CN113167136A

CN113167136A - Hydraulic auxiliary engine brake mechanism for valve train

Info

Publication number: CN113167136A
Application number: CN201980077977.4A
Authority: CN
Inventors: P·埃德克; S·D·帕奇邦德
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2018-11-15
Filing date: 2019-11-15
Publication date: 2021-07-23
Also published as: EP3880941A1; US20210270153A1; WO2020099669A1

Abstract

An exhaust valve rocker arm assembly operable in a drive mode and an engine braking mode includes a rocker shaft, a rocker arm (30), a hydraulic lash adjuster assembly (12), an accumulator assembly (16), and a locking pin (52). The rocker shaft (34) has an oil passage defined therein. The rocker arm (30) has an oil inlet passage fluidly connected to the oil passage. The rocker arm (30) further defines an engine brake release aperture and an accumulator release aperture (46). The accumulator assembly (16) is disposed in the rocker arm (30) and fluidly coupled to the hydraulic lash adjuster through an engine brake release orifice (94). The locking pin assembly (20) is disposed in the rocker arm (30) and is selectively movable from a closed position to an open position by high pressure fluid.

Description

Hydraulic auxiliary engine brake mechanism for valve train

Cross Reference to Related Applications

This application claims the benefit of indian provisional 201811043088 filed on 2018, 11, 15, the contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates generally to engine braking and, more particularly, to hydraulically assisted engine braking.

Background

In addition to wheel brakes, compression engine brakes may be used as auxiliary brakes on relatively large vehicles, such as trucks, driven by heavy or medium duty diesel engines. The compression engine brake system is arranged to provide additional opening of an exhaust valve of an engine cylinder when a piston in the cylinder is near a top dead center position of its compression stroke when activated, such that compressed air may be released through the exhaust valve. This causes the engine to act as an air compressor that consumes power, which slows the vehicle.

In a typical valve train assembly used with a compression engine brake, the exhaust valves are actuated by rocker arms that engage the exhaust valves via a valve bridge. The rocker arm rocks in response to a cam on a rotating camshaft and presses down a valve bridge, which itself presses down an exhaust valve to open it. A hydraulic lash adjuster may also be provided in the valve train assembly to remove any lash or clearance created between the components in the valve train assembly.

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

Disclosure of Invention

An exhaust valve rocker arm assembly operable in a drive mode and an engine braking mode includes a rocker shaft, a rocker arm, a hydraulic lash adjuster assembly, an accumulator assembly, and a locking pin. The rocker arm shaft has an oil passage defined therein. The rocker arm receives the rocker shaft and is configured to rotate about the rocker shaft. The rocker arm has an oil inlet passage fluidly connected to the oil passage. The rocker arm further defines an engine brake release aperture and an accumulator release aperture. The hydraulic lash adjuster assembly is disposed on the rocker arm and has a plunger assembly including a first plunger body and a second plunger body. The first plunger body is movable between a first position and a second position. In the first position, the first plunger body rigidly extends outward. The accumulator assembly is disposed in the rocker arm and fluidly coupled to the hydraulic lash adjuster through an engine brake release orifice. The locking pin assembly is disposed in the rocker arm and is selectively movable from a closed position to an open position by high pressure fluid. In the open position, fluid flows from the accumulator release aperture, causing the plunger assembly to collapse, wherein the first plunger body is movable to the second position.

According to additional features, the accumulator assembly further comprises an accumulator piston and an accumulator biasing member. The rocker arm may define an accumulator chamber that receives the accumulator assembly. The locking pin assembly may include a locking pin and a locking pin biasing member. The rocker arm defines a lock pin receiving body that receives the lock pin biasing member.

In other features, during the drive mode, high pressure oil from the oil gallery is supplied to the lock pin through the rocker arm oil inlet, causing the lock pin to translate to an open position and open the accumulator relief hole. In the drive mode, the plunger assembly is collapsible. During the exhaust lift, the plunger assembly compresses until the first plunger moves past a plunger engine brake release hole in the first plunger and an engine brake release hole in the rocker arm. In the braking mode, low pressure oil from the oil gallery is supplied through the rocker arm oil inlet, allowing the lock pin to move to a closed position and closing the accumulator relief bore. In the braking mode, the plunger assembly is rigid.

According to other features, the angular position of the oil passage on the rocker shaft is positioned such that the oil supply on the rocker arm is selectively positioned with one of a high pressure oil supply and a low pressure oil supply. The lock pin may move to the open position when the oil supply on the rocker arm is aligned with the high pressure oil supply, causing the accumulator assembly to become compressible and provide lost motion in the plunger assembly. The lock pin may move to the closed position when the oil supply on the rocker arm is aligned with the low pressure oil supply, causing the accumulator assembly to become rigid.

