DE2935850A1 - FUEL INJECTION VALVE - Google Patents

Description

The invention relates to a fuel injection valve according to the Preamble to the main claim.

Fuel injectors that work with electromagnetic solenoids, are commonly used in "multipoint" electronic fuel injection systems used by automobiles. Such injectors are arranged on each engine cylinder and spray a nebulized Charge of fuel in the intake manifold close to the associated intake valve. When the intake valve opens, the atomized fuel and air are drawn into the cylinder from the intake manifold and burned. The fact that the duration of the operating times of the injectors with a pulse-width-modulated control signal Controlled from an electronic pulse width calculator, the accuracy of the fuel supply in internal combustion engines vastly improved. The fuel is made taking into account many different engine operating parameters including the air pressure in the intake manifold, the speed of rotation, the temperature and others, precisely measured. With this accuracy is the way to achieve fuel savings, the emissions to regulate or to increase the driving ability, so that conventional carburetors probably in the future by such Injection systems as the main control unit for the fuel are replaced.

Another recent development in fuel control, which can lead to the replacement of the conventional carburetor is the "one-point" injection system. This depends exactly how his Counterpart, the "multipoint" injection system depends on the accuracy with which an electromagnetic solenoid injector is controlled

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ORIGINAL INSPECTED

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"One point" systems usually have one injector, the fuel multiple engine cylinders at a single injection point. They are thus in contrast to the "multi-point systems, b. who have 1: 1 correspondence. These injection points can be varied within the intake port or the throttle bores of an air flow control device, which lead to the intake port, be attached. If the injectors are arranged in the throttle bores, they can be above or below the throttle blades can be provided, as this leads to the most advantageous configuration for the respective injector design. By having an injector Instead of using multiple injectors, the "single point" injection system has the complexity and cost over many "Mehrpunkf" -conceptions lower; nevertheless this system has Most of the operating advantages of the injection system are compared to conventional carburetors.

In such "one point" systems, the injection should be at least once per engine event (revolution) or even as fast as each intake valve opening occurs. As an injector Replaced several injectors, sometimes even four in an eight-cylinder engine with a two-level manifold, the must "Single point" injector provides higher fuel flow rate as a corresponding "multipoint" injector. Using in larger displacement engines, regardless of whether it is a "multipoint" or a "single-point" system, is an electromagnetic one Higher flow rate solenoid injectors are desirable.

ORIGINAL iNortCTED

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Because of the preferred one-point injection time, this higher flow rate must be achieved without the injector being switched on Losing speed. If possible, it should even be possible to control it in such a way that the injector speed also increases. When the higher flow rate comes at the expense of the operating speed, an injector is not as cheap as it is if both goals are achieved. Jfe slower the injector operating time, the less fuel the injector can deliver overall in the high speed range of the engine.

At present, a higher flow rate can be used in injectors can be obtained in that the cross section of the metering opening is enlarged that the inlet pressure is increased or that both measures are used. An increase in the inlet pressure of the fuel in a one-point system would however, mean additional costs for a combination of fuel pump and pressure regulator operating at higher pressure. These The solution is therefore not suitable in view of the basic premise of one-point systems, the reduction in complexity.

The enlargement of the cross section of the measuring opening with which a conventional "multi-point" injector to a "single point" injector upgrading leads to other problems. First of all, the opening time and thus the functionality of the injector are disadvantageous affects as the mass of the needle valve increases. The mass of the needle valve increases proportionally to the increase in volume of the material and not linearly with the increase in flow velocity. In addition, the flow paths of conventional "multipoint" valves are unfavorable for use in "one-way"

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point "systems and do not have a sufficient flow cross-section, with which the increased flow velocity to a larger measuring opening could be managed.

Such "multipoint" valves are disclosed in U.S. Patents 4,007,800 and US Pat 3,967,597. Here a needle valve is used in an electromagnetic injector, which is located on four sides of the shaft Has flat cutouts. This configuration unfavorably throttles and increases the flow through the injector the needle mass when used with a high flow rate injector.

In US Pat. No. 3,069,099 there is a fuel injector nozzle with a three-sided spring retainer plate shown. In this configuration, although the fuel flow is in that illustrated, pressure-driven Injector not throttled; however, this arrangement is not for accurate electromagnetic solenoid injectors suitable where precise dimensions and reliable closing are required.

