Journal bearing device

A first embodiment of the present invention will be described with reference to FIGS. 1 to 4 .

FIG. 1 is a vertical cross-sectional view of a journal bearing device according to the first embodiment of the present invention. The journal bearing device of the present embodiment has a two-piece construction comprised of an upper part and a lower part and is installed such that a rotor 1 of a rotary machine is held between the upper part and the lower part. The upper and lower parts of the journal bearing device are coupled to each other with bolts (not shown). The rotor 1 is supported by the journal bearing device to be rotatable in the direction indicated by an arrow 19 in FIG. 1 .

The lower part of the bearing device includes a lower bearing liner 2 a rotatably supporting the rotor 1 and a lower base metal 3 a attached to the outer circumference of the lower bearing liner 2 a to fix and support the lower bearing liner 2 a . The upper part of the bearing includes an upper bearing liner 2 b rotatably supporting the rotor 1 and an upper base metal 3 b attached to the outer circumference of the upper bearing liner 2 b to fix and support the upper bearing liner 2 b . The inner circumferential surfaces of the lower bearing liner 2 a and upper bearing liner 2 b are lined with, for example, white metal making up sliding surfaces 9 a and 9 b over which the rotor 1 slides.

According to the present embodiment, the lower bearing liner 2 a has a sliding portion and a clearance portion. The sliding portion of the lower bearing liner 2 a is provided with the sliding surface 9 a . The clearance portion of the lower bearing liner 2 a is provided in a downstream end portion of the lower bearing liner 2 a in the rotational direction of the rotor 1 . Further, the clearance portion of the lower bearing liner 2 a is provided by cutting out the sliding surface 9 a of the lower bearing liner 2 a in a downstream end portion thereof, thereby forming a cut-away portion 7 a . The cut-away portion 7 a extends, in the bearing width direction, over a part or a whole of the bearing width thereby forming a space between the lower bearing liner 2 a and the rotor 1 . The cut-away portion 7 a is required to be deep enough to prevent formation of an oil film which causes bearing loss. To facilitate positioning of the lower bearing liner 2 a , it is desirable to leave the downstream end portion of the lower bearing liner 2 a with an appropriate thickness in the radial direction (the depth direction of the cut-away portion) without entirely cutting away the downstream end portion. Also, the border between the cut-away portion 7 a and the sliding surface 9 a may be smooth. The range of the cut-away portion 7 a will be described later with reference to FIG. 3 .

The lower bearing liner 2 a has one or more oil paths 6 a formed on the outer circumferential surface thereof. The oil paths 6 a are used to supply lubricant into the bearing. Each oil path 6 a circumferentially extends over the outer circumference of the sliding surface 9 a (the sliding portion) leading from the back side of the border between the sliding surface 9 a and the cut-away portion 7 a (a border portion between the sliding portion and the clearance portion) to the upstream end, in the rotational direction of the rotor 1 , of the lower bearing liner 2 a . With the oil paths 6 a provided on the back side of the sliding surface 9 a excluding the cut-away portion 7 a , lubricant is caused to pass the back side of the sliding surface 9 a without entering the back side of the cut-away portion 7 a.

The upstream end in the rotational direction of the rotor 1 of each oil path 6 a is communicated with an oil supply hole 5 a open at an upstream end portion in the rotational direction of the rotor 1 of the sliding surface 9 a . In other words, each oil supply hole 5 a extends from the upstream end portion of each oil path 6 a toward the sliding surface. This causes the lubricant coming down each oil path 6 a to flow onto the sliding surface 9 a through the oil supply hole 5 a , i.e. to be provided between the sliding surface 9 a and the rotor 1 .

