TECHNICAL FIELD
[0001] This invention relates to a gear pump that discharges a fluid by rotating while a
pair of gears are intermeshed.
BACKGROUND ART
[0002] A gear pump provided in an oil pressure device, a water pressure device, and so on
includes a body into which a pair of gears is incorporated and a housing that contacts
the body. The body and the housing are fastened to each other by a plurality of bolts.
[0003] During an operation of the gear pump, a force that attempts to move the housing in
a single direction relative to the body is generated by fluid pressure generated in
the body.
[0004] JP6-147133A discloses a conventional gear pump in which processing teeth are formed on an end
surface of the body which contacts the housing. When the body and the housing are
fastened to each other by the plurality of bolts, rib-shaped processing teeth engraved
in the end surface of the body dig into the end surface of the housing, thereby preventing
positional deviation between the body and the housing.
DISCLOSURE OF THE INVENTION
[0005] However, when a cutting depth of the processing teeth engraved in the end surface
of the body is small, positional deviation between the body and the housing cannot
be prevented sufficiently.
[0006] On the other hand, when the cutting depth of the processing teeth is large, a gap
may be formed between the body and the housing, and as a result, fluid may leak from
the gear pump.
[0007] It is therefore an object of this invention to provide a gear pump in which positional
deviation between a body and a housing is prevented without increasing a cutting depth
of processing teeth engraved in an end surface of the body.
[0008] This invention provides a gear pump that discharges a fluid by rotating while a pair
of gears are intermeshed, comprising a body into which the respective gears are incorporated,
a housing that contacts the body, a number of particles that are interposed between
an end surface of the body and an end surface of the housing, which contact each other,
to prevent positional deviation between the body and the housing, and a plurality
of fastening members that fasten the housing to the body.
[0009] According to this invention, a number of particles are interposed between the end
surface of the body and the end surface of the housing, thereby increasing a frictional
force generated in a joint portion between the body and the housing such that positional
deviation generated between the body and the housing by a fluid pressure in the gear
pump can be prevented effectively, and as a result, a pump efficiency of the gear
pump can be maintained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
FIG. 1 is a longitudinal sectional view of a gear pump according to an embodiment
of this invention.
FIG. 2 is a sectional view taken along an A-A line in FIG. 1.
BEST MODES FOR CARRYING OUT THE INVENTION
[0011] An embodiment of this invention will be described below with reference to the figures.
[0012] As shown in FIG. 1, a gear pump 1 comprises a body 2 into which a drive gear 11 and
a driven gear 12 are incorporated as a pair of gears, and housings 3, 4 that contact
the body 2 from either side. Side plates 5, 6 are interposed between respective end
faces of the drive gear 11 and driven gear 12 and the housings 3, 4.
[0013] A gear chamber 9 that houses the drive gear 11 and driven gear 12 is provided on
an inner side of the body 2, and the housings 3, 4 contact respective end surfaces
25, 26 of the body 2.
[0014] The housing 3 includes an end surface 28 that contacts the end surface 25 of the
body 2 so as to close one end of the body 2 and function as a mounting flange attached
to a support member, not shown in the figure.
[0015] A seal ring 41 is interposed between the end surface 25 of the body 2 and the housing
3, and the gear chamber 9 is sealed by the seal ring 41.
[0016] It should be noted that the housing 3 may be formed integrally with the body 2.
[0017] The housing 4 includes an end surface 29 that contacts the end surface 26 of the
body 2 and functions as a cover that closes another end of the body 2.
[0018] A seal 42 is interposed between the end surface 26 of the body 2 and the housing
4, and the gear chamber 9 is sealed by the seal 42.
[0019] The body 2 and the housings 3, 4 are fastened to each other by four bolts 17 to 20.
The bolts 17 to 20, which are provided as fastening members, respectively use axial
force to press the end surface 25 of the body 2 and the end surface 28 of the housing
3 against each other and press the end surface 26 of the body 2 and the end surface
29 of the housing 4 against each other. As a result, the body 2 and the housings 3,
4 are fixed by frictional force generated between the end surface 25 and the end surface
28 and frictional force generated between the end surface 26 and the end surface 29.
[0020] Shafts 13, 15 are formed on either end of the drive gear 11. Shafts 14, 16 are formed
on either end of the driven gear 12. The shafts 13, 14 are supported on the housing
3 to be free to rotate via respective bearings 33, 34, while the shafts 15, 16 are
supported on the cover 4 to be free to rotate via respective bearings 35, 36.
[0021] The shaft 15 of the drive gear 11 is driven to rotate in a clockwise direction, as
shown by an arrow in FIG. 2, while the shaft 16 of the driven gear 12 rotates in a
counter-clockwise direction, as shown by an arrow in FIG. 2.
[0022] When the drive gear 11 and driven gear 12 rotate while intermeshing within the gear
chamber 9, fluid aspirated from a low pressure port 23 positioned in a tangential
direction to an intermeshing surface is transported by a gear intermeshing portion
of the drive gear 11 and driven gear 12 so as to be discharged from a high pressure
port 22. Working oil, for example, is used as the fluid that circulates through the
gear pump 1.
[0023] During an operation of the gear pump 1 described above, a fluid pressure in the high
pressure port 22 is higher than a fluid pressure in the low pressure port 23, and
therefore a force which attempts to move the housings 3, 4 relative to the body 2
in a direction indicated by an arrow B in FIG. 2 is generated in a joint portion between
the body 2 and the housings 3, 4.
[0024] To fix the housings 3, 4 relative to the body 2 against the differential pressure
generated in the gear pump 1, processing teeth 27 are formed on the end surface 26
of the body 2, as shown in FIG. 2. Similarly, processing teeth 27 are formed on the
end surface 26 of the body 2.
