JP4519143B2 - Injector - Google Patents

Description

  The present invention relates to an injector that receives fuel from a predetermined fuel supply source and injects it into an engine.

  Conventionally, an injector is mounted on a direct-injection engine such as a diesel engine, and is used to receive high-pressure fuel from a fuel supply source such as a common rail and directly inject and supply it into a cylinder. The injector includes a needle that opens and closes a nozzle hole provided at a tip, a nozzle chamber into which fuel that exerts pressure in a direction in which the nozzle hole is opened (valve opening direction) with respect to the needle, and the needle Thus, a back pressure chamber is formed in which fuel that exerts pressure in the direction of closing the nozzle hole (the valve closing direction) flows in and out. The injector then causes the fuel to flow out of the back pressure chamber and reduce the pressure in the back pressure chamber, thereby lifting the needle and opening the nozzle hole to inject the fuel.

  In recent years, in order to further increase the combustion efficiency by further atomizing the fuel spray injected from the injector, the fuel injection pressure by the injector has been increased. In addition to simply increasing the fuel supply pressure in the fuel supply source, studies are underway to increase pressure more positively by providing a pressure increasing mechanism in the injector.

  For example, the pressure increasing mechanism includes a pressure increasing piston having a pressure increasing surface on which a fuel as a pressure increasing medium exerts pressure and a pressure increasing surface that exerts pressure on the fuel to be increased. The fuel pressure is increased according to the area ratio. The pressurized fuel flows into the nozzle chamber, exerts pressure on the needle in the valve opening direction, lifts the needle, and is further injected and atomized from the opened nozzle hole (that is, opened to the needle). The pressure of the fuel acting in the valve direction corresponds to the injection pressure injected from the injection hole).

  However, the higher the injection pressure, the stronger the needle at the time of valve opening receives pressure in the valve opening direction. For this reason, when the needle lift speed is increased and it is necessary to shorten the opening period of the nozzle hole as in the case of micro injection, it is difficult to quickly stop the needle lift and to lower the needle to the nozzle hole side. Become. Therefore, when a small amount of injection is required, there is a concern that more fuel than the target amount is always injected, and the combustion efficiency is deteriorated.

  Therefore, when the needle is opened, the lift speed is slowed down, and when the needle is closed, the needle descending speed is increased. Have been proposed (see, for example, Patent Documents 1 and 2). In the injection devices disclosed in Patent Document 1 and Patent Document 2, the back pressure chamber and the high pressure flow channel are connected to the fuel flow channel connecting the back pressure chamber and the three-way switching valve that allows fuel to flow into and out of the back pressure chamber. Two channels, a flow path with a check valve that prevents flow and allows flow from the high-pressure flow path, and a flow path with a throttle to restrict flow are connected in parallel, A difference is provided between the inflow flow rate and the outflow flow rate in the opposite direction.

However, in the disclosed conventional example, it is necessary to form two hydraulic circuits by providing two flow paths and arranging two parts separately, and it is difficult to set because of the size of the body or restrictions on the body There was a problem.
JP-A-8-21332 US Pat. No. 6,644,282

  The present invention has been made to solve the above-mentioned problems, and its object is to simplify the combined structure of a check valve and a throttle for adjusting the operating speed of the needle and to make the hydraulic circuit configuration compact. It is in.

[Means of Claim 1]
According to the injector of the first aspect, the valve is opened or closed with respect to the needle, the nozzle hole provided at the tip for ejecting the fuel, and the needle slidably disposed therein to open and close the nozzle hole. A nozzle body in which fuel is flown in and out so as to supply fuel to the nozzle hole when the needle is opened, and a valve body formed on the side opposite to the nozzle hole of the needle. On the other hand, in an injector having a back pressure chamber through which fuel flows in and out so as to exert pressure in the valve opening or closing direction, the fuel flows into and out of the back pressure chamber. As described above, the back pressure chamber and the fuel flow path connecting the high pressure fuel source and the low pressure flow path, which are the external regions of the back pressure chamber, through the common flow path, and the valve disposed on the fuel flow path and disposed inside when the valve portion of the body is opened by away from the seat portion Through the seat gap of the valve body, a seat gap flow path that allows only fuel to flow from the outside area into the back pressure chamber, and always connected so that fuel can flow between the outside area and the back pressure chamber through the inside of the valve body And a check valve having a valve body flow path.

