GB2039632A - Turbocharger - Google Patents

Abstract

A turbocharger driven by high- temperature exhaust gases from a gasoline or diesel engine wherein an improved lubricant communication system is provided to cool the parts on the side of a turbine more effectively. Lubricant is supplied from the blower side bearings via a passageway 23 to a chamber 24 in the bearing casing. <IMAGE>

Description

SPECIFICATION Turbocharger The present invention relates generally to a turbocharger and more particularly an improvement of a lubricant communication system thereof.

In known turbochargers, lubricating oil is used not only for lubricating bearings which support a common turbine and blower shaft, but also for cooling them as well as the parts adjacent to them. That is, the lubricating oil flows through an oil inlet of a bearing casing to the bearings supporting the common shaft. The lubricating oil is caused to scatter against the seals, wall surfaces and other parts and flows down along them while absorbing heat from them and is returned to an oil sump. In general, the lubricating oil is made to flow in large quantity to the blower side and in small quantity to the turbine side which is heated to high temperatures.As a result, the turbine side is undercooled while the blower side is overcooled so that the compressibility of the seal ring on the turbine side is reduced so that the sealing performance is decreased, resulting in the leakage of lubricating oil. In addition, because of the high temperature the accumulation of carbon in the vicinity of the turbine-side seal ring is accelerated.

Furthermore, the turbine-side bearing is thermally damaged, whereby the durability oftheturbochar- ger is lowered.

According to the present invention, a turbocharger of the type wherein a common turbine and blower shaft is rotatably supported by turbine side and blower-side bearings disposed within a bearing casing and is lubricated with a lubricating oil, comprising a cooling chamber at least partially encircling the common shaft adjacent to the turbine side bearing and to a partition wall between the bearing casing and a turbine casing, at least one oil passage extending through the bearing casing for causing at least part of the lubricating oil from the blower-side bearing and from the vicinity thereof to flow into the said cooling chamber, and a drainage chamber with an oil outlet for discharging the lubricating oil from the cooling chamber.

In one form of the invention, the cooling chamber is separated from the drainage chamber by a partition wall having a semicircular cross sectional configuration.

In another form of the invention, the cooling chamber is divided into coaxial annular spaces by an annular, axially extended partition wall so that the outer annular space may be used as the cooling chamber while the inner annular space is used as an annular oil passage in communication with the turbine-side bearing.

Thus in its preferred form, the invention provides a turbocharger wherein the overall quantity of the lubricating oil remains unchanged or the ratio in volume of the lubricating oil to be supplied to the turbine side to the lubrication oil to be supplied to the blower side remains unchanged; and a relatively large amount ofthe lubricating oil which has cooled the blower side bearing and the parts in the vicinity thnroaf is nnt dimrjlv returned to the oil sumD or the like but is made to flow towards the turbine-side so as to cool the turbine-side bearing and seal ring and the parts in the vicinity thereof so that cooling efficiency may be considerably improved and consequently these parts may be made more durable.

Further features and details of the invention will be apparent from the following description of preferred embodiments which will be given by way of example, with reference to the accompanying drawings in which: Figure lisa longitudinal sectional view of a first embodiment of a turbocharger in accordance with the present invention; Figure 2 is a fragmentary view thereof showing major component parts thereof; Figure 3 is a sectional view taken in the direction of the arrows along the line Ill-Ill of Figure 2; Figure4is a sectional view taken in the direction of the arrows along the line IV-IV of Figure 2; Figure 5 is a sectional view taken in the direction of the arrows along the line V-V of Figure 2; Figure 6 is a fragmentary, longitudinal sectional view of a second embodiment of the present invention;; Figure 7 is a longitudinal sectional view of a third embodiment of the present invention; Figure 8 is a sectional view taken in the direction of the arrows along the line VIII-VIII of Figure 7; Figure 9 is a sectional view taken in the direction of the arrows along the line IX-IX of Figure 7; and Figure 10 is a sectional view taken in the direction of the arrows along the line X-X of Figure 7.

Afirst embodiment (Figures 1-5) of a turbocharger in accordance with the present invention comprises in general a bearing casing 1, a turbine casing 2 and a blower casing 3 which are secured together to form a unitary construction. More particularly, a partition wall 4 of the bearing casing 1 is jointed to the turbine casing 2 and a heat shielding plate 5 is interposed between the turbine casing 2 and the partition wall 4 of the bearing casing 1. The blower casing 3 is joined to the bearing casing 1 with a seal plate 6.

