Zero-feed throttle

Abstract

Zero-delivery throttle (50) for the low-pressure circuit (63) of a high-pressure injection system (14) for an internal combustion engine, comprising an inlet opening (52) for introducing fuel from the suction side of a high-pressure pump (1) into the zero-delivery throttle (50), an outlet opening (53) for diverting fuel from the zero-delivery throttle (50), a zero-delivery channel (51) for conveying fuel and the zero-delivery channel (51) connecting the inlet opening (52) with the outlet opening (53), wherein (51) is curved in the direction of fuel flow.

Description

[0001] The present invention relates to a zero-flow throttle for the low-pressure circuit of a high-pressure injection system according to the preamble of claim 1 and a high-pressure injection system according to the preamble of claim 7. State of the art

[0002] In high-pressure injection systems for internal combustion engines, particularly in common-rail injection systems of diesel or gasoline engines, a high-pressure pump continuously maintains the pressure in the high-pressure accumulator of the common-rail injection system. The high-pressure pump can be driven, for example, by a gear drive connected to the crankshaft of the internal combustion engine, by a belt drive, or by a chain. To supply fuel to the high-pressure pump, pre-supply pumps, such as gear or rotary vane pumps, are used, which are installed upstream of the high-pressure pump. The pre-supply pump delivers the fuel from a fuel tank through a fuel line to the high-pressure pump.

[0003] Piston pumps are among the high-pressure pumps used. A drive shaft is mounted in a housing. Radially to this shaft, pistons are arranged in a cylinder. A roller with a rolling surface rests on the drive shaft, which has at least one cam. The roller is mounted in a roller shoe. The roller shoe is connected to the piston, forcing the piston into an oscillating translational motion. A spring applies a force to the roller shoe, directed radially to the drive shaft, ensuring the roller remains in constant contact with the shaft. The roller's rolling surface contacts the drive shaft, which has at least one cam, via a rolling surface. The roller is mounted in the roller shoe by means of a plain bearing.

[0004] The drive shaft with at least one cam, the guide roller, and the roller shoe are arranged within a lubrication chamber of the high-pressure pump. The drive shaft of the high-pressure pump is positively connected to the feed pump, for example, by means of a coupling. The delivery rate and the resulting delivery pressure of the feed pump are therefore dependent on the speed of the high-pressure pump and are often limited by a restrictor in the intake section of the feed pump. At high engine speeds and low injection quantities, the feed pump generates an excessive delivery rate and flow rate, and consequently, excessive pressure in the fuel line from the feed pump to the high-pressure pump. This problem is preferably addressed by using a spring-loaded bypass valve. The fuel is routed from the fuel line from the feed pump to the high-pressure pump through the lubrication chamber and into the bypass valve.For this reason, a fuel line from the pre-supply pump to the high-pressure pump is fluidly connected to a bypass valve, which is fluidly connected to a lubrication chamber of the high-pressure pump. The bypass valve preferably has two outlet openings. The first outlet opening is always open or opens even at low pressure in the fuel line from the pre-supply pump to the high-pressure pump, directing a small amount of fuel back to the fuel tank via a fuel return channel for cooling purposes. The second outlet opening opens at a pressure in the fuel line from the pre-supply pump to the high-pressure pump, preferably between 3 bar and 7 bar, and directs the fuel directly back into the fuel line to the intake side of the pre-supply pump. This direct return to the intake side of the pre-supply pump allows the vehicle manufacturer to use a smaller fuel filter.

[0005] Fuel delivered by the feed pump is routed through the lubrication chamber of the high-pressure pump to the high-pressure pump. This serves to lubricate the components within the lubrication chamber and to cool them with the fuel flowing through it. The fuel flow from the feed pump to the high-pressure pump thus comprises, in its volumetric flow, both the fuel routed through the lubrication chamber for lubricating and cooling the components of the high-pressure pump within the chamber, and the fuel intended for the high-pressure pump to be delivered under high pressure to the high-pressure rail. A substantially constant pressure should be maintained in the fuel line from the feed pump to the high-pressure pump.

