JPH0566262U - Diesel engine fuel injector - Google Patents

Abstract

(57) [Abstract] [Purpose] Pilot injection and main injection are completely independent, injection pressure drop at the time of main injection is prevented, atomization of fuel is sufficiently performed, and dispersion of injection characteristics is eliminated, and exhaust gas Aim to reduce black smoke inside. [Composition] The pumping unit 3 of the injection pump 1 is divided into a pilot injection pumping unit 3a and a main injection pumping unit 3b, and a supply passage 17 formed in the nozzle body 15 of the injection nozzle 2 is provided as a pilot injection supply passage. 17a and a main injection supply passage 17b, and the pilot injection pressure feed portion 3a and the pilot injection supply passage 17a are connected to each other via a pilot injection injection pipe 16a. The injection supply passage 17b is connected via the main injection pipe 16b.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a fuel injection device for a diesel engine.

[0002]

[Prior Art]

Recently, in the diesel engine, by performing a so-called timing retard for delaying the fuel injection timing, when it is being performed to reduce the NO _X in the exhaust gas, too large timing retard amount, the ignition delay Since it does not increase and NO _X increases on the contrary, the startability also deteriorates, so pilot injection has been conventionally attempted in order to suppress the ignition delay.

2 to 4 show an example of a conventional fuel injection device for a diesel engine that enables pilot injection. The fuel injection device for a diesel engine includes an injection pump 1 and an injection nozzle 2. I have it.

The injection pump 1 includes a pressure-feeding portion 3 formed so as to correspond to a plurality of cylinders of an engine (not shown) in a one-to-one correspondence. The pressure-feeding portion 3 has a fuel suction hole 4. The plunger 6 is inserted in the plunger barrel 5 so that it can slide in the axial direction and the rotation angle about the axis can be set appropriately by driving a control rack (not shown). By engraving a lead groove 10 having a horizontal portion 8 and an inclined portion 9 which communicate with a pumping chamber 7 defined by the top surface of the plunger 6 and the plunger barrel 5 at a required position on the surface of the plunger 6, The pilot injection unit 11 keeps the fuel injection amount substantially constant regardless of the change of the rotation angle of the plunger 6, and the change of the rotation angle of the plunger 6 causes the fuel injection according to the load condition of the engine. A main injection part 12 is formed so as to increase or decrease the amount, and when the upper end of the plunger barrel 5 is biased in the closing direction by a spring 13 and the pressure in the pressure feed chamber 7 reaches a predetermined pressure. The delivery valve 14 that opens is provided.

The injection nozzle 2 has a supply passage 17 through which fuel is pumped from the injection pump 1 through an injection pipe 16, a pressure cylinder chamber 18 communicating with the supply passage 17, and a nozzle body 15. A small-diameter tip injection chamber 19 that can communicate with the pressurization cylinder chamber 18 is formed, and a needle 20 that can shut off the pressurization cylinder chamber 18 and the tip injection chamber 19 in the closed position is provided in the nozzle body 15 as an axis line. The nozzle body 15 is slidably inserted into the nozzle body 15, and a plurality of injection holes 21 opening to the tip injection chamber 19 are radially formed in the tip end portion of the nozzle body 15, and the base end portion of the nozzle body 15 is A spring 22 is provided to bias the needle 20 in the closing direction.

In the fuel injection device for a diesel engine as shown in FIGS. 2 to 4, first, fuel is sucked into the pressure feeding chamber 7 in the plunger barrel 5 from the suction hole 4 in the fuel suction stroke by lowering the plunger 6. In the subsequent fuel pressure feeding stroke, the plunger 6 rises from the state shown in FIG. 2 and the pressure in the pressure feeding chamber 7 rapidly increases immediately after the pilot injection unit 11 completely closes the suction hole 4, and the pressure reaches a predetermined pressure. When reaching, the fuel in the pressure feeding chamber 7 pushes up the delivery valve 14 against the biasing force of the spring 13, and is pressure fed to the supply passage 17 of the injection nozzle 2 via the ejection pipe 16.

