Patent Application
20190170267
The present disclosure relates generally to armature design and operation in electrical actuators, and more particularly to a valve assembly having an electrical actuator armature shaped to limit high velocity flows of fluid displaced by movement of the armature in the valve assembly.
A great many different pump designs are used for transferring and pressurizing fluids. In the context of fuel systems, such as for internal combustion engines, electronically-controlled, high-pressure fuel pumps are commonplace and used to pressurize a fuel such as diesel fuel for injection into an engine cylinder. Highly pressurized fuel injection strategies have been shown to be effective for reduced emissions operation. In one design, a high pressure fuel pump feeds a so-called common rail that provides a fluid reservoir storing a quantity of pressurized fuel for delivery to a plurality of fuel injectors. In other designs, fuel pumps are associated individually with fuel injectors, and are known as unit pumps.
To achieve a high level of control of moving parts within such pumps, electrical actuators such as solenoid actuators are used to control valve positioning and fluid connections. Solenoids produce a magnetic field when electrical current is applied that can generate local forces with sufficient energy to actuate components within the fuel system hardware. Engineers have experimented with a wide variety of different electrical actuator and pump designs over the years. With the drive toward ever-increasing pressure and control over fuel injection amount, fuel injection rate and other properties, the electrical actuators and associated valve components within fuel pumps tend to move relatively rapidly and can impact valve seats, stops, or other surfaces with relatively high forces. One example fuel pump design is known from U.S. Pat. No. 5,743,238 to Shorey et al. In the configuration shown in Shorey et al., an electrical actuator is used to control a valve that apparently varies position to alternately allow or inhibit fuel flow to a pumping chamber.
In one aspect, a valve assembly includes a valve member, and an electrical actuator having a stator and an armature coupled to the valve member. The armature includes an armature plate defining an armature center axis, and being movable between a rest position and an activated position to vary a position of the valve member, in response to a change to an energy state of the electrical actuator. The armature plate includes a top armature surface facing the stator, a bottom armature surface, and an outer perimetric surface extending circumferentially around the armature center axis and axially between the top armature surface and the bottom armature surface. The top armature surface has an inwardly stepped-up profile that forms a raised surface at a radially inward location that is adjacent to the stator at the activated position, and a lower, gap-forming surface at a radially outward location that forms a gap between the armature and the stator at the activated position.
In another aspect, a method of operating a valve assembly includes changing an energy state of an electrical actuator of the valve assembly, and moving an armature coupled with a valve member in the valve assembly from a rest position toward a stator in the electrical actuator in response to the change to the energy state of the electrical actuator. The method further includes stopping the moving of the armature at an activated position at which a raised surface at a radially inward location of the armature is adjacent to a face of the stator. The method further includes forming a gap at the activated position between a lower, gap-forming surface at a radially outward location of the armature and the face of the stator, and displacing a fluid from between the armature and the stator by way of the gap.
In still another aspect, a pump includes a pump housing, and a pumping element movable between a retracted position and an advanced position within a pumping chamber formed in the pump housing. The pump further includes a valve assembly for controlling a flow of a fluid to or from the pumping chamber, and including a valve member, and an electrical actuator for adjusting a position of the valve member. The electrical actuator includes a stator, and an armature having a top armature surface facing the stator, and a bottom armature surface, and the top armature surface having an inwardly stepped-up profile that forms a raised surface at a radially inward location, and a lower, gap-forming surface at a radially outward location. The armature is at a rest position where each of the raised surface and the lower, gap-forming surface are spaced from the stator, and being movable to an activated position where the raised surface is adjacent to the stator and the lower, gap-forming surface is spaced from the stator and forms a gap for displacing fluid from between the armature and the stator.
Referring to
Electrical actuator 30 includes a stator 32 positioned within or coupled with pump housing 12, and an armature 44. Armature 44 may be coupled to valve member 26, and in an implementation can include an armature pin 47 that is attached to and/or formed integrally with valve member 26. Valve member 26 and/or armature pin 47 extends through armature plate 46. Armature 44 and armature plate 46 are terms used interchangeably herein. Changing an energy state of electrical actuator 30 can cause armature 44 to move according to well-known principles relative to stator 32. A change to the energy state will typically include electrically energizing electrical actuator 30, however, embodiments are contemplated where a change to the energy state includes deenergizing electrical actuator 30. Increasing an energy state of electrical actuator 30 from a first energy state to a higher energy state, or decreasing an energy state from a higher energy state to a lower energy state, could also be understood as changing an energy state as contemplated herein. In the illustrated embodiment, stator 32 includes an outer stator portion 34 having an annular shape, and an inner stator portion 35 also having an annular shape. Outer stator portion 34 and inner stator portion 35 can be concentrically arranged with one another, and centered on pump housing longitudinal axis 13, however, the present disclosure is not thereby limited. An annular channel 36 is formed between outer stator portion 34 and inner stator portion 35. In the illustrated embodiment, electrical actuator 30 includes a solenoid electrical actuator having a winding 38 that is positioned within or at least partially within channel 36. Winding 38 includes electrically conductive metallic material in a generally conventional manner. Electrical actuator 30 may also include a non-metallic overmolding 40 encasing winding 38. An electrical plug 42 is coupled with pump housing 12 to provide for electrical connections with winding 38. Stator 32 also includes a stator end face 52 (“stator face 52”) that faces armature 44 and is formed in part by annular end faces (not numbered) of each of outer stator portion 34 and inner stator portion 35 that are positioned in a common plane, and also in part by winding 38. Overmolding 40 thus forms an exposed portion of stator face 52, the significance of which will be apparent from the following description.
Armature plate 46 defines armature center axis 48. At the state depicted in
Referring also now to
During operating pump 10 armature cavity 66 will typically be filled with the working fluid transitioned through pump 10, although of course other fluids could be used. When armature 44 is moved from its rest position, approximately as depicted in
It will be recalled that moving armature 44 to the activated position can include tilting armature 44, ultimately such that a top surface 50 of armature 44 is tilted relative to stator face 52. It is believed that the tilting of armature 44, and some similar armatures, can cause or compound the phenomena potentially leading to erosion as described herein. It can be seen that the known armature profile 160 could result in armature plate 46 contacting stator 32 or nearly contacting stator 32 and limiting or preventing entirely a radially outward flow of fluid, at least in the vicinity of the point(s) of contact or near-contact between armature 44 and stator face 52, when armature 44 reaches the activated position. As a result, fluid being displaced could be expected to be redirected inwardly, circumferentially, and upwardly into slot 72, in the process being accelerated to the point that a jet(s) of high velocity fluid can damage the relatively soft overmolding 40.
Turning now to
Referring to the drawings generally, operating valve assembly 24 can include changing an energy state of electrical actuator 30 as discussed herein, and moving armature 44 from the rest position toward stator 32 in response to the change to the energy state of electrical actuator 30. Armature 44 will move toward the activated position and be stopped at the activated position, such as by contacting valve member 26 with valve seat 28, although depending upon manufacturing tolerances, component wear, and the degree of tilting of armature 44, raised surface 58 could also contact stator face 52. At the activated position, lower surface 60 forms gap 70 such that fluid can be displaced from between armature 44 and stator 32 by way of gap 70. Valve 26 is moved in the manner described herein to vary fluid connections to pumping chamber or plunger cavity 16 in pump 10. When electrical actuator 30 is deenergized, armature 44 can move back toward the rest position under the influence of return spring 68.
Referring now to
The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.