[0006] When using a mechanical pre-supply pump without an electric motor, driven solely by the crankshaft of the internal combustion engine, the fuel flow rate delivered by the mechanical pre-supply pump to the high-pressure pump's fuel suction line is controlled and / or regulated by a metering unit. The pre-supply pump delivers, for example, a fuel flow rate of approximately 400 l / h. Even in a completely closed state, the metering unit exhibits a leakage flow rate of approximately 0.5 l / h. In an operating state of the internal combustion engine where no fuel is consumed, this leakage flow rate would be directed into the high-pressure pump's fuel suction line, then fed by the high-pressure pump into the high-pressure fuel line and the high-pressure rail, continuously increasing the pressure in the high-pressure rail. Therefore, the high-pressure injection system is equipped with a zero-flow throttle with a zero-flow channel.The zero-delivery throttle directs the leakage flow through the zero-delivery channel into a fuel line of the low-pressure circuit. This prevents an increase in fuel pressure in the high-pressure rail when the metering unit is fully closed and the combustion engine is operating without fuel demand. The throttle diameter of the zero-delivery throttle is preferably designed such that, at maximum pressure in the low-pressure section of the high-pressure pump (limited by the bypass valve), the maximum leakage volume from the metering unit can flow through the throttle bore as the zero-delivery channel.In the fuel line, which acts as a fuel discharge channel and into which the zero-flow channel of the zero-flow throttle opens, a higher fuel pressure can occur than in the zero-flow channel of the zero-flow throttle itself. This can happen, for example, due to a small diameter of the fuel line to the fuel tank and / or a long length of this fuel line. This would lead to backflow of fuel from this fuel line through the zero-flow channel of the zero-flow throttle into the fuel suction line of the high-pressure pump. To prevent backflow of fuel through the zero-flow channel of the zero-flow throttle in the opposite direction to the desired flow direction, the pressure at the opening of the zero-flow channel is reduced using the Venturi effect. This is achieved by constricting the cross-section of the channel after the first outlet of the bypass valve, just before the zero-flow channel opens.Due to Bernoulli's equation, the flow velocity increases at the constriction and the pressure decreases. In the area where the zero-delivery channel of the zero-delivery throttle enters this fuel line or channel (in the direction of fuel flow after the first outlet opening), this channel features a straight Venturi section with a smaller cross-sectional area than the area outside the Venturi section of this fuel line. This results in a lower pressure locally only in the Venturi section of this fuel line (Bernoulli's equation), thus preventing backflow of fuel from this fuel line into the zero-delivery channel of the zero-delivery throttle. The fuel line is designed as a throttle tube in the Venturi section. This throttle tube is located in a bore in the housing of the high-pressure pump.On the radial outer side of the throttle tube, sealing rings are arranged axially at the ends between the throttle tube and the bore housing. Furthermore, a small radial bore, straight in the direction of fuel flow, is formed in the throttle tube as the zero-flow channel of the zero-flow throttle. This zero-flow channel opens into the central channel of the throttle tube in the region of its smallest diameter, i.e., the Venturi section of the throttle tube. A disadvantage is that the throttle tube is complex and expensive to manufacture and requires intricate assembly procedures.

[0007] EP 2 708 728 A2 discloses a low-pressure circuit for a fuel injection system, in particular a common-rail injection system for internal combustion engines, comprising a pre-supply pump by means of which fuel can be drawn from a fuel tank and supplied via a fuel line to a low-pressure section of a high-pressure pump, wherein a metering unit for quantity control is arranged in the low-pressure section, a zero-supply line with a zero-supply throttle branches off downstream of the metering unit, and an overflow line with an overflow valve branches off upstream of the metering unit, wherein a shut-off device switchable between an open and a closed state is arranged in the zero-supply line for selectively opening or closing the zero-supply line. Disclosure of the inventionAdvantages of the invention

[0008] A zero-delivery throttle according to the invention for the low-pressure circuit of a high-pressure injection system for an internal combustion engine, comprising an inlet opening for introducing fuel from the suction side of a high-pressure pump into the zero-delivery throttle, an outlet opening for venting fuel from the zero-delivery throttle, a zero-delivery channel for conveying fuel, and a zero-delivery channel connecting the inlet opening to the outlet opening, wherein the zero-delivery channel is preferably curved in the direction of fuel flow. Preferably, the curvature of the zero-delivery channel is substantially constant, in particular with a deviation of less than 30%, 20%, or 10%. Preferably, the curvature of the zero-delivery channel is less than 30 cm, 20 cm, 10 cm, 5 cm, 3 cm, 2 cm, or 1 cm. Preferably, at least 30%, 50%, 70%, 90%, or 95% of the length of the zero-delivery channel is curved.A curved design of the zero-feed channel is also considered to exist if a curvature of at least 3, 5 or 7 straight sections of the zero-feed channel is approximated in the direction of fuel flow.

[0009] In a further embodiment, the zero-flow channel is formed at least partially, and in particular completely, in an annular groove. The cross-section of the annular groove is preferably designed such that, at the maximum pressure occurring in the low-pressure area of ​​the high-pressure pump, which is limited by the overflow valve, the maximum leakage volume of the metering unit can flow through it.

