JPS5865963A - Method for obtaining a desired injection rate pattern in fuel injector for internal-combustion engine - Google Patents

Abstract

PURPOSE:To obtain a desired injection rate pattern by keeping in the partially opened state for a certain time, the supply port of the spool valve for switching and introducing the pressure from a pressure source into the pressure supply system for driving a plunger, in the case of an injection pump. CONSTITUTION:After the first solenoid valve 24 is set in an opened state through current flow at time A, the spool 3 of a spool valve shifts rightward, and a supply port a is partially opened at time G, and then the current flow in the first solenoid valve 24 is suspended, and the closed state is formed. At this time, the fuel in the hydraulic oil chamber 15 of the spool valve is sealed, and the spool 3 is set in recess, so the flow rate of the pressurized fuel which passes- through the supply port (a) and is supplied into the hydraulic oil chamber 21 of a fuel compressing apparatus is reduced, and the lowering speed of the plunger 7 in the fuel compressing apparatus reduces, and the fuel injection rate is reduced. Thus, the initial rise of the injection rate pattern is made gentle, and the engine noise is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining a desired injection rate pattern in a fuel injection system for an internal combustion engine, particularly a diesel engine.

In recent years, from the viewpoint of cleaning engine exhaust gas and saving energy, it has become necessary to increase the pressure and injection rate of fuel injection devices and to perform sophisticated timing control.

Proposals from the gods have been made accordingly. As one of these, an electronically controlled hydraulically driven unit injector has been developed. However, in this type of unit injector, when the pressure is increased and the injection rate is increased, the injection rate increases rapidly, which tends to increase engine noise. In addition, it has been found that if the injection rate suddenly rises rapidly, it not only causes noise but also increases the concentration of NOx. Therefore, in the unit injector of the above type, it is difficult At the same time, it is desired to slow the rise in single-spout load resistance.

However, it has been extremely difficult to change the injection rate pattern both in conventional conventional fuel injection devices and in the above-mentioned type of unit injector.

The object of the present invention is to reduce the initial rise of the introduced pressure by keeping the supply boat of the spool valve partially open for a certain period of time, which switches and introduces the pressure source pressure into the pressure feeding system that drives the plunger. It is an object of the present invention to provide a method for obtaining a desired injection rate pattern by slowing down the rise of the injection rate.

The present invention will now be described in detail with reference to the accompanying drawings, with reference to the apparatus used to carry out the method of the present invention.

Referring to FIG. 1, there is shown a fuel injection device 10 for use in carrying out the method of the present invention, which device includes an injector 1 +
fli controller 60 and fuel supply pressure source 14. The injector 1 has a spool valve, a fuel compression device, a single injection nozzle device, and a solenoid valve device. The spool valve is spool 3. A spring 3a- that presses the spool valve in one direction.
It includes a hole 2 accommodating the spool. The hole 2 is formed with a supply boat (a) and a return boat (b), and defines a hydraulic oil chamber 15 between the hole 2 and the left end surface of the spool 3. The fuel compression device of the injector 1 is a large diameter piston 6
, a hole 4 for accommodating this. A plunger 7, a hole 5 for housing it. It includes a hydraulic oil chamber 21 defined between the large diameter piston and the hole 4, and a fuel chamber 12 defined between the plunger 7 and the hole 5. The injection nozzle device of the injector 1 is a fuel injection nozzle 8.

It includes a spring 8a that presses it. The solenoid valve device of injector 1 consists of 6 2-bot 2-position solenoid valves 24°25-26
The first electromagnetic valve 24 is connected to the hydraulic oil chamber 15 of the spool valve and the fuel supply pressure source 14 via a conduit 30, respectively. The second electromagnetic valve 25 is connected to the hydraulic oil chamber 15 of the spool valve and the low-pressure fuel tank 16 via a conduit 40, respectively. Further, the sixth solenoid valve 2G is connected to the spool valve return boat (
b) and further connected via a line 50 to a low-pressure fuel tank 16. Spool valve supply bow)
(a) shows the fuel supply pressure source 14 via the pipes 30', 30;
is connected to. The fuel chamber 12 of the fuel compression device communicates with a fuel supply pressure source 14 via a check valve 13 and a line 30' and with the nozzle 8 via a passage 8b.

The hydraulic oil chamber 21 of the fuel compression device is connected to the spool valve supply boat (
a) or the return port +-) (b).

The fuel supply pressure source 14 includes a fuel tank 16' and a fuel tank 17'.
- Pump 18 - includes a pressure regulating valve 19 and a pressure accumulator 2'0 provided in the bypass line of the pump.

