AND LASH ADJUSTMENT

FIELD

[0001] The present disclosure relates generally to a carrier based bleeder type engine braking solution.

BACKGROUND

[0002] In engine braking, engine valve lift is modified for producing a valve event particularly for converting an internal combustion engine into an air compressor temporarily. By allowing compressed air to be released, energy absorbed by the engine to compress the gas during the compression stroke is not returned to the engine piston during the subsequent expansion or power stroke, but dissipated through the exhaust and radiator systems of the engine. The net result is an effective braking of the engine.

[0003] Compression engine brakes can be used as auxiliary brakes, in addition to wheel brakes, on relatively large vehicles, for example trucks, powered by heavy or medium duty diesel engines. A compression engine braking system is arranged, when activated, to provide an additional opening of an engine cylinder’s exhaust valve when the piston in that cylinder is near a top-dead-center position of its compression stroke so that compressed air can be released through the exhaust valve. This causes the engine to function as a power consuming air compressor which slows the vehicle.

[0004] 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.

SUMMARY

[0005] A bleeder brake mechanism constructed in accordance to one example of the present disclosure includes a carrier, a latch mechanism and a lost motion assembly. The bleeder brake mechanism is configured to selectively cooperate with an exhaust valve during an engine braking event. The exhaust valve is associated with an exhaust valve rocker arm. The carrier defines an oil gallery. The latch mechanism has a latch that is selectively actuated independently of rocker arm movement between a first non-actuated position and a second actuated position based on an oil pressure in the oil gallery. The lost motion assembly is disposed in the carrier and has a plunger, a collar and a plunger biasing member. The latch is configured to move between the first non-actuated position wherein at least one of the collar and plunger is permitted to undergo lost motion and the second actuated position wherein at least one of the collar and plunger is precluded from translating away from the exhaust valve thereby positioning the exhaust valve at least partially open.

[0006] According to additional features, the plunger forces the exhaust valve open in the second actuated position. The bleeder brake mechanism can further include a latch pin biasing member that biases the latch pin toward the first non-actuated position. A set screw can cap off a bore defined in the carrier that houses the latch mechanism. The latch mechanism is hydraulically actuated into the second actuated position. The lost motion assembly can provide mechanical actuation.

[0007] In additional features, the plunger biasing member biases the plunger toward the exhaust valve. The plunger and the collar can be fixed for concurrent translation relative to the exhaust valve during normal engine operation. The plunger can be threaded relative to the collar whereby the plunger can be rotated relative to the collar for lash adjustment. A bridge can have a bridge sliding pin extending therefrom. The plunger can be in contact with the bridge sliding pin.

[0008] A bleeder brake mechanism constructed in accordance to another example of the present disclosure includes a carrier, a hydraulically actuated latch mechanism and a lost motion assembly. The bleeder brake mechanism is configured to selectively cooperate with an exhaust valve during an engine braking event. The exhaust valve is associated with an exhaust valve rocker arm. The carrier defines an oil gallery. The hydraulically actuated latch mechanism has a latch that is selectively actuated independently of exhaust valve rocker arm movement between a first non-actuated position wherein a latch pin biasing member biases the latch pin toward the first non- actuated position and a second actuated position. In the second actuated position, high pressure oil enters the oil gallery causing the latch to overcome the latch pin biasing member and translate into the actuated position. The lost motion assembly is disposed in the carrier and has a plunger, a collar and a plunger biasing member. The latch is configured to move between the first non-actuated position wherein the plunger is permitted to undergo lost motion and the second actuated position. In the second actuated position, the plunger is precluded by the latch from translating away from the exhaust valve thereby positioning the exhaust valve at least partially open during the engine braking event.

