CA1124146A

CA1124146A - Injector valve with contoured valve seat and needle valve interface

Info

Publication number: CA1124146A
Application number: CA328,649A
Authority: CA
Inventors: William B. Claxton; Joseph C. Cromas
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1978-09-08
Filing date: 1979-05-30
Publication date: 1982-05-25
Also published as: JPS5537598A; FR2435607B1; FR2435607A1; GB2029508A; DE2935850A1; IT1122944B; JPS6363746B2; GB2029508B; IT7925437A0

Abstract

580?78-0908 INJECTOR VALVE WITH CONTOURED
VALVE SEAT AND NEEDLE VALVE INTERFACE
ABSTRACT
An injector valve having a stable fuel flow while metering "single point" fuel volumes is disclosed. A
metering portion of the injector valve comprises a needle valve and a valve housing including a centrally located valve housing bore that terminates in a truncated conical valve seat and cylindrical metering orifice. A
transitional surface connects the valve seat to the metering orifice to gradually change the direction of fuel flow so separation and unstable flow will not occur. The needle valve is concentrically reciprocal within the valve housing bore and closes the metering orifice with a valve tip having a closure surface mating with the valve seat.
The valve tip narrows from the closure surface into a pintle which extends through the metering orifice and ends in a deflection cap which shapes the spray of the valve into a hollow-cone pattern. The valve tip between the pintle and closure surface has a contoured surface that increases the flow area of the valve tip and valve seat interface to a plateau value downstream of the closure surface and then smoothly decreases the flow area from that value to where fuel exits the metering orifice.

Description

BACKGROUND OF THE INVENTION

The invention pertains generally to injector valves and is more particularly directed to injector valves having increased fuel flow rates.
Fuel injectors of the electromagnetic solenoid type have been commonly utilized in "multipoint" electronic fuel injection (EFI) sy-stems in the automotive field.
Such injectors are located at each cylinder of the engine and spray an atomized charge of fuel into the intake mani-fold near the associated intake valve. As the intake valve opens, the atomized fuel and air from the intake manifold are drawn into the cylinder and are combusted.
By controlling the duration of the operational times of the injectors with a pulse width modulated con~rol signal ; 15 from an electronic pulse width computer, the precision of fuel delivery has been greatly improved or the internal combustion engine. The fuel is metered accurately with respect to the many and varied operating parameters of the engine including MAP, RPM, ternperature and others. With this precision is the ability to improve fuel economy, control emissions9 or increase driveability such that the conventional carburetor will probably be displaced in the future by the EFI system as the most prevelant fuel control device.
Ano~her recent development in the fuel control field that may hasten the demise of the conventional carburetor ; is the "single point" EFI system which, like its counter-part the "multipoint" EFI system, depends upon the pre-cision of electronically controlling an electromagnetic solenoid injector.
"Single point" systems usually have one injector for the delivery of fuel to a plurality of cylinders of an engine at a single injection point instead of the "multi-point" system where a one-to-one correspondence occurs.

