MOUNTING OF AN SCP CAMSHAFT ON AN ENGINE

Abstract

A method disclosed for mounting a camshaft and a phaser on an engine, the camshaft being an SCP camshaft formed of concentric inner and outer rotary members each fast in rotation with a respective one of two groups of cams and the phaser enabling the phase of at least one of the rotary members of the camshaft to be varied dynamically relative to the phase of the engine crankshaft and the other rotary member. The method comprises first securing the phaser 30 to one end of the camshaft 10, then mounting the camshaft and phaser as a sub-assembly to the engine, and subsequently securing to the engine an abutment 40 for limiting the axial displacement of the camshaft relative to the engine.

Description

FIELD OF THE INVENTION

The invention relates to the mounting on an engine of an SCP camshaft formed of concentric inner and outer rotary members each fast in rotation with a respective one of two groups of cams and a phaser for enabling the phase of at least one of the rotary members to be varied dynamically relative to the phase of the crankshaft and the other rotary member. This type of camshaft is termed an SCP (single cam phaser) camshaft because it allows the timing of two groups of cams to be varied in relation to one another using a single camshaft by relative rotation of the camshaft tube and the inner drive shaft.

The invention is particularly applicable to an SCP camshaft that has large camshaft bearings and is assembled to the engine from one end of a bearing bore in the cylinder block or cylinder head. Such applications generally utilize a thrust plate to control the axial position of the camshaft within the cylinder head or cylinder block.

BACKGROUND OF THE INVENTION

Many different designs of SCP camshaft are known from the prior art and each requires a method for driving the camshaft from the crankshaft and for introducing a phase shift in the timing of the camshaft tube and/or drive shaft. Generally the phaser requires two driving connections to the SCP camshaft, one to drive the camshaft tube and one to drive the inner shaft. The driving connections can be particularly difficult to design when the camshaft thrust plate is located between the phasing system and the front of the camshaft. Because of this, the phaser conventionally needs to be removed in order to access the fixings securing the thrust plate to the front of the cylinder head or block.

OBJECT OF THE INVENTION

The aim of the present invention is therefore to simplify the mounting of an SCP camshaft on an engine.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a method of mounting a camshaft and a phaser on an engine, the camshaft being an SCP camshaft formed of concentric inner and outer rotary members each fast in rotation with a respective one of two groups of cams and the phaser enabling the phase of at least one of the rotary members of the camshaft to be varied dynamically relative to the phase of the engine crankshaft and the other rotary member, which method comprises securing the phaser to one end of the camshaft, mounting the camshaft and phaser as a sub-assembly to the engine, and subsequently securing to the engine an abutment for limiting the axial displacement of the camshaft relative to the engine.

In a second aspect of the invention, there is provided an engine having a crankshaft, a camshaft formed of concentric inner and outer rotary members each fast in rotation with a respective one of two groups of cams, and a phaser mounted on the camshaft to enable the phase of at least one of the rotary members to be varied dynamically relative to the phase of the crankshaft and the other rotary member, wherein a thrust plate is integrated as part of the camshaft and phaser assembly, the thrust plate being securable in place after the camshaft and phaser have been fitted to the cylinder block or cylinder head of the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an end view of a camshaft and phaser assembly of a first embodiment of the invention,

FIG. 2 is a section in the plane II-II of FIG. 1,

FIG. 3 is an end view of a camshaft and phaser assembly of a second embodiment of the invention,

FIG. 4 is a section in the plane IV-IV in FIG. 3,

FIG. 5 is a perspective view from the rear of the camshaft and phaser sub-assembly of FIG. 4,

FIG. 6 is an end view of a camshaft and phaser assembly of a third embodiment of the invention,

FIG. 7 is a section in the plane VII-VII in FIG. 6,

FIG. 8 is an end view of a camshaft and phaser assembly of a fourth embodiment of the invention,

FIG. 9 is a section in the plane IX-IX in FIG. 8,

FIG. 10 is an end view of a camshaft and phaser assembly of a fifth embodiment of the invention,

FIG. 11 is a section in the plane XI-XI in FIG. 10, and

FIG. 12 is a perspective view from the front of the camshaft and phaser sub-assembly of FIG. 11.

