DE102009052597A1 - Fuel injection system for diesel engine, has ventilation device for conveying fuel to high-pressure pump via suction path for ventilating system and comprising electrical auxiliary pump that is arranged in bypass - Google Patents

Abstract

The system (1) has a tank (2) for storing liquid fuel (3), and an injector (4) for injecting fuel into a combustion chamber of an internal-combustion engine. A suction side of a high-pressure pump (8) is connected with the tank via a suction path (6), where a pressure side of the pump is connected with the injector via a pressure path (9). A ventilation device (44) conveys the fuel to the high-pressure pump via the suction path for ventilating the system and comprises an electrical auxiliary pump (45) that is arranged in a bypass (46). A filter is arranged in the bypass.

Description

The present invention relates to a fuel injection system for an internal combustion engine, in particular of a motor vehicle.

From the DE 102 48 467 A1 a fuel injection system is known which has a tank for storing a liquid fuel and at least one injector for injecting fuel into a combustion chamber of the internal combustion engine. Further, a high pressure pump is provided, which is connected on the suction side via a suction path to the tank and the pressure side via a pressure path with the at least one injector. In the pressure path, a common for several injectors high pressure distributor and at least one pressure booster are also arranged. For leakage quantities or return quantities of the individual injectors Injektorrückläufe are provided, leading to the tank. For leakage quantities or return quantities of the pressure booster pressure booster recirculation are provided, leading to a common return collector, which is connected via a pressure-holding valve to the tank and via a connecting line downstream of a low-pressure pump to the suction side of the high-pressure pump.

Another fuel injection system is out of the DE 199 54 695 A1 known.

During a tanker run or during servicing, the fuel lines or the fuel lines of the fuel injection system fill with air. For commissioning the vehicle, these lines must be vented or filled with fuel. In certain vehicles, the internal combustion engine is difficult to access. In addition, the fuel lines between the tank and the engine can be comparatively long. The refilling with fuel lines of the fuel injection system can be realized for example by means of an external manual feed pump or by a correspondingly long operation of the starter, which heavily loads the vehicle battery and the starter. Particularly large fuel injection systems are very difficult or impossible to vent in this way.

The present invention addresses the problem of providing a fuel injection system of the type mentioned an improved embodiment, which is characterized in particular by a simplified venting.

This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea to provide the fuel injection system additionally with a venting device, which makes it possible, if necessary, to promote fuel via the suction path to the high-pressure pump. With the help of such a venting device, which promotes fuel in the suction path to the high-pressure pump, the venting of the fuel injection system can be carried out particularly easily and quickly, without requiring the starter of the engine operated or an external manual feed pump must be provided.

The venting device may according to an advantageous embodiment have an electric auxiliary pump, which can be put into operation as needed. It is particularly expedient to arrange this auxiliary pump in a bypass which runs along a portion of the suction path parallel to the suction path. This ensures that in normal operation, the auxiliary pump does not have to be flowed through. So that the auxiliary pump does not return via the parallel section of the suction path to the tank or to its suction side, a check valve or a gravimetric valve can be arranged in said section. Furthermore, it may be expedient to provide a further path or return for bypassing the auxiliary pump and possibly for bypassing the check valve or the gravimetric valve, in which a pressure relief valve is arranged. By the pressure relief valve, the maximum achievable with the help of the auxiliary pump filling pressure is limited. Suitably, the auxiliary pump is arranged in the vicinity of the tank. It is particularly advantageous to limit an actuation duration of the auxiliary pump to an activation time determined, for example, by means of experiments, which correlates with the largest expected amount of ventilation. The activation duration can be limited by a corresponding control unit or by a time relay.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawing and from the associated description of the figures with reference to the drawing.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description.

The only 1 shows a greatly simplified schematic diagram of a fuel injection system.

Corresponding 1 includes a fuel injection system 1 a tank 2 for the storage of a liquid fuel 3 serves, as well as at least one injector 4 , by means of which liquid fuel can be injected into a combustion chamber, not shown here, of an internal combustion engine likewise not shown here. The fuel injection system 1 thus serves to supply an internal combustion engine with fuel, the internal combustion engine is preferably arranged in a motor vehicle.

