JPH04191459A - Accumulating type unit injector - Google Patents

Abstract

PURPOSE:To secure the minimum fuel injection quantity under the super high pressure, and maintain the injection pressure at the super high pressure and while change the injection quantity from idle to full open. CONSTITUTION:The fuel inside of a pressure chamber 3, which is pressurized to the super high pressure by a pressure increase piston 12 and a plunger 1, pushes an accumulator valve 18b down, and starts to flow into a first accumulator chamber 13a and a second accumulator chamber 13b through a flow passage 18c, and the pressure of the first accumulator chamber 13a and the second accumulator chamber 13b rises to the super high pressure simultaneously. Under this condition, when the injection signal is input to a solenoid valve 20 and a pressure increase chamber 9 is communicated with an outlet 10, the force of the plunger 1 is reduced to lower the pressure of the pressure chamber 3. Then, the fuel in the first accumulator chamber 13a flows to the pressure chamber 3 through a check valve 19. A needle valve (needle) 17 is pushed up by the super high pressure fuel of the second accumulator chamber 13b, and the super high pressure fuel of the second accumulator chamber 13 is injected from an injection port of the tip 17'.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) This invention relates to a pressure accumulating unit injector used in a diesel engine.

(Prior Art) Conventionally, an accumulator unit injector has been proposed as an injector for a diesel engine, which is equipped with a piston and a plunger and eliminates the need for a high-pressure pump and piping.

An example of such a conventional uni-soto injector is the one shown in FIG. 6 (see Japanese Patent Application No. 1-3713 and Japanese Patent Application Laid-Open No. 59-85433 filed by the present applicant). This will now be explained using the former. Part of the fuel supplied at a predetermined pressure by the feed pump 4 is supplied from the fuel population 6 to the pressurizing chamber (measuring chamber) 3 through the fuel passage 7 and the check valve 7a, and the other part passes through the flow passage 8. , is supplied to the pressure increase chamber 9 via the solenoid valve 20. The electromagnetic valve 20 communicates between the pressure intensifying chamber 9 and the fuel outlet 6 when it is opened (in the direction of arrow A), or communicates between the pressure intensifying chamber 9 and the fuel outlet 10 when it is closed.
is in communication with or is performing one of the following operations. When the solenoid valve 20 connects the pressure increase chamber 9 and the fuel outlet 10, communication between the flow path 8 and the pressure increase chamber 9 is closed, and fuel passes through the fuel passage 7 and fills the pressure chamber 3. Next, the solenoid valve 20
When the fuel population 6 and the pressure intensification chamber 9 are communicated, the fuel is guided to the pressure intensification chamber 9. At this time, the pressure booster piston 12 is pushed down by the fuel pressure, and the pressure of the fuel supplied to the pressure chamber 3 is increased by the area of the pressure booster piston 12 and the pressure receiving part of the plunger 1, pushing down the accumulator valve 18. The amount of fuel compressed by the bulk elasticity of the fuel is pumped to the pressure storage chamber 13 provided in the main body 2. When the forces of the fuel in the pressure accumulation chamber 13 and the pressure chamber 3 are balanced, the needle spring 14 closes the accumulator valve 18, and the pressure accumulation chamber 13 is sealed.

When the solenoid valve 20 is operated to communicate the pressure increase chamber 9 and the fuel outlet 10, the pressure in the pressure increase chamber 9 is released to atmospheric pressure, and the piston 12 is pushed by the bar 15 and rises. At the same time, the pressure in the pressurizing chamber 3 also decreases to the pressure supplied by the feed pump 4. In this way, when the solenoid valve 20 closes, the pressure increase chambers 9 and 1
0, when the pressure in the pressurizing chamber 3 decreases, the pressure in the accumulating chamber 13 causes a force to try to open the valve portion 17' of the needle 17 having the flange (shim) 16.
This exceeds the force of the spring 14 and the lowered pressure inside the pressurizing chamber 3 that tries to close the tip valve part (injection mechanism) 17' of the needle 17, so the needle 17 rises and the fuel inside the pressure accumulating chamber 13 flows into the nozzle. Spray from the tip of 5.

