Patent ID: 12247959

DESCRIPTION OF EMBODIMENTS

Some embodiments of the present invention are now unlimitedly described with reference to the accompanying drawings.

First Embodiment

FIGS.1A to1Dillustrate an exemplary configuration of a flow passage switching valve5of the invention.FIG.1Ashows a cross-sectional view as a plane parallel to an axis (for example, rotational axis, the same shall apply hereinafter) of the flow passage switching valve5.FIG.1Ais taken along the dashed line inFIG.1D.FIG.1Bshows a top view of a rotor seal22, andFIG.1Cshows a top view of a portion of a stator main body21in contact with the rotor seal22. Although the surface of the stator main body21shown inFIG.1Cis actually faces downward and cannot be seen from the above,FIG.1Cshows a shape of the surface as viewed from the above for ease in understanding of overlapping with the rotor seal22.FIG.1Dshows a positional relationship between flow passages of the stator main body21and the rotor seal22when a contact surface of the stator main body21is set to overlap a contact surface of the rotor seal22.

The flow passage switching valve5includes the stator and the rotor. The rotor is configured rotatably with respect to the stator, and rotates around a predetermined rotational axis, for example.

In this embodiment, as illustrated inFIG.1A, the flow passage switching valve5includes the stator main body21for pipe connection, the rotor seal22, a rotor main body23that rotates the rotor seal22, and a housing26that holds the rotor seal22and the rotor main body23. In this embodiment, the stator main body21configures the stator, and the rotor seal22and the rotor main body23collectively configure the rotor.

The rotor main body23is pressed to the stator main body21via the rotor seal22by a spring (not shown) or the like, and thus the rotor seal22is pressed to the stator main body21. The stator main body21is made of, for example, metal or ceramic, and the rotor seal22is made of, for example, metal, ceramic, or resin. The stator main body21and the rotor seal22may each be coated with diamondlike carbon to improve abrasion resistance.

The stator main body21has a plurality of stationary stator flow passages that allow a fluid to flow through the inside of the stator main body21. In this embodiment, as illustrated inFIG.1C, the stator main body21has six stationary stator flow passages31to36that each configure a stator flow passage of this embodiment. In this embodiment, the stationary stator flow passage31is a first stator flow passage, the stationary stator flow passage32is a second stator flow passage, and the stationary stator flow passage36is a third stator flow passage.

The name “stator flow passage” represents that each flow passage is fixed to the stator main body21in this embodiment. Such representation is to clarify comparison with a configuration where a middle stator seal flow passage moves with respect to the stator main body as in Second Embodiment described later, and the representation does not mean in any sense that each flow passage is required to be fixed in another embodiment of the invention.

In this embodiment, the stationary stator flow passages31to36are provided on a circumference around an axis. In other words, distances from the axis of the stator main body21to the stationary stator flow passages31to36are equal to one another. In a possible modification, however, such distances may not be equal. In this embodiment, all cross sections perpendicular to the axis of the stationary stator flow passages31to36have the same shape and the same area. Specifically, in this embodiment, all the cross sections perpendicular to the axis of the stationary stator flow passages31to36have circular shapes having the same radius. In a possible modification, however, the cross sections may have different shapes or areas. In this embodiment, the stationary stator flow passages31to36are provided at even intervals in a circumferential direction. In other words, two adjacent stationary stator flow passages are disposed in respective directions defining an angle of 60° with respect to the axis. In a possible modification, however, the stationary stator flow passages may be provided at uneven intervals in a circumferential direction.

The rotor also has a plurality of rotor flow passages that allow a fluid to flow through the inside of the rotor. In this embodiment, as illustrated inFIG.1B, the rotor seal22has three rotor flow passages241to243. Specifically, in this embodiment, the rotor flow passage241is a first rotor flow passage, and the rotor flow passage242is a second rotor flow passage. In a possible modification, the rotor may not have the rotor seal22. In such a case, the rotor flow passages may be provided in the rotor main body23.

In this embodiment, the rotor flow passages241to243are provided on a circumference around an axis. In other words, the distances from the axis of the rotor seal22to the rotor flow passages241to243are equal to one another. In a possible modification, however, such distances may not be the same. In this embodiment, all cross sections perpendicular to the axis of the rotor flow passages241to243have the same shape and the same area. In a possible modification, however, the cross sections may have different shapes or areas. In this embodiment, the rotor flow passages241to243are provided at even intervals in a circumferential direction. In other words, two adjacent rotor flow passages define an angle of 120° with respect to the axis. In a possible modification, however, the stationary stator flow passages may be provided at uneven intervals in a circumferential direction.

