Abstract:
A control system for an adjustment device for a variable compression ratio engine comprising: a jack head, a jack piston, a sprocket wheel, a movable transmission member, and a control valve. The jack piston is received within a chamber of the jack head defining first and second fluid chambers. The control valve controls the flow of fluid between the first and second fluid chambers. Based on the position of the control valve, fluid flows from the first fluid chamber to the second fluid chamber or vice versa, moving the control rack connecting the jack piston to the sprocket wheel. Reciprocating motion of the sprocket wheel adjusts the position of the cylinder of the engine.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims one or more inventions which were disclosed in Provisional Application No. 60/819,103,, filed Jul. 7, 2006,, entitled “CONTROL METHOD FOR A VARIABLE COMPRESSION ACTUATOR SYSTEM”. The benefit under 35, USC §119(e) of the U.S. provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to the field of variable compression actuator systems. More particularly, the invention pertains to a control method for a variable compression actuator system. 
     2. Description of Related Art 
     Prior art  FIGS. 1 and 2  show an adjustment device for a variable compression ratio engine as disclosed in WO 2005/098219. The engine block  100  has as at least one cylinder in which a piston  2  moves by means of a transmission device  1 . 
     The transmission device  1  has a transmission member  3  integral with piston  2  and cooperating on one side with a rolling guide device  4  and a sprocket wheel  5  on the other side. The sprocket wheel  5  is connected to a connecting rod  6  jointed to crankshaft  9  to determine the transmission of movement between the piston  2  and the crankshaft  9 . 
     The sprocket wheel  5  cooperates on the opposite side of the transmission member  3  with a control rack  7 . The vertical position of the control rack  7  in relation to the engine block  100  is guided by a control device  12 . The control device has a control jack  8  of which its jack piston  13  is guided into a jack cylinder  112  set into the engine block  100 . The jack cylinder  112  is bored or fitted into the engine block  100 . The jack cylinder  112  is secured in an upper part by a jack head  113  that is screwed into the engine block  100 . 
     The sprocket wheel  5  has a first set of serrations  52  for engaging the serrations  74  of the control rack  7  and a second set of teeth  51  on an opposite side of the sprocket wheel  5  for engaging a first rack of the transmission member  3  with corresponding teeth. Opposite the first rack of the transmission member  3  is another rack  37  with teeth that cooperate with a roller  40  of a rolling guide device  4  integral with the engine block  100 . The engine block  100  on the side of a cylinder  110  has a support  41  with racks  46  allowing synchronization of the displacement of the roller  40  with the piston  2 . 
     The jack piston  13  divides a chamber formed between the jack head  113  and control rack  7  in which the control device  12  is received into an upper chamber  121  and a lower chamber  122 . Movement of the jack piston  13  is further controlled by a control rod  20  which is received within a bore of the jack piston  13  along with the lower jack rod  16 . The control rod  20  limits the movement of the jack piston  13  between two springs  22  and loaded stops  130 . The limited movement of the control rod  20 , and thus the jack piston  13  is sufficient to allow the jack piston  13  to pivot slightly, so that the control rack  7  may position itself with in the engine block  100  and align the teeth  74  of the rack  7  with the teeth  52  of the sprocket wheel  5 . 
     The adjustment of the engine&#39;s effective compression ratio is achieved by modifying the original position of the stroke of the piston  2  in relation to the cylinder  110  by sprocket wheel  5 , mounted freely at the top end of a connection rod  6 , a transmission member  3 , integral with the piston  13  and a control rack  7 , in which the position is regulated by the control device  12 . 
     The present invention provides an alternate control system for the adjustment device disclosed in WO 2005/098219,, which provides a quicker response. 
     SUMMARY OF THE INVENTION 
     A control system for an adjustment device for a variable compression ratio engine comprising: a jack head, a jack piston, a sprocket wheel, a movable transmission member, and a control valve. The jack piston is received within a chamber of the jack head defining first and second fluid chambers. The control valve controls the flow of fluid between the first and second fluid chambers. Based on the position of the control valve, fluid flows from the first fluid chamber to the second fluid chamber or vice versa, moving the control rack connecting the jack piston to the sprocket wheel. Reciprocating motion of the sprocket wheel adjusts the position of the cylinder of the engine. 
