Method for heating a sliding camshaft actuator

Abstract

A method for heating a sliding camshaft actuator at cold engine start wherein the sliding camshaft actuator includes at least one magnetic field generating coil having a core, a piston armature disposed in the core of the at least one magnetic field generating coil, a magnet in mechanical communication with the piston armature, and an actuator pin in mechanical communication with the magnet. The method includes detecting a cold engine start condition and reversing an energizing voltage on the at least one magnetic field generating coil when the outside temperature is below a predetermined temperature threshold. The reverse energizing voltage on the at least one magnetic field generating coil is maintained for a predetermined period of time to heat the piston armature, the magnet, and the actuator pin.

Claims

1. A method for heating a sliding camshaft actuator at cold engine start wherein the sliding camshaft actuator includes at least one magnetic field generating coil having a core, a piston armature disposed in the core of the at least one magnetic field generating coil, a pin stop plate, a magnet in mechanical communication with the piston armature wherein the piston armature is operative to be repelled and retracted along the axial core of the at least one magnetic field generating coil when the at least one magnetic field generating coil is energized, and an actuator pin in mechanical communication with the magnet wherein the magnet is disposed intermediate between the at least one magnetic field generating coil and the pin stop plate, the method comprising: detecting a cold engine start condition; reversing an energizing voltage on the at least one magnetic field generating coil; retracting the piston armature, the magnet and the actuator pin toward the at least one magnetic field generating coil when the at least one magnetic field generating coil is energized; and maintaining the reverse energizing voltage on the at least one magnetic field generating coil for a predetermined period of time to heat the piston armature, the magnet, and the actuator pin.

2. The method of claim 1 wherein detecting further comprises reading an outside temperature sensor upon engine ignition.

3. The method of claim 2 wherein reversing further comprises energizing voltage when an outside temperature is less than or equal to a predetermined temperature threshold.

4. The method of claim 3 wherein reading and reversing is performed by a control module.

5. The method of claim 1 wherein reversing comprises creating a magnetic force attraction between the magnet and the at least one magnetic field generating coil.

6. The method of claim 5 further comprising dissipating heat from the at least one magnetic field generating coil to the actuator pin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present exemplary embodiments will be better understood from the description as set forth hereinafter, with reference to the accompanying drawings, in which:

(2) FIG. 1 is an illustration of a cross-sectional view of a sliding camshaft actuator in accordance with aspects of the exemplary embodiment;

(3) FIG. 2 is a functional illustration of a sliding camshaft actuator having a reverse voltage being applied to the magnetic field generating coil in accordance with aspects of an exemplary embodiment; and

(4) FIG. 3 is an illustration of an algorithm of the method of heating a sliding camshaft actuator using a reverse energizing voltage on the magnetic field generating coil in accordance with an exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(5) The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses thereof. FIG. 1 provides an illustration of a cross-sectional view of a sliding camshaft actuator 10 in accordance with aspects of the exemplary embodiment. The sliding camshaft actuator 10 includes a housing 12 having a pin stop plate 14 disposed at its base for limiting the distance an actuator pin (18a, 18b) can travel when in an extended position. The sliding camshaft actuator includes magnets (16a, 16b) attached to actuator pins (18a, 18b), respectively, that are disposed intermediate between magnetic field generating coils (20a, 20b) and the pin stop plate 14. The magnets (16a, 16b) are also mechanically attached to piston armatures (22a, 22b) operative to be repelled and retracted along the axial core of the magnetic field generating coils (20a, 20b) when the coils are energized in accordance with aspects of the exemplary embodiments. The magnetic field generating coils (20a, 20b) are wound on spools (24a, 24b), respectively, formed of ferrous or ferrous composite material that is susceptible to foster magnetic properties in the proximity of magnetic fields.

(6) FIG. 2 is a functional illustration of a sliding camshaft actuator 10 with a reverse voltage being applied to the magnetic field generating coils (20a, 20b) in accordance with aspects of an exemplary embodiment. In a cold start condition, particularly in cold environments, the sliding camshaft actuator 10 may exhibit a degradation in performance due to an increase in friction of the pins and any friction of the magnets sliding in their sleeves. At vehicle ignition, a temperature sensor (not shown) is used to detect the outside temperature and the value is read by a control module (not shown), e.g. engine control module. If the outside temperature is determined to be less than or equal to a predetermined temperature threshold value, e.g. 23 C., then the method for heating a sliding camshaft actuator according to the exemplary embodiment is initiated.

(7) A reverse voltage from the control module is applied to the magnetic field generating coils (20a, 20b) and magnetic flux lines (26a, 26b) create a magnetic force attraction (28a, 28b) between magnets (16a, 16b) and the magnetic field generating coils (20a, 20b), respectively. The application of the reverse voltage is maintained on the magnetic field generating coils (20a, 20b) for a predetermined period of time, e.g. 0.500 seconds, to create and dissipate heat to the piston armatures (22a, 22b), the magnets (16a, 16b), and the actuator pins (18a, 18b) such that the performance of the actuator 10 will not be inhibited by increased electrical resistance due to the coil being held to a colder temperature because the heat is being transferred into the pins.

(8) With reference to FIG. 3, an illustration of an algorithm 100 of the method of heating a sliding camshaft actuator 10 using a reverse energizing voltage on the at least one magnetic field generating coil in accordance with an exemplary embodiment is provided. At block 110, the method begins with detecting a cold start condition upon engine ignition. As stated above, this is accomplished by an engine control module in combination with an outside temperature sensor.

(9) At block 120, the method continues with reversing the energizing voltage on the at least one magnetic field generating coil if it is determined that the outside temperature is less than or equal to a predetermined threshold value which would be considered to be indicative of a condition where the sliding camshaft actuator may have an increased friction of the pins and any friction of the magnets sliding in their sleeves.

(10) At block 130, the method continues with retracting the piston armature, the magnet and the actuator pin toward the at least one magnetic field generating coil. The reverse voltage applied to the at least one magnetic field generating coil creates a magnetic force attraction to accomplish the retraction as according to the exemplary embodiment.

(11) And at block 140, the method continues with maintaining the reverse energizing voltage on the at least one magnetic field generating coil for a predetermined period of time to heat the piston armatures, the magnets, and the actuator pins. It is appreciated that the application of reverse voltage to the at least one magnetic field generating coils creates heat which is dissipated to the piston armature, the magnets, and the actuator pins such that any negative performance characteristics due to increased electrical resistance are eliminated.

(12) The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.