CN215256540U

CN215256540U - Low pressure assembly and fuel injection system

Info

Publication number: CN215256540U
Application number: CN202121666739.8U
Authority: CN
Inventors: 王敏珠; 王譞
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2021-07-21
Filing date: 2021-07-21
Publication date: 2021-12-21
Anticipated expiration: 2031-07-21

Abstract

The utility model provides a low pressure subassembly for fuel injection system, low pressure subassembly includes: a supply pump (1) configured to supply pre-pressurized fuel to the high-pressure module through an oil delivery passage (L2); a metering unit (6) arranged in the oil delivery passage (L2); an overflow valve (8) arranged in the overflow channel, an upstream section of the overflow channel being connected to the oil delivery channel (L2) upstream of the metering unit (6), a downstream section of the overflow channel leading to the oil tank (2); characterized in that the low-pressure assembly further comprises a cushion valve (20) arranged in the downstream section of the overflow channel, the inlet of the cushion valve (20) communicating with the outlet of the overflow valve (8), the outlet of the cushion valve (20) opening into the tank (2), the cushion valve (20) comprising an at least partially flexible cushion (26). A fuel injection system is also provided. This can mitigate or avoid the effects of pressure fluctuations caused by sudden changes in fuel in the low pressure assembly.

Description

Low pressure assembly and fuel injection system

Technical Field

The utility model relates to a low pressure subassembly for fuel injection system to and contain the fuel injection system of this kind of low pressure subassembly.

Background

Fuel injection systems for engines typically include a low pressure assembly and one or more high pressure assemblies supplied with fuel by the low pressure assembly. One known low pressure assembly includes a supply pump (low pressure pump) which draws fuel from a fuel tank. And a main filter is arranged in an oil inlet line between the oil tank and the oil supply pump. The oil supply line of the oil supply pump leads to the high-pressure component, in particular, for example, a plunger pump (high-pressure pump) in the high-pressure component.

In general, a throttle valve, a relief valve and a metering unit are arranged between the low-pressure pump and the high-pressure pump in order to control the fuel flow. With this arrangement, excess fuel fluid is returned through the throttle or spill valve without being delivered to the high pressure components.

In the prior art, the excess fuel fluid is returned directly after passing through a throttle or spill valve. However, this arrangement causes many adverse effects, such as generation of vibration and/or noise. This may reduce the service life of the low pressure assembly or of a fuel injection system comprising such a low pressure assembly.

SUMMERY OF THE UTILITY MODEL

It is an object of the present invention to provide an improved low pressure assembly for a fuel injection system which at least partially solves the problems of the prior art.

To achieve the above object, the present invention provides in one aspect a low pressure assembly for a fuel injection system, the low pressure assembly comprising: a supply pump configured to supply the pre-compressed fuel to the high-pressure component through the fuel delivery passage; a metering unit disposed in the oil delivery passage; an overflow valve arranged in an overflow channel, an upstream section of the overflow channel being connected to the oil transfer channel upstream of the metering unit, a downstream section of the overflow channel leading to the oil tank; characterized in that the low-pressure assembly further comprises a buffer valve arranged in the downstream section of the overflow channel, the inlet of the buffer valve is communicated with the outlet of the overflow valve, the outlet of the buffer valve is communicated with the oil tank, and the buffer valve comprises an at least partially flexible buffer.

Optionally, the trim valve comprises: a valve body defining a chamber therein, the chamber having a front open end and a rear closed end, the open end constituting an inlet of the cushion valve, the cushion being disposed in the chamber; a spring having one end contacting the closed end of the chamber and the other end contacting the buffer; and a through hole opened between the buffer member and the open end of the chamber between the chamber and the outer periphery of the valve body, the through hole constituting an outlet of the buffer valve.

Optionally, the valve body comprises a stem defining the chamber, a front portion of the stem being provided with a threaded section for installation of the cushion valve; and a head located at the rear side of the stem, the closed end being located within the head, the head being configured with features to facilitate cooperation with an installation tool.

