JPS6255458A - Fuel injection device for diesel engine - Google Patents

Abstract

PURPOSE:To improve the acceleration performance by closing a closing valve which is provided to an oil tight passage, so as to suspend the function of a pilot injection device when an engine is accelerated. CONSTITUTION:A solenoid valve 45, which is provided to an oil tight passage 45 which connects a pilot injection device 20 with a fuel tank, is normally open but is closed by a drive signal from a control circuit 50. The control circuit 50 detects an engine acceleration by a change of a voltage signal outputted from an accelerator opening sensor 40 allowing the solenoid valve 45 to drive to the closing position so as to suspend the pilot injection device 20 when an opening speed exceeds the specified one. With this, as the fuel injection is increased, the accelerated fuel increment can be effected at all times in a simple manner so as to improve the acceleration performance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a pilot injection device that is connected to a pressurizing chamber of a fuel injection pump, and is configured to perform pilot injection before main injection of fuel. This invention relates to a fuel injection device for a diesel engine.

[Prior Art] Conventionally, when accelerating a diesel l1l110, it has been thought to increase or lose the amount of fuel injected from the fuel injection pump tJ4 to improve acceleration, and electronically controlled fuel injection using a microcomputer has been proposed. In a diesel engine equipped with a pump, it is possible to carry out an accelerated fuel increase in a good manner.

[Problems to be solved by the invention] However, there is a so-called machine that adjusts the amount of fuel injection by changing the position of the flyweight that is displaced according to the engine speed of a diesel engine and the position of the spill ring according to the amount of depression of the accelerator pedal. For type fuel injection pumps,
Since the fuel injection amount is determined according to the engine speed and load according to preset governor characteristics, it has not been possible to increase the fuel injection amount to improve acceleration when the engine suddenly accelerates.

On the other hand, in recent years, low load, such as during idle operation of diesel engines,
In order to reduce combustion noise in the low rotation range, for example,
Publication No. 9-5166.0 or JP-A-58-285
As described in Publication No. 33, a fuel injection device for a diesel engine is provided with a pilot injection device in communication with a pressurizing chamber of a fuel injection pump, and configured to perform pilot injection before main injection of fuel during fuel injection. There is.

The present invention has been made for the purpose of providing a fuel injection device for a diesel engine that can satisfactorily accelerate and increase the amount of fuel even if it is a mechanical fuel injection pump, the pilot injection device as described above. It was completed by using.

[Means for Solving the Problems] That is, the configuration of the present invention as a means for solving the above problems is as follows: A fuel injection pump that pressurizes fuel in a pressurizing chamber by reciprocating motion of a plunger and pumps it to a diesel engine. a cylinder, an accumulation piston, which is provided in communication with a pressurization chamber of the fuel injection pump, and which is pressed and moved within the cylinder by the fuel pressure in the pressurization chamber; A pilot injection device comprising a spring that biases the piston in a direction and a stopper that limits the amount of movement of the piston, and is configured to perform pilot injection before main injection of fuel. In the fuel injection device, in order to fill the back chamber formed in the cylinder of the pilot injection device with fuel, which is the housing portion of the spring, the low pressure chamber or fuel tank of the fuel injection pump and the back chamber are filled with oil. Acceleration detection means communicates through a sealed passage, and the oil-tight passage is provided with an on-off valve that opens and closes the passage, and detects acceleration of the diesel engine; and the acceleration detection means detects acceleration of the opening and opening of the diesel engine. A fuel injection device for a diesel engine, comprising: a pilot injection inhibiting means for driving the on-off valve in the closing direction of the oil-tight passage to stop the operation of the pilot injection device when the oil-tight passage is closed. It is said that .

[Operation] In the fuel injection device of the present invention configured as described above, when the diesel engine accelerates, the operation of the pilot injection device is stopped and the fuel injection amount is increased.

In other words, pilot jet! ) In the J device, when the fuel in the pressurizing chamber is pressurized by the plunger of the fuel injection pump and fuel injection is started, the accumulate piston moves due to the fuel pressure, temporarily stores the fuel in the cylinder, and pressurizes it. Since the fuel pressure in the chamber is lowered and the fuel injection is temporarily stopped, as shown in Fig. 4, if the operation of the pilot injection position 1) is stopped, the fuel stored in the cylinder at the time of fuel injection is reduced. This makes it possible to increase the amount of fuel injection by that amount.

The acceleration detection means for detecting the acceleration of the diesel engine uses a sensor that detects the accelerator opening degree, engine rotation speed, etc., and when the differential value of the detection result, that is, the acceleration exceeds a predetermined value, the acceleration of the diesel engine is detected. It may be configured to detect.

In addition, the on-off valve that closes the oil-tight passage when acceleration is detected is
A solenoid valve that is normally open and closed when receiving a drive signal may be used.

[Example〕 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing the overall configuration of the fuel injection device of this embodiment.

