Patent Publication Number: US-2004040315-A1

Title: High and low pressure gas selector valve of refrigerator

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to a high-low pressure gas directional control valve of a refrigerator, and particularly relates to a high-low pressure gas directional control valve of a refrigerator that can be made longer in life, higher in efficiency, more compact, and lighter, no wear, no dust formation and which is suitable for using in pulse tube coolers and Gifford McMahon (GM) cryocoolers.  
       BACKGROUND ART  
       [0002] In pulse tube coolers and GM cryocoolers, a high-low pressure gas directional control valve  14  is used to change-over periodically between high-pressure gas and low-pressure gas generated by a compressor  10 , and to send them to a refrigerator  12 , as shown in FIG. 1. In the figure, reference numeral  12 A denotes a pulse tube,  12 B denotes a heat regenerator tube,  12 C denotes a cooling stage,  16  denotes an orifice, and  18  denotes a buffer tank.  
       [0003] As described in Japanese Patent No.2617681 and shown in FIG. 2, for example, a conventional high-low pressure gas directional control valve is composed of: a valve main body  20  that is whirl-stopped to a valve housing  26  by a pin  22  whose form is shown in FIG. 3 and to which spring force is applied toward a valve plate  30  by a coil spring  24 ; the valve housing  26  for accommodating the valve main body  20 ; a valve plate  30  in the form shown in FIG. 4; a drive motor  32  for rotating the valve plate  30 , and a motor casing  34  for accommodating the drive motor  32 .  
       [0004] A space  26   b  on the left side of aforementioned valve main body  20  is connected to the high-pressure gas side of the compressor (not shown) through a high-pressure gas passage  26   a  of the valve housing  26 . On the other hand, a space  34   b  on the right side of the valve plate  30  is connected to the low-pressure gas side of the compressor through a low-pressure gas passage  34   a  of the motor casing  34 . Through actions of the pressure difference and the spring  24 , the valve main body  20  is pressed against the valve plate  30 . This seals the gas flowing through a valve main body high-pressure gas passage  20   a , a valve plate high-pressure gas passage  30   a , a valve plate low-pressure gas passage  30   b , and a valve main body refrigerator side gas passage  20   b , those of which are located along the valve main body  20  and the valve plate  30 .  
       [0005] In FIG. 2, reference numeral  36  denotes a bearing that supports the valve-plate  30  so as that the plate can freely rotate.  
       [0006] Either of the aforementioned valve main body  20  or valve plate  30  (the valve plate  30  in this case) is rotated by the drive motor  32 , and the other (the valve main body  20  in this case) is whirl-stopped. The gas is changed-over at the timing and opening following the pattern formed on the contact face as shown in FIG. 5 (high-pressure supplying state) and FIG. 6 (low-pressure recovering state). As a result, gas flows through passages or space  26   a → 26   b → 20   a → 30   a  → 20   b  → 26   c  (high-pressure supplying state), or passages or space  26   c → 20   b → 30   b → 34   b → 34   a  (low-pressure recovering state as shown in FIG. 2) formed in the interior, and the gas is supplied to or recovered from the refrigerator through valve housing refrigerator side gas passage  26   c.    
       [0007] However, in this kind of high-low pressure gas directional control valve, the valve main body  20  is pressed against the valve plate  30  and is sealed by the sliding surface, hence the valve main body  20  and the valve plate  30  wear out, and periodic replacement is required. Moreover, the sliding surface resistance is high, necessitating use of a large sized high torque motor as the drive motor  32 , which leads to a bigger size of the unit itself. Furthermore, there have been problems such as the passage formed in the valve main body  20  and the valve plate  30  becoming sophisticated in form, which led to increase in pressure loss, and the decrease in performance of the refrigerator.  
