FR2542372A1 - Rocker arm and its method of manufacture - Google Patents

Abstract

The invention relates to a method for manufacturing rocker arms 1 for internal combustion engines comprising movable valves, consisting in moulding in one piece a plate 1003 made of a sintered ferrous alloy with an arm 1001 made of aluminium alloy, in forming a thin film on the outer peripheral surface of the said plate 1003, in forming a porous layer of anodic oxide on the arm 1001 which is then electrolysed in a bath of ammonium thiomolybdate, in forming molybdenum sulphide in the said pores, and finally in removing the said thin film. The invention also relates to a rocker arm 1 comprising an arm 1001 made of aluminium alloy on which is formed a porous layer of anodic oxide whose pores are filled by molybdenum sulphide, and a plate 1003 moulded in one piece with the said arm 1001 and coming into sliding contact on a control cam. This rocker arm 1 has a better resistance to deterioration due to wear and does not require a lining when it is equipped with a unit compensating for the valve play 3.

Description

25423 12

  The present invention relates to a rocker arm for engines with

  internal bust including a set of movable valves, and also features

  a process for manufacturing these rocker arms As the intake and exhaust valves of internal combustion engines are subject to wear due to their use, it is necessary to repair and / or periodically replace the sliding surfaces or to compensate for the play of these surfaces

  friction between the valve seat and the valve head would cause the former

  upper end of the valve stem to be pushed, under the effect of the

  valve comes out, towards the rocker arm, which would not result in a situation

  ation in which the rocker arm would permanently exert pressure on the valve and degrade the tightness of the cylinder Friction between the face

  upper part of the valve stem and the contact surface of the rocker arm increased

  lie between these two elements, which would result in a

  increase in noise and a decrease in output Consequently we use

  reads a play compensator, of the oleopneumatic type, for mainte-

  make contact between the rocker arm and the valve constantly and in

optimal conditions.

  FIG. 1 represents a rocker arm of the prior art, in which a rocker arm 1 is arranged on a rocker arm shaft 300 so as to oscillate

  in correspondence with the rotation of a camshaft 500 and to be moved vertically

  the axial end of an intake or exhaust valve 400 by

  through a valve clearance compensator 3 This compensa-

  valve clearance valve 3 is mounted on a cylindrical element formed in the rocker arm To prevent this cylindrical element from deforming prematurely due to insufficient rigidity, a cylindrical lining 2 is provided in iron or copper This type of device, widely used today

  in the form of a light alloy rocker arm, is preferably used to reduce

  ire its inertia, in order to increase the speed of the motor.

  In other words, the lining is made necessary by the ra-

  following sounds: 1 When the pressurized oil supply device fails, due to a failure or the engine stops, the body 130 of the valve clearance compensator has a stroke of only O to 2 mm , which represents the automatic valve clearance compensation stroke, which prevents homogeneous lubrication of the body; 2 Like the point of contact of a projection 131 situated at the end

  of the body 130 and of the axial end of the valve 400 accompanies the movement

  Oscillating of the rocker arm during the movement of a valve, the body 130 is subjected to intermittent lateral pressures and twists in the clearance space at the junction point of the cylinder, which in turn results in contacts between parts metallic If light alloys are used in this type of device, they are subject to degradation such as seizure

and abrasion.

  With regard to the cylindrical element, the use of a gasket

  When mounting the valve clearance compensator, this entails the following working steps: 1 Force fitting of the seal; and

2 lapping of the internal diameter.

  The grinding conditions and similar treatment must be adapted according to the packing used, which can be of iron or copper, and of the

  bottom of cylinder which is made of light alloy These operations require

  complex and multiple work weights, in addition to an increase in the weight of the packing It was therefore urgent to bring an improvement to

the state of the art.

  The object of the present invention is to offer an inexpensive method of

  manufacture of rocker arms resistant to damage and wear without using

  ser de garniture To achieve this aim, the present invention consists in

  ler in a single piece a sintered ferrous alloy wafer with an aluminum alloy arm, to form a thin film on the outer periphery of said wafer, to form a porous film of anodic oxide on the arm, which is then electrolysed in an ammonium thiomolybdate bath so

  to form molybdenum sulfide inside the pores, and to remove

following said thin film.

