Patent Grant
10683780
The present description relates generally to methods and systems for a variable cam timing system including a locking phase control apparatus with an isolator to reduce knocking resulting from component contact.
Variable cam timing (VCT) is used in engines to advance or retard intake and/or exhaust valve timing. Consequently, intake and/or exhaust valve timing may be adjusted based on engine operating conditions to increase combustion efficiency and decrease emissions, if desired. Additionally, engine power output may be increased across a wider range of engine operating conditions than with fixed valve timing systems.
A locking mechanism, also known as a phase control apparatus, of a VCT system may be configured to lock the VCT system in a desired base configuration when there is insufficient oil pressure to operate the VCT system, such as during engine startup, or during engine idle conditions. Specifically, the locking mechanism may include a locking pin that locks a rotor inside a housing of the phase control apparatus. Backlash and overtravel gaps between components of the locking mechanism, such as between the locking pin and its receiving hole in the housing, are carefully controlled to tight specifications. If backlash or overtravels gaps are too tight, sticking and binding issues may occur between locking components. Conversely, if backlash or overtravel gaps are too large, it may lead to noise, vibration, and harshness (NVH) issues during VCT operation. In some cases, camshaft torque fluctuations can cause the components of the locking mechanism to oscillate within the backlash gaps while in the locked configuration, thereby causing the components to impact each other and causing undesirable noise that may be referred to as knocking.
Other attempts to address NVH issues in VCT systems include methods for setting a locking pin backlash and/or overtravel gap for the locking mechanism that includes either adjusting the backlash during a VCT actuator assembly process or controlling it within tightly controlled tolerances. One example approach for a phase control apparatus is shown by Moetakef et al. in U.S. Pat. No. 9,021,998. Therein, a phase control apparatus is disclosed that includes a locking pin coupled to a vane of a rotor, the locking pin extending into a locking pin recess disposed in a cover plate in a locked configuration. There is locking pin backlash between the locking pin and locking pin recess, as well as VCT overtravel disposed between the vane and housing of the phase control apparatus in order to avoid impact between the vane of the rotor and the housing. Thus, in the locked configuration, a gap exists between the vane including the locking pin and the housing. However, the inventors herein have recognized potential issues with such systems. As one example, controlling the backlash and overtravel during assembly may involve precise measurement techniques that require frequent re-calibration, which may increase the time and cost of assembly. In another example, the backlash and overtravel tolerances may eventually degrade over time with normal wear of locking mechanism components, leading to an increase of NVH issues.
In one example, the issues described above may be addressed by a phase control apparatus for a camshaft including a vane rotor positioned within a housing and including a first vane extending from a central hub; a first chamber formed between walls of the housing and the hub, the first vane arranged within the first chamber; and an isolator pad positioned within a recess of a first wall of the walls and between the first wall and a first sidewall of the first vane. In this way, as the vane rotor is moved to a locked position it may contact the isolator pad, which may be constructed of a rubber or plastic material, without contacting the housing wall, thus reducing the likelihood of metal-to-metal contact. In this way, knocking noises due to metal components hitting one another may be mitigated without having to tightly control natural camshaft torque fluctuations and/or the tight tolerances of backlash and overtravel.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The following description relates to systems and methods for a variable cam timing (VCT) system including a locking phase control apparatus with an isolator pad. The engine shown in
Turning now to
Engine 10 shows an example cylinder 102 (also known as combustion chamber 102) that is part of an engine block region 100 including a cylinder head and an engine block. The cylinder head may include one or more valves for selectively communicating with an intake and an exhaust system, for example, while the engine block may include multiple cylinders, a crankshaft, etc. It will be appreciated that block region 100 may include additional and/or alternative components than those illustrated in
Cylinder 102 of engine 10 includes cylinder walls 104 with piston 106 positioned therein. Piston 106 is shown coupled to crankshaft 108 so that reciprocating motion of the piston is translated into rotational motion of the crankshaft. In some examples, vehicle 5 may be a hybrid vehicle with multiple sources of torque available to one or more vehicle wheels 55. In the example shown, vehicle 5 includes engine 10 and an electric machine 52. Electric machine 52 may be a motor or a motor/generator. Crankshaft 108 of engine 10 and electric machine 52 are connected via a transmission 54 to vehicle wheels 55 when one or more clutches 56 are engaged. In the depicted example, a first clutch 56 is provided between crankshaft 108 and electric machine 52, and a second clutch 56 is provided between electric machine 52 and transmission 54. Controller 12 may send a signal to an actuator of each clutch 56 to engage or disengage the clutch, so as to connect or disconnect crankshaft 108 from electric machine 52 and the components connected thereto, and/or connect or disconnect electric machine 52 from transmission 54 and the components connected thereto. Transmission 54 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various manners including as a parallel, a series, or a series-parallel hybrid vehicle.
Electric machine 52 receives electrical power from a traction battery 58 to provide torque to vehicle wheels 55. Electric machine 52 may also be operated as a generator to provide electrical power to charge battery 58, for example during a braking operation.
