JPH03260369A - Accumulator fuel injection device - Google Patents

Abstract

PURPOSE:To shorten an injection period so as to improve combustion performance by providing an accumulator chamber, which communicates with a fuel reservoir for receiving a fuel pressure of opening a needle valve, and making it possible to pressurize fuel and to hold an injection pressure at a high value during the injection period while variably changing the volume of the accumulator chamber. CONSTITUTION:A fuel injection nozzle 1, in which a needle valve 2 is open- separated from an injection port 10 by receiving a fuel pressure of the predetermined or more value of a fuel reservoir 3 for containing fuel from a fuel injection pump, is provided, and also an accumulator chamber 15, which accumulates fuel in the fuel reservoir 3, is provided. In the accumulator chamber 15, fuel therein can be pressurized while making the volume of the chamber changeable by a fuel pressurizing device 5. A fuel supply system to this fuel injection device is constituted such that a fuel pressure acts on the needle valve 2 through a passage branched from a passage for supplying fuel to the accumulator chamber 15 from the fuel injection pump, on the other hand, fuel pressure in the fuel reservoir tank acts on a back surface of a plunger 14 of the fuel pressurizing device 5 as the fuel pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an accumulator fuel injection device of variable accumulator volume type used in an engine.

[Conventional technology]

2. Description of the Related Art Conventionally, an accumulator fuel injection device as shown in FIG. 9 has been disclosed for engines. The pressure accumulation type fuel injection device has a nozzle hole 10 for injecting fuel into a combustion chamber, a fuel reservoir 3 communicating with a pressure accumulation chamber 29 through a fuel passage 4, and a needle valve 2 for opening and closing the nozzle hole 10. The pressure accumulation chamber 29 is supplied with fuel from a fuel injection pump, and a check valve is provided to temporarily accumulate fuel pressure in the pressure accumulation chamber 29. Normally, the passage 9 and the pressure accumulation chamber 29 are communicated with each other by a check valve 6. is blocking. In the fuel injection system, fuel pumped by a fuel injection pump driven by the engine opens the check valve 6 and enters the pressure accumulation chamber 29 due to the supply pressure of the fuel.

The needle valve 2 normally closes the nozzle hole 10 by the load F3 of the spring 11 etc. applied to the needle valve 2, but the pressure accumulation chamber 29
When the fuel pressure in the fuel reservoir 3, which communicates with is started. When fuel injection starts,
The internal pressure of the pressure accumulation chamber 29 and the fuel reservoir 3 rapidly decreases, and fuel is injected into the combustion chamber until the load F such as the spring force of the spring 11 overcomes the internal pressure of the fuel reservoir 3.

In the above fuel injection device, FIG. 10 shows the state of the pressure accumulator chamber pressure that changes as the fuel injection time elapses during fuel injection. In FIG. 10, the horizontal axis is the injection time T, and the vertical axis is the pressure P in the accumulator chamber. &1 nit indicates the case of high injection amount, and the line 1 indicates the case of low injection amount.

T indicates the start of fuel injection. When fuel is injected at a high injection amount, a predetermined fuel flow rate is injected at pressure accumulator chamber pressure P, I, but at the end of fuel injection T, ! Therefore, the fuel injection period is
T, t=T++z To, and the nozzle closing pressure when the needle valve 2 is closed is P4. In addition, in the case of a low injection amount, a predetermined fuel flow rate is injected at the accumulator chamber pressure P1, but the end of fuel injection is TLt, and the injection period is Tax=
Ttt To, and the nozzle closing pressure when the needle valve 2 is closed is PC.

As can be seen from the graph above, the pressure accumulation chamber 2 during fuel injection
The pressure drop within the fuel cell 9 is significant, and the injection period is long to inject a predetermined fuel flow rate. Moreover, the closing pressure P of the needle valve 2 is always present in the pressure accumulating chamber 29. Or P, or the pressure is higher than the cough closing valve pressure.

In addition, conventionally, as a fuel injection device, JP-A-53-109
There is one disclosed in Publication No. 021.

The fuel injection device is a so-called unit injector type injection nozzle.