[0010] In an additional variant, the zero-feed throttle comprises a throttle ring, preferably cylindrical in shape, and the annular groove on the throttle ring, in particular on a radial outer side of the throttle ring.

[0011] In a supplementary variant, the zero-delivery throttle includes at least a partial overflow valve channel for the passage of fuel from an overflow valve into the low-pressure circuit of the high-pressure injection system.

[0012] In another embodiment, the overflow valve channel has a different flow cross-sectional area and a Venturi section of the overflow valve channel with a smaller flow cross-sectional area than outside the Venturi section is designed for a reduced pressure of the fuel flowing through the Venturi section.

[0013] Preferably, the Venturi section of the overflow valve channel is at least partially limited by the throttle ring, in particular an axial end of the throttle ring.

[0014] A high-pressure injection system according to the invention for an internal combustion engine, comprising a high-pressure pump, a high-pressure rail, a bypass valve, a zero-delivery throttle with an inlet opening for introducing fuel from the suction side of the high-pressure pump into the zero-delivery throttle, an outlet opening for diverting fuel from the zero-delivery throttle, and a zero-delivery channel for conveying fuel, the zero-delivery channel connecting the inlet opening to the outlet opening, a bypass valve channel for conveying fuel from the bypass valve into a low-pressure circuit of the high-pressure injection system, wherein the bypass valve channel has a different flow cross-sectional area and a Venturi section of the bypass valve channel is designed with a smaller flow cross-sectional area than outside the Venturi section for a reduced pressure of the fuel flowing through the Venturi section of the bypass valve channel.a pre-supply pump, a metering unit, wherein preferably the zero-supply channel is curved in the direction of fuel flow.

[0015] In another embodiment, the zero-conveying channel is formed in an annular groove.

[0016] In a supplementary embodiment, the zero-feed throttle comprises a throttle ring, preferably cylindrical in shape, and preferably the annular groove on the throttle ring, in particular on a radial outer side of the throttle ring.

[0017] Advantageously, the cylindrical throttle ring is arranged in a bore of a housing of at least one pump of the high-pressure injection system.

[0018] In a further embodiment, the zero-flow channel is bounded by two different components, in particular by the throttle ring (preferably cylindrical) and the housing of the at least one pump of the high-pressure injection system. Preferably, the two different components are positively and / or frictionally connected to each other, and / or the two different components are not materially bonded to each other. The throttle ring, as a first component, is positively and preferably frictionally attached to the housing of the at least one pump, as a second component, in particular by means of an interference fit in the bore of the housing of the at least one pump.

[0019] In a supplementary embodiment, the Venturi section of the overflow valve channel is limited by the throttle ring, in particular an axial end of the throttle ring.

[0020] Preferably, the Venturi section of the bypass valve channel is bounded by the housing of the at least one pump of the high-pressure injection system. Preferably, the housing of the at least one pump is the housing of the pre-supply pump and / or the housing of the high-pressure pump.

[0021] In a further embodiment, the zero-delivery channel of the zero-delivery throttle and the Venturi section of the bypass valve channel open into a common fuel discharge channel. Preferably, the fuel discharge channel is designed as a fuel line and / or as a fuel bore in a housing of the at least one pump.

[0022] In a supplementary variant, the overflow valve comprises a first stage with a first discharge opening and a second stage with a second discharge opening, and the second discharge opening of the overflow valve leads into the overflow valve channel with the Venturi section.

[0023] In another embodiment, the zero-flow channel is limited by the throttle ring and the pump housing.

[0024] Preferably, the annular groove is formed on the housing of at least one pump.

[0025] In an additional variant, the zero-feed throttle includes a cylindrical throttle ring and the ring groove is formed on a radial inner side of the cylindrical throttle ring.

[0026] In another embodiment, the throttle ring is arranged in a radial direction with respect to a longitudinal axis of the overflow valve and / or the throttle ring between the overflow valve and the housing at the bore.

[0027] In an additional embodiment, an axial end of the throttle ring rests on a step of the bore of the housing, in particular completely circumferentially and / or in a liquid-tight manner.

[0028] In a further embodiment, the Venturi section of the overflow valve channel has a slot-shaped cross-section with a larger extent in a first direction than in a second direction, and the first and second directions are perpendicular to each other, and preferably the extent of the Venturi section in the first direction is greater than 1.1, 1.5, 2, 3, or 4 times the extent of the Venturi section in the second direction.

[0029] In a further embodiment, the boundary of the Venturi section of the bypass valve channel is at least partially straight and / or at least partially curved. A first section of the Venturi section boundary is curved, forming the end of the fuel discharge channel, and a second section of the Venturi section boundary is straight, forming the axial end of the throttle ring.

