Abstract:
A hydraulic control circuit for a transmission is provided including a source of pressurized fluid and at least one selectively engageable torque transmitting mechanism. At least one latching valve is provided in communication with the source and is operable to selectively communicate the pressurized fluid to effect engagement of the at least one torque transmitting mechanism. The at least one latching valve is operable to maintain engagement the at least one torque transmitting mechanism irrespective of the presence of the pressurized fluid. A valve is in fluid communication with the source. A lubrication circuit is provided and is operable to lubricate the transmission. The valve is operable to variably communicate the pressurized fluid to the lubrication circuit. A transmission incorporating the hydraulic control circuit is also disclosed.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to vehicular transmissions and more specifically to a valve configuration for a lubrication circuit of a latched pump applied clutch transmission. 
       BACKGROUND OF THE INVENTION 
       [0002]    In a typical automatic transmission, the amount of torque transmitted through the transmission is proportional to the holding torque of clutches or torque transmitting mechanisms. These torque transmitting mechanisms are typically fluid activated; therefore, the holding torque of the torque transmitting mechanisms is proportional to line pressure developed by a hydraulic pump. As a result, heat generated by bearings, bushings, torque transmitting mechanisms, and gear sets is also proportional to line pressure. Once the torque transmitting mechanisms are filled with fluid and stroked into engagement, and the leakage within the torque transmitting mechanism circuits is satisfied, the remaining fluid flow from the hydraulic pump can be dedicated to lubrication of components within the transmission. Pressurized fluid for lubrication is derived from a cooler feed circuit which originates at a line or main pressure regulator valve. The lubrication circuit of a typical transmission operates passively by flowing surplus pressurized fluid from the hydraulic pump through a fixed orifice. 
         [0003]    In an automatic transmission having a latched-pump applied clutch (LPAC) system, a controllable pump pressure is used to apply torque transmitting mechanisms to effect gear shifting. Once an LPAC clutch is engaged, a latching valve is closed, thereby trapping hydraulic pressure within the hydraulic apply circuit of the torque transmitting mechanism, typically a plate-type clutch pack. Since the torque transmitting mechanism hydraulic circuit is sealed from the pump pressure circuit, by means of the latching valve, the line pressure can be lowered to minimize transmission spin losses. The engagement of the torque transmitting mechanism will be maintained irrespective of the line pressure by virtue of the latching valve. 
         [0004]    In contrast to typical automatic transmissions, LPAC-equipped automatic transmissions do not need to supply pressurized fluid to the torque transmitting mechanism after latching has occurred. This functionality allows line pressure to be reduced while lubrication demand remains high. It is generally desirable to reduce line pressure in order to reduce spin loss and improve the efficiency of the transmission. However, reducing line pressure without increasing the flow of pressurized fluid to the lubrication circuit could prove to be fatal to bushings, bearings, and gear sets within the transmission, since lubrication fluid demand remains high during conditions of high torque transfer. 
       SUMMARY OF THE INVENTION 
       [0005]    A transmission is provided having a source of pressurized fluid and a valve in fluid communication with the source and having a first position and a second position. A lubrication circuit is operable to lubricate the transmission. A valve is operable to communicate the pressurized fluid to the lubrication circuit. First and second orifices are disposed between the valve and the lubrication circuit. The valve is configured to supply the lubrication circuit with the pressurized fluid through each of the first and the second orifices when the valve is in one of the first position and the second position. Furthermore, the valve is configured to supply the lubrication circuit with the pressurized fluid through the second orifice when the valve is in the other of the first position and the second position. 
         [0006]    In an alternate embodiment, a transmission is provided having a source of pressurized fluid and at least one selectively engageable torque transmitting mechanism. At least one latching valve is provided in communication with the source and operable to selectively communicate the pressurized fluid to effect engagement of the at least one torque transmitting mechanism. The at least one latching valve is operable to maintain the engagement of the at least one torque transmitting mechanism irrespective of the presence of the pressurized fluid. A pressure regulator valve is disposed in fluid communication with the source and having a first position, a second position, and a regulation position. The pressure regulator valve is operable to regulate the pressurized fluid when the pressure regulator valve is in the regulation position. A lubrication circuit is operable to lubricate the automatically shiftable transmission. The pressure regulator valve is operable to selectively and variably communicate the pressurized fluid to the lubrication circuit. 
