GB2246841A

GB2246841A - Non-return valve

Info

Publication number: GB2246841A
Application number: GB9115103A
Authority: GB
Inventors: Otto Meyer; Edwin Schauer
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1990-08-09
Filing date: 1991-07-12
Publication date: 1992-02-12
Anticipated expiration: 2011-07-12
Also published as: DE4025266A1; ITRM910461A0; FR2665742A1; IT1248352B; FR2665742B1; GB9115103D0; ITRM910461A1; GB2246841B

Abstract

A non-return gas valve in particular of the kind used for feeding and controlling a supply of secondary air to a vehicle exhaust system is characterised in that it has a control plate (18) which is actuated by an electric or pneumatic positioner responsive to engine-operating parameters. The non-return valve comprises a valve-seat plate (5) with flow passages (6) which are obturated by two closure members (4). The control plate (18) is movable into resting contact with the valve-seat plate (5), and when in this condition the area available for flow of secondary air through the flow passages (6) is reduced. <IMAGE>

Description

1 NON-RETURN VALVE FOR A GAS LINE The invention relates to a non-return

gas valve of the kind in particular for installing in a line for feeding and controlling a supply of secondary air into the exhaust system of an internal combustion engine, with a valve-seat plate equipped with one or more non-return flow passages for the secondary air, and preferably, with at least one device for shutting off the stream of secondary air.

Valves of this kind are used for controlling the supply of secondary air for reducing the amounts of toxic substances in the exhaust gases of internal combustion engines. In the operation of an engine the pressure in the exhaust system fluctuates periodically, dropping at regular intervals to pressures below atmospheric pressure. During these periods of low pressure the non-return valve (sometimes called a secondary air aspirator valve) allows air from the surrounding atmosphere to stream into the exhaust system, where it acts as secondary combustion air. As soon as the exhaust gas pressure returns to above atmospheric pressure, the non-return valve closes, preventing exhaust gases from escaping into the surrounding atmosphere. The secondary air entering the exhaust system produces an oxidation reaction leading to a reduction in the amounts of hydrocarbons (CH) and carbon monoxide (C0) in the exhaust gases.

Non-return valves are often used, in conjunction with air pumps, in exhaust systems equipped with downstream controlled catalysts. The nonretum valve is operated mainly during warming-up of the engine, when a rich combustion mixture is being fed to the engine. The secondary air when mixed with the hot exhaust gases produces a further combustion which has two effects. In the first place it reduces the CO and HC by about 30% and, secondly, helps to warm the catalyst more rapidly up to its operating temperature. When this is reached the stream of secondary air is interrupted, for example by a separate control-pressure-responsive shut-off valve in the secondary air feed line. The separate shut-off valve can be actuated, for example, by an extra electrically powered switch-over valve.

2 From the PEERBURG Druckschrift "AGR-Ventile, SLS-Ventile" Reg No 5/400 150.2 a secondary air valve is known in which the non-return valve and the shut-off valve are housed together in a single housing. And here again the device is actuated by an electrically powered switch-over valve. A disadvantage of suction-actuated non-retum valves of this kind is that the open cross section of the valve, i.e. the area available for the flow of secondary air, cannot be varied. The rate of flow of secondary air is therefore determined at each instant entirely by the pressure existing, at that instant, in the exhaust system. This cannot ensure the best secondary combustion under all engine-operating conditions.

From this starting point, the intention in the present invention is to modify a non-retum valve of the kind described at the beginning in such a way that improved operating efficiency is obtained.

The invention, provides a non-return gas flow control valve, particularly for installing in a line for feeding secondary air into the exhaust system of an internal combustion engine, with a valve-seat plate equipped with one or more passages for the secondary air, and preferably, with at least one device for shutting off the stream of secondary air, which is characterised in that the non-return valve has a control plate actuated by an electric or pneumatic control device, the control plate serving for reducing the area available for air flow through the or each of the passages of the valve-seat plate. Further advantageous developments are described by the characteristics of the subsidiary claims.

