EP0898678B1 - Method for fuel injection in multicylinder engines and device for the implementation of said method - Google Patents

Abstract

A method of injecting fuel in multicylinder engines. A fuel pre-pressure is generated to be converted within acceleration pipes by opening controlled shutoff valves and recirculating fuel to a fuel pump inlet. The fuel under pre-pressure is conveyed via a fuel pump into a pre-pressure common rail common to several engine cylinders. This pre-pressure is only a fraction of the required injection pressure. When the pre-pressure is exceeded, fuel is fed from the pre-pressure common rail, via pressure-limiting valves, into a return common rail common to several engine cylinders. The shutting off of the shutoff valves provokes a steep rise of fuel pressure, due to a water hammer effect. This produces a high-pressure wave since the closed shutoff valve supplies high pressure for fuel injection through the respective injection nozzle associated with the shutoff valve. One acceleration pipe is used for every shutoff valve between the pre-pressure common rail and the return common rail. At least one injection nozzle is actuated in the respective acceleration pipe per shutoff valve.

Description

The invention relates to a method for fuel injection in multi-cylinder engines by generating a fuel admission pressure to deliver the fuel in a flywheel line for the purpose of using the pressure surge principle by means of a shutoff valve in the flywheel line, each injection nozzle assigned to a shutoff valve being supplied with the pressure surge and the fuel not passing the injection nozzle is fed back through the return line in front of the fuel pump via a return line, and a device for carrying out the method.
Technical solutions of this type are required above all for fuel injection in internal combustion engines. Preferred areas of application are multi-cylinder gas engines with diesel pilot injection, multi-cylinder diesel engines, multi-cylinder gasoline engines and multi-cylinder engines for the use of alternative power.

Multi-cylinder engines are predominantly equipped with fuel pumps that are driven by camshafts. The fuel dose supplied to the working cylinders has a marked speed dependency with regard to the droplet size and the length of the fuel jet.
In so-called common rail systems, the required maximum pressure is always present in the rail or in the overall system up to the injection nozzles, but this pressure is only required temporarily when fuel is injected due to the opening of one or more electromagnetically controlled injection nozzles.

In this case, the droplet size and the properties of the fuel jet remain the same regardless of the engine speed. However, the fuel pre-pressure realized by the pump or pumps with the corresponding adverse energy effects is only used to a small extent.
By way of example, in a four-cylinder four-stroke engine with a speed of 3000 ¹ / min. the injection period 40 ms. The injection duration, on the other hand, is only a maximum of 2 ms per injection period, which corresponds to an energetic utilization rate of at most 5%.

Technical solution proposals are known which provide for the use of the pressure surge principle for the provision of the pressure required in the working cylinder during the process of fuel injection in single-cylinder machines. In this case, the admission pressure provided by the fuel pump can remain limited to a fraction of the required fuel pressure at the respective injection nozzle. Such a solution is known from WO-A-92/14925.
In order to use this principle in multi-cylinder machines, the requirements for fuel pump drives, for fuel pumps and for the fuel pre-pressure and fuel return delivery lines are multiplied.

The disadvantages of the known solutions for fuel injection in multi-cylinder engines essentially exist in the case of the use of conventional cam- or camshaft-operated fuel pumps in the speed dependence of the droplet size and the properties of the injected fuel jet.
In the case of the use of common rail systems, the speed dependence of the quality of the fuel injection is avoided, but at the price of an unacceptable energy efficiency, since the pre-pressure provided over the entire injection period is actually only needed during the immediate injection process.

In the case of using what is known for single-cylinder engines Pressure surge principles on multi-cylinder engines would be the same mechanical and control engineering requirements the required number of fuel pumps to be used including pump drives and the required fuel supply and - Return lines to the high pressure units multiply what to disadvantages in terms of costs and an impairment of the mass / performance ratio leads.

The object of the invention is therefore to overcome the disadvantages of to overcome known prior art. One is aimed for technical solution with high energy efficiency and a low mechanical engineering requirements for a Improvement of the mass / performance and the price / performance ratio in the manufacture of multi-cylinder engines.

