JP2009127520A - Injector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To conduct stable close control without being influenced by the fluctuation of nozzle back pressure and improve the controllability of an injection amount with respect to a command pulse in an injector having a two-control valve structure. <P>SOLUTION: There is provided a hydraulic servo valve 4 comprising a valve 41 and a servo piston 42 formed integrally with the valve 41. The valve is disposed in a first back pressure chamber 6 arranged between a nozzle back pressure chamber 12 and a low pressure source 3. The servo piston has on its one end face side a volume chamber 8 communicating with a high pressure source and on the other end face side a second back pressure chamber 7 the pressure of which is controlled by a two-way electromagnetic valve 5. The hydraulic servo valve 4 is operated by the application of the hydraulic pressure of the second back pressure chamber 7 controlled by the two-way electromagnetic valve 5, the hydraulic pressure of the first back pressure chamber 6, and the hydraulic pressure of the volume chamber 8. The stable operation of the hydraulic servo valve is enabled by the application of the hydraulic pressure of one of the second back pressure chamber 7 and the volume chamber 8 in the same direction as the hydraulic pressure of the first back pressure chamber 6 without being influenced by the pressure fluctuation of the nozzle back pressure chamber 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injector, and more particularly to a nozzle needle control structure for switching between fuel injection and stoppage.

An injector used in a common rail fuel injection device for a diesel engine is provided with a nozzle back pressure chamber on the back side of the nozzle needle, and by switching between communication and blocking between the nozzle back pressure chamber and the low pressure source with a control valve, The nozzle needle is moved up and down to highly control the injection timing and the injection amount. Patent Document 1 proposes a two-valve injector that uses a hydraulic servo valve as a control valve and controls the hydraulic pressure acting on the servo valve by another control valve using an actuator such as a solenoid and an on-off valve. ing.
JP 2006-257874 A

  The main part of the injector of Patent Document 1 is shown in FIG. In the drawing, a first back pressure chamber 103 is formed in the middle of the passage leading to the open passage 102 for releasing the pressure in the nozzle back pressure chamber 101 to the low pressure source, and the valve of the servo piston 104 constituting the hydraulic servo valve. The part is arranged. The valve portion of the servo piston 104 is seated on either the high pressure source side seat 106 or the low pressure source side seat 105 provided facing the upper and lower surfaces of the first back pressure chamber 103 and communicates with the first back pressure chamber 103. The pressure in the nozzle back pressure chamber 101 is increased or decreased. A second back pressure chamber 107 is formed on the servo piston 104 in contact with the end opposite to the valve portion, and oil pressure is applied in a direction to close the low pressure source side seat 105.

  The pressure in the second back pressure chamber 107 is controlled by an on-off valve that uses a solenoid 108 as a drive source. The on-off valve has a valve body 110 that opens and closes a port 109 communicating with a low pressure source. When the solenoid 108 sucks an armature 111 provided integrally with the valve body 110, the valve body 110 resists the spring force. Lift. Along with this, the pressure in the second back pressure chamber 107 decreases, the servo piston 104 moves to a position where the high pressure source side sheet 106 is closed, and the nozzle back pressure chamber 101 communicates with the low pressure source side sheet 105. When the pressure in the nozzle back pressure chamber 101 becomes equal to or lower than the valve opening pressure, the nozzle needle starts to lift and fuel is injected.

  In this configuration, the driving force of the servo piston 104 is obtained by hydraulic pressure, and the lift amount of the valve portion can be set to a sufficient size without depending on the driving force of the solenoid 108, so that the actuator can be downsized. Can do.

  As shown in FIGS. 13B and 13C, in the conventional configuration, the pressure applied to the hydraulic servo valve is determined by the oil pressure in the first back pressure chamber 103 in which the valve portion of the servo piston 104 is arranged, and the opening and closing. And the oil pressure of the second back pressure chamber 107 controlled by a valve. Of these, the hydraulic pressure in the second back pressure chamber 107 acts in a direction in which the servo piston 104 closes the low pressure source side seat 105 (valve closing force), and the hydraulic pressure in the first back pressure chamber 103 acts in a direction that impedes this. Yes (inhibitory power). That is, the valve closing force (Fc) and the inhibition force (Fi) are balanced on a one-to-one basis, and when this balance is lost (Fc> Fi), the servo valve starts to close.

  By the way, the oil pressure in the first back pressure chamber 103 which becomes the inhibition force (Fi) communicates with the nozzle back pressure chamber 101 and exhibits substantially the same pressure behavior. However, since the pressure of the nozzle back pressure chamber 101 varies greatly depending on the opening of the nozzle needle and the subsequent lift behavior, the inhibition force (Fi) fluctuates over time due to the influence of this pressure variation. For this reason, when the hydraulic servo valve is controlled to close, the balance point with the valve closing force (Fc) changes with time, and the operation of the servo piston 104 tends to become unstable. As a result, the controllability (linear responsiveness) of the injection amount with respect to the command pulse is deteriorated, and there is a possibility of causing torque variation and emission variation between engine cylinders.

  The present invention has been made in view of such circumstances, and in a configuration including an on-off valve using an actuator and a hydraulic servo valve, the pressure of the second back pressure chamber is controlled by the on-off valve, so that the fluctuation of the nozzle back pressure can be reduced. Enables stable control of the hydraulic servo valve without being affected, and as a result, improves the controllability (linear response) of the injection amount with respect to the command pulse, It is an object of the present invention to provide an injector capable of reducing emission variation.