DETAILED DESCRIPTION

In all the embodiments of the invention to be described herein, the camshaft is an SCP camshaft 10 comprising an inner shaft 12 rotatable relative to an outer tube 14. Cams 16 of a first set are directly mounted on the outer tube 14 for rotation with the outer tube 14 and cams 18 of a second set are free to rotate about the outer tube 14 and are connected for rotation with the inner shaft 12 by means of pins 20 that pass through circumferentially elongated holes in the outer tube 14. The outer tube is supported in the engine cylinder head or block (not shown) by means of bearing journals 13. The journals 13 are larger than the cams 16 and 18 so that the entire camshaft can be slid axially from the front end of the engine into bearing blocks in the engine.

The phaser 30 is a hydraulic vane type phaser having an input sprocket 32 driven from the engine crankshaft and two output members each connected to drive a respective one of the inner shaft 12 and the outer tube 14 of the SCP camshaft. The phaser need not be a vane-type phaser but vane-type phasers are preferred because of their small size. As the construction of both SCP camshafts 10 and phasers 30 are known, it is not deemed necessary for an understanding of the present invention to describe them in further detail in the present context.

FIGS. 1 and 2 show a first embodiment of the invention, where a camshaft thrust plate 40 is pre-mounted between the SCP camshaft 10 and the phaser 30 and the fixings of the thrust plate 40 are positioned such that they can be tightened after the camshaft and phaser have been assembled to the engine.

In this embodiment, it is possible to set the axial clearance of the inner drive shaft of the SCP camshaft in the camshaft tube and the axial clearance within the camshaft phaser with a single shim 42 at the rear of the camshaft, the shim 42 being retained in place by means of a circlip 44.

FIGS. 3 to 5 show a second embodiment of the invention, where a rear adjustment shim 142 also acts as the camshaft thrust plate. In this case, the SCP camshaft 10 and phaser 30 assembly is fitted from the front of the engine and then the rear thrust plate 142 and circlip 144 are fitted and screwed to the rear of the cylinder block/head. This obviates the need for a conventional thrust plate at the front of the engine.

The embodiment of FIGS. 6 and 7 has an alternative design of rear adjustment shim 242 that is retained on the inner shaft of the camshaft 10 by means of a bolt 246 rather than a circlip and cooperates with a thrust plate 244 to resist axial movement of the camshaft.

The embodiment shown in FIGS. 8 and 9 uses a rear engine cover 340 to resist axial movement of the camshaft. This embodiment also employs a further alternative design of a combined clearance adjustment shim and rear thrust plate 342 that is secured to the rear of the camshaft by a bolt 346. The thrust plate 342 controls the axial camshaft position by contacting the rear of the cylinder block 350 and a thrust face provided in the rear cover 340 fitted over the rear of the camshaft. A rear cover of this sort is conventionally used in some engines to retain oil in the rear camshaft bearing and to mount the rear crankshaft oil seal.

The embodiment of the invention shown in FIGS. 10 to 12 uses a shim 442 at the rear end of the camshaft 10 to control the axial clearance of the SCP camshaft and phaser assembly, but does not use a thrust plate at the rear to control the axial position of the camshaft in the engine. Instead the camshaft axial position in the engine is controlled between the front of the cylinder block and the inside of a cover 450 fitted to the front of the engine. A face is provided on the rear of the phaser assembly 30 to resist thrust by contacting the front of the cylinder block and a face is provided on the front of the phaser or camshaft to resist axial thrust by contacting the inside of the front cover 450.

