JP2020051368A - Fuel injection device and work machine - Google Patents

Abstract

To provide a fuel injection device having a structure in which a needle can slide in a nozzle body smoothly.SOLUTION: A fuel injection device includes: a pressure accumulation chamber in which a fuel in a high pressure state is stored; a nozzle body having an injection hole which injects the fuel stored in the pressure accumulation chamber; and a needle which slides along an inner wall of the nozzle body between a closing position in which the needle closes the injection hole and an open position in which the needle opens the injection hole. The needle includes a conical part, in which its diameter reduces in a slide direction, so that the diameter becomes smaller toward the injection hole.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fuel injection device that injects fuel into a cylinder of an engine, and a work machine including an engine having the fuel injection device.

  Patent Literature 1 describes a fuel injection device that injects fuel supplied via a common rail by electrical control. The fuel injection device described in Patent Literature 1 has a fuel reservoir in which fuel supplied from a common rail is stored, a nozzle body in which a fuel injection hole for injecting fuel is formed, and a fuel injection hole that moves up and down in the nozzle body. And a solenoid for controlling the up and down movement of the valve needle.

JP-A-2014-14272

  With the stricter exhaust gas regulation values of diesel engines in recent years, fuel sulfur has been reduced. Therefore, abrasion of the sliding contact portion in the fuel injection device is prevented by adding a lubricity improver instead of the sulfur component which has conventionally functioned as a lubricant. Further, in the fuel injection device having the above-described configuration, it is conceivable to form a circumferential groove on the outer surface of the valve needle in order to promote the formation of an oil film between the nozzle body and the valve needle in sliding contact.

  However, in the configuration of the prior art, when the lubricity improver and the circumferential groove of the valve needle are used together, the deteriorated lubricity improver adheres to the circumferential groove, and the needle in the fuel injection device is moved to the nozzle body. There is a risk of sticking.

  The present invention has been made in view of the above situation, and has as its object to provide a fuel injection device having a configuration in which a needle can slide smoothly in a nozzle body, and an engine having such a fuel injection device. To provide a working machine.

  In order to achieve the above object, the present invention provides a fuel injection device for injecting fuel into a cylinder of an engine, comprising: a pressure accumulating chamber in which fuel in a high pressure state is stored; and an injector for injecting fuel stored in the pressure accumulating chamber. A nozzle body having a hole, a needle that slides along an inner wall of the nozzle body between a closed position that closes the injection hole and an open position that opens the injection hole, wherein the needle is It is characterized in that it includes a conical portion whose diameter decreases in the sliding direction so that the diameter decreases toward the injection hole.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel injection device of a structure which a needle can slide smoothly in a nozzle body can be obtained. In addition, problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

FIG. 1 is a side view of a hydraulic excavator as a representative example of a working machine according to the present invention. FIG. 1 is a schematic diagram showing a configuration of an engine. FIG. 2 is a vertical cross-sectional view schematically showing the internal structure of the injector. The figure which shows the needle of an open position. The figure which shows the needle of a closing position.

  An embodiment of a work machine according to the present invention will be described with reference to the drawings. FIG. 1 is a side view of a hydraulic excavator 1 which is a representative example of a working machine according to the present invention. The front, rear, left and right in this specification are based on the viewpoint of an operator who operates while operating on the excavator 1 unless otherwise specified. Further, a specific example of the work machine is not limited to the hydraulic excavator 1 and may be a dump truck, a motor grader, a wheel loader, or the like.

  As shown in FIG. 1, the excavator 1 includes a traveling unit 2 and a revolving unit 3 that is pivotally mounted on the upper side of the traveling unit 2. The revolving unit 3 includes a revolving frame 5 serving as a base, a cab 7 disposed on the left side in front of the revolving frame 5, a front work machine 4 attached to a front center of the revolving frame 5 so as to be rotatable in a vertical direction, The vehicle includes a counterweight 6 disposed behind the turning frame 5 and an engine 10 that generates a driving force for operating the hydraulic excavator 1.

