GB2246842A

GB2246842A - Non-return valve

Info

Publication number: GB2246842A
Application number: GB9115104A
Authority: GB
Inventors: Osman Sari; Ernst Kuhlen; Edwin Schauer; Albert Denne
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: GB9115104D0; DE4025267C2; DE4025267A1; FR2665743A1; ITRM910460A1; FR2665743B1; ITRM910460A0; IT1248351B; GB2246842B

Abstract

A non-return gas valve in particular for controlling the supply of secondary air to the exhaust system of an internal combustion engine is characterised in that a limiting stop (16) bears with a spring (17) on a valve closure member (15), the latter being movable towards and away from a valve seat (7) for blocking or unblocking passages (9) in the valve seat for the flow of secondary air, the said stop (16) being shiftable by a pneumatically or electromagnetically driven control device to advance towards the valve closure member (15) to a position in which the valve is prevented from opening. <IMAGE>

Description

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

gas valve in particular for controlling a supply of secondary air to an exhaust system for reducing the amounts of toxic substances in the exhaust gases of an internal combustion engine. In the operation of the 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 the above atmospheric pressure, the non- return valve closes, preventing exhaust gases from escaping in to 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-retum valves are often used, in conjunction with air pumps, in exhaust systems equipped with downstream controlled catalysts. The non- return valve is operated mainly during warming-up of the engine, when a rich combustion mixture is being fed to the engine. The secondary air 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 thi s is reached the stream of secondary air is interrupted, for example by a separate control-pressure-responsive shutoff 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 this arrangement is that non-return valves of this kind tend to be noisy even when they have been switched off, because their closure plates are brought into oscillation by the pulsating pressures in the exhaust system. This also produces abrasion of the parts, reducing the working life of the non-return valve.

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 these disadvantages are largely obviated.

Claims

The problem is solved, according to the invention, by the characteristics claimed in Claim 1. Further advantageous features of the invention are described in the subsidiary claims. The new non-return valve is characterised in that for shutting off the secondary air, the limiting stop is driven by a pneumatic or electric actuator to advance towards the closure device, which can be a body of rotation or a strip-like structure, locking it firmly in place so that it cannot be brought into oscillation by the pulsating pressure in the exhaust system. The arrangement also reduces abrasion on the non-return valve, giving it a longer working life. A special advantage of the electrically actuated positioner device, compared to the pneumatically actuated one, is that the secondary air is switched off directly, making it unnecessary to provide a separate electric switch-over valve. 1 j 1 1 1 i i 1 f k 3 The two examples of the invention diagramatically in the drawing will now be described. Figure 1 is a section through a non-return valve. Figure 2 is a section through a variant. Figure 1 shows a non-return valve 1 comprising a housing upper part 2 with an inlet connection 3, for the secondary air, a housing lower part 4 with an outlet connection 5 for the secondary air. Interposed between the two housing parts 2, 4 and separating them from each other, there is a plate-like valve-seat 7 which has passages 9 for the secondary air. A plate-like valve closure member 15 is movable towards the seat 7 to close the passages 9, or it is movable away from the seat 7 to open the passages 9. The outer rim of the valve-seat 7 is clenched between the two housing parts 2, 4 with the help of an elastomeric ring 6, which makes a good seal and helps to dampen out noise. Underneath the valve-seat 7 the drawing also shows a stroke-limiting plate 8 which is also clenched by its outer rim between the two housing parts 2, 4 with the help of the elastomeric ring 6. The housing upper part 2 forms a pneumatic capsule containing, under a flexible diaphragm 13, a pneumatic chamber 10 which communicates with a control connection 11. The pressure in the control connection 11 is governed by an electric switch-over valve which is not in the drawing. Above the flexible diaphragm 13 there is atmospheric pressure. Fixed to the flexible diaphragm 13 is the upper end of an actuator rod 14. In its downward movement the diaphragm is opposed by a compression spring 12. 0 4 The actuating rod 14 penetrates downwards through the valve-seat 7, the actuator rod sliding up and down in the plate-like valve closure members with the up-and-down movements of the flexible diaphragm 13. Fixed to the lower end of the actuator rod 14 there are a limiting stop 16 and a spring 17. In this example of the invention the closure member 15, the limiting stop 16 and the spring 17 are all bodies of rotation. But, if desired, striplike structures can be used. Referring now to the example shown in Figure 2, here the pneumatic capsule of Figure 1 is replaced by an electromagnet 18 contained in the housing upper part 2. The electromagnet 18 comprises a coil 19 which is fed with electric current over leads 20 and 21, a core 22 and an armature 23 to which is fixed the actuator rod 14 with its limiting stop 16 and spring 17. All the other structures in Figure 2 correspond to the relevant structures in Figure 1. As long as the pressure in the control connection 11 of Figure 1 is below atmospheric pressure, the diaphragm 13 remains (as shown in the Figure 1) in its lowered position, with the spring 12 compressed. The actuator rod 14 is therefore also in its lowered position and the limiting stop 16 fixed to the lower end of the actuator rod 14 rests in contact with, and is supported by, the stroke-limiting plate 8. Under these circumstances the spring 17, which retains and guides the mobile closure member 15 both axially and radially, is in a relaxed state, allowing the mobile closure member 15 to move downwards easily, i.e. the mobile closure member 15 ceases to obturate the passages 9. This allows the non-return valve 1 to operate in the conventional manner. Secondary air sucked in through the inlet connection 3 flows through the passages 9 of the valve-seat 7, around the rim of the mobile closure member 15 and out through the outlet connection 5 to the exhaust system of the engine.

