JP2512426Y2 - Fuel injector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is designed to pump fuel from one fuel injection pump to an initial fuel injection nozzle for pilot injection and a main fuel injection nozzle for main injection. Fuel injection device.

[Prior Art] Generally, a conventional fuel injection device configured to inject fuel from an initial fuel injection nozzle for pilot injection and a main fuel injection nozzle for main injection is a fuel injection pump for each fuel injection nozzle. Was installed, and fuel was pumped from each fuel injection pump to each fuel injection nozzle.

However, in such a fuel injection device, since two expensive fuel injection pumps are installed, there is a problem that the cost rises and the device becomes large.

Therefore, in the fuel injection device described in Japanese Examined Patent Publication No. 54-4447, a sub-plunger that moves along with the movement of the main plunger that pressurizes the fuel is installed, and the movement of the sub-plunger causes the fuel to be injected into the initial fuel injection nozzle. And the main fuel injection nozzles are distributed and pressure-fed to each other, which allows the fuel to be pressure-fed to the two nozzles by one fuel injection pump.

That is, the fuel injection pump described in the above publication is the fourth
As shown in the figure, a main cylinder b fitted and fixed to the inner peripheral surface of the upper end portion of the outer cylinder a and a sub-cylinder c fixed to the upper end surface of the outer cylinder a are provided. Pressurization chamber d
A main plunger e for pressurizing the fuel inside is inserted, and a sub plunger g biased downward by a spring f is inserted in the sub cylinder c. The sub-plunger g is formed with a communication hole h, one end of which opens at the lower end surface facing the fuel pressurizing chamber d and the other end of which opens at the outer peripheral surface. When the sub-plunger g moves upward in the sub-cylinder c, the sub-discharge port i communicating with the fuel pressurizing chamber d through the communication hole h is formed, and when the sub-plunger g moves further upward. , A main discharge port j communicating with the fuel pressurizing chamber d through the inside of the sub cylinder c is formed. The sub discharge port i is connected to an initial fuel injection nozzle (not shown), and the main discharge port j is connected to a main fuel injection nozzle (not shown).

In the fuel injection pump having the above structure, when the main plunger e moves upward and the fuel introduction port k is shielded, the fuel pressurizing chamber d
The fuel inside is pressurized, and the sub-plunger g is moved upward by the pressure of the fuel inside the fuel pressurizing chamber d. When the sub-plunger g moves upward and its communication hole h faces the sub-discharge port i, the fuel in the fuel pressurizing chamber d is pressure-fed to the initial fuel injection nozzle, and pilot injection is performed.

When the sub-plunger g moves further upward and the communication hole h separates from the sub-discharge port i, the fuel pressurizing chamber d and the sub-discharge port i are shut off from each other. Thus, the pilot injection ends.

Around the same time as the end of pilot injection, the sub-plunger g
The main discharge port i that was shielded by is opened and communicates with the fuel pressurizing chamber d. As a result, the fuel in the fuel pressurizing chamber d is pressure-fed to the main fuel injection nozzle, and the main injection is performed. When the lead 1 of the main plunger e faces the fuel introduction port k, the substantial fuel pressurization by the main plunger e ends, and the main fuel injection ends accordingly.

[Problems to be Solved by the Invention] In the above conventional fuel injection nozzle, when the sub-plunger g moves upward, the inside of the lower end of the sub-cylinder c forms a part of the fuel pressurizing chamber d. Therefore, if the inner diameter of the sub-cylinder c is increased, so-called dead volume increases, and the fuel pressurization efficiency by the main plunger e decreases. Therefore, the inner diameter of the sub cylinder c must be smaller than the inner diameter of the main cylinder b, and must be as small as possible.

However, when the inner diameter of the sub-cylinder c is reduced, the main plunger e has a significantly higher moving speed than that of the sub-plunger g. Therefore, the outer peripheral surface of the sub-plunger and the inner peripheral surface of the sub-cylinder c are increased. There was a case where so-called seizure occurred between and.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a fuel injection device having a novel configuration in which the pressurization efficiency of the fuel injection pump is not deteriorated and the secondary plunger is not seized. To aim.

