Self-calibrating variable camshaft timing system

• US 5,289,805 A
• Filed: 12/16/1992
• Issued: 03/01/1994
• Est. Priority Date: 03/05/1992
• Status: Expired due to Term

• Current Assignee: Borg-Warner Automotive Incorporated (BorgWarner Incorporated)
• Original Assignee: Borg-Warner Automotive Incorporated (BorgWarner Incorporated)
• Inventors: Ekdahl, Earl W., Quinn, Stanley B. Jr.
• Primary Examiner(s): Nelli, Raymond A.
• Application Number:
  US07/995,661
• Time in Patent Office: 440 Days
• Field of Search: 123/90.17, 123/90.11, 123/90.15, 123/90.16, 123/90.18, 123/90.12, 364/424.01, 364/161, 364/157, 73/394
• US Class Current: 123/90.17
• CPC Class Codes: F01L 1/34409 by torque-responsive means
• CPC Class Codes: F01L 2001/34426 Oil control valves
• CPC Class Codes: F01L 2001/3443 Solenoid driven oil control valves
• CPC Class Codes: F01L 2820/02 Formulas

Abstract

A camshaft (26) has a vane (60) secured to an end thereof for non-oscillag rotation therewith. The camshaft also carries a sprocket (32) which can rotate with the camshaft (26) but which is also oscillatable with the camshaft (26). The vane (60) has opposed lobes (60a, 60b) which are received in opposed recesses (32a, 32b), respectively, of the sprocket (32). The recesses have greater circumferential extent than the lobes (60a, 60b) to permit the vane (60) and sprocket (32) to oscillate with respect to one another, and thereby permit the camshaft (26) to change in phase relative to a crankshaft whose phase relative to the sprocket (32) is fixed by virtue of a chain drive (38) extending therebetween.

Claims

1. In an internal combustion engine having a rotatable crankshaft and a rotatable camshaft (26), said camshaft (26) being position variable relative to said crankshaft, being subject to torque reversals during the rotation thereof, having a vane (60) with at least one lobe (60a, 60b) secured to said camshaft (26) for rotation therewith, and having a housing (32) mounted on said camshaft (26) for rotation with said camshaft (26) and for oscillation with respect to said camshaft (26), said housing (32) having at least one recess (32a, 32b) receiving the at least one lobe (60a, 60b) of said vane (60) and permitting oscillation of the at least one lobe (60a, 60b) within the at least one recess (32a, 32b) as the housing (32) oscillates with respect to said camshaft (26), a device comprising:

means for transmitting rotational movement from said crankshaft to said housing (26);

means for varying the position of said housing (32) relative to said camshaft (26) in reaction to torque reversals in said camshaft (26), said means delivering hydraulic fluid to said vane (60);

check valve means (84,

     86) functionally positioned between said housing (32) and said means for varying the position of said housing (32) to eliminate the need for blocking a backflow of hydraulic fluid by the operation of said means for varying the position of said housing (32);

actuating means (106) for supplying hydraulic fluid to said means for varying the position of said housing (32);

means for initial calibration (105) of said means for varying the position of said housing (32), said means for initial calibration (105) automatically calculating a phase offset;

means for generating pulses (27,

     28) in accordance with the rotational movement of said crankshaft and said camshaft (26);

means for sensing (27a, 28a) said pulses, said sensing means (27a, 27b) transmitting said pulses to be further processed;

means for determining (107) a raw phase angle between said crankshaft and said camshaft (26), said determining means (107) receiving said pulses from said sensing means (27a, 27b), said determining means (107) utilizing said pulses for computing said raw phase angle;

means for compensating (107) said signal corresponding to said raw phase angle for problems encountered during the generation of said pulses;

said compensating means (107) transmitting said compensated signal (20) to be further processed; and

,

means for controlling (108) said actuating means (106), said controlling means (108) receiving said compensated signal (20), comparing said compensated signal (20) to a predetermined setpoint (35), generating a PWM duty cycle in response to said comparison, and issuing said duty cycle to said actuating means (106).

2. The device according to claim 1 wherein said housing (32) comprises a sprocket (32) oscillatingly journalled on said camshaft (26), said sprocket (32) connected to said crankshaft by a chain drive (38).

3. The device according to claim 1 wherein said means for varying the position of the housing (32) comprises a hydraulic cylinder (134) and a proportional spool valve (92), the position of said spool valve (92) being controlled by the pressure of the hydraulic fluid contained in said cylinder (134).

