JP2819963B2 - Accumulator type injector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a pressure accumulating injector provided in a diesel engine or the like.

[0002]

2. Description of the Related Art In a diesel engine, it is desired to improve the combustion performance and improve the exhaust performance and fuel efficiency by increasing the injection pressure of the fuel to atomize the fuel and shorten the injection period.

Therefore, a pressure accumulating injector disclosed in, for example, JP-A-59-85433 is provided with a pressure increasing mechanism for compressing fuel by receiving fuel supply pressure, and through a needle responsive to fuel pressure. Thus, fuel is injected and supplied from the nozzle injection hole to the combustion chamber at an extremely high pressure.

[0004]

However, in such a conventional pressure-accumulation type injector, the fuel injection rate is uniquely determined according to the injection amount. Is too high to cause an increase in NOx. The present invention has been made in view of the above problems, and has as its object to provide a pressure accumulating injector that can adjust the fuel injection rate according to operating conditions.

[0005]

According to the present invention, there is provided a pressure-intensifying piston which slides upon receiving a fuel supply pressure guided to a pressure-increasing chamber in synchronism with engine rotation, and a pressure-increasing chamber in conjunction with the pressure-increasing piston. A plunger that compresses the fuel filled in the pressure chamber, an accumulator valve that guides the fuel pressurized in the pressurizing chamber to the accumulator, and a pressure accumulator and a nozzle nozzle in response to a pressure difference between the pressurizing chamber and the accumulator. In a pressure accumulating injector including a communicating needle, a switching valve that opens and closes a feed-side passage that guides fuel supply pressure to a pressure boosting chamber, a piston that changes the volume of the pressure boosting chamber, an actuator that drives the piston, and a piston A relief-side throttle passage that communicates the pressure-increasing chamber to the low-pressure side when the valve moves in the volume increasing direction by a predetermined amount or more, and means for controlling the operation of the actuator and the switching valve according to engine operating conditions. Kick.

[0006]

[Function / Effect] When the fuel supply pressure is led to the booster chamber in synchronization with the engine rotation, the booster piston compresses the fuel filled in the pressurizer chamber via the plunger, and the pressurized chamber pressurizes the fuel. The pressurized fuel is confined in the accumulator via the accumulator valve. Subsequently, by reducing the fuel pressure guided to the pressure intensifying chamber, the pressure in the pressurizing chamber is also reduced through the pressure intensifying piston and the plunger, and the needle responds to the pressure difference between the pressure in the pressure chamber and the pressure accumulating chamber. A hole is opened and fuel is injected at ultra high pressure. The pressure in the pressurizing chamber decreases in accordance with the movement of the plunger, and the lift speed of the needle is proportional to the speed at which the booster piston lifts through the plunger facing the pressurizing chamber, so that the fuel pressure in the booster chamber drops. By adjusting the speed, the fuel injection rate can be controlled. As the piston facing the pressure boosting chamber lifts, the volume of the pressure boosting chamber changes, and when the piston lifts to some extent, the pressure boosting chamber communicates with the low pressure side via the relief side throttle passage. Therefore, the speed at which the fuel pressure in the pressure intensifying chamber drops, that is, the injection rate, can be adjusted according to the operating state by controlling the piston position. Therefore, the combustibility can be improved over the entire operation range, and the exhaust performance and fuel efficiency of a diesel engine or the like can be improved.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIGS. 1 and 2, as a pressure increasing mechanism for compressing fuel using a fuel supply pressure, a fuel inlet 6 to which fuel of a predetermined pressure is supplied from a feed pump via a feed-side passage; 6, a pressurizing chamber 3 filled with fuel via a passage 7 and a check valve 4, a plunger 11 for varying the volume of the pressurizing chamber 3, and a pressure-increasing piston 12 connected to an upper end of the plunger 11. A spring 15 for urging the pressure-intensifying piston 12 upward to expand the pressurizing chamber 3;
A pressure-intensifying chamber 9 defined by the pressure-increasing piston 12 and an electromagnetic switching valve 44 for opening and closing the pressure-increasing chamber 9 with respect to a feed-side passage or the fuel inlet 6 are provided.

An accumulator valve 18 is slidably provided in the accumulator body 2, and separates the pressurizing chamber 3 from the accumulator chamber 13 by the accumulator valve 18. When the pressure difference between the pressurizing chamber 3 and the pressure accumulating chamber 13 exceeds the urging force of the spring 14, the accumulator valve 18 separates from the lower surface of the intermediate housing 23 and communicates the pressurizing chamber 3 with the pressure accumulating chamber 13. I have.

The nozzle body 5 has a plurality of nozzle orifices 5a at the end thereof facing the combustion chamber, and a needle 17 for opening and closing the nozzle orifices 5a is housed inside the nozzle orifice 5a. The needle 17 slidably penetrates the accumulator valve 18, and its upper end faces the pressurizing chamber 3. A spring 14 is interposed between the needle 17 and the accumulator valve 18 and urges each in the valve closing direction.

