TITLE OF THE INVENTION
TILTING PAD TYPE JOURNAL BEARING
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tilting pad type
journal bearing.
2. Description of the Related Art
The slide bearing is a shaft bearing that supports a
rotary shaft via a thin fluid film. The slide bearings have
higher load bearing performance compared to rolling bearings
and also excel in vibration damping properties and shock
resistance. Therefore, the slide bearings are widely
employed for industrial rotary machines (steam turbines,
generators, gas turbines, compressors, etc.) required to
have high reliability. Tilting pad type journal bearings,
excelling in oscillation stability, are well known as a type
of slide bearings used for these rotary machines.
The tilting pad type journal bearing comprises a
plurality of pads which are arranged along the periphery of
a rotary shaft and a bearing housing which supports the pads
in a tiltable manner via a plurality of pivots. Lubricating
oil is supplied to the gaps between the peripheral surface
of the rotary shaft and sliding surfaces of the pads to form
oil films, and the rotary shaft is supported by the pressure
of the oil films. Since the tilting angle of each pad
changes according to the pressure distribution of the oil
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film, unstable oscillation such as the so-called "oil whip"
can be suppressed.
The tilting pad type journal bearings can be roughly
classified into two types: the oil bath type and the direct
oil supply type. In the oil bath type, the lubricating oil
is supplied to the gaps between the peripheral surface of
the rotary shaft and the sliding surfaces of the pads by
increasing the sealability of the bearing chamber
accommodating the pads and storing the lubricating oil in
the bearing chamber. In contrast, in the direct oil supply
type, the lubricating oil is supplied to the gaps between
the peripheral surface of the rotary shaft and the sliding
surfaces of the pads via nozzles arranged between the pads,
for example (see JP-2004-197890-A, for example).
SUMMARY OF THE INVENTION
In the tilting pad type journal bearing described in
JP-2004-197890-A, the sliding surface of each pad is formed
so that its width in the axial direction is constant from
the front edge (upstream end in the circumferential
direction) to the rear edge (downstream end in the
circumferential direction). Therefore, even though part of
the lubricating oil supplied from the nozzle to a front edge
part of the sliding surface of the pad flows towards a rear
edge part of the sliding surface, the rest of the
lubricating oil flows towards the side edges of the sliding
surface and leaks out. Specifically, since each pad tilts
as mentioned above, the thickness of the oil film formed
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between the peripheral surface of the rotary shaft and the
sliding surface of the pad (i.e., the distance between the
peripheral surface of the rotary shaft and the sliding
surface of the pad) decreases as it goes downstream in the
circumferential direction. Therefore, if the width of the
sliding surface of the pad in the axial direction is
constant as mentioned above, the cross-sectional area of the
oil film formed between the peripheral surface of the rotary
shaft and the sliding surface of the pad (i.e., the crosssectional
area of the gap formed between the peripheral
surface of the rotary shaft and the sliding surface of the
pad) also decreases as it goes downstream in the
circumferential direction. The oil leaks out via the side
edges of the sliding surface of the pad in an amount
corresponding to the decrease in the cross-sectional area of
the oil film. Thus, the amount of oil leakage via the side
edges of the sliding surface of the pad is not small, and
the amount of oil supplied from the nozzle has to be set
greater in consideration of the amount of oil leakage.
Further, in general, part of the lubricating oil
after passing through the rear edge part of the sliding
surface of the pad merges with the lubricating oil supplied
from the nozzle and flows into the front edge part of the
sliding surface of the next pad on the downstream side
(carry-over). Therefore, the amount of oil that has to be
supplied from the nozzle can be reduced if the amount of the
carry-over oil is increased under a condition that the
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temperature rise of the sliding surface of the pad is
relatively slight.
The object of the present invention is to provide a
tilting pad type journal bearing capable of reducing the
amount of oil that has to be supplied to the bearing.