In the first aspect of the present invention, a nozzle back pressure chamber that is provided on the back side of the nozzle needle that opens and closes the injection hole for fuel injection and that generates a back pressure of the nozzle needle in communication with a high pressure source;
A first control valve for switching communication / blocking between the nozzle back pressure chamber and the low pressure source;
An injector having a second control valve for driving the first control valve;
The first control valve includes a valve portion arranged in a first back pressure chamber provided between the nozzle back pressure chamber and a low pressure source, and a servo piston provided so as to be movable integrally with the valve portion. A volume servo chamber communicating with a high pressure source on one end face side of the servo piston is a hydraulic servo valve in which a second back pressure chamber whose pressure is controlled by the driving means is formed on the other end face side.
The second control valve is an on-off valve that is driven by an actuator to switch communication between the second back pressure chamber and the low pressure source.
The hydraulic servo valve is acted on by the oil pressure of the second back pressure chamber, the oil pressure of the first back pressure chamber, and the oil pressure of the volume chamber controlled by the on-off valve, and the first back pressure chamber. The oil pressure of any one of the second back pressure chamber and the volume chamber is applied in the same direction as the oil pressure of the pressure chamber.
An injector having drive means for driving the control valve;
The control valve includes a valve portion disposed in a first back pressure chamber provided between the nozzle back pressure chamber and a low pressure source, and a servo piston provided to be movable integrally with the valve portion. A volume chamber communicating with a high pressure source is formed on one end face side of the piston, and a second back pressure chamber whose pressure is controlled by the driving means is formed on the other end face side,
The driving means includes an on-off valve that is driven by an actuator to switch communication / blocking between the second back pressure chamber and the low pressure source.
The servo piston and the valve portion are displaced by a differential pressure between the oil pressure of the second back pressure chamber controlled by the on-off valve and the oil pressure of the first back pressure chamber and the volume chamber, and the first The direction in which the oil pressure of one back pressure chamber acts is made to coincide with the direction in which either one of the second back pressure chamber and the volume chamber acts.

  In the above configuration, as the on-off valve opens and closes to increase or decrease the pressure in the second back pressure chamber, the hydraulic servo valve is displaced by the differential pressure of the oil pressure in the first back pressure chamber, the second back pressure chamber, and the volume chamber. Then, the valve unit arranged in the first back pressure chamber is switched to a position where the nozzle back pressure chamber and the low pressure source communicate or are blocked. Here, the oil pressure in the first back pressure chamber communicating with the nozzle back pressure chamber fluctuates according to the lift of the nozzle needle, and becomes an impeding force when the valve portion closes the low pressure source. Since the oil pressure of the second back pressure chamber or the volume chamber acts as another acting force in the same direction as the inhibition force, the influence of pressure fluctuation can be mitigated. Therefore, it is possible to stabilize the operation of the hydraulic servo valve, improve the controllability of the injection amount with respect to the command pulse, and reduce the torque variation and the emission variation between the engine cylinders.

  According to a second aspect of the present invention, the second back pressure chamber communicates with a passage leading to the on-off valve via an orifice, and communicates with a high pressure source via another orifice.

  Specifically, the second back pressure chamber can be communicated with a high pressure source and a low pressure source through an orifice, and the pressure can be easily controlled by opening and closing the low pressure source side. When the on-off valve is opened, the second back pressure chamber communicates with the low pressure source and the pressure drops, and becomes constant at a pressure that balances the inflow and outflow by the two orifices. When the on-off valve is closed, only the inflow from the high pressure source becomes possible and the pressure rises and stabilizes.

  According to a third aspect of the present invention, a low-pressure sheet communicating with the low-pressure source and a high-pressure sheet communicating with the high-pressure source are respectively provided on the opposing wall surfaces of the first back pressure chamber, and the hydraulic servo valve is driven by the on-off valve. Accordingly, the valve section is seated on one of the low-pressure seat and the high-pressure seat to form a three-way valve that selectively connects the nozzle back pressure chamber to a low-pressure source or a high-pressure source.

  Specifically, the hydraulic servo valve has a three-way valve structure, and the position of the valve portion disposed in the first back pressure chamber is switched so that the nozzle back pressure chamber communicates with a high pressure source or a low pressure source and the back of the nozzle needle. The pressure can be easily controlled.

  According to a fourth aspect of the present invention, a low-pressure seat communicating with a low-pressure source is provided on the wall of the first back pressure chamber, and the valve portion opens and closes the low-pressure seat as the on-off valve is driven. Use a two-way valve.

  Specifically, the hydraulic servo valve has a two-way valve structure, and the valve portion arranged in the first back pressure chamber opens and closes the low pressure source, thereby switching the communication between the nozzle back pressure chamber and the low pressure source. It is also possible to control the back pressure.

According to a fifth aspect of the present invention, the servo piston is slidably disposed in a cylinder located coaxially with the first back pressure chamber in which the valve portion is disposed, and is disposed on the valve portion side of the cylinder. The second back pressure chamber is provided at the end, the volume chamber is provided at the other end, and the oil pressure of the second back pressure chamber and the oil pressure of the volume chamber act in opposite directions,
The low pressure seat is provided on the servo piston side wall surface of the first back pressure chamber, and when the valve portion is seated on the low pressure seat, the oil pressure of the second back pressure chamber is set to the first back pressure chamber. Acts in the same direction as the oil pressure.

  Specifically, the servo piston and the valve portion are integrally provided on the same axis, and the oil pressure in the first back pressure chamber acting as an obstruction force on the valve portion and the second back pressure acting on the servo piston in the valve closing direction. It can arrange | position so that the oil pressure of a chamber may become the same direction. Thereby, the effect of reducing the influence of the pressure fluctuation of the first back pressure chamber and improving the controllability can be obtained.