The switching valve 44 is connected to the pressure intensifying chamber 9 and the fuel inlet 6 at a position where the pressure increasing chamber 9 is connected to the fuel inlet 6 at a timing synchronized with the engine rotation based on a signal from the control unit 35. Can be switched.

The upper housing 22 is formed with a port 49 opening to the pressure increasing chamber 9 and a cylinder 50 for slidably fitting a piston 41 for changing the volume of the pressure increasing chamber 9. An actuator 42 for moving forward and backward based on a command from the unit 35 is provided.

The upper housing 22 is provided with a pressure increasing chamber 9.
A relief-side throttle passage 43 is formed which communicates with the fuel outlet 10 on the low pressure side. This relief side throttle passage 43
Is opened at a lower portion of the cylinder 50, and the relief-side throttle passage 43 is opened almost at the same time when the piston 41 is lifted from the lowest position where the volume of the pressure increasing chamber 9 is minimized.

Next, the operation of the pressure accumulating injector will be described. At the start of fuel injection, the switching valve 44
Shuts off the pressure increasing chamber 9 and the inlet passage 6, and the piston 41 is controlled at a lowest position in the cylinder 50 so as to close the relief-side throttle passage 43. At this time, the fuel is charged into the pressurizing chamber 3 through the passage 7. After that, when the switching valve 44 is opened,
The pressure-intensifying piston 12 receives the fuel supply pressure and
Press down. The fuel filled in the pressurizing chamber 3 is pressurized by an area ratio of the pressure-intensifying piston 12 and the plunger 11, and the fuel compressed by the volume elasticity of the fuel is accumulated from the pressurizing chamber 3 through the accumulator valve 18. It is pumped to the chamber 13. When the fuel pressures in the pressure accumulating chamber 13 and the pressurizing chamber 3 are balanced,
The accumulator valve 18 is closed by the urging force of the spring 14, and the accumulator 13 is closed. At this time, the tip of the needle 17 is seated on the valve seat of the nozzle body 5 by the urging force of the spring 14 to close the nozzle injection hole 5a.

When the switching valve 44 is closed in a state where the fuel is compressed and stored in the pressure accumulating chamber 13 in this way, the piston 41 is then raised by the actuator 42 to increase the volume of the pressure increasing chamber 9. 9, the pressure-increasing piston 12 rises by the urging force of the spring 15.
The plunger 11 also moves up following the rise of the pressure-intensifying piston 12, and the fuel pressure in the pressurizing chamber 3 decreases. When the fuel pressure in the pressurizing chamber 3 decreases as described above, the needle 17 lifts from the valve seat of the nozzle body 5, and fuel is injected from the nozzle injection hole 5a. If the piston 41 rises even slightly, the relief-side throttle passage 43 starts to open, so that the injection rate rises at an intermediate speed in the initial stage, but thereafter depends on the fuel speed discharged through the relief-side throttle passage 43. As a result, the injection rate gradually decreases.

The movement of the lift of the needle 17 is determined by the pressure chamber 3
And the plunger 11 interlocks with the lifting movement of the pressure-intensifying piston 12.
The fuel injection rate can be controlled by adjusting the lift timing and lift amount of the needle 17 by changing the fuel injection rate.

As shown in FIG. 3, when the piston 41 is raised at one time from the lowest position to the maximum operation amount (100%) at which the opening degree of the relief-side throttle passage 43 is maximized, the volume of the pressure-increasing chamber 9 is suddenly increased. Due to the expansion, the pressure-intensifying piston 12 and the needle 17 are quickly lifted, and the injection rate has a characteristic of rapidly increasing from an initial stage.

As shown in FIG. 4, when the piston 41 is raised at a time by 10% of the maximum operation amount and is maintained at the position until the end of the injection, the piston 41 is changed according to the fuel speed discharged through the relief side throttle passage 43. As a result, the pressure-intensifying piston 12 and the needle 17 are slowly lifted, the injection rate is also gradually increased, and the initial injection rate has a small angle-shaped injection characteristic, and the injection time is relatively long.

As shown in FIG. 5, when the piston 41 is raised by 10% of the maximum operation amount at the first time and then by 100% at the second time after a certain time difference, the injection is suppressed while suppressing the initial injection rate. By injecting a large amount in the latter period, the injection period can be shortened.

As shown in FIG. 6, when the piston 41 is raised at a time by 60% of the maximum operation amount and the position is maintained until the end of the injection, the pressure increasing piston 12 and the needle 1
7 is lifted at a medium speed, the injection rate rises at a medium speed in an initial stage, but thereafter, the fuel is discharged to the low pressure side through the relief side throttle passage 43. The injection rate gradually decreases depending on the fuel speed, and the injection period becomes relatively long.

