inlet passage disposed inside the housing and into which a fluid is introduced from outside; a first discharging unit disposed at a downstream end of the inlet passage; an outlet passage disposed inside the housing, communicating with the first discharging unit, and configured to discharge the fluid outside; a communication chamber communicating with the first discharging unit and including an end communicating with the outlet passage; a valve seat disposed on the first discharging unit; a valve body configured to contact the valve seat and to open and close the first discharging unit; a plunger fixed to the valve body and configured to move the valve body relative to the valve seat; and a driving unit fixed to the housing and supporting the plunger in a movable state. Further, the valve body may comprise a restricting portion configured to restrict movement of the valve body by being interposed between the plunger and the driving unit when the first discharging unit is open.

A second aspect disclosed herein may be the valve device of the first aspect, in which the valve body may be in a diaphragm shape and may comprise an outer peripheral portion fixed to the driving unit, a center portion fixed to the plunger, and a deformable portion disposed between the outer peripheral portion and the center portion and configured to deform when the valve body opens and closes. Further, the deformable portion may be located closer to a bottom surface of the communication chamber at its portion on a center portion side than at its portion on an outer peripheral portion side.

A third aspect disclosed herein may be the valve device of the second aspect, in which when the valve body is closed, a distance between the driving unit and the deformable portion may become larger from the outer peripheral portion toward the center portion.

According to the first aspect, the valve body functions as the cushioning member that buffers the impact application between the plunger and the driving unit. That is, according to the first aspect, the cushioning member dedicated solely to the purpose of suppressing the direct contact between the plunger and the driving unit can be omitted. The space for arranging the cushioning member does not need to be secured between the plunger and the driving unit (only the space for the plunger to move plunger needs to be secured on the opposite side from where the valve body is fixed), and the size of the valve device can be reduced. Further, by omitting the cushioning member, cost of the valve device (such as material cost and production cost) can also be reduced.

If the driving unit is of a configuration that drives the plunger by electrically conducting an electromagnetic coil (a so-called solenoid valve), it is a normally-off type, in which the valve body is normally closed when it is in a nonconductive state and opens in a conductive state. To realize the normally-off type, a spring and the like is disposed between the plunger and the driving unit and the valve body is seated on the valve seat using a biasing force (expanding force) of the spring. In this case, a space for arranging the spring and the like needs to be secured between the plunger and the driving unit. Due to this, in a conventional valve device that arranges the cushioning member between the plunger and the driving unit tends to have a smaller cushioning member size (surface area). As a result, a load (surface pressure) applied on the cushioning member when it is held between the plunger and the driving unit becomes larger, and the cushioning member becomes more susceptible to degradation. That is, durability of the cushioning member is reduced, and life of the valve device becomes shorter. According to the first aspect, by adding a function as the cushioning member to the valve body, a large cushioning member size can be secured and life of the valve device can be elongated.

According to the second aspect, the deformable portion starts to come into contact with the driving unit (starts to be held by the driving unit and the valve body) when the valve body opens (shifts from a closed state to an opened state). As a result, a wide contact area between the deformable portion and the driving unit can be secured, by which the load applied to the valve body (deformable portion) is reduced, and the life of the valve device can further be elongated. Further, since the deformable portion is disposed between the outer peripheral portion and the center portion of the valve body (that is, the deformable portion, the outer peripheral portion, and the center portion of the valve body are integrated), by starting to contact the driving unit from the outer circumferential side of the deformable portion upon when the valve opens, the center portion of the valve body (plunger fixed thereto) can be suppressed from being axially displaced. As a result, the axial displacement of the plunger is suppressed upon when the valve body closes, and a positional displacement between the valve body and the valve seat can also be suppressed. By suppressing the positional displacement between the valve body and the valve seat, sealing performance of the valve body can also be increased.

