COMBUSTION ENGINE.

DESCRIPTION

The invention regards a unit for adjusting the lift of the valves of an internal combustion engine.

As known, internal combustion engines are combustion vehicles that thermodynamically process an operating fluid that is exchanged with the external environment through inlet and outlet openings controlled by means of valves.

The valves are directly or indirectly controlled through mechanical means called tappets which comprise rocker arms actuated by rotating cams whose profile determines the degree and speed of the opening and closure of the aforementioned valves.

The cams are associated to a rotating shaft, thus called camshaft, which rotates at half the speed of the driving shaft and it is controlled by the latter by means of a kinematic unit comprising pulleys driven in rotation by cogged belts, gearwheels and chains, or a gear train.

Current motor vehicle manufacturing developments and studies carried out in this industry reveal that it is advantageous to be able to vary the opening, also referred to as lift, of the valves regardless of the opening value imparted thereto by the cams upon the variation of the engine load and rotational speed conditions.

In addition, should the lift of the valve be nullified, the engine displacement capacity may be varied by deactivating one or more cylinders with an ensuing considerable reduction of consumption and pollutant emissions of the engine. Lastly, the cyclic exclusion of cylinders may represent an efficient method for reducing pumping losses and to increase the actual mean pressure in the operating cylinders, so as to ensure a clean and stable combustion.

There are various technical solutions for controlling the lift of the valves and which are attained according to different embodiments that all reveal the drawback of being costly to obtain, thus justifying the use thereof only on vehicles part of the high market price bracket.

Furthermore, the operation of such known solutions is rather sensitive.

Lastly, such known solutions have a high overall dimension which justifies the use thereof almost exclusively on large-displacement vehicles. The present invention intends to overcome the aforementioned drawbacks. In particular, a first object of the present invention is to obtain a unit for adjusting the lift of the valves of an internal combustion engine that is less expensive to obtain with respect to equivalent adjustment units of the prior art. Another object is that the adjustment unit of the invention has smaller overall dimensions with respect to equivalent prior art adjustment units.

Last but not least, the adjustment unit of the invention has the object of also enabling recovering the clearance of the tappets when the engine is running. The aforementioned objects are attained by an adjustment unit of the invention according to the main claim to which reference is made.

Advantageously, being less costly and having smaller dimensions with respect to adjustment units of the known type, the adjustment unit of the invention may be installed on a wide range of motor vehicles.

Still advantageously, given that the adjustment unit of the invention also enables automatically recovering the clearance of the tappets, it substantially behaves like known hydraulic tappets, with respect to which it also reveals substantially similar overall dimensions.

The objects and advantages listed above shall be further outlined in the description of a preferred embodiment of the invention provided hereinafter by way of non-limiting example with reference to the attached drawings, wherein:

- fig. 1 represents an axonometric view of the adjustment unit of the invention associated to the tappet of an engine, regarding which in the figure there are represented the camshaft and a valve;

- fig. 2 represents a detail of the adjustment unit of the invention represented in fig. 1 ;

- fig. 3 represents an exploded view of a detail of fig. 2;

- fig. 4 represents an exploded view of another detail of fig. 2;

- fig. 5 represents a detail of fig. 2 and fig. 3;

- fig. 6 represents the longitudinal section of fig. 1 ;

- fig. 7 represents a detail of fig. 6 in enlarged view;

- fig. 8 represents a detail of fig. 6 and fig. 7 in enlarged view;

- figures 9 to 15 represent the longitudinal section of the assembly of fig. 1 in different operative positions.

The adjustment unit subject of the invention is represented in axonometric view in fig. 1 and in sectional view in figures 6 and from 9 to 15 where it is indicated in its entirety with 1.

It is used for adjusting the lift of the valves of an internal combustion engine regarding which, in the figures mentioned now, there are represented:

- a valve 2 with relative return spring 2a;

- the valve-seat 2b and the valve-guide 2c;

- the camshaft 3 provided with a cam 4;

- the rocker arm 6 which contrasts with the cam 4 by interposing an idler roller 5 belonging to the rocker arm 6 itself.

In the latter, in particular, there are identified a first part 7 which is associated to a valve 2 of the engine and a second part 9 which is arranged on the opposite side of the first part 7 with respect to the idler roller 5.