At the same time as the injection begins, the pressure in the pressure storage chamber 13 begins to decrease, and all of the compressed fuel due to the bulk elasticity of the fuel is injected, the needle 17 closes, and the injection ends. After that, repeat this operation. Thus, by said operation, the conventional unit injector enables ultra-high pressure injection, thereby atomizing the fuel and shortening the fuel injection period,
The aim is to improve diesel combustion, improve exhaust performance, and improve fuel efficiency.

In addition, in Fig. 6, 21 is a fuel tank, 22 is a pressure gauge, and 23 is a fuel tank.
is an accumulator, and 24 is a valve.

In addition, the fuel injection amount Q mentioned above is the pressure accumulation chamber internal volume va
c, the pressurization start pressure (valve closing pressure) P in the pressure accumulator chamber, 1, the pressurization end pressure (injection pressure) P, 8, and the bulk modulus can be expressed simply as follows.

Q+ = (P---P, t)...(1
) That is, the fuel injection amount is determined by the internal volume of the pressure accumulator and the pressure difference within the pressure accumulator.

(Problem to be Solved by the Invention) However, in such a conventional pressure accumulator unit injector, since the internal volume of the pressure accumulator chamber is constant, there is a problem that the injection amount cannot be changed arbitrarily, making it lacking in convenience. there were. That is, in the above-mentioned equation (1), since the valve closing pressures P and c are mainly determined by the force of the needle closing spring 14, the injection amount Q ends up being equal to the injection pressure P7. ! It is determined only by Conventionally, for this reason, for example, when it is desired to reduce the injection amount Q, the injection pressure P east must necessarily be reduced, resulting in deterioration of combustion efficiency and the like. For this reason, in the past, there was a problem in that the fuel injection JIQ could not be changed while the injection pressure was maintained at an appropriate ultra-high pressure, and ultra-high pressure injection with a small injection amount could not be performed.

In other words, conventionally, the pressure accumulation chamber 13 has a structure in which the needle spring 14 is housed inside, so the internal volume cannot be set to be as small as desired, and the structure inevitably occupies a certain volume. Since the pressure-accumulated fuel is injected from a chamber of a certain size, it becomes difficult to maintain the injection amount from the minimum to maximum injection amount while maintaining the predetermined injection pressure. There was a problem.

This invention was made by focusing on these conventional problems, and by configuring the pressure accumulation chamber volume for fuel injection to be separated from the conventional pressure accumulation chamber, it is possible to minimize the amount of fuel injection under ultra-high pressure. The aim is to ensure that the above-mentioned problems are solved.

[Structure of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention provides a pressure booster piston, a plunger, a pressurization chamber, and an accumulator valve, and utilizes fuel supply pressure to increase the pressure inside the pressure accumulation chamber. In an accumulator unit injector that pressurizes fuel at ultra-high pressure, elastically deforms the fuel in the accumulator chamber, and injects the elastically deformed amount of fuel, the needle is attached in the valve-closing direction. A needle spring is provided in a first pressure accumulating chamber, and the first pressure accumulating chamber is connected to an accumulator and a passage having a check valve that allows fuel to flow from the first pressure accumulating chamber side to the pressurizing chamber but not vice versa. A second pressure accumulation chamber is configured to communicate with the pressurizing chamber via the passage of the valve and has a variable capacity setting mechanism and a needle tip injection mechanism therein, and the second pressure accumulation chamber is connected to the accumulator valve. The pressurizing chamber and the first pressure accumulating chamber are communicated only through the passage, and the pressure accumulating fuel in the second pressure accumulating chamber is injected.

(Function) The first pressure accumulation chamber does not take any part in adjusting the injection amount, but only serves the function of storing the spring that presses the needle. Therefore, if the design of this spring is adjusted as desired, the fuel pressure accumulation can be made to an ultra-high pressure. can. Since the second pressure accumulation chamber communicates with the first pressure accumulation chamber through a passage having a check valve and a passage of an accumulator valve, it also holds pressure accumulation fuel at an extremely high pressure. Since the second pressure accumulating chamber does not have a built-in spring, it can be set as small as desired. Therefore, the amount of fuel injected from the second pressure accumulator can be maintained from the maximum to the minimum injection amount while maintaining the injection pressure at the maximum.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is an overall sectional view showing one embodiment of the present invention.