According to the third aspect, a large distance can be secured between the bottom surface of the communication chamber and the deformable portion of the valve body when the valve device is closed (when the valve body is seated on the valve seat). In other words, the deformable portion can be suppressed from approaching the bottom surface of the communication chamber. By securing the distance between the deformable portion and the bottom surface of the communication chamber, adherence of the deformable portion and the communication chamber caused by the fluid freezing under a low-temperature environment can be suppressed. Further, when deformed granules (a part of the valve body) and the communication chamber adhere to each other, the valve device can no longer function when it is to be driven (when the valve body is to be opened).

DETAILED DESCRIPTION

(Fuel Cell System Equipped with Valve Device)

Firstly, a fuel cell system100that uses a valve device disclosed herein will be described with reference toFIG.1. The fuel cell system100is suitably mounted on a vehicle (fuel cell vehicle). The fuel cell system100comprises a fuel cell stack90, a hydrogen line60for supplying hydrogen gas to the fuel cell stack90, an air line70for supplying air gas (external air) to the fuel cell stack90, and a controller75. The fuel cell system100is configured to generate electric power by using the hydrogen gas supplied from the hydrogen line60and oxygen gas (air gas) supplied from the air line70.

The hydrogen line60comprises a hydrogen gas tank62, a hydrogen supply passage64, and a hydrogen discharging passage68. A pressure reduction valve63is disposed on the hydrogen supply passage64. A pressure of the hydrogen gas supplied from the hydrogen gas tank62to the hydrogen supply passage64is adjusted by the pressure reduction valve63. An injector (not shown) is disposed downstream of the pressure reduction valve63, and the hydrogen gas supplied from the hydrogen gas tank62is supplied to the fuel cell stack90by the injector. A gas-liquid separator66and a hydrogen-discharging valve69are disposed on the hydrogen discharging passage68. The hydrogen-discharging valve69is an example of a valve device. The hydrogen-discharging valve69is disposed downstream of the gas-liquid separator66. The hydrogen gas supply to the fuel cell stack90is controlled by the controller75. That is, the controller75controls on/off of the hydrogen supply passage64and a flow rate of the hydrogen gas flowing through the hydrogen supply passage64.

Hydrogen gas (hydrogen off gas) discharged from the fuel cell stack90is supplied to the gas-liquid separator66. Hydrogen gas contained in the hydrogen off gas is extracted in the gas-liquid separator66. The hydrogen gas extracted in the gas-liquid separator66is returned to the hydrogen supply passage64by a hydrogen circulation pump (not shown) and is supplied to the fuel cell stack90. On the other hand, remainder of the off gas after having extracted the hydrogen gas in the gas-liquid separator66is discharged to the hydrogen discharging passage68and is discharged out of the fuel cell system100through a discharging pipe84. The discharging pipe84is further connected to an air discharging passage80to be described later. A flow rate in the hydrogen discharging passage68is adjusted by the hydrogen-discharging valve69. On/off of the hydrogen discharging passage68and a flow rate of the hydrogen off gas flowing through the hydrogen discharging passage68are also controlled by the controller75. The remainder of the off gas after having extracted the hydrogen gas in the gas-liquid separator66contains generated water that was generated in the fuel cell system100.

The air line70comprises a compressor72, an air supply passage74, an air discharging passage80, a bypass passage78, an air supply valve76, an air-discharging valve50, and a bypass valve79. The compressor72compresses and feeds external air as the air gas into the air supply passage74. Further, an air cleaner (not shown) is disposed upstream of the compressor72. Due to this, clean air gas is supplied to the air supply passage74. The air supply passage74connects the fuel cell stack90and the compressor72. The air supply valve76is disposed on the air supply passage74. Specifically, the air supply passage74comprises an upstream air supply passage74athat connects the compressor72and the air supply valve76and a downstream air supply passage74bthat connects the air supply valve76and the fuel cell stack90. When the compressor72is driven and the air supply valve76communicates the upstream air supply passage74awith the downstream air supply passage74b, the external air is supplied to the fuel cell stack90as the air gas. Here, an intercooler (not shown) is disposed between the compressor72and the air supply valve76. The air gas of which temperature is adjusted (cooled) by the intercooler is supplied to the fuel cell stack90.

