GB2271814A

GB2271814A - Turbocharger heat shield.

Info

Publication number: GB2271814A
Application number: GB9321546A
Authority: GB
Inventors: Malcolm George Leavesley
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-10-21
Filing date: 1993-10-19
Publication date: 1994-04-27
Anticipated expiration: 2013-10-19
Also published as: GB9222133D0; GB9321546D0; GB2271814B

Abstract

A turbocharger apparatus 2 comprises a heat shield 120 for shielding a bearing assembly (11) (fig. 1) and bearing housing 68 from the exhaust gases driving the turbocharger turbine 12. The shield may comprise two separable sections 73, 75 and be retained at its radially inner edge by a locking ring 67. Cooling air may be supplied to the back of the shield in a pipe 152 and slots may be provided in the front wall of the shield to to accomodate adjustable guide vanes 102. <IMAGE>

Description

TURBOCHARGER APPARATUS This invention relates to turbocharger apparatus.

Different types of turbocharger apparatus are known. One known type of turbocharger apparatus comprises a turbocharger housing, a compressor mounted for rotation in a compressor housing, a turbine mounted for rotation in a turbine housing, a first inlet for enabling air to be conducted to the compressor, an outlet for air from the compressor, a second inlet for enabling exhaust gases from an engine to be conducted to the turbine, and a chamber which surrounds the turbine and which receives the exhaust gases from the second inlet before the exhaust gases are conducted to the turbine. This known type of turbocharger apparatus is such that there is a fixed gap through which the exhaust gases in the chamber can pass to the turbine.The size of this gap is chosen to be a compromise between the various different sizes of gap that are ideally required for different engine operating conditions. This means that, for most engine operating conditions, the gap is not exactly correct and the turbocharger apparatus thus operates at less than its optimum performance. For example, with a relatively small gap, the turbocharger apparatus gives a quick response but excessive pressure tends to build up in the chamber. With a larger gap, the build up of excessive pressure in the chamber is avoided but then the response time of the turbocharger apparatus is slow.

In my PCT patent application No. WO 89/11583, I have described variable turbocharger apparatus which obviates or reduces the above mentioned problem.

In Figures 16 and 17 of PCT patent application No. WO 89/11583, I have illustrated a preferred type of turbocharger apparatus which uses a particular design of heat shield. This heat shield is very effective at stopping heat from engine exhaust gases passing to a low pressure side of the turbocharger apparatus and over-heating a bearing assembly which allows the rotation of the compressor and the turbine, and a bearing housing for the bearing assembly. This overheating tends to cause lubricant that is used to lubricate the bearing assembly to become baked onto parts of the bearing assembly and the bearing housing, which in turn leads to premature failure of the bearing assembly.In the said Figures 16 and 17, it will be seen that the heat shield is a ring-shaped member which comprises front, rear, inner and outer wall portions defining a vane-receiving area, aperture means in the front wall portion and through which the vanes on the piston project, and an outer sealing portion which prevents exhaust gases passing over the outside of the heat shield. The vane-receiving area is such that gases in the vane-receiving area cannot pass through the heat shield.

The heat shield shown in the said Figures 16 and 17 is believed to be of an extremely innovative design for variable turbocharger apparatus and at the time of filing PCT patent application No. WO 89/11583 I could not think of any further improvements. However, as the result of further extensive research and development work, I have discovered an area where an improvement can be made, which improvement gives further advantages in helping to prevent the above mentioned lubricant baking and premature failure of the bearing assembly.

The area where the improvement can be made is with regard to the inner portion of the heat shield. As can be seen from Figures 16 and 17 of PCT patent application No. WO 89/11583, the inner portion of the heat shield is constructed as a heat-deflecting baffle. This heatdeflecting baffle deflects much heat but some hot gases are able to pass over the inner lip of the heat-deflecting baffle and thus get behind part of the heat shield, where they are then able to act on the bearing housing adjacent the heat shield. This in turn leads to unwanted heat on the bearing assembly and the bearing housing. Stopping this unwanted heat helps further to prevent the lubricant baking.Still further, if the bearing assembly and the bearing housing can be kept cool enough, then light weight metals such as aluminium can be used for the bearing housing instead of heavier cast iron as presently has to be used. The use of light weight metals such as aluminium in turn enables cheaper and easier methods to be used for the production of the bearing housing, aluminium requiring, for example, only about one third of the time required to machine cast iron.

If a water cooled bearing housing were to be used, this would go some way towards preventing heat build up in the heat shield area of a turbocharger. However, a water cooled bearing housing is very expensive because the water channels have to be cast into the bearing housing and then there is the problem of all of the pipes that have to connect into the engines cooling system.

