JPS59103960A - Fuel injection controller - Google Patents

Abstract

PURPOSE:To reduce the size and the manufacturing cost of a valve device, by a method wherein, in a unit injector, a difference pressure between sections before and behind an orifice is produced by causing a part of high pressure fuel to flow, and the differential pressure produces a driving force to effect the opening motion of a weighing valve. CONSTITUTION:The high pressure fuel in a pressure chamber 26 is transferred to a needle chamber 27D through a fuel passage 29, and when the pressure exceeds the energizing force of a spring 27B, a needle valve 27C is energized upward to open a nozzle 27E, and the fuel in the pressure chamber 26 is injected through the nozzle 27E. A weighing valve 35 and an electromagnetic valve 36, serving as a valve device and located subsequent to the weighing valve, are situated on a fuel feed passage 28 communicated with the pressure chamber 26. The fuel feed passage 28 is communicated with a fuel passage 29 also, and since the high pressure fuel in the pressure chamber 26 is kept from flowing through the weighing valve 35 with the electromagnetic valve 36 closed, the high pressure fuel to a nozzle 27. With the electromagnetic valve 36 opened, a differential pressure between parts located before and behind an orifice 35E opens the weighing valve 35.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control device for a unit injector used in a diesel engine.

A diesel engine typically includes an injection pump that increases the pressure of fuel to perform fuel injection, a fuel injection pipe that supplies the fuel pumped from the injection pump to a nozzle, and a nozzle that injects the high-pressure fuel. However, there is a unit injector that integrates these, and a fuel injection device in which this unit injector is disposed in each cylinder is proposed, for example, in 5AEpaper No. 750773.

Figures 1 and 2 show an example of a unit injector like Jin.
As shown in the figure, the unit injector 1 injects fuel into a pressure chamber 6 by moving a plunger 5 up and down in the figure through a bushing rod 3 and a rocker arm 4, which is driven by a camshaft 2 that rotates in synchronization with the rotation of the engine. increase the pressure of
This high-pressure fuel is introduced into the needle chamber 8 of the nozzle 7, and the needle valve 9 is lifted up against the valve spring 10.
Fuel is injected through the nozzle hole 12 of the spray tip 11.

In this case, the fuel injection amount is controlled by the controller 13.
(The control rack 13 is interlocked with the governor) to rotate the plunger 5 about its axis via the plunger bushing 14.

This is done according to the following. That is, when the plunger 5 descends, the metering recess 15, which is a spiral groove,
By changing the timing at which the upper part of the metering recess 15 communicates with the upper port 16 of the bushing 14 and the lower part of the metering recess 15 with the lower port 17, the injection start and end timings within the pressure chamber 6 are changed. Quantity is controlled.

However, in such a conventional unit injector, the injection amount is controlled by a so-called mechanical method (the control rack 13 rotates the sibling plunger 5).
The injection amount determined by step 3 or the injection amount determined by a mechanical injection timing adjustment device, etc. is changed so that it changes approximately linearly or in a gentle curve (due to the shape of the metering recess 15, etc.). It is only possible.

Therefore, engine operating conditions (rotation speed, output, water temperature, etc.)
There was a problem in that it was not possible to obtain the optimum injection amount in response to changes in the amount of fuel. .

Therefore, it is important to control this injection amount electrically, and to always match it appropriately for fuel consumption, exhaust, noise, output, etc., depending on the characteristics of the engine and vehicle, as well as its operating conditions. The one aimed at is JP-A-54-507.
The unit injector is proposed in Japanese Patent No. 26.

However, in such conventional unit injectors, the solenoid valve directly controls the supply of high-pressure fuel to the injection nozzle (directly controls the injection pressure). If the pressure is 1,000 atm and this pressure acts on the tip of the seat of the valve body of a solenoid valve, a force of about 8 kg/crl is required to open the valve, even if the seat area is as small as 1 mm in diameter. do. - Regarding the response speed of this solenoid valve, when applied to a small high-speed diesel engine, for example, C600rep,
For m, the maximum crank angle is 40' to 45 degrees before TDC.
It is required that fuel be injected during a period of approximately 1-6 mqec, which is extremely short, and furthermore, during low-load operation, this injection period is approximately 0.4 mqec.
Injection must be completed in an even shorter time, m5ec.

Even if it were possible to obtain a solenoid valve having such a high opening force and fast response speed, it would be expensive. Therefore, such a solenoid valve has a problem in that it can only be applied to large diesel engines that are slow and expensive.

Therefore, Japanese Patent Application No. 57-67980 proposes a device in which a valve for measuring the amount of fuel injection is provided separately, and this metering valve is controlled by opening and closing of a solenoid valve.

