JP2636394B2 - Fuel injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Industrial Application Field] The present invention controls the fuel pressure in a storage pipe for storing high-pressure fuel, and switches the supply direction of high-pressure fuel by a directional control valve. The present invention relates to a fuel injection device that controls a valve opening time of a fuel injection valve driven by the engine and injects an appropriate amount of fuel at a pressure corresponding to a load of an internal combustion engine.

2. Description of the Related Art As a conventional fuel injection device of this type, there is, for example, one described in Japanese Patent Application Laid-Open No. 59-165858 (electromagnetic control injection system for diesel engines).

This fuel injection device improves the operating characteristics of the nozzle needles for opening and closing the fuel injection valve, and improves the correspondence between the valve opening time and the fuel injection amount, thereby improving the accuracy of the fuel injection amount. Control is made possible.

On the other hand, fuel pressure is controlled to inject fuel at a pressure corresponding to the load of the internal combustion engine.

This is performed by adjusting the amount of fuel supplied to the storage pipe using a fuel pump. For example, when the pressure is increased, a larger amount of fuel than the fuel injection amount is supplied to the storage pipe by the fuel pump. In this case, the fuel pressure is increased, and when the fuel pressure is reduced, the fuel supply amount by the fuel pump is made smaller than the fuel consumption amount to decrease the fuel pressure.

[Problems to be Solved by the Invention] However, in the conventional fuel injection device described above, the control of the fuel pressure cannot be optimally performed depending on a specific operation state such as a sudden deceleration, and the fuel injection pressure is not appropriate. The problem has arisen. As an example, as shown in FIG. 8 (B), after full load traveling with an accelerator operation amount of 100 [%], coasting with an accelerator operation amount of 0 [%] is performed from time t1, and then at time t2. Consider a case where the accelerator pedal is slightly depressed to perform light load traveling. In this case, when the accelerator operation amount is set to 0 [%] at the time t1, the control target pressure of the fuel greatly decreases as shown in FIG. Conventionally, at this time, the operation of the fuel pump is stopped to stop supplying new fuel, but the fuel in the storage pressure pipe is not consumed because the fuel injection is not performed, and the fuel pressure is As shown by the solid line in FIG. 3A, the light leaks only slightly and slightly. For this reason, when the accelerator is slightly depressed at time t2 and the vehicle travels under a light load, fuel having a pressure higher than the control target pressure of the fuel determined by the accelerator operation amount is injected, and as a result, fuel consumption and exhaust It was also considered that the purification performance was reduced, and that acceleration shock and extra engine noise were generated.

An object of the fuel injection device of the present invention is to solve the above-described problem and to enable the injection of an appropriate amount of fuel at a pressure corresponding to the load of the internal combustion engine.

DETAILED DESCRIPTION OF THE INVENTION [Means for Solving the Problems] As shown in FIG. 1, a fuel injection device of the present invention comprises a storage pressure pipe M1 for storing high-pressure fuel, and a nozzle using high-pressure fuel from the storage pressure pipe M1. A fuel injection valve that receives a force in the valve opening direction on the needle and a force in the valve opening direction on the nozzle needle by high-pressure fuel introduced from the storage pressure pipe M1 into the working chamber.
M3, and a control valve M2 that discharges the high-pressure fuel to the low-pressure side of the fuel system when the valve is opened, and supplies fuel from the fuel pump to the storage pressure pipe M1 to reduce the fuel pressure in the storage pressure pipe M1. Control and the control valve
In a fuel injection device that controls the valve opening time of the fuel injection valve M3 by the drive time of M2 and injects fuel at a pressure corresponding to the load of the internal combustion engine, the fuel pressure in the storage pressure pipe M1 is controlled to a control target pressure. If it is larger, the control valve M2 is driven for a time width shorter than the delay time leading to the start of fuel injection in the fuel injection valve M3, and the high-pressure fuel in the storage pressure pipe M1 is supplied to the low-pressure side of the fuel system. And a control valve driving means M4 for intermittently discharging water.

[Operation] When the fuel pressure in the accumulator pipe M1 is higher than the control target pressure, the fuel injection device of the present invention requires the control valve driving means M4 to operate the fuel injection valve M3 for a time shorter than the delay time before the start of fuel injection. The control valve M2 is driven by the width to continuously discharge the high-pressure fuel in the storage pressure pipe M1 to the low-pressure side of the fuel system. Therefore, the animal pressure piping
Since a part of the fuel in M1 is introduced to the low pressure side of the fuel system, the fuel pressure in the storage pressure pipe M1 drops. As a result, even when the valve opening operation of the fuel injection valve M3 is not performed due to the fuel cut or the like, the fuel pressure immediately follows the control target pressure.

