JPH04353240A - Air-fuel mixture injection device for two-cycle engine - Google Patents

Abstract

PURPOSE:To keep responsiveness and stability in opening operation of an injection nozzle, and avoid current consumption from increasing by increasing a drive current until it reaches at a start current level and, after it reaches at the start current level and a specified time is collapsed, by switching over the drive current to a holding current level. CONSTITUTION:A valve mechanism 6 for opening and closing an injection port opened to a combustion chamber by means of an injection nozzle 6a is provided to increase a drive current to an electromagnetic coil 6b for opening the injection nozzle 6a until it reaches at a start current level required to fully open the injection nozzle 6a. Also a drive current control circuit 8 for switching over the start current level to the holding current level required to keep the opened condition of the injection nozzle 6a after the drive current reaches at the start current level is provided. In this case, the drive current control circuit 8 increases the drive current until it reaches at the start current level and, after it reaches at the start current level and a specified operating time is collapsed, the drive current is switched over to the holding current level.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to an air-fuel injection system for a two-stroke engine, and particularly when the injection port is opened and closed by moving the injection valve using an electromagnetic coil, the response of the opening operation of the injection valve is The present invention relates to an improvement in a drive current control method that ensures both performance and stability.

0002

[Prior Art] Conventionally, as an air fuel injection device employed in a two-stroke engine, for example, Japanese Patent Application Laid-Open No. 61-5030
There is one described in Publication No. 43. This has a valve mechanism that uses an injection valve to open and close an injection port opening toward a combustion chamber, and the opening and closing of the injection valve is performed by an electromagnetic coil. As a method of controlling the drive current to such an electromagnetic coil, conventional methods have been used, for example, as shown in FIG.
As shown in FIG. 1, there is a method in which the drive current I is switched to a holding current level necessary to keep the valve open after the current reaches a predetermined starting current level necessary for driving the valve. It has been adopted. Thereby, current consumption can be reduced.

0003

However, in the above-mentioned air-fuel injection system, in order to improve the responsiveness of the opening operation of the injection valve, an electromagnetic coil whose driving current rises quickly is sometimes used as the electromagnetic coil. However, since the injection valve naturally has an inertial mass, there is a limit to the improvement of its operational response. Therefore, as shown by the two-dot chain line in Fig. 3, if the rise of the drive current is set too quickly, the opening operation will be completed at the time a when the drive current reaches the starting current level and is switched to the holding current level. There are cases where the opening operation is unstable, which causes the problem that the opening operation becomes unstable. Therefore, in order to solve the problem that the opening operation is unstable, conventionally, as shown by the broken line in FIG. 3, the starting current level of the driving current I is set to a temporary level higher than the actually required starting current level. has been adopted. However, in this case, although the opening operation of the injection valve can be stabilized, the amount of current consumption increases by the amount of current flowing than the current value required to start the opening operation.

The present invention has been made in view of the above-mentioned conventional problems, and provides an air-fuel injection device for a two-stroke engine that ensures responsiveness and stability of the opening operation of the injection valve and avoids an increase in current consumption. is intended to provide.

[0005]

[Means for Solving the Problems] The present invention provides a valve mechanism that uses an injection valve to open and close an injection port opening toward a combustion chamber, an electromagnetic coil that opens the injection valve, and a drive current to the electromagnetic coil. a drive current control circuit that increases the starting current level until it reaches the starting current level necessary to fully open the injection valve, and after reaching the starting current level, switches to the holding current level necessary to keep the injection valve open. In the air fuel injection device for a two-stroke engine, the drive current control circuit increases the drive current until it reaches the starting current level, and the starting current level is reached and a certain operating time has elapsed. After that, the current level is switched to the above-mentioned holding current level. Here, the starting current level is set to a level that is the minimum current required to fully open the injection valve plus some margin. Regarding the setting of the operating time, either a method that starts counting from the time when the current supply starts, or a method that starts counting from the time when the starting current level is reached can be adopted. Furthermore, the length of this operation time will be determined through experiments or the like, and will be explained based on this experimental value.

[0006]

[Operation] According to the air fuel injection device of the present invention, the drive current flowing through the electromagnetic coil is increased until it reaches the starting current level, and after a predetermined operating time has elapsed, it is switched to the holding current level. By setting the rise of the drive current quickly, the operational response of the valve can be improved, and even if the drive current is set quickly, the current will not be switched to the holding current level before the valve opening operation is completed. The stability of the opening operation can also be ensured. Further, since the starting current level is not set to an unnecessarily high level as in the prior art, there is no increase in power consumption.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the drawings. 1 and 2 are diagrams for explaining an air fuel injection device for a two-stroke engine according to an embodiment of the present invention,
FIG. 1 is a block diagram showing its overall configuration, and FIG. 2 is a waveform diagram for explaining its operation.

In FIG. 1, reference numeral 1 denotes an air-fuel injection device, which controls an injector body 2 that directly injects and supplies air and fuel into the cylinders of the engine, and a drive current to the injector body 2. It is composed of a drive circuit 3 and a control unit 4 that controls the operation of the drive circuit 3. Note that 5 is an on-vehicle battery, the positive electrode 5a of which is connected to the injection device main body 2, and the negative electrode 5b is grounded.

