JPH0454273A - Pressure storage type unit injector - Google Patents

Abstract

PURPOSE:To set freely an injection quantity with an appropriate super high pressure being maintained and arrange so that a super high pressure injection may be conducted from a low load to a high load, by providing the 2nd pressure storage chamber at the main body outside communicating with a main body pressure storage chamber, and providing a structure according a variable volume of the pressure storage chamber. CONSTITUTION:As for fuel which is supplied under a predetermined pressure by means of a feed pump 4 through a fuel inlet 6, one part of it is supplied to a pressurizing chamber (a measuring chamber) 3 through a fuel passage 7 and a check valve 7a, and the other part of it is supplied to a pressure increase chamber 9 through a flow passage 8 and a solenoid valve 20. When the chamber 9 and a fuel outlet 10 are connected by the closing operation of the valve 20, a needle 17 ascend, and fuel within a pressure storage chamber 13 is injected through the tip of a nozzle 5. In this instance, the 2nd pressure storage chamber 40 is connected to the main body chamber 13, and division is made by means of the cylinder 38b of an adapter 38 and the piston portion 39 of a piston 39. The 2nd chamber 40 volume and the whole pressure storage chamber volume including that of the chamber 13, are set freely by rotating and reciprocating the piston 39.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an accumulator unit injector used in a diesel engine.

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

Examples of such conventional unit injectors include those shown in FIG. 4 and FIG.
433). 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 solenoid valve 20
is the pressure booster chamber 9 and the fuel population 6 due to its opening operation (in the direction of arrow A).
Either the intensifying chamber and the fuel outlet 10 are in communication with each other in a closed operation. When the pressure increase chamber 9 and the fuel outlet 10 are communicated with each other by the electromagnetic valve 20, the communication between the flow path 8 and the pressure increase chamber 9 is closed, and the fuel passes through the fuel passage 7 and is filled into the pressure chamber 3. Next, when the electromagnetic valve 20 is actuated in the direction of arrow A to communicate the fuel population 6 and the pressure boosting chamber 9, the fuel is guided to the pressure boosting chamber 9. At this time, the pressure booster piston 12 is pushed down by the fuel pressure,
The pressure of the fuel supplied to the pressurizing chamber 3 is increased by the area of the pressure increasing piston 12 and the pressure receiving part of the plunger 1, pushing down the accumulator valve 18, and increasing the pressure of the fuel supplied to the pressure accumulating chamber 13 provided in the main body 2.
The amount of fuel compressed by the bulk elasticity of the fuel is pumped to the side. When the forces of the fuel in the pressure storage chamber 13 and the pressure chamber 3 are balanced, the spring 14 causes the accumulator valve 1 to
8 is closed, 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 spring 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, by closing the electromagnetic valve 20 and communicating the pressure intensifying chamber 9 and the fuel outlet 10, when the pressure in the pressurizing chamber 3 decreases, the pressure in the accumulating chamber 13 causes the needle 17 having the flange 16 to open. The force trying to open the valve part 17',
This exceeds the force of the spring 14 and the lowered pressure inside the pressurizing chamber 3 to close the valve portion 17' of the needle 17, so the needle 17 rises and the fuel inside the pressure accumulating chamber 13 flows into the nozzle 5.
Spray from the tip.

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

In addition, in Fig. 4, 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, 5a in FIG. 4 is a guide for the needle 17, which guides the needle 17 on the inner periphery and positions it with the main body on the outer periphery.
The three-sided width portion formed on the outer periphery forms an oil passage (see Fig. 5).

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

v.

Q+ -(P, , -P, c) -(+> That is, the fuel injection amount is determined by the volume within 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 accumulation chamber is constant, the injection amount cannot be changed arbitrarily, resulting in a lack of convenience. In other words, in equation (1) above, since the valve closing pressures P, c are mainly determined by the force of the needle closing spring 14, the injection amount Q, is determined only by the injection pressures P, R, x. Conventionally, for this reason, for example, when the injection amount Q is small and the injection pressure P1.8 is desired to be reduced, it is necessary to reduce the injection pressure P1.8, which results in deterioration of combustion efficiency, etc. Conventionally, when the injection pressure is maintained at a moderately high pressure, the fuel injection amount is Q.