Also, the coolant that is used to cool the bearing system is also hot because it has been heated by the engine.

Accordingly, the present invention provides turbocharger apparatus comprising a compressor housing, a compressor mounted for rotation in the compressor housing, a turbine housing, a turbine mounted for rotation in the turbine housing, a first inlet for enabling air to be conducted to the compressor, an outlet for air from the compressor, a second inlet for enabling exhaust gases from an engine to be conducted to the turbine, a chamber which surrounds the turbine and which receives the exhaust gases from the second inlet before the exhaust gases are conducted to the turbine, a bearing assembly for allowing the rotation of the compressor and the turbine, a bearing housing for the bearing assembly, and a heat shield which is for shielding the bearing assembly from the exchaust gases and which has an outer sealing portion which prevents exhaust gases passing over the outside of the heat shield, and the turbocharger apparatus being characterised in that the heat shield has an inner sealing portion which prevents exhaust gases passing through a centre part of the heat shield such that the exhaust gases get behind a rear part of the heat shield and act on the bearing housing adjacent the rear part of the heat shield.

Because the heat shield has the inner sealing portion, the hot gases cannot get through the centre part of the heat shield and behind the heat shield.

This in turn helps to minimise of the effects of heat on the bearing assembly, the bearing housing, and the lubricant used for the bearing assembly. Still further, the bearing housing may be produced from lightweight material such as aluminium.

Preferably, the turbocharger apparatus includes passage means which is for receiving a coolant and which extends between the rear wall portion of the heat shield and an adjacent part of the bearing housing for the bearing assembly. The coolant is preferably air which may be sucked into the passage means, for example by connecting a pipe to the engine intake system.

Alternatively, air may be forced into the passage means, for example from a pwnp. The air passes through the passage means and provides further means for cooling the bearing assembly, the bearing housing and the lubricant.

The passage means may include an air inlet pipe for receiving air as the coolant.

Preferably, the inner sealing portion is an inner flange which sealingly abuts against a face of the bearing housing. The turbocharger apparatus may include a locking ring for maintaining the inner flange against the face of the bearing housing.

Preferably, the outer sealing portion is an outer sealing flange which is sealingly clamped between a face of the bearing housing and a face of the turbine housing. Prior to sealingly clamping the outer sealing flange in position, the heat shield may be rotateable through 3600 , thereby to enable the turbocharger apparatus to be bolted to different engines at different angles.

The turbocharger apparatus may include a sealing ring which is positioned at the centre part of the heat shield The sealing ring is preferably mounted on a shaft for the turbine.

The heat shield may be separable into two sections.

The turbocharger apparatus may include fork means which engages in a groove in a piston. The fork means enables the piston to be moved backwards and forwards in an axial direction without forcing the piston to one side and thus causing it to bind in the variable turbocharger apparatus. Preferably, the piston comprises a cylindrical body portion having the groove provided at that end of the body portion remote from the gap.

The piston will usually be arranged to slide in a cylindrical part of the housing.

Preferably, the fork means is located on a shaft that is mounted in the housing. The shaft may be connected to an actuator valve which enables movement to be applied to the fork means.

The fork means is preferably a bifurcated fork but other types of fork means may be employed.

The turbocharger apparatus may be one in which the piston is provided with a lug which engages a pin for preventing rotation of the piston.

Usually, the piston will be spring biased to a closed position. Preferably, the piston is spring biased to its closed position by a single coil spring.

Advantageously, the single coil spring is axially positioned inside the actuator valve. In alternative embodiments of the turbocharger apparatus, more than one spring may be employed. Also, if desired, biasing means other than springs may be employed.

The turbocharger apparatus may include sealing means for forming a sliding seal between the piston and the housing. The sealing means may comprise at least one sealing piston ring.

The end of the piston adjacent the gap may be chamfered. This chamfered end of the piston allows a more efficient flow of exhaust gases to the turbine wheel and may help to prevent the build up of products of combustion at this point with some types of engine, for example 2- and 4- stroke petrol driven engines.

Advantageously, the turbocharger housing is separable into at least two parts. This may facilitate assembly of the turbocharger apparatus and it may also facilitate fixing of the turbocharger apparatus in various engine compartments of various vehicles. The turbocharger housing may be separable into three parts comprising two end parts and a central part.

The turbocharger apparatus may be one in which the piston has an end which is formed as a conical diffuser, the conical diffuser being for facilitating gas extraction from the turbine.

The present invention also extends to an engine when provided with the turbocharger apparatus.

