JP2013545914A - Fuel injection system for internal combustion engine - Google Patents

Abstract

The present invention includes a high-pressure fuel pump (3), a metering unit (7) is connected in front of the high-pressure region (5), and the metering unit supplies the amount of fuel conveyed from the storage container (2) The high pressure area (5) is metered and supplied via the pipe (8), and the return pipe (14) is opened from the supply pipe (8) in the narrow area (20) of the venturi throttle (19). The zero delivery pipe (18) branching off, and further, the venturi throttle (19) is connected to the supply part (21) and / or to the opening to the narrow part (20), respectively by one filter ( 22 and 23).
[Selection] Figure 1

Description

  The present invention includes a high-pressure fuel pump, a metering unit is connected in front of the high-pressure region, and the metering unit meteres the amount of fuel conveyed from the storage container into the high-pressure region via a supply pipe. The present invention relates to a fuel injection system for an internal combustion engine in which a zero delivery pipe branched from the supply pipe to the return path in a narrow area of the venturi throttle is branched.

  Modern diesel engine fuel injection systems are today mainly configured as common rail injection systems. In this type of system, high pressure fuel is removed from the accumulator by the individual fuel injectors of the cylinders, and the accumulator receives an appropriate amount of high pressure fuel via the high pressure region of the high pressure fuel pump. Supplied. Normally, a metering unit is connected in front of the high-pressure area of the high-pressure fuel pump, and the metering unit meteres the required amount of fuel at each operating point of the diesel engine, so that only the required amount of fuel is high-pressure. And is conveyed into the high pressure accumulator. However, in certain operating conditions, the amount of fuel delivered to the high pressure accumulator must be zero. In the case of so-called zero delivery, the high pressure region of the high pressure fuel pump is no longer supplied with fuel via the metering unit. However, due to leakage, it is not possible to completely prevent a small amount of fuel from flowing through the metering unit. For this reason, the zero delivery pipe normally branches from the supply pipe to the high pressure region of the high pressure fuel pump, and this leakage amount can be fed back into the return path through the delivery pipe.

  From Patent Document 1, a fuel injection system for an internal combustion engine of this type in which a metering unit is connected in front of a high pressure region of a high pressure fuel pump is known. Through this metering unit, the amount of fuel that is compressed and conveyed to the high-pressure accumulator is distributed to the high-pressure region. In this case, the metering unit is supplied with fuel in a low pressure state from the storage container via a transport pump connected to the front, but the fuel is guided through the filter unit before reaching the metering unit. In this case, an overflow pipe provided with an overflow valve and a lubricant pipe provided with a lubricant restrictor are branched from the supply unit of the metering unit. The lubricant tube supplies fuel in a low pressure state to the low pressure region of the high pressure fuel pump for lubrication and cooling. In order to keep the pressure in front of the metering unit constant even when the conveyance rate by the metering unit is low or in the case of zero delivery, the overflow valve and the piston that is provided in this and loaded with elastic force are connected. Through which the fuel can be transported to the return path of the fuel injection system after a certain pressure level.

  Further, a zero delivery pipe branched from the supply pipe is provided on the side of the supply pipe of the metering unit leading to the high pressure area of the high-pressure fuel pump. In the case of zero delivery, the zero delivery pipe nevertheless flows through the metering unit. The amount of leaking can be conveyed into the return path through the zero delivery pipe. To reduce the opening pressure of the suction valves in the high pressure region as low as possible (this is compared to the fact that these suction valves open relatively early during operation, and in parallel to the pump operating chamber) The zero delivery pipe opening into the return path is configured like a venturi throttle. In this case, the zero delivery pipe opens to the return path in the narrow area of the venturi throttle. As a result, in the case of zero delivery and when fuel flows through the overflow valve and the return path, a negative pressure is generated in the narrow area inside the venturi throttle, and the amount of leakage is reduced through this negative pressure. Suction from the zero delivery pipe into the return path is achieved. As a result, the pressure in the zero delivery pipe is significantly lower than in a system without venturi throttling, resulting in undesired valve opening and inflow of leakage into the high pressure area, and the suction valve in the high pressure area. The valve opening pressure can be selected lower.

German Patent No. 10154133C1

  The object of the present invention is to provide a fuel injection system for an internal combustion engine, which starts from the above-mentioned state of the art and has a reduced incidence of failure in the area of the zero delivery pipe.

  This problem is solved in the context of the characteristic features of claim 1 starting from the preamble of claim 1. Subsequent dependent claims show each advantageous other configuration of the invention.

