JPH06101591A - Accumulator injector - Google Patents

Abstract

PURPOSE:To provide an accumulator injector capable of adjusting the injection ratio of fuel according to operating conditions. CONSTITUTION:An accumulator injector includes a booster piston 12 which slides in response to fuel supply pressure introduced into a booster chamber 9 in synchronization with engine speed and a booster mechanism for compressing fuel via the booster piston 12, and is used for injecting and supplying fuel at ultra high pressure from a nozzle to a combustion chamber via a needle which responds to the fuel pressure of the booster chamber 9. The accumulator injector is provided with a variable aperture solenoid valve 31 for varying the area of a relief-side passage 27 connected to the booster chamber 9 and a control unit 35 for controlling operation of variable aperture solenoid valve 31.

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-accumulation 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 combustibility and improve exhaust performance and fuel efficiency by increasing the fuel injection pressure to atomize the fuel and shorten the injection period.

Therefore, a pressure-accumulation injector disclosed in, for example, Japanese Patent Laid-Open No. 59-85433 has a pressure increasing mechanism that compresses fuel by receiving fuel supply pressure, and a needle that responds to the fuel pressure is used. Fuel is injected and supplied from the nozzle injection holes to the combustion chamber at ultrahigh pressure.

[0004]

However, in such a conventional pressure-accumulation injector, since the fuel injection rate is uniquely determined according to the injection amount, for example, the initial injection rate during low load operation. Is too high, which leads to an increase in NOx.

In view of the above problems, it is an object of the present invention to provide a pressure-accumulation injector capable of adjusting the fuel injection rate according to operating conditions.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a pressure increasing piston which slides in response to a fuel supply pressure guided to the pressure increasing chamber in synchronization with engine rotation, and a pressure increasing chamber which is interlocked with the pressure increasing piston. The plunger that compresses the fuel filled in the pressure chamber, the accumulator valve that guides the fuel pressurized in this pressure chamber to the pressure accumulator chamber, and the pressure accumulator chamber and the nozzle nozzle hole in response to the pressure difference between the pressure chamber and the pressure accumulator chamber. A pressure-accumulation injector including a needle that communicates with a variable throttle valve that changes a relief-side passage area connected to the pressure increasing chamber, and means for controlling the operation of the variable throttle valve according to engine operating conditions.

A variable throttle valve for changing the area of the relief side passage connected to the pressure increasing chamber, and a three-way switch for selectively communicating the pressure increasing chamber with the feed side passage through which the fuel supply pressure is introduced and the relief side passage. Means for controlling the operation of the valve, the variable throttle valve, and the three-way switching valve are provided according to engine operating conditions.

Further, a pressure boosting piston that slides in response to a fuel supply pressure guided to the pressure boosting chamber in synchronization with engine rotation, and the fuel filled in the pressure boosting chamber is compressed in cooperation with the pressure boosting piston. Accumulator type including a plunger, an accumulator valve that guides the fuel pressurized in the pressure chamber to the pressure accumulator chamber, and a needle that communicates the pressure accumulator chamber and the nozzle injection hole in response to the pressure difference between the pressure chamber and the accumulator chamber. In the injector, a piston that changes the volume of the pressure boosting chamber, an actuator that drives the piston, a relief-side throttle passage that communicates with the pressure boosting chamber when the piston reaches a predetermined stroke, and the operation of the actuator are set as engine operating conditions. A means for controlling according to the above is provided.

[0009]

The fuel supply pressure is guided to the pressure increasing chamber in synchronism with the rotation of the engine, so that the pressure increasing piston compresses the fuel filled in the pressure increasing chamber through the plunger and is pressurized in the pressure increasing chamber. Fuel is trapped in the accumulator through the accumulator valve. Then, the pressure of the fuel introduced into the pressure boosting chamber decreases, so that the pressure in the pressure increasing chamber also decreases via the pressure increasing piston and the plunger, and the needle responds to the pressure difference between the pressure increasing chamber and the pressure accumulating chamber to eject the nozzle. The holes are opened and fuel is injected at ultra high pressure.

