DE3545146A1 - FUEL INJECTION PUMP FOR A MULTI-CYLINDER COMBUSTION ENGINE - Google Patents

Description

Müller, Schupfner & Gauger P.O. Box 801369 D-8000 Munich 80

Hans-Jürgen Müller Gerhard D. Schupfner Kano-Peter Gauger " Patent Attorneys 3545 146

European Patent Attorneys Mandataires en brevets europeens

Dr.-Ing. Robert Poschenrieder

(1931-1972) t
Dr.-Ing. Elisabeth Boettner

(1963-1975)

Dipl.-Ing. Hans-Jürgen Müller
Dipl.-Chem. Dr. Gerhard Schupfner * Dipl.-Ing. Hans-Peter Gauger

P.O. Box 8013 69 Lucile-Grahn-Strasse 38 D-8000 Munich 80

Telephone: (0 89) 4 70 60 55/56 Telex: 5 23016 Telegramm / cable: Zetapatent®. Munich

Your reference / Your ref.

Our reference / Our ref. GFK-2810

Munich / Munich,

December 19, 1 985

Subject: / Ref .: Legal File: GFK-2801

FORD-WERKE AKKTIENGESELLSCHAFT
OTTOPLATZ 2, 5000 COLOGNE-DEUTZ (DE)

Fuel injection pump

for a multi-cylinder internal combustion engine

• Office / Office
Karlstrasse 5
2110 Buchholz
Telephone: (04181) 44 57 ■ Telex: 2189 330

Accounts Gauger:

Stadtsparkasse München: 29-16 73 50 (BLZ 701 500 00) Post check Munich: 27 66 88-808 (bank code 700 100 80)

The invention relates to a fuel injection pump a multi-cylinder internal combustion engine of the type indicated by the preamble of claim 1.

In the known fuel injection pumps of this type, for example, if they are provided for a four-cylinder Internal combustion engine the filling chamber of the pump with the mediation of a constantly rotating plunger to the individual fuel channels switched through one after the other, which are connected to the individual machine cylinders are. The constant rotation of the plunger results in the critical one for each injection stroke Phase of a precise alignment of the plunger-side connector at the mouth of the inner distribution channels of the plunger to the inlet port of a through-connection to the relevant injection stroke Filling space experienced fuel channel over the entire injection period, if this injection period variable Is subject to parameters, this critical phase is then often more by influencing these parameters than is overplayed by mechanical and structural measures on the pump. For those operated with a solenoid Overflow valve in the connection area of the filling chamber of the pump to injection pumps equipped with a low-pressure filling system so, for example, the fuel delivery volume and thus indirectly also the delivery pressure through a corresponding Influencing the opening times of this overflow valve with an adapted switching on and off of the excitation current variable controlled essentially in such a way, that in dependence on the changing speeds of the plunger constantly optimally adapted injection quantities

the individual machine cylinders arrive. Apart from the fact that here optimal results can only be achieved with rather complicated ones Control devices for the overflow valve can be achieved, which results in a disadvantageous increase in price factor, Such injection pumps are also unsuitable for possible use wherever there is an internal combustion engine should be operated with higher injection pressures of the fuel. With a successive connection Such higher injection pressures can hardly be affected by then correspondingly excessive side loads can be prevented on the constantly rotating plunger, so that as a result of it an out-of-round run of the plunger and the occurrence of internal leaks along the conveying path of the fuel.

The invention characterized by the claims solves the problem of a particular for use in to train a four-cylinder internal combustion engine suitable fuel injection pump of the specified type in such a way, that without the need for a more complicated design of the control device for the spill valve a comparably exact regulation of the fuel delivery volume during each injection stroke of the plunger with one at the same time greater independence from compliance with a certain injection pressure is possible.

The by the fuel injection pump according to the invention achievable advantages are essentially that it is now provided with the step-by-step rotation of the Plunger is relatively simple, its inner distribution channels to connect to the individual fuel channels in succession. All that is required is this step-by-step rotation of the plunger in relation to the inlet mouths of the Fuel channels are selected by means of mechanical-constructive measures in such a way that the rotation is always interrupted is when the plunger is currently in an injection stroke, so vice versa the plunger only then in each case

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is turned further if it is currently in a suction stroke. That for this gradual rotation of the plunger The switching mechanism provided at the same time results in a simple embodiment of the injection pump that is less prone to failure even when working with higher injection pressures, which are now less critical because at such a step-by-step rotation of the plunger can then also be implemented with simple countermeasures, to avoid any exposure to excessive side loads to prevent the plunger and thus the occurrence of leaks along the conveying path of the fuel.

