JP3329999B2 - Injector for fuel injection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injector for fuel injection, and more particularly to a fuel injection injector having a hydraulic cylinder in a nozzle body, wherein the piston of the hydraulic cylinder presses a nozzle needle against a valve seat to shut off fuel injection. In addition, the present invention relates to a fuel injection injector in which when the hydraulic pressure of the hydraulic cylinder is released, the nozzle needle is lifted by fuel pressure to inject fuel.

[0002]

2. Description of the Related Art As a fuel injection device for a diesel engine, a plunger is pushed up by a cam at every injection, and the engine speed is fed back to a control rack via a camshaft and a mechanical governor. A pressure-accumulation type fuel injection device has been proposed in place of a Bosch type fuel injection pump which controls the supply amount of fuel injected each time.

This device pressurizes fuel by a pressurizing pump, accumulates the pressurized fuel in, for example, a common rail, and releases a pressing force of a piston by switching a three-way valve incorporated in an injector. The fuel is injected by lifting the nozzle needle, the fuel pressure is again applied to the piston at a predetermined timing, and the nozzle needle is pressed against the valve seat to stop the injection.

[0004]

As described above, the pressure accumulating type fuel injection device is different from the usual fuel injection device in that the opening and closing of the nozzle needle is performed by the fuel pressure. The fuel is divided into a path for injecting the fuel in the injector and a path for supplying the fuel to a hydraulic cylinder for controlling the driving of the nozzle needle. In the non-injection state, the nozzle needle is pressed against the valve seat and closed by increasing the force to push down the nozzle needle by the piston of the hydraulic cylinder against the lift force applied to the nozzle needle through the fuel injection path. I have to. On the other hand, when fuel is injected, the fuel pressure to the hydraulic cylinder holding down the nozzle needle is released, and the fuel pressure opens the nozzle needle to inject fuel.

On the other hand, a characteristic required as a fuel injection device for a diesel engine is a characteristic in which the injection rate increases gradually at the start of injection. These characteristics are
This is a characteristic required to prevent diesel knock, lower the combustion temperature, and reduce engine noise and the amount of nitrogen oxides in exhaust gas.

When the injection is stopped, it is necessary that the fuel be cut sharply. That is, the fuel injection characteristics are sharply cut to zero, and such characteristics can prevent the generation of hydrocarbons and black smoke in the exhaust gas.

However, in the above-described pressure-accumulation type fuel injection device, the fuel injection characteristics and the injection stop characteristics are determined by releasing the fuel pressure from the hydraulic cylinder and applying the fuel pressure to the hydraulic cylinder, respectively. Basically, it depends on the fuel pressure. Therefore, there is a problem that conflicting characteristics must be achieved by the common rail fuel pressure at the same pressure.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a fuel injection characteristic in which the fuel injection rate has a hysteresis between the start of injection and the stop of injection. An object of the present invention is to provide an injector for injection.

[0009]

According to the present invention, there is provided a hydraulic cylinder in a nozzle body, wherein a nozzle needle is pressed against a valve seat by a piston of the hydraulic cylinder to cut off fuel injection, When the hydraulic pressure of the cylinder is released, the nozzle needle is lifted by the fuel pressure so that the fuel is injected so that the fuel is injected. In the fuel injector, the outer edge of the hydraulic cylinder is chamfered or curved. The present invention relates to an injector for fuel injection, characterized in that orifices having small holes are stacked at a plurality of levels and arranged at the inlet of the hydraulic cylinder.

In such a configuration, the resistance at the time of releasing the fuel pressure to the hydraulic cylinder is increased by the shape of the small holes of the plurality of orifices arranged so as to overlap with the inlet portion of the hydraulic cylinder. The resistance at the time of applying fuel to the hydraulic cylinder can be reduced, and the characteristics at the start of injection and the characteristics at the time of injection stop can have hysteresis.

