SE537693C2 - Cam follower for a valve lift device in an internal combustion engine - Google Patents

Abstract

Summary The present invention relates to a camshaft for a valve lift device in an internal combustion engine. The cam follower (4) comprises a primary unit (8), a secondary unit (10) and a welding component (13) which is fixed to one of said units (10) and comprises contact surface (13c1) which is adapted to be engaged with a contact surface (8a1) of the second of said units (8), the welding component (13) is applicable in a non-load ldge in which control movements from the secondary unit (10) are not transferable to the primary unit (8) via said contact surfaces (8ai , 13c1), in a partial load ldge and in a fully loaded layer in which control movements from the secondary unit (10) are transferable to the primary unit (8) via said contact surfaces (8ai, 13c1). The contact surfaces (8ai, 13ci) have a complementary shape. They show an incomplete contact with each other in the partially loaded team and an incomplete contact with each other in the fully loaded team. They have an inclination in relation to each other in the partially loaded layer so that when a control movement from the secondary unit (10) is applied to naninda contact surfaces (8ai, 13c1) when they are in the partially loaded layer, the contact surface (13c1) of the welding component will is adjusted in relation to the second contact surface (8a1) until the contact surfaces (8ai, 13c1) obtain full contact with each other and the welding component (13) is in the fully loaded joint.

Description

BACKGROUND OF THE INVENTION AND PRIOR ART The present invention relates to a cam follower for a valve lifting device in an internal combustion engine according to the preamble of claim 1.

A cam follower receives a lifting movement when it comes into contact with a cam on a camshaft. The lifting movement is transmitted, via light-emitting components, to a lifting movement of at least one valve which may be an inlet valve or an exhaust valve of an internal combustion engine. The camshaft can be a horizontal camshaft or an overhead camshaft. Opening and closing movements of conventional inlet valves and exhaust valves are performed when the piston in the respective cylinders of the internal combustion engine is in fixed predetermined layers. The fixed means for opening and closing the valves are a compromise that has been chosen so that the combustion engine will function vd1 regardless of load and speed. The inlet valves and exhaust valves thus do not always open and close at completely optimal times during all operating conditions of the internal combustion engine.

VVA (Variable Valve Actuation) is a collective name for various techniques that make it possible to vary the valves' opening and closing movements in an internal combustion engine.

This may mean that a cam follower is used which consists of an ordinary lifter which transmits a steering movement from a primary cam cam to a valve and an alternative lifter which conveys a steering movement from a secondary cam cam to the ordinary lifter and said valve. In order for the alternative movement of the alternative lifter to be able to be transferred to the ordinary lifter, the lifters must be read together. This can be done with the aid of a welding device which comprises a hydraulically controlled welding pin. When the alternative lifter made a steering movement from the secondary ridge to the ordinary lifter, the welding pin was subjected to a force load. If the welding pin has not had time to shift the entire carriage from a non-load bearing to a complete load when this force load starts, there is a risk that the welding pin gets stuck in a partial load bearing. In the case of a partial load, only a small part of the load pin can be used to transfer grooves from the alternative lifter to the ordinary lifter. The welding pin risks being deformed or otherwise losing its function, which can lead to damage to the internal combustion engine.

To prevent it from having the type of damage, the welding pin can be dimensioned so that it can withstand a certain number of unfavorable activations or deactivations without losing its function. Alternatively, the activation and deactivation of the locking pin is controlled with the view of the camshaft angle divided into several cylinders at a time in the engine. This way of dealing with the problem means that one either has to oversize the components or introduce more and more expensive components.

SUMMARY OF THE INVENTION The object of the present invention is to provide a cam follower comprising a primary unit and a secondary unit which can be connected by means of a welding component having a construction so that it does not risk getting stuck in a partial load layer.

This object is achieved with a valve lifting device of the type mentioned in the introduction, which can be characterized by the features stated in the can-drawing part of claim 1.

