Multi-cycle, engine braking with positive power valve actuation control system and process for using the same

Abstract

An apparatus and method for effectuating multi-cycle engine braking is disclosed. The present invention controls the operation of the engine valves to permit more than one compression release event during a single engine operating cycle. The apparatus includes an assembly for operating at least one exhaust valve of an engine cylinder during a positive power operation. The apparatus further includes an assembly for operating at least one intake valve of the engine cylinder. The apparatus further including an assembly for operating the at least one exhaust valve during an engine braking operation.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to the field of compression release engine retarders for internal combustion engines. In particular, it relates to a method for increasing the retarding power of the retarder by generating two braking events, one per engine revolution, for each cylinder of the engine “two cycle braking.” More specifically, the invention involves modifying the cam and rocker arms on a overhead cam engine to provide a dedicated cam lobe for braking. In addition, the classic compression release retarder housing is eliminated and the compression release retarder is associated with the rocker arms.[0002]The exhaust valves of a typical internal combustion engine open at least once during its two-stroke or four-stroke cycle. A second opening of the exhaust valves can be introduced on the compression stroke to achieve additional compression release retarding. The present invention eliminates the first exhaust valve opening on the normal exh...

AI Technical Summary

Benefits of technology

[0041]Yet another object of the present invention is to provide a mechanism for disabling normal exhaust valve motion in order to engage a second compression release type braking event during the engine cycle.

[0053]In response to this challenge, the inventors of the present invention have developed an innovative and reliable system and apparatus to achieve multi-cycle valve actuation in both engine braking and positive power applications.

Problems solved by technology

Conventional single-cycle engine braking systems have inherent limitations.

Other internal combustion engine limitations have emerged in the thirty years since engine braking technology has been introduced.

Emission controls, turbo-chargers, and exhaust braking have affected the performance of engine braking.

In doing so, the work that is done in compressing the intake air cannot be recovered during the subsequent expansion (or power) stroke of the engine.

By dissipating energy developed from the work done in compressing the intake gases, the compression release-type retarder dissipates energy from the engine, slowing the vehicle down.

Regardless of the specific actuation means chosen, inherent limits wee imposed on operation of the compression release-type retarder based on the allowable loads on the engine.

A number of mechanical factors have historically imposed limitations: the temperature of critical engine parts, such as valves; the seating velocity of the valves; push tube loads; cam stress, the power available from the compression release retarder to overcome the instantaneous cylinder pressure at the point of opening and a variety of other factors.

Delaying the opening of the exhaust valve in the compression release event to a point later in the compression stroke, however, also increased substantially the loading placed on critical engine components.

In addition to these pressures, significant environmental pressures have forced engine manufacturers to explore a variety of new ways to improve the efficiency of their engines.

Yet, the demands on retarder performance have often increased, requiring the compression release-type engine retarder to generate greater amounts of retarding horsepower under more limiting conditions.

The use of the exhaust restrictor, however, essentially “kills” the boost available from the turbo-charger, dramatically reducing the amount of air delivered to the engine on intake.

This, in turn dramatically worsens compression release-type engine brake performance.

Moreover, nothing in the Volvo '890 patent teaches or suggests two-cycle braking.

Historically, engine manufacturers have been reluctant to modify their engine configurations to provide a dedicated cam lobe for the compression release-type brake.

In addition, on fuel injected engines, the fuel injector requires additional space on the cam shaft for the fuel injector cam lobe.

This configuration has historically limited the amount of space available to provide additional cams to actuate the compression release brake system.

Insufficient space has typically been available on the cam shaft, however, to accomplish that objective.

The above-described method and device do not anticipate two-cycle braking.

The process and apparatus disclosed by Sickler is too involved and has not been commercially developed.

Attempts have been made to do so but none of those attempts has yet to produce a commercially viable engine braking system that achieves increased performance.

These devices, however, were too complicated with high manufacturing costs and low reliability.

Furthermore, the others have not taken their development efforts far enough to develop technology for an engagement device for an overhead cam engine.

One of the principle limitations in achieving effective two-cycle engine braking occurs with a cam shaft operated valve train in a four-cycle engine.

The ability to add a second cylinder fill event prior to the second braking event is also challenging.

No prior engine braking systems of which the present inventors are aware have been able to overcome these two limitations and achieve an effective second braking event.

None of these methods, however, provide solutions to certain of the problems of compression release-type retarding.

First, none of these prior systems disclose, teach, or suggest how to achieve reliable, effective two-cycle braking while actuating the valves, namely, without using a “bleeder” type brake.

Second, none discloses, teaches, or suggests how to optimize the actuation of the exhaust valve during the intake and compression strokes in order to achieve the highest possible retarding horsepower from the compression release event without exceeding the mechanical limits of the engine.

In addition, none of these methods discloses, teaches or suggests any method for the use of exhaust gas recirculation to regulate the exhaust pressure in the exhaust manifold least of all in the context of two-cycle braking.

The engine, however, is not always operated at its rated speed and, in fact, is frequently operated at significantly lower speeds.

This is not possible with most prior methods, including those discussed above.

In spite of the existence of the substantial incentives and prior work to develop effective two-cycle braking, none of the known efforts to do so have been successful.

Again, however, in spite of the substantial need for these systems, no effective systems have been able to produce this valve control, let alone in both positive power and engine braking operation.

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