EP3061926B1

EP3061926B1 - Valve actuation system of an internal combustion engine

Info

Publication number: EP3061926B1
Application number: EP16157168.2A
Authority: EP
Inventors: Enzo Ameglio; Roberto FALETTI
Original assignee: FPT Industrial SpA
Current assignee: FPT Industrial SpA
Priority date: 2015-02-24
Filing date: 2016-02-24
Publication date: 2018-12-26
Anticipated expiration: 2036-02-24
Also published as: ES2712462T3; EP3061926A1

Description

Field of the invention

The present invention relates to the field of internal combustion engines and precisely to the field of actuations systems of the valves of the engine.
US5584268 discloses a rocker arm rocker with a hydraulic lash adjusting assembly, with the mass of the adjusting assembly being closely adjacent the pivot axis of the rocker arm to minimize the rotational moment of inertia of the rocker arm.

Prior art

Valve actuators divide substantially into two main categories namely of the "rocker arm" or "finger follower" type.
The two types of actuator differ substantially in the position of the fulcrum of a rocker arm.
The "finger follower" has a point of reference at one end of the rocker arm, a cam slides in relation to an intermediate point thereof, while an opposite end actuates a valve or a pair of valves.
The "rocker arm" has a point of reference in an intermediate part of the rocker arm, a cam slides with respect to one end of the rocker arm, while an opposite end actuates a valve or a pair of valves.
The recovery of valve clearance is generally performed by so-called hydraulic lash adjusters HLA, which consist of small hydraulic pistons which permit recovery of the clearance of the valves during the wear of the respective seats.
These hydraulic components are usually housed in the end of the rocker arm in contact with a valve or with a cross-member which makes it possible to operate two valves at a time.
In some particular operating conditions of the internal combustion engine, the forces which such hydraulic pistons have to endure are particularly relevant, and therefore it is necessary to size these components accordingly.
This results in an increase in the size of the HLA which interferes with the other mechanical components, such as for example the injector or with another HLA relative to other valves of the same cylinder.
This also entails an increase in weight thereof, which housed at a distance from the fulcrum of the rocker arm produces a significant moment of inertia and therefore unsatisfactory dynamic performance.
In some applications, the result is that it is impossible to implement an automatic recovery of valve clearance by the HLA by virtue of the fact that there are no HLAs able to withstand very high compressions especially during engine braking or during any other operation.

Summary of the invention

One aim of the present invention is to propose a valve actuation system of an internal combustion engine which helps to reduce the compression forces acting on the hydraulic valve clearance recovery components HLA.
The basic concept of the present invention is to pivot on one end of the rocker arm, facing towards one or more valves, an additional arm, which, with a first end contacts a valve or a valve group and with a second end, opposite the first, contacts the rocker arm via a HLA housed on said rocker arm.
The present invention relates to a valve actuation of an internal combustion engine corresponding to the description in claim 1.
A preferred variant of the invention also comprises an additional valve actuation system, for example to create an engine braking or internal EGR technique etc.
According to such preferred variant of the invention, such additional actuation is made by moving the entire HLA in relation to its seat by means of an additional actuator comprising a second additional arm having a first end supported by an actuator, preferably hydraulic, a second end, opposite the first, interacting with a cam actuator, while a medial zone of the second additional arm which directly or indirectly contacts said HLA, moves it in its respective seat made in the rocker arm.
The present invention also relates to an internal combustion engine comprising the valve actuation system described above.
Preferably, the internal combustion engine implements a Diesel cycle.
The present invention further relates to a vehicle or a fixed installation comprising the aforesaid internal combustion engine.
The claims describe preferred variants of the invention forming an integral part of the present description.

Brief description of the figures

Further purposes and advantages of the present invention will be clear from the detailed description below of an example of embodiment thereof (and of its variants) and the appended drawings provided merely by way of a non-limiting example, wherein:

Figure 1 is a side view of a preferred embodiment of a valve actuation system according to the present invention;
Figure 2 shows a cross section view, transversal to the camshaft, of the preceding figure 1, in which the housing of the HLA on the rocker arm is clearly visible;
Figure 3 shows a perspective view of a preferred embodiment according to the preceding figures;
Figure 4 shows a side view of a further variant of the valve actuation system according to the present invention in which a further additional actuation arm can be seen;
Figure 5 shows a side view, opposite to the view in Figure 4 in which further details of the aforesaid additional actuation arm are visible;
Figure 6 shows a cross section view, transversal to the camshaft, of the preceding figure 5, in which the interaction between the additional actuation arm and the actuation system described in the preceding figures is clearly visible;
Figures 7 and 8 show different perspective views of an example implementing the valve actuation system for a cylinder head having four valves.