Only the primary unit of the cam follower comprises a contact element for transmitting control movements to the valve. In order for control motions from the secondary control surface to be transmitted to the valve, the secondary unit must be welded together with the primary unit. Therefore, when the secondary control surface is to control the valve lift, the welding component is shifted from a non-load bearing to a load bearing. When the contact means of the secondary unit comes into contact with a cam on the secondary guide surface of the camshaft, the contact surfaces are compressed. At times when the welding component is a whole load layer at night, the contact surfaces already have a complete contact with each other. When the welding component is in the fully loaded layer, the entire contact surfaces can be used to transfer the control movement from the secondary unit to the primary unit. In cases where the welding component only has a partial load layer when the control movement from the secondary unit is to be transferred to the primary unit, the contact surfaces obtain an incomplete contact with each other. The control movement from the secondary unit compresses the contact surfaces so that they are displaced in relation to each other until they obtain complete contact. The steering movement shifts the armed load component from the partially loaded team to the fully loaded team. With such a design of the contact surfaces, it is guaranteed that the welding component always receives a displacement movement from the unloaded 2 layer to the completely oldest layer. The risk of the contact surfaces being deformed opposite the control movement from the secondary unit to the primary unit is thus essentially eliminated.

In the event that the primary control surface is to control the valve lift, the load component is displaced back from the fully loaded layer in the direction of the unloaded layer. In cases where the welding component does not reach the unloaded load before the secondary unit is lifted off the secondary guide surface on the camshaft, a guide movement is provided which presses the contact surfaces against each other. The contact surfaces are shifted in relation to each other until they receive complete contact. In cases where the welding component does not reach the non-Idla ldget before the second unit reaches a ridge on the secondary guide surface, the welding component is thus returned to the fully loaded layer. When the ridge on the second guide surface has been passed, the welding component is moved all the way to the non-reading beam. Both when activating and deactivating the lead component, it is thus automatically moved to the fully loaded layer at times when the movement of the welding component towards the very oldest layer and the non-oldest layer does not have time to be carried out. The welding component according to the invention can thus not get stuck in a partially empty layer. The risk of damage occurring on the contact surfaces as they have complete contact with each other is thus essentially eliminated.

According to an embodiment of the present invention, the contact surfaces consist of flat surfaces. TV flat contact surfaces have a complementary shape. If the lead component does not have time to reach the fullest layer, the said flat contact surfaces form an angle with each other. The compressive force created by the control movement, however, compresses the contact surfaces until the contact surface of the welding component becomes parallel to the contact surface of the unit. In this case, the lead component must have a mobility so that the angle of the contact surface is adjustable in relation to the contact surface of the unit. Alternatively, said contact surfaces may have other types of complementary shapes. One contact surface may have a concave shape which is not circular and the other contact surface has a corresponding convex shape such that the contact surfaces only obtain full contact with each other in an embedding. According to one embodiment of the present invention, the lead component comprises a rotatable shaft. Such a lead component provides rotational motion and the contact surface can be clamed to obtain an adjustable angle relative to the contact surface of the unit. According to an embodiment of the present invention, the cam follower comprises a hydraulically actuatable piston which is adapted to displace the welding component from the unloaded layer to the fully loaded layer. By applying hydraulic oil with a suitable pressure on one side of the piston, it can phase to shift the welding component from the unloaded layer to the fully loaded layer. In cases where the piston does not succeed in displacing the welding component to the fully loaded layer, said contact surfaces help to create a remaining part of the displacement movement. Said shaft may comprise a peripheral recess adapted to be in contact with said piston. This allows the piston to make contact with a part of the shaft which is located at a distance from the center of rotation of the shaft. A rectilinear displacement movement of the piston may have been converted into a rotational movement of the shaft.

According to an embodiment of the present invention, the cam follower comprises a return spring which is adapted to displace the welding component from the fully loaded layer to the non-loaded layer. Such a return spring can be a helical spring. With a suitable attachment of such a spring, the welding component can obtain a displacement movement back to the unloaded layer when the hydraulic piston is not activated. In cases where the return spring does not succeed in pushing the shaft back all the way to the unloaded layer, the shaft is turned to the fully loaded layer with the aid of said contact surfaces. Said shaft may comprise a peripheral recess which is adapted to be in contact with the return spring.

Thereby the spring receives contact with a part of the shaft which is located at a distance from the center of rotation of the shaft. A helical spring can have a rotational displacement of the shaft via a helical displacement movement.

