WO2013072734A1

WO2013072734A1 - Powered model car with an improved transmission system

Info

Publication number: WO2013072734A1
Application number: PCT/IB2012/002319
Authority: WO
Inventors: Maurizio Ficcadenti
Original assignee: Inovo Design S.R.L.
Priority date: 2011-11-14
Filing date: 2012-11-13
Publication date: 2013-05-23
Also published as: ITTO20111048A1

Abstract

The miniature model car (10; 110; 210) comprises: a transmission system (18) comprising a driving shaft (20), adapted to receive mechanical power from a propulsion engine (16); a rear-wheel assembly (24), which cooperates with the driving shaft (20). The transmission system (18) comprises, furthermore, a pair of rear axle shafts (34), which are connected to the rear-wheel assembly (24); and a pair of one-way couplings (35; 135; 235), each one being suited to kinematically and automatically disconnect a respective rear axle shaft (34) from the driving shaft (20), when the rear axle shaft (34) rotates at a higher speed than the driving shaft (20).

Description

Powered model car with an improved transmission system.

* * *

DESCRIPTION

Technical field

The present invention is relative to a propulsion miniature model car.

More in detail, the present invention is relative to a miniature model car according to the preamble of appended claim 1.

Technological background

The term "propulsion miniature model car" (also called dynamic model car) generally indicates a vehicle that is manufactured in a reduced scale and is provided with an engine, which is able to start the vehicle and keep it in motion. Typically, a propulsion miniature model car can be controlled by means of a remote control, e.g. by means of a radio control .

In particular, propulsion miniature model cars are often used in competitions and actual races, in which the drive and the peak speed of the model car play a crucial role. To this regard, in order to increase the drive performances in acceleration of propulsion miniature model cars with rear-wheel drive, transmission systems are known, which use a driving shaft, which transmits mechanical power to a single rigid rear shaft (technically called "pole"), which is associated to the rear-wheel assembly and rigidly couples the rear wheels of the miniature model car to one another, so as to cause them to rotate together.

The above-mentioned propulsion miniature model cars of the known type, though, have some drawbacks. A drawback consists in the fact that the single rigid shaft or "pole" involves a significant reduction in the performances of the propulsion miniature model car while taking a bend, in particulars in terms of steering during the braking phase to slow down when taking a curve, thus making the change of direction more difficult. As a matter of fact, when ^' a model car takes a bend, in the rear-wheel assembly, the rear wheel that is arranged in an outer position with respect to the curve follows a path having a length that is smaller than the length of the path followed by the inner rear wheel. This situation generates an undesired skid of one of the rear wheels with respect to the rolling plane of the rear-wheel assembly, since the rotation speed of the rear wheels (and of the axle shafts associated thereto) is the same due to the fact that they are rigidly coupled by the single rear shaft.

Summary of the invention

The object of the present invention is to provide a propulsion miniature model car, which is able to solve this and other drawbacks of the prior art and which, at the same time, can be produced in a simple and economic way.

According to the present invention, this and other objects are reached by means of a propulsion miniature model car having the features set forth in appended claim 1.

The appended claims are an integral part of the technical teachings provided in the present description with reference to the invention.

Brief description of the drawings

Further features and advantages of the present invention will be best understood upon perusal of the following detailed description, which is provided by way of example and is not limiting, with reference to the accompanying drawings, which specifically illustrate what follows :

- figure 1 is a plan view from the top of a miniature model car according to a first embodiment of the present invention;

figure 2 is a partial and enlarged prospective view of the rear part of the transmission system and of the rear- wheel assembly of the miniature model car shown in figure 1;

figure 3 is a schematic view in longitudinal section of the rear axle shafts of the miniature model car shown in figures 1 and 2;

- figure 4 is a plan view from the top of a miniature model car according to a second embodiment of the present invention;

figure 5 is a schematic view in longitudinal section of a driving shaft of the miniature model car shown in figure 4 ;

figure 6 is a schematic view in longitudinal section of the rear axle shafts of the miniature model car shown in figures 4 and 5 ;

figure 7 is a plan view from the top of a miniature model car according to a third embodiment of the present invention; and

figure 8 is a schematic view in longitudinal section of the rear axle shafts of the miniature model car shown in figure 7.