[0009] In additional features, the lost motion assembly can provide mechanical actuation. The plunger biasing member biases the plunger toward the exhaust valve. The plunger and the collar can be fixed for concurrent translation relative to the exhaust valve during normal engine operation. The plunger can be threaded relative to the collar whereby the plunger can be rotated relative to the collar for lash adjustment. A bridge can have a bridge sliding pin extending therefrom. The plunger can be in contact with the bridge sliding pin.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0011] FIG. 1 is a plot showing a partial cycle bleeder brake event;

[0012] FIG. 2 is a plot showing a full cycle bleeder brake event;

[0013] FIG. 3 is an exemplary bleeder brake mechanism configured on a rocker arm;

[0014] FIG. 4 is an exemplary bleeder brake mechanism configured in the carrier according to one configuration of the present disclosure;

[0015] FIG. 5 is a perspective view of a bleeder braking mechanism constructed in accordance to one example of the present disclosure;

[0016] FIG. 6 is another perspective view of the bleeder braking mechanism of FIG. 5 and shown with an oil gallery at low pressure;

[0017] FIG. 7 is a plan view of the bleeder braking mechanism of FIG. 5;

[0018] FIG. 8 is a sectional view of the bleeder braking mechanism and shown during normal engine cycle with the oil gallery at low pressure;

[0019] FIG. 9 is another perspective view of the bleeder braking mechanism of FIG. 5 and shown with an oil gallery at high pressure;

[0020] FIG. 10 is a plan view of the bleeder braking mechanism of FIG. 9; [0021] FIG. 11 is a sectional view of the bleeder braking mechanism and shown during normal bleeder braking cycle with the oil gallery at high pressure;

[0022] FIG. 12 is another sectional view of the bleeder brake mechanism with the latch pin not actuated showing lost motion principle; and

[0023] FIG. 13 is another sectional view of the bleeder brake mechanism with the latch pin actuated into blocking engagement with a collar precluding lost motion.

DETAILED DESCRIPTION

[0024] During bleeder engine braking, in addition to the main exhaust valve event, one or more exhaust valves are held open throughout the remaining engine cycles (i.e., the intake, compression, and expansion cycles) for a full-cycle bleeder brake or during a portion of the remaining engine cycles (i.e., the compression and expansion cycles) for a partial-cycle bleeder brake. Bleeder braking mechanisms used to open the exhaust valves may be actuated by hydraulic, electric and/or pneumatic sources. FIG. 1 is a plot showing partial cycle bleeder brake event. FIG. 2 is a plot showing a full cycle bleeder brake event.

[0025] Engine braking presents many challenges. High engine braking loads need to be supported by valve train components like rocker arms, push tubes, cams, etc., which must be modified to accommodate the engine braking system increasing their overall weight, height, and cost. Complex compression release engine brake (CREB) systems in larger vehicles and their retrofit to existing engines is largely impossible without substantial modification of the engine cylinder head. CREB system makes high noise generated by the releasing of high-pressure gas or blow down through the exhaust valves during the compression stroke, near the top dead center position of the engine piston. CREB systems require accurate valve lift timing control and hydraulic actuators capable of opening the exhaust valves precisely when required. Thus, they may be comparatively expensive and difficult or impossible to install on certain engines.

[0026] FIG. 3 illustrates an exemplary bleeder brake mechanism 10 configured on a rocker arm 12. FIG. 4 illustrates an exemplary bleeder brake mechanism 30 arranged according to one example of the present disclosure. In particular, instead of configuring the bleeder brake mechanism 30 on a rocker arm 22, the bleeder brake mechanism 30 is instead configured in a carrier 32. As will become appreciated, by arranging the bleeder brake mechanism 30 on the carrier 32, many advantages are realized over the configuration of FIG. 3 that uses the rocker arm 12 to accommodate the bleeder brake mechanism 10. In the examples shown, the bleeder brake mechanism 30 is contained on the carrier 32 that is mounted on a fuel injector support 34. As will become appreciated from the following discussion, the bleeder brake mechanism 10 can be configured elsewhere on the carrier 32 or other component that remains static relative to an engine block 36. The configuration shown in FIG. 4 provides a retrofit braking mechanism with minimal changes in the cylinder head.