These injection points may be variably placed inside the intake manifold or the throttle bores of an air fLow regu-lation device leading to the intake manifold. If placed in the throttle bores, these injectors may be located above or below the throttle blades for the most advan-tageous configuration depending on the particular injector structure. With the substitution of one injector for a plurality of injectors, the "single point" EFI system re-duces complexity and expense compared to many "multipoint"
schemes while retaining most of the attendant EFI system advantages vis a vis the conventional carburetor.
It is desirable to inject such "single point" systems at least once per engine event (revolution) or even as fast at each intake valve opening. Since one injector replaces a plurality of injectors, sometimes as many as four for an eight-cylinder engine with a two-plane mani-fold, the "single point" injector generally must have a higher fuel flow rate than a corresponding "multipoint"
injector. For use in higher displacement engines a higher flow rate electromagnetic solenoid injector would addi-tionally be highly desirable whether "multipointl' or "single point".
This higher flow rate, because of the preferred single point injection timing, must be accomplished with-out the sacrifice of injector speed. If possible, it - would be desirable for increased control that the injector speed shoald even be increased. If a higher flow rate is obtained at the expense of operating speed, such an in-jector will not be as advantageous as if both goals are achieved. The slower the injector opening time, the less overall fuel capacity the injector will be capable of de-livering in the high speed range of the engine.
Presently in ~he art an increased flow rate for an injection vaLve can be obtained by increasing the metering 35 orifice cross-sectional area, increasing the input press~re, or a combination of both~ An increase in the input fuel pressure to a single point system would, how-ever, require the additional expense of a higher pressure fuel pump and pressure regulator combination and is, therefore, unacceptable to the basic premise of single point systems, the reduction of complexity d However, increasing the metering orifice cross-sec-tional area by scaling up a conventional "multipoint"
injector to a "single point" flow rate creates other problems. Initially, the opening time and thus operation capability of the injector is detrimentally affected because of the increase in the mass of the needle valve.
The mass of the needle valve increases in proportion to the volu~e increase of the material and not linearly with the increase in flow rate. Also, the flow paths of con-ventional "multipoint" valves are unfavorably restricted for "single point" applications and do not have sufficient flow area therethrough to ef~iciently handle the increased flow rate to a larger metering orifice.
Such "multipoint" valves are illustrated in U.S.
Patents 4,0G7,800 issued to Hans, et al., and 3,967,597 issued to Schlagmuller, et al. Hans, et al. and SchIag-muller, et al. disclose the use of a needle valve in an electromagnetic injector having flats cut on four sides of the shaft. This configuration unduly restricts flow through the injector valve and increases needle mass when utilized in a high flow injector.
A U.S. Patent 3,069,099 issued to Graham illustrates a fuel injection nozzle with a three-sided spring retainer plate. Although this configuration does not restrict fuel flow in the pressure operated injec~ion nozzle shown, it is not advantageously suitable for precision electromag-netic solenoid injection valves where exact metering and sure closure are re~uired.

Another problem encountered in scaling up a conven-tional "multipoint" injector to a l~single point" ~low rate is that many injectors will not produce a stablë flow at different pressures and times. At one particular pressure, for example, ~he static flow rate will be dif-ferent some of the time and the instability unpredictable as to occurence~ This defect seems to worsen at hiyher flow rates and higher pressures, and is unacceptablé in the "single point" flow rate and pressure range. Changes of between 5~-7% have been noted in the same injector operated at a particular pressure. The unpredictability of a flow rate from an injector will destroy the precision that the EFI systems have brought to the fuel metering art.
This unstable flow problem seems to be centered in the valve seat metering orifice interface where the cylin-drical metering orifice truncates the cone of the valve seat. At higher flow rates it is believed that the fuel accelerates through the closure surface and valve seat in-terface and thent at unpredictable intervals, will not smoothly flow into the exit orifice. I separation occurs at the exit orifice, the fuel will not be precisely metered by the area between the outer wall of the orifice and a pintle of the valve tip. This effect i5 similar to the "vena contracta" phenomenon found in hydraulics where a fluid under pressure flows around a sharp corner and has an extreme change of momentum and therefore separates from the surface of an orifice.
With high flow injector valves the angle at which the valve seat intersects the cylindrical metering orifice is relatively large because of the shallow cone angle of the valve seat necessary to produce high flow rates with mini-mal lift from the needle valve. Reducing this intersec-tion angle without modifying the minimal lift conical valve seat would be highly desirableO A modification to f~