       [0008] Moreover, in Japanese Patent Laid-Open Publication No.2001-91078 as shown in FIG. 7, a rotary valve has been proposed, which consists of a circular horizontally-section rotor  101  that rotates around the central axis, and a housing  102  that accommodates this rotor  101  so as to freely rotate. In this rotary valve, a plurality of ports  105  to  112  are installed on the external circumferential surface of the aforementioned rotor  101 , and a plurality of ports  117  to  122  corresponding to the aforementioned ports  105  to  112  are also installed on the internal circumferential surface of the aforementioned housing  102 . This rotary valve changes-over, by the rotation of the aforementioned rotor  101 , between the state in which the ports in both groups  105  to  108 ,  117 ,  118 ,  120 ,  122  connect communicatively by matching the prescribed ports  105  to  108  of the rotor  101  to the corresponding ports  117 ,  118 ,  120 ,  122  of the aforementioned housing  102 , and the state in which the ports in both groups  105  to  108 ,  117 ,  118 ,  120 ,  122  do not connect communicatively due to disengagement of the aforementioned matching. In the figure, reference numeral  103  denotes an axle-bearing, and reference numeral  104  denotes a motor.  
       [0009] However, there was a problem that it did not operate so well, with increasing leaks from the high-pressure side to the low-pressure side, since all the ports are formed asymmetrical regarding the central axis of the rotor  101 , and the valve is not balanced when pressurized.  
       DISCLOSURE OF THE INVENTION  
       [0010] The present invention was made to solve the aforementioned conventional problems, and it is an object of this invention to provide a high-low pressure gas directional control valve that can be made longer in life, higher in efficiency, more compact, lighter, no wear, and no dust information.  
       [0011] The present invention solved the aforementioned problems by the following means, in the high-low pressure gas directional control valve of a refrigerator that is used to change-over periodically between high-pressure gas and low-pressure gas from a compressor. That is, by providing a housing that has a generally cylindrical-shaped internal circumferential surface, several housing passages that include high-pressure gas passages and low-pressure gas passages formed on a wall surface of the housing, a generally cylindrical-shaped rotor supported by bearings and which rotates with a micro-clearance away from the internal circumferential surface of the aforementioned housing without touching the housing, and a rotor passage formed inside the rotor, through which gas flows at the time its openings align with the aforementioned housing passage, wherein pluralities of high-pressure gas supply ports and low-pressure gas supply ports of the aforementioned housing are provided in symmetrical position regarding the rotating axis of the aforementioned rotor.  
       [0012] Furthermore, a low-pressure gas supply port of the housing is provided in a same plane as the high-pressure gas supply port, so that harmful moment does not affect to a rotor axis due to pressure of the supplied high-pressure gas and low-pressure gas.  
       [0013] Furthermore, the high-pressure gas or low-pressure gas flowing into the aforementioned rotor passage is made to be supplied to the refrigerator, through passages formed along a central axis of the rotor and on an edge face of the housing.  
       [0014] Furthermore, the aforementioned passage formed along the central axis of the rotor is made to have openings on both end faces of the rotor, making the pressure at both ends equal, which cancels the load along the central axis of the rotor, and maintains the position of the rotor at a proper position, and which also reduces the load on the motor.  
       [0015] Furthermore, at least one of the housing and the rotor may be provided with a slit to adjust timing.  
       [0016] The present invention also provides a refrigerator that uses the aforementioned high-low pressure gas directional control valve.  
       [0017] The present invention also provides a cryogenic device that uses the aforementioned refrigerator. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0018]FIG. 1 is a block diagram showing the overall construction of an example of a pulse tube cooler, which is a target application of the present invention.  
     [0019]FIG. 2 is a longitudinal sectional view showing the overall construction of an example of conventional high-low pressure gas directional control valve.  
     [0020]FIG. 3 is a perspective view showing the form of a valve main body in the same valve.  
     [0021]FIG. 4 is a perspective view showing the form of a valve plate in the same valve.  
     [0022]FIG. 5 is a front view showing the relative relation of the valve main body and the valve plate in a high-pressure gas supplying state, in the same valve.  
     [0023]FIG. 6 is a front view showing the relative relation of the valve main body and the valve plate in a low-pressure gas supplying state, in the same valve.  
     [0024]FIG. 7 is a longitudinal sectional view showing a construction of a conventional rotary valve disclosed in Japanese Patent Laid-Open Publication No.2001-91078.  
     [0025]FIG. 8 is a longitudinal sectional view showing the overall construction of an embodiment of a high-low pressure gas directional control valve according to the present invention.  
     [0026]FIG. 9 is a cross sectional view showing a high-pressure gas supplying state in the same embodiment.  
     [0027]FIG. 10 is a cross sectional view showing a low-pressure gas supplying state in the same embodiment.  
