JPH02191865A - Fuel injection device - Google Patents

Abstract

PURPOSE:To enable fuel to be injected in a suitable amount by a pressure in accordance with a load of an internal combustion engine by providing a driving means which controls a direction control valve to a position communicating with a flow path in a low pressure side when a pressure of fuel in a pressure accumulating pipe is larger than the control target pressure. CONSTITUTION:When a drop control process of fuel pressure is started, whether or not an engine is placed in a fuel cut condition is discriminated being based on an output of an accelerator control amount detecting sensor, and when the engine is discriminated to be placed in the fuel cut condition, a fuel pressure Pa is discriminated for whether or not it is larger than a control target pressure Pb. And when the fuel pressure Pa is discriminated to be larger than the control target pressure Pb, a fuel pump 45 is stopped in its operation. Thus, the fuel pressure Pa is prevented from more increasing. Successively, when a three way solenoid valve 51 performs its two-position reciprocating selection within a predetermined time, high pressure fuel in a pressure accumulating pipe is partly returned to a fuel tank by connecting a supply hole 73 to communicate with a discharge hole 75. This process is repeatedly performed before the fuel pressure Pa almost agrees with the control target pressure Pb.

Description

[Detailed Description of the Invention] Purpose of the Invention [Field of Industrial Application] This invention controls the fuel pressure in a pressure accumulation pipe that stores high-pressure fuel, and also controls the supply direction of high-pressure fuel by switching the direction of supply of high-pressure fuel using a directional control valve. The present invention relates to a fuel injection device that injects an appropriate amount of fuel at a pressure depending on the load of an internal combustion engine by controlling the opening time of a driven fuel injection valve.

[Prior Art] A conventional fuel control device 1 of this type is described in, for example, Japanese Patent Application Laid-Open No. 59-165858 (Electromagnetic Controlled Injection System for Diesel Engine).

This fuel injection device improves the operating characteristics of the nozzle needle when opening and closing the fuel injection valve, and improves the correspondence between the opening time and the amount of fuel injection I+ll, thereby increasing the amount of fuel injection. This enables precise control.

On the other hand, fuel pressure is controlled in order to inject fuel at a pressure that corresponds to the load of the internal combustion engine.

This is done by adjusting the amount of fuel supplied to the pressure accumulation pipe using a fuel pump. For example, when increasing the pressure, the fuel pump supplies more fuel to the pressure accumulation pipe than the fuel injection amount. The fuel pressure is increased, and when the pressure is reduced, the amount of fuel supplied by the fuel pump is made smaller than the amount of fuel consumed to lower the fuel pressure.

[Problems to be Solved by the Invention] However, in the conventional fuel injection device described above, fuel pressure control cannot be performed optimally depending on specific operating conditions such as during sudden deceleration, and the fuel A problem has arisen in which the injection pressure is no longer appropriate. - As an example, Figure 9 (
As shown in B), after full-load driving with an accelerator operation amount of 100 [%], coasting is performed with an accelerator operation amount of 0 [%] from time t1, and then at time L2, the accelerator is slightly depressed and light-load driving is performed. Consider the case where In this case, when the accelerator operation amount is set to 0% at time t1, the fuel control target pressure drops significantly, as shown in FIG. Conventionally, in such cases, the operation of the fuel pump is stopped to stop the supply of new fuel, but the fuel in the pressure accumulation pipe is not consumed because fuel injection is not performed, and the fuel pressure remains the same. Diagram (A
), it only decreases slightly due to a small amount of leakage. Therefore, when the accelerator is slightly pressed at time t2 to drive under a light load, fuel is injected at a pressure higher than the fuel control target pressure determined by the accelerator operation amount, and as a result, fuel consumption and exhaust emissions are reduced. There were also cases in which the engine's engine performance deteriorated, acceleration shock, and unnecessary engine noise occurred.

It is an object of the fuel control device of the present invention to solve the above-mentioned problems and to make it possible to inject an appropriate amount of fuel at a pressure that corresponds to the load of an internal combustion engine.

