Patent Application
20170175591
This application claims priority to European patent application no. 15307043.8 filed on Dec. 17, 2015, the contents of which are fully incorporated herein by reference.
The present invention relates to the field of cam follower roller devices used in automotive or industrial applications.
One advantageous application of the invention is the use of the cam follower roller device in a fuel injection pump intended for an internal combustion engine, in particular of a motor vehicle. Another advantageous application of the invention is the use of the device in a rocker system intended for controlling valves of an internal combustion piston engine.
Such a cam follower roller device generally provides an outer tappet body, a pin mounted on the tappet body and a roller movable in rotation relative to the pin around its axis. When the cam follower roller device is in service in a fuel injection pump, the roller collaborates with a cam synchronized with the internal combustion engine camshaft or crankshaft. The rotation of the camshaft, or crankshaft, leads to a periodic displacement of a piston of the pump that rests against the tappet body, to allow fuel to be delivered.
In operation, the device is intended to slide back and forth into a housing, such as a pump housing. Generally, there is an angular misalignment between the axis of the tappet body and the axis of the associated housing. Accordingly, edge stresses may occur at the ends of the roller of the device with the contact against the cam. Accordingly, in operation, the pressure contact between the roller and the cam may be increased.
One aim of the present invention is to overcome these drawbacks.
It is a particular object of the present invention to provide a cam follower roller device having a design adapted to reduce edge stresses on the roller in operation.
In one embodiment, the cam follower roller device provides a tappet body, a pin and a roller mounted on the pin, the tappet body comprising holes for mounting pin ends of the pin on the tappet body. The device further provides one deformable ring disposed between each pin end of the pin and an inner wall of the associated hole of the tappet body.
With such a disposition of each deformable ring, a flexible connection is provided between the pin supporting the roller and the tappet body rather than a rigid connection. With regard to an axis of the pin, each deformable ring is radially disposed between each pin end and the inner wall of the associated hole of the tappet body.
Accordingly, the axis of the pin may tilt relative to a rear abutment surface of the tappet body against which a movable element is intended to bear. When the device is in service in a fuel injection pump, the piston of the pump rests against the rear abutment surface.
The pin supporting the roller is able to move angularly relative to the tappet body to accommodate angular misalignment between the axis of the tappet body and the axis of a housing into which is mounted the device, such as a pump housing. When such a tilting occurs, the rings are deformed. The edge stresses that may occur at the ends of the roller with the contact against the associated cam is reduced. Accordingly, in operation, the pressure contact between the roller and the cam may be reduced.
Preferably, each deformable ring is secured to the tappet body.
Advantageously, an outer surface of each deformable ring is in radial contact with the inner wall of the associated hole of the tappet body.
In one embodiment, a bore of each deformable ring is in radial contact with the associated pin end of the pin. Accordingly, each deformable ring is radially interposed between the associated pin end and the inner wall of the associated hole of the tappet body.
In another embodiment, the device further provides one sleeve interposed between each pin end of the pin and the associated deformable ring. With regard to the axis of the pin, the sleeve is radially interposed between each pin end and the associated deformable ring. Each pin end may be press-fitted into the associated sleeve.
Each sleeve may provide at least one tubular portion interposed between each pin end and the associated deformable ring. In one embodiment, each sleeve provides only the tubular portion. Alternatively, each sleeve may further provide a radial flange connected to the tubular portion and extending radially outwards, the radial flange being axially located on the side opposite to the roller with respect to the tappet body. The radial flange may extend one end of the tubular portion. The radial flange may also come into contact with the associated deformable ring and/or the tappet body. Each sleeve may be made advantageously from rigid material, such as metal.
In one embodiment, each deformable ring is made from deformable material, preferably elastically deformable material. The deformable ring may be made from synthetic material such as plastic material or elastomer or nitrile rubber or polyurethane. The tappet body may be made advantageously from rigid material, such as metal.
The present invention and its advantages will be better understood by studying the detailed description of specific embodiments given by way of non-limiting examples and illustrated by the appended drawings on which:
As shown on
The pin 14 is mounted on the tappet body 12. The tappet body 12 supports the pin 14. The pin 14 provides two opposite pin ends 14b, 14c and a central portion (not referenced) extending between the pin ends. The central portion of the pin delimits a cylindrical outer bearing seat for the roller 16. The portion of the pin 14 left free by the tappet body 12 delimits the central portion. The pin ends 14b, 14c extend axially on either side of the roller 16. The tappet body 12 provides through-holes 12b, 12c for mounting the pin ends 14b, 14c. The through-holes face one another.
As will be described later, the device 10 further provides two annular deformable rings 18, 20 each radially interposed between one of the pin ends 14b, 14c and an inner wall of the associated through-hole 12b, 12c of the tappet body.
In the disclosed example, the tappet body 12 is made in one part. The tappet body 12 delimits a first open cavity 22 inside which is located the roller 16. The roller 16 is mounted inside the cavity 22. The roller 16 axially protrudes outwards with respect to an upper face (not referenced) of the tappet body. The tappet body 12 also delimits a second open cavity 24 oriented axially on the side opposite to the cavity 22. A movable element (not shown), such as a piston of a fuel injection pump, is intended to extend into the cavity 24 and to axially bear against a rear abutment surface 26 of the tappet body. The rear abutment surface 26 is oriented axially on the side opposite to the roller 16. The rear abutment surface 26 is planar and extends radially.
