JPH03286176A - Fuel injection device for diesel engine - Google Patents

Abstract

PURPOSE:To freely select a timing and amount of pilot injection by interposing a piezoelectric element between a spring support for regulating a valve opening pressure and valve main body of a fuel injection valve, connecting a charging system to the piezoelectric element, and carrying out energization to the piezoelectric element by means of a controller into which a crank angle is input. CONSTITUTION:A predetermined residual pressure Pr can be kept inside a fuel injection pipe 6 by means three valves, i.e., a equal-pressure valve 5, a residual pressure regulating valve 7 and a needle valve 10. Upon reaching of a timing required for pilot injection, a switch of a driving controller 16 of a piezoelectric element 14 is turned on in response to a crank angle signal output in synchronism with a crankshaft. A voltage is applied to the piezoelectric element 14 by a power source 15, and the element 14 is deformed to push up a spring support seat 111. As a result, the needle valve 10 which has been pressed by a spring 11 is relieved from pressing force, and is pushed up by the residual pressure Pr inside the injection pipe 6 to be opened, thereby injecting fuel through an injection hole 9. After injection of a predetermined amount of fuel, the switch of the controller 16 is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection device for a diesel engine for all types of land and marine applications.

[Conventional technology]

Figure 4 shows an example of the fuel injection system of a conventional diesel engine, where 1 is the jerky fuel injection pump body;
2 is a plunger barrel, 3 is a plunger, 4 is a discharge valve,
5 is an equal pressure valve, 6 is a fuel injection pipe, 7 is a check valve, 8 is a fuel injection valve main body, 9 is an injection hole, IO is a needle valve, and 11 is a fuel valve spring. In these figures, a residual pressure adjustment system is added to the injection pipe 6, and 7 is a residual pressure adjustment valve, which is connected to a system consisting of a pressure accumulator 12, a pressure accumulation pump 13, and the like.

Next, the operation of the conventional example will be explained.

When the plunger 3 is pushed up by a fuel cam (not shown), the fuel in the barrel 2 is compressed, opens the discharge valve 4 and is sent into the injection pipe 6, and when it reaches the fuel valve 8, the needle valve 10
The fuel is pushed up against the pressing force of the spring 11 to open the valve, and the fuel is injected from the nozzle hole 9 into the cylinder (not shown) of the engine, whereupon the fuel is combusted and engine output is produced.

In order to prevent the secondary injection that occurs at this time, an equal pressure valve 5 is provided near the discharge valve 4 in the opposite direction. To prevent this from happening, the isobar 5 is opened and the high pressure oil in the injection pipe 6 is released until it reaches a predetermined pressure. On the other hand, in order to prevent malfunctions such as the pressure inside the injection pipe 6 abnormally decreasing after the end of injection, and in some cases becoming negative pressure, a check valve 7 for adjusting residual pressure and a pressure accumulator 12 and below are provided for adjusting the residual pressure. The check valve 7 is opened and closed as necessary, and fuel is supplied to the pipe 6 via the check valve 7, pressure accumulator 12, and pump 13 until a predetermined residual pressure is reached.

FIG. 5 shows the injection characteristics of the conventional example, and shows the case where only the main injection is performed once.

Furthermore, in order to perform high-performance ignition combustion to prevent diesel knock, when performing two consecutive injections (pilot injection and main injection) with this injection system, the plunger 3 is divided into two stages by a cam (not shown). Generally, this is done by raising the plunger 3 or by providing a relief groove (not shown) in the upper outer periphery of the plunger 3, thereby realizing two injections, a pilot injection and a main injection, as shown in Fig. 6. has been done.

[Problem to be solved by the invention]

However, in the conventional injection system described above, it is difficult to configure the geometry of pilot injection and main injection using either a cam or a plunger. The disadvantage is that it is difficult to perform pilot injection, and the prevention of diesel knock, which is the purpose of pilot injection, cannot be achieved under favorable conditions depending on the engine operating conditions (load rotational speed, temperature, etc.) and the cetane number of the fuel. was there.

SUMMARY OF THE INVENTION An object of the present invention is to provide a combustion injection system that eliminates the problems of the conventional device, controls diesel knock to a minimum, and allows the timing and amount of pilot injection to be freely selected.

[Means to solve the problem]

The present invention provides a fuel injection device for a jerk type diesel engine, in which a piezoelectric element is interposed between a valve opening pressure adjusting spring support of a fuel injection valve and a valve body, a charging system is connected to the piezoelectric element, and a charging system is connected to the piezoelectric element. Electricity is turned on and off by appropriate timing using a controller 16 that manually controls the crank angle.
It is configured so that

[Effect]

A predetermined residual pressure Pr is maintained inside the injection pipe 6, and when the timing for biloft injection is reached based on a crank angle signal output in synchronization with the crankshaft, the controller 16 for driving the piezoelectric element 14 is switched on. A voltage is applied to the piezoelectric element 14 by the power source 15, the piezoelectric element 14 is deformed, the spring 11 is compressed to push up the spring seat 111, and the needle valve is pushed up by the residual pressure Pr in the injection pipe 6 and opens. Fuel is ejected from the nozzle hole 9. After the predetermined pilot injection is performed, the switch of the controller 16 is turned OFF.
F, the piezoelectric element 14 returns to its original position, and the needle valve 10
The spring force of the spring 11 is applied again to close the valve, and the main injection is in a standby state.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a fuel injection system diagram of the embodiment, FIG. 2 is a pilot injection operation diagram, and FIG. 3 is a fuel injection characteristic diagram.