[Means for Solving the Problems] In order to achieve the above object, the present invention supplies fuel from one fuel injection pump to an initial fuel injection nozzle for pilot injection and a main fuel injection nozzle for main injection, respectively. In the fuel injection device configured to perform pressure feeding, the valve opening pressure of the initial fuel injection nozzle is set lower than the valve opening pressure of the main fuel injection nozzle, and the valve opening pressure is set between the fuel injection pump and the pilot injection fuel injection nozzle. Is a high pressure chamber into which the fuel pumped from the fuel injection pump is introduced, a pilot pressure chamber into which the fuel pumped from the fuel injection pump is introduced through an orifice, and the high pressure chamber and the pilot pressure chamber. A valve spring provided between the pilot pressure chamber side and the high pressure chamber side to urge the valve body toward the high pressure chamber side to seat it on the valve seat. When the pressure is higher than the pressure of the lot pressure chamber and the pressing force against the valve body due to the pressure difference becomes larger than the urging force of the valve spring, the valve body lifts from the valve seat, and the fuel injection pump and the initial fuel injection nozzle are separated from each other. An on-off valve is provided which connects the fuel injection pump and the initial fuel injection nozzle so that the valve body is seated on the valve seat when the pressing force due to the differential pressure becomes smaller than the biasing force of the valve spring. It is characterized by.

[Operation] When pressure feeding of fuel from the fuel injection pump is started, a part of the fuel is introduced into the high pressure chamber of the on-off valve and also into the pilot pressure chamber via the orifice. At this time, the pressure in the high pressure chamber rises instantly, but the pressure in the pilot pressure chamber is delayed compared to the pressure in the high pressure chamber because the high pressure fuel is introduced into the pilot pressure chamber through the orifice. Therefore, a differential pressure is generated between the high pressure chamber and the pilot pressure chamber. Due to this pressure difference, the valve element is lifted from the valve seat against the biasing force of the valve spring, and the on-off valve opens.
As a result, the high-pressure fuel is pumped to the initial fuel injection nozzle.

The other part of the fuel pumped from the fuel injection pump is pumped to the main fuel injection nozzle almost at the same time as the fuel is pumped to the initial fuel injection nozzle.

At this time, since the valve opening pressure of the initial fuel injection nozzle is set lower than the valve opening pressure of the main fuel injection nozzle, fuel is first injected from the initial fuel injection nozzle.

After a lapse of a predetermined short time after the start of fuel injection from the initial fuel injection nozzle, the pressure of the pilot pressure chamber rises due to the fuel flowing through the orifice, and the differential pressure between the high pressure chamber and the pilot pressure chamber is increased by the valve spring. Smaller than the urging force of. Then, the on-off valve closes, and the fuel is not pressure fed to the initial fuel injection nozzle. As a result, fuel injection from the initial fuel injection nozzle ends. Here, the injection time by the initial fuel injection nozzle is almost the same as the opening time of the on-off valve, and is a minute time. Moreover, since the valve opening pressure of the initial fuel injection nozzle is set low, the fuel injection pressure is also low. Therefore, the amount of fuel injected from the initial fuel injection nozzle is small and pilot injection is performed.

At approximately the same time when the pilot injection ends, the pressure of the fuel pumped from the fuel injection pump becomes higher than the valve opening pressure of the main fuel injection nozzle. Therefore, following the pilot injection, main injection is performed from the main fuel injection nozzle.

It should be noted that substantially the same timing includes immediately before and immediately after the end of pilot injection.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a schematic configuration of an embodiment of the present invention, and this fuel injection device includes one fuel injection pump 1
And an initial fuel injection nozzle 2 for performing pilot injection
And a main fuel injection nozzle 3 for performing main injection. Then, the fuel discharged from the fuel injection pump 1 is pressure-fed to the initial fuel injection nozzle 2 via the common pressure feed path A and the first branch path B, and also via the common pressure feed path A and the second branch path C. The fuel is injected into the fuel injection nozzle 3. When the pressure of the fuel sent to the initial fuel injection nozzle 2 exceeds the valve opening pressure of the nozzle spring 21, the needle valve 22 lifts from the valve seat 23, and the fuel is injected from the injection hole 24. Similarly, when the pressure of the fuel pumped to the main fuel injection nozzle 3 exceeds the valve opening pressure of the nozzle spring 31, the needle valve 32 lifts from the valve seat 33 and the fuel is injected from the injection hole 34.

Here, assuming that the valve opening pressure of the initial fuel injection nozzle 2 is PN ₁ and the valve opening pressure of the main fuel injection nozzle is PN ₂ , PN ₁ <PN ₂ is set.

It is needless to say that the initial fuel injection nozzle 2 and the main fuel injection nozzle 3 are installed in the same combustion chamber of the same engine.

