DE2843000A1 - FUEL INJECTION NOZZLE - Google Patents

Description

κ. 500 8

September 12, 1978 Su / Kö

ROBERT BOSCH GMBH, 7000 Stuttgart 1 Fuel injector State of the art

The invention is based on a fuel injection nozzle according to the preamble of the main claim. In known fuel injection nozzles of this type, the valve needle hits the seat cone in the nozzle body ₃ so hard when the needle closes quickly with its needle cone that the valve needle springs back with repeated opening and fuel is subsequently injected. This
Post-injection results in an increase in the toxic components in the exhaust gas and higher fuel consumption. In order to avoid such springback, other known fuel injection nozzles are usually used in

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Closing the same increases the closing pressure acting on the valve needle. Such a device for increasing however, the closing pressure is expensive and not always effective in a sufficient manner.

Advantages of the invention

The fuel injection nozzle according to the invention with the Characteristic features of the main claim has the advantage that a simple means good damping is achieved when the valve needle impacts with immediate completion of the injection. This Sudden termination is further improved and ensured when in accordance with an embodiment of the invention the space at the tapered end of the cone is reduced to a minimum, which is the case with the small angle difference between the needle cone - Seat cone can be reached particularly effectively.

drawing

An embodiment of the subject matter of the invention is shown in the drawing in longitudinal section and explained in more detail in the following description. It Figure 1 shows the valve seat area of a fuel injection nozzle, Figure 2 and Figure 3 show the blind hole of the Functional representations relating to the nozzle.

Description of the example of the invention

In Figure 1 is only partially illustrated

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th nozzle body 1 is also shown only partially valve needle 2 in the seat area. The valve needle 2 has a cone 3 as a sealing surface, to which a cone 4 adjoins. The cone 3 cooperates with the funnel-shaped bore 5, which has almost the same slope and which is in the section the contact with the cone 3 serves as a valve seat. '' By grinding in or by elastic Deformation as a result of the contact pressure, the two conical surfaces nestle completely into one another. Upstream: The pressure chamber 6 of the injection nozzle is arranged on this valve seat. Downstream of the valve seat in the lower Part of the drill funnel 5, the spray openings 7 branch off from a blind hole 8.

The cone 4 of the valve needle closes an angle which is slightly larger than one enclosed by the drill funnel 5 Angle / 2 · The one between the cones and Funnel-formed surfaces included angles has a maximum of 0.5 degrees. With the injector closed there is therefore an extremely small residual volume between the funnel bore 5 and valve needle cone 3 or cone 4 available. When the valve needle is closed, cone 3 is completely supported and almost completely Support of cone 4 on the bore funnel surface 5j especially if it is also taken into account that the nozzle body 1 has a certain elasticity. The impact force of the valve needle in the nozzle body is therefore caught by a relatively large area over which it is distributed, with the one between them Fuel located on surfaces must be displaced before sitting on, which leads to a corresponding damping

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leads. On the one hand, energy is destroyed because the fuel is between the relatively large areas before touching the same is displaced with the formation of eddies and on the other hand causes the metallic flat surface a certain adhesion between nozzle body and valve needle.

The blind hole 8 (D ₀ ) adjoining the funnel bore 5, from which the injection openings 7 branch off, is also reduced to a minimum in order to keep its hydraulically elastic volume as small as possible. As a result of the small blind hole volume, leakage of residual amounts of fuel through the injection openings 7 is reduced to the desired extent. In order to adapt to this shortened blind hole 8, in the example shown in FIG. 1, the valve needle tip 9 is dome-shaped (D,).

In Figure 2, the area of the blind hole 8 is shown on an enlarged scale. In order to minimize the "harmful" space of the blind hole 8, proportions were developed in accordance with the equation below. The seat angle oC, the blind hole cutting angle \ r , D, or D are given. We are looking for the minimum drilling depth φ
^x min '

Based on a cone angle OC (60 to 90 are the most common designs in practice), a diameter D results for the sack diameter _{for a dome diameter D 1.}

■ cC S

hole 8 according to the following equation:
^D s ^{= D} k -COS ^ / 2.

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Of course, production-related minimum dimensions are to be assumed for the blind hole diameter D, in particular because of the branching off of the injection openings 7. By developing from the above formula, the calotte diameter D _k results as follows:

^D k ⁼

The dome diameter can thus be determined from the angle OC and the blind hole diameter D. The minimum dimensions D ₁ and D ₀ can also be determined by further manufacturing limits.

