Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
2002-07-24
2004-06-01
Yu, Justine R. (Department: 3746)
Pumps
Motor driven
Electric or magnetic motor
C417S423120, C417S423140, C415S229000, C415S055100, C384S276000, C384S295000, C384S275000
Reexamination Certificate
active
06743001
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon, claims the benefit of priority of, and incorporates by reference, the contents of Japanese Patent Applications No. 2001-232390 filed Jul. 31, 2001, and No. 2002-123317 filed Apr. 25, 2002.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel pump constructed such that a fixed shaft is at the center of a housing, and a motor unit and a pump unit rotate about the fixed shaft.
2. Description of Related Art
Japanese Patent Laid-Open Publication No. Sho. 63-82086 discloses a fuel pump. Generally, in this fuel pump, as shown in
FIG. 4
, a fixed shaft
12
is fixed at the center of a housing
11
. Bearing members
16
are individually pushed into and fixed to an inner periphery of both ends of a pipe member
15
provided at the center of an armature
14
(a rotor) of a motor unit
13
. These bearing members
16
are rotatably inserted over the fixed shaft
12
to rotatably support the pipe member
15
with the fixed shaft
12
through the bearing members
16
. In this case, the bearing members
16
are pushed into and fixed to the inner periphery of the pipe member
15
, thereby positioning the bearing members
16
between the pipe member
15
and the fixed shaft
12
. An impeller
18
in a pump unit
17
is fitted and fixed to the pipe member
15
, and the armature
14
of the motor unit
13
, the pipe member
15
, and the impeller
18
integrally rotate about the fixed shaft
12
.
However, in the conventional construction described above, since the motor unit
13
and the pump unit
17
are arranged with a gap provided therebetween in the axial direction in the housing
11
, the dimension of the fuel pump becomes large along its axial direction.
In the conventional construction described above, it is necessary to provide spaces for interposing the bearing members
16
between the pipe member
15
for supporting the armature
14
of the motor unit
13
, and the fixed shaft
12
. Accordingly, the outer diameter of the pipe member
15
increases, and storage space for the armature
14
decreases in the housing
11
. As a result, space for armature windings decreases, motor output decreases, and discharge capability of the pump also decreases. On the other hand, when the outer diameter of the housing
11
is increased to secure the winding space of the armature
14
, and to prevent decrease of the motor output and to prevent decrease of the discharge capability, the outer diameter of the fuel pump increases.
In the conventional construction described above, the outer peripheral surface of the bearing members
16
is pressed against the inner peripheral surface of the pipe member
15
, and the inner peripheral surface of the bearing members
16
is slidably in contact with the outer peripheral surface of the fixed shaft
12
. Because of this, precision in dimension and concentricity is required both for the inner diameter and the outer diameter of the bearing members
16
. When the precision of the inner diameter and the outer diameter of the bearing members
16
decreases in dimension and concentricity, the assembly of the fuel pump becomes difficult. Additionally, the armature
14
may vibrate and noise may be generated when the fuel pump is in operation. Thus, it is necessary to precisely machine both the inner diameter and the outer diameter of the bearing members
16
to secure the precision of the inner diameter and the outer diameter in dimension and concentricity. As a result, the time and costs associated with machining the bearing members
16
may increase, and the overall manufacturing cost of the fuel pump may increase.
SUMMARY OF THE INVENTION
A first object of the present invention is to decrease the axial dimension of the fuel pump. A second object of the present invention is to reduce the diameter of the pipe member, which supports the armature of the motor unit, to increase the storage space for the armature in the housing, to increase the pump discharge capability, and to reduce the outer diameter of the fuel pump. A third object of the present invention is to simplify the machining of the bearing members while maintaining precision in dimension and concentricity required of the bearing members. Finally, reducing machining costs is desired.
In a first aspect of the invention, a fuel pump of the present invention includes a pump unit for drawing and discharging fuel, a motor unit for driving the pump unit, a housing for housing the pump unit and the motor unit, a fixed shaft fixed at the center of the housing, a pipe member provided at the center of an armature of the motor unit, and inserted over the fixed shaft, and bearing members individually used for rotatably supporting both ends of the pipe member on the fixed shaft. A part of said armature and a rotational body of the pump unit are arranged on the bearing members located on the side of the pump unit such that they are overlapped with each other to integrally rotate. With this construction, the storage space for the motor unit and the pump unit decreases in the axial direction in the housing, and the axial dimension of the fuel pump decreases.
In one regard, it is preferable to form the fuel pump such that the part of the armature overlapped with the rotational body of the pump unit is engaged with the rotational body to transmit a rotational force of the armature to the rotation body. With this construction, the engagement structure (a coupling structure) between the armature and the rotational body of the pump unit is compactly formed on the bearing member. In another regard, it is preferred that the part of the armature overlapped with the rotational body of the pump unit be made of a resin.
To attain the second object, in another aspect, the ends of the pipe member may be placed between the fixed shaft and the bearing members. With this construction, it is not necessary to provide spaces for interposing the bearing members between the pipe member and the fixed shaft, and the outer diameter of the pipe member can be reduced accordingly. As a result, the storage space for the armature in the housing can be increased, the winding space for the armature can be increased, and the motor output and the pump discharge capability can be increased. In other words, even when the outer diameter of the housing is made small, the winding space secured for the armature is almost as large as that in the conventional case. Additionally, the outer diameter of the fuel pump can be reduced while the discharge capability of the pump can be maintained at the conventional pump level.
To attain the third object, in another aspect, a through hole in a step shape may be formed at the center of the bearing members. Additionally, the fixed shaft may be rotatably inserted into a part of the through hole with a smaller diameter (referred to as a “small diameter hole”), and a part of the through hole with a larger diameter (referred to as a “large diameter hole”) may support the ends of the pipe member. With this construction, since it is not necessary to provide spaces for interposing the bearing members between the pipe member and the fixed shaft, beneficial effects can be obtained.
Since the large diameter hole for supporting the pipe member and the small diameter hole for inserting over the fixed shaft are formed concentrically on the inner peripheral side of the bearing members, the inner peripheral side of the bearing member is machined using a cutting tool while the outer periphery of the bearing member is held by a chuck during machining of the bearing members. Thus, the large diameter hole for supporting the pipe member and the small diameter hole for inserting over the fixed shaft are precisely formed on the inner peripheral side of the bearing members while the shaft centers of both of the holes precisely coincide with each other. Consequently, machining the bearing members becomes simple while dimensional accuracy and precise concentricity required for the bearing members is secured. Additionally, machining costs d
Iwanari Eiji
Sakai Hiromi
Sayoc Emmanuel
Yu Justine R.
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