4. The device of claim 1 wherein said actuating means (106) comprises a solenoid valve (106), said solenoid valve (106) controlling the flow of hydraulic fluid to said hydraulic cylinder (134).

5. The device according to claim 4 wherein said solenoid valve (106) is of the pulse width modulated (PWM) variety.

6. The device of claim 1 wherein said means for controlling (108) said actuating means (106) comprises:

means to control proportional gain (208,

     408);

means to control integral gain (208,

     408);

means to compensate for phase-lead (308,

     508); and

,

means to compensate for outside disturbances (608).

7. The device of claim 1 wherein said means for controlling (108) said actuating means (106) further comprises a means for filtering (35a) a predetermined set point (35) in a single-loop system.

8. The device of claim 1 wherein said means for controlling (108) said actuating means (106) further comprises at least one means of filtering (25) said compensated signal (20) to minimize the presence of high frequency oscillations, whereby producing a filtered signal (30).

9. In an internal combustion engine having a rotatable crankshaft and a rotatable camshaft, the camshaft being position variable relative to the crankshaft and being subject to torque reversals during the operation thereof, the method comprising:

generating pulses in accordance with the rotational movement of both said crankshaft and said camshaft;

sensing said pulses and transmitting said pulses for processing;

initially calibrating said camshaft position relative to said crankshaft after receiving said pulses by automatically calculating and implementing a phase offset;

calculating a raw phase angle between said crankshaft and said camshaft utilizing pulses subsequent in time to said initial calibration;

issuing a signal corresponding to said raw phase angle for further processing;

compensating said signal corresponding to said raw phase angle for discrepancies created during the generation of said pulses;

receiving said compensated signal, comparing said compensated signal to a predetermined setpoint, and transmitting a PWM duty cycle to an actuating means for delivering hydraulic fluid from a main oil gallery to a means for varying the position of a housing;

varying the position of a housing relative to said camshaft in response to torque reversals in said camshaft, said housing mounted to said camshaft, said camshaft having at least one vane, said housing having at least one recess, said housing being rotatable about said camshaft;

eliminating the need for blocking a backflow of said hydraulic fluid by utilizing a check valve means functionally positioned between said camshaft/housing combination and said actuating means; and

,

transmitting rotational movement from said crankshaft to said housing;

10. The method of claim 9 wherein said housing comprises a sprocket oscillatingly journalled on said camshaft, said sprocket connected to said crankshaft by a chain drive.

11. The method according to claim 9 wherein said means for varying the position of the housing comprises a hydraulic cylinder and a proportional spool valve, the position of said spool valve being controlled by the pressure of the hydraulic fluid contained in said cylinder.

12. The method of claim 9 wherein said actuating means comprises a solenoid valve, said solenoid valve controlling the flow of hydraulic fluid to said hydraulic cylinder.

13. The method according to claim 12 wherein said solenoid valve is of the pulse width modulated (PWM) variety.

14. The method of claim 9 wherein the step of compensating said signal further comprises:

controlling proportional gain;

controlling integral gain;

compensating for phase-lead; and

,

compensating for outside engine disturbances.

15. The method of claim 9 further comprising the step of filtering a predetermined set point in a single-loop system.

16. The method of claim 9 further comprising the step of filtering said compensated signal to minimize the presence of high frequency oscillations.

17. The method according to claim 9 wherein said means for varying the position of said housing relative to said camshaft comprises means for permitting the position of said housing to move in a first direction relative to said camshaft in reaction to a torque pulse in said camshaft in a first direction, means for preventing the position of said housing from moving relative to said camshaft in a second direction in reaction to a torque pulse in said camshaft in a second direction, and means for selectively reversing said first and second directions of the movement of said housing relative to said camshaft with respect to said first and second directions of torque pulses in said camshaft.

18. The method according to claim 17 wherein said at least one recess is capable of sustaining hydraulic pressure, wherein said at least one lobe divides said at least one recess into a first portion and a second portion, and wherein the varying of the position of said housing relative to said camshaft comprises:

transferring hydraulic fluid into one of said first portion and said second portion of said recess.

19. The method according to claim 18 wherein the varying of the position of said housing relative to said camshaft further comprises;

simultaneously transferring hydraulic fluid out of the other of said first portion and said second portion of said recess.

20. The method according to claim 18 wherein said hydraulic fluid is engine lubricating oil from said main oil gallery of the engine.