[Problem to be solved by the invention]

Conventionally, in an accumulator-type high-pressure injection nozzle, since the accumulator volume is a constant volume, the difference in the pressure in the accumulator chamber immediately after the start of injection and after the end of injection is a function of the injection amount and the volume of the accumulator chamber.

For example, if the pressure accumulation chamber volume is V, the injection amount is Q, the pressure accumulation chamber pressure immediately before the start of injection is P, the pressure accumulation chamber pressure after -injection is Pz, and the bulk modulus of fuel is E, then Q = (V + VP, / E
)−(V+VPt/E)=V(P+Pg
) /E Now, V = 500 mm3, Q = 40 m
m'P + = 1500 kg/cm", E =
1.54 kg/cm”, P a = 310
kg/cm". Therefore, the injection pressure is about 115 when compared with the pressure immediately after the start of injection.

As the pressure P in the accumulator chamber decreases, the fuel injection speed from the nozzle hole decreases from the beginning to the end of the injection period, and the degree of mixing of fuel and air in the combustion chamber decreases accordingly.

Further, when the pressure accumulation chamber volume is a constant volume, the fuel injection amount is adjusted by changing the pressure P in the pressure accumulation chamber. When the injection amount is small, the initial pressure in the pressure accumulation chamber, that is, the pressure in the pressure accumulation chamber immediately before the start of injection, decreases. In the above example, Q=
1Omm”, Pg = 310 kg/c
m'', then P+ = 610 kg/cm'.

Since the injection start pressure decreases, when Q is small, the fuel injection speed from the nozzle hole decreases, and the degree of mixing of fuel and air in the combustion chamber decreases compared to when Q is large.

As described above, in the case of the conventional pressure accumulation type injection nozzle in which the pressure accumulation chamber has a constant volume, the range in which the optimal mixture of fuel and air within the combustion chamber can be obtained is narrow.

Incidentally, an adiabatic engine in which the cylinder head, cylinder liner, piston head, valve, etc. are made of ceramic material has already been disclosed, but in this adiabatic engine, the temperature at the end of the engine's compression stroke is lower than that of a general engine. Since the temperature becomes extremely high, the time from when the fuel is injected until it ignites, that is, the ignition delay, is significantly shortened.

This results in a reduction in the amount of fuel injected into the combustion chamber before the engine ignition timing, resulting in less premixed combustion immediately after the engine ignition, which has a significant negative impact on engine performance. ing.

Therefore, in an adiabatic engine, in order to shorten the fuel injection period as much as possible and inject a predetermined amount of fuel within that period, it is effective to use a Uni7) injector that is capable of high-pressure injection. Particularly, for an adiabatic engine, an accumulator fuel injection device with a high initial injection rate at the start of injection is most suitable.

Therefore, in order to solve the above-mentioned problems, the present applicant has developed a pressure accumulation type fuel injection device with variable pressure accumulation chamber volume.
The application was filed as No. 281920.

The purpose, structure, and effects of the pressure accumulator fuel injection device are disclosed in detail in the application, so their explanation will be omitted here.

Furthermore, the fuel injection device disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 53-109021 is a so-called unit injector type injection nozzle, and there is no technical idea of accumulating fuel pressure before fuel injection, so the injection rate waveform is Δ Become a type. If the spring force is sufficiently large in the fuel injection device, it becomes possible to accumulate fuel pressure, but if the spring force is increased, the size of the spring increases, and the size of the injection nozzle increases accordingly.
It won't be practical. Furthermore, it is necessary to process grooves and the like on the plunger member, and fuel pressure acts on the solenoid valve at all times, causing problems in the durability of the solenoid valve and the sealing performance of various parts of the injection system.

The purpose of this invention is to solve the above problems,
The nozzle body is configured such that the volume of the pressure accumulation chamber is variable according to the timing of fuel accumulation and injection, and the injection pressure is maintained at a high pressure during the injection period, and the change in injection pressure is small even if the injection amount changes. A plunger installed in a pressure accumulation chamber that communicates with a fuel reservoir installed in By shortening the period and injecting a predetermined fuel flow rate into the combustion chamber, it is possible to maintain the optimum mixing degree of fuel and air in the combustion chamber during the early and late stages of fuel injection, while also reducing the pressure applied to the pressure accumulation chamber and fuel reservoir. It is an object of the present invention to provide a pressure accumulation type fuel injection device that reduces back pressure to a leak side back pressure and improves durability.

