JPH0477148B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows an example of a conventional jerk-type fuel injection valve. Fuel from a fuel injection pump (not shown in FIG. 1) passes through a fuel passage 7 and enters a fuel reservoir 8, where the fuel pressure pushes up the needle valve 4 against the biasing force of the needle valve spring 6, and pushes up the needle valve 4 against the urging force of the needle valve spring 6. 4a and is injected into the cylinder from the nozzle hole 1b. As mentioned above, the conventional jerk-type fuel injection valve injects fuel from one type of nozzle hole 1b at a single injection pressure over the entire operating range from low load to high load. There was a problem in that the fuel injection pressure was too low and combustion was likely to deteriorate due to poor spraying.

The purpose of the present invention is to solve the above-mentioned problems and improve fuel performance by obtaining good spray in all operating ranges including low load and an optimal injection direction to the cylinder, and also to improve fuel performance at a constant level even at low load. To provide a fuel injection valve for a diesel engine which can prevent clogging of the second nozzle hole by appropriately injecting fuel even from the second injection hole which is not normally used in each cycle.

The diesel engine fuel injection valve of the present invention includes:
A first nozzle hole 1a opened separately in the nozzle tip 1
and a first nozzle hole 1b, which has a fuel passage communicating between the fuel supply port and the fuel reservoir 8 at its axial center and opens and closes the passage between the fuel reservoir and the first nozzle hole.
a needle valve 4; and a second needle valve 14 that is fitted onto the first needle valve and opens and closes a passage between the first nozzle hole and the second nozzle hole.
, a first needle valve spring 6 that biases the first needle valve, and a second needle valve spring 6 that biases the first needle valve.
A second needle valve spring 16 that biases the needle valve, and a second needle valve spring 16 that biases the needle valve.
A fluid chamber 20 in which the upper spring receiving piston 19 of the needle valve spring slides in an oil-tight manner and into which a control fluid is introduced which acts on the upper surface of the piston and changes the biasing force of the second needle valve spring. and a means for supplying a control fluid having a pressure that is adjusted according to the operating conditions of the engine and that changes periodically in a low load range, so as to achieve the above object.

An embodiment of a fuel injection valve for a diesel engine according to the present invention will be described below with reference to FIGS. 2 and 3.

Here, the same or equivalent components as those of the conventional device will be described using the same reference numerals.

In FIG. 2, the nozzle tip 1 is firmly fastened to the main body 3 by a cap nut 2. The nozzle tip 1 is equipped with a second needle valve 14 that guides the first needle valve 4. The second needle valve 14 is guided by the nozzle tip 1, and both guide surfaces are slidable and kept oil-tight. There is. The first needle valve 4 is biased by a first needle valve spring 6, and the first seat 4a is normally pressed.

Further, the second needle valve 14 is biased by a second needle valve spring 16, and the second seat 14a is normally pressed. The main body 3 has a fuel passage hole 7 in the center thereof, and an adjustment screw 9 for increasing or decreasing the urging force of the first needle valve spring 6 is screwed into the main body 3 . A piston 19 is provided above the second needle valve spring 16 to increase or decrease this biasing force, and a control fluid is introduced from the outside into a fluid chamber 20 surrounded by the main body 3, the adjustment screw 9, and the piston 19. . The nozzle chip 1 has a fuel reservoir 8 and a first nozzle hole 1a separated by a first needle valve 4, and a second nozzle hole 1b separated from the first nozzle hole 1a by a second needle valve 14. The opening pressure of the second needle valve is set high so that it opens with high fuel oil pressure at high loads, and the opening pressure of the first needle valve 4 is set low so that it opens even under low loads. Therefore, the opening pressure of the second needle valve 14 can be reduced to the same level as the opening pressure of the first valve by reducing the hydraulic pressure and moving the piston 19 upward. One or several second nozzle holes 1b are provided.

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

In FIG. 2, fuel pumped by an injection pump (not shown) enters a fuel reservoir 8 through a passage 7, and the fuel pressure in the reservoir 8 causes the first needle valve 4 to resist the biasing force of the first needle valve spring 6. and push up the first sheet part 4.
a and is introduced into the nozzle chamber 21, and is injected from the first nozzle hole 1a.

In addition, in the high load range, the fuel pressure in the nozzle chamber 21 is sufficiently higher than the opening pressure of the second needle valve 14.
is pushed up against the biasing force of the second needle valve spring 16,
It passes through the seat 14 and is also injected into the cylinder from the second injection hole 1b. The injection direction and area of the first and second nozzle holes 1a and 1b are set to be optimal during high load.

In the low load range, the fuel entering the fuel reservoir 8 pushes up the first needle valve 4 against the biasing force of the first needle valve spring 6, passes through the first seat 4a, is guided to the nozzle chamber 21, and is guided to the nozzle chamber 21 through the first seat 4a. However, since the opening pressure of the second needle valve 14 is higher than the opening pressure of the first needle valve 4, the second needle valve 14 does not open. No injection is made from the nozzle hole 1b. First nozzle hole 1a
is the area where the maximum fuel pressure in the low load range is less than the rated fuel pressure, and the nozzle hole with the injection hole direction suitable for the low load range is selected from among those set to be optimal in the high load range. be done.

