Patent Application
20220290587
The present invention relates to variable cam timing phaser, and more specifically to axial and radial source feeds at a rotor assembly to camshaft interface.
Internal combustion engines have employed various mechanisms to vary the relative timing between the camshaft and the crankshaft for improved engine performance or reduced emissions. The majority of these variable camshaft timing (VCT) mechanisms use one or more “vane phasers” on the engine camshaft (or camshafts, in a multiple-camshaft engine). Vane phasers have a rotor assembly with one or more vanes, mounted to the end of the camshaft, surrounded by a housing assembly defining the vane chambers into which the vanes fit. It is possible to have the vanes mounted to the housing assembly, and the chambers in the rotor assembly, as well. The housing assembly's outer circumference forms the sprocket, pulley or gear accepting drive force through a chain, belt, or gears, usually from the crankshaft, or possible from another camshaft in a multiple-cam engine.
Apart from the camshaft torque actuated (CTA) variable camshaft timing (VCT) systems, the majority of hydraulic VCT systems operate under two principles, oil pressure actuation (OPA) or torsional assist (TA). In the oil pressure actuated VCT systems, an oil control valve (OCV) directs engine oil pressure to one working chamber in the VCT phaser while simultaneously venting the opposing working chamber defined by the housing assembly, the rotor assembly, and the vane. This creates a pressure differential across one or more of the vanes to hydraulically push the VCT phaser in one direction or the other. Neutralizing or moving the oil control valve to a null position puts equal pressure on opposite sides of the vane and holds the phaser in any intermediate position. If the phaser is moving in a direction such that engine valves will open or close sooner, the phaser is said to be advancing and if the phaser is moving in a direction such that engine valves will open or close later, the phaser is said to be retarding. The OCV is typically remotely located from the phaser for OPA VCT systems but can also be located within the phaser or in the center bolt assembly that is mounted within the phaser.
The torsional assist (TA) systems operates under a similar principle with the exception that it has one or more check valves to prevent the VCT phaser from moving in a direction opposite than being commanded, should it incur an opposing force such as cam torque reversals. The oil control valve is typically located within the phaser or in a center bolt assembly that is mounted within the phaser for TA VCT systems.
All variable cam timing systems require a supply of source oil or fluid to be provided for continuous operation or to make up for leakage associated with operation of the VCT phaser.
Conventional VCT phasers have secured advance and retard chamber feed across a rotor to camshaft clamped joint at specific points, however source oil is prevented from passing over the entire camshaft to rotor assembly mating surface. For example, WO 2021/093379 is a variable camshaft timing phaser in which a rotor assembly has a first face with an assembling groove inset from the first face. Within the assembling groove and further inset from the first face is an annular projection. Along the assembly groove are four spaced apart channels. An end of the camshaft is received within the rotor assembly, such that the end abuts against the annular projection and a portion of the outer circumference of the camshaft is exposed to the four spaced apart channels. Each of the channels includes an axial section extending radially inward from the annular projection, the axial section being connected to a radial section which is offset from the first annular cavity at the radially inner side. In other words, advance and retard chamber feeds occur at the camshaft to rotor interface.
According to one embodiment of the present invention, a variable cam timing phaser comprises a housing assembly, a rotor assembly, a camshaft, and a center bolt including a spool valve. The housing assembly has an outer circumference for accepting drive force. The rotor assembly is coaxially located within the housing assembly with a first face and a second face, with at least one chamber defined by the housing assembly and rotor assembly. The rotor assembly comprises: a central hub defining an axial bore and an interface groove with a first seal land, a second seal land, a third land, and a single undercut area, wherein the second seal land is between the single undercut area and a circumferential edge of the central hub, the first seal land is between a circumferential edge of the central hub and the axial bore other than the single undercut area, and a third land a third sealing land between the axial bore of the central hub of the rotor assembly and the center bolt; and a rotor body surrounding the central hub having a plurality of vanes extending axially therefrom; wherein the single undercut area is in fluid communication with at least one undercut supply passage within the rotor body having an axial component, a radial component or an axial and a radial component relative to the axial bore. The camshaft is connected to the rotor assembly, the camshaft having a first end, a second end, and defining a through passage. A clamping interface is between the first end of the camshaft and the first face of the rotor assembly such that a seal is present between first seal land and the first end of the camshaft, and the second seal land and the first end of the camshaft. The fluid from at least a first supply flows into the passage of the camshaft to the single undercut area, through at least one undercut supply passage at the clamping interface between the camshaft and the rotor assembly to a passage within the rotor assembly in fluid communication with at least one chamber.
