DEVICE FOR CONTROLLING POLLUTING EMISSIONS FROM INTERNAL COMBUSTION ENGINES

Abstract: First (3) and second (9) inlet ducts are provided in the carburettor (C) of the engine and are located downstream and upstream respectively of the throttle valve (V) in the air intake direction. A first pneumatic line (2) puts the first inlet duct (3) into communication with the barometric control chamber (S) of an actuator (A) which controls the angle of ignition advance. The same barometric control chamber (S) is also put into communication with the second inlet duct (9) through a second pneumatic line (6) including at least one restricted section (l0) and a third pneumatic line (7). The first (2) and third (7) pneumatic lines have two associated solenoid on-off valves (4, ll), the operation of which is controlled by a sensor (l3) associated with the starter (W) and a heat sensor (l4) sensitive to the temperature of the engine lubri­ cant. When the starter (W) is active, the low pressure downstream of the throttle valve (V) is transferred to the barometric control chamber (S) of the advance angle control actuator (A). When the starter (W) is returned to the rest position, the low pressure upstream of the throttle valve (V) is transferred to the barome­ tric chamber (S) through the second pneumatic line (6) The restricted section (l0) of which delays the propaga­ tion of the pressure gradients towards the barometric control chamber (S) of the actuator (A). This operating condition exists until the temperature of the engine lubricant reaches a threshold level of the order of 45-85° C. When this treshold level is reached the third pneumatic line (7) is opened to put the second inlet duct (9) directly into communication with the barometric control chamber (S) of the actuator (A) for controlling the angle of advance and the ignition.

Description: The present invention relates to devices for controlling polluting emissions from an internal combustion engine and particularly concerns a device intended to be associated with an engine having: a carburettor with a choke tube through which an air intake flow passes, and a main throttle valve pivotally mounted in the choke tube , an actuator for controlling the angle of ignition advance, having a barometric control chamber, a pneumatic system which puts the choke tube of the carburettor into communication with the barometric control chamber of the actuator, and a mixture enrichment unit (starter) operable between at least one activation position and a rest position. Such a device is known, e.g. from US-A- 4 099 497. The solution for controlling the ignition advance angle of the engine in dependence on the vacuum (sub-atmospheric pressure) in the choke tube of the carburettor has been shown to be particularly advantageous in enabling a reduction in the polluting emissions (particularly unburnt hydrocarbons and nitrogen oxides) in the exhaust of an internal combustion engine. From US-A- 4 096 843 a device is known for controlling the polluting emissions of an internal combustion engine during the start and warm up mode. It has been notable, however, that the use of this solution may give rise to problems during the starting and warming-up phase of the engine. These problems show themselves in the form of poor "driveability" of the motor vehicle due to a certain lack of operating stability of the engine. The object of the present invention is to remedy these disadvantages by providing a device for controlling the polluting emissions, in which the ignition advance angle is varied by taking account of the running conditions of the engine (engine just started, engine in warm-up phase, engine under normal running conditions). According to the present invention, this object is achieved by virtue of a device of the type specified above, including: first and second inlet ducts opening into the choke tube of the carburettor downstream and upstream, respectively, of the throttle valve in the air intake flow direction, a first pneumatic line in the pneumatic system which connects the first inlet duct with the barometric chamber controlling the actuator, second and third pneumatic lines in the pneumatic system which connect the second inlet duct to the barometric chamber controlling the actuator; the second pneumatic line including pneumatic delay means which can delay the propagation of the pressure gradients through the second line, a first sensor associated with the mixture enrichment unit, for generating a first signal selectively indicative of the position of the unit in the activation position and the rest position, a second sensor sensitive to the temperature of the engine and, having a respective threshold level, for generating a second signal indicative of the fact that the temperature of the engine surpasses the respective threshold level, a first valve switchable between an open position and a closed position, interposed in the first