[Means to solve the problem]

This invention is based on the above 1! ! In order to solve the problem and achieve the above objectives, it is structured as follows.

That is, the present invention provides a fuel injection nozzle that opens an injection hole in response to a fuel pressure of a predetermined level or more in a fuel reservoir that accommodates fuel from a fuel injection pump; a pressure accumulation chamber that communicates with the fuel reservoir and accumulates fuel; A fuel pressurizing device that adjusts the fuel pressure that pressurizes the fuel in the pressure accumulating chamber to adjust the flow rate injected from the fuel reservoir through the nozzle hole, and a fuel pressure that acts on the fuel pressurizing device from a part of the fuel. The present invention relates to an accumulator fuel injection device comprising a fuel reservoir tank.

In this pressure accumulation type fuel injection device, the fuel pressurizing device has a pressurizing solenoid valve and a leaking solenoid valve disposed on the fuel reservoir tank side, and changes the fuel pressure of the fuel reservoir tank to fuel the fuel. It has a fuel pressure control valve that regulates the pressure acting on the plunger of the pressurizing device.

In this pressure accumulation type fuel injection device, the fuel pressurization device has a pressurization solenoid valve and a leakage solenoid valve arranged on the fuel reservoir tank side, and supplies fuel from the fuel injection pump to the pressure accumulation chamber. The fuel pressure increasing mechanism is provided in the fuel supply system and adjusts the fuel injection pressure from the nozzle hole.

[Effect]

The pressure accumulation type fuel injection device according to the present invention is constructed as described above and operates as follows. That is, this pressure accumulation type fuel injection device adjusts the fuel pressure that pressurizes the fuel in the pressure accumulation chamber that communicates with the fuel reservoir and accumulates the fuel, so as to control the flow rate injected from the fuel reservoir through the nozzle hole. Since a fuel reservoir tank is provided in which the fuel pressure that acts on the fuel pressurization device is introduced from a part of the fuel, the pressure to pressurize the pressure accumulator chamber is set below the opening pressure of the needle valve. If it is, the force holding down the needle valve of the fuel injection nozzle, that is, the fuel pressure supplied to the fuel injection pump, will decrease.
Or, when the fuel pressure from the fuel reservoir tank acts on the fuel reservoir tank and the plunger of the fuel pressurizing device, the needle valve of the fuel injection nozzle rises, the needle valve opens the nozzle hole, and fuel is injected from the nozzle hole. will be started. In order to stop the injection, the fuel pressure acting on the plunger can be immediately lowered by leaking fuel, the pressure in the pressure accumulation chamber can be lowered, and the injection hole can be closed with a needle valve.

〔Example〕

Embodiments of the pressure accumulation type fuel injection device according to the present invention will be described in detail below with reference to the drawings.

First, an embodiment of the pressure accumulation type fuel injection device according to the present invention will be described with reference to FIGS. 1 and 2.

The pressure accumulation type fuel injection device according to the present invention has the same structure as the fuel injection device shown in FIG. 9 except for the difference in the structure of the pressure accumulation chamber, so the same parts are denoted by the same reference numerals. The explanation of those parts and their functions will be omitted.

This pressure accumulation type fuel injection device is a pressure accumulation type fuel injection nozzle with a variable pressure accumulation chamber volume, and due to its structure, the above-mentioned patent application No.
While the pressure accumulation type fuel injection device with a variable pressure accumulation chamber volume disclosed in No. 281920 utilizes a spring force to push the plunger, this pressure accumulation type fuel injection device
The force for pressing the plunger 14 of the fuel pressurizing device 5 which changes the volume of the fuel pressurizing device 5 is applied by hydraulic pressure, that is, fuel pressure, and the tA node of the fuel injection amount from the nozzle hole 10 is controlled by controlling the fuel pressure acting on the plunger 14. This has been achieved.

