JPH0315029B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for an internal combustion engine, which injects fuel by driving a plunger by the hydraulic pressure of a fluid controlled by a spool valve.

In conventional fuel injection systems of this type, a 2-position, 3-port solenoid valve was used to control the movement of the spool valve, and another 2-position, 2-port solenoid valve was used for accurate metering. . Alternatively, two 2-position, 2-port solenoid valves were used instead of the 2-position, 3-port solenoid valve.

In this conventional type, a 2-position 3-port solenoid valve and a 2-position 2-port solenoid valve each have one
A total of two valves were required, or three two-position, two-port solenoid valves were required. Three-port devices sometimes have a complicated structure, are large in size, and are often difficult to manufacture. In addition, a device using a 2-port, 2-position device requires three devices, resulting in an increase in cost. In this case, it has been proposed to configure one of the three valves with a rotary valve, but this also requires a cost comparable to that of a solenoid valve, and is currently not sufficiently effective.

In order to eliminate the drawbacks of the conventional configurations described above, the present invention has developed a system in which the spool return function is not controlled externally by a solenoid valve or the like, but by an on-off valve mechanism such as an annular groove provided in the piston (or plunger). By doing this, the spool can be controlled by a single 2-port 2-position solenoid valve, which reduces the number of parts, reduces the size, reduces costs, and reduces the number of solenoid valves. An object of the present invention is to provide a highly reliable fuel injection device that can realize a simplified control circuit and also can stop a pumping mechanism in a cushioning manner.

The present invention will be explained below with reference to embodiments shown in the drawings.
In FIG. 1, 1 is an injector, and 2 and 3 are hydraulic pressure sources as a whole. The injector 1 consists of a spool valve consisting of a bore 4, a spool 5 and a spring 17 that freely slide within the bore, and an integrated large-diameter piston 8 and plunger 9 that slide within the bores 6 and 7, respectively. The present invention has a fuel compression means constructed as described above, a normal fuel injection nozzle 10 loaded by a spring 10a, and first and second two-position two-port solenoid valves 11 and 13 for controlling these. Plunger 9 lower end surface and bore 7
A fuel chamber 23 formed by is connected to a supply pressure source 3 via a check valve 24 and a second electromagnetic valve 13,
At the same time, it is directly connected to the nozzle 10. On the other hand, a hydraulic oil chamber 14 formed by the left end surface of the spool 5 and the bore 4 is connected to a first passage 15 and a first electromagnetic valve 11.
It is in communication with the supply pressure source 3 via a second passage 25 and with an annular groove 26 provided in the bore 6 . Another annular groove 2 provided in the bore 6
7 is connected to a low pressure fuel tank 16. The two annular grooves 26, 27 cooperate with an annular groove provided in the piston 8 and having two edges 8a, 8b to perform a valve function. Furthermore, one port 19 of the spool valve is connected to the supply pressure source 2 by a pipe 21;
Another port 20 is connected to the fuel tank 16 via a throttle 22. The hydraulic oil chamber 18 formed by the upper surface of the piston 8 and the bore 6 has two ports 1
Either 9 or 20 will be contacted. The supply pressure sources 2, 3 force fuel from fuel tanks 16', 16'' through filters 203, 303 with pumps 201, 301, and maintain a constant pressure by pressure regulating valves 202, 302 and pressure accumulators 204, 304. 30 is a controller that controls energization of two electromagnetic valves 11 and 13 based on signals from sensors S ₁ to S ₅ to be described later.The number of injectors 1 is the same as the number of cylinders of an engine (not shown). .

FIG. 2 shows a block diagram regarding the sensors S ₁ to _{S 5} , the controller 30, and the solenoid valves 11 and 13. S ₁
is the engine rotation speed, S ₂ is the amount of accelerator pedal depression, S ₃ is the engine temperature, S ₄ is the engine cylinder mark, and S ₅ is the emergency situation such as fuel leakage from piping or engine overrun. It is a sensor that detects.