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

As shown in the figure, a valve body sliding hole 3 and a fuel reservoir 5 are formed in the valve casing 2 of the fuel injection valve 1, and a nozzle hole 7 communicating with the fuel reservoir 5 is formed at the tip. I have. The large diameter portion 11 of the nozzle needle 9 is slidably fitted in the valve body sliding hole 3. A connecting portion 13 is provided above the large diameter portion 11 of the nozzle needle 9, and a small diameter portion 15 is provided below the large diameter portion 11.
And the valve body 17 are integrally formed, and the nozzle hole 7 is opened and closed by the valve body 17.

A flange 19, a piston pin 21, and a piston 23 are integrally connected to the tip of the connection portion 13 of the nozzle needle 9. A spring 27 is provided between the flange 19 and the housing 25 to urge the nozzle needle 9 in a valve opening direction.

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

As a fuel supply configuration of this fuel injection device, a fuel pump 45 that pumps fuel from a fuel tank 41 through a flow path 43 is used.
And a storage pressure pipe (common rail) 49 for storing the fuel supplied from the fuel pump 45 through the flow path 47 and supplying it to each fuel injection valve, and switching the fuel supply direction from the storage pressure pipe 49 to the fuel injection valve. A three-way solenoid valve 51 for controlling the opening and closing of the fuel cell 1; a flow path 53 as a path for supplying fuel to the fuel storage chamber 5; a flow path 55 between the storage pressure pipe 49 and the three-way solenoid valve 51;
A flow path 57 between the three-way solenoid valve 51 and the fuel tank 41 is provided.

As shown in FIG. 3 (A), the three-way solenoid valve 51 is provided with a first valve body 65 which is slidably fitted in a sliding hole 63 in a valve body 61. The first valve body 65 is seated on the first valve seat 69 by the urging force of the spring 67. Also, by exciting the solenoid 71, the first valve
65 slides away from the first valve seat 69. Further, a supply hole 73 for supplying high-pressure fuel communicating with the sliding hole 63 is formed, and the sliding hole 63 and the fuel tank 41 are provided.
And a first connection hole 77 that communicates with the outlet 33 of the working chamber of the fuel injection valve via the first valve seat 69. On the other hand, a second valve body 81 is slidably fitted in a sliding hole 79 formed in the first valve body 65, and a second valve seat 83 on which the second valve body 81 is seated has a pressure. A chamber 85 is formed. Further, a communication hole 87 communicating the pressure chamber 85 and the supply hole 73 is formed in the first valve body 65, and a second connection hole 89 communicating with the pressure chamber 85 via the second valve seat 83 is formed. Is formed.

The operation of the three-way solenoid valve 51 is such that, when the solenoid 71 is not excited, the first valve body 65 is seated on the first valve seat 69 by the urging force of the spring 67, as shown in FIG. The first connection hole 77 and the discharge hole 75 are shut off. Also,
The second valve body 81 is separated from the second valve seat 83 by the action force of the pressure of the high-pressure fuel supplied to the pressure chamber 85 via the supply hole 73 and the communication hole 87 until the second valve body 81 hits the regulating portion 91. Be moved. Thereby, the supply hole 73 is provided with the communication hole 87, the pressure chamber 85,
High-pressure fuel is supplied to the working chamber of the fuel injection valve through communication with the first connection hole 77 via the second connection hole 89, and fuel injection is stopped.

When the solenoid 71 is excited, the solenoid 71 lifts up the first valve body 65 against the biasing force of the spring 67, as shown in FIG. Seat 69
Get away from. The first valve body 65 moves, and the second valve body 81 is seated on the second valve seat 83. Thereby, the supply hole 73 is shut off, the connection hole 77 and the discharge hole 75 communicate with each other, and fuel is discharged from the working chamber 31 of the fuel injection valve 1 shown in FIG. 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 via the flow path 53, and fuel injection is performed. That is, the nozzle needle 9 is configured such that the force in the valve opening direction generated by the pressure of the fuel in the fuel storage chamber 5 is the sum of the force in the valve opening direction generated by the pressure of the fuel in the working chamber 31 and the urging force by the spring 27 and the like. When it exceeds, it moves in the valve opening direction.