This pressure accumulation type fuel injection device includes a fuel injection nozzle 1 which opens an injection hole 10 and a needle valve 2 in response to a fuel pressure of a predetermined level or higher in a fuel reservoir 3 containing fuel from a fuel injection pump, and a fuel reservoir 3 that receives fuel from a fuel reservoir 3. A pressure accumulating chamber 15 that accumulates pressure, a fuel pressurizing device 5 that can change the volume of the pressure accumulating chamber 15 and pressurizing the fuel in the pressure accumulating chamber 15, and a fuel that acts on the fuel pressurizing device f5 as part of the supplied fuel. It has a fuel storage tank 20 introduced from the front. This pressure accumulation type fuel injection device supplies fuel from a fuel injection pump 17 to a pressure accumulation chamber 15 through a passage 18 and a check valve 19.
In addition to supplying to i! Fuel pressure Pn is applied to the needle valve 2 of the fuel injection nozzle 1 through a passage 24 connected to the l passage 18, and is applied to the fuel reservoir tank 2 through a check valve 23.
It supplies part of the fuel to 0. As shown in FIG. 4, this pressure accumulation type fuel injection device has fuel injection nozzles 1 arranged for each cylinder, each fuel injection nozzle l attached to the main body of the fuel injection nozzle 1, and a fuel reservoir. The tank 20 can be configured to be shared by each fuel pressurizing device 5. The fuel supplied to the fuel reservoir tank 20 becomes fuel pressure and acts on the back surface of the plunger 14 of the fuel pressurizing device 5, and functions to pressurize the fuel in the pressure accumulating chamber 15.

The fuel pressurizing device 5 also includes a pressurizing solenoid valve 21 in a passage 25 between the fuel reservoir tank 20, a leak solenoid valve 22 in a leak i circuit 27 connected to the passage 25, and a cylinder attached to the nozzle body 7. ] 3 and a plunger 14 that reciprocates within the cylinder 13, and functions as a fuel flow rate adjusting means for adjusting the flow rate injected from the pressure accumulation chamber 15 through the nozzle hole 10 by changing the fuel pressure. A pressure accumulation chamber 15 is formed in the cylinder 13, and the pressure accumulation chamber 15 is connected to the fuel passage 12.
and communicates with the fuel reservoir 3 through a fuel passage 4.

The plunger 14 is configured so that the fuel pressure from the fuel storage tank 20 acts on the back surface of the plunger 14 through a passage 25 to reduce the volume of the pressure accumulation chamber 15, that is, to pressurize the fuel within the pressure accumulation chamber 15. Further, the plunger 14 is configured to return in the direction of increasing the volume of the pressure accumulation chamber 15 by the spring force of the spring I6. The set pressure of the fuel pressure acting on the pressure accumulation chamber 15 is set to a value slightly smaller than the maximum pressure in the pressure accumulation chamber 15, that is, the pressure immediately before the start of fuel injection, in other words, the opening pressure of the needle valve 2. Therefore, immediately before the fuel in the pressure accumulation chamber 15 and the fuel reservoir 3 passes through the nozzle hole 10 and starts fuel injection, the plunger 14
is moving in the direction to make the volume inside the cylinder 13 the maximum volume.

Next, we will discuss the operation of this pressure accumulation type fuel injection device, in particular.
This will be explained with reference to FIG. 2, FIG. 3(A), and FIG. 3(B). FIG. 2 is a schematic explanatory diagram illustrating an example of the operation of this pressure accumulation type fuel injection device, and 3rd rgJ (A) and 3rd (B) are diagrams showing the operating state of each component as time T elapses. . Note that the symbols (1), (If), cm>, (IV), and (V) of the time T in FIG. 3(A) and FIG. 3(B) are replaced by the symbols (1), ( II), (III
), (IV) and (V) correspond to the same symbols, respectively.

In this pressure accumulation type fuel injection device, the fuel pressure applied to the plunger 14 of the fuel pressurization device 5 is utilized by introducing a portion of the fuel from the fuel injection pump 17 into the fuel reservoir tank 20. The fuel pressure in the fuel reservoir tank 20 acts on the plunger 14 of the fuel pressurizing device 5. Fuel is supplied from the fuel injection pump 17 to the fuel injection nozzle 1 through the fuel passage 18. When the internal pressure Pn of the fuel passage 18 exceeds the set value of the check valve 19 using spring force, the check valve 19 opens and the fuel from the fuel injection pump 17 is supplied to the pressure accumulation chamber 15 side, and the pressure accumulation chamber] 5 pressure P acc rises and is stored in the pressure accumulating chamber 15 [(I
) and (II)].