The pressure in the pressurizing chamber decreases as the plunger moves, 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. The rate of fuel injection can be controlled by adjusting the rate at which the fuel drops.

By providing a variable throttle valve that changes the area of the relief-side passage connected to the pressure-increasing chamber, the speed at which the fuel in the pressure-increasing chamber flows out to the relief-side passage is adjusted, and the fuel injection rate is set to the engine operating condition. Can be controlled accordingly.

Further, a three-way switching valve is provided in parallel with the variable throttle valve, and the speed at which the fuel in the booster chamber flows into the relief-side passage is adjusted stepwise, so that the maximum opening area of the relief-side passage is sufficient. Therefore, the fuel injection period can be shortened.

Further, by providing a piston for varying the volume of the pressure increasing chamber and a throttle passage for connecting the pressure increasing chamber to the relief side when the piston reaches a predetermined stroke,
The speed at which the fuel pressure in the booster chamber drops can be adjusted, and the fuel injection rate can be controlled according to the engine operating conditions.

[0014]

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 utilizing the fuel supply pressure to compress the fuel, a fuel inlet 6 is supplied with fuel of a predetermined pressure from a feed pump through a feed side passage. , Fuel inlet 6 to passage 7 and check valve 4
The pressurizing chamber 3 filled with fuel via the pressurizing chamber 3, the plunger 11 that makes the volume of the pressurizing chamber 3 variable, the pressure increasing piston 12 connected to the upper end of the plunger 11, and the pressure increasing piston 12 3. Spring 15 that biases upward as 3 expands
And a pressure boosting chamber 9 defined by a pressure boosting piston 12,
A three-way switching solenoid valve 21 that selectively communicates the pressure boosting chamber 9 with the fuel inlet 6 and the fuel outlet 10 that connects the relief side passage in synchronization with the engine rotation is provided.

An accumulator valve 18 is slidably provided in the pressure accumulating body 2, and the accumulator valve 18 partitions the pressurizing chamber 3 from the accumulator chamber 13. When the differential pressure between the pressurizing chamber 3 and the accumulator chamber 13 exceeds the biasing force of the spring 14 and increases, the accumulator valve 18 separates from the lower surface of the intermediate housing 23 and connects the pressurizing chamber 3 and the accumulator chamber 13. There is.

The nozzle body 5 has a plurality of nozzle injection holes 5a opened at the tip thereof facing the combustion chamber, and a needle 17 for opening and closing each nozzle injection hole 5a is housed inside thereof. The needle 17 slidably penetrates the accumulator valve 18, and the upper end thereof 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 valve 21a of the three-way switching solenoid valve 21 has an inlet side position which communicates the fuel inlet 6 and the pressure boosting chamber 9 and an outlet side position which communicates the pressure boosting chamber 9 and the fuel outlet 10 as shown in FIG. Switching is performed at a timing synchronized with the engine rotation based on a signal from the control unit 35.

In order to control the fuel injection rate, a variable throttle solenoid valve 31 for changing the opening area of the relief side passage 27 connected to the pressure boosting chamber 9 is provided.

In the upper housing 22, a port 29 opening to the booster chamber 9, a conical seat surface 28 on which the valve body 31a of the variable throttle solenoid valve 31 is seated, and the periphery of the valve body 31a and the rod portion 31b. Relief passage 2 defined by
7, and a through hole 26 that connects the relief side passage 27 and the fuel outlet 10 is formed.

The variable throttle solenoid valve 31 includes an electromagnetic actuator 33 that displaces the rod portion 31b in the axial direction by a predetermined amount. The electromagnetic actuator 33 controls the valve body 3 according to the applied voltage controlled by the control unit 35.
1a is displaced to change the size of the gap defined between the valve body 31a and the seat surface 28. As the displacement control element of the electromagnetic actuator 33, a ceramic sheet or the like that is displaced by utilizing the strain induced by the electric field is used.