The downstream end in the rotational direction of the rotor 1 of each oil path 6 a is communicated with an oil supply path 4 formed through the lower base metal 3 a . The oil supply path 4 is connected to an oil supply pump (not shown) provided outside the bearing. The lubricant supplied from outside through each oil supply path 4 enters the corresponding oil path 6 a to be then supplied onto the sliding surface 9 a via the corresponding oil supply hole 5 a . The downstream end of each oil path 6 a in the rotational direction of the rotor 1 is located near the back side of the border between the sliding surface 9 a and the cut-away portion 7 a and, at the downstream end, the oil path 6 a is communicated with the oil supply path 4 .

FIG. 2 is a sectional view, taken along line A-A in FIG. 1 , of the journal bearing device shown in FIG. 1 . In FIG. 2 , the rotor 1 is omitted. Even though, in the present embodiment, the cut-away portion 7 a extends over the whole bearing width, it may be formed to extend over only a part of the bearing width. In the present embodiment, plural oil paths 6 a are provided on the back side of the sliding surface 9 a , in the bearing width direction. This makes it possible to cool the entire sliding surface 9 a . The oil paths 6 a are formed by forming grooves on the outer circumferential surface of the lower bearing liner 2 a.

Next, the range of the cut-away portion formed on the sliding surface 9 a will be described. FIG. 3 is a diagram showing an oil film pressure distribution over the sliding surface 9 of a general journal bearing device. In the oil film pressure distribution 10 over the sliding surface 9 , the oil film pressure is maximum at a downstream portion, in the rotational direction of the rotor 1 , beyond a 90° portion with respect to the upstream 0° portion defined by a horizontal plane crossing the central axis of the bearing. At further downstream of the 90° portion, the oil film pressure sharply drops to allow some portion of the sliding surface 9 to be free of oil film pressure. This occurs at around a 120° portion or at further downstream though dependent on the load applied by the rotor 1 and the operating condition of the bearing. Cutting away such portion free of oil film pressure of the sliding surface 9 does not affect the performance of the bearing. In the present embodiment, therefore, a portion of the sliding surface 9 where no oil film pressure is generated or where the oil film pressure is negative is cut away forming the cut-away portion 7 a . To be more specific, a portion which is, in the rotational direction of the rotor 1 , beyond a 120° portion of the sliding surface 9 , or in other words, a portion which is, in the rotational direction of the rotor 1 , beyond a 30° portion with respect to the direction of the load applied by the rotor 1 (the direction in which the weight of the rotor 1 is applied) is cut away forming the cut-away portion 7 a . Most preferably, the cut-away portion 7 a is as wide as the whole bearing width, but it is still effective even when it is narrower than the bearing width.

The operation and effects of the present embodiment will be described below.

According to the present embodiment, the lubricant supplied from outside the bearing to inside the bearing all flows into the oil paths 6 a via the corresponding oil supply paths 4 . The lubricant then flows, oppositely to the rotational direction of the rotor 1 , through the oil paths 6 a to be supplied to the sliding surface 9 a via the oil supply holes 5 a.

On the sliding surface 9 a , a portion more downstream in the rotational direction of the rotor 1 is higher in temperature. In the present embodiment, fresh lubricant just supplied, i.e. lubricant in a coolest state, is directly supplied to around the back side of the border between the sliding surface 9 a and the cut-away portion 7 a . Namely, the lubricant in a coolest state is first supplied to the portion highest in temperature of the lower bearing liner 2 a . Furthermore, with the lubricant made to flow through the oil paths 6 a oppositely to the rotational direction of the rotor 1 , the lubricant is lower in temperature when flowing over a part higher in temperature of the sliding portion of the lower bearing liner 2 a . This improves the efficiency of cooling by the lubricant. Still furthermore, the whole lubricant to be supplied into the bearing is made to flow through the oil paths 6 a . Hence, the whole lubricant is made use of to cool the high-temperature portion of the sliding portion of the lower bearing liner 2 a . This improves the effect of cooling by the lubricant and suppresses reduction of the strength of a low melting metal making up the sliding surface 9 a.