According to an embodiment of the present invention, the rotatable shaft comprises a recess for receiving the second contact surface when it is in the unloaded layer. In the unloaded layer, the primary control surface is responsible for the valve lift. The control movements that the secondary unit receives from the secondary control surface must thus not be transmitted to the primary unit. With such a recess in the shaft, the secondary unit can provide a pivotal movement around the rocker shaft without coming into contact with the primary unit.

According to an embodiment of the present invention, the cam follower has a design such that it is in the loaded layer opposite a guide movement from the guide surface which provides the largest valve lift. DA the secondary guide surface & ed. & A guide movement to the secondary unit, it provides a pivot movement around the rocker shaft which compresses the contact surfaces.

In this case, a ridge on the primary guide surface results in the primary unit pivoting 4 about the rocker axis in a direction so that the contact surfaces are moved apart. Thus, the contact surfaces will be in contact with each other if the secondary guide surface provides the largest valve lift and separated flanges with each other if the primary guide surface provides the largest valve lift. The control surface that provides the largest valve lift will thus control the valve as the welding component is in the fully loaded layer.

According to an embodiment of the present invention, the cam follower comprises a tubular body which is fixed to one unit and which encloses said rotatable shaft. The rotatable shaft can have a protected position inside such a tubular body. The rudder-shaped body advantageously has an inner surface with a circular cross-section which facilitates the rotational movement of the shaft. The rudder-shaped body advantageously has a parallel stretching with the rocker shaft. Thus, the recess for the piston which rotates the shaft and the contact surfaces can be designed at an axial distance from each other in connection with the respective units.

According to an embodiment of the present invention, the cam follower comprises two primary units each comprising a contact member arranged at an axial distance from each other on the camshaft in contact with two guide surfaces having an identical design. With two such contact means, the cam follower obtains a stable positioning on the camshaft. In this case, the two contact means create an identical lifting movement which can be transferred to separate valves. The secondary unit advantageously comprises a secondary contact means which is arranged between the primary contact means. A centrally located secondary unit can transmit identical control movements to the primary units arranged on opposite sides.

According to an embodiment of the present invention, said contact means are roller means which are adapted to all the roller catches a respective guide surface on the camshaft. The friction between the guide surfaces and the contact members is thus minimal. Alternatively, the contact means can be constituted by suitable sliding means which slide along the guide surfaces. The primary unit may comprise a contact element which substantially directly transmits control motions to a valve without any further motion transmitting mechanism. In this case, the cam follower receives control motions from an overlying camshaft. Alternatively, said contact element of the primary unit can be constituted by a ball shell or the like for receiving a lower end of a push rod as via a rocker arm opposite control movements to a valve. In this case, the cam follower is mounted on a horizontal camshaft.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, as an example, a preferred embodiment of the invention is described with reference to the accompanying drawings, in which: Fig. 1 shows a cam follower according to the present invention, Fig. 2 shows the cam follower in Fig. 1 seen from below, Fig. 3 shows the cam follower in Fig. 1 seen from one side, Fig. 4 shows a sectional view in the plane AA of the cam follower in Fig. 3 when it is in a non-load lap, Fig. 4 shows a sectional view in the plane AA of the cam follower in Fig. 3 when it is in a full load layer, Fig. 5 shows a sectional view in the plane BB of the cam follower in Fig. 3 when it is in a non-load layer and Fig. 5b shows a sectional view in the plane BB of the cam follower in Fig. 3 when it is in a heavy load lap.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Fig. 1 shows a cam follower for a valve lift device of an internal combustion engine. In this embodiment, the internal combustion engine is provided with an overlying camshaft 1 which is rotatable at a speed which is related to the speed of the internal combustion engine (the speed of the crankshaft). The internal combustion engine may alternatively be provided with a Mgt horizontal camshaft. The camshaft 1 is provided with two primary guide surfaces 2 and a secondary guide surface 3. Each of the guide surfaces 2, 3 is provided with a radially projecting part in the form of a cam. A cam follower 4 is adapted to be in contact with the primary and secondary guide surfaces 2, 3. The cam follower 4 comprises two primary contact means in the form of two primary roller means 5 which are in contact with their respective primal guide surface 2 and a secondary contact means in the form of a secondary roller member 6 which is in contact with a secondary guide surface 3. The cam follower 4 is pivotally arranged on a rocker shaft 7.

