High-pressure fuel supply device for internal combustion engine

1. A high-pressure fuel supply device for an internal combustion engine comprising:

a high-pressure fuel pump including an intake valve, a plunger rod which is formed as a separate element from the intake valve, an elastic member which biases the plunger rod in a valve-opening direction of the intake valve, and a solenoid which draws the plunger rod in a valve-closing direction of the intake valve when supplied with electricity; and

a control device including

a first control unit which applies a first current to the solenoid during a pumping cycle to close the intake valve, and

a second control unit which applies a second current to the solenoid during the pumping cycle: i) at a predetermined time that is after a time at which the first current reaches a current value of zero, and ii) before the plunger rod collides with the intake valve during the pumping cycle due to biasing force of the elastic member, wherein

a current value of the second current is smaller than a maximum value of the first current, and

the entire second current is supplied before a piston plunger, which pressurizes a fuel, reaches a top dead center position during the pumping cycle.

2. The high-pressure fuel supply device for an internal combustion engine according to claim 1 , wherein the control device further comprises a third control unit which cuts off the first current and which sets a current of the solenoid to zero.

3. The high-pressure fuel supply device for an internal combustion engine according to claim 1 ,

wherein the control device further comprises a position detecting unit which detects a position of the plunger rod, and

the second control unit applies the second current to the solenoid before a position of the plunger rod reaches a collision position indicating a position where the plunger rod and the intake valve collide with each other.

4. The high-pressure fuel supply device for an internal combustion engine according to claim 3 , wherein the position detecting unit detects the position of the plunger rod based on a measured value of a current or a voltage of the solenoid.

5. The high-pressure fuel supply device for an internal combustion engine according to claim 3 ,

wherein the control device further comprises an estimating unit which detects an inflection point from a measured value of a voltage of the solenoid with a lapse of time after the third control unit cuts off the first current and which estimates the position of the plunger rod at a time of the inflection point as the collision position, and

the second control unit determines timing of applying the second current by using the estimated collision position.

6. The high-pressure fuel supply device for an internal combustion engine according to claim 5 , wherein the second control unit determines timing of applying the second current by using a statistical value of the estimated collision position.

7. The high-pressure fuel supply device for an internal combustion engine according to claim 1 , wherein the second control unit decreases the second current as a temperature correlated with a speed of the intake valve increases.

8. The high-pressure fuel supply device for an internal combustion engine according to claim 7 , wherein the temperature is a temperature of cooling water, a temperature of lubricating oil, or a temperature of fuel.

9. The high-pressure fuel supply device for an internal combustion engine according to claim 1 , wherein the second control unit increases the second current as fuel pressure increases.

10. The high-pressure fuel supply device for an internal combustion engine according to claim 1 , wherein the second control unit increases the second current as an engine rotating speed increases.