JP2005344630A - Fuel injection valve of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a compact and efficient fuel injection system by suppressing the leakage of a fuel from sliding parts to reduce a leak amount so as to reduce a load on a fuel feed pump. <P>SOLUTION: A control chamber 4 is formed above the sliding part 22 of a command piston 2, and a needle 1 is lifted by increasing/decreasing pressure by an electromagnetic valve 5. A step part is formed at the upper end part of a low-pressure chamber 16 in which the body part 21 of the command piston 2 is stored to use it as a seat part 17. When the command piston 2 is slidably moved upward in fuel injection, a large diameter sealing part 23 formed at the top end part of the body part 21 is brought into contact with the seat part 17 to cut off a communication between a clearance around the sliding part 22 and the low-pressure oil chamber 16 so as to suppress the leakage of the fuel from the clearance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection valve for an internal combustion engine, and more particularly to a fuel injection valve suitably used for a common rail fuel injection system.

2. Description of the Related Art Recently, in a diesel engine, a common rail fuel injection system has been adopted in which high pressure fuel is accumulated in a common rail common to each cylinder, and a fuel injection valve is driven at a predetermined timing to inject into a corresponding cylinder. The structure of a fuel injection valve for a common rail fuel injection system is described in, for example, Patent Document 1, and a command piston that slides integrally with a needle that opens and closes an injection hole, and pressure is applied to the needle through the command piston. A control chamber to be operated is provided, and the pressure in the control chamber is increased or decreased by opening and closing between the control chamber and the low-pressure passage using an electromagnetic valve. The high-pressure fuel accumulated in the common rail is introduced into the high-pressure passage of the fuel injection valve and supplied to the nozzle hole, while being introduced as control oil from the high-pressure passage into the control chamber.
JP-A-9-170513

  When the energization of the solenoid valve is off, the space between the control chamber and the low-pressure passage is closed, so that the pressure in the control chamber communicating with the common rail increases through the high-pressure passage. At this time, since the pressure in the control chamber acts on the needle as the nozzle back pressure, fuel injection is not performed. When the energization of the solenoid valve is on, the low pressure passage is opened, so that fuel flows out from the control chamber to the low pressure passage, and the pressure in the control chamber drops. Along with this, the needle is separated and fuel is injected.

  However, as in Patent Document 1, the configuration in which the control chamber is provided in contact with one end of the command piston has a problem that fuel in the control chamber leaks from the sliding portion of the command piston. In order to maintain good slidability, the command piston needs to have a certain clearance between the sliding surface and the sliding hole, and it is difficult to prevent leakage from the sliding portion.

  For this reason, the fuel supply pump must supply a fuel corresponding to the amount of leakage to the common rail in addition to the required injection amount, and an excessive load is applied. Moreover, in recent years, diesel engines have been increasing the pressure of injected fuel and the amount of leakage tends to increase accordingly. Therefore, it is hoped that the common rail fuel injection system will be operated efficiently by minimizing fuel leakage. It is rare.

  Regarding the fuel leak, the fuel injection valve of Patent Document 1 pays attention to the fact that a minute gap is generated due to a processing error between the orifice member and the body member installed between the control chamber and the low pressure passage, and the leak occurs. The sealability is improved by changing the shape of this and fixing it securely. However, since the configuration of Patent Document 1 is not effective in reducing the amount of leakage from the sliding portion, it is necessary to mount a larger fuel supply pump in order to increase the pressure of the injected fuel, and the system becomes larger. There is a problem to do.

  The present invention solves the above problems, suppresses fuel leakage from sliding parts such as the command piston of the fuel injection valve, reduces the amount of leakage, thereby reducing the load on the fuel supply pump, The purpose is to realize a compact and efficient fuel injection system.

  The fuel injection valve according to claim 1 is formed in a sliding member that slides in a sliding hole provided in the body member, a high-pressure oil chamber formed on one end side of the sliding portion of the sliding member, and the other end side. In the configuration having the low-pressure oil chamber, the clearance around the sliding portion and the low-pressure oil chamber communicate with each other on the outer periphery of the sliding member located in the low-pressure oil chamber when the sliding member slides. A sealing portion for blocking is provided.

  In the above configuration, as the sliding member slides at the time of fuel injection, the sealing portion on the outer periphery thereof moves to close the clearance outlet between the sliding hole and the sliding member. Thereby, since the high-pressure oil leakage from the said clearance is suppressed, the amount of leaks can be reduced and the load of a fuel supply pump can be made small. Therefore, an increase in the size of the fuel supply pump accompanying the increase in fuel pressure is prevented, and a compact and efficient fuel injection system is realized.