The fuel injection system 1 has a low pressure pump 5 up, over a suction path 6 with the tank 2 connected is. The pressure side is the low pressure pump 5 via a supply path 7 with a high pressure pump 8th connected. With reference to the high pressure pump 8th counts the supply path 7 to the suction path 6 , the extent the high pressure pump 8th with the tank 2 combines. The high pressure pump 8th is via a high pressure path 9 with the at least one injector 4 connected. In the example are four injectors 4 shown. Accordingly, in the example, the internal combustion engine is a four-cylinder engine. The fuel injection system 1 is preferably used in an engine designed as a diesel engine. In principle, however, it can also be used in a gasoline engine.

In the high pressure path 9 is a high pressure distributor 10 arranged, of all injectors 4 is assigned together, therefore, it is preferably a so-called common rail system. Downstream of the high pressure distributor 10 is ever injector 4 a pressure booster 11 in the high pressure path 9 intended. The respective pressure amplifier 11 can do it in the high pressure path 9 upstream of the respective injector 4 be arranged. However, preferred is the embodiment shown here, in which the respective pressure booster 11 in the associated injector 4 structurally integrated. In operation, both at the pressure amplifiers 11 as well as at the injectors 4 Leakage quantities or return quantities incurred. A pressure booster return 12 connects the respective pressure amplifier 11 with the suction path 6 , An appropriate connection point or connection point is with 13 designated. The pressure booster return 12 thus leads from the respective pressure booster 11 to the suction side of the low-pressure pump 5 , This is the connection point 13 automatically also on the suction side of the high-pressure pump 8th , Basically, the pressure booster return 12 also to the supply path 7 be connected. However, preferred is the embodiment shown here, in which the pressure booster return 12 to the suction side of the low-pressure pump 5 leads. In the pressure booster return 12 Optionally a heat exchanger 14 be arranged, with the help of the recirculated fuel heat can be withdrawn. The heat exchanger 14 can do this to a suitable cooling circuit 15 be connected. Said cooling circuit 15 may for example form a branch of an engine cooling circuit.

Furthermore, the injectors 4 an injector return 16 assigned in the respective injector 4 accumulating leakage quantities or return quantities basically to the tank 2 returns. For this purpose, the injector return 16 in the example shown to a low pressure collector 17 connected, which can also be referred to as a gallery. From the low pressure collector 17 leads a return line 18 to the tank 2 back.

The injector return 16 is via a coupling line 19 with the supply path 7 connected. This makes it possible to injector return 16 to apply an increased pressure. To now according to an arrow 20 a pressure drop from the injector return 16 to the pressure booster return 12 to realize with a predetermined pressure difference, it may be appropriate in the coupling line 19 a throttle 21 to arrange. Additionally or alternatively, in the injector return 16 a pressure-holding valve 22 be arranged. This pressure-holding valve 22 is located between the low pressure collector 17 and a discharge point 23 over which the coupling line 19 in the injector return 16 opens. The pressure holding valve 22 is designed in the example shown as a biased non-return valve.

The coupling line 19 branches over a sampling point 24 from the supply path 7 from. The sampling point 24 is in the example between the high pressure pump 8th and a component 25 arranged, which is a cleaning device. The cleaning device 25 For example, it may be or may be a filter. Additionally or alternatively, it may be configured for dewatering the fuel. In the example, the cleaning device 25 with an additional return 26 equipped, the cleaning device 25 with the low pressure collector 17 combines. The sampling point 24 Alternatively, it can be directly at an inlet 27 the high pressure pump 8th be arranged. It is also possible in principle, the sampling point 24 immediately at an outlet 28 the low pressure pump 5 to arrange.

