The present invention relates to a device for controlling the means for recirculating an engine cooling fluid, in particular for vehicles.
It is known in the sector relating to the production of engines, in particular internal-combustion engines, that there exists the need to cool said engines by recirculating a cooling fluid moved by means of a corresponding recirculating pump, the impeller of which is made to rotate by a shaft actuated by a pulley and by a belt connected to the driving shaft.
It is also known that recirculation of the cooling fluid must be performed at a rate corresponding to the actual cooling requirement determined by the real conditions of use and by the external temperature so as to avoid the constant and needless rotation, at full speed, of devices which draw useful power, increasing the wear of the various component parts and the consumption levels of the vehicle.
It is also known that, in order to solve this problem, friction clutch and parasitic current coupling devices have been proposed, said devices being able to produce two different speeds of rotation - i.e. full speed and slower speed - of the pump shaft.
Examples of these devices are known, for example, from
Although performing their function, these devices nevertheless have drawbacks which limit the application thereof; the first device in that, despite having smaller axial dimensions, it envisages, however, a magnetic induction coupling for the slower speed which is unable to achieve high values of the torque to be unsuitable for high-capacity pumps such as those used in heavy vehicles, in particular of the type having a low engine rpm, but a high number of revolutions of the pump.
The second device instead envisages radial dimensions which, extending beyond the dimensions of the clutch rotor, said rotor being normally incorporated in the pulley connected to the driving shaft, make it difficult to house the pumps in the different engine compartments of the vehicles.
From
The technical problem which is posed, therefore, is that of providing a device for controlling the means for recirculating engine cooling fluids for vehicles and the like, which is able to produce a variation in the speed of rotation of the impeller of the said recirculating means depending on the actual operating requirement of the engine.
Within the scope of this problem it is also required that this device should have small dimensions, in particular radial dimensions, but at the same time should be able to produce high torques also at a slower speed of rotation of the engine so as to be applicable also to high-performance pumps of heavy vehicles with low-revolution engines.
It is also required that the device should be easy and inexpensive to produce and assemble and should be able to be installed easily on the pump body without the need for special adaptation.
These results are obtained according to the present invention by a device for transmitting a rotating movement according to the characteristic features of Claim 1.
Further details may be obtained from the following description of a non-limiting example of embodiment of the subject of the present invention provided with reference to the accompanying drawings, in which:
As shown in
The pump body 11 has, arranged inside it, a sealing bearing 12, coaxial with the shaft 2, and a bearing 13, on the inner race of which the shaft 2 of the impeller is keyed.
The pump body 11 has, keyed onto the outside thereof, a second bearing 40, the outer race 40a of which is integral with a circular ring 21 which is suitably shaped and on the outer circumferential edge of which there is formed a pulley 21a, suitable for engagement with a belt 3 for transmission of the movement to the ring 21.
Since the pulling force of the belt 3 is transmitted to the outer bearing 40 it is possible to limit the size of the inner bearing 13, which is not subjected to dynamic loads, resulting in a longer working life and reduction in the overall dimensions.
The circular ring 21 has an extension in the axial direction 21b which forms the rotor of an electromagnetic coupling 20 which comprises a fixed electromagnet 22 housed inside a corresponding seat of the said rotor 21 and an armature 23 made of friction material and arranged facing the rotor 21 on the opposite side to the electromagnet and integral with a resilient membrane 24 in turn constrained to a driven element consisting of a flange 14 mounted on the shaft 2 by means of a corresponding sleeve 14a.
With this coupling the armature 23 is able to perform movements in the axial direction towards/away from the rotor 21, but is locked as regards relative rotation with respect to the flange 14.
As shown in
The rotor 23 also has, mounted thereon, a conductive support 32a with a magnetizable element 32 which forms the first part of a second Foucault current induction coupling 30, the second part of which is formed by a plurality of small magnets 31 integral with the circular flange 14 connected to the driven shaft 2 so as to be axially opposite the said magnetizable element 32 with a predetermined air gap.
The rotor part 21 with the magnetizable element 32 has interruptions 21c in the magnetic conductivity of the rotor so as to cause suitable annular closing of the magnetic flux lines as shown in
Operation of the pump actuating device is of the conventional type:
It can therefore be seen how with the device according to the invention it is possible to obtain efficient operation of rotating devices such as water pumps for recirculating the cooling fluid of vehicles while maintaining, however, small radial dimensions both of the armature 24 and of the rotor 21.
Owing to this reduction in radial dimensions, together with the arrangement of the armature 23 outside of the rotor 21 in the axial direction, it is possible to obtain a pulley 21a of small diameter with a consequent multiplication of the revolutions transmitted by the belt 3, this making the device, and therefore the pump, suitable also for vehicles with engines which rotate at a low number of revolutions, but require a high speed of rotation of the cooling pump and a high transmission of torque via the friction coupling even though the latter uses an armature/rotor driven surface area smaller than the rotor surface area used for the induction coupling.
In addition to this, the fact that the armature 24 is independent of the coupling 30 improves the operating conditions of the latter since dangerous contact between the magnets integral with the rotor and the support of the magnetizable elements 32 in the event of wear of the said armature is avoided.
The presence of the permanent magnet 60 ensures that, in the event of an electrical failure, the armature is always engaged with the rotor, ensuring recirculation of the cooling fluid ("fail safe" mode).
With this configuration it is possible to obtain operation of the ON/OFF type with a single speed of rotation of the impeller 1 which, otherwise, remains stationary in neutral.
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