02.03.2011 Fuel delivery device and method for operating a fuel delivery device

Abstract

Fuel supply device for a fuel injection device of an internal combustion engine with a feed pump (10) which supplies fuel from a storage tank (12) to a high-pressure pump (16), wherein the high-pressure pump (16) supplies fuel into a high-pressure area (18), wherein the high-pressure pump (16) has an interior (14) in which a drive area (21) is arranged, through which fuel from the feed pump (10) flows, characterized in that a device (24, 34) is provided for monitoring the interior pressure of the high-pressure pump (16) and when a predetermined minimum pressure in the interior (14) of the high-pressure pump (16) is undershot, the pressure in the high-pressure area (18) is limited to a maximum pressure.

Description

[0001] The invention relates to a fuel supply device for fuel injection of an internal combustion engine and a method for actuating such a fuel supply device according to the preamble of the independent claims. State of the art

[0002] Such a fuel supply device and its operation are already known from German patent application DE 103 07 877 A1. This fuel supply device comprises a high-pressure pump that delivers fuel into a high-pressure chamber, from which fuel is drawn for injection into the internal combustion engine. A feed pump is also provided, which delivers fuel from a storage tank to the high-pressure pump. The high-pressure pump has a housing with an interior space in which a drive for at least one pump element of the high-pressure pump is arranged. The pump element has a pump piston that defines a pump working chamber and is driven in a reciprocating motion by the drive. The feed pump delivers fuel into the interior of the high-pressure pump via a hydraulic connection.Fuel from the interior of the high-pressure pump is conveyed to the inlet of the pump working chamber via another hydraulic connection. Disclosure of the invention

[0003] The fuel delivery device according to the invention and the method for actuating such a fuel delivery device with the characterizing features of the independent claims have the advantage that the high-pressure pump does not have to deliver against a high pressure in the high-pressure range during a restart after an emergency shutdown of the internal combustion engine. This situation of emergency shutdown of the internal combustion engine can arise due to an unintentional shutdown of the internal combustion engine (stalling) or due to the activation of an emergency shutdown of the internal combustion engine. When the internal combustion engine is restarted after an emergency shutdown, there is no sufficient quantity of fuel in the interior of the high-pressure pump to serve as lubrication. The pump drive usually still operates in a state of mixed friction and can only deliver against a high pressure in the high-pressure range at low speed.By limiting the pressure in the high-pressure area to a maximum pressure, it is avoided that the high-pressure pump with low fuel lubrication has to work against a high pressure in the high-pressure area and that engine damage to the high-pressure pump occurs.

[0004] It is advantageous if the fuel from the high-pressure section can be diverted into the reservoir via a valve, as this simple component limits the fuel pressure in the high-pressure section to a maximum level. By returning the fuel to the reservoir, the excess fuel is then available to the fuel pump.

[0005] A hydraulic connection between the interior of the high-pressure pump and the pump working chamber of the high-pressure pump is advantageous because the fuel used to lubricate the drive area of ​​the high-pressure pump is conveyed directly into the high-pressure area by the high-pressure pump and therefore does not have to be returned to the reservoir via additional lines.

[0006] An advantageous feature is a device for quantity control in the hydraulic connection between the interior of the high-pressure pump and the pump working chamber of the high-pressure pump, since the quantity control device adapts the amount of fuel delivered by the high-pressure pump to the high-pressure area to the fuel demand in the high-pressure area.

[0007] It is advantageous to have a branch line leading from the hydraulic connection between the high-pressure pump's interior and working chamber to the reservoir, in which a pressure relief valve is installed. The pressure in the hydraulic connection between the high-pressure pump's interior and working chamber is limited to the opening pressure of the pressure relief valve. This prevents excessive pressure in the high-pressure pump's interior and the downstream hydraulic connection, thus avoiding damage to the relevant components.

