Abstract:
A pressure regulator valve is provided having a valve spool slidably disposed within a stepped bore defined by a valve body. A first pressure responsive surface area is defined on the valve spool and is subject to pressurized fluid from a main pressure source. A second pressure responsive surface area is defined on the valve spool and is subject to pressurized fluid from a control source. Additionally, a third pressure responsive surface area is defined on the valve spool and is selectively subject to pressurized fluid from one of the main pressure source and the control source. A sleeve is slidably disposed within the stepped bore, the sleeve being operable to selectively distribute pressurized fluid from one of the main pressure source and the control source to the third pressure responsive surface area to effect a change in pressure gain of the pressure regulator valve.

Description:
TECHNICAL FIELD 
     This invention relates to hydraulic pressure regulator valves, and more specifically to main pressure regulator valves within a shiftable vehicular transmission control system. 
     BACKGROUND OF THE INVENTION 
     Automatically shiftable transmissions used in transportation vehicles, such as cars, buses, and trucks, require a positive displacement pump to supply pressurized hydraulic fluid for engagement of clutches and brakes, torque converter operation, and cooling. 
     These pumps require power from the engine or prime mover to supply the required control pressure. The power absorbed by the pump and therefore supplied by the engine is a function of the pressure and displacement of the pump. The higher the pump output pressure or main pressure of the transmission, the more horsepower required from the engine. 
     Current transmissions utilize control mechanisms having electronic systems. These electronic systems are supplied with signals from the engine, vehicle, and transmission. The signals are utilized to determine the operation of various solenoid valves within the control system to modulate various pressures including the main pressure or line pressure of the transmission. By modulating the main pressure, the fuel economy of the vehicle may be improved. 
     SUMMARY OF THE INVENTION 
     Provided is a pressure regulator valve adapted to be in fluid communication with a main pressure source of pressurized fluid and in selective fluid communication with a main modulation control source of pressurized fluid. The pressure regulator valve includes a valve spool slidably disposed within a stepped bore defined by a valve body. A first pressure responsive surface area is defined by the valve spool and is subject to pressurized fluid from the main pressure source. A second pressure responsive surface area is defined by the valve spool and is subject to pressurized fluid from the control source. A third pressure responsive surface area is defined by the valve spool, and is selectively subject to pressurized fluid from one of the main pressure source and the control source. A sleeve is slidably disposed within the stepped bore. The sleeve operates to selectively distribute pressurized fluid from one of the main pressure source and the control source to the third pressure responsive surface area to effect a change in pressure gain of the pressure regulator valve. The sleeve has a pressure set position and a spring set position. The pressure set position corresponds to a boosted or high gain mode of operation and the spring set position corresponds to an un-boosted or low gain operating mode. 
     Another aspect of the invention is a transmission control system including a main source of pressurized fluid and a control source of pressurized fluid. A main pressure regulator for establishing the pressure output of the main source of pressurized fluid at a main pressure level is provided. The main pressure regulator has first pressure responsive surface area subject to pressurized fluid within the main source. The main pressure regulator also includes a second pressure responsive surface area which, when subjected to pressurized fluid within the control source, will limit the main pressure level. The main pressure regulator further includes a third pressure responsive surface area which, when supplied with pressurized fluid within the control source, will increase the limit of the main pressure level. A sleeve is slidably disposed within the main pressure regulator, the sleeve having a first position and a second position. The sleeve is operable in the first position to exhaust fluid pressure at the third pressure responsive surface area and is operable in the second position to direct pressurized fluid within the control source to the third pressure responsive surface area to enforce an increase in the main pressure level. 
     An additional aspect of the present invention is a transmission control system includes a main source of pressurized fluid and a control source of pressurized fluid. A main pressure regulator for establishing the pressure output of the main source of pressurized fluid at a main pressure level is provided. The main pressure regulator has a first pressure responsive surface area subject to pressurized fluid within the main source. The main pressure regulator also includes a second pressure responsive surface area which, when subjected to pressurized fluid within the control source, will limit the main pressure level. Also included is a third pressure responsive surface area which, when supplied with pressurized fluid within the main source, will decrease the limit of the main pressure level. A sleeve is slidably disposed within the main pressure regulator. The sleeve has a first position and a second position. The sleeve is operable in the second position to exhaust fluid pressure at the third pressure responsive surface area and is operable in the first position to direct pressurized fluid within the main source to the third pressure responsive surface area to provide a decrease in the main pressure level. 
