JPH08158926A - Pressure-type fuel injection timing control device for diesel engine - Google Patents

Abstract

PURPOSE: To prevent the maximum gas pressure inside cylinders from exceeding an allowable value when a ship is operated in stormy weather by using two signals or more, i.e., an injection timing signal that is determined univocally according to the amount of fuel injection and another injection timing signal that is determined univocally according to the difference between the gas pressure within a cylinder and a preset allowable gas pressure within the cylinder. CONSTITUTION: In a fuel injection control device of a large diesel engine for a ship, the amount of fuel injection is set by a speed governor 1 that controls the engine speed. In this case, the displacement detecting end B of a pressure-signal generating pressure reducing valve 3 is pressed by means of a lever 2 provided at the speed governor 1, and a fuel injection timing signal C that corresponds to the amount of displacement of the end B is transmitted. Also, a fuel injection timing signal D is transmitted via a differential pressure/pneumatic pressure signal converter 4 that uses a differential pressure signal A indicating the difference between a gas pressure within a cylinder of the engine and a preset allowable gas pressure within the cylinder. A signal for retarded injection timing is selected by means of a fuel injection timing computing element 5 and given to a positioner 6, so as to regulate the amount of fuel injection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a fuel injection timing control device for a large diesel engine for ships.

[0002]

2. Description of the Related Art A conventional fuel injection timing control device is uniquely determined only by the fuel injection amount. That is, in order to improve the thermal efficiency of the engine, the fuel injection timing is advanced as the amount increases in accordance with the fuel injection amount, and as the fuel injection amount further increases, the injection timing advance angle is advanced so that the cylinder combustion pressure does not rise above the allowable value. Is decided to reduce. Most of the propulsion systems for ships have a propulsion engine and a fixed-pitch propeller mechanically connected to each other, and the load is uniquely determined if the rotational speed of the engine is determined. Therefore, considering a state where the load fluctuation is small, the fuel injection amount and the engine rotation speed have a unique correspondence, and it is no problem to determine the fuel injection timing by the fuel injection amount. However, when the load curve changes due to stormy weather, dirt on the hull, dirt on the propeller, etc., this correspondence is broken. This relationship cannot be maintained especially in bad weather. Assuming that the engine is operating near the rated output during rough weather and the absorption power of the propeller increases and the engine rotation speed decreases, the fuel injection amount and the air amount are instantaneously constant and only the engine rotation speed decreases.
This is because although the engine rotation speed is low, fuel may be injected at an early injection timing corresponding to the fuel injection amount, and the maximum gas pressure in the cylinder may rise to exceed the allowable pressure. Further, in this case, a command for increasing the fuel injection amount is issued in order to recover the state in which the rotational speed has decreased due to the operation of the speed governor with an engine, and the maximum gas pressure in the cylinder increasingly increases. On the other hand, even when operating under a condition of low engine load called stormy weather, if the engine speed changes transiently due to a change in the propeller's absorbed power, the engine speed will decrease despite the actual engine speed being slow. The fuel injection amount is increased to maintain the speed, and the timing of the injection is also advanced. Even in this case, the maximum gas pressure in the cylinder may exceed the allowable value.

[0003]

SUMMARY OF THE INVENTION According to the present invention, the fuel injection timing is set so that the maximum gas pressure in the cylinder does not exceed the permissible value even in an operating state in which the absorption power of the propeller fluctuates periodically such as in stormy weather operation. The purpose is to provide a control device.

[0004]

Means for Solving the Problems In addition to the fuel injection timing signal determined by the fuel injection amount, at least "differential pressure between engine cylinder gas pressure and allowable set cylinder gas pressure" (hereinafter referred to as differential pressure) is unique. A fuel injection timing signal that is determined in advance is provided, and a computing unit or a computing function that computes these signals is provided. Fuel injection is performed according to a signal determined by the calculator or the calculation function.

[0005]

[Function] The fuel injection amount is determined by the load state of the engine. As a result, the fuel injection timing is uniquely determined in consideration of the engine performance. On the other hand, the fuel injection timing is uniquely determined by the pressure difference at that time. When the load change is small, the fuel injection timing is determined by the fuel injection amount, but when there is a large load change, the differential pressure also changes, and the fuel injection timing signal determined by this differential pressure gives a later fuel injection timing signal. Start to serve. These signals are given to a computing unit or a computing function portion, and the actual fuel injection is performed by a signal modified to delay the injection timing by a predetermined computing method. This action delays the fuel injection timing and prevents the maximum gas pressure in the cylinder from exceeding the allowable value.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in the drawings will be described in more detail below.

