Engine brake assembly

Abstract

An engine brake rocker arm assembly (RA) comprising: a rocker arm (11) arranged to swing in response to a cam supported by a camshaft so as to press down at least one exhaust valve; a shaft (20) slidably arranged in one end of the rocker arm, the shaft having a first end and a second end opposite the first end, the first end being provided with an engagement portion (16, 21) facing the exhaust valve, the second end being provided with a stroke stop (24). The castellated members (30, 40, 50) comprise anterior teeth adapted to engage with each other such that the capsule is adapted to assume an extended configuration and a contracted configuration, respectively, according to tooth-to-tooth or tooth-to-valley engagement under the action of an actuator (70) adapted to rotate at least one member of the castellated capsule relative to the other, and a rocker arm (60) arranged to bias the castellated members away from each other so as to force the castellated capsule in said extended state and said contracted state, in which the rocker arm comprises a seat (90) filled with oil to define a damping portion capable of damping the stroke stop (24).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of engine brake actuation systems in the field of medium and heavy duty vehicles. PRIOR ART DESCRIPTION

[0002] In addition to the wheel brakes, compression engine brakes can be used as auxiliary brakes on relatively large vehicles powered by heavy or medium duty diesel engines, such as trucks. During engine brake operation, the engine is not fueled and a compression engine brake strategy is actuated to provide additional opening of the exhaust valve of the engine cylinder as the piston in the engine cylinder approaches the top dead center position of its compression stroke, so that the compressed air is released through the exhaust valve.

[0003] This results in the air trapped in the cylinder not returning the compression energy accumulated during compression. Thus, the engine acts as an air compressor and the consumed torque slows down the vehicle.

[0004] In a typical valve train assembly used with compression engine brakes, the exhaust valve is actuated by a rocker arm that engages the exhaust valve by means of a valve bridge. The rocker arm oscillates in response to a cam on a rotating camshaft and presses down on the valve bridge, which in turn presses down on the exhaust valve to open it.

[0005] In some rocker arm assemblies, an oil circuit pressurizes the mechanism that selectively pushes the exhaust valve during engine braking.

[0006] Eaton Intelligent Power Ltd. has developed several commercially available solutions.

[0007] The EATON® solution is mainly based on the castellation assembly disclosed in WO2022248082A1 and WO2019133658.

[0008] Here, the actuator is arranged to rotate the first castellation member so that the axial tooth face of the first castellation member faces the axial tooth or the valley between the teeth of the second castellation member.

[0009] The first castellation member is rotatably mounted on a shaft that is fixed with the rocker arm.

[0010] In the first case, tooth-to-tooth: both castellation members bring the shaft to maximum extension in order to activate the exhaust valve, while in the second case, tooth-to-valley: the second castellation collapses in the first castellation.

[0011] In the previous period, EATON developed a new solution disclosed in US11428127B2. In this solution, there are three castellated members mounted on a shaft.

[0012] The third castellated member biases the first and second castellated members apart. The engine brake rocker assembly selectively opens the first and second exhaust valves and comprises an exhaust rocker configured to rotate about a rocker shaft. The engine brake capsule assembly is movable between a locked position configured to perform an engine brake operation and an unlocked position not performing an engine brake operation, and a hydraulically controlled actuator assembly is configured to selectively move the engine brake capsule assembly between a first configuration and a second configuration.

[0013] The actuator assembly comprises a pin arranged to rotate the first castellated member of the engine brake capsule assembly. In the fired condition, i.e. when the engine brake operation is stopped, the castellated shaft is configured to slide within a lash adjustment screw.

[0014] Prior art Figure 1 a and Figure 1 b (corresponding to US11428127B2 Figure 3a and Figure 3b ) disclose two configurations of the castellated shaft with respect to the rocker.

[0015] Here, the engine brake capsule can be fixed to the same rocker operating the valve bridge as disclosed in WO2019133658 or to an auxiliary rocker as disclosed in WO2021164950.