In the controller 30, P ₁ is an injection amount setting circuit, P ₂ is an injection start timing setting circuit, and A ₁ is a sensor.
A calculation circuit that determines the injection amount based on the signals of S ₁ and S ₂ , A ₂ is a calculation circuit that determines the injection start timing based on the signals of the sensors S ₁ to _{S 3} , and A ₃ is an output amplification circuit. Specifically, the calculation circuit A ₁ calculates the energization time to the second solenoid valve 13, and the calculation circuit A ₂ calculates the deviation of the energization start time to the first solenoid valve 11 with respect to the cylinder mark. In addition, the output width circuit A ₃ determines the crank position and energizes the solenoid valves (corresponding to 11 and 13) of the necessary cylinders with the necessary tamping, and normally the first solenoid valve 11 is energized for a certain period of time. Only energize.

Next, the operation will be explained. By making the two ports of the first solenoid valve 11 conductive (hereinafter referred to as "open") from the state shown in FIG. 17 overcomes and displaces it to the right. At this time, the annular grooves 26 and 27 are separated from each other by the piston 8, as shown in the enlarged view of FIG. By displacing the spool 5 to the right, the port 20 is closed, and subsequently the port 19 is opened. As a result, the hydraulic oil chamber 18 is brought into communication with the pressure source 2 through the port 19, and the pressure is increased to the area ratio of the piston 8 and the plunger 9, and the fuel in the fuel chamber 23 is transferred to the nozzle 10.
More sprayed. At this time, the check valve 24 prevents the compressed fuel from being returned to the pressure source 3.

After the spool 5 is displaced to the right, the first solenoid valve 11 is closed. After a certain time delay, the piston 8 is displaced downward, but at this point the piston 8
When the piston reaches near the bottom dead center, the edge 8a of the annular groove of the piston overlaps and communicates with the annular groove 27 of the bore 6. Since the edge 8b is designed not to block the annular groove 26 even when the piston is at the bottom dead center (x ₃ > x ₁ > x ₂ at the top dead center position shown in FIG. 3), from now on, as shown in FIG. the annular groove 26 until the bottom dead center position shown.
27 are in communication. In this state, the fuel in the hydraulic oil chamber 14 is discharged into the tank 16 through the pipe 25 and the annular grooves 26 and 27, and the spool 5 is returned to the left by the force of the spring 17. The displacement of spool 5 closes port 19 and subsequently opens port 20. Then, the fuel amount in the hydraulic oil chamber 18 is
It is then released into the tank 16. Subsequently, while the second solenoid valve 13 is opened, the piston 8 and plunger 9 are pushed back upward by the pressure in the fuel chamber 23 as the fuel in the hydraulic oil chamber 18 is released, and the pressure source 3, the fuel to be injected next is led to the fuel chamber 23 through the check valve 24. The opening time of the second electromagnetic valve 13 is controlled so that fuel commensurate with the scheduled injection amount is introduced here. When metering is completed in this way, the piston 8 and plunger 9 stop while the pressures in the hydraulic oil chamber 18 and the fuel chamber 23 are balanced. The throttle 22 has the effect of prolonging the metering time and thus allows for more accurate metering.

Then, by opening the first electromagnetic valve 11 again, fuel is injected, and by repeating this, fuel can be supplied to an internal combustion engine (not shown).

First and second solenoid valves 1 from the controller 30
To explain the signals to 1 and 13 in chronological order, the first solenoid valve 11 opens at time A in FIG. Close the solenoid valve 11. Thereafter, at time C, the annular grooves 26 and 27 open, so the spool 5 returns to a position where metering is possible.Next, when the second solenoid valve 13 is opened at time D, the piston 8 and plunger 9 return, and metering begins. At time E, the solenoid valve is closed to complete metering. Here, the communication between the annular grooves 26 and 27 is cut off immediately after time D due to the rise of the piston 8. Then, time A is variably controlled based on the signals from sensor S ₁ , etc. to optimize the timing, and time A is adjusted based on the signals from sensors S ₁ and S ₂ .
Measurement is performed by variable control of DE.

