JP3355699B2 - Accumulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator for accumulating high-pressure fuel pumped from a fuel supply pump and supplying the accumulated fuel to injectors attached to respective cylinders of a diesel engine.

[0002]

2. Description of the Related Art Conventionally, there is known a common rail type fuel injection device in which high-pressure fuel is accumulated in a kind of surge tank called a common rail, and the accumulated high-pressure fuel is injected into a diesel engine by an injector (Japanese Patent Laid-Open No. Sho 5).
9-165858). In this common-rail fuel injection device, the high-pressure fuel stored in the common rail is extremely high at about 150 MPa, and a reflected wave generated by the operation of one injector is propagated to another cylinder through the common rail, and the injector of that cylinder receives the reflected wave. Since this affects the opening / closing timing, there is a problem that the injection amount and the injection timing injected from the injector vary. Therefore, in the pressure accumulating type fuel injection device disclosed in Japanese Patent Application Laid-Open No. 4-287866, a check valve for restricting pressure propagation from the injector to the common rail is provided at a connection between the fuel pipe for guiding high-pressure fuel to the injector and the common rail. There is disclosed a technique for preventing the reflected wave generated by the operation of the injector of one cylinder from being propagated to another cylinder by installing the cylinder.

[0003]

However, in the prior art disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-287866, the propagation of the reflected wave between the injectors can be prevented by the check valve, but the check valve is provided on the common rail. The respective connectors serving as pipe joints on the injector side and the fuel supply pump side are arranged in series facing type via the horizontal holes. For this reason, the influence of the propagation of the pressure pulsation due to the pressure feed from the fuel supply pump on each injector is greatly different depending on the difference in the passage length and the positional relationship to each injector, so that the injection amount injected from each injector is Variations occur. The present invention has been made based on the above circumstances, and an object of the present invention is to reduce variation in injection amount between cylinders by suppressing pressure pulsation caused by pressure feeding from a fuel supply pump.

[0004]

The present invention employs the following technical means to achieve the above object. (Invention of Claim 1) An accumulator that forms an accumulator that accumulates fuel supplied from a fuel supply pump, and supplies the fuel accumulated in the accumulator to injectors attached to each cylinder of the diesel engine. A partition that divides the pressure accumulation chamber into an upstream pressure accumulation chamber into which fuel flows in and a downstream pressure accumulation chamber through which fuel flows out, and the downstream pressure accumulation chamber is formed coaxially on the outer periphery of the upstream pressure accumulation chamber. a double cylindrical structure is, and the said downstream pressure accumulation chamber and the upstream side pressure accumulation chamber to co providing a large number of small holes communicating with the partition wall, the fuel that occurs in the longitudinal direction of the front Symbol upstream accumulation chamber The hole diameter of the small hole is changed so that the flow path resistance becomes substantially uniform according to the pressure distribution. (Invention of claim 2) In the pressure accumulator according to claim 1, the high-pressure fuel supplied from the fuel supply pump flows into the upstream pressure accumulator from both ends in its longitudinal direction, and the plurality of small holes The two fuel tanks having high fuel pressures are arranged such that the flow path resistance gradually decreases from both ends in the longitudinal direction of the upstream pressure accumulation chamber toward the center.
The hole diameter is small at the end, and the central part where the fuel pressure is low
It is characterized in that the hole diameter is gradually increased toward .

[0005]

According to the pressure accumulator of the present invention having the above-described structure, the partition wall having a number of small holes is provided in the pressure accumulator, so that the high-pressure fuel flowing into the upstream pressure accumulator can flow through each small hole from the upstream pressure accumulator. After passing through, it flows into the downstream accumulator. Accordingly, each small hole serves as a flow path resistance when the high-pressure fuel flows from the upstream pressure accumulating chamber to the downstream pressure accumulating chamber, so that the high-pressure fuel pumped from the fuel supply pump is directly discharged from the upstream accumulating chamber to the downstream pressure accumulating chamber. Instead of flowing into the chamber, the air is temporarily received in the upstream accumulator and then flows into the downstream accumulator through the small holes as a whole and evenly. For this reason, the pressure pulsation due to the pressure feeding from the fuel supply pump propagates to the upstream pressure accumulating chamber into which the fuel flows, but when the high pressure fuel of the upstream pressure accumulating chamber flows through each small hole and flows into the downstream pressure accumulating chamber. The pressure pulsation is attenuated, and the influence of the pressure pulsation is reduced in the downstream pressure storage chamber.