[0016] According to these solutions, the main problem is that the nut arranged to adjust the position of the shaft, commonly referred to as "stroke stop", in the fired condition impacts the seat of the capsule in each swing operation of the rocker.

[0017] These impacts generate noise and cause damage to the assembly rocker / capsule.

[0018] Therefore, the background can be summarized as an engine brake capsule assembly provided with at least two castellated members provided with axial teeth. One of the castellated members is arranged to rotate in such a way that the axial teeth face the axial teeth or the corresponding valleys of the other castellated member. Therefore, the two possible configurations are "tooth-to-tooth" or "tooth-to-valley".

[0019] The actuator is arranged to tangentially contact the rotating castellated member and to rotate it to control its angular position with respect to the other castellated member. The castellated arrangement is on a shaft provided with a nut of a gap adjustment screw. In the firing operating condition, since the castellated capsule is collapsible, the nut alternately moves away and approaches the rocker arm. This alternating movement would cause the generation of impacts, noise and damage.

[0020] US11428127B2 and WO2021164950 are included herein by reference.

[0021] Unless explicitly excluded in the following detailed description, what is described in this chapter will be considered as an integral part of the present detailed description. SUMMARY

[0022] The main purpose of the present invention is to overcome the above-mentioned problems / defects in the solution proposed and commercialized by EATON®.

[0023] The main principle of the present invention is to provide an oil buffer to dampen the adjustment screw.

[0024] In particular, in the rocker arm that houses the brake capsule, a seat is formed, which is filled with oil coming from an oil source. A channel formed in the rocker arm supplies the seat with oil. The channel has at least one outlet in the seat, which represents an oil inlet of the seat. Furthermore, the seat has at least one oil outlet.

[0025] While the oil inlet of the seat is closed by the nut, the oil outlet is always open when the nut is seated in the seat, so as to allow the oil to flow out even during the approaching movement of the nut to the seat.

[0026] Preferably, the seat has an approximately cylindrical shape and the outlet is formed by at least one lateral wall inclined from the base of the seat, so that, due to the approaching movement of the nut, the oil can escape from the seat.

[0027] It should be noted that the valve train is arranged in a closed compartment defined in the engine head and the oil supplied to the valve train flows to the oil sump from which the pump draws the oil and pumps it into the main oil duct hydraulically connected to the valve train, in particular to the rocker arms that support the brake capsules.

[0028] These and other objects are achieved by the appended claims, which describe preferred embodiments of the present invention, forming an integral part of the present description. BRIEF DESCRIPTION OF DRAWINGS

[0029] The present invention will become fully clear from the following detailed description, given only by way of example and non-restrictive illustration, to be read in conjunction with the attached drawings, wherein: - the prior artFigure 1 a and Figure 1 b discloses an example of a switchable brake capsule from EATON® in two opposite situations when the engine is running in non-braking mode (i.e. the engine is fired or is being towed); - Figure 2 A perspective view is disclosed of an example of a rocker arm supporting a switchable brake capsule; - Figures 3a to 3c A part of the valve train according to different operating conditions is disclosed, including a cross section of the rocker arm assembly with the switchable capsule of the rocker arm; - Figure 4 A top view of the rocker arm assembly of figure 3 is disclosed, centered on the nut of the switchable brake capsule; - Figure 5 A longitudinal section of a part of the valve train of the preceding figures is disclosed.

[0030] The same reference numbers and letters in the figures designate the same or functionally equivalent parts.

[0031] According to the present invention, the term “second element” does not imply the existence of a “first element”, the first, second, etc. being used only to improve the clarity of the description and should not be interpreted in a limiting manner. Detailed description of the preferred embodiments

[0032] As mentioned above, the object of the present invention is to solve the impact between the nut of the lash adjust screw and the upper part of the rocker arm.

