GB2056587A

GB2056587A - Seal for a shaft operating a waste gate valve

Info

Publication number: GB2056587A
Application number: GB8022969A
Authority: GB
Original assignee: IHI Corp
Current assignee: IHI Corp
Priority date: 1979-07-14
Filing date: 1980-07-14
Publication date: 1981-03-18
Also published as: IT8023406A0; JPS587175Y2; FR2461869B1; DE3026013A1; IT1131558B; FR2461869A1; DE3026013C2; JPS5615881U; GB2056587B

Abstract

A seal device is provided for an interlocking shaft 16 passing through a pressure casing 10 the shaft being connected to a diaphragm 11 constituting a pressure-sensitive actuator mechanism for automatically controlling the degree of opening of a waste gate valve 27 installed in a turbocharger. The seal device comprises a seal ring 23 and a resilient packing 24 located between the casing and the shaft. The packing is either between the seal ring and the casing or between the seal ring and the shaft. There is in addition a diaphragm 20 connected to the shaft which forms a seal with the casing by means of a spring 22 acting between the two diaphragms 11, 20. <IMAGE>

Description

SPECIFICATION Seal for a shaft operating a waste gate valve The present invention relates to a seal for a shaft operating a waste gate valve, for example in a turbo-charger in an internal combustion engine.

Such a wate gate valve for internal combustion engines is usually connected via an interlocking shaft to a diaphragm which is actuated by the difference between the supercharging pressure of the engine and the pressure prior to supercharging.

Accordingly, it is necessary to seal that portion of a pressure casing from which the interlocking shaft protrudes.

Figure 1 shows a previously proposed seal in which sealing is effected merely by a seal ring 2 slidably fitted around an interlocking shaft 1 and clamped between a bent portion 3a of a side wall of a pressure casing 3 and a holder member 4. While the shaft 1 is repeatedly reciprocated the bent portion 3a and the holder member 4 may each receive a force which tends to move them apart so that a gap may occur between the bent portion 3a and seal ring 2 and between the holder member 4 and seal ring 2.

This adversely affects the seal between the pressure casing 3 and the shaft 1.

The pressure casing 3 and the shaft 1 are supported by different parts of turbocharger body. Thus, that end portion of the shaft 1 which is within the pressure casing 3 is oscillated in a different manner from the outer casing in spite of the fact that both the shaft 1 and pressure casing 3 are oscillated by the engine.

That end portion of the shaft 1 which is within the pressure casing 3 is held by a diaphragm, but its oscillatory movements, which are quite different from those of pressure casing 3 as stated above cannot be sufficiently suppressed by the diaphragm.

Thus, in time, the diaphragm will become damaged.

While waste gate valves for diesel engines may have no negative pressure chamber which may have an adverse effect on the seal they may still suffer from breakage of the diaphragm caused by relatively irregular oscillations.

It is an object of the present invention to eliminate these problems, to improve the sealing effect of the seal and to increase the endurance of the diaphragm.

According to the present invention, a seal for the shaft operating a waste gate valve for controlling the feed rate of exhaust gas to a turbine wheel in a turbo-charger, comprises a seal ring and a packing provided in that portion of a pressure casing through which the shaft passes.

The seal ring may closely fit around the shaft and the packing may be held resiliently between the seal ring and the casing through which the shaft passes or the seal ring may be fixed to the casing wall through which the shaft passes and the shaft may pass through the seal ring with the packing held resiliently between the seal ring and the shaft.

Preferably a diaphragm is fixed to the shaft and resiliently held against the casing to form a seal.

The invention may be carried into practice in various ways and one embodiment will now be described by way of example with reference to Figure 2 of the accompanying drawings, in which, as stated, Figure 1 illustrates a previously proposed seal for the shaft operating a waste gate valve while Figure2 is a diagrammatic section of a seal for the shaft operating a waste gate valve according to the present invention.

Referring to Figure 2, reference numeral 10 denotes a pressure casing constituting the main body of a pressure-sensitive actuator mechanism for controlling the degree of opening of a waste gate.

The interior of the pressure casing 10 is divided into a positive pressure chamber 12 and a negative pressure chamber 13 by a diaphragm 11 which constitutes a pressure-sensitive actuator member. A conduit 14 for supplying supercharging pressure is in communication with the positive pressure chamber 12, while a conduit 15 for supplying presupercharging pressure is in communication with the negative pressure chamber 13.

An interlocking shaft 16 for operating a waste gas valve is fixed at one end to the centre of the diaphragm 11 via washers 17, 18.

The interlocking shaft 16 has an annular recess 19 at a position within the negative pressure chamber 13. An inner thickened edge portion 20a of a second diaphragm 20, located in the negative pressure chamber 13, is closely fitted in the annular recess 19, Thus, the diaphragm 20, can move to accommodate the reciprocating movements of the shaft by virtue of its folded portion.