As mentioned above, the second nozzle hole 1b is not normally used at low loads, but when the fuel remaining in the second nozzle hole 1b during use at high loads is switched to the low load range and is no longer used, it is destroyed by combustion gas. It is necessary to prevent it from being heated to high temperatures, solidifying, and clogging the holes. In other words, when transitioning from a high load area to a low load area, the fluid chamber 2
The fluid pressure from the pump 32 acts on the second needle valve 14 via the second needle valve spring 16 to the second seat 14a.
At this time, in order to prevent the second nozzle hole 1b from clogging as described above, the control device temporarily releases the fluid in the fluid chamber 20 and moves the piston 19 upward to close the second nozzle hole 1b. Fuel is injected from the second injection hole 1b using the valve 14. In other words, in a shorter cycle than when the fuel solidifies, the fluid pressure in the fluid chamber 20 is released, the piston 19 is moved upward, the biasing force of the second needle valve spring 16 is reduced, and the opening pressure of the second needle valve 14 is increased. The valve opening pressure is controlled to be reduced to the same level as a one-needle valve. The left side of FIG. 2 shows this control device, which allows fuel to be appropriately injected from the second nozzle hole 1b, which is not normally used, at every fixed number of injections even under low load, thereby preventing hole clogging.

To summarize the above, in a high load region where no fluid pressure acts on the fluid chamber 20, the first nozzle hole 1a, the second
Fuel is simultaneously injected into the cylinder from the injection hole 1b.

In a low load range, fluid pressure is applied to the second needle valve 14 via the piston 19 so that the second needle valve does not open. This fluid force is configured to be injected from the second nozzle hole 1b by the control device every certain number of injections in order to prevent the second nozzle hole 1b from clogging when not in use in a low load range.

Next, a hydraulic valve opening pressure control device will be explained with reference to FIG. 2.

During normal low-load operation, electrical signals that detect the position of the steering wheel 40 or the state of the engine are converted by the converter 38 into a form that can be compared and judged, and then guided to the theoretical circuit 36. The theoretical circuit 36 compares the specifications stored in the storage device 37 with the state quantity of the engine received from the conversion device, and starts and stops the valve opening pressure control electric motor 32 and turns on the pressure reduction relief valve 34. Issues an OFF command signal. The fluid pressurized by the electric motor 32 flows into the fluid chamber 20 of the fuel valve through the conduit 33 and acts on the upper surface of the piston 19. As a result, the piston 19 moves downward and presses against the second needle valve 14 and the second seat 14a via the second needle valve spring 16, cutting off the supply of fuel to the second injection hole 1b. Note that in order to prevent clogging of the second nozzle hole 1b when shifting to a low load range, the control device temporarily removes the fluid from the fluid chamber 20 and opens the second needle valve 14 in a short cycle as described above. do.
41 is a check valve, 31 is an oil tank, and 35 is a safety valve.

A second embodiment of the invention is shown in FIG. This embodiment differs from the first embodiment shown in FIG. 2 in that the vertical relationship of the second needle valve spring 16 and piston 19 is reversed.

In FIG. 3, the biasing force of the second needle valve spring 16 is set so that the intervening pressure of the second needle valve 14 is approximately the same as that of the first needle valve 4. Second needle valve spring 16
is provided in the fluid chamber 20, and fluid pressure acts directly on the second needle valve 14 via the piston 19, pressing the second needle valve 14 onto the second seat 14a. The effects of the second embodiment are exactly the same as those of the first embodiment.

As mentioned above, the diesel engine fuel injection valve according to the present invention selects a nozzle hole area suitable for low load from among the nozzle hole group having the nozzle hole area, number, and injection direction that are optimal in the high load range. By selecting and narrowing down the fuel pressure to increase the fuel pressure, and keeping the number of injection holes and injection direction optimal for low loads, we can increase the fuel pressure at low loads, improve the spray form, and improve combustion. As a result, fuel consumption is reduced and energy and labor savings can be achieved. Further, even under low load, fuel is appropriately injected from the second nozzle hole which is not normally used at every fixed cycle, so that clogging of the second nozzle hole can be prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional fuel injection valve, FIG. 2 is a sectional view of a first embodiment of the present invention, and FIG. 3 is a sectional view of a second embodiment of the same. 1... Nozzle chip, 1a... First nozzle hole, 1b
...Second injection hole, 4...First needle valve, 4a...First seat, 6...First needle valve spring, 14...Second needle valve,
14a...second seat, 16...second needle valve spring,
20, 31 to 41... Valve opening/closing pressure adjusting means.

Claims (1)

[Claims] 1. A fuel passage is formed in the axial center of the nozzle tip 1 to communicate between the first nozzle hole 1a and the second nozzle hole 1b, which are opened separately, and the fuel supply port and the fuel reservoir 8. A first needle valve 4 that opens and closes a passage between the first nozzle hole and the second nozzle hole, and a second needle valve 1 that is fitted onto the first needle valve and opens and closes a passage between the first nozzle hole and the second nozzle hole.
4, a first needle valve spring 6 that biases the first needle valve, a second needle valve spring 16 that biases the second needle valve, and an upper spring bearing piston 19 of the second needle valve spring inside which is oil-free. a fluid chamber 20 into which a control fluid that slides tightly and acts on the upper surface of the piston to change the biasing force of the second needle valve spring; A fuel injection valve for a diesel engine, comprising means for supplying a control fluid having a pressure that changes periodically in a low load range.