GB2622076A

GB2622076A - Camshaft phaser

Info

Publication number: GB2622076A
Application number: GB2212751.8A
Authority: GB
Inventors: Fernandez-Oxby Owen; Lees Robert; Walton Mark
Original assignee: Mechadyne International Ltd
Current assignee: Mechadyne International Ltd
Priority date: 2022-09-01
Filing date: 2022-09-01
Publication date: 2024-03-06
Also published as: US20240077004A1; GB202212751D0

Abstract

A phasing system for an internal combustion engine having a concentric camshaft. The phasing system comprises an annular stator 22 and first, radial phaser and a second, axial phaser. The stator is rotatable by an engine crankshaft and has inner and outer circumferences and two groups of arcuate cavities 44, 46, at least a first group of the cavities 44 interrupting the inner circumference. The first phaser has a hub 28 concentric with the camshaft and mounted within the centre of the stator, an outer circumference of the hub being in contact with the inner circumference of the stator to serve as a bearing, and a plurality of vanes 48 connected to the hub and extending radially into the first group of cavities to divide them into opposed working chambers. The second phaser comprises first and second end plates 30a, 30b on opposite sides of the stator and fastened to one another to axially seal the cavities in the stator, the end plates being connected to vanes 52 that extend axially through a second group of cavities 46 to divide the cavities into opposed working chambers.

Description

Camshaft phaser

FIELD

The invention relates to camshaft phasers, and particularly camshaft phasers for use with concentric camshafts.

BACKGROUND

A concentric camshaft has an inner shaft with an outer tube. The camshaft has two groups of cam lobes, one group connected for rotation with the outer tube and the other connected for rotation with the inner shaft. Such a configuration allows the two groups of cam lobes to be phased relative to each other when combined with a camshaft phasing system. The concentric camshaft allows the phase of one, or both, of the two groups of lobes to be controlled independently relative to the phase of the engine crankshaft. In a single camshaft engine for example this could allow independent control of intake and/or exhaust valve timing.

Camshaft phasing systems are known to include locking systems, employing locking pins, that act to ensure that the two groups of lobes remain in known positions when unable to be controlled by the phasing system during certain engine operating conditions, for example due to low engine oil pressures such as engine start-up/shut-down, or to act as a fail safe in case of component/software failure.

Dual independent camshaft phasing systems, such as that known from US 6,725,817, are well known for 'light duty' applications. These allow independent control of both sets zs of cam lobes in a concentric camshaft. A typical light duty application comprises either radially or axially stacked hydraulic, mechanical or electric phasers or hybrids combining more than one type, as disclosed in EP 2,456,961 and US 11,041,413. The phasers are arranged to drive the inner shaft or the outer tube of the concentric camshaft.

Being light duty applications, the camshaft's drive arrangement is usually via a drive sprocket utilising a belt or chain, but rarely a gear drive. Due to the restrictive packaging requirements in an automotive engine bay, drive sprockets are typically limited in -2 -diameter because, for example, increasing the diameter of the drive sprocket usually results in increased overall engine height. As such, in order to package within the engine, dual independent phasers of increased axial length are most common.

In a 'heavy duty' application, the camshaft drive arrangement is almost exclusively gear-s type, and these gears are often of much greater diameter than in light duty applications.

In addition, the multitude of machines with which heavy duty engines are designed to interface impose strict limits on the axial packaging space available for a cam phaser. This naturally limits the design of a dual independent camshaft phaser system to those which minimise axial length whilst making use of the increased radial space offered by the large gears. The minimum axial length of a hydraulic phasing system is physically limited by: a) the turning effort (torque) required of the phaser, as reducing the length of the phaser's hydraulic cavities reduces the area upon which the hydraulic fluid acts, reducing the torque output; and b) engagement lengths for mechanical features such as locking pins and threaded fasteners, which for a robust design require minimum engagement lengths; among other requirements. Therefore, a hydraulic phasing system with a reduced axial length requires novel solutions put forward in this application.

