Electronic control valve having an integral non-contact noise mitigation device

#The present disclosure relates to electronic control valves; specifically, to a noise mitigation device for an electronic control valve; more specifically, to such a device acting as a dynamic absorber of valve train motion.

#An electronic control valve (eCV) generates an undesirable audible noise over a given supply current range. This noise is caused by the moving portion of the valve, i.e., the valve train, repetitively impacting a stationary portion of the valve, e.g., the valve seat.

#An eCV may be used, for example, in an automotive air conditioning system to control compressor capacity by regulating gas entering the compressor crankcase. A prior such eCV is shown in FIG. 1. Higher eCV supply current increases compressor capacity and lower eCV supply current decreases compressor capacity. The eCV current can be changed by changing the applied voltage. In the case of today's vehicles, the applied voltage is changed by pulsing battery voltage on and off, typically at 400 Hz. One 400 Hz cycle is 2.5 milliseconds. Thus, a 400 Hz eCV is regulated through pulse width modulation (PWM), i.e., by altering the portion of each 2.5 millisecond period (the PWM cycle) that a voltage pulse is present. Duty cycle is the time fraction of the PWM cycle that the eCV is energized. The duty cycle represents that time fraction of each PWM cycle during which an energizing voltage pulse is present as a percentage, with average voltage and current increasing as a function of an increased duty cycle. At 50% duty cycle, full voltage is applied for 1.25 milliseconds and no voltage is applied for 1.25 milliseconds. Audible eCV noise is greatest near 50% duty cycle because the valve train can be driven at its maximum displacement in both directions. When energized, the eCV is activated and the actuating magnetic field of the valve pushes against the valve train inertia and a return spring. When the actuator is de-energized, the eCV is unactivated and the return spring pushes the valve train back towards its off-mode rest position. At low duty cycle the valve train has less time to accelerate toward the valve seat. At high duty cycle, the valve train has less time to accelerate back towards its rest position. With lower displacement, the valve train velocity is lower and cannot impact the valve seat with such a high contact force.

#The above-mentioned and other features and objects of the invention, and the manner of attaining them, will become more apparent, and the invention itself will be better understood, by reference to the following description of an exemplary embodiment of the invention representing its best mode, taken in conjunction with the accompanying drawings, wherein:

#FIG. 1 is a cross-sectioned horizontal view of a prior eCV;

#FIG. 2A is an enlarged, vertical view of outlined area 2 of FIG. 1, showing an eCV according to a first embodiment of the present invention having an NMD with dual biasing means;

#Corresponding reference characters indicated corresponding parts throughout the several views. Although the drawings represent an embodiment of the present invention, the drawing are not necessarily to scale or to the same scale and certain features may be exaggerated in order to better illustrate and explain the present invention.

#FIG. 1 shows a prior eCV 20 of a known, commercially available type that operates in the above-described manner, for use in the air conditioning system (not shown) of an automobile. Although shown horizontally oriented, the prior and inventive eCVs disclosed herein may be oriented otherwise, and the effects of gravity on the valve train and NMD are herein ignored. The eCV 20 includes a valve body 22 having stationary portions and a central bore 24 that extends along an axis 26. Inside the valve body 22 is an elongate valve train 28 slidably disposed in the bore 24 and having reciprocating movement along the axis 26 relative to the stationary portions of the valve body 22. Surrounding the central bore 24 and extending along the axis 26 is a cylindrical activation coil 30 that is intermittently energized with battery voltage during eCV operation at the forcing frequency, which is typically 400 Hz.

#Included among the members of the valve train 28 is an elongate shaft 32 fixed to and interconnecting other members of the valve train. Included among the other valve train members is a generally cylindrical, ferrous plunger 34 affixed to one end of the shaft 32. The plunger 34 is driven leftwardly, as viewed in FIG. 1, along the axis 26 towards a valve seat 36, by the magnetic actuating field generated by the coil 30 when the eCV 20 is electrically activated. The valve seat 36 is a stationary portion of the valve body 22 and the site 38 where valve train 28 impacts the valve body 22 in the prior eCV 20.