JP3293248B2 - Accumulator of accumulator type fuel injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator type fuel injection device for supplying fuel to an internal combustion engine, and more particularly to an accumulator (common rail) thereof.

[0002]

2. Description of the Related Art For example, an accumulator type fuel injection device is known as one type of fuel injection device for injecting fuel into a diesel engine. This accumulator temporarily stores high-pressure fuel supplied from a fuel supply pump in an accumulator (common rail), adjusts the pressure evenly with the accumulator, distributes and supplies the accumulated pressure fuel to the injectors of each cylinder, and passes through these injectors respectively. The fuel is injected into the cylinder.

[0003] In the case of a diesel engine, it is known that controlling the injection pressure injected from an injector based on fluctuations in the number of revolutions and load is effective for combustion efficiency and measures against exhaust gas. That is, when the rotational speed or the load is high, if the injection pressure of the fuel injected from the injector is increased, the fuel is miniaturized and atomization is promoted, so that the combustion efficiency is improved and harmful exhaust gas is reduced.

For this reason, it is necessary to control the injection pressure in accordance with the operating condition of the engine, and the fuel pressure stored in the accumulator is also changed in accordance with the operating condition of the engine.

[0005]

However, in the accumulator of this type of accumulator type fuel injection device, when the capacity is large, the pressure in the accumulator becomes stable, and the variation in the fuel pressure sent to the injector becomes small. Although the injection pressure is stabilized, as described above, when a command to change the injection pressure is issued due to a change in the operating state of the engine, it takes time to propagate the pressure due to the large capacity, and the response is poor, That is, there is a problem that the pressure followability is poor.

On the other hand, when the capacity of the pressure accumulator is small, the pressure stability in the pressure accumulator is inferior, and the variation in the fuel pressure sent to the injector becomes large, and the stability of the injection pressure decreases. However, there is an advantage that pressure followability is excellent when a command to change the injection pressure is issued.

The conventional pressure accumulator has a constant capacity and cannot satisfy both pressure stability and followability at the same time.

Accordingly, it is an object of the present invention to provide a pressure accumulator of a pressure accumulating fuel injection device in which the pressure stabilization of a pressure accumulating fuel is improved and which is excellent in following up a pressure change command. .

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a pressure-accumulating fuel injection device for accumulating fuel supplied from a fuel supply pump in a pressure accumulator and distributing the fuel from the pressure accumulator to a plurality of injectors. The pressure accumulator includes at least a small-capacity accumulator and a large-capacity accumulator partitioned from each other, and the fuel supply pump and the plurality of injectors are provided in the small-capacity accumulator. And a communication passage connecting the accumulators with different capacities to each other. The difference between the actual pressure of the accumulator with a smaller capacity and the command fuel pressure calculated based on the operating state of the internal combustion engine is provided. the above but in the following state for a predetermined value, along with communicating the small capacity the pressure accumulating chamber and the volume is large the pressure accumulating chamber, a control valve for blocking in the state of this communication that exceeds a predetermined value Characterized by providing the passage.

[0010]

According to the structure of the present invention, since the capacity of the pressure accumulator is variable, when a command to make the injection pressure constant is issued, the communication valve is opened by the control valve to connect the pressure accumulator with a small capacity.
By communicating with a large-volume accumulator, the capacity can be increased and the pressure can be stabilized, and when a command to change the injection pressure is issued, the communication path is closed by the control valve to reduce the capacity.
Cut off the communication between the small accumulator and the large accumulator ,
Therefore, the capacity can be reduced to improve the pressure followability ,
The combustion can be injected into the cylinders of the internal combustion engine from the injector .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to one embodiment shown in the drawings. FIG. 2 is a configuration diagram showing the entire pressure-accumulation type fuel injection device, wherein reference numeral 1 denotes a fuel tank, 2 denotes a low-pressure fuel supply pump, and 3 denotes a high-pressure fuel supply pump. The low-pressure fuel pump 2 supplies the fuel in the fuel tank 1 to the high-pressure fuel pump 3. The high-pressure fuel pump 3 increases the pressure of the introduced fuel to a predetermined high pressure and supplies it to the accumulator (common rail) 10. The high-pressure fuel pump 3 reciprocates a piston 7 in a cylinder 6 by a cam 5 that rotates in synchronization with the rotation of the engine 4. The piston 7 is sent from the low-pressure fuel pump 2. The low pressure fuel is pressurized and pressurized. This high-pressure fuel is supplied to a common rail 10 through a check valve 8 and a supply pipe 9. In this case, the high-pressure fuel pump 3 includes the common rail 1
An electromagnetic valve 30 for controlling the supply pressure is provided to control the pressure of the fuel supplied to zero. This supply pressure control solenoid valve 3
0 operates in response to a command from an electronic control unit (ECU) 50 described later.