Next, the fuel pressure from the fuel injection pump 17, that is, the internal pressure Pn
When P ac begins to decrease, the check valve 19 is activated by the spring force and the pressure P ac
c is closed, and fuel is stored in the pressure accumulating chamber 15. In this state, either the pressure Pn that is the force holding down the needle valve 2 of the fuel injection nozzle 1 through the passage 24 decreases, or the fuel reservoir tank 20 and the back surface of the plunger 14 of the fuel pressurizing device 5 are communicated with each other. When the solenoid valve 21 provided in the passage 25 opens and fuel pressure acts on the plunger 14, the needle valve 2 of the fuel injection nozzle 1 opens.
rises, the needle valve 2 opens the nozzle hole 10, and fuel injection from the nozzle hole 10 is started.

First, in this pressure accumulation type fuel injection device, (I
As shown in II), when fuel injection is started by opening the second valve 21, when the second valve 21 is opened, the i-circuit 25 which applies fuel pressure to the back side of the plunger 14 is activated. The pressure Pi increases, and the plunger 4 moves in the direction of pressing the fuel in the pressure accumulation chamber 15, reducing the volume of the pressure accumulation chamber 15. As a result, the pressure P acc in the pressure accumulator 15 increases.

The pressure P acc in the pressure accumulator is the force holding down the needle valve 2 of the fuel injection nozzle 1 (i.e., the spring 26 at the top of the needle valve 2
When the resultant force of the spring force and the pressure Pn of the IL circuit 24 becomes larger than the resultant force, the needle valve 2 moves upward, as shown in (TV) in FIG. is started.

Next, when stopping fuel injection from the injection hole 10 of the fuel injection nozzle l, as shown in (V) in FIG.
The solenoid valve 21 is closed and the 1it161 valve 22 provided in the leak passage 27 of the passage 25 is opened. That is, when the if magnetic valve 2l is closed and the t2 valve 22 is opened, the force that presses the plunger 14 in the right direction disappears, and the return spring 16 of the fuel pressurizing device 5 and the pressure accumulator 1
Due to the pressure PacC of 5, the plunger 14 moves to the left, the volume of the pressure accumulator chamber 5 increases, the pressure PacC decreases due to the increase in the volume of the pressure accumulator 14, and the needle valve 2 descends to open the fuel injection nozzle. No. 1 nozzle hole 10 is closed, and fuel injection from nozzle hole 10 is stopped.

Next, regarding this pressure accumulation type fuel injection device, when the pressure Pn, which is the force holding down the needle valve 2 of the fuel injection nozzle 1 through the passage 24, decreases, fuel injection is performed from the injection hole 10 of the fuel injection nozzle. Explain the condition. When the required fuel injection amount is small, such as during engine fitting, the operating capacity of the fuel injection pump 17 is reduced, and the pressure Pn in the passage 24 is reduced. At this time, even if the solenoid valve 21 does not open, the pressure that raises the needle valve 2 is formed in the pressure accumulation chamber 15, so that the nozzle 1 of the fuel injection nozzle 1
0 is open and fuel can be injected into the combustion chamber.

Since the pressure accumulator fuel injection device according to the present invention is constructed and operates as described above, the plunger 14 in the fuel pressurization device 5 is provided with a special structure, for example, in the above-mentioned Japanese Patent Application No. 1-28
Unlike the pressure accumulation type fuel injection device with variable pressure accumulation chamber volume disclosed in No. 1920, there is no need to provide grooves, holes, etc., and there is no need to provide a mechanism for rotating the plunger. Therefore, the structure itself of this pressure accumulation type fuel injection device can be simplified.

Or, the fuel storage device 5 in this pressure accumulation type fuel injection device
As shown in Fig. 5, the fuel storage tank 20
A fuel pressure control valve 31 is provided, and the set value is changed by adjusting the fuel pressure control valve 31, and the fuel pressure in the fuel reservoir tank 20 is changed to easily adjust the pressure acting on the plunger 14. It is something that can be done.