[0030] In a supplementary embodiment, the fuel drainage channel is limited by the throttle ring, in particular a radial inner side of the throttle ring, and the housing, in particular a radial outer side of the housing of the overflow valve.

[0031] In another variant, the pump housing, acting as a high-pressure pump and / or pre-supply pump, limits the Venturi section of the overflow valve channel.

[0032] In a supplementary embodiment, a section of the annular groove of the throttle ring forms the inlet opening of the zero-flow throttle.

[0033] In an additional embodiment, a portion of the annular groove of the throttle ring forms the outlet opening of the zero-flow throttle.

[0034] In a supplementary variant, the flow cross-sectional area of ​​the Venturi section of the overflow valve channel is less than 90%, 70%, 50%, 30% or 10% of the flow cross-sectional area of ​​the overflow valve channel outside the Venturi section.

[0035] In an additional embodiment, the flow cross-sectional area of ​​the zero-delivery channel of the zero-delivery throttle is designed such that the leakage volume flow from the metering unit is completely passable during the operation of the high-pressure injection system.

[0036] In a supplementary embodiment, the zero-flow channel is designed such that the volume flow of fuel introduced through the inlet opening of the zero-flow throttle is divided into a first partial volume flow and a second partial volume flow, and the first partial volume flow is conductable through a first sub-area of ​​the zero-flow channel, and the second partial volume flow is conductable through a second sub-area of ​​the zero-flow channel, and preferably the first and second partial volume flows are conductable into one, in particular only one, outlet opening of the zero-flow throttle.

[0037] In another embodiment, the cross-sectional area of ​​the annular groove is designed such that a larger volume flow of fuel than necessary for discharging the zero delivery quantity can pass through. Preferably, an additional zero delivery restrictor is formed upstream in the flow direction of the fuel guided through the annular groove, preferably pressed in and / or screwed in and / or glued in place.

[0038] In an additional embodiment, the housing of the overflow valve and / or the throttle ring and / or the housing of the pump are at least partially, in particular completely, made of plastic and / or steel and / or aluminium.

[0039] In a supplementary variant, the volume flow of the fuel delivered from the pre-supply pump to the high-pressure pump during the operation of the combustion engine can be controlled and / or regulated by using a metering unit to control and / or regulate the flow cross-sectional area of ​​a flow channel from the pre-supply pump to the high-pressure pump.

[0040] In another variant, the pre-supply pump is a gear pump.

[0041] In a further embodiment, the front feed pump is mechanically driven, in particular exclusively, by the internal combustion engine. The front feed pump is, for example, mechanically coupled to and / or driven by a gearbox and at least one shaft connected to the crankshaft of the internal combustion engine.

[0042] Preferably, the high-pressure pump includes a lubrication chamber.

[0043] The pressure that can be generated by the high-pressure pump in the high-pressure rail is, for example, in the range of 100 bar to 3000 bar for diesel engines or between 40 bar and 400 bar for gasoline engines. Short description of the drawings

[0044] Exemplary embodiments of the invention are described in more detail below with reference to the accompanying drawings. These show: Fig. 1 a cross-section of a high-pressure pump for pumping a fluid, Fig. 2 a cut AA according to Fig. 1 of a roller with roller shoe and a drive shaft, Fig. 3 a highly schematic view of a high-pressure injection system, Fig. 4 a perspective view of a throttle ring, Fig. 5 a cross-section of a drainage channel for the zero delivery channel and the overflow valve channel with a view towards one end of the drainage channel with the throttle ring, Fig. 6 a cross-section of a bore in the housing of the high-pressure pump with the overflow valve, throttle ring, discharge channel and Fig. 7 a longitudinal section of the bore in the housing of the high-pressure pump with the overflow valve, throttle ring, discharge channel and Fig. 8 an enlarged partial longitudinal section of the bore in the pump housing with the overflow valve, throttle ring, discharge channel and Embodiments of the invention

[0045] In Fig. Figure 1 shows a cross-section of a high-pressure pump 1 for pumping fuel. The high-pressure pump 1 serves to pump fuel, e.g., gasoline or diesel, to an internal combustion engine (not shown) under high pressure. The pressure that can be generated by the high-pressure pump 1 is, for example, in a range between 40 bar and 3000 bar.