According to the invention, the object is essentially achieved by the protective features of claims 1 and 10.
The method for fuel injection in multi-cylinder engines is characterized in that essentially a single fuel pump delivers the fuel with a pre-pressure into a pre-pressure railchamber common to several engine cylinders, the pre-pressure corresponding to only a fraction of the required injection pressure. If the pre-pressure is exceeded, the fuel is transferred from the pre-pressure railchamber via pressure relief valves to the return railchamber common to several engine cylinders.

Between the pre-pressure railchamber and return railchamber So-called flywheels with shut-off valves are provided, each Shut-off valve a swing line between the pre-pressure Railchamber and Return railchamber is used. Each shut-off valve is in the each swing line actuated at least one injector. The pressure surge occurring when a shut-off valve is closed is used for the Dosing of the fuel used through the respective injection nozzle. The When the shut-off valve is open, the fuel flowing back into the for several engine cylinders promoted common return railchamber. The pressure conditions in the pre-pressure railchamber and in the return railchamber are kept constant with simple means, so that in the swing lines over the entire speed range optimal Flow conditions can be guaranteed. On this The basis is when the shut-off valves are actuated in the respective The pressure surge required for fuel injection via the injection nozzles connected to the respective swing line generated.

In a special embodiment, the method is thereby characterized in that the energy of the in the return railchamber stored fuel is used for the fuel delivery system. This leads to an additional favorable influence on the Energy expenditure for providing the required fuel pressure in the pre-printed Railchamber.

The flywheel can be used in conjunction with devices for Vibration damping are operated. This prevents unwanted ones Impairments to the fuel delivery system.

It is also possible for the production of the form in the form Railchamber to use multiple fuel pumps. The number of the fuel pumps to be operated according to the respective Engine load requirements can be selected.

In a further embodiment of the invention, swing line, Shut-off valve, vibration damper and injector in one High pressure unit can be summarized per cylinder. This High pressure unit can be covered with a jacket if necessary Engine operated thermally insulated and or by a in the jacket integrated cooling medium can be cooled.

It is also possible to cut the shut-off valves in the swing lines of the Injection system for multi-cylinder engines electro-magnetically too operate.

According to the task, the technical solution is also characterized by a device consisting of fuel pumps, flywheel lines with shut-off valves and return lines to the fuel supply system. In this device, a pre-pressure railchamber common to at least one fuel pump and at least one flywheel line is arranged for a cylinder group or for all cylinders of the multi-cylinder engine.
Arranged between the at least one flywheel line and the fuel supply system is a return railchamber common to a cylinder group or to all cylinders of the multi-cylinder engine. In addition, one or more pressure relief valves are arranged between the upstream and the return railchamber.

In a special embodiment of the device Flywheel line, shut-off valve, injection nozzle and if necessary Vibration absorber arranged in a common high pressure module.

In each high pressure module you can choose between the pre-pressure Railchamber and Return railchamber one or more injection nozzles can be arranged.

The shut-off valve and the injection nozzles of a high-pressure unit can constructively in a common component or in several Lines connected components can be arranged.

Furthermore, an embodiment of the device is thereby characterized in that one or more on the pre-printed Railchamber Fuel pumps are arranged.

It is also possible to have one or more on each cylinder To arrange high pressure modules.

In a further embodiment of the device it is provided that for a cylinder group or for all cylinders of the multi-cylinder engine common pre-printed Railchamber and one for one Cylinder group or for all cylinders of the multi-cylinder engine common return railchamber as two chambers in one execute common structural unit. If necessary, the Execution of pre-pressure and return railchambers as two chambers a common railchamber in the partition between the Chamber one or more of the hysteresis and vibration free Pressure relief valves ensuring constant upstream pressure arranged.

The arrangement of the high-pressure module in a thermal is advantageous insulating sleeve. This sleeve can also be used with a Coolant are operated and has a coolant inlet and a cooling medium drain.

The advantages of the invention are that with it a speed-independent High pressure is available, but not always, but only in Generated connection with an immediate fuel injection process becomes.