Detailed description of the invention With reference, in particular, to the figures from 1 to 3, number 10 indicates, as a whole, a propulsion miniature model car according to a first illustrative embodiment of the present invention. Preferably, miniature model car 10 is of the racing type, for example with four driving wheels.

In the first embodiment shown in the figures, propulsion miniature model car 10 comprises a support structure or framework 12. Preferably, framework 12 comprises a platform 14, which is adapted to support the components of miniature model car 10. By way of example, framework 12 generates, as a whole, a structure of the "buggy" type.

Miniature model car 10 comprises an engine 16, preferably an internal combustion engine. In figure 1, engine 16 is represented, in a schematic manner, only by a rectangle drawn with a broken line. Preferably, engine 16 is supported by framework 12, for example on platform 14. By way of the example, engine 16 is a two- stroke internal combustion engine. In other embodiment versions, engine 16 can also be of a different type,^' for example an electric moto .

Model car 10 comprises, furthermore, a transmission system, which is indicated, as a whole, by number 18 and is supported by framework 12, for example on platform 14. Transmission system 18 comprises a driving shaft 20, adapted to receive mechanical power from engine 16. In the embodiment shown in the figures, driving shaft 20 is supported, so as to rotate, by framework 12, for example on platform 14, in manner that is known to a skilled person. Preferably, driving shaft 20 is arranged in a transverse position with respect to the direction of the longitudinal extension of framework 12.

In the embodiment shown in the figures, model car 10 comprises, furthermore, a front -wheel assembly 22 and a rear-wheel assembly 24. By way of example, front-wheel assembly 22 comprises a pair of front wheels 26, while rear-wheel assembly 24 comprises a pair of rear wheels 28. The connection between front wheels 26 and framework 12, as well as the connection between rear wheels 28 and framework 12, is advantageously performed by means of suspensions (not shown) of a type that is known to a skilled person.

In the embodiment shown in the figures, model car 10 has a four wheel drive, since front -wheel assembly 22 and rear-wheel assembly 24 both cooperate with driving shaft 20 to receive mechanical power. With reference, in particular, to figure 1, in the transmission system 18, the structure and the function of the mechanical connections for the transfer of mechanical power between the driving shaft 20 and front-wheel assembly 22 are substantially known in the technical field and, therefore, are not part of the subject-matter of the present invention. As a consequence, said structure and function will not be described in detail hereinafter. In other embodiment versions, model car 10 can have an exclusively rear-wheel drive and, therefore, driving shaft 20 can deliver power only to rear-wheel assembly 24.

Model car 10 comprises, furthermore, a braking system 29, adapted to act on transmission system 18. Preferably, braking system 29 is of the mechanical type.

In the embodiment shown in the figures, transmission system 18 comprises, furthermore, a coupling 30 and a gearbox 32, which cooperate with one another so as to couple to output of engine 16 and driving shaft 20. Preferably, coupling 30 cooperates and is aligned with the output shaft (not numbered) of engine 16. In the embodiment shown in the figures, said output shaft is arranged parallel to driving shaft 20. On the other hand, gearbox 32 presents a first group of gears (not numbered) , which cooperates and is aligned with coupling 30, and a second group of the gears (not numbered, which cooperates with said first group and is coupled to (and aligned with) driving shaft 20.

Transmission system 18 comprises, furthermore, a pair of rear axle shafts 34, which are connected to rear-wheel assembly 24; this means that each one of them is rigidly connected is a known manner to a respective rear wheel 28.