According to a second aspect of the present invention, a hydraulic cylinder is provided in a nozzle body, and a nozzle needle is pressed against a valve seat by a piston of the hydraulic cylinder to interrupt fuel injection, and a hydraulic pressure of the hydraulic cylinder is reduced. When the nozzle needle is lifted by the fuel pressure, the nozzle needle lifts to inject the fuel, and the fuel injection is performed. In the injector, a control plate having a swirl chamber inside and an inlet / outlet of the swirl chamber at the center are formed. An orifice disposed on the opposite side of the control plate to the cylinder and an orifice disposed on the inlet of the hydraulic cylinder. It is.

Therefore, according to such a configuration, when the fuel pressure is released from the hydraulic cylinder, a vortex is generated by the control plate and the orifice which are arranged so as to overlap with the inlet portion of the hydraulic cylinder. In this case, a backflow region occurs and the effective flow path cross-sectional area decreases, and such a vortex is not applied when the fuel pressure is applied, so that the characteristics when releasing the fuel pressure from the hydraulic cylinder and the It is possible to provide a hysteresis between the characteristics when the fuel pressure is applied to the hydraulic cylinder.

According to a third aspect of the present invention, a hydraulic cylinder is provided in a nozzle body, and a nozzle needle is pressed against a valve seat by a piston of the hydraulic cylinder to interrupt fuel injection, and a hydraulic cylinder of the hydraulic cylinder is provided. When the nozzle is lifted by the fuel pressure, the fuel injection is performed by lifting the nozzle needle. An orifice having a small hole in the center and a vertical groove on the outer peripheral side, The present invention relates to an injector for fuel injection, characterized in that a spring for pressing the orifice against a stepped portion for closing the vertical groove opposite to a cylinder is arranged at an inlet portion of the hydraulic cylinder.

Accordingly, the release of the fuel pressure from the hydraulic cylinder is performed through the center hole of the orifice, while the application of the fuel pressure to the hydraulic cylinder is performed by the small hole at the center of the orifice and the vertical groove on the outer peripheral side. And a speed difference can be generated between the release of the fuel pressure and the application of the fuel pressure. Therefore, it is possible to provide hysteresis to the characteristics at the start of fuel injection and the characteristics at the time of fuel injection stop.

[0015]

FIG. 1 shows the overall configuration of a fuel injection device having a fuel injector according to a first embodiment of the present invention. This fuel injection device pressurizes fuel. And a pressurizing pump 10. The pressurizing pump 10 includes a plunger 11, and the plunger 11 is pushed up by a cam 12 attached to a camshaft. Fuel in a pressurizing chamber 13 in a space above the plunger 11 is pressurized. Become so.

The fuel in the fuel tank 15 is stored in a segmenter 16.
The pressure is suctioned by a feed pump 18 through a filter 17 and supplied to a pressurizing chamber 13 above the plunger 11 of the pressurizing pump 10 through a fuel filter 19 provided on the discharge side of the feed pump 18. It has become so. The pressurizing chamber 13 leaks fuel to the tank 15 via the one-way valve 20.

The discharge side of the pressurizing chamber 13 is connected via a one-way valve 22 to a common rail 23 forming a pressure accumulating chamber. A one-way valve 24 is attached to the common rail 23. The one-way valve 24 constitutes a pressure limiter, and opens when the pressure of the common rail 23 exceeds a set pressure to return the fuel to the tank 15 side. The common rail 23 is connected to an injector 26 via a flow limiter 25. The flow limiter 25 performs a shut-off operation when the flow rate of the fuel flowing to the injector 26 abnormally increases, thereby preventing abnormal injection.

An electronic control unit 30 including a computer is provided to control the entire fuel injection system. The electronic control unit 30 is connected to a pressure sensor 31 that detects the pressure in the common rail 23. A pump control valve 32 is connected between the pressurizing chamber 13 of the pressurizing pump 10 and the one-way valve 20 on the leak side, and its electromagnetic coil 33 is controlled by the electronic control unit 30. ing.

