WO2008115424A1

WO2008115424A1 - Engine brake having an articulate rocker arm and a rocker shaft mounted housing

Info

Publication number: WO2008115424A1
Application number: PCT/US2008/003415
Authority: WO
Inventors: Zdenek S. Meistrick
Original assignee: Jacobs Vehicles Systems, Inc.
Priority date: 2007-03-16
Filing date: 2008-03-14
Publication date: 2008-09-25
Also published as: EP2137386A4; US7823553B2; EP2137386A1; JP5094884B2; CN101765705A; US20080223325A1; JP2010521622A; EP2137386B1; CN101765705B

Abstract

A system for actuating an engine valve is disclosed. The system may include a lost motion housing having two spaced collars surrounding a rocker shaft. The lost motion housing may include an internal hydraulic circuit connecting a master piston bore with a slave piston bore. The lost motion housing may include a means for securing the lost motion housing in a fixed position relative to the rocker shaft. A master piston may be disposed in the master piston bore and a slave piston may be disposed in the slave piston bore. A rocker arm may be disposed on the rocker shaft between the spaced collars and may have a first portion adapted to contact a cam and a second portion adapted to contact the master piston. In a preferred embodiment, the system may be used to provide compression release engine braking or bleeder engine braking.

Description

ENGINE BRAKE HAVING AN ARTICULATED ROCKER ARM AND A ROCKER SHAFT MOUNTED HOUSING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application relates to, and claims the priority of, United States Provisional Patent Application Serial Number 60/895,318 filed March 16, 2007, which is entitled "Engine Brake Having an articulated Rocker Arm and a Rocker Shaft Mount Housing."

FIELD OF THE INVENTION

[0002] The present invention relates to a system and method for providing engine braking in an internal combustion engine.

BACKGROUND OF THE INVENTION

[0003] Internal combustion engines typically use either a mechanical, electrical, or hydro-mechanical valve actuation system to actuate the engine valves. These systems may include a combination of camshafts, rocker arms and push rods that are driven by the engine's crankshaft rotation. When a camshaft is used to actuate the engine valves, the timing of the valve actuation may be fixed by the size and location of the lobes on the camshaft.

[0004] For each 360 degree rotation of the camshaft, the engine completes a full cycle made up of four strokes (i.e., expansion, exhaust, intake, and compression). Both the intake and exhaust valves may be closed, and remain closed, during most of the expansion stroke wherein the piston is traveling away from the cylinder head (i.e., the volume between the cylinder head and the piston head is increasing). During positive power operation, fuel is burned during the expansion stroke and positive power is delivered by the engine. The expansion stroke ends at the bottom dead center point, at which time the piston reverses direction and the exhaust valve may be opened for a main exhaust event. A lobe on the camshaft may be synchronized to open the exhaust valve for the main exhaust event as the piston travels upward and forces combustion gases out of the cylinder. Near the end of the exhaust stroke, another lobe on the camshaft may open the intake valve for the main intake event at which time the piston travels away from the cylinder head. The intake valve closes and the intake stroke ends when the piston is near bottom dead center. Both the intake and exhaust valves are closed as the piston again travels upward for the compression stroke.

[0005] The above-referenced main intake and main exhaust valve events are required for positive power operation of an internal combustion engine. Additional auxiliary valve events, while not required, may be desirable. For example, it may be desirable to actuate the intake and/or exhaust valves during positive power or other engine operation modes for compression-release engine braking, bleeder engine braking, exhaust gas recirculation (EGR), or brake gas recirculation (BGR). Fig. 19 of co-pending application serial number 11/123,063 filed May 6, 2005, which is hereby incorporated by reference, illustrates examples of a main exhaust event 600, and auxiliary valve events, such as a compression- release engine braking event 610, bleeder engine braking event 620, exhaust gas recirculation event 630, and brake gas recirculation event 640, which may be carried out by an exhaust valve using various embodiments of the present invention to actuate exhaust valves for main and auxiliary valve events.

[0006] With respect to auxiliary valve events, flow control of exhaust gas through an internal combustion engine has been used in order to provide vehicle engine braking. Generally, engine braking systems may control the flow of exhaust gas to incorporate the principles of compression-release type braking, exhaust gas recirculation, exhaust pressure regulation, and/or bleeder type braking.