According to a sixth aspect of the present invention, the servo piston is slidably disposed in a cylinder located coaxially with the first back pressure chamber in which the valve portion is disposed, and is disposed on the valve portion side of the cylinder. The volume chamber is provided at the end, the second back pressure chamber is provided at the other end, and the oil pressure of the second back pressure chamber and the oil pressure of the volume chamber are applied in opposite directions,
When the low pressure seat is provided on the wall surface of the first back pressure chamber opposite to the servo piston and the valve portion is seated on the low pressure seat, the oil pressure in the volume chamber is changed to the oil in the first back pressure chamber. Act in the same direction as the pressure.

  Specifically, the servo piston and the valve part are integrally provided on the same axis, and the oil pressure of the first back pressure chamber acting as a blocking force on the valve part and the oil pressure of the volume chamber of stable pressure are in the same direction. Can be arranged as follows. Even if it does in this way, the said effect which makes the influence of the pressure fluctuation of a 1st back pressure chamber small, and improves controllability is acquired.

  According to a seventh aspect of the present invention, the actuator is a solenoid that sucks and drives an armature that is displaced integrally with the on-off valve.

  Specifically, a solenoid can be used as an actuator, and an open / close valve can be driven together with an armature to open and close a passage to a low pressure source.

(First embodiment)
Hereinafter, an injector according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an overall schematic configuration of an injector according to a first embodiment of the present invention, and FIG. 2 is an enlarged view of a main part showing a specific configuration thereof. The injector of the present invention is suitably used in, for example, a diesel engine equipped with a common rail fuel injection system. In the common rail system, the injectors are provided in a one-to-one correspondence with the cylinders of the engine, and the fuel supplied by the common rail is injected during a predetermined period under the control of the ECU to maintain a desired operation state.

  In FIG. 1, the injector has a nozzle needle 1 that opens and closes an injection hole 11 for fuel injection, and the back pressure of the nozzle needle 1 is applied to the back side of the nozzle needle 1 by the pressure of fuel supplied from a high pressure source 2 (common rail). A nozzle back pressure chamber 12 is provided. The nozzle back pressure chamber 12 is connected to a high pressure source 2 while being connected to a low pressure source 3 (fuel tank), and a hydraulic servo valve 4 having a three-way valve structure serving as a first control valve is interposed between them. It is designed to switch between communication and disconnection. The hydraulic servo valve 4 is driven by an electromagnetic two-way valve 5 serving as a second control valve. The fuel of the high pressure source 2 is supplied from the high pressure line 21 to the nozzle hole 11 via the fuel reservoir 13 formed around the lower half narrow diameter portion of the nozzle needle 1.

  The hydraulic servo valve 4 includes a valve portion 41 that allows the nozzle back pressure chamber 12 to communicate with either the high pressure source 2 or the low pressure source 3 at a switching position, and a servo piston 42 that can move integrally with the valve portion 41. The servo piston 42 has a volume chamber 8 that is always in communication with the high-pressure line 21 on one end surface side (opposite the valve portion 41), and a second back pressure chamber 7 on the other end surface side (valve portion 41 side). ing. The second back pressure chamber 7 is connected to the low pressure line 31 via the first orifice 32 and the high pressure line 21 via the second orifice 22, and is low pressure by the electromagnetic two-way valve 5 provided downstream of the first orifice 32. The pressure is controlled by switching between connection and disconnection with the source 3. A third orifice 33 is formed between the hydraulic servo valve 4 and the low pressure source 3.

FIG. 2 shows a specific configuration example of the hydraulic servo valve 4 and the electromagnetic two-way valve 5 of the injector in the first embodiment.
In the injector, the nozzle body B1, the distance piece B2, the first valve body B3, the second valve body B4, the solenoid body B5, and the retaining nut B6 constitute a base body having a substantially round bar shape. The nozzle body B1, the distance piece B2, the first valve body B3, the second valve body B4, and the solenoid body B5 are in contact with each other at the opposing end surfaces and are connected to each other by a retaining nut B6. Each body member constituting the base body has various recesses and holes formed therein, in which the constituent members are accommodated and a fuel flow path is formed.

  In the nozzle body B1, the nozzle needle 1 is accommodated in a vertical hole formed in the axial direction of the base. The upper end of the nozzle needle 1 is slidably held in the cylinder 14, and the nozzle back pressure chamber 12 is defined by the upper end surface of the nozzle needle 1, the inner wall surface of the cylinder 14, and the lower end surface of the distance piece B2. . The space around the outer periphery of the nozzle needle 1 serves as a fuel reservoir 13 and supplies fuel to the nozzle hole at the tip of the nozzle body B1 (not shown). The nozzle needle 1 is urged in a seating direction for closing the nozzle hole by a nozzle spring 15 disposed on the outer periphery.

  A high pressure fuel passage 23 is formed through the distance piece B 2, the first valve body B 3, the second valve body B 4, and the solenoid body B 5, and the lower end thereof is connected to the fuel reservoir 13. The high pressure fuel passage 23 communicates with the high pressure source 2 of FIG. 1 and forms a part of the high pressure line 21. When the nozzle needle 1 is separated, the high pressure fuel is injected from the injection hole.