A common, stepped turbine and blower shaft 9 extending through the shaft holes of the partition wall 4 and the seal plate 6 is rotatably supported by turbine-side and blower-side bearings 7 and 8 which are disposed in the shaft bore of the bearing casing 1 and are spaced apart from each other by a suitable distance in the axial direction. The bearings 7 and 8 may be made of floating metal members or the like.

Aturbine wheel 15 and a blower wheel 16 are carried by the common shaft 9 at its ends respectively.

The shaft hole of the partition wall 4 is sealed with a seal ring 10 securely fitted round the common shaft 9. The shaft hole of the seal plate 6 is sealed with a seal ring 11 which in turn is fitted round a thrust collar 14 fitted round the common shaft 9.

A thrust bush 12 is fitted round the common shaft 9 between the thrust collar 14 and a shoulder or step adjacent to the blower-side bearing 8, and an annular groove 1 2a is formed in the peripheral wall of the thrust bushing 12.

A thrust plate 13 which is securely attached to the bearing casing 1 is fitted into the annular groove 12a whereby an annular oil space 22 may be defined between the blower-side bearing 8, the thrust bushing 12 and the thrust plate 13 as best shown in Figures 2 and 5. The thrust plate 13 is formed with an oil passage 21 which communicates between the annular groove 12a of the thrust bushing 12 and an axial oil passage 18 which in turn is in communication with a radial oil inlet 17. The axial oil passage 18 is substantially parallel with the axis of the common shaft 9 in the upper portion of the bearing casing 1 and communicates with the outer peripheral surfaces of the bearings 7 and 8 through oil passages 19 and 20, respectively.

A cooling chamber 24 having an annular cross sectional configuration as best shown in Figure 3 is defined within the bearing casing 1 adjacent to the partition wall 4 and the turbine-side bearing 7 and surrounding the common shaft 9. The cooling chamber 24 communicates with an inlet 13a of the thrust plate 13 through an oil passage 23 which extends obliquely through the upper portion of the bearing casing 1 generally in the axial direction, and will communicate with neither the oil inlet 17 nor the axial oil passage 18. As shown in Figures 1 and 3, the cooling chamber 24 also communicates with a drainage chamber 26 having an oil drainage hole 27.

The cooling chamber 24 and the drainage chamber 26 are only partially separated by a partition wall 24a semicircular in cross section as best shown in Figure 3 which defines the bottom of the cooling chamber 24 and bridges between the partition wall 4 and the boss portion 28 adjacent to the bearing 7.

The shaft bore between the bearings 7 and 8 communicates with the drainage chamber 26 through a radial oil outlet 25.

The mode of operation of the first embodiment constructed as described above, will now be described.

When an engine (not shown) to which the turbocharger is coupled is operating, the lubricating oil flows from a lubrication system into the oil inlet 17 and is distributed to flow into the oil passages 19 and 20 communicating with the bearings 7 and 8, respectively, and into the oil passage 21 of the thrust plate 13 which in turn communicates with the annular oil space 12a.

The lubricating oil flowing into the annular oil space 1 2a lubricates the thrust bearing surfaces of the thrust bushing 12 and the thrust plate 13 which are in contact with each other. Thereafter, the lubricating oil flows into the annular oil space 22 while part ofthe lubricating oil leaking into the space between the thrust plate 13, the thrust collar 14 and the seal plate 6 (see Figure 2), is also returned through the oil hole 13a into the annular oil space 22.

The lubricating oil in the annular oil space 22 flows through the oblique oil passages 23 into the cooling chamber 24 and then into the drainage chamber 26 while cooling the partition wall 4 and the boss portion 28. Thereafter the lubricating oil is returned through the oil outlet 27 into an oil sump (not shown).

The lubricating oil flowing into the oil passages 19 and 20 lubricates the turbine-side and blower-side bearings 7 and 8. The lubricating oil flowing from the left (turbine) side of the bearing 7 flows into the drainage chamber 26 while lubricating oil flowing out from the right (blower) side of the bearing 8 flows into the annular oil space 22. The lubricating oil flowing from the right (blower) side of the bearing 7 and from the left (turbine) side of the bearing 8 into the shaft bore therebetween flows through the oil outlet 25 into the drainage chamber 26.

A second embodiment, shown in Figure 6 is substantially similar in construction to the first embodiment described in detail above with reference to Figures 1 to 5 except that an intermediate seal plate 6a is interposed between the seal plate 6 and the thrust plate 13 and a seal ring 1 1a is interposed between the intermediate seal plate 6a and the thrust collar 14 whereby an additional annular oil space 22a may be defined. The annular oil space 22a communicates with the annular oil space 22 through the communication hole 13a . It should be noted that the thrust plate 13 is also formed with the oil passage 21 (see Figure 1) though it is not shown in Figure 6.