The fuel pressure-fed to the supply passage 17 of the injection nozzle 2 is supplied to the pressurizing cylinder chamber 18, and when the internal pressure of the pressurizing cylinder chamber 18 reaches a predetermined injection start pressure, the needle 20 springs. It moves in the opening direction against the urging force of 22, and the pressurizing cylinder chamber 18 and the front end injection chamber 19 communicate with each other, and fuel is injected from the injection holes 21 into the combustion chamber of the engine as pilot injection before main injection. It

During this time, the plunger 6 continues to rise, and when the horizontal portion 8 of the lead groove 10 comes into contact with the suction hole 4, the pumping chamber 7 and the suction hole 4 communicate with each other via the horizontal portion 8 of the lead groove 10. Therefore, the fuel in the pumping chamber 7 escapes to the suction hole 4 through the horizontal portion 8 of the lead groove 10, so that the pressure in the pumping chamber 7 decreases and the fuel is not injected.

When the plunger 6 further rises and the horizontal portion 8 of the lead groove 10 passes through the suction hole 4 and the main injection portion 12 closes the suction hole 4 again and the pressure in the pumping chamber 7 reaches a predetermined pressure, As in the case of the pilot injection described above, fuel is injected from the injection hole 21 of the injection nozzle 2 into the combustion chamber of the engine as the main injection. In the main injection, the inclined portion 9 of the lead groove 10 of the plunger 6 is sucked into the intake hole 4 Until the plunger 6 reaches the top dead center, the pumping chamber 7 and the suction hole 4 are kept in communication with each other through the inclined portion 9 of the lead groove 10, so that Will no longer be injected.

Further, regarding the fuel injection amount in the main injection, the rotation angle about the axis of the plunger 6 is controlled by a control rack (not shown) driven according to the depression amount of the accelerator pedal or the operation of the governor. Is changed as appropriate, and the distance from when the main injection part 12 of the plunger 6 completely closes the suction hole 4 to when the inclined part 9 of the lead groove 10 reaches the suction hole 4 (referred to as the effective stroke, as shown in FIG. 2). Then, S _{MIN for} low load, S _{MID for} medium load, and S _{MAX for} full load) are changed to increase or decrease according to the load state.

In FIG. 2, D is the diameter of the suction hole 4.

[0012]

[Problems to be solved by the device]

 However, in the fuel injection device of the diesel engine as described above, the pilot injection and the main injection are performed by the one pumping unit 3 of the injection pump 1, so that a part of the pressure energy is consumed during the pilot injection. Therefore, there was a problem that the injection pressure at the time of main injection decreased, the atomization of fuel was not sufficiently performed, and black smoke in the exhaust gas increased.

Further, in the case of the fuel injection device for the diesel engine as described above, the distinction between pilot injection and main injection is made relatively clear at low speed, and the desired injection characteristics are obtained, but at high speed, fuel injection is performed. Due to the viscous resistance of, the main injection is started after the pilot injection and before the fuel is completely exhausted from the intake hole 4, and the fluctuation of the injection characteristics becomes large. This led to an increase in smoke.

In view of the above situation, the present invention completely separates the pilot injection and the main injection, prevents the injection pressure from decreasing during the main injection, and is capable of sufficiently atomizing the fuel, and An object of the present invention is to provide a fuel injection device for a diesel engine that can eliminate variations in characteristics and reduce black smoke in exhaust gas.