Each rotor flow passage is configured to be allowed to couple the two stationary stator flow passages together in correspondence to a rotation state of the rotor. The rotation state of the rotor shows a rotational positional relationship between the stator and the rotor, for example. More specifically, when a reference rotational position of the rotor seal22is defined with respect to the stator main body21, the rotor rotation state may be defined as a relative rotational position of the rotor seal22with respect to the reference rotational position. For example, in the state shown inFIGS.1A and1D, the rotor flow passage241couples the stationary stator flow passages31and32together, the rotor flow passage242couples the stationary stator flow passages35and36together, and the rotor flow passage243couples the stationary stator flow passages33and34together.

As described above, the rotor seal22is pressed to the stator main body21by the rotor main body23to maintain fluid-tightness. Specifically, no liquid is leaked from one of flow passages, i.e., a flow passage including the rotor flow passage241connected to the respective stationary stator flow passages31and32, a flow passage including the rotor flow passage242connected to the respective stationary stator flow passages35and36, and a flow passage including the rotor flow passage243connected to the respective stationary stator flow passages33and34, to another one of the flow passages, or to the outside of the flow passage switching valve5.

The rotor seal22is fixed to the rotor main body23by a pin or the like (not shown), and rotates with the rotor main body23by a motor (not shown) coupled to the rotor main body23. A rotation angle of the rotor is measured by, for example, an encoder provided in the motor. Alternatively, for example, the rotation angle can be measured by optically detecting a position detection groove28provided in the rotor seal22from the outside through a position detection window30provided in the housing26. At this time, a plurality of position detection grooves28or position detection windows30may be provided.

A conventional flow passage switching valve is described usingFIGS.2A to2C. In a state ofFIG.2A, the rotor seal22rotates 60° in a sliding direction29(clockwise), so that a state ofFIG.2Cis given via a state ofFIG.2B. The rotor flow passage241connects the stationary stator flow passages31and32together in the state ofFIG.2A, and connects the stationary stator flow passages32and33together in the state ofFIG.2C. Similarly, the rotor flow passage242connects the stationary stator flow passages35and36together in the state ofFIG.2A, and connects the stationary stator flow passages36and31together in the state ofFIG.2C. The rotor flow passage243connects the stationary stator flow passages33and34together in the state ofFIG.2A, and connects the stationary stator flow passages34and35together in the state ofFIG.2C. After the state has been changed from the state ofFIG.2Ato the state ofFIG.2C, the rotor seal22in the state ofFIG.2Crotates 60° in a direction opposite to the sliding direction29, so that the state returns to the state ofFIG.2Avia the state ofFIG.2B. In this way, the rotor seal22performs a reciprocation motion including 60-degree rotation in the sliding direction29and 60-degree rotation in the direction opposite to the sliding direction29(counterclockwise).

The rotational direction and the rotational amount are specifically shown for convenience in this description and actually need not be matched with the described direction and amount, respectively. For example, the 60-degree rotation in the sliding direction29can also be achieved by 420-degree rotation in the sliding direction29, or 300-degree rotation in the direction opposite to the sliding direction29.

FIGS.3A and3Bare each a schematic diagram of a flow passage of a liquid chromatograph1according to First Embodiment of the invention.FIGS.3A and3Beach show a schematic diagram of the flow passage of the liquid chromatograph1having a flow passage switching valve5of First Embodiment of the invention. The liquid chromatograph1includes a liquid sending pump2, a needle3, a syringe pump4, the flow passage switching valve5, a separation column6, a detector7, and pipes for coupling such components together. The stationary stator flow passages31,32,33,34,35, and36of the flow passage switching valve5are coupled to the liquid sending pump2, the separation column6, a needle port10, a waste liquid tank11, the syringe pump4, and the needle3, respectively.

First, in a state ofFIG.3A, an eluent9sent by the liquid sending pump2flows to the separation column6, the detector7, and a waste liquid tank16through the stationary stator flow passage31, the rotor flow passage241, and the stationary stator flow passage32. The needle port10is coupled to the waste liquid tank11via the stationary stator flow passage33, the rotor flow passage243, and the stationary stator flow passage34, and the syringe pump4is coupled to the needle3via the stationary stator flow passage35, the rotor flow passage242, and the stationary stator flow passage36. In this state, the syringe pump4performs sucking operation so that a sample8is sucked into the needle3.