Detailed description of embodiments

An example of embodiment of a valve actuation system according to the present invention is given with reference to Figures 1 - 3.
A "rocker arm" RA has a longitudinal shape with a medial part RAM hinged on a rocker arm shaft axis BS.
The rocker arm shaft axis BS runs parallel to an alignment of cylinders defining at least one cylinder bank of an internal combustion engine.
A first end of the rocker arm RA' faces towards one or more valves V arranged in a known manner per se on the cylinder head.
A second end of the rocker arm RA", opposite the first RA', comprises a roller RL1 adapted to contact a relative actuation cam CM1 keyed on a cam shaft CS which can be of the type known per se.
The BS rocker arm shaft and the cam shaft CS are substantially parallel to each other, as is the rotation axis of the roller RL1.
Diversely from the prior art, the first end RA' does not contact a valve V or a cross-bar T directly or via a HLA, but via a first additional arm AA.
Said additional arm AA has a longitudinal shape and comprises two mutually opposite ends AA' and AA" and a medial part AAM, connected by a pivot H, in said first end RA' of the rocker arm RA. The axis of rotation of this pivot is parallel with the direction defined by the cam shaft CS and the rocker arm shaft BS.
The first end AA 'directly contacts an actuation valve V or cross-member T of a pair of valves V.
The second end is supported by a HLA. The HLA is stably housed on said rocker arm RA in a medial position of the longitudinal extension of the rocker arm.
For the purpose of an optimal balance of forces, it is preferable that the HLA be housed in an intermediate position between the medial portion RAM and the end portion RA", but depending on the shape of the rocker arm it could also be advantageous to house the HLA in a different position, although not shown.
The HLA has its own longitudinal extension Y which is substantially perpendicular, preferably perpendicular less +/-15°, to the extension XY of the portion of rocker arm to which it is stably associated. Such portion, as described above, intermediates between the medial portion RAM and the end portion RA".
The first additional arm AA hinged in a relative medial part defines a lever having arms a and b.
It is preferable to house the HLA on the rocker arm in a position as far as possible from the hinging point H so that b is greater than a. A favourable lever is thus defined in which the axial forces supported by the HLA are scaled down.
Despite moving the HLA away from the fulcrum of the rocker arm represented by the rocker arm shaft BS, the HLA is closer to it than in the known solutions in which the HLA supports the roller RL1 or is interposed between the rocker arm and valve, therefore the inertia developed by it is reduced and the dynamics of valve actuation improved.
Moreover, housing according to the prior art a HLA in support of the roller RL1, the arm ratio b'/a' compared to the fulcrum BS is unfavourable for the HLA and must therefore be very sturdy, i.e. large and heavy.
Consequently, the present solution makes it possible to scale down the forces on the HLA, permitting the implementation of smaller lighter and cheaper HLAs and, on the other makes it possible to reduce the overall inertia of the actuation system with a definite improvement in performance thereof.
It is preferable that the first additional arm AA is superposed and aligned with the rocker arm RA, so as not to develop twisting movements on the assembly formed of the additional arm AA and rocker arm RA.
The HLA thus lies in a plane perpendicular to the direction indicated by the rocker arm shaft BS and camshaft CS. Moreover, the HLA is perpendicular to an extension axis of said rocker arm.
As regards the operating illustration, as the valve seats V made in the cylinder head (not shown) are gradually worn, the HLA makes it possible to recover the clearance. Meanwhile, the axial forces affecting the HLA are scaled down by effect of the lever defined by the additional arm AA, showing that the arm b is greater than or equal to the arm a (b ≥ a) .
This solution is also advantageous when a = b, or even a < b, in fact it makes it possible in any case to have the HLA arranged in a position that does not interfere with other members, for example with the extraction of the injector and in any case the HLA proves closer to the fulcrum defined by the rocker arm shaft BS compared to other known solutions, with an improvement in the moment of inertia and dynamic performance of the actuation system.
Preferably, the contact between the first end AA' of the first additional arm AA and the cross-member T or the stem of a valve V is made by means of a ball joint known by the nickname "elephant foot".
Preferably, the contact between the second end AA" of the first additional arm AA and the HLA is made using a ball joint or a simple sliding skate.
Preferably, the oil which pressurises the HLA is conducted through the rocker arm shaft BS, therefore, both in the rocker arm shaft and in the rocker arm, appropriate hydraulic oil ducts are made.
From the description it is evident that the HLA is constantly balanced, balanced by the reaction springs SP of the valves, which keep the first end AA' of the first additional arm AA raised, which in turn brings the second end AA" of said additional arm to move towards the rocker arm RA and therefore in contact with the HLA which is interposed between the two.