The first branch path B is provided with an opening / closing valve 4 that opens and closes the first branch path B to connect and disconnect the fuel injection pump 1 and the initial fuel injection nozzle 3. The on-off valve 4 includes a high pressure chamber 41, a pilot pressure chamber 42, and a valve body 43 arranged between the high pressure chamber 41 and the pilot pressure chamber 42. The high pressure chamber 41 is directly connected to the first branch path B. On the other hand, the pilot pressure chamber 42 is connected to the common pressure feeding path A via the orifice 5. The valve body 43 is biased by the valve spring 44 from the pilot pressure chamber 42 side toward the high pressure chamber 41 side, and is seated on the valve seat 45.

In the above configuration, the pressure in the high pressure chamber 41 is the pilot pressure chamber.
When the pressure becomes higher than the pressure of 42 and the differential pressure becomes larger than the urging force of the valve spring 44, the valve body 43 lifts from the valve seat 45 and opens. This allows the fuel injection pump 1 and the initial fuel injection nozzle 2 to communicate with each other. On the contrary, when the differential pressure becomes smaller than the urging force of the valve spring 44, the valve body 43 is seated on the valve seat 45 and the valve is closed. As a result, the connection between the fuel injection pump 1 and the initial fuel injection nozzle 2 is cut off.

On the other hand, in the second branch path B, two check valves 6 and 7 are provided in parallel.

The check valve 6 constantly blocks the flow of fuel from the main fuel injection nozzle 3 side to the fuel injection pump 1 side, while the pressure on the fuel injection pump 1 side becomes higher than the pressure on the main fuel injection nozzle 3 side. When the pressure difference becomes greater than the biasing force of the spring 61, the valve opens to allow the fuel to flow from the fuel injection pump 1 side to the main fuel injection nozzle 3 side.

The check valve 7 constantly blocks the flow of fuel from the fuel injection pump 1 side to the main fuel injection nozzle side 3, while the pressure on the main fuel injection nozzle 3 side becomes higher than the pressure on the fuel injection pump 1 side, and When the differential pressure becomes larger than the biasing force of the spring 71, the valve is opened to allow the fuel to flow from the main fuel injection nozzle 3 side to the fuel injection nozzle 1 side. An orifice 8 is provided near the check valve 7 on the main fuel injection nozzle 3 side.

Next, the operation of the fuel injection device having the above configuration will be described.

When the fuel injection pump 1 starts the pressure feeding of the fuel, the high-pressure fuel is sent to the first branch passage B and the second branch passage C via the common pressure feed passage A.

The fuel pressure-fed to the first branch passage B is the high pressure chamber of the on-off valve 4.
It flows into 41 and instantly increases its pressure. At the same time, high-pressure fuel also flows into the pilot pressure chamber 42 of the on-off valve 4 to try to increase its pressure.
Since the orifice 5 is provided on the upstream side, the pressure increase in the pilot pressure chamber 42 is slightly delayed as compared with the pressure increase in the high pressure chamber 41. Therefore, a differential pressure is generated between the high pressure chamber 41 and the pilot pressure chamber 42. When the pressure difference becomes larger than the biasing force of the valve spring 44, the valve body 43 lifts from the valve seat 45 and opens the valve. As a result, fuel is pumped to the initial fuel injection nozzle 2.

On the other hand, the fuel pumped to the second branch C is pumped to the main fuel injection nozzle 3 via the check valve 6 almost at the same time as the fuel is pumped to the initial fuel injection nozzle 2.

Here, since the valve opening pressure P ₁ of the initial fuel injection nozzle 2 is set to be lower than the valve opening pressure P ₂ of the main fuel injection nozzle 3, fuel is first injected from the initial fuel injection nozzle 2. After a small amount of time has elapsed after the start of fuel injection in the initial fuel injection nozzle 2, the pressure in the pilot pressure chamber 42 is raised by the fuel flowing through the orifice 5. Therefore, the pressure difference between the high pressure chamber 41 and the pilot pressure chamber 42 decreases. Then, when the differential pressure becomes smaller than the biasing force of the valve spring 44, the valve body 43 is seated on the valve seat 45 and the valve is closed. As a result, the fuel is no longer pumped to the initial fuel injection nozzle 2, and the fuel injection by the initial fuel injection nozzle 2 ends. in this case,
The fuel injection time by the initial fuel injection nozzle 2 depends on the on-off valve 4.
The valve opening time is substantially the same as the valve opening time, and the fuel pressure is low corresponding to the low valve opening pressure, so the fuel injection amount by the initial fuel injection nozzle is small. That is, pilot injection is performed by the initial fuel injection nozzle 2.

