Patent Application
20090165749
The present disclosure relates generally to control valves, and relates more particularly to reducing variability in operation of a control valve by closing a valve seat with an annular seating shoulder on the outer diameter of a control valve member.
Control valves are well known and widely used in a great variety of hydraulic systems. It is common for a relatively small and readily adjusted valve member to be used in controlling fluid flow and/or pressure to affect the state of another component, such as another valve, which is more difficult to precisely control. In other instances, a control valve may be used to simply control the initiation or cessation of a flow of fluid in various fluid systems. Common examples of the types of control valves contemplated herein are known from the fuel injector arts.
In one design, a control valve may be coupled with a fuel injector and configured to vary a control pressure on a closing hydraulic surface of an admission valve responsible for injecting fuel into an engine cylinder. By varying the position of the control valve, high pressure or low pressure can be alternately applied to the closing hydraulic surface, controlling whether the admission valve is opened or closed. While the use of relatively high speed control valves has given engineers the opportunity to precisely control fuel injection timing, rate shape and other variables, conventional designs still suffer from a variety of drawbacks.
For example, in some instances deformation of a control valve member and/or other components can result from valve operation. Since control valves are typically expected to actuate millions, or even billions, of times over the course of a fuel injector's service life, the substantial demands placed upon the constituent material of the valve member and related components will be readily appreciated. One specific type of damage is known in the art as “seat beat in” wherein a valve seat and/or associated control valve member becomes damaged over time from the many impacts. Material of the valve member, as well as material of the seat may be worn away or otherwise deformed to the point that valve performance is affected. Because much of the advantage and future promise of relatively high speed control valves relates to the ability to precisely control valve movement, even relatively small changes in valve structure can lead to performance variability. Furthermore, the inherently unpredictable nature of valve component damage can make it difficult to compensate for performance variability by way of conventional means such as electronic trimming.
One control valve assembly is known from U.S. Pat. No. 5,396,926 to Pataki et al. In the design set forth by Pataki et al., a “three-way” control valve is actuated by a solenoid actuator to control whether an outlet passage is connected with a high pressure supply passage or a drain passage. A floating pin is positioned within a cavity of a movable valve member and includes an impact absorbing element which absorbs impact of the movable valve member when the solenoid actuator is de-energized. The design purportedly prevents closing bounce of the valve member, which may be associated with formation of a leakage path.
In one aspect, the present disclosure provides an engine which includes an engine housing having at least one cylinder with a piston movable therein. At least one fuel injector is provided which includes a housing having a direct control needle check positioned therein, a control passage and a nozzle supply passage each connecting with the direct control needle check, and a low pressure drain. The engine further includes a control valve assembly for controlling the injection of fuel into the at least one cylinder via the direct control needle check. The control valve assembly has an electrical actuator configured to adjust a valve member between a first position at which the control passage is blocked from the low pressure drain and a second position at which the control passage is open to the low pressure drain. The valve member includes an outer diameter with an annular seating shoulder thereon. The housing further includes a conical valve seat positioned fluidly between the control passage and the low pressure drain, the conical valve seat being an outer diameter seat closed by the seating shoulder when the valve member is at the first position.
In another aspect, a method of reducing variability in operation of a valve includes a step of moving the valve from a first position at which the valve closes a conical valve seat to a second position at which the valve is out of contact with the conical valve seat at least in part by energizing an electrical actuator. The method further includes a step of deforming at least one of the valve and the conical valve seat by contacting the valve with the conical valve seat a plurality of times. The method still further includes a step of inhibiting change to a seating diameter associated with the conical valve seat at least in part by closing the conical valve seat with an annular seating shoulder positioned on an outer diameter of the valve.
In still another aspect, a control valve assembly includes an electrical actuator, a housing having a fluid inlet, a first fluid outlet, and a second fluid outlet for communicating a pressure of the fluid inlet or the first fluid outlet to a device controllably coupled with the control valve assembly. The control valve assembly further includes a one-piece valve coupled with the electrical actuator and movable within the housing between a first position at which the valve closes a conical valve seat defined by the housing and positioned fluidly between the fluid inlet and first fluid outlet and a second position at which the valve is out of contact with the conical valve seat. At the first position, the second fluid outlet is open to the fluid inlet and blocked from the first fluid outlet. At the second position, the second fluid outlet is open to the first fluid outlet. The valve further includes an outer diameter having an annular seating shoulder located thereon which is configured to contact a frustoconical surface of the conical valve seat when the valve is at the first position, and the annular seating shoulder is further configured to deform in response to contacting the frustoconical surface of the conical valve seat without changing a seating diameter associated therewith.