Transmission system 18 comprises, furthermore, a pair of one-way couplings 35, in which each one of them is associated to a respective rear axle shaft 34; this means that each one-way coupling 35 is adapted to kinematically and automatically disconnect a respective rear axle shaft 34 from driving shaft 20, when respective rear axle shaft 34 rotates at a higher speed than driving shaft 20, e.g. when model car 10 takes a bend or braking system 29 acts on transmission system 18. To sum up, one-way coupling 35 acts between rear axle shaft 34 associated thereto and driving shaft 20 as a "overrunning coupling " or "freewheel" device. In this way, during the acceleration phase, one can obtain the advantage of having an optimal drive (similar to the one that can be obtained with a pole used as rigid connection between rear wheels 28) , while, during the braking phase to slow down when taking a curve, one can achieve the advantage of a better road holding by kinematically disconnecting rear axle shafts 34 from driving shaft 20 (and consequently from one another) , so as to allow rear wheels 28 to roll on the ground with independent speeds .

In the embodiment shown in the figures, transmission system 18 comprises a torque transferring device, adapted to transfer mechanical power from driving shaft 20 to each one of rear axle shafts 34. Preferably, the torque transferring device comprises a pair of mechanisms, in which, for example, each one of them comprises a drive pulley 36, which is coupled to driving shaft 20, a rear pulley 38, which is coupled to a respective rear axle shaft 34, and a belt 40, which connects drive pulley 36 and rear pulley 38. Advantageously, pulleys 36, 38 are provided with a respective external toothing, while belt 40 is provided with an internal toothing, which meshes with the external toothing of pulleys 36, 38.

In the embodiment shown in the figures, braking system 29 comprises a mobile element 44, which kinematically connects rear axle shafts 34 to the above-mentioned torque transferring device. Preferably, mobile element 44 rigidly connects the two mechanisms to one another, for example by coupling the two rear pulleys 38 to one another, so as to cause them to rotate together. Braking system 29 comprises, furthermore, a braking organ 45, adapted to exert a friction on mobile element 44, for example by reducing the rotation speed of rear pulleys 38.

Preferably, each one of rear axle shafts 34 is coupled to mobile element 44, so as to rotate together, by means of a respective one-way coupling 35. Each one of the one-way couplings 35 is mounted between the respective rear axle shaft 34 and mobile element 44, thus directly connecting them to one another.

In the embodiment shown in the figures, one-way coupling 35 comprises a first portion 35a, which is rigidly connected to mobile element 44, and a second portion 35b, which is rigidly connected to the respective axle shaft 34 and, during its rotation, can be decoupled (thanks to known coupling organs that are not shown) from first portion 35b, when the rotation speed of the respective axle shaft 34 is higher that the rotation speed of mobile element 44 (and, therefore, of driving shaft 20) . Preferably, first portion 35a has a hollow tubular shape and houses in its inside second portion 35b.

Preferably, mobile element 44 comprises a disc 46 and a pair of axial extensions 48, which laterally project from opposite sides of disc 46. In the embodiment shown in the figures, axial extensions 48 centrally project from disc 46 and both rear pulleys 38 are coupled around them. Preferably, each one of extensions 48 extends through both rear pulleys 38.

In the embodiment shown in the figures, each one of one-way couplings 35 is coupled between respective lateral extension 48 and respective axle shaft 34. Preferably, each one of axial extensions 48 defines the shape of a tumbler. By way of example, each one of the cavities of axial extensions 48 houses one-way coupling 35. In the embodiment shown in the figures, first portion 35a is fixed in the cavity of respective axial extension 48. Preferably, second portion 35b is substantially cup-shaped and, for example, houses in its inside respective axle shaft 34, advantageously a substantially spherical end thereof.

In the embodiment shown in the figures, mobile element 44 is supported, on framework 12, by a pair of rotational supports 50 (figure 3), for example rolling bearings. Preferably, rotation supports 50 are supported by platform 13. In the embodiment shown in the figures, rotational supports 50 are coupled around axial extensions 48.

A brief description of the operation of model car 10 will now be provided hereinafter.