Next, the operation of this pressure-accumulation injector will be described.

When the three-way switching solenoid valve 21 is in the outlet position where the pressure boosting chamber 9 communicates with the fuel outlet 10, the communication between the fuel inlet 6 and the pressure boosting chamber 9 is cut off, and the fuel is pressurized through the passage 7. The chamber 3 is filled.

Subsequently, when the three-way switching solenoid valve 21 is switched to the inlet side position where the fuel inlet 6 and the pressure boosting chamber 9 communicate with each other, the pressure boosting piston 12 receives the fuel supply pressure and pushes down the plunger 11. The pressure of the fuel filled in the pressurizing chamber 3 is increased by the area ratio of the pressure increasing piston 12 and the plunger 11, and the amount of fuel compressed by the volume elasticity of the fuel is accumulated from the pressurizing chamber 3 via the accumulator valve 18. Room 1
It is pumped to 3. 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 biasing force of the spring 14, and the pressure accumulating chamber 13 is sealed. 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, and
a is closed.

Subsequently, the three-way switching solenoid valve 21 is switched to the outlet side position, or the variable throttle solenoid valve 31 is opened so that the pressure boosting chamber 9 and the fuel outlet 10 are communicated with each other. Pressure gradually decreases and booster piston 1
2 is lifted by the urging force of the spring 15. Following the booster piston 12, the plunger 11 also lifts, and the fuel pressure in the pressurizing chamber 3 drops. When the fuel pressure in the pressurizing chamber 3 decreases in this way, the force of the fuel pressure in the pressure accumulating chamber 13 that pushes up the needle 17 causes the fuel pressure in the pressurizing chamber 3 and the needle spring 14 that push the needle 17 downward. Since the combined force of the urging forces is exceeded, the needle 17 lifts and the tip of the needle 17 separates from the valve seat of the nozzle body 5, so that the fuel is injected from the nozzle injection hole 5a into the combustion chamber at an ultrahigh pressure.

The movement of lifting the needle 17 is performed by the pressurizing chamber 3
Since the pressure-increasing piston 12 is lifted through the plunger 11 and the plunger 11, the lift timing and lift speed of the needle 17 are adjusted by changing the operation timing of the three-way switching solenoid valve 21 or the variable throttle solenoid valve 31, respectively. Thus, the fuel injection rate can be controlled.

As shown in FIG. 3, when the variable throttle solenoid valve 31 is held in the fully closed position, the booster piston 12 and the needle 17 are moved as the three-way switching solenoid valve 21 is switched to the outlet side position. By lifting at once, the injection rate also rises sharply from the initial stage.

As shown in FIG. 4A, when the variable throttle solenoid valve 31 is opened to the half-open position and the three-way switching solenoid valve 21 is held at the inlet side position, the fuel pressure in the pressure boosting chamber 9 is increased. Since the narrowed flow path between the valve body 31a and the seat surface 28 is slowly opened, the injection rate becomes a mountain shape with a small initial injection rate. The switching of the three-way switching solenoid valve 21 to the outlet side position is performed near the end of injection in order to ensure the seating of the needle 17.

As shown in FIG. 4B, after the variable throttle solenoid valve 31 has been opened to the half-open position, there is a certain time lag,
That is, when the three-way switching solenoid valve 21 is switched to the outlet side position during injection, the variable throttle solenoid valve 31 is opened to the half-open position, whereby the booster piston 12 and the needle 17 are gently lifted, and then the three-way switching is performed. Solenoid valve 2
When the pressure boosting piston 12 and the needle 17 are lifted at a stroke as 1 is switched to the outlet side position, fuel injection is quickly terminated. For this reason, the injection amount in the latter stage of injection increases, and the injection period becomes shorter than that of the characteristic shown in FIG.

