JP6603622B2 - Injector - Google Patents

Description

  The present invention relates to an injector for injecting fuel.

2. Description of the Related Art Conventionally, an injector including a needle, a body, a back pressure chamber, an inflow path, an outflow path, and a drive unit described below is well known.
The needle is a valve body that opens and closes a nozzle hole through which fuel is injected.
The body is provided in a cylindrical shape, accommodates the needle on the inner periphery, and has a nozzle hole.
The back pressure chamber is provided to apply a back pressure of fuel to the needle in the direction of closing the nozzle hole.
The inflow path is provided to allow fuel to flow into the back pressure chamber. For example, fuel that has been increased in pressure by a supply pump can flow into the back pressure chamber from the inflow path.
The outflow path is provided to allow fuel to flow out from the back pressure chamber.
The drive unit opens and closes the outflow path based on a control signal supplied from the control unit, thereby reducing or increasing the back pressure and operating the opening and closing of the nozzle hole by the needle.

  And by increasing the back pressure, the seat portion provided on the needle is seated at the seat position on the inner wall of the body to close the nozzle hole, and by reducing the back pressure, the axial direction of the needle at the seat portion and the seat position The lift amount, which is the separation distance, increases to open the nozzle hole.

By the way, in such an injector, when the increase amount of the lift amount per unit time is defined as the lift speed, a configuration for changing the lift speed is known (for example, see Patent Document 1).
Note that, by changing the lift speed, as will be described in detail later, for example, it is possible to achieve both reduction in smoke generation and increase in output.

According to the injector of Patent Document 1, there are two outflow paths, and a drive unit that opens and closes each outflow path is provided. By controlling the opening and closing of the two outflow passages, the amount of fuel outflow from the back pressure chamber can be increased or decreased to change the lift speed.
However, in the configuration of Patent Document 1, two drive units are required for two outflow passages, which causes a problem that the size of the injector is increased. In addition, when there are a plurality of driving units, there is a problem that power consumption during driving of the driving unit increases.

US Patent Application Publication No. 2013/0233941 A1

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide an injector capable of changing a lift speed without providing a plurality of drive units.

According to the first invention of the present application, the injector includes a needle, a body, a back pressure chamber, an outflow passage, a drive unit, a switching valve body, and a switching unit described below.
The needle is a valve body that opens and closes a nozzle hole through which fuel is injected.
The body is provided in a cylindrical shape, accommodates the needle on the inner periphery, and has a nozzle hole.
The back pressure chamber is provided to apply a back pressure of fuel to the needle in the direction of closing the nozzle hole.
The outflow path is provided to allow fuel to flow out from the back pressure chamber.
The drive unit opens and closes the outflow path based on a control signal supplied from the control unit, thereby reducing or increasing the back pressure and operating the opening and closing of the nozzle hole by the needle.

  And a drive part increases a back pressure, and the seat part provided in the needle seats on the seat position of the inner wall of a body, and closes a nozzle hole. Further, the drive unit opens the nozzle hole by decreasing the back pressure to increase the lift amount, which is the separation distance in the axial direction between the seat unit and the needle at the seat position.

Here, if the increase amount of the lift amount per unit time is defined as a lift speed, the needle operates in a first mode that operates at the first lift speed and a second lift speed that is smaller than the first lift speed. Operates in two modes.
The switching valve body is driven by the drive unit to switch opening and closing of the outflow path.
The switching unit switches between the first mode and the second mode by moving with the displacement of the switching valve body.
The projected area on the surface perpendicular to the axial direction of the pressure-receiving surface that applies back pressure to the needle in the first mode is the projected area on the surface that is perpendicular to the axial direction of the pressure-receiving surface that applies back pressure to the needle in the second mode. Smaller than.
The switching unit is relatively displaced with respect to the switching valve body in the first mode, and is not relatively displaced with respect to the switching valve body in the second mode.

Thereby, the volume swept by the pressure receiving surface in the first mode can be made smaller than the volume swept by the pressure receiving surface in the second mode. For this reason, the needle lift amount in the first mode with respect to the fuel outflow amount from the back pressure chamber can be made larger than the needle lift amount in the second mode. Thereby, the lift speed in the first mode can be made larger than the lift speed in the second mode, and the lift speed can be changed.
In addition, since the first mode and the second mode are switched by the movement of the switching unit accompanying the displacement of the switching valve body, no additional driving unit is required, and a plurality of driving units may not be provided.
As a result, an injector capable of changing the lift speed without providing a plurality of drive units can be provided.