The engine may be any general type of engine including diesel and petrol driven engines.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 is a cross section through first variable turbocharger apparatus in accordance with the invention; Figure 2 is a section on an enlarged scale of a heat shield part of the variable turbocharger apparatus shown in Figure 1, but slightly modified; Figure 3 is a section like that shown in Figure 2 but illustrates a further modification; Figure 4 is a section through the heat shield shown in Figure 1; Figure 5 is a front view of the heat shield shown in Figure 4; Figure 6 is a side view of a clamp member; Figure 7 is a front view of the clamp member shown in Figure 6; Figure 8 is a section like that shown in Figures 2 and 3 but illustrates a further modification;; Figure 9 is a section like that shown in Figures 2, 3 and 8 but illustrates a yet further modification; and Figures 10 is a section through non-variable turbocharger apparatus.

Referring to Figures 1, 2 and 4 to 7, there is shown first variable turbocharger apparatus 2. The variable turbocharger apparatus 21 comprises a compressor housing 3 and a compressor 6. The compressor 6 has blades 8. The compressor 6 is mounted for rotation in the compressor housing 3 by being mounted on a central shaft 10. A turbine 12 is also mounted for rotation in a turbine housing 4 by being mounted on the shaft 10. The turbine 12 has blades 14. The shaft 10 rotates in a bearing assembly 11.

The compressor housing 3 has a first inlet 16 for enabling air to be conducted to the compressor 6. The compressor housing 3 also has an outlet 18 for air from the compressor 6. The outlet 18 enables air from the compressor 6 to be conducted to an engine (not shown).

The turbine housing 4 has an inlet 20 for enabling exhaust gases from the engine to be conducted to the turbine 12, A chamber 22 surrounds the turbine 12 and this chamber 22 receives the exhaust gases from the inlet 20 before the exhaust gases are conducted to the turbine 12, The chamber 22 may be regarded as a voluteshaped toroidal chamber.

A piston 24 is positioned between the turbine 12 and the turbine housing 4. The piston 24 is slidable backwards and forwards to form a movable wall separating the turbine 12 from the chamber 22 which surrounds the turbine 12.

The piston 24 is such that in its closed position it terminates short an adjacent part 26 of the turbine housing 4 so that there is always a gap 28 between the end 30 of the piston 24 and the adjacent part 26 of the turbine housing 4. This means that exhaust gases from the chamber 22 can always pass through the gap 28 to act on the blades 14 of the turbine 12. The piston 24 is such that in its open position, the gap 28 is increased.

The piston 24 is biased to its closed position against pressure from exhaust gases in the chamber 22 during use of the variable turbocharger apparatus 2 so that the piston 24 slides backwards and forwards to vary the gap 28 in dependence upon engine operating conditions.

The piston 24 is biased by means of an actuator valve 7.

As can be seen from Figures 1 and 2, the piston 24 comprises a cylindrical body portion 34 having a groove 36 at that end of the body portion 34 remote from the gap 28.

As shown in Figure 1, fork means in the form of a bifurcated fork 21 is located in the groove 36. The fork 21 is also fitted to a shaft 54 which can rotate in a turbine housing 4. On top of the shaft 54 is a metal bar 91 which is connected to the actuator valve 7. The actuator valve 7 thus acts as control means.

When the pressure starts to exceed a given level selected by the strength of a spring in the actuator valve 7, the air pressure inside a housing 9 of the actuator valve 7 pushes a flexible diaphragm, thereby displacing the piston 24 to a more open position. The piston 24 acts as an area control element piston 24.

The displacing of the piston 24 to a more open position in turn increases the gap 28 and reduces the velocity of the gases entering the turbine 12.

The end 30 of the piston 24 is chamfered as shown. This allows a more efficient flow of exhaust gases to the turbine wheel and any products of combustion from the exhaust gases in the chamber 22, which may tend to build up on the part of the piston 24 forming the movable wall, may tend to break away and thus not hinder the sliding movement of the piston 24.

The turbocharger 2 is separable into the compressor housing 3, the turbine housing 4 and a bearing housing 68.

This may facilitate positioning of the variable turbocharger apparatus 2 in various required positions in various engine compartments in vehicles or in other apparatus. The compressor housing 3 is secured to the bearing housing 68 by means of a cir-clip 70. The turbine housing 4 is secured to the bearing housing 68 by clamping plates 72 which are held in position by bolts 74 passing through holes 7 in the clamping plates 72.

The variable turbocharger apparatus 2 is also provided with an oil intake pipe 76 for providing oil for bearings (not shown) on the shaft 10. The shaft 10 is formed with a friction welded head 78 at one end.