However, there was a problem in that it was not possible to change the injection amount, making it impossible to perform ultra-high pressure injection with a small amount of injection.

The present invention addresses these conventional problems by focusing on providing a second pressure accumulation chamber and changing the volume of the pressure accumulation chamber. There are some types that have a second pressure accumulation chamber to change the pressure.

That is, these are JP-A-61-185-9, JP-A-61
-182456 and Japanese Unexamined Patent Publication No. 61-182457.

However, in all of these conventional methods 1, the volume change of the pressure accumulator is carried out in response to the injection pressure, so it is impossible to achieve ultra-high pressure injection under any injection amount, especially at a small injection amount. , which is different from that of this invention.

In view of such conventional examples, the present invention provides a pressure accumulating type that can set or vary the injection quantity to an arbitrary amount under high-pressure injection in order to make the capacity variable in response to the injection quantity using a second pressure accumulation chamber. The present invention aims to solve the above problems by providing a unit injector.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the first invention has the following features:
A piston and a plunger are provided in the injector body, and when a solenoid valve is opened, fuel supply pressure is applied to the upper surface of the piston, and the piston and plunger are moved to pressurize the fuel to be supplied to a pressurizing chamber, and a valve is placed in the pressurizing chamber. High-pressure fuel is sent to a pressure accumulator chamber communicated through the device to accumulate pressure, and the pressure on the top surface of the piston is reduced by the closing operation of a solenoid valve, so that the fuel in the pressure accumulator chamber is injected from the tip valve part by the pressure in the pressure accumulator chamber. In the pressure accumulating unit injector, a second pressure accumulating chamber communicating with the pressure accumulating chamber is provided in the main body to make the pressure accumulating chamber volume variable. Further, in a second aspect of the invention, the volume of the second pressure accumulating chamber is increased as the injection amount increases.

(Function) For example, when the volume of the second pressure accumulation chamber is reduced, the volume of the entire pressure accumulation chamber is reduced. In this case, the injection pressure remains at an extremely high pressure if the fuel supply pressure and the operating time of the solenoid valve are the same. Therefore, when it is desired to operate the engine mainly at a low load, a small amount of injection corresponding to the load can be injected using ultra-high pressure injection, and the combustion efficiency can be improved.

Furthermore, if the volume of the second pressure accumulation chamber is made variable depending on the injection amount, for example, the load, the volume of the pressure accumulation chamber, that is, the injection amount, will change depending on the load, and at this time, the injection pressure will be maintained at an ultra-high pressure. As a result, efficiency is improved over the entire operating range of the engine.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

First, the configuration will be explained with reference to FIG. 1. Components that are the same as those of the prior art will be designated by the same reference numerals and explanations will be omitted.

In this embodiment, what is added to the conventional one is an adapter 38. This adapter 38 is formed with a male screw 38C, a cylinder 38b, and a female screw 38a. It has been concluded. 39 is a piston, and this piston 39 is formed with a male thread 39a and a piston portion 39b, and is screwed into the female thread portion 38a of the adapter 38. 40 is a second pressure accumulation chamber, and the second pressure accumulation chamber 40 communicates with the pressure accumulation chamber 13 of the main body, and is partitioned by the cylinder 38b of the adapter 38 and the piston portion 39b of the piston 39. The second pressure accumulation chamber 40 rotates the piston 39,
The structure is such that the capacity changes by moving it back and forth.

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

By rotating the piston 39 and moving it back and forth, the volume of the second pressure accumulation chamber 40 changes, and by communicating with the pressure accumulation chamber 13, the volume V at of the entire pressure accumulation chamber can be arbitrarily set.

FIG. 2 is a diagram showing the relationship between the injection amount, the injection pressure, and the internal volume of the pressure accumulation chamber. For example, when setting the optimum ultra-high injection pressure P1.8, the pressure accumulation chamber internal volume V me is changed from v, l to vl,
Cell things changed up to (V,, > V,, -> V, 1)
Accordingly, the injection amount can be arbitrarily set from Ql to Q5. As a result, the fuel injection amount Q can be reduced while maintaining the injection pressure P7.8 at an appropriate ultra-high pressure, and ultra-high pressure injection can be performed under low load, thereby improving combustion efficiency.