The high pressure pump 8th is in the example with another return 30 equipped, which is a low pressure side of the high pressure pump 8th with the low pressure collector 17 combines. In this further return 30 can be another pressure relief valve 31 be arranged, which also designed in the example as a spring-loaded check valve is. It is also conceivable, a pressure control valve 31 provide, the part of the high-pressure pump 8th is and passive the supply pressure of the high pressure pump 8th established.

The feedback of the pressure booster return 12 to the suction side of the low-pressure pump 5 also has the advantage of being able to reduce the pressure in the returned fuel very far. To the pressure in the pressure booster return 12 to set to a predetermined value, may be a throttle 32 be provided. This is located in the example in the suction path 6 , upstream of the junction 13 , Alternatively, it is also possible to use this throttle 32 upstream of the junction 13 in the pressure booster return 12 to arrange.

The fuel injection system 1 is also equipped with a pressure relief valve 33 fitted. This can be realized as in the example by a biased check valve. The pressure relief valve 33 connects the high pressure path 9 with a return path 34 , The return path 34 leads from the pressure relief valve 33 to the tank 2 , Here is the return path 34 in the example also to the low pressure collector 17 connected. To open with pressure relief valve 33 adequate lubrication of the high-pressure pump 8th to be able to guarantee, is a recirculation line 35 provided the return path 34 with the suction path 6 combines. As explained above, the suction path leads 6 to the low pressure pump 5 and over the supply path 7 ultimately also to the high-pressure pump 8th , To set a specific amount of emergency lubrication or a particular emergency lubrication pressure, a throttle device 36 be provided in the recirculation line 35 is arranged.

The throttle device 36 can a choke 37 exhibit. In the example is also a pressure relief valve 38 provided, which is again configured in the manner of a biased non-return valve. Overall, the throttle device 36 thus be designed as a throttle check valve. A connection point 39 over which the recirculation line 35 to the suction path 6 is connected, is located in the example upstream of the throttle 32 and thus upstream of the junction 13 , To increase a return amount or recirculation amount via the recirculation line 35 can in the return line 18 from the low pressure collector 17 to the tank 2 a throttle 56 be provided.

The return path 34 can also have a short circuit line 40 directly to the low pressure side of the high pressure pump 8th be connected. In this case, the fuel flows out of the short-circuit line 40 via an unspecified camshaft space of the high-pressure pump 8th Pumpintern downstream of the pressure relief valve or pressure control valve 31 in the return 30 , Preferably, the short circuit line contains 40 this a pressure relief valve 41 , which can be conveniently designed again as a spring-loaded check valve. In the figure is symbolic of the high pressure pump 8th connected short-circuit line 40 with pressure relief valve 41 and the return 30 with pressure relief valve or pressure control valve 31 shown. To limit the over the short circuit line 40 the pressure side of the high pressure pump 8th supplied pressure, the return path can 34 with a throttle 42 be equipped. This is then located between the low pressure collector 17 and a branch point 43 at which the short circuit line 40 from the return path 34 branches. Through the throttle 42 becomes the return path 34 divided into a high pressure area and a low pressure area. During the high pressure area of the pressure relief valve 33 to the throttle 42 leads and the short circuit line 40 includes, the low pressure region extends from the throttle 42 over the low pressure collector 17 and the return line 18 to the tank 2 ,

Furthermore, the fuel injection system shown here 1 with a venting device 44 be equipped in 1 is indicated by a drawn with a broken line frame. This venting device 44 can if necessary via the suction path 6 Fuel to the high pressure pump 8th promote so the fuel injection system 1 to vent. If necessary, fuel flows through a bypass valve 57 a bypass line 58 the low pressure pump 5 from the suction path 6 to the supply path 7 , It is also conceivable that the low-pressure pump 5 is bypassed by hand pump valves, not shown. This requirement can occur when the fuel injection system 1 has been vented in the event of maintenance or tanker travel, so that the paths and lines of the fuel injection system 1 are largely emptied of fuel or filled with air.