Figs. 2 and 3 show a view from below and from one side, respectively, of the cam follower 4. The cam follower 4 comprises two primary units 8 with an identical design. The two primary units 8 are pivotally mounted around the rocker shaft 7 at a central portion. The two primary units 8 each comprise a primary roller member 5 at a duck portion and a contact element 9 at an opposite duck portion. The contact element 9 is adapted to transmit a control movement from the primary unit 8 to a valve which may be an inlet valve or an exhaust valve. The cam follower 4 comprises a secondary unit 10 which is located between the two primary units 8. The secondary unit 10 is pivotally mounted around the rocker shaft 7 at a central portion. The secondary unit 10 comprises secondary roller means 6 at a duck portion and a welding device 11 at an opposite duck portion. The secondary unit can be welded together with the primary units 8 by means of the welding device 11. The welding device 11 comprises a tubular body 12 which is fixed to the secondary unit 10. The tubular body 12 has a transverse extension extending substantially the entire width of the cam follower 4. The rudder-shaped body 12 has a duct portion adjacent to one primary unit 8 and an opposite duct portion adjacent to the other primary unit 8. The rudder-shaped body 12 encloses a welding component in the form of a rotatable shaft 13. The rotatable shaft 13 has a central portion in connection with the secondary unit 10 and two duct portions adjacent to the respective primary units 8. The tubular body 12 is, at the middle portion, provided with a cylindrical projecting portion 14.

Figs. 4a and 4b show a section through the secondary unit 10. It can be seen here that the cylindrical portion 14 comprises a cylindrical space for a return spring 15.

The return spring 15 is hdr a helical spring. The rotatable shaft 13 is provided with a first peripheral recess 13a for receiving a spirit of the return spring 15. The return spring is in contact with the shaft 13 at a distance from its center of rotation. Thereby, the return spring 15 springs after turning the shaft 13 in a clockwise direction. The rotatable shaft 13 is provided with a second recess 13b for receiving a hydraulically displaceable piston 16. In this case, hydraulic fluid can be led to the upper side of the piston 16 and displaced in a straight channel 10a in the secondary unit 10. The hydraulic fluid displacing the piston 16 can be pressurized by a pump driven by the internal combustion engine. The piston 16 is slidably arranged between an upper non-load load and a lower full load load. The piston is shown in the later section of Fig. 4b. As the piston 16 is displaced from the unloaded bearing to the fully loaded bearing, it rotates the shaft 13 in a counterclockwise direction against the action of the return spring 15.

Figs. 5a and 5b show a section through one of the primary units 8. It can be seen here that the tubular body 12 has a peripheral opening adjacent to the primary unit 8. The rotatable shaft 13 hdr has a reduced cross section 13c. The reduced cross section 13c of the rotatable shaft comprises a contact surface 13ct. The reduced cross section of the shaft 13 is created by a recess 13d. The primary unit 8 has a projecting contact portion 8a 7 with a contact surface 8ai. When the piston 16 is in the unloaded load, the contact surface 13c is in the load shown in Fig. 5a. If the secondary unit 10 is lifted off the secondary guide surface 3 and rotated in a counterclockwise direction relative to the primary unit 8, the contact surfaces 8ai, 13ci will not come into contact with each other. Since the piston 16 has rotated the shaft 13 in a counterclockwise direction against the action of the return feeder 15 to the fully loaded lid, the contact surface 13c is in the lid shown in Fig. 5b. If the secondary unit 10 is lifted off the secondary guide surface 3 and rotated in a counterclockwise direction relative to the primary unit 8, the contact surfaces 8ai, 13ci come into contact with each other.

