GB2164099A

GB2164099A - Variable capacity turbochargers

Info

Publication number: GB2164099A
Application number: GB08521763A
Authority: GB
Inventors: Kinshi Takagi
Original assignee: IHI Corp
Current assignee: IHI Corp
Priority date: 1984-06-29
Filing date: 1985-09-02
Publication date: 1986-03-12
Also published as: DE3531296A1; GB2164099B; GB8521763D0

Abstract

In a turbocharger having variable turbine inlet nozzles 19,20 (Fig. 1, not shown) controlling the charging pressure in response to rotation of an adjusting lever 8, the adjusting lever is connected to a first pneumatic piston/cylinder unit 9 which in turn is connected directly or indirectly e.g. via cranked lever 6 to a second pneumatic piston/cylinder unit 4 arranged to move the first unit in the direction of its stroke by a stroke which differs from the stroke of the first unit. By varying the positions of the two piston/cylinder units the adjusting lever may be selectively rotated into any of four predetermined positions. The inlet nozzles are in the form of an annular vane array and the vanes pivot on respective axis parallel to the turbine rotor's. A unison ring displaced circumferentially by the lever 8 controls conjointly their angle of set. <IMAGE>

Description

SPECIFICATION Variable capacity turbochargers The present invention relates to variable capacity turbochargers and in particular to means for controlling the charge pressure of the exhaust gas from an engine.

In the waste gate type turbocharging pres sum control system, either a low speed range or a high speed range is selected which means that the other must be sacrificed which results in a decrease in efficiency.

In an attempt to overcome this problem, a variable capacity turbocharger with a variable nozzle on the side of the turbine has been proposed.

Figure 1 is a schematic sectional view of a variable capacity turbocharger and Figure 2 is a view in the direction of the arrow 11 in Fig. 1. In this turbocharger, exhaust gases from the engine are guided circumferentially through a turbine casing 15 onto a turbine wheel 14 to rotate it. The turbine casing 15 is defined by a wall 16 to which a gas flow regulating unit, generally indicated 17, is attached. The regulating unit 17 comprises a plurality of shafts 18 extending parallel to the axis of the turbine wheel 14 and which are equiangularly (30 in the example shown) spaced apart around the axis of the turbine wheel 14, and a plurality of movable valve members 20 which are positioned in a gas flow path 19 defined by the turbine wheel 14 and turbine casing 15 and which are attached to one end of a respective shaft 18.The other ends of the shafts 18 are respectively provided with respective pivotal links 22. Each link 22 extends perpendicular to the axis of the associated shaft 18 and is fixed to the latter by a nut 21. The free ends of the links 22 are arcuate and movably fitted into receiving grooves 23 which are equiangularly spaced in the inner periphery of a regulating drive ring 24 whereby the ring 24 movably supports the links 22.

The ring 24 is also formed at its inner periphery with a receiving groove 25 into which a drive link 26 is fitted. The link 26 is fixed to a regulating drive shaft 7 which is rotatably supported by the wall 16. A regulating lever 8 is attached to the outer end of the shaft 7 remote from the link 26.

In the turbocharger described above, the variable nozzles are adjusted by simultaneously angularly regulating the valve members 20 into an angular position a by means of the lever 8.

That is to say, the lever 8 is rotated to rotate the drive shaft 7, which in turn rotates the drive link 26, the regulating drive ring 24, the pivot link 22 and the pivot shaft 18, in that order, so that the angles of the valve members 20 and thus the flow rate of the gases to the turbine wheel 14, are simultaneously regulated into a.

However, in this turbocharger, the control of the variable nozzles by means of the regulating lever 8 is found to be very problematic. If it is desired to control the variable nozzles steplessly, the control mechanism becomes very large and very complex constructionally and must incorporate a servomotor or a stepping piston/cylinder unit which is very expèn- sive. In addition, a controller is necessary for controlling the variable nozzles and a further controller for controlling the first controller.