As shown in FIG. 7, when the piston 41 is first lifted by 60% of the maximum operation amount and then lifted by 100% a second time after a certain time lag, an initial injection rate and a late injection rate are obtained. And the injection characteristic line becomes substantially rectangular, and the injection period is shortened.

In any of the above cases, the fuel injection amount is controlled by the fuel supply pressure guided from the feed pump. After the fuel injection is completed, the piston 41 is lowered to the lowest part of the cylinder 50, and then the switching valve 44 is opened to store the fuel in the pressure accumulating chamber 13 to prepare for the next injection.

By controlling the operation amount and operation timing of the piston 41 as described above, the fuel injection rate and the injection period can be adjusted according to the engine load and the rotation speed as shown in FIG. That is, in the low-load low-speed range (1), the initial injection rate is lowered and the injection period is lengthened to reduce the NOx emission amount as shown in FIG. In this low rotation region (1), since the time per one degree of the crank angle is long, even if the combustion is prolonged, the combustion ends before the piston is lowered too much, so that the deterioration of the fuel efficiency is small. In the operation region (2) where the load or the rotation speed is somewhat higher than this, the injection rate in the latter period is increased to shorten the injection period as shown in FIG. In this operation region (2), the combustion period is relatively longer than that in the operation region (1). Therefore, the injection period is shortened to suppress the deterioration of fuel consumption, and the initial injection rate is reduced to reduce the NOx emission amount. Measure.

In the operating basins (3) and (4) where the load or the number of revolutions is higher to some extent, as shown in FIG. 6 or FIG. , The injection period is shortened.

In the high-load and high-speed region (5), as shown in FIG. 3, the initial injection rate is maximized and the injection period is shortened, so that sufficiently atomized fuel is supplied in a short period of time to improve the combustibility. The fuel consumption, the amount of smoke emission, and the output can be improved.

As described above, various injection rate characteristics can be obtained, so that optimum injection rate control can be performed depending on the operation state.
A diesel engine with excellent exhaust characteristics and thermal efficiency can be realized.

The switching valve 44 is opened immediately after the piston 41 is raised, and the fuel supply pressure is introduced into the pressure-intensifying chamber 9, whereby the pressure-increasing piston 12 and the needle 17 can be lowered to interrupt the injection. . According to such control, even a very small amount of fuel can be injected with high accuracy, so that a small amount of injection is performed prior to the main injection to reduce noise and NO
Pilot injection control for reducing x can be performed with high accuracy. Such pilot injection can be performed by reciprocating the piston 41 at high speed. In this case, however, it is difficult to perform injection in a short time due to the responsiveness of the actuator. Can not.
On the other hand, in the injector, the piston 41
Since a small amount of injection can be realized by the operation time difference between the (actuator 42) and the switching valve 44, the opening / closing operation response does not become a problem, and highly accurate pilot injection becomes possible.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a pressure accumulating injector showing an embodiment of the present invention, and is a sectional view taken along line AA of FIG.

FIG. 2 is a side sectional view of the pressure accumulating injector.

FIG. 3 is a view showing an operating state.

FIG. 4 is a view showing an operating state.

FIG. 5 is a view showing an operating state.

FIG. 6 is a view showing an operating state.

FIG. 7 is a view showing an operating state.

FIG. 8 is a control map of the injection rate.

[Explanation of symbols]

 Reference Signs List 3 pressurizing chamber 4 check valve 5a nozzle injection hole 6 fuel inlet 9 booster chamber 10 fuel outlet (low pressure side) 11 plunger 12 booster piston 13 accumulator chamber 17 needle 18 accumulator valve 35 control unit (control means) 41 piston 42 Actuator 43 Restriction side throttle passage 50 Cylinder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI F02M 57/02 320 F02M 57/02 320B 330 330B (58) Fields investigated (Int.Cl. ⁶ , DB name) F02M 45/00 F02M 47/00 F02M 51/00 F02M 57/02 320 F02M 57/02 330

Claims (1)

(57) [Claims] 1. A pressure-intensifying piston that slides in response to a fuel supply pressure guided to a pressure-increasing chamber in synchronization with engine rotation, and that cooperates with the pressure-increasing piston to compress fuel filled in the pressure-increasing chamber. An accumulator comprising a plunger, an accumulator valve for guiding the fuel pressurized in the pressurizing chamber to the accumulator, and a needle for communicating the accumulator with the nozzle orifice in response to the pressure difference between the pressurizing chamber and the accumulator. In the injector, a switch for opening and closing the feed-side passage for guiding the fuel supply pressure to the pressure increasing chamber
A valve, a piston for changing the volume of the pressure-increasing chamber, an actuator for driving the piston, and a pressure-increasing valve when the piston moves by a predetermined amount or more in the direction of increasing the volume.
A pressure- accumulating injector comprising: a relief-side throttle passage that communicates a pressure chamber with a low-pressure side; and means for controlling the operation of the actuator and the switching valve according to engine operating conditions.