CN112639255A

CN112639255A - Balance arm bleeder brake with HLA

Info

Publication number: CN112639255A
Application number: CN201980056996.9A
Authority: CN
Inventors: 马克·范文杰登; 安德鲁·李
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2018-07-12
Filing date: 2019-07-12
Publication date: 2021-04-09
Anticipated expiration: 2039-07-12
Also published as: WO2020014637A1; EP3821114A4; CN112639255B; EP3821114A1

Abstract

A valvetrain assembly configured to selectively perform a bleeder braking operation, the valvetrain assembly comprising: a rocker arm configured to rotate about a rocker shaft; a camshaft having a lobe configured to impart motion to the rocker arm via a pushrod; and a valve bridge assembly operatively coupled to the rocker arm and configured to be selectively engaged by the rocker arm to open at least one of the first and second engine valves. An engine brake bladder is operably associated with the valve bridge assembly and is configured to operate in a drive mode in which the engine brake bladder does not cause the valve bridge assembly to open the first or second engine valve and a brake mode in which the engine brake bladder engages the valve bridge assembly to partially open the first engine valve to perform the bleeder braking operation.

Description

Balance arm bleeder brake with HLA

Cross Reference to Related Applications

This application claims the benefit of U.S. provisional patent application serial No. 62/697119, filed on 12.7.2018, the contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates generally to valvetrain assemblies for internal combustion engines and, more particularly, to valvetrain assemblies for bleeder braking.

Background

Engine braking may be used to slow the forces within the engine to ultimately slow the vehicle. In a typical valvetrain assembly used with engine braking, the exhaust valves are actuated by rocker arms that engage the exhaust valves via valve crossbars. The rocker arm rocks in response to a cam on a rotating camshaft and presses down a valve bridge, which itself presses down the exhaust valve to open it.

One form of engine braking includes bleeder braking. In addition to wheel braking, bleeder braking may be used as an auxiliary brake on relatively large vehicles, such as trucks, powered by heavy or medium duty diesel engines. Bleeder brakes typically include a piston that selectively extends to full stroke. The piston may hold the exhaust valve open a fixed amount throughout the engine cycle during a full stroke. Thus, a mechanical clearance may be created in the valve train. In many cases, such clearances may be incompatible with common Hydraulic Lash Adjusters (HLA). 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 mechanical clearance may allow the HLA to pump up disadvantageously, preventing the exhaust valve from closing once the bleeder brake is deactivated.

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

According to various aspects of the present disclosure, a valvetrain assembly configured to selectively perform a bleeder braking operation is provided. In one example, the valvetrain assembly includes: a rocker arm configured to rotate about a rocker shaft; the engine further includes a camshaft having a lobe configured to impart motion to the rocker arm via a pushrod, and a valve bridge assembly operatively coupled to the rocker arm and configured to be selectively engaged by the rocker arm to open at least one of the first engine valve and the second engine valve. An engine brake bladder is operably associated with the valve bridge assembly and is configured to operate in a drive mode in which the engine brake bladder does not cause the valve bridge assembly to open the first or second engine valve and a brake mode in which the engine brake bladder engages the valve bridge assembly to partially open the first engine valve to perform the bleeder braking operation.

In addition to the above, the described valvetrain assembly may include one or more of the following features: a Hydraulic Lash Adjustment (HLA) tappet disposed between the camshaft and the pushrod; wherein the HLA tappet is a de-activated HLA tappet; wherein the HLA tappet is a roller tappet; the valve cross arm assembly comprises a lever assembly arranged in a cross arm main body; wherein the lever assembly includes a lever pivotably coupled to the bridge body by a bridge pin, the lever configured to engage the first engine valve; wherein the stem assembly further comprises a valve seat pivotally coupled to the lever by a valve seat pin; wherein a pair of stop arms extending from the crossbar body limit upward movement of the valve seat pin; and wherein in the braking mode, the lever is selectively engaged by the engine braking bladder to cause rotation about the cross arm pin and upward movement of the cross arm body which causes rotation of the rocker arm and a downward reaction force into a Hydraulic Lash Adjuster (HLA) tappet to prevent pumping thereof.