Subsequently, the rotor seal22is rotated 60° in the sliding direction29(clockwise) to switch a flow passage, so that the state ofFIG.3Bis given. In the state ofFIG.3B, the needle3holding the sample8is moved and coupled to the needle port10. In such a state, the eluent is sent by the liquid sending pump2to send the sample8in the needle3to the separation column6, the sample8is separated by the separation column6, and the separated sample is detected by the detector7. Subsequently, the eluent is sent to wash the flow passage through which the sample has flown.

In the conventional flow passage switching valve, the rotor seal22in the state ofFIG.3Bis rotated 60° in the direction opposite to the sliding direction29(counterclockwise), so that the state is returned to the state ofFIG.3A. In such a state, the eluent is flown by the liquid sending pump2and the syringe pump4to wash the flow passage. The above operation is repeated for each sample to be analyzed.

The separation column6is internally filled with particles several micrometers in size and has a large fluid resistance. Thus, the liquid sending pump2sends the eluent at a high pressure of tens of megapascal (MPa). On the other hand, since the flow passage led to the syringe pump4is not coupled to a component having a large fluid resistance, liquid sending pressure of the syringe pump4is close to atmospheric pressure (0.1 MPa). In the state ofFIG.3A, therefore, liquid pressure is high in the rotor flow passage241but low in each of the rotor flow passages242and243. As a result, the rotor seal22and the stator main body21are spread by the high liquid pressure and thus contact pressure is reduced in the vicinity of the rotor flow passage241. On the other hand, liquid pressure is small and thus contact pressure is large in the vicinity of each of the rotor flow passages242and243compared with in the vicinity of the rotor flow passage241. Consequently, an area200shown inFIG.2Ahas an increased contact pressure in the whole contact surface of the rotor seal22.

On the other hand, in the state ofFIG.3B, liquid pressure is high in each of the rotor flow passages242and241but low in the rotor flow passage243. As a result, the rotor seal22and the stator main body21are spread by the high liquid pressure and thus contact pressure is reduced in the vicinity of each of the rotor flow passages242and241. On the other hand, liquid pressure is small and thus contact pressure is large in the vicinity of the rotor flow passages243compared with in the vicinity of each of the rotor flow passages242and241. Consequently, an area201shown inFIG.2Chas an increased contact pressure in the whole contact surface of the rotor seal22. A position of the area200moves with rotation of the rotor seal22.

As described above, in the conventional flow passage switching valve, since the rotor seal22performs a reciprocation motion between the state ofFIG.3A(FIG.2A) and the state ofFIG.3B(FIG.2C), only each of the areas200and201has a high contact pressure in the contact surface of the rotor seal22with the stator main body21, and abrasion of such a portion progresses more quickly than other portions. As a result, an area abrased on the sliding surface is localized, leading to a reduction in operating life of the flow passage switching valve.

FIG.4illustrates an exemplary configuration of a flow passage switching valve system including the flow passage switching valve5according to First Embodiment of the invention. The flow passage switching valve system includes the flow passage switching valve5and a control device500that controls rotation of a rotor of the flow passage switching valve5. The control device500can be configured using, for example, a computer having a known configuration, and includes a calculation unit performing calculation and a storage unit storing information. The calculation unit includes, for example, a processor, and the storage unit includes, for example, a semiconductor memory. The storage unit can store a program and the calculation unit executes the program, through which the control device500implements such processing and controls the flow passage switching valve5.

FIG.5is used to describe an operation of the flow passage switching valve5according to First Embodiment of the invention and describe an abrasion area. In this embodiment, the flow passage switching valve5switches a flow passage by continuously rotating the rotor seal22in the same direction, and thus the operating life of the valve is prolonged.

The flow passage switching valve5achieves a plurality of coupling patterns in a switchable manner, and specifically achieves any one of the coupling patterns in correspondence to rotation of the rotor. In this embodiment, six coupling patterns shown inFIG.5can be achieved. In this embodiment, a pattern shown inFIG.5Ais a first coupling pattern, a pattern shown inFIG.5Fis a second coupling pattern, a pattern shown inFIG.5Cis a third coupling pattern, and a pattern shown inFIG.5Bis a fourth coupling pattern.