The air discharging passage80is connected to the fuel cell stack90and discharges air off gas from the fuel cell stack90. The discharged air off gas is discharged outside the fuel cell system100through the discharging pipe84. The air-discharging valve50is disposed on the air discharging passage80. The air-discharging valve50is a butterfly valve, and is controlled by the controller75. An amount of the air off gas is adjusted by adjusting an opening degree of the air-discharging valve50. The air off gas contains generated water generated in the fuel cell system100.

The bypass passage78connects the air supply passage74and the air discharging passage80. Specifically, one end of the bypass passage78is connected to the upstream air supply passage74aand the other end thereof is connected to the air discharging passage80at a point downstream of the air-discharging valve50. The bypass valve79is disposed on the bypass passage78, and when the bypass valve79opens, the air gas in the air supply passage74is supplied to the air discharging passage80.

The hydrogen-discharging valve69will be described with reference toFIGS.2and3. The hydrogen-discharging valve69adjusts the flow rate of the remainder of the off gas after having extracted the hydrogen gas in the gas-liquid separator66(generated water). As shown inFIG.2, the hydrogen-discharging valve69comprises a housing30through which the generated water flows and a valve unit40configured to open and close a channel inside the housing30. The valve unit40is an example of a driving unit. The housing30comprises a fluid introducing unit30ain which an inlet passage38is defined and a fluid discharging unit30bin which an outlet passage32is defined. The fluid introducing unit30ais fixed to the gas-liquid separator66. A coupling hose (not shown) that constitutes the hydrogen discharging passage68is attached to the fluid discharging unit30b. Further, a communication chamber20is disposed between the inlet passage38and the outlet passage32. The generated water introduced into the hydrogen-discharging valve69(into the housing30) from outside the hydrogen-discharging valve69(gas-liquid separator66) flows through the inlet passage38, the communication chamber20, and the outlet passage32and is discharged out of the hydrogen-discharging valve69(hydrogen discharging passage68).

A first discharging unit36is disposed at a downstream end of the inlet passage38. The first discharging unit36is disposed on a sidewall of the inlet passage38and opens into the communication chamber20. The first discharging unit36has a shape protruding into the communication chamber20, and its end surface constitutes a valve seat34on which a valve body18is to be seated (these elements will be explained later). The first discharging unit36has a smaller channel area than the inlet passage38and has an orifice shape. A direction along which the first discharging unit36extends and a direction along which the inlet passage38extends are different. The first discharging unit36extends in a direction that substantially intersects orthogonally the direction along which the inlet passage38extends. Specifically, the first discharging unit36extends in a substantially vertical direction and the inlet passage38extends in a substantially horizontal direction. Due to this, the generated water introduced into the inlet passage38flows in the inlet passage38in the horizontal direction, flows upward inside the first discharging unit36, and is thereafter discharged into the communication chamber20.

An upstream end of the outlet passage32communicates with the communication chamber20. Due to this, the outlet passage32communicates with the inlet passage38via the communication chamber20and the first discharging unit36. The generated water guided into the outlet passage32from the communication chamber20flows downward inside the outlet passage32, and is discharged outside the hydrogen-discharging valve69(hydrogen discharging passage68) from a second discharging unit33disposed at a downstream end of the outlet passage32.

The valve unit40is fixed above the housing30. The valve unit40comprises a cylindrical fixation base4, an electromagnetic coil10disposed on an outer circumference of the fixation base4, an attraction member8disposed inside the fixation base4, a plunger14disposed coaxially with the attraction member8inside the fixation base4, a mount plate16fixed to the fixation base4, a valve body18fixed to the plunger14and the mount plate16, and a cover6.