     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 
         FIG. 1   a  is a schematic representation of a control system for a power transmission illustrating a main regulator valve, consistent with the present invention, in an un-boosted or low gain position; 
         FIG. 1   b  is a schematic representation of the control system for a power transmission shown in  FIG. 1   a  with the main regulator valve in a boosted or high gain position; 
         FIG. 2   a  is a schematic representation of a control system for a power transmission incorporating an alternate embodiment of a main regulator valve in an un-boosted or low gain position; and 
         FIG. 2   b  is a schematic representation of the control system for a power transmission shown in  FIG. 2   a  with the main regulator valve in a boosted or high gain position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings wherein like characters represent the same or corresponding parts, there is seen in  FIGS. 1   a  and  1   b  a portion of a transmission control system  10  including a pump  12  and an electro-hydraulic control, or EHC,  14 . The pump  12  is a conventional positive displacement mechanism that draws hydraulic fluid from a reservoir  16  and delivers the fluid to a main regulator valve  18  though a passage  20 . The main regulator valve  18  is operable to vary the pressure of the fluid delivered by the pump  12 . The fluid is subsequently communicated from a main pressure source  22  to the EHC  14  through a line pressure or main pressure passage  24 . 
     The EHC  14  communicates with an electronic control unit (ECU)  25  having a conventional pre-programmable digital computer. The EHC  14  also includes control valves that distribute hydraulic fluid to the many devices in an automatic transmission including the torque transmitting mechanisms. The ECU  25 , as is well-known, emits electrical control signals to various electronic elements such as solenoid valves, which in turn control the output pressure of the hydraulic valves. The EHC  14  produces a variable hydraulic control signal that is distributed through a trim passage  26  to provide a control signal to modulate the main regulator valve  18 . The hydraulic control signal may be produced by a solenoid valve, such as a variable bleed solenoid valve, within the EHC  14 . 
     The main regulator valve  18  has a valve spool  28  and a sleeve  30  slidably disposed in concentric longitudinal arrangement within a stepped valve bore  32  that is defined by a valve body  34 . The valve spool  28  has spaced equal diameter lands  36 ,  38 , and  40 , and a smaller end land  42 . The end land  42  is positioned in a bore portion  44  of the valve bore  32 , and the lands  36 ,  38 , and  40  are positioned in a bore portion  46  of the valve bore  32 . The lands  36  and  38  are spaced such that a generally annular valley  45  is formed. Similarly, the lands  38  and  40  are spaced such that a generally annular valley  47  is formed. The sleeve  30  is positioned in a bore portion  48  of the valve bore  32 . The sleeve  30  is piloted on a land  49  and is spaced from the land  40  to form a generally annular valley  51 . The bore portion  46  is larger in diameter than the bore portion  44 , while the bore portion  48  is larger in diameter than the bore  46 . A spring  50  is disposed within a spring pocket  52  and operates to bias the sleeve  30 . A spring  54  is disposed within a spring pocket  56 . The spring  54  imposes a bias force on the valve spool  28  to urge the valve spool  28  leftward as viewed in  FIGS. 1   a  and  1   b . It should be noted that in the present embodiment, the spring pockets  52  and  56  do not communicate with one another. 
     The valve body  34  communicates with the main pressure source  22  that is in fluid communication with the passage  20  and the main pressure passage  24 . The valve body  34  is in selective fluid communication with a main modulation control source  58  connected with the passage  26 , an overage port  60 , and exhaust ports  62 ,  64 , and  66 . The exhaust ports  62 ,  64 , and  66  communicate with the reservoir  16 . The main pressure source  22  is in fluid communication with the valley  47 . The main modulation control source  58  is in selective fluid communication with the valley  51  and the spring pocket  56 . The overage port  60  is selectively opened to the main pressure source  22  by the land  38 . The exhaust port  62  is selectively opened and closed by the land  40 . The exhaust port  64  and the main modulation control source  58  are selectively and alternately opened to the spring pocket  56  by the sleeve  30 . 