  The cab 7 has an internal space in which a worker who operates the excavator 1 is mounted. The front work machine 4 includes a boom 4a, an arm 4b, a bucket 4c, and hydraulic cylinders (hydraulic actuators) 4d to 4f. The counterweight 6 is for maintaining a weight balance with the front work machine 4, and is a heavy object having an arc shape.

  In the internal space of the cab 7, the operation of the operator for moving the traveling body 2, rotating the revolving body 3 and operating the front work machine 4 is received, and a signal corresponding to the received operation is sent to a controller (not shown). ) Are provided with operating devices (steering, pedals, levers, switches, etc.). That is, the operator who boarded the cab 7 operates the operating device, so that the excavator 1 operates.

  FIG. 2 is a schematic diagram showing the configuration of the engine 10. As shown in FIG. As shown in FIG. 2, the engine 10 includes a cylinder block 12 in which a cylinder 11 is formed, a piston 13 that reciprocates in the cylinder 11 in a longitudinal direction, and converts a linear motion of the piston 13 into a rotary motion. Connecting rod 15 for rotating the crankshaft 14, an intake valve 17 for opening and closing an intake port 16 for supplying air to the cylinder 11, an exhaust valve 19 for opening and closing an exhaust port 18 for discharging air from the cylinder 11, and a cylinder 11. An injector (fuel injection device) 20 for injecting fuel (for example, light oil).

  The engine 10 repeats the intake stroke, the compression stroke, the combustion stroke, and the exhaust stroke, thereby causing the traveling body 2 to travel, rotating the revolving body 3, and generating a driving force for operating the front work machine 4. The traveling body 2, the revolving superstructure 3, and the front work machine 4 correspond to the "operating unit" of the present invention.

  The suction stroke is a stroke in which the piston 13 is lowered in the cylinder 11 with the intake valve 17 opened and the exhaust valve 19 closed. Thereby, air flows into the cylinder 11 through the intake port 16. The compression stroke is a stroke in which the piston 13 is raised in the cylinder 11 with the intake valve 17 and the exhaust valve 19 closed. As a result, the air in the cylinder 11 is compressed to a high temperature and high pressure state.

  The combustion stroke is a stroke in which the fuel injected from the injector 20 is burned. Specifically, when fuel is injected from the injector 20 into the cylinder 11, the fuel mixes with high-temperature and high-pressure air and ignites spontaneously. Thereby, the air in the cylinder 11 expands and pushes down the piston 13. The exhaust stroke is a stroke in which the piston 13 is raised in the cylinder 11 with the intake valve 17 closed and the exhaust valve 19 opened. As a result, the burned fuel and air are discharged from the cylinder 11 through the exhaust port 18.

  In the intake stroke, the compression stroke, the combustion stroke, and the exhaust stroke, the piston 13 that moves up and down in the cylinder 11 rotates the crankshaft 14 via the connecting rod 15. By driving the drive wheels, the generator, the hydraulic pump, and the like by the rotation of the crankshaft 14, the hydraulic excavator 1 operates.

  The fuel stored in the fuel tank 51 is supplied to the injector 20 via a hydraulic pump 52 and a common rail 53. The hydraulic pump 52 pumps the fuel stored in the fuel tank 51 to the common rail 53 by pressure. The common rail 53 accumulates the fuel supplied from the hydraulic pump 52 in a high pressure state and supplies the fuel to the injector 20 through the high pressure passage 54. Further, the injector 20 injects the fuel supplied from the common rail 53 into the cylinder 11 and recirculates the leaked fuel to the fuel tank 51 through the low-pressure passage 55.

  The operation of the excavator 1 including the hydraulic pump 52 and the injector 20 is controlled by an ECM (Engine Control Module) 56. Although not shown, the ECM 56 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory).

  The ECM 56 controls the operation of the excavator 1 in cooperation with software and hardware by reading and executing the program code stored in the ROM by the CPU. However, the specific configuration of the ECM 56 is not limited to this, and may be realized by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

  Next, the configuration of the injector 20 according to the present embodiment will be described with reference to FIGS. FIG. 3 is a longitudinal sectional view schematically showing the internal structure of the injector 20. FIG. 4 is a diagram illustrating the needle 21 in the open position. FIG. 5 is a diagram illustrating the needle 21 in the closed position. As shown in FIG. 3, the injector 20 mainly includes a nozzle body 30, a needle 21, a control piston 22, a control valve 23, and a solenoid 24. The nozzle body 30 mainly includes a pressure accumulation chamber 31, an injection hole 32, a back pressure control chamber 33, and a control valve chamber.