Figures 4 - 6 show a further preferred variant of the invention which does not necessarily implement a HLA, but in any case uses the architecture consisting of the rocker arm on which the first additional arm AA is hinged.
Such preferred variant of the invention comprises a second additional arm BA comprising a first end BA' in contact or hinged on a moving part of an actuator ACT, preferably hydraulic, and a second end BA" opposite the first interacting with a second cam CM2 keyed on the camshaft CS or on a further camshaft parallel to the aforementioned camshaft CS.
The actuator ACT has a fixed part integral with a point of the head of the internal combustion engine.
The HLA or rigid component is slidingly joined to the rocker arm RA, in which a special housing is made. Such seat of the HLA, made in the rocker arm, defines a cavity passing through the rocker arm.
Said through cavity defines a longitudinal extension coinciding with a direction moving the end AA" towards/away from the rocker arm.
Said HLA or rigid component has a longitudinal extension and comprises two opposite ends of which a first end is in contact with the second end AA' of the first additional arm AA, while a second end interacts, passing through the rocker arm, with a medial point of the second additional arm BA.
The actuator ACT is adapted to move the first end BA' of the second additional arm so as to induce the second additional arm BA to interact with the HLA or with a rigid element housed in its place, so as to move the latter concordantly with the actuation provided by the second cam CM2.
Conversely, when the actuator withdraws its respective moving part, the second additional arm is in a distal position with respect to the HLA, which remains fixed in its respective seat.
The rigid component or HLA comprises a contact point BT in the respective seat made in the rocker arm, so that the coupling defines a minimum point of raising the rigid component or HLA from the rocker arm. In other words, the rigid component or HLA cannot slip off from below.
When a HLA is implemented, given that the respective shape is predetermined, it is preferable for the second additional arm to comprise a pin PIN in one piece with the second additional arm, which intercepts from below the base of the HLA determining a relative axial sliding which determines the distancing of the end AA" from the rocker arm.
When the first end BA' is suitably raised by the actuator ACT, the movement of the second additional arm BA actuated by the second cam CM2 also makes the first additional arm AA move concordantly, realising an appropriate additional valve actuation strategy. For example an internal EGR or engine brake strategy.
From the comparison of figures 4 and 5 it is evident that the second additional arm BA, intersects the rocker arm, passing under it. In other words, according to an overhead view, while the first additional arm AA is aligned and superposed with respect to the rocker arm RA, the second additional arm and the rocker arm form an X. This choice is advantageous, although not essential, in order to better balance the forces, so that neither of the first additional arm and the second additional arm BA undergoes torsional stresses.
Preferably, the second end BA" of the second additional arm is fitted with a suitable second roller RL2 which contacts the second cam CM2.
The second additional arm can also be hinged to be supported by the rocker arm shaft, but this is not mandatory. It is preferable, instead that the first end BA' of the second additional arm BA is hinged on the mobile end of the actuator ACT.
Preferably, a reaction spring SPR is interposed between the second additional arm BA and the rocker arm, preferably fitted around the pin PIN or rigid element which can replace the HLA in the valve actuation according to the actuation of the second cam CM2.
Figures 7 and 8 show perspective views of the present invention according, respectively, to the first variant and the second variant described above, wherein, the implementation of the rocker arm with the first additional arm AA is used both to actuate the intake valves IN and the exhaust valves EX. This means that the rocker arms for both the intake and exhaust, can be identical, while what varies is the first additional arm.
It may be noted immediately that the first additional intake arm is longer than the corresponding part of the exhaust section. This aspect does not affect the sizing of the HLA, since the most relevant stresses are generally borne by the exhaust section. Therefore, contrary to the known solutions, the HLA of the intake section IN can be identical to the HLA of the exhaust section. This to the further benefit of a simpler inventory management.
In figures 7 and 8 one can also appreciate the dimensional ratio existing between the distance cross bars T of the intake and exhaust sections and the size of the injector INJ. It can thus be seen that the space is so small that often the implementation of the HLA for recovering is avoided, preferring manual calibration of the rocker arms.
The present invention thus permits optimisation of the space, greater dynamic efficiency of the actuation system in general, a reduction in the size of the HLA and standardization of the intake and exhaust sections which may differ, possibly only for the first additional arm, which, being of simple construction does not requires special machining tolerances as instead is necessary in the construction of the rocker arms.