A minimum clamping distance is present between the first face of the rotor assembly and the first end of the camshaft. In one embodiment, the minimum clamping distance is 1.0 mm.
In embodiments of the present invention, source feeds via the undercut supply passages are present at the camshaft to rotor assembly interface, not advance or retard chamber feeds.
A housing assembly 100 of the VCT phaser has an outer circumference (not shown) for accepting drive force as well as a first end plate 100a and a second end plate 100b. A rotor assembly 105 is coaxially located within the housing assembly 100 and is connected to the camshaft 126. The rotor assembly 105 has a central hub 105c defining a central axial bore 140 and an interface 157 with a first seal land 156 and a second seal land 154. The central hub 105c is surrounded by a rotor body 105e having a first circumferential edge 105d and an outer circumference 105f. Extending axially from the rotor body 105e of the rotor assembly 105 are a plurality of vanes 104 separating chambers formed between the housing assembly 100 and the rotor assembly 105 into advance chambers and retard chambers (not shown). The vanes 104 are capable of rotation to shift the relative angular position of the housing assembly 100 and the rotor assembly 105. At least one of the vanes 104 includes a bore 162 which receives a lock pin 163.
The first end plate 100a defines a central axial bore 110 which receives a bearing on an outer diameter 126a of the camshaft 126, such that the outer diameter 126a of the camshaft 126 is adjacent to and clamped relative to the first face 105a of the rotor assembly 105. More specifically, the outer diameter 126a of the camshaft 126 is received between the first circumferential edge 105d of the central hub 105c on first rotor face 105a and the central axial bore 140 within the interface 157. Within the interface 157 is a single undercut area 155. Within the single undercut area 155 are one or more undercut supply passages 150 at the interface between the rotor assembly 105 and the camshaft 126. The one or more undercut supply passages 150 include an axial component 150, a radial component 152 or both an axial 150 and a radial component 152 extending within the rotor assembly 105 as shown in
In one embodiment, the single undercut area 155 has a single undercut supply passage 150 which has axial components 151 relative to a central axis of the camshaft 126 or the central axis of the axial bore or the rotor assembly 105.
In another embodiment, the single undercut area 155 has a single undercut supply passage 150 which has radial components 152 relative to a central axis of the camshaft 126 or the central axis of the axial bore of the rotor assembly 105.
It is noted that the maximum number of undercut supply passages within the single undercut area 155 is preferably two.
While the figures show an external bearing design, the clamped interface can similarly be applied to an internal bearing design, where inner plate 100a would design a clearance diameter and the clearance between the rotor assembly and house assembly at the rotor minor diameter.
An interface 153 is formed between the outer diameter 126a of the camshaft 126 and the first rotor face 105a to form a seal across the interface 157 which results in a first seal land 156 of a first width w1 that extends from the first circumferential edge 105d of the first rotor face 105a to the central axial bore 140 of the interface 157 and a second seal land 154 between the first circumferential edge 105d of the first rotor face 105a and the single undercut area 155 of the interface 157 with a width w2. The width w1 of the first seal land 156 is greater than the width w2 of the second seal land 154. The width w1 is preferably equal to the width of the interface 157. Therefore, the minimum clamping distance is at least equal to the width w1 of the first sealing land 156 between the first circumferential edge 105d and the central axial bore 140 and in the area of the single undercut area 155, the minimum clamping distance is at least equal to the width w2 of the second sealing land 154. It is noted that the first sealing land 156 extends around the circumference of the central axial bore 140 except in the single undercut area 155. A smaller second sealing land 154 is present between the single undercut area 155 and the first circumferential edge, so that there is either a single sealing land of a smaller width, w2 or a sealing land of a larger width, w1 around the entire circumference of the central axial bore 140. A third sealing land 158 is present between central axial bore 140 of the rotor assembly 405 and the outer diameter of the shank body 172 of the center bolt 170. With sealing lands 154, 156, 158 present around the entire circumference of the central axial bore 140, fluid can only flow through the single undercut area 155 and not across the interface 157. The first and second sealing lands 154, 156 also prevent air ingestion in the event of an engine condition of low source oil pressure or condition. While the third sealing land 158 is shown between a center bolt 170 and the central axial bore 140, the third sealing land 158 could instead be formed between the central axial bore 140 and a sleeve of a spool valve that does not use a center bolt.
The second end plate 100b has a multistep bore 160 which receives a center bolt 170. The center bolt 170 has a shaft 171 connected to a shank body 172. The shaft 171 can have threads 174. The shank body 172 is connected to a head 175. A bore 176 is present in the head 175 and shank body 172 and is connected to a through passage 177 in the shaft 171 of the center bolt 170. The center bolt 170 is received within the central axial bore 140 of the central hub 105c of the rotor assembly 105 and the camshaft 126. Therefore, the shaft 171 is present within a bore 126b of the camshaft 126, the shank body 172 is present within the rotor assembly 105 and the head 175 is present adjacent the rotor assembly 105 and within the second end plate 100b of the housing assembly 100.
