JP2015034529A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent low temperature brittle fracture of a common rail.SOLUTION: A common rail 1 is formed with a discharge passage 15 which extends along the longitudinal direction of the common rail, and fuel discharged via an orifice part 312 of a pressure reducing valve 3 is returned to a fuel tank 6 via the discharge passage 15. With this, when the fuel, which passes the orifice part 312 and is raised in temperature, passes through the discharge passage 15, the common rail 1 is warmed by the high temperature fuel and as a result, low temperature brittle fracture of the common rail 1 is prevented.

Description

  The present invention relates to a fuel injection device including a common rail that stores high-pressure fuel.

  Conventionally, as this type of fuel injection device, for example, there is one described in Patent Document 1. The fuel injection device described in Patent Document 1 adjusts the pressure of the fuel in the pressure accumulating chamber by discharging the fuel in the pressure accumulating chamber to the low pressure portion via the orifice portion of the common rail having the pressure accumulating chamber for storing high pressure fuel. A pressure reducing valve is provided.

JP 2012-26421 A

  However, in the case of a common rail using non-tempered steel that is brittle at low temperatures, there is a risk of low-temperature brittle fracture in cold regions.

  In view of the above points, an object of the present invention is to prevent low temperature brittle fracture of a common rail.

  In order to achieve the above object, according to the first aspect of the present invention, a cylindrical common rail having a pressure accumulating chamber for storing high-pressure fuel and fuel in the pressure accumulating chamber by discharging the fuel in the pressure accumulating chamber through an orifice portion. A fuel injection device comprising: a pressure reducing valve that adjusts the pressure of the fuel; and a pipe that guides fuel discharged from the pressure reducing valve to a low pressure portion, wherein the common rail extends along a longitudinal direction of the common rail, and the orifice It has a discharge passage through which fuel discharged through the section passes, and the discharge passage is connected to the low pressure section through the piping.

  By the way, it is known that the fuel that has passed through the orifice portion of the pressure reducing valve is several tens of degrees Celsius higher than the fuel in the pressure accumulating chamber (may be about 50 degrees Celsius depending on the operating condition).

  Therefore, when the fuel discharged through the orifice passes through the discharge passage extending along the longitudinal direction of the common rail, the common rail is warmed up by the high temperature fuel, and as a result, the low temperature brittle fracture of the common rail is prevented. .

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a figure which shows the structure of the fuel-injection apparatus which concerns on 1st Embodiment of this invention. It is AA sectional drawing of FIG. It is a figure which shows the modification of 1st Embodiment. It is BB sectional drawing of FIG. It is a figure which shows the structure of the fuel-injection apparatus which concerns on 2nd Embodiment of this invention. It is CC sectional drawing of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
A first embodiment of the present invention will be described.

  The fuel injection device includes a cylindrical common rail 1 having a pressure accumulating chamber 11 that stores high-pressure fuel, a pressure reducing valve 3 that discharges the fuel in the pressure accumulating chamber 11 and adjusts the pressure of the fuel in the pressure accumulating chamber 11, and the pressure accumulating chamber 11 And a pressure sensor 4 for outputting an electric signal corresponding to the fuel pressure.

  The common rail 1 is made of metal and has a substantially cylindrical shape. The pressure accumulating chamber 11 penetrates from one end in the longitudinal direction of the common rail 1 to the other end. A pressure reducing valve 3 is attached to one end of the common rail 1 so as to close one end of the pressure accumulating chamber 11. A pressure sensor 4 is attached to the other end of the common rail 1 so as to close the other end of the pressure accumulating chamber 11. A connection space 12 that is an annular space is formed between the inner peripheral surface on one end side of the common rail 1 and the outer peripheral surface of the pressure reducing valve 3.

  The common rail 1 includes one inflow port 13 that communicates with the pressure accumulation chamber 11, and high-pressure fuel pumped from a supply pump (not shown) is supplied to the pressure accumulation chamber 11 through the inflow port 13.

