JPH0438910B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a pressure booster plunger type fuel injection device, and more specifically, the present invention relates to an improvement in a pressure booster plunger type fuel injection device, and more specifically, the invention relates to an improvement in a pressure booster plunger type fuel injection device. The present invention relates to a pressure boosting plunger type fuel injection device that is improved so that it can be sequentially changed to multiple stages.

[Prior Art] In a fuel injection device for an engine, especially a fuel injection device for a diesel engine, the maximum fuel injection amount is determined by the amount of supercharging at startup, and the plunger of the fuel injection pump draws air into the plunger barrel. The amount of fuel to be used is determined. For this reason, in conventional fuel injection pumps, the volume of the fuel chamber in the plunger barrel is large for use when starting the engine, and the stroke through which the plunger can move is also set to be long.

However, the fuel injection amount during normal operation is only 50 to 70% of the maximum fuel injection amount of the fuel injection device, so with a normal fuel injection device, 30 to 50% of the fuel sucked into the fuel injection pump is required. There is always surplus fuel, which is returned to the fuel chamber of the pump housing. For this reason, conventional fuel injection systems are large just to ensure the maximum amount of fuel injected during startup, and as a result, the engine is constantly forced to do extra work during normal operation, reducing fuel pressure. There was also the problem that the rate of rise was slow.

In addition, pressure booster plunger fuel injection systems that use hydraulic pressure to pressurize fuel perform high-pressure injection, but high-pressure injection increases the injection rate.
The fuel burns instantly and the cylinder pressure rises compared to a mechanical fuel injection system, as shown in Figure 2. This resulted in an increase in crank torsional stress and a lack of reliability.

The relationship between the fuel injection period and fuel pressure in the case of a diesel engine will be explained with reference to FIG.
The relationship between the engine load, fuel injection period, and injection pressure is as shown in Figure A, where the injection amount is large, that is, the engine operates well during the period from the start of injection to the end of injection in the range of curve H where the load is large. It is adjusted to correspond to the optimum injection period. The optimum injection period is said to be within a crank angle of approximately 30 degrees from top dead center.

On the other hand, in the period L range where the load is small and the fuel injection amount is small, the necessary fuel injection ends in a period much shorter than the optimum injection period. If the required fuel injection period is short in this way, the premix combustion period will be shortened, leading to a problem of increased NOx. In order to avoid this problem, it is necessary to extend the range of the injection amount L to the range shown by the dotted line in Figure A to match the injection period to the optimum injection period.

Furthermore, when the engine is running at low speed (low load), the pump driven by the engine is sending less pressure, so the fuel pressure is low, and as shown in the curve labeled "low speed" in Figure 6B, Figure A The required fuel injection will be performed within a period much longer than the optimum injection period.

If fuel injection is performed far outside the optimal injection period in this way, smoke will worsen. In order to improve this smoke problem, it is necessary to drive the plunger pump so that the injection of the necessary fuel is completed within the optimum injection period, as shown by the curve indicated as high speed.

[Purpose of the invention]

The present invention prevents the generation of NOx by simply extending the injection period to the shape of the curve L with a small injection amount shown by a dotted line from the curve L shown with a solid line with a small injection amount shown in FIG. The present invention provides a pressure-increasing plunger type fuel injection device for an engine that generates less smoke by adjusting the injection period as shown in the figure.

[Structure of the invention]

To achieve the above object, a pressure booster plunger type fuel injection device according to the present invention is a pressure booster plunger type fuel injection device that pressurizes fuel using hydraulic pressure, and has three or more cylinders with different diameters in a main body. They are arranged on the same axis to form a stepped cylinder, and the plunger fitted into the cylinder is formed into a stepped plunger having a different diameter to match the stepped cylinder, and one end is attached to the stepped portion of the plurality of cylinders. Connecting paths are provided in which each of the connecting paths is opened and the other end is assembled at a predetermined point, and the openings of the connecting paths are sequentially opened or closed depending on the engine load and engine rotation to supply fuel at the meeting point of the connecting paths. It is equipped with a switching valve that can sequentially adjust the amount of fuel supplied to the injection nozzle.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the principle of the pressure booster plunger type electronic fuel injection device of the present invention, and the operating principle of the device according to the present invention will be explained with reference to this figure to help understand the present invention.

Note that, in place of the pressure increase plunger 3 shown in FIG. 1, the present invention uses a stepped plunger shown in FIG. 3 having three or more stages with different diameters, a stepped cylinder that accommodates this plunger, and a stepped portion of this cylinder. The present invention provides an apparatus including a pressure increasing plunger having a communication path in its main body, one end of which is connected to the switching valve, and the other end of which is connected to the switching valve.

