The invention relates to a hydraulic control system for providing an oil or pressurized fluid supply to a variable cam phasing system in an engine.
In engines having one or more cylinders with dual camshafts, one for actuating the engine intake valves and a second camshaft for actuating the engine exhaust valves, a cam phaser on one or both of the camshafts may be provided for adjusting within predetermined ranges the angular positions or phases of the camshafts relative to the engine crankshaft. A single cam phaser may be mounted on the exhaust camshaft of the engine or a dual cam phasing system, with independent cam phasers on the exhaust camshaft and intake camshaft respectively, may be used.
A dual independent cam phasing system allows for variable overlap of intake and exhaust valve events and hence has improved power, torque and smoothness of operation of the engine. A control system, such as a hydraulic control system, enables the operation of a dual independent cam phasing system.
The invention relates to an apparatus (i.e. a hydraulic control system) for providing an oil or pressurized fluid supply to a variable cam phasing or timing system in an engine, especially an overhead valve engine. The apparatus includes a valve housing attachable to a front cover assembly of the engine. Alternatively, the valve housing may be integrally formed with the front cover assembly as a unitary component. A first valve is installed in the valve housing (i.e. in a first valve bore defined by the valve housing). The housing has an inlet passage hydraulically communicating with the first valve to carry pressurized fluid from a fluid source to the first valve. In one aspect of the invention, the front cover assembly has a first and a second outlet passage hydraulically communicating with the first valve to allow the pressurized fluid to flow to a cam phasing system operatively connected to the first and the second outlet passages, thereby variably moving a camshaft assembly operatively connected to the cam phasing system.
In another aspect of the invention, the pressurized fluid is oil provided from within a cylinder block of the engine. In another aspect of the invention, the first valve is a solenoid valve which is movable to control the flow of the pressurized fluid.
In another aspect of the invention, a generally tubular insert has a first groove and is attachable to the front cover assembly. A fluid communication device, also referred to as a spigot, is placed within the insert such that it is rotatable within the insert. The spigot has a first and a second longitudinal hole. The first longitudinal hole hydraulically connects the first outlet passage to the cam phasing system. The first groove and the second longitudinal hole hydraulically connect the second outlet passage to the phasing system. The second longitudinal hole is plugged at an outer end of the spigot.
An apparatus to transfer fluid from a plurality of passages in a stationary element to a rotating element without intermixing the fluid in each passage is also provided. The apparatus includes a generally tubular insert attachable to the stationary element and a rotatable fluid distribution device, also referred to as a spigot, placed within the insert sufficiently to allow for rotation of the spigot. The spigot is attachable to the rotating element and has a first longitudinal hole within it to operatively connect a first passage to the rotating element. The insert defines a first groove that is connected to a second longitudinal hole in the spigot through a first opening in the spigot. The first groove in the insert and the second longitudinal hole in the spigot operatively connect a second passage to the rotating element.
In another aspect of the invention, a plurality of seals is placed around the spigot to separate the fluid flow to or from the first and the second longitudinal holes.
In another aspect of the invention, the front cover assembly also defines a first tank port passage in hydraulic communication with the first valve to drain away residual fluid from the first valve bore. The first tank port passage drains out of the front cover assembly to a space defined between the front cover assembly and the cylinder block. In another aspect of the invention, the valve housing defines a first bore for installation of the first valve. The first bore hydraulically communicates with the first valve and with the first and the second outlet passages. By providing a separately attachable valve housing, machining complex bores that require plugging of multiple portions may be avoided; thus ease of manufacture is realized.
In another aspect of the invention, a second valve is installed in the valve housing. The second valve is a solenoid valve which is movable to control the flow of the pressurized fluid. The inlet passage hydraulically communicates with the second valve in the housing, to carry the pressurized fluid from the fluid source to the second valve.
In another aspect of the invention, the front cover assembly has a third and a fourth outlet passage that hydraulically communicate with the second valve to sufficiently channel the pressurized fluid to the cam phasing system. The cam phasing system is operatively connected to the third and the fourth outlet passages. The valve housing defines a second bore for installation of the second valve. The second bore hydraulically communicates with the second valve and with the third and the fourth outlet passage. In another aspect of the invention, the front cover assembly has a second tank port passage hydraulically communicating with the second valve to drain away residual fluid from the second valve bore.