Optionally, the cushion valve further comprises a stopper disposed in the chamber, the stopper configured to limit a farthest position at which the cushion is movable toward the open end of the chamber.

Optionally, a limit step is formed in the cavity, the limit step being configured to limit the farthest position at which the buffer is movable toward the open end of the cavity.

Optionally, the closed end of the chamber is formed by a steel ball press fit into the rear end of the chamber.

Optionally, the cushion valve further comprises a stiffener disposed on an upper surface and/or a lower surface of the cushion and being rigid.

Optionally, the through hole is a plurality of radial through holes, wherein at least one radial through hole is located at an axial position different from other radial through holes.

Optionally, the low pressure assembly further comprises: and the upstream section of the throttling channel is connected to the oil delivery channel at the downstream of the metering unit, and the downstream section of the throttling channel is communicated to the inlet of the buffer valve, or communicated to an oil tank, or communicated to the inlet end of an oil supply pump.

The utility model discloses on the other hand provides a fuel injection system, a serial communication port, include: the low voltage assembly as described above; and a high pressure module connected to the oil delivery passage of the low pressure module and supplied with fuel from the low pressure module through the oil delivery passage.

According to the utility model discloses, can provide a fuel injection system's low pressure subassembly to and contain the fuel injection system of this kind of low pressure subassembly, its operation is more stable, weakens and avoids the vibration and/or the noise that the sudden change of fuel flow rate caused even. Thus, the low pressure assembly of the present application and the fuel system including such a low pressure assembly are more efficient and have a longer service life.

Drawings

The foregoing and other aspects of the present invention will be more fully understood from the following detailed description, taken together with the following drawings.

Fig. 1 is a schematic structural diagram of a possible embodiment of the fuel injection system of the present invention.

Fig. 2 is a partial cross-sectional view of a trim valve of the present invention that may be used in a low pressure assembly.

Fig. 3 is a partial cross-sectional view of another trim valve of the present invention that may be used in a low pressure assembly.

Fig. 4 is a partial cross-sectional view of yet another trim valve of the present invention that may be used in a low pressure assembly.

Fig. 5 is a schematic structural diagram of another possible embodiment of the fuel injection system of the present invention.

Fig. 6 is a schematic structural diagram of yet another possible embodiment of the fuel injection system of the present invention.

Detailed Description

The present application relates to a low pressure assembly for a fuel injection system and to a fuel (in particular diesel) injection system comprising such a low pressure assembly.

Fig. 1 shows an overall arrangement for a fuel injection system according to the invention. Fuel injection systems are used to inject fuel, such as diesel fuel, into an engine. The fuel injection system includes one or more high pressure assemblies, and a low pressure assembly that supplies pre-pressurized fuel to the high pressure assemblies.

In the following description, "upstream" and "downstream", "front" and "rear" will be used, which are defined with respect to the flow of fuel in the respective passages at the time of the fuel supply operation of the low pressure assembly.

The utility model discloses a low pressure subassembly includes fuel feed pump (being low-pressure pump) 1, and its access connection is taking oil passageway L1, and the exit linkage is oil delivery passageway L2.

The oil inlet passage L1 extends to the oil tank 2. The main filter 4 is disposed in the oil inlet passage L1 for filtering foreign substances in the fuel. A manual pump 5 for manual oil supply is connected to the oil feed passage L1 upstream or downstream of the main filter 4.

The oil delivery passage L2 extends to the high-pressure module. The metering unit 6 is disposed in the oil delivery passage L2. The low pressure assembly also includes a throttle passage L4. The throttle passage L4 is disposed downstream of the metering unit 6 and connected to the oil delivery passage L2. A throttle valve 7 is arranged in the throttle passage L4.