1 is a pressure booster plunger 3 that pumps fuel from a fuel tank 2
This is a fuel pump that feeds fuel under pressure to a fuel chamber 4 and a cylinder chamber 7, and a regulator 13 is provided in its oil feeding path to maintain a constant fuel pressure. Further, a spool valve 5 which is a three-way switching valve is provided between the fuel pump 1 and the cylinder chamber 7, and this spool valve 5 is connected to a solenoid 10.
The spool 11 is moved by the action of , so that the cylinder chamber 7 of the pressure booster plunger 3 is connected to the fuel pump 1 during the injection stroke, and the cylinder chamber 7 of the pressure booster plunger 3 is connected to the reflux pipe 8 during the metering stroke. It's summery.

The plunger 3 of the pressure booster plunger 3 is composed of a two-stage plunger, a large diameter plunger 6a and a small diameter plunger 6b. The gap 17 between the diameter cylinder 3A is
It is connected to the fuel chamber 4 of the pressure booster plunger 3 via an electromagnetic three-way valve 30.

The remaining connection port of the electromagnetic three-way valve 30 is connected to the fuel tank 2.
This electromagnetic three-way valve 30 connects the gap 17 to the fuel tank 2 by switching the spool 32 to which the solenoid 31 is energized, and connects the gap 17 to the fuel tank 2 when the solenoid 31 is not energized.
7 is connected to the fuel chamber 4.

Therefore, during the metering stroke in which the solenoid 31 of the electromagnetic three-way valve 30 is energized, the plunger 6 of the pressure booster plunger 3 sends the fuel from the fuel pump 1 to the fuel chamber 4 via the metering solenoid valve 9 and the check valve 14. The fuel in the cylinder chamber 7 of the pressure booster plunger 3 is returned to the fuel tank 2 from the reflux pipe 8 via the spool valve 5. and,
After a set time, the amount of fuel entering the fuel chamber 4 is metered by shutting off the solenoid valve 9.

In the injection stroke after completion of metering, the spool 11 is switched by the action of the solenoid 10, and fuel from the fuel pump 1 is introduced into the cylinder chamber 7 of the pressure booster plunger 3. Then, the fuel, which has been made highly pressurized by the ratio of the area of the large-diameter plunger 6a to the area of the small-diameter plunger 6b, is forced out of the fuel chamber 4 and injected from the fuel injection nozzle 12.

In addition, during the metering stroke in which the solenoid 31 of the electromagnetic three-way valve 30 is in a non-energized state, the fuel sent from the fuel pump 1 via the metering solenoid valve 9 and the check valve 14 flows into the fuel chamber 4, and the electromagnetic It also flows into the cavity 17 through the three-way valve 30 and pushes up the plunger 6. Therefore, in this state, the amount of injected fuel supplied to the pressure booster plunger 3 can be increased up to the sum of the volumes of the fuel chamber 4 and the cavity 17 at the maximum.

In the injection stroke, the spool 11 is switched by the action of the solenoid 10, and when the fuel from the fuel pump 1 is introduced into the cylinder chamber 7 of the pressure booster plunger 3, the plunger 6 descends and the fuel chamber 4 and Both fuels in the gap 17 are injected from the fuel injection nozzle 12. The fuel injection pressure at this time is equal to the pressure of the fuel applied to the cylinder chamber 7 because the pressure receiving area of the large-diameter plunger 3a and the sum of the pressurizing areas of the fuel chamber 4 and the cavity 17 are equal.

The timing of energizing the solenoids 10, 31 and the electromagnetic valve 9 is determined by signals from a control device 20 connected thereto. The control device 20 detects the engine speed and the engine load condition, measures the optimal injection amount for the engine operating condition at that time based on the valve opening time of the solenoid valve 9, and energizes the solenoid 10. Therefore, the injection timing is determined, and by energizing the solenoid 31, the injection amount and injection pressure are determined.

In the pressure booster plunger type fuel injection system configured as described above, during normal operation, the electromagnetic three-way valve 30 is energized to separate the cavity 17 from the fuel chamber 4. Then, the pressure increase plunger 3 operates in the same manner as the conventional pressure increase plunger 3 to increase the pressure of the fuel to the area ratio of the small diameter plunger 6b and the large diameter plunger 6a, and inject it from the fuel injection nozzle 12.

