JP6476998B2 - Fuel injection device - Google Patents

Description

  The present invention relates to a fuel supply device mounted on a vehicle such as an automobile, and more particularly to a common rail type (accumulation type) fuel supply device known as a fuel injection system for a diesel engine. The present invention relates to a fuel injection device (hereinafter also referred to as “injector”).

[Conventional technology]
This type of injector, which has been widely used conventionally, has a valve body (hereinafter also referred to as an “injector body”) in which a passage for high-pressure fuel is formed, and moves in the axial direction inside the valve body. And a valve member (hereinafter also referred to as “nozzle needle”) for opening and closing the nozzle hole.

However, in recent years, in order to further improve the performance, a pressure control chamber is provided inside the valve body, and a control means for controlling the movement of the valve member by the fuel pressure in the pressure control chamber is award. As a typical example, an injector as disclosed in Patent Document 1 (particularly, see FIG. 6) is known.
Such an injector will be briefly described with reference to FIG. 7. The injector 5 is formed inside the injector body 80 on the side opposite to the nozzle hole with the nozzle needle 52 interposed therebetween, and introduces high-pressure fuel to move the nozzle needle 52 in the axial direction. And a control member (hereinafter also referred to as “floating plate”) 72 that can be displaced in the axial direction and that opens and closes the inflow passage 74. ing. The floating plate 72 closes the inflow passage 74 to stop introduction of high-pressure fuel into the pressure control chamber 71 and discharge the fuel in the pressure control chamber 71 from the outflow passage 75 to the outside. By the operation 72, the pressure in the pressure control chamber 71 can be quickly lowered, and the nozzle needle 52 controlled by the pressure of the fuel in the pressure control chamber 71 opens the nozzle hole immediately. Therefore, the response performance of the injector 5 can be improved.

[Problems of the prior art]
However, it has been pointed out that it is difficult to ensure stable fuel injection characteristics with the control means as described above.

  As a result of repeated experiments and researches to find out the cause, the present inventors have found that the following events are inhibiting factors.

(1) The control function by the control means will be verified below with reference to FIG.
The floating plate 72 is provided with an orifice 72a for discharging the fuel in the pressure control chamber 71 to the outflow passage 75. By reducing the pressure in the pressure control chamber 71 through the orifice 72a, the nozzle needle 52 can be opened promptly.
The nozzle needle 52 is restricted in its maximum ascending position (maximum stroke position) when a part 52c of the nozzle needle 52 abuts against the shoulder 76a of the cylindrical member 76, and a predetermined fuel injection characteristic is obtained. .

(2) However, after the nozzle needle 52 reaches the maximum stroke position, a phenomenon that the fuel injection characteristic is disturbed was observed.
The pressure control chamber 71 is defined by a fluid-tight fitting between the cylindrical member 76 and the head portion 52b of the nozzle needle 52. Therefore, the maximum stroke position of the nozzle needle 52 (one of the nozzle needles 52) is formed. The volume of the pressure control chamber 71 is constant at the abutting position between the portion 52c and the shoulder portion 76a of the cylindrical member 76, but this mechanism may cause the above-described disordered fuel injection characteristics. found.
(3) That is, even after the nozzle needle 52 reaches the maximum stroke position, the pressure in the pressure control chamber 71 decreases because the fuel continues to flow out through the orifice 72a. Due to this slight pressure drop, the floating plate 72 receiving the fuel pressure from the inflow passage 74 is pushed down to open the inflow passage 74, so that high-pressure fuel is introduced into the pressure control chamber 71. Then, the floating plate 72 rises immediately and the inflow passage 74 is closed again, so that the floating plate 72 repeats vertical vibration. In response to the behavior of the floating plate 72, the nozzle needle 52 slightly moved up and down, and the fuel injection characteristics were disturbed.

(4) As countermeasures, it is conceivable that [a] the maximum stroke position of the nozzle needle 52 is not restricted, and [b] the rise to the maximum stroke position of the nozzle needle 52 is moderated. However, the former means [a] increases the axial length of the injector 5 in order to ensure the required stroke of the nozzle needle 52, the injector 5 itself becomes large, and the latter means [b] Performance is sacrificed and neither is practical.

JP2011-226659A

  The present invention has been made in view of the above circumstances, and the object of the present invention is to stabilize the behavior of the control member (floating plate) with a simple configuration change and to ensure good fuel injection characteristics. It is an object of the present invention to provide a fuel injection device (injector) that can be used.