The low pressure assembly further includes a spill valve 8 for draining excess fuel from the fuel delivery passage L2; and an overflow channel including a first channel (also referred to as an upstream section of the overflow channel) L5a, a second channel L5b, and a third channel L5c (which together are also referred to as a downstream section of the overflow channel). The illustrated relief valve 8 is of a spring type having a valve housing in which an oil inlet port 8a, an oil outlet port 8b, and a spring chamber port 8c are formed. The oil inlet port 8a is connected to a first passage L5a, and the first passage L5a is connected to an oil delivery passage L2 at a position between the feed pump 1 and the metering unit 6. The oil outlet port 8b is connected to the second passage L5 b.

The low pressure assembly also includes a trim valve 20 for dampening vibration and/or noise caused by sudden changes in flow rate in the passage. The cushion valve 20 is disposed in a downstream section of the overflow passage, specifically, between the second passage L5b and the third passage L5 c. The fuel flowing in the second passage L5b continues to flow through the trim valve 20 into the third passage L5 c. The trim valve 20 includes an inlet port and an outlet port. The fuel in the second passage L5b enters the interior of the trim valve 20 through the inlet port of the trim valve 20 and exits the trim valve 20 through the outlet port of the trim valve 20. The third passage L5c leads to the fuel tank 2.

The spring chamber port 8c is connected to a fourth passage L5d, the fourth passage L5d being connected to a throttle passage L4 downstream of the throttle valve 7; alternatively, the fourth passage L5d is directly connected to the oil inlet passage L1, for example, to a connection (or a micro tank) between the throttle passage L4 and the oil inlet passage L1. Thus, both the fourth passage L5d and the throttle passage L4 are actually connected to the oil intake passage L1.

It should be noted that the spring chamber port 8c of the relief valve 8 may meet or connect with the downstream section of the throttle passage L4, or may meet or connect with the second passage L5b or the third passage L5 c.

The trim valve 20 may be configured as a one-way valve oriented to allow fuel in the second passage L5b to flow through the trim valve 20 into the third passage L5c, but not to allow reverse flow.

The various elements of the low pressure assembly, connected by the passages, except for the main filter 4 and the manual pump 5, are mounted in a common housing 12. High voltage components may also be mounted in the housing 12. In this way, the low-pressure component and the high-pressure component form an integrated high-pressure fuel pump. For a diesel injection system, the output port of the high pressure assembly may be connected to the common rail 11. The main filter 4 is removably mounted to the housing 12 for ease of maintenance or replacement. Each channel is at least partially formed in the common housing 12 in the form of a groove or a hole. The portion of the channel that is outside the common housing 12 may be formed by a channel. The cushion valve 20 and the third passage L5c may be formed in the common housing 12, and more preferably, may be formed outside the common housing 12 for easy removal and replacement.

The metering unit 6 is connected downstream and fluidly connected to the high pressure assembly 3. The high-pressure assembly 3 may comprise one or more high-pressure pumps, typically realized as plunger pumps. Two plunger pumps 9 are shown in fig. 1. The high-pressure module 3 supplies pressurized high-pressure fuel into the common rail 11 by the reciprocating motion of the plunger pump 9 in the plunger housing 10. The fuel in the common rail 11 is then injected into the internal combustion engine via an injection nozzle (not shown) to be sufficiently mixed with air for combustion. The remaining fuel (the portion of fuel not injected into the internal combustion engine through the nozzle) in the common rail 11 enters the return passage L3 through the check valve 12. The return passage L3 opens out into the tank 2.

The implementation of damping when using the fuel injection system shown in fig. 1 is described below.

When the low-pressure module supplies the high-pressure module with fuel, the feed pump 1 is started, which draws in fuel from the fuel tank 2 through the fuel inlet passage L1 and pumps the fuel into the fuel delivery passage L2. A first part of the fuel pumped by the feed pump 1 is supplied in metered manner to the high-pressure module 3 via a metering unit 6. The throttle passage L4 returns an excess portion (portion that does not enter the high-pressure assembly) of the fuel metered by the metering unit 6 to the oil-intake passage L1, and is sucked into the feed pump 1 again. A second portion of the fuel pumped by the feed pump 1 (the portion not metered by the metering unit 6) is returned via a spill channel (comprising a spill valve 8 opening at the fuel pressure). In the case where the fuel flows through the spill valve 8, the fuel enters the cushion valve 20 through the inlet port of the cushion valve 20 and then flows out of the cushion valve 20 through the outlet port of the cushion valve 20 before the fuel flowing through the spill valve 8 returns to the fuel tank 2. This configuration improves the pressure fluctuation of the fuel and reduces the vibration of the fuel injection system.