[0033] In Figure 1 a and Figure 1 b, the first castellation 1 constitutes a mechanical capsule comprising an annular shroud 80 coupled to a rack 75 of an actuator 70. This mechanical capsule can be drop-in assembled in the capsule hole 17 (see Figure 2 ). The hole end 171 comprises a clearance hole 172 through hole through which the shaft 20 can slide. The rocker arm 11 is shown comprising a capsule hole 17 with a locating washer 18 and a snap ring 19 to retain the castellation 1 therein. The return spring 60 and the castellation members 30, 50, 40 can be dropped into the capsule hole 17 with the shaft 20 passing through the capsule hole 17. The washer 18 and snap ring 19 or other locking means (such as a set screw, a press-in bushing, etc.) prevent the castellation 1 from falling out of the capsule hole 17. The washer 18 or snap ring 19 or other locking means can serve as a travel limiter for the shaft 20, such as by impeding the travel of the foot 21 or e-foot 16.

[0034] The biasing spring 60 is disposed between the second and third castellation members and is configured to bias the second castellation member away from the third castellation member such that the castellation capsule assumes an extended configuration.

[0035] The lash sleeve 23 or lash adjusting screw is fitted or fixed to the lash end 22 of the shaft 20, for example by threading or press fit. The lash sleeve 23 can be positioned on the shaft 20 to control the lash of the castellation device 1. A travel stop 24 can be included to catch on the lash hole 172 or bore end 171. The shaft 20 includes a foot 21 configured to press on a valve stem, valve bridge, other rocker arm or other valve train component to effect the compressed air release for engine brake operation. The foot device 16 can also be implemented on the shaft 20 by attaching an appropriate socket arrangement to the shaft 20.

[0036] In the tooth-to-valley configuration, the shaft 20 is free to slide within the bore as the castellation member retracts. In particular, as the rocker arm attempts to push down on the valve stem of an exhaust valve, the spring of the exhaust valve is more rigid than the spring 60 of the castellation capsule 1, and thus, in response to the rocker arm approaching the exhaust valve stem, the castellation capsule retracts and the shaft 20 slides axially within the capsule, as illustrated from Figure 1 a and Figure 1 b, as clearly seen in the comparison of

[0037] Conversely, in the tooth-to-tooth configuration, as the castellation member extends, the foot is forced away from the rocker arm, and thus the approach motion of the rocker arm causes the exhaust valve stem to be pushed down, as illustrated in Figure 1 a.

[0038] The rack 75 of the actuator 70 is coupled to one of the castellation members.

[0039] The actuator 70 defines a “rack and pinion” type arrangement, for example the axial motion of the actuator forces one of the castellation members to rotate. Since the EATON product is already on the market and is fully disclosed in a number of patents, no further details need to be described.

[0040] With reference to figure 3, the rocker arm 11 is further provided with: - a seat 90, which is complementary to the lash end 22 of the shaft 20; - an oil channel 93, which is arranged to fill the seat 90 with hydraulic oil; and the seat comprises an outlet opening 92, which is arranged to discharge the oil at least when the lash end 22 approaches the seat.

[0041] The shape of the outlet opening 92 is calibrated so that the oil in the seat defines a cushion, which is able to cushion the approach of the end 22, and at the same time allows the lash end to pass through the seat.

[0042] Preferably, the end 22 of the shaft defines a nut having a flat shape, so as to be screwed on the shaft 20 to allow the lash adjustment.

[0043] The lower portion 24 of the end 22 of the shaft 20, which penetrates the seat, is preferably cylindrical.

[0044] The lower portion 24 of the end 22 is shaped so that, when approaching the seat 90, the lower portion 24 closes the inlet opening 91 which communicates with the channel 93.

[0045] Therefore, in the first approach phase, the lower portion 24 closes the inlet 91, then the lower portion 24 pushes the oil outside through the outlet 92.

[0046] Figure 4 The top view discloses the end portion 22 defined by a hexagonal nut and three outlet openings 92 made in the peripheral wall of the seat.