In another aspect of the invention, a second groove in the insert and a third longitudinal hole in the spigot operatively connect the third outlet passage to the cam phasing system. A third groove in the insert and a fourth longitudinal hole in the spigot operatively connect the fourth outlet passage to the cam phasing system. The third and the fourth longitudinal holes are plugged at the outer end of the spigot. The first, second, and third grooves connect to the second, third and fourth longitudinal holes, respectively, through first, second and third openings on the surface of the spigot.
In another aspect of the invention, the cam phasing system includes an intake cam phaser and an exhaust cam phaser. The cam phasing system includes a front vane plate integrally formed with a plurality of exhaust vanes, a rear vane plate integrally formed with a plurality of intake vanes, and a middle housing having a plurality of cavities that engage with the intake and the exhaust vanes. The intake and the exhaust vanes each have a first and a second side. The intake and the exhaust vanes are rotatable in a clockwise and a counter-clockwise direction with respect to the middle housing through pressure of the pressurized fluid exerted on the first and the second sides of the respective intake and the exhaust vanes.
In another aspect of the invention, the first valve is operatively connected to and delivers fluid pressure to both the first and second sides of the intake vanes; and the second valve is operatively connected to and delivers fluid pressure to both the first and second sides of the exhaust vanes.
In another aspect of the invention, the movement of the first and the second valve modulates the pressure on the intake and the exhaust vanes of the cam phasing system, causing the intake and the exhaust vanes to rotate, thereby variably moving a camshaft assembly operatively connected to the cam phasing system. A method of supplying pressurized fluid to a hydraulic control system of a variable cam phasing system in an engine is also provided.
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.
The engine front cover assembly 12 (shown in
The inlet passage 15 includes a portion 17, shown in
Two oil control valves are installed in the valve housing 18. As shown in
In the preferred embodiment, the front cover assembly 12 and the valve housing 18 each define different portions of four outlet oil passages, different pairs of which are in fluid communication with the first and the second valves 20, 22, respectively, (thus making a total of four oil passages 30, 32, 34, 36), to channel oil pressure and flow to a cam phasing system 23 of
Multiple variations in the number of solenoid valves and oil passages may be made within the scope of the invention. For example, in an intake-only or exhaust-only cam phasing system, there may be one solenoid valve with one inlet passage and two outlet passages connected to the solenoid valve.
The control valve housing 18 may be made integrally as part of the front cover assembly 12, or may be formed as a separate housing that fastens onto the front cover assembly 12. As described above, the control valve housing 18 includes the inlet passage portions 15A, 15B to channel oil from the main gallery of the cylinder block 14 (see
In the preferred embodiment, the valve housing 18 is a unitary component, with a plurality of bores drilled or formed in the valve housing 18 for the installation of the first and second valves 20, 22 and for each passage going through the valve housing 18. Alternatively, the first and second valves 20, 22 may be mechanically attached to the valve housing 18 rather than inserted in bores formed therein. As shown in
The front cover assembly 12 includes a generally cylindrical annular tubular section, referred to here as an insert 44 (see
Four separate channels are formed for each of the four outlet oil passages 30, 32, 34, 36. One outlet oil passage (passage 30 in the preferred embodiment) connects to one of the four longitudinal holes 54 that is open at the outer end 55 of the spigot 52 (see
The three grooves 46 connect to the three longitudinal holes 54 that are plugged at the outer end 55 through three separate openings 48 (see
The front cover assembly 12 forms a plurality of tank port passages 60, 62 (see
As seen in
The first and the second valve 20, 22 are operatively connected to a cam phasing system 23 (see
The intake and exhaust cam phasers 76, 78 may be integrated into a single housing or they may be housed separately, however they operate independently of each other. In the preferred embodiment, the intake cam phaser 76 includes a rear vane plate 80 with intake vanes 82 integrally formed or attached to the rear vane plate 80, and a middle housing 84 having cavities 86A, as shown in
The exhaust cam phaser 78 includes a front vane plate 88 with exhaust vanes 90 integrally formed or attached to the front vane plate 88, and the middle housing 84 having cavities 86B. The exhaust vanes 90 fit into the cavities 86B with a sufficient clearance to allow for rotation of the exhaust vanes 90. Generally, the middle housing 84 includes three cavities 86A to engage with three intake vanes 82 and three cavities 86B to engage with exhaust vanes 90, respectively. The middle housing 84 also includes sprocket teeth 96 that are driven by a crankshaft (not shown) through a cam drive chain (not shown).