The specific configuration of the trim valve 20 is described below.

Referring to fig. 2, a schematic diagram of a trim valve of the present invention is shown that may be used in a low pressure assembly. The cushion valve 20 includes a valve body having a length extending in a front-rear direction (a vertical direction as shown in fig. 2). The valve body has two ends opposite to each other in the front-rear direction: a first end (front end in fig. 2) and a second end (back end in fig. 2). The trim valve 20 also includes a chamber 24 defined within the valve body. The chamber 24 extends in the front-rear direction. The chamber 24 has an opening 24a at a first end of the valve body and a closed end proximate a second end of the valve body.

The valve body may include a stem 21 that receives a chamber 24. The front portion of the stem 21 is provided with a threaded section for the installation of said cushion valve 20. This can facilitate installation into a low pressure assembly of the fuel injection system. The valve body may further comprise a head 22 located at the rear side of said stem 21. Optionally, a flange 23 may also be arranged on the valve body. For example, a flange may be provided at the top end of the head 22. The presence of the flange 23 may further facilitate installation of the trim valve 20 into a low pressure assembly of a fuel injection system. The valve body further comprises at least one through hole 25. When the number of the through holes 25 is two or more, a plurality of the through holes 25 may be distributed around the circumference of the valve body. Preferably, a plurality of through holes 25 are distributed equidistantly around the circumference of the valve body. It is also preferable that adjacent through holes 25 are not on the same horizontal line. A through bore 25 fluidly communicates the chamber 24 with the outside of the valve body. The through-holes may be configured as radial through-holes. The "radial direction" is shown as the horizontal direction in fig. 2.

The head 22 may be configured in any suitable shape to facilitate installation. For example, the head 22 may be at least partially configured in a prismatic shape, such as a hexagonal prism, a quadrangular prism, or the like. Additionally or alternatively, the surface of the head 22 may be provided in part as a rough surface. Additionally or alternatively, the bottom surface of the head 22 may be configured with a groove having a depth, and the shape of the groove may be configured in a prismatic shape, such as a hexagonal prism, a quadrangular prism, or the like.

The diameter of the head 22 is preferably larger than the diameter of the stem 21. The diameter of the head 22 may be equal to or smaller than the diameter of the stem 21. Note that the diameter of the head portion 22 and the diameter of the stem portion 21 herein are measured in the front-rear direction perpendicular to the valve body.

A spring 27 is arranged at the closed end of the chamber 24 near the second end of the valve body. The spring 27 is arranged in place preloaded. A buffer 26 is provided above the spring 27. The buffer 26 may be configured as a plate having a certain thickness. The bumper 26 may be made at least partially of a flexible material, such as a flexible material in its entirety. In use, fuel flows into the chamber 24 from the opening 24a of the chamber 24 at the first end of the valve body, contacting and pressing the bumper member 26 (specifically the upper surface of the bumper member 26). When the bumper 26 is pressurized by the fuel, the flexible material of the bumper 26 is compressed and the spring 27 may also be compressed downward (toward the closed end of the chamber), and accordingly, the bumper 26 moves downward. In this manner, fuel flowing into the chamber 24 of the trim valve 20 is dampened. The buffered fuel then flows out through the through-hole 25.

The trim valve 20 may be used in conjunction with the housing 30. The casing 30 has a cavity and an opening fluidly connecting the cavity to the outside of the casing 30. In use, the sleeve 30 is wrapped around the valve body of the cushion valve 20 such that the through-hole 25 of the valve body is completely received in the cavity of the sleeve 30, thereby allowing the through-hole 25 to communicate with the cavity inside the sleeve 30. The opening of the jacket 30 is further communicated with the third passage L5 c.

