Title:
AUTOMATIC DEVICE FOR CONTROLLING CATALYTIC MUFFLERS
United States Patent 3837165


Abstract:
A device for automatically controlling a by-pass electro-valve of a catalytic muffler comprising three inlet stages, the first inlet stage is responsive to the speed or number of engine revolutions, the second inlet stage is responsive to the throttle position and includes a retarding circuit and store, and the third inlet stage is responsive to the temperature of the catalyst and includes means for comparing the temperature of the catalyst with a maximum allowable temperature (TMAX.) and a predetermined running temperature (TS). The three inlet stages are electrically coupled to an outlet stage which includes a timer for producing a pulse of predetermined duration.



Inventors:
Arrigoni, Virgilio (San Donato Milanese, IT)
Gaetani, Bruno (Milano, IT)
Marchesi, Gianfranco (San Donato Milanese, IT)
Zanoni, Gianfranco (San Donato Milanese, IT)
Application Number:
05/287009
Publication Date:
09/24/1974
Filing Date:
09/07/1972
Assignee:
SNAM PROGETTI SPA,IT
Primary Class:
Other Classes:
60/288, 60/294
International Classes:
F16K31/06; F01N3/08; F01N3/20; F02D41/14; (IPC1-7): F02B75/10
Field of Search:
60/288,287,285,294,277
View Patent Images:



Primary Examiner:
Hart, Douglas
Attorney, Agent or Firm:
Watson, Ralph M.
Claims:
What we claim is

1. An automatic control device for controlling a by-pass electro-valve in an arrangement comprising an engine having a throttle and an exhaust system, said exhaust system having a catalytic muffler containing a catalyst and a by-pass duct, around said muffler, containing said by-pass electro-valve, comprising:

2. An automatic control device as claimed in claim 1 wherein:

3. An automatic control device for controlling a by-pass electro-valve in an arrangement comprising an engine having a throttle and an exhaust system, said exhaust system having a catalytic muffler containing a catalyst and a by-pass duct, around said muffler, containing said by-pass electro-valve, comprising:

4. An automatic control device as claimed in claim 3 including:

5. An automatic control device as claimed in claim 4 wherein:

6. An automatic control device for controlling a by-pass electro-valve in an arrangement comprising an engine having a throttle and an exhaust system, said exhaust system having a catalytic muffler containing a catalyst and a by-pass duct, around said muffler, containing said by-pass electro-valve, comprising:

Description:
The present invention relates to a device for the automatic control of catalytic mufflers like the ones used at present time in order to reduce the outlet of pollutants in exhausts of motor vehicles having a controlled ignition. For increasing the life of the muffler catalyst it is suitable to cut out therein the flow of the gases in those cases in which said flow would result particularly damaging or useless, i.e., when the motor presents already a low outlet of pollutants, this being the case, e.g., at high speeds outside inhabited places, and when a too high temperature occurs in the catalyst due to running defects.

The cutting out of the gas flow through the catalytic muffler is generally obtained by-passing the muffler through a by-pass valve operated by a control device.

Object of the present invention is to provide a control device allowing the automatic opening of the by-pass valve once reached determined conditions of temperature, speed or number of revolutions and throttle opening. Said device according to the invention comprises three stages responsive to the vehicle speed or number of revolutions of the engine, to the opening degree of the throttle and to the catalyst temperature respectively, and an outlet stage which, controlled by said inlet stages, operates a by-pass valve.

According to an essential feature of the invention the stage responsive to the opening degree of the throttle delivers a by-pass valve opening signal to the outlet stage only if the throttle opening keeps higher than a certain value for a determined time, this being the case, e.g., for highway runnings; the catalytic muffler is therefore switched on, as necessary, for full and short-timed accellerations (city traffic).

According to a further essential feature of the invention the stage responsive to the catalyst temperature is responsive both to the temperature gradient as to the time (derivative action), so as to intervene before a destructive temperature Tmax is reached, and to the integral as to the time of the temperature-rise over the prefixed temperature Ts, so as to prevent the permanence of temperatures which, even if not destructive, will age rapidly the catalyst. Summing up the device according to the present invention keeps automatically opened the by-pass valve, cutting out thereby the gas flow through the catalytic muffler, in the following cases:

When the vehicle speed or the number of revolutions of the engine exceeds a prefixed value, e.g., 50 km/h in third gear;

When the throttle opening exceeds a determined value, e.g., about 80°, for a determined period of time, so that the catalytic muffler is switched on when the full accelerations are short-timed;

when the catalyst temperature exceeds a limit value Tmax beyond which the catalyst would be damaged, or assumes a gradient as to the time higher than a prefixed value so as to prevent the reaching of destructive high temperatures;

when the temperature exceeds for a certain time (integral action) a prefixed value Ts whose permanence shortens the catalyst life.

