The present invention relates to a servo-assisted butterfly valve provided with a flat leaf spring and a spiral spring to establish the limp-home position.
Petrol driven internal combustion engines are normally provided with a butterfly valve which regulates the flow of air supplied to the cylinders. Typically, the butterfly valve comprises a valve body housing a valve seat engaged by a butterfly disc which is keyed on a shaft in order to rotate between an open position and a closed position under the action of an electric motor connected to this shaft by means of a gear transmission. The shaft bearing the butterfly valve is associated with a position sensor which is adapted to detect the angular position of the shaft and therefore of the butterfly valve in order to enable a control unit to control, by feedback, the electric motor which determines the position of the butterfly valve.
The butterfly valve normally comprises a torsion spiral return spring which is mounted coaxially with the shaft and is mechanically coupled to the shaft in order to exert a torque on this shaft which tends to bring the shaft towards the closed position; and a torsion spiral opposing spring which is mounted coaxially with the shaft and is mechanically coupled to the shaft in order to exert a torque on this shaft which tends to bring the shaft into a partially open position (called the limp-home position) against the action of the return spring and as a result of the presence of an abutment body which defines an abutment for the opposing spring against which the opening movement determined by this opposing spring is stopped. The torque generated by the opposing spring is greater than the torque generated by the return spring; for this reason, when the motor is not activated the shaft is disposed in the limp-home position and the motor itself then has to generate a respective drive torque both to bring the shaft into the position of maximum opening and to bring the shaft into the closed position.
US20020129791 discloses a throttle device for an internal-combustion engine, in which, on one side of the side wall of a throttle body, there are formed a space for mounting a reduction gear mechanism which transmits the power from a motor to a throttle valve shaft and a default opening setting mechanism for holding a throttle valve opening at a specific opening (default opening) when the ignition switch is in off position, and a gear cover mounting frame which edges the mounting space; the frame is formed lower than the mounting level of the reduction gear mechanism. A gear cover for covering the gear mounting space is attached on the frame; a stopper for defining the default opening and a stopper for defining the full-closed position of the throttle valve are juxtaposed so as to enable position adjustments in the same direction. These stoppers serve to stop a default lever and a throttle gear, thereby enabling downsizing, weight reduction, and rationalization of fabrication and adjustments of an electronically controlled throttle device.
The solution described above in which the limp-home position is established by two spiral springs is normally used in the butterfly valves available commercially; however, this solution has some drawbacks as it is very bulky and relatively complex and time-consuming to assemble.
The object of the present invention is to provide a servo-assisted butterfly valve provided with a flat leaf spring and a spiral spring to establish the limp-home position which is free from the drawbacks described above and which is, in particular, simple and economic to embody.
The present invention therefore relates to a servo-assisted butterfly valve comprising a valve body, a valve seat formed in the valve body, a butterfly disc adapted to engage the valve seat, a shaft on which the butterfly disc is keyed, an electric motor coupled to the shaft by means of a gear transmission comprising at least a first toothed wheel in order to rotate the butterfly disc between a position of maximum opening and a closed position of the valve seat, a spiral return spring adapted to rotate the butterfly disc towards the closed position, and an opposing spring adapted to rotate the butterfly disc towards a partially open or limp-home position defined by an abutment body against the action of the return spring; the butterfly valve being characterised in that the opposing spring is a flat leaf spring and is mounted on a moving member which is mounted coaxially and idly on the shaft and comprises a projection adapted to engage in abutment against the abutment body, a first end of the opposing spring being free and being disposed alongside the first toothed wheel so as to face an inner surface of this first toothed wheel, this first toothed wheel comprising a projection which projects in a perpendicular manner with respect to the inner surface so as to bear against the second end of the opposing spring during the rotation of the first toothed wheel.
The present invention is described below with reference to the accompanying drawings which show a non-limiting embodiment thereof, and in which:
In
As shown in
The electric motor 3 comprises a shaft 15 ending in a toothed wheel 16 which is mechanically connected to the shaft 6 by means of an idle toothed wheel 17 interposed between the toothed wheel 16 and a final gear 18 keyed on the shaft 6. The toothed wheel 17 comprises a first set of teeth 19 coupled to the toothed wheel 16 and a second set of teeth 20 coupled to the final gear 18; the diameter of the first set of teeth 19 differs from the diameter of the second set of teeth 20 with the result that the toothed wheel 17 has a transmission ratio which is not unitary. The final gear 18 is formed by a solid central cylindrical body 21 keyed on the shaft 6 and provided with a circular crown portion 22 provided with a set of teeth coupled to the toothed wheel 17. The whole gear transmission 8, i.e. the toothed wheel 16, the toothed wheel 17 and the final gear 18 are normally made from plastics material.
The gear transmission 8 and the plate 10 are disposed in a chamber 23 of the valve body 2 which is closed by a detachable cover 24 (shown in
As shown in
As shown in
As shown in
As shown in
The rotation in the clockwise direction with reference to
The return spring 35 has an end (not shown in detail) connected mechanically to the valve body 2 and an end 38 which is mechanically connected to the final gear 18 which is in turn keyed on the shaft 6 as it is inserted in a housing 39 obtained in this final gear 18. The opposing spring 36 is mounted on a cylindrical moving member 40 which is mounted coaxially and idly on the shaft 6, i.e. there are no direct mechanical connections between the shaft 6 and the moving member 40. An end 41 of the opposing spring 36 is rigid with the moving member 40; at the end 41 of the opposing spring 36, the moving member 40 comprises a projection 42 which is adapted to engage in abutment against the abutment body 37 of the valve body 2 as shown in
In the absence of the action of the electric motor 3, the torque generated by the return spring 35 rotates the shaft 6 in an anti-clockwise direction with reference to
In the embodiment shown in
According to an alternative embodiment shown in
It should be noted that the unit formed by the shaft 6, the return spring 35 and the moving member 40 provided with the opposing spring 36 may be pre-assembled separately and inserted by means of a single assembly operation, which may be automated, in the valve body 2.
In comparison with the conventional solution in which the return and opposing springs are both spiral springs, the solution for the butterfly valve 1 as described above in which the return spring 35 is a spiral spring and the opposing spring 36 is a flat leaf spring has various advantages as it enables a reduction of friction and bulk, is more reliable and makes it possible to reduce assembly times.
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Number | Date | Country | |
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20050263731 A1 | Dec 2005 | US |