The trim valve 20 may also be implemented in other forms. For example, as shown in fig. 3, a schematic of another trim valve of the present invention is shown that may be used in a low pressure assembly. The trim valve 20 illustrated in FIG. 3 may generally take the configuration of the trim valve 20 illustrated in FIG. 2, and additionally further include a retainer 28, and a detent cooperating with the retainer 28. The stop 28 is configured to limit the furthest position that the bumper 26 is movable toward the open end of the cavity 24. The stop 28 may be configured as a ring in the form of a snap ring. Correspondingly, at the level between the buffer 26 and the through hole 25, a positioning groove is provided on the inner wall of the valve body, said positioning groove being arranged to be able to mount said stop 28 and fix it in place. The stop 28 is preferably resilient so that it can telescope in the radial direction. In this way, the stopper 28 can be introduced from the opening 24a and fitted to the positioning groove. Such an operation is simple and convenient, and facilitates the manufacturing process of the cushion valve 20. With the stopper 28 seated in the positioning groove, the cushion 26 is prevented from being detached or dislocated. Thus, a more advantageous cushion valve 20 is obtained.

Additionally, the trim valve 20 may further include a reinforcement 29. The reinforcement 29 may take the form of a metal plate, an alloy plate, or the like. The reinforcement 29 may be disposed on the upper surface and/or the lower surface of the buffer 26. The stiffener 29 is rigid. The rigid reinforcement 29 makes up for the disadvantages caused by the flexibility of the buffer 26: for example, the cushion member 26 is deformed or even damaged by an excessively high pressure due to a large amount of fuel flowing into the chamber 24 of the cushion valve 20 in a short time.

FIG. 4 illustrates yet another trim valve that may be used in a low pressure assembly. The trim valve 20 of fig. 4 includes a limit step 31. The stop step 31 may be configured to limit the furthest position that the bumper 26 may move towards the open end of the cavity 24. A stop step 31 is arranged on the inner wall of the valve body at the level between the buffer 26 and the through hole 25 and extends in a radial direction towards the centre of the chamber 24. In this way, the cushion 26 is prevented from becoming detached or misaligned. Thus, a more advantageous cushion valve 20 is obtained. Such a limiting step 31 can replace the limiting member 28 and the positioning groove used in cooperation with the limiting member 28. Such a stop step 31 may also be used as a supplement to the stop 28 and the positioning groove used in cooperation with the stop 28.

Alternatively, the stop step 31 is formed at the intersection of the upper and lower chamber sections by drilling from top to bottom to form an upper chamber section having a first diameter and from bottom to top to form a lower chamber section having a second diameter (wherein the first diameter is smaller than the second diameter). Forming the stopping step 31 in this manner requires a steel ball 30 of a third diameter (wherein the third diameter is slightly larger than the second diameter) to be interference-fitted into the chamber 24 of the valve body in a bottom-up direction to form a closed end of the chamber 24.

The valve body may be constructed of any suitable material capable of withstanding the operating pressures, such as a rigid material. Optionally, a soft/flexible material is used to form at least a portion of the valve body. Preferably, the material constituting at least a part of the valve body has flame retardancy, electrical conductivity, and/or antistatic property.

Fig. 5 shows another general layout for a fuel injection system according to the invention.

The fourth passage L5d is not communicated to the throttle passage L4 as shown in fig. 1, but is communicated to the second passage L5 b. In this way, fuel is made to exist in the spring chamber of the relief valve 8 near the spring chamber port 8c, so that the relief valve 8 operates normally.

In addition, the throttle passage L4 may be communicated to the second passage L5 b. Preferably, the junction of the throttle passage L4 and the second passage L5b is located downstream of the junction of the fourth passage L5d and the second passage L5 b. In this way, the spring chamber of the relief valve 8 near the spring chamber port 8c can obtain a more stable fuel supply.

