Abstract:
A seal carrier that is used to transmit hydraulic fluid to control pistons in a transmission includes a center passage and connecting passages to one or more oil passages. As the seal carrier rotates during operation, the seal carrier acts as a centrifuge and entrapped air in the hydraulic fluid is separated from the hydraulic fluid. The released air moves into the center passage and out through one of the connecting passages, ultimately to a tank or reservoir. A poppet valve in the hydraulic fluid drain rail maintains a positive pressure on the hydraulic fluid at all times to create a pressure differential between the central passage and the tank.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to hydraulic implements and more particularly to a seal carrier that removes air from a hydraulic fluid in a transmission. 
       BACKGROUND 
       [0002]    A transmission or power takeoff (PTO) is a machine that uses one or more of a torque converter, pumps, planetary gear sets, clutches, and valves to convert power from a source, such as a gas or diesel engine into power usable at an output, such as tires, tracks, or pumps, among others. Hydraulic fluid is driven by the pump and channeled by the valves to operate clutches and actuate gear levers. 
         [0003]    The effectiveness of the transmission or similar equipment in terms of mechanical efficiency and smooth, accurate gear changes is a function of the volume of the hydraulic fluid or oil. The oil can vary in volume primarily due to entrapped air and can dramatically affect the shift quality of the transmission. However, due to the complexity of the system and the cramped quarters, a traditional deaerator that tangentially injects oil into a canister with a top-facing hole, such as in EP1166841 is not practical. 
       SUMMARY 
       [0004]    According to one aspect of the disclosure, a deaerator system may include a seal carrier having a cylindrical outer surface, a central passage located around an axial centerline of the seal carrier and a radial passage having a proximal end at the central passage and a distal end at the cylindrical outer surface. The seal carrier may also include an axial passage carrying hydraulic fluid through the seal carrier. The axial passage may be displaced from the axial centerline of the seal carrier and non-overlapping with the central passage. The seal carrier may further include a second radial passage connecting the axial passage to the central passage, wherein the second radial passage has a smaller diameter than the axial passage. 
         [0005]    In another aspect of the disclosure, a method of centrifuging air from an oil supply may include rotating a component having first and second fluid passages, introducing oil to a first passage, the first passage displaced from an axial centerline of the component, and collecting air displaced from the oil in a second passage of the component. The second passage may be coupled to the first passage and may have a smaller cross section than the first passage. The method may also include venting the air in the second passage to a tank. 
         [0006]    In yet another aspect of the disclosure, an apparatus that deaerates oil in a transmission, may include a shaft with a first passage that couples fluid to a piston and a second passage that couples the first passage to a vent. The apparatus may also include a backpressure device coupled to the first passage, the backpressure device creating a positive pressure between the first passage and the vent. When the shaft is rotated, air displaced via rotation of the shaft is vented via the second passage. 
         [0007]    These and other benefits will become apparent from the specification, the drawings and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a transmission; 
           [0009]      FIG. 2  is a side view of the transmission of  FIG. 1 ; 
           [0010]      FIG. 3  is a simplified and representative diagram showing a seal carrier and related components of a transmission; 
           [0011]      FIG. 4  is another simplified and representative diagram showing another embodiment of a seal carrier and related components of a transmission; 
           [0012]      FIG. 5  is a cutaway view of a seal carrier configured for oil deaeration; 
           [0013]      FIG. 6  is a cutaway view of a poppet valve in a drain rail; and 
           [0014]      FIG. 7  is a simplified and representative diagram showing another embodiment of the deaerator apparatus; 
           [0015]      FIG. 8  is a simplified and representative diagram showing another embodiment of the deaerator apparatus; 
           [0016]      FIG. 9  is a simplified and representative diagram showing another embodiment of the deaerator apparatus; 
           [0017]      FIG. 10  is a simplified and representative diagram showing another embodiment of the deaerator apparatus; 
           [0018]      FIG. 11   a  and  FIG. 11   b  is a simplified and representative diagram showing another embodiment of the deaerator apparatus; 
           [0019]      FIG. 12   a  and  FIG. 12   b  is a simplified and representative diagram showing another embodiment of the deaerator apparatus; 
           [0020]      FIG. 13  is a flowchart of a method of using a seal carrier for deaerating oil or other hydraulic fluid. 