It should be observed that the rocker arm could simultaneously control several valves given that the one represented in the mentioned figures is only a possible reference embodiment for description.

As concerns the adjustment unit 1 , it should be observed that it comprises a housing 10 in which there are contained a mobile rod 11 inserted into a sliding seat 12 present in the housing 10 and having a first end 13 arranged at contact with the second part 9 of the rocker arm 6.

A second end 14 of the mobile rod 11 , opposite to the first end 13, is arranged in a hydraulic chamber 15 present in the housing 10 and suitable to contain oil. It should be observed that the housing 10, in the embodiment described herein, takes the shape of a cartridge body.

However, other embodiments in which the housing 10 can belong to the engine and be obtained, for example, in the cylinder head of the engine or in other parts thereof, are possible.

There is also identified a fulcrum area F for the rotation of the rocker arm 6 which, as observable in figures 6 and from 9 to 15, is defined in the contact area between the first end 13 of the mobile rod 11 and the second part 9 of the rocker arm 6.

In particular, the first end 13 of the mobile rod 11 and the second part 9 of the rocker arm 6 are configured with a suitable profile respectively concave and convex so that the contact area that forms the fulcrum area F is substantially the surface of a spherical cover.

Also the elastically yieldable means 16 that cooperate with the mobile rod 11 and a mobile shutter 17 are part of the adjustment unit 1. As observable, the mobile shutter projects into the hydraulic chamber 15 and it is slidingly housed in a through hole 18 obtained in the housing 10.

In addition, the mobile shutter 17 has a projecting end 19 faced towards the external of the housing 10 which is connected to actuator means, indicated in their entirety with 20, which will be described in detail hereinafter.

As regards the mobile rod 11 and the elastically yieldable means 16, they are configured to synergically cooperate and change the position of the fulcrum area F when, during the rotation of the camshaft 3, the actuator means 20 displace the shutter 17 in the hydraulic chamber 15, as described in detail hereinafter when illustrating the operating method of the adjustment unit of the invention.

Particularly, it should be observed that the mobile rod 11 , as described in detail hereinafter, contrasts with an elastic element 31 belonging to the elastically yieldable means 16, which is coaxial to the mobile rod 11 and contrasts with it through an interposed compression ring nut 30.

It should be also observed that the mobile rod 11 , the elastically yieldable means 16 and the shutter 17 are coaxial to each other according to a longitudinal axis Y which also defines the longitudinal axis of the housing 10. Furthermore, the elastically yieldable means 16 are arranged externally with respect to the mobile rod 11 and the latter is aligned coaxial to the shutter 17. The mobile rod 11 , in particular, has an inner longitudinal channel 11a and the hydraulic chamber 15 is divided into two parts comprising a pressure chamber 15a into which the shutter 17 is submerged and a compensation chamber 15b which is defined in a portion of the inner longitudinal channel 11a of the mobile rod 11.

As observable, the aforementioned chambers 15a, 15b are placed in communication with each other and in particular the pressure chamber 15a is placed in communication with a duct 48 for supplying pressurised oil through a one-way valve 49 which enables the oil to flow from the aforementioned supply duct 48 towards the pressure chamber 15a.

In the inner longitudinal channel 11a of the mobile rod 11 there is inserted an elastic element 21 which is comprised between an annular area 23 obtained in the first end 13 of the mobile rod 11 and a slidable sealing cap 22 arranged at the second end 14 of the mobile rod 11 and faced towards the mobile shutter 17. The elastic element 21 has a rigidity and assembly load such that in inoperative conditions it is compressed just for a minute section by the pressure of the oil coming from the one-way valve 49.

It should be observed that in the annular area 23 of the mobile rod 11 there is obtained a through hole 25 which places the inner longitudinal channel 11a of the mobile rod 11 in communication with the outer part of the first end 13 of the latter, so that the oil that flows into the inner longitudinal channel 11a can reach the fulcrum area F and lubricate it.

As concerns the elastically yieldable means 16, it should be observed that they comprise the previously mentioned compression ring nut 30 arranged externally coaxial to the mobile rod 11 in proximity of the first end 13 thereof and the previously mentioned elastic element 31 arranged externally coaxial to the mobile rod 11 and axially comprised between the compression ring nut 30 and an annular seat 32 obtained in the housing 10.