The electronic control unit 30 is provided with an accelerator sensor 35 for detecting an amount of depression of an accelerator pedal, an engine rotation sensor 36 for detecting an engine speed, a cylinder discriminating sensor 37 provided in the engine, and a pump. The cylinder discrimination sensors 38 are respectively connected.

Next, the structure of the injector 26 connected to the common rail 23 via the flow limiter 25 will be described. As shown in FIGS. 1, 2 and 3, a nozzle body 40 is provided at the tip end of the injector 26. Is installed. The nozzle body 40 is the nozzle needle 4
The nozzle needle 41 is slidably held.
Is pressed against the valve seat 42 to control the injection of fuel from the injection port 43. A fuel reservoir 44 is provided in the nozzle body 40, and a fuel pressure is constantly applied to the fuel reservoir 44 via a fuel passage 45.

The nozzle needle 41 has a push rod 48
Is pressed downward. The push rod 48 is pressed downward by a pressing spring 49, and the upper end of the push rod 48 is
Is pressed. The piston 50 is slidably supported in a hydraulic cylinder 51 provided on the body of the injector 26, and the hydraulic cylinder 5
Two orifices 52 and 53 so as to close the inlet side of
Are arranged one on top of the other.

The orifices 52 and 53 will be described in more detail. The hydraulic cylinder 51 provided in the nozzle body so as to slidably hold the piston 50 is provided.
As shown in FIG. 4, two orifices 52 and 53 are arranged so as to be superimposed on each other, particularly at the inlet portion. These orifices 52, 53 are provided with small holes 56, 57 at their center, respectively.

Here, the small hole 56 of the upper orifice 52 has a larger size than the small hole 57 of the lower orifice 53. The entrances of these small holes 56 and 57 are both chamfered to form an inclined surface 58. These inclined surfaces 58 are larger at the lower orifice 53 than at the upper orifice 52. The orifices 52, 53 having the small holes 56, 57, respectively, as described above.
Are overlapped with each other, and the inclined surfaces 58 of the chamfers are formed at their inlet portions, respectively, so that the equivalent circuit of the one-way valve 54 and the throttle 55 shown in FIG. The characteristic of the fuel injection rate has a hysteresis by giving a difference between the characteristic at the time and the characteristic at the time of stopping the fuel injection. .

Inside the injector 26, a three-way valve 59 shown in FIGS. The three-way valve 59 is pressed downward by the compression coil spring 60 and is urged upward by the solenoid coil 61. And the solenoid coil 61
2A, the fuel passage 6 is not energized as shown in FIG. 2A.
2 communicates with the port 63 of the three-way valve 59. An opening 64 that is open downward is formed below the three-way valve 59 so as to communicate with the port 63.

The three-way valve 59 shuts off the fuel passage 62 and the fuel passage 65 when the solenoid coil 61 is not excited. The fuel passage 65 communicates with a port 66 for releasing fuel.

Next, the operation of fuel injection by the system shown in FIG. 1 will be described. The feed pump 18 and the pressurizing pump 10 are driven by a part of the output of the engine. The feed pump 18 sucks the fuel in the tank 15 through the segmenter 16 and the filter 17 and
The fuel is filled into the pressurizing chamber 13 of the pressurizing pump 10 through the pump.

The fuel in the pressurizing chamber 13 is pressurized by the plunger 11 pushed up by the cam 12, and is supplied to the common rail 23 through the one-way valve 22, and the common rail 23 accumulates the fuel. Here, at the time of pressurization by the cam 12 of the pressurizing pump 10, the pump control valve 32 is controlled to be opened and closed by an electromagnetic coil 33, and the computer of the electronic control unit 30 determines the target pressure and the pressure of the common rail 23. The time during which the pump control valve 32 is closed is appropriately calculated in accordance with the deviation, and control is performed so as to always reach the target pressure.