[0047] Obviously, preferably, the seat is defined by a blind cylindrical opening having a through hole in its center, so as to allow the accommodation of the shaft 20, and the lower portion 24 of the end 22 of the shaft 20, in addition to the outlet openings 92, has a cylindrical shape complementary to the seat.

[0048] The cross section of the outlet openings 92 decreases towards the base face of the cylindrical shape of the seat, in such a way as to slow down the flow of oil in the last phase of approach of the end 22 to the seat.

[0049] Example embodiments are provided so as to be thorough and to convey the full scope of the disclosure. Numerous specific details are set forth, such as examples of specific components, devices, and methods, in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to one skilled in the art that specific details need not be present in order to practice the present embodiments. For example, well-known structures, devices, and techniques have been described without detail in order to avoid obscuring the present embodiments. In some example embodiments, well-known structures, devices, and techniques are not described in detail.

[0050] Many variations, modifications, variations, and other uses and applications of the present application will become apparent to those of ordinary skill in the art after considering the specification and the accompanying drawings, which disclose preferred embodiments of the application as described in the claims.

[0051] The features disclosed in the background of the prior art section are presented only to better understand the present application, and are not admitted to be prior art. Moreover, the features disclosed in the background of the prior art section define the context of the present application, therefore these features should be considered as common to the detailed description.

[0052] Further implementation details will not be described, as the person skilled in the art is able to perform the present application starting from the teachings described above.

Claims

1. An engine braking assembly (RA), comprising: - A rocker arm (11), which is arranged to swing in response to a cam supported by a camshaft, so as to press down at least one exhaust valve. - A shaft (20) slidably disposed in one end of the rocker arm, the shaft (20) having a first end and a second end opposite to the first end, the first end being provided with a joint (16, 21) facing the exhaust valve, and the second end being provided with a stroke stop (24), the shaft being supported by a scalloped bladder (1). - The crenellated capsule (1) includes crenellated members (30, 40, 50) which include front teeth adapted to mesh with each other, such that the capsule is adapted to present an extended configuration and a contracted configuration respectively under the action of the actuator (70) according to tooth-to-tooth or tooth-to-valley meshing; - The actuator (70) is adapted to rotate at least one member of the basal capsule relative to another member in order to force the basal capsule into the extended state and the contracted state. - Elastic elements (60) are arranged to bias the crenellated members away from each other. The rocker arm includes: -- A seat (90), which is complementary to the travel stop (24), the seat being arranged such that the travel stop (24) of the shaft (20) passes through the seat during the rocker arm's disengagement from the exhaust valve, and -- Oil passage (93), which is arranged inside the rocker arm to fill the seat (90) with hydraulic oil, and The seat includes at least one outlet opening (92), the shape of which is calibrated to allow oil to flow out, such that the oil in the seat defines a buffer portion that can cushion the approach of the travel stop (24).

2. The component according to claim 1, wherein, The seat includes at least one outlet opening (92) whose shape is calibrated to allow the oil to escape from the seat during the approach of the travel stop.

3. The component according to claim 2, wherein, The travel stop is shaped like a hexagonal nut, and three outlet openings (92) are formed in the peripheral wall of the seat.

4. The component according to claim 2 or 3, wherein, A section of the outlet opening (92) decreases towards the cylindrical bottom surface of the seat to slow the flow of oil during the final stage when the travel stop (24) approaches the bottom surface of the seat.

5. The component according to any one of the preceding claims, wherein, The oil passage (93) has an outlet opening (91), and the travel stop (24) is arranged to close the outlet (91) when approaching the bottom surface of the seat.

6. The component according to claim 5, which is dependent on claim 4, wherein, The at least one outlet opening and the inlet opening (91) are arranged such that the travel stop closes the inlet opening before the approach movement toward the bottom surface of the seat ends.

7. A combustion engine including an engine braking system, said engine braking system comprising components according to any one of claims 1-6.

Images