       
    
    
     DESCRIPTION 
       [0021]    The following discussion pertains to transmissions, particularly transmissions that use hydraulic fluid to activate clutches or other assemblies that effect the changes in input-to-output shaft speed and torque. In the following discussion, the terms hydraulic fluid and oil may be used interchangeably. 
         [0022]      FIG. 1  is a perspective view of a transmission  100 . The view of  FIG. 1  illustrates a plurality of shaft casings  102  into which shafts and seal carriers are disposed.  FIG. 1  also illustrates oil passages  104  that are coupled to the shaft casings  102 . A poppet valve  108 , shown in more detail below, may be mounted at a top (with respect to gravity) of a drain rail  106 , that carries low pressure oil. 
         [0023]      FIG. 2  is a side view of the transmission  100  of  FIG. 1  showing the shaft casings  102 , oil passages  104 , drain rail  106 , and poppet valve  108 . 
         [0024]      FIG. 3  is a simplified and representative diagram showing a seal carrier  103  and selected components of a transmission  100 . In this embodiment, the seal carrier  103  and the shaft  130  are bolted together. The seal carrier  103  may be coupled to the shaft casing  102  by a bearing (not depicted) in a known manner. The seal carrier  103  and shaft  130  illustrated include two hydraulic circuits including oil passages  104   a  and  104   b  that are connected to the rotating seal carrier  103  using seals  150  at each oil passage  104   a  and  104   b . Oil passage  104   a  may be connected to a piston  146  that operates clutch  148  by oil under pressure delivered through radial passages  116  and  144 , and axial passage  114 . Oil passage  104   b  may be connected to a piston  140  that operates piston  142  via radial passages  124  and  138 , and axial passage  120 . The axial passages  114  and  120  are offset from an axial centerline  112  of the seal carrier  103  and shaft  130 . 
         [0025]    Pressurized oil from a source  136  may be coupled to oil passages  104   a  and  104   b  by control valves  132  and  134  respectively. When not connected to the source  136 , the oil passages  104   a  and  104   b  may be connected to the drain rail  106 . In an embodiment, the control valves  132  and  134  may dispense a low volume of oil into the oil passages  104   a  and  104   b  to maintain the fluid levels in the transmission even when not connected to the high pressure source  136 . The control valves  132  and  134  may operate independently of each other. The process of pressurizing oil at the source  136  may cause air to be entrapped in the oil. As discussed above, air entrapped in the oil cause the transmission  100  to operate less effectively. 
         [0026]    To aid in removing entrapped air in the oil, the seal carrier  103  may include a central passage  110  along the centerline  112  of the seal carrier  103 . A radial passage  118  may connect the central passage  110  with an inner-facing surface of the axial passage  114 . Similarly, a radial passage  126  may connect the central passage  110  with an inner-facing surface of the axial passage  120 . When the seal carrier  103  and shaft  130  spin, oil is forced away from the centerline  112 . The air, which is lighter than oil can separate from the oil via centrifugal action so that oil  152  and  156  collects away from the centerline  112  and air  154  and  158  collects nearer the centerline  112  in the axial passages  114  and  120 , respectively. The central passage  110  may penetrate an entire length of the seal carrier  103  but a stopper  160  can be used to prevent leakage via the central passage  110 . 
         [0027]    Air that is collected in the central passage  110  may be expelled to a tank  162  (see  FIG. 6 ) via another radial passage  128 . A pressure differential between the air  154 ,  158  released in the axial passages  114 ,  120  and the tank  162  may be created by the poppet valve  108  so that the released air is driven outward to the tank  162 . The poppet valve  108  may be set for a low pressure such as 0.5 psi to 5 psi. In another embodiment, the poppet valve  108  may be designed to provide between 1.5 psi and 2.5 psi of back pressure. Even though oil may be ejected via the poppet valve  108  when the control valves  132  and  134  connect the oil passages  104   a  and  104   b  to the drain rail  106 , the positive pressure is enough to force air out through the radial passage  128  into the tank  162 . 