An embodiment of the fuel injection pump according to the invention is shown schematically in the drawing and is described in more detail below. It shows

Figure 1 is a longitudinal section of the injection

pump,

Figures 2 to 4 cross sections of the injection pump

according to the lines H-II, IH-III and IV-IV of Figure 1 in an enlarged Scale,

FIG. 5 shows a longitudinal section on an enlarged scale

Scale of the overflow valve used in the injection pump according to FIG. 1,

Figure 6 shows a detail of the overflow valve

according to Figure 5 on an enlarged scale and

FIGS. 7 and 8 are circuit diagrams that can be used for the overflow valve according to FIG Control device according to two different embodiments.

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The fuel injection pump shown in longitudinal section in FIG is intended for a four-cylinder internal combustion engine. The injection pump includes a machine driven one Camshaft 10, which is in the lower part of a pump housing 12 is mounted and consequently four identically designed and equally spaced cam shoulders 14 in the circumferential direction has, which move a plunger 16 for the execution of one intake and one injection stroke per machine cylinder. The rotation of the camshaft 10 for this linear movement of the plunger 16 is controlled by one of its cam shoulders The following roller 18 translated, which is mounted on a pin 20 of a guide bush 22 for a driver 24 to which the plunger 16 is attached and which is biased into contact with the roller 18 by a spring 26 is.

The upper end of the plunger 16 engages in a guide bore 28 of a head part 30 of the pump housing 12, in which four in the circumferential direction equally spaced bores 32 are formed as a fuel channels Connection of the guide bore 28 to the four cylinders of the internal combustion engine result. In each of these fuel channels 32 a pressure valve 34 is also arranged, which opens under a predetermined delivery pressure of the fuel.

The guide bore 28 is through a valve device 36 closed, via which a connection to a low-pressure filling system provided for filling the guide bore 28 with fuel is realized. The guide bore 28 thus results in a filling space 68 for fuel, which is on a with this valve device 36 formed overflow channel 38 in its transition to a continuing partial length 40 through an overflow valve 42 receives a controlled connection with the low-pressure filling system whenever this Overflow valve 42 is open. In addition, the filling space 68 is always connected to the via a connecting channel 44 Low pressure filling system connected when the plunger 16

corresponding to the representation in Figure 1 is lowered below the mouth level of this connection channel.

The plunger 16 has a permanently connected to the filling space 68 Axial bore 46 and a radial bore 48 at its lower end, which at its mouth with a connection slot 50 is enlarged. The filling space 68 is successively switched through via this connection slot 50 towards the individual fuel channels 32, which takes place during each upward movement of the plunger 16, which consequently results in its injection stroke. On every other downward movement of the plunger resulting in a suction stroke 16, the filling space 68 is again filled with new fuel from the connected low-pressure filling system, with the plunger 16 then simultaneously during this filling undergoes a rotation which is then essentially ended again at the beginning of the injection stroke of the plunger 16. During each injection stroke of the plunger, the filling space 68 is pushed against the connecting channel by the plunger during an early phase 44 is blocked and then immediately afterwards it is switched through to the next fuel channel 32, However, via which fuel is only conveyed to the connected machine cylinder, if then subsequently with the intermediary of the overflow valve 42, the filling space 68 is also blocked off towards the overflow channel 40 and finally the amount of fuel locked in the filling chamber by the plunger, which continues to move upwards, under a delivery pressure is set, which allows the pressure valve 34 arranged in the connected fuel channel 32 to open. By that Spill valve 42 is a solenoid actuated embodiment has, which will be explained in more detail later, it is consequently with a corresponding control of the current passage possible through the excitation coil of the solenoid, which the individual machine cylinders via the connected fuel Channels to regulate the amount of fuel supplied during each injection stroke of the plunger 16.

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At a central portion of the plunger 16 are one behind the other a straight spline 52 and a helical spline 54 are formed, Via these differently designed splines, there are two with the plunger 16, of course, that fit together Splined gears provided ratchet wheels 56 and 58 of a switching mechanism connected through which the Plunger 16 undergoes incremental rotation in only one direction of rotation while it rotates in the opposite direction Direction of rotation is blocked by a locking device cooperating with this switching mechanism, which is applied to each of the two ratchet wheels is formed with two locking pins 62, which by springs 64 for cooperation with respect the axis of the plunger offset stop shoulders are biased. The two switching wheels 56, 58 have a sandwich arrangement between the pump head 30 and a support disk 66 provided for the spring 26, whereby the Switching wheels in the axial direction of the plunger 16 immovable are at the same time allowing a rotation only in one direction of rotation, which is through the helical extending splines 54 and their associated switching wheel 58 during each suction stroke of the plunger 16 is conveyed. For the helical splines 54 of the plunger 16, a Pitch angle -Θ »given the following general Equation fulfilled:

