Engine valve actuation mechanism for producing a variable engine valve event

Abstract

An engine valve actuation mechanism for producing a variable engine valve event includes a cam, a rocker arm, a rocker arm shaft, an eccentric rocker arm bushing, and a bushing actuation device. The eccentric rocker arm bushing is disposed in an axial hole in the rocker arm, the rocker arm shaft being disposed in the eccentric rocker arm bushing with the rocker arm shaft and the eccentric rocker arm bushing having offset axial centerlines. One end of the rocker arm and the cam is connected to form a kinematic pair and the other end of the rocker arm is located above the engine valve with a gap between the cam and the engine valve. The bushing actuation device is placed in the rocker arm and drives the eccentric rocker arm bushing to rotate, and the rotation of the eccentric rocker arm bushing changes the gap to generate the variable engine valve event.

Claims

1. An engine valve actuation mechanism for producing a variable engine valve event comprises: a cam; a rocker arm; a rocker arm shaft; an eccentric rocker arm bushing; and a bushing actuation device, wherein the eccentric rocker arm bushing is disposed in an axial hole in the rocker arm, the rocker arm shaft being disposed in the eccentric rocker arm bushing with the rocker arm shaft and the eccentric rocker arm bushing having offset axial centerlines, one end of the rocker arm and the cam being enagaged to form a kinematic pair and the other end of the rocker arm being located above the engine valve, and wherein the bushing actuation device is placed in the rocker arm and drives the eccentric rocker arm bushing to rotate, the rotation of the eccentric rocker arm bushing changes the position of the rocker arm's rocking center line and thus the engine valve event.

2. The engine valve actuation mechanism according to claim 1, wherein the bushing actuation device comprises an actuation piston located in the rocker arm, and the actuation piston drives the eccentric rocker arm bushing to rotate on the rocker arm shaft.

3. The engine valve actuation mechanism according to claim 2, wherein the actuation piston moves in a piston hole in the rocker arm and has a stroke, one end of the actuation piston is actuated by a spring, while the other end is actuated by a fluid force.

4. The engine valve actuation mechanism according to claim 1, wherein the variable engine valve event comprises an engine braking valve event, the cam comprises at least one braking cam lobe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view showing an engine auxiliary valve actuation mechanism according to one embodiment of the present application;

(2) FIG. 2 is a schematic view showing an engine auxiliary valve actuation mechanism according to another embodiment of the present application;

(3) FIG. 3 is a schematic diagram illustrating an arrangement positional relationship between an auxiliary rocker arm of the engine auxiliary valve actuation mechanism and a conventional rocker arm according to the present application; and

(4) FIG. 4 is a schematic diagram illustrating a conventional valve lift profile and an auxiliary valve lift profile (engine brake valve lift) of the engine auxiliary valve actuation mechanism according to one embodiment of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

First Embodiment

(5) As shown in FIGS. 1, 3 and 4, an auxiliary valve actuation mechanism in the present embodiment is an engine brake mechanism, and an auxiliary engine valve event produced by the auxiliary valve actuation mechanism is an exhaust valve event for engine braking. A normal valve event for the normal (ignition) engine operation is generated by a conventional valve actuation mechanism 200. The conventional valve actuation mechanism 200 and the auxiliary valve actuation mechanism 2002 are two mechanisms independent from each other.

(6) The conventional valve actuation mechanism 200 includes many components, including a conventional cam 230, a cam follower 235, a conventional rocker arm 210, a valve bridge 400 and exhaust valves 300. Exhaust valves 300 consist of a valve 3001 and a valve 3002, and the exhaust valves 300 are biased against valve seats 320 on an engine cylinder block 500 by engine valve springs 3101 and 3102 so as to control the gas flowing between an engine cylinder (not shown) and exhaust manifolds 600. The conventional rocker arm 210 is pivotally mounted on a conventional rocker arm shaft 205 for transmitting motion from the conventional cam 230 to the exhaust valves 300 for cyclic opening and closing of the exhaust valves 300. The conventional valve actuation mechanism 200 also includes a valve lash adjusting screw 110 and an elephant foot pad 114. The valve lash adjusting screw 110 is fixed on the conventional rocker arm 210 by a nut 105. The conventional cam 230 has a conventional cam lobe 220 on an inner base circle 225 to generate the conventional valve lift profile (see 2202 in FIG. 4) for the conventional engine (ignition) operation.