[0046] The high-pressure pump 1 has a drive shaft 2 with two cams 3, which performs a rotational movement about a rotational axis 26. The rotational axis 26 lies in the plane of the drawing. Fig. 1 and is perpendicular to the drawing plane of Fig. 2. A piston 5 is mounted in a cylinder 6, which is formed by a housing 8. A working chamber 29 is bounded by the cylinder 6, the housing 8, and the piston 5. An inlet port 22 with an inlet valve 19 and an outlet port 24 with an outlet valve 20 open into the working chamber 29. Fuel flows into the working chamber 29 through the inlet port 22 with an inlet opening 21 and flows out of the working chamber 29 under high pressure through the outlet port 24 with an outlet opening 23. The inlet valve 19, e.g., a check valve, is designed such that only fuel can flow into the working chamber 29, and the outlet valve 20, e.g., a check valve, is designed such that only fuel can flow out of the working chamber 29. The volume of the working chamber 29 is changed due to an oscillating stroke movement of the piston 5. The piston 5 is indirectly supported on the drive shaft 2.At the end of the piston 5 or pump piston 5, a roller shoe 9 with a roller 10 is attached. The roller 10 can perform a rotational movement, the axis of rotation 25 of which lies in the plane of the drawing according to . Fig. 1 lies and perpendicular to the drawing plane of Fig. 2 stands. The drive shaft 2 with the at least one cam 3 has a shaft rolling surface 4 and the roller 10 has a roller rolling surface 11.

[0047] The roller running surface 11 of the roller 10 rolls on the shaft rolling surface 4 of the drive shaft 2 at a contact surface 12 with the two cams 3. The roller shoe 9 is mounted as a plain bearing in a roller shoe bearing formed by the housing 8. A spring 27 or coil spring 27, acting as an elastic element 28, which is clamped between the housing 8 and the roller shoe 9, exerts a compressive force on the roller shoe 9, so that the roller running surface 11 of the roller 10 is in constant contact with the shaft rolling surface 4 of the drive shaft 2. The roller shoe 9 and the piston 5 thus jointly perform an oscillating stroke movement. The roller 10 is mounted in the roller shoe 9 by a plain bearing 13.

[0048] In Fig. Figure 3 shows a highly schematic representation of a high-pressure injection system 14 for a motor vehicle (not shown) with a high-pressure rail 30 or a fuel distribution pipe 31. Fuel is injected from the high-pressure rail 30 or fuel distribution pipe 31 through high-pressure fuel lines 44 and by means of valves (not shown) into the combustion chambers (not shown) of the internal combustion engine (not shown). The fuel is supplied to a high-pressure fuel line 44 through the outlet channel 24 and the outlet opening 23 and introduced into the high-pressure rail 30 via the high-pressure fuel line 44.

[0049] A pre-supply pump 15 delivers fuel from a fuel tank 32 through a fuel line 33, a pre-filter 34, a main filter 36, and a metering unit 35 to the high-pressure pump 1. The pre-supply pump 15 is a mechanical pre-supply pump 15, which is mechanically coupled to the crankshaft of the internal combustion engine and delivers a maximum of 400 l / h of fuel, depending on the engine speed. The high-pressure pump 1 is also driven by the crankshaft of the internal combustion engine, so that the high-pressure pump 1 and the pre-supply pump 15 deliver the fuel depending on the engine speed. The pre-supply pump 15 is designed as a gear pump 16, for example, an internal gear pump 17 or an external gear pump 18. The high-pressure pump 1 is driven by the drive shaft 2, and the drive shaft 2 is driven by the crankshaft of the internal combustion engine.The metering unit 35 controls and / or regulates the volume of fuel supplied to the high-pressure pump 1 per unit of time. The metering unit 35 is, for example, designed as a slide valve with a linear solenoid (not shown). The slide valve is opened by the linear solenoid into different positions with varying flow cross-sections for the fuel, so that the volume flow of fuel supplied from the metering unit 35 to the high-pressure pump 1 via a fuel suction line 45 is controlled and / or regulated depending on the fuel demand in the internal combustion engine.

[0050] The fuel is delivered by the pre-supply pump 15 through the main filter 36 into the metering unit 35. The high-pressure rail 30 serves to inject the fuel into the combustion chamber of the internal combustion engine via injectors (not shown). Fuel delivered by the high-pressure pump 1 into the high-pressure rail 30, but not required by the internal combustion engine, is returned to the fuel tank 32 via a fuel return line 46. After pressure reduction by a pressure regulating valve (not shown), the return line 46 prevents the fuel pressure in the high-pressure rail 30 from exceeding a predetermined pressure, thus ensuring that the injectors have a predetermined fuel pressure available at the inlet. The fuel return line 46 is part of a low-pressure circuit 63.