In still another aspect, a fuel injector includes a housing having a high pressure passage, a low pressure drain and a control passage. The fuel injector further includes a direct control needle check positioned in the housing and including a control surface exposed to a fluid pressure of the control passage, and a control valve assembly coupled with the direct control needle check. The control valve assembly has an electrical actuator coupled with a valve member which is configured to adjust the valve member between a first position at which the control passage is blocked from the low pressure drain and a second position at which the control passage is open to the low pressure drain. The valve member includes an outer diameter with an annular seating shoulder thereon. The housing further includes a conical valve seat positioned fluidly between the control passage and the low pressure drain, and wherein the conical valve seat comprises an outer diameter valve seat closed by the seating shoulder when the valve member is at the first position.
Referring to
It is also contemplated that the use of control valve assemblies 40 according to the present disclosure will enable relatively greater ease in compensating for whatever performance variability does occur, for example by electronic trimming, as will be further apparent from the following description. While engine 10 is described herein as a direct injection compression ignition diesel engine, in other embodiments engine 10 might be a spark ignited engine, a port injected engine, or of some other configuration. Moreover, engine 10 might only include a single cylinder and single fuel injector in some embodiments, and certain aspects of the present disclosure might even be applied outside the context of fuel systems.
Turning to
Control valve assembly 40 may include a housing 51 which has a control valve member 50 positioned at least partially therein. In one embodiment, valve member 50 may be coupled with electrical actuator 42 such that at a desired time valve member 50 may be adjusted to vary a fluid pressure in control passage 47. Operation of control valve assembly 40 to alternately apply relatively higher pressure versus relatively lower pressure to closing hydraulic surface 35 may occur in a conventional manner. It may be noted that orifices 33a and 33b may be configured to allow needle 36 to move from a closed position blocking outlet 38 toward an open position without contacting a mechanical stop. This configuration is known in the art wherein needle 36 may be understood as “hovering” when in a retracted position rather than surface 35 contacting another part of injector 20. A drain passage 45 may further be formed in housing 51 to enable valve member 50 to alternately connect control passage 47 with high pressure fluid from passage 49, or low pressure from passage 45, again in a conventional manner known from three-way valves. A first biaser 46 may be positioned in injector body 60, as well as a second biaser 48, which assist in moving valve member 50 in a desired manner. Yet another biaser 37 may be coupled with needle 36. Each of biasers 46, 48 and 37 may comprise helical springs.
Turning now to
Another conical valve seat 76 may be fluidly positioned between inlet 84 and outlet 86. It will be readily understood by those skilled in the control valve arts that valve member 50 may be moved between a first position at which passage 47 is blocked from passage 45 but open to passage 49, and a second position at which passage 47 is open to passage 45 but blocked from passage 49. Valve member 50 may further include a first end 57 which is coupled with electrical actuator 42, and a second end 59 which may be coupled with biaser 48 via a spacer 46. Accordingly, energizing of electrical actuator 42 can move valve member 50 from its first position to its second position, approximately as shown, at which it is out of contact with seat 72 and closes seat 76, by tensioning/expanding biaser 48. Valve member 50 may be returned to its first position, blocking seat 72, at least in part via a bias of biaser 48.
In one embodiment, seat 76 comprises an inner diameter seat wherein a seating diameter G is defined by housing 51. An outer diameter frustoconical surface 74 of valve member 50 will contact seat 76 at the second position of valve member 50 to block fluid flow past seat 76. In some embodiments, this configuration for seat 76, a high pressure seat, may be similar to that of certain conventional control valve assemblies. In contrast, a configuration of seat 72 differs from known designs. Seat 72 may comprise an outer diameter seat which is closed by an annular seating shoulder 78 located on an outer diameter 70 of valve member 50. A seating diameter D associated with seat 72 is thus defined by annular seating shoulder 78 of valve member 50, the significance of which will be apparent from the following description.
Designing valve member 50 with the illustrated configuration is considered to allow valve member 50 and/or seat 72 to deform from repeated contact therebetween without inducing change to seating diameter D. By inhibiting change to the seating diameter associated with valve seat 72, reduced variability in operation of control valve assembly 40 and an associated device such as injector 20 over time can be expected, as further described herein.
Other advantages associated with the present disclosure relate to the geometry of valve member 50 and the manner in which valve member 50 is guided within housing 51. A lower segment 64 of valve member 50 may be understood as that portion of valve member 50 which extends between shoulder 78 and spacer 46 and is opposite an upper segment 61. Upper segment 61 may be understood as that portion of valve member 50 which includes a uniform outer diameter 82 extending between an edge 83 on valve member 50 and actuator 42. Shoulder 78 may thus be located between and adjoining each of lower segment 64 and a middle segment 62. Middle segment 62 adjoins lower segment 64 and upper segment 61, and extends between edge 83 and shoulder 78.