[0007] During compression-release type engine braking, the exhaust valves may be selectively opened to convert, at least temporarily, a power producing internal combustion engine into a power absorbing air compressor. As a piston travels upward during its compression stroke, the gases that are trapped in the cylinder may be compressed. The compressed gases may oppose the upward motion of the piston. As the piston approaches the top dead center (TDC) position, at least one exhaust valve may be opened to release the compressed gases in the cylinder to the exhaust manifold, preventing the energy stored in the compressed gases from being returned to the engine on the subsequent expansion down-stroke. In doing so, the engine may develop retarding power to help slow the vehicle down. An example of a prior art compression release engine brake is provided by the disclosure of the Cummins, U.S. Pat. No. 3,220,392 (November 1965), which is hereby incorporated by reference.

[0008] During bleeder type engine braking, in addition to, and/or in place of, the main exhaust valve event, which occurs during the exhaust stroke of the piston, the exhaust valve(s) may be held slightly open during remaining three engine cycles (full-cycle bleeder brake) or during a portion of the remaining three engine cycles (partial-cycle bleeder brake). The bleeding of cylinder gases in and out of the cylinder may act to retard the engine. Usually, the initial opening of the braking valve(s) in a bleeder braking operation is in advance of the compression TDC (i.e., early valve actuation) and then lift is held constant for a period of time. As such, a bleeder type engine brake may require lower force to actuate the valve(s) due to early valve actuation, and generate less noise due to continuous bleeding instead of the rapid blow-down of a compression-release type brake. [0009] Exhaust gas recirculation (EGR) systems may allow a portion of the exhaust gases to flow back into the engine cylinder during positive power operation. EGR may be used to reduce the amount of NO_x created by the engine during positive power operations. An EGR system can also be used to control the pressure and temperature in the exhaust manifold and engine cylinder during engine braking cycles. Generally, there are two types of EGR systems, internal and external. External EGR systems recirculate exhaust gases back into the engine cylinder through an intake valve(s). Internal EGR systems recirculate exhaust gases back into the engine cylinder through an exhaust valve(s). Embodiments of the present invention primarily concern internal EGR systems.

[0010] Brake gas recirculation (BGR) systems may allow a portion of the exhaust gases to flow back into the engine cylinder during engine braking operation. Recirculation of exhaust gases back into the engine cylinder during the intake and/or early compression stroke, for example, may increase the mass of gases in the cylinder that are available for compression-release braking. As a result, BGR may increase the braking effect realized from the braking event. SUMMARY OF THE INVENTION

[0011] Applicants have developed an innovative system for actuating an engine valve comprising: a rocker shaft; a lost motion housing having a collar surrounding the rocker shaft, and having an internal hydraulic circuit connecting a master piston bore with a slave piston bore; means for securing the lost motion housing in a fixed position relative to the rocker shaft; a master piston disposed in the master piston bore; a slave piston disposed in the slave piston bore; and a rocker arm disposed on the rocker shaft, said rocker arm having a first portion adapted to contact a cam and a second portion adapted to contact the master piston.

[0012] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and which constitute a part of this specification, illustrate certain embodiments of the invention and, together with the detailed description, serve to explain the principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to assist the understanding of this invention, reference will now be made to the appended drawings, in which like reference characters refer to like elements. The drawings are exemplary only, and should not be construed as limiting the invention. [0014] Figure 1 is a pictorial view of an engine brake system having an articulated rocker arm and a rocker shaft mounted housing for master and slave pistons constructed in accordance with a first embodiment of the present invention and disposed in an internal combustion engine.

[0015] Figure 2 is an overhead exploded pictorial view of an engine brake system having an articulated rocker arm, rocker shaft mounted housing, and a rocker arm return spring in accordance with the first embodiment of the present invention. [0016] Figure 3 is an overhead exploded pictorial view of the underside of the engine brake system shown in Figure 2 as arranged in accordance with the first embodiment of the present invention. [0017] Figure 4 is a cross-sectional side view of a rocker shaft mounted housing of

Figures 2 and 3 which shows the master and slave pistons arranged in accordance with the first embodiment of the present invention.

[0018] Figure 5 is a second cross-sectional side view of the rocker shaft mounted housing of Figures 2 and 3 which shows the control valve in hydraulic communication with the rocker shaft and the master and slave pistons as arranged in accordance with the first embodiment of the present invention.

[0019] Figure 6 is a cross-sectional front view of the rocker shaft mounted housing of

Figures 2 and 3 showing the control valve and the slave piston as arranged in accordance with the first embodiment of the present invention.