The compression ring nut 30 may also be possibly obtained in a single body with the mobile rod 11.

The elastically yieldable means 16 also comprise a damper unit, indicated in its entirety with 35, which serves to decelerate the valve 2 during the closing and opening step, as described during the illustration of the operation of the adjustment unit.

The aforementioned damper unit 35, which is also observable in the detailed figures 2 to 5, comprises an auxiliary rocker arm 36 pivoted to the rocker arm 6 through the previously mentioned first pin 6a at the end of the valve 2 and to the housing 10 through a second pin 38.

Furthermore, the auxiliary rocker arm 36 has an area with a shaped profile 39 which rests on a compression ring 40 housed in a cylindrical seat 42 obtained in the housing 10 externally with respect to the elastic element 31.

Furthermore, the compression ring 40 is arranged externally coaxial to the compression ring nut 30 and it is axially comprised between the shaped profile 39 and an elastic body 41.

In addition, the elastic body 41 is housed in a cylindrical chamber 43 obtained in longitudinal continuity with the annular seat 32 that houses the elastic element 31.

In particular, it should be observed that the compression ring 40 has an annular recession 44 which defines with the cylindrical chamber 42 in which it is received an annular channel 45.

As observable, the annular channel 45 communicates with a duct 46 for supplying pressurised oil through a one-way valve 47 having the opening direction enabling the flow of oil from the aforementioned supply duct 46 towards the annular channel 45 through a supply duct 48.

As regards the actuator means 20, according to an embodiment thereof described herein, they comprise a connecting rod 50 having a first end 51 fixed to a rotary shaft 52 associated to a driving member (not represented) and a second end 53 associated to the projecting end 19 of the shutter 17.

The connection between the second end 53 of the connecting rod 50 and the projecting end 19 of the shutter 17 occurs through a sliding joint belonging to the mobile shutter 17 and indicated in its entirety with 54, comprising a pin 54a inserted into a slotted hole 55 obtained in the second end 53 of the connecting rod 50.

Thus, when the shaft 52 is driven in rotation by the drive means to which it is connected, the sliding joint 54 transforms the rotation of the connecting rod 50 into an axial movement of the mobile shutter 17 which, being guided by the through hole 18, coaxially approaches towards or moves away from the mobile rod 11 along the longitudinal direction Y depending on the direction of rotation of the rotary shaft 52.

As mentioned, the described embodiment is just one of the possible embodiments according to which the actuator means 20 for controlling the mobile shutter 17 can be obtained.

In particular, as regards the shutter 17, it is observed in the detail of fig. 8 that the end thereof present in the pressure chamber 15a, indicated in its entirety with 60, is provided with a terminal collar 61 having a smaller diameter with respect to the body of the shutter 17, so as to enable the fitting insertion thereof into the terminal opening 11 b of the mobile rod 11 and thus into the compensation chamber 15b defined in the portion of the inner longitudinal channel 11a of the mobile rod 11.

As described further in detail hereinafter, such particular embodiment of the end 60 of the mobile shutter 17 serves to adjust the gradient according to which the pressure varies when the oil contained in the hydraulic chamber 15 is transferred between the pressure chamber 15a and the compensation chamber 15b. Actually, the coupling precision represents a valid impediment to the pressure drop of the oil in the pressure chamber 15a due to seeping.

However, the one-way valve 49 possibly provides for supplementing possible losses due to seepage.

Operatively, the adjustment unit 1 of the invention enables continuously varying the lift of the valve 2, regardless of the positions the cam 4 takes with respect to the rocker arm 6 and independently from the design geometric features of the cam 4.

Regarding this, it should be observed that in the engine the valve 2 in question may indistinctly be the intake valve or the discharge valve, or both.

As will be observable in the description that follows, the variation of the lift occurs by varying the position of the fulcrum area F of the rocker arm 6 during the rotation of the camshaft 3.

Substantially, the adjustment unit 1 of the invention intervenes during the rotation of the camshaft 3 imposing a displacement to the fulcrum area F of the rocker arm 6 which modifies the value of the lift of the valve 2 imposed by the profile of the cam 4.

Fig. 9 represents the inoperative condition in which the valve 2 is closed against the respective seat 2b and the idler roller 5 of the rocker arm 6 is at contact with the base circle 4a of the cam 4.