[0051] The fuel drawn from the fuel tank 32 by the pre-supply pump 15 is supplied by the pre-supply pump 15 at a pre-supply pressure, e.g., of 4 bar, through the fuel line 33 of the high-pressure pump 1, i.e., supplied to the inlet port 22 of the high-pressure pump 1. The delivery rate of the pre-supply pump 15 is generally greater than the maximum delivery rate of the high-pressure pump 1, so that in various operating states of the internal combustion engine, a sufficient supply of fuel to the high-pressure pump 1 is always ensured and that a sufficient amount of fuel flows through and is supplied to the lubrication chamber 37 of the high-pressure pump 1 as lubricant.

[0052] The lubrication chamber 37 is formed within the housing 8 of the high-pressure pump 1. The drive shaft 2, the roller 10, the roller shoe 9, and part of the piston 5 are arranged in the lubrication chamber 37. These components 2, 5, 9, and 10 are lubricated by the fuel passing through the lubrication chamber 37. For this purpose, a channel 38 for introducing fuel into the lubrication chamber 37 and a channel 39 for discharging fuel from the lubrication chamber 37 are formed within the housing 8 as a separate fuel line. The channel 38 for introducing fuel into the lubrication chamber 37 is connected to the fuel line 33 upstream of the metering unit 35, so that the excess fuel from the feed pump 15, which is not routed through the metering unit 35, is routed through the lubrication chamber 37.

[0053] A bore 41 is machined into the housing 8 of the high-pressure pump 1 ( Fig. 6, Fig. 7 and Fig. 8) and a bypass valve 40 is arranged in this bore 41. The bypass valve 40 has the function of diverting the excess fuel delivered by the feed pump 15, which is not required by the high-pressure pump 1 and has passed through the lubrication chamber 37, into the fuel tank 32 and / or into the fuel line 33 as the suction line of the feed pump 15, and to maintain the fuel pressure in the lubrication chamber 37 essentially constant. This excess fuel is introduced through the channel 38, the lubrication chamber 37, and the channel 39 into an inlet port of the bypass valve 40. The bypass valve 40 is designed as a spool valve with a valve piston 43 and a valve spring 42. The fuel pressure at the inlet port of the bypass valve 40 counteracts the force exerted by the valve spring 42 on the valve piston 43.The overflow valve 40 has a first outlet opening 47 as a first stage and a second outlet opening 48 as a second stage (. Fig. 3 and Fig. 8) At a low pressure, for example from 0.5 bar at the inlet port of the bypass valve, fuel is discharged through the first outlet port 47 with a small flow cross-sectional area due to the movement of the valve piston 43. If the pressure at the inlet port of the bypass valve 40 increases further, the valve piston 43 is moved further against the pressure force applied to the valve piston 43 by the valve spring 42, and the second outlet port 48 is opened from a pressure of, for example, 4 bar, and a large volume flow of fuel is directed through the second outlet port 48.

[0054] The pre-supply pump 35 delivers not only the fuel required for the high-pressure pump 1, but also an additional quantity of fuel for the lubrication of the high-pressure pump 1, i.e., the fuel flowing through the lubrication chamber 40. To prevent a pressure increase at the fuel line 33 upstream of the overflow valve 41 when the pre-supply pump 35's delivery rate increases, the second outlet opening 48 of the overflow valve 40 preferably opens when the fuel pressure upstream of the overflow valve 40 rises, e.g., from a pressure of 4 bar. This provides a larger cross-sectional area for the fuel flow through the overflow valve 40 until the pressure upstream of the overflow valve 40 is again less than 4 bar.This allows a substantially constant supply pressure of approximately 4 bar to be provided in channel 39 upstream of the bypass valve 40 during operation of the internal combustion engine 3, even with fluctuations in the delivery rate of the feed pump 35. The bypass valve 40 is responsible for maintaining a nearly constant fuel pressure upstream of the metering unit 35 and in the lubrication chamber 37 to ensure high control accuracy of the metering unit 35 and reliable fuel flow through the bearings of the high-pressure pump 1. Another function of the bypass valve 40 is to return a volume of fuel, which is directed through a first outlet opening 47 and a fuel return channel 54, back into the fuel tank 32. This fuel is then replaced by the feed pump 15 with generally cooler fuel from the fuel tank 32, thus ensuring cooling of the high-pressure pump 1.