     While torque actuation is provided as an example, other types of actuation through the control valve may be used. In using oil pressure actuation, the control valve controls the flow of fluid to and from the first and second fluid chambers and based on the position of the control valve, fluid flows from the first fluid chamber to sump and from supply to the second fluid chamber or vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic of an adjustment device of the prior art for a variable compression ratio engine. 
         FIG. 2  shows another schematic of the prior art adjustment device. 
         FIG. 3  shows a schematic of the control system of the present invention with the jack piston moving to a first position. 
         FIG. 4  shows a schematic of the control system of the present invention with the jack piston moving to a second position. 
         FIG. 5  shows a schematic of the control system of the present invention with the jack piston in a holding position. 
         FIG. 6  shows a schematic of the control system of the present invention with the jack piston in a holding position with alternate venting. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The control system of the present invention replaces the control device  12  disclosed in WO 2005/098219. The control rod  20 , valve  21 , stops  130 , and springs  22  are removed the adjustment device. 
     In the control system of the present invention, recirculation of oil is controlled by a spool valve located outside of the control jack  8  but within the jack head  113 . 
       FIGS. 3 through 5  show the control system of the present invention in multiple positions. The control system includes a control rack rod  225  inserted into and fixed to the jack piston  13 , replacing control rod  20 , valve  21 , stops  130 , and springs  22 . On a first end of the control rack rod  225 , outside of the jack head  113  is a position sensor  216 . Linear reciprocating movement of the control rack rod  225  fixed to the jack piston  13  allows the position of the jack piston  13  to be measured by the position sensor  216 , providing feedback to an ECU (not shown). The jack piston  13  divides a chamber formed between the jack head  113  and the control rack  7  into an upper chamber  121  and a lower chamber  122 . Seals  230  between the control jack rod  225  and the fluid chambers  121  and  122  may be necessary. Movement of the jack piston  13  is further controlled by a spool valve  209 . The spool valve  210  includes a spool  209  with a plurality of lands  209   a, ,  209   b , slidably received within a bore  211  in the jack head  113 . A vent  226  to atmosphere is present off of the bore  211  in the jack head  113 . 
     The spool  209  is biased in a first direction by a spring  213  within the bore  211  and an actuator  212  in a second direction, opposite the first direction. The actuator  212  is controlled by the ECU (not shown). The ECU (not shown) receives position signals from position sensor  216 , and through the actuator  212  adjusts the position of the spool  209 , which in turn adjusts the jack piston  13  to a corresponding set point. The actuator  212  may be a variable force solenoid, a differential pressure control system (DPCS), regulated pressure control system (RPCS), a stepper motor, an air actuator, a vacuum actuator, a hydraulic actuator, or any type of actuator that has force or position control. 
     Passages  202 ,  204 ,  206 ,  223  are drilled into the jack head  113  allowing the flow of fluid from a main oil gallery (MOG) or supply to the spool  209  and from the spool  209  to the upper and lower chambers  121 ,  122 . Located within the passages  206 ,  223  are check valves  214 ,  215 ,  224 . 
     Referring to  FIG. 3 , the jack piston  13  is moving towards an up position, away from the crankshaft  9 . To move towards an up position, the force of the actuator  212  on the spool  209  is greater than the force of the spring  213 , moving the spool  209  until the force of the spring  213  equals the force of the actuator  212 . In this position, the first land  209   a , blocks the lower chamber passage  202  and an upper chamber passage  204  and a central passage  206  connecting to the upper and lower passages  204 ,  202  through check valves  215 ,  214  are open. Fluid in the upper chamber  121  exits the chamber through the upper chamber passage  204  and flows through the spool  209  to the central passage  206 , through the lower chamber check valve  214 , into the lower chamber passage  202 , supplying fluid to the lower chamber  122 . With fluid exiting the upper chamber  121  and entering the lower chamber  122 , the jack piston  13  is moved away from the crankshaft  9 . By moving the jack piston  13  away from the crankshaft  9 , the control rack  7  is moved away from the crankshaft  9  and the sprocket wheel  5  is moved so that the original position of the stroke of the piston  2  in relation to the cylinder  110  is modified. 