In other examples, vehicle 5 is a conventional vehicle with only an engine, or an electric vehicle with only electric machine(s). In conventional vehicle examples, crankshaft 108 may be coupled to at least one drive wheel of a vehicle via an intermediate transmission system without an intermediate electric machine. Further, a conventional starter motor may be coupled to crankshaft 108 via a flywheel (not shown) to enable a starting operation of engine 10.
Cylinder 102 receives intake air from intake manifold 110 via intake passage 112 and exhausts combustion gases via exhaust passage 114. Intake manifold 110 and exhaust passage 114 can selectively communicate with cylinder 102 via respective intake valve 116 and exhaust valve 118. In some embodiments, cylinder 102 may include two or more intake valves and/or two or more exhaust valves. In some examples, engine 10 may be a variable displacement engine (VDE), having one or more cylinders 102 with selectively deactivatable intake valves 116 and selectively deactivatable exhaust valves 118.
In some embodiments, one or more of the intake passages may include a boosting device such as a turbocharger or a supercharger. For example,
In some embodiments, each cylinder of engine 10 may include a spark plug 120 for initiating combustion. Ignition system 188 can provide an ignition spark to combustion chamber 102 via spark plug 120 in response to spark advance signal SA from controller 12, under select operating modes. However, in some embodiments, spark plug 120 may be omitted, such as where engine 10 may initiate combustion by auto-ignition or by injection of fuel, as may be the case with some diesel engines.
Fuel injector 122 is shown coupled directly to combustion chamber 102 for injecting fuel directly therein in proportion to the pulse width of signal FPW received from controller 12 via electronic driver 168. In this manner, fuel injector 122 provides what is known as direct injection of fuel into cylinder 102. While
Intake manifold 110 is shown with throttle 124 including throttle plate 126 whose position controls airflow. In this particular example, the position of throttle plate 126 may be varied by controller 12 via a signal provided to an electric motor or actuator included with throttle 124, a configuration that may be referred to as electronic throttle control (ETC). In this manner, throttle 124 may be operated to vary the intake air provided to cylinder 102 along with other cylinders within engine 10. It will be appreciated that in alternate embodiments, throttle 124 may be positioned upstream of compressor 152, or there may be a first throttle positioned upstream of compressor 152 and downstream of compressor 152. Intake passage 112 may include a mass air flow (MAF) sensor 128 and a manifold absolute pressure (MAP) sensor 130 for providing respective signals MAF and MAP to controller 12.
Exhaust gas sensor 132 is shown coupled to exhaust passage 114 upstream of catalytic converter 170. Exhaust gas sensor 132 may be any suitable sensor for providing an indication of exhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor. The exhaust system may include light-off catalysts and underbody catalysts, as well as exhaust manifold, upstream and/or downstream air-fuel ratio sensors. Catalytic converter 170 can include multiple catalyst bricks, in one example. In another example, multiple emission control devices, each with multiple bricks, can be used. Catalytic converter 170 can be a three-way type catalyst in one example. Engine 10 may further include one or more exhaust gas recirculation passages (not shown) for recirculating a portion of exhaust gas from the engine exhaust to the engine intake. As such, by recirculating some exhaust gas, an engine dilution may be affected which may be advantageous for engine performance by reducing engine knock, peak cylinder combustion temperatures and pressures, throttling losses, and NOx emissions.
Engine 10 includes an oil delivery system 180 for providing oil for component cooling and lubrication, as well as for oil pressure actuated (OPA) systems. The VCT system in the depicted embodiment is one non-limiting example of an OPA system. Oil delivery system 180 may include an oil pump 182 coupled to the engine and the VCT system that receives instructions from controller 12 to adjust oil output pressure and/or flow. In one example, oil pump 182 may be a variable displacement oil pump or a variable flow oil pump, including but not limited to an axial piston pump, a bent axis pump, or a variable displacement vane pump. In other examples, oil pump 182 may be a fixed rate oil pump with a regulator or actuatable valve to selectively control pump output, or another suitable type of oil pump with variable output. In another non-limiting example, oil delivery system 180 may include an active relief valve (not shown). Therein, oil pressure output may be increased or decreased as a result of actuation of the active relief valve. Further, the active relief valve may be controlled via a control solenoid that may be actuated by controller 12.
An oil pressure sensor 184 in oil delivery system 180 may be used to determine the oil pressure generated by the oil pump 182. In some examples, control of the oil pump may be feedback-based, wherein controller 12 receives a signal from oil pressure sensor 184 to adjust the operation of oil pump 182 to reach a desired oil pressure or to maintain a desired oil pressure. Oil pump 182 may be coupled to crankshaft 108 to provide rotary power for operating oil pump 182. In one example, oil pump 182 includes a plurality of internal rotors (not shown) that are eccentrically mounted. At least one of the internal rotors may be controlled by controller 12 to change the position of that rotor relative to one or more other rotors to adjust an output flow rate of oil pump 182 and thereby adjust the oil pressure. For example, the electronically controlled rotor may be coupled to a rack and pinion assembly that is adjusted via the controller 12 to change the position of the rotor. The oil pump 182 may selectively provide oil to various regions and/or components of engine 10 to provide cooling and lubrication, or to actuate movement of components. The output flow rate or oil pressure of the oil pump 182 may be adjusted by the controller 12 to accommodate varying operating conditions to provide varying levels of cooling and/or lubrication. Further, the oil pressure output from the oil pump 182 may be adjusted to reduce oil consumption and/or reduce energy consumption by the oil pump 182.