In the figure, 1 is a distribution type fuel injection pump, and inside the pump housing 11 there is a cam plate 13 connected to a dry shaft 12 via a coupling, and a pump plunger that rotates and reciprocates integrally with the cam plate 13. 14 are arranged. This pump plunger 14 is a suction boat 1 that sucks fuel in the pump housing 11.
5, and pressurizes the sucked fuel in the pressurizing chamber 17. pump plunge t1
4 includes a distribution boat 14'a for distributing this Gallo-pressurized fuel to each distribution passage 18 at a predetermined timing and for feeding the fuel under pressure to each cylinder of the diesel engine via one delivery valve, and a pressurized fuel. Spill boat 14 spilling fuel
b is provided.

On the other hand, 20 is a pilot injection device provided in communication with the pressurizing chamber 17 of the pump cylinder 16.
5. Pilot injection can be performed by lowering the fuel pressure in the pressurized chamber.

That is, as shown in FIG. 2, the pilot injection device 20 is pushed and moved to the right in the figure by the cylinder 21 that is attached in communication with the pressurizing chamber 17 of the fuel injection pump 1 and the fuel pressure in the pressurizing chamber 17. an accumulation piston guide 22 that fits the accumulation piston 22, an accumulation piston guide 23 that fits the accumulation piston 22, a stopper 24 that limits the movement of the accumulation piston 22, and a stopper 24 that limits the movement of the accumulation piston 23, A pressure bottle 25 and a return spring 26 are provided to press against the pressurization chamber 17 side against the pressure. A cap 29 is provided that communicates the rear chamber 27 with a fuel tank (not shown) via a passage 28.

Next, a spill ring 31 is slidably fitted onto the pump plunger 14 near the spill boat 14b, and controls the timing at which the pump plunger 14 finishes pressurizing the fuel, thereby controlling the fuel injection amount. This spill ring 31 is connected by a supporting lever 32 to a governor sleeve 34 that responds to the movement of a flyweight 33, and is also connected to a control lever 37 that is linked to an accelerator pedal by a tension lever 35 and a governor spring 36, and is connected to a control lever 37 that is linked to an accelerator pedal and It moves according to the depression of the accelerator pedal.

3 is a timer that is operated according to the fuel pressure in the pump housing 11 and controls the fuel injection timing, and 4o is a voltage that corresponds to the amount of movement of the control lever 37, that is, the amount of depression of the accelerator pedal (accelerator opening). This is an accelerator opening sensor that outputs a signal Va.

Next, 45 is a solenoid valve provided in an oil-tight passage 46 connecting the return passage 28 of the pilot injection device 20 and a fuel tank (not shown), and opens and closes this oil-tight passage 46, and 50 is an output from the accelerator opening sensor 40. voltage signal va
The acceleration of the diesel engine is detected from the change in the solenoid valve 45.
This is a control circuit that outputs a drive signal VS to the drive signal VS. Furthermore, the above 'R
As is clear from the figure, the electromagnetic valve 5 is a two-position valve that is normally open and closed by a drive signal Vs from the control circuit 50.

As shown in FIG. 3, the electronic control circuit 50 includes a differentiation circuit 51 that differentiates the voltage signal Va output from the accelerator opening sensor 40 and outputs a voltage signal va corresponding to the opening speed of the accelerator pedal; The voltage signal @va output from the circuit 51 is compared with the reference voltage V1, and when va>vl, 1-
a comparator circuit 52 that outputs a signal at a level of 1-high;
The drive circuit 54 starts a timer 53 and outputs a drive signal Vs to the solenoid valve 45 for a predetermined period of time when it receives a gh level signal from the comparison circuit 52. For example, 10deg/sec
(However, accelerator pedal fully closed to fully open; 0 to 50 dec+
) or above, the acceleration of the diesel engine is detected and the electromagnetic valve 45 is driven in the closing direction. Note that this driving time is determined by the timer 53, and is, for example, 200 to 1500+s.
It is set to a value of about ec.

In the fuel injection system of this embodiment configured as described above, when the diesel engine is not accelerating, the fuel in the pump cylinder 16 is pressurized by the movement of the pump plunger 14, and the fuel is transferred to the diesel engine via the delivery valve 19. When pressure feeding of fuel to the engine is started, the fuel pressure in the pressurizing chamber 17 presses and moves the seven-cumulate rate piston 22 in the pilot injection device 20 until it comes into contact with the stopper 24. Then, the fuel in the pressurizing chamber 17 is accumulated in the cylinder 21 by the amount of the moving force, the fuel pressure in the pressurizing chamber 17 is temporarily lowered, and the pressure of fuel from the fuel injection pump 1 to the diesel engine, that is, the fuel injection is stopped. Stop. Thereafter, when the fuel in the pressurizing chamber 17 is further pressurized, fuel injection is started again, and the fuel injection is continued until the fuel in the pressurizing chamber 17 overflows via the spill boat 14a.