  The present invention includes the technical doctrine that the venturi throttle has one filter each in the supply section and / or in the opening to the narrow section. By providing the filter in the supply portion before the narrow portion of the venturi throttle, the opening portion to the narrow portion of the venturi throttle, or both regions, the risk of particles being taken into the venturi throttle can be significantly reduced. This is because in this region the venturi flow diameter is usually between 0.1 mm and 2 mm, so that the particles can stick there and clog the return path. If the return pipe is clogged, the function is impaired. In contrast, by providing at least one fine filter according to the present invention, the degree of failure occurrence due to particle uptake is significantly reduced.

  In contrast, in the case of the fuel injection system described in Patent Document 1, a failure may occur because the venturi throttle is blocked by particles. Indeed, particles from the storage container are restrained by a filter connected in front of the metering unit and the overflow valve, but particles taken in thereafter are not removed.

  In another configuration of the invention, each one filter is a mesh screen. Alternatively, each one filter is a laser-made screen. In both cases, a fine filter with low manufacturing cost can be configured.

  Corresponding to one configuration of the present invention, a transport pump is provided for transporting fuel from the storage container to the low pressure region of the high pressure fuel pump and the metering unit supply. With this configuration, sufficient fuel is supplied to the metering unit and the low pressure region of the high pressure fuel pump. In this case, advantageously, the overflow pipe of the overflow valve branches off from the supply of the metering unit. As a result of this measure, the metering unit performs metering, so that the excess portion of the fuel amount that is constantly provided by the transport pump can be returned via the overflow valve. Advantageously, the overflow valve returns this excess to the supply pipe of the transport pump after the first pressure level in the overflow pipe and back to the return path after the second pressure level. Thereby, it returns to the front of a conveyance pump first, and it is made to convey only to the return path which leads to a storage container, when return amount becomes larger than this. Thereby, even if a leak occurs, the leak can be reduced by removing the stress of the fuel to the return pipe and the storage container and subsequently compressing to a low pressure.

  In another configuration of the present invention, a throttle portion is provided between the opening of the return pipe and the supply portion of the transport pump. This has the advantage that the pressure fluctuation in front of the supply part of the transport pump, which occurs because the return pipe opens to the supply pipe of the transport pump, can be sufficiently reduced.

  According to another advantageous configuration of the invention, the conveying pump is a gear pump. This makes it possible to realize a robust and reliable implementation of the transport pump.

  Next, other solutions for improving the present invention will be described in detail together with the description of advantageous embodiments of the present invention using the drawings.

1 is a diagram of a fuel injection system according to the present invention in accordance with an advantageous embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view of an area of a venturi restriction of the fuel injection system of FIG. 1.

  FIG. 1 shows a fuel injection system according to the invention of an internal combustion engine according to an advantageous embodiment of the invention. In this embodiment, a high-pressure fuel comprising a low-pressure region 4 and a high-pressure region 5 in which a fluid in the form of fuel is sucked from the storage container 2 via a conveying pump 1 which is advantageously implemented as a gear pump. It is conveyed to the pump 3. The fuel passes through the low pressure region 4 (shown here only as a black box) and is used to lubricate and cool the movable member. Following this, the fuel reaches the supply 6 of the metering unit 7. The metering unit meteres the amount of fuel in accordance with the demands required for the operation of the internal combustion engine, via the supply pipe 8 and the suction valve 9 arranged therein (also shown in detail in the same manner). Not supplied) to the high pressure region 5. Thereafter, the supplied fuel is compressed to a high pressure inside the high pressure region 5 in a manner known to those skilled in the art, and is supplied to the accumulator 10 (only part of which is shown here). Can be removed from the accumulator for operation of the internal combustion engine.

  Further, as can be seen from FIG. 1, an overflow pipe 11 having an overflow valve 12 is branched from the supply unit 6 of the metering unit 7. The overflow valve 12 has a piston (suggested here schematically) that is connected from the overflow pipe 11 to the return pipe 13 after the pressure in the overflow pipe 11 reaches the first pressure level. The flow of fuel is enabled, and further, the flow into the return path 14 leading to the storage container 2 is enabled after the pressure in the overflow pipe 11 reaches the second pressure level. In this case, the piston of the overflow valve 12 is loaded backward by the spring and the prevailing pressure in the return pipe 13, but alternatively, in a corresponding relationship with the return path 14, A rear load due to the spring and the pressure prevailing in the return path 14 is also conceivable. The return pipe 13 opens to the supply pipe 15 of the transport pump 1. As a result, after the pressure in the overflow pipe 11 reaches the first pressure level, the return pipe 13 is first returned to the supply pipe 15, When the pressure increases further, the return to the return path 14 leading to the storage container 2 is also performed. The pressure in the overflow pipe 11 rises because a substantially constant amount of fuel is transported to the metering unit 7 by the transport pump 1, but the metering unit is a part necessary for the operation of the internal combustion engine each time. This is because only the high pressure region 5 is transferred.