  The common rail 1 includes four outflow ports 14 communicating with the pressure accumulating chamber 11, and an injector (not shown) for injecting fuel into a four-cylinder internal combustion engine (not shown) is connected to the outflow port 14. 11 is supplied to the injector through the outflow port 14.

  The common rail 1 includes a discharge passage 15 that extends along the longitudinal direction of the common rail 1. More specifically, the discharge passage 15 extends in parallel with the pressure accumulation chamber 11 adjacent to the pressure accumulation chamber 11. Further, the discharge passage 15 is a hole having a circular cross section processed from the other end side to the one end side of the common rail 1, one end side thereof communicating with the connection space 12, and the other end side being a press-fit plug 16. It is blocked by

  The common rail 1 includes a single discharge port 17 that communicates with the discharge passage 15. A pipe 5 is connected to the discharge port 17, and the discharge passage 15 is connected to the fuel tank 6 as a low pressure part via the pipe 5.

  The pressure reducing valve 3 includes a bottomed cylindrical housing 31. At the center in the radial direction of the bottom of the housing 31, there are a bottom discharge hole 311 communicating with the pressure accumulating chamber 11, and an orifice portion 312 that is arranged in series with the bottom discharge hole 311 and has a smaller passage area than the bottom discharge hole 311. A valve seat 313 surrounding the opening end of the orifice 312 is formed.

  A cylindrical portion discharge hole 314 that penetrates the cylindrical portion is formed in the cylindrical portion of the housing 31, and the cylindrical portion discharge hole 314 communicates with the connection space 12.

  Inside the housing 31 are a valve body 32 that opens and closes between the orifice portion 312 and the cylindrical portion discharge hole 314 by contacting and separating from the valve seat 313, an armature 33 integrated with the valve body 32, the valve body 32, and the armature 33. And a cylindrical coil 35 that forms a magnetic field when energized. The opening of the housing 31 is closed by the stator core 36.

  The housing 31, the armature 33, and the stator core 36 are all made of a magnetic metal and form a magnetic circuit. The valve element 32 and the armature 33 are attracted toward the stator core 36 (that is, in the valve opening direction) by energizing the coil 35.

  In the above configuration, when the coil 35 of the pressure reducing valve 3 is not energized, the armature 33 and the valve body 32 are urged toward the valve closing direction by the spring 34, the valve body 32 abuts on the valve seat 313, and the orifice portion 312. And the cylindrical portion discharge hole 314 are blocked.

  On the other hand, when the coil 35 of the pressure reducing valve 3 is energized, the armature 33 is attracted to the stator core 36 side, the valve body 32 moves together with the armature 33, the valve body 32 moves away from the valve seat 313, and the orifice portion 312 and the cylindrical portion. The discharge holes 314 communicate with each other.

  As a result, the high-pressure fuel in the pressure accumulating chamber 11 is discharged to the fuel tank 6 via the bottom discharge hole 311, the orifice part 312, the cylindrical part discharge hole 314, the connection space 12, the discharge passage 15, and the pipe 5. Incidentally, the pressure reducing valve 3 opens, for example, every time fuel is injected from the injector, and discharges the high pressure fuel in the pressure accumulating chamber 11 to the fuel tank 6, whereby the pressure of the fuel in the pressure accumulating chamber 11 is set to a predetermined pressure. Adjust to.

  Here, the common rail 1 is also at a low temperature immediately after starting the internal combustion engine in a cold region, but when the fuel whose temperature has increased through the orifice 312 passes through the discharge passage 15, the common rail 1 is heated by the high temperature fuel. 1 is warmed up, and as a result, the low temperature brittle fracture of the common rail 1 is prevented.

  According to this embodiment, the common rail 1 can be warmed up by the fuel whose temperature has risen after passing through the orifice portion 312, and low temperature brittle fracture of the common rail 1 can be prevented.

  In addition, by appropriately setting the wall thickness, material hardness, yield point, and auto-fragment pressure, the strength of the partition wall 18 between the pressure accumulation chamber 11 and the discharge passage 15 is made lower than the strength of other parts, In the common rail 1, the partition wall 18 is destroyed before the outer peripheral wall, and the fuel leaks from the pressure accumulating chamber 11 to the discharge passage 15 side. Therefore, external leakage of fuel can be prevented.