Received within the bore 176 of the head 175 and shank body 172 of the center bolt 170 is a spool valve 409. Supply 200 provides hydraulic fluid to the spool valve 409 through line 418 by flowing through the stepped central bore 126b of the camshaft 126 as described in further detail below.
The head 175 of the center bolt 170 present within the bore 160 of the second end plate 100b is aligned with an actuator 220, such that the actuator 220 actuates the spool valve 409 present within the bore 176 of the shank body 172 of the center bolt 170. In this embodiment, a variable force solenoid (VFS) 220 actuates the spool valve 409 against the force of spring 405 through plug 437a.
Referring to
The interface 153 between the first face 105a of the rotor assembly 105 and the end 126a of the camshaft 126 is a clamped interface. In one embodiment, clamping force is provided by tightening the center bolt 170 to the camshaft 126 through turning of the center bolt 170 within the central axial bore 140 of the rotor assembly 105 and the stepped central bore 126b of the camshaft 126 such that the threads 174 engage the stepped central bore 126b of the camshaft 126, drawing the camshaft 126 towards the rotor assembly 105. The clamping force prevents leakage across the first and second sealing lands 154, 156.
In another embodiment, clamping force can be provided by a plurality of small bolts connecting the end 126a of the camshaft 126 and the rotor assembly 105.
In yet another embodiment, the end 126a of the camshaft 126 is welded to the first face 100a of the rotor assembly 105.
In all of the embodiments, a minimum clamping distance is maintained between the first face 105a of the rotor assembly 105 and the end 126a of the camshaft 126 that prevents fluid from leaking between the inner diameter defining bore 126b of the camshaft 126 to the outer diameter 126a of the camshaft 126 and to the crankcase. In one example, the minimum clamping distance is 1.0 mm, but may vary based on mating surface conditions and material properties of the end 126a of the camshaft 126 or the first face 100a of the rotor assembly 105.
If the phaser was to be retarded as shown in
In a camshaft torque reversal, high oil pressure is generated in the advance chamber. The fluid in the advance chamber is expelled into the rotor annulus 190 through advance port 180 and into port 426. The high pressure oil overcomes the force of spring 432b and moves disc 431b to an open position, allowing the high pressure oil to mix with source oil. The oil then passes through sleeve port 427 to retard port 182 and to rotor annulus 191. The oil then enters the retard chamber, thus retard the phaser.
If the phaser was to be advanced (not shown), fluid flows, from the source 200 through intersecting cross bore 202 into the stepped central bore 126b, around the shaft 171 of the center bolt 170 to the single undercut area 155. From the single undercut area 155, fluid flows into passage 230 and through the intake check valve 232 and flows to supply passage 418. From supply passage 418, fluid flows through port 181 into the center bolt 170. From port 181, fluid flows through the cylindrical sleeve 425 and to lands 409a and 409b via the central spindle 409c of the spool valve 409.
In a camshaft torque reversal, high oil pressure is generated in the retard chamber. The fluid in the retard chamber is expelled into the rotor annulus 191 through retard port 182 and into port 427. The high pressure oil overcomes the force of spring 432a and moves disc 431a to an open position, allowing the high pressure oil to mix with source oil. The oil then passes through sleeve port 426 to advance port 180 and to rotor annulus 190. The oil then enters the advance chamber, thus advancing the phaser.
It is also noted that while not shown, fluid from the passage connected 230 to the undercut supply passages 150 can also supply source oil to a lock pin 163 to control locking and unlocking of the phaser.
It is noted that by adding a single undercut supply passage 150 with axial and radial components 151, 152 to the rotor assembly 105, shorter axial packaging is achievable as the source annulus is packaged in the camshaft 126 and not in the rotor assembly 105. Furthermore, the camshaft 126 provides a combination of supply oil feed and a vent to the crankcase as the center bolt 170 is used to separate the two different flow paths. Additionally, with the source or inlet check valve 232 in the rotor assembly 205 can be packaged off to the side of the rotor assembly 105. This enables shorter axial packaging as the inlet check valve 232 can be packaged radially instead of requiring additional axial length of the inlet check valve 232 to reside.
Additionally, undercut supply passage 150 with axial and radial components 151, 152 can improve fluid flow by reducing pressure drops between the camshaft and the source check disc via larger cross-section and shorter length.
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
