Pulley tensioner for a belt drive for use in contact with oil
A tensioner for a belt drive comprises a pivot defining an axis, a support hinged to the axis and defining a guiding surface preferably having a circular profile, an elastic element for actuating the support and a crown pulley eccentric with respect to the axis and surrounding the guiding surface. The tensioner further comprises a journal bearing to support the pulley on the guiding surface.
1. A tensioner for a belt drive comprising a pivot defining an axis (A), a support hinged to said axis (A) and defining a guiding surface having a circular profile, an elastic element for actuating said support and a crown pulley mounted on said support about said guiding surface and rotatable about a second axis (B) eccentric with respect to said axis (A), and a journal bearing to support said pulley on said guiding surface wherein said journal bearing comprises a first conduit transversal to said axis (A) and defining an outlet for feeding oil onto said guiding surface, and said guiding surface is axially delimited by first and second shoulders and defines an axially symmetric recess fluidly connected to said first conduit to exert a symmetric action on said pulley.
2. A tensioner according to claim 1 , wherein said support is manufactured in a material having a first thermal expansion coefficient and in that said pulley is manufactured in a material having a second thermal expansion coefficient lower than said first thermal expansion coefficient.
3. A tensioner according to claim 1 , further comprising a ring axially interposed between one of said first and second shoulders and said pulley.
4. A tensioner according to claim 3 , wherein said first conduit ( 31 ) is defined by said support ( 4 ).
5. A tensioner according to claim 4 , wherein said pivot defines a second conduit adapted to be fed by a flow rate of pressurised fluid and fluidly connected to said first conduit.
6. A tensioner according to claim 5 , wherein said support is radially supported on said pin by means of a bushing defining a gap to allow the passage of oil between said first conduit and said second conduit.
7. A tensioner according to claim 1 wherein at least one of said first and second shoulders is defined by an elastic ring.
8. A tensioner according to claim 7 , wherein said seal comprises an o-ring carried by said support and cooperating with said pin.
9. A tensioner according to claim 1 , further comprising a seal to avoid leakage of oil along an axial direction.
10. A tensioner according to claim 9 , wherein said seal comprises an element loaded in axial direction by means of a second elastic element.
11. A tensioner according to claim 10 , further comprising a friction element ( 9 ) cooperating in relative motion with a contact surface ( 11 ) transversally arranged with respect to said axis (A), said elastic element ( 12 ) maintaining contact with said friction element ( 9 ) and said contact surface ( 11 ).
12. A tensioner according to claim 11 , wherein said friction element ( 9 ) presents at least one groove ( 10 ) facing said contact surface ( 11 ).
13. A tensioner according to claim 1 , wherein said first conduit precedes the resultant of the action of said belt on said pulley by an angle comprised between 60° and 130°.
14. A tensioner for a belt drive comprising:
a pivot defining an axis (A),
a support hinged to said axis (A) and having a guiding surface with a circular profile,
an elastic element for actuating said support,
a crown pulley mounted on said support about said guiding surface and rotatable about a second axis (B) eccentric with respect to said axis (A),
a journal bearing to support said pulley on said guiding surface and adapted to be fed by a flow rate of pressurised fluid with the fluid flow for the journal bearing passing through interconnected conduits defining a specific path through the pivot and through said support, and
a seal radially positioned between the pivot and the support to avoid oil leaks in an axial flow direction.
15. A tensioner according to claim 14 , wherein said support is manufactured in a material having a first thermal expansion coefficient and in that said pulley is manufactured in a material having a second thermal expansion coefficient lower than said first thermal expansion coefficient.
16. A tensioner according to claim 15 , wherein said journal bearing includes a first conduit positioned transverse to said axis A and an outlet for feeding oil onto said guiding surface.
17. A tensioner according to claim 16 , wherein said guiding surface is axially delimited by a first and second shoulders and defines an axially symmetric recess fluidly connected to said first conduit to exert a symmetric action on said pulley.
18. A tensioner according to claim 14 , further comprising a sealing element loaded in axial direction by means of a second elastic element to avoid leakage of oil along an axial direction.
19. A tensioner for a belt drive comprising a pivot defining an axis (A), a support hinged to said axis (A) and defining a guiding surface having a circular profile, an elastic element for actuating said support and a crown pulley mounted on said support about said guiding surface and rotatable about a second axis (B) eccentric with respect to said axis (A), and a journal bearing to support said pulley on said guiding surface, said journal bearing comprising a first conduit positioned transverse to said axis (A) and defining an outlet for feeding oil onto said guiding surface, and said first conduit precedes the resultant of the action of said belt on said pulley by an angle comprised between 60° and 130°.