According to the second invention of the present application, the injector includes the switching unit.
Here, the switching unit switches between the first mode and the second mode by moving with the displacement of the switching valve body.
When the flow path that restricts the amount of fuel flowing out from the back pressure chamber to the outflow passage is a throttle, the cross-sectional area perpendicular to the flow direction of the throttle fuel in the first mode is the fuel of the throttle in the second mode. Greater than the cross-sectional area perpendicular to the flow direction.
The switching unit is relatively displaced with respect to the switching valve body in the first mode, and is not relatively displaced with respect to the switching valve body in the second mode.

Thereby, the outflow amount of the fuel from the back pressure chamber in the first mode can be made larger than that in the second mode, and the lift amount of the needle in the first mode can be made larger than the lift amount of the needle in the second mode. For this reason, the lift speed in the first mode can be made larger than the lift speed in the second mode, and the lift speed can be changed.
In addition, since the first mode and the second mode are switched by the movement of the switching unit accompanying the displacement of the switching valve body, no additional driving unit is required, and a plurality of driving units may not be provided.
As a result, an injector capable of changing the lift speed without providing a plurality of drive units can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing an entire injector (Example 1). It is principal part sectional drawing of an injector (Example 1). (A) Operation | movement explanatory drawing when the displacement amount of a switching valve body is small, and (b) When the displacement amount of a switching valve body is large (Example 1). (A) Lift amount and (b) Time variation of injection rate (Example 1). (A) It is a comparison figure of the injection rate with respect to the magnitude | size of the lift speed immediately after a lift start, (b) Spray length, and (c) Smoke generation amount (conventional example). (A) A theoretical cycle and the present PV diagram, and (b) A comparison figure of the injection rate with respect to the magnitude of lift speed (conventional example). (Example 2) which is principal part sectional drawing of an injector. (A), (b) It is principal part sectional drawing of an injector (modification). It is principal part sectional drawing of an injector (modification).

  Hereinafter, modes for carrying out the invention will be described based on examples. In addition, an Example discloses a specific example, and it cannot be overemphasized that this invention is not limited to an Example.

[Example 1]
The structure of the injector 1 of Example 1 is demonstrated using FIG.
The injector 1 is one element that constitutes a fuel supply device together with a supply pump (not shown), a common rail (not shown), and an ECU 2 that is a control unit. The supply pump increases the pressure of the fuel, and the common rail temporarily stores the fuel increased in pressure by the supply pump.
Then, high-pressure fuel is distributed and supplied from the common rail to the injector 1.
The ECU 2 calculates the injection amount based on the load of the internal combustion engine (not shown), the rotational speed of the internal combustion engine, and the like, and according to the rail pressure of the common rail supplied to the injector 1, the injection start time and the injection amount An injection period corresponding to is calculated.

The injector 1 is mounted on an internal combustion engine, and is used, for example, to directly inject high-pressure fuel exceeding 250 MPa into a cylinder.
The injector 1 includes a needle 4, a body 5, a back pressure chamber 6, an outflow path 7, and a drive unit 8 described below. In the following description, the axial front end side and the axial rear end side are simply referred to as the front end side and the rear end side.
The needle 4 has a cylindrical shape and is a valve body that opens and closes a nozzle hole 9 through which fuel is injected. The needle 4 is provided with a seat portion 10 that opens and closes the nozzle hole 9 at the tip.

The body 5 has a cylindrical shape, and accommodates the needle 4 slidably on the inner periphery. A nozzle hole 9 is formed at the tip of the body 5. In addition, a seat surface 11 on which the seat portion 10 is seated and detached is formed on the inner wall of the body 5. Here, the position at which the seat portion 10 is seated on the seat surface 11 is defined as a seat position 12.
When the seat portion 10 is separated from the seat position 12, the injection hole 9 is opened and fuel is injected, and when the seat portion 10 is seated at the seat position 12, the injection hole 9 is closed and fuel injection is stopped.

The back pressure chamber 6 is defined by the rear end surface of the needle 4 and is provided to apply a fuel back pressure to the needle 4 in the direction of closing the nozzle hole 9.
The outflow passage 7 allows the fuel to flow out from the back pressure chamber 6.
Details of the back pressure chamber 6 and the outflow passage 7 will be described later.