In order to do so, model car 10 will be now considered during an acceleration phase while running on a straightway. Engine 16 delivers mechanical power to transmission system 18 by means of coupling 30 and of gearbox 32. Therefore, driving shaft 20 controls the rotation of the torque transferring device in correspondence to its two mechanisms. In this way, both drive pulleys 36 rotate and drag belts 40, which cause the rotation of rear pulleys 38, which are rigidly connected to mobile element 44. Mobile element 44, thus, assumes the same rotation speed of rear pulleys 38 and causes the rotation of rear axle shafts 34 in an integral manner with relative rear wheels 28. In this condition, the one-way couplings 35 keep rear axle shafts 34 coupled to mobile element 44, so as to cause them to rotate together, thus kinematically connecting said rear axle shafts 34 to driving shaft 20. As a consequence, rear axle shafts 34 act as a single rigid shaft, which is caused to be integral by mobile element 44. Therefore, the drive exerted , by rear- wheel assembly 24 is exploited in an optimal manner during the acceleration. Model car 10 should now be considered in a braking phase to slow down when taking a curve. Braking organ 45 acts on mobile element 44, thus exerting a friction on the latter, influencing the torque transferring device, and dissipating a portion of the mechanical power delivered by its two mechanisms. Therefore, there is a decrease in the rotation speed of driving shaft 20, which is kinematically connected to mobile element 44 by means of rear pulleys 38, belts 40, and drive pulleys 36. On the contrary, rear wheels 28, which are rigidly connected to axle shafts 34, continue to roll on the ground due to inertia with respective rotations speeds that are different form one another. Both the rotation speeds mentioned above assume a value that is higher than the rotation speed of mobile element 44 (and, therefore, of driving shaft 20) . In this condition, one-way couplings 35 decouple rear axle shafts 34, during their rotation, from mobile element 44, thus kinematically and automatically disconnecting them from one another and from driving shaft 20. In this way, each assembly consisting of rear axle shaft 34 and of respective rear wheel 28 can act irrespective of the other assembly and of driving shaft 20. As a consequence, the road holding offered by rear-wheel assembly 24 when taking a curve is exploited in an optimal manner.

With reference to the figures from 4 to 6 , number 110 indicates, as a whole, a model car according to a second embodiment of the present invention.

Details and elements that are similar to those of the embodiment described above or fulfill a similar function are associated to the same alphanumeric references. For the sake of brevity, the description of these details and elements will not be repeated below, but reference is made to what was previously explained in the description of the first embodiment.

As to those details and elements that present substantial differences with respect to the first embodiment in terms of structure and/or function, they are associated to the same alphanumeric references, but with the addition of 100.

In model car 110, the torque transferring device is substantially similar to the one described in the first embodiment .

Braking system 29 comprises a pair of mobile elements 144, which cooperate with said torque transferring device. Preferably, furthermore, each one of the mechanisms is connected to a respective mobile element 144. By way of example, each one of mobile elements 144 is rigidly coupled to a respective rear pulley 38.

In the embodiment shown in the figures, the torque transferring device is coupled to driving shaft 20, so as to rotate with it, by means of one-way couplings 135. In this case, each one of the mechanisms is coupled to driving shaft 20, so as to- rotate with it, by means of a respective one-way coupling 135. Each one of one-way couplings 135, therefore, is mounted between the respective mechanism and driving shaft 20, thus directly connecting them to one another .

Preferably, each drive pulley 36 is coupled to driving shaft 20, so as to rotate with it, by means of respective one-way coupling 135. Each one of one-way couplings 135 is mounted between respective drive pulley 36 and driving shaft 20, thus directly connecting them to one another. In the embodiment shown in the figures, each mobile element 144 comprises a disc 146 and a respective lateral extension 148.

Each lateral extension 148 is a tubular section, which axially extends through disc 146 in a central portion of its. Preferably, each mobile element 144 is supported, during its rotation, by a pair of bearings 50, which are arranged on opposite sides of lateral extension 148 with respect to disc 146.

Each one of axle shafts 34 is coupled to respective mobile element 144. Preferably, each one of axle shafts 34 is rigidly connected to lateral extension 148 of respective mobile element 144. Preferably, each one of axle shafts 34 is rigidly coupled in the cavity defined by lateral extension 148 of respective mobile element 144.