  The nozzle back pressure chamber 12 is always in communication with the first back pressure chamber 6 provided in the first valve body B3 through an orifice passage 16 penetrating the distance piece B2. The hydraulic servo valve 4 accommodates the valve portion 41 in the first back pressure chamber 6 and performs flow path switching. In the first back pressure chamber 6, a high pressure port 61 that passes through the distance piece B <b> 2 and communicates with the fuel reservoir 13 is opened at the center of the lower surface, and a peripheral portion of the opening is a lower seat (high pressure seat) 62. On the other hand, a low pressure port 63 is opened at the center of the upper surface facing the high pressure port 61, and an upper sheet (low pressure sheet) 64 is formed at the periphery of the opening. The low pressure port 63 communicates with the low pressure source 3 of FIG. 1 via the third orifice 33 and a low pressure passage 34 that forms part of the low pressure line 31 of FIG.

  The valve portion 41 of the hydraulic servo valve 4 is substantially bowl-shaped, and when the upper conical surface is seated on the upper seat 64, the high-pressure port 61 is opened, and the nozzle back pressure chamber 12 is communicated with the high-pressure source 2 to form a cylindrical lower bottom surface. Is seated on the lower seat 62, the low pressure port 63 is opened, and the nozzle back pressure chamber 12 is communicated with the low pressure source 3. A valve spring 43 is disposed around the lower portion of the columnar shape, and the upper tapered surface of the valve portion 41 is biased in the direction in which the valve seat 41 is seated on the upper seat 64.

  The servo piston 42 of the hydraulic servo valve 4 slidably accommodates a large-diameter piston portion 45 in a cylinder 44 provided in the second valve body B4, and a shaft portion 46 projecting from the lower surface thereof has a first piston 46. It extends into the low pressure port 63 of the valve body B3 and is connected to the top surface of the valve portion 41. Thereby, the valve part 41 and the servo piston 42 can move integrally. In the second valve body B4, a volume chamber 8 that always communicates with the high-pressure fuel passage 23 in the passage 24 is formed on the upper end surface side of the servo piston 42, and a second back pressure chamber 7 is formed on the lower end surface side. The The second back pressure chamber 7 communicates with a passage 35 that reaches the electromagnetic two-way valve 5 via the first orifice 32, and always communicates with the high-pressure fuel passage 23 via the second orifice 22. A spring 47 is disposed in the second back pressure chamber 7 to urge the large-diameter piston portion 45 toward the volume chamber 8 side.

  The electromagnetic two-way valve 5 includes an armature 53 and an on-off valve 52 that are driven by a solenoid 51 serving as an actuator in a solenoid body B5. The on-off valve 52 has a shaft-like portion integral with the armature 53 facing the solenoid 51 and a valve body held at the lower end thereof, and the flat lower end surface of the valve body communicates with the passage 34 and is a second valve. Opposite the low pressure port 36 that opens to the center of the upper end surface of the body B4. A low-pressure seat 37 on which the on-off valve 52 is seated is provided around the low-pressure port 36, and the low-pressure passage 31 communicating with the low-pressure source 3 is formed by recessing the periphery thereof in a ring shape. The on-off valve 52 is urged in a direction to close the low-pressure port 36 by a spring 54 housed in a cylindrical solenoid 51 internal space. When the solenoid 51 sucks the armature 53, the open / close valve 52 integrated therewith is pulled up, and the low pressure port 36 is opened.

The operation of the injector configured as described above and the behavior of each back pressure chamber will be described with reference to FIGS.
1 and 2 show a state in which the electromagnetic two-way valve 5 is not energized, and the on-off valve 52 is in a position to be seated on the low pressure seat 37 and close the low pressure port 36. The second back pressure chamber 7 and the low pressure source 3 are disconnected from each other, and the second back pressure chamber 7 has a high pressure by the high pressure fuel supplied from the high pressure source 2 via the second orifice 22 and the high pressure fuel passage 23. It has become. At this time, the oil pressure in the second back pressure chamber 7 and the biasing force of the spring 47 are large on the one surface of the large-diameter piston portion 45 of the servo piston 42 and the oil pressure in the volume chamber 8 communicating with the high-pressure source 2 is large. Acting on the other surface of the diameter piston portion 45, the hydraulic pressure of the first back pressure chamber 6 and the urging force of the valve spring 43 act on the valve portion 41. The oil pressure in the first back pressure chamber 6 acts in the same direction as the oil pressure in the second back pressure chamber 7, and the oil pressure in the volume chamber 8 acts in the opposite direction. The hydraulic servo valve 4 is held at a position where the valve portion 41 is seated on the upper seat 64 and the low pressure port 63 reaching the low pressure passage 34 is closed.

  This is shown as state (A) in FIG. In this state, the first back pressure chamber 6 passes through the fuel reservoir 13 and the high-pressure fuel passage 23 so that the valve portion 41 is seated on the upper seat 64 and is separated from the lower seat 62 to open the high-pressure port 61. The high pressure source 2 is connected to the high pressure source. The nozzle back pressure chamber 12 communicating with the first back pressure chamber 6 via the orifice passage 16 is also at a high pressure. As shown schematically in the figure, the oil pressure in the nozzle back pressure chamber 12 and the nozzle spring 13 The urging force acts in the valve closing direction to seat the nozzle needle 1 on the nozzle seat 17.

  From this state, when the solenoid 51 of the electromagnetic two-way valve 5 is energized, the armature 53 is sucked, the open / close valve 52 is separated from the low pressure seat 37, and the low pressure port 36 is opened. As shown in FIG. 4, the second back pressure chamber 7 communicates with the low pressure system that reaches the low pressure source 3 through the first orifice 32, and passes through the passage 35, the low pressure port 36, and the low pressure passage 34, and then passes through the second back pressure chamber 7. As the fuel flows out of the chamber 7, the pressure gradually decreases. When the pressure in the second back pressure chamber 7 decreases to a predetermined pressure (dotted line in the figure), the oil pressure in the volume chamber 8 acting on the hydraulic servo valve 4, the first back pressure chamber 6 and the second back pressure chamber 7 The balance with the oil pressure is lost, and the valve portion 41 is separated from the upper seat 64 to open the low pressure port 63.