The drive unit 8 opens and closes the outflow path 7 based on a control signal given from the ECU 2.
Then, the drive unit 8 operates to open and close the nozzle hole 9 by the needle 4 by reducing or increasing the back pressure by opening and closing the outflow passage 7.

  Here, the drive unit 8 is accommodated in the holding body 13. The holding body 13 and the body 5 are fastened by a retaining nut 16 with metal plates 14 and 15 interposed therebetween. Further, high pressure passages 17, 18, 19, and 20 are formed in the holding body 13, the plates 14, 15, and the body 5, respectively, for guiding high pressure fuel supplied from the common rail to the injection holes 9.

  The plate 14 has an outflow passage 7 formed therein and holds the switching valve body 21 in the valve chamber 22. Here, the switching valve body 21 is driven by the driving unit 8 to switch opening and closing of the outflow passage 7. The outflow passage 7 is connected to a low pressure passage 23 in which the drive unit 8 is accommodated. Further, the valve chamber 22 and the outflow passage 7 are connected by a flow path 24. Here, the flow path 24 is a restriction 25 because it limits the amount of fuel flowing out from the back pressure chamber 6 to the outflow path 7.

  Further, the plate 15 is formed with a through hole 26 penetrating in the axial direction communicating with the valve chamber 22 and the space where the rear end surface of the needle 4 exists. Further, the plate 15 is provided with inflow passages 27 and 28 for allowing fuel to flow into the back pressure chamber 6. Here, the inflow passages 27 and 28 are branched from the high-pressure passage 19, and allow the pressurized fuel to flow into the back pressure chamber 6. Here, the inflow path 28 is connected to the through hole 26 through the restriction 28a.

The drive unit 8 is, for example, a piezo actuator, and includes a piezo element 30, a piezo piston 31, a valve piston 32, and the like.
The piezo element 30, the piezo piston 31, and the valve piston 32 are coaxially accommodated in the holding body 13 in this order from the rear end side.
The piezo element 30 is extended by applying a voltage, thereby displacing the piezo piston 31 and the valve piston 32 toward the tip side.

And the displacement transmission shaft 33 distribute | arranged between the valve piston 32 and the switching valve body 21 is displaced to the front end side. Then, when the switching valve body 21 moves to the distal end side together with the displacement transmission shaft 33, the valve portion of the switching valve body 21 separates from the valve seat and opens. When the switching valve body 21 is opened, the outflow passage 7 is opened and the back pressure is reduced.
As the back pressure decreases, the seat portion 10 is separated from the seat position 12, the nozzle hole 9 is opened, and the lift amount, which is the separation distance in the axial direction of the needle 4, increases.
The switching valve body 21 is always urged toward the rear end side by the return spring 35.

On the other hand, the piezo element 30 returns to its original length by stopping the application of voltage, the switching valve body 21 is moved to the rear end side by the return spring 35, and the valve portion of the switching valve body 21 is moved to the valve seat. The outflow passage 7 is closed and the back pressure increases.
As the back pressure increases, the seat portion 10 is seated at the seat position 12 and the nozzle hole 9 is closed.

[Features of Example 1]
The features of the first embodiment will be described with reference to FIG.
The injector 1 has a surrounding portion 40 and a back pressure chamber forming portion 41 described below.
The surrounding portion 40 has a cylindrical cylindrical shape, and its inner peripheral surface is in sliding contact with the outer peripheral surface of the needle rear end portion 43 including the rear end of the needle 4. A through hole 45 penetrating in the axial direction is provided in the top portion 44 that closes the rear end side of the surrounding portion 40.
Here, the needle 4 has a large diameter portion 46 having a diameter larger than the diameter of the needle rear end portion 43 provided on the front end side from the needle rear end portion 43.

The back pressure chamber forming portion 41 forms the back pressure chamber 6 and has a cylindrical shape. The back pressure chamber forming portion 41 has an inner peripheral surface in sliding contact with the outer peripheral surface of the large diameter portion 46.
The back pressure chamber forming portion 41 is urged to the rear end side by a spring 47 compressed and held between the needle 4 and abuts against the front end surface of the plate 15. The surrounding portion 40 is biased toward the rear end side by a spring 48 that is compressed and held between the rear end surface of the large-diameter portion 46 and abuts against the front end surface of the plate 15.
The back pressure chamber forming portion 41 is arranged so as to surround the surrounding portion 40 coaxially with the surrounding portion 40. An inflow passage 27 is connected to a space S1 defined by the surrounding portion 40 and the back pressure chamber forming portion 41 via a throttle 27a.