In such configuration, the end 60 of the shutter 17 is spaced from the terminal opening 11 b of the mobile rod 11 , thus the pressure chambers 15a and the compensation chambers 15b are placed in communication with each other. Starting from this position, the rotation of the camshaft 3 moves the shaped profile 4b of the cam 4 in contrast with the idler roller 5 lowering the rocker arm 6 up to the maximum lowering condition represented in fig. 10, that is achieved when the contact of the cam 4 with the idler roller 5 occurs in the end point of the shaped profile 4b of the cam 4.

Fig. 10 shows that the fulcrum area F lowered with respect to the initial inoperative condition represented in fig. 9 but the valve 2 remained closed against the respective seat 2b during the entire rotation of the cam 4.

Actually, the lowering that the fulcrum area F of the rocker arm 6 has been subjected to by the thrust of the cam 4 has caused the elastic lowering of the mobile rod 11 that has absorbed the entire potential lift of the cam, without such lift being transferred to the valve. The lowering of the fulcrum area F ensuing the lowering in the vertical direction of the mobile rod 11 is caused by the thrust that the cam 4 exerts on the rocker arm 6 and it is enabled by the lower rigidity of the elastic element 31 placed at contact with the compression ring nut 30 and arranged externally coaxial to the mobile rod 11 , with respect to the return spring 2a of the valve 2.

During the lowering of the mobile rod 11 , the end 60 of the mobile shutter 17 does not obstruct the passage of oil from the pressure chamber 15a to the compensation chamber 15b and thus the oil acts against the slidable sealing cap 22 compressing the elastic element 21.

Thus, as long as the position of the end 60 of the shutter 17 is such not to prevent the overflow of the oil from the pressure chamber 15a to the compensation chamber 15b, the valve 2 will remain closed regardless of the angular position of the camshaft 3 and the respective cam 4.

When the adjustment of the actuator means 20 obtains such configuration, the latter corresponds to the conditions in which the operation of the cylinder affected by the valve is excluded.

The situation now described and represented in fig. 10 remains until when, through the actuation of the actuator means 20, the end 60 of the shutter 17 ends up obstructing the terminal opening 11 b of the inner longitudinal channel 11a of the mobile rod 11 , so as to prevent the overflow of oil from the pressure chamber 15a to the compensation chamber 15b.

When this occurs, given that the volume of the pressure chamber 15a is substantially constant, the pressure of the oil therein increases due to the incompatibility thereof and exerts a thrust on the surface of the circular crown 11 c which delimits the terminal opening 11 b of the mobile rod 11 , preventing any further displacement by the latter.

The fact that the volume of the pressure chamber 15a remains substantially constant enables the fine control of the adjustment.

Thus, generally, during the rotation of the cam 4 the position of the fulcrum area F lowers until the end 60 of the shutter 17 closes the terminal opening 11 b of the mobile rod 11 and the lowering travel thereof depends on the position that the actuator means 20 impose on the shutter 17 inside the longitudinal channel 11a of the mobile rod 11.

When the end 60 of the shutter 17 closes the terminal opening 11 b of the mobile rod 11 , the displacement of the fulcrum area F ends and the valve 2 begins the opening thereof through the action of the cam 4.

Figures 1 1 to 13 illustrate, by way of example, different conditions for the lift of the valve 2 as a function of the position of the shutter 17 in the internal longitudinal channel 11a of the mobile rod 11.

Thus, fig. 1 1 shows the adjustment condition in which the adjustment unit 1 maintains the lift H1 of the valve 2 equivalent to 1 /4 of the maximum design lift H defined by the shaped profile 4b of the cam 4 as observable in fig. 13.

Fig. 12 represents the adjustment condition in which the adjustment unit of the invention maintains the lift H2 of the valve equivalent to half the maximum design lift H defined by the shaped profile 4b of the cam 4 as observable in fig. 13.

Lastly, fig. 13 represents the adjustment condition in which the adjustment unit of the invention maintains the lift of the valve equivalent to the maximum design lift H.

Upon the occurrence of the condition in which the actuator means 20 adjust the shutter 17 so that the end 60 thereof penetrates into the inner longitudinal channel 11a of the mobile rod 11 already when the contact between the idler roller 5 of the rocker arm 6 and the cam 4 occurs on the base circle 4a of the latter, then the entire lift imposed by the cam 4 will be transformed into a useful lift for the valve 2, as observable in fig. 13.