     [0028]FIG. 11 is a perspective view showing a valve housing that is used in the aforementioned embodiment.  
     [0029]FIG. 12 is a perspective view showing a rotor that is used in the same embodiment.  
     [0030]FIG. 13 is a piping diagram showing an example where the present invention is applied to a four-valve type pulse tube cooler.  
     [0031]FIG. 14 is a piping diagram showing an example where the present invention is applied to an active-buffer type pulse tube cooler. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
     [0032] A detailed description of embodiments of the present invention will be described in detail hereafter, with references to the drawings.  
     [0033] A high-low pressure gas directional control valve of this embodiment is provided with the following, as shown in FIG. 8 (longitudinal sectional view), FIG. 9 (cross sectional view in a state of high-pressure gas being supplied to a refrigerator), and FIG. 10 (cross sectional view in a state of low-pressure gas being supplied to a refrigerator): a valve housing  42  having a generally cylindrical-shaped internal circumferential surface, of a form shown in FIG. 11; a pair of high-pressure gas passages  42   a  and a pair of low-pressure gas passages  42   b  (generically called housing passages) formed axially symmetrical on the wall surface of the valve housing  42 ; a generally cylindrical-shaped rotor  46  as shown in FIG. 12, which is supported by bearings  44  and  45 , and which rotates with a micro-clearance  43  away from the internal circumferential surface of the housing  42  without touching the valve housing  42 ; a direction control gas passage  46   a  and a refrigerator side gas passage  46   b  (generically called rotor passages) that are formed inside the rotor  46 , and through which gas flows at the time its openings align with the passages  42   a  or  42   b  of the valve housing  42 .  
     [0034] Sealing of the gas is done by the micro-clearance  43  between the rotor  46  and the housing  42 . Consequently, the micro-clearance  43  can be made to be, for example, from 5 to 100 μm. That is, it is preferable to have a clearance of 5 μm or greater to prevent contact, and 100 μm or less to prevent unfavorable effects on the performance of the refrigerator.  
     [0035] In FIG. 8, reference numeral  50  denotes a drive motor for rotating the rotor  46  through a coupling  52 , and reference numeral  54  denotes a casing of the drive motor  50 , and reference numeral  54   a  denotes a space inside the casing  54 .  
     [0036] In this embodiment, the rotor  46  supported by the two bearings  44  and  45  rotates without touching the housing  42 . passages are formed in the rotor  46  and housing  42 , and gas flows through the rotor passage at the time each of their openings aligns. That is, as shown in FIG. 9, high-pressure gas is supplied to the refrigerator through passages or space  42   a → 46   a → 46   b → 42   c , when the high-pressure gas passages  42   a  of the valve housing  42  and the direction control passage  46   a  of the rotor  46  face to each other. On the other hand, as shown in FIG. 10, low-pressure gas is recovered from the refrigerator through passages or space  42   c → 46   b → 46   a → 42   b , when the low-pressure gas passages  42   b  of the valve housing  42  and the direction control passage  46   a  of the rotor  46  face to each other.  
     [0037] Two channels of high-pressure gas supply ports  42   a  from the compressor are installed on symmetrical positions regarding the rotor  46  axis, and both of them are connected in a vertical direction regarding the rotor axis. Since there are two channels in axially symmetrical positions, vertical load on the rotating axis of the rotor  46  due to the pressure of the supplied high-pressure gas is cancelled, and the clearance  43  between the rotor  46  and the housing  42  is maintained at a proper level, preventing unbalanced clearance and partial wear of the rotor, and reducing the load on the motor  50 .  
     [0038] Low-pressure gas supply ports  42   b  from the compressor are of the same construction as the high-pressure gas side, and form passages at the same plane but with 90 degrees angle relative to high-pressure gas passages  42   a.    
     [0039] A space  54   a  inside the casing, where the drive motor  50  is installed, is connected communicatively to the space  42   c  that is used for supplying to the refrigerator, through the rotor passage  46   b . This cancels the axial load on the rotor  46  by maintaining the same pressure all the time, and keeps the rotor  46  at a proper position, preventing unbalanced clearance and partial wear of the rotor, and also reducing the load on the motor  50 .  