To achieve the above object, a tilting pad type
journal bearing according to the present invention
comprises: a plurality of pads which are arranged along the
periphery of a rotary shaft; a bearing housing which
supports the pads in a tiltable manner via a plurality of
pivots, and a plurality of nozzles which are each arranged
between the pads to supply lubricating oil to sliding
surfaces of the pads. The sliding surface of each of the
pads is formed so that the width of the sliding surface
increases as it goes from a front edge part towards a rear
edge part of the sliding surface. A tip end part of at
least one of the nozzles has a groove part which induces a
flow heading from lateral parts towards the center in the
width direction, in an oil flow from the rear edge part of
the sliding surface of an upstream pad to the front edge
part of the sliding surface of a downstream pad.
As above, in the tilting pad type journal bearing
according to the present invention, the sliding surface of
each pad is formed so that its width increases as it goes
from the front edge part towards the rear edge part (i.e.,
so that the width of the front edge part is small and the
width of the rear edge part is large). With this
configuration, the cross-sectional area of the oil film
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formed between the peripheral surface of the rotary shaft
and the sliding surface of the pad does not decrease as it
goes downstream in the circumferential direction, or the
decrease can be suppressed. Accordingly, the amount of oil
leakage via the side edges of the sliding surface of the pad
can be decreased. Consequently, the amount of oil that has
to be supplied from the nozzle can be reduced.
Further, the groove part formed in the tip end part
of the nozzle induces the flow heading from the lateral
parts towards the center in the width direction in the oil
flow from the rear edge part of the sliding surface of the
pad on the upstream side to the front edge part of the
sliding surface of the pad on the downstream side.
Accordingly, the ratio of the amount of the lubricating oil
flowing into the front edge part of the sliding surface of
the downstream pad while merging with the lubricating oil
supplied from the nozzle to the amount of the lubricating
oil flowing out from the rear edge part of the sliding
surface of the upstream pad can be increased. In other
words, the amount of the carry-over oil can be increased.
Therefore, the amount of oil that has to be supplied from
the nozzle can be reduced.
According to the present invention, the amount of oil
that has to be supplied to the bearing can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
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Fig. 1 is a circumferential cross-sectional view
showing the structure of a tilting pad type journal bearing
according to a first embodiment of the present invention.
Fig. 2A is a circumferential cross-sectional view
showing a tilting state of a pad in the first embodiment of
the present invention.
Fig. 2B is a graph showing variations in the
thickness of an oil film formed between the peripheral
surface of the rotary shaft and a sliding surface of the pad
in the first embodiment of the present invention.
Fig. 3 is a perspective view showing the structure of
the pad in the first embodiment of the present invention.
Fig. 4 is a perspective view showing the structure of
a nozzle in the first embodiment of the present invention.
Fig. 5 is a circumferential cross-sectional view
showing the structure of a tilting pad type journal bearing
as a first comparative example.
Fig. 6 is a perspective view showing the structure of
a pad in the first comparative example.
Fig. 7 is a perspective view showing the structure of
a nozzle in the first comparative example.
Fig. 8 is a circumferential cross-sectional view
showing the structure of a tilting pad type journal bearing
as a second comparative example.
Fig. 9 is a developed view showing the oil flow on
the pad sliding surfaces and the nozzle top surfaces in the
first comparative example.
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Fig. 10 is a developed view showing the oil flow on
the pad sliding surfaces and the nozzle top surfaces in the
second comparative example.
Fig. 11 is a developed view showing the oil flow on
the pad sliding surfaces and the nozzle top surfaces in the
first embodiment of the present invention.
Fig. 12 is a circumferential cross-sectional view
showing the structure of a tilting pad type journal bearing
according to a second embodiment of the present invention.
Fig. 13 is a circumferential cross-sectional view
showing the structure of a tilting pad type journal bearing
according to a third embodiment of the present invention.
Fig. 14 is a perspective view showing the structure
of a pad in a modification according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A first embodiment of the present invention will be
described below with reference to figures.