  The fuel injection valve according to claim 2 is a control valve that is electrically driven to increase or decrease the pressure in the control chamber, and a command piston that slides in a sliding hole provided in the body member as the pressure in the control chamber increases or decreases. And a needle for moving up and down together with the command piston to open and close the nozzle hole, forming the control chamber on one end side of the sliding hole, and forming a low-pressure oil chamber in which the main body of the command piston is housed on the other end side. Yes. The low-pressure oil chamber has a seat portion at the end of the command piston in the sliding direction, and when the command piston slides, a sealing portion provided on the outer periphery of the main body contacts the seat portion, Communication between the clearance around the sliding portion and the low-pressure oil chamber is blocked.

  Specifically, in a configuration having a control chamber whose pressure is controlled by a control valve, a sealing portion is provided in a main body portion of a command piston facing the control chamber, and is brought into contact with a seat portion of an opposing low-pressure oil chamber. As a result, the clearance between the outer periphery of the sliding portion of the command piston and the low pressure oil chamber are blocked, and the fuel in the control chamber is prevented from leaking from the clearance. Therefore, the leak amount can be reduced, the load of the fuel supply pump can be reduced, and a compact and efficient fuel injection system can be realized.

  Specifically, the sliding hole is formed in a stepped shape in which the inner diameter on the other end side forming the low-pressure oil chamber is larger than the one end side, and the boundary thereof The step portion of the portion is referred to as the sheet portion. On the other hand, the command piston has a part of the main body portion having a large diameter as the sealing portion.

  According to the above configuration, the clearance can be closed by making the command piston and the sliding hole have a simple change in shape so that they are brought into contact with each other when the command piston slides. Therefore, since the fuel leakage can be easily suppressed with a simple configuration, the utility is high.

  The pressure in the control chamber is increased or decreased by connecting the control chamber to the low-pressure passage and the high-pressure passage through an orifice, respectively, and opening and closing the control chamber and the low-pressure passage with the control valve. A configuration may be adopted. By providing the orifice, the inflow and outflow of fuel to the control chamber are restricted, and the injection amount can be easily controlled.

  A first embodiment in which the present invention is applied to a common rail injection system for a diesel engine will be described below with reference to the drawings. FIG. 1 shows the overall configuration of the fuel injection valve I, and FIG. 2 shows the main configuration. In FIG. 1, the fuel injection valve I has a cylindrical nozzle body B1 having a reverse convex cross section in which the needle 1 is accommodated, and a substantially cylindrical body member B disposed in close contact therewith. The nozzle body B1 and the body member B are fixed in an oil-tight manner by a retainer B2. A command piston 2 as a sliding member is accommodated in a cylindrical hole (sliding hole) 15 of the body member B, and a control chamber 4 as a high-pressure oil chamber is formed on the upper end side thereof. Above the body member B, an electromagnetic valve 5 as a control valve is provided.

  In the cylinder portion of the body member B, two fuel passages extending in the axial direction (vertical direction in the drawing) are formed so as to penetrate one, and one is a high pressure passage 31 and the other is a low pressure passage 32. The high-pressure passage 31 communicates with an external common rail (not shown) via a fuel introduction pipe portion 33 protruding from the upper side of the body member B. The low-pressure passage 32 reaches the upper end portion of the body member B through the electromagnetic valve 5 and communicates with an external fuel tank (not shown) through the fuel outlet pipe portion 34. High pressure fuel is pumped to the common rail from a fuel supply pump (not shown) and controlled to a predetermined injection pressure.

  A stepped needle 1 is slidably held in the cylinder of the nozzle body B1. The lower end of the high-pressure passage 31 extends into the nozzle body B1 and communicates with the fuel reservoir 11 provided on the outer periphery of the stepped portion of the needle 1. A nozzle hole 12 for injecting fuel and a nozzle sheet 13 on which the needle 1 is seated are formed at the tip of the nozzle body B1, and when the needle 1 is seated away from the nozzle sheet 13, the nozzle hole 12 and the fuel pool are collected. 11 communicates. At this time, the high-pressure fuel in the fuel reservoir 11 is supplied to the nozzle hole 12 through an annular gap between the lower half of the small diameter of the needle 1 and the inner wall of the nozzle body B1.

  A plate member P1 constituting an in-orifice 41 and an out-orifice 42 communicating with the control chamber 4 is disposed at the upper end opening of the body member B, and between the valve body B3 of the electromagnetic valve 5 mounted from above. Is sandwiched between. The electromagnetic valve 5 functions as a control valve for increasing or decreasing the pressure in the control chamber 4, and has a T-shaped armature 6 sucked and driven by a cylindrical solenoid 51 and a ball valve 61 as a valve body. doing. The armature 6 is biased downward by a return spring 52 accommodated in the cylinder of the solenoid 51 with the upper end surface facing the lower end surface of the solenoid 5.