In the following description, respective positions of the stationary stator flow passages31to36ofFIGS.5A to5Fcorrespond to the positions shown inFIG.3A or3B.

In the coupling pattern ofFIG.5A, the rotor flow passage241couples the stationary stator flow passages31and32together, the rotor flow passage242couples the stationary stator flow passages35and36together, and the rotor flow passage243couples the stationary stator flow passages33and34together. As known from the above-described relationship between the liquid pressure and the contact pressure, contact pressure is high in the vicinity of the area200of the rotor seal22inFIG.5A.

Subsequently, the rotor seal22is rotated 60° in the sliding direction29, so that a state ofFIG.5Bis given. In the coupling pattern ofFIG.5B, the rotor flow passage241couples the stationary stator flow passages32and33together, the rotor flow passage242couples the stationary stator flow passages36and31together, and the rotor flow passage243couples the stationary stator flow passages34and35together. In such a state, contact pressure is high in the vicinity of the area201on the rotor seal22.

Subsequently, the rotor seal22is further rotated 60° in the sliding direction29, so that a state ofFIG.5Cis given. In the coupling pattern ofFIG.5C, the rotor flow passage241couples the stationary stator flow passages33and34together, the rotor flow passage242couples the stationary stator flow passages31and32together, and the rotor flow passage243couples the stationary stator flow passages35and36together. In such a state, contact pressure is high in the vicinity of the area202on the rotor seal22. At this time, the area200on the rotor seal22does not return to the original position but moves to a position rotated 120° in the sliding direction29, i.e., moves to the upper left position inFIG.5C.

Subsequently, the rotor seal22is further rotated 60° in the sliding direction29, so that a state ofFIG.5Dis given. In the coupling pattern ofFIG.5D, the rotor flow passage241couples the stationary stator flow passages34and35together, the rotor flow passage242couples the stationary stator flow passages32and33together, and the rotor flow passage243couples the stationary stator flow passages36and31together.

Subsequently, the rotor seal22is further rotated 60° in the sliding direction29, so that a state ofFIG.5Eis given. In the coupling pattern ofFIG.5E, the rotor flow passage241couples the stationary stator flow passages35and36together, the rotor flow passage242couples the stationary stator flow passages33and34together, and the rotor flow passage243couples the stationary stator flow passages31and32together.

Subsequently, the rotor seal22is further rotated 60° in the sliding direction29, so that a state ofFIG.5Fis given. In the coupling pattern ofFIG.5F, the rotor flow passage241couples the stationary stator flow passages36and31together, the rotor flow passage242couples the stationary stator flow passages34and35together, and the rotor flow passage243couples the stationary stator flow passages32and33together.

Subsequently, the rotor seal22is further rotated 60° in the sliding direction29, so that the state ofFIG.5Ais given again. Thus, when the rotor seal22is constantly switched at 60-degree intervals in the sliding direction29in flow passage switching, the areas200to206that have experienced the state of high contact surface pressure are dispersed around the entire circumference on the rotor seal22. This disperses the abrasion area of the rotor seal22, leading to a long operating life compared with a case using a conventional drive method.

To disperse the abrasion area around the entire circumference on the rotor seal22, the rotor seal22does not necessarily need to be constantly rotated in the same direction as in First Embodiment. In a possible modification, the rotor seal22may be rotated in the opposite direction according to a condition.

FIG.6illustrates an exemplary operation according to such a modification. In this example, the control device500can operate in any one of a plurality of modes. For example, the control device500can operate in any one of modes, including a mode in which the coupling pattern ofFIG.5Aand the coupling pattern ofFIG.5Bare alternately achieved (first mode), a mode in which the coupling pattern ofFIG.5Cand the coupling pattern ofFIG.5Dare alternately achieved (second mode), and a mode in which the coupling pattern ofFIG.5Eand the coupling pattern ofFIG.5Fare alternately achieved (third mode).