Alternatively, for the fuel pressurizing device 5 in this pressure accumulation type fuel injection device, as shown in FIG. 6 or 7, the fuel injection nozzle 1 and the fuel supply system that supplies fuel from the fuel injection pump to the fuel reservoir 3 are connected is provided with a separate fuel pressure increase mechanism 30, and increases the fuel pressure supplied to the fuel injection nozzle 1 by the fuel pressure increase mechanism 30, thereby increasing the fuel injection pressure from the nozzle hole 10! It is something to be observed. This fuel pressure increase mechanism 30 can be provided anywhere in the fuel supply system to the fuel injection nozzle 1. For example, as shown in FIG. 6, the fuel pressure increase mechanism 30 can be disposed downstream of the connection point 28 between the passage B18 and the fuel reservoir tank 20. Alternatively, the fuel pressure boosting mechanism 30 may be configured, for example, as shown in FIG.
8 and the fuel reservoir tank 20 on the upstream side of the connection point 28.

An example of this fuel pressure increase mechanism 30 is shown in FIG. 8, but the principle of pressure increase is disclosed in, for example, Japanese Patent Application Laid-Open No. 64-32063, so a detailed explanation will be omitted here. do. In this fuel pressure increasing mechanism 30, fluid introduced from the side A is introduced into the pressure increasing chamber 33 using the check valve 34, and a portion of the fluid is introduced into the pressurizing chamber 32. Plunge medium 3 arranged astride the pressurizing chamber 32 and the pressurizing chamber 33
5, the pressing surface facing the pressurizing chamber 32 side is formed larger than the pressing surface facing the increasing pressure chamber 33 side. Therefore, when fuel pressure acts on the pressurizing chamber 32, the pressure of the fuel in the pressurizing chamber 33 is increased by the action of the plunger 35.

Therefore, regarding the pressure accumulation type fuel injection device according to the present invention, the conventional pressure accumulation type fuel injection device has a pressure accumulation chamber 2 at the time of fuel injection.
9, the pressure drop in the combustion chamber was noticeable, and the injection period was long to inject a predetermined amount of fuel into the combustion chamber.
The pressure inside the pressure accumulation chamber 15 during fuel injection hardly decreases,
A predetermined fuel flow rate can be immediately injected into the combustion chamber within a short period of time. Therefore, this pressure accumulation type fuel injection device can be used in an adiabatic engine to achieve extremely effective fuel injection. Moreover, the conventional pressure accumulation type fuel injection device
While the pressure accumulation chamber 29 is always at the valve closing pressure P of the needle valve 2, or a pressure higher than the valve closing pressure, the pressure accumulation type fuel injection device according to the present invention The leak pressure P or Pf inside the pressure accumulation chamber 15 is considerably lower than the nozzle closing pressure, and the durability of the pressure accumulation chamber 15 can be improved.

〔Effect of the invention〕

Since the pressure accumulation type fuel injection device according to the present invention is configured as described above, it has the following effects. That is, this pressure accumulation type fuel injection device includes a fuel injection nozzle that opens an injection hole in response to a fuel pressure of a predetermined level or higher in a fuel reservoir that accommodates fuel from a fuel injection pump, and a fuel injection nozzle that opens a nozzle hole in response to a fuel pressure of a fuel reservoir containing fuel from a fuel injection pump, and a fuel injection nozzle that communicates with the fuel reservoir to accumulate fuel. a pressure accumulator that pressurizes the fuel in the pressure accumulator; a fuel pressurizing device that adjusts the fuel pressure to pressurize the fuel in the pressure accumulating chamber to adjust the flow rate injected from the fuel reservoir through the injection hole; and a fuel pressurizing device that adjusts the fuel pressure acting on the fuel pressurizing device. Since the fuel reservoir tank is introduced from a part of the fuel reservoir tank, the force holding down the needle valve of the fuel injection nozzle, that is, the fuel pressure supplied to the fuel injection pump, may decrease, or the pressure on the fuel reservoir tank and the plunger of the fuel pressurizing device may decrease. By applying fuel pressure from the fuel storage tank,
Fuel injection is easily started from the nozzle hole. ! ! If the pressure to pressurize the pressure accumulator is set below the opening pressure of the needle valve, the plunger will press the pressure accumulator just before the start of injection when the fuel supplied from the fuel injection pump is injected from the nozzle hole. When the fuel injection pump moves to a position where the indoor volume is maximized and fuel is further supplied to the pressure accumulation chamber from the fuel injection pump in that state, the needle valve opens the injection hole when the fuel pressure exceeds a predetermined level. Since the fuel pressure in the fuel reservoir tank acts on the fuel in the pressure accumulation chamber throughout the plunge, the pressure of the fuel in the fuel reservoir is increased and is injected at high pressure. In addition, in order to stop IJ'N, if the fuel pressure acting on the plunger is suddenly reduced by opening the leak electromagnetic valve and causing fuel to leak, the fuel pressure in the pressure accumulator will also immediately drop, causing the needle valve to drop. closes the nozzle and injection is immediately stopped. Moreover, the fuel pressure is only applied to the pressure accumulating chamber and the like during the plunge during injection, which improves the sealing performance of each part of the injection system and the durability of the fuel pressurizing device.