[Means for Solving the Problem] The fuel injection device of the present invention, as illustrated in FIG. A fuel injection valve M3 is driven by the high pressure fuel by switching the supply direction of the high pressure fuel by M2.
In a fuel injection device that controls a valve opening time to inject an appropriate amount of fuel at a pressure depending on a load between internal combustion engines, the direction control valve M2 is connected to the pressure accumulation pipe M1 in the process of switching the fuel supply direction a flow path M4 that communicates with the low pressure side of the fuel system, and when the pressure of the fuel in the pressure accumulation pipe Ml is higher than the control target pressure, a direction in which the direction control valve M2 is driven to a position where the flow path M4 is communicated with the low pressure side of the fuel system; It is characterized by comprising a control valve driving means M5.

As the direction control valve driving means M5, when the pressure of the fuel in the pressure accumulation pipe M1 is higher than the control target pressure, the direction control valve driving means M5 drives the direction control valve M2.
The directional control valve M2 may be switched and driven in a time width shorter than the delay time from switching to the start of fuel injection at the fuel injection valve M3 to intermittently communicate the flow path M4.

[Function] In the fuel injection device of the present invention, when the pressure of the fuel in the pressure accumulation pipe M1 is higher than the control target pressure, the directional control valve driving means M
5, the directional control valve M2 is driven to a position where its flow path M4 is communicated with, thereby communicating the pressure accumulation pipe Ml with the low pressure side of the fuel system. That is, part of the fuel in the pressure accumulation pipe Ml is introduced into the low pressure side of the fuel system to lower the pressure of the fuel in the pressure accumulation pipe Ml. As a result, even if the fuel injection valve is not opened due to a fuel cut or the like, the fuel pressure quickly follows the control target pressure.

In the present invention, when the pressure of the fuel in the pressure accumulation pipe M1 is higher than the control target pressure, the directional control is performed within a time period that is less than the delay time from switching the directional control valve M2 to starting fuel injection at the fuel injection valve M3. Flow path M by switching and driving valve M2
In this structure, the opening and closing of the fuel injection valve M3 and the communication between the pressure accumulation pipe M1 and the low pressure side of the fuel system are both adjusted by adjusting the switching interval of the directional control valve M2.

[Embodiment] In order to further clarify the structure and operation of the present invention described above, a fuel injection system for a multi-cylinder diesel engine as a preferred embodiment of the present invention will be described next. FIG. 2 is a schematic configuration diagram of the fuel injection device mainly showing the fuel injection valve and piping system for one cylinder.

As shown in the figure, a valve body sliding hole 3 and a fuel reservoir chamber 5 are formed in the valve casing 2 of the fuel injection valve 1, and a nozzle hole 7 communicating with the fuel reservoir chamber 5 is formed at the tip. There is. A large diameter portion 11 of a nozzle needle 9 is slidably fitted into the valve body fingering hole 3 . A connecting part 13 is integrally formed in the upper part of the large diameter part 11 of this nozzle needle 9, and a small diameter part 15 and a valve body part 17 are integrally formed in the lower part.
7 opens and closes the nozzle hole 7.

A flange 19, a piston pin 21, and a piston 23 are integrally connected to the tip of the connecting portion 13 of the nozzle needle 9. The flange 19 and housing 25
A spring 27 is installed between the two and applies a spring force to the nozzle needle 9 in the valve closing direction.

The piston 23 is slidably fitted into the cylinder 29 and forms an operating chamber 31 together with the cylinder 29. A plate valve 37 having an orifice 35 is brought into contact with a high-pressure fuel inlet 33 provided in the upper part of the working chamber 31 and is pressed by the biasing force of a spring body 39 supported by the upper end surface of the piston 23 .

The fuel supply mechanism of this fuel injection device includes a fuel pump 45 that pumps fuel from a fuel tack 41 through a flow path 43, and a fuel pump 45 that pumps fuel through a flow path 47, and a fuel pump 45 that accumulates pressure and supplies the fuel to each fuel injection valve. It is equipped with a pressure accumulation pipe (common rail) 49 to switch the supply direction of fuel from the pressure accumulation device 49 and a three-way solenoid valve 5I that controls opening and closing of the fuel injection valve 1, and also supplies fuel to the fuel reservoir chamber 5. a flow path 53 as a path for connecting, a flow path 55 between the pressure accumulation pipe 49 and the three-way solenoid valve 51, a flow path between the three-way solenoid valve 51 and the fuel tank 41;
A flow path 57 is provided.

