Drive device for electromagnetic fuel injection valve

1. A drive device for a fuel injection valve having an electromagnet with a stationary core and an electromagnetic coil, a movable core driven with the electromagnet, a valve plug assembled into the movable core, a pressure member of giving the movable core a pressure in a valve closing direction, the drive device comprising:

an engine control unit that is configured to determine a fuel injection pulse width and an injection timing; and

a drive circuit unit that is configured to control a voltage to be applied to the electromagnetic coil and to supply a current to the electromagnetic coil, wherein

the drive circuit unit controls the voltage to be applied to the electromagnetic coil in accordance with the fuel injection pulse width,

the drive circuit unit is configured to, in between termination of an electromagnetic coil-voltage application equivalent to termination of a first fuel injection period and initiation of an electromagnetic coil-voltage application equivalent to initiation of a second fuel injection period subsequent to the first fuel injection period, apply the electromagnetic coil with a voltage at a level of not opening the valve to supply an intermediate current for the electromagnetic coil in the same direction as a direction of a drive current for opening the valve, and

the drive circuit unit sets the voltage application for the intermediate current to initiate after turning off the electromagnetic coil-voltage application in the first fuel injection period before a first point in time when the valve plug sits on a valve seat and terminate before half a period of time between the first point in time and a second point in time when initiating an application of a drive voltage for opening the valve in the second fuel injection period.

2. The drive device according to claim 1 ,

wherein the engine control unit is further configured to set a split injection of splitting fuel mass per a one-time injection stroke into several times which are the first fuel injection period and the second fuel injection period.

3. The drive device according to claim 2 , further comprising a booster circuit that boosts a voltage supplied from a power source to a higher voltage than that of the power source, and the voltage application for the intermediate current is generated with the voltage booster circuit.

4. The drive device according to claim 3 ,

wherein the drive circuit unit is further configured to terminate the voltage for the intermediate current before a magnitude of the intermediate current reaches a magnitude required for a magnetic force separating the valve plug having sat on the valve seat from the valve seat.

5. The drive device according to claim 4 ,

wherein the engine control unit is further configured to set such that each of the first fuel injection period and the second fuel injection period includes two kinds of voltage application periods, one of which is a boosted voltage application period of applying the electromagnetic coil with a boosted voltage equivalent to a drive voltage for a valve open, the other of which is a power source-voltage application period of applying the electromagnetic coil with a voltage of the power source for holding the valve-open by means of switching subsequent to the boosted voltage application period,

wherein a maximum value of the intermediate current is set to be greater than a maximum value of a current supplied to the electromagnetic coil by the voltage of the power source in the power source-voltage application period, and set to be smaller than a maximum value of a current supplied to the electromagnetic coil by the boosted voltage in the boosted voltage application period.

6. The drive device according to claim 1 ,

wherein the drive circuit unit is further configured to generate a voltage application for supplying the intermediate current by controlling a pulse width of an injection pulse output from an engine control unit.

7. The drive device according to claim 1 ,

wherein the fuel injection valve to which the drive device applied is, comprises the movable core having a relative motion with respect to the valve plug to absorb the impact between the valve plug and the valve seat, and a pressure member applying the movable core with a force in a valve opening direction; and

wherein timing of terminating the voltage application is obtained by dividing the product of a velocity of impact between the valve plug and the valve seat and a mass of the movable core by the force of the pressure member.

8. A drive device for a fuel injection valve having an electromagnet with a stationary core and an electromagnetic coil, a movable core driven with the electromagnet, a valve plug assembled into the movable core, a pressure member of giving the movable core a pressure in a valve closing direction, the drive device comprising:

an engine control unit that is configured to determine a fuel injection pulse width and an injection timing; and

a drive circuit unit that is configured to control a voltage to be applied to the electromagnetic coil and to supply a current to the electromagnetic coil, wherein

the drive circuit unit controls the voltage to be applied to the electromagnetic coil in accordance with the fuel injection pulse width,

the drive circuit unit is configured to, in between termination of an electromagnetic coil-passage of current equivalent to termination of a first fuel injection period and initiation of an electromagnetic coil-passage of current equivalent to initiation of a second fuel injection period subsequent to the first fuel injection period, supply the electromagnetic coil with an intermediate current for in the same direction as a direction of a drive current for opening the valve, and

the drive circuit unit sets the intermediate current to initiate after turning off the electromagnetic coil-passage of current in the first fuel injection period before a first point in time when the valve plug sits on a valve seat and terminate before half a period of time between the first point in time and a second point in time when initiating an electromagnetic coil-passage of current in the second fuel injection period.

9. The drive device according to claim 2 ,

wherein the fuel injection valve to which the drive device applied is, comprises the movable core having a relative motion with respect to the valve plug to absorb the impact between the valve plug and the valve seat, and a pressure member applying the movable core with a force in a valve opening direction; and

wherein timing of terminating the voltage application is obtained by dividing the product of a velocity of impact between the valve plug and the valve seat and a mass of the movable core by the force of the pressure member.

