JPS618459A - Fuel injection device - Google Patents

Abstract

PURPOSE:To both enhance quantity control accuracy of fuel and obtain an optional waveform of its injection rate, by providing two fuel compressing devices, each of which separately operates, and respectively adjusting a quantity of compressed fuel and/or timing of the fuel supplied from these fuel compressing devices. CONSTITUTION:The first and the second fuel compressing devices 6, 7 are connected with an oil reservoir 32 in a fuel injection nozzle 3 through oil paths 4, 5 interposing a check valve 4a, 5a. Each fuel compressing device 6, 7, containing in a stepped cylinder tube 10 a servo piston 12 comprising large and small contoured pistons 11a, 11b, respectively connects each piston chamber 13 with an oil hydraulic power supply 14 or a fuel tank 19 through the first and the second selector valve 15, 26 and each compression chamber 16 with the oil reservoir 32. Further the compressing chamber 16 is connected with the oil hydraulic power supply 14 when each selector valve 15, 26 is switched to a position II. And a control unit 23 controls each selector valve 16, 26 so as to be successively opened in each injection timing of fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fuel injection device for an internal combustion engine.

2. Description of the Related Art Accumulator or high-pressure fuel injection devices have been used as fuel injection devices for internal combustion engines. This type of fuel injection device, as seen in Japanese Patent Laid-Open No. 57-13266, for example, includes a fuel compression device in which a piston is provided for compressing fuel supplied in advance in response to fuel pressure; A fuel injection control comprising a fuel injection nozzle that injects compressed fuel compressed by a device, and a switching valve that controls pressure applied to a nozzle needle holder that presses a nozzle needle of the fuel injection nozzle in a closing direction. The injection timing and injection period are controlled by controlling the pressure applied to the two pistons of the nozzle needle presser. With this fuel injection device,
When the pressure applied to the nozzle needle presser by the fuel injection control means becomes smaller than the fuel pressure applied by the fuel compression device, fuel is injected.

Problems to be Solved by the Invention Incidentally, it is generally desired that a fuel injection device for an internal combustion engine be able to perform pyro-injection, injection, change of injection rate, etc. However, the metering accuracy is insufficient and it is difficult to make one cycle of injection less than a predetermined time, so it has the drawback that it is extremely difficult to control pilot injection and changes in the injection rate. This is mainly due to the structure of the fuel compression device using a servo piston, which allows fuel corresponding to the required maximum injection amount to be introduced into the cylinder in a limited amount of time. There is a lower limit to the flow rate, and metering accuracy depends on the resolution of the time control of the solenoid valve for switching the hydraulic path, and as a result, it is extremely difficult to make minute adjustments to the inflow rate. It is.

It is an object of the present invention to perform metering control with high precision, to be able to arbitrarily adjust the amount of pilot injection, and to
It is an object of the present invention to provide a fuel injection device for an internal combustion engine in which the injection rate waveform can be freely changed.

Means for Solving the Problems The configuration of the present invention includes a fuel injection nozzle, a nozzle needle presser that presses the nozzle needle of the fuel injection nozzle in a closing direction, and a high-pressure fuel pressure supplied from a fuel pump. first and second fuel compression devices each comprising a large-diameter piston that receives fuel pressure, and a small-diameter piston that operates in conjunction with the large-diameter piston and compresses previously supplied fuel when the large-diameter piston receives fuel pressure; passage means for feeding each compressed fuel from the second fuel compression device to the fuel injection nozzle, and independently adjusting the fuel pressure supplied from the hydraulic pump to the first and second fuel compression devices; It is characterized in that it is equipped with a control means for.

According to the above-described configuration, two fuel compression devices that operate independently are provided, so that the amount of compressed fuel supplied from these fuel compression devices and/or the timing can be adjusted. The combined injection waveform output from the injection nozzle can be arbitrarily determined. As a result, it goes without saying that the waveform of the injection rate can be set freely;
By appropriately setting the amount of compressed fuel output per unit time from the two fuel compression devices, metering control can be performed with extremely high accuracy.

Example Hereinafter, the present invention will be explained in detail with reference to the illustrated embodiments.