  The present invention further aims to provide a rocker which

  resists deterioration and wear without using a lining For reali-

  For this purpose, the present invention is characterized in that it provides an aluminum alloy arm on which is formed a porous film of anodic oxide in the pores of which molybdenum sulfide is formed, 3- as well as '' a plate which is molded in one piece with the said arm and

  which comes into sliding contact with a control cam.

  An embodiment of the present invention will now be described, by way of nonlimiting example, with reference to the accompanying drawings in which: FIG. 1 is a front view of a conventional rocker arm equipped with a play compensator device valve;

  Figure 2 is a view explaining the movement of a rocker rocker

  read according to the present invention; and

  FIG. 3 is a front view of an embodiment of a cul-

  scorer according to the present invention.

  In FIGS. 2 and 3, a rocker arm 1 comprises an arm 1001 and a plate 1003 of sintered alloy which is molded in one piece with the arm 1001 and comes into sliding contact with a lifting surface 501 and a> 15 guard 502 both arranged on a camshaft 500 Since the valve clearance compensator 3 does not have a lining,

  cylinder 1000 has a diameter substantially smaller than a suitable cylinder

  tional A hatched area A in FIG. 3 designates a plate 1003 and the

  adjacent area, which will be provided with a mask, while the zo-

  remainder of rocker arm 1001 will be subjected to an alunite treatment to

  add a solid lubricant This mask is produced by immersing zone A in an adherent bath of plastic or paraffin, then exposing it to the open air to allow it to cool and solidify.

  a very simple way, a mask of plastic or of adherent coating.

  Three areas that specifically require treatment

  alunite, are shown in Figure 3 The first area is the wall

  1000 a of the cylinder 1000 on which the body 130 of the device slides slidingly

  positive valve clearance compensator The second area is the top of the cy-

  lindre 1000 b, on which the valve acts by means of an element of-

  housing 110, which will be described below, coming to bear against it The third

  sth zone is the inner peripheral surface 1002 a of the axial hole 1002, in which a rocker shaft 300, which will be described below, is slidably inserted Alunite layers of a predetermined thickness, for example from 10 to 40 microns , are formed on the surfaces of the wall 1000 a, of the top f of the cylinder 1000 b, of the inner peripheral surface 1002 a, etc. The manufacturing method of the embodiment described above will now be described. An aluminum alloy ADC 12 (JIS) is used for

  die casting arm 1001 A plate 1003 of fried ferrous alloy

  tee being arranged in advance in the mold, the plate 1003 and its adjacent zone

  cente being molded in one piece with arm 1001.

  The plate 1003 and the z 6 ne of the arm 1001 adjacent to the said plate

  quette are then immersed, for about 2 seconds in a bath heated to 150-160 OC of molten thermoplastic resin, this resin being composed of paraffin and polyethylene and having a melting point of 1300 C, then the whole is brought to cool A thin thermoplastic coating of 2 to 3 mm

  thick is thus formed on the wafer 1003.

  In a similar way to the technology known according to the Japanese patent

  nais NO 56-4155, arm 1001 is electrolysed directly in an acid bath consisting of an aqueous solution of sulfuric acid and oxalic acid, so as to form a porous film of anodic oxide on the surface of arm 1001, this film then being rinsed with water The arm 1001 is then

  immersed in an aqueous solution of nitric acid in order to activate its surface

  this, then also rinsed with water The arm 1001 is then electrolysed, using

  continuous rant, in an aqueous solution of ammonium thiomolybdate heated to -20 OC, the anode being constituted by the arm 1001 and the cathode by a rod

  carbon, then rinsed with water.