pneumatic line and controlled by the first signal so as to open and close the first pneumatic line when the mixture enrichment unit is in the activation position and the rest position respectively, and a second valve switchable between an open position and a closed position, interposed in the third penumatic line and controlled by the second signal so as to open the third pneumatic line when the temperature of the engine surpasses the respective threshold level. The invention will now be described purely by line of non-limiting example, with reference to the appended drawings, in which: Figure l illustrates schematically the connection arrangement of the device of the invention, Figure 2 is a side view of a device according to the invention, Figure 3 is a front view of the device of Figure 2, and Figure 4 corresponds approximately to a section taken on the line IV-IV of Figure 3. In the drawing the carburettor associated with an internal combustion engine, not illustrated in its entirety, is generally indicated C. The carburettor C can be seen to comprise essentially a choke tube D through which passes an air intake flow coming from the external environment through an air filter F and moving in the direction indicated by the arrow in the drawing, and a main throttle valve V pivotally mounted in the choke tube D. Between the air filter F and the main throttle valve V (that is, upstream of the throttle valve in the direction of movement of the air intake flow) in the choke tube is an auxiliary throttle valve W which acts as a device (starter) for enriching the mixture supplied to the engine. More particularly, the auxiliary valve W is movable between a rest position shown in full outline and indicated R in the drawing, and an active position shown in broken outline and indicated O in the drawing. In well-known manner, in the rest position R, the auxiliary valve W extends parallel to the main axis of the choke tube D and does not influence the composition of the mixture supplied to the engine. On the other hand, when it is brought into its active position (which may be achieved by the operation of a manual control - not illustrated - by the driver of the motor vehicle), the auxiliary valve W is oriented in a position inclined to the main axis of the choke tube D partially to obstruct it and hence favour the formation of a richer mixture. For clarity of description, it will be stressed that, in the schematic representation of the drawing, the jets which admit the fuel to the choke tube D are not illustrated. A pneumatic actuator of known type is generally indicated A and allows the variation of the ignition advance angle of the engine with which the carburettor C is associated. The actuator A has a barometric operating chamber S: the (sub-atmospheric) pressure in the operating chamber S determines the angle of ignition advance in a univocal manner. In general, the angle of advance increases upon a reduction in the pressure, that is, an increase in the vacuum present in the control chamber S. According to a conventional solution, of which the solution of the invention is a development, the barometric chamber S is put into communication with the interior of the choke tube D of the carburettor C so that, when the pressure in the choke tube D falls (that is, when, according to the current language, the vacuum increases), the actuator A increases the ignition advance angle. The control device according to the invention, generally indicated l, is constituted essentially by a system of pneumatic ducts in which first, second and third pneumatic lines can be seen. The first pneumatic line, shown schematically by a continuous line and indicated 2, extends from an inlet duct 3 opening into the choke tube D of the carburettor C downstream of the main throttle valve V (in the direction of flow of the intake line). At its opposite end, the first pneumatic line 2 joins a control duct S' which opens into the barometric chamber S of the actuator A after having passed through a first solenoid valve 4 which is selectively switchable between an open position and a closed position, and a one-way flow valve 5 which is located so as to prevent the propagation of positive pressure gradients from the manifold C to the control chamber S. In other words, the valve 5 has the purpose of keeping the vacuum within the chamber S after it has been created by the suction action exerted through the first pneumatic line 2. The second and third pneumatic lines are shown by continuous lines and indicated 6 and 7 respectively. In the embodiment illustrated, both these pneumatic lines have a common inlet duct 8 terminating at a second inlet duct 9 which opens into the choke tube D of the carburettor C upstream of the main throttle valve V. A delay valve l0 is interposed in the second pneumatic line 6 and is constituted essentially by a restricted section of the second pneumatic line 6, which can delay the