On the other hand, in the main fuel injection nozzle 3, when the pressure of the fuel rises with the lapse of time after the start of the fuel pressure pumping from the fuel injection pump 1, and the valve opening pressure P ₂ is reached, the fuel injection starts. In this case, the fuel injection by the main fuel injection nozzle 3 is
The orifice 5 is adjusted so as to start immediately before or after the fuel injection end timing by the initial fuel injection nozzle 2.

That is, if the flow resistance of the orifice 5 is increased,
Since the delay of the pressure rise in the pilot pressure chamber 42 becomes large,
The closing timing of the on-off valve 4 is delayed, and the injection end timing of the initial fuel injection nozzle 2 is delayed accordingly. On the contrary, if the flow resistance of the orifice 5 is reduced, the delay in the rise of the pressure in the pilot pressure chamber 42 becomes smaller, so that the closing timing of the opening / closing valve 4 becomes earlier, and accordingly, the injection end timing of the initial fuel injection nozzle 2 becomes shorter. Will be faster. Thus, the injection end timing of the initial fuel injection nozzle 2 can be changed by the flow resistance of the orifice 5, so that the injection start timing of the main fuel injection nozzle 3 can be adjusted by adjusting it appropriately. Can be adjusted immediately before or after the end of injection.

The flow resistance of the orifice 5 is determined by an experiment.

After the fuel injection from the main fuel injection nozzle 3 is started, when the fuel pressure pumping from the fuel injection pump 1 is completed, the pressure of the fuel on the fuel injection pump 1 side becomes lower than the pressure on the main fuel injection nozzle 3 side. While the valve is closed, the check valve 7 is opened. By opening the check valve 7, the pressure of the fuel on the main fuel injection nozzle 3 side decreases. Then, the valve element 32 of the main fuel injection nozzle 3 is seated on the valve seat 33, and the fuel injection by the main fuel injection nozzle 3 is completed. At this time, a so-called reflected wave is generated by an impact when the valve body 32 is seated on the valve seat 33, and this reflected wave is attenuated by the orifice 8 and
Fuel injection pump 1 through orifice 8 and check valve 7
Almost disappeared by going to the side. Therefore, the main fuel injection nozzle 3 does not open again due to the reflected wave, and it is possible to prevent the so-called back drooping phenomenon from occurring. The pressure between the check valves 6 and 7 and the main fuel injection nozzle 3 after the main fuel injection is completed, that is, the residual pressure is defined by the spring 71.

As described above, in the fuel injection device of this invention,
The valve opening pressure PN ₁ of the initial fuel injection nozzle 2 is set lower than the valve opening pressure PN ₂ of the main fuel injection nozzle 3, and the fuel injection pump 1 pumps pressure between the fuel injection pump 1 and the initial fuel injection nozzle 2. Since the on-off valve 4 is installed which opens by the fuel to be injected and then closes after a lapse of a short time, the initial fuel injection nozzle 2 is provided with only one fuel injection pump 1. It is possible to perform pilot injection and main injection from the main fuel injection nozzle 3, respectively. Moreover, since the sub-plunger in the above-described conventional fuel injection device is not required at all, various problems caused by providing the sub-plunger can be solved at once.

Next, a more specific embodiment of the above fuel injection device will be described with reference to FIGS. 2 and 3. In addition,
The same parts as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 2, reference numeral 10 is a pump body of the fuel injection pump 1. The pump body 10 has a casing 10b having a through hole 10a penetrating in the vertical direction, a cylinder 10c inserted into the upper end of the through hole 10a, and a barrel 10d inserted into the upper end of the cylinder 10c. The delivery valve seat 10e that shields the upper end opening of the barrel 10d and the delivery valve holder 10f that is abutted against the upper end surface of the delivery valve seat 10e are the main constituent members, and by tightening the bolt 10g, the tubular body 10c, barrel 10d, delivery valve seat 10e and delivery valve holder 10f are fixed to casing 10b. The axes of the through hole 10a, the cylindrical body 10c, and the barrel 10e are aligned with each other.

A plunger 11 is slidably inserted through the cylindrical body 10c. The lower end of the plunger 11 is pressed against a cam shaft (not shown) by a spring 12 so that the plunger 11 moves up and down following the rotation of the cam shaft. The upper end of the plunger 11 is slidably inserted into the barrel 10d, and the fuel pressurizing chamber 13 is formed inside the barrel 10d by the plunger 11 and the delivery valve seat 10e.

