VCT control with a direct electromechanical actuator

• US 5,497,738 A
• Filed: 05/03/1993
• Issued: 03/12/1996
• Est. Priority Date: 09/03/1992
• Status: Expired due to Term

• Current Assignee: Borg-Warner Automotive Incorporated (BorgWarner Incorporated)
• Original Assignee: Borg-Warner Automotive Incorporated (BorgWarner Incorporated)
• Inventors: Quinn, Stanley B. Jr., Siemon, Edward C.
• Primary Examiner(s): Lo, Weilun
• Application Number:
  US08/056,635
• Time in Patent Office: 1,044 Days
• Field of Search: 123/90.15, 123/90.17, 123/90.31, 74/568 R, 137/312, 137/625.65, 464/1, 464/2, 464/160
• US Class Current: 123/90.17
• CPC Class Codes: F01L 1/34409 by torque-responsive means
• CPC Class Codes: F01L 1/3442 using hydraulic chambers with variable volume to transmit the rotating force
• CPC Class Codes: F01L 2001/0537 Double overhead camshafts [DOHC]
• CPC Class Codes: F01L 2001/34426 Oil control valves
• CPC Class Codes: F01L 2001/3443 Solenoid driven oil control valves
• CPC Class Codes: F01L 2800/00 Methods of operation using a variable valve timing mechanism
• CPC Class Codes: F02B 2075/027 four
• CPC Class Codes: Y10T 137/5762 With leakage or drip collecting

Abstract

A camshaft (126) has a vane (160) secured to an end thereof for non-oscillating rotation therewith. The camshaft also carries a sprocket (132) which can rotate with the camshaft but which is also oscillatable with the camshaft. The vane has opposed lobes (160a, 160b) which are received in opposed recesses (132a, 132b), respectively, of the sprocket. The recesses have greater circumferential extent than the lobes to permit the vane and sprocket to oscillate with respect to one another, and thereby permit the camshaft to change in phase relative to a crankshaft whose phase relative to the sprocket is fixed by virtue of a chain drive extending therebetween. The camshaft tends to change in reaction to pulses which it experiences during its normal operation, and it is permitted to change only in a given direction, either to advance or retard, by selectively blocking or permitting the flow of hydraulic fluid, preferably engine oil, through the return lines (194, 196) from the recesses by controlling the position of a vented spool (200) within a valve body (198) of a control valve (192) in response to a signal indicative of an engine operating condition from an engine control unit (208) via cable (238). The vented spool is selectively positioned within the valve body by a electromechanical actuator (201) which is controlled by the engine control unit. The spool is centered when an optimum phase angle between crankshaft and camshaft is achieved.

Claims

1. An internal combustion engine, comprising:

a crankshaft, said crankshaft being rotatable about an axis;

a camshaft (126), said camshaft being rotatable about a second axis, said camshaft being subject to torque reversals during rotation thereof;

a vane (160), said vane having first and second circumferentially spaced apart lobes (160a, 160b), said vane being attached to said camshaft, said vane being rotatable with said camshaft and being non-oscillatable with respect to said camshaft;

a housing (132), said housing being rotatable with said camshaft and being oscillatable with respect to said camshaft, said housing having first and second circumferentially spaced apart recesses (132a, 132b), each of said first and second recesses receiving one of said first and second lobes and permitting oscillating movement of said one of said first and second lobes therein;

means for transmitting rotary movement from said crankshaft to said housing; and

,

means for controlling the oscillation of said housing, said control means being reactive to torque reversals in said camshaft for varying the position of said housing relative to said camshaft, said control means comprising;

a spool valve body (198);

a spool (200), said spool being reciprocable within said body and having first and second spaced apart lands (200a, 200b), said spool further having a vent to atmosphere (198d);

a first return line means (194) extending from one of said first recess and said second recess to said spool valve body, one of said first and second lands blocking flow through said first return line means in a first range of positions of said spool within said valve body and permitting flow through said first return line means in a second range of positions of said spool within said valve body;

a second return line means (196) extending from the other of said first recess and said second recess to said valve body, the other of said first and second lands blocking flow through said second return line means in said second range of positions of said spool within said valve body, permitting flow through said second return line means in a first portion of said first range of positions of said spool within said valve body, and blocking flow through said second return line means in a second portion of said first range of positions of said spool within said valve body;

an inlet line means (182) extending from said valve body to each of said first recess and said second recess, said inlet line means permitting hydraulic fluid to flow from said valve body to said each of said first recess and said second recess regardless of the position of said spool, said inlet line means having check valve means (184,

     186) for preventing the flow of hydraulic fluid from each of said first recess and said second recess to said valve body;

means for sensing (207a, 207b) the positions of said crankshaft and said camshaft;

an engine control unit (208), said engine control unit for receiving information from said sensing means and for calculating a relative phase angle between said crankshaft and said camshaft using said information;

an electromechanical actuator (201), said electromechanical actuator comprising a variable force solenoid, said variable force solenoid for controlling the position of said spool in response to a signal issued from said engine control unit; and

,

means for biasing (202) said spool valve, said biasing means for urging said spool valve to a full advance position during periods when said electromechanical actuator is deenergized.