On the other hand, when it is necessary to increase the amount of fuel supplied, such as during startup, the electromagnetic three-way valve 30 is de-energized and the gap 17 is communicated with the fuel chamber 4. Then, the fuel metered into the metering valve 9 is supplied to both the fuel chamber 4 and the cavity 17, so even if the capacity of the fuel chamber 4 of the pressure booster plunger 3 is small, the fuel is supplied into the pressure booster plunger 3. The amount of fuel can be increased.

In this case, the injection pressure of the fuel injected from the pressure booster plunger 3 is the same as the pressure of the fuel applied to the cylinder chamber 7, so when the pressure of the fuel applied to the cylinder chamber 7 is, for example, 200 kg/ ^cm2 , Set the nozzle opening pressure to about 150-180Kg/ ^cm2 . For example, a large diameter plunger 6a and a small diameter plunger 6b
When the area ratio of is 6:1, when the plunger 6 is fully stroked, the amount of fuel injected is equal to that of the fuel chamber 4.
This makes it possible to increase the capacity up to six times the capacity of .

FIG. 3 shows a cross section of a pressure booster plunger used in a pressure booster plunger type fuel injection device according to an embodiment of the present invention.

The plungers 6 used in the pressure booster plunger 3 of the present invention have four different diameters: 6a, 6b,
It is composed of 6c and 6d. When the difference in level between the plungers 6d and 6c is 16, the difference in level between the plungers 6c and 6b is 26, and the difference in level between the plungers 6b and 6a is 36, these steps 16, 2
The gaps 6, 36 and the pressure increase plunger 3 are 17, 27, 37, respectively.

Communication passages 18, 28, and 38 are connected to the gaps 17, 27, and 37, respectively, and these are all communicated with the fuel chamber 4 via a rotary type on-off control valve 40. There is.

The opening/closing control valve 40 has a structure as shown, for example, in FIG. It is partitioned into two communication grooves 42A (upper side) and 42B (lower side) by a partition wall 43 provided. The communication groove 42A is connected to a fuel supply path, and the communication groove 42B is connected to the oil pan 2 through a fuel discharge path (not shown). Further, the rotating shaft 41 is provided to protrude from a gear 44, and a pinion 45 driven by a step motor 46 or the like is meshed with the gear 44.

In the state shown in FIG. 3A, fuel is supplied only to the fuel chamber 4 of the pressure booster plunger 3, and when the rotary shaft 41 is rotated from this state to the state shown in FIG. 3B by the step motor 46, the fuel is connected. Groove 42A,
When the fuel chamber 4 and the cavity 17 are supplied through the communication passage 18 and the rotation shaft 41 is rotated to the state shown in FIG.
When the rotating shaft 41 is rotated to the state shown in FIG.
8 and 38, the fuel chamber 4 and all the voids 17,
27 and 37.

Therefore, when the rotation shaft 41 is in the state shown in FIG. 3D,
Since the pressure receiving area of the plunger 6a with the largest diameter of the cylinder chamber 7 and the sum of the pressurizing areas of the cavities 17, 27, 37 and the fuel chamber 4 are equal, at this time, the amount of fuel injected from the pressure booster plunger 3 is maximum. , the fuel injection pressure is the lowest at the same pressure as the fuel pressure applied to the cylinder chamber 7, and conversely, when the rotation shaft 41 is in the position A in FIG. 3, the fuel injection amount from the pressure booster plunger 3 is the lowest and the fuel injection pressure is the highest. becomes. The fuel injection pressure can be set to an intermediate value between the minimum pressure (fuel oil pressure) and the maximum pressure depending on the settings of the diameters of the plunger 6b and the plunger 6c.

Figure 5A shows the pressure increase ratio (injection pressure) on the vertical axis,
This is a diagram in which the horizontal axis corresponds to the states of the valves in Figures A, B, C, and D, in which the pressure increase ratio is the highest in state a, which corresponds to diagram A, and in state d, which corresponds to diagram D. In this state, the pressure increase ratio is the smallest, and by sequentially rotating the rotating shaft 41 of the rotary on-off control valve 40, the pressure increase ratio can be sequentially changed, thereby sequentially changing the injection pressure. can do.

On the other hand, the fuel injection pressure required from the engine side is as shown in FIG. 5B. This diagram is drawn with the engine load on the vertical axis and the engine rotation on the horizontal axis. In the present invention, the range a to d surrounded by the curves is arbitrarily selected, It is possible to select and adjust the optimum conditions in relation to the load.

This means that even during the injection period L when the amount of fuel injected is small as shown in Figure 6A, the fuel injection is carried out commensurate with the optimum injection period shown by the dotted line.
It is possible to keep NOx to a minimum.