The other end of the shaft is screw threaded as shown to receive a nut 80, which is effective to hold the compressor 6 in position. An oil return pipe (not shown) is also provided for enabling the oil provided for the bearings via the oil intake pipe 76 to drain away.

The second inlet 20 is provided with a flange 86.

The flange 86 has bolt holes 88 so that the flange 86 can be bolted to an exhaust outlet (not shown) of the engine.

The compressor 6 is surrounded by a chamber 90 which is somewhat similar to the chamber 22. In order to prevent the loss of air from the chamber 90 as the air passes to the outlet 18, a seal in the form of an O-ring seal 92 is provided as shown.

By being able to vary the size of the gap 28, the exhaust gases from the engine are able to drive the turbine 12 at substantially always the required rate to enable the compressor 6 to provide the amount of air required by the engine from the variable turbocharger appratus 2, via the outlet 18.

The bleeding of air along the air bleed passage 60 is effective to act on the actuator valve 7 to cause the piston 24 to slide towards its open position in which the size of the gap 28 is increased. After the exhaust gases have driven the turbine 12, they are exhausted via an exhaust outlet 5 defined by an end 13 of the piston 24 which is in the shape of a conical diffuser.

As shown in Figure 3, the piston 24 is such that the face 107 of the end 30 is provided with vanes 102.

The vanes 102 are arranged in a circle and they are oriented so that they direct the incoming gas flow in a tangential direction to provide the appropriate gas flow. The vanes 102 are cast or otherwise provided in the end 30 of the piston 24.

The turbocharger apparatus 2 has a heat shield 120, The heat shield 120 is a ring shaped member. The heat shield 120 has a front wall portion 122, a rear wall portion 124, an inner wall portion 126 and an outer wall portion 128. The various wall portions define a vanereceiving area 130. The vane-receiving area 130 is such that gases in the vane-receiving area 130 cannot pass through the heat shield 120.

The front wall portion 122 has aperture means in the form of slots 132 through which the vanes 102 on the piston 24 project.

The heat shield 120 has an outer sealing portion in the form of an outer flange 134 which is sealingly clamped between a face 136 of the bearing housing 68 and a face 140 of the turbine housing 4.

The heat shield 120 has an inner sealing portion 142 which is caused to sealingly abut face 144 when the bolts 74 are tightened. The seal formed by the inner sealing portion 142 prevents exhaust gases passing through a centre part 146 of the heat shield 120.

In Figure 3 there is shown a sealing arrangement 301, 302 where a seal 301 is employed in the centre hole 146 of the heat shield 120 so to prevent hot gases from reaching the bearing housing face in hot applications.

The turbocharger apparatus 2 has passage means 148 extending between the rear wall portion 124 of the heat shield 120 and an adjacent part 150 of the bearing housing 68 of the bearing assembly 11. The passage means 148 receives cooling air, which can be sucked in or pumped in. Air may be sucked in through pipe 152 through vent hole 100. Air is then passed over faces 124 and 126 of the heat shield, and the bearing housing face 150 so to keep this area of the bearing system cool.

This cooling system is possible because the heat shield design does not allow exhaust gases that pass over the vanes of the piston to enter the rear of the heat shield, because the heat shield and bearing system are of a sealed design.

Figures 8 and 9 show two heat shields 120 that may be fitted to the turbocharger apparatus 2. In both of Figures 8 and 9, two parts 73, 75 of a heat shield 120 are such that are clamped together at areas 136,140, areas 142, 144 and area 157.

With the design shown in Figures 8 and 9, the heat shields 120 have two sections that are not welded permanently together, so that when the turbocharger apparatus 2 is in need of service or repair, these two sections may easily be disassembled for cleaning. Figure 8 also shows a locking ring 67. The locking ring may be a split ring or a cir-clip. The locking ring 67 acts to maintain the inner flange of the heat shield 120 against the face 144 of the bearing housing 68, thereby to prevent air or gas leakage past the centre part 146 of the heat shield 120.

The turbocharger apparatus 2 gives the following advantages.

1. The vanes 102 are always in the gas flow, so the gases will always be guided at the most efficient angle to the turbine 12 throughout the full operating range of the turbocharger apparatus 2.

2. With the heat shield 120, the hot exhaust gases are prevented from leaking past the heat shield 120 and into the low pressure side of the turbocharger apparatus, so all of the gases have to work on the turbine 12 which gives greater efficiency.

3. With the heat shield 120, there are two layers of protection which are formed by the front and rear wall portions 122, 124 and which prevent heat from working on the back face 150 of the bearing housing 68.