  As shown in FIG. 2, a hemispherical recess is formed at the lower end of the armature 6, and a ball valve 61 that opens and closes the out orifice 42 is held in the recess. A low pressure chamber 63 that communicates with the low pressure passage 32 via the communication passage 62 is provided around the lower end of the armature 6. When the armature 6 is in the lower end position, the ball valve 61 closes the out orifice 42 that opens to the bottom surface of the low pressure chamber 63, and the low pressure chamber 63 and the control chamber 4 are disconnected. Since the control chamber 4 is always in communication with the high-pressure passage 31 via the in-orifice 41, the control chamber 4 has a high pressure. When the armature 6 is attracted by the solenoid 51 and moves upward, the high-pressure fuel in the control chamber 4 pushes up the ball valve 61 and flows out into the low-pressure chamber 63.

  The pressure in the control chamber 4 acts on the needle 1 below the command piston 2. A return spring 14 for urging the needle 1 downward is disposed on the outer periphery of the lower end of the command piston 2. When the ball valve 61 closes the out orifice 42 and the control chamber 4 is at a high pressure, the needle 1 Is pressed against the nozzle sheet 13 by the pressure of the control chamber 4 and the biasing force of the spring 14. When the ball valve 61 opens the out orifice 42, the pressure in the control chamber 4 drops, and when the force acting in the valve closing direction falls below the fuel pressure in the fuel reservoir 11 acting in the valve opening direction, the needle 1 is released from the nozzle seat 13. It sits away and rises with the command piston 2.

  Here, the fuel injection valve I of the present embodiment is configured such that the high-pressure control chamber 4 is located in contact with the sliding portion 22 of the command piston 2. As illustrated, the control chamber 4 is defined by the upper end portion of the sliding portion 22 of the command piston 2, the upper end portion of the cylindrical hole 15 of the body member B, and the wall surface of the plate member P1. A low pressure oil chamber 16 in which the main body 21 of the command piston 2 is accommodated is formed in the lower half of the cylindrical hole 15. The inside of the cylinder hole 15 is filled with fuel, and the control chamber 4 has a higher pressure than the clearance around the low-pressure oil chamber 16 and the sliding portion 22. The low pressure oil chamber 16 communicates with the low pressure passage 32 through a communication passage (not shown). In such a configuration, there is a problem that the fuel in the control chamber 4 leaks to the low pressure oil chamber 16 through the clearance around the sliding portion 22.

  Therefore, in this embodiment, the clearance outlet of the sliding portion 22 can be closed by devising the shapes of the command piston 2 and the cylindrical hole 15. Specifically, the cylindrical hole 15 is formed in a stepped manner so that the diameter of the low pressure oil chamber 16 is larger than the diameter of the cylindrical hole 15 around the sliding portion 22, and a step portion is formed at the upper end of the low pressure oil chamber 16. Sheet portion 17. On the other hand, a large diameter portion is provided at the upper end portion of the main body portion 21 of the command piston 2 to form a sealing portion 23 that contacts the seat portion 17 during a sliding operation. The sealing portion 23 has an upper end annular surface serving as a contact surface facing the seat portion 17 at a predetermined interval, and comes into contact with the seat portion 17 when the command piston 2 moves upward during fuel injection. Therefore, when the command piston 2 slides, the clearance around the sliding portion 22 and the low-pressure oil chamber 16 can be blocked to prevent fuel from leaking from the control chamber 4.

  The operation of the fuel injection valve I of the present embodiment will be described. 1 and 2 show a state in which the solenoid 51 of the electromagnetic valve 5 is not energized, and the armature 6 pushes down the ball valve 61 to close the out orifice 42 and cut off the communication between the control chamber 4 and the low pressure chamber 63. The control chamber 4 is at a high pressure because high pressure fuel flows through the in-orifice 41. At this time, the command piston 2 receives the pressure of the control chamber 4 to press the needle 1 in the valve closing direction, and the needle 1 is seated on the nozzle seat 13.

  Next, when the solenoid 51 of the electromagnetic valve 5 is energized and the armature 6 is drawn upward, the ball valve 61 is opened by the fuel pressure in the control chamber 4 acting upward via the out orifice 42. As a result, the control chamber 4 communicates with the low pressure passage 32 via the out orifice 42, the low pressure chamber 63, and the communication passage 62, and the pressure starts to decrease. When the fuel pressure in the fuel reservoir 11 acting in the valve opening direction of the needle 1 exceeds the force in the valve closing direction by the small-diameter piston 22 and the return spring 14, the needle 1 is separated and fuel injection is started. . At this time, since the pressure drop in the control chamber 4 is moderated by the orifices 41 and 42, the injection amount control becomes easy.