         [0007]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1   a  is a schematic illustration of a hydraulic circuit of a latched pump applied clutch transmission illustrating a logic valve, in a spring set position, operable to communicate pressurized fluid to a lubrication circuit of the latched pump applied clutch transmission; 
           [0009]      FIG. 1   b  is a schematic illustration of the hydraulic circuit of  FIG. 1   a  illustrating the logic valve, in a pressure set position; 
           [0010]      FIG. 2   a  is a schematic illustration of an alternate embodiment of the hydraulic circuit of  FIGS. 1   a  and  1   b  illustrating a pressure regulator valve, in a spring set position, operable to selectively and variably communicate pressurized fluid to the lubrication circuit of the latched pump applied clutch transmission; 
           [0011]      FIG. 2   b  is a schematic illustration of the hydraulic circuit of  FIG. 2   a  illustrating the pressure regulator valve, in a pressure set position; 
           [0012]      FIG. 2   c  is a schematic illustration of the hydraulic circuit of  FIGS. 2   a  and  2   b  illustrating the pressure regulator valve, in a regulation position; 
           [0013]      FIG. 3   a  is a schematic illustration of an alternate embodiment of the hydraulic circuits of  FIGS. 1   a ,  1   b ,  2   a ,  2   b , and  2   c  illustrating a logic valve and pressure regulator valve, each in a spring set position, operable to selectively and variably communicate pressurized fluid to the lubrication circuit of the latched pump applied clutch transmission; 
           [0014]      FIG. 3   b  is a schematic illustration of the hydraulic circuit of  FIG. 3   a  illustrating the logic valve, in a pressure set position, and the pressure regulator valve, in a regulation position; 
           [0015]      FIG. 4   a  is a schematic illustration of an alternate embodiment of the hydraulic circuit of  FIGS. 1   a ,  1   b ,  2   a ,  2   b ,  2   c ,  3   a , and  3   b  illustrating a snap action valve, in a spring set position, operable to selectively and variably communicate pressurized fluid to the lubrication circuit of the latched pump applied clutch transmission; and 
           [0016]      FIG. 4   b  is a schematic illustration of the hydraulic circuit of  FIG. 4   a  illustrating the snap action valve, in a pressure set position. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Referring to the drawings wherein like reference numbers correspond to like of similar components throughout the several figures, there is shown in  FIG. 1   a  a portion of a vehicular transmission  10 . The transmission  10  includes a hydraulic circuit  12 , a portion of which is shown in  FIG. 1   a . The hydraulic circuit  12  includes a hydraulic pump  14 , such as a positive displacement pump, operable to draw fluid  16  from a reservoir  18  and provide pressurized fluid to a main pressure regulator  20 . The pressurized fluid, indicated by arrows  22 , is communicated from the main pressure regulator  20  to a latching valve  24  and a logic valve assembly  26 . The latching valve  24  is operable to selectively communicate pressurized fluid  22  to a hydraulically actuated clutch or torque transmitting mechanism  28  to effect the engagement thereof. Once the torque transmitting mechanism  28  is engaged, the latching valve  24  maintains the engagement of the torque transmitting mechanism  28  irrespective of the presence or magnitude of the pressurized fluid  22 . Therefore, the transmission  10  may be characterized as a latched pump applied clutch, or LPAC, transmission. Those skilled in the art will recognize that the transmission  10  may include multiple latching valves  24  and torque transmitting mechanisms  28 ; however, only one of each is shown in the figures for clarity. 
         [0018]    The logic valve assembly  26  is in communication with a passage  30 , control passage  32 , first lubrication branch  34 , second lubrication branch  36 , and exhaust port  38 . A solenoid valve  40 , such as a variable bleed solenoid valve or an on/off solenoid valve, is operable to selectively communicate fluid, indicated by arrows  42 , from an actuator feed source  44  to the logic valve assembly  26 . The logic valve assembly  26  includes a spool valve  46  biased in a spring set position by a spring  48 , as shown in  FIG. 1   a . A lubrication circuit  50  is provided in communication with the logic valve assembly  26  through both of a first and second orifice  52  and  54 , respectively, or only the second orifice  54  depending on the state of operation of the hydraulic control circuit  12 . In the preferred embodiment, the first orifice  52  is more restrictive than the second orifice  54 . 