4. The heat shield 120 stops all leakage of hot exhaust gases past the heat shield, so that the bearing assembly 11 and the bearing housing 68 are kept as cool as possible, leading to minimisation of lubricant baking and the possibility of using aluminium for the bearing housing 68.

5. With the heat shield 120, the bearing housing 68 and the turbine housing 4 are rotateable independently of each other, so the turbocharger apparatus can be bolted to different engines with substantially equal ease and engine components that might have been in the way can easily be avoided by simply relatively rotating the bearing housing 68 and the turbine housing 4.

6. With the heat shield 120, the bearing housing 68 and the turbine housing 4 are rotate able so that the oil outlet 82 can always be arranged to point vertically downwards, thus giving a good gravity feed of oil back to the engine.

Referring now to Figure 3, cooling air passes through passage 148. Also, in Figure 3, air inlet pipe 152 is connected to clamp ring 72. A very similar arrangement is shown in Figure 2. In Figure 1, the air inlet pipe 152 is connected in a different manner which may receive less leakage of air when the turbocharger apparatus 2 is bolted together.

Referring now to Figure 10, there is shown nonvariable turbocharger apparatus. Similar parts as in previous Figures have been given the same reference numerals for ease of comparison and understanding.

In Figure 10, the turbocharger apparatus 2 is such that the heat shield 120 does not have slots in it for the vanes. Thus the heat shield 120 only needs one section to seal the heat shield 120 and the bearing housing 68.

In Figure 10, the cooling system can be used on a waste-gated or a non-waste-gated turbocharger apparatus.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example, the vanes 102 may take a different shape to those shown, and more or less vanes than those shown may be employed. If desired, the vanes may be reversed to allow a reverse rotation of the turbine 12. The turbocharger apparatus 2 may be produced in various sizes commensurate with the size of engine to which the turbocharger apparatus 2 is to be fitted. The shape of the housing 4 can be varied as may be desired. The housing 4 and the various components within the housing 4 can be made of any desired and suitable materials. Also, sealing rings can be added or dispensed with as desired. More than one vent hole 100 may be employed if desired.

In Figure 10, the sealing area in the centre part of the heat shield 120 can be achieved in various different ways.

If desired, the turbocharger apparatus of the present invention may be one in which cooling is effected by air or water.

Instead of a locking ring 67 as shown in Figure 8, a nut may alternatively be used.

Claims

1. Turbocharger apparatus comprising a compressor housing, a compressor mounted for rotation in the compressor housing, a turbine housing, a turbine mounted for rotation in the turbine housing, a first inlet for enabling air to be conducted to the compressor, an outlet for air from the compressor, a second inlet for enabling exhaust gases from an engine to be conducted to the turbine, a chamber which surrounds the turbine and which receives the exhaust gases from the second inlet before the exhaust gases are conducted to the turbine, a bearing assembly for allowing the rotation of the compressor and the turbine, a bearing housing for the bearing assembly, and a heat shield which is for shielding the bearing assembly from the exhaust gases and which has an outer sealing portion which prevents exhaust gases passing over the outside of the heat shield, and the turbocharger apparatus being characterised in that the heat shield has an inner sealing portion which prevents exhaust gases passing through a centre part of the heat shield such that the exhaust gases get behind a rear part of the heat shield and act on the bearing housing adjacent the rear part of the heat shield.

2. Turbocharger apparatus according to claim 1 and including passage means which is for receiving a coolant and which extends between the rear wall portion of the heat shield and an adjacent part of the bearing housing of the bearing assembly.

3. Turbocharger apparatus according to claim 2 in which the passage means includes an air inlet pipe for receiving air as the coolant.

4. Turbocharger apparatus according to any one of the preceding claims in which the inner sealing portion is an inner flange which sealingly abuts against a face of the bearing housing.

5. Turbocharger apparatus according to claim 4 and including a locking ring for maintaining the inner flange against the face of the bearing housing.

6. Turbocharger apparatus according to any one of the preceding claims in which the heat shield defines an area into which vanes on a piston enter through slots in the heat shield, and in which the rear part of the heat shield is such that it prevents hot gases from passing beyond the rear part of the heat shield.

7. Turbocharger apparatus according to any one of the preceding claims in which the outer sealing portion is an outer flange which is sealingly clamped between a face of the bearing housing and a face of the turbine housing.

8. Turbocharger apparatus according to any one of the preceding claims in which the aperture means are slots.

9. Turbocharger apparatus according to any one of the preceding claims and including a sealing ring which is positioned at the centre part of the heat shield.

10. Turbocharger apparatus according to any one of the preceding claims in which the heat shield is separable into two sections.

11. Turbocharger apparatus substantially as herein described with reference to the accompanying drawings.