Internal-combustion engines – Engine speed regulator – Responsive to deceleration mode
Reexamination Certificate
1999-12-20
2001-08-14
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Responsive to deceleration mode
C060S324000, C188S273000, C251S214000
Reexamination Certificate
active
06273058
ABSTRACT:
The present invention relates to a decelerator device mounted in the exhaust gas circuit of a vehicle equipped with a combustion engine, comprising at least one valve provided with a body defining a channel and a movable shutter arranged at right angles in said channel and coupled to a drive shaft, and means of controlling this shutter comprising a device for balancing the back-pressure exerted by the shutter on the gas, this balancing device being designed to go into action when the shutter is in the closed position and when a predetermined back-pressure threshold is reached and to open an outlet pipe as soon as the back-pressure reaches said threshold, and to keep it open beyond said threshold whatever the engine's speed, so as to create a suitable exhaust gas leak rate, the balancing device comprising a calibrated flap-valve arranged in said outlet pipe and a compression spring arranged at the rear of said calibrated flap-valve, this spring being calibrated to said threshold value.
This type of decelerator is well known, particularly in the field of industrial vehicles equipped with a combustion engine. Taking into account their high inertia, in addition to their own braking system, these vehicles require a decelerator device housed in the exhaust gas circuit, preferably between the engine and the silencer, and generally mounted on the outlet side of the turbocompressor fed by the exhaust head. It is usually controlled by a pedal activated by the driver's left foot to prevent the latter from disengaging the clutch at the same time. This decelerator device makes it possible to generate a back-pressure in the exhaust circuit. This back-pressure is high or low depending on the position of the shutter and its degree of opening. It has the effect of slowing down the engine and therefore provides additional braking of the vehicle. The higher the back-pressure is, the more efficient the deceleration is. However, this back-pressure has to be limited to the maximum set-point pressure allowable by the exhaust head, in order to prevent the reopening of the inlet valves. This back-pressure depends of course on the exhaust gas pressure exerted on the shutter which is an asymptotic function of the engine speed. Consequently, there is a level of back-pressure and therefore a deceleration level which corresponds to each engine speed. What is currently being sought is to make this function constant and at most equal to the maximum allowable set-point pressure whatever the engine speed and right from the low speeds, with the aim of optimizing the deceleration.
One of the techniques proposed is described in the publication EP-A-536 284 in which an exhaust modulator device comprises two leak holes closed by spring blades with different rigidities in a shutter. When a first level of back-pressure is reached, a first spring blade opens a first leak hole and releases part of the exhaust gas. When a second level of back-pressure is reached, the second spring blade opens a second leak hole thus increasing the exhaust gas flow rate. This device makes it possible to limit the backpressure but generates deceleration stages. It therefore is not optimum. Furthermore, the spring blades are subject to temperature constraints and to the aggressiveness of the exhaust gas. As a result, the way they operate deteriorates in time, thus affecting their performance when opening and closing. Indeed, under the heat of the exhaust gas, the spring blades become less rigid and the holes will always stay open, thus reducing the back-pressure and the deceleration efficiency.
Another technique is described in the publication CH-A-428 318 and provides for a flap-valve arranged in the body of the butterfly valve on shaft. For this purpose, the body comprises two specific pipes forming a by-pass circuit when the flap is activated. This construction requires a specific housing to be made outside the decelerator to receive the flap and ensure that this housing is tight and lets in no the exhaust gas. However, the flap as it is built does not make it possible to ensure this tightness. Furthermore, this outside housing creates space problems. An additional spring is necessary between the flap and the shutter to keep the latter oriented upwards against an axial stop provided on the drive shaft and avoids the vibrations from said shutter. The configuration of this axial stop makes it necessary to make the body of the decelerator in two parts which also causes tightness problms. Furthermore, no sealing device is provided for around the shutter's drive shaft.
The aim of the present invention is to improve current decelerator devices by proposing a device for balancing the back-pressure which is simple, compact, costs less, and makes it possible to achieve constant and maximum deceleration performances whatever the engines speed whilst ensuring reliability and operating stability in time, without any risk of damage due to the attacks of the exhaust gas and the high temperature.
This aim is achieved by a decelerator device such as defined in the preamble and characterized in that the balancing device is incorporated into the body of the valve and comprises a guide bush crossed by the shaft and provided with an axial housing designed to receive said calibrated flap and its spring coaxial to said shaft and in that the outlet pipe is arranged substantially perpendicular to the shaft and opens into the channel downstream from said shutter so as to create, in association with said balancing device, a circuit for diverting part of the flow of exhaust gas.
In a preferred form of embodiment, the guide bush comprises at least one peripheral orifice communicating with the part downstream from the outlet pipe.
Preferably, the guide bush comprises an annular seat designed to receive said calibrated flap when it abuts, this seat comprising an opening which allows said calibrated flap to communicate with the channel upstream from the shutter.
The annular seat can be made up of a circlip arranged in a corresponding groove provided in said guide bush, the inside diameter of the circlip being greater than that of the shaft and delimiting said opening.
Advantageously, the shutter comprises a cavity arranged opposite the calibrated flap and communicating with the channel upstream from the shutter, when the latter is in the closed position.
In the preferred form of embodiment, the calibrated flap comprises a gasket arranged around the shutter's shaft and in its axial housing the guide bush comprises a ring provided with a gasket which is also arranged around the shutter's shaft, these gaskets being sheet gaskets made of graphite.
Advantageously, the guide bush comprises a base arranged opposite a corresponding face of the shutter to constitute a first axial stop.
The valve also comprises a second guide bush designed to guide the other end of said drive shaft, this second bush comprising a base arranged opposite a corresponding face of the shutter to constitute a second axial stop.
Preferably, the guide bushes have an outside threading, they are screwed into corresponding housings provided in said body and they are treated to offer a low coefficient of friction and withstand high temperatures and the oxidation of the exhaust gas.
REFERENCES:
patent: 4682674 (1987-07-01), Schmidt
patent: 4750459 (1988-06-01), Schmidt
patent: 5372109 (1994-12-01), Thompson et al.
patent: 5503367 (1996-04-01), Thompson et al.
patent: 428318 (1967-07-01), None
patent: 4116371 (1992-11-01), None
patent: 2307718 (1997-06-01), None
Argenbright Tony M.
Davis & Bujold P.L.L.C.
Fowa le Frein Moteur S. A.
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