(7) The auxiliary valve actuation mechanism 2002 includes an auxiliary cam 2302 (which is a dedicated brake cam in the present embodiment), an auxiliary cam follower 2352, an auxiliary rocker arm shaft 2052, an auxiliary rocker arm 2102 (which is a dedicated brake rocker arm in the present embodiment), an eccentric rocker arm bushing 188 and a bushing actuation device 100. The eccentric rocker arm bushing 188 is disposed between the auxiliary rocker arm shaft 2052 and the dedicated brake rocker arm 2102, and is provided with a protruding portion 142 of a pin-like shape (the protruding portion can also be a pin installed on the eccentric rocker arm bushing separately) placed in a cutting groove 137 in the dedicated brake rocker arm 2102. One end of the dedicated brake rocker arm 2102 is connected to the dedicated brake cam 2302 through the auxiliary cam follower 2352, and the other end thereof is located above the exhaust valve 3001. In the present embodiment, a brake pressing block 116 in the valve bridge 400 and above the exhaust valve 3001 is an optional component. That is to say, the dedicated brake rocker arm 2102 can act directly on the valve bridge 400 or on the exhaust valve 3001 and an extended valve stem thereof. The auxiliary valve actuation mechanism 2002 also includes a brake valve lash adjusting screw 1102 and an elephant foot pad 1142. The brake valve lash adjusting screw 1102 is fixed on the dedicated brake rocker arm 2102 by a nut 1052. The dedicated brake rocker arm 2102 is generally biased onto the dedicated brake cam 2302 by a brake spring 198 so as to avoid any impact between the dedicated brake rocker arm 2102 and the exhaust valve 3001.

(8) The dedicated brake cam 2302 has dedicated brake cam lobes 232 and 233 on the inner base circle 2252 for producing valve compression release and exhaust gas recirculation of the exhaust valve respectively. Cam lobes 232 and 233 are used to generate the auxiliary valve lift profiles for engine braking (see 2322 and 2332 in FIG. 4). In the present embodiment, the brake cam lobe 233 for exhaust gas recirculation is an optional component.

(9) The bushing actuation device 100 of the auxiliary valve actuation mechanism 2002 is a hydraulic actuation system, including a brake controller (not shown), an actuation piston 164 located in a piston hole 260 of the dedicated brake rocker arm 2102, and a fluid network connecting the brake controller and the actuation piston 164. The fluid network includes an axial fluid passage 211 and a radial fluid passage 212 in the auxiliary rocker arm shaft 2052, a fluid passage 213 in the eccentric rocker arm bushing 188, and a fluid passage 214 in the dedicated brake rocker arm 2102. An annular groove 226 is provided on the actuation piston 164. The protruding portion 142 on the bushing 188 fits into the annular groove 226, such that a linear motion of the actuation piston 164 is converted into a rotation of the eccentric rocker arm bushing 188 on the auxiliary rocker arm shaft 2052. The actuation piston 164 is generally biased downward by a spring 156 (see FIG. 1), and when the eccentric rocker arm bushing 188 is in an non-operating position (the thinnest part of the eccentric rocker arm bushing 188 is located at the lowest point of the auxiliary rocker arm shaft 2052), a rocking centerline of the dedicated brake rocker arm 2102 is at the highest position, and the dedicated brake rocker arm 2102 is away from the exhaust valve 3001 (or away from an opening direction of the exhaust valve 3001). A gap 132 is formed between the dedicated brake cam 2302 and the exhaust valve 3001, thus the motion from the dedicated brake cam lobes 232 and 233 cannot be transmitted to the exhaust valve 3001, and the entire engine brake mechanism is separated from the normal engine operation.