  Thereafter, the pressure in the second back pressure chamber 7 continues to decrease. The second back pressure chamber 7 is connected to the upstream high pressure system via the second orifice 22, and is connected to the downstream low pressure system via the first orifice 32. It becomes constant at the pressure that balances the flow of flow determined by the difference and the diameter of the throttle. The throttle diameter is designed so that the constant pressure is lower than the stable pressure (constant pressure) of the second back pressure chamber pressure. When the hydraulic servo valve 4 is lifted, the servo piston 42 pushes the fuel in the second back pressure chamber 7 and the pressure rises momentarily (the enclosed portion in the figure), but the lift amount / mass of the hydraulic servo valve 4 is the nozzle. Since it is very small compared to the needle 1, it can be almost ignored.

  On the other hand, as shown in FIG. 3 as the state (B), when the hydraulic servo valve 4 is lifted and the valve portion 41 is switched to the position where it is seated on the lower seat 62, the low pressure port 63 is opened. The first back pressure chamber 6 is connected to the low pressure source 3 through the third orifice 33 and the low pressure passage 34, and the pressure gradually decreases because the fuel flows out. When the pressure in the first back pressure chamber 6 and the nozzle back pressure chamber 12 communicating with the first back pressure chamber 6 decreases to the nozzle opening pressure, the nozzle needle 1 starts to lift and fuel is injected.

  However, at this time, the pressure in the first back pressure chamber 6 varies as shown in the figure. The reason for this is explained as follows. First, the first back pressure chamber 6 and the nozzle back pressure chamber 12 are connected by a pipe line, and can be considered as one room exhibiting substantially the same pressure behavior. As the nozzle needle 1 is opened, the force for lifting the nozzle needle 1 is rapidly increased, and the nozzle needle 1 is raised. The pressure in the nozzle back pressure chamber 12 and the first back pressure chamber 6 fluctuates (vibrates) due to the inertial force and the elasticity (volume elastic modulus) of the fuel in the nozzle back pressure chamber 12 and the first back pressure chamber 6. ). As time passes, the fluctuation (vibration) is reduced by the balance between the amount of outflow to the low pressure system and the amount of fuel pushed in by the needle rise. At that time, the pressure becomes a constant value.

  In the conventional configuration, due to the influence of the pressure fluctuation, the balance point changes and becomes unstable when switching from the state (B) to the state (A) again to stop the injection, but in the configuration of the present embodiment, the volume chamber By providing 8 and acting as an auxiliary force, the influence of pressure fluctuations can be minimized. This will be described below.

  FIG. 5A shows the force acting on the conventional hydraulic servo valve shown in FIGS. 13B and 13C, and the second back pressure chamber serving as the valve closing force of the low pressure source side seat 105 is shown. For the oil pressure 107 (downward arrow in the figure), the pressure (upward arrow in the figure) of the first back pressure chamber 103 that becomes an inhibition force is established by a one-to-one balance. For this reason, the force balance point is likely to change due to pressure fluctuation, and the valve closing start of the hydraulic servo valve fluctuates. For example, as shown as point A behavior in FIG. 6, when the pressure in the first back pressure chamber 103 is greatly reduced and the pressure in the second back pressure chamber 107 balances with the pressure in the second back pressure chamber 107, the hydraulic servo valve at a time earlier than desired characteristics. Starts to move to the closed position where the valve portion is seated on the low pressure source side seat 105. For this reason, the nozzle needle starts to descend early, and the injection amount becomes smaller than the desired characteristic.

  Conversely, as shown as point B behavior in FIG. 7, when the pressure in the first back pressure chamber 103 rises again and balances with the pressure in the second back pressure chamber 107, the hydraulic servo is at a point later than the desired characteristic. The valve portion of the valve starts to move to the closed position where the valve portion is seated on the low pressure source side seat 105. For this reason, the lowering start of the nozzle needle is delayed, and the injection amount becomes larger than the desired characteristic.

  On the other hand, in the present embodiment, as shown in FIG. 5B, the oil pressure in the second back pressure chamber 7 that becomes the valve closing force of the upper seat 64 reaching the low pressure source 3 becomes the inhibition force. The oil pressure from the volume chamber 8 that acts in the same direction as the pressure in the back pressure chamber 6 (upward arrow in the figure) and communicates with the high pressure source 3 that is a stable pressure source in the opposite direction is an auxiliary force. It works (downward arrow in the figure). In this way, by exerting another acting force in the same direction as the inhibiting force and driving the hydraulic servo valve 4 by balancing the three acting forces, the influence of the fluctuation of the inhibiting force can be alleviated. That is, as shown in the figure, the sum of the valve closing force and the inhibition force has a small pressure fluctuation over time, and the balance point of the force with the auxiliary force that becomes the valve closing start point of the hydraulic servo valve 4 varies. It becomes difficult.

  Accordingly, since fluctuations in the valve closing timing are suppressed, the desired characteristics shown in FIGS. 6 and 7 can be obtained, and the linearity of the increase in controllability of the injection amount according to the command pulse can be maintained. As a result, torque variation and emission variation between engine cylinders can be prevented and fuel injection performance can be improved.

(Second Embodiment)
8 and 9 show an injector according to a second embodiment of the present invention. In the present embodiment, a part of the hydraulic servo valve 4 serving as a control valve is changed to another configuration in the configuration of the first embodiment, and the same operation is performed on portions that perform substantially the same operation as the first embodiment. It is numbered. Hereinafter, the difference from the first embodiment will be mainly described.