FIG. 1 shows a configuration diagram of an embodiment of a fuel injection device according to the present invention. The fuel injection device 1 is for injecting and supplying the required fuel to a diesel engine 2, and is equipped with a fuel injection nozzle 3.

The fuel injection nozzle 3 is connected to the first and second fuel compression devices 6 via oil passages 4 and 5 provided with check valves 4m and 5m, respectively.
, 7 respectively, and a desired amount of compressed fuel obtained by a metering operation to be described later is supplied to the fuel injection nozzle 3 from the first and second fuel compression devices 6.7, respectively. The fuel injection nozzle 3 is provided with a nozzle needle presser 8 for pressing the nozzle needle 28 in the closing direction.
Compressed fuel from the first and second fuel compression devices 6 and 7 is supplied to the fuel injection nozzle 3 through oil passages 4 and 5, respectively.

The first fuel compression device 6 has a large diameter 79a and a small diameter 79a.
Cylinder tube l formed above and below in communication with 9b
O, and inside the diameter 9aeeb is a piston l1m with an inner diameter.
and a small-diameter piston 11b and a good sir-stop piston 12
A piston chamber 13 is provided above the large-diameter piston 11m of the piston 12, and the piston chamber 13 is connected to a hydraulic power source 14 and a first switching valve 15.
connected via. Further, a compression chamber M16 is provided below the piston 11b by a fitting cylinder 79b, and the compression chamber 16 is connected to the fuel injection nozzle 3 via the oil passage 4. Therefore, when pressure oil is supplied to the piston chamber 13, the servo piston 12 is moved downward to pressurize the fuel in the compression chamber 16, and the pressurized fuel is force-fed to the fuel injection nozzle 3.

The oil pressure source 14 is connected to the oil supply cylinder 7p18 via the filter 17.
An electronic pressure reducing valve 20 and an accumulator 21 are provided at the discharge part of the oil supply bong 7618, and the first switching valve 1 is connected to the first switching valve 1 through an oil passage 22.
5.

The oil feed pump 18 is driven by the diesel engine 2, and an electronic pressure reducing valve 20 controls its supply pressure in proportion to the load. This pressure is controlled by an output signal sl from the control unit 23.

The first switching valve 15 is a 2-position, 4-boat, electronically operated valve that is switched in response to an output signal S2 from the control unit 23, and when the first switching valve 15 is in the The discharge side of f18 communicates with the piston chamber 13 of the first fuel compression device 6.

Also in that position, the compression chamber 16 is in the throttle position 24.
, and communicates with the tank side via the check pulp 25. Therefore, the pressure oil is supplied into the piston chamber 13 and presses the piston 11m, and the servo piston 12 descends to pump the fuel in the compression chamber 16. When the first switching valve 15 is switched to the position ①, the discharge side of the pump 18 is connected to the compression chamber 1.
6, and the piston chamber 13 communicates with the tank 19. Therefore, the pressure oil is throttled by the restrictor 24 and gradually supplied into the compression chamber 16, and the pressure oil in the piston chamber 13 is returned to the tank 19.

The second fuel compression device 7 is set so that the amount of compressed fuel delivered per unit time is larger than that of the first fuel compression device 6. Since it has the same configuration as the compression device 6, corresponding parts are given the same reference numerals and their explanation will be omitted. The piston chamber 13 of the second fuel compression device 7 is connected to the control unit 23.
The compression chamber 16 is connected to the oil pressure source 14 via the second switching valve 26 operated by the output signal S3 from the oil passage 5.
It is connected to the fuel injection nozzle 3 via.

The fuel injection nozzle 3 is made up of a main body 27 and a nozzle needle 28 disposed inside the main body 27. The nozzle needle 28 is seated on the valve seat by the pressing force applied from the nozzle needle holder 8 via the pressure pin 29, and the nozzle needle 28 is seated on the valve seat. Hole 30 is closed. The fuel compressed by the first and second fuel compression devices 6.7 is transferred from each oil passage 4, 5 to a passage 3 formed in the main body 27.
1 is sent to the oil sump 32. The fuel injection is the first
and/or the second switching valve 15, 26 is switched to position (3), the fuel compressed by the fuel compression device 6 and/or 7 is sent to the injection nozzle 3, and the fuel pressure in the oil sump 32 is increased to the nozzle needle 28. The nozzle needle 28 softens and the orifice 30 opens when the pressure exceeds the pressure applied to the pressure pin 29 pressing on the nozzle needle 28 . The fuel injection ends when the first and second switching valves 15, 26 are respectively switched to the ■ position.