In addition to the above, the described valvetrain assembly may include one or more of the following features: wherein the valve bridge assembly is a straight-through bridge assembly having a pin assembly disposed within the bridge body; wherein the pin assembly is disposed within an aperture formed in the crossbar body and comprises a contact pin and a valve seat, the contact pin configured to be engaged by the engine brake capsule to impart motion to the valve seat to engage the first engine valve in the braking mode; and wherein the contact pin extends through a hole formed in the cross arm body, and wherein a shoulder at least partially defines the aperture, and the hole is configured to limit upward movement of the valve seat.

In addition to the above, the described valvetrain assembly may include one or more of the following features: wherein the valve bridge assembly is a solid bridge assembly having a first end configured to engage and pivot on the first engine valve and a second end configured to engage and pivot on the second engine valve; wherein the engine brake capsule comprises an outer body defining an upper chamber and a lower chamber; wherein the engine brake capsule further comprises a pin disposed in the upper chamber and a biasing mechanism configured to bias the pin downward toward the lower chamber; wherein the engine braking capsule further comprises a plunger and check ball assembly disposed in the lower chamber, the plunger configured to slide along the lower chamber between a retracted position and an extended position; and wherein the check ball assembly includes a check ball, a seat, and a biasing mechanism configured to bias the check ball toward the upper chamber to seal the passage.

In another aspect, a method of operating a valvetrain assembly having: a rocker arm configured to rotate about a rocker shaft; a camshaft having a lobe configured to impart motion to the rocker arm via a pushrod; a valve bridge assembly operatively coupled to the rocker arm and configured to be selectively engaged by the rocker arm to open at least one of the first and second engine valves; and an engine braking bladder operatively associated with the valve bridge assembly. In one example, the method includes operating in a drive mode in which the engine braking bladder does not cause the valve bridge assembly to open the first or second engine valve and a braking mode in which the engine braking bladder engages the valve bridge assembly to partially open the first engine valve to perform the bleeder braking operation.

In addition to the above, the described method may comprise one or more of the following features: wherein operating in the braking mode comprises supplying pressurized fluid to the engine brake capsule; and wherein operating in the drive mode comprises not supplying pressurized fluid to the engine brake capsule.

Drawings

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

FIG. 1 is a partial cross-sectional view of a valvetrain assembly constructed in accordance with one example of the present disclosure;

FIG. 2 is a perspective view of a valve bridge assembly of the valve train assembly of FIG. 1 constructed in accordance with one example of the present disclosure;

FIG. 3 is a cross-sectional view of an engine brake bladder of the valve train assembly shown in FIG. 1 in a first mode constructed according to one example of the present disclosure;

FIG. 4 is the engine brake capsule shown in FIG. 3 in a second mode;

FIG. 5 is a side view of a valve train assembly and a valve bridge assembly constructed in accordance with another example of the present disclosure; and is

FIG. 6 is a side view of a valve train assembly and a valve bridge assembly constructed in accordance with yet another example of the present disclosure.

Detailed Description

Systems and methods for combining bleeder braking with a Hydraulic Lash Adjuster (HLA) using a balanced valve bridge having a pivoting arm in a diesel engine valve train are described herein. Bleeder braking, which keeps the exhaust valve open to generate a braking force, may cause the valve train with HLA to "pump up" and prevent the exhaust valve from closing during normal drive mode operation. The system described herein utilizes a fixed brake capsule with oil control (oilcontrol) to keep one exhaust valve open during engine braking operation, which is commonly referred to as "bleeder braking". The additional use of a balanced valve bridge with a biased pivot arm may create a reaction load when acted upon by a fixed brake bladder. This reaction force is transferred back into the normal valve train to prevent the HLA from pumping up (e.g., expanding).

During bleeder engine braking, in addition to the main exhaust valve event, one or more exhaust valves remain open throughout the remaining engine cycle (i.e., intake, compression, and expansion cycles) for full-cycle bleeder braking, or remain open during a portion of the remaining cycle (e.g., compression and expansion cycles) for partial-cycle bleeder braking.