         [0019]    The latching nature of the latching valve  24  permits the pressure of the pressurized fluid  22 , often times referred to as line pressure, to be reduced once the torque transmitting mechanism  28  has engaged thereby increasing the operating efficiency, through a reduction in spin-losses, of the transmission  10 .  FIG. 1   a  illustrates the hydraulic circuit  12  when operating with the pressurized fluid  22  at high pressure. In this high line pressure mode of operation, the solenoid valve  40  restricts communication of fluid  42  to the logic valve assembly  26 . As such, the spool valve  46  is biased into the spring set position by the spring  48 . With the spool valve  46  in the spring set position, the pressurized fluid  22  is allowed to pass from the passage  30  into the first lubrication branch  34 . The pressurized fluid  22  is subsequently communicated to the lubrication circuit  50  though the first and second orifices  52  and  54 . The pressure drop through the first and second orifices  52  and  54  are preferably tuned for the high pressure conditions such that a sufficient amount of pressurized fluid  22  is communicated to the lubrication circuit  50  to avoid damaging components within the transmission  10 . 
         [0020]    Referring now to  FIG. 1   b , there is shown the hydraulic circuit  12  when operating with the pressurized fluid  22  at low pressure. In this low line pressure mode of operation, the solenoid valve  40  communicates fluid  42  from the actuator feed source  44  to the logic valve assembly  26  via the control passage  32 . As such, the spool valve  46  is biased into a pressure set position, as shown in  FIG. 1   b , against the bias force of the spring  48 . With the spool valve  46  in the pressure set position, the pressurized fluid  22  is allowed to pass from the passage  30  into the second lubrication branch  36 . The pressurized fluid  22  is subsequently communicated to the lubrication circuit  50  though only the second orifice  54 . The pressure drop and flow through the second orifice  54  is preferably tuned for the low pressure conditions such that a sufficient amount of pressurized fluid  22  is communicated to the lubrication circuit  50  to avoid damaging the transmission  10 . The logic valve assembly  26  therefore provides two discrete flow states relative to the pressure of the pressurized fluid  22  from the main pressure regulator  20 . 
         [0021]    Referring now to  FIG. 2   a , there is shown an alternate embodiment of the transmission  10  of  FIGS. 1   a  and  1   b , generally indicated at  10 A. The transmission  10 A includes a hydraulic circuit  12 A. The hydraulic circuit  12 A includes a pressure regulator valve assembly  56 . The pressure regulator valve assembly  56  includes a spool valve  58  and a spring  60  operable to bias the spool valve  58  into a spring set position as illustrated in  FIG. 2   a . The pressure regulator valve assembly  56  is in communication with a passage  62 , control passage  64 , regulator outlet passage  66 , feedback passage  68 , and exhaust port  70 . 
         [0022]    In operation, with the spool valve  58  in the spring set position, the pressurized fluid  22  is substantially blocked or prevented from passing from the passage  62  to the regulator outlet passage  66  by the spool valve  58 , thereby eliminating the flow of pressurized fluid  22  to the lubrication circuit  50 . Any fluid contained within the lubrication circuit  50  will exhaust through the regulator outlet passage  66  via the exhaust port  70 . 
         [0023]    Referring to  FIG. 2   b , the pressure regulator valve assembly  56  is illustrated with the spool valve  58  in a pressure set position. In this condition, the solenoid valve  40 , which is preferably a variable bleed solenoid valve, commands an amount of pressure necessary such that fluid  42  will bias the spool valve  58  against the bias force of the spring  60 . With the spool valve  58  in the pressure set position, the pressurized fluid  22  may pass, substantially unregulated, from the passage  62  into the regulator outlet passage  66  for subsequent introduction to the lubrication circuit  50 . An orifice  72  provides a predictable relationship between pressure and flow of pressurized fluid  22  entering the lubrication circuit  50 . 
         [0024]    Referring now to  FIG. 2   c  the pressure regulator valve assembly  56  is illustrated with the spool valve  58  in a regulation position. In this condition, the solenoid valve  40 , which is preferably a variable bleed solenoid valve, commands a variable amount of pressure such that fluid  42  will bias the spool valve  58  against the bias force of the spring  60  into the regulation position thereby allowing the spool valve  58  to modulate. With the spool valve  58  in the regulation position, the pressurized fluid  22  is regulated as it passes from the passage  62  into the regulator outlet passage  66  for subsequent introduction to the lubrication circuit  50 . An amount of the regulated pressurized fluid  22  is communicated to the pressure regulator valve assembly  26  via the feedback passage  68  to provide the spool valve  58  with a feedback signal. The pressure regulator valve assembly  56  is effective in controlling the flow of pressurized fluid  22  to the lubrication circuit  50  over a broad range, i.e. zero to full pressure provided by the main pressure regulator  20  (minus the offset created by the spring rate of the spring  60 ). 