     [0040] In this kind of structure, sealing is done by the rotor  46  and the housing  42  in a non-contact state, hence there are no sliding surfaces, and regular replacement of parts are not required. It should be noted that, there are some leaks because it is a non-contact sealing, but this problem is small compared to the flow rate supplied to the refrigerator.  
     [0041] Furthermore, by balancing the pressure, the load on the drive motor  50  is decreased by making the rotating resistance of the rotor  46  as small as possible. Hence smaller motors can be adopted, enabling smaller and lighter units, and enabling lower power consumption.  
     [0042] Furthermore, by balancing the pressure, the micro-clearance  43  for sealing can be secured with stability. Furthermore, a high efficiency operation with little pressure loss is possible, since the passage shape is simple.  
     [0043] In this embodiment, slits  42   s  and  46   s  are provided to both the housing  42  and the rotor  46 . So, change-over timing of the valve can be changed easily. However, one of the slits  42   s  and  46   s  or both may be omitted.  
     [0044] The loss due to leak from the micro-clearance  43  for sealing of the high-low pressure gas directional control valve in the following conditions was approximately 40W, which was 0.5% of compressor input, and was within the range of being negligible. Here, the outer diameter of the valve rotor  46  was 20 mm, the overall length of the valve rotor was 24 mm, the inner diameter of the gas passages  42   a  to  42   c ,  46   a , and  46   b  each were 3 mm, and the micro-clearance  43  for sealing was 15 μm. A geared compact DC motor, with a variable selectable frequency of 1 to 10 Hz by the change of the drive voltage, was used for the drive motor  50 , using drive voltage 1-24V and DC drive current 5 mA (at DC 3V drive). And bearings  44 ,  45  with general-use specifications were used.  
     [0045] The valve unit according to the present invention can also be applied to a phase control mechanism for a pulse tube cooler, aside from various pulse tubes.  
     [0046] In case of a four-valve type pulse tube cooler, as shown in FIG. 13, a phase control at a high temperature end of the pulse tube  12 A is achieved by means of two switching valves  61  and  62  instead of a buffer. One end of each of the two valves  61  and  62  is connected to the high temperature end of the pulse tube  12 A via a common orifice  16 . The other ends thereof are connected to the high-pressure gas supply line and the low-pressure gas supply line of the compressor  10 , respectively. The two valves are controlled so as to periodically open and close according to a predetermined timing chart to provide an optimal phase between the pressure variation and the gas displacement inside the pulse tube, thereby obtaining a desired refrigerating performance.  
     [0047] This phase control valve is operated in the same manner as that of the high-low pressure switching valve unit  14  arranged between the regenerator  12 B and the compressor  10 . Thus, the valve unit according to the present invention can be applied to the four-valve type phase control valve.  
     [0048] In case of an active-buffer type pulse tube cooler, as shown in FIG. 14, the phase control at the high temperature end of the pulse tube  12 A is not achieved by the combination of one buffer and an orifice, but by the combination of two or more buffers  18  and  19  and the same number of switching valves  61  and  62 . These buffers  18  and  19  are kept in a medium pressure state which is a state between the high pressure and low pressure states of the compressor. However, the respective pressures in the buffers are different from each other. The buffers are connected to the high temperature end of the pulse tube via the respective switching valves. The respective switching valves are controlled so as to periodically open and close, according to a predetermined timing chart to provide an optimal phase between the pressure variation and the gas displacement inside the pulse tube, thereby obtaining a desired refrigerating performance.  
     [0049] This phase control valve is operated in the same manner as that of the high-low pressure switching valve unit  14  arranged between the regenerator  12 B and the compressor  10 . Thus, the valve unit according to the present invention can be applied to the active-buffer type phase control valve.  
     [0050] Further, since there is no wear, it can also be applied to a low temperature application.  
     [0051] Industrial Applicability  
     [0052] The present invention can be used in a high-low pressure gas directional control valve of a refrigerator for extremely low temperature, such as GM cryocoolers and pulse tube coolers etc.  
     [0053] According to the present invention, it is possible to maintain the clearance between the rotor and the housing at a proper level, and also to reduce the load on the motor, by having a balanced axial and vertical load on the rotating axis of the rotor. Therefore, it is possible to make the high-low pressure gas directional control valve longer in life, higher in efficiency, more compact, lighter, no wear and no dust formation enabling a long term, stable operation, and a drive motor that is more compact and lower in power consumption.