As a result, it is possible to provide a difference in the flow rate of the fuel into and out of the back pressure chamber, resulting in a slow pressure reduction and recovery (pressurization) of the pressure in the back pressure chamber. As a result, the operating speed of the needle is reduced. Can be adjusted. In addition, since the seat clearance channel and the valve body channel are integrally formed with the check valve, the number of components can be reduced and simplified.
Furthermore, the valve body of the check valve has an open end on the opposite side of the valve portion, and the open end is provided with a plurality of radial slits through which the fuel flowing through the valve body passage passes. It has the reservoir part where the fuel which passed the sheet | seat clearance flow path and the valve body flow path merges in the radial direction outer side.
As a result, even if the open end of the valve body comes into contact with the valve body, the fuel that has passed through the valve body flow channel smoothly flows out to the reservoir through the slit. Combined, a large amount of suitable fuel can be directed to the nozzle back pressure chamber.

[Means of claim 2]
According to the injector of the second aspect, the valve body flow path is disposed at the axial center of the valve body, and the flow direction of the fuel passing through the seat gap flow path in the valve body and the valve body flow path are defined. It is characterized by substantially matching the flow direction of the fuel passing therethrough.
Thereby, the fuel flowing through the seat gap flow path and the valve body flow path can be combined into one hydraulic circuit, which can be simplified. In addition, this one hydraulic circuit can be connected as a common flow path for fuel inflow and outflow.

[Means of claim 3]
According to the injector of claim 3, the flow passage in the valve body is arranged in series with the throttle portion, which is arranged on the outer region side and restricts the amount of fuel flowing between the outer region and the back pressure chamber. And a spring chamber that serves as both housing of a spring member that distributes and biases the valve body toward the external region and fuel circulation.

  As a result, the flow rate of the fuel is regulated, and it is possible to provide an appropriate difference in the flow of the fuel, and the pressure of the back pressure chamber is reduced and the recovery (pressurization) is slow. The lift speed can be reduced and the needle lowering speed can be increased. Further, the hydraulic circuit can be simplified, the structure becomes compact, and the physique can be kept small.

[Means of claim 4]
According to the injector of the fourth aspect, the pressure increasing mechanism that supplies the fuel to the nozzle chamber by increasing the pressure to a pressure higher than the pressure in the back pressure chamber is provided, and the fuel increased by the pressure increasing mechanism is supplied to the nozzle chamber. It is characterized by spraying.
Thus, even in the case of a pressure-increasing injector that includes a pressure-increasing mechanism and supplies pressure-increased fuel to the nozzle chamber, the same effect as that of the first aspect can be obtained.

[Means of claim 5]
According to the injector of the fifth aspect, the back pressure chamber communicates with the common rail for accumulating the fuel via the fuel flow path, and the fuel flows in and out via the check valve.
Thus, even if high pressure fuel flows into and out of the back pressure chamber by communicating with the common rail that accumulates fuel in a high pressure state, the same effect as in the first aspect can be obtained.

  The injector according to the best mode 1 of the present invention opens or closes a needle, a nozzle hole provided at the tip for ejecting fuel, and a needle slidably disposed therein to open and close the nozzle hole. A nozzle body in which a pressure is applied in the valve direction and fuel flows into and out of the nozzle so that the fuel is supplied to the nozzle when the needle is opened; and a valve body formed on the side opposite to the nozzle of the needle. On the other hand, it has a back pressure chamber into which fuel flows in and out so as to exert pressure in the valve opening or closing direction.

  Further, in this injector, the high-pressure fuel source and the low-pressure flow path which are the external region of the back pressure chamber and the back pressure chamber are arranged so that the fuel flows into and out of the back pressure chamber. When the valve body arranged inside the fuel flow path is connected through the common flow path, only the inflow of fuel from the external region to the back pressure chamber is allowed through the seat clearance of the valve body. And a check valve having a valve body flow path that always connects the outer region and the back pressure chamber through the inside of the valve body so that fuel can flow.

A throttle part that regulates the amount of fuel flow is provided at the shaft center on the outer region side of the valve body, and a spring chamber that serves as both housing of the spring member and fuel flow is provided in series with the throttle part. It energizes to the region side and forms a valve body flow path. As a result, the flow direction of the fuel in the seat gap flow path and the flow direction of the fuel in the flow path in the valve body can be substantially matched to be combined into a single fuel flow path. It is possible to provide an appropriate difference in the flow rate of the fuel flow, and the slowdown of pressure reduction and recovery (pressurization) of the back pressure chamber is obtained. As a result, the operating speed of the needle is adjusted and the hydraulic circuit The configuration is simplified and compact.
The best mode of the present invention will be described together with Example 1 shown in the drawings. In the following description, the nozzle side of the injector is referred to as one end side, and the solenoid valve side is referred to as the other end side.