This operation will be described in more detail. The control valve 32 provided in the pressurizing pump 10 is
The pump control valve 3
When the plunger 11 is pushed up when the plunger 11 is closed, the fuel is pressurized, and when the plunger 11 is pushed up when the control valve 32 is opened, the fuel is supplied to the control valve 32 and the one The pressure is returned to the tank 15 through the directional valve 20, and the pressure is released by the control valve 32. The pressurizing pump 10 turns on and off the control valve 32 to change the discharge amount, and is feedback-controlled so that the signal of the pressure sensor 31 of the common rail 23 becomes the target value given to the computer of the electronic control unit 30. It has become.

When the feedback control of the pressure in the common rail 23 by the electronic control unit 30 as described above is not performed properly due to some abnormality, and the pressure in the common rail 23 exceeds the set pressure of the one-way valve 20, The one-way valve 24 constituting the pressure limiter is opened, and the fuel pressure escapes to the tank 15 side.

As described above, a constant pressure is accumulated in the common rail 23, and this pressure is applied to the injector 26 via the flow limiter 25.

FIG. 2A shows the injector 26 when no injection is performed, and the solenoid coil 61 is in a non-excited state.
Therefore, the three-way valve 59 is pressed downward by the compression coil spring 60, and the distal end thereof blocks the fuel passages 62 and 65. Therefore, the port 66 is in the shut-off state, and the fuel pressure of the common rail 23 is changed to the fuel passage 62 and the port 6 of the three-way valve 59.
3, opening 64, orifices 52, 5 of hydraulic cylinder 51
The third small hole 56, 57 acts on the upper surface of the piston 50.

The fuel pressure of the common rail 23 simultaneously acts on the nozzle needle 41 through the fuel passage 45 and the fuel sump 44.

The force acting downward at this time is the sum of the downward force received by the piston 50 of the hydraulic cylinder 51 due to the fuel pressure and the force of the pressing spring 49 pressing the push rod 48 downward. On the other hand, the upward force is the force that the nozzle needle 41 receives so as to act upward by the fuel pressure at the fuel reservoir 44.

Here, the diameter of the piston 50 of the hydraulic cylinder 51 is much larger than the diameter of the sliding seal portion of the nozzle needle 41, and the downward force applied by the pressing spring 49 is much greater. Therefore, the front end portion of the nozzle needle 41 is pressed against the valve seat 42, and the nozzle needle 41 blocks fuel at the valve seat 42, so that no injection is performed.

The electronic control unit 30 detects the amount of depression of the accelerator pedal by an accelerator sensor 35,
The rotation speed of the engine is detected by the rotation detection sensor 36. Further, an optimum injection time and injection timing are calculated based on other information as needed. Then, the solenoid coil 61 is excited at a predetermined timing.

Then, the three-way valve 59 is set to the solenoid coil 61
2B, as shown in FIG. 2B.
9 lifts upward. Therefore, the three-way valve 59 is separated from the valve seat, and the space above the hydraulic cylinder 51 is communicated with the port 66 via the fuel passage 65. Therefore, the fuel pressure pressing the piston 50 of the hydraulic cylinder 51 leaks through the small holes 56 and 57 of the orifices 52 and 53 of the hydraulic cylinder 51, the fuel passage 65, and the port 66. Therefore, the force of pressing the piston 50 of the hydraulic cylinder 51 downward by the fuel pressure is released.

Therefore, the nozzle needle 41 is moved to the fuel sump 44.
The pressing force of the pressing spring 49 overcomes the pressing force by the fuel pressure applied to the nozzle needle 41, the nozzle needle 41 is lifted upward, and the tip side portion of the nozzle needle 41 is separated from the valve seat 42. Therefore, fuel is injected through the injection port 43.

When releasing the fuel pressure acting on the upper part of the piston 50 of the hydraulic cylinder 51, a pair of orifices 52 arranged at the inlet of the hydraulic cylinder 51,
Since the small holes 56 and 57 of the 53 are throttles, the release of the fuel pressure is performed slowly. Therefore, the rising speed of the nozzle needle 41 with respect to the valve seat 42 is buffered.

