Patent Publication Number: US-9845712-B2

Title: Three-step sliding variable cam

Description:
TECHNICAL FIELD 
     This disclosure generally relates to variable cam systems. 
     BACKGROUND 
     Camshafts are rotating mechanical linkages used for transforming rotary motion into linear motion. Some internal combustion engines utilize camshafts to operate valves that control intake and exhaust from cylinders. 
     SUMMARY 
     A cam system for operating a first engine valve and a second engine valve is provided. The cam system includes a first sliding lobe pack and a second sliding lobe pack. 
     The first sliding lobe pack is translatable relative to the first engine valve, and is configured to operate the first engine valve with one of a high lift lobe, a low lift lobe, and a zero lift lobe. The second sliding lobe pack is translatable relative to the second engine valve, and is configured to operate the second engine valve with one of a high lift lobe or a low lift lobe. 
     A shift barrel is attached to the first sliding lobe pack and the second sliding lobe pack. The shift barrel has a first groove configured to translate the first sliding lobe pack and the second sliding lobe pack in a first direction, and a second groove configured to translate the first sliding lobe pack and the second sliding lobe pack in a second direction, which is opposite the first direction. 
     A shift actuator has a first pin, a second pin, and a third pin. The first pin, second pin, and third pin are each selectively actuatable to engage one of the first groove and the second groove of the shift barrel. 
     The above features and advantages, and other features and advantages, of the present subject matter are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the disclosed structures, methods, or both. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a cam system for a vehicle, illustrating two sliding lobe packs variably actuating valves of two cylinder banks at a high lift state. 
         FIG. 2  is a schematic circumferential or unspooled view of a first shift groove and a second shift groove in a shift barrel of the cam system shown in  FIG. 1 . 
         FIG. 3A  is a schematic view of the cam system of  FIG. 1  illustrating a shift actuator firing a second pin into the first shift groove. 
         FIG. 3B  is a schematic view illustrating a low lift state resulting from  FIG. 3A . 
         FIG. 4A  is a schematic view of the cam system of  FIG. 1  illustrating the shift actuator firing a first pin into the first shift groove. 
         FIG. 4B  is a schematic view illustrating a cylinder deactivation state resulting from  FIG. 4A . 
         FIG. 5A  is a schematic view of the cam system of  FIG. 1  illustrating the shift actuator firing the second pin into the second shift groove. 
         FIG. 5B  is a schematic view illustrating the low lift state resulting from  FIG. 5A . 
         FIG. 6A  is a schematic view of the cam system of  FIG. 1  illustrating the shift actuator firing a third pin into the second shift groove. 
         FIG. 6B  is a schematic view illustrating the high lift state resulting from  FIG. 6A . 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, like reference numbers correspond to like or similar components whenever possible throughout the several figures. There is shown in  FIG. 1  a cam system  10  for operating at least one first engine valve  12  and at least one second engine valve  14  of a vehicle (not shown). The first engine valves  12  and the second engine valves  14  are within respective first and second cylinders (not shown) or cylinder banks of an internal combustion engine (not shown). The cam system  10  shown may also be used on a single cylinder. 
     A camshaft assembly  16  is supported by a plurality of bearings  18 , such that the camshaft assembly  16  is rotatable relative to the cylinder banks. As described herein, rotation of the camshaft assembly  16  variably actuates the first engine valves  12  and the second engine valves  14  to facilitate combustion within the cylinder banks and production of mechanical energy by the engine. Additional bearings  18  may be incorporated into the camshaft assembly  16 . 
     The first engine valves  12  and the second engine valves  14  are poppet valves used to control the timing and quantity of fuel and air flow into the engine. The structures of the cylinders—such as valve seats, cylinder walls, etc.—are not shown in the figures. 
     While the present disclosure may be described with respect to specific applications or industries, those skilled in the art will recognize broader applicability. Those having ordinary skill in the art will recognize that terms such as “above,” “below,” “upward,” “downward,” et cetera, are used descriptively of the figures, and do not represent limitations on the scope of the disclosure, as defined by the appended claims. Any numerical designations, such as “first” or “second” are illustrative only and are not intended to limit the scope of the disclosure in any way. 
     Features shown in one figure may be combined with, substituted for, or modified by, features shown in any of the figures. Unless stated otherwise, no features, elements, or limitations are mutually exclusive of any other features, elements, or limitations. Furthermore, no features, elements, or limitations are absolutely required for operation. Any specific configurations shown in the figures are illustrative only and those shown are not limiting of the claims or the description. 