  In FIG. 8, the injector drives a hydraulic servo valve 4 that switches communication / blocking between the nozzle back pressure chamber 12 and the low pressure source 3 by an electromagnetic two-way valve 5 to control the lift of the nozzle needle 1. In the present embodiment, the valve portion 41 of the hydraulic servo valve 4 is a two-position three-way valve that allows the nozzle back pressure chamber 12 to communicate with the high pressure source 2 or the low pressure source 3, and the servo piston 42 has a high pressure on the valve portion 41 side. The volume chamber 8 that is always in communication with the line 21 is configured to have the second back pressure chamber 7 on the side opposite to the valve portion 41. The second back pressure chamber 7 is connected to the low pressure line 31 via the first orifice 32 and the high pressure line 21 via the second orifice 22, and the pressure is reduced by the electromagnetic two-way valve 5 provided downstream of the first orifice 32. The configuration to be controlled is the same as in the first embodiment.

  FIG. 9 is a diagram illustrating a specific configuration example of the hydraulic servo valve 4 of the injector according to the second embodiment. In the injector, the nozzle body B1, the distance piece B2, the first valve body B3, the second valve body B4, and the solenoid body B5 are coupled to each other by a retaining nut B6, and the components such as the nozzle needle 1 are accommodated. Become. The nozzle back pressure chamber 12 provided in the nozzle body B1 is always in communication with the first back pressure chamber 6 provided in the first valve body B3 through the orifice passage 16 penetrating the distance piece B2.

  The hydraulic servo valve 4 has a valve portion 41 accommodated in the first back pressure chamber 6 and a servo piston 42 in which a large-diameter piston portion 45 is accommodated in a cylinder 44 provided in the second valve body B4. Yes. In the first back pressure chamber 6, a low pressure port 63 is opened at the center of the lower surface, and a lower seat (low pressure seat) 66 is formed at the periphery of the opening. A third orifice 33 is formed in the distance piece B2 following the low pressure port 63, and communicates with the low pressure source 3 of FIG. On the other hand, a high pressure port 61 is opened at the center of the upper surface facing the low pressure port 63, and a tapered upper sheet (high pressure sheet) 65 is provided at the peripheral edge of the opening. The high pressure port 61 communicates with the high pressure fuel passage 23 via the passage 25.

  The valve portion 41 of the hydraulic servo valve 4 has a block shape having tapered surfaces at the upper and lower end portions, and the upper end tapered surface faces the upper seat 67 and the bottom surface faces the lower seat 66. The servo piston 42 has a shaft portion 46 protruding from the lower surface of the large-diameter piston portion 45 extending into the high-pressure port 61 and is connected to the top surface of the valve portion 41 so as to move integrally. When the servo piston 42 is lowered, the valve portion 41 is seated on the lower seat 66 on the low pressure side, the communication between the nozzle back pressure chamber 12 and the low pressure port 63 is cut off, and the high pressure port 61 is communicated. When the servo piston 42 is raised, the valve portion 41 is seated on the upper seat 65 on the high pressure side to close the high pressure port 61, and the nozzle back pressure chamber 12 and the low pressure port 63 are communicated.

  In the present embodiment, the second back pressure chamber 7 is formed on the upper end surface side of the servo piston 42, and the volume chamber 8 that is always in communication with the high-pressure fuel passage 23 is formed in the passage 25 on the lower end surface side. The second back pressure chamber 7 communicates with the low pressure port 36 opened at the upper end surface of the second valve body B4 via the first orifice 32, and always communicates with the high pressure fuel passage 23 via the second orifice 22. is doing. A spring 47 is disposed in the second back pressure chamber 7 to urge the large-diameter piston portion 45 toward the volume chamber 8 side. The electromagnetic two-way valve 5 that opens and closes the low-pressure port 36 has the same configuration as in the first embodiment.

  The basic operation of the injector having the above configuration is almost the same as that of the first embodiment. The electromagnetic two-way valve 5 increases or decreases the pressure in the second back pressure chamber 7 to switch the seat position of the hydraulic servo valve 4 to thereby inject fuel. To control. In a state in which the electromagnetic two-way valve 5 is not energized, the on-off valve 52 is seated on the low pressure seat 37 to close the low pressure port 36 and the second back pressure chamber 7 and the low pressure source 3 are disconnected. The second back pressure chamber 7 is at a high pressure by the fuel supplied from the high pressure fuel passage 23 through the second orifice 22. This oil pressure and the urging force of the spring 47 act on one end side of the servo piston 42 (opposite the valve portion 41), and on the other end side of the servo piston 42 (valve portion 41 side) Is working. Further, the pressure in the first back pressure chamber 6 acts on the valve portion 41, and these balances hold the valve portion 41 at the seating position of the lower seat 66 and close the low pressure port 63. At this time, the volume chamber 8 and the first back pressure chamber 6 communicate with the high-pressure fuel passage 23 via the high-pressure port 61, and both are at high pressure.

  When the solenoid 51 of the electromagnetic two-way valve 5 is energized, the on-off valve 52 is separated from the low pressure seat 37 and the low pressure port 36 is opened. The second back pressure chamber 7 communicates with the low pressure source 3 via the low pressure port 36 and the first orifice 32, and the pressure decreases, so that the balance of the force acting on the hydraulic servo valve 4 is lost. Then, the valve portion 41 is separated from the lower seat 66 to open the low pressure port 63, and then is seated on the upper seat 65 to close the high pressure port 61.