The invention makes it possible to combine the design and control of the fuel injection system according to the invention with the advantageous properties of a modern common rail. A common pre-pressure railchamber for all or for individual groups of working cylinders of a multi-cylinder engine as well as controlled valves are operated in a direct functional connection with injection nozzles. A decisive advantage of the solution found is that only a part of about a tenth of the required maximum pressure has to be constantly provided in the pre-pressure railchamber and that the maximum pressure is only a short-term pressure wave immediately before fuel metering via the injection nozzle by controlling the respective shut-off valve in front of one individual or a group of injection nozzles. For this purpose, the system is composed of a pre-pressure module, the pressure supply system, and high pressure modules. The high pressure required is generally 8 to 10 times the pre-pressure. In practice, the technical solution according to the invention is implemented in that a pressure accumulator is loaded by the admission pressure generated by a fuel pump, which prevents disruptive pressure fluctuations when the fuel is drawn from this pressure accumulator. The memory is designed as a common component in the form of a pre-pressure railchamber for several high-pressure modules connected to it. Defined opening of the controlled shut-off valves in one high-pressure module causes an acceleration of the fuel in the associated flywheel, which is returned to the return railchamber. The fuel is withdrawn from the fuel pump (s) primarily from the respective return railchamber using the available residual pressure, only the amount of fuel withdrawn from the system via the injection nozzles being withdrawn from the fuel tank.
The abrupt closing of the shut-off valves in the respective high-pressure module results in a conversion of the predominant part of the kinetic energy of the fuel in the flow into pressure energy.

The pressure increase brought about reaches a multiple of the static admission pressure in the admission pressure railchamber and propagates in the form of a pressure wave in the direction of the individual or more injection nozzles connected to the flywheel of the respective high pressure module, where it can be used for fuel injection.
When using vibration absorbers, the pressure wave generated is reduced to the level of the pre-pressure generated in order to avoid undesirable reflections and impair the function of the injection system.

Fig. 1:

die schematische Darstellung eines Krafstoffeinspritzsystems für eine Vierzylinder-Kraftmaschine.

The invention will be explained in more detail below using an exemplary embodiment.
In the accompanying drawing, the

Fig. 1:

the schematic representation of a fuel injection system for a four-cylinder engine.

Embodiment:

For a fuel injection system for a multi-cylinder engine 1, the form to be provided as a function of Requirement map of the machine in question via a Fuel pump 3 realized, in the fuel tank 1 to protect against Contamination a pre-filter 2 is installed. This form arrives via a supply line in one for all cylinders of the machine common form Railchamber 4, which with an integrated additional fuel fine filter.

The pre-pressure Railchamber 4 feeds the high pressure modules for the single working cylinder consisting of the flywheel 11, shut-off valve 10, Vibration damper 9, inclusion of the flywheel 12 and injection nozzle 13 exist. The pre-printed Railchamber 4 not only functions as a Fuel distribution system but because of its dimensions at the same time as Pressure fluctuations reducing pressure accumulator. When open Shut-off valves 10 in the high pressure modules will be under pressure standing fuel in the flywheel 11 accelerates and over a common return Railchamber 6 for all working cylinders Fuel pump 3 returned. The kinetic energy of the river located fuel is by suddenly closing the Electromagnetically operated shut-off valve 10 predominantly in Converted pressure energy, which takes the form of a pressure wave Injection nozzle 13 and the vibration damper 9 to the end of Flywheel 11 continues. Through the vibration damper 9 Pressure of the pressure wave to avoid unwanted reflections steamed at least to the level of the form. The one in the blast The pressure level to be recorded is average or depends on the injection quantity is approximately 10 times the pre-set pressure and is used for fuel metering in the respective working cylinder the flywheel 11 connected injector 13 used. Between the pre-pressure railchamber 4 and the return railchamber 6 are one Short-circuit line arranged to keep constant vibration of the admission pressure is equipped with a pressure relief valve 5. The in the return railchamber 6 available fuel pressure directly to the fuel pump 3 to the pre-pressure system. Around the high pressure module is for noise insulation and for heat protection an insulating sleeve 7 is arranged, which via a cooling medium inlet 8a and a cooling medium outlet 8b is flowed through with cooling liquid.