In one embodiment, middle segment 62 includes a step 66 having a diameter greater than seating diameter D and providing additional hydraulic surface area for assisting in moving valve member 50 towards its second position. Upper segment 61 may have a diameter equal to seating diameter D, whereas lower segment 64 has an average diameter less than seating diameter D. Middle segment 62 may further have a length L between step 66 and shoulder 78 which is greater than a service life distance described further below with regard to
The present guiding arrangement contrasts with earlier designs wherein a control valve member is guided via interaction between a housing and both an upper portion and a lower portion of the valve member. This strategy has also been found to reduce or eliminate pressure spikes associated with moving valve member 50 to its first position against seat 72. This is believed to be due at least in part to the fact that eliminating a lower guide portion, and providing lower segment 64 with a relatively small average diameter, provides a relatively large fluid volume to damp pressure spikes. Many earlier systems also include a flow restriction in their drain passage. In at least certain embodiments, control valve assembly 40 will not have a flow restriction in drain passage 45, a design feature believed to further assist in reducing or eliminating pressure spikes.
Yet another feature of the present valve geometry is an increased surface area below shoulder 78. Pressure in passage 45 will typically be relatively low. As further discussed hereinbelow, seat beat in may result in an increased travel distance of valve member 50. Increasing the travel distance can make it relatively more difficult for electrical actuator 42 to lift valve member 50 away from its position against seat 72. The relatively large surface area below shoulder 78 due to the guiding arrangement and associated small diameter of lower segment 64 enables whatever hydraulic pressure is available below seat 72 to give greater assistance in lifting valve member 50 from seat 72 than that of earlier designs.
As previously discussed, control valve assembly 40 may be actuated to move valve member 50 between its first and second positions, alternately blocking and opening seats 72 and 76. Moving valve member 50 in this manner allows the pressure in passage 47 of injector 20 to be varied, controlling pressure applied to closing hydraulic surface 35 of needle 36, and allowing needle check 34 to open to allow fuel to spray out of orifices 38 as desired. For example, a typical fuel injection for an expansion cycle in engine 10 might include a relatively small pilot injection, a relatively larger main injection, then another relatively small, post injection. The injection timing, rate shape and other factors can be varied with needle check 34 by controlling pressure acting on surface 35 via control valve assembly 40. Over the course of many cycles of operation, control valve member 50 may begin to deform. In earlier systems, where the low pressure seat was an inner diameter seat, deformation of the control valve member and/or seat tended to result in changes in the responsiveness of the control valve. In particular, it was common for the valve member to become relatively difficult to lift from its position against the low pressure seat. This tended to result from the travel distance of the valve increasing, and the tendency for the valve to become hydraulically unbalanced.
Turning now to
As material 73 wears away or valve member 50 is otherwise deformed, the actual position at which seating shoulder 78 is located may tend to migrate up outer diameter 70 a distance X toward a location represented with point Q. Migration of the position of seating shoulder 78 may change the travel distance of valve member 50 between its two seats by distance X. Outer diameter 70 may have a right cylindrical shape in a region adjoining shoulder 78, and hence a uniform width, over a length which is at least as great as distance X. This will assist in inhibiting change to seating diameter D due to valve deformation, further described herein. The change in travel distance X may be expected to be at least somewhat uniform among different control valve assemblies, and may therefore have relatively predictable effects on operation of each control valve assembly 40 of engine 10 and their associated fuel injectors 20. Accordingly, in many instances individual injectors 20 may be electronically trimmed based on nominal values of certain operating parameters for the entire group of injectors 20. Earlier designs, using traditional inner diameter seats as their low pressure seats, tended to have less predictable changes in operation and are therefore difficult or impossible to electronically trim.
In
The presently disclosed control valve configuration and operation differs from designs where the element defining the seating diameter of a particular seat is part of the seat itself, instead of the seating diameter being defined by the valve member. Many earlier designs utilize a seating edge formed in the housing which bears against a frustoconical surface on the outer diameter of a valve. In
In particular, in at least certain known designs deformation of the seating edge of an inner diameter low pressure seat tended to result in the seating diameter becoming smaller, as the initially relatively sharp seating edge formed in the housing is deformed to a more conical shape. Inducing this sort of deformation in an inner diameter seat can also tend to occlude or eliminate a portion of the valve member which was previously exposed to hydraulic pressure when the associated seat was closed. In other words, deformation of the seating edge in an inner diameter seat may have a tendency to change hydraulic balancing of the associated valve member. In the present disclosure, since seating diameter D stays the same even after seat beat in, the effective hydraulic areas, and hence hydraulic balance, of valve member 50 are not altered. Moreover, due to the geometry of valve member 50, control valve assembly 40 may be relatively faster in opening than other valve configurations, and less bias force required to close.
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 embodiment without departing from the full and fair scope and spirit of the present disclosure. For example, while one configuration disclosed herein includes valve member 50 guided only via its upper segment, conventionally guided valve members may still fall within the scope of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims.