[Means of Claim 1]
In the fuel injection device (injector) according to claim 1, a valve body (injector body) having a nozzle hole formed at a tip portion for injecting high-pressure fuel into a combustion chamber of the engine, and an axial movement of the valve body move. A valve member (nozzle needle) that opens and closes the nozzle hole at one end thereof, and is formed on the opposite side of the nozzle hole across the valve member inside the valve body, and introduces high-pressure fuel to A pressure control chamber that is controlled by the pressure of the fuel, a cylindrical member that receives the other end of the valve member, partitions the pressure control chamber, and is interposed between the valve member and the cylindrical member, and closes the valve member A return spring that presses in the direction, an inflow passage that introduces high-pressure fuel into the pressure control chamber, an outflow passage that allows the fuel in the pressure control chamber to flow out to the low-pressure side outside, and the pressure control chamber can be displaced in the axial direction. Control member that opens and closes the inflow passage (flow A coating plate), a has a basic structure.
As a return spring, a spring having a unique spring characteristic in which an initial displacement amount is large and a late displacement amount is small is used.

According to the said structure, since the valve member (nozzle needle) can be opened quickly at the time of valve opening, the outstanding response performance is obtained. And since it can raise gently before the maximum stroke position, time (injection time) until it reaches a maximum stroke position after a valve member opens can fully be ensured. Thereby, it is not necessary to deliberately regulate the maximum stroke position of the valve member, and inappropriate behavior (vertical vibration) is not caused to the control member (floating plate).
In addition, the return spring is an existing essential part, and the above functions can be obtained only by changing the specifications of the spring. Therefore, no special modification or additional parts are required.
Therefore, it is possible to provide a fuel injection device (injector) that can ensure high response performance and good fuel injection characteristics while having a compact and inexpensive configuration.

The overall structure of the co-Monreru fuel supply device is a diagram schematically showing (Reference Example). It is a longitudinal cross-sectional view which shows the basic composition of a fuel-injection apparatus ( reference example 1 ). It is a longitudinal cross-sectional view which expands and shows the principal part of a fuel-injection apparatus ( reference example 1 ). For the explanation of the spring characteristics of the return spring employed in the fuel injection device , (a) and (b) are characteristic diagrams showing the spring characteristics of the reference example , and (c) are conventional spring characteristic diagrams. (A)-(d) is a schematic diagram with which it uses for description of the specific structural example of the spring which implement | achieves the spring characteristic shown to Fig.4 (a) ( reference example 1 ). (A), (b) is a schematic diagram with which it uses for description of the specific structural example of the spring which implement | achieves the spring characteristic shown in FIG.4 (b) ( reference example 1 ). It is a longitudinal cross-sectional view which expands and shows the principal part of the conventional fuel injection apparatus (prior art).

Hereinafter, it explains in detail using a drawing .

First, a common rail type (accumulation type) fuel supply device for a diesel engine will be described as a representative example of the fuel supply device.
This fuel supply device is mounted in an engine room of a vehicle such as an automobile. For example, a high-pressure fuel is injected and supplied to each cylinder to a diesel engine having a plurality of cylinders. The overall configuration of the system will be outlined with reference.

  The common rail fuel supply apparatus CR includes a feed pump 2 that pumps fuel from a fuel tank 1 that is a fuel supply source, a high-pressure fuel pump 3 that sucks and pressurizes the fuel discharged from the feed pump 2, and the high-pressure fuel pump. A common rail 4 into which high-pressure fuel discharged from 3 is introduced, a plurality (four in this example) of injectors (fuel injection devices) 5 to which high-pressure fuel is distributed and supplied from each fuel outlet of the common rail 4, an engine An electronic control unit (hereinafter abbreviated as “ECU”) 6 serving as a general control tower for exhibiting a desired fuel supply control function according to the operation state of E is provided. The high-pressure fuel accumulated in the common rail 4 is supplied from each injector 5 into the combustion chamber EN of each cylinder of the engine E in accordance with the fuel injection timing.

  The feed pump 2 is a low-pressure fuel pump that pressurizes the fuel sucked from the fuel tank 1 and sends it to the high-pressure fuel pump 3 through the fuel supply pipe 2a. In this example, the feed pump 2 is an in-tank installed in the fuel tank 1. Although illustrated as an electric fuel pump of the type, a fuel pump of a type that is integrally assembled with the high-pressure fuel pump 3 and is coaxially driven by the pump drive shaft may be employed.

Although the detailed structure of the high-pressure fuel pump 3 is omitted, a pump drive shaft (camshaft) driven by a crankshaft of the engine E, a pump housing that rotatably supports the camshaft, and pressurized fuel This is a well-known pump structure including a plurality of plungers to be fed and a plurality of cylinders that are fitted and supported so that the plungers can be reciprocated. The plunger reciprocates in the cylinder to further pressurize the fuel supplied from the feed pump 2 to generate high-pressure fuel, and function as a supply pump that pumps the fuel to the common rail 4 via the high-pressure fuel pipe 3a. Fulfill.
The high pressure fuel pump 3 includes an electromagnetic fuel metering valve that controls the amount of fuel discharged from the high pressure fuel pump 3 by adjusting the amount of fuel drawn from the feed pump 2 into the fuel pressurizing chamber. doing.

