Hydraulic system

A hydraulic system (30), comprising:

• a normally open-type hydraulic clutch (50) which connects or disconnects a power transmission line between an engine (6) and a wheel (RW);
• an actuator (40), which is a hydraulic actuator (40), and which supplies a hydraulic pressure to the hydraulic clutch (50);
• an oil flow path (61) which connects the actuator (40) to the hydraulic clutch (50);
• a valve unit (60) being provided on the oil flow path (61), including:
• a valve member (62, 62A), which is a solenoid valve, and which is provided on the oil flow path (61), and which enables to switch between an open state where the oil flow path (61) communicates and a closed state where the oil flow path (61) closes;
• a downstream-side hydraulic pressure sensor (64B) provided on a downstream side of the valve member (62, 62A);
• an upstream-side hydraulic pressure sensor (64A) provided on an upstream side of the valve member (62, 62A),
• a bypass flow path (61C) which bypasses the valve member (62, 62A), and
• a one-way valve (63), which permits a supply of a hydraulic pressure from an actuator (40) side to a hydraulic clutch (50) side and which shuts off a supply of a hydraulic pressure from the hydraulic clutch (50) side to the actuator (40) side, is provided on the bypass flow path (61C),
• wherein in the actuator (40), an oil pump (42) being driven by an electric motor (41) is adapted to draw hydraulic fluid from a reservoir (43) and to supply the hydraulic fluid to the hydraulic clutch (50) through a master cylinder (44), the oil flow path (61) and the valve unit (60),
• wherein the hydraulic system (30) comprises a control unit (90) which controls the actuator (40) and the valve member (62, 62A),
• wherein the control unit (90)
• activates the actuator (40) and opens the valve member (62, 62A) to engage the hydraulic clutch (50), and thereafter stops the actuator (40) and closes the valve member (62, 62A),
• activates the actuator (40) while keeping the valve member (62, 62A) closed to supply a hydraulic pressure to the hydraulic clutch (50) side through the one way valve (63) when a detection value of the hydraulic pressure sensor (64B) provided on a downstream side of the valve member (62, 62A) decreases below a predetermined hydraulic pressure (LP) with the hydraulic clutch (50) kept engaged, and
• stops the actuator (40) when a detection value of the hydraulic pressure sensor (64B) provided on the downstream side of the valve member (62, 62A) reaches or exceeds the predetermined hydraulic pressure (LP), and
• wherein the control unit (90)
• opens the valve member (62, 62A) while keeping the actuator (40) stopped to release a hydraulic pressure on the hydraulic clutch (50) side when a detection value of the hydraulic pressure sensor (64B) provided on a downstream side of the valve member (62, 62A) exceeds a further predetermined hydraulic pressure (HP) with the hydraulic clutch (50) kept engaged, and
• closes the valve member (62, 62A) when a detection value of the hydraulic pressure sensor (64B) provided on the downstream side of the valve member (62, 62A) is less than the further predetermined hydraulic pressure (HP).

A hydraulic system (30), comprising:

• a normally open-type hydraulic clutch (50) which connects or disconnects a power transmission line between an engine (6) and a wheel (RW);
• an actuator (40) which supplies a hydraulic pressure to the hydraulic clutch (50);
• an oil flow path (61) which connects the actuator (40) to the hydraulic clutch (50);
• a valve member (62, 62A) which is provided on the oil flow path (61), and which enables to switch between an open state where the oil flow path (61) communicates and a closed state where the oil flow path (61) closes;
• a hydraulic pressure sensor (64B) which is provided on the oil flow path (61);
• and
• an accumulator (65) on a downstream side of the valve member (62, 62A),
• wherein the hydraulic system (30) further comprises a bypass flow path (61C) which bypasses the valve member (62, 62A), and
• wherein a one-way valve (63), which permits a supply of a hydraulic pressure from an actuator (40) side to a hydraulic clutch (50) side and which shuts off a supply of a hydraulic pressure from the hydraulic clutch (50) side to the actuator (40) side, is provided on the bypass flow path (61C),
• wherein the hydraulic system (30) comprises a control unit (90) which controls the actuator (40) and the valve member (62, 62A), and
• wherein the control unit (90)
• activates the actuator (40) and opens the valve member (62, 62A) to engage the hydraulic clutch (50), and thereafter stops the actuator (40) and closes the valve member (62, 62A),
• activates the actuator (40) while keeping the valve member (62, 62A) closed to supply a hydraulic pressure to the hydraulic clutch (50) side through the one-way valve (63) when a detection value of the hydraulic pressure sensor (64B), which is provided on a downstream side of the valve member (62, 62A) decreases below a predetermined hydraulic pressure (LP) with the hydraulic clutch (50) kept engaged, and
• stops the actuator (40) when a detection value of the hydraulic pressure sensor (64B) provided on the downstream side of the valve member (62, 62A) reaches or exceeds the predetermined hydraulic pressure (LP), and
• wherein the control unit (90)
• opens the valve member (62, 62A) while keeping the actuator (40) stopped to release a hydraulic pressure on the hydraulic clutch (50) side when a detection value of the hydraulic pressure sensor (64B) provided on a downstream side of the valve member (62, 62A) exceeds a further predetermined hydraulic pressure (HP) with the hydraulic clutch (50) kept engaged, and
• closes the valve member (62, 62A) when a detection value of the hydraulic pressure sensor (64B) provided on the downstream side of the valve member (62, 62A) is less than the further predetermined hydraulic pressure (HP).