Liquid discharge head

1 . A liquid discharge unit comprising:

a discharge port which discharges liquid;

a supply path which supplies the liquid to the discharge port; and

a pressure control unit which controls a pressure of the liquid supplied from a liquid supply source to the supply path, wherein

the pressure control unit comprises:

a fluid chamber having an inflow port into which the liquid from the liquid supply source flows and an outflow port which causes the liquid having flowed in through the inflow port to flow out to the supply path;

a valve body configured to be capable of taking a closed position where the inflow port is closed and an open position where the inflow port is opened;

a movable member configured to be capable of taking a first position acting on the valve body such that the valve body is located at the closed position and a second position acting on the valve body such that the valve body is located at the open position in the fluid chamber; and

an urging member which applies an urging force to the movable member for causing the movable member to be located at the first position,

the movable member moves from the first position to the second position when a magnitude of a pressure in the fluid chamber becomes greater than the urging force of the urging member,

in a state where the liquid discharge unit is attached to a liquid discharge device which discharges the liquid to recording media by using the liquid discharge unit, a direction in which the liquid flows into the inflow port is a direction intersecting with a gravity direction,

the inflow port is opened in a wall surface extending along a first direction intersecting with the gravity direction in wall surfaces forming the fluid chamber,

the valve body has an annular projection brought into contact with and surrounding the inflow port with respect to the wall surface, when the valve body is at the closed position,

a direction in which the urging force of the urging member acts is a second direction intersecting with the gravity direction and is orthogonal to the first direction,

the first direction and the second direction are directions orthogonal to the gravity direction,

the pressure control unit further comprises a power transmitting member provided capable of rotational movement around a rotation axis orthogonal to both the first direction and the second direction and having one end capable of being brought into contact with the movable member and the other end coupled with the valve body,

the movable member is brought into contact with the one end when moving from the first position to the second position by pressure in the fluid chamber against the urging force, and

the power transmitting member moves the valve body from the closed position to the open position by rotationally moving in accordance with displacement of the movable member brought into contact with the one end.

2 . The liquid discharge unit according to claim 1 , wherein

the movable member is displaced in the second direction between the first position and the second position.

3 . The liquid discharge unit according to claim 1 , wherein

when viewed in the second direction, an opening center of the inflow port is located below the center of the movable member in the gravity direction.

4 . The liquid discharge unit according to claim 1 , wherein

the liquid is ink containing titanium oxide.

5 . The liquid discharge unit according to claim 1 , wherein

the supply path is connected to a plurality of recording element boards having a nozzle row constituted by plural discharge ports.

6 . The liquid discharge unit according to claim 1 , wherein

two pressure control units are coupled such that a direction in which the liquid flows into the inflow port of each is the same direction.

7 . The liquid discharge unit according to claim 1 , wherein

two pressure control units are coupled such that a direction in which the liquid flows into the inflow port of each is opposite to each other.

8 . The liquid discharge unit according to claim 1 , wherein

the urging member is a first spring, and the movable member is urged in a direction separated from the power transmitting member by the first spring,

the power transmitting member is urged by a second spring in a direction in which the valve body is located at the closed position, and

the first spring constant is determined by the following equation (1):

(

k

d

⁢

x

d

+

P

2

⁢

S

d

)

*

L

1

=

(

-

k

v

⁢

x

v

+

(

P

1

-

P

2

)

*

S

v

)

*

L

2

(

1

)

where, on a plane on which the power transmitting member is rotationally moved,

L 1 : Length obtained by suspending vertically downward from a fulcrum of the power transmitting member in rotational movement to a line of action of force with which the movable member presses the power transmitting member

L 2 : Length obtained by suspending vertically downward from the fulcrum to a line of action of force pressing a center of the valve body

P 1 : Pressure by ink on an upstream side of the inflow port

P 2 : Pressure by ink in the fluid chamber

k d : Spring constant of the first spring

x d : Spring displacement of the first spring

k v : Spring constant of the second spring

x v : Spring displacement of the second spring

S d : Pressure-receiving area from ink of the movable body

S v : Pressure-receiving area from ink of the valve body.

9 . The liquid discharge unit according to claim 1 , wherein

the second position of the movable member is fluctuated in accordance with a pressure in the fluid chamber.