[Configuration of Example 1]
The structure of the injector of Example 1 is demonstrated using FIG. FIG. 1 is an explanatory diagram schematically showing the configuration of the injector and the flow path of the fuel.
The injector 1 includes, for example, a fuel supply pump (not shown) for increasing the pressure of the fuel, a common rail 2 for accumulating the fuel increased in pressure by the fuel supply pump in a high pressure state, and the like, and a fuel for the engine (not shown). An accumulator fuel injection device for injection supply is configured. The injector 1 is mounted on the engine and injects fuel into each cylinder of the engine.

  The injector 1 is a pressure-increasing type that accepts high-pressure fuel from a common rail 2 as a high-pressure fuel source, and further injects the received high-pressure fuel into a cylinder. The pressure increasing type injector 1 includes a nozzle 3 for injecting fuel, a pressure increasing mechanism 4 for increasing and supplying fuel to the nozzle 3, and a command from a predetermined electronic control unit (ECU: not shown). An electromagnetic valve 5 that opens and closes, and a three-way switching valve 6 that switches between a flow path for operating the pressure increase mechanism 4 and a flow path for stopping the operation of the pressure increase mechanism 4 according to the opening and closing of the electromagnetic valve 5. And is operated by a hydraulic circuit that reduces the pressure by discharging the fuel, which is a working medium, to the low pressure side, and is connected to the return flow paths 7, 8 that are low pressure flow paths. In this embodiment, the external region refers to, for example, a component, a part, or a part other than the injector 1, and the common rail 2 as a high-pressure fuel source and the return channels 7 and 8 as low-pressure channels are external regions. It is said.

  The pressure boosting mechanism 4 boosts the fuel based on the Pascal principle, and has a pressure boosting piston 25 whose diameter changes in two steps, large and small, toward one end in the axial direction. The pressure-increasing mechanism 4 receives the pressure of the fuel at the large-diameter pressure-increasing surface 26 and increases the fuel pressure by applying an urging force based on this pressure to the fuel through the small-diameter pressure-increasing surface 27.

  That is, the pressure-increasing piston 25 includes a small-diameter piston portion 28 on one end side and a large-diameter piston portion 29 on the other end side. One end surface of the small-diameter piston portion 28 forms a pressure-increasing surface 27 and the large-diameter piston portion 29. The other end face forms a pressure increasing surface 26. The pressure-increasing piston 25 is accommodated in a cylinder 31 whose diameter changes in two steps of large and small toward one end side in the axial direction (hereinafter, a small diameter portion on one end side of the cylinder 31 is referred to as a small diameter cylinder portion 32, and a large diameter on the other end side). The outer peripheral surface of the large-diameter piston portion 29 is in sliding contact with the inner peripheral surface of the large-diameter cylinder portion 33, and the outer peripheral surface of the small-diameter piston portion 28 is in contact with the inner peripheral surface of the small-diameter cylinder portion 32. Is in sliding contact.

  The small-diameter piston portion 28 seals the small-diameter cylinder portion 32 from the other end side to form the pressurized chamber 16 into which the fuel to be boosted flows in and out, and the large-diameter piston portion 29 becomes the large-diameter cylinder portion. 33 is sealed from one end side to form a pressure increasing chamber 17 into which fuel as a pressure increasing medium flows in and out.

  Further, the large-diameter piston portion 29 seals the large-diameter cylinder portion 33 from the other end side to form a pressure increasing operation chamber 34 into which fuel for operating pressure increasing flows. One end surface of the large-diameter piston portion 29 forms a pressure increasing operation surface 35 that receives the pressure of the fuel in the pressure increasing operation chamber 34, and the area of the pressure increasing operation surface 35 is the area of the pressure increasing surface 26 and the surface to be pressurized 27. It is almost the same as the difference with the area. The pressure increasing operation chamber 34 accommodates a spring 36 that biases the pressure increasing piston 25 to the other side.

  Here, the pressure increasing chamber 17 communicates with the common rail 2 through the fuel flow path 18 and receives fuel accumulated in the common rail 2 as a pressure increasing medium. Further, the pressure increasing chamber 17 communicates with a fuel flow path 39 of the three-way switching valve 6 described later by a fuel flow path 38. The pressure increasing operation chamber 34 is communicated with the fuel flow path 41 of the three-way switching valve 6 by the fuel flow path 40, and the fuel flow path 42 branched from the fuel flow path 40 is connected to the pressure increase chamber 16. The fuel flow path 42 is provided with a check valve 43 that allows only fuel to flow into the pressurized chamber 16.