     Although the cam system  10  is described and illustrated with reference to the technology of internal combustion engines, which includes spark-ignited and compression ignited engines, the structures and functions of the cam system  10  are usable in other technological areas. The cam system  10  is applicable to any cam-driven valve technology, including valves used to control flow of other fluids or solids. For example, plastic molding equipment may utilize iterative injection of solid or liquid plastics into molds. Additionally, the cam system  10  may be used to control other iterative structures, technologies, or assemblies, such as actuating manufacturing devices. In general, cams provide iterative and controllable physical actuation from rotating movement, and the cam system  10  may be utilized with any such system. 
     As shown in  FIG. 1 , the cam system  10  includes a fixed shaft  20 , which is rotatable relative to the first engine valves  12  and the second engine valves  14 , but does not otherwise translate horizontally or move vertically (as viewed in the figures). A first sliding lobe pack  22  is translatable relative to the first engine valves  12  and the fixed shaft  20 , and a second sliding lobe pack  24  is translatable relative to the second engine valves  14  and the fixed shaft  20 . The first sliding lobe pack  22  and the second sliding lobe pack  24  may be splined, or otherwise keyed, for common rotation with the fixed shaft  20 . 
     The first sliding lobe pack  22  is configured to operate the first engine valves  12  with one of a high lift lobe  26 , a low lift lobe  27 , and a zero lift lobe  28 . The second sliding lobe pack  24  is configured to operate the second engine valves  14  with one of a high lift lobe  26  or either of two low lift lobes  27 , which impart substantially identical displacement, and may be combined into a single low lift lobe  27  in some configurations. Any of the individual lobes described herein and shown in the figures may be referred to numerically, as first, second, third, or the like. 
     As described herein, translation of the first sliding lobe pack  22  and the second sliding lobe pack  24  selectively aligns the high lift lobes  26 , the low lift lobes  27 , and the zero lift lobes  28  with the first engine valves  12  and the second engine valves  14 . Alignment of the specific lobes selectively varies the displacement of the first engine valves  12  and the second engine valves  14 . 
     The lobes are illustrated only schematically in the figures, such that the lobes shown represent only relative maximum displacement of the first engine valves  12  and the second engine valves  14 . Therefore, the high lift lobes  26  impart greater motion to the first engine valves  12  and the second engine valves  14  than the low lift lobes  27 . The zero lift lobes  28  impart substantially no lift to the first engine valves  12 , such that the first engine valves  12  may be selectively deactivated. 
     The first sliding lobe pack  22  and the second sliding lobe pack  24  may be separately translatable relative to the first engine valves  12  and the second engine valves  14 . However, in the configuration shown, the first sliding lobe pack  22  and the second sliding lobe pack  24  are connected for common translation by a shift barrel  30  that is attached to the first sliding lobe pack  22  and the second sliding lobe pack  24 . 
     Based on alignment of the high lift lobes  26 , the low lift lobes  27 , and the zero lift lobes  28  relative to the first engine valves  12  and the second engine valves  14 , the cam system  10  operates at a plurality of variable cam stages or states, including: a high lift state, a low lift state, and a cylinder deactivation or active fuel management state. Each of the operating states varies the amount of air and fuel entering the first cylinder bank and the second cylinder bank, which varies the operation of the engine. 
     Referring also to  FIG. 2 , there is shown a circumferential or unspooled view of the shift barrel  30 . The view of  FIG. 2  illustrates the shift barrel  30  as if its exterior has been rolled onto a flat plane. As shown in  FIG. 2 , and partially viewable in  FIG. 1 , the shift barrel  30  has a first groove  32  and a second groove  34 , which join into a common groove  36 . 
     As shown in  FIG. 1 , a shift actuator  40  is fixedly disposed adjacent the shift barrel  30 . The shift actuator  40  has a first pin  42 , a second pin  44 , and a third pin  46 . The shift actuator  40  selectively deploys, fires, or actuates the first pin  42 , the second pin  44 , and the third pin  46 , which may then engage one of the first groove  32  and the second groove  34  of the shift barrel  30 . 
     The first groove  32  and the second groove  34  are configured to act in opposing directions. Therefore, firing one of the pins into the first groove  32  translates both the first sliding lobe pack  22  and the second sliding lobe pack  24  in a first direction (leftward, as illustrated in the figures); and firing one of the pins into the second groove  34  translates both the first sliding lobe pack  22  and the second sliding lobe pack  24  in the opposite direction (rightward, as illustrated in the figures). In the configuration shown, the shift actuator  40  is a single actuator for all of the first engine valves  12  and the second engine valves  14 , as opposed to having one actuator related to the first cylinder bank and another related to the second cylinder bank. 
