JP2005023811A - Control method for fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for opening/closing operation of a fuel injection valve by current control of an open loop so as to supply fuel to an engine, wherein appropriate and stable opening/closing operation of a fuel injection valve can be materialized even if a duty cycle changes. <P>SOLUTION: Suction time S1 and holding time H1 of a fuel injection valve movable part at the ON time F1 of a certain cycle in a pulse signal, and current value A1 of a coil, are set. When the OFF time interval of the pulse signal becomes short between T1 and T2, the suction time from S1 to S2 and the holding time from H1 to H2 are respectively made short. When the OFF time interval of the pulse signal becomes long between T1 and T3, the suction time from S1 to S3 and the holding time from H1 to H3 are respectively made long. By doing so, current having the set current value A1 always flows through the coil. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling a fuel injection valve in a system that supplies fuel to an engine by a fuel injection valve that is opened and closed by open loop current control.
[0002]
[Prior art]
It is well known that gasoline, which is liquid fuel, is supplied to an engine by a fuel injection valve. As shown in FIG. 1A, the gasoline in a fuel container (fuel tank) 1 is pressurized by a fuel pump 2 and a supply line is supplied. 3, and the surplus fuel is supplied to the engine 8 by being adjusted to a predetermined pressure by a pressure regulator 6 installed in a return line 5 that returns the fuel to the fuel container 1 and injected from the fuel injection valve 4 to the intake manifold 7. On the other hand, for example, as described in JP-A-6-17709, LPG is also known to be supplied to an engine as vaporized gas having a predetermined positive pressure. As shown in FIG. Cylinder) 1 LPG is delivered to the supply line 3 at its own pressure, and is supplied to the engine 8 by being injected into the intake manifold 7 from the fuel injection valve 4 as a predetermined positive pressure vaporized gas by the pressure regulator 10.
[0003]
The fuel injection valve 4 is opened and closed according to the driving signal output from the electronic control device 9 according to the operating state of the engine 8. In this case, the value of the current flowing through the solenoid coil that is the actuator of the fuel injection valve 4 is always set. It is necessary to control to be constant. For this purpose, the current flowing through the coil is detected and compared with a preset current value so that the current of the set current value is supplied to the coil or measured during a test performed on the product. The obtained control value is set, and current control is performed so that the current of the set value is always supplied to the coil.
[0004]
The former current control is a feedback method that detects and compares the current value and controls the coil supply current based on the comparison result, so that the purpose of keeping the current value constant can be achieved. Since the current value comparison function and the current control function are necessary, the system is remarkably plural and expensive. On the other hand, the latter current control is an open loop system in which neither detection nor comparison is performed, and a current control system for opening and closing the fuel injection valve can be easily and inexpensively constructed.
[0005]
Here, in the system that opens and closes the fuel injection valve by open-loop current control, the current value in the suction time and holding time of the movable portion of the fuel injection valve, which is the ON time of the drive signal, that is, the pulse signal, In this case, it is determined by obtaining an appropriate value when the pulse signal has a certain period, and this determined current value is set as a control value in the electronic control device, and the current of the set control value is supplied to the coil. To be.
[0006]
[Problems to be solved by the invention]
However, in an open loop system that performs current control so as to achieve the control value set as described above, it is not only possible to know the current value that is actually flowing, but the actual current value is different from the control value. However, this cannot be corrected. For this reason, when the control value is set in the cycle composed of the on time F1 and the off time T1 shown in FIG. 3A, for example, the on time shown in FIG. When the cycle is changed to the period consisting of the time F1 and the off time T2, the current which is strongly affected by the off-surge and has the current value A1 shown in (B) in (A) is shown in (D) in (C). Thus, a current having a current value A2 larger than A1 flows through the coil. For this reason, there is a risk that the temperature of the fuel injection valve rises and in the worst case, it burns out, and there is a concern that the suction force increases, leading to early deterioration of the movable part.
[0007]
To cope with these problems, it is necessary to select the parts of the drive circuit to match the large current value for the increase in current, and it is necessary to use high heat resistance and high strength parts for the fuel injection valve. Therefore, not only will the manufacturing price be raised, but the drive circuit must also take measures against heat generation. As another countermeasure, it is considered that the current value set in the electronic control device is reduced so that the current value A2 at the short off time T2 remains small as shown in FIG. However, the current value A1 at the time of the long off time T1 shown in (A) is further reduced, and the opening of the fuel injection valve is delayed or cannot be opened, and the fuel flow rate is changed to impair the engine operability. This causes a problem.
[0008]
The present invention has a system that opens and closes a fuel injection valve by open-loop current control to inject fuel and supply it to the engine. When the duty cycle of the pulse signal changes, the fuel injection valve and the drive circuit are adversely affected. Or to make the operation of the fuel injection valve incomplete, and when the duty cycle changes regardless of the period of the pulse signal, the current value is always constant. It is an object of the present invention to provide a control method that can supply a current of 5 to a coil to cause a fuel injection valve to perform an appropriate opening / closing operation.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a variable off-state so that the current value of the current flowing through the coil of the fuel injector is always constant when the off-time of the pulse signal for opening / closing the fuel injector changes. The suction time and the holding time of the movable part of the fuel injection valve at the on time are changed according to the time.