  With the above configuration, the pressure increasing mechanism 4 performs pressure increase and stop of pressure increase through the flow of fuel into and out of the pressure increase operation chamber 34. That is, when the fuel flows out from the pressure increasing operation chamber 34, the high pressure fuel flows into the pressure increasing chamber 17, the pressure increasing piston 25 is displaced to one end side, the fuel in the pressure increasing chamber 16 is increased, and the nozzle chamber 12. To be supplied. Further, when the fuel flows into the pressure increasing operation chamber 34, the pressure increasing piston 25 is displaced to the other end side and the check valve 43 is opened, and the fuel flows into the pressure increasing chamber 16 and the pressure increasing chamber 16. The fuel pressure increase is stopped and the fuel is not supplied to the nozzle chamber 12.

  The electromagnetic valve 5 is an open / close valve for operating the flow of fuel from the back pressure chamber 45 of the three-way switching valve 6 to be described later, and opens and closes in response to a command from the ECU. The electromagnetic valve 5 is connected between a fuel flow path 46 communicating with the back pressure chamber 45 of the three-way switching valve 6 and a return flow path 7 of a low pressure flow path that is an external region of the injector 1. The fuel flowing out by the valve is discharged to the return flow path 7. The fuel flow path 46 is provided with a throttle 47 between the back pressure chamber 45 and the solenoid valve 5 for regulating the flow rate of fuel outflow from the back pressure chamber 45.

  The three-way switching valve 6 operates the pressure-increasing mechanism 4 by switching between a flow path for the fuel to flow out from the pressure increase operation chamber 34 and a flow path for the fuel to flow into the pressure increase operation chamber 34. Thus, the pressure of the fuel is increased, or the pressure increase mechanism 4 is stopped to stop the pressure increase of the fuel.

  Here, the three-way switching valve 6 includes a valve body 60 slidably accommodated in a cylinder 49 provided in the valve body 20. The valve body 60 includes a piston portion 50 that slides in the cylinder 49 and two valve portions 61 and 62 that make a pair for switching the flow path of fuel in and out. The cylinder 49 includes two fuel seats 39, 41, 52 on the side wall and the peripheral wall, and includes two valve seats 63, 64 that form a pair that can block communication between each. A switching valve structure is formed by a combination of each of the pair of valve portions 61 and 62 and each of the pair of valve seat portions 63 and 64.

  In addition, a reservoir 53 through which fuel flows in and out through the three fuel flow paths 39, 41, 52 is formed on one end side of the valve body 60, and the fuel flow path 39 collects on one end side from the fuel flow path 41. The fuel flow path 41 opens to the reservoir 53 at one end side from the fuel flow path 52. The fuel flow path 39 communicates with the pressure increasing chamber 17 via the fuel flow path 38, communicates with the common rail 2 via the fuel flow path 18, the pressure increasing chamber 17, and the fuel flow path 38. The flow path 40 leads to the pressure increasing operation chamber 34, and the fuel flow path 52 leads to the return flow path 8 of the low pressure flow path that is an external region of the injector 1.

  In addition, a back pressure chamber 45 is formed on the other end side of the valve body 60. The back pressure chamber 45 flows into and out of the fuel that urges the valve body 60 toward the one end side. A fuel flow path 51 branched from the fuel flow path 18 is connected to the back pressure chamber 45, and fuel flows from the common rail 2 into the back pressure chamber 45 through the fuel flow paths 18 and 51. The fuel flow path 51 is provided with a throttle 48 that regulates the flow rate of fuel flowing into the back pressure chamber 45. Further, the back pressure chamber 45 is connected to the electromagnetic valve 5 through the fuel flow path 46.

  When the back pressure chamber 45 is opened by energization of the electromagnetic valve 5 and the back pressure chamber 45 communicates with the return flow path 7, the valve body 60 is displaced to the other end side and the valve portion 61 is seated on the valve seat portion 63. When the valve part 62 is separated from the part 64, the fuel flow path 41 and the fuel flow path 52 communicate with each other, and the fuel flows out from the pressure increasing operation chamber 34 to the return flow path 8. As a result, the displacement of the pressure-increasing piston 25 toward one end is promoted, and the fuel in the pressure-increasing chamber 16 is increased and supplied to the nozzle 3.

  Further, when the valve body 60 is displaced to one end side and the valve portion 62 is seated on the valve seat portion 64 and the valve portion 61 is separated from the valve seat portion 63, the fuel flow path 39 and the fuel flow path 41 communicate with each other. The high pressure fuel flows from the common rail 2 into the pressure increasing operation chamber 34. As a result, the displacement of the pressure-increasing piston 25 toward the other end side is promoted, the pressure increase of the fuel in the pressure-increasing chamber 16 is stopped, and the fuel is not supplied to the nozzle 3.