It is envisaged that in this embodiment of the invention the front cover may be fitted with an oil-feed spigot 460 against which the camshaft/phaser thrust would also be resisted. The oil-feed spigot 460 is threaded into the cover 450 with a coarse thread so that its position can be altered by a small angle of rotation in order to set the end float of the camshaft once the cover has been fitted to the engine. The spigot is secured in position by a locknut 462 fitted to the outside of the cover 450 and a seal 464 is provided between the spigot 460 and its counter bore in the cover to make sure that there is no leakage between oil feeds. This spigot design has the advantage of ensuring that the oil ways in the spigot line up with the corresponding oil passages in the phaser because the spigot is controlling the axial position of the phaser.

In some cases the control oil feeds are fed to the phaser via the front camshaft bearing, in which case the cover could be provided with an adjustable thrust plate of a much simpler design because it would not have any internal oil passages.

The various embodiments of the invention described above offer the following advantages when compared to existing designs:

• • The timing of the phaser and camshaft is fixed before assembly to the engine.
  • The phaser does not need to be a separate unit that can be handled in isolation from the camshaft, which allows greater design integration of the two parts.
  • The end float of the phaser and the inner drive shaft within the camshaft tube may be set with a single ‘shim’ for the whole assembly.
  • The thrust plate need not compromise the design of the phaser connection to the camshaft.

Claims

1. A method of mounting a camshaft and a phaser on an engine, the camshaft being an SCP camshaft formed of concentric inner and outer rotary members each fast in rotation with a respective one of two groups of cams and the phaser enabling the phase of at least one of the rotary members of the camshaft to be varied dynamically relative to the phase of the engine crankshaft and the other rotary member, which method comprises securing the phaser to one end of the camshaft, mounting the camshaft and phaser as a sub-assembly to the engine by sliding the camshaft axially from the front end of the engine into bearing blocks in the engine, and subsequently securing to the engine an abutment for limiting the axial displacement of the camshaft relative to the engine.

2. A method as claimed in claim 1, wherein the abutment is formed as a thrust plate integrated as part of the camshaft and phaser sub-assembly.

3. A method as claimed in claim 1, wherein the abutment comprises a thrust plate located on the opposite end of the camshaft from the phaser.

4. A method as claimed in claim 1, wherein the abutment is constituted by an engine front cover contacting the front face of the phaser.

5. (canceled)

6. An engine having a crankshaft, a camshaft formed of concentric inner and outer rotary members each fast in rotation with a respective one of two groups of cams, bearing Journals on the camshaft having a larger radius than the largest cam lobe radius to enable the camshaft to slide axially from the front end of the engine into bearing blocks in the engine, a phaser mounted on the camshaft to enable the phase of at least one of the rotary members to be varied dynamically relative to the phase of the crankshaft and the other rotary member, and a thrust control member capable of being secured to the engine after the camshaft and phaser have been fitted as a sub-assembly to the cylinder block or cylinder head of the engine.

7. An engine as claimed in claim 6, wherein a thrust plate serves to control the axial position of the camshaft relative to the engine and is Located on the opposite end of the camshaft from the phaser.

8. An engine as claimed in claim 6, wherein the axial position of the camshaft is defined by the rear of a cylinder block or cylinder head and a surface of a cover fitted to the rear of the engine.

9. An engine as claimed in claim 6, wherein the axial position of the camshaft is determined in use by the phaser coming into contact with a front face of a cylinder block or a cylinder head and a surface of a cover fitted to the front of the engine and overlying the phaser.

10. An engine as claimed in claim 9, wherein the front cover is fitted with an adjustable thrust member to allow the axial clearance of the camshaft to be set upon assembly of the engine.

11. An engine as claimed in claim 10, wherein the adjustable plate serves additionally to transmit oil to the phaser.

12. An engine as claimed in claim 6, wherein the axial clearance within the camshaft assembly and the phaser is controlled by a single shim.

13. An engine as claimed in claims claim 12, wherein the axial clearance adjusting shim acts as the thrust plate.