[0055] Even when the slide valve is fully closed, the metering unit 35 is not completely sealed, allowing a leakage flow rate of approximately 0.5 l / h to pass through the metering unit 35 into the fuel suction line 45. If the internal combustion engine does not require fuel, this leakage flow rate, due to its introduction into the fuel suction line 45, would cause a continuous increase in pressure in the high-pressure rail 30. A zero-flow throttle 50 of the high-pressure injection system 14 prevents the unimpeded pressure increase in the high-pressure rail 30 caused by the leakage flow rate from the metering unit 35. A channel 49, acting as a fuel line and / or channel in the housing 8, directs the leakage flow rate from the fuel suction line 45 through a zero-flow throttle 50 with a zero-flow channel 51 into a fuel return channel 56, also acting as a fuel line and / or channel in the housing 8.Fuel from the second outlet port 48 of the bypass valve 40 is introduced into a bypass valve channel 55, forming a second bypass valve channel 55. The zero-delivery channel 51 of the zero-delivery throttle 50 and the bypass channel 55 open into a common fuel discharge channel 56. The fuel discharge channel 56 opens into the fuel line after the pre-filter 34 and before the lift pump 15. A fuel return channel 54, acting as a fuel line and / or channel in the housing 8, directs the fuel from the first outlet port 47 of the bypass valve 40 through the end section of the fuel return line 46 into the fuel tank 32. The fuel return channel 54 forms a first bypass valve channel 54 because the fuel is discharged from the first outlet port 47 of the bypass valve 40 through the fuel return channel 54.

[0056] A throttle ring 58 is arranged concentrically and coaxially to the overflow valve 40 in the bore 41 ( Fig. 5 to 8). The throttle ring 58 is thus arranged radially with respect to a longitudinal axis 61 of the overflow valve 40 and the throttle ring 58 between the overflow valve 40 and the housing 8 at the bore 41. A fully circumferential annular groove 59 is formed on a radial outer surface of the throttle ring 58. One axial end of the throttle ring 58 rests on a step 62 of the bore 41, and the other axial end 60 of the throttle ring 58 partially delimits a venturi section 57 of the overflow valve channel 55 ( Fig. 8) The second outlet opening 48 of the overflow valve 40 opens into an annular space 55 as an overflow valve channel 55 between a radial inner surface of the throttle ring 58 and the radial outer surface of the housing of the overflow valve 40. This annular space 55 as an overflow valve channel 55 has only one opening, namely the venturi section 57. The venturi section 57 ( Fig. 7 and Fig. 8) is from the one in Fig. The upper axial end 60 of the throttle ring 58 and the housing 8 at the end of the fuel discharge channel 56 are bounded, and the flow cross-sectional area is significantly smaller compared to the remaining overflow valve channel 55. The venturi section 57 has an elongated and slotted cross-section.

[0057] The annular groove 59 of the throttle ring 58 aligns with the end of the channel 49 at the bore 41, so that the aligned section of the annular groove 59 at the channel 49 forms an inlet opening 52 of the zero-fuel channel 51. The annular groove 59 of the throttle ring 58 aligns with the end of the fuel outlet channel 56 at the bore 41, so that the aligned section of the annular groove 59 at the fuel outlet channel 49 forms an outlet opening 53 of the zero-fuel channel 51. Outside the end of channel 49 and the end of fuel discharge channel 56, the annular groove 59 is covered by the housing 8 at bore 41, so that the fuel flows in the annular groove 59 as the curved zero delivery channel 51 with substantially constant radius of curvature in the direction of fuel flow from channel 49 into fuel discharge channel 56 to introduce the leakage volume flow from metering unit 35 into fuel discharge channel 56.The volume flow of fuel entering through the inlet opening 52 is divided into a first partial volume flow as shown in . Fig. 6 to the left of the inlet opening 52 and in a second partial volume flow as shown in Fig.6 to the right and below the inlet opening 52. The first and second partial volume flows, which flow through two separate sections of the annular groove 59, are introduced into the outlet opening 53. In the venturi section 57 of the bypass valve channel 55, the flow cross-sectional area is greatly reduced, so that the pressure of the fuel flowing through the venturi section 57 drops sharply, and this low pressure also occurs partially at the end of the fuel discharge channel 56 near the outlet opening 53 of the zero-delivery channel 51. This prevents backflow of fuel from the fuel discharge channel 56 through the zero-delivery channel 51 into the fuel suction line 45 when the fuel pressure in the fuel discharge channel 56 is higher than in the fuel suction line 45.Fuel lines and fuel channels of the high-pressure injection system 14, excluding the high-pressure fuel line 45, form a low-pressure circuit 63 of the high-pressure injection system 14.