propagation of the pressure gradients through the second pneumatic line. In the third pneumatic line 7, however, is inserted a further solenoid valve ll substantially the same as the solenoid valve 4 and switchable between an open position and a closed position. The second and third pneumatic lines 6 and 7 are also connected to the control duct S' which terminates at the barometric chamber S of the actuator A. An electrical control circuit for the solenoid valves 4 and ll is indicated l2, to which are connected a first sensor l3 associated with the mixture enriching unit (starter) W and able to generate a signal selectively indicative of the position of this unit in the activation position and the rest position, and a second thermal-type sensor l4 sensitive to the temperature of the engine. More particularly, the sensor l4 is sensitive to the temperature of the engine lubricant and can detect when the temperature of the lubricant surpasses a predetermined threshold level preferably chosen in the range 45-85°C, giving a corresponding signal. The connection arrangement of the control circuit l2 and the sensors l3 and l4 is such that: the solenoid valve 4 is opened to open the first pneumatic line 2 when the mixture enriching unit W is brought into its activated position O, and closed, to shut off the first pneumatic line 2 when the unit is brought to the rest position R, and the solenoid valve ll remains in the closed position, shutting off the third pneumatic line 7, as long as the temperature of the lubricant remains below the aforesaid threshold level, and is brought into the open position, opening the third pneumatic line 7, when the temperature of the lubricant surpasses this threshold level. As can be seen, in the embodiment illustrated, there is no provision for the use of a solenoid valve for controlling the opening and the closing of the second pneumatic line 6. In effect, the use of such a solenoid valve is unnecessary since the propagation of the pressure gradients through the second pneumatic line 2 is actually controlled, as will be best seen from the following description, by the solenoid valves 4 and ll. A pneumatic delay member of known type is generally indicated B and is intended to restrain the oscillation of the main throttle valve V, after it has been pivoted towards its position of maximum opening - that is, to the position in which the valve V is disposed in a direction approximately parallel to the main axis of the choke tube D - following action on the accelerator pedal (not illustrated), when it is returned to the closed position indicated in the drawings. Thus, according to known criteria, the delay member B performs the normally termed "minimum speed" action for preventing sharp release of the accelerator pedal from causing the supply of an inappropriate mixture to the engine for several moments, with the consequent emission of a considerable quantity of unburnt hydrocarbons. The delay member B includes a respective barometric chamber S B having at least one resilient wall which is deformed, varying the volume of the barometric chamber S B , when the throttle valve V is brought to its position of maximum opening during an acceleration. A vent duct T in which a further delay valve Q is located opens into the barometric chamber S B . At the opposite end to the barometric chamber S B , the vent duct T has a free end E which may be opened or closed selectively by a pneumatically-operated valve l5 forming part of the device l. When the end E is closed, the delay member B is practically deactivated. The mass of air present in its barometric chamber S B and the duct T in fact constitutes a resiliently deformable mass which cooperates with the return spring normally associated with the throttle valve V to return the valve V to its closed position. On the other hand, when the end E is opened and the throttle valve V is brought gradually into the position of maximum opening, the barometric chamber S B expands (or contracts) to cause the intake (or expulsion) of air through the duct T. The delay valve Q does not display any appreciable operation in these conditions since the orienting movement of the throttle valve V and the consequent passage of air through the duct T occurs gradually. When the accelerator pedal is released quickly, the throttle valve V tends to be returned sharply towards its closed position by the resilient return members associated with it. The pivoting movement towards the closed position is thus hindered by the action of the member B, since the return of the valve V to the closed position involves a gradual return of the barometric chamber S B to its initial undeformed condition. This return movement, in fact, results in an inflow (or out flow) of air through the pipe T in which the delay valve Q is connected and this reduces the inflow (or outflow) of air , thus slowing the orienting movement of the throttle valve V. The valve