Vice versa, if the actuator means 20 impose to the shutter 17 a position in which the end 60 thereof never penetrates into the inner longitudinal channel 11a of the mobile rod 11 , the travel of the latter will never be stopped and will lead to the continuous lowering of the fulcrum area F and thus the valve 2 will always remain closed during the entire rotation of the cam 4.

Under these operating conditions, the oil contained in the hydraulic chamber 15 will be alternatively transferred from the pressure chamber 15a to the compensation chamber 15b and vice versa, depending on which section of the shaped profile 4b of the cam 4 is at contact with the rocker arm 6.

When the engine is operating in the conditions in which the shutter 17 is arranged in intermediate positions in the inner longitudinal channel 11a of the mobile rod 11 , as observable for example in figures 14 and 15, the contact of the idler roller 5 of the rocker arm 6 occurs, as observable, along the intermediate sections of the cam 4 which impose high displacement speeds to the valve 2. As a matter of fact, both the start of the opening motion of the valve 2 - i.e. when the valve detaches from the valve seat 2b in which it is housed - and the end of the closing motion - when the valve 2 settles in the seat 2b again - occur on sections of the cam indicated with 4e and 4f in figures 14 and 15 which impose high valve translation speeds.

Thus, there arises the need to provide for suitable solutions to absorb such accelerations and decelerations which would otherwise cause mechanical damage to the various components.

Firstly, it has already been said that the end 60 of the shutter 17 has a terminal collar 61 which increases the pressure in the pressure chamber 15a with a desired gradient so as to progressively decelerate the mobile rod 11 which supports the rocker arm 6 and thus progressively decelerate the valve 2.

In order to decelerate the valve 2 during the settling in the seat 2b in the closing step there is also provided for the previously described damper unit 35, which is arranged on the top part of the housing 10 and comprises the auxiliary rocker arm 36 hinged to the rocker arm 6 and the housing 10.

The hydraulic reaction of the damper unit 35, generated by the compression of the fluid contained in the hydraulic chamber 43 and the elastic body 41 , is transferred to the valve 2 through the auxiliary rocker arm 36 articulated between the rocker arm 6 and the housing 10 through the pins 6a and 38 respectively.

As previously mentioned, the area with shaped profile 39 of the auxiliary rocker arm 36 which is arranged resting against the compression ring 40 of the damper unit 35 is shaped in a manner such that the damper intervenes only for given distances of the valve 2 from the inoperative position.

During the operative step of the damper unit 35, the contact between the idler roller 5 and the cam 4 is never lost given that all clearances are recovered by the elasticity of the mobile rod 11.

Thus, in the light of the above, it is clear that the adjustment unit subject of the invention attains all pre-set objects.

Firstly, according to the outlined description it is clear that the adjustment unit of the invention is easier to construct with respect to the equivalent prior art adjustment units and thus it is less expensive to manufacture.

Advantageously, this enables mounting the adjustment unit of the invention in engines that are installed on a wide range of motor vehicles and especially on vehicles of the low-price bracket.

Furthermore, the operation of the invention has smaller overall dimensions with respect to the equivalent prior art adjustment units.

In addition, the embodiment of the adjustment unit of the invention is such to enable it to also perform the function of recovering the clearance of the tappets which is normally carried out by the known hydraulic tappets.

It should be observed that the adjustment unit of the invention thus described may also be obtained according to embodiments different from the one illustrated in the figures.

Thus, for example, the housing 10, which is configured in the form of a cartridge body in the figures, may also be constituted by a seat or a housing obtained in the cylinder head or cylinder block of the engine or in any part thereof suitable for the purpose.

Furthermore, in the implementation step, the described elements that form the adjustment unit may be subjected to variants or modifications such to enable the arrangement thereof in different ways inside the housing 10, as long as they enable the same operation.

Lastly, the actuator means 20 for the actuation of the shutter 17 may be of any type and obtained in any form as long as they are suitable to generate the displacement of the shutter 17 in the chambers.

Should such and other possible variants fall within the scope of protection of the claims that follow, they shall definitely be deemed to be protected by the present patent.