The common rail 4 is a pressure accumulating container that stores high-pressure fuel corresponding to the required injection pressure. A pressure regulator (pressure limiter) 7 is attached to one end of the common rail 4, and a common rail pressure sensor (fuel pressure sensor) 8 is attached to the other end.
The common rail 4 has a plurality (four in this example) of fuel outlets 4a corresponding to the number of injectors 5 arranged between both ends thereof, and each fuel outlet 4a has a fuel distribution pipe. The injector 5 is connected via 4b.

  With the above configuration, the common rail 4 temporarily stores the high-pressure fuel from the high-pressure fuel pump 3 and distributes it to the plurality of injectors 5 through the fuel distribution pipes 4b while maintaining the pressure. In addition, the common rail pressure sensor 8 detects the pressure and temperature of the fuel in the common rail 4 and outputs it to the ECU 6. The pressure regulator 7 keeps the pressure of the fuel in the common rail 4 constant, and depressurizes the excess fuel and discharges it to the low pressure side. The surplus fuel that has passed through the pressure regulator 7 is returned to the fuel tank 1 via the fuel return pipe 4c.

  The injector 5 includes a valve portion 50 that is exposed and disposed in the combustion chamber EN of each cylinder, and is a device that injects and supplies high-pressure fuel stored in the common rail 4 to the combustion chamber EN of each cylinder (the present invention). Device). Although details of the specific structure and function will be described later, the injector 5 controls the injection amount of the high-pressure fuel supplied from the common rail 4 in accordance with a control signal from the ECU 6. In the injector 5, a part of the high-pressure fuel supplied from the fuel distribution pipe 4b and not injected from the valve portion 50 is discharged from the injector 5 to the fuel discharge pipe 5a and returned to the fuel. It returns to the fuel tank 1 through the pipe 4c.

  In addition to the common rail pressure sensor 8 described above, the ECU 6 includes various sensors such as a rotation speed sensor that detects the rotation speed of the engine E, a throttle sensor that detects the throttle opening degree, and an airflow sensor that detects the intake air intake amount. Electrically connected. Based on information from each of these sensors, the ECU 6 sends a command signal for controlling the opening and closing of the solenoid valve of the high-pressure fuel pump 3 and the valve unit 50 of each injector 5 to the electromagnetic fuel metering of the high-pressure fuel pump 3. It outputs to a valve and the solenoid valve part (after-mentioned) of each injector 5. FIG.

[ Reference Example 1 ]
Next, the basic configuration and function of the injector 5 of Reference Example 1 will be described with reference to FIGS.

  In general, the injector 5 includes a valve unit 50, an electromagnetic valve unit 60, a pressure control unit 70, and an injector body (valve body) 80 that houses or holds these units 50 to 70 and forms an outer shell. Yes. The outer injector body 80 is mainly composed of three members: a lower portion nozzle body 81, an upper portion holder 82, and an orifice plate (intermediate block) 83 disposed therebetween.

  The valve portion 50 that is exposed and disposed in the combustion chamber EN of each cylinder is provided at the tip end portion (lower end portion) of the nozzle body 81, and an injection hole 51 that injects high-pressure fuel, and the injection hole 51 on one end side. It is a basic composition provided with the nozzle needle (valve member) 52 opened and closed by the point part (lower end part) 52a. The nozzle needle 52 is movable in the axial direction of the nozzle body 81 in the nozzle chamber 84 of the nozzle body 81, and forms a fuel reservoir 84 a with the nozzle body 81.

  The specific and detailed structures of the electromagnetic valve unit 60 and the control unit 70 will be described later, but the two units cooperate to control various high-pressure fuel passages formed in the injector body 80. It plays a central function of controlling the opening and closing of the nozzle needle 52. The electromagnetic valve unit 60 includes an electromagnetic valve 61, and the control unit 70 includes a pressure control chamber 71, a floating plate (control member) 72, and a return spring 73 as basic main components.