the valve seat and valve tip interface of an injector is illustrated at Figure 4 of a U.S. Patent 3,241,768 issued to Croft, but is for the purpose of developing a constant flow area.
Another problem that prior art injection valves with high flow rates incur i5 a residual fuel drop being re-tained on the injector or injector tip surface which effects the precision of fuel injection on subsequent openings. The residual fuel left on the injector will also cause contamination if it evaporates and can obstruct the metering orifice.
Spray pattern shaping has been attempted with "multi-point" fuel injectors and with "single point" injectors.
The shaping of the pattern is important in the "single point" applications, since one injector is entraining the fuel in the air flow at a particular time and the conse-quent change is to be delivered to particular multiples of the cyllnders. If the air fuel ratio precision is to be maintained and cylinder-to-cylinder distribution errors minimized, the flow pattern must be correctly designed and reproducible with every injection. This will minimize wall wetting and unwanted condensation of the fuel on the throttle and other surfaces.
One of the spray patterns ~ecoming popular in "single point" injection is the hollow-cone pattern where the fuel is limited to a volume between two dif~erently-sized cones having their apex at the injector tip. It would be advan-tageous to be able to reproduce such a pattern with the same injector structure over a wide range of operatiny pressures and flow rates.

SUMMARY OF THE INVENTION

The invention provides an improved high flow rate in jector valve having a stable flow, minimal residual con-tamination, and a hollow-cone spray pattern.

'*~

According to the present invention there is provided a ~uel injection va]ve having a high flow ra-te metering por-tion, the valve including a valve housing providing a fuel flo~ passage which communicates fuel from a pressurized source toatruncated conical valve seat which intersects a cylindrical metering orifice. A needle valve is reciprocal in the valve passage and includes a valve tip having a closure surface which is operable to close the injection valve when brought into contact with the valve seat, the valve tip forming an interface area.with the valve seat downstream of the closure surface. A transitional surface COnneGts the valve seat through the orifice, the transitional surface changing the direction of the fluid flow through the interface area of the valve ~radually so as not to induce separation from the transitional surface.
According to a specific embodimeilt of the invention the needle valve is concentrically reciprocal within the valve housing and closes the metering orifice with a valve tip having a closure surface mating with the valve seat. The valve tip narrows from the closure surface into a pintle which extends throu~h the meterin~ orifice and ends in a deflection cap.
According to another aspect of a specific embodiment of the invention, the valve tip between the closure surface and pintle is contoured to increase the flow area of the valve tip and valve seat interface to a plateau level and then smoothly decreases the flow area to where the fuel e~its the metering orifice. The valve tip contour allows the recovery of pressure from the closure surface restriction to promote stable fuel flow and assists the transitional surface to -6~

provide reproducible injections.
According -to still another aspect of a specific embodimen-t of the invention, the deflection cap on the pint].e shaft forms a pinula which has a flat deflection surface ending in an edge sub-;, -6a-stantially peependicular to the spray axis of the injector valveO By controlling the diameter of the circular base of the deflection cap and its distance rom the annular flow channel formed between ~he metering orifice and 5 pintle, the included angles of a hollow-cone spray pattern can be regulated without affecting the metered flow from the valre. The hollow-cone pattern can be effected with this configuration over a wide range of pressures and flow rates.
The straight pintle stem, sharp edge of the deflec-tion surface, and the capillary ac~ion of the annular flow channel further combine to form a con$iguration which is less susceptible to the formation of residual fluid on the end of the injector valve when closed. The configuration 15 minimize~ the surface area available for formation and tends to hold any residual fluid adjacent to the annular flow channel by capillary action Therefore, it is an object of the invention to prevent unstable flow from occurring in injector valves 20 having "single point" fIow rates.
It is another object of the invention to produce a stable flow rate from an injector valve by contouring the interface between valve seat and metering orifice.
It is still another object of the invention to 25 produce a stable flow rate from an injector valve by contouring the valve tip between the closure surface and the pintle to increase the flow area at that point.
Yet another object of the invention is to prevent residual drop formation on the end of the injector while 30 providing a controllable hollow-cone spray pattern gener-ator.
These and other objects, features, and aspects of the invention will be clearer and more fully understood from a reading of the detailed description when taken in conjunc-35 tion with the appended drawings wherein:

~ J

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a cross-sectional side view of an in-jector housing and needle valve metering combination shown in a closed position that has been constructed in accor-5 dance with the invention;
FIGURE 2 is a cross-sectional side view of the in-jector housing and needle valve com~ination illustrated in Figure 1 which is shown in an open position;
FIGURE 3 is an enlarged fragmentary side view in cross-section of the contoured valve seat and needle valve interface for the metering combination illustrated in Figures 1 and 2; and FIGURE 4 is a graphical representation of the flow area as a function of various positional points along the valve seat and needle valve inter~ace illustrated in Figure 3.