Here, a transmission shaft 50 provided integrally with the switching valve body 21 is disposed between the surrounding portion 40 and the switching valve body 21. The transmission shaft 50 has a gap with the through hole 26 and is inserted through the through hole 26, and transmits the displacement of the switching valve body 21 to the surrounding portion 40. Further, a gap is formed between the front end of the transmission shaft 50 and the rear end of the surrounding portion 40.
Here, the through hole 45 and the through hole 26 of the surrounding portion 40 are always in communication. That is, the space S2 defined by the surrounding portion 40 and the needle rear end portion 43 and the valve chamber 22 are always in communication.
The space S1 and the space S2 constitute an internal space of the back pressure chamber 6.

[Operation of Embodiment 1]
The operation of the injector 1 will be described with reference to FIGS.
The switching valve body 21 opens the outflow passage 7 by applying a voltage to the piezo element 30 based on a control signal given from the ECU 2.

By starting the outflow of fuel from the outflow passage 7, the pressure in the back pressure chamber 6 decreases.
For this reason, the force received by the tip of the needle 4 exceeds the back pressure and the biasing force of the spring 47. As a result, the needle 4 is pushed up to the rear end side, starts to be displaced, and the seat portion 10 of the needle 4 is separated from the seat position 12 of the body 5, thereby opening the nozzle hole 9.
Note that the force received by the tip of the needle 4 before the seating is the force received by the outer peripheral portion of the needle 4 from the seat portion 10.

First, the case where the displacement amount of the switching valve body 21 is small will be described.
At this time, as shown in FIG. 3A, the outflow path 7 is opened, but the transmission shaft 50 is not in contact with the surrounding portion 40.
For this reason, the fuel discharge speed in the space S2 is related to the lift speed.
That is, the projected area on the surface perpendicular to the axial direction of the pressure receiving surface that applies back pressure to the needle 4 is as shown in FIG.

Next, a case where the displacement amount of the switching valve body 21 is large will be described.
At this time, as shown in FIG. 3B, the surrounding portion 40 moves to the distal end side by the transmission shaft 50.
Thereby, not only the space S2 but also the fuel discharge speed in the space including the space S1 is related to the lift speed. That is, by the movement of the surrounding part 40, the surrounding part 40 communicates the space S2 on the inner peripheral side and the space S1 on the outer peripheral side, and expands the space region related to the lift speed.
For this reason, the projected area on the surface perpendicular to the axial direction of the pressure receiving surface that applies the back pressure to the needle 4 is as shown in FIG.
In Example 1, first, the needle 4 operates in a state where the displacement amount of the switching valve body 21 is small, and then the needle 4 operates in a state where the displacement amount of the switching valve body 21 is large.

In addition, since the outflow amount to the outflow passage 7 is limited by the restriction 25, the outflow amount does not change regardless of the displacement amount of the switching valve body 21.
Further, when the maximum displacement amount of the switching valve body 21 is L1 and the axial separation distance between the transmission shaft 50 and the surrounding portion 40 is L2, there is a relationship of L1> L2 (see FIG. 2).
The amount of displacement of the switching valve body 21 can be adjusted by the voltage applied to the piezo element 30.

[Effect of Example 1]
Here, in the needle 4, the increase amount of the lift amount per unit time is defined as the lift speed, and the operation at the first lift speed is performed at the first mode and the second lift speed smaller than the first lift speed. This is the second mode.
In Example 1, after the lift started, the pressure-receiving surface projected area changed from a small state to a large state. When the projected area of the pressure receiving surface is small, the lift amount of the needle 4 is large with respect to the amount of fuel outflow from the back pressure chamber 6, and when the projected area of the pressure receiving surface is large, the amount of fuel outflow from the back pressure chamber 6 is large. The lift amount of the needle 4 is reduced.

That is, after the lift starts, the needle 4 first operates in the first mode and then operates in the second mode.
In addition, the first mode and the second mode are switched by the surrounding portion 40 moving in accordance with the displacement of the switching valve body 21. That is, the surrounding unit 40 has the function of the switching unit 51.