It will be appreciated that any suitable oil pump configuration may be implemented to vary the oil pressure and/or oil flow rate. In some embodiments, instead of being coupled to the crankshaft 108, oil pump 182 may be coupled to a camshaft, or may be powered by a different power source, such as a motor or the like. Oil pump 182 may include additional components not depicted in
Oil pumped by oil pump 182 may be routed through one or more channels 186 to components based on their oil flow and pressure demands. For example, oil may be pumped by oil pump 182 through a first channel of channels 186 to engine block region 100 to provide oil flow to a first group of components. In one example, the first group of components may include a variable camshaft timing (VCT) system 160. In other non-limiting examples, oil may be pumped by oil pump 182 via a second channel of channels 186 to a second group of components including, for example, turbocharger 150, bearings (not shown), and a piston cooling jet (not shown) in the engine block region 100. The second group of components may be grouped separately from the first group of components based on their higher pressure and lower oil flow demands for component cooling and lubrication. It will be appreciated that any number of engine components that utilize oil may be coupled to oil delivery system 180.
Cylinder head and engine block region 100 houses a variable valve operation system such as the VCT system 160. In this example, an overhead cam system is illustrated, although other approaches may be used. Specifically, camshaft 166 of engine 10 is shown communicating with rocker arms 162 and 164 for actuating intake valve 116 and exhaust valve 118, respectively. VCT system 160 may be oil-pressure actuated (OPA). By adjusting a plurality of hydraulic valves to thereby direct a hydraulic fluid, such as engine oil, into the cavity (such as an advance chamber or a retard chamber) of a phase control apparatus, valve timing may be changed (e.g., advanced or retarded). One non-limiting example of a phase control apparatus is shown in
Camshaft 166 is hydraulically coupled to housing 169. Housing 169 forms a toothed wheel having a plurality of teeth 171. In the example embodiment, housing 169 is mechanically coupled to crankshaft 108 via a timing chain or belt (not shown). Therefore, housing 169 and camshaft 166 rotate at a speed substantially equivalent to each other and synchronous to crankshaft 108. In an alternate embodiment, as in a four stroke engine, for example, housing 169 and crankshaft 108 may be mechanically coupled to camshaft 166 such that housing 169 and crankshaft 108 may synchronously rotate at a speed different than camshaft 166 (e.g. a 2:1 ratio, where the crankshaft rotates at twice the speed of the camshaft). In the alternate embodiment, teeth 171 may be mechanically coupled to camshaft 166.
By manipulation of the a vane rotor contained within housing 169 as described herein, the relative position of camshaft 166 to crankshaft 108 can be varied by hydraulic pressures in retard chamber 172 and advance chamber 174. For example, by allowing high pressure hydraulic fluid to enter retard chamber 172, the relative relationship between camshaft 166 and crankshaft 108 may be retarded. As a result, intake valve 116 and exhaust valve 118 may open and close at a time later than normal relative to crankshaft 108. Similarly, by allowing high pressure hydraulic fluid to enter advance chamber 174, the relative relationship between camshaft 166 and crankshaft 108 may be advanced. As a result, intake valve 116 and exhaust valve 118 may open and close at a time earlier than normal relative to crankshaft 108.
While this example shows a system in which the intake and exhaust valve timing are controlled concurrently, variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, dual equal variable cam timing, or other variable cam timing may be used. Further, variable valve lift may also be used. Further, camshaft profile switching may be used to provide different cam profiles under different operating conditions. Further still, the valve train may be roller finger follower, direct acting mechanical bucket, electrohydraulic, or other alternatives to rocker arms.
Continuing with VCT system 160, teeth 171, rotating synchronously with camshaft 166, allow for measurement of relative cam position via cam timing sensor 176 providing signal VCT to controller 12. Teeth 1, 2, 3, and 4 may be used for measurement of cam timing and are equally spaced (for example, in a V-8 dual bank engine, spaced 90 degrees apart from one another) while tooth 6 may be used for cylinder identification. In addition, controller 12 sends control signals (LACT, RACT) to conventional solenoid valves (not shown) to control the flow of high pressure hydraulic fluid either into retard chamber 172, advance chamber 174, or neither. In one embodiment, the high pressure hydraulic fluid may be the oil pumped by the oil pump 182.
Relative cam timing can be measured in a variety of ways. In general terms, the time, or rotation angle, between the rising edge of the PIP signal and receiving a signal from one of the plurality of teeth 171 on housing 169 gives a measure of the relative cam timing. For the particular example of a V-8 engine, with two cylinder banks and a five-toothed wheel, a measure of cam timing for a particular bank is received four times per revolution, with the extra signal used for cylinder identification.
As described above,
Controller 12 is shown in
The controller 12 may receive signals from the various sensors of
In some examples, adjusting oil pump 182 may include adjusting an actuator of oil pump 182 to adjust the oil output of the oil pump. Adjusting an actuator of the oil pump may include the controller sending a signal, based on a first relationship between oil pressure, engine load, and engine speed and a second relationship between oil pressure, engine oil temperature, and engine speed, to the actuator of the oil pump in order to adjust the oil output of the oil pump.