Fig. 1 is a circumferential cross-sectional view
showing the structure of a tilting pad type journal bearing
according to a first embodiment of the present invention.
Fig. 2A is a circumferential cross-sectional view showing a
tilting state of a pad in this embodiment. Fig. 2B is a
graph showing variations in the thickness of an oil film
formed between the peripheral surface of the rotary shaft
and a sliding surface of the pad in this embodiment. Fig. 3
is a perspective view showing the structure of the pad in
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this embodiment. Fig. 4 is a perspective view showing the
structure of a nozzle in this embodiment.
The tilting pad type journal bearing in this
embodiment is a shaft bearing for supporting the radialdirection
load of a rotary shaft 1 extending in the vertical
direction, for example. The bearing comprises a plurality
of (five in Fig. 1) pads 2 which are arranged along the
periphery of the rotary shaft 1, a bearing housing 4 which
supports the pads 2 in a tiltable (pivotable) manner via a
plurality of (five in Fig. 1) pivots 3, and a plurality of
(five in Fig. 1) nozzles 5 which are each arranged between
the pads 2.
On the peripheral side of the bearing housing 4, an
oil guide groove 6 is formed to extend circumferentially.
The oil guide groove 6 of the bearing housing 4 is provided
with a plurality of oil guide holes 7 penetrating the
bearing housing 4 in the radial direction. The oil guide
holes 7 are each connected to the nozzles 5. The oil guide
groove 6 of the bearing housing 4 is connected to an oil
tank 12 via an oil guide hole 9 of a casing 8, a pipe 10,
and a pump 11.
By the driving the pump 11, lubricating oil stored in
the oil tank 12 is supplied to the oil guide groove 6 of the
bearing housing 4, and further to the gap between the
peripheral surface 13 of the rotary shaft 1 and the sliding
surface 14 of each pad 2 via the oil guide hole 7 of the
bearing housing 4 and the nozzles 5. The sliding surface 14
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of the pad 2 is formed of metal having a low melting point
(e.g., white metal) or resin.
The lubricating oil supplied to the gap between the
peripheral surface 13 of the rotary shaft 1 and the sliding
surface 14 of each pad 2 rotates following the rotary shaft
1 and forms an oil film (unshown). The rotary shaft 1 is
supported by the pressure of the oil film. In this case,
each pad 2 tilts as shown in Fig. 2A depending on the
pressure distribution in the oil film. Specifically, as
shown in Fig. 2B, the thickness of the oil film formed
between the peripheral surface 13 of the rotary shaft 1 and
the sliding surface 14 of each pad 2 decreases as it goes
downstream in the circumferential direction (i.e.,
rotational direction of the rotary shaft 1 indicated by the
arrow A in Figs. 1 and 2A). More specifically, the oil film
thickness takes on the maximum value at the front edge
(circumferential-direction position  = 0) of the sliding
surface 14 of the pad 2, decreases as it goes downstream in
the circumferential direction, and hits the minimum at a
circumferential-direction position B. Thereafter, the oil
film thickness slightly increases as it goes towards the
rear edge (circumferential-direction position  = A) of the
sliding surface 14.
As shown in Fig. 3, the sliding surface 14 of the pad
2 has a width dimension W1 at the front edge and a greater
width dimension W2 at the rear edge (W2 > W1). The sliding
surface 14 is formed so that its width increases as it goes
downstream in the circumferential direction from the front
11
edge to the rear edge. While Fig. 11 (explained later)
shows an example in which the sliding surface 14 is formed
so that its width increases linearly, the width may also be
increased differently (e.g. according to a curve).