In summary, in the injector 1 according to the first embodiment, the needle 4 has a first mode that operates at the first lift speed and the first lift speed when the increase amount of the lift amount per unit time is the lift speed. Operate in a second mode that operates at a smaller second lift speed.
The switching unit 51 switches between the first mode and the second mode by moving with the displacement of the switching valve body 21.
The projected area of the pressure receiving surface that applies back pressure to the needle 4 in the first mode onto the plane perpendicular to the axial direction is the projection onto the surface perpendicular to the axial direction of the pressure receiving surface that applies back pressure to the needle in the second mode. Smaller than the area.

Thereby, the lift speed in the first mode can be made larger than the lift speed in the second mode, and the lift speed can be changed.
Further, since the first mode and the second mode are switched in accordance with the displacement of the switching valve body 21, no additional driving unit is required, and a plurality of driving units may not be provided.
As a result, the injector 1 capable of changing the lift speed without providing a plurality of drive units can be provided.

Here, FIG. 4 shows changes over time in the lift amount and the fuel injection rate in the first embodiment.
In the first embodiment, the needle 4 operates first in the first mode with a high lift speed, and then operates in the second mode with a low lift speed.
Here, 1st in the figure is a period during which the needle 4 is operating in the first mode, and 2nd is a period during which the needle 4 is operating in the second mode.

Here, immediately after the lift is started, the injection rate, which is the amount of fuel injected per unit time, can be increased by operating the needle 4 in the first mode with a high lift speed. Therefore, the spray length, which is the distance at which the fuel diffuses from the nozzle hole 9, can be increased, and the fuel can be burned at a position further away from the nozzle hole 9 (FIGS. 5A and 5B). reference.).
For this reason, the combustion of fuel in the vicinity of the oxygen-deficient nozzle hole 9 is suppressed, so that the generation of smoke can be reduced (see FIG. 5C).

Next, by lowering the lift speed of the needle 4, the fuel injection period can be lengthened, and the amount of fuel supplied with the increase in the volume of the combustion chamber can be increased, so that isobaric combustion The area can be increased. As a result, the combustion cycle can be brought close to the theoretical cycle, so that the output of the internal combustion engine can be increased (see FIG. 6A).
Further, since the peak value of the fuel injection rate is reduced, noise generated due to rapid fuel supply can be suppressed (see FIG. 6B).

By the way, in the case of an injector in which the lift speed does not change, if the lift speed is adjusted fast, even if the generation of smoke can be reduced, the fuel injection period is shortened and the peak value of the fuel injection rate is increased. It cannot cope with an increase in the output of the internal combustion engine and suppression of noise generation. On the other hand, if the lift speed is adjusted to be slow, the generation of smoke cannot be reduced even if the increase in the output of the internal combustion engine and the suppression of the generation of noise can be accommodated.
That is, an injector that operates at a single lift speed cannot achieve both reduction in smoke generation, increase in output, and suppression of noise generation.
However, in the injector 1 of the first embodiment, by changing the lift speed, it is possible to achieve both reduction in smoke generation, increase in output, and suppression of noise generation.

Moreover, the surrounding part 40 which is the switching part 51 is a celestial cylindrical body which slidably contacts the outer peripheral surface of the needle rear end part 43 including the rear end of the needle.
Further, the back pressure chamber 6 is provided in the distal end side of the needle rear end portion 43 and is in a cylindrical shape which is in sliding contact with the outer peripheral surface of the large diameter portion larger in the radial direction than the needle rear end portion 43 and includes the switching portion 51 on the inner peripheral side. The back pressure chamber forming portion 41 is formed.
The switching unit 51 switches between the first mode and the second mode by switching the communication interruption between the inner space S2 and the outer space S1 by movement.
Thereby, it can be set as the structure which changes the lift speed of the needle 4 only by combining a some cylindrical body.

[Example 2]
The features of the second embodiment will be described with reference to FIG.
In the second embodiment, the same functions as those in the first embodiment are denoted by the same reference numerals.
In the second embodiment, the cross-sectional area perpendicular to the fuel flow direction of the through hole 45 provided in the top portion 44 of the surrounding portion 40 is smaller than the cross-sectional area perpendicular to the fuel flow direction of the flow path 24.
That is, when the displacement amount of the switching valve body 21 is small, the through hole 45 becomes the throttle 25. For this reason, the amount of fuel flowing out from the back pressure chamber 6 to the outflow passage 7 is reduced, and the lift speed is reduced.
On the other hand, when the displacement amount of the switching valve body 21 is large, the flow path 24 becomes the restriction 25 and the cross-sectional area of the restriction 25 becomes large. For this reason, the amount of fuel outflow from the back pressure chamber 6 to the outflow passage 7 increases and the lift speed can be increased.