According to the present embodiment, by improving a route inside a bearing through which lubricant is supplied into the bearing from outside the bearing, it is possible to improve the cooling performance of the lubricant and to suppress rising of the bearing temperature. This makes it possible to reduce the amount of lubricant to be used and to realize a bearing device requiring less lubricant.

Also, according to the present embodiment, the cut-away portion 7 a is provided on the sliding surface making the sliding area of the lower bearing liner 2 a smaller. This reduces the bearing loss due to oil film shearing.

A second embodiment of the present invention will be described below. Constituent elements identical to those used in the first embodiment will be assigned identical reference numerals and their description will be omitted.

FIG. 4 is a vertical cross-sectional view of a journal bearing device according to the second embodiment of the present invention. The second embodiment differs from the first embodiment in that

the lower bearing liner 2 a has, in an upstream end portion thereof in the rotational direction of the rotor 1 , another clearance portion. The another clearance portion is provided by cutting out the sliding surface 9 a of the lower bearing liner 2 a in a upstream end portion thereof, thereby forming a cut-away portion 7 b . The cut-away portion 7 b extends, in the bearing width direction, over a part or a whole of the bearing width thereby forming a space between the lower bearing liner 2 a and the rotor 1 .

Referring to FIG. 3 showing the oil film pressure distribution 10 , the oil film pressure is small over a portion ranging from 0° to 40° in angle, measured in the rotational direction of the rotor 1 , of the sliding surface 9 a (in other words, over a portion ranging from 50° to 90° in angle measured, in the counter-rotational direction of the rotor 1 , from the direction of the load applied by the rotor 1 ). Forming the cut-away portion 7 b on the above portion of the sliding surface 9 a extending in the bearing width direction over a part or a whole of the bearing width does not much affect the oil film pressure distribution 10 while doing so makes it possible to further reduce the bearing loss. With both the cut-away portion 7 a and the cut-away portion 7 b provided, each oil supply hole 5 a is provided downstream of the border between the cut-away portion 7 b and the sliding surface 9 a . This embodiment, while also realizing the effects of the first embodiment, makes it possible to further reduce the bearing loss due to oil film shearing.

A third embodiment of the present invention will be described below with reference to FIGS. 5 to 7 . In FIGS. 5 to 7 , constituent elements identical to those used in the first or second embodiment will be assigned identical reference numerals and their description will be omitted.

FIG. 5 is a vertical cross-sectional view of a journal bearing device according to the third embodiment of the present invention. The third embodiment differs from the first and second embodiments in the construction of the upper bearing liner 2 b . The upper bearing liner 2 b of the third embodiment has grooves 8 (cut-away portions) extending in the circumferential direction on the surface of the upper bearing liner 2 b.

FIG. 6 is a sectional view, taken along line B-B in FIG. 5 , of the journal bearing device shown in FIG. 5 . In FIG. 6 , the rotor 1 is omitted. According to the third embodiment, the upper bearing liner 2 b has a sliding surface 9 b formed on the inner surface thereof to be in a middle portion in the bearing width direction with a groove 8 extending in the circumferential direction provided on each side in the bearing width direction of the sliding surface 9 b . Each groove 8 makes up a cut-away portion extending in the circumferential direction on each side of the sliding surface 9 b thereby forming a space between the upper bearing liner 2 b and the rotor 1 . This construction reduces the sliding surface area of the upper part of the bearing.

The upper part of the bearing serves as a guide in case the rotor 1 is caused, by whatever factor, to swingingly rotate and it need not support the load of the rotor 1 . The area of the sliding surface of the upper part of the bearing can, therefore, be reduced. The present embodiment, while also realizing the effects of the first embodiment, makes it possible to further reduce the bearing loss by reducing the sliding area of the upper part of the bearing.