     The land  42  forms a pressure responsive surface area A 1 . While the lands  40  and  49  form a pressure responsive differential surface area A 2 . The land  49  forms a pressure responsive surface area A 3 . In operation, the main regulator valve  18  regulates or controls the fluid pressure within the main pressure passage  24 , which is subsequently introduced to the EHC  14 .  FIG. 1   a  illustrates the main regulator valve  18  with the valve spool  28  in the low gain or un-boosted condition. With the valve spool  28  in the spring set position, as shown in  FIG. 1   a , the fluid pressure within the main pressure passage  24  is substantially unregulated and is generally the same pressure as the fluid within passage  20 . As the fluid pressure within the main pressure source  22  increases, the force acting on surface area A 1  of the land  42  increases, thereby moving the valve spool  28  rightward, as viewed in  FIGS. 1   a  and  1   b , against the bias of spring  54 . As the valve spool  28  moves rightward, the land  38  will open the main pressure source  22  to the valley  45  allowing pressurized fluid to flow to the overage port  60 . The overage port  60  communicates fluid to other portions of the vehicles transmission such as, for example, a lubrication circuit or a cooler. By diverting an amount of pressurized fluid from the main pressure source  22  to the overage port  60 , the fluid pressure within the main pressure passage  24  may be regulated to the desired level. The main modulation control source  58  selectively and variably provides fluid pressure to valley  51 . This pressure acts on the differential surface area A 2  to counteract the movement of the valve spool  28  in response to the fluid pressure within the main pressure source  22 . With the sleeve  30  in the spring set position, as shown in  FIG. 1 , the pressurized fluid within the main modulation control source  58  is blocked from entering the spring pocket  56  and subsequently acting on the surface area A 3  of land  49 . Instead, the spring pocket  56  exhausts through the exhaust port  64 . 
     By controlling the ratio of A 1  to A 2  in the design stage of the main regulator valve  18 , the gain rate for the un-boosted condition may be controlled. This is stated in equation form as Pmain*A 1 =Pmm*A 2 +F, where Pmain is the fluid pressure within the main pressure source  22 , Pmm is the fluid pressure within the main modulation control source  58 , and F is the spring force exerted by the spring  54 . 
     As the fluid pressure requirement of the EHC  14  increases, the main pressure regulator  18  will operate in a high gain or boosted condition, as shown in  FIG. 1   b . The fluid pressure within the main pressure source  22  increases in response to the higher fluid pressure within the main modulation control source  58 . As the pressure within the valley  51  increases, the fluid pressure biases the sleeve  30  against the bias force exerted by the spring  50 . When the bias force is overcome, the sleeve  30  will move to a pressure set position within the bore  32 , as shown in  FIG. 1   b . With the sleeve  30  in the pressure set position, the exhaust port  64  is blocked such that the spring pocket  56  will no longer exhaust. Instead, the sleeve  30  will communicate pressurized fluid from the main modulation control source  58  to the spring pocket  56 . The pressurized fluid within the main modulation control source  58  acts on both the differential surface area A 2  and the surface area A 3 . 
     By controlling the ratio of A 1  to (A 2 +A 3 ) in the design stage of the main regulator valve  18 , the gain rate in the boosted operating mode may be controlled. This is stated in equation form as Pmain*A 1 =Pmm*(A 2 +A 3 )+F. 
     An alternate embodiment of the present invention is shown in  FIGS. 2   a  and  2   b . Referring to  FIGS. 2   a  and  2   b  a portion of a transmission control system  10 ′ is shown having a main pressure regulator  18 ′. The main pressure regulator  18 ′ is similar in construction to the main pressure regulator  18 , shown in  FIGS. 1   a  and  1   b . A sleeve  30 ′ is slidably disposed within the valve bore  32  that is defined by the valve body  34 . The sleeve  30 ′ defines an annular groove or valley  68  that is operable to selectively pressurize a passage  70  with pressurized fluid from the main pressure source  22 . When the sleeve  30 ′ in the spring set position, as shown in  FIG. 2   a , pressurized fluid is communicated from the main pressure port  22  to the passage  70  via valley  68 . The passage  70  communicates pressurized fluid to act on a pressure responsive differential surface area A 4  created by the valve lands  36  and  42 . Alternately, with the sleeve  30 ′ in the pressure set position, as shown in  FIG. 2   b , the passage  70  will exhaust to the exhaust port  64  via the valley  68 . In this embodiment, the spring pockets  56  and  52  are in fluid communication with one another. 
