Abstract:
A valve and method of constructing same for a purge control device are provided. The valve includes an integral body. The valve further includes a resilient member inserted into the integral body. The resilient member is electromagnetically responsive so that the member can be selectively actuated between respective open and close conditions. An electromagnetic actuator is affixed to the integral body to generate an electromagnetic field for selectively actuating the resilient member between the open and closed conditions. The mass of the resilient member is sufficiently low so that the level of noise produced by the valve is correspondingly low.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is generally related to purge control devices, and, more particularly, to a unibody electromagnetic valve for controlling the flow of fuel vapors. The invention is further related to valve-constructing techniques that enable to produce a valve with low acoustic noise and reduced permeability relative to the fuel vapors passing through the valve. 
     Environmental regulations for automotive-related emissions have been evolving over the years to more rigorously prescribe the levels of emissions that may be discharged into the atmosphere, such as fuel vapors that may accumulate in the fuel tank of an automobile. Accordingly, evaporative systems for reducing the discharge of these vapors into the atmosphere have to accurately meet such regulations. At the same time, the evaporative systems should be reliably and affordably constructed to enable suppliers in the automotive industry to successfully compete in the marketplace. 
     Known purge control devices generally use an assembly of many discrete parts, which incrementally add to the cost and weight of the device and tend to adversely impact the overall reliability of the device. FIG. 1 illustrates one known purge control device  10  including a solenoid valve  12  having a relatively heavy plunger  14 . The valve may operate using pulse width modulation (PWM) techniques at a preset frequency, such as 16 Hz. Although the valve provides appropriate flow control to the fuel vapors that pass therethrough, this type of valve may generate objectionable levels of acoustic noise during its operation. Most customers view low noise as a desirable feature in automotive applications, and, consequently, the ability to provide a valve that in operation has low levels of acoustic noise is a very desirable feature for suppliers of automotive components, such as the assignee of the present invention. 
     The body of a valve, such as that illustrated in FIG. 1, is generally made from plastic, and it is known that there might be some diffusion of fuel vapors through the body of the valve. The level of this diffusion is relatively low and this has not been an issue in view of present environmental regulations. However, it is anticipated that there may be requirements that may be enacted in the future that would mandate eliminating or substantially reducing the levels of such a diffusion. 
     In view of the foregoing considerations, it would be desirable to provide a valve, such as may be used in a purge control device, that in operation produces relatively low levels of acoustic noise. It would be further desirable to provide a valve made of materials with reduced permeability relative to the fuel vapors passing through the valve. It would be further desirable to provide a valve with fewer parts relative to the number of parts traditionally used in the industry so as to enable incremental cost and weight savings as well as improved reliability. 
     BRIEF SUMMARY OF THE INVENTION 
     Generally, the present invention fulfills the foregoing needs by providing in one aspect thereof, a valve for a purge control device. The valve includes an integral body. The valve further includes a resilient member inserted into the integral body. The resilient member is electromagnetically responsive so that the member can be selectively actuated between respective open and close conditions. An electromagnetic actuator is affixed to the integral body to generate an electromagnetic field for selectively actuating the resilient member between the open and closed conditions. The mass of the resilient member is sufficiently low so that the level of noise produced by the valve is correspondingly low. 
     In another aspect thereof, the present invention further fulfills the foregoing needs by providing a method for constructing a valve for a purge control device. The method allows constructing an integral body. The method further allows inserting a resilient member into the integral body. The resilient member is electromagnetically responsive so that the member can be selectively actuated between respective open and close conditions. An electromagnetic actuator is coupled to the integral body to generate an electromagnetic field for selectively actuating the resilient member between the open and closed conditions. The mass of the resilient member is sufficiently low so that the level of noise produced by the valve is correspondingly low. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which: 
     FIG. 1 illustrates one known purge control device to assist the reader understand some of the problems which are overcome in accordance with aspects of the present invention. 
     FIG. 2 is a cross-sectional view of one exemplary embodiment of a unibody purge valve embodying a reed valve in accordance with aspects of the present invention. 
     FIG. 3 is a cross-sectional view of another exemplary embodiment of a unibody purge valve embodying a diaphragm valve in accordance with other aspects of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2 is a cross-sectional view of one exemplary embodiment of a unibody purge valve  100  embodying aspects of the present invention. As used herein the expression “unibody” refers to an integral structure for the body of the valve, as opposed to a multi-part body. As shown in FIG. 2, valve  100  includes a normally closed reed  102  that may deflect to an open condition, represented by reed position  103 , in response to an appropriate voltage signal connected to an associated electromagnetic reed actuator  104 , such as may be made up of an armature  106  and a winding  108 . Purge valve  100 , in response to the voltage signal applied to actuator  104 , allows to selectively communicate an inlet port  110  with an outlet port  112  through an opening  114 . In one exemplary embodiment the inlet port may be connected to a canister port, and the outlet port may be connected to the intake manifold of an internal combustion engine. The inlet port in operation may be at atmospheric pressure while outlet port  112  may be at the engine intake manifold pressure (e.g., vacuum). That is, at a pressure less than atmospheric pressure. 