The injector body 80 includes a fuel supply path A, a fuel introduction path B, and a fuel discharge path C as high-pressure fuel paths formed inside. The details of these three paths (fuel supply path A, fuel introduction path B, and fuel discharge path C) will be described later. The fuel supply path A is connected from the common rail 4 to the inlet port 85 via the fuel distribution pipe 4b. This is a basic flow path for guiding the supplied high-pressure fuel to the nozzle chamber 84 (fuel reservoir 84a), and the fuel introduction path B is branched from the fuel supply path A to allow the high-pressure fuel to flow into the pressure control chamber 71. The fuel discharge path C discharges the high-pressure fuel in the pressure control chamber 71 to the outside of the injector (the fuel discharge pipe 5a in FIG. 1).
The injector 5 opens the force (F1) applied to the nozzle needle 52 in the nozzle hole opening direction by the fuel pressure inside the nozzle chamber 84 (fuel reservoir 84a). The force applied to the nozzle needle 52 in the nozzle hole closing direction by the fuel pressure is applied to the nozzle needle 52 in the nozzle hole closing direction by the first valve closing force (F2) and the biasing force of the return spring 73. When the force is defined as the second valve closing force (F3), the valve is opened when the relationship [F1> F2 + F3] is established, and is “closed” when the relationship [F1 <F2 + F3] is established. The floating plate 72 is a key control member that balances these forces.

  The electromagnetic valve unit 60 is housed in a holder 82 of the injector body 80 and has an electromagnetic valve 61 that controls opening and closing of the fuel discharge path C. The electromagnetic valve 61 includes an electromagnetic driving unit 61a and an opening / closing unit 61b that is opened and closed by the driving unit 61a. The drive unit 61a receives a command signal from the ECU 6 and drives the opening / closing unit 61b to open the fuel discharge path C. Conversely, when the command signal is not supplied from the ECU 6 to the drive unit 61a, the opening / closing unit 61b closes the fuel discharge path C.

The control unit 70 is constructed across the nozzle body 81 and the orifice plate 83 in the injector body 80.
The orifice plate 83 is provided with an inflow passage 74 for introducing high-pressure fuel into the pressure control chamber 71 and an outflow passage 75 for allowing the high-pressure fuel in the pressure control chamber 71 to flow out to the external low-pressure side.
The inflow passage 74 forms a fuel introduction path B, and one end communicates with the fuel supply path A and the other end opens into the pressure control chamber 71. The outflow passage 75 forms a fuel discharge path C, one end of which opens to the pressure control chamber 71 and the other end of the fuel discharge pipe 5a (FIG. 1) via the opening / closing part 61b of the electromagnetic valve 61. Communicating with
Both the inflow passage 74 and the outflow passage 75 are appropriately provided with orifices for adjusting the fuel flow rate with the flow path (orifices 72a and communication grooves 72b described later) on the pressure control chamber 71 side. Yes.

  The pressure control chamber 71 is defined by a head (upper end) 52 b that is the other end of the nozzle needle 52 and a cylindrical member 76. The cylindrical member 76 has a cylindrical shape, receives the columnar head portion 52b of the nozzle needle 52, and holds the head portion 52b in a substantially liquid-tight state so as to be slidable. Therefore, the volume of the pressure control chamber 71 is increased / decreased by the axial displacement (vertical movement) of the cylindrical head portion 52b in the cylindrical member 76.

The floating plate (control member) 72 has a disk shape, is fitted into the cylindrical member 76 with a clearance fit, and can be displaced in the pressure control chamber 71 in the axial direction. And the function which opens and closes the inflow passage 74 eccentrically opened to the pressure control chamber 71 is achieved.
In the floating plate 72, an orifice 72a penetrating in the thickness direction is provided at the center portion, and an axial communication groove 72b is formed on the outer peripheral surface. Therefore, the upper surface side and the lower surface side of the floating plate 72 can be communicated with each other via the orifice 72a and the communication groove 72b.
Further, the orifice 72 a faces the outflow passage 75 that opens to the central portion of the pressure control chamber 71.
Accordingly, when the floating plate 72 is pressed against the orifice plate 83 (sitting state), the inflow passage 74 is completely closed, and the orifice 72 a communicates only with the outflow passage 75. That is, the floating plate 72 blocks the pressure control chamber 71 and the inflow passage 74 and connects the pressure control chamber 71 (via the orifice 72a) and the outflow passage 75.
Further, when the floating plate 72 is separated (separated) from the orifice plate 83, the inflow passage 74 is opened. Thereby, the inflow passage 74 communicates with the pressure control chamber 71 via the orifice 72a and the communication groove 72b.

The return spring 73 is interposed between the cylindrical member 76 and the nozzle needle 52 and presses the nozzle needle 52 in the valve closing direction.
The maximum stroke position (maximum valve opening position) of the nozzle needle 52 is regulated by a part 52c of the nozzle needle 52 striking against a shoulder 76a formed on the inner periphery of the lower end of the cylindrical member 76.

  Next, the basic operation of the injector 5 having the above configuration will be described with reference to FIGS.