Under certain conditions of pressure, the one way valve being otherwise open to permit flow, when the control plate rests in contact with a valveseat plate and because it has one or more passages, the area of these being smaller than that of the corresponding passages in the valve-seat plate, the effect achieved is that flow is increased as compared with what it would be if the control plate were not so engaged. The causes of this effect are explained below.

I i 1 j i i 1 1 i 1 i i 1 i i Z7 1 1 i 3 1.

This proposal makes it possible to vary the effective sizes of the passages available for the stream of secondary air to suit the existing operating parameters of the engine. For example, when the engine is operating at or near full load the open cross section or area available for the flow of secondary air should be reduced, compared to what is necessary when the engine is idling or nearly idling, or operating at part-loads. This increases the flow of secondary air into the exhaust system and reduces the amount of toxic substances in the exhaust gases, for the reasons which will now be explained.

The fact that reducing the flow areas of the passages increases the flow of secondary air, at or near full-load operation of the engine, is due to the effect of periodic pressure peaks in the exhaust system, as will now be described.

Under all engine operating conditions, the flow of secondary air sucked into the exhaust system through the non-return valve depends of the belowatinospheric pressure peaks occurring periodically in the exhaust system. But when the engine is operating at or near full load these belowatmospheric pressure peaks are sharply reduced by the comparatively large flow cross sections required, in the non-return valve, for idling or near idling, or part-load operation of the engine. Consequently at or near full load, only comparatively little secondary air is sucked into the exhaust system.

By reducing the flow cross section in the non-return valve for full load and near-full-load operating conditions the below-atmospheric pressure peaks are increased, due to the lower pressure drop in the flow cross section of the non-return valve, increasing the flow of secondary air sucked into the exhaust system.

Moreover, a backwards flow of exhaust gases, out into the atmosphere, is largely prevented because the non-return valve operates in a one-way-only flow mode over the entire range of engine-operating parameters.

4 n The pneumatically or electrically powered positioner device preferably also actuates a valve-seat plate which cooperates with a valve seat in shutting off the stream of secondary air. In this process a control rod connected to the control plate advances into the positioner device against the influence of a coupling spring.

One example of the invention shown diagramatically in the drawing will now be described.

The drawing shows a non-return valve 1 comprising a one-way flow valve section 2 which has a valve-seat plate 5 with for example two passages 6 for the secondary air whose flow is to be controlled. The passages 6 can be obturated by two closure plates 4 so that flow is permitted only in the direction towards outlet connections 10 leading to the vehicle exhaust pipe. The stroke of the movable eg. flexible closure plates 4 when they lift is limited by stops 3.

The action of the one-way valve section 2 is controlled by a pneumatic positioner capsule 7. The valve section 2 and the pneumatic positioner capsule 7 are contained together in a housing equipped, on the one hand, with an inlet connection 8 containing a filter 9 for admitting the secondary air and, on the other hand, with the outlet connections 10.

The pneumatic positioner capsule 7 responds to the pressure in a control connection 11 which is connected (although this is not shown in the drawing) to an electrically powered switch-over valve, which itself responds to the operating parameters of the engine. In the pneumatic positioner capsule 7 the pressure in the control connection 11 acts on a flexible diaphragm 15 which is held, in its middle portion, against the influence of a spring 12, between two diaphragm plates 13 and 14.

i 1 i Z 1 i Penetrating centrally and axially through the two diaphragm plates 13 and 14 there is a control rod 17 capable of sliding against the influence of a coupling spring 16. To the other end of the control rod 17 there is fixed a control plate 18 equipped with one or more passages 19 for the secondary air. And it should be observed that the passages 19 are smaller in cross section than the passages 6 of the valve-seat plate 5. In the version illustrated, the diaphragm plate 13, when it slides up rod 17, acts as a plate valve cooperating with a valve seat 20 to cause the flow of secondary air to be shut off.

