Electric power steering system

Patent metadata

Field	Value
Publication number	US-9227656-B2
Application number	US-201414219446-A
Country	US
Kind code	B2
Filing date	Mar 19, 2014
Priority date	Mar 26, 2013
Publication date	Jan 5, 2016
Grant date	Jan 5, 2016

Abstract

A drainage device of an electric power steering system has a drain case and a drain valve. The drain case has a groove portion formed in a peripheral edge portion of a case inlet. The drain valve has a main body, and a flange disposed so as to face the case inlet. The flange has a bulged portion bulged toward the case inlet, and an annular seal portion. When the seal portion is brought into tight contact with the peripheral edge portion of the case inlet, the drainage device is placed in a valve closed state to form an annular space between the groove portion and the seal portion. When the seal portion is elastically deformed to form a gap between the seal portion and the peripheral edge portion of the case inlet, the drainage device is placed in a valve open state.

First claim

What is claimed is:

1. An electric power steering system comprising:
an electric motor disposed parallel to a rack shaft;
a speed reducer including a pulley provided on a shaft portion of the electric motor and a pulley provided on a ball nut rotatably fitted to a ball screw shaft portion of the rack shaft, the pulley provided on the shaft portion and the pulley provided on the ball nut being connected to each other so that torque is transmittable between the pulleys;
a rack housing that houses the speed reducer and a main portion of the rack shaft; and
a drainage device disposed below the speed reducer housed in the rack housing,
wherein driving force produced by the electric motor is transmitted to the rack shaft via the speed reducer, and
wherein the drainage device has a drain valve made of an elastic member, and a drain case having a case inlet that communicates with an internal space of the rack housing and a case outlet that communicates with an outside of the rack housing, wherein
the drain case has a groove portion formed in a peripheral edge portion of an inner face of the case inlet,
the drain valve comprises a main body formed in a columnar shape, the columnar shape having (1) a first end that is proxminal to and faces the case inlet, and (2) a second end that is distal from and faces away from the case inlet, the main body being fixed to the drain case,
the drain valve further comprises a flange formed at the first end of the columnar shape of the main body and disposed so as to face the case inlet,
the flange has a bulged portion formed at a center portion of the flange and bulged toward the case inlet, an annular seal portion formed at a peripheral edge portion of the flange, and an annular intermediate portion between the bulged portion and the annular seal portion, the annular intermediate portion having an upper surface facing the case inlet and a lower surface facing away from the case inlet, the lower surface of the annular intermediate portion sloping down from the first end towards the second end with increasing distance from an central axis of the columnar shape, the central axis extending between the first end and the second end, the lower surface of the annular intermediate portion being closer to the case inlet than the second end, the bulged portion being located at the first end of the columnar shape of the main body, the second end of the columnar shape of the main body protruding away from the flange in a direction away from the inlet,
when the seal portion is brought into tight contact with the peripheral edge portion of the inner face of the case inlet, the drainage device is placed in a valve closed state to form an annular space between the groove portion and the seal portion, and

when the seal portion is elastically deformed to form a gap between the seal portion and the peripheral edge portion of the inner face of the case inlet, the drainage device is placed in a valve open state.

2. The electric power steering system according to claim 1 , wherein:
a bottom face of the drain case has a protrusion protruded toward the case inlet, and the second end of the columnar shape of the main body of the drain valve has a recessed portion in which the protrusion is fitted; and
the drain valve is fixed to the drain case by fitting the protrusion in the recessed portion.

3. The electric power steering system according to claim 1 , in a direction parallel to the central axis, the annular seal portion being closer to the case inlet than the second end and being further away from the case inlet than the first end.

4. The electric power steering system according to claim 1 , wherein:
the entire seal portion is sealed with the peripheral edge portion in the valve closed state.

5. The electric power steering system according to claim 1 , wherein:
the bulged portion is distanced from the groove portion in the valve closed state.

Assignees

• Jtekt Corp

Inventors

• Tojo Hirokazu

Classifications

• B62D5/0424 Primary

  the axes of motor and final driven element of steering gear, e.g. rack, being parallel · CPC title

• F16K15/148

  the closure elements being fixed in their centre · CPC title

• B62D5/0421 Primary

  Electric motor acting on or near steering gear · CPC title