The three-way solenoid valve 51 is provided with a first valve body 65 that is slidably fitted into a sliding hole 63 in the valve body 61, as shown in FIG. 3(A). The first valve body 65 is seated on a first valve 69 by the biasing force of a spring 67. Further, by energizing the solenoid 71, the first valve body 65 is slid and separated from the first valve chamber 69. Further, a supply hole 73 through which high-pressure fuel is supplied, which communicates with the sliding hole 63, is bored, and a discharge hole 75 through which the sliding hole 63 communicates with the fuel tank 41, and a first valve seat 69 are provided. A first connection hole 77 is formed which communicates with the outflow inlet 33 of the working chamber of the fuel injection valve. On the other hand, the sliding hole 79 formed in the first valve body 65 has a second
A second valve chamber 83 is formed in the pressure chamber 85, into which the valve body 81 is slidably fitted, and in which the second valve body 81 is seated.

Furthermore, a communication hole 87 that communicates between the pressure chamber 85 and the supply hole 73 is bored in the first valve body 65, and a second connection hole 89 that communicates with the pressure chamber 85 via the second valve seat 83 is bored. It is formed.

The operation of the three-way solenoid valve 51 is such that when the solenoid 71 is not energized, the first valve element 65 is seated on the first valve seat 69 due to the urging force of the spring 67, as shown in FIG. The first connection hole 77 and the discharge hole 75 are blocked off. In addition, the pressure chamber 85 is
The pressure of the high-pressure fuel supplied to the second
The valve body 81 is spaced apart from the second valve seat 83 and the regulating portion 91
will be moved until it hits. As a result, the supply hole 73
is communicated with the first connection hole 77 via the communication hole 87, the pressure chamber 85, and the second connection hole 89, high-pressure fuel is supplied to the working chamber of the fuel injection valve, and fuel injection is stopped.

In addition, when the solenoid 71 is energized as shown in FIG.
is separated from the first valve seat 69.

The first valve body 65 moves, and the second valve body 81 moves to the second valve seat 83.
sit down. As a result, the supply hole 73 is blocked, the connection hole 77 and the discharge hole 75 are brought into communication, and fuel is discharged from the working chamber 31 of the fuel injection valve 1 shown in FIG. 2. As a result, the nozzle needle 9 is moved in the valve opening direction by the high pressure fuel supplied to the fuel injection valve 1 through the flow path 53, and fuel injection is performed. That is, in the nozzle needle 9, the force in the valve opening direction generated by the pressure of the fuel in the fuel reservoir chamber 5 is the sum of the force in the valve closing direction generated by the pressure of fuel in the working chamber 31 and the urging force by the spring 27 etc. When the value exceeds , the valve moves in the direction of opening the valve.

In this embodiment, the movement of the fuel is restricted by the orifice 35, so after switching the three-way solenoid valve 51, the force in the valve opening direction exceeds the force in the valve closing direction, and the nozzle needle 9 does not move upward. Approximately 0.4 [m5e
c] is required. Further, the subsequent moving speed of the nozzle needle 9 also depends on the moving speed of the fuel from the working chamber 31 of the fuel injection valve 1 shown in FIG.

As a result, in the fuel injection valve 1 of this embodiment, excessive injection of high-pressure fuel at the initial stage of valve opening is prevented, and the correspondence between the energization time (and thus the valve opening time) and the fuel injection amount is good.

FIG. 4 is a graph showing the characteristics of the fuel injection using fuel pressure as a parameter. The horizontal axis represents the switching time of the three-way solenoid valve 51, and the vertical axis represents the fuel injection amount. No matter what fuel pressure is, the three-way solenoid valve 51 is energized to 0. 4 [ms ec
] After the elapsed time, fuel injection is started.

Next, a flow path that connects and blocks the pressure accumulation pipe 49 of this fuel injection device and the low pressure side of the fuel system will be explained. This three-way solenoid valve 5
1, in response to the excitation of the solenoid 71 as described above,
It can be switched to two positions as shown in FIGS. 3(A) and 3(B).

At this time, as shown in FIG. 2C, the supply hole 73 on the pressure accumulation pipe side is connected to the low pressure side of the fuel system for a significant period of time via the communication hole 87, the second connection hole 89, and the first connection hole 77. It communicates with a discharge hole 75 on the fuel tank 41 side.

As a control mechanism for the fuel injection valve l and fuel supply mechanism described above, as shown in FIG.
It includes a pump control device 95 for the fuel pump 45, a pressure sensor 97 provided in the pressure accumulation pipe 49 to detect the pressure of the accumulated fuel, and an electronic control unit (ECU) 99.