  Next, the nozzle 3 has a needle 10 that opens and closes the nozzle hole 9, and a back pressure chamber 11 into which fuel that exerts pressure in the direction of closing the nozzle hole 9 with respect to the needle 10 (valve closing direction) A nozzle chamber 12 into which fuel that exerts pressure in the direction in which the hole 9 is opened (valve opening direction) flows in and out is formed. The nozzle 3 also houses a spring 13 that urges the needle 10 in the valve closing direction in the back pressure chamber 11. That is, the needle 10 is urged in the valve closing direction by the fuel pressure (nozzle back pressure) in the back pressure chamber 11 and the spring 13, and by the fuel pressure in the nozzle chamber 12 (referred to as nozzle chamber pressure). It is energized in the valve opening direction.

  Here, the nozzle chamber 12 communicates with the pressurized chamber 16 through the fuel flow path 15. The pressurized chamber 16 is a fuel chamber in which fuel is increased in the pressure increasing mechanism 4, and the pressure increasing mechanism 4 increases the fuel to a pressure higher than the nozzle back pressure and supplies the fuel to the nozzle chamber 12.

  The back pressure chamber 11 is connected to a fuel flow path 19 that branches from a fuel flow path 18 that connects the pressure increasing chamber 17 and the common rail 2, and fuel flow to the back pressure chamber 11 is connected to the fuel flow path 19. A check valve 22 including a valve body 56 having a throttle portion 21 that regulates the flow rate is provided in a direction that allows inflow of fuel into the back pressure chamber 11 and restricts outflow from the back pressure chamber 11. Yes. A forward flow in which a large amount of fuel flows from the common rail 2 to the back pressure chamber 11 via the fuel flow paths 18 and 19 and the check valve 22 is formed, and in the reverse direction, fuel flows from the back pressure chamber 11 in the reverse direction. Only a predetermined flow rate regulated by the throttle portion 21 of the check valve 22 is formed so as to flow out through the fuel flow path 19, so that the fuel flows out of the back pressure chamber 11 and the fuel into the back pressure chamber 11. There is a difference in the inflow flow rate.

  Thereby, the decompression of the back pressure chamber 11 can be performed slowly and the recovery (pressurization) can be performed quickly. Further, the fuel flow path 19 has a common flow path between the high pressure flow path from the high pressure fuel source during forward operation of the connected check valve 22 and the low pressure flow path that discharges to the low pressure side of the external region during reverse operation. It will be used as a road.

  Here, the check valve 22 including the valve body 56 having the throttle portion 21 of the present invention will be described with reference to FIG. FIG. 2A is an axial cross-sectional view showing the configuration of the check valve 22 provided with the throttle portion 21, and FIGS. 2B and 2C are cross sections taken along arrows XX and YY, respectively. FIG.

  The check valve 22 includes a valve body 56 slidably accommodated in a cylinder 55 provided on the other end side of the valve body 20 and a spring 57 that biases the valve body 56 toward the other end side. The valve body 56 is a cylindrical member having a predetermined length, and has a frustoconical valve portion 72 on the other end, a slit 73 having a predetermined width and depth on one end, and an intermediate portion on the outer periphery. Is provided with four chamfers 74, leaving a part of the circular arc of the columnar shape, and further, in the inner circumference, a bottomed end on the other end side and a cylindrical inner cylinder portion opened on one end side, A spring chamber 71 is also provided which serves as both housing of the spring 57 and fuel circulation.

  Accordingly, the valve portion 72 of the valve body 56 is disposed on the other end side of the check valve 22, that is, on the outer region side of the injector 1, and the compression coil type spring 57 is attached to the spring chamber 71, thereby The check valve 22 has a valve body structure that allows only the inflow of the high-pressure fuel in the external region and allows the outflow to the low-pressure flow path to be closed by the biasing force of the spring 57. It can be.

  Further, the valve body 56 is provided with a throttle portion 21 having a predetermined hole diameter at the center of the bottomed portion on the other end side, and is connected to the spring chamber 71 in series with a flow passage B in the valve body (indicated by a thick solid line in the figure). The flow amount of the fuel is regulated by configuring an arrow from above to below. Therefore, forming the throttle portion 21 in the bottomed portion that forms the cylindrical spring chamber 71 allows the spring chamber 71 that houses the spring 57 to also serve as the flow path of the valve body flow path B. In addition, since the narrowed portion 21 is only processed into a small hole having a predetermined diameter, it is effective for simplification.

  The four chamfers 74 form a crescent-shaped fuel passage 68 in combination with the cylinder 55. Therefore, the fuel passage 68 may be secured even if it is a three-chamfer, two-chamfer, or multi-chamfer. .

