Kayaba Industry Company, Ltd.

Yoshiharu Miya

Hideki Tsuchiya

Tomoyuki Fujita

Koichiro Akatsuka

Hideki Yamagata

Mamoru Hosogai

Kenji Yazaki

Ryuji Naide

Masato Ikeguchi

A solenoid actuator () attached to hydraulic equipment comprises a shaft () connected to the hydraulic equipment, a plunger () fixed to the shaft (), a coil () which magnetically drives the plunger (), and a first bearing () and a second bearing () supporting the shaft () on either sides of the plunger (). A plunger front chamber () is formed between the first bearing () and the plunger (), and a plunger rear chamber () is formed between the plunger () and the second bearing (). By providing a plunger exterior oil passage () on the outside of the plunger () to connect the plunger front chamber () to the plunger rear chamber (), working oil flows through the plunger exterior oil passage () every time the plunger () strokes, thereby preventing a deposit of contaminant on the plunger () without increasing a stroke resistance of the plunger ().

Solenoid actuator

An electromagnetic proportional flow rate control valve capable of performing precise flow rate control in a low flow rate side of an operating region is provided. In an electromagnetic proportional flow rate control valve, in which a valve memberis driven in a valve closing direction in accordance with the increase in a driving current I of a solenoid coil, a solenoid driving force F is set such that it decreases accompanying the displacement of the valve memberin the valve closing direction with respect to an identical driving current in the solenoid coil. Thus, an amount of change in an area of a valve opening with respect to unit changes in the driving current I becomes smaller in a region at which the stroke is small compared to a case of having flat characteristics, whereby the flow rate control precision in the low flow rate region can be improved.

Electromagnetic proportional flow rate control valve

A solenoid actuator () comprises a case () made of a magnetic material and housing a coil () wound on a bobbin (), and a pressure tube () made of a non-magnetic material and fitted into a hollow portion of the bobbin (). A base () and a sleeve () made of a magnetic material are disposed in the pressure tube (). A plunger () provided in an operation chamber () formed in the base () and the sleeve () strokes according to energization of the coil () to axially drive a shaft () fixed to the plunger (). The pressure tube () ensures that magnetic flux is transferred between the case () and the sleeve () while preventing pressure variation in the operation chamber () from being transmitted to the bobbin (), thereby achieving a high response and a pressure tightness in the solenoid actuator ().

A solenoid actuator () attached to a hydraulic equipment comprises a shaft () connected to the hydraulic equipment, a plunger () fixed to the shaft (), a coil () which magnetically drives the plunger (), and a first bearing () and a second bearing () supporting the shaft () on both sides of the plunger (). A plunger front chamber () is formed between the first bearing () and the plunger (), a plunger rear chamber () is formed between the plunger () and the second bearing (), and a second bearing rear chamber () is formed on the opposite side of the second bearing () to the plunger rear chamber (). To secure an oil flow between these chambers, a plunger exterior oil passage (), a second bearing oil passage (), and a shaft-penetrating oil passage () are provided, thereby realizing a preferable balance between oil pressures acting on the second bearing ().

Provided are a hydraulic pump, an electromagnetic flow rate control valvethat controls the flow rate of hydraulic oil supplied from the hydraulic pumpto a power steering device PS, and a pressure compensating valvethat maintains a fixed pressure difference between upstream and downstream sides of the electromagnetic flow rate control valveand bypasses an excess flow rate. The electromagnetic flow rate control valvemaintains a predetermined initial opening when a control current is zero, while an opening of the electromagnetic flow rate control valve decreases to become a minimum opening when the control current increases from zero, and the opening gradually becomes larger toward a maximum opening when a predetermined control current is exceeded.

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Sagamihara, Japan

Yoshiharu Miya