Another problem with upgrading conventional "multi-point" injectors To "one-point" injector occurs is that many injectors do not have a stable flow at different Press and generate times. For example, the static flow velocity differs at a certain pressure temporarily; the occurrence of the instability cannot be predicted. This error worsens at higher flow velocities and higher pressures and is in the range of "one point" flow rates and pressures no longer acceptable. Ver

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ORiGINAL INSPECTED

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Changes between 5 and 7% were noted with the same injector operating at a given pressure. The unpredictability the flow rate from the injector contradicts the accuracy achieved with the electronic injection systems can be achieved in the dimensioning of fuel.

The problem described with the unstable flow seems to be due to the interface between the valve seat and the measuring opening to be where the cylindrical metering opening passes through the cone of the valve seat. It is believed that the fuel is changing as it passes through through the intermediate surface between the closing surface and the valve seat accelerated and then flows unevenly into the outlet opening at unpredictable intervals. When a severance takes place at the outlet opening, the fuel is thru the surface between the outer wall of the opening and a nozzle pin of the Valve tip no longer precisely measured. This effect is similar to the "vena contracta" phenomenon found in hydraulics, if a pressure medium flows around a sharp edge and experiences an extreme change in momentum and therefore moves away from the surface of a opening.

In the case of injection valves with a higher flow rate, the is Angle at which the valve seat surface meets the cylindrical measuring opening cuts, relatively large, since a shallow cone angle of the valve seat is necessary to handle the high flow velocities to be generated with the smallest possible stroke of the needle valve. This cutting angle should be reduced if possible, without modifying the conical valve seat surface, which operates with minimal lift. A modification of the interface between

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see valve seat and valve tip of an injector is in Fig. 4 in US Pat. No. 3,241,768, but serves the purpose of creating a constant flow area.

Another problem which occurs with known injection valves with high flow velocities is residual fuel drip on the injector or on the injector tip surface remains behind. This affects the accuracy of the fuel injection at subsequent openings. If a residual fuel remains on the injector, it also leads to contamination when it vaporizes; it can clog the measuring opening.

A shaping of the spray pattern was used with "multi-point" fuel injectors and also tried "Einpunkf" injectors. The shape of the Pattern is important in "single point" applications as an injector injects the fuel into the air stream at a specific time and the following batch is to be delivered to a certain number of cylinders. If the accuracy is in the ratio between Maintaining air and fuel and minimizing cylinder-to-cylinder distribution errors must be the flow pattern correctly formed and reproducible with each injection process. This makes the wall wetting and a desirable one Condensation of the fuel on the throttle and on other surfaces minimized

A spray pattern that is becoming increasingly popular with "single point" injection is the pattern of a hollow cone. Here the fuel is on a volume between two cones of different sizes limited whose apex is at the injector tip. This mu-

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ster should be over a wide area with the same injector design be reproducible across operating pressures and flow velocities.

The object of the present invention is to provide a fuel injection valve to develop the genus specified in the preamble of the main claim in such a way that the above-described, desired Has advantages.

This task is described in the characterizing part of the main claim Invention solved; advantageous developments are specified in the subclaims.

An exemplary embodiment of the invention is explained in more detail below with reference to the drawing; show it

Fig. 1 is a cross section through a dimensional combination of injector housing and needle valve, which is shown in the closed position;

Fig. 2 shows a cross section through the combination of injector housing and needle valve shown in Figure 1 in the open position;

3 shows an enlarged partial side view in cross section of the contoured interface between the valve seat and the needle valve in the measurement combination shown in Figures 1 and 2;

4 is a graph in which the flow zone as a function of various points along the interface between The valve seat and needle valve shown in Fig. 3 is shown.

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In Fig. 1, the metering portion of an injector, the one fuel flow rate suitable for use in "single point" systems possesses, shown in the closed position. It comprises a valve housing 100 and a needle valve 107 which is in an injector housing 104 of the valve is mounted. The construction of the injector valve, as far as it does not concern the measuring section, is Not shown; it is conventional and irrelevant to the discussion of the invention. These omitted parts include, for example a solenoid which is connected to the needle valve 107 on the armature. This is for example in the above-mentioned US-PS 4 007 800 shown.

The valve housing 100 is received in a mounting chamber 102 of the injector housing 104 and _f erh & lt through a C-shaped distance

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washer 106 an exact distance "" Their dimensions will be exact adjusted by machining both end faces. The valve housing 100 is held in the mounting chamber 102 by the Edge 114 of the injector housing 104 over an outer shoulder of the valve housing is crimped. A suitable O-ring 112 seals the The intermediate surface of the assembly chamber 102 and the valve housing 1OO.