[0008] The use of a valve, arranged in a connecting line between the high-pressure section and the interior of the high-pressure pump, is advantageous as a device for monitoring the internal pressure of the high-pressure pump, since the invention can be implemented with only a minor modification to the existing fuel delivery system. Furthermore, no separate hydraulic connection to the reservoir is required, as excess fuel from the interior of the high-pressure pump is diverted to the reservoir via the branch line.

[0009] It is advantageous to use a cone valve with a spring on the side facing the interior of the high-pressure pump, since the desired valve requirements can only be met with mechanical elements without electrical control. By appropriately selecting the cross-sectional area of ​​the contact surfaces for the fuel on the two opposite sides, the pressure values ​​in the high-pressure area and in the interior of the high-pressure pump at which the valve opens can be determined. The spring ensures that the cone valve closes when the fuel pressure in the high-pressure area is limited to the maximum pressure.

[0010] It is advantageous to position the valve within the pump housing of the high-pressure pump or in the high-pressure section, as this integrates the valve into a rigid structure and provides greater strength. Furthermore, a valve in one of these positions is technically simpler to implement, since there is only one connection point to the connecting line between the high-pressure pump and the high-pressure section.

[0011] The use of a pressure sensor inside the high-pressure pump and a connected control unit is advantageous for monitoring the internal pressure of the high-pressure pump, as this allows for particularly precise pressure measurement. The connection to the pressure regulating valve in the high-pressure section, controlled by the control unit, enables highly accurate control of the fuel flow from the high-pressure section to the storage tank. Examples of implementation

[0012] Preferred embodiments of the invention are illustrated in the drawing and explained in more detail in the following description.

[0013] They show: Fig. 1 shows a fuel delivery device in a schematic representation according to a first embodiment of the invention; Fig. 2 a cone valve in a non-scale representation and Fig. 3 a fuel delivery device in a schematic representation according to a second embodiment of the invention.

[0014] The Fig. 1 and Fig. Figure 3 shows a fuel supply system in a schematic representation. The fuel supply system includes a feed pump 10, which draws fuel from a reservoir 12. The feed pump 10 delivers fuel to the suction side of at least one high-pressure pump 16, which is also part of the fuel supply system. The feed pump 10 can be driven mechanically via a clutch, gear, or toothed belt by the internal combustion engine or the high-pressure pump 16. Alternatively, the feed pump 10 can have an electric drive, which can be operated with variable power and thus variable speed, or with constant power and speed.

[0015] Fuel is pumped by at least one high-pressure pump 16 into a high-pressure section 18 of the fuel supply system, which may include, for example, a high-pressure accumulator. From the high-pressure section 18, one or more injectors 20 are supplied with fuel, with one injector 20 being assigned to each cylinder of the internal combustion engine.

[0016] The high-pressure pump 16 has at least one pump element, which in turn has a pump piston driven in a reciprocating motion and delimits a pump working chamber 22. The high-pressure pump 16 has its own drive section 21, through which the reciprocating motion of the pump piston is effected via a cam or eccentric. The drive section 21 of the high-pressure pump 16 is driven mechanically, for example via a gearbox or a belt drive, by the internal combustion engine, so that the rotational speed of the high-pressure pump 16 is proportional to the rotational speed of the internal combustion engine.

[0017] The high-pressure pump 16 has an interior 14 in which the drive section 21 of the high-pressure pump 16 is located. Fuel from the feed pump 10 flows through the interior 14 of the high-pressure pump 16. The feed pump 10 is connected to the interior 14 of the high-pressure pump 16 via a hydraulic line 13. A fuel filter 38 can be arranged in the hydraulic line 13 to prevent dirt particles from entering the high-pressure pump 16 and the high-pressure section 18.