  The high-pressure fuel supplied from the common rail 4 flows into the fuel supply path A from the inlet port 85 of the injector 5. The high-pressure fuel that has flowed into the fuel supply path A is introduced into the nozzle chamber 84 of the nozzle body 81.

When the control signal is not supplied (energized) from the ECU 6 to the electromagnetic valve part 60 and the electromagnetic valve 61 is in the closed state, the outflow passage 75, that is, the fuel discharge path C is closed by the opening / closing part 61b. Yes.
In this case, since the outflow of the fuel from the pressure control chamber 71 is stopped, the floating plate 72 is pushed down by the fuel pressure in the inflow passage 74 forming the fuel introduction path B and is separated from the orifice plate 83 and flows in. The passage 74 is opened. As a result, a flow path from the fuel supply path A to the inflow path 74 (fuel introduction path B) → the orifice 72a and the communication groove 72b of the floating plate 72 → the pressure control chamber 71 is formed, and the pressure control chamber 71 is filled with high-pressure fuel. The

In this way, the nozzle needle 52 receives the valve opening force (F1) in the direction to be pushed up by the fuel pressure in the nozzle chamber 84 (the nozzle hole opening direction) and is pushed down by the fuel pressure in the pressure control chamber 71 ( The valve closing force (F2) in the nozzle hole closing direction) is received.
Here, the pressure receiving area that receives the fuel pressure in the pressure control chamber 71 at the head 52b of the nozzle needle 52 is more than the pressure receiving area that receives the fuel pressure in the nozzle chamber 84 at the tip 52a of the nozzle needle 52. A large urging force (valve closing force F3) for urging the nozzle needle 52 in the nozzle hole closing direction is applied to the nozzle needle 52 by the return spring 73. For this reason, the condition of [F1 <F2 + F3] is satisfied, and the nozzle needle 52 closes the injection hole 51.

When the injection timing (fuel injection timing) of the injector 5 is reached from the state as described above, the electromagnetic valve 61 is energized and opened by the ECU 6, so that the outflow passage 75 (fuel discharge route C) is opened. As a result, a fuel discharge passage is formed from the pressure control chamber 71 → the orifice 72 a of the floating plate 72 → the outflow passage 75 (fuel discharge passage C) → the fuel discharge pipe 5 a → the fuel tank 1. For this reason, the fuel pressure in the control chamber 12 decreases as the fuel in the pressure control chamber 71 flows out through the flow path. At this time, since the floating plate 72 is pushed up and seated on the orifice plate 83 and closes the inflow passage 74, the inflow of high-pressure fuel from the inflow passage 74 to the pressure control chamber 71 is blocked.
Therefore, the fuel pressure in the pressure control chamber 71 decreases in a short time. That is, the fuel pressure in the control chamber 71 rapidly decreases, and the pressure difference between the fuel pressure in the nozzle chamber 84 and the fuel pressure in the pressure control chamber 71 increases rapidly.

The valve opening force (F1) acting on the nozzle needle 52 is greater than the sum of the valve closing force (F2) due to the fuel pressure in the pressure control chamber 71 and the valve closing force (F2) due to the urging force of the return spring 73. When the condition of [F1> F2 + F3] is satisfied and the nozzle needle 52 opens the injection hole 51, the high-pressure fuel introduced into the nozzle chamber 84 is injected from the injection hole 51.
Thus, the injector 5 starts fuel injection into the combustion chamber EN of the cylinder of the engine E.

  Thereafter, when a predetermined valve opening period of the injector 5 (command injection period determined from the fuel injection amount and the command injection pressure) elapses from the above injection timing, energization from the ECU 6 to the solenoid valve 61 is stopped, and the solenoid valve 61 is Close the valve.

  As described above, when the electromagnetic valve 61 is closed, the outflow passage 75 (fuel discharge path C) is closed, so that the outflow of fuel from the pressure control chamber 71 is stopped. On the other hand, since the fuel pressure in the pressure control chamber 71 is lowered, the floating plate 72 is pushed down by the fuel pressure in the inflow passage 74 and is separated from the orifice plate 83 to open the inflow passage 74. As a result, a flow path from the fuel supply path A to the inflow path 74 (fuel introduction path B) → the orifice 72a and the communication groove 72b of the floating plate 72 → the pressure control chamber 71 is formed, and high-pressure fuel flows into the pressure control chamber 71. . Thereby, the fuel pressure in the pressure control chamber 71 rises rapidly.

  When the pressure difference between the fuel pressure in the nozzle chamber 84 and the fuel pressure in the pressure control chamber 71 decreases and the condition [F1 <F2 + F3] is satisfied, the nozzle needle 52 moves in the nozzle hole closing direction. Thus, the nozzle hole 51 is closed, and the valve unit 50 returns to the closed state. Therefore, the fuel injection from the nozzle hole 51 is completed.