     Fluid may be supplied from supply or the main oil gallery through an inlet passage  223  with a check valve  224  as necessary to makeup for leakage. 
     Once the desired position of the jack piston  13  is achieved, the spool valve  209  is commanded back to the null or hold position to maintain the desired position as shown in  FIG. 5 . The position sensor  216  mounted to the control rack rod  225  is used as feedback to the control loop to compare the actual control rack position to the desired rack position. 
     Referring to  FIG. 4 , the jack piston  13  is moving towards a down position, towards the crankshaft  9 . 
     To move towards the down position, the force of the actuator  212  on the spool  209  is less than the force of the spring  213 , and the spring  213  moves the spool  209  until the force of the actuator  212  equals the force of the spring  213  on the spool  209 . In this position, the second land  209   b , blocks the upper chamber passage  204  and the lower chamber passage  202  and the central passage  206  connected to the upper and lower passages  204 ,  202 , through check valves  215 ,  214  are open. Fluid in the lower chamber  122  exits the chamber through the lower chamber passage  202  and flows through the spool  209  to central passage  206 , through the upper chamber check valve  215 , into the upper chamber passage  204 , supplying fluid to the upper chamber  121 . With fluid exiting the lower chamber  122  and entering the upper chamber  121 , the jack piston  13  is moved toward the crankshaft  9 . By moving the jack piston  13  towards the crankshaft  9 , the control rack  7  is moved away from the crankshaft  9  and the sprocket wheel  5  is moved so that the original position of the stroke of the piston  2  in relation to the cylinder  110  is modified. 
     Fluid may be supplied from the MOG or supply through an inlet passage  223  with a check valve  224  as necessary to makeup for leakage. 
     Once the desired position of the jack piston  13  is achieved, the spool valve  209  is commanded back to the null or hold position to maintain the desired position as shown in  FIG. 5 . The position sensor  216  mounted to the control rack rod  225  is used as feedback to the control loop to compare the actual control rack position to the desired rack position. 
       FIG. 5  shows the jack piston  13  in a hold position. In this position, the force from the actuator  212  on the spool  209  equals the force on the spool  209  by the spring  213 , and the spool  209  is in a position where the first land  209   a , blocks the flow of fluid to and from the lower chamber passage  202  leading to the lower chamber  122  and the second land  209   b , blocks the flow of fluid to and from the upper chamber passage  204  leading to the upper chamber  121 . The central passage  206  is open to receiving fluid from the MOG or supply for makeup purposes only. If makeup fluid is necessary, fluid flows from the MOG through the inlet line  223  and check valve  224  to spool  209 . From the spool  209 , fluid flows into the central passage  206  and through the upper and lower chamber check valves  215 ,  214  to the upper and lower chambers  121 ,  122 . 
       FIG. 6  shows the jack piston in a hold position with alternate venting of the spool. A passage  227  is present that runs through the length of the spool  209  connecting the end of the bore  211  with the spring  213  to a vent  228  at the opposite end of the spool  209 , which leads to sump through line  229 . 
     Alternatively, the spool valve  210  may be replaced with any of the spool valves present in U.S. Pat. No. 7,000,580,, entitled “CONTROL VALVE WITH INTEGRATED CHECK VALVES” issued Feb. 21, 2006, and which is hereby incorporated by reference. It should be noted that if the spool valves of U.S. Pat. No. 7,000,580, are used, the check valves  214 ,  215 , and central line  206  would be eliminated. 
     The actuation of the control system is shown to use torque actuation as an example, however oil pressure actuation or any other type of actuation may also be used through the control valve. 
     Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.