NS
Tan θ

Td

where N = number of machine cylinders S = stroke of plunger 16
d = pitch diameter of the spline 54

The helical course of the spline 54 is thus designed with four machine cylinders in such a way that during each injection stroke of the plunger 16, the ratchet wheel 58 rotates in the counterclockwise direction by exactly 90 °

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relative to the then with the ratchet 5 6 by its assigned Locking pins 62 experienced non-rotatably held plunger. On the other hand, during each subsequent The suction stroke of the plunger 16 continues to rotate gradually at exactly 90 ° can then also be obtained in an anti-clockwise direction, then together with the ratchet wheel 56 and relative to the ratchet 58, which during each suction stroke of the plunger 16 consequently by him associated locking pins 62 is then held in a corresponding non-rotatable manner. This driving principle of the gradual Further rotation of the plunger 16 with the mediation of the two Switching wheels 56,58 can therefore be used for any number of machine cylinders of the internal combustion engine can be realized if only the aforementioned equation for the helical splines 54 is fulfilled. For the camshaft 10, of course, a correspondingly adapted number N of in Cam shoulders 14 equally spaced in the circumferential direction be provided to be adapted for the plunger 16 Obtain a number of 2N strokes per machine cylinder. To the gradual rotation of the plunger 16 also with To stabilize more critical high speeds, the shoulders with the stop shoulders of the ratchet wheels 56, 58 cooperating locking pins 62 in pairs after opposite Directions offset from the axis of the plunger 16, with reference to the off The information shown in Figure 2 fulfills the following equation:

IE

where: F = preload force of spring 64 I = moment of inertia of plunger 16 and the ratchet 58

E = maximum angular deceleration of the plunger 16 [I = coefficient of friction
a, b = geometric dimensions.

- i-vr ^ - · - 3545U6

In the cross section of FIG. 4 it is also shown that the plunger 16 is next to that in the connection slot 50 opening bore 48 has two further bores 72, likewise ending in an enlarged opening 70, which with a connection to the axial bore 46 of the plunger with respect to the bore 48.50 effective pressure equalization channels result. With this approximately Y-shaped arrangement of the holes 48.50 and 70.72 is the effect of a side load on the plunger 16 even at higher fuel feed pressures Avoided at the time of each connection of the filling space to one of the fuel channels 32.

From the sectional view according to FIG. 5 it can be seen that the valve device formed with the overflow valve 42 36 comprises a housing 74 with which a guide sleeve 75 for a control piston of the overflow valve 42 is formed. The guide sleeve 75 centers a core sleeve 76 pushed onto it, with a spacer is underlaid and how this and a further coaxially arranged core sleeve 80 made of a soft magnetic material consists. Between the two core sleeves 76 and 80 there is also a further sleeve 82 made of an anti-magnetic material arranged coaxially for the common holding of an excitation coil 84, and this arrangement is then outside another housing cap 86 made of a likewise non-magnetic material is pushed over in a sealed manner, which together with a further spacer washer 90 still placed on the outer core sleeve 80 by means of bolts 88 with the housing 74 is screwed. On the control piston of the overflow valve 42 is made of a soft magnetic material existing armature 92 is attached via a hub 94 made of an anti-magnetic material in such a way that that between this armature 92 and the two core sleeves 80 and 7 6 an outer air gap 96 and an inner air gap 98 are formed, which because of the sleeve 82 made of an anti-magnetic material from each other are separated. The size of these air gaps 96.98 is due to the opposing forces of two

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Springs 100 and 102 determined, both of which act on the hub 94, wherein the supported on the guide sleeve 75 a spring 100 is stronger than the spring 102, which is on a on the control piston of the overflow valve 42 attached cap 104 is supported. When the excitation coil 84 is de-energized is, therefore the control piston of the overflow valve 42 is biased by the spring 100, the cap 104 against a stop 106, so that between the filling space 68 and There is an open connection to the connected low-pressure filling system via the overflow channel 38, 40. the The size of the air gaps 96, 98 is also determined by the thickness of the two disks 78 and 90, the thickness of the disk 78 influences the size of the air gaps when the overflow valve is closed, while the thickness of the disk 90 results in an influence on their size when the overflow valve is open.