During operation of the internal combustion engine, an engine control unit (not shown) essentially continuously receives information regarding several engine parameters such as, for example, engine speed and load. Using this information, the motor control unit decides whether the valves are to be controlled by the primary control surfaces 2 or by the secondary control surface 3. In cases where the motor control unit determines that the valves are to be controlled by the primary control surfaces 2, the piston 16 is not activated. do not load the load of the return feeder 15 as shown in Fig. 4a. When the rolling means 6 of the secondary unit 10 comes to the ridge on the guide surface 3, the secondary unit 10 receives a lift which results in it being rotated in a counterclockwise direction around the rocker shaft 7. The contact surface 13e1 of the shaft is rotated in a rotational position with the contact surfaces 8ai of the primary units. The recess 13d of the shaft can hdr receive the contact portions 8a and contact surfaces 8ai of the primary units. The 10 movements of the secondary unit do not affect the control movements of the primary units 8 to the valves at all. When the rolling means 5 of the primary units 8 come to the ridge on the guide surfaces 2, the primary units 8 receive a pivotal movement in a counterclockwise direction around the rocker shaft 7. The contact portions 8ai of the primary units move away from the contact portion 13ci of the shaft. The movement of the primary units 8 is propagated to lifting movements of the valves via the contact elements 9. When the piston 9 and the shaft 13 are in the unloaded position, the valves are controlled by the primary guide surface 2.

At times when the motor control unit determines that the valves are to be at least partially controlled by the secondary guide surface 3, the piston 16 is activated. The piston 16 is thereby driven against the action of the return feeder 15 against the load shown in Fig. 4. The shaft 13 is rotated so that the shaft contact surface 13c a position in close proximity to the contact surfaces 8ai of the primary units 8 as shown in Fig. 5b. When the rolling member 6 of the secondary unit comes to the ridge on the guide surface 3, the secondary unit 10 receives after lifting which results in a pivotal movement in a counterclockwise direction around the rocker shaft 7 relative to 8 the primary units 8. Steering movement from the secondary guide surface 3 is transmitted via the the secondary unit 10, the shaft 13 and said contact surfaces 8ai, 13ci, to the primary units 8. The control movement is transferred from the primary units 8 via the contact elements 9 to the valves. The secondary guide surface 3 in this case stands for the lifting of the valves. The rolling members 5 of the primary units 8 are held in a raised position from the primary guide surfaces 2. When the rolling members 5 of the primary units 8 come to the ridge of the secondary guide surfaces 2, the rolling members 5 provide a lifting movement which results in the primary units 8 being rotated counterclockwise direction around the rocker shaft 7. As long as the secondary guide surface 3 provides a larger valve lift than the primary guide surface 2, the secondary guide surface 3 controls the lifting of the valves. If the primary guide surface 2 gives a stone stroke to the secondary guide surface 3, it takes over the lifting of the valves.

In the cases where the valves are to be controlled by the secondary guide surface 3, the piston 16 is activated so that it is moved from the unloaded layer towards the fully loaded layer. The piston 16 rotates the armed shaft 13 against the action of the return shaft 15. As a rule, the piston 16 has time to turn the shaft 13 to the fully loaded layer before the rolling means 6 of the secondary unit 10 reaches the ridge on the second guide surface 2. If the shaft 13 does not have time to turn to the fully loaded, the shaft 13 is in a partially loaded position. This means that only part of the contact surface 13ci comes into contact with a part of the contact surfaces 8ai of the primary units 8. However, the contact surfaces 8ai, 13ci are not parallel as the contact surface 13ci of the shaft has not had time to turn the whole carriage to the fully loaded layer. When the rolling member 6 of the secondary unit 10 reaches the cam on the second guide surface 2, the secondary unit 10 receives a guide movement which presses the contact surfaces 8ai, 13ci against each other. As a result, the shaft 13 is rotated against the action of the return spring 15 until the contact surfaces 8ai, 13ci become completely parallel to each other. When the contact surfaces 8ai, 13ci are parallel, the shaft has been turned to the fully loaded layer. With the aid of said contact surfaces 8ai, 13ci it can always be guaranteed that the shaft is turned to the loaded layer. In this case, the risk of the shaft 13 getting stuck in a partially loaded layer between the unloaded Paget and the fully loaded layer is thus eliminated. At the same time, it is guaranteed that the entire contact surfaces 8ai, 13ci are used to transmit the control movement from the secondary unit 10 to the primary units 8.