  However, when the process was thoroughly examined in the above-mentioned injection mechanism, the following events were observed.

(1) In the valve opening process of the nozzle needle 52, the maximum stroke position (maximum valve opening position) of the nozzle needle 52 is regulated by a part 52 c of the nozzle needle 52 by the shoulder 76 a of the cylindrical member 76. However, when the nozzle needle 52 is restricted at the maximum stroke position, the fuel injection characteristic is disturbed after the nozzle needle 52 reaches the maximum stroke position.

(2) When the cause is investigated, the pressure control chamber 71 is partitioned by the fitting of the cylindrical member 76 and the head 52b of the nozzle needle 52, so that the pressure control is performed at the maximum stroke position of the nozzle needle 52. The volume of the chamber 71 does not change and becomes substantially constant. On the other hand, since the orifice 72a is provided in the floating plate 72, the fuel in the pressure control chamber 71 continues to flow out through the orifice 72a even after the nozzle needle 52 reaches the maximum stroke position. As a result, when the pressure in the pressure control chamber 71 decreases even slightly, the slight pressure drop causes the floating plate 72 receiving the fuel pressure from the inflow passage 74 to be pushed down to open the inflow passage 74. It is introduced into the pressure control chamber 71. Then, the floating plate 72 rises immediately and the inflow passage 74 is closed again, so that the floating plate 72 repeats vertical vibration. As a result, it was analyzed that the nozzle needle 52 slightly moved up and down in response to the behavior of the floating plate 72 and the fuel injection characteristics were disturbed.

(3) By the way, when the maximum stroke position of the nozzle needle 52 is not regulated, the pressure in the pressure control chamber 71 is reduced by reducing the volume of the pressure control chamber 71 while the head 52b of the nozzle needle 52 continues to rise. Thus, it was confirmed that the floating plate 72 would not vibrate up and down.

(4) Therefore, the inventors have come up with a method for preventing the nozzle needle 52 from reaching the maximum stroke position during the fuel injection period.

[Features of Reference Example 1 ]
Reference Example 1 focuses on the return spring 73 in the injector 5 having the basic configuration as described above, and makes the maximum stroke of the nozzle needle 52 dependent on the amount of displacement of the return spring 73, so that during the fuel injection period, the nozzle needle 52 did not reach the maximum stroke position .

In the first reference example , a spring 73 having a unique spring characteristic in which the initial displacement amount is large and the late displacement amount is small is employed as the return spring 73.

Conventional return springs that have been employed so far use simple cylindrical coil springs, and as shown in FIG. 4C, the urging force F3 and the displacement amount H change with a linear correlation. It had a linear spring characteristic. The nozzle needle 52 is raised (opened) to the maximum stroke position D against the urging force F3 of the return spring.
In contrast, the return spring 73 has a specific spring characteristic that the displacement amount of the initial amount of displacement is large late decreases, during the fuel injection period, the nozzle needle 52 does not reach the maximum stroke position D Like that.

As shown in FIG. 4A, the return spring 73 of the first form has a large amount of displacement H when the urging force F3 is small and becomes curved as the urging force F3 increases. It has a non-linear spring characteristic in which the displacement amount H is small.
According to the above configuration, when the valve is opened, the initial spring characteristic of the return spring 73 can be utilized to quickly raise the nozzle needle 52 to open the valve. Then, as the nozzle needle 52 approaches the maximum stroke position D, the spring characteristics of the latter stage of the return spring 73 can be utilized to gain time until the nozzle needle 52 reaches the maximum stroke position D. Thus, the predetermined injection period can be ended before the nozzle needle 52 reaches the maximum stroke position D.
Thus, the vertical vibration of the floating plate 72 can be suppressed without making the volume of the pressure control chamber 71 constant during the fuel injection period.

The return spring 73 having the non-linear spring characteristic {FIG. 4 (a)} as described above can be realized by a single coil spring. A typical structure example will be described with reference to FIG.
In FIG. 5, coil springs 73 </ b> A to 73 </ b> D having four forms are schematically shown.
In FIG. 5, the spring 73 </ b> A of FIG. 5A has a so-called “conical” shape in which the cross-sectional shape (one turn diameter) in the axial direction has a different diameter that increases from one end to the other end. Further, the spring 73B of (b) has a so-called “slung type” shape in which the diameter in the central region in the axial direction is smaller than the diameters of both end portions. On the other hand, the spring 73C in (c) has a so-called “drum-type” shape in which the diameter in the central region in the axial direction is larger than the diameters of both end portions. Further, the spring 73D of (d) has an unequal pitch shape in which the pitch of each winding in the axial direction increases from one end to the other end.
In addition, the nonlinear specific curve shape shown to Fig.4 (a) can be selected suitably by selecting the form of four types of coiled springs 73A-73D, and the specific of each coiled spring 73A-73D. Of course, an arbitrary non-linear curve shape can be obtained by appropriately changing the target shape (for example, changing the diameter or pitch of one turn).