Drawings

The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1A is a front perspective view of an engine braking rocker arm constructed according to one example of the present disclosure;

FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. 1A and showing the locking pin in a closed position blocking the accumulator release hole during an engine brake event;

FIG. 1C is a cross-sectional view taken along line 1C-1C of FIG. 1A;

FIG. 1D is a cross-sectional view taken along line 1D-1D of FIG. 1A;

FIG. 2A is a partial front perspective view of the engine braking rocker arm of FIG. 1A;

FIG. 2B is a cross-sectional view taken along line 2B-2B of FIG. 2A;

FIG. 2C is a graph illustrating valve lift versus cam degrees for an exemplary engine braking event performed by the engine braking rocker arm of FIG. 1A;

FIG. 3A is a cross-sectional view taken along line 3A-3A of FIG. 2A and showing the locking pin in an open position opening the accumulator release hole during the drive mode;

FIG. 3B is a cross-sectional view taken along line 3B-3B of FIG. 2A and showing the locking pin in an open position;

FIG. 4A is a cross-sectional view of the engine brake rocker arm of FIG. 1A and showing the locking pin in a closed position;

FIG. 4B is a cross-sectional view of the engine braking rocker arm of FIG. 1A and showing the latch member in a closed position;

FIG. 5A is a cross-sectional view of the engine brake rocker arm of FIG. 1A and showing the locking pin just prior to reset;

FIG. 5B is a cross-sectional view of the engine braking rocker arm of FIG. 5A just after reset;

FIG. 6A is a schematic illustration of an oil supply on a rocker arm being aligned with a low pressure source on an oil passage of a rocker shaft; and is

FIG. 6B is a schematic illustration of the alignment of the oil supply on the rocker arm with the high pressure source on the oil passage of the rocker shaft.

Detailed Description

Referring to the drawings, an engine brake rocker arm assembly is shown and generally indicated by reference numeral 10. In an exemplary embodiment, the engine brake rocker arm assembly 10 provides an engine braking operation with the aid of a Hydraulic Lash Adjuster (HLA)12, an accumulator assembly 16 and a locking pin assembly 20. The engine brake rocker arm assembly 10 also provides a reset function that allows the maximum lift to be the same as the drive mode.

Engine braking is typically used to effectively slow the vehicle down a downhill grade by opening the exhaust valve during the compression stroke. The function of the engine brake pod is to absorb lift from the cam in the engine brake off mode. The engine brake rocker arm assembly 10 described herein is configured to achieve lift absorption using the HLA 12, accumulator assembly 16 and locking pin assembly 20 in conjunction with the hydraulic circuit 26.

Referring specifically to fig. 1A-1D, the rocker arm assembly 10 will be further described. The rocker arm assembly 10 generally includes a rocker arm 30 defining an axle receiving bore 32 and configured to receive and rotate about a rocker arm shaft 34 (fig. 6A). The rocker arm 30 further defines an accumulator chamber 38 that receives an accumulator piston 40 and an accumulator biasing member 42 of the accumulator assembly 16. The rocker arm 30 defines a relief bore 46 configured to drain oil from the accumulator chamber 38 depending on the position of the locking pin assembly 20, as will be understood herein. The rocker arm 30 defines an oil inlet passage 48 that delivers high pressure oil to the locking pin assembly 20. The rocker arm 30 defines a locking pin receiving body 50 that receives a locking pin 52 and a locking pin biasing member 54 of the locking pin assembly 20. Rocker arm 30 further defines an HLA receiving aperture 58 (fig. 1C).

Referring now to fig. 1C and 1D, the HLA 12 will be further described. It should be understood that the HLA 12 may be configured differently within the scope of the present disclosure. The HLA 12 generally includes a compartment or plunger assembly 60 that includes a first plunger body 62 and a second plunger body 64. The second plunger body 64 may be partially received by the first plunger body 62. The plunger assembly 60 is received by the HLA receiving aperture 58. The first plunger body 62 may have a closed end 68 defining a plug 70 that is received in a first socket 72 that ultimately acts against the valve stem. Check ball assembly 80 may be positioned between first plunger body 62 and second plunger body 64. The check ball assembly 80 may include a first biasing member 82, a cage 84, and a check ball 90. Snap ring 92 nests in a radial recess provided in bore 58 of rocker arm 30. The snap ring 92 retains the first plunger body 62 in the bore 58.

The engine brake rocker arm assembly 10 is operable between a drive mode (fig. 3A, 3B) and an engine brake mode (fig. 4A and 4B). In the drive mode, high pressure oil is supplied to the pin 52 through the rocker arm oil inlet 48. This pushes the pin 52 rearwardly and opens the oil path to the accumulator relief hole 46. During a BGR event, the engine brake chamber 60 is spongy and able to absorb BGR lift since the accumulator release orifice 46 is open. During the exhaust lift, the capsule 60 is compressed until the second (inner) plunger 64 moves through the plunger engine brake release hole 94 in the first plunger 62 and the engine brake release hole 95 in the rocker arm 30. After the engine brake release hole 94 is sealed, the entire cam lift is transmitted.