  The pressure accumulating chamber 31 is a space for storing the fuel supplied from the common rail 53 through the high-pressure channel 54 while maintaining the high-pressure state. The injection hole 32 penetrates the outer wall of the nozzle body 30 and connects the pressure accumulation chamber 31 to the outside of the nozzle body 30. The tip of the injection hole 32 is arranged in the cylinder 11. The back pressure control chamber 33 is a space connected to the high pressure passage 54 through the inlet orifice 35 and connected to the control valve chamber 34 through the outlet orifice 36. Further, a part of the wall that partitions the back pressure control chamber 33 is configured by the control piston 22. The control valve chamber 34 is connected to the back pressure control chamber 33 through the outlet orifice 36, and is connected to the fuel tank 51 through the low pressure passage 55.

  Needle 21 is arranged in accumulator 31. The needle 21 is configured to be slidable between the open position shown in FIG. 4 and the closed position shown in FIG. 5 along the cylindrical inner wall of the accumulator 31. At the tip of the needle 21, a nozzle sheet 25 for opening and closing the injection hole 32 is provided. When the needle 21 is located at the closing position, the nozzle sheet 25 contacts the outer edge of the injection hole 32 and closes the injection hole 32. On the other hand, when the needle 21 is located at the open position, the nozzle sheet 25 separates from the injection hole 32 and opens the injection hole 32.

  One end of the control piston 22 constitutes a part of the inner wall of the back pressure control chamber 33, and the other end is connected to the needle 21. That is, the control piston 22 is configured to be movable in the nozzle body 30 integrally with the needle 21.

  The control valve 23 is disposed in a control valve chamber 34 and opens and closes an outlet orifice 36. The control valve 23 is urged by a coil spring 27 which is a form of an urging member in a direction to close the outlet orifice 36. The control valve 23 is formed of a magnetic material (for example, metal). The solenoid 24 is an electromagnet that generates a magnetic force when electric power is supplied from the ECM 56 and loses the magnetic force when the supply of electric power from the EMC 56 is stopped.

  In the injector 20 having the above configuration, the needle 21 is urged toward the open position by the pressure of the fuel stored in the pressure accumulating chamber 31. The needle 21 is urged toward the closed position by a coil spring 26 which is a form of an urging member. Further, the control piston 22 urges the needle 21 toward the closed position by the pressure of the fuel stored in the back pressure control chamber 33.

  When power is not supplied to the solenoid 24, the outlet orifice 36 is closed by the control valve 23, and the fuel in the back pressure control chamber 33 is maintained at a high pressure. As a result, the urging force of the control piston 22 and the coil spring 26 becomes larger than the urging force of the pressure accumulation chamber 31, and the needle 21 is held at the closed position. That is, no fuel is injected from the injection holes 32.

  Next, when electric power is supplied to the solenoid 24, the control valve 23 is drawn to the solenoid 24 against the urging force of the coil spring 27, and the outlet orifice 36 is opened. As a result, the fuel stored in the back pressure control chamber 33 flows out to the low pressure flow path 55 through the control valve chamber 34. Here, since the fuel flowing out of the back pressure control chamber 33 through the outlet orifice 36 is designed to be larger than the fuel flowing into the back pressure control chamber 33 through the inlet orifice 35, the fuel stored in the back pressure control chamber 33 is stored. The fuel pressure is reduced. As a result, the urging force of the pressure accumulation chamber 31 becomes larger than the urging forces of the control piston 22 and the coil spring 26, and the needle 21 moves from the closed position to the open position. That is, fuel is injected from the injection holes 32.