  That is, in this embodiment, as shown in FIG. 10B, the hydraulic pressure of the second back pressure chamber 7 acts on the hydraulic servo valve 4 in the direction of closing the low pressure port 63 (valve closing force: FIG. In the opposite direction, the oil pressure (auxiliary force) of the volume chamber 8 and the oil pressure (inhibitory force) of the first back pressure chamber 6 act in the opposite direction (upward arrow in the figure). Also in this case, the oil pressure (auxiliary force) from the volume chamber 8 communicating with the high-pressure source 3 that is a stable pressure source is in the same direction as the oil pressure (inhibition force) of the first back pressure chamber 6 that is likely to fluctuate. As a result, the effect of mitigating the influence of the fluctuation of the inhibition force can be obtained as compared with the conventional configuration shown in FIG. Therefore, the balance point between the sum of the inhibition force + the assisting force and the valve closing force is unlikely to fluctuate, and the control of the valve closing start point of the hydraulic servo valve 4 is stabilized, so that the injection controllability is improved.

(Third embodiment)
11 and 12 show an injector according to a third embodiment of the present invention. In the present embodiment, the hydraulic servo valve 4 serving as a control valve is configured as a two-way valve in the configuration of the second embodiment, and the same number is assigned to a portion that operates substantially the same as the first and second embodiments. Is attached. Hereinafter, the difference from the second embodiment will be mainly described.

  In FIG. 11, the injector controls the lift of the nozzle needle 1 by driving the hydraulic servo valve 4 by the electromagnetic two-way valve 5. In the present embodiment, the valve portion 41 of the hydraulic servo valve 4 is a two-position two-way valve that switches communication / shutoff between the nozzle back pressure chamber 12 and the low pressure source 3, and the nozzle back pressure chamber 12 has a fourth orifice. 26 is connected to a high-pressure line 21 leading to the high-pressure source 2 through 26. The servo piston 42 includes a volume chamber 8 that is always in communication with the high pressure line 21 on the valve portion 41 side, and a second back pressure chamber 7 on the opposite side of the valve portion 41. The second back pressure chamber 7 is connected to the low pressure line 31 via the first orifice 32 and the high pressure line 21 via the second orifice 22, and the pressure is reduced by the electromagnetic two-way valve 5 provided downstream of the first orifice 32. The configuration to be controlled is the same as in the first and second embodiments.

  FIG. 12 is a diagram illustrating a specific configuration example of the hydraulic servo valve 4 of the injector according to the third embodiment. The hydraulic servo valve 4 has a valve portion 41 accommodated in the first back pressure chamber 6 and a large-diameter servo piston 42 accommodated in a cylinder 44 provided in the second valve body B4. In the first back pressure chamber 6, a low pressure port 63 is opened at the center of the lower surface, and a lower seat (low pressure seat) 66 is formed at the periphery of the opening. A third orifice 33 is formed in the distance piece B2 following the low pressure port 63, and communicates with the low pressure source 3 of FIG. On the other hand, a fourth orifice 26 communicating with the high pressure fuel passage 23 is opened on the side surface of the first back pressure chamber 6, and is always in communication with the high pressure source 2.

  The valve portion 41 of the hydraulic servo valve 4 has a cylindrical shape, and its upper end extends into the cylinder 44 of the second valve body B4 and is directly connected to the lower surface of the servo piston 42 so that it can move integrally. When the servo piston 42 is lowered, the valve portion 41 is seated on the lower seat 66 on the low pressure side, and the communication between the nozzle back pressure chamber 12 and the low pressure port 63 is blocked. When the servo piston 42 is lifted, the valve portion 41 opens the lower seat 66 and allows the nozzle back pressure chamber 12 and the low pressure port 63 to communicate with each other.

  In the present embodiment, similarly to the second embodiment, the second back pressure chamber 7 is formed on the upper end surface side of the servo piston 42 and the volume chamber 8 is always in communication with the high pressure fuel passage 23 through the passage 25 on the lower end surface side. Is formed. The second back pressure chamber 7 communicates with the low pressure port 36 opened at the upper end surface of the second valve body B4 via the first orifice 32 and constantly communicates with the high pressure fuel passage 23 via the second orifice 22. A spring 47 is disposed in the second back pressure chamber 7 to urge the large-diameter piston portion 45 toward the volume chamber 8 side.

  Also in the present embodiment, as shown in FIG. 10B, the hydraulic pressure of the second back pressure chamber 7 acts on the hydraulic servo valve 4 in the direction of closing the low pressure port 63 (valve closing force). The oil pressure (auxiliary force) in the volume chamber 8 and the oil pressure (inhibition force) in the first back pressure chamber 6 act in the opposite direction (upward arrow in the figure). Therefore, an effect of reducing the influence of the fluctuation of the inhibition force is obtained, and the balance point of the force with the valve closing force is less likely to fluctuate, so that the closing control of the hydraulic servo valve 4 is stabilized and the injection controllability is improved.

  As described above, according to the present invention, among the forces acting on the hydraulic servo valve 4, by supplying the acting force in the direction that is easily influenced by the pressure fluctuation of the nozzle back pressure chamber from the two pressure chambers, Even when one of the pressures fluctuates, the operation of the hydraulic servo valve 4 can be stabilized. Therefore, the controllability (linear response) of the injection amount with respect to the command pulse is improved, and a high-performance injector can be realized with reduced variations.