Engine speed signal RPM is generated by controller 12 from signal PIP in a conventional manner and manifold absolute pressure signal MAP from manifold absolute pressure sensor 130 provides an indication of vacuum, or pressure, in the intake passage 112. During stoichiometric operation, one or more of the MAF and MAP sensors can be used to provide an indication of engine load. Use of the MAF and/or MAP sensors, along with engine speed, may provide an estimate of charge (including air) inducted into an engine cylinder, which may be used to determine engine load. In some examples, engine load may be a calculated load value (CLV) or an absolute load value (ALV). It will be appreciated that engine load may be characterized using a plurality of methods. One example method of quantifying engine load is the ratio of current airflow through an engine cylinder divided by the maximum possible airflow through that cylinder. This ratio may be 1 at wide-open-throttle. Boosted engines may be able to achieve an engine load greater than 1 as compressed air (e.g., air at a pressure greater than barometric pressure) is forced into the engine cylinders. Likewise, it will be appreciated that calibration of oil pump 182 may likewise use data regarding indications of engine load other than engine load based on MAF or MAP sensor indications. In one example, oil flow pressure from oil pump 182 may be adjusted responsive to an indication of engine torque, or to an indication of engine vacuum. Further, it will be appreciated that calibration of the oil pump 182 may use data regarding indications of engine temperature other than engine oil temperature. In one example, oil flow from oil pump 182 may be adjusted responsive to engine coolant temperature or another suitable temperature indication.
In one example, Hall effect sensor 138, which is also used as an engine speed sensor, produces a predetermined number of equally spaced pulses per revolution of the crankshaft. As will be described below, engine speed, engine load, and engine oil temperature measurements may be used to determine oil pump output.
As another example, adjusting the oil flow delivered to the VCT system 160 may include the controller 12 receiving an indication of VCT phaser position from cam timing sensor 176, an engine speed from Hall effect sensor 138, and an indication of engine oil temperature from engine oil temperature sensor 142. In one non-limiting example, responsive to those indications, including a request to move the VCT phase to a home position (e.g., locked position) from a position of more than a non-zero threshold distance away from the home position, the controller 12 may command an actuator of the oil pump 182 to increase output of the oil pump 182 in order to provide an increased amount of oil flow to the VCT system 160 and urge the vane rotor toward the home position.
Turning now to
As shown, engine 200 includes the first cylinder 202 and a second cylinder 222. However, it will be appreciated that the number of cylinders in the engine may be varied in other examples. For instance, the engine 200 may include four cylinders, in one example.
The cylinders are arranged in an inline configuration. That is to say that a flat plane extends through the centerline of each cylinder. However, other cylinder positions have been contemplated. The intake valve 204 and the exhaust valve 206 of the first cylinder 202 are shown. It will be appreciated that the valve may be positioned, respectively, in an intake port and an exhaust port. Likewise, an intake valve 224 and an exhaust valve 226 are coupled to the second cylinder 222. The intake valve 224 and the exhaust valve 226 are configured to open during combustion operation. Specifically, the intake valve 224 may enable fluidic communication between the second cylinder 222 and the intake manifold 110, shown in
The VCT system 250 may include an intake camshaft 208 and/or an exhaust camshaft 228. The intake camshaft 208 may include intake cam 210 and intake cam 230 coupled thereto. The intake cams 210 and 230 are configured to cyclically actuate the intake valves during combustion operation. Likewise, the exhaust camshaft 228 may include exhaust cam 212 and exhaust cam 232 coupled thereto. The exhaust cams 212 and 232 are configured to cyclically actuate the exhaust valves during combustion operation. It will be appreciated that the circumferential position of the intake and/or exhaust cams may vary to enable actuation of the intake and exhaust valves at different time intervals.
The VCT system 250 further includes a first phaser 214 (e.g., intake phase control apparatus) and a second phaser 234 (e.g., exhaust phase control apparatus). As shown, the first phaser 214 is coupled to the intake camshaft 208, and the second phaser 234 is coupled to the exhaust camshaft 228. The first and second phasers may be configured to adjust the phase between the crankshaft 108, shown in
The first, intake phaser 214 may include a locking mechanism 218 generically depicted via a box. Likewise, the second, exhaust phaser 234 may also include a locking mechanism 238. The locking mechanisms (218 and 238) may be identical, in one example, or may have dissimilar configurations. In some examples, locking mechanism may include an actuatable pin that engages with a locking recess in order to lock a phaser in a home position. In some embodiments, the locking mechanism may include a vane rotor, such as the vane rotors described below in reference to
The controller 12 (shown in
Camshaft bearings 270 are coupled to the intake camshaft 208 and the exhaust camshaft 228. The camshaft bearings 270 are configured to support as well as enable rotation of the camshaft to which they are coupled. The spark plug 221 is also shown coupled to the first cylinder 202. A second spark plug 241 or other suitable ignition device may be coupled to the second cylinder 222.