     In operation, the main regulator valve  18 ′ regulates or controls the fluid pressure within the main passage  24 , which is subsequently introduced to the EHC  14 .  FIG. 2   a  illustrates the main regulator valve  18 ′ with the valve spool  28  in the low pressure gain or un-boosted condition. With the valve spool  28  in the spring set position, as shown in  FIG. 2   a , the fluid pressure within the main pressure passage  24  is substantially unregulated and is generally the same pressure as the fluid within passage  20 . As the fluid pressure within the main pressure source  22  increases, the force acting on surface area A 1  of the land  42  increases, thereby moving the valve spool  28  rightward, as viewed in  FIGS. 2   a  and  2   b , against the bias of spring  54 . Additionally, with the sleeve  30 ′ in the spring set position, pressurized fluid within the main pressure source  22  is communicated to the passage  70  via valley  68 . The pressurized fluid within the passage  70  acts on the differential surface area A 4 , which further biases the valve spool  28  against the bias of spring  54 . As the valve spool  28  moves rightward, the land  38  will open the main pressure source  22  to the valley  45  allowing pressurized fluid to flow to the overage port  60 . The overage port  60  communicates fluid to other portions of the vehicle transmission such as, for example, a lubrication circuit or a cooler. By diverting an amount of pressurized fluid from the main pressure source  22  to the overage port  60 , the fluid pressure within the main pressure passage  24  is regulated to the desired level. The main modulation control source  58  selectively and variably provides fluid pressure to valley  51 . This pressure acts on the differential surface area A 2  to counteract the movement of the valve spool  28  in response to the fluid pressure within the main pressure source  22 . 
     By controlling the ratio of (A 1 +A 4 ) to A 2  in the design stage of the main regulator valve  18 ′, the gain rate for the un-boosted condition may be controlled. This is stated in equation form as Pmain*(A 1 +A 4 )=Pmm*A 2 +F. It should be appreciated that the sum of (A 1 +A 4 ) is equal to the sum of (A 2 +A 3 ). 
     As the Fluid pressure requirement of the EHC  14  increases, the main pressure regulator  18 ′ will operate in a high gain or boosted condition, as shown in  FIG. 2   b . The fluid pressure within the main pressure source  22  will increase in response to the higher fluid pressure within the main modulation control source  58 . As the pressure within the valley  51  increases, the fluid pressure biases the sleeve  30 ′ against the bias force exerted by the spring  50 . When the bias force is overcome, the sleeve  30 ′ will move to a pressure set position within the bore  32 , as shown in  FIG. 2   b . With the sleeve  30 ′ in the pressure set position, the main pressure source  22  is blocked, thereby disallowing any flow of pressurized fluid into the passage  70 . Instead, the sleeve  30  will allow pressurized fluid within the passage  70  to exhaust to the exhaust port  64  via valley  68 . By exhausting the passage  70 , the pressurized fluid acting on the differential surface area A 4  is also exhausted, such that the force urging the valve spool  28  rightward against the bias force of the spring  54  and the force of the pressurized fluid within the main modulation control source  58  acting on the differential surface area A 2  are reduced. 
     By controlling the ratio of A 1  to A 2  in the design stage of the main regulator valve  18 ′, the gain rate in the boosted operating mode may be controlled. This is stated in equation form as Pmain*A 1 =Pmm*A 2 +F. 
     The main pressure regulators  18  and  18 ′ provide two modes of operation, un-boosted and boosted. By providing an un-boosted mode of operation, the low pressure limit for regulation is reduced while improving resolution and system stability. Additionally, by providing a boosted operating mode, the high pressure limit may be increased. In one such transmission, the minimum operating pressure range is as low as 25 pounds per square inch, or psi, while the maximum is as high as 275 psi. This affords an effective regulation range ratio of over 10 to 1 compared to 5 to 1 for other transmissions. 
     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.