JPH01121560A - Fuel injection device of diesel engine - Google Patents

Abstract

PURPOSE:To prevent hunting and black smoking in an injection valve operated by an oil hydraulic piston and a spring interlocked therewith by controlling the valve opening pressure to a low level at low speed with low load and to a high at low speed with high load. CONSTITUTION:A controller commands a hydraulic proportional control valve so that a fuel characteristic suitable for current operating condition is provided by reference to a previously input open pressure valve map, an injection timing map, an injection amount map, and an operational data. When the oil pressure from the hydraulic proportional control valve is applied to a piston 6, it sinks to raise the spring valve opening pressure through a piston rod 10. When the valve opening pressure becomes high, the rate of injection becomes high, and the injection time is shortened, and no black smoke will be generated even in the conditions at low speed and high load which should involve a smaller air excessive rate. No hunting will either be generated if the valve opening pressure is sunk at the time of low speed and low load. Therefore, the engine can be operated with valve opening pressure suitable for all operational ranges through controlling of fuel injection nozzle by this method.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a diesel engine, and in particular, the valve opening pressure of a fuel injection nozzle is controlled by a controller depending on the engine rotation speed and load condition, and the valve opening pressure is controlled at low speeds and low loads. lowers the valve opening pressure and stabilizes the injection rate.

This invention relates to a fuel injection device for a diesel engine that increases valve opening pressure at low speeds and high loads to prevent the generation of black smoke.

(Prior Art) Conventional electronically controlled fuel injection systems often control the fuel injection timing and fuel injection amount according to the engine speed and load condition. At present, attempts have been made to use a solenoid in the nozzle holder to increase the valve opening pressure in the high speed range.

(Problem to be solved by the invention) In the case of the conventional method that does not control the valve opening pressure.

The valve opening pressure is too high during low speed/low load operation.

Since the injection rate does not vary for each cylinder, it often causes a hunting phenomenon in which the rotational speed fluctuates, so when operating at low speeds and high loads, the valve opening pressure must be set in conjunction with high loads at medium speeds or above. Because it is.

Since the valve opening pressure is too low, the injection period becomes longer.

In addition, since the excess air ratio is small, many generate black smoke.Also, if the valve opening pressure is controlled by the engine rotation speed, the hunting phenomenon will not occur during low speed and low load operation, but at low speeds・Many products generate black smoke during high-load operation.

This invention aims to solve the above problems.

(Means and effects for solving the problem) This invention was made in view of the above problem, and the fuel injection nozzle has a piston lowered by hydraulic pressure at the upper part of the center of the nozzle holder, and the movement of the piston is transmitted to the spring retainer. A rod is provided, and when hydraulic pressure from a hydraulic proportional control valve built into the hydraulic control electronic governor of the fuel supply pump or hydraulic pressure from a dedicated hydraulic proportional control valve is applied to the piston of the nozzle holder, the piston descends. The rod is a variable valve opening pressure nozzle that compresses a spring and increases the spring force to increase the valve opening pressure, and the valve opening pressure 77b is input. The valve opening pressure is set to low at low speeds and low loads by the hydraulic pressure from the hydraulic proportional control valve that operates according to instructions from the controller.
It is controlled to be high when the load is high. Therefore, it is an object of the present invention to provide a fuel injection device for a diesel engine that eliminates hunting at low speeds and low loads and can prevent the generation of black smoke at low speeds and high loads.

(Example) Embodiments of the invention will be described based on the drawings.

FIG. 1 is a block diagram of an embodiment of the invention.

FIG. 2 shows a sectional view showing the structure of the variable valve opening pressure nozzle.

In the figure, reference numeral 1 denotes a variable valve opening pressure nozzle, and the variable valve opening pressure nozzle 1 receives fuel pumped by a fuel supply pump 3 having a hydraulically controlled electronic governor 2.

Spraying into the cylinder.

4 is a controller;

Compare the pre-input valve opening pressure map, injection timing map, and injection amount map with the operating data.