In this plan, when the solenoid valve opens, the fuel pressure operates the piston, which drives the metering valve to release the fuel pressure in the pressure chamber, and the supply pressure from the fuel supply pump is applied to the piston. , a certain amount of supply pressure (
For example, 5 to several lOKg/cd) is required. Furthermore, in order to improve control characteristics, it is necessary to make the metering valve larger, which in turn requires a larger piston. For this reason, it was still not sufficient to downsize pistons and poppet valves.

The present invention further improves this idea by providing a cam that rotates in synchronization with the engine, a pressure chamber that is supplied with fuel to a fuel supply pump through multiple fuel supply passages, and a pressure chamber that responds to the cam. a nozzle that communicates with the pressure chamber and opens at a pressure equal to or higher than the valve opening pressure; a metering valve that is interposed in a fuel supply passage that communicates with the pressure chamber and releases high-pressure fuel when the valve is opened; A unit injector comprising a pressure passage that guides a portion of the high-pressure fuel from the pressure chamber to the back of the valve body, and a valve device that is interposed in the fuel supply passage after the metering valve and releases pressure from the back of the valve body when the valve is opened. By providing a control means for opening and closing the valve device based on a signal from a means for detecting the operating state of the engine, a portion of the high-pressure fuel is caused to flow and a differential pressure is generated between the front and rear to open and close the metering valve. The metering valve is closed by the driving force generated by the difference in seat diameter at the tip of the valve body, and the valve device is used to release the pressure in the air ring chamber at the back of the valve body of the metering valve. An object of the present invention is to provide a fuel injection control device that reduces the size of a valve device.

The present invention will be explained below based on illustrated embodiments.

FIG. 3 is a schematic configuration diagram of an embodiment of the present invention. In the figure, a cylinder 2 bored in a unit injector 200
A plunger 23 is slidably fitted into the plunger 2, and the plunger 23 is urged upward in the figure by a spring 24 interposed between the head of the plunger 23 and the main body 21. When the head comes into contact with a cam 25 that rotates in synchronization with the engine, the sylanger 23 is pushed down every time the cam rotates 25°, pressurizing the fuel in the pressure chamber 26.

The pressure chamber 26 is connected to a fuel supply passage 2 that communicates with a fuel tank 39.
8, a fuel supply bond 37 which is interposed in the fuel supply passage 28 and rotates in synchronization with the engine is connected to the fuel tank 39.
The fuel inside is supplied to the pressure chamber 26.

A nozzle 27 is formed in the lower part of the main body 21 for injecting high-pressure fuel pressurized in a pressure chamber 26 into a combustion chamber (not shown).

Specifically, the nozzle 27 has a needle chamber 27D, a needle chamber 27D, which communicates with the pressure chamber 26 through a fuel passage 29.
C, a spring 27B, a nozzle hole 27E, and a spring chamber 27A. Normally, the spring 27B urges the needle valve 27C downward to close the nozzle hole 27E, but the high-pressure fuel in the pressure chamber 26 flows through the fuel passage. 29 to the needle chamber 27D, and when this pressure overcomes the biasing force of the spring 27B (the valve opening pressure of the nozzle 27),
The needle valve 27C is urged upward to open the nozzle hole 27E, and the fuel in the pressure chamber 26 is injected from the nozzle hole 27F.

A metering valve 35 is provided in the fuel supply passage 28 communicating with the pressure chamber 26.
And after that (on the right side in the figure) there is a solenoid valve 36 as a valve device.
is interposed. This fuel supply passage 28 also communicates with a fuel passage 29, and when the solenoid valve 36 closes, the high-pressure fuel in the pressure chamber 26 cannot escape via the metering valve 35, so the high-pressure fuel is supplied to the nozzle 27. In other words, the metering valve 35 has a spring chamber 35B on the back of the valve body 35A.
The valve body 35A is biased to the left in the figure by a spring 35C provided in the spring chamber 35B. Furthermore, a pressure passage 35D is formed in the valve body 35A to guide high-pressure fuel from the pressure chamber 26 to the spring chamber 35B, and an orifice 35E for pressure adjustment is formed on the pressure chamber 26 side of this passage 35D. .

Therefore, if the solenoid valve 36 opens, the pressure chamber 26
A portion of the high-pressure fuel from the metering valve 35 passes through the pressure passage 35D,
It escapes from the spring chamber 35B to the fuel supply passage 28 via the solenoid valve 36. At this time, a pressure difference between the front and rear of the orifice 35E is generated by the orifice 35E for pressure adjustment (the pressure on the spring chamber 35B side after the orifice 35E is also lower than the pressure on the pressure chamber 26 side in front of the orifice 35E), and this front and rear difference A large driving force is generated by the pressure, and this driving force quickly moves the valve body 35A to the right in the figure against the spring 35C to open the metering valve. Here, the biasing force of the spring 35C is determined so as not to impair the driving force due to the differential pressure between the front and rear. When the metering valve 35 opens, the high-pressure fuel flows through the fuel relief passage 3
The fuel pressure reaching the nozzle 27 is lowered below the valve opening pressure, and fuel injection is cut off.