In this embodiment, since the movement of the fuel is restricted by the orifice 35, the force in the valve opening direction exceeds the force in the valve closing direction after switching the three-way solenoid valve 51, and the nozzle needle 9
It takes about 0.4 [msec] for the to start moving upward. 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 the present embodiment, the excessive injection of the high-pressure fuel in the early stage of valve opening is prevented, and the correspondence between the energization time (and, consequently, the valve opening time) and the fuel injection amount is improved. FIG. 4 is a graph showing the characteristics of the fuel injection using the 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. Regardless of the fuel pressure, the three-way solenoid valve 51 is energized and fuel injection is started after 0.4 [msec] has elapsed.

Next, a description will be given of a flow path that connects and shuts off the storage pressure pipe 49 of the fuel injection device and the low pressure side of the fuel system. This three-way solenoid valve 51
Is set to the third value according to the excitation of the solenoid 71 as described above.
The position is switched to the two positions shown in FIGS. At this time, as shown in FIG.
Communicates with the discharge hole 75 on the fuel tank 41 side, which is the low pressure side of the fuel system, through the communication hole 87, the second connection hole 89, and the first connection hole 77 for a significant time.

As described above, as a control mechanism of the fuel injection valve 1 and the fuel supply mechanism, as shown in FIG. 2, this fuel injection device is provided in a pump control device 95 for the fuel pump 45 and in the storage pressure pipe 49. And a pressure sensor 97 for detecting the pressure of the stored fuel, and an electronic control unit (ECU) 99.

The electronic control unit 99, as shown in FIG.
01, ROM103, RAM105, etc., is configured as a logical operation circuit, the output of the pressure sensor 97, the accelerator operation amount detection sensor
107, an input port 113 for inputting outputs of a crankshaft rotational position detection sensor 109, a crankshaft rotational speed detection sensor 111, etc.
And an output port 115 for outputting control signals to the three-way solenoid valve 51, the pump control device 95, and the like. This means that the valve opening time of the fuel injection valve 1 and the control target pressure of the fuel are calculated from the output of each sensor according to a predetermined program, and the control of the three-way solenoid valve 51 and the pump control device 95, etc. is performed based on these calculation results. By doing so, as shown in FIG. 4, it is possible to realize suitable fuel injection amount control over a wide dynamic range. Next, a control device for lowering the fuel pressure by the fuel injection device of the embodiment configured as described above will be described with reference to the flowchart of FIG.

When the fuel pressure lowering control process shown in FIG. 6 is started, first, it is determined whether or not the vehicle is in a fuel cut state based on an accelerator operation amount detection sensor (step 200). If it is determined, it is determined whether the fuel pressure Pa is higher than the control target pressure Pb (step 21).
0). If it is determined that the vehicle is not in the fuel cut state, or if the fuel pressure is
If it is determined that Pa is equal to or lower than the control target pressure Pb, the process ends. In these cases, the fuel pressure Pa can be made to follow the control target pressure Pb by adjusting the fuel supply amount by the fuel pump 45.

If it is determined that the fuel is cut and the fuel pressure Pa is higher than the control target pressure Pb, the fuel pump 45
Is stopped (step 220). This gives the fuel pressure P
Prevent further rise of a. Then, the three-way solenoid valve 51
Is performed within a predetermined time (step 23).
0). At the time of the 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.
Part of the high-pressure fuel in the storage pressure pipe is returned to the fuel tank. 2
The predetermined time for performing the position reciprocal switching is, for example, 0.3 [msec].
In this case, as shown in FIG. 4, the time is 0.4 [msec] or less, which is the minimum required for performing the fuel injection. Therefore, fuel injection is not performed by the two-position reciprocating switching.

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

FIG. 7 shows the result of fuel injection by the fuel injection device of the embodiment configured as described above. Figures (A) and (B)
As shown in FIG. 7, when the accelerator operation amount changes from 100 [%] to 0 [%] at time t1 and the control target pressure Pb of the fuel largely decreases, the three-way solenoid valve 51 is set to 0.3 [msec] as shown in FIG. And a part of the fuel in the storage pressure pipe 49 is returned to the fuel tank 41. As a result, the fuel in the storage pressure pipe 49 is slightly consumed as shown in FIG. 3D, and the fuel pressure Pa decreases as shown in FIG. In this experimental result, after switching the three-way solenoid valve 51 for 0.3 [msec] several times, the fuel pressure Pa is substantially the same as the control target pressure Pb. Therefore, next, as shown in FIG.
Even when the vehicle is slightly stepped on at time t2 to perform light load traveling, the fuel pressure Pa
Is already substantially the same as the control target pressure Pb, as shown in FIG. 7A, so that the fuel injection amount becomes an appropriate amount corresponding to the accelerator operation amount. That is, according to the fuel injection device of the embodiment, the fuel pressure Pa can be made to follow the control target pressure Pb with good responsiveness even at the time of sudden deceleration such that the access operation amount is 0 [%]. Thus, an appropriate amount of fuel can be always injected at an optimum pressure according to the load of the internal combustion engine.

