EP2098719A1 - Diesel combustion engine - Google Patents

Abstract

The engine has an electromagnetic injector (1) for injection of a fuel obtained from vegetable oil with a nozzle needle (19). A high pressure supply (8) is connected with a chamber volume (6) and a valve control chamber over an inlet throttle (3). A fuel return line (7) stays in connection with the valve control chamber over an outlet throttle (2) and a valve ball (16). An electrical heating ring (20) and a heating wire (21) are provided in the control chamber for a control fuel staying in connection with the fuel return line, where the fuel for injection in the chamber volume is not heated.

Description

The invention relates to a diesel engine-operated internal combustion engine according to the preamble of claim 1.

With the shortage of crude oil reserves and the associated increase in fuel prices, there is an increasing attempt to use alternative fuels. These include ethanol, the so-called biodiesel, but also pure vegetable oil. In particular, when operating with pure vegetable oil or biodiesel must be made to a diesel engine-driven internal combustion engine, which is designed for operation with normal diesel fuel, changes. These changes are needed because fuel produced from vegetable oil behaves differently than diesel fuel. If, for example, diesel fuel has an almost constant viscosity over a relatively wide temperature range, the viscosity of vegetable oil changes relatively strongly with temperature. In extreme cases, vegetable oil - depending on the variety - can already turn into a solid state even at temperatures around the freezing point.

In order to adapt an engine, which is normally to be operated with diesel fuel, to be suitable for operation with vegetable oil, particular changes are made to ensure that the vegetable oil is always in a low-viscosity state and is thus well supplied to the injection nozzles via the fuel supply system can. For example, heat exchangers are used to heat the fuel in the pipes. Also, new fuel delivery systems have been designed to immediately return leakage fuel from the high pressure pump and the small loop injection system to the fuel delivery pump during the launch phase. In this way, hardly any cold fuel from the fuel tank is needed, but it can be used in each case already preheated fuel. However, these measures do not prevent cold vegetable oil from being in the injectors during startup. They only reach shortly after the start phase.

The biggest problems arise from the use of vegetable oil in the new high-pressure injection engines. In particular, in engines that operate on the common rail principle, even at outside temperatures of 10 ° C, such difficulties arise that starting the engine with vegetable oil is virtually impossible. To avoid these problems, so-called two-tank systems are used, in which the engine is started with normal diesel fuel and only switched to vegetable oil when the engine has reached its operating temperature. Disadvantage of these two-tank systems, however, is that the fuel lines must be flushed again with diesel fuel before stopping the engine. If this flushing process is forgotten and there is still vegetable oil in the fuel supply and in the injection nozzles, a restart of the engine after its cooling is no longer guaranteed.

The invention has for its object to design a diesel engine operated internal combustion engine, which is operated with vegetable oil, so that the cold start problem can be greatly reduced or even eliminated.

The object is achieved according to the invention by a diesel engine-powered internal combustion engine having the features of claim 1. In such internal combustion engines with a high-pressure injection, for example, common rail technology, the usual injectors can not be used because they are not able to do so are to interrupt the fuel flow under a pressure of more than 1,000 bar.

Therefore, new injectors are used, which have a servo-control, in which the high pressure of the upcoming fuel is also used for closing the valve. These new injectors have a nozzle needle with control piston, a chamber filled with fuel chamber volume into which the nozzle needle dips, a filled with tax fuel valve control chamber into which the control plunger dips, a fuel supply, which is connected to the chamber volume and an inlet throttle to the valve control chamber, and a fuel return, which communicates via an outlet throttle and a drain valve with the valve control chamber.

It has now surprisingly been found that, for the cold start problem, it is not the fuel in the chamber volume that is to be injected that is responsible, but mainly the control fuel in the valve chamber. Consequently, if the cold start problem is to be solved, it does not matter if the fuel for injection is heated in the chamber volume.

Since in modern high-pressure injectors the nozzle needle is controlled exclusively hydraulically via the valve chamber, it must be ensured that the pilot fuel is in a state that corresponds to that of diesel fuel even at low temperatures. In contrast, if the pilot fuel is too viscous, the valve needle can not open and no injection can take place. If, however, it is possible to lift the valve needle and open the injection nozzle, the fuel is almost at the pressure of the high-pressure pump at the opening and can be easily injected into the combustion chamber even in the viscous state.

In these injectors, the high-pressure fuel supply usually splits within the injector into a strand to the chamber volume and into a string to the valve chamber. The control fuel supplied to the valve space is practically completely discharged again via the fuel return and is not supplied to the combustion chamber via the chamber volume. Consequently, in order to solve the cold start problem, it is only necessary to heat up this pilot fuel which is to be discharged again, but not the fuel intended for the injection. Previous less successful attempts to solve this problem, however, have always focused on heating the fuel intended for injection.