The valve housing 100 has a substantially centrally extending Housing bore 116 provided. The needle valve 107 includes a shaft portion 108 passing through the C-shaped spacer washer 106 fits through and then widens into a radially outwardly extending spacer collar 110. The spacer collar 110 is adjacent to one A central section which is essentially triangular in cross section and has three bearing surfaces 118 on the same side. These are about the Valve housing bore 116 evenly distributed and center the

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Needle valve 107 within the bore.

The middle section leads to a valve tip 122. This has a closing surface 124 which is a frustoconical valve seat surface 126 is adapted, and then tapers to an elongated nozzle post 128. The nozzle post 128 extends through a cylindrical metering opening 132 and terminating in a baffle cap 130. The bearing surfaces 118 slide in the bore 116 and are connected to one another via recessed surfaces 120, the fluid channels between them and the valve housing bore 116 form.

Pressurized fuel flows into the fuel channels between the needle valve and the housing bore 116 from a pressure source (not shown) which feeds fuel through the opening in the spacer disk 106. The escape of the fuel from an annular channel which is formed between the cylindrical opening 132 and the nozzle pin 128 is prevented by means of a closing force 105 which presses the needle valve tip tightly against the valve seat surface 126.

In Fig. 2, fuel is metered from the valve by applying an opening force 134. This lifts the needle valve 107 away from the seat surface and allows fuel to pass through the intermediate surface 126 between the closing surface 124 and the valve seat surface and then through the opening 132. The needle valve 107 is raised until the spacer collar 110 strikes the disk 106. The opening force 134 and the closing force 105 can be in various ways, for example by a solenoid, by pressure

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or mechanically.

When the valve is open, fuel is passed through the annular channel between Nozzle pin 128 and cylindrical measuring opening 132 measured. The flow area of the channel is precisely controlled so that a desired amount is injected per unit of time at the operating pressure of the valve. The flow of fuel becomes a hollow cone pattern formed by the baffle cap 130. The pattern has an outer cone angle A and an inner cone angle B. Between This is where practically the entire fuel flow is located.

3 shows an enlarged cross section through the intermediate surface between valve tip 122 and valve seat 126. From the figure it can be seen that the interface between the valve seat surface and measuring opening, at which previously a sharp edge with a relative large angle (indicated by the dashed line 140) was now formed into a transition surface 144, which between the conical surface of the valve seat and the cylindrical opening changed their direction smoothly. The transition surface 144 is shown as a curve which begins at the outlet opening and extends to a point where it is tangential to the valve seat surface 126 is.

This is the preferred form; its cross-section can be an arc of a circle or a curve of a higher order. Any transition surface, which the direction of the propellant has changed gradually enough without a separation or cavitation of the propellant flow taking place suitable for the intermediate surface. The simplest form of the transition surface is a truncated cone surface, which acts on the valve seat surface.

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starts and leads to the cylindrical measuring opening. The conical transition surface then has a greater inclination than the valve seat surface, but less than the perpendicular angle of the Abmeßöf opening.

The valve tip 122 is also used to supplement the transition area between the closing surface and the nozzle pin compared to the previous one The shape shown by the dashed line 142 is modified to the surface configuration shown at 146. If one takes the flow cross-section at different positions between the valve tip and the valve seat interface, so it can be seen from Fig. 4 that this decreases from point A to point B due to the throttling of the closing surface and the valve seat. It grows slowly from point B to point D; a plateau is reached at points D-F. From point F to the flow cross section of the annular channel I, the flow cross-section decreases gradually and evenly.

The flow area between points B and F lets the fuel regain the pressure lost by the restricted area between A and B and slow down the speed. From point F onward, the smooth entry of the fuel along the transition surface into exit port 132 prevents the Fluid drops below vapor pressure so that the flow rate is stable and there is cavitation and separation be prevented.

The contour of the valve tip 122 and the contour of the transition surface 144 both help create a metering valve, the one

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has a stable flow rate. Any measure can, however can also be used individually to bring about stability in injection valves. However, these are preferred Features are shared, thus connecting their individual contributions.

The formation of the spray pattern as a hollow cone is done by the deflection cap 130, which is at the end of the nozzle pin as a cone flat deflection edge 138 and as a small rounding 150, which leads to the shaft of the nozzle pin 128 is formed. The spray axis C-C indicates the direction of the fluid impulse when the fuel is running out emerges from the opening 132. If a constant pressure is assumed for the injector, the spray pattern becomes the hollow cone generated by controlling three variables. These are: the annular flow cross-section of the fuel channel between the measuring opening and the nozzle pin; is the distance between the end of the injector housing and the flat baffle 148, which is designated by d ..; the difference between the diameter of the opening and the diameter of the base of the deflector cap, which is marked with d_.