Gear-type drive arrangements, compared to belt or chain driven sprocket types (which make use of a flexible intermediary belt/chain to transmit drive), impose much stricter requirements on the positional accuracy and runout of each gear, as such, any camshaft phaser which mounts a gear must accurately position this gear relative to the camshaft's support bearings, which further complicates the design of the phasing system.

OBJECT

The invention seeks to provide a dual independent cam phaser which is applicable to heavy duty internal combustion engines, being capable of incorporation with a drive gear whilst minimising axial length

SUMMARY

According to the present invention, there is provided a phasing system as hereinafter set forth in Claim 1 of the appended claims Preferred features of the phasing system are set forth in claims 2 to 15 of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a concentric camshaft and a camshaft phasing system, Figure 2 is an exploded view of the phasing system shown in figure 1, Figure 3 is a section through a stator of a first embodiment of the phasing system, Figure 4 is a section through a stator of a second embodiment of the phasing system, Figure 5 is an exploded view of a locking pin, Figures 6a and 6b are sections through the phaser, showing the locking pin, deployed axially with respect to the camshaft, in a locked and an unlocked configuration, Figure 7 shows an exploded view of a stator and rotor having a locking pin deployed in a radial manner, Figure 8 shows a second embodiment of the rotor, and Figure 9 shows a spring and a spring holder mounted to the stator.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a dual independent camshaft phasing system 18 for use in a gear driven, cam-in-block internal combustion engine. The system 18 is mated to a concentric camshaft 10 having two groups of cam lobes 12, 14, mounted respectively for rotation with the outer tube and the inner shaft of the concentric camshaft 10, and bearings 16, 38 to allow the camshaft to rotate in the engine. the bearings 16, 38 may be rigidly mounted to the outer tube of the camshaft 10. The phasing system 18 serves to control the phase of the first and second group of cam lobes 12, 14 independently in relation to the crankshaft (not shown).

The camshaft 10 may further comprise a target wheel 20 for a sensor, the sensor being mounted to the engine (not shown). The sensor and target wheel 20 serve to detect the -4 -phase of the cam lobes relative to a part of the engine which is coupled to the crankshaft, such as a camshaft drive gear 22 In embodiments of the invention described below, the camshaft drive gear 22 serves as the stator of the phasing system.

The axial ends of inner shaft 24 and the outer tube 26 of the camshaft 10 are shown in Figure 2. The phasing system 18 comprises an annular stator 22, a first phaser output member 28 in the form of a hub concentrically positioned with the stator 22, a second phaser 30 output member comprising two end plates 30a, 30b axially straddling the stator 22, a spiral spring 32, a spring cover 34, and an inner fixation 36. The spring 32, cover 34, and inner fixation 36 are optional as they are not required to change the phase of the cam lobes 12, 14. Their purpose and construction will be described below in relation to figure 9.

The first phaser output member 28 is configured for rotation with the outer tube 26, and therefore the first group of cam lobes 12, by mounting its inner circumference directly to the outer tube 26 and fastening the first phaser output member 28 to a bearing 38 at the drive end of the camshaft 10, the bearing 38 being rigidly mounted to, and rotatable with, the outer tube 26 and having threaded holes therein to enable it to be secured to the first phaser output member 28 by means of fasteners 37 passing through arcuate slots 39 in the end plate 30b.

The second phaser is connected for rotation with the inner shaft 24 by means of a slot 40 located in the second end plate 30b. The slot 40 is of a shape complimentary to protrusions 42 on the inner camshaft 24, so that any rotational movement of the second end plate 30b results in corresponding rotation of the inner camshaft 24. The first end plate 30a and the second end plate 30b which sandwich the stator 22 between them and are connected to one another by fasteners 41 clamping through a plurality of vanes 52.

As known in the art, the cam lobes 14 of the second group are connected to the inner camshaft 24 by means of pins passing through circumferential slots in the outer tube 26, and into the lobes 14, the latter being free to rotate about the outer tube 26 The stator 22, as most clearly shown in figure 3, has a toothed outer circumference and is configured to be driven from the crankshaft by means of a gear train. The stator 22 comprises two sets of arcuate cavities 44, 46 each associated with a respective one of the output members. The cavities 44 in Figure 3 interrupt the inner circumference of the stator 22, and receive vanes 48 connected to the output member 28 of the first phaser.