It has been found that for the light-off problems at low temperatures mainly the drain throttle is responsible. This constriction normally ensures that the pressure applied to the open injection nozzle does not flow via the outlet throttle into the leakage chamber and thus into the fuel return. However, if cold, viscous vegetable oil is present in the cavities of the injector, the outlet throttle prevents the pressure in the valve control chamber, which holds the control piston and the valve needle in the lower closed position, from being opened to open the injector. The opening of the valve and the injection of fuel is thus impossible. By heating this area can be targeted the vegetable oil, which serves only as a pilot fuel, are brought to a temperature in which the function of the outlet throttle is guaranteed. The heating of this relatively small area can be done very quickly and with little energy. The heating could be done for example via a component within the injection nozzle. It would even be conceivable to use a component which actually fulfills a completely different function as a heating element.

The heater is particularly advantageous designed as an external heating. It must be made by this no particularly critical interventions on the injection nozzle itself. Also, the injector can be retrofitted in a very simple manner so that they can be operated not only with diesel fuel, but also with vegetable oil.

Injection nozzles are advantageously used, the inlet throttle is arranged in the same area in which the outlet throttle is located. The inlet throttle can also lead to cold start problems, but this is by far not as critical as the outlet throttle. However, if the inlet throttle is located in the heated area in which the outlet throttle is located, a small heating device can eliminate any problems caused by both throttles.

It is desirable to build the exterior heating from inexpensive standard components. In a first embodiment, the external heating therefore has a glow plug.

Advantageously, the glow plug is attached via a sleeve to the injection nozzle. This sleeve can be made of a solid part, but also designed as a screw sleeve in the form of an open ring. In any case, ensure that the sleeve is in intimate and large-area contact with the outer wall of the injector.

Due to the heavy loads, which act for example by vibrations on the sleeve, the sleeve should be made of a material with high strength. At the same time, however, it should be noted that the material has a good thermal conductivity to the heat energy from the glow plug as efficiently as possible to bring into the injector.

In a further embodiment, an electrical heating ring is provided. These heating rings are also available as standard components. They are heated electrically directly. Using the heating ring, the heat energy can be more effectively introduced exactly into the region of the injection nozzle in which the outlet throttle is located.

In another embodiment, the injection nozzle is heated in the region of the outlet throttle by an induced eddy current. This has the advantage that no heat has to be transferred to the injection nozzle, but can be generated directly in the injection nozzle. According to the invention, a coil placed annularly around the injection nozzle is provided for this purpose. An alternating current is applied to the coil. The penetration depth of the induced eddy current depends on the frequency of the applied alternating current.

Advantageously, the heater is operable before the start of the internal combustion engine. This means that, for example, via a control device that controls the starting process, the heating is activated, even before the actual starting process is initiated with the activation of the starter. In this way, during the start-up process, low-viscosity vegetable oil is already available at the outlet throttle, so that problem-free injection of the fuel into the combustion chamber can take place.

The invention is applicable to the so-called electro-magnetic injection nozzles, in which the fuel return is controlled by an electro-magnetic valve. In their function very similar to the new piezo-electrically operated injectors are constructed. These much faster switchable injectors also have a control piston, a valve control chamber and an outlet throttle. Again, there is the same cold start problem as in the electro-magnetic injection nozzles. The invention is therefore also very advantageous to the new piezoelectric injectors applicable, in which the fuel return is controlled by a piezoelectric valve.

Further details and advantages of the invention will become apparent from the dependent claims in connection with the description of exemplary embodiments, which are explained in detail with reference to the drawings.

Fig. 1

eine schematische Darstellung einer Hochdruck-Einspritzdüse der erfindungs- gemäßen dieselmotorischen Brennkraftmaschine und

Fig. 2

ein weiteres Ausführungsbeispiel einer beheizten Hochdruck-Einspritzdüse.

It shows:

Fig. 1

a schematic representation of a high-pressure injector of the inventive diesel engine internal combustion engine and

Fig. 2

another embodiment of a heated high pressure injector.

The illustrated injection nozzle is designed as an electro-magnetic injector 1. In the injector 1, a number of cavities are provided, which are all in communication with each other. The leakage chamber 4 is connected directly to the return line 7 in the fuel tank. Below the leakage chamber 4 is the valve control chamber 5 (see Fig. 2 ). This is connected via the outlet throttle 2 with the leakage chamber 4. About the inlet throttle 3, the valve control chamber 5 is connected to the high-pressure inlet 8. Also communicates with the high-pressure inlet 8, the chamber volume 6 in conjunction.

When the injector 1 is open, the contents of the chamber volume 6 are injected via the injection holes 9 into the combustion chamber (not shown here). The cavity around the nozzle spring 10, which fills with leakage fuel from the chamber volume 6 and the valve control chamber 5, is also connected via a bore to the leakage chamber 4.