As shown in Fig. 4, the nozzle 5 is formed of a round
pipe 15 which is connected to the oil guide hole 7 of the
bearing housing 4 and a hollow nozzle head 16 (tip end part)
which is connected to the tip end of the round pipe 15. The
nozzle head 16 has a width dimension W3 greater than the
aforementioned width dimension W2 of the rear edge of the
sliding surface 14 of the pad 2. Thus, a top surface (tip
end surface) 17 of the nozzle head 16 has the width
dimension W3.
A groove part 18 is formed on the top surface 17 of
the nozzle head 16. The groove part 18 has a substantially
trapezoidal shape when viewed in the direction of the normal
to the top surface 17. In this embodiment, the width
dimension of the front edge of the groove part 18 is W2,
which equals the width dimension W2 of the rear edge of the
sliding surface 14 of the pad 2, and the width dimension of
the rear edge of the groove part 18 is W1, which equals the
width dimension W1 of the front edge of the sliding surface
14 of the pad 2. At the bottom of the groove part 18, a
plurality of oil discharge ports 19 connecting to the inside
of the nozzle head 16 and the round pipe 15 are formed. The
oil discharged from these oil discharge ports 19 is supplied
to the sliding surface 14 of the pad 2 arranged on the
downstream side.
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A concavity 20 as an oil pool is formed around the
oil discharge ports 19 (i.e., formed in a part of the groove
part 18). With the concavity 20 formed as an oil pool, the
oil can be supplied to the sliding surface 14 of the pad 2
even when the pump 11 stopped temporarily for some reason.
However, the concavity 20 may also be left out as shown in
Fig. 11 (explained later).
Next, the effects of this embodiment will be
explained below by using comparative examples.
Fig. 5 is a circumferential cross-sectional view
showing the structure of a tilting pad type journal bearing
as a first comparative example. Fig. 6 is a perspective
view showing the structure of a pad in the first comparative
example. Fig. 7 is a perspective view showing the structure
of a nozzle in the first comparative example. Fig. 8 is a
circumferential cross-sectional view showing the structure
of a tilting pad type journal bearing as a second
comparative example. Fig. 9 is a developed view showing the
oil flow on the pad sliding surfaces and the nozzle top
surfaces in the first comparative example. Fig. 10 is a
developed view showing the oil flow on the pad sliding
surfaces and the nozzle top surfaces in the second
comparative example. Fig. 11 is a developed view showing
the oil flow on the pad sliding surfaces and the nozzle top
surfaces in this embodiment. Elements in the first and
second comparative examples equivalent to those in the first
embodiment are assigned the already used reference
13
characters and repeated explanation thereof is omitted
properly.
The tilting pad type journal bearing as the first
comparative example comprises a plurality of (five in Fig.
5) pads 30 and a plurality of (five in Fig. 5) nozzles 31
which are each arranged between the pads 30. As shown in
Fig. 6, a sliding surface 32 of each pad 30 is formed so
that its width is constant (W2) from the front edge to the
rear edge.
As shown in Fig. 7, the nozzle 31 is formed of a
round pipe 15 and a hollow nozzle head 33 which is connected
to the tip end of the round pipe 15. No groove part 18 is
formed on the top surface 17 of the nozzle head 33. The top
surface 17 of the nozzle head 33 is provided with a
plurality of oil discharge ports 19. The width dimension of
the nozzle head 33 (i.e., the width dimension of the top
surface 17 of the nozzle head 33) is W3.
Part of the lubricating oil supplied from the nozzle
31 to a front edge part of the sliding surface 32 of the pad
30 flows towards a rear edge part of the sliding surface 32
as indicated by the arrows F1 in Fig. 9, while the remaining
lubricating oil flows towards the side edges of the sliding
surface 32 and leaks out as indicated by the arrows F2 in
Fig. 9. More specifically, since the oil film thickness
decreases as it goes downstream in the circumferential
direction as shown in the aforementioned Figs. 2A and 2B,
the cross-sectional area of the oil film also decreases as
it goes downstream in the circumferential direction. The
14
oil leaks out via the side edges of the sliding surface 32
of the pad 30 in an amount corresponding to the decrease in
the cross-sectional area of the oil film. Thus, the amount
of oil leakage via the side edges of the sliding surface 32
of the pad 30 is not small, and the amount of oil supplied
from the nozzle 31 has to be set greater in consideration of
the amount of oil leakage.