l5 which controls the opening and closing of the end E of the duct B is constituted essentially by a movable obturator l6 acting on the end E, the movement of which is controlled by the pressure within a further barometric chamber l7 which communciates with the pneumatic line 2 and the third pneumatic line 7 immediately downstream of the delay valve 5 and the solenoid valve ll, respectively. In particular, when a sub-atmospheric pressure (vacuum) is present in the barometric chamber l7, the obturator l6 closes the end E of the duct T. In order to explain the operation of the device according to the invention, with reference to Figure l, an initial condition of use will be considered in which the engine is cold and the mixture enriching unit W has been brought into its operative position 0 so as to facilitate starting. The sensor l3 detects the activation of the mixture enriching unit W and outputs a respective signal (first signal) which, through the control circuit l2, causes the solenoid valve 4 to open; the first inlet duct 3 is thus put into communication with the barometric chamber S of the actuator A. The solenoid valve ll is kept in the closed position, shutting off the third pneumatic line 7, while the second pneumatic line 6, due to the presence of the delay valve l0, offers a resistance to the propagation of the pressure gradient which is much greater than that offered by the first pneumatic line 2, whereby it can also be considered as being effectively shut off. Under these conditions of use, the pressure (vacuum) in the choke tube D of the carburettor C downstream of the throttle valve V is transferred directly to the barometric chamber S of the actuator A. The pressure applied to the barometric chamber S is, under these conditions, very small (high vacuum) whereby the engine is made to operate with an ignition advance angle corresponding to the maximum allowable values. The non-return valve 5 has the purpose of keeping the pressure in the chamber S at the minimum value (maximum vacuum) whatever the variations in pressure at the mouth of the inlet duct 3. This minimum pressure (high vacuum) is also transmitted to the barometric chamber l7 of the valve l5 whose obturator l6 closes the end E of the duct T to keep the delay member B deactivated. Upon starting of the engine (which starts to warm up), the mixture enriching unit W is returned to its rest position R and the sensor l3, through the circuit l2, causes the solenoid valve 4 to close. The first pneumatic line 2 is thus shut off. In these conditions, both the pneumatic lines (the first 2 and the third 7) controlled by the solenoid valves 4 and ll are shut off and the only path of propagation of the pressure signal from the carburettor C to the actuator A is constituted by the second line 6 incorporating the delay valve l0. In these conditions, the pressure (vacuum) signal detected by the inlet duct 9 which is disposed upstream of the throttle valve V and is hence exposed to a pressure slightly greater (slightly less vacuum) than that detected by the inlet duct 3 - is transmitted to the actuator A for controlling the advance angle. In general, there will thus be an overall reduction in the angle of ignition advance. The valve l0, however, delays the propagation of the pressure gradients from the inlet duct 9 to the barometric chamber S so as to avoid sharp variations in the ignition advance angle which could harm the characteristics of "drivability" of the vehicle. At the same time, the absence of a pressure (or better, vacuum) signal at the output of the first pneumatic line 2 and the third pneumatic line 7 means that the obturator l6 of the valve 5 frees the end E of the duct T to activate the delay member B which effects the "minimum speed" action, contributing further to the assurance of good drivability of the vehicle, together with low emission levels. These operating conditions exist as long as the temperature of the engine lubricant remains below the threshold level of the sensor l4. When this threshold level is reached, the sensor l4 outputs a respective signal (second signal) which, through the circuit l2, causes the opening of the solenoid valve ll. The third pneumatic line 7 is thus opened whereby the pressure signal detected by the inlet duct 9 is transmitted directly to the barometric chamber S of the actuator A. In these conditions (engine under running conditions), in fact, the second pneumatic line 6, which has a high resistance to the propagation of pressure gradients, is shut off and the actuator A varies the angle of ignition advance in dependence on the pressure in the choke tube D of the carburettor C upstream of the main throttle valve V. At the same time, the presence of the pressure signal (vacuum) at the output of the third valve l5 returns to its position of closing the end E of the duct T of the delay member B, which is thus deactivated again. With reference to the three