  Further, when the supply of electric power to the solenoid 24 is stopped, the control valve 23 closes the outlet orifice 36 by the urging force of the coil spring 27. As a result, high-pressure fuel is supplied to the back pressure control chamber 33 through the inlet orifice 35, and the urging force of the control piston 22 increases. As a result, the urging force of the control piston 22 and the coil spring 26 becomes larger than the urging force of the pressure accumulation chamber 31, and the needle 21 moves from the open position to the closed position. That is, the fuel injection from the injection holes 32 stops.

  As described above, when the supply of electric power to the solenoid 24 is started and stopped, the injection of the fuel from the injector 20 can be started and stopped by moving the needle 21 between the closed position and the open position. Then, in order to start and stop the fuel injection with high accuracy under the control of the ECM 56, the needle 21 needs to slide smoothly along the inner wall of the accumulator 31.

  Therefore, as shown in FIGS. 4 and 5, the needle 21 according to the present embodiment has a conical portion 21a and a cylindrical portion 21b. In addition, the conical portion 21a is disposed at a position closer to the nozzle sheet 25 (in other words, the injection hole 32) than the cylindrical portion 21b. As a typical example, a conical portion 21a is arranged at the tip of the cylindrical portion 21b, and the nozzle sheet 25 is arranged at the tip of the conical portion 21a.

  The conical portion 21a has, for example, a truncated conical outer shape. The conical portion 21a is tapered by reducing its diameter in the sliding direction (axial direction) of the needle 21 so that the diameter decreases toward the injection hole 32. That is, as shown in FIGS. 4 and 5, when the longitudinal section of the conical portion 21 a is viewed from the side, the outer surface of the conical portion 21 a is a smooth inclined surface whose width becomes narrower as approaching the injection hole 32. In other words, the conical portion 21a has a tapered shape. In other words, the distance between the conical portion 21a and the inner wall of the pressure accumulation chamber 31 increases as the distance from the injection hole 32 increases.

  Here, in the present embodiment, “reducing the diameter” indicates that there is no portion whose diameter increases from the base end side to the tip end side of the conical portion 21a. In other words, if the diameter is measured at any two places of the conical portion 21a, the diameter measured on the distal side is always smaller than the diameter measured on the proximal side. That is, the conical portion 21a according to the present embodiment does not have a circumferential groove or the like. The expression “smooth inclined surface” also indicates the same thing.

  The cylindrical portion 21b has, for example, a cylindrical outer shape. The cylindrical portion 21b is a portion having the same diameter in the sliding direction of the needle 21 continuously from the base end of the conical portion 21a. That is, as shown in FIGS. 4 and 5, when the vertical cross section of the cylindrical portion 21b is viewed from the side, the outline of the cylindrical portion 21b is parallel. In other words, the distance between the cylindrical portion 21b and the inner wall of the accumulator 31 is the same in the sliding direction of the needle 21.

In the needle 21 having the above configuration, the diameter a of the distal end (the end on the side of the injection hole 32) of the conical portion 21a is smaller than the diameter b of the base end (the end on the side opposite to the injection hole 32) of the conical portion 21a. More preferably, the diameters a and b satisfy 0.1 μm ≦ (ba) ≦ 3 μm. Further, in the sliding direction of the needle 21 (the axial direction), the length _{L 0} of the combined conical portion 21a and a cylindrical portion 21b, and the length L of the cylindrical portion _{21b, 0.1 × L 0 ≦ L} ≦ 0 .4 × L ₀ is satisfied.

  According to the above-described embodiment, for example, the following effects can be obtained.

  In the injector 20 having the above configuration, the high-pressure fuel supplied through the high-pressure channel 54 is stored in the pressure accumulating chamber 31. However, part of the fuel in the pressure accumulating chamber 31 leaks from a gap on the side opposite to the injection hole 32 with respect to the needle 21 (for example, around the installation position of the coil spring 26), and flows into the fuel tank 51 through the low-pressure flow path 55. Reflux. Therefore, the pressure of the fuel in the pressure accumulating chamber 31 is higher as it is closer to the injection hole 32, and becomes lower as it is away from the injection hole 32. As a result, especially in the case where the needle 21 is located at the closed position, the fuel in the accumulator 31 moves from the high pressure side to the low pressure side as shown by the arrow in FIG.