First, to explain the configuration, 13a is a first pressure accumulation chamber,
This first pressure accumulation chamber 13a is a chamber that can be sealed by the needle holder portion 23, the check valve 19, and the accumulator valve 18b.

Further, the first pressure accumulating chamber 13a can communicate with the pressurizing chamber 3 via the check valve 19 or the flow path 18c (see FIG. 2) of the accumulator valve 18b. The check valve 19 has a structure that opens in the direction in which fuel flows out from the first pressure accumulation chamber 13a, but prevents it from flowing in the opposite direction. 13b is a second pressure accumulation chamber, and this second pressure accumulation chamber 13b is a chamber that can be sealed by an injection mechanism, that is, a needle tip 17' having an injection port, an accumulator valve 18b, and a piston 30. 2a is a cylinder formed in the main body 2, and a piston 30 is screwed into the cylinder 2a. That is, by rotating the knob 25 fitted into the piston 30, the piston 30 is moved in the direction of the arrow by the threaded portion 2b, and the second pressure accumulation chamber 1 is moved.
It is possible to change the volume of 3b. 18b
is an accumulator valve, and this accumulator valve 18b has a vertical passage 18c that allows communication between the pressurizing chamber 3, the first pressure accumulating chamber 13a, and the second pressure accumulating chamber 13b when the valve 18b is lowered. A flow path 18d is provided in a direction perpendicular to this (see FIG. 2).

Incidentally, the cylinder 2 a s piston 30 and the knob 25 constitute a variable capacity setting mechanism 50 .

The rest of the configuration is the same as the conventional example (FIG. 6), so the explanation will be omitted.

Next, the operation of the above embodiment will be explained.

The fuel in the pressure chamber 3 pressurized to an extremely high pressure by the pressure booster piston 12 and the plunger 1 pushes down the accumulator valve 18b and begins to flow into the first pressure accumulation chamber 13a and the second pressure accumulation chamber 13b through the flow path 18c. The first pressure accumulation chamber 13a and the second pressure accumulation chamber 13b become extremely high pressure at the same time.

The tip 17' of the needle 17, which closes and seals the nozzle hole during the above process, remains closed due to the pressing force of the needle spring 14.

When the pressures in the pressurizing chamber 3, the first pressure accumulating chamber 13a, and the second pressure accumulating chamber 13b are balanced, the accumulator valve 18b is pushed up by the needle spring 14, and the first pressure accumulating chamber 13 is pushed up.
a, the second pressure accumulation chamber 13b, and the pressurization chamber 3 are each sealed.

In this state, when an injection signal is input to the solenoid valve 20, that is, when the pressure intensifying chamber 9 is communicated with the outlet 10 to lower the pressure to atmospheric pressure, the force of the plunger 1 pressurizing the pressurizing chamber 3 is lost, and the pressure increases. The pressure in pressure chamber 3 begins to drop.

When the pressure in the pressurizing chamber 3 begins to decrease, the fuel in the first pressure accumulating chamber 13a passes through the check valve 19 to the pressurizing chamber 3, and the pressure in the pressurizing chamber 3 decreases to the fuel supply feed pressure. .

In the process of decreasing the pressure in the pressurizing chamber 3, the force pushing up the needle valve 17 due to the ultra-high pressure fuel in the second pressure accumulating chamber 13b is combined with the force pushing down the needle valve 17 due to the fuel pressure in the pressurizing chamber 3. Since the needle spring 14 exceeds the force pushing down the needle valve, the needle valve is pushed up and the second
The ultra-high pressure fuel in the pressure accumulation chamber 13 is injected from the nozzle at the tip 17'.

Simultaneously with the injection, the pressure in the second pressure accumulator 13b begins to decrease,
The needle valve 17 is pushed down and injection ends.

Other operations are the same as before.