It is a block diagram of the injector which becomes 1st Embodiment of this invention. It is sectional drawing of the principal part of the injector of 1st Embodiment. It is the schematic diagram and timing chart of an injector principal part for demonstrating the behavior of a 1st back pressure chamber pressure. It is the schematic diagram and timing chart of an injector principal part for demonstrating the behavior of a 2nd back pressure chamber pressure. (A) is the schematic diagram for demonstrating the force which acts on the conventional injector, and a figure which shows the change of an oil pressure, (b) is the schematic diagram and oil for demonstrating the force which acts on the injector of this invention It is a figure which shows the change of a pressure. It is a figure which shows the dispersion | variation in the injection amount by the fluctuation | variation of a 1st back pressure chamber pressure compared with a desired characteristic. It is a figure which shows the dispersion | variation in the injection amount by the fluctuation | variation of a 1st back pressure chamber pressure compared with a desired characteristic. It is the schematic of the typical example of the conventional injector compared with the said injector which shows the flow of the fuel as control oil. It is a block diagram of the injector which becomes 2nd Embodiment of this invention. It is sectional drawing of the principal part of the injector of 2nd Embodiment. It is a figure explaining the action | operation of the injector which becomes 2nd Embodiment of this invention. It is a block diagram of the injector which becomes 3rd Embodiment of this invention. It is sectional drawing of the principal part of the injector which becomes 3rd Embodiment. (A) is principal part sectional drawing of the conventional injector, (b) is the elements on larger scale of (a), (c) is a timing chart for demonstrating the behavior of the conventional injector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle needle 11 Injection hole 12 Nozzle back pressure chamber 13 Fuel pool 14 Cylinder 15 Nozzle spring 2 High pressure source 21 High pressure line 22 First orifice 23 High pressure fuel passages 24-26 Passage 3 Low pressure source 31 Low pressure line 32 Second orifice 33 Third Orifice 34 Low pressure passage 35 Passage 4 Hydraulic servo valve (control valve)
41 Valve part 42 Servo piston 43 Valve spring 44 Cylinder 45 Large diameter piston part 47 Spring 5 Electromagnetic two-way valve 51 Solenoid 52 On-off valve 53 Armature 54 Spring 6 First back pressure chamber 61 Low pressure port 62 Upper seat (low pressure seat)
63 High pressure port 64 Lower seat (high pressure seat)
65 Spring 7 Second back pressure chamber 8 Volume chamber

Claims (7)

A nozzle back pressure chamber that is provided on the back side of the nozzle needle that opens and closes the nozzle hole for fuel injection, and that communicates with a high pressure source to generate the back pressure of the nozzle needle;
A first control valve for switching communication / blocking between the nozzle back pressure chamber and the low pressure source;
An injector having a second control valve for driving the first control valve;
The first control valve includes a valve portion disposed in a first back pressure chamber provided between the nozzle back pressure chamber and a low pressure source, and a servo piston provided to be movable integrally with the valve portion. A hydraulic servo valve in which a volume chamber communicating with a high pressure source is formed on one end face side of the servo piston, and a second back pressure chamber whose pressure is controlled by the driving means is formed on the other end face side;
The second control valve is an on-off valve that is driven by an actuator to switch communication / interruption between the second back pressure chamber and the low pressure source;
The hydraulic servo valve is acted on by the oil pressure of the second back pressure chamber, the oil pressure of the first back pressure chamber, and the oil pressure of the volume chamber controlled by the on-off valve, and the first back pressure chamber. An injector characterized in that the oil pressure of one of the second back pressure chamber and the volume chamber is applied in the same direction as the oil pressure of the pressure chamber.   The injector according to claim 1, wherein the second back pressure chamber communicates with a passage leading to the on-off valve via an orifice and communicates with a high pressure source via another orifice.   A low-pressure sheet communicating with a low-pressure source and a high-pressure sheet communicating with a high-pressure source are respectively provided on opposite wall surfaces of the first back pressure chamber, and the hydraulic servo valve is connected to the valve portion when the on-off valve is driven. 3. The injector according to claim 1, wherein the injector is a three-way valve that is seated on one of the seat and the high-pressure seat to selectively connect the nozzle back pressure chamber to a low-pressure source or a high-pressure source.   2. A low-pressure seat communicating with a low-pressure source is provided on a wall surface of the first back pressure chamber, and the hydraulic servo valve is a two-way valve that opens and closes the low-pressure seat as the valve is driven. Or the injector of 2. The servo piston is slidably disposed in a cylinder located coaxially with the first back pressure chamber in which the valve portion is disposed, and the second back pressure is provided at an end of the cylinder on the valve portion side. The chamber is provided with the volume chamber on the other end side, and the oil pressure of the second back pressure chamber and the oil pressure of the volume chamber act in opposite directions,
The low pressure seat is provided on the servo piston side wall surface of the first back pressure chamber, and when the valve portion is seated on the low pressure seat, the oil pressure of the second back pressure chamber is set to the first back pressure chamber. The injector according to claim 3 or 4, wherein the injector acts in the same direction as the oil pressure. The servo piston is slidably disposed in a cylinder located coaxially with the first back pressure chamber in which the valve portion is disposed, and the volume chamber is provided at an end of the cylinder on the valve portion side. The second back pressure chamber is provided on the other end side, and the oil pressure of the second back pressure chamber and the oil pressure of the volume chamber act in opposite directions,
When the low pressure seat is provided on the wall surface of the first back pressure chamber opposite to the servo piston and the valve portion is seated on the low pressure seat, the oil pressure in the volume chamber is changed to the oil in the first back pressure chamber. The injector according to claim 3 or 4, wherein the injector is applied in the same direction as the pressure.   7. The injector according to claim 1, wherein the actuator is a solenoid that sucks and drives an armature that is displaced integrally with the on-off valve.

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