The electromagnetic coil10is disposed in a recess defined in an outer circumferential surface of the fixation base4. A size of an upper end of the attraction member8is greater than a cross-sectional size (inner diameter) of the cylindrical fixation base4. The upper end of the attraction member8contacts an upper end surface of the fixation base4and separates inside of the cylindrical fixation base4from outside. An O-ring2is disposed between the upper end of the attraction member8and an upper end surface of the fixation base4, and this O-ring2seals the cylindrical fixation base4. The attraction member8is a magnetic body, and a part thereof faces a part of the electromagnetic coil10.

A coil spring12is disposed between the attraction member8and the plunger14. The coil spring12is fixed to both the attraction member8and the plunger14and thereby suppresses these members from coming into contact with each other. The plunger14extends through a through hole defined at a center of the mount plate16. A distal end of the plunger14(opposite end from the attraction member8) has the valve body18fixed thereon. A size of the plunger14on a distal end side (its portion housed inside the communication chamber20) is greater than a size of the through hole of the mount plate16.

The valve body18is constituted of rubber and is in a diaphragm shape. A center portion18aof the valve body18is fitted in the distal end of the plunger14, and the valve body18and the plunger14are thereby fixed to each other. An outer peripheral portion18cof the valve body18is fixed to the mount plate16. That is, the outer peripheral portion18cof the valve body18is fixed to the valve unit40being the driving unit. Specifically, the outer peripheral portion18cof the valve body18is fixed to the valve unit40by having the outer peripheral portion18cheld by a surface of the mount plate16on a housing30side and a surface of the housing30on a mount plate16side. A deformable portion18bconfigured deformable compliant to an operation of the plunger14is disposed between the center portion18aand the outer peripheral portion18c. A restricting portion18dthat covers a distal end portion of the plunger14(portion thereof with the size larger than that of the through hole of the mount plate16) is disposed inside the deformable portion18b(on a center portion18aside). Specifically, the restricting portion18dcovers an upper portion (mount plate16side) of the distal end portion of the plunger14and is interposed between the distal end portion of the plunger14and the mount plate16. Here, a thickness of the deformable portion18bis constant except for the restricting portion18d.

The mount plate16is fixed to an upper surface of the housing30. When the mount plate16is fixed to the housing30, the valve body18comes to face the valve seat34. More specifically, the center portion18aof the valve body18is pressed onto the valve seat34(is seated thereon) by a biasing force (expanding force) of the coil spring12, by which the first discharging unit36is closed. While the valve body18(center portion18a) is seated on the valve seat34, the inlet passage38and the outlet passage32do not communicate with each other, thus the generated water is not discharged from the hydrogen-discharging valve69. Further, the cover6is fixed to an upper surface of the mount plate16and covers the fixation base4and the electromagnetic coil10, and further isolates the fixation base4and the electromagnetic coil10from outside.

As shown inFIG.3, when the electromagnetic coil10is electrically conducted, the attraction member8is magnetically excited and the plunger14is thereby attracted to the attraction member8. That is, the plunger14is attracted toward the attraction member8by a magnetic excitation force of the attraction member8and moves upward by compressing the coil spring12. The valve unit40is of a normally-off type. When the plunger14moves upward, the center portion18aof the valve body18moves upward together with the plunger14, and the valve body18separates from the valve seat34. When the valve body18separates from the valve seat34, the inlet passage38communicates with the outlet passage32and the generated water is discharged from the hydrogen-discharging valve69.

Next, states of the valve body18when the hydrogen-discharging valve69is actuated will be described with reference toFIG.4AandFIG.4B.FIG.4Ashows a closed state (in a nonconductive state) andFIG.4Bshows an opened state (in a conductive state). Firstly, the state of the valve body18in the closed state (a) will be described. As described above, the valve body18has its center portion18afixed to the plunger14and its outer peripheral portion18cfixed to the mount plate16(held between the mount plate16and the housing30). The deformable portion18bextends substantially linearly (by being flat) from the outer peripheral portion18ctoward the center portion18a, and the deformable portion18bis thus not warped. In other words, when the valve body18is closed, the deformable portion18bis located closer to a bottom surface of the communication chamber20from the outer peripheral portion18ctoward the center portion18a. As a result, a distance between the deformable portion18band the bottom surface of the communication chamber20can be secured in the closed state.