The venting device 44 is in the suction path 6 arranged. Preferably, the venting device 44 with an electric auxiliary pump 45 fitted. This auxiliary pump 45 can be activated especially for the case of need. In normal operation of the fuel injection system 1 it can be disabled. The auxiliary pump is expedient 45 in a bypass 46 arranged a section 47 of the suction path 6 bypasses. The mentioned section 47 of the suction path 6 extends between two connection points 48 and 49 over which the bypass 46 to the suction path 6 connected. In the bypass 46 can be on the suction side of the auxiliary pump 45 a filter 50 be arranged. This allows the auxiliary pump 45 from impurities in the fuel 3 to be protected. Particularly advantageous is the use of a Pressure relief valve 51 , This is configured in the example as a biased check valve. The venting device 44 is with the pressure relief valve 51 equipped to bleed the fuel injection system 1 to avoid an overpressure in the fuel. For this purpose, the pressure relief valve 51 in a return 52 arranged, the pressure side of the auxiliary pump 45 connects with its suction side. This is the return 52 over connections 53 and 54 to the bypass 46 connected. In that regard, the return forms 52 also a short circuit of the auxiliary pump 45 , So that the auxiliary pump 45 not in the tank during operation 2 is in the section 47 a non-return valve 55 arranged. Instead of a non-return valve 55 can also be provided a gravimetric valve. The respective valve 55 locks towards the tank 2 so that the auxiliary pump 45 pressure side to the control pressure of the pressure relief valve 51 can build up a pressure.

With the help of the venting device 44 can the fuel 3 in the low-pressure area of the fuel injection system 1 with the help of the auxiliary pump 45 be promoted, whereby the entire fuel system can be easily and quickly vented. The venting device is expedient 44 or their auxiliary pump 45 close to the tank 2 arranged. In particular, it is possible for the auxiliary pump 45 in the tank 2 directly to accommodate. The activation duration of the auxiliary pump 5 may be limited for example by a control unit, not shown, or a time relay, not shown. The drive time is adjusted so that the auxiliary pump 45 as long as it is in operation, that even the largest expected amount of ventilation can be realized.

The during the venting process from the lines or paths of the fuel injection system 1 displaced air can be expelled from the system along venting paths. Such a venting path begins, for example, in the cleaning device 25 , leads over the return 26 to the low pressure collector 17 and passes through the return line 18 in the tank 2 , Another return path begins, for example, at the low pressure side of the high pressure pump 8th and leads over the return 30 back to the low pressure collector 17 and passes through the return line 18 also in the tank 2 ,

The respective venting process can be started, for example, by a single push of a button. This will cause the auxiliary pump 45 activated. As a result, it comes to a filling of the entire fuel system with fuel. As soon as the maximum filling pressure is reached, the pressure relief valve opens 51 , causing the auxiliary pump 45 while maintaining the maximum filling pressure in the circle promotes. As soon as the predetermined active time or venting time has elapsed, the corresponding control or a corresponding relay switches the auxiliary pump 45 out. The auxiliary pump 45 is configured so that in the deactivated state, it blocks a flow in the opposite direction. The fuel system thus remains filled. Subsequently, the user can start the engine easily. An unnecessary long operation of the starter can be avoided.

In normal operation, the fuel 3 from the tank 2 from the low pressure pump 5 sucked. The low pressure pump 5 can be mechanical or electrical. The through the low pressure pump 5 pressurized fuel 3 next flows through the purifier 25 , which preferably integrates a filter and a water separator. The fuel purified from particles and water 3 then passes to the high pressure pump 8th and gets into the high-pressure distributor 10 or accumulator 10 promoted. The one from the injectors 4 from the high pressure distributor 10 taken fuel 3 is by pressing the respective, in the injector 4 integrated pressure amplifier 11 again compacted and injected. By actuating the respective pressure booster 11 creates an unusable for the injection amount of fuel. This amount of fuel or leakage is in the pressure booster return 12 and through the heat exchanger 14 or cooler 14 back to the suction side of the low-pressure pump 5 directed. The pressure in the pressure booster return 12 is through the throttle 32 adjusted to the desired pressure. The cooling of the pressure booster return 12 may be necessary as the fuel is of a very high pressure in the high pressure distributor 10 is relaxed to near ambient pressure.