It follows that in this manner shown in figure 5, the fuel flowing out of the throttle 7 can also be buffered by the buffer valve 20 and then returned to the tank 2. This way, the fuel can be returned directly to the fuel inlet passage L1 after flowing out of the throttle valve 7 as shown in fig. 1. Also, this way has the advantageous function of performing a damping action on both the relief passage and the throttle passage by means of the damping valve 7.

Fig. 6 shows a further general layout for a fuel injection system according to the invention. In some cases, such as where the fuel flow through the throttle valve 7 is small and stable, the throttle passage L4 may be communicated to the return passage L3 without being dampened by the trim valve 20. In this way, the damping valve 20 can be used exclusively for damping the fuel flowing out of the overflow valve 8.

Although the invention is described herein with reference to specific embodiments, the scope of the invention is not intended to be limited to the details shown. Various modifications may be made to these details without departing from the basic underlying principles of the invention.

Claims

1. A low pressure assembly for a fuel injection system, the low pressure assembly comprising:

a supply pump (1) configured to supply pre-pressurized fuel to the high-pressure module through an oil delivery passage (L2);

a metering unit (6) arranged in the oil delivery passage (L2);

an overflow valve (8) arranged in an overflow channel, an upstream section of which is connected to an oil delivery channel (L2) upstream of a metering unit (6), a downstream section of which opens into the oil tank (2);

characterized in that the low-pressure assembly further comprises a cushion valve (20) arranged in the downstream section of the overflow channel, the inlet of the cushion valve (20) communicating with the outlet of the overflow valve (8), the outlet of the cushion valve (20) opening into the tank (2), the cushion valve (20) comprising an at least partially flexible cushion (26) therein.

2. The low pressure assembly of claim 1, wherein the trim valve (20) comprises:

a valve body defining a chamber (24) therein, the chamber (24) having a front open end and a rear closed end, the open end constituting an inlet of the cushion valve (20), the cushion member (26) being disposed in the chamber;

a spring (27) having one end contacting the closed end of the chamber (24) and the other end contacting the buffer (26); and

and a through hole (25) that opens between the buffer (26) and the open end of the chamber (24) and that opens between the chamber (24) and the outer periphery of the valve body, wherein the through hole (25) constitutes an outlet of the buffer valve (20).

3. The low-pressure assembly according to claim 2, characterized in that the valve body comprises a stem (21) defining the chamber (24), the front portion of the stem (21) being provided with a threaded section for the installation of the cushion valve (20); and

a head (22) located behind the stem (21), the closed end being located within the head (22), the head (22) being configured with features to facilitate engagement with an installation tool.

4. The low pressure assembly of claim 3, wherein the trim valve (20) further comprises a stop (28) disposed in the chamber (24), the stop (28) configured to limit a furthest position of the damper (26) movable toward the open end of the chamber (24).

5. The low pressure assembly of claim 3, wherein the chamber (24) has a limit step (31) formed therein, the limit step (31) being configured to limit the furthest position that the bumper (26) is movable toward the open end of the chamber (24).

6. The low pressure assembly of claim 2, wherein the closed end of the chamber (24) is formed by a steel ball (30) press fit into the rear end of the chamber (24).

7. The low pressure assembly according to claim 2, characterized in that the cushion valve (20) further comprises a reinforcement (29), the reinforcement (29) being arranged on an upper surface and/or a lower surface of the cushion (26) and being rigid.

8. Low pressure assembly as claimed in any one of claims 2 to 7, characterized in that said through holes (25) are a plurality of radial through holes, at least one of which is present in an axial position different from the other radial through holes.

9. The low pressure assembly of any of claims 1 to 7, further comprising: a throttle channel (L4) provided with a throttle valve (7), the upstream section of the throttle channel (L4) being connected to the oil delivery channel (L2) downstream of the metering unit (6), the downstream section of the throttle channel (L4) leading to the inlet of the buffer valve (20), or to the oil tank, or to the inlet end of the feed pump (1).

10. A fuel injection system, comprising:

the low-voltage assembly of any one of claims 1-9; and

and a high pressure module connected to the oil delivery passage of the low pressure module and supplied with fuel from the low pressure module through the oil delivery passage.