views of Figures 2, 3 and 4, a single body of moulded plastics material, generally indicated 20, is inserted in a protective casing 20' of plastics or metal, the profile of which is indicated by a double chain line. The body 20 can be seen to consist of: four tubular connectors to which the end E of the duct T, the second inlet duct 3, the duct S', and the inlet duct 8, 9, respectively, are connected in use of the device of the invention; for simplicity of illustration, each connector has been indicated by the same number or letter as that used in Figure l to indicate the respective duct; a plurality of ducts whose structure will be more fully described below, and a combination of shaped parts defining seats for the mounting of the two solenoid valves 4 and ll, the non-return valve 5, the delay valve l0 and the valve or actuator l5. More precisely, the body 20 can be likened essentially to a flat plate having an associated flange 2l at about 90° to the plate for its assembly on the body of the motor vehicle. The plate constituting the body 20 has two opposing faces. The seats for the mounting of the non-return valve 5 and the delay valve l0 are provided on one of these faces. The seats for the mounting of the solenoid valves 4 and ll are provided on the opposite face. The seat for the mounting of the valve or obturator l5, however, is provided in an end position. If the structure of the body 20 is examined in greater detail, it is possible to see that the seat for mounting the non-return valve 5 faces the seat for mounting the solenoid valve 4. The seat for the delay valve l0, however, faces the seat for the solenoid valve ll. In each seat, in addition to mechanical retaining elements not specifically shown in the drawings, there are provided, for each valve or solenoid valve, two apertures or connecting openings, visible in Figure 4 and indicated in that drawing by pairs of the same reference numerals as those used to indicate the corresponding valve or solenoid valve. The ducts provided in the body 20 are indicated by the progressive numerals 22-26; the development of these ducts is indicated by twin broken lines in Figure 4. The duct 22 extends from one of the connecting openings of the delay valve l0 to the connector for connection of the second inlet duct 8 and passes through one of the connecting openings of the solenoid valve ll; it thus defines, with reference to Figure l, the portions of the second and third pneumatic lines 6, 7 which are to the left of the delay valve l0 and the solenoid valve ll in the diagram of the device. The duct 23 branches from the other of the connecting openings of the solenoid valve ll towards the other connecting opening of the delay valve l0, and from the latter to one of the connecting openings of the non-return valve and the control inlet of the valve or actuator l5. The duct 23 further includes an auxiliary branch, indicated 23a, which branches towards the connector intended for connection to the duct S'. Still with reference to Figure l, it is possible to see that the duct 23 and the auxiliary branch 23a define the portions of the second and third pneumatic lines 6, 7 which are to the right of the delay valve and the solenoid valve ll. The duct 24 connects the other connecting opening of the delay valve 5 to one of the connecting openings of the solenoid valve 4. It thus defines the portion of the first pneumatic line 2 which in Figure l extends beneath the non-return valve 5 towards the solenoid valve 4. The duct 25 extends from the other connecting opening of the solenoid valve 4 to the connector intended for connection to the first inlet duct 3 which opens into the choke tube of the carburettor C. The duct 26 finally connects the valve or actuator l5 (end E) to the connector intended for connection to the duct T which controls the operation of the delay member B. In order to form the moulded body 20, at least two different solutions may be used. The first provides for the body being formed in a single moulded piece, for example moulded plastics. Alternatively, the body 20 may be constituted by at least two moulded pieces, the first of which carries the system of ducts 22- 26 impressed in the form of low- relief channels and the other of which is a plate applied to the first piece so as to close the channels and give them the necessary pneumatic sealing characteristics. The pieces constituting the body 20 can then be connected together by gluing or ultrasonic welding. Naturally, the principle of the invention remaining the same, the constructional details and forms of embodiment may be varied widely with respect to that described and illustrated, without thereby departing from the scope of the present invention. In particular, variants can be envisaged in which, in order to detect the temperature of the engine, the heat sensor l4 is placed in contact with another operating liquid in the engine, for example the coolant.