[0025] The processing teeth 27 are constituted by cutting a large number of narrow grooves
using a milling machine. The processing teeth 27 are formed to extend in a vertical
direction that is substantially orthogonal to a slippage direction indicated by the
arrow B in FIG. 2.
[0026] It should be noted that the processing teeth 27 are not limited to this constitution,
and may be formed in a mesh form, for example.
[0027] The body 2 is formed from a harder material than the housings 3, 4.
The body 2 is formed from an iron-based material, for example, whereas the housings
3, 4 are respectively formed from an aluminum-based material, for example.
[0028] When the housings 3, 4 are fastened to the body 2 using the bolts 17 to 20, the processing
teeth 27 of the hard body 2 dig into the end surfaces 28, 29 of the housings 3, 4.
As a result, positional deviation occurring when the housings 3, 4 are moved relative
to the body 2 by the fluid pressure in the gear pump 1 is suppressed.
[0029] However, when a cutting depth of the processing teeth 27 engraved in the end surfaces
25, 26 of the body 2 is small, positional deviation of the housings 3, 4 cannot be
prevented sufficiently. On the other hand, when the cutting depth of the processing
teeth 27 is large, a gap may be formed between the body 2 and the housings 3, 4, and
as a result, fluid may leak from the gear pump 1.
[0030] In response to this problem, in this invention a large number of fine particles 30
are interposed in the joint portion between the body 2 and the housings 3, 4 so that
positional deviation between the body 2 and the housings 3, 4 is prevented without
increasing the cutting depth of the processing teeth 27.
[0031] The particles 30 are constituted by a material that is harder than the materials
of the body 2 and the housings 3, 4, such as shavings of steel, cast iron, carbon
material, and so on, for example.
[0032] By using hard particles 30, the particles 30 dig into the end surfaces 25, 26 of
the body 2 and the end surfaces 28, 29 of the housings 3, 4, thereby increasing a
frictional force generated along the joint portion between the body 2 and the housings
3, 4 such that positional deviation there-between can be prevented effectively.
[0033] The particles 30 are intermixed with a coating agent 31 and applied to the two end
surfaces 25, 26 of the body 2 together with the coating agent 31.
[0034] The coating agent 31 adheres to the joint portion between the body 2 and the housings
3, 4, thereby eliminating gaps and preventing corrosion such as electrolytic corrosion.
[0035] As described above, this invention provides the gear pump 1 that discharges fluid
by rotating while the drive gear 11 and the driven gear 12 are intermeshed, and comprises
the body 2 into which the drive gear 11 and driven gear 12 are incorporated, the housings
3, 4 that contact the body 2, the large number of particles 30 that are interposed
between the end surfaces 25, 26 of the body 2 and the end surfaces 28, 29 of the housings
3, 4, which contact each other, to prevent positional deviation between the body 2
and the housings 3, 4, and the plurality of bolts (fastening members) 17 to 20 that
fasten the housings 3, 4 to the body 2.
[0036] By interposing the large number of particles 30 between the end surfaces 25, 26 of
the body 2 and the end surfaces 28, 29 of the housings 3, 4, positional deviation
generated along the joint portion between the body 2 and the housings 3, 4 by the
fluid pressure in the gear pump 1 can be prevented effectively, and therefore a pump
efficiency of the gear pump 1 can be maintained.
[0037] In this embodiment, the particles 30 are formed from a harder material than the body
2 and the housings 3, 4.
[0038] Hence, the hard particles 30 dig into the end surfaces 25, 26 of the body 2 and the
end surfaces 28, 29 of the housings 3, 4, and as a result, positional deviation generated
between the body 2 and the housings 3, 4 by the fluid pressure in the gear pump 1
can be prevented effectively.
[0039] In this embodiment, the processing teeth 27 are formed on at least one of the end
surfaces 25, 26 of the body 2 and the end surfaces 28, 29 of the housings 3, 4, and
positional deviation between the body 2 and the housings 3, 4 is prevented via both
the particles 30 and the processing teeth 27.
[0040] Hence, the body 2 and the housings 3, 4 are positioned by both the processing teeth
27 and the particles 30, and therefore positional deviation of the housings 3, 4 can
be prevented sufficiently even when the cutting depth of the processing teeth 27 is
small. As a result, fluid leakage between the body 2 and the housings 3, 4 can be
prevented by making the cutting depth of the processing teeth 27 small.
[0041] In this embodiment, the particles 30 are intermixed with the coating agent 31, whereupon
the particles 30 are applied together with the coating agent 31 to at least one of
the end surfaces 25, 26 of the body 2 and the end surfaces 28, 29 of the housings
3, 4.
[0042] Hence, the particles 30 can be distributed evenly over the end surfaces 25, 26 of
the body 2 or the end surfaces 28, 29 of the housings 3, 4, and therefore positional
deviation generated between the body 2 and the housings 3, 4 by the fluid pressure
in the gear pump 1 can be prevented effectively.
[0043] By using an anti-corrosion agent as the coating agent 31, corrosion such as electrolytic
corrosion can be prevented on the joint portion between the body 2 and the housings
3, 4.
[0044] In another embodiment, the particles 30 are formed from a softer material than the
body 2 and the housings 3, 4 such that the particles 30 are compressed between the
body 2 and the housings 3, 4. As a result, frictional force is increased via the compressed
particles 30.
[0045] In another embodiment, both the end surfaces 25, 26 of the body 2 and the end surfaces
28, 29 of the housings 3, 4 are formed smooth, and positioning is performed between
the body 2 and the housings 3, 4 using the particles 30 alone, i.e. without using
the processing teeth 27.
INDUSTRIAL APPLICABILITY
[0046] The gear pump according to this invention is suitable for use as a pump provided
in an oil pressure device, a water pressure device, or similar.