In operation, the lubricating oil which leaks into the annular oil space 22a flows through the communication hole 13a into the annular oil space 22 which communicates with the cooling chamber 24.

Since the intermediate seal plate 6a and the seal ring 11a are interposed, the leakage of lubricating oil into the blower may be further minimised.

A third embodiment, Figures 7 to 10 is also substantially similar in construction to the first embodiment shown in Figures 1 to 5 except that an annular, axially extended partition wall 4a bridges between the partition wall 4 and the boss portion 28 adjacent to the turbine bearing 7. The partition wall 4a defines an annular oil passage 29 and the cooling chamber 24 surrounds the annular oil passage 29 as best shown in Figure 8. The cooling chamber 24 communicates not only with the annular oil space 22 through the oblique oil passages 23 as in the first and second embodiments, but also with the drainage chamber 26 through a drainage opening 24b.

The annular oil passage 29 communicates with the drainage chamber 26 through a drainage opening 29a as best shown in Figure 7.

In operation, the lubricating oil flows through the inlet 17 and the axial oil passage 18 into the oil passages 19 and 20 leading to the bearings 7 and 8, respectively, and into the oil passage 21 extending through the thrust plate 13.

The lubricating oil flowing from the left (turbine) side of the bearing 7 flows into the annular oil passage 29 and then into the drainage chamber 26.

The lubricating oil flowing out from the right (blower) side of the bearing 8 flows into the annular oil space 22. The oil passing through the oil passage 21 in the thrust plate 13 also flows into the annular oil space 22 after having lubricated the thrust bushing 12 and the thrust metal 13 in the manner described previously. The lubricating oil in the annular oil space 22 flows into the upper portion of the cooling chamber 24 through the oblique oil passages 23 and then into the drainage chamber 26 through the drainage opening 24a while cooling the partition walls 4 and 4a.

The lubricating oil flowing out from the right (blower) side of the bearing 7 and from the left (turbine) side of the bearing 8 into the shaft bore therebetween flows into the drainage chamber 26 through the outlet 25.

The lubricating oils discharged from the annular oil space 29, the cooling chamber 24 and the shaft bore between the bearings 7 and 8 join in the drainage chamber 26 and are further discharged through the outlet 27 to the sump (not shown).

The partition walls 4 and 24a or 4a may be formed integral with the bearing casing 1 by casting, but when it is possible to design the partition walls 4 and 24a or 4a in the form of a frustum of a cone, they may be fabricated from steel sheets and securely jointed to the bearing casing 1 in any suitable manner. Furthermore, it is to be understood that various modifications may be effected without departing from the true scope of the present invention.

In summary, the circulating lubricating oil may effectively absorb heat not only from the partition wall between the turbine casing and the bearing casing but also from the turbine-side bearing 7 both of which rise to high temperatures so that they may be cooled very satisfactorily. As a result, problems such as the decrease in tension of the turbine-side seal ring, accumulation of carbon in the vicinity of the seal ring, and to the turbine-side bearing due to heat may be overcome, so that reliable operation of the turbocharger may be ensured.

Claims (5)

1. A turbocharger of the type wherein a common turbine and blower shaft is rotatably supported by turbine-side and blower-side bearings disposed within a bearing casing and is lubricated with a lubricating oil, which comprises a cooling chamber at least partially encircling the common shaft adjacent to the turbine-side bearing and to a partition wall between the bearing casing and a turbine casing, at least one oil passage extending through the bearing casing for causing at least part of the lubricating oil from the blower-side bearing and from the vicinity thereof to flow into the said cooling chamber, and a drainage chamber with an oil outlet for discharging the lubricating oil from the cooling chamber.

2. Aturbocharger as claimed in Claim 1 in which the cooling chamber is separated from the drainage chamber by a partition wall having a semicircular cross sectional configuration.

3. Aturbocharger as claimed in Claim 1 in which the cooling chamber is divided into coaxial annular spaces by an annular, axially extended partition wall so that the outer annular space may be used as the cooling chamber while the inner annular space is used as an annular oil passage in communication with the turbine-side bearing.

4. A turbocharger as claimed in any one of the preceding claims in which a thrust collar is fitted round the common shaft and an intermediate seal plate is mounted on the thrust collar with a seal ring interoosed therebetween.

5. Aturbocharger having a cooling system as specifically described herein with reference to Figures 1 to 5, or Figure 6, or Figures 7 to 10 of the accompanying drawings.