Generally speaking, the smaller the distance d., The smaller the distance the spray pattern is wider when the injector is open. Similarly, the greater the spray pattern angle, the smaller the distance d ~ is. One restriction is that the distance d .. must be greater than that which is necessary to prevent throttling of the measuring opening. The deflection cap 130 is used in the valve described Purpose to separate the form function from the measure function.

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As the fuel flow exits and strikes the deflector surface 148 , it changes the direction of the fluid flowing through the deflection distance d_, thereby forming the spray cone with the two cone angles. The fluid which is deflected by the deflector surface 138 substantially perpendicular to the spray axis CC causes a movement away from the spray axis in a horizontal direction which is related to the flow rate and the amount of the deflected flow. The greater the amount of deflected flow compared to the total flow, the smaller the angles of the hollow cone pattern.

For example, a spray pattern with an inner cone angle B of 60 ° and an outer cone angle of 30 ° can be formed by using an injector with a measuring opening of 0.84 mm diameter and a nozzle pin diameter of 0.56 mm . The distance d ₁ in this injector is approximately 0.41 mm; the distance d_ is 0.25 mm. The outer diameter of the base of the deflector cap is 0.81 mm. Such an injector works at

a pressure of approximately 0.8 kg / cm and a "one point" flow rate of about 20 kg / h.

An injector operating at a lower pressure of about 1 kg / cm and the same speed with an inner cone angle B of 30 and an outer cone angle A of 10 ° can be obtained by making the measuring opening 1.12 mm and the outer diameter of the Nozzle pin is 0.64 mm. This valve has a distance d ₁ of 0.61 mm. For this spray angle, a difference of 0.05 mm or a distance d "is required between the outer diameter of the base of the deflection cap and the measuring opening, ie

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the diameter of the base of the deflector cap is 1.07mm.

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Claims (9)

The Bendix Corporation ' Executive Offices, Bendix Center, August 31, 1979 Southfield, Michigan, USA. File M-5015 Fuel injector Claims / Fuel injection valve with a metering section for high A flow rate comprising: a valve housing having a fuel flow channel that carries fuel from a pressure source to a frustoconical valve seat surface conducts which intersects a cylindrical metering opening; a needle valve which reciprocates in the valve channel and includes a valve tip that has a closing surface and closes the injection valve when in contact is brought to the valve seat surface, the valve tip being an interface with the valve seat downstream of the closing surface, characterized in that a transition surface (144) the valve seat surface (126) with the measuring opening (132) which gradually changes the direction of fluid flow through the interface of the valve in such a way changed so that no separation from the transition surface (144) he follows. 03ü01? / 0812 O! V; .- M / 4 INGPECTtD - ² - 2935050 2. Injection valve according to claim 1, characterized in that the transition surface (144) is designed as a truncated conical surface with a larger conical angle of inclination than the valve seat (126). 3. An injection valve according to claim 2, characterized in that the transition surface (144) is formed as a curved surface which connects the valve seating surface (126) with the metering orifice (132). 4. Injection valve according to claim 3, characterized in that the curvature is an arc of a circle which extends between the inlet end of the measuring opening (132) up to a point at which it is tangential to the conical valve seat surface (126). 5. Injection valve according to one of claims 1 to 4, characterized in that the valve tip (122) tapers to a nozzle pin (128) which extends through the measuring opening (132) , the valve tip (122) between the closing surface (124) ) and the nozzle pin (128) has such a contour that the flow area of the valve tip (122) and the valve seat intermediate surface increases to a plateau value and then decreases smoothly to the point at which the fuel emerges from the metering opening (132) . 6. Injection valve according to claim 5, characterized in that the valve tip (122) terminates in a baffle cap (130) having a baffle which in a substantially ends perpendicular to the edge running r the injection-spray axis. 030012 / on 12 7. Injection valve according to claim 6, characterized in that the Deflecting surface in a controllable manner generates a hollow conical spray pattern with an inner cone angle and an outer cone angle, by varying the distance between the deflecting surface and the end of the outlet opening (132). 8. Injection valve according to claim 7, characterized in that the inner cone angle and the outer cone angle can be formed in a controllable manner by changing the distance between the diameter the base of the baffle and the diameter of the metering opening (132) is varied. 9. Injection valve according to claim 8, characterized in that the inner and outer cone angles are controllably formed by the flow area of the annular propellant channel between the nozzle pin (128) and the measuring opening (132) is varied. D s: j 1 ? ι η κ 1? ORIGINAL INSPECTED