The electronic control unit 99 is a well-known CP, as shown in FIG.
Ul0I, ROM103. A human-powered boat 113 is configured as a logic operation circuit using a RAM 105 and the like, and manually controls the output of the pressure sensor 97, the accelerator operation amount detection sensor 17, the crankshaft rotational position detection sensor 109, the crankshaft rotational speed detection sensor 111, etc. and three-way solenoid valve 5
1. An output capo 4115 is provided for outputting a control signal to the pump control device 95 and the like. This calculates the valve opening time of the fuel injection valve 1 and the target fuel control pressure from the output of each sensor according to a predetermined program, and controls the three-way solenoid valve 51, pump control device 95, etc. based on these calculation results. By doing so, as shown in FIG. 4, suitable fuel injection amount control can be realized over a wide dynamic range.

Next, the process of the fuel pressure drop control section performed by the fuel injection device of the embodiment configured as described above will be explained with reference to the flowchart of FIG. 6.

When the fuel pressure reduction control process shown in FIG. 6 is started, first, it is determined whether or not the fuel is cut off based on the output of the accelerator operation amount detection sensor (step 200).
), if it is determined that the fuel pressure is in the energized state, it is determined whether the fuel pressure Pa is greater than the target pressure pb (step 21O). If it is determined that the fuel is not in the fuel cut state, or if it is determined that the fuel pressure Pa is equal to or lower than the control target pressure pb even if the fuel is in the fuel cut state, this process ends. In these cases, the fuel pressure P can be adjusted by adjusting the fuel supply amount by the fuel pump 45.
This is because a can be made to follow the control target pressure pb.

If it is determined that the fuel is in the fuel cut state and the fuel pressure Pa is greater than the control target pressure pb, the operation of the fuel pump 45 is stopped (step 220). This prevents the fuel pressure Pa from increasing further. Subsequently, two-position reciprocating switching of the three-way solenoid valve 51 is performed within a predetermined time (step 23o).

During this two-position reciprocating switching, as shown in FIG. 3(C),
The supply hole 73 and the discharge hole 75 of the three-way solenoid valve 51 communicate with each other,
A portion of the high pressure fuel in the pressure accumulation pipe is returned to the fuel tank. 2
The predetermined time for switching positions back and forth is, for example, 0. 3 [
lTl5 e c], as shown in FIG.
A crystal low limit of 0.0 is required to perform fuel injection. 4 [1115e
c] The time is as follows. Therefore, fuel injection is not performed by this two-position reciprocating switching.

Such processing is repeated until the fuel pressure Pa substantially matches the control target pressure pb.

FIG. 7 shows the results of fuel injection by the fuel injection device of the embodiment configured as described above. Figures (A) and (B)
As shown in , the accelerator operation amount is 100% at time t1.
When the target pressure Pb of the fuel control section decreases significantly, the three-way solenoid valve 51 is set to 0.0% as shown in FIG.
3 [ms e c] returns to 41. This results in
The fuel in the pressure accumulator 149 has been slightly consumed as shown in (D) in the same figure, and the fuel pressure Pa decreases as shown in (A) in the same figure. In this implementation result, the three-way solenoid valve 51 was operated several times at 0. After the switching of 3 [ms e c], the fuel pressure Pa is between the control target pressure pb and the road. Therefore, even if the accelerator is then slightly depressed at time t2 to perform light load driving, as shown in FIG.
Therefore, the amount of fuel required is an appropriate amount corresponding to the amount of accelerator operation. In other words, the fuel injection device of the embodiment can cause the fuel pressure Pa to follow the control target pressure Pb with good responsiveness even during sudden deceleration such as when the accelerator operation amount is reduced to 0%. , it is possible to always inject the appropriate amount of fuel at the optimal pressure according to the load between the internal machines.

Further, the fuel injection device of the embodiment has a configuration in which the pressure accumulation distribution W49 is communicated with and cut off from the fuel tank 41 which is the low pressure side, and the communication is achieved by the three-way solenoid valve 51 that controls the opening and closing of the fuel injection valve 1. The overall size and weight can be reduced.

Although one embodiment of the present invention has been described above, the present invention is not equally limited to this embodiment, but can be implemented in various ways.