[0006]

Next, a first embodiment of the pressure accumulator according to the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a pressure storage container. The pressure accumulating vessel 1 of the present embodiment stores fuel pumped from a fuel supply pump 3 through a high-pressure pipe 2 at a predetermined pressure and supplies the fuel to injectors (not shown) attached to respective cylinders of a diesel engine. Is what you do. The pressure accumulator 1 has a cylindrical container body 4, two sets of cylindrical partition walls 5 coaxially arranged inside the container body 4, and a pair of screwed outer ends of the container body 4. It is composed of a retaining nut 6.

[0007] The container body 4 has an annular fitting portion 40 protruding inwardly at the center in the longitudinal direction. Also,
Four fuel joints 7 are provided on the wall surface of the container body 4 at longitudinally opposed positions at four positions. The fuel joint 7 forms an outlet for high-pressure fuel, and is connected to a fuel pipe (not shown) for guiding high-pressure fuel to each injector.

The cylindrical partition wall 5 is a cylindrical body having a flange portion 5a on the outer periphery, and a connector 5b forming an inlet for high-pressure fuel is formed on the outer periphery of one end side (left side in FIG. 1) of the flange portion 5a. The high pressure pipe 2 connected to the connector 5b communicates with the fuel discharge port 3a of the fuel supply pump 3. On the other end side of the flange portion 5a, a cylindrical portion 5c having a number of orifices 8 on the peripheral wall surface is provided. The two sets of cylindrical partition walls 5 are fitted to the inner surface of the fitting portion 40 of the container body 4 in a liquid-tight manner with the tip surfaces of the cylindrical portions 5c facing each other. The flange portion 5a is connected to the retaining nut 6 with a sealing member 9 interposed therebetween.
And the retaining nut 6 is fixed by tightening the retaining nut 6 to the container body 4.

Thus, the pressure accumulator 1 has a double cylindrical structure including the container body 4 and the cylindrical portion 5c, and has an inner pressure accumulating chamber 10 formed on the inner periphery of the cylindrical portion 5c and the outer periphery of the cylindrical portion 5c. An annular outer pressure accumulating chamber 11 is formed between the outer pressure accumulating chamber 11 and the inner periphery of the container body 4. Therefore, the inner pressure accumulating chamber 10 and the outer pressure accumulating chamber 11 are formed by a large number of orifices 8 formed in the cylindrical portion 5c.
Is communicated by The outer pressure accumulating chamber 11 is separated into one side (the left side in FIG. 1) and the other side of the pressure accumulating vessel 1 by the fitting portion 40, but the inner pressure accumulating chamber 10 formed on the inner periphery of the cylindrical portion 5c is They are in communication with each other. Further, the fuel joints 7 provided on the container body 4 are provided at four places on one side and four places on the other side of the accumulator 1 with the fitting part 40 as a boundary, and are respectively communicated with the outer accumulator 11. ing.

Next, the operation of this embodiment will be described. The high-pressure fuel pressure-fed from the fuel supply pump 3 flows through the high-pressure pipe 2 into the internal pressure accumulating chamber 10 from the connectors 5b disposed at both ends of the pressure accumulating vessel 1. The high-pressure fuel that has flowed into the inner pressure accumulating chamber 10 flows into the outer pressure accumulating chamber 11 through a number of orifices 8 and is supplied to each injector from each fuel joint 7 through a fuel pipe. Accordingly, since each orifice 8 becomes a flow path resistance when the high-pressure fuel flows from the inner pressure accumulating chamber 10 to the outer pressure accumulating chamber 11, the high-pressure fuel pressure-fed from the fuel supply pump 3 is directly discharged from the inner pressure accumulating chamber 10 to the outer pressure accumulating chamber 10. Instead of flowing into the chamber 11, once received in the inner pressure accumulating chamber 10, it flows into the outer accumulating chamber 11 entirely and evenly through each orifice 8.