     The inventor of the present invention has innovatively recognized that lowering the mass of the moving member of the valve may substantially decrease acoustic energy generated by the valve, i.e., noise. The exemplary embodiment illustrated in FIG. 2 comprises a valve wherein reed  114  comprises a generally flexible, resilient ferromagnetic member, such as may be made up of magnetic stainless steel or other such materials. In one exemplary embodiment, the body of the valve comprises a unibody construction that may be made of plastic or any other suitable polymer material using standard molding or injection techniques. To simplify the manufacturing process, the reed may be insert molded into the body of the valve. As can be appreciated in FIG. 2, the reed  102  may include a step-wise structure  105  that allows for even a more secure mechanical connection of the reed relative to the body of the valve. The step-wise structure also provides an advantage from an electromagnetic point of view being that such step-wise structure effectively decreases the air gap g 1  between the reed and the armature and consequently the sensitivity of the reed to the electromagnetic actuator is enhanced. The solenoid actuator  104  may be externally affixed to the body of the valve using standard techniques for affixing a solenoid relative to a plastic body. 
     In another exemplary embodiment, the body of the valve may be produced using Zinc-casting techniques, such as may be commercially available from Fishercast Div. Of Fisher Gauge Limited, Canada, or injection molding of thixotropic semi-solid alloy available from Thixomat of Ann Arbor, Mich., USA. As will be appreciated by those skilled in the art, insert molding or insert casting can be highly efficient techniques as compared to more traditional techniques for constructing the valve that rely on the assembly of discrete parts, such as through soldering, connectors, fasteners, adhesives, etc. The benefits of insert molding/casting over such traditional techniques may include at least the following: reduced assembly and labor cost, reduced size and weight, increased reliability and increased design flexibility. For readers desirous of background information regarding Zinc Casting, see, for example, article titled “Revolution in Zinc Casting” by William Mihaichuk, as reprinted from “Machine Design” Dec. 8, 1988, which article is herein incorporated by reference. As will be appreciated by those skilled in the art, a valve having a metal body would be particularly useful for applications that require stricter control of fuel vapor diffusion through the walls of the valve since a metal valve would have reduced permeability relative to the fuel vapors passing through the valve, as compared to a plastic valve. The use of the expression Zinc Casting is meant to use terminology well-understood in the art of casting and is not meant to limit the invention to the use of zinc material since other metals, such as aluminum, magnesium and alloys, such as Zinc/aluminum and Zamak alloys could be employed in lieu of zinc. 
     In one exemplary embodiment in order to keep the length of the air gap g between the tip of the reed and the armature relatively small, it may be desirable to configure the cross section of the canister port rectangular in lieu of circular so that the air gap g corresponds to the smaller dimension of the rectangular cross section. In essence, the aspect ratio of the rectangular cross section would be selected to meet the volumetric flow requirements of the valve while ensuring that the air gap is sufficiently small so that no excessive electromagnetic energy is required to actuate the reed. It will be appreciated that the present invention is not limited to circular or rectangular cross-sections since other configurations, such as elliptical could be used. 
     FIG. 3 is a cross-sectional view of another exemplary embodiment of a unibody purge valve  200  embodying aspects of the present invention. As shown in FIG. 2, valve  200  includes a normally closed diaphragm  202  that may deflect to an open condition, represented by diaphragm position  203 , in response to an appropriate voltage signal connected to an associated electromagnetic diaphragm actuator  204 , such as may be made up of an armature  206  and a winding  208 . Purge valve  200 , in response to the voltage signal applied to actuator  204 , allows to selectively communicate the inlet port  110  with the outlet port  112  through an opening  214 . 
     Diaphragm  202  comprises a generally flexible, resilient ferromagnetic member, such as may be made up of magnetic stainless steel or other such materials. As shown in FIG. 3, the diaphragm may be configured to provide a circumferentially-extending spring structure  210  that normally urges the diaphragm against the opening  214 , and, in response to the actuating force from the actuator  204 , allows the diaphragm to extend to the open condition. As described in the context of FIG. 2, the body of the valve may comprise a unibody construction that may be made of plastic or any other suitable polymer material using standard molding or injection techniques. In this embodiment, the diaphragm may be insert molded into the body of the valve. The diaphragm may include a plurality of anchor holes that would allow the molding or casting material to form an even stronger insert connection. 
     While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.