Claims: Device for controlling the polluting emissions of an internal combustion engine having: a carburettor (C) with a choke tube (D) through which an air intake flow passes, and a main throttle valve (V) pivotally mounted in the choke tube (D), an actuator (A) for controlling the angle of ignition advance, having a barometric control chamber (S), a pneumatic system (2,6,7) which puts the choke tube (D) of the carburettor (C) into communication with the barometric control chamber (S) of the actuator (A), a mixture enrichment unit (W) operable between at least one activation position (O) and a rest position (R), first (3) and second (9) inlet ducts opening into the choke tube (D) of the carburettor (C) downstream and upstream, respectively, of the throttle valve (V) in the air intake flow direction, a first pneumatic line (2) in the pneumatic system, which connects the first inlet duct (3) to the barometric chamber (S) controlling the actuator (A), second (6) and third (7) pneumatic lines in the pneumatic system which connect the second inlet duct (9) to the barometric chamber (S) controlling the actuator (A); the second pneumatic line (6) including pneumatic delay means (l0) which can delay the propagation of the pressure gradients through the second line (6), a first sensor (l3) associated with the mixture enrichment unit (W), for generating a first signal selectively indicative of the position of the unit (W) in the activation position (O) and in the rest position (R), a second sensor (l4) sensitive to the temperature of the engine and having a respective threshold level, for generating a second signal indicative of the fact that the temperature of the engine surpasses the respective threshold level, a first valve (4) switchable between an open position and a closed position, interposed in the first pneumatic line (2) and controlled by the first signal so as to open and close the first pneumatic line (2) when the mixture enrichment unit (W) is in the activation position (O) and the rest position (R), respectively, and a second valve (ll) switchable between an open position and a closed position, interposed in the third penumatic line (7) and controlled by the second signal so as to open the third pneumatic line (7) when the temperature of the engine surpasses the respective threshold level. Device according to Claim l, characterised in that a non-return valve (5) is connected in the first pneumatic line (2) for preventing the propagation of positive pressure gradients from the choke tube (D) of the carburettor (C) to the barometric chamber (S) controlling the actuator (A). Device according to Claim l or Claim 2, characterised in that the second sensor (l4) is sensitive to the temperature of an operating liquid in the engine. Device according to Claim 3, characterised in that the sensor (l4) is sensitive to the temperature of the engine lubricant. Device according to any one of Claims l to 4, characterised in that the respective threshold level is substantially in the range 45 - 85°C. Device according to any one of the preceding claims, applicable to an engine in which the throttle valve (V) of the carburettor (C) has an associated pneumatic delay member (B) which can slow the oscillating movement of the throttle valve (V), characterised in that the first (2) and third (7) pneumatic lines have at least one further associated on-off valve (l5) for preventing the operation of the pneumatic delay member (B) when one of the first (2) and third (7) pneumatic lines is open. Device according to Claim 6, in which the pneumatic delay member (B) comprises a respective barometric control chamber (S B ) communicating with the external environment through a vent duct (T), characterised in that said at least one further on-off valve (l5) can occlude the vent duct (T) in order to prevent the pneumatic delay member (B) from operating. Device according to Claim 6 or Claim 7, characterised in that said at least one further on-off valve (l5) has a respective further barometric control chamber (l7) communicating with the first (2) and third (7) pneumatic lines. Device according to Claim 2 and Claim 6, characterised in that it includes a body (20) of moulded material in which there are provided connectors (3, 8, S', T) for connecting the first (3) and second (9) inlet ducts to the actuator (A) for controlling the advance angle and the pneumatic delay member (B), together with ducts defining the pneumatic system (2, 6, 7); the moulded body also having shaped parts (4, 5, l0, ll) defining seats for mounting the non-return valve (5), the pneumatic delay means (l0), the first (4) and second (ll) switchable valves, and the further on-off valve (l5). Device according to Claim 9, characterised in that the moulded body (20) includes a plate portion with two opposing faces, and in that the shaped parts (5, l0) defining the seats for mounting the non-return valve (5) and the pneumatic delay means (l0) are provided on one of the faces of the plate portion and the shaped parts (4, ll) defining the seats for mounting the first (4) and the second (ll) switchable valves are provided on the other face of the plate portion. Device according to Claim l0, characterised in that the shaped parts (4, 5) defining the seats for mounting the non-return valve (5) and the first switchable valve (4) and the shaped parts (l0, ll) defining the seats for mounting the pneumatic delay means (l0) and the second switchable valve (ll), respectively, face each other. Device according to Claim l0 or Claim ll, characterised in that the shaped parts defining the seat for mounting the further on-off valve (l5) are provided at one end of the plate part. Device according to any one of Claims 9 to l2, characterised in that the moulded body (20) has an appendage (2l) defining a support flange for the body (20) itself. Device according to any one of Claims 9 to l3, characterised in that the body (20) is constituted by a single piece of moulded material. Device according to Claim 9 or Claim l4, characterised in that the body (20) is made of moulded plastics material.

Inventors: BONARDO, RINALDO, CUCCHI, CARLO, MORBELLI, GIANFRANCO
Applicants: FIAT AUTO S.P.A.
Application year: 1986
Main classification: F02P5
IPC codes: F02P5, F02D41