That is, the cross-sectional area perpendicular to the fuel flow direction of the throttle in the first mode is larger than the cross-sectional area perpendicular to the fuel flow direction of the throttle in the second mode.
Thereby, the outflow amount of the fuel from the back pressure chamber in the first mode can be made larger than that in the second mode, and the lift amount of the needle 4 with respect to the outflow amount of the fuel from the back pressure chamber in the first mode can be increased. For this reason, the lift speed in the first mode can be made larger than the lift speed in the second mode, and the lift speed can be changed.

In addition, since the first mode and the second mode are switched by the movement of the switching unit 51 accompanying the displacement of the switching valve body 21, no additional driving unit is required, and a plurality of driving units may not be provided.
As a result, the injector 1 capable of changing the lift speed without providing a plurality of drive units can be provided.
In the second embodiment, the behavior of the lift speed of the needle 4 with respect to the amount of displacement of the switching valve body 21 is opposite to that in the first embodiment.

  Further, even when the displacement amount of the switching valve body 21 is large, there is a concern that the lift speed is limited by the fuel outflow speed through the through hole 45, but the fuel pressure acting on the rear end face of the large diameter portion 46 is concerned. Since the force acting on the rear end side of the needle 4 increases due to the decrease, the outflow speed of the fuel through the through hole 45 also increases, so there is no problem.

[Modification]
Various modifications can be considered for the present invention without departing from the gist thereof.
In addition, in a modification, the same function thing as Example 1, 2 is attached | subjected and represented.
In the first embodiment, the needle 4 is operated in the second mode after the first mode. However, the needle 4 may be operated in the first mode after the second mode.
Thereby, the minute injection amount can be controlled with high accuracy.

In the first and second embodiments, the rear end surface of the surrounding portion 40 is flat, but the rear end surface of the surrounding portion 40 may be tapered as shown in FIG. At this time, if the diameter of the sheet portion 60 in contact with the plate 15 is r1, and the diameter of the needle rear end portion 43 is r2, there is a relationship of r1 <r2.
Thereby, the pressure of the fuel from the inflow path 27 can be applied also to the inner diameter side of the needle rear end portion 43, and the surrounding portion 40 can be quickly moved to the front end side. For this reason, the back pressure of the back pressure chamber 6 can be quickly increased, and the valve closing operation by the needle 4 can be accelerated.
In this configuration, since the fuel can be introduced into the space S2 and the like by moving the surrounding portion 40 to the tip side by the fuel pressure of the inflow path 27, the inflow path 28 is not necessary.

  In the first and second embodiments, the space S2 and the valve chamber 22 are communicated with each other through the through hole 26 and the through hole 45 provided in the top portion 44 of the surrounding portion 40. However, as shown in FIG. In this way, the communication passage 62 may be provided in the transmission shaft 50 and the valve body 21. At this time, the communication path 62 can be the throttle 25.

In the first and second embodiments, the number of the surrounding members 40 as the switching unit 51 is one, but a configuration having a plurality of switching units 51 as shown in FIG.
In this case, the needle 4 has a large-diameter portion 63 having a larger diameter than the diameter of the large-diameter portion 46 on the distal end side of the large-diameter portion 46.
In this configuration, as the displacement amount of the switching valve body 21 increases, the projected area on the surface perpendicular to the axial direction of the pressure receiving surface that applies the back pressure to the needle 4 is the needle rear end portion 43, the large diameter portion 46, It changes to the area of the large diameter portion 63.