On the other hand, in those cases where it is preferred to use a nonreturn valve in which the flow of secondary air cannot be shut off, the diaphragm plate 13, the valve seat 20 and the coupling spring 16 are all omitted, the control rod 17 being fixed, in this case, to the diaphragm plate 14.

In a further variant of the invention (not shown in the drawing) an electromagnet responsive to engine operating parameters is used for directly controlling movement of the control plate 18 fixed to the other end of the control rod 17. In this case, the annature of the electromagnet supports, not the diaphragm 15, but the diaphragm plate 14, or the valve plate 13. In this variant the electromagnetic switch-over valve for controlling the pneumatic positioner capsule 7 can be omitted.

Method of functioning As long as there is atmospheric pressure in the control connection 11 the non-return valve 1 remains closed. The diaphragm plate 13 is up against its seat 20 and no secondary air flows from the inlet connection 8, through the valve portion 2 and out through the outlet connections 10 to the exhaust system of the engine. The control rod 17 is in its raised position.

6 On the other hand, (for example, as soon as the engine slows to idling speed, or changes to part-load operation), when a pressure lower than atmospheric pressure comes to prevail in the control connection 11, and therefore in the positioner capsule 7, this allows the surrounding air, which is at atmospheric pressure, to thrust the diaphragm 15 downwards, lowering the diaphragm plates 13 and 14, the control rod 17 and the control plate 18, against the influence of the spring 12, the control plate 18 moving down well clear of the valve-seat plate 5.

Under these circumstances secondary air, entering through the inlet connection 8, and after passing through the filter 9 and the passage formed by the valve seat 20, flows readily through the passages 19 of the control plate 18 which, as already mentioned, is at this time standing well clear of the valve-seat plate 5. After passing through the passages 19 of the control plate 18, the secondary air is sucked upwards through the passages 6 of the valve-seat plate 5, around the edges of the (now open) closure plates 4 and up through the outlet connections 10 to the exhaust system of the engine.

Nevertheless, under certain circumstances, in particular when the engine is running at or near full load, it can be desirable to increase the control pressure in the positioner capsule 7, lifting the control plate 18 up into contact with the valve-seat plate 5 and leaving only the smaller passages 19 available for the flow of secondary air. In this condition the device will appear as shown in the drawing.

1 1 a 1 i 1 1 i i i i 7

Claims

1. A non-return gas valve, particularly for installing in a line for feeding secondary air into the exhaust system of an internal combustion engine, with a valve-seat plate (5) equipped with one or more non-return flow passages (6) for the supply of secondary air, characterised in that the non-return valve has a control plate (18) actuated by an electric or pneumatic control device (7), the control plate (18) serving for reducing the area available for flow through the passages (6) of the valve-seat plate (5).

2. A non-return valve as claimed in claim 1, characterised in that the electric or pneumatic control device (7) responds to engine-operating parameters and in that there is present at least one device (13, 20) for shutting off the stream of secondary air.

3. A non-return valve as claimed in claims 1 or 2, characterised in that the control plate (18) is fixed to the control device (7) by means of a control rod (17).

4. A non-return valve according to any one of claims 1 to 3 and in which the control plate (18) has flow passages (19) the total area of which is. lower than the total area of the flow passage or passages in the valveseat plate (5).

5. A non-return valve as claimed in claims 1 or 2, characterised in that the electric or pneumatic positioner capsule (7) also actuates a valve plate (13) which cooperates with a valve seat (20) to interrupt the stream of secondary air; a control rod (17) connected to the control plate (18) being provided for this purpose, the control rod (17) advancing into the positioner capsule (7) against the influence of a spring (12).

6. A non-return valve according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawing.

Published 1992 at The Patent Office. Concept House. Cardiff Road. Nmpori. Gwent NP9 111H. Further copies max, be obtained fron, Sales Branch. UnJt 6. Nine Mile Point. Cwnifelinfach. Cross Keys. Newport NPI 7HZ. Printed by Multiplex techniques ltd. St Marv Cra%. Kent-