As previously mentioned, the output of an oil pump, in one example, a variable displacement oil pump, may be actively controlled by a vehicle controller to meet the engine cooling, lubrication, and actuation demands of an engine for a given operating condition. Specifically, a controller, such as controller 12 of
Turning now to
An inner surface 310 of cover plate 302 may couple to an outer surface 312 of an outer plate 314. In one example, outer plate 314 may serve as a spacer mounted between a housing 322 and cover plate 302, such that an inner surface 318 of outer plate 314 couples to an outer surface 320 of housing 322. It will be appreciated that housing 322 may be similar to housing 169 described in
The housing 322 at least partially encloses the vane rotor 308 and, specifically, a plurality of vanes 324 of the vane rotor 308. When assembled, each vane of vanes 324 of the vane rotor 308 is positioned within a respective chamber of a plurality of chambers 326 of housing 322. Thus, the vane rotor 308 may be referred to as being positioned within the housing 322. The relative angular position (e.g., position about rotational axis 301) of the vane rotor 308 and the drive wheel 304 may be adjusted via manipulation of the phase control apparatus 300 of the VCT system. In this way, the phase of the cams may be adjusted to alter valve timing.
In the depicted example, a first vane of vanes 324 includes a locking pin 325 positioned within a bore 342 of the first vane that may be configured to move into and out of a locking pin recess 327 of the cover plate 302 to lock the phase control apparatus (e.g., lock rotation of the vane rotor relative to the housing). The locking pin may be configured with a biasing force (e.g., spring 344) that urges the pin toward the locking pin recess. This will be described in further detail below.
An outer surface 328 of an inner plate 330 may couple to an inner surface 332 of housing 322. The housing 322 holds an isolator pad within a recess, as will be described further below in reference to
A spool valve 338 is configured to direct hydraulic fluid (e.g., oil) to certain portions of the phase control apparatus 300 for phase adjustment. In one example, the spool valve 338 may be centrally located (e.g., axially aligned with rotational axis 301), but in other examples it may be a remotely mounted spool valve. The spool valve 338 may be coupled to the camshaft and the vane rotor 308 to control cam timing by positioning the vane rotor 308 with respect to the housing 322 in an advanced or retarded position.
Turning now to
In the depicted example, the vane rotor 308 includes three vanes including a first vane 402, a second vane 404, and a third vane 406 extending radially outward from annular hub 432 of the vane rotor 308. However, an alternate number of vanes may be used. In one example, the vane rotor 308 may include a single vane. In other examples, the vane rotor 308 may include four or more vanes. Each vane 324 is housed within one of a plurality of hydraulic chambers 326 (also known simply as chambers) of the housing 322. Specifically, first vane 402 of vane rotor 308 is positioned within a first chamber 408 of housing 322, second vane 404 of vane rotor 308 is positioned within a second chamber 410 of housing 322, and third vane 406 of vane rotor 308 is positioned within a third chamber 412 of housing 322. In this way, the second vane 404 is separated from both the first vane 402 and the third vane and arranged within the second chamber 410 of the housing, which is spaced away from both the first chamber 408 and the third chamber 412. In some embodiments, both the vane rotor and the housing are constructed of a metal material, although other materials have been contemplated. The vane rotor and the housing may be made of an identical material, or may be constructed of different types of material.
First chamber (e.g., first hydraulic chamber) 408 is formed between a first wall 416 of the housing 322, a second wall 420 of the housing, a first inner circumferential wall 430 of the housing, and the hub 432 (e.g., an outer circumferential wall 438 of hub 432) of the vane rotor 308, where the first wall 416 is arranged opposite the second wall 420 in a direction of a circumference of the housing 322, and where the first inner circumferential wall 430 is coupled to each of the first wall 416 and second wall 420, and wherein only the first wall 416 includes a recess that includes an isolator pad, as described below. First inner circumferential wall 430 may be contacting, or in close proximity to, outer circumferential surface 436 of first vane 402. Additionally, no walls of the second chamber 410 or third chamber 412 include a recess with an isolator pad. Rotating the vane rotor 308 into the fully retarded position (which may also be a locked configuration when the locking pin is engaged with the locking pin recess) includes moving the first vane 402 of the vane rotor 308 toward the first wall 416 of the housing and into contact with the first surface 418 of the isolator pad 401. At the same time, rotating the vane rotor 308 into the fully retarded position includes moving the second vane 404 of the vane rotor 308 toward a surface 440 of the housing forming, in part, a second hydraulic chamber 410 that is spaced away from the first hydraulic chamber 408, and maintaining a gap 442 between the second vane 404 and the surface 440, and where the surface 440 does not include a recess with an isolator pad. Due to the presence of gap 442, even when the vane rotor is locked in the fully retarded position, there is no need for an isolator pad in the surface 440 of the second hydraulic chamber 410 of the housing. Similarly, rotating the vane rotor 308 into the fully retarded position includes moving the third vane 406 of the vane rotor 308 toward a surface 452 of the housing forming, in part, the third hydraulic chamber 412 that is spaced away from the first hydraulic chamber 408 and the second hydraulic chamber 410, and maintaining a gap 454 between the third vane 406 and the surface 452, and where the surface 452 does not include a recess with an isolator pad. Due to the presence of gap 454, even when the vane rotor is locked in the fully retarded position, there is no need for an isolator pad in the surface 452 of the third hydraulic chamber 412 of the housing.