When a current flow through the excitation coil 84 is switched on, the armature 92 is attracted against the core sleeves 76, 80 and thus the overflow valve 42 is closed. During a continued injection stroke of the plunger 16 consequently then becomes the one locked in the filling space 68 Amount of fuel put under an increased pressure until finally a pressure level is reached below which the pressure valve 34 of the respectively connected fuel channel 32 then for injecting the fuel into the assigned machine cylinder is opened. The injection can be done arbitrarily by switching off the current flow can be canceled by the excitation coil 84 at any desired point in time, so that with this measure a variable regulation of the fuel delivery volume is possible. To use the overflow valve at higher delivery pressures 42 still being able to keep it closed with a relatively weak tightening force is otherwise with regard to its control piston the special feature of the provision of an axial bore 108 through which the overflow channel 38 is then realized is switched through to the cap 104, so in order to

When the overflow valve is closed, the cap 104 is then reinforced to pretension against the stop 106. If this axial bore 108 realized for the control piston of the overflow valve 42 is, then the spring 102 does not necessarily have to be the IN ANY, since it is then just as possible, only with a size of the end face cooperating with the cap 104 that differs from the closing end face on the other Pressure is applied to the end 110 of the control piston of the control piston, which precisely closes and opens the overflow valve 42 each time it is switched on and off the current flow through the excitation coil 84 ensures.

The fuel delivery volume regulated by the valve device 36 is determined by the duration of the voltage pulse with which the excitation coil 84 closes the overflow valve 42 is acted upon, minus the delay that occurs when the valve is activated, and vice versa plus the delay that is unavoidable even when it is deactivated. These delay times can turn out differently because they essentially depend on material and also processing-related influencing variables, which are, however, standardized for the specification of a precise and at the same time Working of the injection pump are clearable that the size of the air gaps 96.98 with the use of different Thicknesses of the disks 78 and 90 are given consideration of such possible error sizes. Another Measure can consist in that, according to the circuit diagrams of FIGS. 7 and 8, the one provided for the excitation coil 84 The control circuit is supplemented with a variable resistor 112 connected either in series or in parallel with the excitation coil is, so with a higher resistance value in the control circuit according to Figure 7 a reduced and in the Control circuit according to Figure 8 an enlarged current flow through the excitation coil 84 and thus the promotion of a to obtain a correspondingly smaller or a correspondingly larger amount of fuel.

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Claims (10)

Claims Λ J Fuel injection pump for a multi-cylinder internal combustion engine, with a plunger that mediates the delivery of fuel from a filling chamber of the pump into fuel channels leading to the machine cylinders, which is movable by a machine-driven camshaft for the execution of one intake and one injection stroke per machine cylinder and has inner distribution channels through which the filling chamber connected to a low-pressure filling system via a solenoid-operated overflow valve to regulate the fuel delivery volume is connected to the fuel channels successively by a rotation of the plunger, characterized in that the plunger (16) for successive switching of the Filling space (68) is rotated gradually towards the fuel channels (32). 2. Fuel injection pump according to claim 1, characterized in that the stepwise Rotation of the plunger (16) is effected only during one of its two stroke movements and the Plunger is guided non-rotatably during the second stroke. 3545U6 3. Fuel injection pump according to claim 2, characterized in that the plunger (16) for successive connection of its inner distribution channels (46, 48, 50) to the fuel channels (32) only rotated during an injection stroke during each successive intake stroke will. 4. Fuel injection pump according to one of claims 1 to 3, characterized in that each fuel channel (32) with a delivery pressure below a predetermined the pressure valve (34) which opens the fuel supplied from the connected filling space (68) is. 5. Fuel injection pump according to one of claims 1 to 4, characterized in that the plunger (16) with the mediation of only one direction of rotation working rear derailleur (56,58) is rotated step by step. 6. Fuel injection pump according to claim 5, characterized in that the switching mechanism (5, 6.58) by a locking device (62) in the direction of rotation opposite to its working direction is blocked. 7. Fuel injection pump according to claim 4 or 5, characterized in that the switching mechanism is formed with two ratchet wheels (56,58) which with the plunger (16) via a straight and a helical spline (52 and 54) connected and arranged such that by the one ratchet wheel (56) during each injection stroke of the plunger (16) the rotation of which is prevented while at the same time allowing a relative rotation of the second switching _- ₃ _ ■■ - 35A5U6 wheel (58), which then enables a joint rotation of the plunger with the one ratchet wheel (56) (16) cannot be rotated during each intake stroke. 8. Fuel injection pump according to one of the claims 5 to 7, characterized in that the locking device for the switching mechanism (56,58) with in the circumferential direction equally spaced locking pins (62) is formed, which with respect to the axis of the plunger (16) offset stop shoulders of the rear derailleur cooperate. 9. Fuel injection pump according to one of claims 1 to 8, characterized in that the inner distribution channels of the plunger (16) with a the filling chamber (68) connected to the axial bore (46) and one in an enlarged connection slot (50) ending radial bore (48) formed and with respect to the connection slot (50) effective Druckkausgl ei chs channels (70,72) are connected. 10. Fuel injection pump according to claim 9, characterized in that the radial bore (48,50) and two pressure equalization channels (70,72) are Y-shaped.