The tilting pad type journal bearing as the second
comparative example comprises the pads 2 in the first
embodiment instead of the pads 30. As mentioned above, the
sliding surface 14 of the pad 2 is formed so that its width
increases as it goes downstream in the circumferential
direction from the front edge to the rear edge. With this
configuration, the cross-sectional area of the oil film does
not decrease as it goes downstream in the circumferential
direction, or the decrease can be suppressed. Accordingly,
the amount of oil leakage via the side edges of the sliding
surface 14 of the pad 2 can be reduced. In other words,
most of the lubricating oil supplied from the nozzle 31 to
the front edge part of the sliding surface 14 of the pad 2
flows towards the rear edge part of the sliding surface 14
as indicated by the arrows F1 in Fig. 10. Therefore, the
amount of oil that has to be supplied from the nozzle 31 can
be reduced in comparison with the first comparative example.
In the second comparative example, however, in the
total amount of lubricating oil flowing out from the rear
edge part of the sliding surface 14 of the pad 2 on the
upstream side (see arrows F3 in Fig. 10), the ratio of the
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amount of lubricating oil flowing into the front edge part
of the sliding surface 14 of the pad 2 on the downstream
side while merging with lubricating oil supplied from the
oil discharge ports 19 of the nozzle 31 (see arrows F4 in
Fig. 10) decreases. In other words, the amount of the
carry-over oil decreases.
The tilting pad type journal bearing according to
this embodiment comprises the aforementioned nozzles 5
instead of the nozzles 31. As mentioned above, the groove
part 18 is formed on the top surface 17 of the nozzle 5. In
the oil flow from the rear edge part of the sliding surface
14 of the upstream pad 2 to the front edge part of the
sliding surface 14 of the downstream pad 2, the groove part
18 induces a flow heading from lateral parts towards the
center in the width direction (see arrows F5 in Fig. 11).
Accordingly, the ratio of the amount of the lubricating oil
flowing into the front edge part of the sliding surface 14
of the downstream pad 2 while merging with the lubricating
oil supplied from the oil discharge ports 19 of the nozzle 5
(see arrows F6 in Fig. 11) to the amount of the lubricating
oil flowing out from the rear edge part of the sliding
surface 14 of the upstream pad 2 (see arrows F5 in Fig. 11)
can be increased. In other words, the amount of the carryover
oil can be increased. Therefore, the amount of oil
that has to be supplied from the nozzle 5 can be reduced.
As described above, according to this embodiment, the
amount of oil that has to be supplied to the bearing can be
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reduced in comparison with the first and second comparative
examples.
A second embodiment of the present invention will be
described below with reference to Fig. 12. Fig. 12 is a
circumferential cross-sectional view showing the structure
of a tilting pad type journal bearing according to the
second embodiment of the present invention. Elements in
this embodiment equivalent to those in the above embodiment
and comparative examples are assigned the already used
reference characters and repeated explanation thereof is
omitted properly.
The tilting pad type journal bearing in this
embodiment is a shaft bearing for supporting the radialdirection
load of a rotary shaft 1 extending in a horizontal
direction, for example. One of the pads 2 is arranged under
(right under) the rotary shaft 1, and thus the load on the
particular pad 2 is higher than that on each of the other
pads 2. Put another way, the temperature rise of the
sliding surface 14 of the particular pad 2 situated under
the rotary shaft 1 is greater in comparison with the sliding
surfaces 14 of the other pads 2.