FIG. 3 shows an example.

In this embodiment, a hole 41b and a spline 41a are formed inside the piston 41 attached to the inside of the adapter 38 of the previous embodiment, and the shaft 44a of the step motor 44 is connected to the spline 41a.
1a and the key 42 are inserted into the hole 41b so as to match, and a step motor 44 is fixed to the adapter 38 with screws 43.

Here, due to the rotation of the step motor 44, the piston 41, which is integral with the shaft 44a in the rotational direction, does not rotate, but moves forward and backward through screw engagement. At this time, the key 42 slides within the keyway of the piston 41.

A tachometer 48 and a torque sensor 49 are attached to a crankshaft 50 of the engine, and are connected to a microcomputer 47. A pressure sensor 52 is attached to the fuel port 6 and connected to the microcomputer 47.

The microcomputer 47 is connected to the step motor 44 and the solenoid valve 20 via amplifiers 45 and 46, and further connected to the motor 54 of the feed pump 4 via an amplifier 55.

Next, the operation of this embodiment will be explained.

The microcomputer 47 receives signals from the tachometer 48, torque sensor 49, pressure sensor 52, and accelerator amount 53, and the microcomputer 47 adjusts the injection amount Q, while maintaining the optimum injection pressure P1.8 as shown in FIG. 2, for example. , depending on the rotational torque load,
In order to change Q1 to Q5, the internal volume of the pressure accumulation chamber v, c is changed to v,
A signal for changing the voltage from 1 to v is given to the step motor 44. At the same time, the voltage of the motor 54 that drives the feed pump 4 is changed depending on the rotation and torque load to control the optimum injection pressure.

Thus, in this embodiment, in the entire engine operating range,
It automatically changes the injection amount and enables ultra-high pressure injection.

[Effects of the Invention] As described above, according to the present invention, the second pressure accumulation chamber is provided outside the main body communicating with the pressure accumulation chamber of the main body, and the capacity of the pressure accumulation chamber can be made variable. Therefore, the injection amount can be set arbitrarily while maintaining a moderate ultra-high pressure.
The effect is that ultra-high pressure injection can be performed from low to high loads.

Further, according to the second aspect of the invention, it is possible to automatically set the optimal ultra-high pressure and the internal volume of the pressure accumulator chamber for producing the required fuel injection amount.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, Fig. 2 is a performance curve graph showing the relationship between injection pressure and injection amount due to changes in the pressure accumulation chamber volume, and Fig. 3 is an overall diagram of another embodiment. A cross-sectional view showing the configuration, Fig. 4 is a cross-sectional view of the conventional one, and Fig. 5 is a cross-sectional view of the conventional one.
It is a v-■ sectional view of the figure. 1... Plunger 2... Main body 3... Pressurizing chamber (metering chamber) 4... Feed pump 5... Nozzle 6... Fuel population 9... Pressure boosting chamber 12... Increase Pressure piston 13...Accumulation chamber 18...Accumulator valve 20...Solenoid valve 21...Fuel tank 38
...Adapter 39...Piston 40...
Second pressure accumulator

Claims (2)

[Claims] (1) A piston and a plunger are provided in the injector body, and when a solenoid valve is opened, fuel supply pressure is applied to the upper surface of the piston, and the piston and plunger are moved to pressurize the fuel supplied to the pressurizing chamber. High-pressure fuel is sent to a pressure accumulator connected through a valve device to accumulate pressure, and the pressure on the top surface of the piston is reduced by the closing operation of a solenoid valve, so that the fuel in the pressure accumulator is injected from the tip valve part by the pressure in the pressure accumulator. A pressure accumulation type unit injector characterized in that a second pressure accumulation chamber communicating with the pressure accumulation chamber is provided in the main body, and the volume of the pressure accumulation chamber is made variable. (2) The pressure accumulation type unit injector according to claim 1, wherein the volume of the second pressure accumulation chamber is increased as the injection amount increases.