Abstract:
A combined rocker arm apparatus for actuating auxiliary valve of engine, comprises an auxiliary actuator, a main rocker arm and a secondary rocker arm. The auxiliary actuator comprises an auxiliary rocker arm and an auxiliary cam. The auxiliary rocker arm and the main rocker arm are mounted on the rocker arm shaft in parallel. The auxiliary rocker arm is connected to the auxiliary cam at one end and adjacent to the secondary rocker arm at the other end. The auxiliary rocker arm includes a drive mechanism which provided with a piston. In the non-operation mode of the drive mechanism, the piston is drawn back, then the auxiliary rocker arm is disconnected with the secondary rocker arm; in the operation mode of the drive mechanism, the piston is pushed out, then the auxiliary rocker arm is connected with the secondary rocker arm.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national filing in the U.S. Patent &amp; Trademark Office of International Patent Application PCT/CN2011/000775 filed May 3, 2011. and claims priority of Chinese Patent Application NO. 201010604203.3 filed Dec. 21, 2010. 
     FIELD OF THE INVENTION 
     The present application relates to the mechanical field, specifically to the valve actuation technology for vehicle engines, particularly to a combined rocker arm device for an auxiliary engine valve event. 
     BACKGROUND OF THE INVENTION 
     In the prior art, the method of conventional valve actuation for a vehicle engine is well known and its application has more than one hundred years of history. However, due to the additional requirements on engine emission and engine braking, more and more engines need to produce an auxiliary engine valve event, such as an exhaust gas recirculation event or an engine braking event, in addition to the normal engine valve event. The engine brake has gradually become the must-have device for the heavy-duty commercial vehicle engines. 
     The engine braking technology is also well known. The engine is temporarily converted to a compressor, and in the conversion process the fuel is cut off, the exhaust valve is opened near the end of the compression stroke of the engine piston, thereby allowing the compressed gases (being air during braking) to be released. The energy absorbed by the compressed gas during the compression stroke cannot be returned to the engine piston at the subsequent expansion stroke, but is dissipated by the engine exhaust and cooling systems, which results in an effective engine braking and the slow-down of the vehicle. 
     There are different types of engine brakes. Typically, an engine braking operation is achieved by adding an auxiliary valve event for engine braking event into the normal engine valve event. Depending on how the auxiliary valve event is generated, an engine brake can be defined as:
         1. Type I engine brake: the auxiliary valve event is introduced from a neighboring existing cam in the engine, which generates the so called Jake Brake;   2. Type II engine brake: the auxiliary valve event generates a lost motion type engine brake by altering existing cam profile;   3. Type III engine brake: the auxiliary valve event is produced from a dedicated cam for engine braking, which generates a dedicated brake valve event via a dedicated brake rocker arm;   4. Type IV engine brake: the auxiliary valve event is produced by modifying the existing valve lift of the engine, which normally generates a bleeder type engine brake; and   5. Type V engine brake: the auxiliary valve event is produced by using a dedicated valve train to generate a dedicated valve (the fifth valve) engine brake.       

     An example of engine brake devices in the prior art is disclosed by Cummins in U.S. Pat. No. 3,220,392. The engine brake system based on the patent has enjoyed a great commercial success. However, this engine brake system is a bolt-on accessory that fits above the engine. In order to mount the brake system, a spacer needs to be positioned between the cylinder and the valve cover. This arrangement may additionally increase height, weight, and cost to the engine. 
     Among these above five types of engine brakes, the third one, i.e. the dedicated cam or the dedicated rocker arm brake, has the best engine brake power. However, the existing dedicated rocker arm brake device cannot be applied to the engines with the valve bridge being parallel or almost parallel to the rocker arm. 
     SUMMARY OF THE INVENTION 
     An object of the present application is to provide a combined rocker arm device for producing an auxiliary engine valve event, so as to solve the technical problem in the prior art that the dedicated rocker arm brake system cannot be applied to the engines with the valve bridge being parallel to the rocker arm and to address the technical problems of increased engine height, weight and cost of a conventional engine brake device. 
     The combined rocker arm device for producing an auxiliary engine valve event of the present application is used to generate an auxiliary valve event of an engine, and the engine including a conventional valve actuator, the conventional valve actuator including a cam, a rocker arm shaft, a conventional rocker arm and a valve, wherein the combined rocker arm device includes an auxiliary actuator and a transition rocker arm, the auxiliary actuator acts on the transition rocker arm, and the transition rocker arm acts on the valve. 
     Further, the auxiliary engine valve event generated by the combined rocker arm device includes a valve event for engine braking. 