[0018] Fuel from the interior 14 of the high-pressure pump 16 enters the pump working chamber 22 of the high-pressure pump 16 via a hydraulic connection 15. A spring-loaded check valve is arranged as an inlet valve 23 at the transition between the hydraulic connection 15 and the pump working chamber 22. A connection leads from the pump working chamber 22 to the high-pressure area 18, in which a spring-loaded check valve, opening from the pump working chamber 22 to the high-pressure area 18, is arranged as an outlet valve 31.

[0019] In the hydraulic connection 15 between interior 14 and pump working chamber 22 of the high-pressure pump 16, a device for quantity control 26 can be arranged to adapt the quantity of fuel supplied by the feed pump 10 to the requirements of the high-pressure pump 16.

[0020] Furthermore, a branch line 19 can branch off from the hydraulic connection 15 between the interior 14 and the pump working chamber 22 of the high-pressure pump 16. If a quantity regulation device 26 is provided, the branch line 19 branches off from the area of ​​the hydraulic connection 15, which is located between the interior 14 of the high-pressure pump 16 and the quantity regulation device 26. A pressure relief valve 28 is arranged in the branch line 19, which opens when a predetermined opening pressure is exceeded and releases fuel into the reservoir 12. The pressure relief valve 28 prevents the fuel pressure, which corresponds to this opening pressure, from being exceeded in the hydraulic connection 15 and in the interior 14 of the high-pressure pump 16.

[0021] According to the invention, a device 24, 32, 34 is provided for monitoring the internal pressure of the high-pressure pump 16. This device 24, 32, 34 for monitoring the internal pressure monitors the pressure in the interior 14 of the high-pressure pump 16. If the pressure in the interior 14 of the high-pressure pump 16 falls below a minimum pressure, the pressure in the high-pressure area 18 is limited to a maximum pressure.

[0022] The pressure in the interior 14 of the high-pressure pump 16 can drop below the specified minimum pressure if the feed pump 10 no longer pumps fuel from the reservoir 12 via the hydraulic line 13 into the interior 14 of the high-pressure pump 16. An interruption in the fuel supply by the feed pump 10 can occur not only when the internal combustion engine is switched off in a controlled manner when the vehicle is brought to an end, but also when the internal combustion engine is switched off in an emergency. The situation of an emergency shutdown of the internal combustion engine can arise from the internal combustion engine stalling or from the activation of an emergency shutdown of the internal combustion engine. When the internal combustion engine is switched off in an emergency, the supply of fuel by the feed pump 10 is stopped.No more fuel is pumped from the reservoir 12 via the hydraulic line 13 into the interior 14 of the high-pressure pump 16, so that the pressure in the interior 14 of the high-pressure pump 16 approaches atmospheric pressure.

[0023] When restarting the internal combustion engine after an emergency shutdown, the high-pressure pump 16 normally has to work against a high fuel pressure in the high-pressure section 18. Since the feed pump 10 has not yet built up a sufficiently high fuel pressure in the high-pressure pump's interior 14, insufficient lubrication can lead to damage in the drive section 21 of the high-pressure pump 16. To prevent this damage in the drive section 21 of the high-pressure pump 16, the device 24, 32, 34 monitors the pressure in the high-pressure pump's interior 14. If the pressure in the high-pressure pump's interior 14 falls below the specified minimum pressure, the pressure in the high-pressure section 18 is checked.If the pressure in the high-pressure area 18 exceeds the specified maximum pressure, fuel is diverted from the high-pressure area 18 until the pressure in the high-pressure area 18 is limited to the maximum pressure. The fuel from the high-pressure area 18 is diverted into the reservoir 12 through a valve 24 or pressure control valve 30. The high-pressure pump 16 therefore only has to deliver fuel in the high-pressure area 18 against a low pressure that is equal to or lower than the maximum pressure.