Thereafter, when the excitation of the solenoid coil 61 is released again as shown in FIG.
The three-way valve 59 is moved downward by the
Cut off the fuel passages 62 and 65. In addition, the orifice 5 passes through the fuel passage 62, the port 63, and the opening 64.
Hydraulic cylinder 51 via small holes 56, 57 of 2, 53
The fuel pressure is actuated on the upper surface of the piston 50 to strongly press the nozzle needle 41 downward as shown in FIG. 2A.

As shown in FIGS. 4 and 5, the injector 26 for injecting fuel in this manner is provided at the inlet portion of the hydraulic cylinder 51 with the hole diameters of the small holes 56 and 57 and the inclined surface 5.
The two types of orifices 52 and 53 having different chamfer sizes from each other are stacked on each other to ensure a maximum flow difference of 1.5 depending on the fuel flow direction.

That is, the orifices 52 and 53 having different hole diameters of the small holes 56 and 57 and the size of the inclined surface 58 are overlapped in two steps. The method of overlapping the orifices 52 and 53 depends on the hydraulic cylinder 51 side. Small hole 57 with small hole diameter
An orifice 53 having a large chamfered inclined surface 58 is provided, and a small hole 56 having a large hole diameter is provided thereon, and the orifice 52 having a small chamfered inclined surface 58 is arranged. .

At the start of injection, the hydraulic cylinder 5
The fuel escapes from 1. The fuel flow at this time is shown in FIG. That is, the lower orifice 5
Peeling occurs at the edge of the lower end of the third small hole 57, resulting in a partial pressure loss. Thereafter, when entering the small hole 56 to further pass through the small hole 56 of the orifice 52, peeling occurs again at the edge of the lower end of the small hole 56, and a pressure loss occurs. As described above, the fuel pressure is released in a state where the pressure loss occurs at two places.

On the other hand, when the fuel pressure is applied to the hydraulic cylinder 51 and the nozzle needle 41 is pressed by the piston 50, the fuel flows as shown in FIG. At this time, at the entrance of the small hole 56 of the orifice 52,
The fuel flows smoothly by the inclined surface 58. Also, when passing through the small hole 57 of the orifice 53, the fuel smoothly flows due to the inclined surface 58 of the chamfer. Therefore, there is no place where separation occurs when the fuel pressure is applied to the hydraulic cylinder 51.

As described above, when the fuel pressure from the hydraulic cylinder 51 is released, the small holes 56 and 5 of the orifices 52 and 53 are released.
At the edge of the inlet side of the nozzle 7, separation is caused, and when the fuel pressure is applied into the hydraulic cylinder 51, the small holes 56, 57 of the orifices 52, 53 are used.
Since the separation is prevented from occurring due to the inclined surface 58 formed by chamfering the inlet portion of the fuel cell, the configuration is equivalent to the parallel circuit of the one-way valve 54 and the orifice 55 shown in FIG. It is possible to give hysteresis to the characteristics at the time of injection and the characteristics at the time of injection stop.

That is, the lift of the nozzle needle 41 pressed by the piston 50 of the hydraulic cylinder 51 is as shown in FIG. 6, and while the lift of the nozzle needle 41 at the start of injection becomes gentle, the lift of injection The descent of the nozzle needle 41 at the time of stop has a steep characteristic. Accordingly, as shown in FIG. 7, the fuel injection rate also gradually increases at the start of the injection, and suddenly stops at the stop of the injection.

According to the characteristic that the fuel injection amount is gradually increased at the start of the fuel injection, the diesel knock is reduced, thereby suppressing the rise in the combustion temperature in the cylinder. Therefore, it is possible to reduce nitrogen oxides in the exhaust gas. Further, since the fuel is sharply cut when the injection is stopped, incomplete combustion in the latter half of the combustion is prevented, and hydrocarbons and black smoke in the exhaust gas can be reduced.

