CROSS-REFERENCE TO RELATED APPLICATIONS

This Patent Application claims priority from Italian Patent Application No. 102022000003500 filed on February 24, 2022, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a control system for an engine brake, in particular to a control system for a decompression engine brake.

The present invention is applicable, preferably but not exclusively, in the decompression engine braking for medium- sized/heavy-duty vehicles such as commercial vehicles, trucks, buses or trucks. Reference will be made to such an application in the following by way of example.

BACKGROUND ART

Vehicle braking is normally carried out by imparting a braking torque to the wheel hubs that causes the rotational energy of the latter to dissipate in the form of heat in order to brake the same.

It is clear that, in some operating conditions, in the case of high or continuous stresses, the quantity of heat that is generated by known braking means is high and can lead to the collapse of the wheel hub or fires, both of which can potentially lead to accidents such as running off the road or rear-end crashes.

In order to provide vehicles with an additional braking torque, different types of engine brakes are known that are designed to regulate the release/injection of the gases in the combustion cylinders of internal combustion engines in different ways in order to produce a braking torque.

A known system is to use a butterfly valve at the exhaust (closing it totally or partially) in order to produce a back pressure in the cylinder.

Another system, known as a bleeder, involves keeping the exhaust valve slightly open during all operating cycles of the cylinder.

A further system, known as a decompression brake, involves re-opening the exhaust valve at top dead centre of the piston in the cylinder, thereby releasing the energy accumulated there.

In all cases, braking is proportional to the displacement of the engine and to the speed of rotation. In order to avoid heat dissipation to the wheel hubs, it is thus increasingly required to use engine braking systems of the above type.

Systems of an exhaust butterfly or bleeder type, however, are configured to provide braking powers in the order of 15- 20 kW/litre while systems of a decompression engine brake type can provide higher braking powers between 25 and 35 kW/litre. They thus prove very advantageous in the case of heavy-duty vehicles with a large engine displacement.

However, decompression engine braking systems are normally extremely complex. Furthermore, in the case of a mechanical actuation of the valve opening, it has proven impossible to use hydraulic tappets designed to reinstate the clearance of the valve/rocker; the use of mechanical tappets thus requires periodic maintenance for the adjustment of the tappets. Such an operation increases vehicle downtime and is thus unpopular with consumers.

There is thus a need to provide a control system for decompression engine brakes that is, compatibly, simple, compact and that avoids the need for periodic maintenance for the adjustment of the tappets.

The object of the present invention is to meet the needs set forth in the foregoing in an optimized and cost-effective manner.

SUMMARY OF THE INVENTION

The aforementioned object is achieved by a decompression engine brake control system as claimed in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, a preferred embodiment is described in the following as a nonlimiting example and with reference to the accompanying drawings, wherein:

• Figure 1 is a perspective view of an engine brake control system according to a first embodiment of the invention;

• Figure 2 is an exploded perspective view of the control system of Figure 1;

• Figure 3 is a longitudinal sectional view of the control system of Figure 1 in a first operational state;

• Figure 4 is a longitudinal sectional view of the control system of Figure 1 in a second operational state;

• Figure 5 is a perspective view of an engine brake control system according to a second embodiment of the invention;

• Figure 6 is a longitudinal sectional view of the control system of Figure 1 in a first operational state;

• Figure 7 is a longitudinal sectional view of the control system of Figure 1 in a second operational state;

• Figures 8A-8C are schematic views of different profiles of cams of the control system that can be used in both embodiments of the present invention;

• Figures 9A-9C are schematic views of different profiles of cams of the control system that can be used as an alternative to the second embodiment of the present invention; and

• Figures 10A-10C are longitudinal sectional views of an actuating portion of the control system of both embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The accompanying figures schematically illustrate a pair of intake valves 1, a pair of exhaust valves 2 for a duct of a cylinder system 3, depicted merely schematically for the purposes of example, of an internal combustion engine (not depicted).

The cylinder system 3, as is known, defines respective seats 4 configured to be selectively plugged by the valves 1 and 2, illustrated in a simplified manner in the accompanying figures for the sake of clarity.

To this end, the valves 1 and 2 comprise a stem portion la, 2ba extending longitudinally along an axis parallel to an axis A and a plugging portion lb, 2b carried by a lower portion 1', 2' of the stem portion la, 2a and configured to selectively cooperate with the seat 4 in order to selectively plug the same so as to allow, or deny, the entry of compressed air or allow or deny the exit of compressed air with respect to the cylinder 3.

The pairs of intake and exhaust valves 1, 2 are controlled by means of a control system 5 according to the invention configured to simultaneously control the opening and closing of the intake and exhaust valves 1, 2 in order to allow the cylinder 3 to produce driving torque and in order to selectively control the opening and closing of the exhaust valves 2 in order to allow the cylinder 3 to produce braking torque.