  The arm 1001 is then immersed in water heated to 40 OC to

  soften the thin coating of thermoplastic resin, to facilitate removal

  vement of the latter by an operator who separates it from the wafer 1003 and from the zene of the arm 1001 which is adjacent to it A molybdenum sulfide is then

  formed to clog the tiny pores of the anodic oxide film

  than on arm 1001 A valve clearance compensator 1004, as-

  seems in advance, is then inserted into cylinder 1000 in order to complete

assembling the rocker arm 1.

  The tiny pores of the alunite film covering the surface of the arm 1001, with the exception of the wafer 1003, being blocked by molybdenum sulfide, the coefficient of friction of this treated surface is reduced

  to half or a third of that of a surface simply subjected to the

  alunite additionally, the surface hardness of this treated surface

  dyes around 400 Hv (Vickers hardness), and improves its resistance to rubbing

  Thus the valve clearance compensator 1004 easily slides inside the cylinder 1000 in which it is inserted, does not cause damage such as seizure and abrasion, and more particularly facilitates

  lite its activation during the operations of starting and stopping the mo-

  The sliding surface 1002 a which is in contact with the rocker shaft 300 of the arm 1001 also undergoes an alunite treatment just like the cylinder 1001 and receives a film of molybdenum sulphide Consequently, its rotation on the shaft 300 of rocker arm 1 is done gently, losses

  mechanical are smaller and durability is improved.

  Plate 1003 and the zombie which is adjacent to it, having undergone a

  treatment of alunite in an electrolytic bath after receiving a coat

  ment of thermoplastic resin, then having received molybdenum sulfide, it

  is possible to prevent attack of the wafer 1003 by the electrolytic bath

  tick during treatment Such a coating can be obtained by dipping

  only the wafer 1003 and its adjacent area in a thermoplastic resin

  liquid, and the coating layer, made up of a thin film, can be removed manually or using a simple tool by an operator, by immersing it in water heated to 40 OC and waiting for the coating

be softened.

  Its resistance to friction and its hardness being improved, the arm

  1001 degrades less quickly, even without a trim Failure to use

  Trim trim reduces the weight of the movable valves, which translates to

  in turn by an increase in the permissible rotation speed without rebounding

  This also reduces the twists in normal operation,

  and decreases the weight of the engine itself.

  In the embodiment described above, the wafer 1003 is

  made of a sintered ferrous alloy, and is therefore coated with a thermal resin

  plastic before being subjected to the alunite treatment If the wafer 1003

  was made of a ceramic material, this coating would not be natural-

not necessary.

  The operation and construction of the valve clearance compensator device as well as the rocker arm comprising this device will now be described with reference to FIG. 2 In FIG. 2, a rocker arm 1 is

  axially mounted on a rocker shaft 300 and actuates a valve

  mission 400 to open and close an intake lumen, not shown In other words, the rocker arm 1 is arranged to oscillate on a support axis constituted by a rocker arm 300, between a camshaft 500 and a valve intake or exhaust 400. The arm 1001 includes a valve clearance compensator 3 constituted by the insertion of the cylinder 1000, provided on the face opposite to the valve, over a clearance compensator block 1004 This compensator block of set 1004 comprises a spacer element 110, a body 130, and a piston 180 The arm 1001 forms a convex surface 700 of cam contact on the face 100 b opposite the camshaft 500, and oscillates in the direction of a arrow B when it is pressed by the lifting surface 501 of the cam at the same time as

  the camshaft 500 is rotated.

  The top of the cylinder 1000 b is spherical in shape, the center of curvature being aligned with the longitudinal axis 1 of the cylinder, and is in sliding contact with the spacer 110 having a curved surface 100

  opposite the bottom of the cylinder, which has approximately the same shape as the top

  met of cylinder 10 00 b, and whose center of curvature Q is aligned with the longitudinal axis 1 of the cylinder, this surface being hereinafter simply designated

  by the term "spherical surface of the spacer" The spacer

  110 has a surface 120 opposite the support element on the face opposite to

  the spherical surface 110 of the spacer, the center of the latter

  re having a hole 111 The spacer 110 can thus slide in a

  tation on the top of cylinder 1000 b with respect to the center of curvature Q. Against the wall 1000 a of cylinder 1000 the body 130 is slidably mounted

