Power steering apparatus

Claim 2

In a power steering apparatus comprising a hydraulic motor for boosting manually applied steering torque, which motor is supplied through a hydraulic circuit including supply and discharge passages leading to said motor, two rotatably steering shaft members aligned with each other and arranged to permit relative rotation therebetween, one of which shaft members is operably connected to control means in said hydraulic circuit and the other of which shaft members is operably connected to a steering wheel, said control means comprising a main valve member aligned between said steering shaft members and mounted within a valve chamber to divide said chamber into two parts, first and second flap valves mounted within said two valve chamber parts respectively to distribute pressure fluid to said hydraulic motor selectively through relative rotation therebetween, one of said flap valves being connected to rotate with said one shaft member and the other flap valve being driven by said one shaft member through a resilient connection, at least two passageways in said main valve member extending between said first and second flap valve members, and a pair of axially spaced pressure-exerting pistons slidably mounted in each of said passageways in contact with said flap valves, the improvement which comprises means for absorbing surge pressures in said hydraulic circuit including free piston means mounted in parallel with said motor between the supply and discharge passages leading to said motor, and spring means biassing said pistons against said flap valves to dampen vibrations of said valves and Biassing said free piston means in opposite directions.

Claim 3

Power steering apparatus as claimed in claim 1 further comprising at least one constriction in one of the supply and discharge passages leading to said hydraulic motor.

Claim 4

In a power steering apparatus comprising a hydraulic motor for boosting manually applied steering torque, which motor is supplied through a hydraulic circuit including supply and discharge passages leading to said motor, two rotatable steering shaft members aligned with each other and arranged to permit relative rotation therebetween, one of which shaft members is operably connected to control means in said hydraulic circuit and the other of which shaft members is operably connected to a steering wheel, said control means comprising a main valve member aligned between said steering shaft members and so mounted within a valve chamber as to divide said chamber into two parts, first and second flap valves positioned within said two valve chamber parts respectively and adapted to distribute pressure fluid to said hydraulic motor selectively through relative rotation therebetween, one of said flap valves being connected to rotate with said one shaft member and the other flap valve being driven by said one shaft member through a resilient connection, at least two passageways in said main valve member extending between said first and second flap valve members, and a pair of axially spaced pressure-exerting pistons slidably mounted in each of said passageways, the improvement which comprises means for absorbing surge pressures in said hydraulic circuit including a free piston slidably mounted between each pair of pressure-exerting pistons, one compression spring inserted between each pressure-exerting piston and the adjacent free piston, and ducts in said main valve member between said pressure-exerting pistons and said free piston connecting the passageways in said valve member to the supply and discharge passages leading to said hydraulic motor.

Claim 5

In a power steering apparatus comprising a hydraulic motor for boosting manually applied steering torque, which motor is supplied through a hydraulic circuit including supply and discharge passages leading to said motor, two rotatable steering shaft members aligned with each other and arranged to permit relative rotation therebetween, one of which shaft members is operably connected to control means in said hydraulic circuit and the other of which shaft members is operably connected to a steering wheel, said control means comprising a main valve member aligned between said steering shaft members and so mounted within a valve chamber as to divide said chamber into two parts, first and second flap valves positioned within said two valve chamber parts respectively and adapted to distribute pressure fluid to said hydraulic motor selectively through relative rotation therebetween, one of said flap valves being connected to rotate with said one shaft member and the other flap valve being driven by said one shaft member through a resilient connection, at least two passageways in said main valve member extending between said first and second flap valve members, and a pair of axially spaced pressure-exerting pistons slidably mounted in each of said passageways, the improvement which comprises means for absorbing surge pressures in said hydraulic circuit including a free piston slidably mounted between each pair of pressure-exerting pistons, one compression spring inserted between each pressure-exerting piston and the adjacent free piston, and ducts in said main valve member between said pressure-exerting pistons and said free piston connecting the passageways in said valve member to the supply and discharge passages leading to said hydraulic motor.

Claim 6

Power steering apparatus as claimed in claim 3 further comprising at least one constriction in one of the supply and discharge passages leading to said hydraulic motor.

Claim 7

In a power steering apparatus comprising a hydraulic motor for boosting manually applied steering torque, which motor is supplied through a hydraulic circuit including supply and discharge passages leading to said motor, two rotatable steering shaft members aligned with each other and arranged to permit relative rotation therebetween, one of which shaft members is operably connected to control means in said said hydraulic circuit and the other of which shaft members is operably connected to a steering wheel, said control means comprising a main valve member aligned between said steering shaft members and so mounted within a valve chamber as to divide said chamber into two parts, first and second flap valves positioned within said two valve chamber parts respectively and adapted to distribute pressure fluid to said hydraulic motor selectively through relative rotation therebetween, one of said flap valves being connected to rotate with said one shaft member and the other flap valve being driven by said one shaft member through a resilient connection, at least two passageways in said main valve member extending between said first and second flap valve members, a pair of axially spaced pressure-exerting pistons slidably mounted in each of said passageways with a compression spring therebetween which urges said pistons into vibration damping contact with said flap valves, a valve housing containing said valve chamber, and means for conducting pressure fluid from one of the parts of said valve chamber into the space formed between said two pressure-exerting pistons, the improvement which comprises means for absorbing surge pressures in said hydraulic circuit including a valve body externally secured to said valve housing, an auxiliary valve chamber in said valve bOdy, a free piston slidably mounted in said auxiliary valve chamber, and compression springs in said auxiliary valve chamber for urging said free piston in opposite directions, the spaces in the auxiliary valve chamber defined between said free piston and the ends of said auxiliary valve chamber being respectively connected to the supply and discharge passages leading to said hydraulic motor.

Claim 8

In a power steering apparatus comprising a hydraulic motor for boosting manually applied steering torque, which motor is supplied through a hydraulic circuit including supply and discharge passages leading to said motor, two rotatable steering shaft members aligned with each other and arranged to permit relative rotation therebetween, one of which shaft members is operably connected to control means in said said hydraulic circuit and the other of which shaft members is operably connected to a steering wheel, said control means comprising a main valve member aligned between said steering shaft members and so mounted within a valve chamber as to divide said chamber into two parts, first and second flap valves positioned within said two valve chamber parts respectively and adapted to distribute pressure fluid to said hydraulic motor selectively through relative rotation therebetween, one of said flap valves being connected to rotate with said one shaft member and the other flap valve being driven by said one shaft member through a resilient connection, at least two passageways in said main valve member extending between said first and second flap valve members, a pair of axially spaced pressure-exerting pistons slidably mounted in each of said passageways with a compression spring therebetween which urges said pistons into vibration damping contact with said flap valves, a valve housing containing said valve chamber, and means for conducting pressure fluid from one of the parts of said valve chamber into the space formed between said two pressure-exerting pistons, the improvement which comprises means for absorbing surge pressures in said hydraulic circuit including a valve body externally secured to said valve housing, an auxiliary valve chamber in said valve bOdy, a free piston slidably mounted in said auxiliary valve chamber, and compression springs in said auxiliary valve chamber for urging said free piston in opposite directions, the spaces in the auxiliary valve chamber defined between said free piston and the ends of said auxiliary valve chamber being respectively connected to the supply and discharge passages leading to said hydraulic motor.

Claim 9

Power steering apparatus as claimed in claim 5 further comprising at least one constriction in one of the supply and discharge passages leading to said hydraulic motor.