[0010]
Alternatively, the suction time and holding time of the movable part of the fuel injection valve and the current value of the current flowing through the coil during the ON time of the pulse signal for opening and closing the fuel injection valve in a certain cycle are set, and the pulse signal is turned off. When the time is shorter than the off time in a certain cycle, the suction time / holding time of the movable part is changed to a time shorter than the set suction time / holding time according to the shortened off time, When the OFF time of the pulse signal is longer than the OFF time in a certain period, the suction time and holding time are changed to a time longer than the set suction time and holding time according to the longer OFF time and are always set. The current of the current value was made to flow through the coil.
[0011]
Alternatively, the suction time and holding time of the movable part of the fuel injection valve during the on time when the duty cycle of the pulse signal for opening and closing the fuel injection valve is minimum, and the current value of the current flowing through the coil are set. As the OFF time of the pulse signal becomes shorter, the suction time / holding time is changed to a time shorter than the set suction time / holding time so that the current of the set current value flows through the coil.
[0012]
Furthermore, the suction time and holding time of the fuel injection valve during the on time when the duty cycle of the pulse signal for opening and closing the fuel injection valve is maximum, and the current value of the current flowing through the coil are set, and the pulse signal is thereby determined. The suction time / holding time was changed to a time longer than the set suction time / holding time so that the current of the set current value would flow through the coil as the OFF time of the battery increased.
[0013]
Since the pulse signal is output by the electronic control device, its period and duty cycle are always recognized. Therefore, in general, for fuel injection valves that open and close within the dynamic range, the suction time / holding time and current value at a certain duty cycle in a certain period are set, and the off time becomes shorter and longer than that. The suction time / holding time is sequentially changed to a short time and a long time in multiple stages in response to changes in the time, and the off time is set by setting the suction time / holding time and current value at the minimum duty cycle or maximum duty cycle. As the time becomes longer or shorter, the suction time / holding time is appropriately changed to a short time or a long time in a plurality of stages, and as a result, the current flowing through the coil can be more stably maintained at the set current value.
[0014]
This can be done by setting and mapping control constants for off-time in multiple stages, preferably multiple stages, in the test conducted on the product, and changing the suction time and holding time based on this control constant. It can be easily implemented.
[0015]
In this way, the current supplied to the coil as the suction current for sucking and moving the movable part of the fuel injection valve from the valve closing position to the valve opening position and the holding current for holding the movable part at the valve opening position are set to the cycle of the pulse signal. Regardless of this, even if the off-time changes, the fuel injection valve can be made to perform an appropriate opening / closing operation stably by making it always the same. In particular, the phenomenon that the current value increases due to the effect of the off-surge of the fuel injection valve when the off time becomes short can be prevented by shortening the suction time and holding time to the set current value. Problems such as burnout, early deterioration, and overload on the drive circuit are eliminated.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention will be described with reference to FIG. 2. A standard duty cycle in a certain cycle is selected for a pulse signal for opening and closing the fuel injection valve in accordance with the operating state of the engine. In this embodiment, it is set to 50%, and the on time F1 at that time and the on time F1 at the off time T1 are the suction time S1 and the holding time H1 of the movable part of the fuel injection valve 4, and the current supplied to the coil Select the value A1. These suction time S1, holding time H1, and current value A1 are selected so that the fuel injection valve 4 can be opened and closed accurately and stably in the selected duty cycle, and input to the electronic control device in advance. Set it. (A-1), (A-2), and (A-3) in FIG. 2 are waveform diagrams respectively showing the pulse signal, suction time and holding time, and current.
[0017]
The pulse signal has the same period depending on the engine operating state, but when the ON time increases from F1 to F2 and the OFF time decreases from T1 to T2 as shown in (B-1), (B-2 ), The suction time is changed from S1 to S2, and the holding time is changed from H1 to H2, respectively, so that the current value is the same as the set current value A1 as shown in (B-3). Further, when the pulse signal has the same cycle but the on-time is shortened from F1 to F3 and the off-time is long from T1 to T3 as in (C-1), (C-2) Thus, the suction time is changed from S1 to S3, and the holding time is changed from H1 to H3, respectively, so that the current value is the same as the set current value A1 as shown in (C-3).
[0018]
By setting multiple times in the electronic control device, the time point when the suction time / holding time is changed from S1, H1 to shorter and longer times and each time at that time is set over the entire duty cycle range. A current having a current value A1 can be applied to the coil. Needless to say, A1 is set to a value that is less affected by off-surge and can reliably open and close the fuel injection valve.
[0019]
Next, the present invention is not limited to the above, and can be carried out based on the minimum or maximum duty cycle. That is, for example, assuming that the duty cycle shown in FIG. 2C-1 is the minimum, the current value at that time can reliably open and close the fuel injection valve, and the influence of the off surge when the off time becomes the shortest. When the minimum value A1 and the suction time S3 and the holding time H3 are set, and the OFF time becomes shorter from T3 to T1 and T2 in this order (A-1) and (B-1), each time point Thus, the suction time and the holding time are sequentially changed from S3, H3 to S1, H1, and S2, H2 so that the current of the set current value A1 flows through the coil.