For this reason, the pressure pulsation accompanying the fuel pumping of the fuel supply pump 3 propagates to the inner pressure accumulating chamber 10 communicating with the fuel discharge port 3a of the fuel supply pump 3 via the high pressure pipe 2, but the inner pressure accumulating chamber 3 10 and the outer pressure accumulating chamber 11 are communicated with each other through a number of orifices 8, so that the inner pressure accumulating chamber 10
When the internal high-pressure fuel flows into the outer pressure accumulating chamber 11, the pressure pulsation transmitted to the inner pressure accumulating chamber 10 is attenuated, and the influence of the pressure pulsation in the outer pressure accumulating chamber 11 is reduced.

Further, in the present embodiment, the outer pressure accumulating chamber 11 formed on one side of the pressure accumulating vessel 1 and the outer pressure accumulating chamber 11 provided on the other side of the pressure accumulating vessel 1 have a liquid-tight structure. By alternately operating (injecting) an injector that receives a supply of high-pressure fuel from one of the outer pressure accumulating chambers 11 and an injector that receives a supply of high-pressure fuel from the other outer pressure accumulating chamber 11, the pulsation (reflected wave) associated with the injection ) Can be prevented. Note that the discharge capacity of the fuel supply pump 3 is feedback-controlled by detecting the pressure in the inner pressure accumulating chamber 10, so that a single pressure sensor may be used even if the outer pressure accumulating chamber 11 is separated.

In this embodiment, since the high-pressure fuel flows into the inner pressure accumulating chamber 10 from both sides of the pressure accumulating vessel 1, the inner pressure accumulating chamber 10 has a high central portion as shown in FIG. A low pressure distribution results. Therefore, contrary to the pressure distribution in the inner pressure accumulating chamber 10, as shown in the schematic diagram of FIG. 3, the hole diameter of the orifice 8 is set small at both ends where the pressure is high, and the orifice 8 moves toward the central part where the pressure is low. By setting the hole diameter of 8 large, fuel can be evenly distributed from the inner pressure accumulating chamber 10 to the outer pressure accumulating chamber 11. In this embodiment, the fuel joints 7 are provided on both sides of the container body 4 in the radial direction.
Is provided, but may be provided only on one side.

Next, a second embodiment of the present invention will be described. FIG. 4 is a sectional view of the pressure storage container 1 according to the present embodiment. The pressure accumulator 1 of the present embodiment includes a hollow container main body 4 and a mesh filter 12 forming a partition having a large number of small holes according to the present invention. The container main body 4 is composed of a container 4a and a container 4b that are divided into two in the longitudinal direction (the vertical direction in FIG. 4), and the fitting portions 4a 'and 4b' of the two containers 4a and 4b are screw-connected to each other, thereby The container body 4 which forms the pressure accumulating chamber 13 is formed. At the end face of the container 4a forming one end face (lower face in FIG. 4) of the accumulator chamber 13, two inflow-side fuel joints 14 for connecting the high pressure pipe 2 are formed, and the other end face of the accumulator chamber 13 (upper face in FIG. ) Is formed with one mounting hole 15 for mounting a pressure sensor (not shown), and an outlet fuel joint 16 for connecting a fuel pipe (not shown) is formed in the end face of the container 4b. It is formed in several places.

The inflow-side fuel joint 14 forms a fuel inlet through which high-pressure fuel pumped from the fuel supply pump 3 flows into the accumulator 13. The high-pressure pipe 2 connects the fuel discharge port 3 a of the fuel supply pump 3 to the fuel discharge port 3 a. Have been contacted. As shown in FIG. 5 (a plan view of the container 4b), the mounting hole 15 for the pressure sensor is provided at the center of the end surface of the container 4b (the center of the accumulator). The outflow-side fuel joint portion 16 forms a fuel outlet through which high-pressure fuel flows out of the accumulator 13, and is connected to an injector (not shown) by a fuel pipe. Each outflow side fuel joint 16 is provided with a mounting hole 1 for a pressure sensor.
5 are provided on the same radius from the center of the container 4b in which they are provided, and are provided at equal intervals in the circumferential direction. The mesh filter 12 is formed by forming a mesh-like metal material of about 10 μm in a circular shape, and is configured such that the accumulator chamber 13 communicates with the inflow fuel joint 14 and the inflow accumulator 13 a communicates with the outflow fuel joint 16. It is sandwiched and held between the container 4a and the container 4b so as to be divided into two into the side pressure accumulating chamber 13b.