The injection device main body 2 includes a valve mechanism 6 consisting of an injection valve 6a that opens and closes an injection port opening toward the combustion chamber, and an electromagnetic coil 6b that opens and operates the injection valve 6a. One end of the electromagnetic coil 6b is connected to the positive electrode 5a of the battery 5, and the other end is connected to the power transistor 7 of the drive circuit 3. The control unit 4 outputs a drive pulse signal P (see FIG. 2) and an operating time t to the control circuit 8 of the drive circuit 3 via output terminals 4a and 4b. The drive pulse signal P is set so as to obtain the injection start timing and injection pulse width according to various conditions such as the operating state of the engine. The operating time t is set to a time required to complete the opening operation depending on the inertial mass of the injection valve 6a.

The drive circuit 3 includes the power transistor 7 for supplying a drive current I to the electromagnetic coil 6b.
Then, the transistor 7 is turned on by the drive control signal S.
It is composed of a control circuit 8 that performs off control. The collector 7a of the power transistor 7 is connected to the electromagnetic coil 6.
The base 7b is connected to the output 8a of the control circuit 8, and the emitter 7c is grounded via a current detection resistor 9. Further, the value detected by the current detection resistor 9 is input to the control circuit 8 via the input terminal 8b, and the battery voltage V is input to the control circuit 8 via the input terminal 8c.

As shown in FIG. 2, the drive control signal S output from the control circuit 8 to the power transistor 7 has an activation control level corresponding to the drive current required to fully open the valve; The waveform has a holding control level that corresponds to the drive current necessary to hold the valve in the open state, and the time length of this activation control level is set to the operating time t. Further, when the voltage V of the battery 5 is lower than a predetermined value, the control circuit 8 corrects the operation time t from the control unit 4 to a longer value, and adjusts the time length of the holding control level to the corrected operation time. Set to .

In this way, the drive current I supplied to the electromagnetic coil 6b increases until it reaches the starting current level corresponding to the starting control level, and this starting continues until the operating time t has elapsed from the energization start time. The current level is held, and then the holding current level is switched to the holding current level corresponding to the holding control level.

Next, the effects of this embodiment will be explained. In the air fuel injection device 1 for the engine according to the present embodiment, a drive pulse signal P having an injection timing and an injection pulse width according to the operating state of the engine, and an injection valve are sent from the control unit 4 to the control circuit 8 of the drive circuit 3. 6a
The operation time t corresponding to the opening operation completion time is output. Then, a drive control signal S consisting of an activation control level and a holding control level is supplied from the control circuit 8 to the base 7b of the power transistor 7, so that a drive current I shown in FIG. 2 flows through the electromagnetic coil 6b of the valve mechanism 6. That is, the drive current I increases until it reaches the starting current level necessary to fully open the injection valve 6a, and is maintained at this starting current level until a predetermined operating time t has elapsed from the start of energization, after which the injection valve 6a is switched to and held at the holding current level necessary to hold it open. As a result, the injection valve 6a is moved downward by the electromagnetic force of the electromagnetic coil 6b to open the injection port, and as a result, fuel is injected and supplied into the combustion chamber together with compressed air.

As described above, in this embodiment, the driving current I is limited to the starting current level necessary to start the opening operation, and the energization time is secured to the operation time t necessary to complete the opening operation. By setting the rise of the current in the electromagnetic coil 6b quickly, it is possible to improve the responsiveness of the opening operation of the injection valve 6a and to ensure the stability of the opening operation. Furthermore, since the drive current I is not set higher than necessary, no increase in power consumption occurs. In the above embodiment, the driving current I is switched to the holding current level when the operating time t has elapsed from the start of current supply, but this means that the driving current I is switched to the holding current level when the operating time t has elapsed from the time when the starting current level has been reached. It may be possible to switch at a certain point. In this case, of course, the time t' is set shorter than the time t.

[0015]

As described above, according to the air-fuel injection device for a two-stroke engine according to the present invention, the drive current supplied to the electromagnetic coil is limited to the starting current level, and after a predetermined period of time has elapsed, the drive current is maintained. Since the current level is switched, both the responsiveness and stability of the opening operation of the injection valve can be ensured, and an increase in power consumption can be avoided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an air-fuel injection device for a two-stroke engine according to an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the above embodiment.

FIG. 3 is a waveform chart for explaining the problems of the conventional air-fuel injection device.

[Explanation of symbols]

1 Air fuel injection device 6 Valve mechanism 6a Injection valve 6b Electromagnetic coil 8 Control circuit (drive current control circuit) I Drive current t Operating time

Claims (1)

[Claims] 1. A valve mechanism for opening and closing an injection port opening toward a combustion chamber with an injection valve, an electromagnetic coil for opening the injection valve, and a drive current to the electromagnetic coil for fully opening the injection valve. and a drive current control circuit that increases the starting current level until it reaches the starting current level necessary for the engine, and after reaching the starting current level, switches to the holding current level necessary to hold the injection valve in the open state. In the air-fuel injection device, the drive current control circuit increases the drive current until it reaches the starting current level, and returns the drive current to the holding current level after reaching the starting current level and after a certain operating time has elapsed. An air-fuel injection system for a two-stroke engine, characterized in that it is configured to switch.