  On the other hand, the other end side of the cylinder 55 is provided with a seat portion 75 in which the valve portion 72 of the valve body 56 is seated and sealed in the axial direction, and the other end side of the seat portion 75 is connected to the fuel flow path 59. is doing. In addition, one end side of the cylinder 55 forms a space having an inner diameter larger than the inner diameter of the cylinder 55 and is brought into contact with one end side of the valve body 20 to form a reservoir portion 66. The reservoir portion 66 and the valve body 56 is communicated with the open end of the inner cylinder portion via a slit 73, and the reservoir portion 66 is connected to a fuel flow path 67.

  With this configuration, for example, when high-pressure fuel flows from the fuel flow path 59 on the other end side of the check valve 22, the urging force due to the fuel pressure wins against the urging force of the spring 57, and the valve body 56 has one end. Displace to the side. As a result, the valve portion 72 is separated from the seat portion 75, the valve body 56 is opened, and the fuel passes through the seat gap 76 between the valve portion 72 and the seat portion 75 where the valve body 56 is opened. A sheet clearance channel A (an arrow from the upper side to the lower side indicated by a thick solid line in the figure) that flows to the accumulation portion 66 via the fuel passage 68 along the axial direction of the outer periphery of 56 is formed.

  Further, the fuel from the valve body flow path B passing through the throttle portion 21 also flows into the spring chamber 71 of the valve body 56 and flows into the pool portion 66 via the slit 73. At this time, the flow direction of the fuel passing through the seat gap flow path A and the valve body flow path B is both the axial direction, and the fuel flowing through both the seat gap flow path A and the valve body flow path B is It merges with the reservoir 66 and flows into the back pressure chamber 11 of the nozzle 3 via the fuel flow path 67 as a large amount of fuel flow. Therefore, both fuel flow rates can be flowed together in one hydraulic circuit.

  Conversely, for example, when the fuel flows out from the fuel flow path 67 to the fuel flow path 59 via the check valve 22, the fuel pressure in the fuel flow path 67 and the two urging forces of the spring 57 cause the valve to flow. The body 56 is pushed to the other end side, and the valve portion 72 and the seat portion 75 are seated to seal the fuel flow, so that the fuel flows through the valve body flow passage B from the lower side to the upper side in the figure, and the throttle portion 21. Therefore, only the regulated flow rate is allowed to flow.

  That is, when the valve body 56 is opened, the seat gap flow path A that allows only fuel to flow into the back pressure chamber 11 from the outside area through the seat gap 76 of the valve body 56, and the outside area through the inside of the valve body 56 And the back pressure chamber 11 is provided with a valve body passage B that is always connected so that fuel can flow, and passes through the seat gap passage A and the flow direction of the fuel and the valve body passage B. This is a check valve 22 configured to substantially match the fuel flow direction. Accordingly, the high pressure fuel source and the low pressure flow path, which are the external regions of the back pressure chamber 11, can be connected to the fuel flow path 19 that connects the common flow paths with only one hydraulic circuit.

  As described above, the check valve 22 including the valve body 56 having the throttle portion 21 allows the nozzle 3 to be fuel pressure accumulated in the common rail 2 when the needle 10 is lifted in the valve opening direction and the nozzle hole 9 is opened. The back pressure chamber 11 that is always in communication with the (rail pressure) generates an urging force in the valve closing direction of the needle 10, and coupled with this urging force, the back flow chamber 11 further restricts the outflow flow rate by closing the check valve 22. The pressure in the pressure chamber 11 is gradually reduced, so that the lift speed of the needle 10 becomes slower.

  Further, when the pressurized fuel does not flow into the nozzle chamber 12, the urging force due to the nozzle chamber pressure becomes weaker than the resultant force of the urging force due to the nozzle back pressure and the urging force due to the spring 13. 10 is lowered in the valve closing direction, and at the same time, the check valve 22 is opened and the fuel flows into the back pressure chamber 11 through the fuel flow paths 18 and 19. At this time, since the fuel flowing through the check valve 22 flows in a large amount with low resistance in the forward direction, the recovery (pressurization) of the pressure in the back pressure chamber 11 is executed quickly, and the needle 10 descends quickly. The injection hole 9 is closed, and the rapid end of fuel injection (sharp cut) can be realized.

[Operation of Example 1]
The operation of the injector 1 according to the first embodiment will be described focusing on the operation of the check valve 22 including the throttle portion 21.
First, in the three-way switching valve 6, the gap between the fuel flow path 39 and the fuel flow path 41 is opened and the gap between the fuel flow path 41 and the fuel flow path 52 is closed. In this state, the common rail 2 and the pressure increasing operation chamber 34 communicate with each other, the pressure increasing mechanism 4 is not operated, and fuel pressure is not increased.