Therefore, in this embodiment, the aforementioned
nozzle 31 is arranged on the upstream side of the particular
pad 2 situated under the rotary shaft 1, by which the amount
of the carry-over oil for the particular pad 2 situated
under the rotary shaft 1 is reduced and the temperature rise
of the sliding surface 14 of the particular pad 2 is
suppressed. On the other hand, the aforementioned nozzle 5
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is arranged on the upstream side of each of the other pads
2, by which the amount of the carry-over oil for the other
pads 2 is increased. Thus, also in this embodiment, the
amount of oil that has to be supplied to the bearing can be
reduced in comparison with the aforementioned first and
second comparative examples.
A third embodiment of the present invention will be
described below with reference to Fig. 13. Fig. 13 is a
circumferential cross-sectional view showing the structure
of a tilting pad type journal bearing according to the third
embodiment of the present invention. Elements in this
embodiment equivalent to those in the above embodiments and
comparative examples are assigned the already used reference
characters and repeated explanation thereof is omitted
properly.
The tilting pad type journal bearing in this
embodiment is a shaft bearing for supporting the radialdirection
load of a rotary shaft 1 extending in a horizontal
direction, for example. One of the nozzles is arranged
under (right under) the rotary shaft 1, and thus the load on
each of two pads 2 situated upstream and downstream of the
particular nozzle is higher than that on each of the other
pads 2. Put another way, the temperature rise of the
sliding surfaces 14 of the two pads 2 upstream and
downstream of the particular nozzle situated under the
rotary shaft 1 is greater in comparison with the sliding
surfaces 14 of the other pads 2.
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Therefore, in this embodiment, the aforementioned
nozzle 31 is arranged under the rotary shaft 1 and another
nozzle 31 is arranged at the position upstream of the former
nozzle 31 across one pad 2, by which the amount of the
carry-over oil for the two pads 2 upstream and downstream of
the particular nozzle 31 situated under the rotary shaft 1
is reduced and the temperature rise of the sliding surfaces
14 of the two pads 2 is suppressed. On the other hand, the
aforementioned nozzle 5 is arranged on the upstream side of
each of the other pads 2, by which the amount of the carryover
oil for the other pads 2 is increased. Thus, also in
this embodiment, the amount of oil that has to be supplied
to the bearing can be reduced in comparison with the
aforementioned first and second comparative examples.
Although not particularly mentioned in the above
second and third embodiments, it is also possible to
increase the number and/or the diameter of the oil discharge
ports 19 of the nozzle 31 in comparison with the oil
discharge ports 19 of the nozzle 5.
While the above description of the embodiments has
been given assuming, for example, that the tilting pad type
journal bearing comprises four of the nozzles 5 (i.e., the
groove parts 18 are formed in the tip end parts of four
nozzles) in the second embodiment and three of the nozzles 5
(i.e., the groove parts 18 are formed in the tip end parts
of three nozzles) in the third embodiment, the number of the
nozzles 5 is not limited to these examples. It is
sufficient if the tilting pad type journal bearing comprises
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at least one nozzle 5 (i.e., the groove part 18 is formed in
the tip end part of at least one nozzle).
While the above description of the first through
third embodiments has been given by using examples in which
the outline width dimension of the top surface 17 of the
nozzle 5 (or 31) is greater than the width dimension W2 of
the rear edge of the sliding surface 14 of the pad 2, the
outline width dimension of the top surface 17 of the nozzle
5 (or 31) may also be set equal to the width dimension W2 of
the rear edge of the sliding surface 14 of the pad 2.
While the above description of the first through
third embodiments has been given by using examples in which
the sliding surface 14 of the pad 2 is formed so that its
width in the axial direction increases as it goes downstream
in the circumferential direction from the front edge to the
rear edge (i.e., the front edge part and the rear edge part
are also formed so that its width in the axial direction
increases as it goes downstream in the circumferential
direction) as shown in Figs. 3 and 11, the configuration of
the sliding surface 14 of the pad 2 is not limited to these
examples and can be modified without departing from the
subject matter and technical idea of the present invention.