The sliding surface 9 b and the grooves 8 need not necessarily be arranged as shown in FIG. 6 . For example, as shown in FIG. 7 , the upper part of the bearing may have two sliding surfaces 9 b separated from each other in the bearing width direction with a groove 8 formed between them and with another groove 8 formed on the outer side of each of them. This arrangement also reduces the sliding surface area, so that it is effective in reducing the bearing loss.

A fourth embodiment of the present invention will be described below.

FIG. 8 is a vertical cross-sectional view of a journal bearing device according to the fourth embodiment of the present invention. In the fourth embodiment, the oil paths 6 a provided in the lower part of the bearing are branched to be communicated with one or more oil paths 6 b formed on the upper bearing liner 2 b . The oil path 6 b extends in the circumferential direction along the back side of the sliding surface 9 b of the upper part of the bearing and is communicated with an oil supply hole 5 b open at an upstream end portion, in the rotational direction of the rotor 1 , of the sliding surface 9 b.

FIG. 9 is a sectional view, taken along line C-C in FIG. 8 . The sliding surface 9 b of the upper part of the bearing is provided in a center portion in the bearing width direction with a groove 8 extending in the circumferential direction on each side of the sliding surface 9 b . With the grooves 8 provided, the area of the sliding surface 9 b is reduced, so that, compared with the lower part having the oil paths 6 a , the upper part of the bearing may have fewer oil paths 6 b . The oil path 6 b is provided on the outer circumferential side of the sliding surface 9 b.

In the present embodiment, part of the lubricant flowing down the oil paths 6 a enters the oil path 6 b of the upper part of the bearing to be supplied to the sliding surface 9 b via the oil supply hole 5 b . In this arrangement, the lubricant is supplied to both the sliding surface 9 a and the sliding surface 9 b , so that, in case the rotor 1 swingingly rotates, damage to the sliding surface 9 b can be suppressed.

The positional arrangement of the sliding surface 9 b , grooves 8 , and the oil path 6 b need not necessarily be as shown in FIG. 9 . For example, as shown in FIG. 10 , the upper part of the bearing may have two sliding surfaces 9 b separated from each other in the bearing width direction with a groove 8 provided between them and with another groove 8 provided on the outer side of each of them. In this arrangement, an oil path 6 b is provided on the outer circumferential side of each of the two sliding surfaces 9 b . Thus, there are cases in which, as shown in FIG. 10 , the upper part of the bearing has plural sliding surfaces depending on the sliding surface and groove arrangement in the upper part of the bearing. In such cases, it is effective to provide, in the upper part of the bearing, as many oil paths 6 b as the number of sliding surfaces.

Next, an example of rotary machine to which the journal bearing device according to the present invention is applied will be described. The journal bearing device according to the present invention can be applied to, for example, turbomachinery such as steam turbines, gas turbines, and compressors in particular.

FIG. 11 is a schematic diagram showing main components of a steam turbine. Generally, a steam turbine used at a thermal power generation plant has a multi-span construction in which a high pressure turbine 12 , an intermediate pressure turbine 13 , a low pressure turbine 14 , and a generator 15 are coupled by a rotor 1 for efficiency improvement. Even though it is desirable to adopt the journal bearing device according to the present invention for every one of the bearing devices 11 shown in FIG. 11 , adopting the journal bearing device according to the present invention for only some of the bearing devices 11 will also contribute toward reducing loss in the turbine and the amount of lubricant used for the turbine.

FIG. 12 is a schematic diagram showing main components of a gas turbine. The gas turbine includes a compressor 16 for compressing air, a combustion device 18 which generates combustion gas by combusting fuel together with the air compressed by the compressor 16 , and a turbine 17 rotationally driven by the combustion gas generated by the combustion device 18 . The compressor 16 and the turbine 17 are coupled by the rotor 1 . The rotor 1 is rotatably supported by bearing devices 11 . In this case, too, adopting the journal bearing device according to the present invention for the bearing devices 11 shown in FIG. 12 will contribute toward reducing loss in the turbine and the amount of lubricant used for the turbine.