2. An engine according to claim 1 wherein each of said first and second lobes respectively divides each of said first and second recesses into a first portion and a second portion, each of said one of said first portion and said second portion of said each of said first and second recesses being capable of sustaining hydraulic pressure.

3. An engine according to claim 2 wherein said control means is capable of being reversed to transfer hydraulic fluid out of said one of said first portion and said second portion of said each of said first and second recesses and to transfer hydraulic fluid into said other of said first portion and said second portion of said each of said first and second recesses.

4. An engine according to claim 3 wherein said hydraulic fluid comprises engine lubricating oil, said engine further comprising at least one conduit means (230a) for transferring engine lubricating oil from a pressurized lubricating oil source (230) to said control means and back again in response to said torque reversals of said camshaft.

5. An engine according to claim 4 further comprising means for hydraulically connecting (182a) one of said first portion and said second portion of one of said first recess and said second recess with one of said first portion and said second portion of the other of said first recess and said second recess to permit hydraulic fluid to flow between said one of said first portion and said second portion of said one of said first recess and said second recess and said one of said first portion and said second portion of said other of said first recess and said second recess.

6. An engine according to claim 5 further comprising at least one other conduit means (220a), said other conduit means providing communication for the flow of hydraulic fluid through said valve body to said inlet line means, said other conduit means having second check valve means (222a) for preventing the flow of hydraulic fluid from said inlet line means through said valve body.

7. An engine according to claim 1 wherein said variable force solenoid comprises:

a coil (201a), said solenoid coil for receiving an electrical current from said engine control unit;

an armature (201b), said armature being substantially surrounded by said coil, said armature being connected to said spool, said coil, when energized, for creating a magnetic field sufficient to cause said armature to exert a force upon said spool and induce movement in said spool, said movement corresponding to said signal from said engine control unit;

an air gap, said air gap for separating said coil from said armature; and

,

a housing, said housing for providing an enclosure for said coil, said armature, and said air gap.

8. An engine according to claim 1 wherein said electromechanical actuator further comprises a stroke amplifier, said stroke amplifier providing a net gain in force as applied to said vented spool.

9. An engine according to claim 8 wherein said stroke amplifier comprises a lever arrangement (201e).

10. In an internal combustion engine having a variable camshaft timing system for varying the phase angle of a camshaft relative to a crankshaft, a method of regulating the flow of hydraulic fluid from a source to a means for transmitting rotary movement from said crankshaft to a housing, comprising the steps of:

sensing the positions of said camshaft and said crankshaft;

calculating a relative phase angle between said camshaft and said crankshaft, said calculating step using an engine control unit for processing information obtained from said sensing step, said engine control unit further issuing a electrical signal corresponding to said phase angle;

controlling the position of a vented spool slidably positioned within a spool valve body, said controlling step being in response to said signal received from said engine control unit, said controlling step utilizing an electromechanical actuator to vary the position of said vented spool, said electromechanical actuator comprising a variable force solenoid;

supplying hydraulic fluid from said source through said spool valve to a means for transmitting rotary movement to said camshaft, said spool valve selectively allowing and blocking flow of hydraulic fluid through an inlet line and through return lines; and

,

transmitting rotary movement to said camshaft in such a manner as to vary the phase angle of said camshaft with respect to said crankshaft said rotary movement being transmitted through a housing said housing being mounted on said camshaft, said housing further being rotatable with said camshaft and being oscillatable with respect to said camshaft.

11. The method of claim 10 wherein said variable force solenoid comprises:

a coil, said coil being adapted to receive said electrical signal from said engine control unit;

an armature, said armature being substantially surrounded by said coil, said armature being connected to said spool, said coil, when energized, creating a magnetic field sufficient to cause said armature to exert a force upon said spool and induce movement in said spool, said movement corresponding to said signal from said engine control unit;

an air gap, said air gap separating said coil from said armature; and

,

a housing, said housing providing an enclosure for said coil, said armature, and said air gap.

12. The method of claim 10 wherein said electromechanical actuator further comprises a stroke amplifier, said stroke amplifier for providing a net gain in force as applied to said spool.

13. The method of claim 12 wherein said stroke amplifier comprises a lever arrangement.