In particular, the control system 5 comprises a control system with cams 6 comprising a rotating shaft 7 which rotates about its longitudinal axis B transverse to the axis A of the direction of movement of the valves 1 and 2.

The control system with cams 6 comprises a first cam mechanism 8 designed to control the opening and closing of the intake valves 1, a second cam mechanism 9 designed to control the opening and closing of the exhaust valves 2 and a third cam mechanism 10 designed to control the opening and closing of the exhaust valves 2 in a decompression braking mode, alternatively to the second cam mechanism 9.

In particular, each cam mechanism 8, 9, 10 comprises a rocker 12, 13, 14 carried so as to be rotationally free on a support shaft 15, preferably common to the three rockers. As shown in the figures, the support shaft 15 is carried in a rigid manner by a base portion 16 configured to accommodate the rotating shaft 7 in a rotationally free manner and to be fixed to an engine casing not illustrated for the sake of clarity .

Each rocker 12, 13, 14 comprises a cam follower end 12'', 13'', 14'' and an actuator end 12', 13', 14' extending so as to project from opposite sides with respect to a coupling portion 12''', 13''', 14''' with respect to an axis perpendicular to the axis A.

In particular, the coupling portion 12''', 13''', 14''' defines an annular portion designed to fit onto the support shaft 15 so as to allow the rotation of the rocker 12, 13, 14 on the same as a function of the force acting on the cam follower portion 12'', 13'', 14''.

Each cam follower end 12'', 13'', 14'', as mentioned, cooperates with a respective cam profile 18, 19, 20 formed on the rotating shaft 7 and described in the following with reference to Figures 8A-8C, 9A-9C.

Each coupling end 12', 13', 14' cooperates with at least one of the pairs of valves 1, 2 as explained in detail in the following in the two different embodiments of the invention.

In particular, at least the coupling ends 12', 13' of the first and second cam mechanisms 12, 13 cooperate in contact with a common support 21 which actuates the pair of intake and exhaust valves 1,2. In particular, an upper end 1'', 2'' of the valves 1, 2 is fixed to the common support 21.

Even more specifically, the common support 21 defines a pair of lateral portions 21' extending transversely with respect to the directions defined by the axes A and B and a central portion 21'' configured to cooperate in contact with the coupling end 12', 13'.

In particular, the coupling end 12', 13' cooperating with the common support 21 comprises a hydraulic tappet 22 in contact with the common support 21.

Referring to the third cam mechanism 14, this is supported on the shaft 15 by an actuator mechanism 30 configured to vary the stroke of the actuating portion 14'' between a maximum stroke X and a minimum stroke X'. In particular, the actuator mechanism 30 comprises an eccentric device 31 radially interposed between the shaft 15 and the intermediate portion 14''' of the third cam mechanism 14.

More specifically, the eccentric device 31 comprises an annular portion 31' configured to fit on the shaft 15 and an actuating portion 31'' extending radially with respect to the annular portion 31'. In particular, it can be seen that the centre of rotation P of the shaft 15 is displaced eccentrically with respect to the centre of rotation P' of the annular portion 31'.

In particular, the actuating portion 31'' comprises a pair of pins 32, 33 extending from the actuating portion 31'', preferably parallel to the axis B.

The actuator mechanism 30 comprises an actuator device 34 configured to move the eccentric device 31 in order to rotate it about the axis B, advantageously providing a force to at least one of the pins 32, 33. In particular, the actuator device 34 is of a hydraulic type and comprises at least one pin 35 carried in a movable way by the support 16 and configured to assume a first extended configuration or a second retracted configuration in order to cooperate or not cooperate with the at least one pin 32, 33.

Advantageously, the illustrated actuator device 34 comprises a pair of pins 35 cooperating with the pair of pins 32, 33 and controlled in an alternative mode by the actuator device 34 so that one pin 35 is extracted from the support 16 and the other is retracted.

Referring in particular to the actuator device 34, the hydraulic control circuit advantageously comprises a solenoid valve 36 configured to convey fluid to an intermediate valve 37, advantageously a pressure-actuated, two-way, two-position valve configured to regulate the passage of fluid to or from the pin 35. Preferably, the hydraulic control circuit of the actuator device 34 is integrated in the support 16. Advantageously, the solenoid valve 36 is electronically connected to and controlled by the engine control unit.

Advantageously, the control system 5 also comprises elastic means 38 configured to keep the rocker 14 in the maximum stroke position X during the operation of the control system as an engine, so as to avoid collisions and rebounds due to the continuous cam/roller contact. In particular, such elastic means 38 comprise a coil spring 39 operatively interposed between a flange 16' integral with the support 16 and the cam follower portion 14' of the same and designed to exert a force opposite to that of the actuator device 34 so as to maintain the rocker 14 in said position, i.e. in contact with the cam profile.