[0015]

[Means for Solving the Problems]

 According to the present invention, the plunger is slidable in the axial direction in the plunger barrel having the suction hole and the rotation angle about the axis can be changed appropriately, and the rotation angle of the plunger is changed on the outer peripheral surface of the plunger. When a lead groove is formed to increase or decrease the fuel injection amount according to the load condition of the engine, when the plunger barrel is urged toward the closing direction and the pressure inside the plunger barrel reaches a predetermined pressure. And an injection pump having a delivery section provided with a delivery valve that opens to a nozzle, a supply passage through which fuel is delivered from the injection pump through an injection pipe to the nozzle body, and a pressure cylinder chamber communicating with the supply passage. And a small-diameter tip injection chamber that can communicate with the pressurizing cylinder chamber, and the nozzle body is urged in the closing direction and blocks the pressurizing cylinder chamber and the front end ejecting chamber at the closed position. Of a diesel engine, in which a possible needle is slidably inserted in the axial direction, and a plurality of injection holes are formed at the tip of the nozzle body to open to the tip injection chamber. In the injection device, the fuel injection amount of the injection pump is adjusted so that the fuel injection amount is increased / decreased according to the load condition of the engine by changing the rotation angle of the pilot injection pressure transfer unit and the plunger in which the fuel injection amount is substantially constant. In addition to the in-injection pressure feed section, the supply path formed in the nozzle body of the injection nozzle is divided into a pilot injection supply path and a main injection supply path, and the pilot injection pressure supply section and the pilot injection And the main supply line are connected via a pilot injection injection pipe, and the main injection pressure feed section and the main injection supply line are connected via a main injection injection pipe. It is an feature.

[0016]

Therefore, first, the fuel is pressure-fed from the pilot-injection pressure-feeding portion to the pilot-injection supply path of the injection nozzle through the pilot-injection injection pipe, and the fuel pressure-fed to the pilot-injection supply path is added. When it is supplied to the pressure cylinder chamber and the internal pressure of the pressure cylinder chamber reaches a predetermined injection start pressure, the needle moves in the opening direction, the pressure cylinder chamber and the tip injection chamber communicate with each other, and fuel is injected from the injection hole. It is injected into the combustion chamber of the engine as pilot injection before main injection, and then fuel is pressure-fed from the main injection pressure-feeding section to the main injection supply path of the injection nozzle via the main injection injection pipe, The fuel pressure-fed to the injection supply passage is supplied to the pressurizing cylinder chamber, and when the internal pressure of the pressurizing cylinder chamber reaches the predetermined injection start pressure, the needle moves in the opening direction and the pressure cylinder chamber It communicates with the tip injection chamber, and fuel is injected from the injection hole into the combustion chamber of the engine as the main injection.

[0017]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, the parts denoted by the same reference numerals as those in FIG. 2 represent the same thing, and the basic structure is the same as that of the conventional example shown in FIG. However, the feature of this embodiment is that, as shown in FIG. 1, the pumping unit 3 of the injection pump 1 is divided into a pilot injection pumping unit 3a and a main injection pumping unit 3b. The supply path 17 formed in the nozzle body 15 of the injection nozzle 2 is divided into a pilot injection supply path 17a and a main injection supply path 17b, and the pilot injection pressure feed portion 3a and the pilot injection supply path 17a are divided into two parts. Is connected via a pilot injection injection pipe 16a, and the main injection pressure feeding portion 3b and the main injection supply passage 17b are connected via a main injection injection pipe 16b.

In the pilot injection pressure-feeding section 3a, a plunger 6a is provided in a plunger barrel 5a having a fuel suction hole 4a, and the plunger 6a is slidable in the axial direction and its rotation angle about the axis is not shown in the control. The rack 6 is fitted and inserted so that it can be set appropriately, and a lead groove 10a communicating with the top surface of the plunger 6a and the pressure feeding chamber 7a defined by the plunger barrel 5a is formed at a required position on the outer peripheral surface of the plunger 6a. As a result, only the pilot injection portion 11 having a substantially constant fuel injection amount is formed on the plunger 6a regardless of the change of the rotation angle of the plunger 6a, and the upper end portion of the plunger barrel 5a is closed by the spring 13a. And a delivery valve 14a that is opened when the pressure in the pumping chamber 7a reaches a predetermined pressure. Have a configuration.