Next, the operation of this embodiment will be described. The high-pressure fuel guided to the accumulator 1 via the high-pressure pipe 2 flows into the inflow-side accumulator 13 a through the inflow-side fuel joint portion 14,
After passing through the mesh filter 12 and flowing into the outflow side pressure accumulating chamber 13b, it is supplied from the outflow side fuel joint 16 to each injector via a fuel pipe. Here, the mesh filter 12 is composed of the large number of orifices 8 described in the first embodiment.
Since the high-pressure fuel flows from the inflow side pressure accumulating chamber 13a to the outflow side pressure accumulating chamber 13b, it has a flow path resistance. For this reason, the high-pressure fuel in the inflow-side pressure accumulation chamber 13a flows into the outflow-side pressure accumulation chamber 13b as a whole and uniformly by passing through the mesh filter 12, so that the pressure pulsation propagated in the inflow-side pressure accumulation chamber 13a flows out. Side accumulator 13
It is not propagated into b. Note that, instead of the mesh filter 12, a disk having a large number of small holes in a portion corresponding to the filter portion of the mesh filter 12 may be used.

[0017]

According to the pressure accumulator of the present invention, the pressure accumulator is divided into an upstream accumulator into which fuel flows and a downstream accumulator from which fuel flows by a partition having many small holes. The high-pressure fuel pressure-fed to the container passes through the small holes from the upstream accumulator and flows into the downstream accumulator uniformly and uniformly. For this reason, the pressure pulsation propagated to the upstream pressure accumulating chamber due to the high-pressure fuel pumping is attenuated in the downstream pressure accumulating chamber, so that the variation in the injection amount of the injector can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a pressure accumulator according to a first embodiment.

FIG. 2 is a graph showing a pressure distribution in an inner pressure storage chamber.

FIG. 3 is a schematic diagram when an orifice hole diameter is set according to a pressure distribution.

FIG. 4 is a sectional view of a pressure accumulator according to a second embodiment.

FIG. 5 is a plan view of a pressure accumulator according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Accumulator 3 Fuel supply pump 3a Fuel outlet 5b Connector (fuel inlet) 5c Cylindrical part (partition wall) 7 Fuel joint part (fuel outlet) 8 Orifice (small hole) 10 Inner accumulator (upstream accumulator / first chamber) 1 embodiment) 11 outer pressure accumulator (downstream pressure accumulator / first embodiment) 12 mesh filter (partition wall having many small holes)
Second Embodiment 13 Accumulator (second embodiment) 13a Inlet accumulator (upstream accumulator / second embodiment) 13b Outlet accumulator (downstream accumulator / second embodiment) 14 Inlet fuel Joint (fuel inlet) 16 Outlet fuel joint (fuel outlet)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 55/02 310 F02M 55/02 350

Claims (2)

(57) [Claims] An accumulator for forming an accumulator for accumulating fuel supplied from a fuel supply pump, and for supplying the fuel accumulated in the accumulator to an injector mounted on each cylinder of a diesel engine, A partition is provided to divide the accumulator into an upstream accumulator into which fuel flows and a downstream accumulator from which fuel flows, and the downstream accumulator is formed coaxially around the upstream accumulator. a double cylindrical structure, and said downstream pressure accumulation chamber and the upstream side pressure accumulation chamber to the <br/> both providing multiple small holes communicating with and the partition wall, occurs in the longitudinal direction of the front Symbol upstream accumulation chamber The small holes are formed so that the flow path resistance becomes substantially uniform according to the pressure distribution of the fuel.
A pressure accumulator , wherein the diameter of the hole is changed . 2. The pressure accumulator according to claim 1, wherein the high-pressure fuel supplied from the fuel supply pump flows into the upstream pressure accumulator from both ends in the longitudinal direction of the upstream pressure accumulator. The hole diameter is formed small at both ends of the fuel pressure, so that the flow path resistance gradually decreases from both ends in the longitudinal direction of the upstream side pressure accumulation chamber toward the center .
A pressure accumulator having a hole diameter gradually increasing toward a central portion having a low fuel pressure .