     Referring now to  FIGS. 3A-6B , and with continued reference to  FIGS. 1-2 , there are shown additional views of the cam system  10  that illustrate interaction between the shift actuator  40  and the shift barrel  30  to place the cam system  10  into one of three states. Based on location of the first sliding lobe pack  22  and second sliding lobe pack  24 , the cam system  10  operates at either the high lift state, the low lift state, or the cylinder deactivation state. 
     In the high lift state, the first sliding lobe pack  22  actuates the first engine valves  12  with the high lift lobes  26  and the second sliding lobe pack  24  actuates the second engine valves  14  with the high lift lobes  26 . In the low lift state, the first sliding lobe pack  22  actuates the first engine valves  12  with the low lift lobes  27  and the second sliding lobe pack  24  actuates the second engine valves  14  with the low lift lobes  27 . In the cylinder deactivation state, the first sliding lobe pack  22  actuates the first engine valves  12  with the zero lift lobes  28  and the second sliding lobe pack  24  actuates the second engine valves  14  with the low lift lobes  27 . 
       FIG. 3A  shows the cam system  10  in the high lift state, but with the shift actuator  40  firing the second pin  44  into the first shift groove  32 . Therefore, the second pin  44  and the first shift groove  32  will cause the first sliding lobe pack  22  and the second sliding lobe pack  24  to translate to the left (as viewed in the figures).  FIG. 3B  shows the result of the actuation shown in  FIG. 3A . In  FIG. 3B , the cam system  10  has been placed into the low lift state by actuation of the second pin  44  of the shift actuator  40 . 
     After the second pin  44  moves through the first shift groove  32  to the common shift groove  36 , which occurs during approximately one rotation of the cam assembly  16 , the second pin  44  retracts or ejects from the shift barrel  30 . The common groove  36  may include a retraction feature, such as a ramp or other structure, configured to release or push away whichever pin is engaged therewith. For example, and without limitation, the end of the common groove  36  (at the bottom, as viewed in  FIG. 2 ) may taper or angle the common groove  36  to zero depth, such that the pins would then ride on the surface of the shift barrel  30 . 
     Alternatively, or in combination with retraction features in the common groove  36 , the shift actuator  40  may be configured to retract whichever pin has been deployed into the shift barrel  30 . For example, and without limitation, return springs may constantly bias the first pin  42 , the second pin  44 , and the third pin  46  back into the shift actuator  40 , such that actuation or deployment of the pins continues only while an actuation force opposing the spring force is applied thereto. 
       FIG. 4A  shows the cam system  10  in the low lift state, but with the shift actuator  40  firing the first pin  42  into the first shift groove  32 . Therefore, the first pin  42  and the first shift groove  32  will cause the first sliding lobe pack  22  and the second sliding lobe pack  24  to translate to the left (as viewed in the figures).  FIG. 4B  shows the result of the actuation shown in  FIG. 4A . 
     In  FIG. 4B , the cam system  10  has been placed into the cylinder deactivation state by actuation of the first pin  42  of the shift actuator  40 . Note that in the cylinder deactivation state, the first engine valves  12  are at zero lift or displacement, such that the first cylinder bank is not producing any mechanical energy. However, the second engine valves  14  are at low lift or displacement, such that the second cylinder bank is producing mechanical energy. 
       FIG. 5A  shows the cam system  10  in the cylinder deactivation state, but with the shift actuator  40  firing the second pin  44  into the second shift groove  34 . Therefore, the second pin  44  and the second shift groove  34  will cause the first sliding lobe pack  22  and the second sliding lobe pack  24  to translate to the right (as viewed in the figures).  FIG. 5B  shows the result of the actuation shown in  FIG. 5A . 
     In  FIG. 5B , the cam system  10  has been placed into the low lift state by actuation of the second pin  44  of the shift actuator  40 . Note that firing the second pin  44  into either the first shift groove  32  or the second shift groove  34  results in the cam system  10  operating at the low lift state. 
       FIG. 6A  shows the cam system  10  in the low lift state, but with the shift actuator  40  firing the third pin  46  into the second shift groove  34 . Therefore, the third pin  46  and the second shift groove  34  will cause the first sliding lobe pack  22  and the second sliding lobe pack  24  to translate to the right (as viewed in the figures).  FIG. 6B  shows the result of the actuation shown in  FIG. 6A . In  FIG. 6B , the cam system  10  has been placed into the high lift state by actuation of the third pin  46  of the shift actuator  40 . 