Further, the main injection pressure-feeding section 3b shows a plunger 6b in a plunger barrel 5b having a fuel suction hole 4b, which is slidable in the axial direction and has a rotation angle about the axis. It is fitted and inserted so that it can be set appropriately by driving a control rack, and a lead groove 10b communicating with the pressure feeding chamber 7b defined by the top surface of the plunger 6b and the plunger barrel 5b is formed at a required position on the outer peripheral surface of the plunger 6b. By providing the plunger 6b, only the main injection portion 12 is formed so as to increase or decrease the fuel injection amount according to the load condition of the engine by changing the rotation angle of the plunger 6b. A delivery mechanism that is urged in the closing direction by the spring 13b and opens when the pressure in the pressure feed chamber 7b reaches a predetermined pressure. The valve 14b is provided.

In the case of the present embodiment, the lift positions of the top surface of the plunger 6a of the pilot injection pressure-feeding portion 3a and the top surface of the plunger 6b of the main injection pressure-feeding portion 3b are made to coincide with each other, and suction is performed in the pilot injection pressure-feeding portion 3a. By lowering the opening position of the hole 4a relative to the opening position of the suction hole 4b in the main injection pressure-feeding portion 3b by a required amount, the pilot injection has a cam angle of 0 ° <θ ≦ 10 with respect to the main injection. The pilot injection amount is set to be 1 to 5% of the main injection amount by adjusting the shape and the forming position of the lead grooves 10a and 10b as appropriate while starting within the range of 0 °. is there.

In order to start the pilot injection earlier than the main injection within a required range, the opening position of the suction hole 4a in the pilot injection pressure feed portion 3a and the suction in the main injection pressure feed portion 3b are set. The opening position of the hole 4b is made to coincide in height, and the top surface of the plunger 6a of the pilot injection pumping portion 3a is located above the top surface of the plunger 6b of the main injection pumping portion 3b by a required amount. You may make it pre-lift so that it does.

Next, the operation of the above embodiment will be described.

During the fuel intake stroke due to the lowering of the plungers 6a, 6b, fuel is sucked from the suction holes 4a, 4b into the pressure feed chambers 7a, 7b in the plunger barrels 5a, 5b, and in the subsequent fuel pressure stroke, the plungers 6a, 6b are Ascending from the state of FIG. 1, first, immediately after the pilot injection part 11 completely closes the suction hole 4a, the pressure in the pumping chamber 7a suddenly rises, and when the pressure reaches a predetermined pressure, the pressure in the pumping chamber 7a is increased. The fuel pushes up the delivery valve 14a against the biasing force of the spring 13a, and is pressure-fed to the pilot injection supply passage 17a of the injection nozzle 2 via the pilot injection injection pipe 16a.

The fuel pressure-fed to the pilot injection supply path 17 a of the injection nozzle 2 is supplied to the pressure cylinder chamber 18, and when the internal pressure of the pressure cylinder chamber 18 reaches a predetermined injection start pressure, the needle 20 Moves in the opening direction against the urging force of the spring 22, the pressurizing cylinder chamber 18 and the tip injection chamber 19 communicate with each other, and fuel is injected from the injection hole 21 into the combustion chamber of the engine as pilot injection before main injection. Is jetted.

During this time, the plunger 6a continues to rise, and when the lead groove 10a is inserted into the suction hole 4a, the pressure feeding chamber 7a and the suction hole 4a are in communication via the lead groove 10a, and the fuel in the pressure feeding chamber 7a is Since it escapes to the suction hole 4a through the lead groove 10a, the pressure in the pumping chamber 7a drops, and thereafter, fuel injection is not performed until the main injection described later is completed.