In the leakage chamber 4 is an electro-magnetic valve for closing the outlet throttle 2. This electro-magnetic valve has a solenoid 13, a valve spring 12, an armature spring 11 and the armature 15. On the lower plate of the armature 15, the valve ball 16 is mounted for closing the outlet throttle 2. The outlet throttle 2 forms a drain valve together with the magnetic valve. The magnet coil 13 is connected to the connection socket 14. Via the connection socket 14, an electrical control unit is connected, with which the electrical pulses necessary for the proper operation of the injector 1 are generated.

In the lower part of the injector 1 is the nozzle needle 19, with which the chamber volume 6 is closed against the injection holes 9. At the top, the nozzle needle 19 continues via the pressure shoulder 18 into the control piston 17. The upper end face of the control piston 17 forms the lower boundary wall of the valve control chamber fifth

In the embodiment according to Fig. 1 a heating ring 20 is provided which heats the area in which the outlet throttle 2 and the inlet throttle 3 are located. In the heating ring 20, a heating wire 21 bent in upright loops extends. The electrical connection for this heating wire 21 is not visible in the illustration.

After a long break in operation at low ambient temperature, the vegetable oil cools in the interconnected cavities of the injector 1 from. Depending on the variety used, the vegetable oil becomes relatively viscous. This viscous liquid would block the two throttles 2 and 3, which connect the valve control chamber 5 with the return line 7 or with the high-pressure inlet 8. Problems would arise here in particular during the passage of the cold vegetable oil through the outlet throttle 2. This throttle has a smaller diameter than the inlet throttle 3. Also is at the inlet throttle 3 always the full pressure of the high-pressure inlet 8, while the outlet throttle 2 must be consistent even at lower applied pressure. It is therefore applied even before the starting process of the heating wire 21 in the heating ring 20 with a voltage. As a result, in a very short time in the area enclosed by the heating ring 20 region of the injector 1, a temperature at which the vegetable oil is thin and the two throttles 2 and 3 are no longer blocked. When this condition is reached, the starting process can be started.

In the illustration shown, the injector 1 is in the closed state. The solenoid 13 is not energized and the valve spring 12 pushes the armature 15 in its lowest position. The valve ball 16 closes the outlet throttle 2. About the high-pressure inlet 8 and the inlet throttle 3 prevails in the valve control chamber 5 of the pressure applied to the high-pressure inlet 8. This pressure also acts on the upper face of the control piston 17. The same pressure prevails in the chamber volume 6. Here, the pressure of the vegetable oil acts on the pressure shoulder 18. Here, however, the pressure at an angle of approximately 45 degrees to the direction of movement of the nozzle needle 19 acts is the force acting on the nozzle needle 19 is less than the force exerted by the pressure in the valve control chamber 5 on the nozzle needle 19. For this purpose, the force of the nozzle spring 10 is still added. These two forces hold the nozzle needle 19 - against the force resulting from the pressure in the chamber volume 6 - in its closed position.

If now vegetable oil are injected into the combustion chamber, not shown here on the injection holes 9, the solenoid 13 is energized accordingly. In this case, the upper plate of the armature 15 is tightened, which rises against the force of the valve spring 12. The valve ball 16 lifts off from the outlet throttle 2 and releases the connection between the valve control chamber 5 and the leakage chamber 4. It is now possible to leave vegetable oil from the valve control chamber 5, whereby the high pressure in this room decreases. As a result, the ratio of the forces acting on the control piston 17 changes forces. Since the pressure on the pressure shoulder 18 remains unchanged, but reduces the pressure on the upper end face of the control piston 17, the nozzle needle 19 moves upward and releases the spray holes 9.

To close the injector 1, the magnetic coil 13 is de-energized again. The valve spring 12 now pushes the armature 15 back into its lower position, in which the valve ball 16 closes the outlet throttle 2. Via the inlet throttle 3, the pressure applied to the high-pressure inlet 8 builds up very quickly in the valve control chamber 5 again. The control piston 17 and the associated nozzle needle 19 are pressed down again and close the spray holes 9. Thus no vegetable oil from the chamber volume 6 more escape into the combustion chamber.

As soon as the injector 1 has reached its normal operating temperature, in particular due to the waste heat of the engine, the power supply of the heating ring 20 can be switched off. In this state, the injector 1 is at a temperature level at which also inflowing vegetable oil immediately upon entering the high-pressure inlet 8 assumes the temperature that is necessary for trouble-free operation.

At the in Fig. 2 illustrated embodiment, a glow plug 25 is used for heating the injector 1 before starting. These glow plugs are commonly used for Starting from diesel engines used are highly heat resistant and achieve a long service life. In order to transfer the heat of the glow plug 25 to the injector 1, a threaded bushing 23 is provided, into which the glow plug 25 is screwed. The inner surface of the threaded bushing 23 corresponds as closely as possible to the outer surface of the glow plug 25, so that the largest possible intensive contact between the two components is established. The heat from the glow plug 25 is transferred very efficiently to the threaded bushing 23 in this way.