  When the solenoid valve 5 is actuated to open the back pressure chamber 45 of the three-way switching valve 6, the fuel in the back pressure chamber 45 of the three-way switching valve 6 flows into the return flow path 7 and the back pressure in the back pressure chamber 45 decreases. To do. As a result, the three-way switching valve 6 is activated, the valve body 60 starts to be displaced to the other end side, the valve part 61 is seated on the valve seat part 63, and the gap between the fuel flow path 39 and the fuel flow path 41 is established. While being closed, the valve portion 62 and the valve seat portion 64 are separated from each other, the space between the fuel flow path 41 and the fuel flow path 52 is opened, and the fuel in the pressure increasing operation chamber 34 flows out to the return flow path 8. The back pressure in the pressure increasing operation chamber 34 is reduced. For this reason, the pressure-increasing piston 25 is displaced to one end side, and the fuel is increased in pressure to the pressure increase chamber 16 and supplied to the nozzle chamber 12.

  When the increased fuel is supplied to the nozzle chamber 12, the urging force due to the increased nozzle chamber pressure becomes stronger than the resultant force of the urging force due to the reduced nozzle back pressure and the urging force due to the spring 13, and the needle 10 The nozzle hole 9 is opened by being displaced in the valve opening direction. As a result, fuel is injected from the injection hole 9 by the increased injection pressure, and the fuel flows out from the back pressure chamber 11 through the fuel flow path 59 of the one flow path structure of the check valve 22 and the fuel flow path 19 almost simultaneously. To do.

  At this time, since the fuel flows through the check valve 22 in the reverse direction, the check valve 22 is closed, and the fuel flowing out only through the valve body passage B is regulated to a predetermined flow rate. The depressurization of the needle 10 becomes gradual, and therefore the lift speed of the needle 10 becomes slow.

  Further, when the pressure increase of the fuel by the pressure increase mechanism 4 is stopped, the increased pressure fuel does not flow into the nozzle chamber 12. As a result, the urging force due to the nozzle chamber pressure becomes weaker than the resultant force of the urging force due to the nozzle back pressure and the urging force due to the spring 13, so that the needle 10 is displaced in the valve closing direction and at the same time the check valve 22 is opened. The fuel flows into the back pressure chamber 11 from the fuel passage 19 through the seat gap passage A. At this time, since the fuel in the seat gap flow path A of the check valve 22 flows in a large amount with low resistance in the forward direction, the injection hole 9 is quickly closed and a rapid end of fuel injection (sharp cut) is realized. .

[Effect of Example 1]
According to the injector 1 of the first embodiment, in the region outside the back pressure chamber 11 and the back pressure chamber 11, the fuel flows into the back pressure chamber 11 and the fuel flows out of the back pressure chamber 11. When a valve body 56 disposed on the fuel flow path 19 and disposed inside the fuel flow path 19 that connects a high-pressure fuel source and a low-pressure flow path through a common flow path is opened, the valve body The fuel flows between the outer space and the back pressure chamber 11 through the inside of the valve body 56 and the seat space flow path A that allows only the fuel to flow into the back pressure chamber 11 from the outer region through the seat clearance 76 of 56. And a check valve 22 having a valve body flow path B that is always connected.

  In addition, a throttle portion 21 that regulates the amount of fuel flow is provided at the shaft center on the outer region side of the valve body 56, and a spring chamber 71 that serves as both housing of the spring 57 and fuel flow is provided in series with the throttle portion 21. Accordingly, the valve body channel B is formed while being urged toward the external region side. As a result, the fuel flow direction in the seat gap flow path A and the fuel flow direction in the valve body flow path B can be substantially matched to be combined into one fuel flow path. Since it is possible to provide an appropriate difference in the flow rate of the fuel flowing into and out of the chamber 11, the pressure in the back pressure chamber 11 is reduced and the recovery (pressurization) is slow. As a result, the operating speed of the needle 10 is reduced. Can be adjusted.

  Therefore, even if the injection pressure of the injected fuel is high, the outflow flow rate of the fuel from the back pressure chamber 11 is regulated, and the pressure reduction in the back pressure chamber 11 occurs slowly, so the lift speed of the needle 10 is slow and the injection hole The injection amount (injection rate) from 9 does not rise suddenly from zero but rises gently. Thereby, it becomes possible to perform the micro injection by the injector 1 with high accuracy. Further, since the flow rate of fuel into the back pressure chamber 11 is large, and the pressure recovery (pressurization) of the back pressure chamber 11 occurs quickly, the descending speed of the needle 10 is increased and the fuel injection is rapidly performed. It can be finished (sharp cut).