[0020]
Alternatively, assuming that the duty cycle shown in FIG. 2 (B-1) is the maximum, the current value at that time minimizes the effect of off-surge and reliably opens and closes the fuel injection valve when the off-time becomes the longest. Set operable value A1 and suction time S2, hold time H2, and set at each time when OFF time becomes longer from T2 to T1, T3 in that order (A-1), (C-1) The suction time and holding time are sequentially changed from S2, H2 to S1, H1, and then S3, H3 so that the current of current value A1 flows through the coil.
[0021]
It should be noted that the present invention is applied as it is even when the cycle of the pulse signal is changed. When the cycle becomes longer but the off time becomes shorter due to the longer on time, the cycle becomes longer and the on time becomes longer. If the off-time becomes longer regardless of change / no change, the cycle becomes shorter, but if the off-time becomes longer due to the shorter on-time, the cycle becomes shorter and the off-time becomes longer regardless of the change / no change in the on-time. The suction time and the holding time can be changed so that the current flowing through the coil maintains the set current value A1 in response to various changes in the pulse signal.
[0022]
Thus, according to the present embodiment in which the current value of the current flowing through the coil of the fuel injection valve is always the same as the preset current value, it is particularly short when the OFF time of the pulse signal changes. The current flowing through the coil is kept at a constant current value, and these are safely protected without taking special heat and strength measures on the fuel injection valve or taking special heat measures on the drive circuit. On the other hand, even when the off-time changes to a longer one, it is possible to reliably open and close, and to make the fuel injection valve always perform an appropriate opening and closing operation.
[0023]
【The invention's effect】
As described above, according to the present invention, a current of a constant current always flows through the coil of the fuel injection valve that is opened and closed by open-loop current control regardless of the change in the OFF time of the pulse signal, and the proper opening and closing operation is stabilized. That can be done.
[Brief description of the drawings]
FIGS. 1A and 1B are schematic arrangement views showing different examples of a fuel injection device to which the present invention is applied.
FIG. 2 is a waveform diagram of a pulse signal, a suction time and a holding time, and a current illustrating an embodiment of the present invention.
FIG. 3 is a waveform diagram of a conventional pulse signal and current.
[Explanation of symbols]
4 fuel injection valve, 5 engine, 7 electronic control unit, F1, F2, F3 on time, T1, T2, T3 off time, S1, S2, S3 suction time, H1, H2, H3 holding time, A1 current value

Claims (6)

When opening and closing the fuel injection valve by open loop current control to inject fuel and supply it to the engine,
When the off time of the pulse signal for opening and closing the fuel injector changes, the current value of the current flowing through the coil of the fuel injector is always constant, so that the fuel injector at the on time is changed according to the changed off time. Change the suction time and holding time of the movable part,
A control method for a fuel injection valve. When opening and closing the fuel injection valve by open loop current control to inject fuel and supply it to the engine,
The suction time and holding time of the movable part of the fuel injection valve and the current value of the current flowing through the coil during the ON time in a certain cycle of the pulse signal for opening and closing the fuel injection valve are set, and the OFF time of the pulse signal is set. When it becomes shorter than the off time in the certain period, the suction time / holding time is changed to a time shorter than the set suction time / holding time according to the shortened off time, and the pulse signal When the off time becomes longer than the off time in the certain cycle, the suction time / holding time is changed to a time longer than the set suction time / holding time according to the off time that has become longer. Make the current of the current flow through the coil,
A control method for a fuel injection valve. 2. The suction time / holding time of the movable part is changed in a plurality of stages for each of when the off time of the pulse signal becomes shorter and longer than the off time in the certain period. 2. A method for controlling the fuel injection valve described in 2. When opening and closing the fuel injection valve by open loop current control to inject fuel and supply it to the engine,
Set the suction time and holding time of the movable part of the fuel injection valve during the ON time when the duty cycle of the pulse signal for opening and closing the fuel injection valve is minimum, and the current value of the current flowing through the coil, and then the pulse signal As the OFF time becomes shorter, the suction time / holding time is changed to a time shorter than the set suction time / holding time so that the current of the set current value flows through the coil.
A control method for a fuel injection valve. When opening and closing the fuel injection valve by open loop current control to inject fuel and supply it to the engine,
Set the suction time and holding time of the movable part of the fuel injection valve during the on time when the duty cycle of the pulse signal that opens and closes the fuel injection valve is maximum, and the current value of the current flowing through the coil. As the OFF time of the is increased, the suction time / holding time is changed to a time longer than the set suction time / holding time so that the current of the set current value flows through the coil.
A control method for a fuel injection valve. 6. The method for controlling a fuel injection valve according to claim 4, wherein the suction time / holding time of the movable part is changed in a plurality of steps between the longest and shortest of the off times.

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