Referring initially to FIG. 1, an exemplary valvetrain assembly constructed in accordance with one example of the present disclosure is shown and generally identified by the numeral 10. The valvetrain assembly 10 may generally include a camshaft 12 having one or more lobes configured to indirectly actuate a first end of a rocker arm 14 via a pushrod 16.

In some examples, a Hydraulic Lash Adjuster (HLA) lifter 18 is implemented between the cam lobe 12 and the pushrod 16. In other examples, the HLA tappets 18 are de-energized HLA roller tappets configured to operate between an activated mode and a deactivated mode. In the activated mode, the HLA roller lifter 18 transmits the motion of the cam lobe 12 to the pushrod 16 to cause rotational motion of the rocker arm 14. In the deactivated mode, the HLA roller lifter 18 absorbs motion of the cam lobe 12 such that the lifter 18 does not impart motion to the pushrod 16 and does not cause rotation of the rocker arm 14.

In operation, as the cam lobe 12 rotates, the rocker arm 14 pivots about the fixed rocker shaft 20 and the opposite second end of the rocker arm 14 actuates one or

more engine valves

22, 24 through the balanced valve bridge assembly 26.

The brake bladder 28 is secured to a cylinder head (not shown) of the engine and is configured to selectively extend to hold the valve 22 open for a predetermined time period (e.g., during all engine strokes that generate a braking force). When activated, the brake bladder 28 moves from the retracted position to the extended position to contact the valve bridge assembly 26. This causes the valve bridge assembly 26 to generate a reaction force "F1" into the rocker arm 14, which is then transferred to the HLA lifter 18 to prevent pumping when braking is activated.

Referring now to FIG. 2, the valve bridge assembly 26 will be described in greater detail. As shown, the valve bridge assembly 26 includes a lever assembly 40 disposed within a bridge body 42. The cross arm body 42 includes a first end 44 and a second end 46. The first end 44 may be configured to engage the valve 24, and the lever assembly 40 may be pivotably coupled to the second end 46.

In the exemplary embodiment, lever assembly 40 generally includes a pivot arm or lever 48, a pivot or bridge pin 50, an e-foot (e-foot) or valve seat 52, and an e-foot shaft (e-foot axle) or valve seat pin 54. The lever 48, shown transparent in fig. 2, may be pivotally coupled to the cross-arm body 42 by a cross-arm pin 50 that extends through opposing holes 56 formed in the cross-arm body 42.

In the illustrated example, the lever 48 generally includes an engagement surface 58 and an opposing opening 60. As described in greater detail herein, the engagement surface 58 is configured to be selectively engaged by the brake bladder 28, and the opposing opening 60 is configured to receive the valve seat pin 54, which is restricted from moving upward by the stop arm 62 of the crossbar body 42.

In an exemplary embodiment, the valve seat 52 may include a body 64 having a bore 66 formed therein. The body 64 is configured to receive a portion of the valve 22 and the bore 66 is configured to receive the valve seat pin 54 therethrough.

Thus, the lever 48 is selectively engageable at the engagement surface 58, which may cause rotation about the cross arm pin 50 and upward movement of the opposite end 68 of the lever opposite the surface 58. This upward movement of the lever end 68 is transmitted via the crossbar pin 50 to cause upward movement of the crossbar body 42, which in turn causes rotation of the rocker 14 and a downward reaction force into the HLA tappet 18 to prevent pump lift.

While described as balancing the valve bridge assembly 26, it should be understood that other arrangements and valve bridge assemblies may be used with the system described herein. For example, fig. 5 shows an alternative embodiment utilizing a straight-through cross arm assembly 126, and fig. 6 shows an alternative embodiment utilizing a solid cross arm assembly 226.

Referring now to fig. 3 and 4, the engine brake capsule 28 will be described in more detail. In the exemplary embodiment, brake capsule 28 generally includes an outer body 70 that defines an upper chamber 72 and a lower chamber 74. A cap 76 seals the upper end of the upper chamber 72 and a pin 78 and biasing mechanism 80 (e.g., a spring) are disposed in the upper chamber 72. The biasing mechanism 80 is configured to bias the pin 78 downward toward the lower chamber 74.