On the other hand, the cavities 46 do not interrupt the inner circumference of the stator and they receive vanes 52 fastened to the plates 30a and 30b that together act as the output member of the second phaser.

The stator 22 is mounted to the outer diameter of the first phaser output member 28. As the output member 28 is mounted directly onto the outer tube 26, and the stator 22 is mounted to the outer diameter of the first phaser output member 28, the stator is thereby accurately positioned having its drive gear mounted concentrically to the camshaft 10. This is crucial to maximise component durability and reduce the running noise of the drive gear in operation. The accurate location of the stator 22 is more important in engines utilising gear-driven cams because there is no flexible element, such as a belt or chain, to accommodate any minor misalignment.

The number of cavities 44, 46 and their positions relative to each other are chosen such that the area of contact (the bearing area) between the inner circumference of the stator 22 and the outer circumference of the first phaser output member 28 is maximised. Maximising the bearing area helps to position the stator 22 accurately during assembly of the engine, and also reduces wear due to less pressure at the interface.

The first cam phaser output member 28 features radial slots extending inwards from its outer circumference. These slots allow the first phaser output member 28 to make use of vanes 48 which extend into the cavities 44 and act as a sealing wall, splitting each cavity 44 into two sections. As such, there will be as many slots and vanes 48 as there are cavities 44 for the first phaser output member 28. When hydraulic pressure is increased on one side of the vane 48, it will cause the vanes 48 to move within the cavities 44, thereby causing the phaser output member 28 to rotate. This ultimately leads to the first group of cam lobes 12 changing phase. The vanes 48 may be radially sprung such that -6 -the vane tips remain in light contact with the outer extremities of their cavities 44, thereby providing a suitable hydraulic seal Oil passageways 50 may be formed from axial and radial drillings in the first phaser output member 28 and serve to direct pressurised oil from oil control valves, located elsewhere in the engine, through the phaser output member 28 and to the hydraulic cavities 44, 46 of the first and second phasers 28, 30 as required by a control module (such as an ECU) of the engine.

The second cam phaser, as earlier mentioned, has a different construction from the first in order to maximise the aforementioned bearing area. The two end plates 30a, 30b are positioned either side of the stator 22 and are fastened together through the vanes 52. The cavities 46 associated with the second phaser 30 do not interrupt the internal circumference of the stator 22 and are instead radially and circumferentially enclosed by the stator 22. The first end plate 30a of the second phaser 30 includes vanes 52. The vanes 52 may be located on the face of the first end plate 30a by dowel pins 54, or alternatively formed as part of the end plate 30a. The vanes 52 associated with the second group of cavities 46 serve a similar purpose to the vanes 48 associated with the first group of cavities 44 in that they split each cavity 46 into two working chambers. The vanes 52 may comprise sprung sealing elements 56 to seal the cavity 46.

The inner circumference of the stator 22 features circumferential slots 62 so that hydraulic fluid can enter and exit the second group of cavities 46, and thereby control the phase of the second group of cam lobes 14, irrespective of the angular position of the first phaser output member 28 in relation to the stator 22.

The first end plate 30a of the second phaser 30 may further feature stiffening elements 58. The stiffening elements 58 may be fastened to the first end plate 30a in the same manner as the vanes 52 and serve to reduce the distance between fastenings holding the first and second end plates 30a, 30b together. The stiffening elements 58 have the same axial length as the vanes 52 and therefore together act to reduce the deflection of the end plates 30a, 30b when the system is under hydraulic pressure. Consequently, the level of leakage of hydraulic fluid is reduced. Further, the addition of stiffening elements 58 and -7 -fastenings reduces the stress placed on the fastenings located in the vanes 52. Arcuate slots 60 are provided within the stator 22 to allow clearance of the stiffening elements 58 throughout their range of motion.