In particular, the pressurizing force that acts on the plunger of this fuel pressurizing device is a fluid, which increases the degree of freedom in design compared to conventional devices, making it easier to adjust the force that presses the plunger, and ,! Since the control of tt can be coupled by controlling the hydraulic pressure that acts during the plunge, there is no need to perform special processing such as grooves during the plunge, there is no need for a control rank, etc., and the volume of the fuel injection nozzle can be reduced. Moreover, since the fuel reservoir tank can be shared by each fuel injection nozzle arranged in each cylinder, the pressure of the fuel reservoir tank can always be maintained at the desired pressure, and the fuel pressure applied to the plunger can always be made uniform. , it is possible to improve the response of the plunger to release the pressure of the fuel into the pressure accumulation chamber. Moreover, the fuel can be stored in the pressure accumulation chamber before fuel injection, the injection waveform becomes square, and the injection amount can be controlled extremely well, improving the response of the injection amount control. can.

Therefore, during the fuel injection period, the injection pressure can be maintained at a high pressure, preventing a drop in the fuel injection pressure and reducing the fuel injection speed, shortening the fuel injection period and maintaining a predetermined fuel flow rate. The fuel can be injected into the combustion chamber through the nozzle hole, and an optimum degree of mixing of fuel and air in the combustion chamber can be maintained at the early stage of fuel injection and at the late stage of fuel injection.

Furthermore, if the pressure accumulation chamber is configured as in the pressure accumulation type fuel injection device according to the present invention, the required pressure accumulation chamber volume formed in the fuel injection nozzle itself is configured to be smaller than in the case where the pressure accumulation chamber volume is a constant volume in the related art. be able to. Therefore, the required amount of oil to be fed by the fuel injection pump is also reduced, and the capacity of the fuel injection pump can be reduced. Furthermore, since the fuel injection amount is adjusted on the nozzle side, the main control item on the fuel injection pump side is only the injection timing control, eliminating the need for a governor, etc., and the pump itself can be inexpensive and compact. Moreover, it is possible to reduce the pressure applied to the pressure accumulation chamber and the fuel reservoir to the leak side back pressure, thereby avoiding application of unnecessary pressure, and improving the durability of the pressure accumulation type fuel injection device itself.

Alternatively, the fuel pressurizing device includes a fuel pressure control valve that changes the fuel pressure in the fuel reservoir tank to adjust the pressure acting on the plunger of the fuel pressurizing device, so that by adjusting the fuel pressure control valve, The pressure acting on the plunger can be easily adjusted by changing the set value and changing the fuel pressure in the fuel reservoir tank.

Alternatively, the fuel pressurizing device includes a fuel pressure increasing mechanism that is provided in a fuel supply system that supplies fuel from the fuel injection pump to the pressure accumulation chamber and that increases the fuel injection pressure from the nozzle hole by m. The pressure increase mechanism can increase the fuel pressure supplied to the fuel injection nozzle and adjust the pressure increase of the fuel injection pressure from the nozzle hole, and the fuel pressure increase mechanism can be connected to any one of the fuel supply systems to the fuel injection nozzle. It can be installed at any desired location.