The minimum drilling depth T results from the geometric relationships as shown in FIG. . This results as follows:

From triangle MAE results: U From triangle MTS results: U + V From (U + V) - U results: V

The two-beam BESB or BAESBG results in:

¹ InIn _ Z -

V
And after reshaping:

I ₁ . = - - / 1 -COs

^min 2. sintf / 2

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According to the calculation, the cap just touches the drill cone 11 of the blind hole. To a resting due to manufacturing inaccuracies and to prevent wear, the tapping depth actually selected should be:

^T = ^T min ^{+ (0} > ° ⁵ - °> ² ^ ⁾ roughly the proportions are:

D _k = (100 - 150 %) D _s

T- = / 1 s 5 - 20) % D ₁ mxn \ ' / k

In Figure 3, the valve needle tip 9 'is designed as a cone 12, in order to be able to reduce the harmful space in the blind hole 8 even more. The foot diameter of the cone 12 is designated by D and must in any case be slightly smaller than the blind hole diameter D ·. For the cone diameter D. according to Figure 3:

The given values are 0 £ and t ^ and the minimum values determined by the manufacturer: D and Tj _n ^ _n . Is calculated

Figure 3: The triangles ACD and BCD result in χ and Z.

ζ = T.

tg * / 2

min 1 - day ° C / 2. cot ^ -72

D. = D ₀ - 2 ζ
^{b S} tg <* / 2

^D b ^{= D} s " ^{2 T} min 1 - tgOC / 2. Cot ^ 12

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For the drilling depth the result is in turn:

^T : ⁼ : ^T min ^{+ (0} > ° ⁵ "°» ² * O

As a rough estimate, the following proportions can be assumed will:

D _b = 35 to 85 %

^T min = 5-15

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Claims (9)

■ *. se whether. I2.9.I978 Su / Kö ROBERT BOSCH GMBH, 7000 Stuttgart 1 Claims 1.J fuel injector for internal combustion engines with fluid-controlled valve needle that opens against the direction of flow of the fuel and is conical downstream of the valve seat adjoining surfaces in the nozzle body and on the valve needle, with between the cone angle of these surfaces are differences, characterized in that these differences at least 15 arc minutes and at most 50 arc minutes, but in particular between 15 and 30 arc minutes be. 2. Fuel injection nozzle according to claim 1, characterized in that the cone angles in the region of the valve seat (3 3 5) are the same. 3. Fuel injection nozzle according to one of claims 1 or 2, characterized in that the remaining volume is at closed injection nozzle between valve needle (2) and nozzle body (1) downstream of the valve seat is minimized. 030017/0020 - 2 - row 5 00 0 4. Fuel injection nozzle according to claim 3 _3, characterized in that a blind hole (8) connects to the valve seat and the connected cone bore (5), from which in particular the injection openings (7) branches off and which is minimized with respect to the liquid-filled volume. 5. Fuel injection nozzle according to claim 4, characterized in that that the tip (9) of the valve needle (2) is dome-shaped and the proportions between the blind hole (8) and the valve needle tip (9) the following equations are sufficient: a) Cap diameter from the blind hole diameter: D, = 4 ^K cos * / 2 b) The minimum tapping depth of the blind hole is equal to ^{T min =} 2. ----- ~ "' ⁽¹ " ^cos where OC is the cone angle of the valve needle or the valve seat and if is the angle of intersection of the bottom of the blind hole. 6. Fuel injection nozzle according to claim 5, characterized in that the dome diameter = 100 to 150 'of the blind hole diameter and that the minimum hole depth = 1.5 to 20 % of the blind hole diameter. 030017/0020 " ³ " . - 3 - ■ κ. ^r - ο ο it 7 · Fuel injection nozzle according to claim 4, characterized j that the needle tip (9 ') is designed as a cone (12), the angle of which corresponds to the basic cone of the blind hole (8) corresponds and that the foot diameter of the cone tip of the needle (12) is smaller than the blind hole diameter (D_). 8. Fuel injection nozzle according to claim 7 _S, characterized in that the dimensional proportions satisfy the following equations: a) the cone root diameter of the needle tip D ^ = D 2 T ( ^tgC ^ ^{/ 2} , * min 'U - tgcC / 2 · cot ^ / 2 2y b) The depth of the blind hole is equal to the minimum depth of the blind hole plus Q.05 to 0.2 mm: T = T _min _ + (0.05 - 0 _} 2 \) 9. Fuel injection nozzle according to claim 8, characterized in that the conical tip base diameter is equal to 35 to 85 % of the blind hole diameter and that the minimum blind hole depth is 5 to 15 % of the blind hole diameter. 030017/0020