  Thus, as in the above-described embodiment, by reducing the diameter of the conical portion 21a toward the injection hole 32, the distance between the needle 21 and the inner wall of the pressure accumulation chamber 31 increases as the position is closer to the injection hole 32. Thereby, the movement of the fuel from the high pressure side to the low pressure side described above becomes smooth, and an oil film is easily formed between the needle 21 and the inner wall of the accumulator 31. As a result, the sticking of the needle 21 to the inner wall of the pressure accumulating chamber 31 is prevented, and the needle 21 can slide smoothly.

  If (ba) is too small, the function of smoothing the fuel movement described above cannot be sufficiently exhibited. On the other hand, if (ba) is too large, the possibility that “one-side contact” in which the needle 21 is biased in the pressure accumulating chamber 31 is increased. If the distance between the needle 21 and the inner wall of the pressure accumulating chamber 31 is too large, it is difficult to form an oil film. Therefore, it is desirable that the diameters a and b at both ends of the conical portion 21a satisfy the above-described relationship.

  Further, in the above embodiment, the outer surface of the cylindrical portion 21b functions as a guide surface for guiding the sliding of the needle 21. Therefore, by providing the cylindrical portion 21b, it is possible to prevent the one-side contact and to slide the needle 21 more stably. However, the cylindrical portion 21b can be omitted.

If the length L of the cylindrical portion 21b is too short, the function as the guide surface cannot be sufficiently exhibited. On the other hand, if the length L of the cylindrical portion 21b is too long, the conical portion 21a becomes relatively short, so that the function of smoothing the fuel movement cannot be sufficiently exhibited. Therefore, it is desirable that the lengths L ₀ and L of the needle 21 in the sliding direction satisfy the above-described relationship.

  The embodiments described above are examples for describing the present invention, and are not intended to limit the scope of the present invention only to those embodiments. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

1 Hydraulic excavator (work machine)
2 Running body 3 Revolving body 4 Front work machine 5 Revolving frame 10 Engine 11 Cylinder 12 Cylinder block 13 Piston 14 Crankshaft 15 Connecting rod 16 Intake port 17 Intake valve 18 Exhaust port 19 Exhaust valve 20 Injector (fuel injection device)
DESCRIPTION OF SYMBOLS 21 Needle 21a Conical part 21b Cylindrical part 22 Control piston 23 Control valve 24 Solenoid 25 Nozzle seat 26, 27 Coil spring 30 Nozzle body 31 Pressure accumulation chamber 32 Injection hole 33 Back pressure control room 34 Control valve room 35 Inlet orifice 36 Outlet orifice 51 Fuel tank 52 Hydraulic pump 53 Common rail 54 High pressure channel 55 Low pressure channel 56 ECM

Claims (5)

A fuel injection device for injecting fuel into a cylinder of an engine,
A pressure accumulating chamber in which fuel in a high pressure state is stored, a nozzle body having an injection hole for injecting the fuel stored in the pressure accumulating chamber,
A needle that slides along an inner wall of the nozzle body between a closed position that closes the injection hole and an open position that opens the injection hole,
The fuel injection device according to claim 1, wherein the needle includes a conical portion whose diameter decreases in a sliding direction so that the diameter decreases toward the injection hole. The fuel injection device according to claim 1,
The difference between the diameter of the end of the conical portion on the side of the injection hole and the diameter of the end of the conical portion on the side opposite to the injection hole satisfies the condition of 0.1 μm or more and 3 μm or less. Fuel injector. The fuel injection device according to claim 1,
The fuel injection device is characterized in that the needle has a cylindrical portion having the same diameter in the sliding direction, continuing from an end of the conical portion opposite to the injection hole. The fuel injection device according to claim 3,
The axial length of the cylindrical portion is set to be 10% or more and 40% or less of the combined axial length of the conical portion and the axial length of the cylindrical portion. A fuel injection device characterized in that: A fuel injection device according to claim 1,
An engine that generates driving force by burning fuel injected from the fuel injection device,
A working unit comprising: an operating unit that operates with a driving force generated by the engine.

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