On the other hand, the plunger 6b is also rising together with the plunger 6a, and after the pilot injection is performed, when the suction hole 4b is closed by the main injection unit 12 and the pressure of the pressure feeding chamber 7b reaches a predetermined pressure. , The fuel in the pressure feed chamber 7b pushes up the delivery valve 14b against the biasing force of the spring 13b, and is pressure-fed to the main injection supply passage 17b of the injection nozzle 2 through the main injection pipe 16b. The fuel pressure-fed to the passage 17b is supplied to the pressurizing cylinder chamber 18, and when the internal pressure of the pressurizing cylinder chamber 18 reaches a predetermined injection start pressure, the needle 20 resists the urging force of the spring 22 and opens. To the front end injection chamber 19, the fuel is injected from the injection hole 21 into the combustion chamber of the engine as the main injection. , The lead groove 10b of the plunger 6b continues until it reaches the suction hole 4b, and thereafter, the pumping chamber 7b and the suction hole 4b are in communication with each other through the lead groove 10b until the plunger 6b reaches the top dead center. As it is kept as it is, fuel injection is not performed.

In this way, the pilot injection and the main injection can be made completely independent, the injection pressure can be prevented from lowering during the main injection, and the fuel can be atomized sufficiently, and the low speed or the high speed can be distinguished. Therefore, it is possible to obtain desired injection characteristics that do not vary, and reduce black smoke in exhaust gas.

The fuel injection device for a diesel engine according to the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0030]

[Effect of the device]

 As described above, according to the fuel injection device for a diesel engine of the present invention, the pilot injection and the main injection are completely independent, the injection pressure is prevented from decreasing during the main injection, and the fuel is sufficiently atomized. It is possible to obtain the excellent effect that it is possible to eliminate the dispersion of the injection characteristics and reduce the black smoke in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a side sectional view of an embodiment of the present invention.

FIG. 2 is a side sectional view of a conventional example.

3 is a sectional view taken along line III-III in FIG.

4 is a perspective view of the plunger shown in FIG. 2. FIG.

[Explanation of symbols]

 1 Injection Pump 2 Injection Nozzle 3 Pressure Feeding Part 3a Pilot Injection Pressure Feeding Part 3b Main Injection Pressure Feeding Part 4 Suction Hole 4a Suction Hole 4b Suction Hole 5 Plunger Barrel 5a Plunger Barrel 5b Plunger Barrel 6 Plunger 6a Plunger 6b Plunger 10 Reed Groove 10a Groove 10b Lead groove 14 Delivery valve 14a Delivery valve 14b Delivery valve 15 Nozzle body 16 Injection pipe 16a Pilot injection pipe 16b Main injection injection pipe 17 Supply passage 17a Pilot injection supply passage 17b Main injection supply passage 18 Pressurized cylinder Chamber 19 Tip injection chamber 20 Needle 21 Injection hole

Claims (1)

[Scope of utility model registration request] 1. A plunger is slidable in an axial direction in a plunger barrel having a suction hole so that a rotation angle about the axis can be changed as appropriate, and an outer peripheral surface of the plunger is
A lead groove for enlarging or decreasing the fuel injection amount according to the load state of the engine is engraved by changing the rotation angle of the plunger, and the upper end of the plunger barrel is urged in the closing direction and the pressure in the plunger barrel is increased. To an injection pump having a delivery section provided with a delivery valve that opens when a predetermined pressure is reached, a supply path through which fuel is delivered from the injection pump via an injection pipe, and a communication path to the supply path. Forming a pressure cylinder chamber and a small-diameter tip injection chamber that can communicate with the pressure cylinder chamber, and the nozzle body is biased in the closing direction by the pressure cylinder chamber and the tip injection chamber in the closed position. Diesel equipped with an injection nozzle in which a needle capable of shutting off is inserted slidably in the axial direction, and a plurality of injection holes opening to the tip injection chamber are bored at the tip of the nozzle body. In the fuel injection device of the engine, the fuel injection amount of the injection pump is changed so that the fuel injection amount is increased or decreased according to the load condition of the engine by changing the rotation angle of the pilot injection pressure transfer unit and the plunger in which the fuel injection amount is substantially constant. And a main injection pressure feeding section, and a supply path formed in the nozzle body of the injection nozzle is divided into a pilot injection supply path and a main injection supply path. Fuel injection of a diesel engine, characterized in that the fuel injection passage is connected via a pilot injection injection pipe, and the main injection pressure feeding section and the main injection supply passage are connected via a main injection injection pipe. apparatus.