  In the present embodiment, the valve body channel B is disposed on the outer region side, and the throttle portion 21 that regulates the amount of fuel flowing between the outer region and the back pressure chamber 11 is centered on the shaft of the valve body 56. In addition, since it is arranged in series with the spring chamber 71 of the valve body 56 and the fuel is made to flow in a manner substantially matching the flow direction of the fuel passing through the seat gap flow path A, the structure is simplified and the fuel is supplied. It is possible to combine them as a single hydraulic circuit, and the size and size can be reduced.

[Modification]
In the injector 1 of the first embodiment, the pressure increasing mechanism 4 that increases the fuel pressure to be higher than the pressure in the back pressure chamber 11 and supplies the fuel to the nozzle chamber 12, and the back pressure chamber 11 stores the fuel in a high pressure state. The present invention has been described with respect to an example in which the common rail 2 is always in communication. However, the present invention is not limited to this example, and the back pressure chamber 11 and the common rail 2 are always in communication even in a normal injector that does not include the pressure increasing mechanism 4. The present invention can be employed in any case even in an injector having a configuration that does not, and similar effects can be obtained.

It is explanatory drawing which shows the structure of an injector, and the flow path of a fuel typically (Example 1). (A) is an axial sectional view showing the configuration of a check valve provided with a throttle part, (b) is a sectional view taken along the line XX, and (c) is taken along the line YY. (Example 1) which is sectional drawing.

Explanation of symbols

1 Injector 2 Common rail (high pressure fuel source, fuel supply source)
3 Nozzle 4 Pressure increase mechanism 5 Solenoid valve 6 Three-way switching valve 7, 8 Return flow path (low pressure flow path)
DESCRIPTION OF SYMBOLS 9 Injection hole 10 Needle 11 Back pressure chamber 12 Nozzle chamber 13 Spring 19 Fuel flow path 20 Valve body 21 Restriction part 22 Check valve 56 Valve body 57 Spring (spring member)
71 Spring chamber 76 Seat gap A Sheet gap channel B Valve body channel

Claims (5)

Needle,
Pressure is applied in the valve opening or closing direction to a nozzle hole provided at the tip for ejecting fuel and the needle slidably disposed therein to open and close the nozzle hole, and the needle is opened. A valve body in which a nozzle chamber into which fuel flows in and out to supply fuel to the nozzle hole is sometimes formed;
A back pressure chamber that is provided on the side opposite to the injection hole of the needle and into which fuel flows in and out so as to exert pressure on the needle in a valve opening or closing direction;
The back pressure chamber and a high pressure fuel source and a low pressure flow path that are external regions of the back pressure chamber are arranged so that fuel flows into the back pressure chamber and fuel flows out of the back pressure chamber. A fuel flow path connected through a shared flow path;
When the valve portion of the valve body arranged on the fuel flow path and separated from the seat portion opens and opens , the seat space of the valve body passes through the gap between the external region and the back pressure chamber. A non-return check having a seat gap flow path that allows only fuel to flow in, and a valve body flow path that always connects the outer region and the back pressure chamber through the inside of the valve body so that fuel can flow. A valve ,
The valve body of the check valve has an open end opposite to the valve portion, and the open end is provided with a plurality of radial slits through which the fuel flowing through the valve body passage passes. An injector having a reservoir portion where fuel that has passed through the seat gap flow path and the valve body flow path joins on a radially outer side of the slit . The injector according to claim 1, wherein
The valve body flow path is disposed at the axial center of the valve body, and the flow direction of fuel passing through the seat gap flow path and the flow of fuel passing through the valve body flow path inside the valve body An injector characterized by substantially matching the direction. Injector according to claim 1 or 2,
The valve body flow path is disposed on the outer region side and restricts the amount of fuel flowing between the outer region and the back pressure chamber, and is disposed in series with the restrictor. An injector comprising: a spring chamber that serves as both housing of a spring member biased toward the outer region side and fuel circulation. The injector according to any one of claims 1 to 3,
A pressure-increasing mechanism that boosts the fuel to a pressure higher than the pressure in the back pressure chamber and supplies the fuel to the nozzle chamber, and supplies the fuel boosted by the pressure-increasing mechanism to the nozzle chamber and injects the fuel; Injector. Injector according to any one of claims 1 to 4,
The back pressure chamber communicates with the common rail for accumulating fuel via the fuel flow path,
An injector wherein fuel flows in and out through the check valve.

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