GB2172657A

GB2172657A - Turbochargers

Info

Publication number: GB2172657A
Application number: GB08606502A
Authority: GB
Inventors: Geoffrey Kershaw
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-03-18
Filing date: 1986-03-17
Publication date: 1986-09-24
Also published as: GB2172657B; GB8506929D0; GB8606502D0

Abstract

A turbocharger 10 for an internal combustion engine comprises a turbine 12, a compressor 16, at least one waste-gate 20 for enabling exhaust gases to be diverted to avoid the turbine 16, and a control 24 which is set in a selected one of a plurality (such as two) different positions, each of which enables a different value of boost pressure (tapped from, for example, points, A or B) to open or alter the opening of the or at least one of the waste-gates 20, the position in which the control 24 is set being changeable during operation of the turbocharger 10, enabling the power output of the engine to be controlled. A switch 32 can be operated in conjunction with the engine's gear-box to prevent the use of high boost pressure in low gears. <IMAGE>

Description

SPECIFICATION Turbochargers The present invention relates to turbochargers for internal combustion engines.

As is well known, a turbocharger for an internal combustion engine utilises the pressure of exhaust gases from the engine's exhaust manifold to drive a turbine rotor. The turbine rotor is connected to a compressor rotor for feeding compressed air to the engine's inlet manifold. This boosting of the inlet pressure increases the air density and thus increases the power output.

Too high a boost pressure is undesirable, for example because of early ignition problems, and a pressure relief valve is therefore normally provided. The pressure relief valve opens when the boost pressure exceeds a preset value. More particularly, a waste-gate is normally provided through which some of the exhaust gases can be diverted to avoid the turbine. A spring-operated valve shuts the waste-gate until such time as the boost pressure exceeds the preset value and is thus sufficient to overcome the force of the spring to open the valve. The extent to which the waste-gate is opened depends on the instantaneous value of the boost pressure. As soon as the boost pressure falls below the preset value, the spring-operated valve shuts the waste-gate so that all of the exhaust gases are once again delivered to the turbine.

The object of the present invention is to enable the power output of the engine to be controlled rather than be merely curtailed.

A turbocharger for an internal combustion engine, in accordance with the present invention, comprises a turbine, a compressor, at least one waste-gate for enabling exhaust gases to be diverted to avoid the turbine, and a control which is set in a selected one of a plurality of different positions, each of which enables a different preset value of boost pressure to open or alter the opening of the or at least one of the waste-gates, the position in which the control is set being changeable during operation of the turbocharger.

The control would normally be operable by the driver of a vehicle incorporating the turbocharged engine, or possibly by an instructor accompanying the driver.

Preferably, there are just two positions in which the control may be set, and there is just a single waste-gate to which boost pressure tapped from different locations may be directed. Indeed, one of said control positions may correspond to tapping of boost pressure from a volute following the compressor, and the other of said control positions may correspond to tapping of boost pressure from the inlet to the volute. In alternative arrangements, however, there may be more than two positions for the control corresponding to a range of boost pressures which are not to be exceeded. If there is a plurality of waste-gates, they may have different opening characteristics so that boost pressure tapped from the same source may nonetheless be capable of controlling the power output of the engine.

The opening and shutting of the or each waste-gate may be effected in any convenient manner such as by use of a poppet valve, sliding valve or flap valve.

Preferably, the or each waste-gate includes a valve associated with a source of mechanical power continuously tending to close the waste-gate (such as a spring, more particularly a helical compression spring) in contrast to the source of pneumatic power constituted by the boost pressure for selectively tending to open the waste-gate.

Operation of the control may directly switch the pneumatic power into opposition to the mechanical power, or may indirectly effect the switching by means of an electrically operated solenoid. Naturally, the reverse arrangement may in particular circumstances be preferred, in which the source of mechanical power acts to open the waste-gate, and the source of pneumatic power acts to close the wastegate.

For vehicles having a gear-box for either manual or automatic transmission, the use of high boost pressure(s) in low gear(s) can be prevented by providing that the control is operable in conjunction with the gear-box.

The accompanying schematic drawing illustrates a typical embodiment of a turbocharger for an internal combustion engine in accordance with the present invention.

A turbocharger 10 includes a turbine 12 into which exhaust gases are delivered through a passage 14 leading from an exhaust manifold (not shown). The turbine 12 is connected to a compressor 16 for feeding compressed air through a volute 18 leading to an inlet manifold (not shown). A waste-gate 20 in the passage 14 is initially fully closed by a poppet valve 22. All of the exhaust gases are thus delivered to the turbine 12.

Compressed air from the compressor 16 may be tapped either at point A of the volute 18 or at point B at the inlet to the volute diffusion system where the static pressure is lower.

Assuming that a driver switch 24 is set so that an electrically operated switching pneumatic valve 26 allows compressed air from the point A to be in communication with the poppet valve 22, it will be appreciated that if the pressure of that compressd air exceeds a preset value it acts against a diaphragm 28 in opposition to the force of a spring 30 to move the poppet valve 22 in the direction of the arrow X. The waste-gate 20 begins to open. Some of the exhaust gases are thus diverted through the waste-gate 20 and the power output of the engine is curtailed. This condition of "low" power will be maintained until such time as the driver switch 24 is operated to cause the electrically operated switching pneumatic valve 26 to direct compressed air tapped from the point B to the poppet valve 22. Because the static pressure at the point B is lower than at the point A, whereas the characteristics of the spring 30 remain the same, the instantaneous reaction to the altered status of the driver switch 24 is for the poppet valve 22 to move in the direction closing the waste-gate 20. More exhaust gases are allowed to reach the turbine 12, and the boost pressure attained by the compressor 16 is allowed to increase. The wastegate 20 will not open until the boost pressure from the point B is sufficient to overcome the spring 30, which corresponds to a higher power output from the engine.

A second switch 32 in series with the driver switch 24 can be operated in conjunction with the gear-box to prevent the use of high boost pressures in low gears.

Claims

1. A turbocharger for an internal combustion engine comprising a turbine, a compressor, at least one waste-gate for enabling exhaust gases to be diverted to avoid the turbine, and a control which is set in a selected one of a plurality of different positions, each of which enables a different preset value of boost pressure to open or alter the opening of the or at least one of the waste-gates, the position in which the control is set being changeable during operation of the turbocharger.

2. A turbocharger according to claim 1, in which there are two positions in which the control may be set.

3. A turbocharger according to claim 1 or claim 2, in which there is a single waste-gate to which boost pressure tapped from different locations may be directed.

4. A turbocharger according to claim 2 and claim 3, in which one of said control positions corresponds to tapping of boost pressure from a volute following the compressor, and the other of said control positions corresponds to tapping of boost pressure from the inlet to the volute.

5. A turbocharger according to any preceding claim, in which the or each waste-gate includes a valve associated with a source of mechanical power continuously tending to close the waste-gate in contrast to the source of pneumatic power constituted by the boost pressure for selectively tending to open the waste-gate.

6. A turbocharger according to claim 5, in which operation of the control indirectly switches the pneumatic power into opposition to the mechanical power by means of an electrically operated solenoid.

7. A turbocharger according to any preceding claim, when forming part of a vehicle having a gear-box for either manual or automatic transmission, the use of high boost pressure(s) in low gear(s) being prevented by providing that the control is operable in conjunction with the gear-box.

8. A turbocharger for an internal combustion engine substantially as hereinbefore described with reference to the accompanying drawing.