When the solenoid valve 36 closes, the differential pressure across the orifice disappears, but the high-pressure fuel in the pressure chamber 26 is guided into the spring chamber 35C, and this fuel pressure acts as back pressure on the valve body 35A, creating a large driving force. (Actually, a force generated due to the difference in seat diameter at the tip of the valve body 35A) is generated, and the driving force due to this fuel pressure and the biasing force of the spring 35C cause the valve body 35A to
to the left in the figure and close the metering valve 35.

The above-mentioned solenoid valve 36 has a valve chamber 36A and a valve body 36B.

When the solenoid 36C is energized by a signal from the control circuit 40, the valve body 36B
The control circuit 40 closes the valve chamber 36A and opens the valve when the energization is removed to release the pressure in the spring chamber 35B to the fuel supply passage 28. For example, a rotation speed sensor 4 that detects the engine rotation speed
1. Accelerator sensor 4 that detects the pedal angle of 7 degrees
2. Based on the detection signals from the water temperature sensor 43 that detects the engine cooling water temperature, the crank angle sensor that detects the crank angle, etc.), a signal having a drive pulse width that is optimal for the engine operating conditions is output to the solenoid 36C. , controls the opening and closing of the solenoid valve 36.

An annular groove 32 formed in the upper part of the cylinder 22 communicates with a fuel tank 39 via a fuel return passage 33, and also communicates with a metering valve 35 via a fuel relief passage 31, and a fuel relief passage that branches from the fuel relief passage 31. They communicate with the spring chamber 27A via the spring chamber 31A, respectively, and return excess fuel to the fuel tank 39.

Further, a pressure regulating valve 38 interposed in a passage that communicates the fuel supply passage 28 and the fuel return passage 33 is connected to the fuel supply passage 28.
The fuel pressure is maintained at a predetermined value, and when the pressure exceeds the predetermined value, the valve is opened to release the fuel to the fuel return passage 33.

The operation of the above configuration will be explained based on FIGS.

The fuel in the fuel tank 39 is pre-pressurized by the fuel supply pump 37, and the fuel is supplied from the fuel supply passage 28 to the solenoid valve 36, which is open.
, is supplied to the pressure chamber 26 via the metering valve 35, and the pressure chamber 26
The pressure is the supply pressure from the fuel supply pump 37 (see FIG. 30).

In addition, as shown in FIG. 4, the fuel supply passage 28 and the pressure chamber 26
If these are directly communicated through a communication passage 45 and a check valve 46 is interposed therebetween, which allows flow to flow from the passage 28 to the pressure chamber 26 side but closes in the opposite direction, the plunger 23 can be drawn in more quickly. The process can be accomplished.

The plunger 23 is driven by a cam 25 that rotates in synchronization with the engine.
() in Fig. 3 indicates the point at which it starts to descend), pressurizes the fuel in the pressure chamber 26, but at this point the solenoid valve 36 is open and a part of the pressurized fuel flows through the orifice 35E.
1 pressure passage 35D1 spring chamber 35B to solenoid valve 36
It escapes to the fuel supply passage 28 through the valve chamber 36A. Therefore, a differential pressure is generated across the orifice 35E, and the driving force due to this differential pressure drives the valve body 35A to the right in the figure against the spring 35C, thereby opening the metering valve 35. When the metering valve 35 opens, the pressurized fuel escapes to the fuel relief passage 31.
The nozzle 27 does not exceed the valve opening pressure and no fuel is injected.

When the syringer 23 further descends and the solenoid 360 is energized at a predetermined crank angle to close the electromagnetic valve 36, there is no place for the fuel in the spring chamber 35B to escape, so the fuel pressure in the spring chamber 35B increases and the orifice 35E
The differential pressure between the front and rear is eliminated. In a state where this differential pressure between the front and rear is eliminated, high-pressure fuel acts as back pressure on the valve body 35A, and a large driving force generated due to the difference in seat diameter at the tip of the valve body 35A moves the valve body 35A along with the spring 35C to the left in the figure. After the electromagnetic valve 36 is closed for a predetermined period of time, the metering valve 35 is energized.
Close.