The tappet body 12 provides an outer axial sleeve portion 12d and an inner radial portion 12e extending radially an inner bore of the sleeve portion. The radial portion 12e delimits the rear abutment surface 26. The sleeve portion 12d has a tubular form. The through-holes 12b, 12c are formed on the axial sleeve portion 12d. The through-holes 12b, 12c are made into the thickness of the sleeve portion 12d and open into the cavity 22. Each through-hole 12b, 12c is delimited in the radial direction by its inner wall or bore. The cavity 22 is delimited axially by the radial portion 12e. The cavity 22 is delimited radially by the bore of the sleeve portion 12d. Similarly to the cavity 22, the cavity 24 is delimited axially by the radial portion 12d and radially by the bore of the sleeve portion 12e. The cavities 22, 24 are disposed on either side of the radial portion 12e.
Each pin end 14b, 14c is mounted into the deformable ring 18, 20 itself inserted into the associated through-hole 12b, 12c of the tappet body. Each deformable ring 18, 20 is radially located between the pin end 14b, 14c and the inner wall of the associated through-hole 12b, 12c. In the illustrated example, each deformable ring 18, 20 is in radial contact with the pin end 14b, 14c on one side and in radial contact with the tappet body 12 on the other side. Each deformable ring 18, 20 comes radially into contact with the inner wall of the associated through-hole 12b, 12c. Each deformable ring 18, 20 comes radially into contact with the outer surface of the associated pin end 14b, 14c. Accordingly, as previously mentioned, each deformable ring 18, 20 is radially interposed between one of the pin ends 14b, 14c and the tappet body 12.
Each deformable ring 18, 20 provides an axial cylindrical outer surface 18a, 20a in radial contact with the bore of the associated through-hole 12b, 12c, and a cylindrical bore 18b, 20b radially opposed to the outer surface and in radial contact with the outer surface of the associated pin end 14b, 14c.
Each deformable ring 18, 20 also provides two opposite inner and outer lateral surfaces (not referenced) which axially delimit the outer surface 18a, 20a and the bore 18b, 20b. In the illustrated example, the inner lateral surface of each ring 18, 20 is axially offset outwards with respect to an inner wall of the tappet body. Alternatively, the inner lateral surface may be coplanar with the inner wall or may axially slightly protrude towards the roller 16. An axial gap 28, 30 is provided between each frontal surface of the roller and the tappet body 12.
Each deformable ring 18, 20 is secured to the tappet body 12. Each deformable ring 18, 20 is secured into the associated through-hole 12b, 12c, by any appropriate means, for example by gluing or overmoulding. Each deformable ring 18, 20 is made from deformable flexible material, for example elastically deformable material. Each deformable ring 18, 20 may be made from synthetic material such as plastic material or elastomer or nitrile rubber or polyurethane.
With the disposition of the deformable rings 18, 20 between the pin ends 14b, 14c of the pin and the through-holes 12b, 12c of the tappet body 12, a flexible connection is provided between the pin and the tappet body. Accordingly, an angular tilting of the pin 14 supporting the roller 16 with respect to the tappet body 12 may be obtained. The axis 14a of the pin may tilt angularly relative to the abutment surface 26 of the tappet body. Such a tilting may be obtained since the axial gaps 28, 30 are provided between the roller 16 and the tappet body 12. The deformable rings 18, 20 are locally compressed in this case.
When the device 10 is mounted into the associated housing, such as a pump housing, the pin 14 is able to move angularly relative to the tappet body 12 to accommodate angular misalignment between the axis of the housing and the axis 12a of the tappet body. With a contact between the roller 16 of the device and the cam of the internal combustion engine, the roller supported by the pin 14 may tilt angularly relative to the tappet housing 12. This has the effect of reducing the edge stresses that may occur at the ends of the roller 16. Accordingly, in operation, the pressure contact between the roller 16 and the cam may be reduced.
The example illustrated on
Each deformable ring 18, 20 is in radial contact with the associated sleeve 32, 34 on one side and in radial contact with the tappet body 12 on the other side. Each deformable ring 18, 20 comes radially into contact with the outer surface of the associated sleeve 32, 34. The bore 18a, 20a of each deformable ring is mounted in radial contact with the associated sleeve 32, 34. Each pin end 14b, 14c of the pin is inserted into an axial bore or hole delimited by the associated sleeve 32, 34. Each pin end 14b, 14c is fixed into the hole of the associated sleeve 32, 34 for example by push-fitting. Preferably, each sleeve 32, 34 is made from metal. Alternatively, each sleeve may be made from other rigid material, for example from a synthetic material such as PA.
Each sleeve 32, 34 provides an axial tubular portion 32a, 34a delimiting the outer surface in contact with the associated deformable ring 18, 20 and the hole into which is inserted the associated pin end 14b, 14c. The tubular portion is radially interposed between each pin end 14b, 14c and the associated deformable ring 18, 20.
Each sleeve 32, 34 further provides a radial flange 32b, 34b extending radially outwards from one end of the tubular portion 32a, 34a. Each flange 32b, 34b is axially located on the side opposite to the roller 16 with respect to the tappet body 12. In the illustrated example, each flange 32b, 34b comes axially into contact with the outer lateral surface of the associated deformable ring 18, 20 and with the tappet body 12. Alternatively, a slight axial gap may be provided therebetween. The flange 32b, 34b of each sleeve prevents an axial flow or creep of the associated deformable ring 18, 20 when a tilting of the pin 14 occurs. However, in another embodiment, it could be possible to design the sleeves 32, 34 without the flanges.
In the illustrated examples, each deformable ring of the device is made from an elastically deformable material. Alternatively, each deformable ring may be made from a plastically deformable material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 15307043.8 | Dec 2015 | EP | regional |