         [0028]    In alternate embodiments, one or all of the radial passages  118 ,  126 , and  128  may be cut as a groove in the shaft-end of the seal carrier  103  so that attaching the seal carrier  103  to the shaft  130  closes the groove and creates the respective passage. 
         [0029]      FIG. 4  is a variation of the embodiment illustrated in  FIG. 3 . In this embodiment, the central passage  110  does not penetrate the length of the seal carrier  103 . In both the embodiments of  FIG. 3  and  FIG. 4 , the central passage  110  may be manufactured, by drilling from a side nearer the shaft  130  although other manufacturing techniques may be utilized. The shaft  130  itself may act as a stop to block air flow in the direction of the shaft  130 . Because of the low pressures involved, special seals at the shaft  130  may not be required. 
         [0030]      FIG. 5  is a cutaway view of a seal carrier  103 . The seal carrier  103  may include axial passage  114  with radial passage  116 . The seal carrier  103  may also include an axial passage  120  with radial passage  124 . While the illustrated embodiment has two axial passages for oil, other embodiments may have more or fewer axial passages, depending on the requirements of the application. Passages  118  and  126  may connect the respective axial passages  114  and  120  with a central passage  110 . Radial passage  128  may carry air that centrifuge action releases from the oil. The stopper  160  may prevent oil/air mixture from escaping via the central passage  110 . As shown in the illustration of  FIG. 5 , radial passages  118  and  126  may be much smaller than the axial passages  114  and  120  in order to limit the loss of oil via the central passage  110 , especially when under pressure during clutch activation. The radial passage  128  may be larger than the passages  118  and  126  to provide an exit path for both air and any oil that passes into the central passage  110 . 
         [0031]      FIG. 6  is a cutaway view of a poppet valve  108  in a drain rail  106 . The poppet valve  108  connects the drain rail  106  to a tank  162 . The poppet valve  108  may include a housing  164 , a piston  166 , and a spring  168 . The spring  168  may be selected to provide the desired pressure in the drain rail  106  before opening to allow oil to enter the tank  162 , such as 2 psi, in one embodiment. 
         [0032]    The poppet valve  108  creates a slight positive pressure between the oil and the tank, which in turn forces the air from the central passage  110  out to the tank  162 . Under some conditions, such as very low rotation speeds or very high pressures in the axial passages  114  or  120 , there may be some oil flow through the radial passages  118  or  126  to the central passage  110 , which is then discharged via the radial passage  128  to the tank  162 . Because the radial passages  118  and  126  have a relatively small diameter this flow is minimized. 
         [0033]      FIG. 7  is a simplified and representative diagram showing another embodiment of a deaerator apparatus. In this embodiment, a central passage  111  is not aligned with the axial centerline  112  but is closer to the centerline than the oil-carrying axial passages  114  and  120 . In this embodiment, the air is still moved inward from the axial passages and then vented out through radial passage  128 . 
         [0034]      FIG. 8  is a simplified and representative diagram showing another embodiment of a deaerator apparatus. In this embodiment, there is no radial passage  128 , rather, air, and any entrained oil may be vented via an opening in the central passage  110 . In this embodiment, more oil may be discharged with the air that other embodiments with a secondary passage, such as passage  128 . Also illustrated in this embodiment is a shaft  131  with the seal carrier functions built in so that a separate seal carrier is not incorporated in the shaft  130  of the other illustrated embodiments. In many cases the oil deaeration functions can be incorporated in a shaft design that does not use a separate seal carrier. 
         [0035]      FIG. 9  is a simplified and representative diagram showing another embodiment of a deaerator apparatus. This embodiment is similar to that of  FIG. 8  other than the central passage  110  is extended to the end of the piston  142  end of shaft  130  rather than the opposite end depicted in  FIG. 8 . 