     Further, the auxiliary actuator of the combined rocker arm device includes an auxiliary rocker arm and an auxiliary cam, the auxiliary rocker arm and the conventional rocker arm are mounted on the rocker arm shaft side by side, one end of the auxiliary rocker arm is connected to the auxiliary cam, and the other end of the auxiliary rocker arm is placed adjacent to the transition rocker arm; the auxiliary rocker arm includes an actuation mechanism being provided with an actuation piston, the actuation mechanism includes an non-operating position and an operating position; in the non-operating position, the actuation piston of the actuation mechanism retracts, and the auxiliary rocker arm is separated from the transition rocker arm; and in the operating position, the actuation piston of the actuation mechanism extends, and the auxiliary rocker arm is connected to the transition rocker arm. 
     Further, a rocking axis of the transition rocker arm maintains relatively static during the auxiliary engine valve event. 
     Further, in the combined rocker arm device, the auxiliary rocker arm is a brake rocker arm, the auxiliary cam is a brake cam, the brake rocker arm includes a brake actuation mechanism being provided with a brake piston, the brake actuation mechanism includes an non-operating position and an operating position; in the non-operating position, the brake piston of the brake actuation mechanism retracts, and the brake rocker arm is separated from the transition rocker arm; and in the operating position, the brake piston of the brake actuation mechanism extends, and the brake rocker arm is connected to the transition rocker arm. 
     Further, in the combined rocker arm device, the transition rocker arm is rotationally mounted on the conventional rocker arm of the engine, and the transition rocker arm has a rocking shaft parallel to a rocker arm shaft of the conventional rocker arm. 
     Further, in the combined rocker arm device, the transition rocker arm shares the rocker arm shaft with the conventional rocker arm. 
     Further, the combined rocker arm device also includes an auxiliary spring located between the auxiliary rocker arm and the transition rocker arm. 
     Further, the transition rocker arm of the combined rocker arm device includes a rocking limiter. 
     The working principle of the present application is as follows, when the auxiliary engine valve event is needed, i.e. when the engine needs to be converted from the normal engine operation state to the engine braking state, the engine braking controller is turned on. The brake actuation mechanism in the brake rocker arm is converted from the non-operating position to the operating position, and the brake rocker arm is connected to the transition rocker arm. The motion from the auxiliary cam. i.e. the brake cam, is transmitted to the exhaust valve through the brake rocker arm and the transition rocker arm, thereby producing the auxiliary valve event for engine braking. When engine braking is not needed, the engine braking controller is turned off. The brake actuation mechanism retracts from the operating position to the non-operating position, and the brake rocker arm is separated from the transition rocker arm. The motion from the brake cam cannot be transmitted to the exhaust valve, and the engine is disengaged from the braking operation, and back to the normal operation state. 
     The present application has positive and obvious effects over the prior art. In the present application, less or no height, size and weight of the engine need to be increased, the application scope of the dedicated cam or the dedicated rocker arm brake device is enlarged, the engine braking performance is improved, and the affect of the engine braking operation on the engine ignition operation is reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating the positional relationship among a transition rocker arm, a conventional rocker arm and a valve actuator of a combined rocker arm device according to an embodiment of the present application; 
         FIG. 2  is a side view of the transition rocker arm of the combined rocker arm device for an auxiliary engine valve event according to an embodiment of the present application; 
         FIG. 3  is a top view of the transition rocker arm of the combined rocker arm device for an auxiliary engine valve event according to an embodiment of the present application; 
         FIG. 4  is a schematic diagram illustrating the positional relationship between a brake rocker arm and the conventional rocker arm of the combined rocker arm device for an auxiliary engine valve event according to an embodiment of the present application; 
         FIG. 5  is a schematic diagram illustrating the brake rocker arm and its relative position with the combined rocker arm device for an auxiliary engine valve event according to an embodiment of the present application; and 
         FIG. 6  is a schematic diagram illustrating the conventional valve lift profile and the auxiliary valve lift profile (engine brake valve lift) for the combined rocker arm device for an auxiliary engine valve event according to an embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiment 
       FIG. 1  is a schematic diagram illustrating the positional relationship among a transition rocker arm  2103 , a conventional rocker arm  210  and a valve actuator  200  of a combined rocker arm device for an auxiliary engine valve event according to an embodiment of the present application. The auxiliary valve event generated by the combined rocker arm device of the present embodiment is an exhaust valve event for engine braking. The conventional engine exhaust valve event is generated by the engine exhaust valve actuator  200 . The auxiliary exhaust valve event for engine braking is generated by an auxiliary actuator  2002 . The auxiliary actuator  2002  includes an auxiliary rocker arm (shown as a brake rocker arm)  2102  and an auxiliary cam (shown as a brake cam  2302  shown in  FIG. 5 ). It should be noted that the embodiment should not be regarded as limitation on the scope of the claims, but rather as exemplification of the present application. 