That is, when the diesel engine is not accelerating, the pilot injection device 7)'l operates and pilot injection is executed.

Meanwhile, the control circuit 50 detects acceleration of the diesel engine,
When the solenoid valve 45 is driven in the closing direction, the area behind the pilot injection amount @ 20 becomes oil-tight, and even if the fuel pressure in the pressurizing chamber 17 increases, the accumulate piston 22 does not move and the pilot The operation of the injection device 20 will be stopped. Then, the fuel accumulated in the cylinder 21 of the pilot injection device by the movement of the accumulation piston 22 during pilot injection is transferred to the delivery valve 19.
The fuel is then pumped to the diesel engine via the

In other words, by stopping the operation of the pilot injection device when the diesel engine accelerates, it becomes possible to increase the amount of fuel injection.

As explained above, in the fuel injection device of this embodiment, the amount of fuel injection is increased by stopping the operation of the pilot injection device when the diesel engine accelerates. Therefore, with a fuel injection pump equipped with a pilot injection rA device, when the diesel engine is accelerating, it is possible to always increase the fuel injection amount regardless of the accelerator WIA degree, and it is possible to improve acceleration performance. Moreover, since no modification is made to the fuel injection II adjustment Il1 mechanism of the injection pump, it is possible to satisfactorily accelerate and increase the amount of fuel without impairing the governor characteristics of the injection pump itself.

In this embodiment, the acceleration of a 1-meter diesel jump is detected from the opening speed of the accelerator pedal. A rotation speed sensor is provided to detect the vs function rotation speed of the diesel engine, and the detected engine speed is differentiated to find the rotational acceleration, and when the value exceeds a predetermined value, the diesel vs function is detected.
The acceleration of rIA may be detected, or a combination of these two may be used.

Furthermore, in this embodiment, when the opening speed of the accelerator pedal exceeds a predetermined value, the predetermined time 'i! Although the i-magnetic valve 45 is driven, a plurality of comparison circuits may be provided and the driving time of the solenoid valve 45 may be changed depending on the degree of acceleration of the diesel engine.

Furthermore, in this embodiment, the rear chamber 27 of the pilot jet G-proofing device 20
The rear chamber 27 and the fuel tank were configured to communicate with each other in order to fill it with fuel. It may be configured to be filled with

[Effects of the Invention] As detailed above, in the fuel injection cylinder of the present invention, when the diesel engine accelerates, the pilot injection device is stopped and the fuel stored in the cylinder by the driving of the pilot injection device is injected into the diesel engine. It is designed to supply Therefore, even if a mechanical fuel injection pump is provided with a pilot injection device, it is possible to easily accelerate and increase the amount of fuel at any time, thereby improving acceleration performance.

Further, in the present invention, since no modification is made to the fuel injection OA amount metering mechanism inside the fuel injection pump, acceleration increase can be performed satisfactorily without impairing the governor characteristics of the fuel injection pump itself.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a schematic configuration diagram showing the entire fuel injection device of this embodiment, FIG. 2 is a sectional view showing the configuration of the pilot injection device, and FIG. 3
The figure is a block diagram showing the circuit configuration of the control circuit, and FIG. 4 is a diagram showing the difference in fuel injection amount depending on the presence or absence of pilot injection. 1... Fuel injection pump 14... Pump plunger 17... Pressurizing chamber 20... Pilot injection device 21... Cylinder 22... Accumulate piston 24... Stopper 26... Return spring 27... Back chamber 28... Return passage 40... Accelerator opening sensor 45... Solenoid valve 46... Oil tight passage 50... Control circuit

Claims (1)

[Scope of Claims] A fuel injection pump that pressurizes fuel in a pressurizing chamber by reciprocating motion of a plunger and pressure-feeds it to a diesel engine; a cylinder that is provided in communication with the pressurizing chamber of the fuel injection pump; An accumulation piston that is pressed and moved by the fuel pressure in the pressurization chamber, a spring that presses and urges the accumulation piston toward the pressurization chamber, and a stopper that limits the amount of movement of the piston. A fuel injection device for a diesel engine, comprising: a pilot injection device, and configured to perform pilot injection before main injection of fuel, wherein the spring housing portion is formed in the cylinder of the pilot injection device; In order to fill a certain back chamber with fuel, the low pressure chamber or fuel tank of the fuel injection pump and the back chamber are communicated through an oil-tight passage, and the oil-tight passage is provided with an on-off valve for opening and closing the passage. , acceleration detecting means for detecting acceleration of the diesel engine; and when the acceleration detecting means detects acceleration of the diesel engine, driving the on-off valve in a direction to close the oil-tight passage to control the pilot injection device. A fuel injection device for a diesel engine, comprising: a pilot injection inhibiting means for stopping operation; and a fuel injection device for a diesel engine.