Therefore, according to this pressure accumulation type fuel injection device, even if the temperature at the end of the compression stroke of the engine becomes extremely high and the time from fuel injection to ignition is significantly shortened, the initial injection rate can be maintained by high-pressure injection. By increasing the pressure and causing the pressure in the pressure accumulation chamber to leak, a predetermined amount of fuel can be injected into the combustion chamber of the engine in a short period of time. For example, in an adiabatic engine, the temperature at the end of the compression process becomes high and the time from fuel injection to ignition is significantly shortened. In addition, since it has a function of leaking the pressure in the pressure accumulation chamber, a predetermined amount of fuel can be injected into the combustion chamber in a short time. Therefore, in an adiabatic engine made of ceramic material, the temperature at the end of the engine's compression process becomes extremely high compared to a normal engine, and the time from the start of fuel injection to ignition, that is, the ignition delay, is significantly shortened. Even if such a phenomenon occurs, the fuel injection pressure can be maintained at a high pressure state, the fuel injection speed can be maintained at a high speed, and a predetermined fuel flow rate can be injected into the combustion chamber in a short time.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the pressure accumulation type fuel injection device according to the present invention, and FIG. 2 is a schematic explanatory diagram illustrating an example of the operation of this pressure accumulation type fuel injection device, and the table and FIG. 3 (A) 3(B) is a diagram showing the operating state of each part as time T elapses, FIG. 4 is a perspective view showing the overall outline of this pressure accumulation type fuel injection device, and FIG. 5 is a diagram showing the pressure control valve. FIG. 6 is an explanatory diagram showing an example in which a fuel pressure increase mechanism is incorporated, FIG. 7 is an explanatory diagram showing another example in which a fuel pressure increase mechanism is incorporated, and FIG. 8 is an explanatory diagram showing an example in which a fuel pressure increase mechanism is incorporated. FIG. 9 is a schematic diagram showing an example of a conventional pressure accumulation type fuel injection device, and FIG. 10 is a diagram showing changes in pressure in the pressure accumulation chamber with respect to injection time of the pressure accumulation type fuel injection device shown in FIG. 9. It is an explanatory diagram showing a state. 1---- one fuel injection nozzle, 2--- one needle valve, 3- one--- fuel reservoir, 4.12.18, 24.25-.
-・- passage, 5- fuel pressurizing device, 10---- nozzle hole,
13----- cylinder, 14--1-- plunger,
15- Pressure accumulation chamber, 17- Fuel injection pump, 19. 2
3--111 check valve, 0 2 1 fuel reservoir tank, 21- pressurizing solenoid valve, leak solenoid valve, 3 (1-1--fuel pressure increase mechanism, fuel pressure control valve.

Claims (3)

[Claims] (1) A fuel injection nozzle that opens an injection hole in response to a fuel pressure of a predetermined level or more in a fuel reservoir that accommodates fuel from a fuel injection pump, a pressure accumulator that communicates with the fuel reservoir and accumulates fuel pressure, and the pressure accumulation chamber a fuel pressurizing device that adjusts the fuel pressure that pressurizes the fuel to adjust the flow rate injected from the fuel reservoir through the nozzle hole; and a fuel that introduces the fuel pressure that acts on the fuel pressurizing device from a part of the fuel. A pressure accumulation type fuel injection device consisting of a reservoir tank. (2) The fuel pressurizing device has a pressurizing solenoid valve and a leaking solenoid valve disposed on the fuel reservoir tank side, and
The pressure accumulation type fuel injection device according to claim 1, further comprising a fuel pressure control valve that changes the fuel pressure in the fuel reservoir tank to adjust the pressure acting on the plunger of the fuel pressurizing device. (3) The fuel pressurizing device has a pressurizing solenoid valve and a leaking solenoid valve disposed on the fuel reservoir tank side, and
The pressure accumulation type fuel injection device according to claim 1, further comprising a fuel pressure increasing mechanism provided in a fuel supply system that supplies fuel from the fuel injection pump to the pressure accumulation chamber and adjusting the fuel injection pressure from the nozzle hole.