[0024] In a first embodiment of the invention according to Fig. A connecting line 17 is arranged between the interior 14 of the high-pressure pump 16 and the high-pressure section 18. A valve 24 is located in the connecting line 17, which serves as a device 24 for monitoring the internal pressure of the high-pressure pump 16. If the pressure in the interior 14 of the high-pressure pump 16 drops, the pressure in the high-pressure section 18 is limited to a maximum pressure. The valve 24 in the connecting line 17 opens when the pressure in the interior 14 of the high-pressure pump 16 falls below a minimum pressure and the pressure in the high-pressure section 18 exceeds a maximum pressure. Fuel from the high-pressure section 18 flows through the connecting line 17 from the high-pressure section 18 into the interior 14 of the high-pressure pump 16.If a pressure greater than the opening pressure of the pressure relief valve 28 occurs in the interior 14 of the high-pressure pump 16 and in the subsequent hydraulic connection 15, the fuel is diverted through the opened pressure relief valve 28 via the branch line 19 into the storage tank 12.

[0025] The valve 24, which serves as a device for monitoring the internal pressure of the high-pressure pump 16, can be located at any point in the connecting line 17 between the high-pressure section 18 and the internal chamber 14 of the high-pressure pump 16. Arrangements are also possible in which the valve 24 is located directly on or in the pump housing of the high-pressure pump 16 or in the high-pressure section 18. Alternatively, the valve 24 can be integrated into a separate housing.

[0026] In Fig. Figure 2 shows a cone valve 35, which is one possible embodiment of a valve 24 in the connecting line 17 between the interior 14 of the high-pressure pump 16 and the high-pressure area 18. This cone valve 35 serves as a device 24 for monitoring the internal pressure of the high-pressure pump 16. The cone valve 35 shown is located in the connecting line 17, which is arranged between the high-pressure area 18 and the interior 14 of the high-pressure pump 16. The elements of the fuel delivery system and the subsequent hydraulic lines are not shown to scale. The cone valve 35 has a frustoconical closing element 25, which has a small contact area 26 for the fuel on the side facing the high-pressure area 18 and a large contact area 27 for the fuel on the side facing the interior 14 of the high-pressure pump 16.Furthermore, the cone valve 35 can have a spring 29 on the side facing the interior 14 of the high-pressure pump 16, which spring presses the closing element 25 into the valve seat after the fuel pressure in the high-pressure region 18 has been limited to the maximum pressure. The force of the spring 29 and the cross-sectional areas of the large contact surface 27 and the small contact surface 26 of the closing element 25 are designed such that the cone valve 35 opens when the fuel pressure in the interior 14 of the high-pressure pump 16 falls below the minimum pressure and the fuel pressure in the high-pressure region 18 exceeds the maximum pressure. The cone valve 35 closes as soon as the fuel pressure in the high-pressure region 18 is limited to the maximum pressure. The cone valve 35 also closes when a pressure higher than the minimum pressure occurs in the interior 14 of the high-pressure pump 16.

[0027] Fig.3 shows a second exemplary embodiment of the invention. A pressure sensor 34 in the interior 14 of the high-pressure pump 16 and a control unit 32, which are connected to one another, form the device 24 for monitoring the interior pressure of the high-pressure pump 16. The pressure sensor 34 is arranged in the interior 14 of the high-pressure pump 16 and transmits the pressure value measured in the interior 14 of the high-pressure pump 16 to the control unit 32. The control unit 32 is connected to a pressure control valve 30 in the high-pressure region 18. Depending on the pressure measured in the interior 14 of the high-pressure pump 16, the control unit 32 controls the pressure control valve 30 in the high-pressure region 18 and limits the pressure in the high-pressure region 18 to a maximum pressure if the pressure in the interior 14 of the high-pressure pump 16 falls below the minimum pressure.To limit the pressure in the high-pressure area 18, the pressure regulating valve 30 opens and diverts fuel via a hydraulic connection 36 into the reservoir 12. The pressure regulating valve 30 closes as soon as the pressure in the high-pressure area 18 is limited to the maximum pressure or a pressure higher than the minimum pressure is established in the interior 14 of the high-pressure pump 16.