  First, the loss of the fuel injection system can be reduced by returning the fuel in the low pressure state to the supply pipe 15 of the transport pump 1 through the return pipe 13. In order to reduce the pressure fluctuation in the supply region of the transport pump 1 at that time as much as possible, a throttle portion 16 is provided between the opening of the return pipe 13 and the supply portion of the transport pump 1. Further, a discharge pipe 17 coming from the low pressure region 4 of the high pressure fuel pump 3 is also opened in the pipe line 14.

  Further, as can be seen from FIG. 1, a zero delivery pipe 18 branches from the supply pipe 8 to the high pressure region 5 behind the metering unit 7. Via this zero delivery pipe 18, inevitable that occurs via the metering unit 7 in an operating state in which high fuel pressure should not be generated, and therefore in an operating state in which fuel should not be supplied to the high pressure region 5. The amount of leakage is discharged. If the leak amount is not discharged, the leak amount accumulates in the supply pipe 8, and after a certain amount accumulates and pressure is generated at the same time, the suction valve 9 is opened, and thus into the high pressure region 5. May flow in. The zero delivery pipe 18 opens into the return path 14, which in this case has a venturi restriction 19 illustrated in detail in FIG.

  As can be seen from FIG. 2, the zero delivery pipe 18 opens at a narrow portion 20 of the venturi throttle 19. Thereby, in the case of zero delivery via the metering unit 7 (this results in a suitable amount of fuel flowing through the overflow valve 12 and thus also through the return passage 14) Due to the fuel flowing in the passage 14 and the resulting venturi effect, it is achieved that the fuel leaking from the zero delivery pipe 18 is sucked into the return passage 14 by the formation of a negative pressure in the region of the narrow spot 20. The As a result, the zero delivery pipe 18 is preferably emptied, and as a result, the valve opening pressure of the suction valve 9 before the high pressure region 5 can be lowered.

  The fuel injection system according to the present invention is characterized by having one fine filter 22 and 23 at the supply portion 21 of the venturi throttle 19 and the opening to the narrow portion 20 respectively. These filters 22 and 23 may each be implemented as a mesh screen or a screen made of laser. The two filters 22 and 23 can effectively prevent particles from being taken into the region of the narrow portion 20 of the venturi throttle 19. If this is not the case, the return path 14 will be clogged, and thus the function of the fuel injection system of the internal combustion engine will be severely impaired.

  Therefore, the configuration according to the present invention can significantly reduce the degree of failure of the fuel injection system of the internal combustion engine.

DESCRIPTION OF SYMBOLS 1 Transfer pump 2 Storage container 3 High pressure fuel pump 4 Low pressure area 5 High pressure area 6 Supply part 7 Metering unit 8 Supply pipe 11 Overflow pipe 12 Overflow valve 13 Return pipe 14 Return path 15 Supply pipe 16 Restriction part 18 Zero delivery pipe 19 Venturi restriction 20 Narrow part 21 Supply section 22, 23 Filter

Claims (8)

The metering unit (7) includes a high-pressure fuel pump (3), and is connected to the metering unit (7) in front of the high-pressure region (5). The metering unit supplies the amount of fuel conveyed from the storage container (2) to the supply pipe (8). The zero-delivery is metered into the high-pressure area (5) via the supply pipe (8) and opens to the return path (14) in the narrow area (20) of the venturi throttle (19). In the fuel injection system for an internal combustion engine in which the pipe (18) is branched,
The venturi throttle (19) has one filter (22, 23) in the supply part (21) and / or in the opening to the narrow part (20), respectively. The fuel injection system.   2. The fuel injection system according to claim 1, characterized in that each one filter (22, 23) is a mesh screen.   The fuel injection system according to claim 1, characterized in that each one filter (22, 23) is a laser-made screen.   A transport pump (1) for transporting fuel from the storage container (2) to the low pressure region (4) of the high pressure fuel pump (3) and the supply unit (6) of the metering unit (7) is provided. The fuel injection system according to claim 1, wherein the fuel injection system is a fuel injection system.   The fuel injection according to any one of the preceding claims, characterized in that the overflow pipe (11) of the overflow valve (12) branches off from the supply section (6) of the metering unit (7). system.   After the first pressure level in the overflow pipe (11), the overflow valve (12) returns to the supply pipe (15) of the transfer pump (1) through the return pipe (13), and the second 6. The fuel injection system according to claim 5, wherein after the pressure level, the fuel is fed back to the return path (14).   7. The fuel injection system according to claim 6, wherein a throttle part (16) is provided between the opening of the return pipe (13) and the supply part of the transport pump (1).   The fuel injection system according to any one of claims 4 to 7, characterized in that the transport pump (1) is a gear pump.

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