The phase control apparatus 300 shown in
On the other hand, when the phase control apparatus 300 is in an unlocked configuration, the relative position of the vanes 324 and the housing 322 may be adjusted via a control valve such as one of the control valves 220 and 240, shown in
As shown, the first surface 418 of isolator pad 401 may be correspondingly contoured to first surface 414 of first vane 402 such that the full first surface 418 of isolator pad 401 may contact a portion of first surface 414 of first vane 402. Specifically, the first surfaces 414 and 418 are planar in the depicted example and therefore may be referred to as planar surfaces. However, other surface contours have been contemplated, as will be described below in reference to
The first surface 418 of the isolator pad 401 may correspond to a retarded cam timing position (e.g., fully retarded cam timing position). Therefore, when first surface 414 is in face-sharing contact with first surface 418, the phase control apparatus 300 may be in a retarded (e.g., fully retarded) cam timing position. Likewise, a second wall 420 of the housing 322 may correspond to an advanced cam timing position. Thus, when the second wall 420 of the housing 322 is in face-sharing contact with a second surface 422 of the first vane 402 the phase control apparatus 300 may be in an advanced cam timing position (e.g., fully advanced cam timing position). In this way, the housing 322 may define the advanced and retarded valve timing boundaries of the phase control apparatus 300. The cutting plane 475 defining the cross sectional views shown in
Turning now to
The isolator pad 401 may extend along an entire length of the housing, the length defined in a direction of a rotational axis of the vane rotor (parallel with the z-axis of coordinate system 350). In this way, an outer surface 516 of the isolator pad 401 may be in the same plane as the outer surface 320 of housing 322 when assembled. Similarly, an inner surface 518 of isolator pad 401 may be in the same plane as the inner surface 332 of housing 322 (shown in
The second end 510 of the isolator pad 401 may include a planar first surface 418 adapted to have face-sharing contact with a planar surface of the first sidewall (e.g., first surface 414 of
Turning now to
The first wall 416 of the housing 322 includes a planar, first section 602 arranged adjacent to an angled, second section 604 depressed inward, into the housing 322, from the first section, wherein the first section is positioned closer to the hub 432 than the second section and wherein only the first section includes the isolator pad recess 506 (also known as recess 506). In some examples, second section 604 may be depressed inward in order to provide an avenue for hydraulic fluid. In other examples, second section 604 may be depressed inward in order to increase assurance that the first vane 402 may contact the isolator pad 401 and not the second section 604 of the housing.
Turning now to
In the embodiment shown, the planar surface 706 of the first sidewall (e.g., first surface 414) is arranged within an indentation 708 that protrudes into the first vane a depth 720 from an outer surface of the first sidewall, and wherein the second end 510 of the isolator pad 401 is adapted to extend into the indentation 708, at a distance of the depth 720, and have face-sharing contact with the planar surface 706 of the first sidewall (e.g., first surface 414) of the first vane 402. In this way, first surface 418 of isolator pad 401 may be in face-sharing contact with planar surface 706 when the phase control apparatus is in the locked (e.g., fully retarded) configuration.
Turning now to
Method 800 begins at 802, where the method includes estimating and/or measuring engine operating conditions. In one example, the engine operating conditions may include engine speed, pedal position, operator torque demand, an engine key-off signal, ambient conditions (ambient temperature, pressure, humidity), engine temperature, manifold air pressure (MAP), manifold air flow (MAF), oil pressure, etc. In other examples, estimating and/or measuring engine operating conditions may include a vehicle controller, such as the example controller 12 shown in
In this way, engine operating conditions may be defined in order to, at 804, adjust vane rotor position according to the current engine operating conditions. As an example, the controller may actuate a control valve, such as one of the example control valves 220 and 240 shown in
At 806, the method includes determining whether the controller has received a request to lock the rotor (e.g., vane rotor of the phase control apparatus). In one example, a request to lock the vane rotor may be received when the engine is shut down. In another example, a request to lock the vane rotor may be received at an engine cold start (e.g., upon engine startup when engine temperature is below a threshold temperature) or an engine idle condition. As discussed previously, a locked position is the position where the locking pin (e.g., locking pin 325 of
If a request to lock the rotor is received, then at 808, the method includes rotating the vane rotor into a retarded cam position wherein a first surface of a first vane (e.g., first surface 414 of first vane 402 of
At 810, the method includes moving a locking pin (e.g. locking pin 325 of
In one example, a hydraulic pressure or other actuating force may be exerted on the locking pin to counteract the biasing force (e.g., spring) urging the pin toward the recess. Moving the locking pin into the locking pin recess may include actuating a solenoid to control a valve to decrease (e.g., discontinue) the hydraulic pressure or other actuating force exerted on the locking pin, thereby allowing dissipation of the hydraulic pressure acting on the locking pin. Therein, a spring, such as the example spring 344 shown in
At 812, the method includes maintaining a gap between the first surface of the first vane and the first wall of the housing via a portion of the isolator pad extending between the first surface of the first vane and the first wall of the housing.