Directly to the threaded bushing 23, the heating sleeve 22 is connected. The connection of the two components is advantageously carried out via a weld or a braze. Thus, a good heat transfer between the threaded bushing 23 and the heating sleeve 22 is ensured. The heating sleeve 22 can either also be connected via a soldering process with the injector 1 or it is designed as an open sleeve and is clamped by means of screws on the injector. Again, it is important to achieve an intimate contact between the heating sleeve 22 and the lateral surface of the injector 1, so that a good heat transfer can take place.

Since the upper part of the injector 1 is usually located between the valve levers and the distance between the valve levers is relatively small, it must be ensured, in particular with a screwed heating sleeve, that the heating sleeve 22 does not rotate due to the vibrations acting on it. As a result, the threaded bush 23 could come with the glow plug 25 in the region of the moving valve lever. This twisting would therefore result in high damage. On the underside of the threaded bushing 23, therefore, the locking pin 24 is mounted in a fixed opening, for. B in a screw in the head of the internal combustion engine, immersed. A rotation of the heating sleeve 22 is no longer possible.

In the figures, the invention has been described with reference to an electro-magnetic injector. In order to be able to achieve shorter switching times and a longer life of the injectors, piezoelectric injectors have also recently been on the market. Instead of the magnetic coil 13 and the armature 15, a piezo control module is used here, which is composed of a plurality of stacked piezoelectric plates. Even if the cavities are constructed slightly differently in this injector, a valve control chamber is also present here. The pressure in this valve control chamber, which in turn is responsible for the movement of the nozzle needle, is also controlled here via an outlet throttle and an inlet throttle. Since the same cold start problem occurs with these piezoelectric injectors, remedying the critical area can also be remedied here. The inventive diesel engine internal combustion engine can therefore be operated with piezoelectric injectors.

LIST OF REFERENCE NUMBERS

1

injector

2

outlet throttle

3

inlet throttle

4

leakage chamber

5

Valve control chamber

6

chamber volume

7

returns

8th

High-pressure inlet

9

spiracle

10

nozzle spring

11

armature spring

12

valve spring

13

solenoid

14

socket

15

anchor

16

valve ball

17

spool

18

pressure shoulder

19

nozzle needle

20

heating ring

21

heating wire

22

heating socket

23

threaded bushing

24

safety pin

25

Glow plug

Claims (12)

Diesel engine-operated internal combustion engine having at least one injection nozzle (1) for injecting fuel oil obtained from vegetable oil with a nozzle needle (19) with control piston (17), a fuel-filled chamber volume (6) into which the nozzle needle (19) dips, one with control fuel filled valve control chamber (5), in which the control piston (17) dips, a fuel supply (8) which is connected to the chamber volume (6) and via an inlet throttle (3) to the valve control chamber (5) and a fuel return (7), the via an outlet throttle (2) and a drain valve (2, 16) with the valve control chamber (5) is in communication, characterized in that at least for the associated with the fuel return (7) control fuel in the valve control chamber (5) has a heater (20, 21, 22-25) is provided, wherein the pending for injection fuel in the chamber volume (6) is not heated. Diesel engine-driven internal combustion engine according to claim 1, characterized in that only for the area in which the outlet throttle (2) is arranged, a heater (20, 21, 22-25) is provided. Diesel engine-operated internal combustion engine according to claim 2, characterized in that the heater (20, 21, 22-25) is designed as an external heater. Diesel engine-operated internal combustion engine according to claim 2, characterized in that in the heated area, the inlet throttle (3) is arranged. Diesel engine-driven internal combustion engine according to claim 3, characterized in that the external heating (22-25) has a glow plug (25). Diesel engine-driven internal combustion engine according to claim 5, characterized in that the glow plug (25) via a sleeve (22) is attached to the injection nozzle (1). Diesel engine driven internal combustion engine according to claim 6, characterized in that the sleeve (22) is made of a material of high strength and good thermal conductivity. Diesel engine-operated internal combustion engine according to claim 3, characterized in that the external heating (20, 21) has an electric heating ring (20). Diesel engine-operated internal combustion engine according to claim 2, characterized in that eddy currents are generated by an annular coil in the injection nozzle (1). Diesel engine-operated internal combustion engine according to claim 1, characterized in that the heater (20, 21, 22-25) is operable prior to the start of the internal combustion engine. Diesel engine-powered internal combustion engine according to claim 1, characterized in that the fuel return via an electro-magnetic valve (2, 13, 15, 16) is controlled. Diesel engine-operated internal combustion engine according to claim 1, characterized in that the fuel return is controlled by a piezoelectric valve.

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