An alternative embodiment of a phasing system is shown in figure 4. To avoid unnecessary repetition, components serving the same purpose as previously described have been allocated reference numeral with the same last two significant digits. In this alternative embodiment, the inner circumference of the stator 122 is interrupted by cavities 144 relating to the first phaser output member 128, but also by cavities 146 relating to the second phaser 130. Because the vanes 152 of the second phaser 130 are no longer enclosed by the cavity 146, the radially inner sealing element 156 runs directly on the outer circumference of the first phaser output member 128. Such a configuration has the benefit of simplifying manufacture of the stator 122 because, for example, circumferential slots 62 are no longer required. This therefore reduces manufacturing time and cost. Such a configuration is, however, at the expense of bearing area support for the stator 122.

In order to lock the rotational position of phasers 28 and 30 relative to the stator 22, locking pins as known in the art may be used Optionally, the intermeshing locking pin as shown in figures 5, 6a and 6b and described below may be implemented. An embodiment incorporating the intermeshing locking pin advantageously may further reduce the axial length of the phaser.

Figure 5 shows an intermeshing locking pin assembly 64 having three components, namely a pin 66, a spring 68, and a spring seat 70. The pin 66 is cylindrical in shape, and is hollow for receiving the spring 68, and comprises one or more circumferentially spaced axially extending slots 72 in its side wall. The spring seat 70, which may be a formed sheet metal part, has a generally disk like end plate with axially extending protrusions 74 from its perimeter. The seat 70 could take other forms if manufactured from other processes (e.g., sintering or metal injection moulding, etc.). The protrusions 74 on the seat 70 match and align with the slots 72 on the pin 66, so as to engage one another to prevent relative rotation and allow the protrusions 74 to slide within the slots 72 as the -8 -spring 68 is compressed. A spring guide 76 is also provided on the end plate of the spring seat The compression spring 68 acts on the spring seat 70 to urge the pin 66 away from the spring seat 70 into an extended position, thereby advancing the pin 66 as shown in figure 6a, when hydraulic pressure that forces the spring to compress is below a pre-set threshold This then locks the appropriate phaser output member 28, 30 for rotation with the stator 22. If hydraulic pressure is sufficient, the retracted position shown in figure 6b is adopted which allows rotation of the phaser output member 28, 30 relative to the stator io 22 The locking pin assembly 64 may be used in an axial or radial orientation, and so may be used to lock rotation of either the first phaser output member 28, the second phaser output member 30, or both. The advantage of using a locking pin arrangement with matching protrusions and slots is that the overall length of the pin assembly 64 can be reduced, whilst still maintaining the pin length required for adequate engagement in a phaser This reduction in length is particularly useful when the assembly 64 is disposed axially in relation to the camshaft 10, as it allows the axial length of the phaser, and therefore the engine as a whole, to be reduced. This is critical for heavy duty applications as explained above, where the axial dimension needs to be minimised due to the engine being used across multiple machines.

The locking device is housed within a member. Where disposed axially, the member may be the stator 22 having an axial through bore 78 (as shown in figures 2, 3, 4, 6a and 6b).

When disposed radially, the member may be a housing 80 (shown most clearly in figures 2, 7, and 8) which can be located within the stator 22. The spring seat 70 is an interference fit within the housing 80 or through bore 78, with the axial protrusions 74 increasing the area of interference and thereby aiding the alignment and security of the assembly 64.

During operation, hydraulic pressure acts on the end of the pin 66. If the hydraulic pressure is under a specified threshold, the spring force is sufficient such that the locking pin 66 remains in a hole, slot, indentation or similar 82, 84 provided in the first and second phaser output members 28, 30, as shown in figure 6a. In the advanced position, -9 -the protrusions 74 of the spring seat 70 must retain a minimum engagement into the locking pin slot 72. This is to ensure that the spring seat 70 and locking pin 66 are unable to rotate into misalignment relative to each other and lock the pin in the advanced position. When the force exerted by the pressurised oil exceeds the installed spring force, the locking pin 66 retracts from the hole 82 in the outer diameter of the first phaser output member 28, as shown in figure 6b, and/or the hole 84 formed in the first end plate 30a of the second phaser 30. Once this retraction has occurred, the phaser output members 28, 30 are able to rotate relative to the stator 22. Due to sufficient clearance, both radially and axially between the spring seat protrusions 74 and the lock pin slots 72, the locking pin 66 is not restricted through its range of motion and is able to fully retract into the stator 22.