The method then proceeds to 814, where the routine includes determining whether a request to unlock the vane rotor has been received by the controller. In one example, a request to unlock the rotor may be received when operating conditions indicate that adjustment (e.g., advancement) of camshaft timing would increase engine performance, such as when the engine is warm and the controller receives a signal indicating the operator has requested an increase in engine torque. In one example, a request to unlock the rotor and advance camshaft timing may be received when the engine temperature or the engine oil temperature is above a predetermined temperature threshold. In another example, a request to unlock the rotor and advance camshaft timing may be received when the engine speed is above a predetermined level. As discussed previously, an unlocked position is the position where the locking pin of the vane of the rotor is retracted from the locking pin recess of the cover plate of the phase control apparatus. This may be known as an active condition, wherein the locking pin extending from a rotor vane is decoupled from a locking pin recess disposed in the cover plate coupled to the housing, allowing the rotor to rotate with respect to the housing as controlled by the inflow of hydraulic oil into respective hydraulic chambers of the housing. If a request to unlock the rotor has not been requested, then the method includes continuing to maintain a gap between the first surface of the first vane and the first wall of the housing via a portion of the isolator pad extending between the first surface of the first vane and the first wall of the housing.
If a request to unlock the rotor is received at 814, then at 816, the method includes moving the locking pin away from and out of the locking pin recess and rotating the rotor into a desired cam position. As previously described, hydraulic pressure or other actuating force may be selectively introduced or drained to exert a force on the locking pin that may counteract the biasing force (e.g., spring) that urges the pin toward the locking pin recess. In one example, moving the locking pin away from and out of the locking pin recess may include actuating a solenoid to increase the opening of a control a valve to permit entrance of hydraulic fluid into the locking pin recess (e.g., cavity) thereby increasing the hydraulic pressure exerted on the locking pin. Therein, the hydraulic pressure exerted on the locking pin, in a direction opposite the biasing force exerted by the locking pin spring, may increase so that it overcomes the spring force, thereby moving the locking pin into the unlocked position by causing it to slide axially along a bore in the housing, in a direction away from the locking pin recess and toward an inner plate of the phase control apparatus. When the locking pin is decoupled from the locking pin recess, the rotor may be rotated as specified by the controller to a desired cam position, as determined by engine operating conditions. The method then ends.
In this way, the isolator pad 401 may serve to dampen the impact between components of the phase control apparatus 300 as it is moved to the locked configuration and may prevent metal-to-metal contact, thereby reducing component wear, as well as reducing issues with NVH such as knocking. Further, this can be accomplished without attempting to tightly control the natural camshaft torque fluctuations and/or the backlash between the locking pin and the locking pin recess, which is costly to manufacture and may degrade with normal wear of system components.
The technical effect of slidably positioning the isolator pad partially within a recess of the housing, where it is held in place by the inner plate and outer plate of the phase control apparatus when assembled, is that complicated and costly methods of attaching the isolator pad can be avoided.
As one embodiment, a system for a phase control apparatus for a camshaft includes a vane rotor positioned within a housing and including a first vane extending from a central hub; a first chamber formed between walls of the housing and the hub, the first vane arranged within the first chamber; and an isolator pad positioned within a recess of a first wall of the walls and between the first wall and a first sidewall of the first vane. In a first example of the system, the vane rotor includes a second vane separated from the first vane and arranged within a second chamber of the housing, the second chamber spaced away from the first chamber, and wherein only the first vane includes a locking pin adapted to lock rotation of the vane rotor within the housing. A second example of the system optionally includes the first example and further includes wherein the first wall includes a planar, first section arranged adjacent to an angled, second section depressed inward, into the housing, from the first section, wherein the first section is positioned closer to the hub than the second section and wherein only the first section includes the recess. A third example of the system optionally includes one or more of the first and second examples, and further includes wherein the isolator pad extends along an entire length of the housing, the length defined in a direction of a rotational axis of the vane rotor, and wherein the isolator pad extends along only a portion of width of the first wall, the width defined between a first inner circumferential wall of the housing arranged proximate an outer circumferential surface of the first vane and a second inner circumferential wall of the housing arranged closer to the hub of the vane rotor than the first inner circumferential wall. A fourth example of the system optionally includes one or more of the first through third examples, and further includes wherein the isolator pad includes a first end positioned entirely within the recess and a second end extending outward from the first end and protruding outward from the first wall. A fifth example of the system optionally includes one or more of the first through fourth examples, and further includes wherein the first end is wider than the second end and wherein the isolator pad is adapted to slide within the recess. A sixth example of the system optionally includes one or more of the first through fifth examples, and further includes an outer plate and an inner plate sandwiching the vane rotor within the housing and adapted to hold the isolator pad within the recess, on either end of the housing. A seventh example of the system optionally includes one or more of the first through sixth examples, and further includes wherein the second end includes a planar surface adapted to have face-sharing contact with a planar surface of the first sidewall when the vane rotor is locked against a cover plate coupled to the housing. An eighth example of the system optionally includes one or more of the first through seventh examples, and further includes wherein the planar surface of the first sidewall is arranged within an indentation that protrudes into the first vane from an outer surface of the first sidewall and wherein the second end of the isolator pad is adapted to extend into the indentation and have face-sharing contact with the planar surface of the first sidewall. A ninth example of the system optionally includes one or more of the first through eighth examples, and further includes wherein when the vane rotor is locked against a cover plate coupled to the housing via a locking pin extending through the first vane, the first sidewall of the first vane and the first wall of the housing are separated from one another via a gap, the isolator pad extending between the first wall and first sidewall, across the gap. A tenth example of the system optionally includes one or more of the first through ninth examples, and further includes wherein the first chamber is formed between the first wall of the walls of the housing, a second wall of the walls of the housing, a first inner circumferential wall of the housing, and the hub, where the first wall is arranged opposite the second wall in a direction of a circumference of the housing, and where the first inner circumferential wall is coupled to each of the first wall and second wall, and wherein only the first wall of the walls includes the recess including the isolator pad. An eleventh example of the system optionally includes one or more of the first through tenth examples, and further includes wherein the vane rotor and the housing are constructed of a metal material and the isolator pad is constructed of a rubber or plastic material.
