A hydrostatic drive system is disclosed which allows for simpler and more robust control of hydraulic vibration. The system comprises first and second hydraulic drive units and a variable damping device. At least the first hydraulic drive unit is a variable displacement type and comprises a displacement control. The variable damping device comprises at least one variable element. The system comprises a first linkage apparatus between the displacement control and the variable element and is operable to control the variable element in accordance with the displacement of the displacement control.

Solar tracker systems include a torque tube, a column supporting the torque tube, a solar panel connected to the torque tube, and a damper assembly. The damper assembly includes a first end pivotably connected to the torque tube and a second end pivotably connected to the column. The damper assembly further includes an outer shell, a piston within and moveable relative to the outer shell, a first chamber wall and a second chamber wall within the outer shell at least partially defining a chamber, and a valve within the chamber. The valve includes a first axial end defining a slot and is biased to a first position within the chamber in which the first axial end is spaced from the first chamber wall. The valve is moveable within the chamber from the first position to a second position to passively change a flow resistance of the damper assembly.

A hydraulic pressure cushioning device includes: a cylinder; a rod movably provided in the cylinder; a first piston valve section that is provided on the rod. The first piston valve section includes: a first piston member and a second piston member that form a channel; and a single first damping valve with which a first flow of the fluid from the first side to the second side in the channel and a second flow of the fluid from the second side to the first side in the channel are controlled; a bypass path which differs from the channel; and a free piston provided on the rod in such a manner that a flow of the fluid is switched between the channel and the bypass path in accordance with a movement position of the rod.

A hydraulic pressure cushioning device includes: a cylinder; a rod movably provided in the cylinder; a first piston valve section that is provided on the rod. The first piston valve section includes: a first piston member and a second piston member that form a channel; and a single first damping valve with which a first flow of the fluid from the first side to the second side in the channel and a second flow of the fluid from the second side to the first side in the channel are controlled; a bypass path which differs from the channel; and a free piston provided on the rod in such a manner that a flow of the fluid is switched between the channel and the bypass path in accordance with a movement position of the rod.

A damping valve includes a valve seat member that includes a port and a first valve seat, a shaft member disposed on the valve seat member, an annular main valve element that is mounted on the shaft member, seats on and separates from the first valve seat, and includes a second valve seat on an opposite side of the valve seat member, a sub valve element that is mounted on the shaft member, and seats on and separates from the second valve seat, a valve-element-between chamber that is disposed between the main valve element and the sub valve element, and on an inner peripheral side of the second valve seat, a restrictive passage that causes the port to be communicated with the valve-element-between chamber to provide a resistance to a flow of a passing fluid, a main valve element biasing part biasing the main valve element to the valve seat member side, and a sub valve element biasing part biasing the sub valve element to the main valve element side. The restrictive passage is formed of a ring-shaped gap between the main valve element and the shaft member.

A damping valve includes a valve seat member that includes a port and a first valve seat, a shaft member disposed on the valve seat member, an annular main valve element that is mounted on the shaft member, seats on and separates from the first valve seat, and includes a second valve seat on an opposite side of the valve seat member, a sub valve element that is mounted on the shaft member, and seats on and separates from the second valve seat, a valve-element-between chamber that is disposed between the main valve element and the sub valve element, and on an inner peripheral side of the second valve seat, a restrictive passage that causes the port to be communicated with the valve-element-between chamber to provide a resistance to a flow of a passing fluid, a main valve element biasing part biasing the main valve element to the valve seat member side, and a sub valve element biasing part biasing the sub valve element to the main valve element side. The restrictive passage is formed of a ring-shaped gap between the main valve element and the shaft member.

A damping valve includes a main valve opening and closing a main passage, and a pilot passage reducing a pressure of the upstream of the main passage by a throttle to guide as a back-pressure biasing the main valve to the closing direction. A pressure control valve being disposed on the downstream of the throttle and including a seating portion controlling the back-pressure, and a switching valve including a circular depressed portion opening and closing the pilot passage are integrated and controlled by a single solenoid. The damping valve includes fail passages being branched from the downstream of the throttle to bypass the main valve, and a fail valve opening and closing the fail passage. The switching valve is arranged on the upstream of the pressure control valve in the pilot passage. The fail passages are branched from the upstream of the switching valve of the pilot passage.

A damping valve includes a main valve opening and closing a main passage, and a pilot passage reducing a pressure of the upstream of the main passage by a throttle to guide as a back-pressure biasing the main valve to the closing direction. A pressure control valve being disposed on the downstream of the throttle and including a seating portion controlling the back-pressure, and a switching valve including a circular depressed portion opening and closing the pilot passage are integrated and controlled by a single solenoid. The damping valve includes fail passages being branched from the downstream of the throttle to bypass the main valve, and a fail valve opening and closing the fail passage. The switching valve is arranged on the upstream of the pressure control valve in the pilot passage. The fail passages are branched from the upstream of the switching valve of the pilot passage.

Provided is a damper with which the energy efficiency for attenuating input vibration corresponding to the unsprung resonance frequency and the sprung resonance frequency can be improved. Also provided is a method for manufacturing this damper. In this damper the electrical resonance frequency, as specified by the inductance of an electromagnetic motor and the capacitance of a capacitor, is set within ±20% of the unsprung resonance frequency, thereby enabling the input vibration corresponding to the sprung resonance frequency as well as the input vibration corresponding to the unsprung resonance frequency to be reduced.

Solar tracker systems include a torque tube, a solar panel attached to the torque tube, and a damper assembly. The damper assembly includes a housing defining first and second chambers, a first fluid passageway extending between the first and second chambers, and a second fluid passageway extending from the second chamber. A piston is moveable relative to the housing and a valve is positioned within the first chamber and moveable to passively control fluid flow. An active lock includes a shaft extending into the second chamber with a seal attached to the shaft. The shaft is selectively moveable between an unsealed position in which the seal is spaced from a chamber wall and a flow path is defined between the first fluid passageway and the second fluid passageway, and a sealed position in which the seal contacts and seals against the chamber wall to obstruct the flow path.