DETAILED DESCRIPTION OF THE :PREFERRED EMBODIMENT

An injector valve metering portion havîng a "single point" fuel flow rate is illustrated in Figure 1 in a closed position and comprises a valve housing 100 and needle valve 107 mounted in an injector housing 104 of the valve. The construction of the injector valve other than the metering portion is not shown as it is conventional and not pertinent to a discussion of the invention. Such portions could, for example, comprise a solenoid connected at the armature to the needle valve 107 as illustrated in the referenced Hans, et al.

The valve housing 100 is received into a mounting chamber 102 of an injec~or housing 104 and is spaced ex-actly by a C-shaped spacer washer 106 which has its ,s~,, L~

dimensions accurately controlled by machining both facial surfaces. The valve housing 100 is held securely in the mounting chamber 102 by crimping the rim 114 of the in-jector housing 104 over an outside shoulder of the valve housing. A suitable O-ring 112 is used to seal the inter-face of the mounting chamber 102 and the valve housing 100.
The valve housing 100 is provided with an essentially central valve housing bore 116. The needle valve 107 com-prises a shank portion 108 which fits throuyh C-shaped spacer 106 and then flares into a radially outgoing spacer collar 110~ The spacer collar 110 adjoins a generally triangular cross-section medial section having three equi-lateral bearing surfaces 118 spaced equally about the valve housing bore 116 to center the needle valve 107 within the bore.
The medial section connects to a valve tip 122 having a closure surface 124 which mates with a truncated conical valve seat 126 and then narrows to finally become an elon~ated pintle 128. The pintle 128 extends through a cylindrical metering orifice 132 and terminates in a deflection cap 130. The bearing surfaces 118 slide within the bore 116 and are connected by relieved surfaces 120 forming fuel flow passages between them and the valve housing bore 116c Fuel unex pressure flows in~o ~he fuel passages between the needle valve and valve housing bore 116 from a pressuriæed source (not shown) which feeds fuel through the opening in the spacer washer 106. The fuel is pre-vented from exiting an annular fuel passage formed betweenthe cylindrical orifice 132 and the pintle 128 by means of a closure force 105 forcing the needle valve tip into sealing relationship with the valve seat 126.
In Figure 2, fuel is metered from ~he valve by apply-ing an opening force 134 lifting the needle valve 107 away from the seat and allowing fuel to pass through theclosure surface 124 and valve seat interface 126 and, thereafter, the orifice 132. The needle valve 107 is lifted to where the spacer collar 110 abuts washer 106.
The opening force 134 and closure force 105 can be pro-vided by a number of means such as a solenoid, pressure, or mechanical. Preferably, said force is provided by an electromagnetic solenoid with its armature attached to the shank portion 108 of the needle valve 108.

When the valve is open, fuel is metered through the annular passage formed by the pintle 128 and cylindrical metering orifice 132~ The flow area of the passage is precisely controlled to permit a desired amount per unit time at the operating preSC;ure of the valve to be injected. The fuel flow is shaped into a hollow-cone pattern by the deflection cap 130. The pattern has an outer cone angle A and an inner cone angle B between which substantially all of the fuel flow is contained.
Figure 3 shows an enlarged cross-sectional view of the interface between the valve tip 122 and the valve seat 126. It is seen from the figure that the valve seat and metering orifice intersection, which was previously a sharp corner with a relatively large angle as indicated by dotted line 140, has been contoured into a transitional surface 144 which smoothly changes the direction from the conical face of the valve seat to the cylindrical orifice.
The transitional surface 144 is shown as a curve beginning at the exit orifice and sweeping to where it becomes tangent to the valve seat surface 126.