As shown in FIG. 5A, when the variable throttle solenoid valve 31 is opened to the fully open position and the three-way switching solenoid valve 21 is held at the inlet side position, the fuel pressure in the pressure boosting chamber 9 is increased. The valve body 31a and the seat surface 28 that are open more than in FIG.
The initial injection rate is as shown in FIG.
It is larger than (a) and smaller than the characteristic of FIG. In addition,
The switching of the three-way switching solenoid valve 21 to the outlet side position is performed near the end of injection as in the above.

As shown in FIG. 5B, when the three-way switching solenoid valve 21 is switched to the outlet side position with a certain time lag after the variable throttle solenoid valve 31 has been opened to the fully open position, the variable throttle solenoid valve 31 is opened. When the valve 31 is opened to the fully open position, the pressure boosting piston 12 and the needle 17 are lifted at a medium speed, the injection rate is increased at a medium speed at an initial stage, and then the three-way switching solenoid valve 21 is moved to the outlet side position. As the pressure boosting piston 12 and the needle 17 are lifted all at once in response to the switching, the fuel injection is quickly terminated, the injection rate characteristic approaches a rectangle, and the injection period is longer than that of the characteristic of FIG. 5A. Becomes shorter. Therefore, the injection period is controlled by the timing at which the three-way switching solenoid valve 21 is switched to the outlet side position.

In any of the above cases, the fuel injection amount is controlled by the fuel supply pressure introduced from the feed pump.

In this way, the fuel injection rate and injection period can be adjusted via the variable throttle solenoid valve 31 and the three-way switching solenoid valve 21 in accordance with the engine load and the rotational speed as shown in FIG.

That is, in the low load / low rotation region (1), the initial injection rate is lowered and the injection period is lengthened to reduce the NOx emission amount as shown in FIG. 4 (a). In the low rotation speed region (1), since the time per 1 degree of the crank angle is long, even if the combustion is prolonged, the combustion is completed before the piston is lowered so much, so that the fuel efficiency is not deteriorated.

In the operating region (2) where the load or the rotational speed is somewhat higher than this, the injection rate in the latter period is increased and the injection period is shortened as shown in FIG. 4 (b). Since the combustion period in this operating range (2) is longer than that in the operating range (1), the initial injection rate is reduced and the NOx emission amount is reduced while the injection period is shortened to suppress deterioration of fuel efficiency.

In operating regions (3) and (4) in which the load or the rotational speed is higher than this to some extent, (a) and (b) in FIG.
As shown in each of the above, the initial injection rate is relatively increased, the combustion is activated, and the injection period is shortened corresponding to the combustion period.

In the high load / high rotation region (5), as shown in FIG. 3, the initial injection rate is maximized and the injection period is shortened, and sufficiently atomized fuel is supplied in a short period to improve the combustibility. It is possible to reduce fuel consumption, reduce smoke emission, and improve output.

Since various injection rate characteristics are obtained in this way, optimum injection rate control becomes possible depending on the operating condition,
It is possible to realize a diesel engine with excellent exhaust characteristics and thermal efficiency.

Next, in another embodiment shown in FIG. 7, a piston 41 which makes the volume of the pressure boosting chamber 9 variable, and this piston 4
1 and an electromagnetic actuator 42 for driving the
Is provided with a relief-side throttle passage 43 that communicates the pressure boosting chamber 9 with the fuel outlet 10 by reaching a predetermined stroke, and a control unit 45 that controls the operation of the actuator 42 according to engine operating conditions.

The upper housing 22 is provided with a port 49 opening to the pressure increasing chamber 9 and a cylinder 50 into which the piston 41 is slidably fitted, so that the lift of the piston 41 changes the volume of the pressure increasing chamber 9. It has become.

One end of the relief side throttle passage 43 is opened to the lower part of the cylinder 50, and the relief side throttle passage 43 is opened almost at the same time when the piston 41 is lifted.