In addition, as shown in Figure 6B, when the engine is running at low revolutions, even when the oil pressure from the hydraulic pump is low, the pressure increase ratio is changed to perform high-speed injection, compared to the conventional system. It is possible to obtain a much higher injection pressure and to prevent the smoke from worsening.

If the plunger 6 of the pressure booster plunger 3 is configured with four types of plungers with different diameters,
The injection pressure and injection amount of fuel injected from the pressure booster plunger 3 (with the plunger stroke being the same) can be controlled in four stages, and by changing the stroke, the injection amount can be changed from the minimum injection amount to the maximum injection amount. Can be varied in stages. Therefore, if the on-off control valve 40 is switched according to the operating state of the engine,
The optimum fuel injection pressure and injection amount can be given to the engine operating condition.

〔Effect of the invention〕

As explained above, the pressure booster plunger type fuel injection device of the present invention is a pressure booster plunger type fuel injection device that pressurizes fuel using hydraulic pressure. The plunger fitted into the cylinder is formed into a stepped plunger having a different diameter to match the stepped cylinder, and one end is opened at each step of the plurality of cylinders. A communication path is provided with the other end converging at a predetermined location, and the opening of this communication path is sequentially opened or closed depending on the engine load and engine rotation, and the fuel injection nozzle is injected at the meeting point of the communication path. The structure includes a switching valve that can sequentially adjust the amount of fuel supplied to the engine.

Therefore, three or more stepped cylinders with diameters are formed in the main body, and the stepped plunger is housed in the main body,
Since it is possible to gradually increase or decrease the area of the tip surface of the plunger with the smallest diameter and the gap formed in the stepped portion with a single pressure-increasing plunger, the increase shown in FIG. 5A is possible. In addition to being able to obtain a pressure ratio, it is also possible to obtain an optimum pressure increase ratio in the relationship between engine rotation and engine load shown in FIG. 5B, so that the response speed of the fuel injection device can be increased.

In addition, the fuel injection pressure and injection amount can be freely controlled depending on the engine rotation and load, reducing the amount of NOx generated and optimizing the fuel injection speed at low engine speeds, resulting in the generation of smoke. It is possible to significantly improve engine performance, such as by reducing

Further, since many members can be housed inside one main body, it is possible to downsize the fuel injection device.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the pressure boosting plunger type fuel injection device of the present invention, FIG. 2 is a diagram showing the pipe internal pressure with respect to the crank angle of the pressure boosting plunger type fuel injection device, and FIG. 3 A is a sectional view of a pressure increase plunger showing another embodiment of the pressure increase plunger type fuel injection device of the present invention, and FIGS. 3B to 3D are main part sectional views showing possible positions of the opening/closing control valve of the same A, FIG. 4 is a perspective view showing the drive mechanism of the opening/closing control valve shown in FIG. 3. Fig. 5 is an explanatory diagram of the operating state when the pressure booster plunger type fuel injection device shown in Fig. 3 is used, in which Fig. A shows the relationship between the valve state and the pressure increase ratio, and Fig. B shows the engine rotation. It is a figure showing the relationship between and engine load. Figure 6 is a diagram showing the injection pressure corresponding to the fuel injection amount, Figure A is a diagram showing the relationship between the optimal injection period and injection pressure, and Figure B is a diagram showing the relationship between engine rotation, injection period, and injection pressure. FIG. 3... Pressure booster plunger, 5... Spool valve, 9
...Measuring valve, 10, 31...Solenoid, 12...
...Fuel injection nozzle, 16, 26, 36... Step part, 17, 27, 37... Gap part, 18, 28,
38... Communication path, 20... Control device, 30... Solenoid three-way valve, 40... Open/close control valve, 41... Rotating shaft, 42... Communication groove, 43... Partition wall, 46... Step motor.

Claims (1)

[Scope of Claims] 1. In a pressure booster plunger type fuel injection device that pressurizes fuel using hydraulic pressure, three or more cylinders with different diameters are arranged in the main body on the same axis to form a stepped cylinder. , the plunger fitted into the cylinder is formed into a stepped plunger having a different diameter to match the stepped cylinder, one end of which opens at each step of the plurality of cylinders, and the other end of which is assembled at a predetermined location. At the meeting point of these communication paths, the openings of these communication paths are sequentially opened or closed depending on the engine load and engine rotation to sequentially adjust the amount of fuel supplied to the fuel injection nozzle. A pressure booster plunger type fuel injection device equipped with a switching valve.