10. The drive device according to claim 3 ,

wherein the fuel injection valve to which the drive device applied is, comprises the movable core having a relative motion with respect to the valve plug to absorb the impact between the valve plug and the valve seat, and a pressure member applying the movable core with a force in a valve opening direction; and

wherein timing of terminating the voltage application is obtained by dividing the product of a velocity of impact between the valve plug and the valve seat and a mass of the movable core by the force of the pressure member.

11. The drive device according to claim 4 ,

wherein the fuel injection valve to which the drive device applied is, comprises the movable core having a relative motion with respect to the valve plug to absorb the impact between the valve plug and the valve seat, and a pressure member applying the movable core with a force in a valve opening direction; and

wherein timing of terminating the voltage application is obtained by dividing the product of a velocity of impact between the valve plug and the valve seat and a mass of the movable core by the force of the pressure member.

12. The drive device according to claim 5 ,

wherein the fuel injection valve to which the drive device applied is, comprises the movable core having a relative motion with respect to the valve plug to absorb the impact between the valve plug and the valve seat, and a pressure member applying the movable core with a force in a valve opening direction; and

wherein timing of terminating the voltage application is obtained by dividing the product of a velocity of impact between the valve plug and the valve seat and a mass of the movable core by the force of the pressure member.

13. The drive device according to claim 6 ,

wherein the fuel injection valve to which the drive device applied is, comprises the movable core having a relative motion with respect to the valve plug to absorb the impact between the valve plug and the valve seat, and a pressure member applying the movable core with a force in a valve opening direction; and

wherein timing of terminating the voltage application is obtained by dividing the product of a velocity of impact between the valve plug and the valve seat and a mass of the movable core by the force of the pressure member.

14. A drive device for a fuel injection valve having an electromagnet with a stationary core and an electromagnetic coil, a movable core driven with the electromagnet, a valve plug assembled into the movable core, a pressure member of giving the movable core a pressure in a valve closing direction, the drive device comprising:

an engine control unit that is configured to determine a fuel injection pulse width and an injection timing; and

a drive circuit unit that is configured to control a voltage to be applied to the electromagnetic coil and to supply a current to the electromagnetic coil, wherein

the drive circuit unit controls the voltage to be applied to the electromagnetic coil in accordance with the fuel injection pulse width,

the drive circuit unit is configured to, in between termination of an electromagnetic coil-voltage application equivalent to termination of a first fuel injection period and initiation of an electromagnetic coil-voltage application equivalent to initiation of a second fuel injection period subsequent to the first fuel injection period, apply the electromagnetic coil with a voltage at a level of not opening the valve to supply an intermediate current for the electromagnetic coil in the same direction as a direction of a drive current for opening the valve,

the drive circuit unit sets the voltage application for the intermediate current to initiate after turning off the electromagnetic coil-voltage application in the first fuel injection period before a first point in time when the valve plug sits on a valve seat and terminate before half a period of time between the first point in time and a second point in time when initiating an application of a drive voltage for opening the valve in the second fuel injection period,

the fuel injection valve to which the drive device applied is, comprises the movable core having a relative motion with respect to the valve plug to absorb the impact between the valve plug and the valve seat, and a pressure member applying the movable core with a force in a valve opening direction, and

timing of terminating the voltage application is obtained by dividing the product of a velocity of impact between the valve plug and the valve seat and a mass of the movable core by the force of the pressure member.

15. The drive device according to claim 14 , wherein the drive circuit unit is further configured to generate a voltage application for supplying the intermediate current by controlling a pulse width of an injection pulse output from an engine control unit.

16. The drive device according to claim 14 , wherein the engine control unit is further configured to set a split injection of splitting fuel mass per a one-time injection stroke into several times which are the first fuel injection period and the second fuel injection period.

17. The drive device according to claim 16 , further comprising a booster circuit that boosts a voltage supplied from a power source to a higher voltage than that of the power source, and the voltage application for the intermediate current is generated with the voltage booster circuit.

18. The drive device according to claim 17 , wherein the drive circuit unit is further configured to terminate the voltage for the intermediate current before a magnitude of the intermediate current reaches a magnitude required for a magnetic force separating the valve plug having sat on the valve seat from the valve seat.

19. The drive device according to claim 18 , wherein the engine control unit is further configured to set such that each of the first fuel injection period and the second fuel injection period includes two kinds of voltage application periods, one of which is a boosted voltage application period of applying the electromagnetic coil with a boosted voltage equivalent to a drive voltage for a valve open, the other of which is a power source-voltage application period of applying the electromagnetic coil with a voltage of the power source for holding the valve-open by means of switching subsequent to the boosted voltage application period,

wherein a maximum value of the intermediate current is set to be greater than a maximum value of a current supplied to the electromagnetic coil by the voltage of the power source in the power source-voltage application period, and set to be smaller than a maximum value of a current supplied to the electromagnetic coil by the boosted voltage in the boosted voltage application period.

20. The drive device according to claim 16 , wherein

the fuel injection valve to which the drive device applied is, comprises the movable core having a relative motion with respect to the valve plug to absorb the impact between the valve plug and the valve seat, and a pressure member applying the movable core with a force in a valve opening direction, and

timing of terminating the voltage application is obtained by dividing the product of a velocity of impact between the valve plug and the valve seat and a mass of the movable core by the force of the pressure member.