In another embodiment, a method for operating a variable cam timing (VCT) system includes: in response to a request to lock rotation of a rotor within a housing of a drive wheel of the VCT system: rotating the rotor into a retarded cam position where a first surface of a first vane of the rotor is in face-sharing contact with an isolator pad slidably positioned within a first recess within a first surface of the housing, wherein the first vane is positioned in a first hydraulic chamber of the housing formed, in part, by the first surface of the housing; and moving a locking pin into a locking pin recess disposed in a cover plate coupled to the housing, the locking pin extending from the first vane. In a first example of the method, rotating the rotor into the retarded position includes moving a second vane of the rotor toward a second surface of the housing forming, in part, a second hydraulic chamber that is spaced away from the first hydraulic chamber, and maintaining a gap between the second vane and the second surface, and where the second surface does not include a recess with an isolator pad. A second example of the method optionally includes the first example and further includes holding the isolator pad within the recess with an outer plate coupled to a first, outer surface of the housing and an inner plate coupled to a second, outer surface of the housing and wherein the rotor is positioned within the housing, between the outer plate and inner plate. A third example of the method optionally includes one or more of the first and second examples, and further includes while rotation of the rotor is locked and the rotor is in the retarded cam position, maintaining a gap between the first surface of the first vane and the first surface of the housing via a portion of the isolator pad extending between the first surface of the vane and the first surface of the housing.
In a further embodiment, a system for a variable cam timing system includes: a camshaft including a plurality of cams, each cam of the plurality of cams adapted to actuate a valve of a cylinder; a phase control apparatus coupled to the camshaft and including: a cover plate including a drive wheel; a housing fixed to the drive wheel and positioned proximate to the cover plate at a first end of the housing; a vane rotor including a first vane and positioned within the housing, the first vane positioned within a first hydraulic chamber of the housing formed between a hub of the vane rotor, a first inner circumferential wall of the housing, and first and second sidewalls of the housing, the first and second sidewalls each coupled to the first inner circumferential wall; and an isolator pad positioned within a recess formed within the first sidewall, where the first sidewall is a retarded side of the first hydraulic chamber, and where the first vane is positioned at the retarded side when the camshaft is actuated into a retarded position. In a first example of the system, the vane rotor further includes a second vane positioned within a second hydraulic chamber of the housing, the second hydraulic chamber spaced away from the first hydraulic chamber, and wherein no walls of the second hydraulic chamber include a recess with an isolator pad. A second example of the method optionally includes the first example and further includes wherein the cover plate includes a locking pin recess and further comprising a locking pin positioned within a bore of the first vane and movable into a locked position where the locking pin engages the recess, wherein in the locked position a retarded side of the first vane is in face-sharing contact with the isolator pad and separated from the first sidewall via a gap, the isolator pad extending from the recess to the retarded side of the first vane, across the gap. A third example of the method optionally includes one or more of the first and second examples, and further includes an outer plate coupled between the first end of the housing and the cover plate and an inner plate positioned against an opposite, second end of the housing, wherein the isolator pad extends within the recess between the inner plate and outer plate, and wherein the isolator pad extends only partially across an entire width of the first sidewall, the width defined between the first inner circumferential wall and a second inner circumferential wall of the housing, where the second inner circumferential wall is positioned proximate to the hub.
In another representation, a phase control apparatus for a camshaft, comprises: a vane rotor positioned within a housing and including a first vane and a second vane, each, extending from a central hub; a first chamber formed between walls of the housing and the hub, the first vane arranged within the first chamber; a second chamber formed between walls of the housing and the hub, the second vane arranged within the second chamber; a locking pin arranged within a bore of only the first vane and adapted to lock rotation of the vane rotor relative to the housing; and an isolator pad positioned only within a recess of a first wall of the walls of the first chamber and between the first wall and a first sidewall of the first vane, where the walls of the housing of the second chamber do not include a recess with an isolator pad.
Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system, where the described actions are carried out by executing the instructions in a system including the various engine hardware components in combination with the electronic controller.
It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.
The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
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