The common rail 10 is shown in detail in FIG. 1 and will be described with reference to FIG. In the main body 11 of the common rail, a first pressure accumulating chamber 12 having a small capacity is provided.
And a second pressure accumulating chamber 13 having a capacity larger than that of the second pressure accumulating chamber 13. These first pressure accumulating chamber 12 and second
Are communicated with each other by a communication passage 14 formed substantially at the center thereof. A control valve 15 is provided in the communication passage 14, and the control valve 15 opens and closes the communication passage 14 or changes the passage area. This control valve 15
Is, for example, a pulse-controlled electromagnetic on-off valve, and when a pulse current is applied to the solenoid 16, the plunger 17 is operated,
Thereby, the communication passage 14 is opened and closed or its passage area is changed. Therefore, by the opening and closing operation of the control valve 15, the communication between the first pressure accumulating chamber 12 and the second pressure accumulating chamber 13 is established and cut off.
Is changed.

The first accumulator 12 communicates with the high-pressure fuel pump 3 through the supply pipe 9. In addition, this first
A pressure sensor 35 for detecting the fuel pressure in this chamber is attached to the pressure accumulating chamber 12.

As shown in FIG. 2, a plurality of injection pipes 20 are connected to the first pressure accumulating chamber 12, and injectors 21 are connected to the injection pipes 20, respectively. The injectors 21 are mounted corresponding to the cylinders of the engine 4. As shown in FIG. 1, a check valve 22 is provided between the first accumulator chamber 12 and each of the injection pipes 20 to prevent the reflected waves from the injectors 21 from being transmitted to the common rail 10. I have.

The electronic control unit (ECU) 50 includes:
Information on the number of revolutions and load of the engine is input from a cylinder discriminating sensor 51, a crank angle sensor 52, and a load sensor 53, and from the injectors 21 in accordance with the operating state of the engine determined by these signals. The fuel injection pressure, the injection timing, and the injection amount to be injected are determined. The fuel injection pressure controls the fuel pressure supplied from the high-pressure fuel pump 3 to the common rail 10 by operating the supply pressure control solenoid valve 30 of the high-pressure fuel pump 3, thereby changing the fuel pressure in the common rail 10. It has become. Further, the injection timing and the injection amount are controlled by operating a needle valve (not shown) of the injector 21 by an electromagnetic action, and controlling a timing at which the needle valve opens and closes the injection hole.

Further, when changing the fuel injection pressure, the ECU 50 simultaneously sends a command signal to the control valve 15 of the common rail 10 to operate the control valve 15. That is, the control valve 15 changes the duty ratio of the pulse current from 0 to 1 in accordance with the command signal from the ECU 50.
00%, whereby the plunger 17 is actuated to change the opening of the communication passage 14 from 0 to 100%.

The pressure sensor 35 provided on the common rail 10 sends this detection signal to the ECU 50. The ECU 50 operates the control valve 15 according to the pressure state of the first pressure accumulation chamber 12 measured by the pressure sensor 35, as described later.

An accumulator type fuel injection device according to an embodiment having such a configuration will be described with reference to an operation characteristic diagram of FIG. During the operation of the engine 4, the fuel in the fuel tank 1 is supplied to the high-pressure fuel pump 3 by the low-pressure fuel pump 2, and the high-pressure fuel pump 3 increases the pressure of the introduced fuel to a predetermined pressure and supplies it to the common rail 10. . Common rail 10
, The introduced fuel is temporarily stored to balance the pressure, and this pressure fuel is distributed and supplied to the injectors 21 through the injection pipes 20. ECU 50
When the injector 21 is actuated in response to a command from the engine, the injection hole is opened, and pressurized fuel is injected into the cylinder from the injection hole.

