CONTROL METHOD FOR A VARIABLE COMPRESSION ACTUATOR

SYSTEM

REFERENCE TO RELATED APPLICATIONS

This application claims one or more inventions which were disclosed in Provisional Application Number 60/819,103, filed July 7, 2006, entitled "CONTROL METHOD FOR A VARIABLE COMPRESSION ACTUATOR SYSTEM". The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

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.

DESCRIPTION OF RELATED ART

Prior art Figures 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'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.

Figures 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 209a, 209b 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 Figure 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 209a 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 Figure 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 Figure 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 209b 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 Figure 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.

Figure 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 209a blocks the flow of fluid to and from the lower chamber passage 202 leading to the lower chamber 122 and the second land 209b 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.

Figure 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. Patent No. 7,000,580, entitled "CONTROL VALVE WITH INTEGRATED CHECK VALVES" issued February 21, 2006 and which is hereby incorporated by reference. It should be noted that if the spool valves of U.S. Patent 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.