This leads to a further increqse in cost. On the other hand, if the variable nozzles are to be controlled in a few steps, the low or high speed range must be sacrificed which reduces the efficiency.

It is an object of the present invention to provide a turbocharger of the general type described above which has a maximum number of control steps but a minimum number of component parts, whereby the control mechanism is compact and light and also inexpensive to manufacture but has a high turbocharging efficiency.

According to one aspect of the present invention the turbocharger includes variable nozzles for controlling the charging pressure in response to movement of an adjusting lever, the adjusting lever being connected to be moved by a first actuating means which is connected to second actuating means arranged to move the first actuating means and also to move the adjusting lever whereby the adjusting lever may be moved selectively into a plurality of predetermined positions.

According to a further aspect of the present invention a turbocharger includes variable nozzles for controlling the charging pressure in response to rotation of an adjusting lever, the adjusting lever being connected to be rotated by a first actuating means comprising a first piston/cylinder unit having a first stroke, the first actuating means being connected to second actuating means comprising a second piston/cylinder unit having a second stroke, the second actuating means being arranged to move the first actuating means in the direction of the first stroke by a stroke which differs from the first stroke whereby the adjusting lever may be selectively rotated into four predetermined positions.

The first and second actuating means which preferably comprise pneumatic piston/cylinder units may be indirectly connected, e.g. by a pivotally mounted L-shaped link or alternatively they may be directly connected in which event the ratio of the first and second strokes is preferably 1:2.

Further features and details of the present invention will be apparent from the following description of one specific embodiment of turbocharger in accordance with the invention which is given by way of example with reference to Fig. 3 of the accompanying drawings which is a schematic view of the turbocharger control mechanism.

The control mechanism shown in Fig. 3 is fitted to a turbocharger of the type shown in Figs. 1 and 2. The mechanism includes a compressed air tank 1 connected to deliver compressed air 2 through a solenoid-operated selector valve 3 to an overall-drive air cylinder 4, whose piston rod is fixed at its free end 4', to extend or retract the latter. The actuating end of the air cylinder 4 is connected substantially at right angles to the free end of the short arm 6a of an L-shaped link 6 which also has a longer arm 6b and is mounted to pivot about a pivot pin 5 at the junction of the long and short arms. The ratio of the length of the short and long arms 6a and 6b is l: 21=1: 2.

One end of another air cylinder 9 is connected substantially at right angles to the free end of the long arm 6b of the L-shaped link 6 while the other end is connected to one end of an adjusting lever 8 whose other end is connected to a drive shaft 7 for adjusting the variable nozzles of the turbocharger (as seen in Figs. 1 and 2). A solenoid-operated selector valve 10 is connected between the compressed air tank 1 and the cylinder 9 selectively to control the extension and retraction of the latter. In this embodiment, the first and second air cylinders 4 and 9 have the same stroke. In response to a signal 11 representative of the rotational speed of the engine and to a load signal 12, a control device 13 automatically activates the first and second selectors 3 and 10.

The degree of opening of the variable nozzles may be varied in four steps. More specifically, when the end of the adjusting lever 8 is brought to the position a,b,c and d the variable nozzles are 4, 2t 2 and fully open, 4' 2' 4 respectively. The stroke of the second cylinder 9 is such that the cylinder 9 is extended or retracted to move the lever 8 and thus close or open the variable nozzle by 4 the adjustment range. The first cylinder 4, which is connected to the shorter arm 6a of the Lshaped link 6 has the same stroke as the cylinder 9 and by virtue of the fact that the ratio of the lengths of the longer and shorter arms 6b and 6a is 2:1. Actuation of the cylinder 4 moves the lever 8 and thus the variable nozzles by 2 of the adjustment range.

In Fig. 3, the first and second air cylinders 4 and 9 are illustrated in their extended state.

The position of the first cylinder 4 is added to that of the second cylinder 9 so that the end of the adjusting lever 8 is at the position a at which the variable nozzles are 3 closed, i.e. 4 open.