         [0036]      FIG. 10  is a simplified and representative diagram showing another embodiment of the deaerator apparatus. In this exemplary embodiment, the central passage  110  is extended into the shaft  130  and a radial shaft  129  is disposed in the shaft  130  rather that in the seal carrier  103  as shown in previous embodiments. As illustrated here, the other radial passages, e.g., passage  118  and/or  126  may also be disposed in the shaft  130 . 
         [0037]      FIG. 11   a  and  FIG. 11   b  is a simplified and representative diagram showing another embodiment of the deaerator apparatus.  FIG. 11   a  illustrates that the air discharge passage need not be radial, but may be on an angle, but still exit through the outer surface of the seal carrier  103  as shown by passages  119  and  127 . In another embodiment, the passages may exit via the front of the seal carrier  103 . 
         [0038]    The passages  119  and  127  may be larger in diameter at the outer surface and a smaller diameter at the axial passages  114  and  120 . This small diameter portion reduces the oil loss via the passages  119  and  127  and also accommodates manufacturing by reducing the length of the small bore portion of the passages  119 ,  127 . 
         [0039]      FIG. 11   b  illustrates that the passages  119  and  127  extend to the outer surface of the seal carrier in this embodiment, although, as discussed above, the passages  119  and  127  may extend at a lower angle through the front surface as well. 
         [0040]      FIG. 12   a  and  FIG. 12   b  is a simplified and representative diagram showing another embodiment of the deaerator apparatus. In this embodiment, radial passages  170  and  172  may be bored directly into the oil passages  114  and  120 , respectively, in the shaft  130  rather than the seal carrier  103 .  FIG. 12   b  illustrates an end view of the passage  114  and its air shaft  170  and passage  120  and its air shaft  172 . 
       INDUSTRIAL APPLICABILITY 
       [0041]      FIG. 13  is a flowchart of a method  180  of using a seal carrier  103  for deaerating oil or other hydraulic fluid. At a block  182 , a seal carrier  103  may be provided. The seal carrier  103  may include an axial passage  114  generally parallel to and displaced from an axial centerline  112  of the seal carrier  103 . The seal carrier  103  may also include a central passage  110  aligned with the axial centerline  112 . In an embodiment, the central passage  110  and axial passage  114  do not overlap. 
         [0042]    At a block  184 , the seal carrier may be rotated about its axial centerline  112 . In an embodiment, the seal carrier may rotate at between 0 rpm and 5000 rpm. At a block  186 , oil may be introduced to the axial passage  114 . As the seal carrier  103  and the associated shaft  130  are rotated, centrifugal/centripetal forces will develop in the axial passage  114  and air embedded in the oil may begin to separate from the oil. 
         [0043]    At a block  188 , air displaced from the oil in the axial passage  114  during rotation may be collected at the central passage  110  of the seal carrier  103 . At a block  190 , the air in the central passage  110  may be vented via a radial passage  118  in the seal carrier  103 . wherein venting the air may include venting to the air to a tank  162 . In an embodiment, pressure in the axial passage  114  may be maintained by a poppet valve  108  disposed between a drain rail  106  and the tank  162 . In an embodiment, the poppet valve  108  may be set to maintain a pressure in the axial passage  114  of between about 1 psi and 3 psi. While the description of  FIG. 13  illustrates axial passage  114 , the method applies to all passages in the various embodiments discussed above. The seal carrier  103  and method  180  may be used at each shaft  130 /shaft casing  102  in the transmission  100 . 
         [0044]    The oil deaerator and method described above has been shown in one embodiment to improve oil volume consistency by 200%, which directly translates to improved shift quality. The existing rotation of the seal carrier  103  and shaft  130  are utilized to provide the deaerating function with virtually no loss of energy in the system and without additional parts other than the simple poppet valve  108 , saving valuable engine compartment space. Because each shaft casing  102  and its associated seal carrier  103  in the system can be adapted to the functions described, the deaeration functions can be distributed throughout the transmission  100 , allowing deaeration to occur even as different shift combinations are engaged. 
         [0045]    In accordance with the provisions of the patent statutes and jurisprudence, exemplary configurations described above are considered to represent a preferred embodiment of the invention. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.