Furthermore, since the first solenoid valve 11 only needs to be energized when the valve is open, power can be saved compared to a conventional two-position, three-port solenoid valve.

In the above embodiment, the annular grooves 26, 27 and the edge 8
Although a and 8b are configured in the piston 8 of the bore 6, it is clear that they may also be configured in the plunger 9, or they may be configured in a hole and an annular groove instead of two annular grooves.

Furthermore, by providing the plunger with a spill mechanism that determines the end of injection, it is possible to accurately determine the end of injection and the return timing of the spool from the design value of the opening lift.

Although only one cylinder is shown in FIG. 1, it goes without saying that multiple cylinders can be used. Also the first
Although the figure shows a normal nozzle 8 that is loaded by a spring, a nozzle that is loaded by hydraulic pressure or the like may also be used. Furthermore, the pressure source may be separate for metering and spool drive, or conversely, all including the piston drive may be constituted by one pressure source, and the pressure medium other than metering may be other than fuel.

Further, it goes without saying that the controller may be constructed of either an analog circuit or a digital circuit.

As described above, the present invention provides a valve mechanism that opens and closes in conjunction with the pressure feeding mechanism between the spool hydraulic oil chamber and the fuel tank, controls the return stroke of the spool, and connects the spool hydraulic oil chamber and the pressure source. The forward stroke of the spool and therefore the injection timing are controlled by installing an electromagnetic on-off valve between the pump chamber and the pressure source. It is possible to reduce the number of injectors, provide a small and inexpensive injector with a simple structure, and not only save operating energy, but also greatly improve reliability because the pumping mechanism is stopped as a buffer. This effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention;
Figure 2 is a block diagram of the sensor, controller, and solenoid valve in Figure 1, and Figures 3 and 4 are enlarged views of the drive piston in Figure 1, at top dead center and bottom dead center, respectively. FIG. 5 is a timing chart for explaining the operation of the present invention. 1...Injector, 2, 3...Pressure source, 5...
... Spool, 8 ... Piston, 9 ... Plunger, 10 ... Fuel injection nozzle, 11 ... First solenoid valve, 13 ... Second solenoid valve, 14 ... Spool hydraulic oil chamber, 16 ... Fuel Tank, 23... fuel chamber, 26, 27... annular groove forming the main part of the opening/closing valve mechanism, 30... controller.

Claims (1)

[Scope of Claims] 1. A supply pressure source that pumps high-pressure fluid, a slidably disposed piston, and a plunger that pressurizes fuel in a fuel chamber in conjunction with the piston when the piston receives hydraulic pressure. a fuel injection nozzle that injects pressurized fuel in the fuel chamber; and a spool operating chamber that slides against a biasing force when high-pressure fluid is supplied, and this sliding applies hydraulic pressure to the piston. a spool valve to control; an electromagnetic on-off valve to control the inflow of high-pressure fluid from the supply pressure source to the spool working chamber; a metering electromagnetic on-off valve to control the amount of fuel supplied to the fuel chamber; A passageway for releasing high-pressure fluid in the spool working chamber to a low-pressure side; and an on-off valve mechanism that opens this passageway by a pressure-feeding operation of the pressure-feeding mechanism of the piston and the plunger, and the on-off valve mechanism includes a pressure-feeding mechanism. The control state of the spool valve is switched from the pumping state to the stop suction state by opening the mechanism just before the bottom dead center of the pumping operation to release the high-pressure fluid in the spool working chamber, thereby supplying high-pressure fluid to the piston. 1. A fuel injection device for an internal combustion engine, characterized in that the pumping stroke of the pumping mechanism is stopped.