For example, the control device500operates in the first mode and the rotor seal22performs a reciprocating motion between the states ofFIGS.5A and5Buntil a predetermined criterion is satisfied. Subsequently, when the predetermined criterion is satisfied, the rotor seal22is rotated 120° only once so that the mode is shifted to the second mode (for example, the state ofFIG.5Cis given). The control device500then operates in the second mode and the rotor seal22performs a reciprocating motion between the states ofFIGS.5C and5Duntil the predetermined criterion is satisfied again. Subsequently, when the predetermined criterion is satisfied again, the rotor seal22is rotated 120° only once so that the mode is shifted to the third mode (for example, the state ofFIG.5Eis given). The control device500then operates in the third mode and the rotor seal22performs a reciprocating motion between the states ofFIGS.5E and5Funtil the predetermined criterion is satisfied again. When the predetermined criterion is further satisfied, the rotor seal22is rotated 120° only once so that the mode is returned to the first mode (for example, the state is returned to the state ofFIG.5A). Such an operation can also disperse the abrasion area around the entire circumference on the rotor seal22.

Each mode may include not only the above combination of the states but another combination of the states. For example, the first mode may include the states ofFIGS.5F and5A, the second mode may include the states ofFIGS.5B and5C, and the third mode may include the states ofFIGS.5D and5E.

The predetermined criterion for shifting the mode can be optionally designed. For example, the control device500may switch the mode based on the total rotation amount of the rotor. The total rotation amount refers to, for example, the number of rotations of the rotor seal22(or an integrated value of angles) up to that time. Alternatively, the control device500may switch the mode based on the total rotation time of the rotor. The total rotation time refers to, for example, an integrated value of time, during which the rotor seal22has performed the rotational operation, up to that time. Alternatively, the control device500may switch the mode based on the total operation time of the flow passage valve system. The total operation time refers to, for example, an integrated value of time, during which the flow passage valve system has been on, up to that time. Alternatively, the control device500may switch the mode based on fluid passing frequency in any one of the flow passages (i.e., any one of the stationary stator flow passages31to36and the rotor flow passages241to243). The fluid passing frequency corresponds to execution frequency of analysis operation in the liquid chromatograph1.

Alternatively, the liquid chromatograph1may include a device that measures a state of a fluid in any one flow passage, and the control device500may receive a signal from such a device and switch a mode based on the signal. For example, the control device500may switch the mode based on pressure in any one flow passage, based on the amount of change in pressure in any one flow passage, based on the total flow rate (for example, the total amount of the eluent) in any one flow passage, based on the leakage amount from any one flow passage, based on a change in the leakage amount from any one flow passage, or based on the carry-over amount in any one flow passage. The carry-over amount can be detected using the detector7by a predetermined analysis method, for example.

A condition, which is defined by combining at least two or all of the above-described criteria, may be used. Predefining such a criterion makes it possible to switch the mode at an appropriate timing and disperse the abrasion area more appropriately.

Second Embodiment

In First Embodiment, the structure on the stator side of the sliding surface is fixed at any time. In Second Embodiment, the structure on the stator side of the sliding surface is partially rotatable. Differences from First Embodiment are now described.

FIGS.7A to7Dillustrate an exemplary configuration of a flow passage switching valve5according to Second Embodiment of the invention. Second Embodiment differs from First Embodiment in that a middle stator seal330is provided between the stator main body21and the rotor seal22as shown inFIGS.7A to7D. In Second Embodiment, the stator main body21and the middle stator seal330collectively configure the stator.

FIG.7Ashows a cross-sectional view as a plane parallel to an axis of the flow passage switching valve5,FIG.7Bshows a top view of the rotor seal22, andFIG.7Cshows a top view of a portion of the middle stator seal330in contact with the rotor seal22. Although the surface of the middle stator seal330shown inFIG.7Cis actually faces downward and cannot be seen from the above,FIG.7Cshows a shape of the surface as viewed from the above for ease in understanding of overlapping with the rotor seal22.FIG.7Dshows a positional relationship between each flow passage of the middle stator seal330and the rotor seal22when a contact surface of the middle stator seal330is set to overlap a contact surface of the rotor seal22.

A liquid chromatograph having a flow passage switching valve5of Second Embodiment of the invention is described withFIGS.3A and3B,FIGS.7A to7D, andFIGS.8A to8C. The middle stator seal330is rotatably fixed to the stator main body21. The rotational axis of the middle stator seal330is the same as the rotational axis of the rotor. The middle stator seal330is rotated with respect to the stator main body21, thereby an abrasion area on the contact surface can be dispersed not only on a rotor side but also on a stator side.

The middle stator seal330has middle stator seal flow passages331to336that are each coupled to any one of the stationary stator flow passages31to36. A particular middle stator seal flow passage and a particular stationary stator flow passage to be coupled together are each different depending on a rotational position of the middle stator seal330with respect to the stator main body21. The middle stator seal flow passages331to336each configure a stator flow passage of this embodiment.