According to the embodiment of Figures 1 to 4, the actuating portion 14'' carries a pushrod 40 configured to cooperate in contact with a portion 42 rigidly carried by the rocker 13 of the second cam mechanism 9. In this embodiment, the common support 21 rigidly carries both upper ends of the exhaust valves 2.

According to Figures 8A-8C, the intake cam 18 comprises a profile having a single actuating portion 18', correctly phased on the axis B. Similarly, the exhaust cam 19 comprises a profile having a single actuating portion 19' correctly phased on the axis B. The brake cam 20, on the other hand, comprises a profile defining a pair of actuating portions 20', 20'' appropriately phased in order to actuate the movement of the respective rocker 14 at the BCR (brake compression release) and CR (compression release) points.

The embodiment described in the foregoing works as follows.

When rotating, the rotating shaft 7 carries the intake cam 18, the exhaust cam 19 and the brake cam 20 with it. The corresponding actuating portions 18', 19' and 20' rotate around the axis B and cooperate in contact with the respective cam follower portions 12', 13', 14'. The first and second rockers 12, 13 actuated by the actuating portions 18', 19' rotate around the axis B and, via the hydraulic tappet 22, push the common support 21, thus regulating the opening and closing of the intake and exhaust valves 1, 2. The third rocker 14, in the standard engine operating configuration, is spaced apart and kept in its maximum stroke X by the elastic means 38 so that, when the actuating portions 20', 20'' of the cam 20 cooperate with the cam follower portion 14', the movement of the rocker 14 is not sufficient to make the pushrod 40 touch the portion 42. Consequently, the system 5 controls the standard engine operation.

When necessary, however, the actuator device 34 commands the extraction of the pin 35 and the extraction of the opposite pin. A force is thus exerted on the pin 33 which rotates the eccentric device 31 within the seat of the intermediate portion 14''' of the rocker 14. As a result of the eccentricity between the centres of the intermediate portion 14''' and the annular portion 31' of the eccentric device 31, which is housed around the shaft 15, the rocker

14 modifies its inclination and passes to a minimum stroke X' while counteracting the force provided by the elastic means 38 which would tend to keep it in the maximum stroke X. In such a configuration, when the actuating portions 20', 20'' of the cam 20 cooperate with the cam follower portion 14' of the rocker 14, they push the pushrod 40 against the portion 42 which, integral with the common support 21, opens the exhaust valves 2, thus obtaining the decompression brake effect.

When it is necessary to return to the engine operating configuration, the actuator device 34 commands the retraction of the pin 35 (and in the described case, the exit of the pin opposite the same) so that the elastic means 38 return the eccentric device 31 to the maximum stroke configuration X.

According to the embodiment of Figures 5 to 7, the actuating portion 14'' carries a pushrod 40 configured to cooperate in contact with a portion 42 movably housed in a hole 43 of the common support 21 and integral with the upper portion of an exhaust valve 2. In particular, the movable portion 42 and the hole 43 define a shoulder designed to allow both the single actuation of the portion 42 by means of the pushrod 40 and the actuation together with the common support 21.

In this embodiment, the profiles of the cams follow the profiles illustrated in Figures 8A-8C described above and not reiterated here for the sake of brevity.

The embodiment described in the foregoing works as follows.

When rotating, the rotating shaft 7 carries the intake cam 18, the exhaust cam 19 and the brake cam 20 with it. The corresponding actuating portions 18', 19' and 20' rotate around the axis B and cooperate in contact with the respective cam follower portions 12', 13', 14'. The first and second rockers 12, 13 actuated by the actuating portions 18', 19' rotate around the axis B and, via the hydraulic tappet 22, push the common support 21, thus regulating the opening and closing of the intake and exhaust valves 1, 2. The third rocker 14, in the standard engine operating configuration, is spaced apart and kept in its maximum stroke X by the elastic means 38 so that, when the actuating portions 20', 20'' of the cam 20 cooperate with the cam follower portion 14', the movement of the rocker 14 is not sufficient to make the pushrod 40 touch the portion 42. Consequently, the system 5 controls the standard engine operation.

When necessary, however, the actuator device 34 commands the extraction of the pin 35 and the extraction of the opposite pin. A force is thus exerted on the pin 33 which rotates the eccentric device 31 within the seat of the intermediate portion 14''' of the rocker 14. As a result of the eccentricity between the centres of the intermediate portion 14''' and the annular portion 31' of the eccentric device 31, which is housed around the shaft 15, the rocker 14 modifies its inclination and passes to a minimum stroke X' while counteracting the force provided by the elastic means 38 which would tend to keep it in the maximum stroke X. In such a configuration, when the actuating portions 20', 20'' of the cam 20 cooperate with the cam follower portion 14' of the rocker 14, they push the pushrod 40 against the portion 42 which, moving inside the common support 21, causes a single exhaust valve 2 to open.