In the engine braking mode, low pressure oil is supplied to the pin 52 from a low pressure chamber 94 (fig. 6A) on the rocker shaft 34 through the rocker oil inlet 48. This holds the pin 52 in place and keeps the accumulator release hole 46 closed. During a BGR event, the engine brake chamber 60 is rigid and delivers BGR/CR lift as the accumulator release orifice 46 closes. During exhaust lift, oil fed to the pin 52 may be positioned such that after a desired rotation, the oil inlet 48 is connected to a high pressure cavity 96 (fig. 6B) on the rocker shaft 34, thereby providing a reset function.

During a reset event, the oil passage 100 is disposed in the rocker shaft 34 to which the main oil passage is connected (see fig. 6A and 6B). The angular position of oil passage 100 on rocker shaft 34 is such that it connects with oil supply 110 on rocker arm 30 at the instant that reset is required. After it is connected, the high pressure oil opens the locking pin 52, causing the accumulator assembly 16 to soften (compress) providing the desired lost motion in the compartment 60. Fig. 5A shows the locking pin 52 prior to reset. Fig. 5B shows the locking pin 52 after reset. Once rocker arm 30 moves back (fig. 6A), it is disconnected from high pressure oil 96, and locking pin 52 then closes again and compartment 60 becomes rigid. The rocker arm assembly 10 also functions for reversing operating pressures, such as, for example, engine brake actuation at high and low pressures in a drive mode. In the illustrated example, the rocker arm assembly 10 is actuated with high pressure in a drive mode and actuated with low pressure in an engine brake mode.

The foregoing description of these examples has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. Which can also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. An exhaust valve rocker arm assembly operable in an actuation mode and an engine braking mode, the exhaust valve rocker arm assembly comprising:

a rocker shaft having an oil passage defined therein;

a rocker arm receiving the rocker shaft and configured to rotate about the rocker shaft, the rocker arm having an oil inlet passage fluidly connected to the oil passage, the rocker arm further defining an engine brake release orifice and an accumulator release orifice;

a hydraulic lash adjuster assembly disposed on the rocker arm, the hydraulic lash adjuster assembly having a plunger assembly including a first plunger body and a second plunger body, wherein the first plunger body is movable between a first position and a second position, wherein in the first position the first plunger body rigidly extends outward;

an accumulator assembly disposed in the rocker arm and fluidly coupled to the hydraulic lash adjuster assembly through an engine brake release orifice; and

a locking pin assembly disposed in the rocker arm and selectively movable by high pressure fluid from a closed position to an open position, wherein in the open position fluid flows from the accumulator release bore causing the plunger assembly to collapse, wherein the first plunger body is movable to the second position.

2. The exhaust valve rocker assembly of claim 1 wherein the accumulator assembly further comprises an accumulator piston and an accumulator biasing member.

3. The exhaust valve rocker arm assembly of claim 2 wherein the rocker arm defines an accumulator chamber that receives the accumulator assembly.

4. The exhaust valve rocker assembly of claim 1 wherein the locking pin assembly comprises a locking pin and a locking pin biasing member.

5. The exhaust valve rocker arm assembly of claim 4 wherein the rocker arm defines a locking pin receiving body that receives the locking pin biasing member.

6. The exhaust valve rocker assembly of claim 1 wherein in the drive mode, high pressure oil from the oil gallery is supplied to the locking pin through the rocker oil inlet, causing the locking pin to translate to an open position and open the accumulator release orifice.

7. The exhaust valve rocker assembly of claim 6 wherein the plunger assembly is collapsible in the drive mode.

8. The exhaust valve rocker assembly of claim 7 wherein during exhaust lift the plunger assembly compresses until the first plunger moves past a plunger engine brake release hole in the first plunger and an engine brake release hole in the rocker arm.

9. The exhaust valve rocker assembly of claim 8 wherein in the braking mode, low pressure oil from the oil gallery is supplied through the rocker arm oil inlet, allowing the locking pin to move to the closed position and close the accumulator release orifice.

10. The exhaust valve rocker arm assembly of claim 9 wherein the plunger assembly is rigid in the braking mode.

11. The exhaust valve rocker arm assembly of claim 10 wherein the angular position of the oil passage on the rocker shaft is such that the oil supply on the rocker arm is selectively positioned with one of a high pressure oil supply and a low pressure oil supply.

12. The exhaust valve rocker arm assembly of claim 11 wherein the locking pin moves to the open position when the oil supply on the rocker arm is aligned with the high pressure oil supply, thereby causing the accumulator assembly to become compressible and provide lost motion in the plunger assembly.

13. The exhaust valve rocker assembly of claim 11 wherein the locking pin moves to the closed position when the oil supply on the rocker arm is aligned with the low pressure oil supply, thereby causing the accumulator assembly to become rigid.