Also in this embodiment, the electromagnetic valve 44 is provided which connects the fuel inlet 6 and the pressure increasing chamber 9 at a predetermined timing.
The solenoid valve 44 is a two-way switching valve (open / close valve) that does not have an outlet side position that communicates with the pressure boosting chamber 9 and the fuel outlet 10 as in the above embodiment, and that only opens and closes the inlet side.

Next, the operation of this pressure-accumulation injector will be described.

When the piston 41 is lifted through the actuator 42 and the volume of the pressure increasing chamber 9 is increased in a state where the fuel is compressed and stored in the pressure increasing chamber 13, the pressure of the pressure increasing chamber 9 decreases, The pressure boosting piston 12 rises due to the urging force of the spring 15. Following the rise of the booster piston 12, the plunger 11 also rises and the fuel pressure in the pressurizing chamber 3 drops. When the fuel pressure in the pressurizing chamber 3 is thus lowered, the needle 17 is lifted from the valve seat of the nozzle body 5, and the fuel is injected from the nozzle injection hole 5a into the combustion chamber. When the piston 41 is lifted even slightly, the relief side throttle passage 43 is opened and the injection rate rises at a medium speed in the initial stage, but thereafter, it depends on the fuel speed discharged through the relief side throttle passage 43. As a result, the injection rate gradually drops.

The movement of the needle 17 lifting is caused by the pressurizing chamber 3
Since the pressure-increasing piston 12 is lifted via the plunger 11 and the plunger 11, the volume of the pressure-increasing chamber 9 is increased by the piston 41.
It is possible to control the fuel injection rate by adjusting the lift timing and lift amount of the needle 17 by changing the fuel injection rate.

As shown in FIG. 8, when the piston 41 is lifted up to 100% at a time, the volume of the pressure boosting chamber 9 is suddenly expanded, so that the pressure boosting piston 12 and the needle 17 are lifted at a stroke, and the injection rate is also the initial value. It rises sharply from the stage.

As shown in FIG. 9, when the piston 41 is lifted by 10% at a time, the pressure boosting piston 12 and the needle 17 are gently lifted according to the fuel velocity discharged through the throttle passage 43, and the injection is performed. The injection rate also rises moderately, and the injection rate becomes a mountain shape with a small initial injection rate, and the injection period becomes relatively long.

As shown in FIG. 10, when the piston 41 lifts 10% at the first time and lifts 100% at the second time with a certain time lag, a large amount of fuel is injected in the latter period while suppressing the initial injection rate, Shorten the injection period.

As shown in FIG. 11, when the piston 41 lifts by 60% at a time, the injection rate rises at the medium speed in the initial stage because the pressure boosting piston 12 and the needle 17 rise at the medium speed. However, after that, the injection rate gradually decreases depending on the fuel velocity discharged through the relief side throttle passage 43, and the injection period becomes relatively long.

As shown in FIG. 12, when the piston 41 lifts by 60% at the first time and lifts by 100% at the second time with a certain time lag, the injection rate in the initial period and the injection rate in the latter period are increased to form a rectangular shape. The injection characteristics are close, and the injection period is shortened.

As described above, the initial injection rate of fuel and the injection period can be adjusted via the piston 41 according to operating conditions without using an expensive valve such as a three-way switching solenoid valve.

[0052]

As described above, according to the present invention, the pressure boosting piston that slides in response to the fuel supply pressure guided to the pressure boosting chamber in synchronization with the rotation of the engine, and the pressure boosting piston is operated in conjunction with the pressurizing piston. A plunger for compressing the fuel filled in the chamber, an accumulator valve for guiding the fuel pressurized in the pressure chamber to the pressure accumulator chamber, a pressure accumulator chamber and a nozzle injection hole in response to a pressure difference between the pressure chamber and the pressure accumulator chamber. In a pressure-accumulation injector including a needle for communicating with each other, a variable throttle valve that changes a relief-side passage area connected to the pressure increasing chamber and a means for controlling the operation of the variable throttle valve according to engine operating conditions are provided. It is possible to adjust the fuel injection rate according to the engine operating conditions, improve the combustibility over the entire operating range, and improve the exhaust performance and fuel consumption of a diesel engine or the like.