In the case where the valves are to be controlled again by the primary guide surfaces 2, the piston 16 is deactivated so that the return spring 15 widens back the shaft 13 towards the unloaded layer. As a rule, the shaft 13 has time to be turned back to the unloaded layer before the rolling means 6 of the secondary unit 10 reaches the ridge on the second guide surface 2. If the shaft 13 does not have time to turn the whole Nagen to the unloaded layer, the shaft 13 the secondary unit 9 opposite a guide movement on the shaft 13 and the primary units 8. The pressure which the guide movement exerts on the contact surfaces 8ai, 13ci results in the shaft 13 providing a rotational movement against the action of the return spring until the contact surfaces 8ai, 13ci become parallel to each other. When the contact surfaces are parallel 8ai, 13ci, the shaft 13 has been turned again to the fully loaded position. If the shaft 13 does not have time to turn to the unloaded layer before the rolling means 6 of the secondary unit 10 reaches the ridge on the second guide surface 2, the shaft 13 is thus turned back to the loaded layer. This happens quickly and the main part of the control movement takes place via the contact surfaces 8ai, 13ci when they are parallel. This ensures that the shaft 13 also does not get stuck in a partial load bearing when the piston 16 is deactivated.

As soon as the secondary unit 10 has passed the cam on the secondary guide surface 3, the return spring 15 can turn the shaft 13 back to the unloaded layer. The transmission of a control movement from the secondary unit, via the shaft 13, to the primary units 8 thus essentially always takes place when the flat contact surfaces 8ai, 13ci are parallel. The contact surfaces have a complete contact with each other. The power transmission obtained between the contact surfaces is distributed armed over a relatively large area. The risk of the contact surfaces being deformed is thus non-existent.

In this case, a cam follower 4 is used which comprises two primary units 8, each with its own rolling member 5 which rolls along each of its primary guide surfaces 2. The guide surfaces 2 have an identical profit. The secondary unit 10 has a rolling member 6 which rolls along a guide surface 3 which is coated between the guide surfaces 2 of the primary unit. The secondary unit 10 has a central location between the primary units 8. Such a design of the cam follower 4 causes symmetrical loads through the cam follower both the primary units 8 and the secondary unit 10 are used to transmit lifting movements to the valves. With such a design, the cam follower 4 becomes compact and robust.

In the above-mentioned example, the cams on the guide surfaces can be displaced so that the valves obtain an earlier lift by means of the secondary guide surface 3. Alternatively, a secondary unit 10 of the cam follower 4 can also be used to provide a later closing of the valves or a stone lifting of the valves. 3 in relation to the lift provided with the primary unit 8 of the cam follower 4. The valves can thus be inlet valves or exhaust valves. Control of the exhaust valve opening time can be used to raise the exhaust temperature. By opening the exhaust valve earlier than normal, the expansion will be interrupted at a higher temperature, which results in an increased exhaust temperature. In overcharged internal combustion engines, the exhaust turbine is dimensioned so that it can provide high charge pressures at low engine speeds. This 10 causes the turbine to overheat at high engine speeds and loads. To avoid this, part of the exhaust flow is led past the turbine through a so-called waste gate. The need for a waste gate can be reduced by delaying the opening time of the exhaust valve. This would also increase efficiency.

Controlling the inlet valve closing time can be beneficial from several aspects. With such a control, the degree of filling of the cylinders can be optimized at different engine speeds, which is desirable at a high engine load. Control of the inlet valve closing time is also possible to control the effective compression ratio.

A delay in the closing time of the inlet valve in relation to the closing time which gives the optimum degree of filling means that the compression is drilled later and compression takes place during a shorter part of the piston movement. However, the subsequent expansion is unchanged. This means that the expansion ratio is higher than the compression ratio, which, under certain operating conditions, is favorable from an efficiency point of view. However, it is not possible to close the inlet valve late during all operating conditions. During, for example, starting an internal combustion engine, the compression ratio is set so that ignition is absent.

With overcharged internal combustion engines, an early opening of the exhaust valves gives more energy to the exhaust turbine and clamed possibility to higher charge pressure. A late opening of the exhaust valve gives more energy to the internal combustion engine, which thus obtains a higher efficiency. Thus, with variable opening times of the exhaust valve, the efficiency and performance of the internal combustion engine can be varied. With transients, it can also be advantageous to open the exhaust valves earlier and thus get a faster & fling of charge air pressure.