     As illustrated by  FIGS. 5A-6B , consecutively actuating the second pin  44  and the third pin  46  of the shift actuator  40  into the second shift groove  34  moves the cam system  10  from the cylinder deactivation state to the high lift state, via the low lift state. Similarly, as illustrated by  FIGS. 3A-4B , consecutively actuating the second pin  44  and the first pin  42  of the shift actuator  40  into the first shift groove  32  moves the cam system  10  from the high lift state to the cylinder deactivation state, via the low lift state. 
       FIG. 1  schematically illustrates the cam system  10  with a control system or controller  50  that is in communication with the shift actuator  40 , as illustrated in  FIG. 1 . The controller  50  is configured to instruct the shift actuator  40  to actuate one of the first pin  42 , the second pin  44 , and the third pin  46 . The controller  50  may also monitor the current state of the cam system  10 , and may be involved with determining which of the states is currently preferred for operation of the vehicle. 
     The controller  50  may be representative of the entire control and computational architecture of the vehicle, or may be dedicated to the cam system  10 . The controller  50  includes a sufficient amount of memory and processing power to receive signal inputs from, and output commands, data, or instructions to, all systems over which the controller  50  is in command or monitoring. 
     The controller  50  is an electronic device that is configured, i.e., constructed and programmed, to regulate systems and components of the vehicle. The controller  50  may be configured as a central processing unit (CPU) that is also configured to regulate operation of the engine or other primary movers. Alternatively, the controller  50  may be a dedicated controller for only the systems discussed herein. The controller  50  includes a memory, at least some of which is tangible and non-transitory. The memory may be any recordable medium that participates in providing computer-readable data or process instructions. Such a medium may take many forms, including but not limited to non-volatile media and volatile media. 
     Non-volatile media for the controller  50  may include, for example, optical or magnetic disks and other persistent memory. Volatile media may include, for example, dynamic random access memory (DRAM), which may constitute a main memory. Such instructions may be transmitted by one or more transmission medium, including coaxial cables, copper wire and fiber optics, including the wires that comprise a system bus coupled to a processor of a computer. Memory of the controller  50  may also include a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, etc. The controller  50  can be configured or equipped with other required computer hardware, such as a high-speed clock; requisite Analog-to-Digital (A/D) and Digital-to-Analog (D/A) circuitry; input output circuitry and devices (I/O); as well as appropriate signal conditioning and buffer circuitry. Any algorithms required by the controller  50  or accessible thereby may be stored in the memory and automatically executed to provide the required functionality. 
     The cam system  10  may also include a sensor  52  in communication with the shift actuator  40  and the controller  50 , as illustrated in  FIG. 1 . The sensor  52  is configured to determine whether one of the first pin  42 , the second pin  44 , and the third pin  46  has been actuated, and may be, for example and without limitation, a hall effect sensor. The single actuator  40  may allow the cam system to use only the single sensor  52 , as opposed to multiple sensors associated with each of the first sliding lobe pack  22  and the second sliding lobe pack  24 . 
     In many configurations, it may be difficult to determine the exact position of the first sliding lobe pack  22  and the second sliding lobe pack  24  or the amount of displacement of the first engine valves  12  and the second engine valves  14 . This may cause uncertainty, particularly if one of the pins fires but is unsuccessful in engaging the first shifting groove  32  or the second shifting groove  34 , or if one of the pins is commanded to fire but does not do so. 
     The specific operating state of the cam system  10  may be known or determined based on iteration, such that the controller  50  records each state transition from a base point. Alternatively, the cam system  10  may determine the operating state through absolute means, such that the controller  50  determines or knows the operating state by sensing, for example, operating conditions of the engine. 
     Successful firing and engagement of the second pin  44  always places the cam system  10  into the low lift state, regardless of the previous state of operation. Therefore, the second pin  44  may be consecutively fired to ensure that the cam system  10  is in a known state (somewhat like a home position). Note that firing of the second pin  44  while the cam system  10  is already in the low life state may result in the second pin  44  simply striking the shift barrel  30  or the common groove  36 , which does not move the cam system  10  away from the low lift state. 
     The detailed description and the drawings or figures are supportive and descriptive of the subject matter discussed herein. While some of the best modes and other embodiments for have been described in detail, various alternative designs, configurations, and embodiments exist.