In the illustrated example, a plunger 82 and a check ball assembly 84 are disposed in the lower chamber 74. Plunger 82 is configured to slide along lower chamber 74 between a retracted position (fig. 3) and an extended position (fig. 4). A clamp or stop 86 is configured to limit downward movement of plunger 82. The check ball assembly 84 may include a check ball 88, a seat 90, and a biasing mechanism 92 (e.g., a spring). The biasing mechanism 92 is configured to bias the check ball 88 toward the upper chamber 72 to seal the passage 94.

In an exemplary implementation, the engine brake capsule 28 is operable in a drive mode (FIG. 3) and a brake mode (FIG. 4). In the drive mode, pressurized fluid is not supplied to engine brake capsule 28, and in particular to lower chamber 74, causing plunger 82 to collapse or retract into lower chamber 74. In the braking mode, pressurized fluid (e.g., oil) is supplied to engine brake capsule 28 through one or more ports 96. When the pin 78 biases the check ball 88 downward, pressurized fluid enters and fills the lower chamber 74 via the passage 94. This forces the plunger 82 downward into the extended position to contact the engagement surface 58 to facilitate performing the bleeder braking operation.

Referring now to fig. 5, the valvetrain assembly 10 is shown with the balanced valve bridge assembly 26 replaced by a straight through bridge assembly 126. In an exemplary embodiment, the through cross arm assembly 126 generally includes a pin assembly 140 disposed within a cross arm body 142. The cross arm body 142 includes a first end 144 and a second end 146. The first end 144 may be configured to engage the valve 24, and the pin assembly 140 is slidably disposed within the second end 146.

In the exemplary embodiment, pin assembly 140 is disposed within a cutout or aperture 148 formed in cross arm second end 146 and generally includes a contact pin 150 and a valve seat 152. The contact pin 150 extends through a bore 154 formed in the cross arm second end 146 and a stop or shoulder 156 that partially defines the aperture 148 and the bore 154 limits upward movement of the valve seat 152. The contact pin 150 includes an engagement surface 158, and the valve seat 152 is configured to receive a portion of the valve 22.

Thus, in the drive mode, no pressurized fluid is supplied to engine brake capsule 28, and plunger 82 is retracted into lower chamber 74 and does not engage contact pin 150. In the braking mode, pressurized fluid is supplied to the engine brake bladder 28 to force the plunger 82 downward into the extended position to contact the engagement surface 158 to open the valve 22 to facilitate performing a bleeder braking operation.

Referring now to FIG. 6, the valvetrain assembly 10 is shown with the balance valve bridge assembly 26 replaced with a solid bridge assembly 226. In the exemplary embodiment, the solid cross arm assembly 226 generally includes a cross arm body 242 having a first end 244 and a second end 246. The first end 244 may be configured to engage and pivot on the valve 24 and the second end 246 may be configured to engage and pivot on the valve 22.

Thus, in the drive mode, no pressurized fluid is supplied to engine brake capsule 28, and plunger 82 is retracted into lower chamber 74 and does not engage cross arm second end 246. In the braking mode, pressurized fluid is supplied to the engine brake bladder 28 to force the plunger 82 downward into the extended position to contact the engagement surface 258 of the second end 246 to open the valve 22 to perform a bleeder braking operation.

Systems and methods for coupling bleeder braking with a Hydraulic Lash Adjuster (HLA) by utilizing a valve bridge assembly are described herein. A brake bladder is movable between a retracted position and an extended position, the brake bladder being configured to engage a portion of the valve bridge assembly and open the exhaust valve a predetermined distance to perform a bleeder braking operation.