1 1 1 i 1 1 I 1 i 1 i i X When the engine has become warm enough for normal operation, or when the catalyst has become warm enough, atmospheric pressure is admitted to the control connection 11, allowing the compression spring 12 to lift the diaphragm 13 to its raised position. With the diaphragm 13, the actuator rod 14 also travels upwards, lifting the limiting stop 16 and applying upwards thrust to the spring 17. This locks the mobile closure member 15 in its raised position, obturating the passages 9 of the valve-seat 7.

The non-return valve shown in Figure 2 functions in a similar manner. As long as no current flows through the coil 19 the non-return valve remains blocked. No secondary air flows into the exhaust system of the engine. The compression spring 10 retains the actuator rod 14 in its raised position, holding the limiting stop 16 in its raised position and thrusting the valve closure member 15 up against the valve-seat 7, obturating the passages 9. On the other hand, as soon as electric current flows through the coil 19 this pulls actuator rod 14 downwards (as shown in Figure 2), relaxing the spring 17 and unlocking the mobile closure member 15, allowing secondary air flow into the exhaust system of the engine.

J k 6 CLAIMS 1. A non-return gas valve, particularly for use in controlling and feeding a supply of secondary air to the exhaust system of an internal combustion engine, with a valve-seat (7) equipped with one or more passages for the medium which is to be controlled and with at least one valve closure member (15), a spring and a limiting stop, characterised in that the limiting stop (16) can be shifted by a control device (10, 18) into either one of two alternative positions, that is, either into a firstposition in which it locks the closure member (15) in its closed position, obturating the passages (9) in the valve seat (7), or into second position in which it unlocks the closure member (15), unblocking the passages (9).

2. A non-return valve as claimed in Claim 1, characterised in that the control device is a chamber (10) of a pneumatic capsule, the pressure in the chamber (10) being controlled by a switch-over valve.

3. A non-return valve as claimed in Claim 1, characterised in that the control device is an electromagnet.(18)-

4. A non-return valve as claimed in one of the Claims 1 to 3, characterised in that the valve closure member (15), the spring (17) and the limiting stop (16) are all either bodies of rotation or strip-like structures.

5. A non-return gas valve substantially as hereinbefore described with reference to either of the accompanying drawings.

Published 1992 at The Patent Office, Concept House. Cardiff Road. Newport. Gwent NP9 I RH. Further copies may be obtained from Sales Branch. Unit

6. Nine Mile Point. Cwrnfelinfach. Cross Keys. Newport. NPI 7HZ. Printed ky Multiplex techniques ltd. St Mary Cray. Kent i i 1 1 i 1 i i 1 1 1 i i