J, ~ 0 --This shape is the preferred form and can be in cross-section a circular arc or higher ordered curve, but any transitional surface which changes fuel direction gradu-ally enough to not cause separation or cavitation in the 5 fuel flow would be acceptable for the interface. The simplest form of the transitional surface could be a trun-cated cylindrical surface beginning at the valve seat and connecting the cylindrical metering orifice. The transi-tional conical surface could have a greater slope than the 10 valve seat, but less than the vertical angle of the meter-ing orifice.
To compliment the transitional area, the valve tip 122 between the closure surface and the pintle has also been contoured from its previous shape, as shown by the 15 dotted line at 142, to the present surface illustrated at 146. Taking cross-sectional flow area at different posi-tions between the valve tip and the valve seat interface, it is seen in Figure 4 that the flow area decreases from point A to point B because of the closure surface and 20 valve seat restriction. From point B to point D it gradu-ally increases to where a plateau level is reached at points D-F~ From point F to the flow area of the annular passage, I, the flow area gradually and smoothly de-creases.
The flow area between points B and points F allows the fuel to recover pressure lost going through the re-stricted area from A to B and slows the velocity. From point F the smooth entry of the fuel along the transi-tional surface into the exit orifice 132 keeps the fluid from dropping below the vapor pressure so the flow rate is stable and cavitation and separation are prevented.
The contour of the valve tip 122 and the contour of the transitional surface 144 both contribute to providing a meter;ng valve which is stable in flow rate. Each can, however, be used individually ~o effect stability in in-jection valves, but the features preferably are used in combination to create a uniting of their individual con-trib~tions.
The shaping of the hollow cone spray pattern is ac-5 complished by the deflection cap 130 which is formed onthe end of the pintle as a cone with a flat deflection edge 138 and small fillet 150 connecting to the shaft of the pintle 128. A spray axis C C indicates the direction of fluid momentum as the fuel exits the orifice 132. Assum-ing a constant pressure for the injector, the hollow-cone spray pattern is generated by controlling three variables which are: the annular flow area of the fuel passage between the metering orifice and pintle, the distance between the injector housing end and the flat deflection surface 148 designated dl, and the difference in the ori-fice diameter and the diameter of the base of the deflection cap designated d2.
Generally, the smaller the distance dl, the wider the spray pattern will be when the injector is open. Similar-ly~ the smaller the distance d2 is, the wider the spraypattern angle. One limitation is that the distance dl must be greater than that necessary to prevent restriction of the metering orifice as the deflection cap 130 is for the purpose of separating the shaping function from the metering function in the present valve.
The fuel flow, as it comes out and impinges upon the deflection surface 1~8, changes the direction of the fluid flowing the deflection distance d2 to form the two hollow-cone sprays. The fluid deflected substantially perpen-dicular to the spray axis C-C by the de~lection surface 138 wili cause movement away from spray axis in the hori-zontal direction by a component related to the amount of flow and the amount of flow deflected. The larger the amount of flow deflected to that of the entire flow, the smaller the angles of the hollow-cone pattern.

As an example, a hollow-cone spray pattern with an inner cone angle a of ~0 and an outer cone angle A of 30~
can be formed by an injector having a metering orifice of O033ll diameter and a pintle diame~er of .022". The 5 distance dl for this injector would be approximately .~16"
and the distance d2 would be .001", or having a deflection cap with an outside base diameter o .Q32". Such an in-jector would be designed to run at approximately 40 PSI
and have a single 1Oat point flow rate of between 40 or 50 10 lbs./hr.
A lower pressure injector running at approximately 15 PSI and the same flow rate with an inner cone angle B of 30 and an outer cone angle A o 10 can be advantageously manufactured by having a metering orifice o .044" with a 15 pintle outside diameter of .025". This valve would have distance dl o .024". For this spray angle, a difference of .002", or distance d2, between the outside diameter of the base of the deflection cap and the metering orifice is desired, or where the base of the deflection cap equals .042" in diameter.
While the preferred embodiments of the invention have been shown, it will be obvious to those skilled in the art that modifications and changes may be made to the dis-closed system without departing from the spirit and scope 25 of the invention as defined by the appended claims.