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. A valvetrain assembly configured to selectively perform bleeder braking operations, the assembly comprising:

a rocker arm configured to rotate about a rocker shaft;

a camshaft having lobes configured to impart motion to the rocker arm through a pushrod;

a valve bridge assembly operably coupled to the rocker arm and configured to be selectively engaged by the rocker arm to open at least one of a first engine valve and a second engine valve; and

an engine braking bladder operably associated with the valve bridge assembly, the engine braking bladder configured to operate in an actuation mode in which the engine braking bladder does not cause the valve bridge assembly to open the first or second engine valve, and a braking mode in which the engine braking bladder engages the valve bridge assembly to partially open the first engine valve to perform the bleeder braking operation.

2. The valve train assembly of claim 1, further comprising a Hydraulic Lash Adjustment (HLA) lifter disposed between the camshaft and the push rod.

3. The valve train assembly of claim 2, wherein the HLA tappet is a de-energized HLA tappet.

4. The valve train assembly of claim 2, wherein the HLA lifter is a roller lifter.

5. The valve train assembly of claim 1, wherein the valve bridge assembly comprises a lever assembly disposed within a bridge body.

6. The valve train assembly of claim 5, wherein the lever assembly comprises a lever pivotably coupled to the bridge body by a bridge pin, the lever configured to engage the first engine valve.

7. A valve train assembly as claimed in claim 6, wherein the lever assembly further comprises a valve seat pivotally coupled to the lever by a valve seat pin.

8. The valve train assembly of claim 7, wherein a pair of stop arms extending from the cross arm body limit upward movement of the valve seat pin.

9. The valvetrain assembly of claim 6, wherein in the braking mode, the lever is selectively engaged by the engine brake capsule causing rotation about the bridge pin and upward movement of the bridge body which causes rotation of the rocker arm and a downward reaction force into a Hydraulic Lash Adjuster (HLA) tappet to prevent pumping thereof.

10. The valve train assembly of claim 1, wherein the valve bridge assembly is a straight-through bridge assembly having a pin assembly disposed within a bridge body.

11. The valve train assembly of claim 10, wherein the pin assembly is disposed within an aperture formed in the crossbar body and includes a contact pin and a valve seat, the contact pin configured to be engaged by the engine brake capsule to impart motion to the valve seat to engage the first engine valve in the braking mode.

12. The valve train assembly of claim 11, wherein the contact pin extends through a hole formed in the crossbar body, and wherein a shoulder at least partially defines the aperture, and the hole is configured to limit upward movement of the valve seat.

13. The valve train assembly of claim 1, wherein the valve bridge assembly is a solid bridge assembly having a first end configured to engage and pivot on the first engine valve and a second end configured to engage and pivot on the second engine valve.

14. The valve train assembly of claim 1, wherein the engine brake capsule comprises an outer body defining an upper chamber and a lower chamber.

15. The valve train assembly of claim 14, wherein the engine brake capsule further comprises a pin disposed in the upper chamber and a biasing mechanism configured to bias the pin downward toward the lower chamber.

16. The valve train assembly of claim 14, wherein the engine brake capsule further comprises a plunger and check ball assembly disposed in the lower chamber, the plunger configured to slide along the lower chamber between a retracted position and an extended position.

17. The valve train assembly of claim 16, wherein the check ball assembly includes a check ball, a seat, and a biasing mechanism configured to bias the check ball toward the upper chamber to seal a passage.

18. A method of operating a valve train assembly having: a rocker arm configured to rotate about a rocker shaft; a camshaft having lobes configured to impart motion to the rocker arm through a pushrod; a valve bridge assembly operably coupled to the rocker arm and configured to be selectively engaged by the rocker arm to open at least one of a first engine valve and a second engine valve; and an engine braking bladder operably associated with the valve bridge assembly; the method comprises the following steps:

operating in a drive mode in which the engine braking bladder does not cause the valve bridge assembly to open the first engine valve or the second engine valve; and

operating in a braking mode in which the engine braking bladder engages the valve bridge assembly to partially open the first engine valve to perform a bleeder braking operation.

19. The method of claim 18, wherein operating in the braking mode comprises supplying pressurized fluid to the engine brake capsule.

20. The method of claim 19, wherein operating in the drive mode comprises not supplying pressurized fluid to the engine brake capsule.