According to a further essential feature of the invention the outlet stage of the control device is realized so as to prevent the continuous opening and closing of the by-pass valve when the logical valve opening signals, coming from the inlet stages, fluctuate around limit values of intervention. This is practically obtained by exciting with an outlet signal of a gate circuit "OR," at the inlet of which there is convergence of the logical signals coming from the other inlet stages, a retarding logic consisting of a timer delivering a pulse of controlled duration, and sending the outlet signal of said gate circuit "OR" and the outlet signal of said timer to the inlet of another gate circuit "OR" whose outlet controls directly the by-pass valve. In this way, even if for any reason, e.g., fluctuation around the limit values of intervention, there is no by-pass valve opening signal at the inlet of the first gate circuit "OR," the timer, once excited, keeps on delivering the signal for keeping opened said by-pass valve for the whole prefixed period of time.

Finally it has to be pointed out that the whole automatic control device according to the invention may be fed by the vehicle battery or by the network for roller tests.

The invention will be now illustrated with reference to the enclosed drawing showing a preferred form of practical realization given only by way of example, since many technical and network variants may be thought without departing from the scope of the present invention.

FIG. 1 shows schematically in a block diagramm the by-pass of a catalytic muffler through an electro-valve automatically controlled by a control electro-mechanical device according to the invention;

FIG. 2 shows in a block diagramm the circuit schema of the control electro-mechanical device of FIG. 1 according to the invention.

With reference to figures, 1 indicates the catalytic muffler to be protected, 2 indicates the by-pass electro-valve and 3 the automatic control device. Said automatic control device 3 comprises according to the invention three inlet stages responsive to the vehicle speed or the number of engine revolutions, to the throttle opening degree and to the catalyst temperature of the catalytic muffler 1 respectively, and an outlet stage reached by the logical signals coming from said inlet stages and which controls the by-pass valve 2.

The inlet stage responsive to the vehicle speed or the number of engine revolutions comprises (see FIG. 2) a speedometer dynamo 4 or a device indicating the number of the engine revolutions, which delivers a voltage proportional to the engine speed or number of revolutions, this voltage being compared in node 5 with a reference voltage set up by a potentiometer 6. The difference between the two said voltages operates then a speed level discriminator 7 whose outlet is connected with the "OR" gate circuit 8 of the outlet stage. In this way at the outlet of discriminator 7 a valve opening signal will appear only if the voltage delivered by the speedometer dyamo or by the device indicating the number of revolutions is higher than the voltage set up on potentiometer 6, i.e., therefore, when the speed or the number of the revolutions of the engine exceeds the prefixed value corresponding, e.g., to 50 Km/h in third gear.

The inlet stage responsive to the throttle opening degree comprises a level discriminator 9 at the inlet of which one applies the difference between the voltage-signal proportional to the position of throttle 10, obtained, e.g., by means of a potentiometer whose slider is rigidly connected with the throttle, and the reference voltage set up through potentiometer 11.

Here too, therefore, it is possible to have a signal at the outlet of discriminator 9 only if said difference is positive, i.e., if the throttle opening degree is higher than the set up reference value, corresponding, e.g., to a throttle rotation of 80°. This discriminator outlet signal is not however directly sent to "OR" gate circuit 8 of the outlet stage, but is applied at the same time to a retarding circuit 12, delivering a pulse after a prefixed period of time, and to an "AND" type circuit 13 reached too by the retarding pulse. The "AND" circuit outlet excites then a store 14 whose outlet is directly connected with said "OR" gate circuit of the outlet stage. In this way, store 14 will deliver to the outlet stage a valve opening signal not when there is a signal at the outlet of discriminator 9, i.e., when the throttle opening exceeds a certain prefixed level, but only when the throttle opening keeps higher than said level for a period of time at least corresponding to the delay time of retarding circuit 12. In fact "AND" gate circuit 13 opens and excites store 14 only when there are at its inlet both signals and therefore, even if there is the outlet signal of discriminator 9 but its duration is lower than the one required by retarding circuit 12 to give its pulse, "AND" circuit 13 does not open. It is possible in this way to prevent that by-pass valve 2 opens in case of full accellerations having a short duration, e.g., accellerations occurring at the changing of gears (city traffic).