WHAT IS CLAIMED IS:

Claims

1. A fuel injection valve having a high flow rate metering portion comprising:
a valve housing having a fuel flow passage which communicates fuel from a pressurized source to a truncated conical valve seat which intersects a cylindrical metering orifice;
a needle valve, reciprocal in said valve pas-sage, including a valve tip having a closure surface which is operable to close the injection valve when brought into contact with said valve seat, said valve tip forming an interface area with said valve seat downstream of said closure surface;
a transitional surface connecting said valve seat to said orifice, said transitional surface changing the direction of the fluid flow through the interface area of the valve gradually so as not to induce separation from the transitional surface.

2. A fuel injection valve with a metering portion as defined in Claim 1 wherein:
said transitional surface is formed as a trun-cated conical surface with a greater conical slope than said valve seat.

3. A fuel injection valve with a metering portion as defined in Claim 2 wherein:
said transitional surface is formed as a curva-ture connecting said valve seat and said metering orifice.

4. A fuel injection valve with a metering portion as defined in Claim 3 wherein:
said radius of curvature is formed by a circular radius being extended from the inlet end of said metering orifice to where it is tangent to said conical valve seat.

5. A fuel injection valve with a metering portion as defined in Claim 1 wherein:
said valve tip narrows into a pintle which extends through said metering orifice, said valve tip being contoured between said closure surface and said pintle such that the flow area of the valve tip and valve seat interface increases to a plateau valve and subsequently decreases smoothly to where the fuel exits the metering orifice.

6. A fuel injection valve having a high flow rate metering portion comprising:
a valve housing having a fuel flow passage which communicates fuel from a pressurized source to a truncated conical valve seat which intersects a cylindrical metering orifice;
a needle valve, reciprocal in said valve passage, including a valve tip having a closure surface which is operable to close the injection valve when brought into contact with said valve seat, said valve tip forming an interface area with said valve seat downstream of said closure surface;
said valve tip narrowing into a pintle which extends through said metering orifice and terminating in a deflection cap having a deflection surface ending in an edge substantially perpendicular to the injector spray axis; and a transitional surface connecting said valve seat to said orifice, said transitional surface changing the direction of the fluid flow through the interface area of the valve gradually so as not to induce separation from the transitional surface.

7. An injection valve with a metering portion as defined in Claim 6 wherein:
said deflection surface controllably forms a hollow-cone spray pattern with an inner cone angle and outer cone angle by varying the distance of the deflection surface with respect to the end of the exit orifice.

8. An injection valve with a metering portion as defined in Claim 7 wherein:
said inner and outer cone angles are control-lably formed by varying the distance between the diameter of the base of said deflection surface and the diameter of said metering orifice.

9. An injection valve with a metering portion as defined in Claim 8 wherein:
said inner and outer cone angles are control-lably formed by varying the flow area of the annular fuel passage formed between said pintle and said metering orifice.

10. A fuel injection valve having a high flow rate metering portion comprising:
a valve housing having a fuel flow passage which communicates fuel from a pressurized source to a truncated conical valve seat which intersects a cylindrical metering orifice;

a needle valve, reciprocal in said fuel flow passage, including a valve tip having a closure surface

Claim 10 cont'd....

which is operable to close the injection valve when brought into contact with said valve seat, said valve tip and said valve seat forming an enlarging flow area between said closure surface and said cylindrical metering orifice;
said valve tip narrowing into a pintle extending through said metering orifice forming an annular flow channel therebetween and terminating in a deflection cap having a deflection surface substantially perpendicular to the injector spray axis and ending in an edge having a perimeter similar to the perimeter of said cylindrical metering orifice;
an abruptless transitional surface connecting the conical face of said valve seat to said cylindrical metering orifice, said transitional surface changing the direction of the fluid flow through said annular fuel passage or the valve gradually so as not to induce flow separation from said transitional surface.