Referring to FIG. 2, the control device 60 includes the controller 23
and sensors (Syo~s6). The sensor (S) is the engine rotation speed, the sensor (S2) is the amount of accelerator pedal depression, the sensor (S3) is the engine temperature, and the sensor (84) is the engine cylinder mark sensor (S5) is the fuel from the pipe. Emergency situations such as leaks or engine overruns,
The sensors (s6) each detect the pressure of the fuel pressure supply source 14. The controller 23 is an injection amount setting circuit (PI)
, ``J = injection start timing setting circuit (P2) + first calculation circuit that determines the injection amount (A,,) + second instrumentation circuit that determines the control start timing (Aρ and output amplification circuit (
A,). The first calculation circuit (A1) is a sensor (Sl
Calculate the energization time for the sixth solenoid valve 26 based on the signal from -82). The second calculation circuit (A) calculates the deviation of the time when energization to the first electromagnetic valve 24 starts to be energized with respect to the cylinder mark based on the signal from the sensor (S, 52-83).

The output amplification circuit (A3) determines the crank position and energizes the solenoid valves 24-25-26 of the related cylinders at a predetermined timing. This output amplification circuit (A3) normally energizes the first and sixth solenoid valves 24, 26 for a certain period of time, but when an emergency signal from the sensor (s5) or an emergency signal from the sensor (S6
) It is also possible to de-energize or keep energized in response to a pressure signal from the pressure source.

The conventional operation of the fuel injection device 10 shown in FIG. 1 will be explained with reference to FIG. 6. In the state shown in FIG. 1, when the first solenoid valve 24 is energized at time A and the two boats are placed in communication (hereinafter referred to as "open"), fuel is supplied from the fuel supply pressure source 14. It is introduced into the hydraulic oil chamber 15 of the spool valve, and moves the spool 3 to the right against the force of the spring 3a.

During this time, the boats of 2502 second solenoid valves are placed in a non-communicating state (hereinafter referred to as closed). As the spool 3 of the spool valve moves to the right in the hole 2, the return boat (b
) is closed and 5th supply bow) (a) is opened. As a result, the hydraulic oil chamber 21 of the fuel compression device communicates with the fuel supply pressure source 14 via the supply port (a) of the spool valve to receive pressurized fuel and connect the large diameter piston 6 and plunger 7. The plunger 7 is driven downward by the difference in pressure receiving area, and the fuel in the fuel chamber 12 is injected through the passage 8b and the nozzle 8.

At this time, the fuel in the fuel chamber 12 is prevented from flowing back to the fuel supply pressure source 14 through the conduit 30'' by the check valve 13.

Next, the first solenoid valve 24 is de-energized at time B, and
After the two boats are in the closed state, the second solenoid valve 25 is energized at time C, the two boats are in the open state, and the inside of the hydraulic oil chamber 15 of the spool valve is turned on. of fuel is led to the low-pressure fuel tank 16, whereby the spool 3 of the spool valve moves to the left in the hole 2 by the force of the spring 3a. As the spool 3 moves to the left inside the hole 2, the supply bow)
(a) is closed and the primary return boat (b) is opened.

After the spool 3 reaches the left end of the hole 2, the second solenoid valve 25
is de-energized (time D).

In this state, when the sixth solenoid valve 26 is energized at time E and the two boats are opened, the fuel in the hydraulic oil chamber 21 of the fuel compression device is drained from the spool valve. (bL) is discharged to the low pressure fuel tank 16 via the sixth electromagnetic valve 26 and the pipe 50. In this way, the third
While solenoid valve 26 is energized, fuel from fuel pressure source 14 passes through line 30'' and check valve 13 to the fuel compression device as fuel is discharged from hydraulic fluid chamber 21 of the fuel compression device. into the fuel chamber 12.

Push up the large diameter piston 6 and plunger 7.

Therefore, the amount of fuel injected from the fuel chamber 12 through the nozzle 8 is determined by the energization time of the sixth electromagnetic valve 260. When the third electromagnetic valve 26 is turned off at time F and placed in a closed state, the respective pressures in the hydraulic oil chamber 21 and the fuel chamber 12 of the fuel compression device are adjusted to the area ratio of the large-diameter piston 6 and the plunger 7. The large-diameter piston 6 and the plunger 7 stop in a balanced manner according to. The throttle 22 serves to extend the metering time of the fuel in the fuel chamber 12 of the fuel compression device, allowing accurate metering.

The above steps are repeated to supply fuel to the engine. Here, the time A when the first electromagnetic valve 24 is in the open state is variably controlled based on signals from the sensor S, etc. to optimize the injection timing.

Further, the time interval EF during which the sixth electromagnetic valve 26 is energized and placed in an open state is determined based on the signals from the sensor 5l-82, etc., at a predetermined time interval EF of the fuel; iI7! The amount of I can be reduced to 1-. There is a certain degree of freedom in setting the opening and closing times A to F of each electromagnetic valve - some of these times may be simultaneous.