[0058] Overall, the zero-delivery throttle 50 and the high-pressure injection system 14 according to the invention offer significant advantages. The throttle ring 58 with annular groove 59, due to its arrangement in the bore 41 of the housing 8, forms the zero-delivery throttle 50 in a simple manner. The throttle ring 58 is simple and inexpensive to manufacture, resulting in advantageously low production costs for the zero-delivery throttle 50 and the high-pressure injection system 14. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 2 708 728 A2

[0007]

Claims

[1] Zero-feed throttle (50) for the low-pressure circuit (63) of a high-pressure injection system (14) for an internal combustion engine, comprising - an inlet opening (52) for introducing fuel from the suction side of a high-pressure pump (1) into the zero-feed throttle (50), - an outlet opening (53) for discharging fuel from the zero-feed throttle (50), - a zero feed channel (51) for passing fuel and the zero feed channel (51) connects the inlet opening (52) to the outlet opening (53), characterized by that the zero feed channel (51) is curved in the flow direction of the fuel. [2] Zero feed throttle according to claim 1, characterized by that the zero-feed channel (51) is formed at least partially, in particular completely, in an annular groove (59). [3] Zero feed throttle according to claim 2, characterized bythat the zero-feed throttle (50) comprises a throttle ring (58), preferably in the shape of a cylinder jacket, and the annular groove (59) is formed on the throttle ring (58), in particular on a radial outer side of the throttle ring (58). [4] Zero feed throttle according to claim 3, characterized by that the zero-feed throttle (50) at least partially comprises an overflow valve channel (55) for passing fuel from an overflow valve (40) into the low-pressure circuit (63) of the high-pressure injection system (14). [5] Zero feed throttle according to claim 4, characterized by that the overflow valve channel (55) has a different flow cross-sectional area and a Venturi section (57) of the overflow valve channel (55) is designed with a smaller flow cross-sectional area than outside the Venturi section (57) for a reduced pressure of the fuel flowing through the Venturi section (57). [6] Zero feed throttle according to claim 5, characterized by that the Venturi section (57) of the overflow valve channel (55) is at least partially delimited by the throttle ring (58), in particular an axial end (60) of the throttle ring (58). [7] High-pressure injection system (14) for an internal combustion engine, comprising - a high-pressure pump (1), - a high-pressure rail (30), - an overflow valve (40), - a zero-feed throttle (50) with an inlet opening (52) for introducing fuel from the suction side of the high-pressure pump (1) into the zero-feed throttle (50), an outlet opening (53) for discharging fuel from the zero-feed throttle (50) and with a zero-feed channel (51) for passing fuel, and the zero-feed channel (51) connects the inlet opening (52) to the outlet opening (53), - an overflow valve channel (55) for conducting fuel from the overflow valve (40) into a low-pressure circuit (63) of the high-pressure injection system (14), wherein the overflow valve channel (55) has a different flow cross-sectional area and a Venturi section (57) of the overflow valve channel (55) is designed with a smaller flow cross-sectional area than outside the Venturi section (57) for a reduced pressure of the fuel flowing through the Venturi section (57) of the overflow valve channel (55), - a pre-feed pump (15), - a metering unit (35), characterized by that the zero feed channel (51) is curved in the flow direction of the fuel. [8] High-pressure injection system according to claim 7, characterized by that the zero-feed channel (51) is formed in an annular groove (59). [9] High-pressure injection system according to claim 8, characterized bythat the zero-feed throttle (50) comprises a throttle ring (58), preferably in the shape of a cylinder jacket, and the annular groove (59) is formed on the throttle ring (58), in particular on a radial outer side of the throttle ring (58). [10] High-pressure injection system according to claim 9, characterized by that the cylinder jacket-shaped throttle ring (58) is arranged in a bore (41) of a housing (8) of at least one pump (1, 15) of the high-pressure injection system (14). [11] High-pressure injection system according to one or more of claims 7 to 10, characterized by that the zero-feed channel (51) is delimited by two different components (8, 58), in particular the zero-feed channel (51) is delimited by the throttle ring (58), preferably in the form of a cylinder jacket, and the housing (8) of the at least one pump (1, 15) of the high-pressure injection system (14). [12] High-pressure injection system according to one or more of claims 9 to 11, characterized bythat the Venturi section (57) of the overflow valve channel (55) is delimited by the throttle ring (58), in particular an axial end (60) of the throttle ring (58). [13] High-pressure injection system according to one or more of claims 7 to 12, characterized by that the Venturi section (57) of the overflow valve channel (55) is delimited by the housing (8) of the at least one pump (1, 15) of the high-pressure injection system (14). [14] High-pressure injection system according to one or more of claims 7 to 13, characterized by that the zero-feed channel (51) of the zero-feed throttle (50) and the Venturi section (57) of the overflow valve channel (55) open into a common fuel discharge channel (56). [15] High-pressure injection system according to one or more of claims 7 to 14, characterized bythat the overflow valve (40) comprises a first stage with a first discharge opening (47) and a second stage with a second discharge opening (48), and the second discharge opening (48) of the overflow valve (40) opens into the overflow valve channel (55) with the Venturi section (57).

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