Next, another embodiment will be described with reference to FIGS. In this embodiment, as shown in FIGS. 8 and 9, a control plate 68 is arranged so as to overlap with an orifice 55 having a small hole 56 at an inlet portion of a hydraulic cylinder 51. The control plate 68 is eccentric with respect to a center side concave portion 69 formed at the center thereof to form a pair of eccentric holes 70 symmetrical to each other.
Is connected to the lower surface, and the eccentric hole 70 is connected to the central concave portion 69 by a tangential passage 71.

As shown in FIG. 9, the control plate 68 having the orifice 52 and the concave portion 69 forming the vortex chamber is disposed so as to overlap the inlet of the hydraulic cylinder 51, and the nozzle needle 41 is connected to the valve seat 42. When fuel injection is started by raising the nozzle needle 41 from a state in which the fuel is press-fitted to the eccentric hole 7 of the control plate 68 from the lower side to the upper side in FIG.
0, center side recess 69, and small hole 56 of orifice 52
Through from the bottom to the top.

At this time, when the fuel flows from the eccentric hole 70 of the control plate 68 to the center side concave portion 69 through the tangential passage 71, a swirling flow is generated in the concave portion 69 and narrowed by the small hole 56 of the orifice 52. Sometimes accelerated by the nature of free vortices. Due to such acceleration, a backflow region is generated at the center of the vortex chamber 69, and the effective flow path cross-sectional area is reduced.

The generation of the vortex shown in FIG. 9 occurs only when the fuel flows upward from the hydraulic cylinder 51.
The fuel is applied to the hydraulic cylinder 51 and the nozzle needle 41
Is pressed against the valve seat 42 to stop fuel injection, since the small hole 56 of the orifice 52 is smaller than the swirl chamber 69 of the control plate 68, the fuel flow does not swirl, The cross-sectional area of the orifice 52
When the nozzle needle 41 is pressed, the fuel flows into the hydraulic cylinder 51 quickly.

The flow of fuel when releasing the fuel pressure in the hydraulic cylinder 51 is theoretically described as follows. As shown in FIG. 10, assuming that the pressure difference before and after the orifice having the diameter d through which the fluid passes is ΔP, from Bernoulli's principle,

(Equation 1) Becomes here

(Equation 2) Then

(Equation 3) ,

(Equation 4) Here, from ΔP = P ₁ −P ₂ and Q = AV,

(Equation 5) Actually, there is a flow coefficient C, and when this flow coefficient C is taken into consideration,

(Equation 6) Becomes As shown in FIG. 10, when the edge of the entrance of the small hole of the orifice is finished in an arc shape,

(Equation 7) Becomes

Next, when the dimensions of the respective parts when the eddy current is generated are set as shown in the lower right diagram, the flow coefficient C is

(Equation 8) The characteristic value K of the spiral chamber is

(Equation 9)

(Equation 10) Given by, by the r _c / r _e as a parameter, it is possible to determine the C from K. For example, in the above equation, if K is determined so that C = 0.2, K = 0.23. Therefore

[Equation 11] r _i = 3mm, and put a _{r e = 0.5mm, S i =} 1.
08 mm ² . Ie

(Equation 12) By swirling the 0.5 mm orifice, the flow velocity can be reduced to 1/5 depending on the flow direction.

Next, still another embodiment will be described with reference to FIGS.
7 will be described. In this embodiment, the piston 50
An orifice 52 having a center hole 56 and an orifice 53 having a center hole 57 are arranged vertically at an inlet portion of a hydraulic cylinder 51 in which is slidably accommodated. Here, the orifice 53 is pressed downward by a spring 74, while the upper orifice 52 is pressed upward by a spring 73. In particular, the feature of this embodiment is that the orifice 52 located on the upper side has not only the center hole 56 but also a vertical groove 72 on the outer peripheral side.