Next, a second form of the return spring 73 having a spring characteristic in which the initial displacement amount is large and the late displacement amount is small will be described.
In the second form , the return spring 73 is composed of a composite spring having a bent linear characteristic in which two or more kinds of linear characteristics having different correlations in inclination are combined as a spring characteristic.
As an example of the spring characteristics of the spring, as shown in FIG. 4 (b), the first linear portion S1 having a large displacement H when the biasing force F3 is small and the latter when the biasing force F3 is large. Has a one-stage folded linear spring characteristic such as the second linear portion S2 in which the displacement amount H decreases as the urging force F3 increases.
Then, as shown in FIG. 6, this spring is realized by a composite spring 73E in which a first coiled spring 73X having a long axial length and a second coiled spring 73Y having a short axial length are combined. You can. In FIG. 6, a composite spring 73E shown in FIG. 6A has a first coiled spring 73X having a large diameter and is disposed outside the second coiled spring 73Y. The composite spring 73E shown in FIG. Conversely, the spring 73E has a first coiled spring 73X having a small diameter and is disposed inside the second coiled spring 73Y.

According to said 2nd form , the function similar to the 1st form can be acquired. That is, when the valve is opened, the nozzle needle 52 can be quickly raised and opened by utilizing the initial spring characteristic of the return spring 73 (first linear portion S1 = first coiled spring 73X only). Then, as the nozzle needle 52 approaches the maximum stroke position D, the latter spring characteristics of the return spring 73 (second linear portion S2 = both the first and second coiled springs 73X and 73Y) are utilized, and the nozzle needle The time until 52 reaches the maximum stroke position D can be earned. Thus, the predetermined injection period can be ended before the nozzle needle 52 reaches the maximum stroke position D.

  Note that the one-stage folded linear spring characteristic shown in FIG. 4B is obtained by changing the length and diameter of the first coiled spring 73X and the second coiled spring 73Y, and the first linear portion S1 and the second linear spring characteristic. It can be appropriately selected by changing the inclination of each part S2 and the position of the junction (bending point) between the parts S1 and S2. Of course, if three or more coiled springs are combined, two or more multi-stage bent linear spring characteristics can be obtained.

[Effect of Reference Example 1 ]
Since the injector 5 of the reference example 1 exhibits the functions as described above, the following effects can be achieved.
(1) Since the nozzle needle 52 can be quickly opened with the initial spring characteristics of the return spring 73, excellent response performance can be obtained when the valve is opened.
(2) Since the nozzle needle 52 can be gently raised from before the maximum stroke position D with the spring characteristics of the latter stage of the return spring 73, a predetermined injection period until the nozzle needle 52 reaches the maximum stroke position D. Can be terminated. For this reason, inappropriate behavior (vertical vibration) of the floating plate 72 caused by the volume of the pressure control chamber 71 becoming constant is not caused.
(3) The return spring 73 is an existing indispensable part, and the above function can be obtained only by changing the specifications of the spring. Therefore, no special modification or additional parts are required.
(4) Therefore, it is possible to provide the injector 5 that can ensure high response performance and good fuel injection characteristics while having a compact and inexpensive configuration.

[ Examples and modifications ]
Although the reference example has been described in detail above , examples and modifications will be described below.

(1) In the first reference example , as a precaution, positioning means for forcibly restricting the maximum stroke position (maximum valve opening position) D of the nozzle needle 52 (a part 52c of the nozzle needle 52 and the shoulder of the cylindrical member 76). In this embodiment, since the portion 52c of the nozzle needle 52 is not abutted against the shoulder portion 76a of the cylindrical member 76, such positioning means is actively abolished, and the maximum of the nozzle needle 52 is provided. The stroke position (D) is made to depend only on the displacement amount (H) of the return spring 73.
In addition, by eliminating the positioning means in this way, a robust structure for positioning becomes unnecessary, and not only the structure can be further simplified, but also the impact noise at the time of valve opening (hit) is reduced. This can be eliminated and the degree of freedom of the channel structure can be increased.

(2) In the reference example 1 described above, the spring characteristics of the return spring 73 have been broadly described as non-linear and bent linear , but various combinations such as non-linear and multi-stage bent linear can be achieved by combining both forms. Spring characteristics can be realized.

Effects notable features and the present invention, in summary listed according Each unit has mounting serial in the claims is as follows.