The operation of model car 110 is similar to the one described for the first embodiment, in particular in terms of function and behavior of one-way couplings 136, and, therefore, it will not be repeated hereinafter.

According to alternative embodiment versions (not shown) of this second embodiment, a skilled person can also choose to insert one-way couplings 135 in different positions of transmission system 18. For example, according to one version, similarly to what described for the first embodiment, both one-way couplings 135 can couple both mobile elements 144 to respective rear axle shafts 34, so as to cause them to rotate together, while the torque transferring device (for example both mechanisms, preferably in correspondence to respective drive pulleys 36) is rigidly connected to driving shaft 20. Furthermore, according to a further version, both one-way couplings 135 can couple the torque transmitting device (for example both mechanisms, preferably in correspondence to respective rear pulleys 38) to both mobile elements 144, so as to cause them to rotate together, while both mobile elements 144 are rigidly connected to rear axle shafts 34.

With reference to figures from 7 and 8, number 210 indicates, as a whole, a model car according to a third embodiment of the present invention.

Details and elements that are similar to those of the first embodiment or fulfill a similar function are associated to the same alphanumeric references. For the sake of brevity, the description of these details and elements will not be repeated below, but reference is made to what was previously explained.

As to those details and elements that present substantial differences with respect to the first embodiment in terms of structure and/or function, they are associated to the same alphanumeric references, but with the addition of 200.

As to those details and elements that were not provided in the first embodiment, the reference numbers associated thereto correspond to the continuation of the numbering used for the first embodiment, with the addition of 200.

In model car 210, the torque transferring device comprises a single mechanism, which, for example, comprises a single drive pulley 236, which is coupled to driving shaft 20, a single rear pulley 238, which is kinematically connected to rear axle shafts 34, and a belt 240, which connects drive pulley 236 and rear pulley 238. In the embodiment shown in the figures, braking system 29 comprises a pair of mobile elements 244, in which each of them is coupled to the torque transferring device, so as to rotate with it, by means of respective one-way coupling 235.

Preferably, each mobile element 244 is coupled to the single mechanism, so as to rotate with it, by means of respective one-way coupling 235. Each one of one-way couplings 235 is mounted between the respective mechanism and respective mobile element 244, thus directly connecting them to one another.

Advantageously, each mobile element 244 is coupled to rear pulley 238, so as to rotate with it, by means of a respective one-way coupling 235. Each one of one-way couplings 235 is mounted between single rear pulley 238 and respective mobile element 244, thus directly connecting them to one another.

In the embodiment shown in the figures, each mobile element 244 comprises a disc 246 and an inner lateral extension 252, which axially projects from disc 246, for example form a central portion of the latter. Preferably, each inner lateral extension 252 is coupled to the torque transferring device (in this case, to its only mechanism) by means of the respective one-way coupling 235.

By way of example, rear pulley 238 is coupled, preferably on laterally opposite sides, to both inner lateral extensions 252, so as to rotate with them, by means of one-way couplings 235. In the embodiment shown in the figures, rear pulley 238 presents a tubular section 254, which centrally extends through it and is oriented in an axial direction. Advantageously, inner lateral extensions 252 are coupled, so as to rotate therewith, to parts of tubular section 254, which are axially opposite with respect to disc 246. Preferably, each inner lateral extension 252 comprises a pin.

In the third embodiment, each mobile element 244 is rigidly connected to respective axle shaft 34. Preferably, each mobile element 244 comprises an outer lateral extension 248, which axially projects from disc 246 on an opposite side with respect to inner lateral extension 252. Outer lateral extension 248 is substantially shaped as a tumbler and presents a cavity in which axle shaft 34 is firmly coupled, for example in correspondence to a spherical end of the latter.

According to alternative embodiment versions (not shown) of this third embodiment, a skilled person can also choose to insert one-way couplings 235 in different positions of transmission system 18. By way of example, similarly to what described for the first embodiment, both one-way couplings 235 can couple both mobile elements 244 to respective rear axle shafts 34, so as to cause them to rotate together, while the torque transferring device (for example only rear pulley 238) is rigidly connected to both mobile elements 244.