In such a configuration, when no injection is performed, the downward force applied to the nozzle needle 41 via the piston 50 of the hydraulic cylinder 51 is applied to the upward force accompanying the fuel pressure applied to the nozzle needle 41. To overcome this, the nozzle needle 41 is pressed against the valve seat 42.

At this time, a pair of upper and lower orifices 52 and 53 provided at the inlet of the hydraulic cylinder 51 are in the state shown in FIG. 15, respectively, and the lower orifice 53 is the upper end of the hydraulic cylinder 51. , And the upper orifice 52 is stationary in contact with the step 75. At this time, the three-way valve 59 is in the state shown in FIG. 2A, applies the fuel pressure to the piston 50 of the hydraulic cylinder 51, and shuts off the fuel passage 65 side.

Next, at the start of fuel injection, FIG.
As shown in B, the three-way valve 59 shuts off the supply of fuel to the upper side of the hydraulic cylinder 51 and makes the passage 65 communicate with the fuel to leak the fuel. At this time, the nozzle needle 4
Since 1 rises due to the fuel pressure, the piston 50 also rises, and the lower orifice 53 rises against the spring 74 as shown in FIG.

However, at this time, the upper orifice 5
2 is in contact with the stepped portion 75 and has a vertical groove 72 on the outer peripheral side.
Is closed by a step 75. Therefore, the fuel escapes upward only through the central hole 56 having a small area of the orifice 52, and the rising speed of the nozzle needle 41 is reduced. As a result, the initial injection rate is reduced, diesel knock is prevented, the combustion temperature is suppressed, and the amount of nitrogen oxides in the exhaust gas is reduced.

When fuel injection is stopped, the fuel passage 65 of the three-way valve 59 is shut off as shown in FIG. 2A, fuel pressure is applied to the piston 50 of the hydraulic cylinder 51, and the nozzle needle 41 descends. At this time, the upper orifice 52 descends as shown in FIG.
2 is opened at the upper edge and a sufficient amount of fuel is supplied to the orifice 53.
And a sufficient amount of fuel flows into the hydraulic cylinder 51 through the center hole 57 of the orifice 53. Therefore, the application of the fuel pressure to the piston 50 of the hydraulic cylinder 51 is performed quickly, and a sharp cut of the fuel is achieved. Therefore, the fuel cutoff at the end of the injection is improved, the fuel efficiency is improved, and the amount of hydrocarbons and black smoke in the exhaust gas is reduced.

[0059]

According to the first aspect of the present invention, a plurality of orifices having small holes whose outer edges are chamfered or curved are stacked on the hydraulic cylinder and arranged at the inlet of the hydraulic cylinder. It is like that.

Therefore, the plurality of orifices can provide a hysteresis between the characteristics when the hydraulic pressure is released from the hydraulic cylinder and the characteristics when the hydraulic pressure is applied, thereby enabling the fuel injection. A gentle injection characteristic is obtained at the start, and a sharp cut can be achieved when the injection is stopped.

According to a second aspect of the present invention, there is provided a control plate having a swirl chamber inside, and a small hole forming an entrance and exit of the swirl chamber at a center portion, the control plate being disposed on the opposite side to the cylinder with respect to the control plate. The orifice is arranged so as to overlap the inlet of the hydraulic cylinder.

Therefore, the effective cross-sectional area can be reduced by the vortex generated in the swirl chamber when the hydraulic pressure is released from the hydraulic cylinder, and the characteristic at the time of releasing the hydraulic pressure can be made smaller than the characteristic at the time of applying the hydraulic pressure. And the characteristics at the start of fuel injection and the characteristics at the time of fuel injection stop have a hysteresis, and it becomes possible to provide an injector for fuel injection with optimal injection characteristics. .

According to a third aspect of the present invention, the orifice has a small hole in the center and a vertical groove on the outer peripheral side, and presses the orifice against a step portion closing the vertical groove on the side opposite to the hydraulic cylinder. And a spring to be disposed at the inlet of the hydraulic cylinder.