The invention is in no way limited to the embodiment described in the drawing but can be varied freely within the scope of the claims. A cam follower with a similar welding device can also be used to transmit control movements from a laid camshaft to adjustable lifting of valves 3 via a push rod and a rocker arm. The shaft 13 is fixed to the secondary unit 10 in the exemplary embodiment shown. It could alternatively be attached to the primary units 8. In this case, the shaft would have a contact surface which cooperated with a contact surface on the secondary unit. 11

Claims (13)

Patent claims A cam follower for a valve lifting device in an internal combustion engine, the cam follower (4) comprising - a primal unit (8) movably arranged around a rocker shaft (7) and comprising a primary contact means (5) which receives steering motions from a primary guide surface ( 2) on a camshaft (1) and a contact element (9) which is adapted to emit guide movements from the primary unit (8) for lifting at least one valve, - a secondary unit (10) which is movably arranged around the rocker shaft (7) and comprises a secondary contact means (6) which receives stiffness from a secondary guide surface (3) on the camshaft (1) and - a welding component (13) which is fixed to the secondary unit (10) and comprises a contact surface (13c1) which is adapted to fans for engaging a contact surface (8a1) of the primary unit (8), the welding component (13) being applicable in a non-load ldge in which control movements from the secondary unit (10) are not transferable to the primary unit (8) via naninda contact surfaces (8a1, 13c1), in a partial las and in a fully loaded layer in which control movements from the secondary unit (10) are transferable to the primary unit (8) via nanindic contact surfaces (8a1, 13c1), characterized in that said contact surfaces (8ai, 13c1) have a complementary shape , that they have an incomplete contact with each other in the partially fixed layer and a complete contact with each other in the fully loaded layer, and that they have an inclination in relation to each other in the partially loaded layer so that then a control movement from the secondary unit (10) is applied to said contact surfaces (8ai, 13ci), then the contact surface (13ci) of the welding component will be adjusted in adhesion to the second contact surface (8a1) until the contact surfaces (8ai, 13c1) obtain full contact with each other and the welding component (13) is in it completely loaded ldget. Cam follower according to claim 1, characterized in that said contact surfaces (8a1, 13c1) consist of flat surfaces. Cam follower according to Claim 1 or 2, characterized in that the welding component consists of a rotatable shaft (13). Cam follower according to claim 3, characterized in that it comprises a hydraulically actuatable piston (16) which is adapted to rotate said shaft (13) from the unloaded load to the fully loaded load. 12 Cam follower according to claim 4, characterized in that the shaft (13) comprises a peripheral recess (13b) which is adapted to be in contact with said piston (16). Cam follower according to any one of claims 3 to 5, characterized in that it comprises a return jig (15) which is adapted to turn said shaft (13) back from the fully loaded layer to the unloaded layer. Cam follower according to claim 6, characterized in that the shaft (13) comprises a peripheral recess (13a) which is adapted to be in contact with said return spring (15). Cam follower according to any one of claims 3 to 7, characterized in that the rotatable shaft (13) comprises a recess (13d) for receiving the second contact surface (8a1) when it is in the unloaded space. Camshaft according to any one of claims 3 to 8, characterized in that it comprises a tubular body (12) which is fixed to one unit (10) and which encloses said rotatable shaft! (13). Cam follower according to any one of the preceding claims, characterized in that it has a design such that when the welding component (13) is in the fully loaded body so that it converts to the valve from the control surface (2, 3) which gives the largest valve lift. A camshaft according to any one of the preceding claims, characterized in that it comprises two primary units (8) each comprising a contact member (5) arranged at an axial distance from each other in contact with two guide surfaces (2) on the camshaft ( 1) with an identical design. Cam follower according to claim 11, characterized in that the secondary unit (10) comprises a secondary contact means (6) which is arranged in a position between the primary contact means (5). Cam follower according to any one of the preceding claims, characterized in that said contact means consist of roller means (5, 6) which are adapted to roll along their respective guide surfaces (2, 3) on the camshaft (5). 13