Next, with reference to FIG. 2, a control operation when fuel injection is performed with a required injection rate waveform using the apparatus shown in FIG. 1 will be described.

control unit) 23 j'), time N t
= ts'ka et al. 1-1. The output signal Sz (FIG. 2(a)) remains at rHJ level until time 1=1. From t
When the output signal Ss (FIG. 2(b)) which is at the rHJ level until =ts is output, the first switching valve 15
The second switching valve 26 is switched to the ■ position during the period when the output signal S2 is at the "H" level, and the second switching valve 26 is switched to the ■ position during most of the period when the output signal S3 is at the rHJ level. Therefore, from the first fuel compression device 6, fuel of DQl per unit time is delivered at time t.
The flow rate waveform W1 of the supplied fuel, which is supplied to the fuel injection nozzle 3 from l to t2, is shown in FIG. 2(c). On the other hand, the second fuel compression device 7 outputs DQs per unit time.
of fuel is supplied to the fuel injection nozzle 3 from time t2 to ts, and the flow rate waveform of the supplied fuel W! is Fig. 2(d)
is shown.

The compressed fuel from the first and second fuel compression devices 6.7 is both supplied to the fuel injection nozzle 3 via the passage 4.5, so that the fuel injected from the fuel injection nozzle 3 is The waveform is shown in Figure 2 (C).

The injection waveform Qt· shown in FIG. 2(,) is obtained by combining the flow rate waveforms Wl, W,· shown in (d).

In the example shown in FIG. 2, the second switching valve 26 is turned on at time t2.
Although the second switching valve 26 was controlled to be switched to the ■ position only from time t1 to tl, an injection rate pattern in which more fuel is injected at the start of injection can be obtained by switching the second switching valve 26 to the ■ position from time t1 to t2. You can do it like this. Furthermore, by operating only one of the fuel compression devices for a short period of time prior to the activation of the other fuel compression device, it is possible to perform the fuel injection very easily.

Oka, since the fuel delivery amounts per unit time ib of the first and second fuel compression devices are different, the first and second switching valves 1
By appropriately selecting the switching timing and switching time of 5.26, fuel injection can be performed with an arbitrary injection rate waveform, and the injection amount can be controlled with high precision.

Effects of the Invention According to the present invention, as described above, since the fuel compression devices that operate independently are arranged in parallel, the fuel delivery period and timing from these fuel compression devices can be appropriately set. In addition to being able to freely set the injection rate waveform, metering control can be performed with extreme precision by appropriately setting the amount of compressed fuel output per unit time from each fuel compression device. It has excellent effects.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the fuel injection device according to the present invention, and FIGS. FIG. DESCRIPTION OF SYMBOLS 1... Fuel injection device, 3... Fuel injection nozzle, 4° 5... Oil path, 6... First fuel compression device, 7... Second fuel compression device, 8... Nozzle Needle presser, 15.
...first switching valve, 26...second switching valve, 23...control unit. Patent applicant: Diesel Kiki Co., Ltd. Agent: Patent attorney: Masatoshi Takano Figure 2 L+ tz t3 1 hour procedural amendment (
(Voluntary) August 3, 1982

Claims (1)

[Claims] 1. A fuel injection nozzle, a needle holder that presses the nozzle needle of the fuel injection nozzle in a closing direction, a large diameter piston that receives high pressure fuel supplied from a hydraulic pump, and a large diameter piston that operates in conjunction with the large diameter piston. first and second fuel compression devices comprising small-diameter pistons that compress previously supplied fuel when the first and second fuel compression devices receive fuel pressure, and each compressed fuel from the first and second fuel compression devices is delivered to the fuel nozzle. 1. A fuel injection device comprising: a passage means for controlling the fuel pressure supplied from the hydraulic pump to the first and second fuel compression devices; and a control means for independently adjusting the pressure of fuel supplied from the hydraulic pump to the first and second fuel compression devices.