Exhaust modulator

Details Exhaust modulator Exhaust modulator

1992-12-23

1994-12-13

Argenbright, Tony M.

Internal-combustion engines

Engine speed regulator

Responsive to deceleration mode

60324, F02D 906

Patent

active

053721098

DESCRIPTION:

BRIEF SUMMARY
This invention relates to an exhaust modulator, in particular for use in the exhaust system of a commercial diesel engine vehicle.
Devices known as `exhaust modulator valves` can be fitted into the vehicle exhaust system, which by generating a back pressure can assist the vehicle in braking, assist in cab heating by giving a faster engine warm up, or assist in exhaust emission control.
In general, the greater the back pressure generated the more effective the braking effect becomes. But the maximum level of back pressure generated must be held at a level conducive to the engine, depending upon the loads generated by the valve springs for example.
To limit the back pressure, the exhaust brake gate, normally a butterfly valve or a sliding gate must either be locked into a position which is almost closed, allowing some exhaust gas to escape or have one or more bleed holes formed in the butterfly or sliding gate. It is usual in practice to drill a hole or holes, (the latter method), and allow the butterfly or gate to sit in a fully closed position.
The leakage rate is fixed by the size and number of holes in the butterfly and is dictated by the maximum allowable back pressure when the engine is running at the higher speeds and the flow of exhaust gas through the exhaust brake is at its maximum.
It follows that at lower engine speeds, especially in the normal driving range the `bleed holes` in the butterfly or gate are larger than is necessary to reach the maximum back pressure at these lower speeds.
U.S. Pat. No. 4,682,674 discloses an exhaust modulator or exhaust-type engine suppressor in which the maximum back pressure imposed thereby is limited by means of a pressure-relief valve operable to admit flow of exhaust gases along a bleed flowpath only when a prescribed back pressure is reached. The valve is spring loaded so as to open by an amount which varies depending upon the amount by which the prevailing back pressure exceeds the prescribed limit.
An exhaust modulator for use in cab-heating or emission control is required to operate at low engine speeds and hence low exhaust gas flows, whereas for exhaust braking the engine is normally operating a high speed and exhaust gas flow rates, the maximum permissible back pressure being relatively high in the latter case.
One object of the present invention is to provide an exhaust modulator suitable for use in various modes, more particularly in a cab-heating and/or emission control mode as well as in an exhaust braking mode.
In accordance with the present invention, we propose an exhaust modulator having means for controlling the flow of exhaust gases along one or more bleed flowpaths to achieve different predetermined levels of back pressure imposed upon the engine, as required to operate in selected modes, said flow control means being operable in response to one or more sensed engine operating parameters.
In accordance with a preferred embodiment of the invention an exhaust modulator in, or to be fitted in, the exhaust system of an engine, particularly a diesel engine in a commercial vehicle comprises a body defining therethrough a flowpath for engine exhaust gases, a gate in the exhaust flowpath, one or more bleed flowpaths communicating between opposite sides of the gate and flow control means operable in use, in response to one or more sensed engine operating parameters, to control the flow of exhaust gases along the said one or more bleed flowpaths so as to limit the back pressure applied to the engine to different predetermined levels as required for operation of the modulator in selected modes.
Thus, the flow of exhaust gas along the bleed flowpath is variable in accordance with the operating conditions pertaining, to achieve any desired back pressure/exhaust gas flow characteristic or profile. The characteristic or profile may be varying but in the preferred embodiment is stepped between the said first and second predetermined levels, in accordance with predetermined control data or settings appropriate to or representative of the conditions prevailing

REFERENCES:
patent: 3234924 (1966-02-01), May
patent: 4682674 (1987-07-01), Schmidt
patent: 4707987 (1987-11-01), Atkin
patent: 4750459 (1988-06-01), Schmidt
Patent Abstracts of Japan, vol. 9, No. 187 (M-401) [1910], Aug. 1985, abstract of JP, A, 6053630.
Patent Abstracts of Japan, vol. 9, No. 7 (M-350) [1730], Jan. 1985, abstract of JP, A, 59158325.

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