When the engine speed and load are low,
The injection pressure of the fuel to be injected from the injectors 21 may be relatively low. Therefore, the ECU 50 operates the supply pressure control solenoid valve 30 of the high pressure fuel pump 3 to supply the fuel supplied from the high pressure fuel pump 3 to the common rail 10. Send with reduced pressure. This fuel pressure in the common rail 10 by, like p ₁ in (a) of FIG. 3, remains relatively low. At this time, in response to a command from the ECU 50, the control valve 15 is opening as shown in FIG. 3C, and the communication passage 14 is thus opened. Therefore, the common rail 10 has a large capacity because the first pressure accumulating chamber 12 and the second pressure accumulating chamber 13 communicate with each other. Therefore, even when a local pressure fluctuation occurs in the common rail 10 as in the case where fuel is injected through any one of the injectors 21, the pressure can be dispersed and absorbed throughout the large-capacity common rail 10. Fluctuations can be reduced. As a result, a stable pressure state can be maintained without affecting the fuel pressure distributed to the other injectors 21.

[0020] When the engine speed or load increases, the EC
If U50 issues a command to increase the fuel injection pressure, EC
The supply pressure control solenoid valve 30 of the high-pressure fuel pump 3 is operated by the command of U50, and the pressure of the fuel supplied from the high-pressure fuel pump 3 to the common rail 10 is increased as indicated by p2 in FIG. send. Therefore, the fuel pressure in the common rail 10 increases. This fuel pressure is detected by a pressure sensor 35 provided in the first pressure accumulating chamber 12, and the detected value is transmitted to the ECU 50. ECU 50
Compares the command fuel pressure calculated based on the engine speed and load fluctuation with the actual pressure detected by the pressure sensor 35, and the difference is equal to or larger than a predetermined difference, that is, as shown in FIG. 3 (b). When the value exceeds the predetermined value A shown in FIG.
(B) The level of -A shown between times I and II in the figure (where
The state where the fixed value A) is exceeded, and the time in FIG.
+ A level (predetermined value A) shown between III-IV
In the state, a command is issued to close the control valve 15 of the common rail 10. This command causes the control valve 15 to change the duty ratio of the pulse current to 1 as shown in FIG.
It changes to 00% and it becomes a fully closed state. Therefore, the communication passage 14
Is closed, the common rail 10 is disconnected from the first pressure accumulating chamber 12 and the second pressure accumulating chamber 13, and only the first pressure accumulating chamber 12 communicates with the high pressure fuel pump 3 side and the injectors 21. Is reduced. Therefore, the high-pressure fuel p2 supplied from the high-pressure fuel pump 3 is sent only to the first pressure accumulating chamber 12, and at this time, since the capacity in the common rail 10 is small, the pressure in the first pressure accumulating chamber 12 is quickly increased,
Responsiveness to pressure rise is improved. As a result, the high-pressure fuel p2 is quickly distributed to the injectors 21 and the high-pressure injection is immediately performed by the injectors 21. Therefore, the fuel is fined, that is, atomized, and the combustion efficiency is increased. Can be.

In FIG. 3A, the control valve 15 controls the communication path 14 with respect to the fluctuation characteristic of the command value indicated by the solid line.
(A) shows the fluctuation of the actual pressure when the shut-off control is performed, and the actual pressure fluctuation when the communication path 14 is not cut off by the control valve 15 is shown by the dashed line in the (a).
From these characteristics, it can be understood that controlling the communication passage 14 with the control valve 15 is more excellent in pressure responsiveness.

Since the timing of transmission of the command value from the ECU 50 and the fluctuation of the pressure in the first pressure accumulating chamber 12 have a slight timing delay, there is a difference between the command fuel pressure and the actual pressure detected by the pressure sensor 35. When a pressure difference of a time difference is generated, and the pressure difference exceeds A shown in FIG. 3B, the control valve 15 operates as described above to close the communication passage.
Immediately after the control valve 15 is closed, the difference between the command fuel pressure and the pressure in the first pressure accumulating chamber 12 is further increased.
Is closed, the pressure in the first pressure accumulating chamber 12 increases, so that the pressure difference between the two accumulates. When the pressure difference becomes equal to or less than B shown in FIG. 3B, the ECU 50 issues a command to open the control valve 15. In response to this command, the control valve 15 opens as shown by II in FIG. 3C. Therefore, the first pressure accumulating chamber 12 and the second pressure accumulating chamber 13 are communicated again, and the capacity of the common rail 10 is increased. That is, at this time, the common rail 10 accumulates fuel in a high pressure state, and can stabilize the fuel in this high pressure state.