     The exhaust valve actuator  200  has many parts, including a cam  230 , a cam follower  235 , a conventional rocker arm  210 , a valve bridge  400  and exhaust valves  300  ( 3001  and  3002 ). The exhaust valves  300  are biased on valve seats  320  in an engine cylinder block  500  by engine valve springs  310  ( 3101  and  3102 ) to prevent gases flowing between the engine cylinder and an exhaust manifold  600 . The conventional rocker arm  210  is rotationally mounted on a rocker arm shaft  205  and transmits the motion from the cam  230  to the exhaust valves  300  for cyclic opening and closing of the exhaust valves  300 . The exhaust valve actuator  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 rocker arm  210  by a nut  105 . On an inner base circle  225 , the cam  230  has a conventional cam lobe  220  to generate the conventional valve lift profile (see  2202  in  FIG. 6 ) for the conventional engine (ignition) operation. 
     As shown in  FIGS. 1, 2 and 3 , the transition rocker arm  2103  is rotationally mounted on the conventional rocker arm  210 . A cutting groove  270  is provided at a lower portion of the conventional rocker arm  210 , two ears  272  and  274  are respectively formed at two sides of the cutting groove  270 , and a shaft hole  276  is formed in the two ears  272  and  274 . A transition rocker arm shaft  2052  is disposed in a shaft hole  278  of the transition rocker arm  2103  (see  FIG. 2  and  FIG. 3 ), and then is installed in the shaft hole  276 . The transition rocker arm shaft  2052  and the rocker arm shaft  205  are parallel to each other. Therefore, the transition rocker arm  2103  can rock with respect to the conventional rocker arm  210  with the rocking range controlled by a rocking limiter. The rocking limiter includes a limiting end  217  of the transition rocker arm  2103 . The rocking range of the transition rocker arm  2103  is controlled by controlling a distance between the limiting end  217  and the conventional rocker arm  210 . The rocking range of the transition rocker arm  2103  is determined by a rocking range of the auxiliary rocker arm (i.e. the brake rocker arm)  2102  (the brake rocker arm  2102  is described more specifically in  FIG. 4  and  FIG. 5 ) due to the reason that the transition rocker arm  2103  is located under the brake rocker arm  2102  and is actuated by the brake rocker arm  2102 . The transition rocker arm  2103  is also located above a brake pushrod  116  (the exhaust valve  3001 ). The transition rocker arm  2103  may not need the brake pushrod  116 , but directly act on the valve bridge  400  or the exhaust valve  3001 . The auxiliary spring or brake spring  198  in  FIG. 1  is used to prevent the transition rocker arm  2103  and the brake rocker arm  2102  from not-following or colliding. 
       FIGS. 2 and 3  are the side view and top view of the transition rocker arm  2103  respectively, which are used to further describe the positional relationship among the transition rocker arm  2103 , the brake rocker arm  2102  and the brake pushrod  116  (or the exhaust valve  3001 ). The brake rocker arm  2102  acts on an upper surface  2181  on an end  218 , near the exhaust valve, of the transition rocker arm  2103 , while a lower surface  2182  of the transition rocker arm  2103  acts on the brake push rod  116  (or the exhaust valve  3001 ). A distance between the two acting points is shown by the reference numeral  279  (see  FIG. 3 ). 
       FIG. 4  is a schematic diagram illustrating the positional relationship between the auxiliary rocker arm (i.e. the brake rocker arm)  2102  and the conventional rocker arm  210  of the combined rocker device according to the embodiment of the present application, wherein the brake rocker arm  2102  and the conventional rocker arm  210  are installed on the rocker arm shaft  205  side by side. 
       FIG. 5  is a schematic diagram illustrating the brake rocker arm  2102  and its relative position with the combined rocker arm device according to the embodiment of the present application. The brake rocker arm  2102  includes a brake actuation mechanism  100 . The brake actuation mechanism  100  includes an actuation piston (a brake piston)  160  which is moveable between a non-operating position and an operating position. When in the non-operating position as shown in  FIG. 5 , i.e. when engine braking is not needed, the brake piston  160  of the brake actuation mechanism  100  retracts, and the brake rocker arm  2102  is separated from the transition rocker arm  2103  thereby forming a gap  132  between the brake rocker arm  2102  and the transition rocker arm  2103 . The gap  132  is adjustable by an adjusting screw  1102  of a brake valve lash adjusting mechanism, such that the motion generated by the auxiliary cam lobes (the brake cam lobes)  232  and  233  on the inner base circle  2252  of the brake cam  2302  cannot be transmitted to the exhaust valve  3001 . 