(Feature 1 = Means of claim 1 )
The injector 5 of claim 1 does not have positioning means for forcibly restricting the maximum stroke position D of the nozzle needle (valve member) 52, and the maximum stroke position D of the nozzle needle 52 is the amount of displacement of the return spring 73. It is characterized by being determined depending only on (H) (see the embodiment ).
According to the above means, by eliminating the positioning means positively, a robust structure for positioning becomes unnecessary, and not only can the structure be further simplified, but also impact noise at the time of valve opening (hit). And the degree of freedom of the channel structure can be increased.

(Feature Point 2 = Means of Claim 2 )
In the injector (fuel injection device) 5 according to claim 1 ,
The return spring 73 is composed of one coiled spring 73A to 73C having a different cross-sectional shape in the axial direction, or one coiled spring 73D having an unequal pitch in the axial direction. And having a non-linear spring characteristic ( see FIG. 5).
According to the above means, the return spring 73 can be constituted by a single coil spring 73A to 73D, and desired nonlinear spring characteristics can be easily obtained by simply selecting the winding diameter and pitch as appropriate.

(Feature point 3 = Means of claim 3 )
In the injector (fuel injection device) 5 according to claim 1 ,
The return spring 73 is composed of a composite spring 73E in which a coiled spring 73X having a long axial length and a coiled spring 73Y having a short axial length are combined, and is characterized by having a bent linear spring characteristic. ( See FIG. 6).
According to the above means, although the return spring 73 is constructed by a plurality of springs, it can be configured using a coil spring having a simple shape and structure, and the length and number of the coil springs are appropriately selected. The desired spring characteristics can be obtained simply by doing so.

DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 5 ... Injector (fuel injection apparatus), 50 ... Valve part, 51 ... Injection hole, 52 ... Nozzle needle (valve member), 52a ... Point part (one end side), 52b ... Head part (other end side) ), 70... Control unit, 71. Pressure control chamber, 72. Floating plate (control member), 73. Return spring, 73 A. Conical spring (coiled spring of different diameter), 73 B. Diameter coiled spring), 73C ... drum type spring (coiled spring of different diameter), 73D ... coil spring of unequal pitch, 73E ... compound spring, 73X ... first coiled spring (with axial length) Long coiled spring), 73Y ... second coiled spring (coiled spring with a short axial length), 74 ... inflow passage, 75 ... outflow passage, 76 ... cylindrical member, 80 ... Kutabodi (valve body), A ... fuel supply line, B ... fuel introduction path, C ... fuel discharge path, CR ... common rail fuel supply system, E ... Engine, EN ... combustion chamber.

Claims (3)

A valve body (80) in which passages (A to C) for high-pressure fuel are formed, and an injection hole (51) for injecting the high-pressure fuel into the combustion chamber (EN) of the engine (E) is formed at the tip. When,
A valve member (52) that moves in the axial direction of the valve body (80) inside the valve body (80) and opens and closes the nozzle hole (51) at one end side (52a);
An inside of the valve body (80) is formed on the opposite side of the nozzle hole (51) with the valve member (52) interposed therebetween, and the high-pressure fuel is introduced to control the movement of the valve member (52). A pressure control chamber (71) controlled by the pressure of
A cylindrical member (76) for receiving the other end side (52b) of the valve member (52) and defining the pressure control chamber (71);
A return spring (73) interposed between the valve member (52) and the tubular member (76) and pressing the valve member (52) in the valve closing direction;
An inflow passage (74, B) for introducing the high-pressure fuel into the pressure control chamber (71);
An outflow passage (75, C) for allowing fuel in the pressure control chamber (71) to flow out to the external low pressure side (1);
A control member (72) that is displaceable in the axial direction in the pressure control chamber (71) and opens and closes the inflow passage (74, B),
As the return spring (73), springs (73A to 73E) having a spring characteristic in which an initial displacement amount is large and a late displacement amount is small are used .
There is no positioning means for forcibly regulating the maximum stroke position (D) of the valve member (52), and the maximum stroke position (D) of the valve member (52) is the displacement of the return spring (73). Fuel injection device (5), characterized in that it depends only on the quantity (H ). The fuel injection device (5) according to claim 1,
The return spring (73) is one coil spring (73A to 73C) having a different cross-sectional shape in the axial direction, or one coil shape having an unequal pitch in the axial direction. A fuel injection device (5) comprising a spring (73D) and having non-linear spring characteristics . The fuel injection device (5) according to claim 1 ,
The return spring (73) is composed of a composite spring (73E) in which a coiled spring (73X) having a long axial length and a coiled spring (73Y) having a short axial length are combined. a fuel injection apparatus characterized by having (5).

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