As illustrated inFIGS.7A to7D, the rotor seal22of the flow passage switching valve5of Second Embodiment is pressed to the middle stator seal330by the rotor main body23, which maintains fluid-tightness of each of the three flow passages. In the state shown inFIGS.7A to7D, the three flow passages include a flow passage configured of the rotor flow passage241, the stationary stator flow passages31and32, and the middle stator seal flow passages331and332(FIG.7Ashows such a flow passage), a flow passage configured of the rotor flow passage242, the stationary stator flow passages35and36, and the middle stator seal flow passages335and336, and a flow passage configured of the rotor flow passage243, the stationary stator flow passages33and34, and the middle stator seal flow passages333and334.

The rotor seal22is fixed to the rotor main body23by a pin (not shown), and rotates by a motor (not shown) coupled to the rotor main body23.

FIGS.8A to8Cillustrate an operation method of the flow passage switching valve5according to Second Embodiment. The state ofFIG.8Ashows one of coupling patterns achieved in the first mode, which corresponds to the state ofFIGS.7A to7D. The flow passage switching valve5operates while switching between two coupling patterns including the coupling pattern ofFIG.8A. For example, the coupling pattern ofFIG.8Aand a coupling pattern in a state, which is given by rotating the rotor in the state ofFIG.8Aby 60° in the sliding direction29, are achieved while being switched to each other.

When the middle stator seal330in the state ofFIG.8Ais rotated 120° in the sliding direction29, a state ofFIG.8Bis given. The state ofFIG.8Bshows one of coupling patterns achieved in the second mode. The flow passage switching valve5operates while switching between two coupling patterns including the coupling pattern ofFIG.8B. For example, the coupling pattern ofFIG.8Band a coupling pattern in a state, which is given by rotating the rotor in the state ofFIG.8Bby 60° in the sliding direction29, are achieved while being switched to each other.

In the state ofFIG.8B, the middle stator seal flow passage335, the rotor flow passage241, and the middle stator seal flow passage336are each coupled to the liquid sending pump2and the separation column6inFIGS.3A and3B. The middle stator seal flow passage331, the rotor flow passage243, and the middle stator seal flow passage332are each coupled to the needle port10and the waste liquid tank11. The middle stator seal flow passage333, the rotor flow passage242, and the middle stator seal flow passage334are each coupled to the needle3and the syringe pump4inFIGS.3A and3B.

When the middle stator seal330in the state ofFIG.8Ais rotated 240° in the sliding direction29(when the middle stator seal330in the state ofFIG.8Bis rotated 120° in the sliding direction29), a state ofFIG.8Cis given. The state ofFIG.8Cshows one of the coupling patterns achieved in the third mode. The flow passage switching valve5operates while switching between two coupling patterns including the coupling pattern ofFIG.8C. For example, the coupling pattern ofFIG.8Cand a coupling pattern in a state, which is given by rotating the rotor in the state ofFIG.8Cby 60° in the sliding direction29, are achieved while being switched to each other.

In the state ofFIG.8C, the middle stator seal flow passage333, the rotor flow passage241, and the middle stator seal flow passage334are each coupled to the liquid sending pump2and the separation column6inFIGS.3A and3B. The middle stator seal flow passage335, the rotor flow passage243, and the middle stator seal flow passage336are each coupled to the needle port10and the waste liquid tank11. The middle stator seal flow passage331, the rotor flow passage242, and the middle stator seal flow passage332are each coupled to the needle3and the syringe pump4inFIGS.3A and3B.

A method and a configuration for rotating the middle stator seal330can be optionally designed by those skilled in the art. For example, the middle stator seal330may be manually rotated by a user of a liquid chromatograph or may be automatically rotated by the control device500or another device. In a possible configuration in case of the manual rotation, for example, a tool (not shown) is inserted into a rotation groove328of the middle stator seal330through the position detection window30inFIGS.7A to7Dto rotate the middle stator seal330. For example, an axially protruding convex portion (not shown) is provided in the center of rotation of the middle stator seal330, an axially depressed concave portion (not shown) is provided in the center of the stator main body21, and such convex and concave portions are physically combined and rotatably engaged together, thereby a rotational axis of the middle stator seal can be configured. A structure (such as a locking mechanism) that fix and hold the middle stator seal330to the stator main body21may be provided to prevent corotation of the middle stator seal330during rotation of the rotor seal22.