Although the diaphragm 20 is not fixed to that portion of the pressure casing 10 which defines the negative pressure chamber 13 it does form a seal with the inner surface of that wall of the pressure casing 10 through which the shaft extends. A spring 22 for constantly urging the shaft 16 in the valveclosing direction (toward the positive pressure chamber 12) is located between a pressure-receiving washer 21, which contacts the pressure-receiving surface of the diaphragm 20, and the pressurereceiving washer 17 on the diaphragm 11.

The diaphragm 20 is thus held, by the force of the spring 22, between the inner surface of the wall of the negative pressure chamber 13 through which the shaft protrudes and the pressure-receiving washer 21. The force exerted by the diaphragm 20 is increased when the shaft 16 is moved in the valve-opening direction since the spring 22 is compressed, thus exerting a greater pressure on the diaphragm 20 and so ensuring a good seal.

The diaphragm 20 has an engagement edge 20b in the form of a circumferential flange. The engagement edge 20b engages the pressure-receiving washer 21 to prevent the diaphragm 20 from slipping from its position between the wall of the casing 10 and the pressure-receiving washer 21. Thus, the space between the wall of the negative pressure chamber 13 through which the shaft passes and the shaft 16 itself is sealed by the diaphragm 20.

The shaft 16 is further sealed at a position outside the diaphragm 20 by a seal ring 23 which is fitted closely around the shaft 16. The seal ring 23 is pressed and held on both sides, between that wall 10a of the negative pressure chamber 13 through which the shaft passes and a seal holder member 25.

The holder member 25 is welded to the inner circumferential surface of the casing 10 inwardly of wall 10a. An annular packing 24 of a rubber-like elastic material is located between the inner surface of the casing which is opposed to the seal ring 23 and the circumferential surface of the seal ring 23.

In an alternative embodiment the seal ring 23 is fixed to that portion of the casing 10 which defines the negative pressure chamber 13, and the annular packing 24 may be located between the shaft 16 and seal ring 23.

Thus the space around the shaft 16 as it passes through the casing is sealed by the seal ring 23 and the packing 24, as well as by the diaphragm 20 described above. The diaphragm 20 of this double seal may be omitted when only a low sealing capability is required or when the provision of the seal ring 23 alone would be sufficient or in the case of a waste gate valve for diesel engines (as will be described below) since such a valve requires no negative pressure chamber.

In use, a waste gate valve 27 is connected to the outer end of the shaft 16 via a lever 26 and is adapted to open and close an exhaust bypass passage 28 for a turbocharger, thereby controlling the flow rate of exhaust gas applied to a turbine. When the supercharging pressure introduced into the positive pressure chamber 12 overcomes the force of the spring 22, or when a pre-supercharging pressure overcoming the force of the spring 22 is applied to the negative pressure chamber 13, the diaphragm 11 serving as a pressure-sensitive actuator is operated.

As a result, the waste gate valve 27 is operated in response to the movement of the diaphragm 11, via the shaft 16 and the lever 26.

Awaste gate valve for diesel engines is slightly different from the waste gate valve described above, in that the former does not require a negative pressure chamber 13. Therefore, the sealing capability of the seal ring 23 and the packing 24 is not as important in such an arrangement. However, such a waste gate valve must be capable of suppressing irregular movements of the end portion of the interlocking shaft, which cause the diaphragm to be damaged within the pressure casing. In the case of a waste gate valve for a diesel engine, the embodiments described in accordance with the present invention may not only improve the sealing performance of the seal device and the endurance of the diaphragm but may also exhibit other advantageous practical effects, since it permits a proper and smooth operation of the diaphragm and may provide a more effective control over the degree of opening of the waste gate valve in response to the movement of the diaphragm.

Claims

1. A seal for the shaft operating a waste gate valve for controlling the feed rate of exhaust gas to a turbine wheel in a turbocharger, comprising a-seal ring and a packing provided in that portion of a pressure casing through which the shaft passes.

2. A seal as claimed in Claim 1, in which the seal ring is fitted closely around the shaft, and the packing is resiliently held between the seal ring and the wall of the pressure casing through which the shaft passes.

3. A seal as claimed in Claim 1, in which the seal ring is fixed to the wall of the pressure casing through which the shaft passes, the shaft is passed through the seal ring and the packing is resiliently held between the seal ring and the shaft.

4. A seal as claimed in any preceding claim in which a diaphragm is fixed to the shaft and resiliently held against the casing to form a seal.

5. A seal as claimed in any preceding claim in which the shaft is provided with an annular recess at a position within the pressure casing, a diaphragm is closely fitted in the recess, the diaphragm is in contact at or near its outer periphery with a sidewall of said pressure casing which extends at right angles to the axis of the shaft, and in which resilient means acts to urge the diaphragm towards the seal ring.

6. A seal for the shaft operating a waste gate valve constructed and arranged substantially as herein specifically described with reference to and as shown in Figure 2 of the accompanying drawings.