(10) When the auxiliary engine valve event is needed, i.e. the engine braking is needed, the engine brake controller is turned on to supply oil to the auxiliary valve actuation mechanism. Engine Oil flows through the fluid network, including fluid passages 211, 212, 213 and 214, and then flows to the actuation piston 164. Oil pressure overcomes a force of the spring 156 and pushes the actuation piston 164 in the piston hole 260 upwards. The annular groove 226 on the actuation piston 164 drives, via the protruding portion 142, the eccentric rocker arm bushing 188 to rotate on the stationary auxiliary rocker arm shaft 2052 from the non-operating position shown in FIG. 1 to an operating position (a wall thickness of the eccentric rocker arm bushing 188 at the lowest point of the auxiliary rocker arm shaft 2052 is increased). The rocking centerline of the dedicated brake rocker 2102 gets close to (downward) the exhaust valve 3001 (or gets close to the opening direction of the exhaust valve 3001), thereby eliminating the gap 132 between the dedicated brake cam 2302 and the exhaust valve 3001, such that the dedicated brake rocker arm 2102 and the exhaust valve 3001 are connected. The motion from the dedicated brake cam lobes 232 and 233 is transmitted to the exhaust valve 3001, thereby producing the auxiliary engine valve event for engine braking.

(11) When engine braking is not needed, the engine brake controller is turned off to drain oil. The spring 156 pushes the actuation piston 164 downward into the piston hole 260. The annular groove 226 on the actuation piston 164 drives, via the protruding portion 142, the eccentric rocker arm bushing 188 to move from the operating position back to the non-operating position shown in FIG. 1. The rocking centerline of the dedicated brake rocker arm 2102 is away from (upwards) the exhaust valve 3001, thereby forming the gap 132 between the dedicated brake cam 2302 and the exhaust valve 3001, such that the dedicated brake cam 2302 is separated from the exhaust valve 3001. The motion from the dedicated brake cam 2302 can not be transmitted to the exhaust valve 3001, and the engine is disengaged from the braking operation and back to the normal (ignition) operation.

(12) FIG. 3 is a schematic diagram showing an arrangement relationship between the auxiliary rocker arm and the conventional rocker arm. The auxiliary rocker arm shaft 2052 of the auxiliary exhaust valve actuation mechanism 2002 in FIGS. 1 and 2 and the conventional rocker arm shaft 205 of the conventional exhaust valve actuation mechanism 200 share the same rocker arm shaft. At this point, the auxiliary rocker arm, i.e. the dedicated brake rocker arm 2102, and the conventional rocker arm 210 are installed side-by-side on the conventional rocker arm shaft 205, thereby forming a positional relationship shown in FIG. 3.

(13) Of course, other arrangements (left and right, up and down, inside and outside, and etc.) are also possible.

(14) FIG. 4 is a schematic diagram illustrating a conventional valve lift profile 2202 and auxiliary valve lift (i.e. the engine brake valve lift) profiles 2322 and 2332 of the engine auxiliary valve actuation mechanism according to one embodiment of the present application. The conventional valve lift profile 2202 corresponds to the conventional cam lobe 220 on the inner base circle 225 of the conventional cam 230 in FIG. 1, which is generated by the conventional valve actuation mechanism 200. The auxiliary valve lift (i.e. the engine brake valve lift) profiles 2322 and 2332 correspond to the dedicated brake cam lobes 232 and 233 on the inner base circle 2252 of the dedicated brake cam 2302 in FIG. 1, which is generated by the dedicated brake rocker arm 2102.

(15) In FIG. 4, the conventional valve lift profile 2202 and the auxiliary valve lift profiles 2322 and 2332 are separated, that is, opening phases of the two valve events are staggered. The conventional rocker arm 210 is stationary when the dedicated brake cam 2302 actuates the dedicated brake rocker arm 2102. The valve lift (i.e. the opening magnitude) of the auxiliary valve lift profiles 2322 and 2332 is less than that of the conventional valve lift profile 2202. The conventional valve lift profile (timing and the opening magnitude) 2202 is enlarged during braking operation in the integrated rocker arm brake systems in the prior art, which may cause the decline of engine braking power and the increase of injector tip temperature. Since the auxiliary exhaust valve actuation mechanism 2002 and the conventional exhaust valve actuation mechanism 200 of the present application are two mechanism independent from each other, the conventional valve lift profile 2202 (timing and the opening magnitude) will not be enlarged during engine braking operation. That is, the conventional valve lift profile 2202 will be the same during both the normal (ignition) engine operation and the engine braking operation. Therefore, the present application eliminates the drawbacks of the integrated rocker arm brake systems in the prior art, that the braking power is decreased and the injector tip temperature is increased.