In the above structure, when the plunger 11 starts moving upward and the lateral hole 11a is blocked by the timing sleeve 14, the fuel in the fuel pressurizing chamber 13 is pressurized. After that, the lead 11b of the plunger 11 is connected to the intake / exhaust hole 1 of the timing sleeve 14.
When facing 4a, the fuel in the fuel pressurization chamber 14
The gas flows into the fuel storage chamber 15 through the vertical hole 11c, the horizontal hole 11a, the lead 1b, and the suction / discharge hole 14a of the timing sleeve 14. This completes the substantial pressurization by the plunger 11. On the other hand, when the plunger 11 moves downward, the fuel in the fuel storage chamber 15 is sucked and introduced into the fuel pressurizing chamber 14 through the horizontal hole 11a and the vertical hole 11c.

By displacing the timing sleeve 14 in the vertical direction with the timing rod 16, the plunger 11
It is possible to adjust the distance that the plunger 11 moves upward, that is, the prestroke, after the start of the upward movement until the fuel is substantially pressurized. In addition, the plunger is controlled by the control rod 17 via the control sleeve 18.
By rotating and displacing 11 in the forward and reverse directions, the fuel injection amount can be adjusted.

An open / close valve 4 and check valves 6 and 7 are provided between the butting surfaces of the delivery valve seat 10e and the delivery valve holder 10f, as shown in FIG. In this embodiment, the open / close valve 4 is directly connected to the fuel pressurizing chamber 14, and the fuel pressurizing chamber 14 also serves as the high pressure chamber of the open / close valve 4. Further, the check valves 6 and 7 are respectively provided in the fuel pressurizing chamber 1
Connected to 4.

The operation of the fuel injection device having the above structure is the same as that shown in FIG.

[Advantages of the Invention] As described above, according to the fuel injection device of the present invention, the valve opening pressure of the initial fuel injection nozzle is set lower than the valve opening pressure of the main fuel injection nozzle, and the fuel injection pump and the initial fuel injection are performed. Since an on-off valve that opens with the fuel pumped from the fuel injection pump and closes after a lapse of a short time is installed between the injection nozzle and the injection nozzle, even if only one fuel injection pump is provided. Regardless, pilot injection can be performed from the initial fuel injection nozzle and main injection can be performed from the main fuel injection nozzle. Moreover, since the sub-plunger provided in the conventional fuel injection device is not required at all, various problems caused by providing the sub-plunger can be solved.

[Brief description of drawings]

FIG. 1 is a schematic structural view showing an embodiment of the present invention, FIGS. 2 and 3 are other embodiments of the present invention, FIG. 2 is a longitudinal sectional view thereof, and FIG. FIG. 4 is an enlarged development view of a valve, a delivery valve seat and a delivery valve holder for showing two check valves, and FIG. 4 is a longitudinal sectional view showing an example of a conventional fuel injection device. 1 ... Fuel injection pump, 2 ... Initial fuel injection nozzle, 3
...... Main fuel injection nozzle, 4 …… Open / close valve, 5 …… Orifice, 41 …… High pressure chamber, 42 …… Pilot pressure chamber, 43 …… Valve element, 44 …… Valve spring, 45 …… Valve seat.

Claims (1)

(57) [Scope of utility model registration request] 1. A fuel injection device in which fuel is pumped from one fuel injection pump to an initial fuel injection nozzle for pilot injection and a main fuel injection nozzle for main injection, respectively. The valve pressure is set lower than the valve opening pressure of the main fuel injection nozzle, and between the fuel injection pump and the pilot injection fuel injection nozzle,
Between the high pressure chamber into which the fuel pumped from the fuel injection pump is introduced, the pilot pressure chamber into which the fuel pumped from the fuel injection pump is introduced through an orifice, and between these high pressure chamber and the pilot pressure chamber And a valve spring for biasing the valve body from the pilot pressure chamber side toward the high pressure chamber side to seat it on the valve seat, and the pressure of the high pressure chamber is the pressure of the pilot pressure chamber. When the pressure is higher and the pressing force against the valve body due to the pressure difference becomes larger than the urging force of the valve spring, the valve body lifts from the valve seat to communicate the fuel injection pump with the initial fuel injection nozzle, and the difference When the pressing force due to the pressure becomes smaller than the urging force of the valve spring, the valve element is seated on the valve seat, and an on-off valve is provided to shut off between the fuel injection pump and the initial fuel injection nozzle. Injection device.