A command is given to the hydraulic proportional control valve 5 of the hydraulically controlled electronic governor 2 to obtain fuel injection characteristics suitable for each operating condition.

The hydraulic proportional control valve 5 is configured to apply hydraulic pressure based on a command from the controller 4 to the piston 6 of the variable valve opening pressure nozzle 1.

The piston 6 is fitted into the nozzle holder 7 in a vertically movable state, and the piston 6 moves against the spring force of a spring 9 provided above the needle pulp 8 to press the needle valve 8 against the valve seat. When lowered by hydraulic pressure, the movement of the piston 6 has a loft of 10. The force is transmitted to the spring retainer 1), which further compresses the spring 9, increasing the spring force and increasing the valve opening pressure. The relationships between hydraulic pressure and valve opening pressure, and between valve opening pressure and injection rate are shown in Figure 3, and the higher the valve opening pressure, the higher the injection rate.
The injection period is shortened and no black smoke is generated even at low speeds and high loads when the excess air ratio is small. Also, lowering the valve opening pressure at low speeds and low loads stabilizes the injection rate.

Hunting will no longer occur.

As a result, the fuel injection system for diesel engines has been created, which lowers the valve opening pressure at low speeds and low loads to prevent hunting, and increases the valve opening pressure at low speeds and high loads to prevent the generation of black smoke.

(Effects of the Invention) Since this invention is made as described above, during low speed and low load operation, the hydraulic pressure is lowered by the command from the controller and the valve opening pressure is lowered, so the rack is stabilized and hunting does not occur. During low-speed, high-load operation, the hydraulic pressure is increased by commands from the controller, increasing the valve opening pressure and increasing the injection rate, making it possible to prevent the generation of black smoke. This resulted in an inexpensive fuel injection system for diesel engines that can operate the engine at a valve opening pressure that is suitable for all operating ranges.

[Brief explanation of the drawing]

Fig. 1 shows a block diagram of an embodiment of the present invention, Fig. 2 shows a structural cross-sectional view of a variable valve opening pressure nozzle, and Fig. 3 (
al, (bl are graphs showing the relationship between valve opening pressure and oil pressure, and injection rate and time, respectively. 1... Variable valve opening pressure nozzle. 2... Hydraulic control electronic governor. 3... Fuel Supply pump, 4... Controller. 5... Hydraulic proportional control valve, 6... Piston. 7... Nozzle holder, 8... Needle valve. 9... Spring, 10... Rod. 1) ...Spring restraint. Patent Applicant Komatsu Ltd. Agent (Patent Attorney) Osamu Matsuzawa Figure 1 Insertion 2nd Reason

Claims (4)

[Claims] (1) A diesel engine fuel injection system consisting of a variable prestroke mechanism, a fuel supply pump with a hydraulically controlled electronic governor, a variable valve opening pressure nozzle, and a controller that controls them. (2) The above variable valve opening pressure nozzle has a piston at the top center of the nozzle holder that moves downwards by hydraulic pressure against the spring force, a rod below the piston that transmits the movement of the piston to the spring retainer, and a needle valve attached to the valve seat. Fuel injection for a diesel engine according to claim (1), wherein the fuel injection device is constituted by a pressing spring, and when the piston moves downward in response to hydraulic pressure, the spring is compressed and the valve opening pressure is increased. Device. (3) The piston for adjusting the valve opening pressure mentioned above is lowered by hydraulic pressure branched from a hydraulically controlled proportional valve built into the hydraulically controlled electronic governor, or by hydraulic pressure from an independently provided dedicated hydraulically controlled proportional valve. A fuel injection device for a diesel engine according to claim (1). (4) The above controller lowers the valve opening pressure to stabilize the injection rate in low speed and low load areas, and increases the injection rate and shortens the injection period in low speed and high load areas to prevent black smoke generation. The fuel injection device for a diesel engine according to claim 1, wherein the valve opening pressure is controlled to increase the valve opening pressure.