As described above, the generated water introduced into the housing30flows through the inlet passage38, the communication chamber20, and the outlet passage32. Due to this, even in the closed state, the generated water may still remain inside the communication chamber20. The generated water still remaining inside the communication chamber20in the closed state may freeze under a low-temperature environment. If the distance between the deformable portion18band the bottom surface of the communication chamber20is secured when the generated water freezes, the deformable portion18band the communication chamber20can be suppressed from adhering to each other. By suppressing adherence of the deformable portion18band the communication chamber20, the valve body18can be ensured to open upon shifting to the opened state (conductive state). Further, by suppressing the adherence between the deformable portion18band the communication chamber20, deterioration of the deformable portion18bcan also be suppressed.

Further, in the closed state, a distance between the mount plate16and the deformable portion18b(space between a surface of the mount plate16on a deformable portion18bside and a surface of the deformable portion18bon a mount plate16side) becomes gradually larger from an outer peripheral portion18cside toward a center portion18aside. Due to this, in shifting from the closed state (a) to the opened state (b), the deformable portion18bstarts to make contact with the mount plate16from the outer peripheral portion18cside. As a result, almost the entire surface of the deformable portion18bcomes into contact with the mount plate16(entirety of the deformable portion18bfrom the outer peripheral portion18cside toward the center portion18aside comes into contact with the mount plate16), and a wide contact area can be secured between the deformable portion18band the mount plate16. For example, when the deformable portion is to make contact with the mount plate from the center portion side upon shifting to the opened state, a middle portion of the deformable portion (on the center portion side and the outer peripheral portion side) may not come into contact with the mount plate due to the center portion side and the outer peripheral portion side of the deformable portion being restrained by the outer peripheral portion of the valve body being fixed. As a result, a load applied to the deformable portion increases and durability of the deformable portion (valve body) is thereby decreased. Upon shifting from the closed state (a) to the opened state (b), the load applied to the deformable portion can be reduced and the durability of the deformable portion (valve body) can be improved by configuring the deformable portion18bto start coming into contact with the mount plate16from the outer peripheral portion18cside.

Further, by configuring the deformable portion18bto start coming into contact with the mount plate16from the outer peripheral portion18cside upon shifting from the closed state (a) to the opened state (b), an axial displacement of the plunger14upon shifting to the opened state is suppressed, as a result of which an axial displacement of the plunger14upon shifting to the opened state is also suppressed. By suppressing the axial displacement of the plunger14, the center portion18aof the valve body18comes into sufficient contact with the valve seat34upon shifting to the closed state, and the sealing performance of the valve body18is also improved.

As shown in the opened state (b), the restricting portion18dis held by the mount plate16and the plunger14in the opened state. As a result, movement of the plunger14(upward movement toward the attraction member8) is restricted, and the upward movement of the plunger14is stopped. In a state where the upward movement of the plunger14is stopped (opened state (b)), a small space exists between the plunger14and the attraction member8. That is, in the hydrogen-discharging valve69, the plunger14and the attraction member8do not come into direct contact or into indirect contact via a cushioning member in the opened state. In the hydrogen-discharging valve69, an impact application between the plunger14and the attraction member8in the opened state can be suppressed without arranging a cushioning member between the plunger14and the attraction member8. The hydrogen-discharging valve69does not need to secure a space for arranging the cushioning member between the plunger14and the attraction member8, and device size reduction is thereby achieved.