For example, the front edge part of the sliding surface of
the pad (e.g., front part of the sliding surface within 1/5
circumferential length of the sliding surface from the front
edge) may be formed to have a constant width in the axial
direction, or the rear edge part of the sliding surface of
the pad (e.g., a part from the circumferential-direction
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position B where the oil film thickness hits the minimum to
the rear edge, or a rear part of the sliding surface within
1/5 circumferential length of the sliding surface from the
rear edge) may be formed to have a constant width in the
axial direction. Also in these modifications, the amount of
oil leakage via the side edges of the sliding surface of the
pad can be decreased and the amount of oil that has to be
supplied to the bearing can be reduced.
While the above description of the first through
third embodiments has been given by using examples in which
the pad 2 is formed so that its total width in the axial
direction increases as it goes downstream in the
circumferential direction from the front edge (upstream end
in the circumferential direction) to the rear edge
(downstream end in the circumferential direction), the
configuration of the pad 2 is not limited to these examples
and can be modified without departing from the subject
matter and technical idea of the present invention. For
example, as shown in Fig. 14, a pad 2A may be configured to
have a step surface 21 (specifically, a step surface 21 more
recessed than the sliding surface 14 and forming no oil film
between itself and the peripheral surface 13 of the rotary
shaft 1) on each side of the sliding surface 14 in the axial
direction. The pad 2A may also be configured so that its
total width (including the sliding surface 14 and the step
surfaces 21) in the axial direction is constant (W2) from
the front edge (upstream end in the circumferential
direction) to the rear edge (downstream end in the
21
circumferential direction). Also in such a modification,
the amount of oil that has to be supplied to the bearing can
be reduced similarly to the above embodiments. Further, in
this modification, the gap between each side face of the pad
2A and a wall surface facing the side face becomes narrower
than those in the above embodiments. Therefore, mobility of
the pad 2A in the axial direction decreases and mountability
of the pad 2A is improved.

We claim:
1. A tilting pad type journal bearing comprising:
a plurality of pads which are arranged along the
periphery of a rotary shaft;
a bearing housing which supports the pads in a
tiltable manner via a plurality of pivots; and
a plurality of nozzles which are each arranged
between the pads to supply lubricating oil to sliding
surfaces of the pads, wherein
the sliding surface of each of the pads is formed so
that the width of the sliding surface increases as it goes
from a front edge part towards a rear edge part of the
sliding surface, and
a tip end part of at least one of the nozzles has a
groove part which induces a flow heading from lateral parts
towards the center in the width direction, in an oil flow
from the rear edge part of the sliding surface of an
upstream pad to the front edge part of the sliding surface
of a downstream pad.
2. The tilting pad type journal bearing according to
claim 1, wherein:
the tip end part of each of the nozzles has a top
surface whose outline width dimension is greater than or
equal to the width dimension of the rear edge part of the
sliding surface of the pad, and
the groove part is formed on the top surface of the
at least one of the nozzles.
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3. The tilting pad type journal bearing according to
claim 2, wherein:
each nozzle not having the groove part includes at least
one oil discharge port formed on the top surface, and
each nozzle having the groove part includes at least one
oil discharge port formed at the bottom of the groove part.
4. The tilting pad type journal bearing according to
claim 2, wherein:
the rotary shaft extends in a horizontal direction, and
the groove part is formed on at least one of the nozzles
excluding a nozzle on the upstream side of a pad situated under
the rotary shaft.
5. The tilting pad type journal bearing according to
claim 2, wherein:
the rotary shaft extends in a horizontal direction, and
the groove part is formed on at least one of the nozzles
excluding a nozzle situated under the rotary shaft and a nozzle
situated upstream of the former nozzle across a pad.
6. The tilting pad type journal bearing according to
claim 1, wherein the pad is configured so that the total width
of the entire pad including the sliding surface and step
surfaces is constant from its front edge to its rear edge.