[0020] Figure 7 is a cross-sectional side view of the engine brake system of Figures 2 and 3 showing the articulated rocker arm, rocker shaft mounted housing, and cam lobe as arranged in accordance with the first embodiment of the present invention when the engine brake system is turned off.

[0021] Figure 8 is a cross-sectional side view of the engine brake system of Figures 2 and 3 showing the articulated rocker arm, rocker shaft mounted housing, and cam lobe as arranged in accordance with the first embodiment of the present invention when the engine brake system is turned on and rocker arm is contacting the cam base circle.

[0022] Figure 9 is a cross-sectional side view of the engine brake system of Figures 2 and 3 showing the articulated rocker arm, rocker shaft mounted housing, and cam lobe as arranged in accordance with the first embodiment of the present invention when the engine brake system is turned on and the rocker arm is contacting the cam compression-release bump.

[0023] Figure 10 is a cross-sectional side view of an engine brake system showing the articulated rocker arm, rocker shaft mounted housing, and cam lobe as arranged in accordance with a second embodiment of the present invention when the engine brake system is turned off.

[0024] Figure 11 is an exploded pictorial view of an engine brake system having an articulated rocker arm, rocker shaft mounted housing, and a rocker arm return spring in accordance with the second embodiment of the present invention. [0025] Figure 12 is a cross-sectional side view of the engine brake system of Figs. 2 and 3 showing the oil passage schematic between the engine oil supply passage, solenoid valve and rocker shaft.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION [0026] Reference will now be made in detail to a first embodiment of the present invention, an example of which is illustrated in the accompanying drawings. With reference to Fig. 1 , a system 50 for actuating engine valves arranged in accordance with a first embodiment of the present invention is shown. Figs. 2-9 show different views of the system shown in Fig. 1 and/or its components. The system 50 may include a cam 100, an articulated half rocker arm 200, a brake housing 300, a rocker shaft 400, and a solenoid valve 500. The rocker arm 200 may be biased away from (or alternatively towards) the cam 100 by a return spring 210 (see also Fig. 11 ). The brake housing may be secured in position by a anti-rotation bolt 310.

[0027] With reference to Figs. 2 and 3, the rocker arm 200 may further include a cam roller 220, a lug 230, and a central collar 240. The rocker arm return spring 210 may bias the rocker arm 200 towards the brake housing 300 such that the lug 230 contacts the master piston 340. The brake housing 300 may further include an anti-rotation bolt boss 312, a control valve 320, a master piston 340, a slave piston 350 and rocker shaft collars 360 and 362. A slave piston return spring 352 may bias the slave piston 350 up into a slave piston bore formed in the brake housing 300.

[0028] With reference to Fig. 4, the rocker shaft collars 360 and 362 of the brake housing 300 may be mounted on the rocker shaft 400. The brake housing may be secured in a fixed position relative to the rocker shaft 400 by the anti-rotation bolt 310 (not shown). The brake housing 300 may include a master piston 340 slidably disposed in a master piston bore 302 and a slave piston 350 slidably disposed in a slave piston bore 304. A master-slave hydraulic fluid passage 306 may extend between the master piston bore 302 and the slave piston bore 304. The slave piston return spring 352 may bias the slave piston 350 upward and against a slave piston lash adjustment screw 354 which extends into the slave piston bore 304. The rocker shaft 400 may include a first hydraulic passage 410 adapted to provide lower pressure hydraulic fluid to the rocker arm 200 (not shown in Fig. 4) for lubrication purposes. The rocker shaft 400 may also include a second hydraulic passage 420, the purpose of which is explained in connection with Fig. 5. [0029] With reference to Fig. 5, adjacent to the slave piston 350 (shown in Fig. 4) the brake housing 300 may further include control valve 320. The control valve 320 may fill the master and slave bores with hydraulic fluid when low pressure hydraulic fluid is supplied to the lower portion of the control valve via a supply passage 308. A connection hydraulic passage 422 provided in the rocker shaft 400 may extend between the second hydraulic passage 420 and the supply passage 308 provided in the brake housing 300. As a result, hydraulic fluid may be supplied to the control valve, and the master and slave bores, by the selective supply of low pressure hydraulic fluid in the second hydraulic passage 420. [0030] A front cross-sectional view of the brake housing 300 is shown in Fig. 6. With reference to Fig. 6, the control valve 320 is shown in a "brake off' position during which the control valve body 322 is biased into its lower most position by the control valve spring 326. When the brake is turned on, hydraulic fluid from the second hydraulic passage 420 in the rocker shaft 400 (shown in Fig. 5) may be supplied to the lower portion of the control valve body 322. The supply of hydraulic fluid may cause the control valve body 322 to move upward until the annular opening provided in the mid-portion of the control valve body registers with the slave bore supply passage 309. The hydraulic fluid pressure applied to the lower portion of the control valve 320 may be sufficient to push the check valve 324 open so that hydraulic fluid flows into the slave piston bore 304 via the slave bore supply passage 309. With renewed reference to Fig. 4, the hydraulic fluid may further flow from the slave piston bore 304 through the master-slave hydraulic fluid passage 306 into the master piston bore 302. While the brake is in a "brake on" position, hydraulic fluid may be supplied freely to the master-slave piston circuit by the control valve 320, while the check valve 324 within the control valve prevents the reverse flow of fluid. As a result, the master-slave hydraulic circuit in the brake housing 300 may experience high hydraulic fluid pressures without substantial back flow of hydraulic fluid. [0031] The brake may be returned to the "brake off' position shown in Fig. 6 by reducing the hydraulic fluid pressure, preferably by evacuating the hydraulic fluid, applied to the lower portion of the control valve 320. When this happens, the control valve body 322 may slide downward until the slave bore supply passage 309 is exposed to the control valve bore 328, thereby allowing the hydraulic fluid in the master-slave hydraulic circuit to escape. The selective supply of hydraulic fluid to the control valve 320 may be controlled by the solenoid 500 shown in Fig. 1. Alternative placements of the solenoid 500 are considered within the scope of the present invention.