         [0025]    Referring now to  FIG. 3   a  there is shown an alternate embodiment of the transmission  10  of  FIGS. 1   a  and  1   b  and transmission  10 A of  FIGS. 2   a  through  2   c , generally indicated at  10 B. The transmission  10 B includes a hydraulic circuit  12 B. The hydraulic circuit  12 B includes a pressure regulator valve assembly  74  and a logic valve assembly  76 . The pressure regulator valve assembly  74  includes a spool valve  78  and a spring  80  operable to bias the spool valve  78  into a spring set position as illustrated in  FIG. 3   a . Similarly, the logic valve assembly  76  includes a spool valve  82  and a spring  84  operable to bias the spool valve  82  into a spring set position as illustrated in  FIG. 3   a . The pressure regulator valve assembly  74  is in communication with a passage  86 , control passage  88 , regulator output passage  90 , feedback passage  92 , and exhaust port  94 . The logic valve assembly  76  is in communication with the passage  86 , control passage  88 , regulator output passage  90 , first lubrication branch  96 , second lubrication branch  98 , and exhaust port  100 . The first lubrication branch  96  is operable to communicate pressurized fluid  22  to the lubrication circuit  50  through a first and second orifice  102  and  104 , respectively. The second lubrication branch is operable to communicate pressurized fluid  22  to the lubrication circuit  50  through only the second orifice  104 . Preferably the first orifice  102  is more restrictive than the second orifice  104 . 
         [0026]      FIG. 3   a  illustrates the hydraulic circuit  12 B when operating with the pressurized fluid  22  at low pressure. In this low line pressure mode of operation, the solenoid valve  40 , preferably a variable bleed solenoid valve, restricts communication of fluid  42  to the pressure regulator valve assembly  74  and the logic valve assembly  76 . As such, the spool valve  78  of the pressure regulator valve assembly  74  is biased into the spring set position by the spring  80 ; likewise, the spool valve  82  of the logic valve assembly  76  is biased into the spring set position by the spring  84 . With the spool valve  82  in the spring set position, the pressurized fluid  22  is allowed to pass from the passage  86  into the second lubrication branch  98 . The pressurized fluid  22  is subsequently communicated to the lubrication circuit  50  though the second orifice  104 . The flow through the second orifice  104  is preferably tuned for the low pressure conditions such that a sufficient amount of pressurized fluid  22  is communicated to the lubrication circuit  50  to avoid damaging the transmission  10 B. With the spool valve  78  in the spring set position, the pressure regulator valve assembly  74  substantially blocks or prevents the communication of pressurized fluid  22  to the logic valve assembly  76  via the regulator outlet passage  90 . 
         [0027]    Referring now to  FIG. 3   b , there is shown the hydraulic circuit  12 B when operating with the pressurized fluid  22  at high pressure. In this high line pressure mode of operation, the solenoid valve  40  communicates fluid  42  from the actuator feed source  44  to the pressure regulator valve assembly  74  and the logic valve assembly  76  via the control passage  88 . As such, the spool valve  78  is biased into a regulation position, as shown in  FIG. 3   b , against the bias of the spring  80 , while the spool valve  82  is biased into a pressure set position against the bias of spring  84 . With the spool valve  82  of the logic valve assembly  76  in the pressure set position, the pressurized fluid  22  is blocked or prevented from to passing from the passage  86  into the second lubrication branch  98 . Instead pressurized fluid  22  from within the passage  86  is regulated by the pressure regulator valve assembly  74  and subsequently communicated to the logic valve assembly  76  via the regulator outlet passage  90 . Those skilled in the art will recognize that the variable bleed nature of the solenoid valve  40  will allow the spool valve  78  to modulate against the bias of spring  80  and the pressurized fluid  22 , thereby regulating the pressurized fluid  22  communicated to the regulator outlet passage  90 . Pressurized fluid  22  entering the feedback passage  92  provides a feedback signal to the spool valve  78 . The pressurized fluid  22  is communicated from the logic valve assembly  76  to the first lubrication branch  96  where the pressurized fluid  22  is subsequently introduced to the lubrication circuit  50  through the first and second orifices  102  and  104 . The pressure of the pressurized fluid  22  is therefore controlled or regulated by modulating the spool valve  78  of the pressure regulator valve assembly  74 , while the flow of pressurized fluid  22  to the lubrication circuit  50  is controlled by the first and second orifices  102  and  104 , respectively. 