When the selector 10 is switched in response to the signal from the control device 13, the second cylinder 9 is retracted so that the lever 8 is moved to position b, whereby the variable nozzles are moved through 4 of the adjustment range and are thus 2 open.

The control device 13 next actuates the two selector valves to cause the first cylinder 4 to retract while simultaneously causing the second cylinder 9 to extend. The adjusting lever 8 is thus moved a distance equal to the difference in distance moved by the piston rod of the cylinder 9 and the free end of the arm 6b, are rotated to position c where the variable 3 nozzles are 34 open.

When the second cylinder 9 is retracted, the adjusting lever 8 is caused to move a distance equal to the stroke of the second cylinder 9 and is thus rotated to position d where the variable nozzles are fully opened.

Thus in the embodiment described above, the degree of opening of the variable nozzles can be varied in four steps only by means of the first and second air cylinders 4 and 9 so that the exhaust gases from the engine are utilized economically and consequently the charging pressure can be effectively controlled.

It will be understood that various modifications may be effected to the embodiment described above. For instance, while the shorter arm 6a of the L-shaped link 6 has been described as being connected to the first cylinder 4 and the longer arm 6b to the second cylinder 9, the shorter arm 6a may be connected to the second cylinder 9 and the longer arm 6b to the first cylinder 4. The stroke of the first and second cylinders 4 and 9 may be varied and the ratio of the lengths of the shorter and longer arms 6a and 6b of the Lshaped link varied accordingly. Furthermore, if the ratio of the stroke of the first and second cylinders 4 and 9 is selected to be 1:2, the Lshaped link 6 may be eliminated.

Thus, in the control mechanism for a variable capacity turbocharger in accordance with the present invention, two cylinders are provided so that in response to the coaction between them, the charging pressure can be varied in four steps with a minimum number of component parts. As a result, the control mechanism can be compact, lightweight and inexpensive to fabricate and the turbocharging effect considerably improved.

Claims

1. A turbocharger including variable nozzles for controlling the charging pressure in response to the movement of an adjusting lever, the adjusting lever being connected to be moved by a first actuating means which is connected to second actuating means arranged to move the first actuating means and also to move the adjusting lever whereby the adjusting lever may be moved selectively into a plurality of predetermined positions.

2. A turbocharger including variable nozzles for controlling the charging pressure in response to rotation of an adjusting lever, the adjusting lever being connected to be rotated by first actuating means comprising a first pis ton/cylinder unit having a first stroke, the first actuating means being connected to second actuating means comprising a second piston/ cylinder unit having a second stroke, the second actuating means being arranged to move the first actuating means in the direction of the first stroke by a stroke which differs from the first stroke whereby the adjusting lever may be selectively rotated into four predetermined positions.

3. A turbocharger as claimed in claim 1 or claim 2 in which the first and second actuating means comprise pneumatic piston/cylinder units.

4. A turbocharger as claimed in any one of the preceding claims in which the first and second actuating means are connected by an L-shaped link mounted to rotate about a point positioned substantially at the junction of the two arms.

5. A turbocharger as claimed in claim 4 in which the ratio of the lengths of the two arms of the L-shaped links is substantially 1:2 and the first and second actuating means have the same stroke.

6. A turbocharger as claimed in any one of claims 1 to 3 in which the first and second actuating means are directly connected and have different strokes.

7. A turbocharger as claimed in claim 6 in which the ratio of the lengths of stroke of the first and second actuating means is 1:2.

8. A turbocharger substantially as specifically herein described with reference to Figs.

1 and 2 modified in accordance with Fig. 3.

9. In a control device for a variable capacity turbocharger having variable nozzles for controlling supercharging pressure in response to rotation of an adjusting lever, the improvement comprising a drive air cylinder with a predetermined stroke for causing rotation of said adjusting lever and an overall-drive air cylinder for causing said drive cylinder to shift at a stroke different from that of said drive air cylinder, whereby said adjusting lever is brought to and held at one of four stepped positions.