An embodiment of the fuel injection timing control device in the case where the fuel injection timing is controlled by vertically displacing the fuel barrel 8 will be described with reference to FIG. A known technique is used for a mechanism for setting the fuel injection timing by displacing the fuel barrel 8. The governor 1 that controls the engine rotation speed sets the fuel injection amount with respect to the engine load. The lever 2 provided on the speed governor 1 corresponding to the fuel injection amount causes the displacement detecting end B of the pressure reducing valve 3 for generating a pressure signal.
The fuel injection timing signal C corresponding to the amount of displacement is transmitted. On the other hand, the fuel injection timing signal D is transmitted via the differential pressure / air pressure signal converter 4 based on the differential pressure signal A. Known techniques are used for the pressure detector and the differential pressure setting device, which are not shown in the drawing. A fuel injection timing calculator 5 (in this embodiment, a signal switcher: a function of giving priority to a lower signal) gives a signal of a later injection timing to the positioner 6 to move the fuel barrel 8 up and down through the rack 7. The fuel injection is performed at the fuel injection timing based on the signal D. E is a pneumatic source for producing a pneumatic signal. In this figure, the signal D is selected as the fuel injection timing is late on the differential pressure signal side.

Referring to FIG. 2, an embodiment of the fuel injection timing control device when the fuel injection timing is controlled by the mechanical link system will be described. A known technique is used for a mechanism for setting the fuel injection timing and the injection stop timing by opening and closing the fuel injection start valve 12 and the fuel injection stop valve 13 by the mechanical link system 9. The governor 1 that controls the engine rotation speed sets the fuel injection amount with respect to the engine load. The fuel injection timing and the amount of injected oil are set by the fulcrum G and the fuel injection timing setting cam plate 11 via the link system 9 corresponding to the injection amount. On the other hand, the injection timing signal based on the differential pressure is set as the displacement oil amount F and given to the positioner 14 to change the position of the fulcrum H to determine the injection timing and open the fuel injection start valve 12. .

In this embodiment, the fuel injection timing signal is an air pressure signal or an example of a mechanical operation function by moving a fulcrum of a mechanical link is shown. However, it can be controlled by an operation result by an electric signal, a hydraulic pressure signal, or the like. Of course, analog signals and digital signals can be used.

[0010]

[Effects of the Invention] FIG. 3 (a) shows the "in-cylinder gas pressure (P) -crank angle (θ)" when this controller is not adopted.
Diagram "is shown. Curve I shows a state where there is no load fluctuation and the engine is operated at 75% of the rated output. The curve J shows a state in which the fuel injection amount increases due to the load fluctuation, the engine rotation speed decreases and the rotation speed is maintained, and the fuel injection timing advances by 0.7 degrees. As a result, the maximum gas pressure in the cylinder is 1.16 times, which exceeds the allowable value of 13 MPa in the engine of this example. On the other hand, FIG.
(B) shows an example in which this device is adopted. The curve K shows the case where the fuel injection timing of the conditions of the curve J is delayed by 0.7 degree by this apparatus. In this case, it is 1.12 times, which is within the allowable value. In this case, an example in which the injection timing is set so that the maximum gas pressure in the cylinder is within the allowable value is shown, but it can be further lowered by the set value. The increase in the maximum gas pressure in the cylinder also causes the increase in the gas temperature in the cylinder, which causes the cylinder liner, cylinder cover, piston,
It will damage the crank bearings. It is an advantage of this device that these can be prevented.

[Brief description of drawings]

FIG. 1 is a system schematic diagram showing a case where a fuel injection timing is set by an air pressure signal as one embodiment of the present invention.

FIG. 2 is a system schematic diagram showing a case where an injection start valve and an injection stop valve are controlled by a mechanical link system as one embodiment of the present invention.

FIG. 3 (a) shows a comparison of predictive calculation engine performance curves when a rough weather engine is operated and when the present invention is not used, and when the engine is normally operated.

FIG. 3 (b) shows a comparison of predictive calculation engine performance curves in the case of operating the engine in rough weather and in the normal operation when the present invention is adopted.

[Explanation of symbols]

1 ... Governor 2 ... Lever 3 ... Pressure reducing valve for generating pressure signal 4 ... Differential pressure / pneumatic signal converter 5 ... Fuel injection timing calculator 6 ... Positioner 7 ...・ Rack 8 ・ ・ ・ Fuel barrel 9 ・ ・ ・ Link system 10 ・ ・ ・ Fuel injection control device 11 ・ ・ ・ Cam plate 12 ・ ・ ・ Injection start valve 13 ・ ・ ・ Injection stop valve 14 ・ ・ ・ Positioner A ・ ・・ Differential pressure signal B ・ ・ ・ Displacement detection end C ・ ・ ・ Injection timing signal determined by fuel oil amount D ・ ・ ・ Injection timing signal determined by differential pressure E ・ ・ ・ Air source F ・ ・ ・ Displacement oil determined by differential pressure Quantity G ... Support point H ... Support point I ... Normal cylinder pressure-crank angle curve at 75% load J ... Cylinder pressure-crank angle curve without this device K ... This device Cylinder pressure-crank angle curve

Claims (1)

[Claims] 1. A control signal for determining a fuel injection timing in a fuel injection timing control device of a diesel engine, an injection timing signal uniquely determined by a fuel injection amount, and at least an engine cylinder gas pressure and an allowable set cylinder gas. 2 of the injection timing signal that is uniquely determined by the pressure difference from the pressure
Using signals or more, provide a part to calculate those signals,
Fuel injection timing control device for controlling fuel injection timing by an injection timing signal calculated so as not to exceed a predetermined cylinder gas pressure