For example, the two-position reciprocating switching time of the three-way solenoid valve 51 is 0.3
[It does not have to be n1 sec; it is sufficient that it is shorter than the time required for the fuel injection valve 1 to start opening. When the fuel pressure is considerably higher than the control target pressure, the three-way solenoid valve 5
The three-way solenoid valve may be switched back and forth between two positions a plurality of times during the -degree fuel pressure reduction control process by shortening the first switching time. Furthermore, the magnitude of the current flowing through the three-way solenoid valve 51 is adjusted to reduce the rate at which the first valve body 65 is pulled up by the solenoid 71, thereby increasing the time during which the pressure accumulation pipe 49 and the fuel tank 41 are in communication. Good too.

Effects of the Invention As detailed above, the fuel injection device of the present invention is capable of controlling the direction control valve used to open and close the fuel injection valve when the pressure of the fuel accumulated in the pressure accumulation pipe is higher than the control target pressure. By communicating the pressure accumulation pipe with the low pressure side of the fuel system and introducing a portion of the fuel into the low pressure side of the fuel system, the fuel pressure can be reduced even without fuel injection, so the fuel pressure can be controlled. It is possible to perform follow-up control to the target pressure with good responsiveness, and it has the excellent effect of being able to perform stationary fuel injection at a pressure that corresponds to the load of the internal combustion engine.

Therefore, according to the fuel injection device of the present invention, even in a specific driving state such as during sudden deceleration when the accelerator is not pressed and fuel injection is not performed, the fuel pressure decreases, and the next time the accelerator is pressed, the fuel pressure is reduced to an appropriate amount. Because this type of fuel injection is performed, it is unlikely that more than the appropriate amount of fuel is injected as in the past, reducing fuel efficiency and exhaust purification, or causing acceleration shock or unnecessary engine noise. Good engine operating conditions can be obtained.

Furthermore, since the fuel injection device of the present invention communicates between the pressure accumulation pipe and the low pressure side of the fuel system by driving and controlling the directional control valve used to open and close the fuel injection valve, the entire device can be made small and lightweight. Can be done.

In addition, in the present invention, when the pressure of the fuel in the pressure accumulation pipe is higher than the control target pressure, the directional control valve is operated in a time width that is less than the delay time from switching the directional control valve to starting fuel injection at the fuel injection valve. If a configuration is adopted in which 1a"Jo is intermittently communicated by switching drive, opening and closing of the fuel injection valve and communication between the pressure accumulation pipe and the low pressure side of the fuel system can be done simply by adjusting the switching interval of the - direction control valve. can be adjusted together.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the basic configuration of the present invention;
Fig. 2 is a schematic configuration diagram of a fuel injection IJ4 device as an embodiment of the present invention, Fig. 3 (A) or C) is a sectional view of its three-way solenoid valve, and Fig. 4 shows its fuel injection characteristics. 5 is a schematic configuration diagram of the electronic control device, FIG. 6 is a flowchart showing the fuel pressure control process, FIG. 7 is a timing chart showing the result of fuel injection, and FIG. 8 is a diagram of the conventional device. 5 is a timing chart showing the results of fuel injection. 1...Fuel injection valve 41...Fuel tank 49...Pressure accumulation pipe 51...Three-way solenoid valve 99...Electronic control device

Claims (1)

[Claims] 1. Controlling the fuel pressure in a pressure accumulation pipe that stores high-pressure fuel, and controlling the opening time of a fuel injection valve driven by the high-pressure fuel by switching the supply direction of the high-pressure fuel using a directional control valve. In the fuel injection device that injects an appropriate amount of fuel at a pressure depending on the load of the internal combustion engine, the directional control valve is configured to communicate the pressure accumulation pipe to the low pressure side of the fuel system in the process of switching the fuel supply direction. and directional control valve driving means for driving the directional control valve to a position where the flow path is communicated when the pressure of the fuel in the pressure accumulation pipe is higher than the control target pressure. fuel injection device. 2. In the fuel injection device according to claim 1, when the pressure of the fuel in the pressure accumulation pipe is higher than the control target pressure, the directional control valve driving means delays the switching of the directional control valve to the start of fuel injection at the fuel injection valve. A fuel injection device configured to switch and drive the directional control valve in a time span of less than 1 hour to intermittently communicate a flow path that communicates a pressure accumulation pipe with a low pressure side of a fuel system.