As described above, in the hydrogen-discharging valve69, a small space exists between the plunger14and the attraction member8in the opened state (b). The impact application between the plunger14and the attraction member8can be suppressed by arranging the cushioning member in this space. However, in this case, when the device size reduction is to be realized (when the space between the plunger14and the attraction member8is made smaller), a thickness of the cushioning member becomes thinner, and the impact between the plunger14and the attraction member8cannot suitably be reduced. Further, when the thickness of the cushioning member is made thinner, life of the cushioning member also decreases. The hydrogen-discharging valve69can therefore be evaluated as being compact with high durability.

Further, as described above, the coil spring12is disposed between the plunger14and the attraction member8. Due to this, if the cushioning member is to be disposed between the plunger14and the attraction member8, the cushioning member needs to be disposed where the coil spring12is not disposed. As a result, a surface area of the cushioning member becomes small, and the impact between the plunger14and the attraction member8cannot sufficiently be reduced (or the durability of the disposed cushioning member decreases). A large area for arranging the cushioning member can be secured by designing the size of the coil spring12to be small, and the surface area of the cushioning member can thereby be increased. However, in this case, the biasing force of the coil spring12decreases, and the sealing performance of the valve body18decreases in the opened state (b).

The hydrogen-discharging valve69can achieve advantages such as device size reduction, improvement in device durability, and improvement in the sealing performance of the valve body18decreases in the opened state (b) by suppressing contact between the plunger14and the attraction member8using the restricting portion18ddisposed on the valve body18without arranging a cushioning member between the plunger14and the attraction member8.

OTHER EMBODIMENTS

In the above embodiment, the fuel cell system100provided with the hydrogen-discharging valve69and the air-discharging valve50has been described. The structure of the hydrogen-discharging valve69may be applied to the air-discharging valve50. That is, a valve device identical to that of the hydrogen-discharging valve69may be used as the air-discharging valve50.

In the above embodiment, a configuration was described in which the thickness of the deformable portion is constant except for the restricting portion. That is, in the hydrogen-discharging valve (valve device) of the embodiment, the thickness of the restricting portion is different from the thickness of the deformable portion not including the restricting portion. However, the thickness of the restricting portion may be same as the thickness of the deformable portion not including the restricting portion. The thickness of the restricting portion can freely be selected in accordance with the force applied to the restricting portion in the opened state.

In the above embodiment, a configuration was described in which, in the closed state, the deformable portion gradually approaches closer to the bottom surface of the communication chamber from an outer peripheral portion side toward a center portion side of the valve body. However, this configuration is merely one of preferred embodiments, and for example, a portion closer to the bottom surface of the communication chamber than a centermost portion may exist in a middle portion of the deformable portion (between an outermost peripheral portion and the centermost portion thereof). So long as the deformable portion and the communication chamber are not in contact at least in the closed state, the deformable portion and the communication chamber can be suppressed from adhering to each other when the generated water freezes.

Further, in the above embodiment, a configuration was described in which, in the closed state, the distance between the mount plate and the deformable portion becomes larger from the outer peripheral portion side toward the center portion side of the valve body. Further, it also has been explained that a wide contact area can thereby be secured between the deformable portion and the mount plate (portion not contacting the mount plate does not exist in the middle portion of the deformable portion). However, this is also merely one of preferred embodiments. For example, a groove and the like may be defined in the deformable portion to allow the thickness of the deformable portion to change, and the entire deformable portion can be brought into contact with the mount plate even if the deformable portion comes into contact with the mount plate from the center portion side upon shifting to the opened state due to the thickness of the deformable portion changing (a length of the deformable portion in a planar direction changing).

Specific examples of the invention disclosed herein have been described in detail, however, these are mere exemplary indications and thus do not limit the scope of the claims. The art described in the claims includes modifications and variations of the specific examples presented above. Technical features described in the description and the drawings may technically be useful alone or in various combinations, and are not limited to the combinations as originally claimed. Further, the art described in the description and the drawings may concurrently achieve a plurality of aims, and technical significance thereof resides in achieving any one of such aims.