1 Injector 2 ECU (Control Unit) 4 Needle 5 Body 6 Back Pressure Chamber
7 Outflow path 8 Drive part 9 Injection hole 10 Seat part 12 Seat position 21 Switching valve body 55 Switching part

Claims (4)

A needle (4) as a valve body for opening and closing a nozzle hole (9) for fuel injection;
A body (5) provided in a cylindrical shape and containing the needle on the inner periphery, and having the nozzle hole;
A back pressure chamber (6) for applying a back pressure of fuel to the needle in a direction of closing the nozzle hole;
An outflow passage (7) through which fuel flows out from the back pressure chamber;
A drive unit (8) for operating the opening and closing of the nozzle hole by the needle by reducing or increasing a back pressure by opening and closing the outflow path based on a control signal given from the control unit (2);
By increasing the back pressure, the drive unit seats the seat (10) provided on the needle at the seat position (12) on the inner wall of the body, closes the nozzle hole, and reduces the back pressure. In the injector (1) that opens the nozzle hole by increasing a lift amount, which is a distance in the axial direction of the needle between the seat portion and the seat position by decreasing,
The needle has a first mode that operates at a first lift speed and a second lift speed that operates at a second lift speed that is smaller than the first lift speed, where the increase amount of the lift amount per unit time is defined as a lift speed. Operates in two modes,
A switching valve body (21) that is driven by the drive unit and switches between opening and closing of the outflow path;
A switch (51) for switching between the first mode and the second mode by moving with the displacement of the switching valve body,
The projected area of the pressure receiving surface that applies back pressure to the needle in the first mode onto the surface perpendicular to the axial direction is a surface that is perpendicular to the axial direction of the pressure receiving surface that applies back pressure to the needle in the second mode. rather smaller than the projected area of the to,
Injector the switching unit, wherein in the first mode and relatively displaced with respect to the switching valve body, and in the second mode, characterized that no such relatively displaced with respect to the switching valve body. The injector according to claim 1, wherein
The back pressure chamber is provided on the rear end side of the needle,
The switching unit is a cylindrical body that is in sliding contact with the outer peripheral surface of the needle rear end including the rear end of the needle,
The back pressure chamber is provided on the distal end side of the needle rear end portion and is in sliding contact with the outer peripheral surface of the large diameter portion (46) larger in the radial direction of the needle than the needle rear end portion, and the switching portion is disposed on the inner peripheral side. Formed by a cylindrical back pressure chamber forming part (41) included in
The said switching part switches the said 1st mode and the said 2nd mode by switching the communication interruption | blocking with the space of an inner peripheral side and the outer peripheral side by movement, The injector characterized by the above-mentioned. A needle as a valve body for opening and closing a nozzle hole for fuel injection;
A cylindrical body that houses the needle on the inner periphery and has the nozzle hole;
A back pressure chamber for applying a back pressure of fuel to the needle in a direction of closing the nozzle hole;
An outflow passage through which fuel flows out from the back pressure chamber;
A drive unit that opens or closes the outflow path based on a control signal given from the control unit, thereby reducing or increasing a back pressure to operate opening and closing of the nozzle hole by the needle;
The drive unit increases the back pressure so that the seat portion provided on the needle is seated on the seat portion of the inner wall of the body, closes the nozzle hole, and reduces the back pressure. In the injector that opens the nozzle hole by increasing the lift amount, which is the separation distance in the axial direction of the needle between the portion and the seat position,
The needle has a first mode that operates at a first lift speed and a second lift speed that operates at a second lift speed that is smaller than the first lift speed, where the increase amount of the lift amount per unit time is defined as a lift speed. Operates in two modes,
A switching valve body that is driven by the drive unit and switches between opening and closing of the outflow path;
By moving along with the displacement of the switching valve body, it has a switching unit that switches between the first mode and the second mode,
When a flow path that restricts the amount of fuel flowing out from the back pressure chamber to the outflow path is a throttle (25), the cross-sectional area perpendicular to the fuel flow direction of the throttle in the first mode is larger than cross sectional area perpendicular to the flow direction of the fuel stop the in 2 mode rather,
Injector the switching unit, wherein in the first mode and relatively displaced with respect to the switching valve body, and in the second mode, characterized that no such relatively displaced with respect to the switching valve body. Injector according to claim 3,
The back pressure chamber is provided on the rear end side of the needle,
The switching unit is a cylindrical body that is in sliding contact with the outer peripheral surface of the needle rear end including the rear end of the needle,
The back pressure chamber is provided on a distal end side of the needle rear end portion, and is in sliding contact with an outer peripheral surface of a large diameter portion larger in the radial direction of the needle than the needle rear end portion and includes the switching portion on the inner peripheral side. Formed by the back-pressure chamber forming portion,
The switching portion is closed at the rear end side by the closing portion (44) and has a through hole (45) penetrating the closing portion, and the movement does not cause the through hole to become the throttle. An injector characterized by switching between the first mode and the second mode by switching.

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