     When the auxiliary valve event, i.e. the engine braking, is needed, the engine brake controller (not shown) is turned on to supply engine oil, and the engine oil acts on the brake actuation mechanism  100 , such that the brake piston  160  is extended from the retracted non-operating position (as shown in  FIG. 5 ) to the operating position, thereby eliminating the gap  132  between the brake rocker arm  2102  and the transition rocker arm  2103 , that is the brake rocker arm  2102  is connected to the transition rocker arm  2103 . Through the cam follower  2352 , the brake rocker arm  2102  and the brake actuation mechanism  100  thereof, the transition rocker arm  2103  and the brake pushrod  116 , the motion generated by the auxiliary cam lobes (the brake cam lobes)  232  and  233  on the inner base circle  2252  of the brake cam  2302  is transmitted to the exhaust valve  3001 , thereby generating the auxiliary engine valve event for engine braking. 
     The auxiliary spring or the brake spring  198  in  FIG. 1  is shown again in  FIG. 5 . The auxiliary spring  198  is located between the brake rocker arm  2102  and the transition rocker arm  2103  to separate the above two components. An upward force of the spring  198  biases the brake rocker arm  2102  on the brake cam  2302 . A downward force of the spring  198  biases the transition rocker arm  2103  on the brake pushrod  116 . When the brake push rod  116  is pushed downward along with the valve bridge  400  and the exhaust valve  300  by the exhaust valve actuator  200  (see  FIG. 1 ), the downward force of the spring  198  biases the transition rocker arm  2103  on the conventional rocker arm  210  (see  FIG. 1 ). If the deformation of the spring  198  is large enough, the transition rocker arm  2103  does not need to have the rocking limiter, that is, the limiting end  217  is not needed. In this way, the transition rocker arm  2103  becomes a “semi-rocker arm” and is always in contact with the brake pushrod  116  (or the exhaust valve  3001 ). It should be noted that the force of the auxiliary spring or the brake spring  198  is much smaller than the preload force of the engine valve spring  3101 . 
       FIG. 6  is a schematic diagram illustrating the conventional valve lift profile  2202  and the auxiliary valve lift profiles (the engine brake valve lift)  2322  and  2332  for the combined rocker arm device according to the embodiment of the present application. The conventional valve lift profile  2202  generated by the valve actuator  200  corresponds to the conventional cam lobe  220  on the inner base circle  225  of cam  230  as shown in  FIG. 1 . The auxiliary valve lift (the engine brake valve lift) profiles  2322  and  2332  generated by the brake rocker arm  2102  and the transition rocker arm  2103  correspond to the auxiliary cam lobes (the brake cam lobes)  232  and  233  on the inner base circle  2252  of the brake cam  2302  as in  FIG. 5 . 
     In  FIG. 6 , the conventional valve lift profile  2202  is separated from the auxiliary valve lift profiles  2322  and  2332 , thus the actuation timing of the conventional rocker arm  210  is staggered from that of the brake rocker arm  2102 . When the brake rocker arm  2102  actuates the transition rocker arm  2103 , the conventional rocker arm  210  is stationary. Therefore, the rocking shaft  2052  (as shown in  FIG. 1 ) of the transition rocker arm  2103  mounted on the conventional rocker arm  210  is also stationary. In other words, when the auxiliary cam lobes  232  and  233  of the cam  2302  (as shown in  FIG. 5 ) actuates the brake rocker arm  2102 , the transition rocker arm  2103  and the valve  3001  to produce the auxiliary valve lift profiles  2322  and  2332 , a rocking axis of the transition rocker arm  2103  is stationary. 
     Therefore, the rocking shaft  2052  of the transition rocker arm  2103  can also be installed on other portions of the engine, for example, sharing the rocker shaft  205  with the conventional rocker arm  210 , as long as the rocking axis of the transition rocker arm  2103  can remain relatively static when the auxiliary rocker arm produces the auxiliary valve event. In addition, the actuation mechanism on the auxiliary rocker arm  2102  can also be transferred onto the transition rocker arm  2103 . 
     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 combined rocker arm device 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. 
     In addition, the combined rocker arm device described herein can be used not only for overhead cam engines, but also for push rod/tubular engines, and can be used not only for exhaust valve actuation, but also for intake valve actuation. 
     Also, the auxiliary actuator  2002  described herein can include not only the brake rocker arm and the brake cam, but also other actuation mechanisms, including mechanical, hydraulic, electromagnetic, or a combined mechanism. 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.