  Furthermore, if the partition 18 is cracked at a predetermined pressure or more by setting the strength of the partition 18 strictly, the function of limiting the maximum fuel pressure in the pressure accumulating chamber 11 can be exhibited, and the conventional pressure limiter can be eliminated. .

  In this case, a thin portion 19 may be provided in a portion of the partition wall 18 facing the hole of the discharge port 17, and the strength of the partition wall 18 may be managed by the thin portion 19. Incidentally, the thin wall portion 19 can be machined through a cutting tool in the hole of the discharge port 17.

  In the above embodiment, the discharge passage 15 is processed from the other end side of the common rail 1 (that is, the pressure sensor 4 side). However, as in the modification shown in FIGS. You may process from one end side (namely, pressure-reducing valve 3 side).

(Second Embodiment)
A second embodiment of the present invention will be described. In this embodiment, the configuration of the discharge passage 15 is changed, and the other parts are the same as those in the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  As shown in FIGS. 5 and 6, the discharge passage 15 of the present embodiment is a groove having a rectangular cross section formed on the outer peripheral surface of the common rail 1. The discharge passage 15 can be formed by cutting or forging.

  The discharge passage 15 extends along the longitudinal direction of the common rail 1, and more specifically, extends in parallel with the pressure accumulation chamber 11 adjacent to the pressure accumulation chamber 11. The discharge passage 15 communicates with the connection space 12 through the communication hole 21.

  The opening of the discharge passage 15 is closed with a metal lid 22. More specifically, the lid 22 is attached to the common rail 1 with bolts 24 with a rubber seal member 23 sandwiched between the common rail 1 and the lid 22.

  The lid 22 includes a single discharge port 25 that communicates with the discharge passage 15. A pipe 5 is connected to the discharge port 25, and the discharge passage 15 is connected to the fuel tank 6 through the pipe 5.

  According to this embodiment, the same effect as that of the first embodiment can be obtained.

(Other embodiments)
In addition, this invention is not limited to above-described embodiment, In the range described in the claim, it can change suitably.

  In each of the above-described embodiments, it is needless to say that elements constituting the embodiment are not necessarily essential unless explicitly stated as essential and clearly considered essential in principle. Yes.

  Further, in each of the above embodiments, when numerical values such as the number, numerical value, quantity, range, etc. of the constituent elements of the embodiment are mentioned, it is clearly limited to a specific number when clearly indicated as essential and in principle. The number is not limited to the specific number except for the case.

  Further, in each of the above embodiments, when referring to the shape, positional relationship, etc. of the component, etc., the shape, unless otherwise specified and in principle limited to a specific shape, positional relationship, etc. It is not limited to the positional relationship or the like.

1 Common rail 3 Pressure reducing valve 5 Piping 6 Fuel tank (low pressure part)
11 Accumulation chamber 15 Discharge passage 312 Orifice

Claims (4)

A cylindrical common rail (1) having a pressure accumulating chamber (11) for storing high-pressure fuel;
A pressure reducing valve (3) for discharging the fuel in the pressure accumulating chamber through an orifice (312) to adjust the pressure of the fuel in the pressure accumulating chamber;
A fuel injection device comprising a pipe (5) for guiding the fuel discharged from the pressure reducing valve to the low pressure part (6),
The common rail includes a discharge passage (15) that extends along a longitudinal direction of the common rail and through which fuel discharged through the orifice portion passes.
The fuel injection apparatus, wherein the discharge passage is connected to a low pressure portion through the pipe.   The fuel injection device according to claim 1, wherein the discharge passage is a hole. The discharge passage is a groove formed on the outer peripheral surface of the common rail,
The fuel injection device according to claim 1, wherein the opening of the groove is closed by a lid (22).   The fuel injection device according to any one of claims 1 to 3, wherein the pressure reducing valve is attached to one end of the common rail in a longitudinal direction.

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