Claims

Valve actuation system of an internal combustion engine comprising at least one rocker arm (RA) hinged on a rocker arm shaft (BS) and having a first end (RA') facing at least one valve (V) to be actuated and a second end (RA") adapted to interact with a first actuation cam (CM1), the system comprising a first additional arm (AA) having:
- a medial part (AAM) hinged in said first end (RA') of the rocker arm (RA),

- a first end (AA') arranged to directly contact said at least one valve (V),

- a second end (AA") opposite said first end (AA'),
in which a hydraulic valve lifter (HLA) is interposed between the rocker arm (RA) and said second end (AA') of the first additional arm (AA),
the system being characterized in that said HLA is stably associated to the rocker arm so as to be entirely arranged in an intermediate position between a portion (RAM) in which the rocker arm (RA) is hinged on the rocker arm shaft (BS) and the relative second end (RA").
System according to claims 1, wherein a first distance (a) between said medial part (AAM) of the first additional arm (AA) and the relevant first end is less than or equal to a second distance (b) between said medial part (AAM) and the relevant second end (AA") so that said HLA is subjected to a favourable lever.
System according to claim 1, wherein said HLA has its own longitudinal extension (Y) which is substantially perpendicular to the longitudinal extension (XY) of a portion of the rocker arm to which the HLA is stably associated.
System according to any of the preceding claims, wherein the first additional arm (AA) is superimposed on and aligned with the rocker arm (RA), according to a plan view of the system and/or
wherein a pivot that connects said medial part (AAM) of the first additional arm (AA) and said first end (RA') of the rocker arm identifies a direction parallel to said rocker arm shaft (BS).
System according to any of the preceding claims, wherein the HLA lies in a plane perpendicular to a direction identified by the rocker arm shaft (BS) and/or wherein said rocker arm defines a longitudinal extension axis (Y) and wherein the HLA lies in a plane perpendicular to a direction identified by the rocker arm shaft (BS) and is perpendicular with respect to said extension axis of the rocker arm.
System according to any of the preceding claims, wherein said HLA is slidingly housed in a relative seat of the rocker arm (RA), and wherein said seat defines a cavity passing through the rocker arm, and wherein the system comprises a second additional arm (BA) having
- a first end (BA') associated with a moving part of an actuator (ACT),

- a second end (BA"), opposite the first, associated with a second actuation cam (CM2)

- a medial part suitable to interact with said HLA through said through cavity in relation to a position of said actuator (ACT) and in relation to a command offered by said second actuation cam (CM2).
System according to claim 6, wherein, according to an overhead view, said second additional arm (BA) intersects, passing under, the rocker arm (RA).
System according to one of the claims 6 or 7, wherein the second additional arm, in said medial part comprises a pin (PIN) designed to fit at least partially in said through cavity defining the seat of the HLA to interact with said HLA.
System according to one of the claims from 6 to 8, wherein said seat of the HLA defines a contact point (BT) for the HLA so as to define a minimum point of raising the HLA from the respective seat in the rocker arm.
Internal combustion engine comprising at least one cylinder and a relevant valve (V) and a valve actuation system according to any one of the preceding claims 1 - 9.
Engine according to claim 10, wherein said cylinder comprises at least:
- an intake valve and a relevant first rocker arm (RA) and

- an exhaust valve and a relevant second rocker arm and
wherein
Said first and second rocker arms are identical to each other while respective first additional arms can differ from each other.
Land vehicle or fixed installation comprising an internal combustion engine according to one of claims 10 or 11.