LIST OF REFERENCE NUMBERS

1 -

Fuel tank

2 -

prefilter

3 -

Fuel pump

4 -

Form rail Chamber

5 -

Pressure relief valve

6 -

Return rail Chamber

7 -

insulating sleeve

8a -

Cooling medium inlet

8b -

Cooling medium flow

9 -

vibration absorber

10 -

shut-off valve

11 -

acceleration line

12 -

Inclusion of the swing line

13 -

injection

Claims (19)

1. A method of injecting fuel in multi-cylinder engines by generating a fuel pre-pressure for the fuel hauling into an acceleration pipe for the use of the water hammer principle by shutoff valves within acceleration pipes whereby any injector provided in relationship with a shutoff valve receives a high pressure wave which is generated by the water hammer principle, whereby the not injected fuel is fed back through the opened shutoff valve to the input of the pre-pressure pump,
   wherein the pre-pressure fuel pump (3) feeds the pre-pressure into a pre-pressure common rail (4) which is common to several engine cylinders, whereby the pre-pressure is only a fraction of the required injection pressure,
   wherein the fuel is fed back, when the pre-pressure is exceeded, from the pre-pressure common rail (4) via pressure-limiting valves (5) into a return common rail (6) which is common to several engine cylinders,
   wherein to any shutoff valve (10) corresponds an acceleration pipe (11) which is connected between the pre-pressure common rail (4) and the return common rail (6),
   wherein for any shutoff valve (10) in the corresponding acceleration pipe (11) is operated at least one injector (13),
   wherein by shutting off a shutoff valve (10) the fuel high pressure wave generated by water hammer effect is captured by a corresponding injector (13) for injecting the fuel,
   wherein the fuel which is fed back through a shut off valve (10) during their opening feeds into the return common rail (6) which is common for several engine cylinders
2. The method according to claim 1, wherein the energy of the fuel stored in the return common rail (6) is used to convey the fuel.
3. The method according to claims 1 and 2, wherein the acceleration pipe (11) is operated in connection with wave dampers.
4. The method according to claims 1 and 3, wherein several fuel pumps (3) are used for producing the pre-pressure in the pre-pressure common rail (4).
5. The method according to claim 4, wherein the number to fuel pumps (3) to be operated is selected in accordance with the engine load requirements.
6. The method according to claims 1 to 5, wherein acceleration pipe (11), shutoff valve (10), wave damper (9) and injector (13) are combined in one high-pressure unit.
7. The method according to claim 6, wherein the high-pressure unit is thermally isolated versus the engine via a thermal isolator or is cooled by a cooling medium.
8. The method according to claims 1 to 7, wherein the shutoff valve (10) is operated electromagnetically.
9. The method according to claims 1 to 7, wherein the shutoff valve (10) is operated mechanically.
10. Device for the implementation of the said method according to claims 1 to 9, consisting of fuel pumps, acceleration pipe with shutoff valve and return pipe to the fuel storage system,
    wherein a pre-pressure common rail (4) for a group of engine cylinders or for all engine cylinders is provided between fuel pumps (3) and an acceleration pipes (11),
    wherein a return common rail (6) for a group of engine cylinders or for all engine cylinders is provided between acceleration pipes (11) and the fuel storage system,
    wherein, one or more pressure limiting valves (5) are provided between the pre-pressure common rail (4) and the return common rail (6).
11. Device according to claim 10, wherein acceleration pipe (11), shutoff valve (10), wave damper (9) and injector (13) are combined in one high-pressure unit.
12. Device according to claims 10 and 11, wherein in every high-pressure unit between both pre-pressure common rail (4) and return common rail (6) are provided one or more injectors.
13. Device according to claims 10 to 12, wherein the shutoff valve (10) and the injectors (13) of a high-pressure unit are combined in one common part or consist on several parts which are connected by pipes.
14. Device according to the claims 10 to 13, wherein one or more fuel pumps (3) are connected to a pre-pressure common rail (4).
15. Device according to the claims 10 to 14, wherein one or more high-pressure units are provided for one engine cylinder.
16. Device according to claims 10 to 15, wherein the pre-pressure common rail (4) for a group of engine cylinders for all engine cylinders and the return common rail (6) for a group of engine cylinders or for all engine cylinders are arranged as two chambers in a common part.
17. Device according to claim 16, wherein for the arrangement of pre-pressure common rail (4) and return common rail (6) as two chambers in a common part, one or more pressure limitation valves (5) for the maintenance of constant pre-pressure, free of oscillations and hysteresis are provided in the separation wall between both chambers.
18. Device according to claim 11, wherein the high-pressure unit is wrapped in a thermal isolator (7).
19. Device according to claims 11 and 18, wherein the high-pressure unit is wrapped in a socket with cooling circuit with coolant intake (8a) and coolant outlet (8b).

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