Patent Application
20080000438
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term “module” refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
Referring to
Referring now to
As depicted in
The fluid supply from the hydraulic lash adjuster is controlled by a solenoid or CV, as depicted in
In a high-lift mode (not shown), the ECM 16 instructs the CV 30 to increase the fluid pressure in the locking pin housing 162 to a higher pressure state (P2) sufficiently such that the locking pins 164a, 164b compress the springs 170a, 170b, respectively and is in an engaged position resulting in the outer arm assembly 152 being locked to the inner, low lift arm 150 and thus prevented to independently pivot about the pivoting pin 154. The outer arm assembly 152 pivots to a third position in accordance with the high-lift cam lobe geometry causing the valve to open to a second predetermined amount greater than the first predetermined amount. The present invention recognizes that in various embodiments, switching the fluid supply from P1 to P2 can cause the locking pins 164a, 164b to retract and therefore disengage the outer arm assembly 152 from the inner arm assembly 150 and prevent the valve (not shown) from following the high lift cam (not shown) that interfaces with the high-lift contacts 158.
Additionally, the present invention envisions further embodiments that may require maintaining a fluid supply at a pressure state of P2 in which P2 represents “normal” operation of the SRFF mechanism 28. In such embodiments, the ECM 16 instructs the CV 30 to decrease the fluid pressure in the locking pin housing 162 to a lower pressure state (P1) in order to engage or disengage the locking pins 164a, 164b. The present invention further envisions an embodiment having a single locking pin 164 serve to engage the outer arm assembly 152.
Referring now to
The command module 40 commands the CV 30 to change its state of operation by generating and transmitting a state change command to the CV 30. In accordance with the state change command, the CV 30 switches the fluid supply provided to the locking pin housing 162 via the hydraulic lash adjuster from a low pressure state (P1) to a higher pressure state (P2). When the command module 40 commands the CV 30 to change its state, a timer module 42 stores the clock time of this command as Ta. A comparison module 44 monitors the fluid pressure sensor 18 and compares the pressure within the fluid gallery of the hydraulic lash adjuster 29 to a predetermined pressure threshold. When the comparison module 44 detects a signal from the fluid pressure sensor 18 that the pressure exerted by the fluid supply within the fluid gallery of the hydraulic lash adjuster 29 has exceeded or fallen below a predetermined threshold, the timer module 42 stores this second clock time as Tb. The timer module 42 then calculates the time difference between Ta and Tb as the time response, Tact, of the CV 30 to the change of state command.
An update module 46 receives signals from the engine speed sensor 22, the engine voltage sensor 24, and the engine temperature sensor 26 indicating the engine operating condition. The update module 46 then retrieves a desired time, Tdes, of the CV 30 from a lookup table 50 that corresponds to the engine operating condition sensed by the update module 46. The update module 46 compares the value of Tact to Tdes. If the value of Tact has exceeded a predetermined time range about Tdes, the update module 46 assigns a new value to Tdes by setting Tdes equal to Tact and stores the new value Tdes in the look-up table 50 as a function of the engine operating condition.
Referring now to
If the RPMop is within the predetermined RPM range, the SRFF positioning module 38, in step 104, determines whether a two-step change flag 34 is set indicating that the engine requires a change in the lift mode of SRFF mechanism 28. If a position change of the SRFF mechanism 28 is not required and the two-step change flag 34 is not set, the process ends. If the two-step change flag 34 is set, the SRFF positioning module 38 enables the command module 40. In step 106, the command module 40 generates and transmits a state change command directing the CV 30 to change its state of operation by switching the fluid supply provided to the locking pin housing 162 from either a low pressure state (P1) to a higher pressure state (P2) or from P2 to P1. Additionally in step 106, the timer module 42 stores the time of the sate change command as a first time, Ta.
In step 108, when the comparison module 44 detects that the pressure exerted by the change in fluid supply has either exceeded or fallen below a predetermined pressure threshold within the locking pin housing 162, the timer module 42 stores the corresponding time as a second time, Tb. In step 110, the timer module 42 calculates the time difference between Ta and Tb as Tact. The response time of the hydraulic control system 32 is based on Tact. In step 112, the update module 46 determines the engine operating condition by monitoring the engine speed sensor 22, the engine voltage sensor 24, and the engine temperature sensor 26.
In step 114, the update module 46 retrieves a desired time of the hydraulic control system 32, Tdes, from a look-up table 50 that corresponds to engine operating condition in step 112. In step 116, the update module 46 compares the value Tact t to Tdes. If the update module 46 determines that Tact is within a predetermined time range, about Tdes, the process ends. If the update module 46 determines that Tact t has exceeded the predetermined time range about Tdes, the update module 46 assigns a new value to Tdes by setting Tdes equal to Tact in step 118. In step 120, the look-up table 50 stores the value Tdes as a function of the engine operating point read in step 112. The process ends in step 122. Important to note is that the applicability of the present invention is not limited to embodiments that employ SRFF technology but is additionally applicable to valve train technologies that utilize a CV to control the activation of a hydraulic system to regulate valve events. Such valve train technologies include but are not limited to Displacement on Demand technologies and other related VVA technologies.
Additionally, the scope of the invention is not limited to embodiments that solely implement engine component or system control valves. The current invention is applicable to various systems that employ valve control operations including but not limited to transmission torque converters, clutches and brakes.
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.