Here, the fuel injected according to this embodiment is in the second pressure accumulation chamber 1.
3b is the only fuel, and its minimum setting volume can be made extremely small structurally, and at the same time, it can be made variable. For this reason, the fuel injection amount increases in proportion to the injection pressure, while the pressure accumulation chamber volume is reduced to an extremely small volume V. Since the maximum volume can be varied from the minimum injection amount (when idling) to the maximum injection amount (when fully open) Qm, while maintaining the injection pressure at an ultra-high pressure,
You can freely set up to . Furthermore, since the pressure can be made variable while keeping the injection amount Q constant, the best combustion can be produced under each operating condition.

FIG. 4 is a diagram showing the relationship between injection pressure and injection amount in the conventional example. It can be seen that in this conventional example, the injection amount depends only on the injection pressure, and there is little freedom. On the other hand, FIG. 3 is a diagram showing the injection amount Q and injection pressure P depending on the pressure accumulator volumes v and c of the invention, and the combination of the injection amount and injection pressure is maintained, for example, at the highest injection pressure Pm1. It is possible to change the injection amount from Ql, . . . to Q□8, and the combination can be created completely freely.

FIG. 5 shows another embodiment.

In this embodiment, the piston 3o of the first embodiment is automatically operated using a control unit 40. 21 is a step motor, the shaft 22 of the step motor 21 and the piston 3o are screwed together, the piston 30 and the cylinder 2a are spline connected, and the piston 3o
When the piston 30 rotates, the piston 30 moves.

The control unit 40 receives signals of the ENG rotation speed, torque, and accelerator opening. step motor 2
1. By controlling the feed pressure of the fuel supply source 5o, it is possible to set the optimum fuel injection amount and fuel injection pressure under various driving conditions.

[Effects of the Invention] As explained above, according to the present invention, the structure of the pressure accumulator chamber can be varied from an extremely small volume to an arbitrarily large volume, so that the injection pressure can be maintained at an ultra-high pressure. The effect is that the injection amount can be varied from idle to full throttle.

[Brief explanation of the drawing]

FIG. 1 is an overall sectional view showing an embodiment of the present invention, FIG. 2 is a perspective view showing the main parts of FIG. 1, and FIG. 3 is a performance showing the relationship between injection pressure and injection amount according to the present invention. Curve diagram, Figure 4 is a performance curve diagram showing the relationship between injection pressure and injection amount in the conventional example, and Figure 5 is
The figure is a sectional view showing another embodiment of the present invention, and FIG. 6 is a sectional view of a conventional example. 1... Plunger 2... Main body 2a... Cylinder 3... Pressurizing chamber 12... Pressure increasing piston 13a... First pressure accumulating chamber 13b... Second pressure accumulating chamber 14... Needle Spring 17... Needle (needle valve) 18b... Accumulator valve 18c... Channel 19... Check valve 20... Solenoid valve 23... Needle holder 30... Piston agent Patent attorney Hide Miyoshi Sum injection pressure P Figure 3 Injection pressure P Figure 4

Claims (1)

[Claims] (1) A pressure booster piston, a plunger, a pressurizing chamber, and an accumulator valve are provided, and the fuel is pressurized in the pressure accumulating chamber at an ultra-high pressure using the fuel supply pressure, and the fuel in the accumulating chamber is elastically deformed at the ultra-high pressure. In a pressure accumulator unit injector that injects a deformed amount of fuel, a needle and a needle spring that biases the needle in the valve closing direction are provided in a first pressure accumulation chamber, and the first pressure accumulation chamber is connected to the first pressure accumulation chamber. It is configured to communicate with the pressurizing chamber via the passage of the accumulator valve and a passage having a check valve that allows fuel to flow from the pressure accumulating chamber side to the pressurizing chamber but not vice versa, and has a variable capacity setting. A second pressure accumulation chamber having a mechanism and a needle tip injection mechanism therein is provided, and the second pressure accumulation chamber is configured to communicate with the pressure chamber and the first pressure accumulation chamber only through a passage of the accumulator valve. A pressure accumulation type unit injector, characterized in that the pressure accumulation fuel in the second pressure accumulation chamber is injected.