Naturally, the principle of the present invention being set forth, the embodiments and the implementation details can be widely changed with respect to what described above and shown in the drawings as a mere way of non- limiting example, without in this way going beyond the scope of protection provided by the accompanying claims.

For example, each mechanism has been described as a device comprising a plurality of pulleys and a belt; though, it is also possible to use mechanisms and apparatuses of a different type. Furthermore, a skilled person clearly understands that, if possible, the technical features differentiating the different versions of the embodiments described and illustrated above can freely be exchanged between said versions and embodiments.

Claims

1. Propulsion miniature model car (10; 110; 210) comprising

a transmission system (18) comprising a driving shaft (20), adapted to receive mechanical power from a propulsion engine ( 16 ) ;

a rear-wheel assembly (24), which cooperates with said driving shaft (20) ; and

said model car being characterized in that said transmission system (18) comprises, furthermore,

a pair of rear axle shafts (34), which are connected to the rear-wheel assembly (24); and

a pair of one-way couplings (35; 135; 235), each of them being adapted to kinematically and automatically disconnect a respective rear axle shaft (34) from the driving shaft (20) , when said respective rear axle shaft (34) rotates at a higher speed than said driving shaft (20) .

2. Model car (10; 110; 210) according to claim 1 , wherein said transmission system comprises a torque transferring device (36, 38, 40; 236, 238, 240), which is adapted to transfer mechanical power from said driving shaft (20) to each one of said rear axle shafts (34); said model car comprising, furthermore, a braking system (29) comprising at least one mobile element (44; 144; 244), which kinematically connects said rear axle shafts (34) to said torque transferring device (36, 38, 40; 236, 238, 240), and comprising, furthermore, a braking organ (45) , which is adapted to exert a friction on said at least one mobile element (44; 144; 244) .

3. Model car (10; 110; 210) according to claim 2, wherein at least one of said one-way couplings (35; 135; 235) couples, so as to cause them to rotate together:

said at least one mobile element (44) and a respective rear axle shaft (34); or

said driving shaft (20) and said torque transferring device (36, 38, 40); or

said torque transferring device (236, 238, 240) and said at least one mobile element (44) .

4. Model car (10) according to claim 2 or 3 , wherein said braking system (29) comprises a mobile element (44), which is kinematically connected to said torque transferring device (36, 38, 40); at least one of said rear axle shafts

(34) being coupled to said mobile element (44), so as to rotate with it, by means of a respective one-way coupling

(35) .

5. Model car (10) according to claim 4, wherein said torque transferring device comprises a pair of mechanisms (36, 38, 40), which are coupled to said mobile element (44), so as to rotate with it.

6. Model car (110; 210) according to claim 2 or 3, wherein said braking system (29) comprises a pair of mobile elements (144; 244), which are kinematically connected to said torque transferring device (36, 38, 40 ; 236, 238, 240) .

7. Model car (110) according to claim 6, wherein said torque transferring device comprises a pair of mechanisms (36, 38, 40), each of them being kinematically connected to a respective mobile element (144) .

8. Model car (110) according to claim 7, wherein at least one of said mechanisms (36, 38, 40) is coupled to said driving shaft (20), so as to rotate with it, by means of a respective one-way coupling (135) .

9. Model car (210) according to claim 6, wherein said torque transferring device comprises a mechanism (236, 238, 240) , which kinematically connects said mobile elements (244) to one another.

10. Model car (210) according to claim 9, wherein at least one of said mobile elements (244) is coupled to said mechanism (236, 238, 240), so as to rotate with it, by means of a respective one-way coupling (235) .

11. Model car (10; 110; 210) according to any of the claims 5 and from 7 to 10, wherein at least one said mechanisms comprises a drive pulley (36; 236), which is kinematically connected to said driving shaft (20), a rear pulley (38; 238), which is kinematically connected to said at least one mobile element (144; 244), and a belt (40; 240), which connects said driving shaft (36; 236) and said rear pulley (238) .