Abstract: A critical state is assumed in which a position of one end of the opening of the input port in the axial direction and a position of the other end of the groove in the axial direction accord with each other with respect to the axial direction. In the critical state, when a straight line is extended in the axial direction as well as radially outward of the spool without changing a direction of the straight line in a circumferential direction of the spool from one end of the groove bottom in the axial direction with the same inclination as the inclination of the groove bottom at the one end of the groove in the axial direction relative to the axial direction, the straight line passes through the opening of the output port to contact a wall surface of the output port.

Abstract: A spool valve includes a sleeve and a spool. The sleeve has an inflow opening through which fluid flows in and an outflow opening through which the fluid flows out. The inflow opening opens in a radial direction of the sleeve and the outflow opening opens a same side with the inflow opening. The spool has a recess recessed from an outer peripheral part of the spool to a center axis of the spool. The spool is configured movable in the sleeve in an axial direction of the sleeve. The spool controls a communication state between the inflow opening and the outflow opening through the recess by regulating a position of the recess in the axial direction. A closed space is formed at a portion of the sleeve opposite to where the outflow opening is located.

Abstract: A critical state is assumed in which a position of one end of the opening of the input port in the axial direction and a position of the other end of the groove in the axial direction accord with each other with respect to the axial direction. In the critical state, when a straight line is extended in the axial direction as well as radially outward of the spool without changing a direction of the straight line in a circumferential direction of the spool from one end of the groove bottom in the axial direction with the same inclination as the inclination of the groove bottom at the one end of the groove in the axial direction relative to the axial direction, the straight line passes through the opening of the output port to contact a wall surface of the output port.

Abstract: A spool valve includes a valve housing and a spool. The spool is slidable in an axial direction in the valve housing. A linear solenoid drives the spool against a spring. The valve housing has a feedback chamber to apply a force to the spool, an input port to receive a hydraulic pressure, an output port to produce an output pressure according to an axial position of the spool, and an drain port to exhaust oil to an outside. The spool valve has multiple supply paths to cause oil to flow from the input port to the output port and/or multiple exhaust paths to cause oil to flow from the output port to the drain port.

Abstract: A spool valve includes a valve housing and a spool. The spool is slidable in an axial direction in the valve housing. A linear solenoid drives the spool against a spring. The valve housing has a feedback chamber to apply a force to the spool, an input port to receive a hydraulic pressure, an output port to produce an output pressure according to an axial position of the spool, and an drain port to exhaust oil to an outside. The spool valve has multiple supply paths to cause oil to flow from the input port to the output port and/or multiple exhaust paths to cause oil to flow from the output port to the drain port.

Abstract: Since an output port is formed at a front end portion of a sleeve, an electromagnetic valve is arranged in series with a control valve. Thus, a system becomes small, and it becomes easy to attain a mounting space. Further, since a feedback chamber is formed in the vicinity of the linear solenoid, it is possible to install a spool after the sleeve is attached to the linear solenoid. Thus, unidirectional assembling becomes possible, and the number of assembling steps is decreased. Furthermore, since a small-diameter land is provided in the spool at a side of the linear solenoid, a small-diameter inner wall for slidably guiding the small-diameter land is concentrated to one place at the side of the linear solenoid. Thus, forming a small-diameter hole in the sleeve becomes easy, and forming accuracy is improved.

Abstract: Since an output port is formed at a front end portion of a sleeve, an electromagnetic valve is arranged in series with a control valve. Thus, a system becomes small, and it becomes easy to attain a mounting space. Further, since a feedback chamber is formed in the vicinity of the linear solenoid, it is possible to install a spool after the sleeve is attached to the linear solenoid. Thus, unidirectional assembling becomes possible, and the number of assembling steps is decreased. Furthermore, since a small-diameter land is provided in the spool at a side of the linear solenoid, a small-diameter inner wall for slidably guiding the small-diameter land is concentrated to one place at the side of the linear solenoid. Thus, forming a small-diameter hole in the sleeve becomes easy, and forming accuracy is improved.