Second Embodiment

(16) FIG. 2 is a schematic view showing an auxiliary valve actuation mechanism according to a second embodiment of the present application. The difference between this embodiment and the first embodiment lies in the bushing actuation device 100. The first embodiment has a built-in type of bushing actuation device 100, with the actuation piston 164 locating in the auxiliary rocker arm (i.e. the dedicated brake rocker arm) 2102 (see FIG. 1). The present embodiment has an externally driven type of bushing actuation device 100, wherein the eccentric rocker arm bushing 188 has a swing arm 1422 (see FIG. 2) being provided with a pin slot 139. Through a pin 141 located in the pin slot 139, an actuation member (which is an actuation rod herein) 1642 of the bushing actuation device 100 located outside of the auxiliary rocker arm (i.e. the dedicated brake rocker arm) 2102 drives the eccentric rocker arm bushing 188 to rotate between the non-operating position and the operating position. The actuation rod 1642 can be an extension of the actuation piston or other actuation members, such as an actuation wire. The bushing actuation device 100 can have various forms, from a simple, manually operated bicycle brake wire actuation mechanism to an automatic continuously variable actuation mechanism, and can be mechanical, hydraulic, electromagnetic or a combination of several forms. When the bushing actuation device 100 employs a continuously variable actuation mechanism, a rotation range (i.e. the operating position) of the eccentric rocker arm bushing 188 is continuously adjustable, and the engine exhaust valve lift (i.e. the opening) is also continuously adjustable. Such that during the engine braking operation, the braking valve lift can be adjusted according to the engine speed and the braking load so as to optimize the braking performance.

(17) In the present application, the conventional exhaust valve actuation mechanism 200 (see FIG. 1) and the auxiliary exhaust valve actuation mechanism 2002 (see FIGS. 1 and 2) are two mechanisms independent from each other, thereby eliminating the mutual influence between the normal (ignition) operation and the engine braking operation of the integrated rocker arm brake systems in the prior art. For example, during the startup and shutdown processes of the integrated rocker arm brake system in the prior art, an integrated rocker arm and an internal eccentric bushing thereof will withstand the forces imposed by the exhaust valves (the valve spring force and the cylinder pressure), which causes startup and shutdown difficulties and longer reaction time of engine braking. Also, in the prior art, the normal engine (ignition) operation and the engine braking operation share the same cam and the same rocker arm, thus the braking components, such as the eccentric rocker arm bushing, have much higher operating frequencies and increased probability of failure due to wear. The auxiliary exhaust valve actuation mechanism 2002 of the present application, using the dedicated brake cam 2302 and the dedicated brake rocker arm 2102, will not withstand the force imposed by the exhaust valves in the processes of startup and shutdown (as shown in FIG. 1, the exhaust valves are pushed away by the conventional exhaust valve actuation mechanism 200 to be separated from the dedicated brake rocker arm 2102), such that the required actuation force and the reaction time for braking operation are reduced. The braking components of the present application, such as the eccentric bushing, the dedicated brake cam 2302 and the dedicated brake rocker arm 2102, has operating frequencies much lower than the ignition frequency (operating frequencies are less than 10% of the ignition frequency). The wear and failure probability decreases, and the engine reliability and durability are greatly increased.

(18) While the above description contains many specific embodiments, these embodiments should not be regarded as limitations on the scope of the present application, but rather as specific exemplifications of the present application. Many other variations are likely to be derived from the specific embodiments. For example, the auxiliary valve actuation mechanism described herein can be used to produce the auxiliary engine valve event not only for engine braking, but also for exhaust gas recirculation and other auxiliary engine valve events.

(19) In addition, the auxiliary valve actuation mechanism described herein can be used not only for overhead cam engines, but also for push rod/tubular engines, and can not only be used to actuate the exhaust valves, but also be used to actuate the intake valves.

(20) Also, the auxiliary valve actuation mechanism described herein can be used not only to actuate a single valve, but also to actuate multiple valves, such as dual valves.

(21) Therefore, the scope of the present application should not be defined by the above-mentioned specific examples, but by the appended claims and their legal equivalents.