Therefore, when the hydraulic pressure of the hydraulic cylinder is released, the vertical groove is closed by the step portion, and the hydraulic pressure is released only by the center hole, and when the hydraulic pressure is applied, the vertical groove is closed by the center hole of the orifice. Hydraulic pressure can be applied through the vertical groove on the outer peripheral side. Therefore, the injection rate at the start of the injection can be made gradual, and a sharp injection rate characteristic can be obtained when the injection is stopped.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a pressure accumulating fuel injection device.

FIG. 2 is a longitudinal sectional view showing the operation of the injector.

FIG. 3 is a longitudinal sectional view showing a specific configuration of an injector.

FIG. 4 is a longitudinal sectional view showing a configuration of an orifice at an inlet portion of a hydraulic cylinder.

FIG. 5 is a vertical sectional view of a main part showing a flow of fuel in an orifice when injection is stopped.

FIG. 6 is a graph showing characteristics of a lift of a nozzle needle.

FIG. 7 is a graph showing a change in a fuel injection rate.

FIG. 8 is an exploded perspective view showing a configuration of an orifice and a control plate attached to an inlet portion of a hydraulic cylinder.

FIG. 9 is a longitudinal sectional view of the same.

FIG. 10 is a longitudinal sectional view of an orifice.

FIG. 11 is a schematic longitudinal sectional view of a vortex chamber.

FIG. 12 is a plan view of the vortex chamber.

FIG. 13 is a plan view of an orifice provided with a vertical groove on the outer peripheral side.

FIG. 14 is a longitudinal sectional view of the same.

FIG. 15 is a longitudinal sectional view showing the arrangement of upper and lower orifices.

FIG. 16 is a longitudinal sectional view showing an operation of releasing the fuel pressure.

FIG. 17 is a longitudinal sectional view showing an operation of applying a fuel pressure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 pressure pump 11 plunger 12 cam 13 pressure chamber 15 tank 16 segmenter 17 filter 18 feed pump 19 fuel filter 20 one-way valve 22 one-way valve 23 common rail (accumulation chamber) 24 one-way valve (pressure limiter) 25 flow limiter 26 Injector 30 Electronic control unit (computer) 31 Pressure sensor 32 Pump control valve 33 Electromagnetic coil 35 Accelerator sensor 36 Engine rotation sensor 37 Cylinder discrimination sensor (engine) 38 Cylinder discrimination sensor (pump) 40 Nozzle body 41 Nozzle needle 42 Valve seat 43 Injection port 44 Fuel reservoir 45 Fuel passage 48 Push rod 49 Press spring 50 Piston 51 Hydraulic cylinder 52, 53 Orifice 54 One-way valve 55 Orifice 56, 57 Small hole 58 Inclined surface Chamfering) 59 three-way valve 60 the compression coil spring 61 solenoid coil 62 the fuel passage 63 port 64 opening 65 fuel passage 66 port 68 control plate 69 center side recess 70 eccentric hole 71 tangential passage 72 outer peripheral side circumferential groove 73, 74 the spring 75 step portion

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI F02M 61/20 F02M 61/20 P Examiner Naoto Yaita (56) References JP-A-2-146255 (JP, A) (58) ) Field surveyed (Int.Cl. ⁷ , DB name) F02M 47/00 F02M 47/02 F02M 45/00 F02M 45/08 F02M 61/10 F02M 61/20

Claims (1)

(57) [Claims] A hydraulic cylinder is provided in a nozzle body, and a nozzle needle is pressed against a valve seat by a piston of the hydraulic cylinder to interrupt fuel injection, and when the hydraulic pressure of the hydraulic cylinder is released, the fuel is released. An orifice having a small hole whose outer edge is chamfered or curved with respect to said hydraulic cylinder, wherein said nozzle is lifted by pressure to inject fuel. Are arranged at the inlet of the hydraulic cylinder in a plurality of stages.