Claims

[1] Fuel delivery device for a fuel injection device of an internal combustion engine with a feed pump (10) which feeds fuel from a reservoir (12) to a high-pressure pump (16), wherein the high-pressure pump (16) feeds fuel into a high-pressure region (18), wherein the high-pressure pump (16) has an interior (14) in which a drive region (21) is arranged, through which fuel from the feed pump (10) flows, characterized by that a device (24, 34) is provided for monitoring the interior pressure of the high-pressure pump (16) and when a predetermined minimum pressure in the interior (14) of the high-pressure pump (16) is undershot, the pressure in the high-pressure region (18) is limited to a maximum pressure. [2] Fuel delivery device according to claim 1, characterized by that fuel from the high-pressure area (18) can be diverted into the storage tank (12) through a valve (24) or pressure control valve (30). [3] Fuel delivery device according to one of the preceding claims, characterized by that a hydraulic connection (15) exists between the interior space (14) of the high-pressure pump (16) and at least one pump working chamber (22) of the high-pressure pump (16) in order to guide the fuel from the feed pump (10) through the interior space (14) to the pump working chamber (22) of the high-pressure pump (16). [4] Fuel delivery device according to claim 3, characterized by that a device for quantity regulation (26) is arranged in the hydraulic connection (15) between the interior space (14) of the high-pressure pump (16) and the pump working space (22) of the high-pressure pump (16). [5] Fuel delivery device according to claim 3 or 4, characterized bythat the hydraulic connection (15) between the interior space (14) of the high-pressure pump (16) and the pump working chamber (22) of the high-pressure pump (16) has a branch line (19) to the reservoir (12) in which a pressure relief valve (28) is arranged, by means of which fuel is diverted into the reservoir (12) when an opening pressure in the hydraulic connection (15) between the interior space (14) of the high-pressure pump (16) and the pump working chamber (22) of the high-pressure pump (16) is exceeded. [6] Fuel delivery device according to one of the preceding claims, characterized bythat the device (24) for monitoring the interior pressure of the high-pressure pump (16) is a valve (24) which is arranged in a connecting line (17) between the high-pressure region (18) and the interior (14) of the high-pressure pump (16), through which fuel is diverted from the high-pressure region (18) into the interior (14) of the high-pressure pump (16) until the fuel pressure in the high-pressure region (18) is limited to the maximum pressure, when the fuel pressure in the interior (14) of the high-pressure pump (16) falls below the minimum pressure. [7] Fuel delivery device according to claim 6, characterized by that the valve (24) is a cone valve (35) which has a spring (29) acting in the closing direction. [8] Fuel delivery device according to one of claims 6 to 7, characterized by that the valve (24) is integrated in the pump housing of the high-pressure pump (16) or in the high-pressure area (18). [9] Fuel delivery device according to one of claims 2 to 5, characterized by that the device (24, 34) for monitoring the interior pressure is a pressure sensor (34) in the interior (14) of the high-pressure pump (16) and a control unit (32) which are connected to one another, wherein the control unit (32) controls the pressure regulating valve (30) in the high-pressure region (18) by means of which fuel is diverted from the high-pressure region (18) via a hydraulic connection (36) into the reservoir (12) until the fuel pressure in the high-pressure region (18) is limited to the maximum pressure when the fuel pressure in the interior (14) of the high-pressure pump (16) falls below the minimum pressure. [10] Method for operating a fuel delivery device according to one of the preceding claims, characterized by , that - if the specified minimum pressure in the interior (14) of the high-pressure pump (16) is undershot, the pressure in the high-pressure area (18) is checked and - when the maximum pressure in the high-pressure area (18) is exceeded, fuel is diverted from the high-pressure area (18) until the fuel pressure in the high-pressure area (18) is limited to the maximum pressure or until the fuel pressure in the interior (14) of the high-pressure pump (16) has reached the minimum pressure.

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