         [0028]    The combination of the pressure regulator valve assembly  74  and the logic valve assembly  76  allows precise regulation of the pressure of the pressurized fluid  22 , while also permitting the pressure of the pressurized fluid  22  to drop to a value substantially equal to the pressurized fluid exiting the main pressure regulator valve  20 . Since latched pump applied clutch transmission, such as transmission  10 B are able to operate at relatively low line pressure values, the combination of the pressure regulator valve assembly  74  and the logic valve assembly  76  allows the hydraulic circuit  12 B to operate at the minimum line pressure required to maintain adequate flow of pressurized fluid  22  to the lubrication circuit  50  to avoid damaging components within the transmission  10 B. 
         [0029]    Referring now to  FIG. 4   a  there is shown an alternate embodiment of the transmission  10  of  FIGS. 1   a  and  1   b , transmission  10 A of  FIGS. 2   a  through  2   c , and transmission  10 B of  FIGS. 3   a  and  3   b , generally indicated at  10 C. The transmission  10 C includes a hydraulic circuit  12 C. The hydraulic circuit  12 C includes a snap action valve assembly  106 . The snap action valve assembly  106  includes a spool valve  108  and a spring  110  operable to bias the spool valve  108  into a spring set position as illustrated in  FIG. 4   a . A differential area, denoted by the letter A, is defined on the spool valve  108 . The snap action valve assembly  106  is in communication with a passage  112 , passage  114 , passage  116 , first lubrication branch  118 , second lubrication branch  120 , and exhaust port  122 . The first lubrication branch  120  is operable to communicate pressurized fluid  22  to the lubrication circuit  50  through a first and second orifice  124  and  126 , respectively. The second lubrication branch  120  is operable to communicate pressurized fluid  22  to the lubrication circuit  50  through only the second orifice  126 . Preferably the first orifice  124  is more restrictive than the second orifice  126 . 
         [0030]      FIG. 4   a  illustrates the hydraulic circuit  12 C when operating with the pressurized fluid  22  at low pressure. In this low line pressure mode of operation, the pressure of the pressurized fluid  22  operating on the differential area A from passage  114  is insufficient to shuttle or move the spool valve  108  from a spring set position, shown in  FIG. 4   a , to a pressure set position, shown in  FIG. 4   b . As such, the spool valve  108  remains in the spring set position and allows the communication of pressurized fluid within the passage  116  to the second lubrication branch  120  where it is subsequently introduced to the lubrication circuit through the second orifice  126 . Preferably, the second orifice  126  is sized to allow adequate flow of pressurized fluid  22  to the lubrication circuit  50  at low line pressure modes of operation. 
         [0031]      FIG. 4   b  illustrates the hydraulic circuit  12 C when operating with the pressurized fluid  22  at high pressure. In this high line pressure mode of operation, the pressure of the pressurized fluid  22  operating on the differential area A from passage  114  is sufficient to shuttle or move the spool valve  108  from the spring set position to the pressure set position as shown in  FIG. 4   b . Once the spool valve  108  is in the pressure set position, the pressurized fluid  22  acting on the differential area A is exhausted through the exhaust port  122 . Therefore, the pressurized fluid  22  within passage  112  retains the spool valve  108  in the pressure set position. The pressurized fluid  22  within passage  116  is communicated to the first lubrication branch  118 , via the snap action valve assembly  106 , where the pressurized fluid  22  is subsequently introduced to the lubrication circuit  50  through the first and second orifices  124  and  126 . The pressure drop and flow restriction through the first and second orifices  124  and  126  are preferably tuned for the high line pressure conditions such that a sufficient amount of pressurized fluid  22  is communicated to the lubrication circuit  50  to avoid damaging components within the transmission  10 C. 
         [0032]    As described hereinabove with reference to  FIGS. 4   a  and  4   b , the snap action valve  106  may be used to provide two distinct flow characteristics to the lubrication circuit  50 . The area of the differential area A and the spring rate of the spring  110  should be chosen for the line pressure at which the spool valve  108  will shuttle or move from the spring set position to the pressure set position. The snap action valve assembly  106  is a low cost option for controlling the flow of pressurized fluid  22  to the lubrication circuit  50  since the solenoid valve  40  of  FIGS. 1   a ,  1   b ,  2   a ,  2   b ,  2   c ,  3   a , and  3   b  is not required to effect movement of the spool valve  108 . 
         [0033]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims. A damping orifice is preferably used with any valve described within the present disclosure.