The operation of the fuel injection system 10 shown in FIG. 1 according to the invention will be explained with reference to FIG. In the state shown in FIG. 1, after the first electromagnetic valve 24 is energized at time A and placed in the open state, the spool 3 of the spool valve moves to the right to partially control the supply bow (a). At the time G when the first solenoid valve 2 is opened.
4 is stopped and brought into a closed state. At this time, the fuel in the hydraulic oil chamber 15 of the spool valve is sealed, and the spool 3
is at rest, the flow rate of the pressurized fuel supplied to the hydraulic oil chamber 21 of the fuel compression device through the supply boat (a) is small, and therefore the descending speed of the plunger 7 of the fuel compression device is small, causing fuel injection. rate is small. Next, at 1 time H, when the first solenoid valve 24 is energized again and opened, the spool 3 moves further to the right, completely opening the supply bow (a), and then opening the spool 3. Reach the right end of 2. During this time, since the supply bow (a) is completely opened, the descending speed of the plunger 7 is high - and therefore the fuel noise resistance is also high. After the fuel injection is finished and the spool 3 stops at the right end of the hole 2.

The first electromagnetic valve 24 is de-energized at time B and is placed in a closed state. From this point on, the second and sixth solenoid valves are opened and closed in the same manner as the conventional one in the Kiro diagram.

In FIG. 5, the injection rate pattern according to the present invention shown by the solid line is compared with the conventional injection rate pattern shown by the chain line.

It is shown that the rise is gradual. According to experiments conducted by the inventor, it has been found that the effect of the present invention is more pronounced when the spring 8a pressing the nozzle 8 is weaker. In the embodiment of the present invention shown in FIG. 4, the injection rate pattern shown by the solid line in FIG. 5 was obtained by manipulating the operation of the first solenoid valve 24; The injection rate pattern shown by the solid line in FIG. 5 can also be obtained by operating the valve 25 (for example, by turning it into the open state at 1-hour intervals). Furthermore, if the spool valve is driven by a solenoid, the current flowing through the spool valve solenoid can be temporarily kept constant to stop the spool, or the current flowing through the solenoid can be controlled to slowly move the spool. The injection rate pattern is also shown by the solid line in Figure 5. You can obtain the injection rate pattern like this.

The present invention is applicable not only to a fuel injection device having the configuration shown in FIG.
, the number of pressure sources, the type and number of hydraulic oil, piping, the type and number of solenoid valves, the spool type, the nozzle type and metering method, etc., and the controller is not an analog circuit but a digital one or a combination of both. It is clear that the present invention is equally applicable even if the number of types of sensors is different.

According to the present invention, the spool is temporarily stopped or decelerated when the hydraulic oil supply boat of the spool valve is partially opened.

Thereafter, by moving the spool at a constant speed, the initial rise of the injection rate pattern is made gradual. This has the effect of reducing the noise of the internal combustion engine and purifying the exhaust gas.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a fuel injection device used to carry out the method of the present invention. FIG. 12 is a block diagram of the control device of the apparatus shown in FIG. FIG. 6 is a diagram showing the control timing of each element according to the conventional method, FIG. FIG. 2 is a diagram showing an injection rate pattern. In fig. 1...Injector 3...Spool 6...Large diameter piston 7...Plunger 8... ...Nozzle 10...Fuel injection device 14...Fuel pressure supply trace 15-21...
..... Hydraulic oil chamber 23 ..... Controller 24-25-26 ..... 1st. 2nd and 6th Solenoid Valve Agents: 4 people, Akira Asamura

Claims (1)

Claims: (1) A switching control valve mechanism having a spool valve that switches pressure from a pressure source, and a pressure feeding mechanism having a piston and plunger operated by the pressure. and a method for obtaining a desired injection rate pattern in a hydraulically driven fuel injection device including a nozzle that injects pressure-fed fuel, wherein the switching control valve communicates the pressure-fed & paulownia t-stone hydraulic oil chamber with the pressure source. A method for obtaining a desired injection rate pattern in a fuel injection device, characterized in that the switching speed of the switching control valve mechanism is reduced or temporarily reduced to zero after a control boat of the mechanism is partially opened. (2. In the method according to claim 1, one of the two on-off valves of the switching control valve mechanism that operates the spool valve is opened and closed at the initial stage of injection. A method for obtaining a desired injection rate pattern in a fuel injection device characterized by decelerating or temporarily reducing the switching speed to zero. (3) In the method according to claim 1, the switching speed is actuated by electromagnetic force. A method for obtaining a desired injection rate pattern in a fuel injection device, characterized in that the switching speed of the spool valve is reduced or temporarily reduced to zero by changing the current value of the spool valve at an early stage of injection.