  constituting the body of a cylindrical piston, as well as a projection 131 in the ex-

  end of the body 130, which is in contact with the upper end surface of the valve stem projecting through an opening 800 The side of the cylinder top 1000 b of the body 130 is disposed some distance from the side of said cylinder, thus forming a vacuum 150 between them This vacuum 150 communicates with a

  oil inlet 160, oil being introduced, under a determined pressure

  born, in the valve clearance compensating device from a central light

  trale of oil 170 from a hollow rocker shaft 300 via the oil inlet 160 The center of the cylinder top 1000 b and the oil inlet 160 are in communication, in order to reduce the resistance to slip

  the top of the cylinder 1000 b and the spherical surface of the spreading element

  ment 100 A cylindrical piston 180 is slidably inserted into the body 130.

  The piston 180 internally comprises a hollow chamber 181, the end of which is in sliding contact with the opposite surface 120 of the pressing element of the spacer element and forming an element 183, hereinafter designated by the term " head ", opposite to the projection 131 of the body The head 183 and the projection 131

  of the body are respectively provided with a surface forming an oil chamber.

  the pressure 190 The chamber 190 can be connected, via an oil port 184, to the hollow chamber 181 of the piston The port 184 is designed so as to be opened and closed by a control valve disposed at the inside the pressurized oil chamber 190 A ball 201, the diameter of which is greater than that of the oil port 184 of the control valve, a spring 202, intended to resiliently press the ball 201 onto

  the periphery of the light 184, as well as a structure 203 supporting the res-

  exit 202 to press the latter against the head 183 of the piston, are provided

to achieve this construction.

  The pressure chamber 190 is further provided with a spring 210, hereinafter designated by the term "adjustment spring", for pressing the projection 131 against the side of the upper end 140 of the valve stem so as to maintain the projection 131 of the body separated from the piston head 183 This spring

  adjustment 210 pressurizes the structure 203 against the head 183.

  The operation of the valve clearance compensator 5 will

  now be described An oil pressure is applied, via-

  re of the oil inlet 160, in the vacuum of the cylinder head 150, from the central lubrication lumen 170 of the rocker shaft constituting the origin of the supply of oil under pressure, and this oil pressure

  is transmitted inside the hollow chamber 181 through the hole 111 of the element

  spacer The oil pressure of the hollow chamber 181 is applied, via the lubrication lumen 184, to the ball 201 This ball 201 does not move towards the oil chamber under pressure 190 unless it receives , in the form of an oil pressure, a force greater than that of the spring 202, and introduces the oil located on the side of the hollow chamber 181 into the oil pressure chamber 190 The ball 201 then closes the light at oil 184 by the force of spring 202 when the pressure of the chamber 190 reaches approximately that of the hollow chamber 181, and prevents the oil

  located inside the oil pressure chamber 190 of exhaust

  per by the lubrication light 184, even if the pressure of the chamber 190 increases If oil is introduced under a determined pressure into the chamber 190 since the arrival -180 when the engine has been started, the

  piston 180 presses, at its upper part, the spacer 110 with the-

  which it is in contact, and the body comes into contact with the projection 131 against the upper end face 140 of the valve stem In this case, and as long as the cam contact surface 700 of the rocker arm 1 is on

  the guard surface 502, when it moves away from the lifting surface

  ment 501 of the cam, the piston 180 and the body 130 are moved in the direction

  of the longitudinal axis 1 of the cylinder by the oil pressure and the a-

  justage 210, so as to fill all the gaps between the oppo-

  seat 120 of the pressing element of the spacer and the extreme surface

  upper 140 of the valve stem -

  On the other hand, as long as the cam contact surface 700 is subjected to the pressure of the lifting surface 501 of the cam, the piston 180 and the

  body 130, which have been moved as far as possible by the control spring 210

  the surface opposite to the pressure element of the spacer element 120 and the upper surface 140 of the valve stem do not act to reduce

  the distance between these two elements under the pressure of chamber 190 when

  that they are compressed in the direction of the longitudinal axis 1 of the cylinder.