When it is necessary to return to the engine operating configuration, the actuator device 34 commands the retraction of the pin 35 (and in the described case, the exit of the pin opposite the same) so that the elastic means 38 return the eccentric device 31 to the maximum stroke configuration X.

According to a further embodiment not illustrated and comprising the actuation of a single exhaust valve 2 as in the second embodiment, the tappet 22 is of a collapsible type, i.e. it can be hydraulically controlled to discharge the fluid inside it, thus rendering the actuation of the common support 21 impossible. Advantageously, the hydraulic circuit of the actuator device 34 can be realized in common with the control circuit of the collapsible tappet 22. Alternatively, an electronic control unit is configured to synchronize the operation of the two hydraulic circuits.

In this embodiment, the profiles of the cams follow the profiles illustrated in Figures 9A-9C, the intake cam 18 comprises a profile having a single actuating portion 18' correctly phased on the axis B. Similarly, the exhaust cam 19 comprises a profile having a single actuating portion 19' correctly phased on the axis B. The brake cam 20, on the other hand, comprises a profile defining two pairs of actuating portions 20', 20'', 20a, 20b appropriately phased to actuate the movement of the respective rockers 14 at a pair of BCR (brake compression release) points, and a pair of CR (compression release) points.

The embodiment described in the foregoing works as follows .

When rotating, the rotating shaft 7 carries the intake cam 18, the exhaust cam 19 and the brake cam 20 with it. The corresponding actuating portions 18', 19' and 20' rotate around the axis B and cooperate in contact with the respective cam follower portions 12', 13', 14'. The first and second rockers 12, 13 actuated by the actuating portions 18', 19' rotate around the axis B and, via the hydraulic tappet 22, push the common support 21, thus regulating the opening and closing of the intake and exhaust valves 1, 2. In particular, the hydraulic tappet 22 is in an expanded/pressurized configuration and allows the actuation of the exhaust valves 2. The third rocker 14, in the standard engine operating configuration, is spaced apart and kept in its maximum stroke X by the elastic means 38 so that, when the actuating portions 20', 20'' of the cam 20 cooperate with the cam follower portion 14', the movement of the rocker 14 is not sufficient to make the pushrod 40 touch the portion 42. Consequently, the system 5 controls the standard engine operation.

When necessary, however, the actuator device 34 commands the extraction of the pin 35 and the extraction of the opposite pin. A force is thus exerted on the pin 33 which rotates the eccentric device 31 within the seat of the intermediate portion 14''' of the rocker 14. As a result of the eccentricity between the centres of the intermediate portion 14''' and the annular portion 31' of the eccentric device 31, which is housed around the shaft 15, the rocker 14 modifies its inclination and passes to a minimum stroke X' while counteracting the force provided by the elastic means 38 which would tend to keep it in the maximum stroke X. Furthermore, the hydraulic tappet 22 is collapsed/depressurized in this configuration.

In such a configuration, when the actuating portions 20', 20'', 20a, 20b of the cam 20 cooperate with the cam follower portion 14' of the rocker 14, they push the pushrod 40 against the portion 42 which, moving within the common support 21, causes just one of the exhaust valves 2 to open. Similarly, the actuating portion 19' of the second cam 19 moves the corresponding rocker 13; however, as the tappet 22 is collapsed, it is not able to actuate the common support 21, thus preventing the opening of both exhaust valves 2.

When it is necessary to return to the engine operating configuration, the actuator device 34 commands the retraction of the pin 35 (and in the described case, the extraction of the pin opposite the same) so that the elastic means 38 return the eccentric device 31 to the maximum stroke configuration X. Similarly, the tappet 22 is re-pressurized so as to enable an actuation of the command of the common support 21.

The advantages of a decompression engine brake control system according to the invention are evident from the foregoing.

With the proposed system, it is possible to mechanically control a decompression brake functionality of an engine system by means of a compact and reliable system.

It is consequently possible to provide greater braking powers without substantial modifications to known systems, simply by varying the mechanical system for controlling the engine cylinder head. In particular, it is possible to use an engine brake control system using hydraulic tappets: this obviates the need to adjust clearances of the cam mechanisms, thus increasing the service life of the control system and thereby reducing the maintenance costs of the engine system.

Furthermore, the proposed control system can be used to control both "1.0 stroke" configurations of the decompression brake system (via the cams in Figures 8A-8C) as well as a "1.5 strokes" system configuration (via the cams in Figures 9A-9C), thus providing greater braking powers in a simple manner by varying the cam profile 20.

Finally, it is clear that the decompression engine brake control system according to the present invention can be modified and varied without, however, departing from the scope of protection defined by the claims.

It is evident that it is possible to provide cam or actuator devices, and thus corresponding rockers, shafts and tappets, of different shapes and types than those described.