Through this relaxation, heat energy is released. The heat exchanger 14 can be charged with cooling water or another liquid.

In a diesel common rail system, further fuel leakages may occur. For example, from the high-pressure distributor 10 , from the injectors 4 , from the filter device 25 and from the high pressure pump 8th , These leaks are in the example shown in the low pressure collector 17 or in the gallery 17 merged. The thus merged fuel can optionally be returned to the tank 2 or on the suction side of the low-pressure pump 5 be directed. The desired amount and pressure difference between the low pressure collector 17 and the suction side of the low pressure pump 5 can with the throttle device 36 be set. By the interpretation of this throttle device 36 also results in an influence on the recirculation amount, the tank return quantity, the low-pressure pump input quantity and the temperature balance.

By the feedback of the pressure booster return 12 on the suction side of the low-pressure pump 5 The pressure in the returned fuel can be greatly reduced, which is the preparation of the fuel for the suction side of the high-pressure pump 8th considerably simplified.

So when opening the pressure relief valve 33 a lubrication of the high-pressure pump 8th or the components to be lubricated within the high-pressure pump 8th Maintains an emergency lubrication amount via the recirculation line 35 from the return path 34 (and about the low pressure collector 17 ) to the suction path 6 reach. In addition, can be provided by means of a suitable control, by appropriate operation or control of the low-pressure pump 5 to set the pump lubrication pressure or pump lubrication quantity. If internal, so inside the high-pressure pump 8th an additional lubrication path is realized, which leads to the components to be lubricated, such as bearings or cams, it is possible, the low-pressure pump 5 smaller interpret. In addition, for example, an increase in the engine speed or flow rate of the low-pressure pump 5 be dispensed with in emergency mode.

The coupling of the injector return 16 with the supply path 7 causes the pressure in the injector return 16 higher than in the pressure booster return 12 , This is especially true when the booster return 12 to the suction side of the low-pressure pump 5 connected. This results in a positive pressure difference, the fuel from the injector return 16 through the respective injector 4 and by the respectively hydraulically coupled pressure amplifier 11 into the pressure booster return 12 drives. This leaves the pressure booster 11 flushed, even if, for example, during a coasting operation of the internal combustion engine, no fuel injection takes place.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10248467 A1 [0002]
• DE 19954695 A1 [0003]

Claims (6)

Fuel injection system for an internal combustion engine, in particular of a motor vehicle, - with a tank ( 2 ) for the storage of liquid fuel ( 3 ), - with at least one injector ( 4 ) for injecting fuel into a combustion chamber of the internal combustion engine, - with a high-pressure pump ( 8th ), the suction side via a suction path ( 6 ) with the tank ( 2 ) and on the pressure side via a pressure path ( 9 ) with the at least one injector ( 4 ), - with a venting device ( 44 ), which, if necessary, for venting the fuel injection system ( 1 ) Fuel ( 3 ) via the suction path ( 6 ) to the high pressure pump ( 8th ) promotes Fuel injection system according to claim 1, characterized in that the venting device ( 44 ) an electric auxiliary pump ( 45 ) having. Fuel injection system according to claim 2, characterized in that the auxiliary pump ( 45 ) in a bypass ( 46 ), which has a section ( 47 ) of the suction path ( 6 ) bypasses. Fuel injection system according to claim 3, characterized in that in the bypass ( 46 ) on the suction side of the auxiliary pump ( 45 ) a filter ( 59 ) is arranged. Fuel injection system according to one of claims 2 to 4, characterized in that a pressure relief valve ( 51 ) in a return ( 52 ) is arranged, which the pressure side of the auxiliary pump ( 45 ) with its suction side connects. Fuel injection system according to one of claims 3 to 5, characterized in that in the section ( 47 ) a check valve ( 55 ) which is directed towards the tank ( 2 ) locks.

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