The presence of store 14 is then necessary since the outlet signal of "AND" circuit 13 is a short-timed pulse whereas the valve opening signal must be a signal keeping on till the throttle opening has gone under the prefixed level. Store 14, comprising a series of flip-flop or "NOR" circuits, has indeed the duty of storing and transforming the exciting pulse at its inlet into a continuous signal at its outlet and of keeping this signal till at the outlet of discriminator 9 there is a signal. When there is no more this latter signal, since the throttle opening has gone under the prefixed level, store 14 is set to zero by the same outlet signal of discriminator 9 inverted by inverter 15.

In FIG. 2 it has been shown too indicator 16 by means of which it is possible to visualize the value of the speed or of the number of engine revolutions and the throttle opening degree.

The third inlet stage responsive to the catalyst temperature of catalytic muffler 1 is, on the contrary, constituted by a thermoelement 17 whose voltage signal, proportional to said temperature, is amplified by means of operational amplifier 18 and visualized by indicating device 19. The outlet signal of amplifier 18 is then differentiated by means of differentiating RC circuit, comprising resistance 20 and capacitor 21, and then compared in node 22 with the reference signal to be prefixed on pretentiometer 23 and corresonding to the limit destructive temperature Tmax, e.g., 800°C. The resulting difference signal is then sent to a level discriminator 24 whose outlet is connected with said "OR" gate circuit of the outlet stage. In this way in node 22 there is only a signal which is the sum of the signal proportional to the temperature and of its derivative as to the time and therefore the discriminator 24 delivers a valve opening signal at its outlet not when the catalyst temperature reaches Tmax value, but when this value is reached by said sum signal. Summing up discriminator 24 releases by-pass valve 2 before Tmax temperature is reached and prevents therefore the reaching of high destructive temperatures. On the other side the signal of thermoelement 17, amplified by operational amplifier 18, is compared too in node 25 with a reference signal, delivered by potentiometer 26. proportional to a certain running temperature Ts, e.g., 500°C, a catalyst temperature-rise as to the latter being not destructive but at the long run shortening the catalyst life.

The temperature-rise signal resulting in node 25 is then sent, at the same time, to a terminal of a relay 27 and to the inlet of a mean level discriminator 28 whose outlet, exciting the above mentioned relay, switches on the same signal on the outlet of an integrator 29 which, integrating this temperature-rise signal, will take a time proportional to the magnitude of this signal for reaching the integral threshold level T1, predetermined by potentiometer 30. The reaching of the integral threshold limit T1, this meaning that the temperature-rise as to the running temperature lasts for a certain period of time and is therefore harmful for the catalyst of the catalytic muffler, is detected by level discriminator 31 which excites store 32 whose outlet is connected with said "OR" gate circuit 8 of the outlet stage.

Said store 32 is like and has the same function of store 14 already cited and, like the latter, is set to zero by the outlet signal of discriminator 28 inverted by inverter 33.

By means of this latter part of the device circuit it is possible therefore to send to the outlet stage a valve opening signal every time that the catalyst temperature exceeds a certain critical value Ts whose lasting, harmful for the catalyst, allows the outlet of integrator 29 to reach the integral threshold value T1.

FIG. 2 visualizes too potentiometer 37 for calibrating operational amplifier 18.

Finally the outlet stage of the device according to the invention comprises the already cited "OR" gate circuit 8 reached by the logical valve opening signals coming from the inlet stages, whose outlet excites a timer 34 capable of delivering a pulse of duration to be prefixed. Said duration-prefixed pulse, produced by timer 34 once excited, is sent together with the outlet signal of "OR" gate circuit 8 to the inlet of another "OR" gate circuit 35 whose outlet 36 operates directly by-pass electro-valve 2.

In this way by-pass valve 2 keeps opened not only when there is a single logical signal at the inlet of "OR" gate circuit 8, but keeps opened even if said logical signal disappears because, e.g., of its fluctuation around its limit value of intervention. In fact, timer 34, once excited, keeps on delivering a valve opening signal for the whole period of time therein prefixed.