  When the rocker arm 1 rotates clockwise

  tre, the projection 131 of the body receives a pressure from the upper surface of the valve stem, acting in reaction in the direction of the center of curvature P of the projection 131 This projection 131 concurrently receives a relative frictional force generated by the displacement of its spherical surface on the point of contact with the upper end 140 of the valve stem, accompanying the movement of rotation in a clockwise direction

  of the rocker arm 1001 The result of these forces, as well as the

  lateral sion thus generated and the torque in relation to the center of curvature P, applies an eccentric load on the body 130 The body 130 therefore moves to tilt towards the vacuum Cb between the walls 1000 a The vacuum values Ca between the body 130 and the piston 180 are adjusted

  on a value lower than that of the vacuum Cb, and the piston 180 tilts exac-

  as the body 130 In this case, the spherical surface of the spacer element 119 slides on the top of the cylinder 1000 b relative to the center of curvature Q of the latter, and is thus put into action This then transmits the prevailing pressure from the side of the body 130, in an approximately uniform manner, at the side of the top of the cylinder 1000 b The body 130, which has received this pressure,

  slides on the opposite surface 120 of the pressing element of the spreading element

  at the same time as the piston 180, comes into contact with the inner wall

  of the packing 2 and uniformly transmits its lateral pressure When the

  spacer 110 becomes substantially inclined to the center of curvature

  Q, the upper part of the piston 180 can slide more easily over the

  face 120 The center of curvature Q of the spherical surface 100 of the element

  spacing being only slightly deviated from the center of curvature

  re P of the projection 131 and being very close together, the body 130 and the piston 180 can easily rotate when the spacer receives a torque, and the sliding movement on the top of the cylinder 1000 b of

  the spacer 110 becomes regular.

  The above description also remains valid when the arm of

  rocker arm 10001 rotates anticlockwise: the body 130 then tilts in the opposite direction to the above, and the spacer 110 also moves in the opposite direction to

act similarly.

Claims (1)

CLAIMS 1 Method for manufacturing a rocker arm (1), characterized in that it consists in molding in one piece a plate (1003) of sintered ferrous alloy with an arm (1001) of aluminum alloy, to be formed a thin film on the outer peripheral surface of the wafer (1003); forming a porous layer of anodic oxide on the arm (1001) followed by electrolysis in an ammonium thiomolybdate bath, forming molybdenum sulfide in the pores and removing said thin film. 2 A method of manufacturing a rocker arm (1) according to claim 1, characterized in that the plate (1003) is immersed in a bath of molten thermoplastic resin, then cooled to form a thin film on its outer peripheral surface. 3 A method of manufacturing a rocker arm (1) according to claim 2, characterized in that the thermoplastic resin consists of paraffin and polyethylene, and is removed after softening by heating. 4 Method of manufacturing a rocker arm (1) according to claim 1, characterized in that the plate (1003) made of sintered ferrous alloy comprising the sliding surface on the cam is molded in one piece with the arm (1001 ) made of aluminum alloy, in that a cylinder (1000) is simultaneously formed on the arm (1001), in that a thin film is formed on the outer peripheral surface of the wafer (1003), that a porous layer of anodic oxide is formed on the arm (1001) by electrolysis in an ammonium thiomolybdate bath to form a molybdenum sulfide in the pores, in that the thin film is then removed, and a valve clearance compensator block (3) is inserted into the cylinder (1000) to fill the void above the upper surface (140) of the intake or exhaust valve (400) of the motor. Rocker arm (1) characterized in that it is provided with an arm (1001) made of aluminum alloy comprising molybdenum sulphide formed in the pores of a porous layer anodically oxidized, and of a molded plate (1003) in one piece with said arm (1001), and which is in sliding contact with the control cam. 6 rocker arm (1) according to claim 5, characterized in that a 254237 Z   1 1 valve clearance compensator block is inserted in the cylinder (1000) formed on the arm (1001) in order to fill the void above the upper surface   (140) of the engine intake or exhaust valve (400).