[0032] The arrangement of the various elements of the system 50 when the engine brake is in a "brake off' position is shown in Fig. 7. With reference to Fig. 7, the cam lobe 100 is illustrated as having two valve actuation bumps. A first cam bump 102 may provide a compression-release valve actuation event and a second cam bump 104 may provide a brake gas recirculation (BGR) valve actuation event. Alternative cam lobes with more, less, or different cam bumps are contemplated as being within the scope of the present invention.

[0033] The system 50 is positioned adjacent to an engine valve, such as an exhaust valve 600. The system 50 may actuate the exhaust valve 600 through a sliding pin 620 that extends through a valve bridge 610. Use of such a sliding pin and valve bridge arrangement may permit a separate valve actuation system to actuate multiple engine valves for positive power operation and a single engine valve 600 for non-positive power operation, such as engine braking.

[0034] With continued reference to Fig. 7, when the brake is in a "brake off' position, hydraulic fluid pressure in the second hydraulic passage 420 is reduced or eliminated. As a result, there is no hydraulic fluid pressure maintained in the master-slave hydraulic fluid circuit connecting the master piston 340 and the slave piston 350. Accordingly, the bias of the slave piston return spring 352 may be sufficient to push the slave piston 350 all the way into the slave piston bore against the lash adjustment screw 354. Furthermore, the bias of the rocker arm return spring 210 may be sufficient to rotate the rocker arm 200 such that the rocker arm lug 230 pushes the master piston 340 all the way into the master piston bore. The rotation of the rocker arm 200 in this manner may create a lash space 106 between the cam roller 220 and the cam lobe 100. The lash space 106 may be designed to have a magnitude x that is as great or greater than the height of the cam bumps 102 and 104. Thus, when the system 50 is in a "brake off' position, the cam bumps 102 and 104 may not have any effect on the rocker arm 200 or the master and slave pistons 340 and 350.

[0035] The arrangement of the various elements of the system 50 when the engine brake is in a "brake on" position is shown in Fig. 8. With reference to Fig. 8, when the brake is turned "on," hydraulic fluid is supplied through the second hydraulic passage 420 to the control valve 320 (not shown) and the master-piston hydraulic circuit in the brake housing. When the cam lobe 100 is at base circle, as shown in Fig. 8, the hydraulic fluid pressure in the master-slave hydraulic fluid circuit connecting the master piston 340 and the slave piston 350 may push the master piston 340 out of its bore, overcoming the bias of the rocker arm return spring 210 and rotating the rocker arm 200 backwards until the cam roller 220 contacts the cam lobe 100. As a result, the lash space 106 may be eliminated. At this time (cam lobe at base circle), the hydraulic pressure in the master- slave hydraulic circuit is not sufficient, however, overcome the bias of the slave piston return spring 352 and push the slave piston 350 out of the slave piston bore. [0036] With reference to Fig. 9, when the cam roller 220 encounters the cam bump 102 (and 104), the rocker arm 200 is rotated slightly clockwise. Rotation of the rocker arm 200 may push the master piston 340 into the master piston bore thereby displacing hydraulic fluid through the master-slave hydraulic fluid passage 306 and into the slave piston bore. As a result, the bias of the slave piston return spring 352 is overcome and the slave piston 350 may be displaced downward against the sliding pin 620, which in turn, may actuate the exhaust valve 600 for a compression-release event or some alternative valve actuation event.