In some embodiments, the hub constituting the first phaser output member 28 is formed using a process of sintering from powdered metal as shown in figure 8. In such embodiments, the hole 82 may instead be a through slot 182. Such a configuration allows the slot 182 to be formed during the compaction step of the sintering process, thereby reducing the cost of manufacture.

The above-described phaser system 18 may also make use of a spiral spring 32 in order to improve the performance balance of the system. As shown in Figure 9, the spiral spring 32 follows the form of a square inner fixation 36 and then spirals radially outward towards the outer diameter of the spring cover 34, and hooks around a peg 86 provided on the stator 22. Various other methods of mounting the spring will also be apparent to the skilled person. The spring cover 34 may cover the entire spring 32. It may also provide a camshaft position sensor target in the form of circumferential slots 88.

It should be noted that the above description describes only a small number of possible embodiments and should not be interpreted as limiting. Various modifications or adaptations may be made by the skilled person without departing from the scope of the appended claims. For example, the inner shaft of the concentric camshaft may be tubular.

In another example, the slot 40 and protrusion interface between the second end plate 30b of the second phaser 30 and the inner shaft 24 may be switched, meaning that the inner shaft features a slot into which protrusions of the second phaser fit. Further, the -10 -vanes 48 of the first phaser output member 28 may be integrally formed with the main hub of the phaser.

Claims

-11 -CLAIMS 1. A phasing system for an internal combustion engine having a concentric camshaft, the phasing system comprising: an annular stator, rotatable by the crankshaft of the internal combustion engine, having an inner circumference, an outer circumference, and two groups of arcuate cavities, at least a first group of the cavities interrupting the inner circumference of the stator; a first phaser having an output member in the form of a hub to be concentrically located relative to the camshaft and mounted within the centre of the stator, the outer circumference of the output member being in contact with the inner circumference of the stator to serve as a bearing for the stator, the first phaser further having a plurality of vanes connected to the output member and extending radially into the first group of cavities to divide the cavities into opposed working chambers; and a second phaser comprising a first end plate and a second end plate located on opposite sides of the stator and fastened to one another in order to axially seal the cavities in the stator, the end plates serving as the output member of the second phaser and being connected to vanes that extend axially through the second group of cavities to divide the cavities into opposed working chambers.
2. The phasing system of claim 1, wherein the second group of cavities also interrupts the inner circumference of the stator.s The phasing system of claim 1 or 2, wherein the output member of the first phaser features oil passageways for both groups of cavities.4. The phasing system of any preceding claim, wherein the second phaser comprises stiffening elements extending between the end plates that serve as the output member of the second phaser, the stiffening elements extending through arcuate slots formed in the stator.-12 - 5. The phaser of any preceding claim, further comprising at least one locking pin assembly disposed within the stator, for locking the stator relative to the output member of at least one of the phasers 6. The phaser of claim 5, wherein the locking pin assembly comprises a pin, a spring having one end received within a hole in the pin, and a spring seat abutting the opposite end of the spring, and wherein the seat has a plurality of axially extending protrusions about its perimeter, aligned with matching slots in the side wall of the pin.7. The phaser of any of claims 5 or 6, wherein the locking pin assembly is disposed axially with respect to the camshaft.8. The phaser of claim 7, wherein the locking pin assembly is located within a through hole in the stator.9. The phaser of any of claims 5 to 8, further comprising a second locking pin assembly disposed within the stator.The phaser of claim 9, wherein the second locking pin assembly is disposed radially with respect to the camshaft.11 The phaser of claim 10, wherein the second locking pin assembly is disposed within a housing.12. The phaser of claim 10 or 11, wherein the first phaser output member features a through slot on its outer circumference configured to receive the pin of the second locking pin assembly.13. The phaser of any preceding claim, further comprising a spiral spring for applying a balancing torque to the output member of at least one of the two phasers.