A difference is provided between the valve opening pressure A and the valve closing pressure B of the control valve 15 (A> B), whereby hysteresis is given to ensure the operation.

When the control valve 15 is opened, it is gradually opened as shown by the angle α in FIG. 3 (c). This can be realized by slowly changing the duty ratio of the pulse current supplied to the control valve 15 from 100% to 0%. When the control valve 15 is momentarily opened, the first accumulator 1
There is a concern that the high pressure of No. 2 and the low pressure of the second pressure accumulating chamber 13 are conducted and the pressure fluctuates rapidly, causing pulsation and the like and the injection amount varies from each injector, but the control valve 15 is gradually opened. As a result, the above problem can be solved.

The control valve 15 of the above embodiment is an electromagnetically driven valve operated by a pulse current, and controls the opening by changing the duty ratio from 0 to 100%. However, the present invention is not limited to this, and the opening of the communication passage 14 may be controlled by, for example, a rotary valve or the like.

[0026]

According to the present invention, as described above, according to the present invention, low
At least a small-capacity accumulator and a large-capacity accumulator
Calculate the communication path based on the operating state of the internal combustion engine
Difference between the commanded fuel pressure and the actual pressure in the accumulator with small capacity
Control valve that opens and closes according to
Communication and disconnection between the accumulator and the large capacity accumulator
When a command to make the injection pressure constant is issued, the pressure accumulation chamber with a small capacity and the pressure accumulation with a large capacity
A chamber by increasing the capacity to communicate with the pressure can be stabilized, and, if the command injection pressure change was issued capacity
Block the communication between the low pressure accumulator and the high capacity accumulator.
Fuel supply pump and multiple injectors
The pressure followability can be improved by using a pressure storage chamber with a small capacity to which the pressure is connected . Accordingly, the pressure stability and pressure followability of both functions internal combustion engine by a single accumulator
There is an advantage that can be satisfied during normal operation .

[Brief description of the drawings]

FIG. 1 is a sectional view of a pressure accumulator showing one embodiment of the present invention.

FIG. 2 is a configuration diagram schematically showing the whole pressure accumulating fuel injection device of the embodiment.

FIG. 3 is an operation characteristic diagram of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel tank 2 ... Low pressure fuel supply pump 3 ... High pressure fuel supply pump 4 ... Engine 10 ... Accumulator (common rail) 11 ... Main body of common rail 12 ... First accumulator 13 ... Second accumulator 14 ... Communication passage 15 ... Control valve 20 ... Injection pipe 21 ... Injector 30 ... Supply pressure control solenoid valve 35 ... Pressure sensor 50 ... Electronic control unit (ECU)

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 55/02 310 F02M 55/02 350 F02M 59/44 F02M 47/02 F02M 47/00

Claims (1)

(57) [Claims] 1. An accumulator type fuel injection device for accumulating fuel supplied from a fuel supply pump in an accumulator and distributing the fuel from the accumulator to a plurality of injectors, wherein the accumulators are separated from each other and have at least a small capacity. A pressure storage chamber having a large capacity, a pressure storage chamber having a large capacity, and a communication passage connecting the fuel supply pump and the plurality of injectors to the pressure storage chamber having a small capacity, and communicating the pressure storage chambers having different capacities with each other. When the difference between the actual pressure of the small-capacity accumulator and the command fuel pressure calculated based on the operating state of the internal combustion engine is equal to or less than a predetermined value, the small-capacity accumulator and the large-capacity accumulator are used. A pressure accumulator for a pressure accumulating fuel injection device, characterized in that a control valve is provided in the communication passage for communicating with the control valve and shutting off when the communication exceeds the predetermined value .