The intake vanes 82 and exhaust vanes 90 may be rotated with respect to the middle housing 84 in both a clockwise and a counter-clockwise direction, through oil pressure exerted on either the first side 98 or second side 100 of each respective vane. In order to provide a source of oil pressure exerted on the first side and second side of a vane, two of the four outlet passages 30, 32, 34, 36 each are designated to operatively connect with the intake and exhaust cam phasers 76, 78. The rotation of the plurality of vanes of the cam phasing system 23 modulates the position of an intake camshaft 102 and an exhaust camshaft 104 that are operatively connected to the cam phasing system 23.
Thus, the first valve 20 is operatively connected to and delivers a fluid signal or fluid pressure to both the first and second sides 98, 100 of the intake vanes 82 in the intake cam phaser 76. Likewise, the second valve 22 is operatively connected to and delivers a fluid signal or fluid pressure to both the first and second sides 98, 100 of the exhaust vanes 90 in the exhaust cam phaser 78. [00431 The intake cam phaser 76 and the exhaust cam phaser 78 are connected to the intake camshaft 102 and an exhaust camshaft 104, respectively.
In summary, pressurized oil is transferred from a stationary front cover assembly 12 into a rotating spigot 52 that is attached to the cam phasing system 23 and the concentric camshaft assembly 106. Further, depending on the oil pressure exerted on either the first side 98 or second side 100 of a respective vane 82, 90, the vanes can be made to rotate in clockwise or counter-clockwise directions with respect to the middle housing 84 to modulate the positions (advancing and retarding) of the intake and exhaust camshafts 102, 104 and the crankshaft (not shown), which is fixed together in phase through a cam drive chain (not shown).
The engine control module (ECM) (not shown) sends a pulse-width modulated (PWM) signal which controls the movement of the first and the second valves 20, 22. The engine control module is electronically linked to the first and the second valves 20, 22. As noted above, the movement of the first and the second valves 20, 22 modulates the position of the concentric camshaft assembly 106 with respect to the crankshaft (not shown), which is operatively connected to the concentric camshaft assembly 106 through a cam drive chain (not shown). This is done through fluid pressure on both the first and second sides 98, 100 of the intake and exhaust vanes 82, 90 in the intake cam phaser 76 and the exhaust cam phaser 78, respectively.
The engine control module (ECM) continuously monitors the position of the crankshaft, comparing it to target values from a pre-determined table and computing deviations from the target values. Oil flow is modulated in order to provide a constant correction from the target values. Thus, a feedback loop is set up, enabling the modulation of oil flow in order to keep the deviation of the crankshaft and cam phasing system position from the desired target position to a minimum. Alternative suitable valves and control systems may also be used.
In summary, the first and the second valves 20, 22 are pulse-width-modulated by an electronic control system which provides closed-loop or feedback control of camshaft angular position, with respect to the crankshaft. An exhaust cam position sensor 110 (see
Alternatively, the exhaust cam position sensor 110 may be installed in the front cover and the intake cam position sensor may be installed in the lifter oil manifold assembly (not shown), or other engine structure, in order to “read” the pattern formed as part of the rear plate of the cam phasing system 23. In order to detect the angular position of a camshaft, the system may utilize a “tone” wheel, with a toothed form that can be “read” by a camshaft position sensor and decoded by the electronic control system so as to provide continuous angular position feedback. These toothed wheels are integrated into or formed as part of the front and rear vane plates. Alternative suitable connections may also be used.
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.