FIG. 1 shows an outline of the configuration of the present invention. The feature is that a piezoelectric element (particularly a laminated piezoelectric element) 14 is provided in the fuel injection valve 8, and by applying voltage to this element, the pressing force of the spring 11 that presses down the needle valve 10 is controlled, and the injection pipe The pilot injection is performed using the energy stored as the residual pressure Pr in the fuel tank 6.

The basic structure of the injection system is similar to the conventional example shown in Fig. 4, and the same parts as the conventional example include 1 the jerk type fuel injection pump body, 2 the plunger barrel, 3 the plunger, and 4 the discharge valve. , 5 is an equal pressure valve, 6 is a fuel injection pipe, 7 is a check valve, 8 is a fuel injection valve body, 9 is an injection hole, 10 is a needle valve, 1
1 indicates a fuel valve spring. In these figures, a residual pressure adjustment system is added to the injection pipe 6, and 7 is a residual pressure adjustment valve, which is connected to a system consisting of a pressure accumulator 12, a pressure accumulation pump 13, and the like.

Next, as a characteristic part of the present invention, a piezoelectric element 14 is provided between the spring receiver 111 and the injection pump main body in the fuel injection valve, and a crank angle signal from a power source 15 and a crank angle detector 17 is used to drive the piezoelectric element 14. A human-powered controller 16 is provided,
The controller turns on the piezoelectric element at an appropriate timing,
It is configured to turn off. Therefore, the structure is such that the pyro injection is performed by electrical control without geometrical constraints as in the conventional case.

Next, the operation of the embodiment described above will be explained with reference to FIGS. 2 and 3.

As shown in Fig. 2, a predetermined residual pressure Pr is maintained within the fuel injection pipe 6 by three valves: an iso-thinking valve 5, a residual pressure adjustment valve 7, and a needle valve IO, and is synchronized with a crankshaft (not shown). When the necessary timing for biloft injection is reached according to the crank angle signal output from the above, the controller 16 for driving the piezoelectric element 14 is switched on, and a voltage is applied to the piezoelectric element 14 by the power supply 15, causing the piezoelectric element 14 to deform. and push up the spring seat 111. As a result, the needle valve 10 that had been pressed by the spring 11 loses its pressing force, and the needle valve is pushed up and opened by the residual pressure Pr in the injection pipe 6, and fuel is injected from the injection hole 9. do. When a predetermined amount of fuel is ejected, the switch of the controller 16 is turned to O.
FF, the piezoelectric element 14 returns to its original position, and the needle valve 10
The biasing force of the spring 11 is applied again to close the valve.

Next, a cam (not shown) pushes up the plunger 3 of the fuel injection pump to perform main injection, but in this case, since the circuit of the piezoelectric element is OFF, the oil pressure inside the fuel injection pipe 6 increases, causing the needle valve to close. When the valve opening pressure exceeds 10, the needle valve 10 opens and main injection starts again from the nozzle hole 9. The details of the pilot injection according to the present invention are as shown in the injection characteristic diagram in FIG.

As described above, the viroft injection of the present invention is controlled by electric manual power, and the main injection is controlled by mechanical systems such as cams and plungers, so that the viroft injection can be controlled at any desired timing and amount with respect to the main injection. Since it can be easily controlled, an ideal fuel injection system for diesel engines that can prevent diesel knock can be realized.

〔Effect of the invention〕

Since the present invention is configured as described above, the injection characteristics shown in Fig. 3 can be obtained, and the optimal viroft injection timing and amount can be realized depending on the engine operating conditions and the cetane number of the fuel, and smooth ignition and combustion can be realized. can.

As a result, it is possible to realize a high-performance diesel engine that is quiet without diesel knock, has low exhaust pollution, and has high thermal efficiency.It also prevents diesel knock even when using low cetane number fuel, and can be used with a variety of fuels. A compatible diesel engine can be created.

[Brief explanation of drawings]

1 to 3 are related to the present invention; FIG. 1 is a configuration diagram of the fuel injection system, FIG. 2 is an explanatory diagram of the operation of the fuel injection system, FIG. 3 is a fuel injection characteristic diagram of the injection system, and FIG. Figures 4 to 6 are related to conventional examples. Figure 4 is a diagram corresponding to Figure 1, Figure 5 is a conventional fuel injection characteristic diagram without pilot injection, and Figure 6 is a diagram of conventional fuel injection characteristics when biloft injection is performed. FIG. 3 is a conventional fuel injection characteristic diagram. 8... Fuel injection valve, 10... Needle valve, 11... Spring, 14... Piezoelectric element, 15... Power source, 16... Controller, 111... Spring receiver. Crank angle e Crank angle O Fig. 5 Crack angle O Fig. 6

Claims (1)

[Claims] In a diesel engine fuel injection device consisting of a jerk-type fuel injection pump, a high-pressure injection pipe, a residual pressure adjustment device, and an automatic valve-type fuel injection valve, the spring bearing for adjusting the opening pressure of the fuel injection valve and the valve body are connected to each other. A fuel injection device for a diesel engine, characterized in that a piezoelectric element is interposed between the piezoelectric elements, a charging system is connected to the piezoelectric element, and means for controlling energization to the piezoelectric element is provided.