[0027] FIGS. 5-13 illustrate a bleeder brake mechanism constructed in accordance to one example of the present disclosure and identified generally at reference 30. The bleeder brake mechanism 30 is configured for use at least partially in a carrier housing 32. The carrier housing 32 defines an oil gallery 48. Oil is delivered to and from the oil gallery 48 from an oil source (not shown) based on a control signal corresponding to engine braking operational status. The bleeder brake mechanism 30 includes a latch pin mechanism 40 and a lost motion assembly 50. The latch pin mechanism 40 generally provides hydraulic actuation. The lost motion assembly 50 generally provides mechanical actuation.

[0028] The lost motion assembly 50 is configured to engage a modified bridge 58. The latch pin mechanism 40 can include a latch pin 60 and a latch pin biasing member 62. A set screw 64 caps off a bore 66 that the latch pin 60 translates within. The lost motion assembly 50 generally includes a plunger 70, a collar 72 and a plunger biasing member 74. In the example shown the plunger 70 and the collar 72 are fixed for concurrent translation. The plunger 70 can be threaded relative to the collar 72 for lash adjustment.

[0029] During normal engine cycle (FIGS. 6-8), cam motion is transferred to both exhaust valves 80, 82 associated with a cylinder of the engine via the valve bridge 58. In the illustrated example, the first exhaust valve 80 is a non-braking exhaust valve that is biased by a valve spring 90, and the second exhaust valve 82 is a braking exhaust valve that is biased by a valve spring 92. The exhaust rocker arm 22 rotates around a rocker shaft 96 (FIG. 4) based on a lift profile of a cam shaft (not shown).

[0030] The bleeder brake mechanism 30 of the present disclosure is operated independent of the cam cycle by a hydraulic signal given directly from the oil gallery 48 in the carrier 32 for every brake cycle surpassing valve train components. During normal engine cycle, the oil gallery 48 is at low pressure and the latch pin 60 is not actuated. In particular, the latch pin biasing member 62 biases the latch pin 60 in a direction leftward as viewed in FIG. 8, or in a direction away from the plunger 70. As the oil pressure in the bore 66 is not enough to overcome the biasing force of the latch pin biasing member 62, the latch pin 60 is moved to the position shown in FIG. 8 during normal engine cycle. The plunger 70 is in contact with a bridge sliding pin 78. Because the latch pin 60 is not translated rightward (low oil pressure in oil gallery 48), the latch pin biasing member 62 biases the latch pin away from the collar 72. The plunger 70 and the collar 72 undergo lost motion during non-braking cycle as shown in FIG. 8. Explained further, the plunger 70 is permitted to translate upward as viewed in FIG. 8 against the bias of the plunger biasing member 74. Notably, the collar 72 is not blocked from such upward motion by the latch pin 60.

[0031] In other advantages of the instant bleeder brake configuration, the timing of the hydraulic signal to the latch pin 60 does not require precise time control since the latch pin 60 translates as soon as the collar 72 moves downward (see FIG. 8) per engine cycle. During engine braking, the actuated latch pin 60 blocks the collar 72 from translating upwards, as will be described with respect to FIG. 1 1 , during the same cycle thus precluding the exhaust valve 82 from sitting completely and bleeding the air for engine braking.

[0032] During normal bleeder braking cycle (FIGS. 9-1 1 ), the oil gallery 48 is at high pressure and the latch pin 60 is actuated rightward (FIG. 1 1 ) and into blocking engagement with the collar 72 such that the collar 72 is precluded from moving upward. The plunger biasing member 74 biases the plunger 70 toward the bridge 58. In this regard, the latch pin 60 blocks upward lost motion of the plunger 70 and the collar 72. In this regard, as the bridge 58 returns to an unactuated position, the exhaust valve 82 remains at least partially displaced downwardly (or at least partially open). Thus, one exhaust valve (the exhaust valve 82) will be kept open by a lift of X mm (FIG. 1 1 ) for every bleeder braking cycle.

[0033] FIG. 12 is another sectional view of the bleeder brake mechanism with the latch pin 60 not actuated showing lost motion principle. Lost motion is provided a distance Y mm. FIG. 13 is another sectional view of the bleeder brake mechanism with the latch pin 60 actuated into blocking engagement with the collar 72 precluding lost motion.

[0034] The foregoing description of the examples has been provided 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. The same may 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.