Further, the fuel injection device of the embodiment is configured to communicate and shut off the storage pressure pipe 49 with the fuel tank 41 on the low pressure side, and the three-way solenoid valve 51 for controlling the opening and closing of the fuel injection valve 1 achieves the communication. The size and weight of the entire device can be reduced.

Although the embodiment of the present invention has been described above, the present invention is not limited to such an actual example, and can be implemented in various modes. For example, a three-way solenoid valve
The two-way reciprocating switching time 51 may not be 0.3 [msec], and it is sufficient that the time is shorter than the time required for the fuel injection valve 1 to start opening. When the fuel pressure is considerably larger than the control target pressure, the switching time of the three-way solenoid valve 51 is shortened,
Multiple times during one fuel pressure drop control process, the two-way solenoid valve
The position may be switched back and forth. Also, three-way solenoid valve
The magnitude of the current flowing through 51 may be adjusted to reduce the speed at which the first valve body 65 is pulled up by the solenoid 71, so that the communication state between the storage pressure pipe 49 and the fuel tank 41 may be extended.

Effect of the Invention As described above, the fuel injection device of the present invention can provide a fuel injection device with a fuel injection valve, when the pressure of the stored fuel is higher than the control target pressure, the delay time before the fuel injection in the fuel injection valve starts. By driving the control valve within a time interval of less than one hour, high-pressure fuel in the accumulator pipe is intermittently discharged to the low-pressure side of the fuel system, and a part of the fuel is introduced to the low-pressure side of the fuel system to perform fuel injection. The fuel pressure can be reduced even without the pressure, so that the fuel pressure can be controlled to follow the control target pressure with good responsiveness, and the best fuel injection can be performed at a pressure corresponding to the load of the internal combustion engine. It works.

Therefore, according to the fuel injection device of the present invention, for example, even in a specific operating state such as during rapid deceleration without performing fuel injection without stepping on the accelerator, the fuel pressure decreases and an appropriate amount is depressed when the next accelerator is depressed. Since fuel injection of more than an appropriate amount is performed as in the past, it is unlikely that fuel consumption and exhaust purification performance will be reduced, acceleration shock and extra engine noise will occur, and always good The operating state of the engine can be obtained.

In the fuel injection device of the present invention, the communication between the storage pressure pipe and the low-pressure side of the fuel system is performed by controlling the drive of a control valve used to open and close the fuel injection valve. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of the present invention, FIG. 2 is a schematic configuration diagram of a fuel injection device as one embodiment of the present invention, and FIGS. FIG. 4 is a sectional view of the valve, FIG. 4 is a graph showing characteristics of the fuel injection, FIG.
FIG. 6 is a schematic configuration diagram of the electronic control unit, FIG. 6 is a flowchart showing the fuel pressure control process, FIG. 7 is a timing chart showing the result of the fuel injection, and FIG. It is a timing chart shown. 1 ... fuel injection valve 41 ... fuel tank 49 ... storage pressure pipe 51 ... three-way solenoid valve 99 ... electronic control unit

Claims (1)

(57) [Claims] An accumulator pipe for storing high-pressure fuel, a force in a valve opening direction to a nozzle needle by high-pressure fuel from the accumulator pipe, and a nozzle in the nozzle chamber by high-pressure fuel introduced into the working chamber from the accumulator pipe. A fuel injection valve that receives a force in a valve closing direction on the needle, and a control valve that discharges the high-pressure fuel to a low-pressure side of a fuel system when the valve is driven to open. A fuel injection device that controls the fuel pressure in the storage pressure pipe, controls the valve opening time of the fuel injection valve by the drive time of the control valve, and injects fuel at a pressure according to the load of the internal combustion engine. When the fuel pressure in the storage pressure pipe is larger than the control target pressure, the control valve is driven with a time width less than a delay time leading to the start of fuel injection in the fuel injection valve, and the fuel pressure in the storage pressure pipe is controlled. High pressure fuel to the fuel system A fuel injection apparatus characterized by comprising a control valve drive means for intermittently discharged to the low pressure side.