Such rotation of the middle stator seal330achieves, in a more balanced manner, a state of high liquid pressure of each of the middle stator seal flow passages331and332, a state of high liquid pressure of each of the middle stator seal flow passages333and334, and a state of high liquid pressure of each of the middle stator seal flow passages335and336. For example, the rotation achieves, in a more balanced manner, a state of high contact pressure of an area opposed to the middle stator seal flow passages331and332, a state of high contact pressure of an area opposed to the middle stator seal flow passages333and334, and a state of high contact pressure of an area opposed to the middle stator seal flow passages335and336. As a result, an abrasion area of the middle stator seal330is dispersed, leading to a long operating life compared with a case using a conventional drive method.

The timing for rotating the middle stator seal330can be determined based on a criterion similar to the criterion for timing to switch the mode as described in the modification shown inFIG.6. The mode switching of rotor rotation as inFIG.6and the mode switching of rotation of the middle stator seal330according to Second Embodiment may be performed in a combined manner. When such mode switching operations are performed in a combined manner, both switching timings are preferably designed so as not to coincide with each other to avoid a fixed positional relationship between the rotor seal22and the middle stator seal330.

Other Modifications

In the described First and Second Embodiments, the number of the flow passages or the coupling patterns may be appropriately changed depending on applications of the flow passage switching valve. At least three stator flow passages (stationary stator flow passages in First Embodiment, middle stator flow passages in Second Embodiment), at least two rotor flow passages, and at least four coupling patterns may be provided. For example, in case of a flow passage configuration having stator flow passages including only the stationary stator flow passages31,32, and36as shown inFIGS.5A to5Fand rotor flow passages including only the rotor flow passages241and242as shown inFIGS.5A to5F, at least four coupling patterns corresponding toFIGS.5A to5Dmay be achieved. In such a case, each rotor flow passage need not necessarily be configured to couple two stator flow passages together in any of the coupling patterns (for example, in the pattern ofFIG.5A, when the stationary stator flow passages33to35do not exist, the rotor flow passage242is in communication with only the stationary stator flow passage36without coupling two stator flow passages together).

All the structurally achievable coupling patterns need not necessarily be evenly achieved. For example, in the example ofFIG.6, the control device500may operate only in the first and second modes without the third mode while switching between the first and second modes. In such a case, although the coupling patterns ofFIGS.5E and5Fare not achieved, the abrasion area can also be dispersed in some degree (not around the entire circumference but in two or more points).

Although three modes are defined in the example ofFIG.6, the number of modes may be at least two. For example, the number of modes may be two so that two coupling patterns are alternately achieved in the first mode while other two coupling patterns are alternately achieved in the second mode. For the example ofFIGS.5A to5F, the coupling pattern ofFIG.5Aand one of the coupling patterns ofFIGS.5B and5Fmay be alternately achieved in the first mode, and two specific coupling patterns, which are not achieved in the first mode, may be achieved in the second mode. The above “two specific coupling patterns that are not achieved in the first mode” includes the coupling pattern ofFIG.5Cand another coupling pattern. The above “another coupling pattern” includes, for example, one of the coupling patterns ofFIGS.5B and5F, which is not achieved in the first mode, but may be the coupling pattern ofFIG.5Dor an appropriately configured coupling pattern other than such coupling patterns.

LIST OF REFERENCE SIGNS

1liquid chromatograph2liquid sending pump3needle4syringe pump5flow passage switching valve6separation column7detector8sample9eluent10needle port11,16waste liquid tank21stator main body (stator)22rotor seal (rotor)23rotor main body (rotor)26housing28position detection groove29sliding direction30position detection window31stationary stator flow passage (first stator flow passage)32stationary stator flow passage (second stator flow passage)33,34,35stationary stator flow passage36stationary stator flow passage (third stator flow passage)200,201,202area241rotor flow passage (first rotor flow passage)242rotor flow passage (second rotor flow passage)243rotor flow passage328rotation groove330middle stator seal331middle stator seal flow passage (first stator flow passage)332middle stator seal flow passage (second stator flow passage)333,334,335middle stator seal flow passage336middle stator seal flow passage (third stator flow passage)500control device
All references, including publications, patents, and patent applications, cited herein are incorporated herein by reference.