For this reason, the fuel in the pressure chamber 26 is confined, increases in pressure as the plunger 23 descends, and this high-pressure fuel is transmitted to the needle chamber 27D of the nozzle 27 via the fuel passage 29. When the pressure in the needle chamber 27D exceeds the biasing force of the spring 27B (the opening pressure of the nozzle 27) that biases the needle valve 27C downward, the needle valve 27C is pushed upward to open the nozzle hole 27E, and the pressure chamber 26 is High-pressure fuel is injected into a combustion chamber (not shown) (see FIG. 3 (Q)).

When the plunger 23 further descends, the energization to the solenoid 36C is stopped at a predetermined crank angle, and the solenoid valve 36 is opened, a portion of the high pressure fuel in the pressure chamber 26 passes through the orifice 35E and the pressure passage 35D as described above. This escape creates a pressure difference between the front and back of the georifice 35E, and this pressure difference causes a large driving force to quickly drive the metering valve 35 open against the spring 35C, allowing most of the high-pressure fuel to escape into the fuel relief passage 31. , the pressure in the fuel passage 29 quickly decreases to below the opening pressure of the nozzle 27, and fuel injection is stopped (see FIG. 3, 0).

When the plunger 23 starts to rise again after reaching the lowest point, the pressure in the pressure chamber 26 decreases, so the metering valve 35 closes again, but the solenoid valve 36 is open, and from the solenoid valve 36 to the spring chamber 35B, the pressure passage Fuel is supplied to the pressure chamber 26 through the orifice 35D and the orifice 35E (see FIG. 30).

That is, fuel injection is performed from a predetermined time after the solenoid valve 36 is closed to when the solenoid valve 36 is opened.

Therefore, by changing the timing and duration of energization of the solenoid 36C that opens and closes the electromagnetic valve 36 according to the operating conditions, the timing and amount of fuel injected from the nozzle 27 can be controlled.

The opening/closing drive of the metering valve 35, which directly controls the supply of high-pressure fuel, is driven by the driving force generated by the differential pressure across the orifice.
The solenoid valve 3 is closed by the driving force due to the difference in seat diameter at the tip of the valve body 35A using back pressure from the high-pressure fuel led to the spring chamber 35B and the biasing force of the spring 35C.
6, it is sufficient to release or confine the pressure in the spring chamber 35B and no large driving force is required.

Therefore, unlike JP-A-54-50726, in which a solenoid valve is used as a metering valve and requires a high opening force and fast response speed to directly control high-pressure fuel, the solenoid valve 36 is small and inexpensive. Anything is fine.

Also, the fuel supply pump has a certain amount of power (e.g. 5 to 101').
Unlike Japanese Patent Application No. 57-67980, which requires a supply pressure of fI/cJ) and requires a piston to drive the metering valve, the fuel supply pump 37 can be a low-pressure, inexpensive one, and a piston is not required. Easy to configure.

As described above, according to the present invention, a pressure difference is created between the front and rear by flowing a portion of the high-pressure fuel, and the driving force generated by this pressure difference is used to open the metering valve, and the back pressure caused by the high-pressure fuel is also reduced. The metering valve is closed using the driving force generated by the difference in seat diameter at the tip of the valve body and the biasing force of the spring, and the valve device is used to release the pressure in the spring chamber at the back of the valve body. The device may be small and inexpensive, and at the same time, the fuel supply pump may be low-pressure and inexpensive, resulting in the effect of reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a conventional device, Fig. 2 is a sectional view of the main part of Fig. 1, and Fig. 3 is a schematic configuration diagram of an embodiment of the present invention. FIG. 4 is a schematic diagram of another embodiment of the present invention. 20... Unit injector, 23... Silant gloss, 25... Cam, 26... Pressure chamber, 27... Nozzle, 28... Fuel supply passage, 35... Metering valve, 3
5A... Valve body, 35B... Spring chamber, 35D.
...Pressure passage, 35E... Orifice, 36... Solenoid valve, 37... Fuel supply pump, 40... Control circuit. Patent applicant: Nissan Motor Co., Ltd. Figure 2 Figure 3 (A) Figure 3 (B) Figure 3 (C) Figure 3 (E) 3ff 4 Figure 1θ

Claims (1)

[Claims] A cam that rotates in synchronization with the engine, a pressure chamber to which fuel is supplied by a fuel supply pump via a fuel supply passage, and a sylanger that pressurizes fuel in the pressure chamber in response to the cam.
a nozzle that communicates with the pressure chamber and opens at a pressure equal to or higher than the valve opening pressure; a metering valve that is interposed in a fuel supply passage that communicates with the pressure chamber and releases high-pressure fuel when the valve opens; and a metering valve that releases a portion of the high-pressure fuel from the pressure chamber. 1. A fuel injection control device comprising: a body back device; and a control device that opens and closes the valve device based on a signal from a device that detects the operating state of the engine.