  When the command piston 2 moves upward in accordance with the lift of the needle 1, the sealing portion 23 at the upper end of the main body 21 comes into contact with the seat portion 17 so that the clearance around the sliding portion 22 and the low pressure oil chamber 16 are between. Shut off (see FIG. 3). Therefore, it is possible to suppress fuel leakage from the sliding portion 22 of the command piston 2 with a simple configuration change, and to reduce the amount of fuel leakage. As a result, since the load of the fuel supply pump is reduced, a compact and efficient fuel injection system can be realized. In addition, since the sealing part 23 is separated from the sheet part 17 by stopping energization, the sealing part 23 does not prevent the fuel as the lubricating oil from flowing around the outer periphery of the sliding part 22 and maintains a good slidability.

  In the first embodiment, the contact surface between the sealing portion 23 and the sheet portion 17 is in a horizontal contact with the horizontal surface. However, the present invention is not limited to this. For example, as shown in FIG. 4 as the second embodiment, if the contact surface of the sealing portion 23 is not a horizontal surface but a tapered surface, the command piston 2 comes into close contact with the seat portion 17 when moved upward, so that the seal portion 23 is sealed. Thus, the amount of fuel leakage can be further reduced. The sheet portion 17 side may be a tapered surface, or both the sealing portion 23 and the sheet portion 17 may be tapered surfaces, and the same effect can be obtained. As described above, in the present invention, it is sufficient that the sealing portion 23 and the seat portion 17 come into contact with the sliding of the command piston 2 to have a valve function of closing the clearance.

  Although the example which suppresses the fuel leak from the sliding part of the command piston 2 was shown in the said embodiment, it is a sliding member used for a fuel injection valve, and a high pressure oil chamber and a low pressure via the sliding part If the oil chamber communicates, the same effect can be obtained by applying the configuration of the present invention.

  In the above embodiment, an electromagnetic valve is used as a control valve. However, the present invention is not limited to this, and any valve that is driven by energization to increase or decrease the pressure in the control chamber can be used. Further, although the control valve has a two-way valve structure, it may have a three-way valve structure. Of course, the configuration of the solenoid valve, the control room, and the like can be changed.

It is a whole sectional view of a fuel injection valve in a 1st embodiment of the present invention. It is principal part sectional drawing of the fuel injection valve of 1st Embodiment. It is principal part sectional drawing of the fuel injection valve for demonstrating the action | operation of 1st Embodiment. It is principal part sectional drawing of the fuel injection valve in the 2nd Embodiment of this invention.

Explanation of symbols

B Body member B1 Nozzle body B2 Retainer B3 Valve body 1 Needle 11 Fuel reservoir 12 Injection hole 13 Nozzle seat 14 Return spring 15 Cylinder hole (sliding hole)
16 Low Pressure Oil Chamber 17 Seat 2 Command Piston 21 Body 22 Slider 23 Sealing Portion 31 High Pressure Passage 32 Low Pressure Passage 4 Control Chamber 41 In Orifice 42 Out Orifice 5 Solenoid Valve (Control Valve)
51 Solenoid 6 Armature 61 Ball valve (valve)
62 Communication path 63 Low pressure chamber

Claims (4)

  An internal combustion engine having a sliding member that slides in a sliding hole provided in a body member, a high-pressure oil chamber formed on one end side of a sliding portion of the sliding member, and a low-pressure oil chamber formed on the other end side In the fuel injection valve, on the outer periphery of the sliding member located in the low pressure oil chamber, the clearance around the sliding portion and the low pressure oil chamber are disconnected from each other during the sliding operation of the sliding member, A fuel injection valve for an internal combustion engine, comprising a sealing portion that seals leakage from the clearance.   A control valve that is electrically driven to increase or decrease the pressure in the control chamber, a command piston that slides in a sliding hole provided in the body member as the pressure in the control chamber increases or decreases, and a jet that moves up and down together with the command piston. In a fuel injection valve for an internal combustion engine having a needle for opening and closing a hole, the control chamber is formed on one end side of the sliding hole, and a low pressure oil chamber is formed on the other end side in which the main body of the command piston is accommodated. The outer periphery of the main body portion located in the low pressure oil chamber is in contact with the seat portion formed at the sliding direction end of the low pressure oil chamber during the sliding movement of the command piston, and around the sliding portion of the command piston. A fuel injection valve for an internal combustion engine, wherein a sealing portion is provided for blocking communication between the clearance and the low-pressure oil chamber and sealing leakage from the clearance.   The sliding hole is formed in a stepped shape in which the inner diameter on the other end side forming the low-pressure oil chamber is larger than the one end side, and the stepped portion at the boundary is used as the seat portion, The fuel injection valve for an internal combustion engine according to claim 2, wherein a part of a main body of the command piston has a large diameter and is used as the sealing portion.   4. The pressure in the control chamber is increased or decreased by communicating the control chamber with a low-pressure passage and a high-pressure passage through an orifice, respectively, and opening and closing between the control chamber and the low-pressure passage with the control valve. The fuel injection valve of any one of the internal combustion engines.

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