[0037] An alternative embodiment of the present invention is shown in Figs. 10 and 11. With reference to Figs. 10 and 11 , the rocker arm return spring 210 may be provided in the form of a coil spring as opposed to a mouse-trap type spring. Furthermore, the return spring 210 may extend between an overhead element 212 and a rear portion of the rocker arm 200 such that the rocker arm is biased into continual contact with the cam lobe 100 when the system is in a "brake off' position, as shown in Fig. 10. As a result, instead of creating a lash space between the cam lobe 100 and the cam roller 220 when the brake is off, a lash space 202 may be created between the rocker arm lug 230 and the master piston 340.

[0038] With reference to Fig. 12, the communication between an engine oil supply passage 430 and the first and second hydraulic passages 410 and 420 are shown. The solenoid 500 may be disposed between the engine oil supply passage 430 and the rocker shaft 400.

[0039] It will be apparent to those skilled in the art that variations and modifications of the present invention can be made without departing from the scope or spirit of the invention.

Claims

WHAT IS CLAIMED IS:

1. A system for actuating an engine valve comprising: a rocker shaft; a lost motion housing having a collar surrounding the rocker shaft, and having an internal hydraulic circuit connecting a master piston bore with a slave piston bore; means for securing the lost motion housing in a fixed position relative to the rocker shaft; a master piston disposed in the master piston bore; a slave piston disposed in the slave piston bore; and a rocker arm disposed on the rocker shaft, said rocker arm having a first portion adapted to contact a cam and a second portion adapted to contact the master piston.

2. The system of Claim 1 further comprising a hydraulic passage extending through the rocker shaft and in communication with internal hydraulic circuit in the lost motion housing.

3. The system of Claim 1 wherein the lost motion housing has two collars surrounding the rocker shaft.

4. The system of Claim 3 wherein the rocker arm is disposed between the two collars.

5. The system of Claim 4 further comprising: a control valve bore provided in the lost motion housing, said control valve bore communicating with the internal hydraulic circuit; and a control valve disposed in the control valve bore.

6. The system of Claim 5 further comprising a check valve disposed in the control valve.

7. The system of Claim 6 further comprising a means for biasing the rocker arm towards the master piston.

8. The system of Claim 6 further comprising a means for biasing the rocker arm towards the cam.

9. The system of Claim 6 wherein the means for securing the lost motion housing comprises a boss extending from said lost motion housing collar and a bolt extending from said boss into an engine component.

10. The system of Claim 6 wherein the master piston bore is oriented obliquely relative to the slave piston bore.

11. The system of Claim 6 further comprising a cam having a compression release engine braking lobe adapted to contact the first portion of the rocker arm.

12. The system of Claim 6 further comprising a cam having a lobe selected from the group consisting of: a bleeder braking lobe or a partial bleeder braking lobe, wherein said lobe is adapted to contact the first portion of the rocker arm.

13. The system of Claim 1 further comprising: a control valve bore provided in the lost motion housing, said control valve bore communicating with the internal hydraulic circuit; and a control valve disposed in the control valve bore.

14. The system of Claim 13 further comprising a check valve disposed in the control valve.

15. The system of Claim 1 further comprising a means for biasing the rocker arm towards the master piston.

16. The system of Claim 1 further comprising a means for biasing the rocker arm towards the cam.

17. The system of Claim 1 wherein the means for securing the lost motion housing comprises a boss extending from said lost motion housing collar and a bolt extending from said boss into an engine component.

18. The system of Claim 1 wherein the master piston bore is oriented obliquely relative to the slave piston bore.

19. The system of Claim 1 further comprising a cam having a compression release engine braking lobe adapted to contact the first portion of the rocker arm.

20. The system of Claim 1 further comprising a cam having a lobe selected from the group consisting of: a bleeder braking lobe or a partial bleeder braking lobe, wherein said lobe is adapted to contact the first portion of the rocker arm.

21. The system of Claim 19 wherein the cam further comprises a brake gas recirculation lobe adapted to contact the first portion of the rocker arm.