Further, a three-way switching valve is provided in parallel with the variable throttle valve to adjust the speed at which the fuel in the booster chamber flows into the relief-side passage in a stepwise manner, so that the maximum opening area of the relief-side passage is sufficiently large. Therefore, the fuel injection period can be shortened.

Further, a piston for varying the volume of the pressure increasing chamber, an actuator for driving the piston, a relief side throttle passage communicating with the pressure increasing chamber when the piston reaches a predetermined stroke, and an operation of the actuator. Even if a means for controlling the engine according to the engine operating condition is provided, the fuel injection rate can be adjusted in accordance with the engine operating condition.

[Brief description of drawings]

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

FIG. 2 is a side sectional view of the accumulator injector.

FIG. 3 is a diagram similarly showing an operating state.

FIG. 4 is a view showing an operating state of the same.

FIG. 5 is a diagram showing an operating state of the same.

FIG. 6 is also a control map of the injection rate.

FIG. 7 is a front sectional view of a pressure-accumulation injector showing another embodiment of the present invention.

FIG. 8 is a characteristic diagram of injection rate.

FIG. 9 is a characteristic diagram of injection rate.

FIG. 10 is a characteristic diagram of injection rate.

FIG. 11 is a characteristic diagram of injection rate.

FIG. 12 is a characteristic diagram of injection rate.

[Explanation of symbols]

 3 Pressurizing Chamber 4 Check Valve 5a Nozzle Injection Hole 6 Fuel Inlet 9 Pressure Boosting Chamber 11 Plunger 12 Pressure Boosting Piston 13 Accumulation Chamber 17 Needle 18 Accumulator Valve 21 Three-way Switching Solenoid Valve 27 Relief Side Passage 31 Variable Throttle Solenoid Valve 35 Control Unit 30 Transmission rod 41 Piston 42 Actuator 43 Relief side throttle passage 45 Control unit

Claims (3)

[Claims] 1. A pressure-increasing piston that slides in response to a fuel supply pressure guided to the pressure-increasing chamber in synchronization with engine rotation, and the fuel filled in the pressure-increasing chamber is compressed in cooperation with the pressure-increasing piston. Accumulator type including a plunger, an accumulator valve that guides the fuel pressurized in the pressure chamber to the pressure accumulator chamber, and a needle that communicates the pressure accumulator chamber and the nozzle injection hole in response to the pressure difference between the pressure chamber and the accumulator chamber. The injector is provided with a variable throttle valve that changes a relief-side passage area connected to the pressure increasing chamber, and a means for controlling operation of the variable throttle valve according to engine operating conditions. 2. A variable throttle valve that changes a relief-side passage area connected to the pressure-increasing chamber, and a three-way switch that selectively connects the pressure-increasing chamber to the feed-side passage to which the fuel supply pressure is introduced and the relief-side passage. 2. The pressure-accumulation injector according to claim 1, further comprising means for controlling operations of the valve, the variable throttle valve and the three-way switching valve according to engine operating conditions. 3. A pressure-increasing piston that slides in response to a fuel supply pressure guided to the pressure-increasing chamber in synchronization with engine rotation, and a fuel filled in the pressure-increasing chamber is compressed in cooperation with the pressure-increasing piston. Accumulator type including a plunger, an accumulator valve that guides the fuel pressurized in the pressure chamber to the pressure accumulator chamber, and a needle that communicates the pressure accumulator chamber and the nozzle injection hole in response to the pressure difference between the pressure chamber and the accumulator chamber. In the injector, a piston that changes the volume of the pressure boosting chamber, an actuator that drives the piston, a relief-side throttle passage that communicates with the pressure boosting chamber when the piston reaches a predetermined stroke, and the operation of the actuator are set as engine operating conditions. A pressure-accumulation injector characterized in that it is provided with a means for controlling according to the above.