Patent Description:
The present invention is particularly applicable to vehicles and other machines driven by electric motors.

In the motor vehicle field, there are known transmission systems capable of transmitting the driving torque generated by the motor to the vehicle wheels, for the purpose of propulsion, and to various auxiliary components of the vehicle such as hydraulic pumps, cooling pumps, air conditioning compressors, etc., for the purpose of driving these elements.

In vehicles with internal combustion engines, the driving shaft, as is known, has a single direction of rotation. In such vehicles, the auxiliary components driven by the motor are therefore configured so that they also operate with a single direction of rotation, while suitable transmission components (usually called "reverse gear"), for reversing the rotary motion before transmitting it to the wheels, are required in order to transmit a reverse motion to the vehicle.

In vehicles with electric motors, however, it is possible to reverse the direction of rotation of the motor, and therefore of the driving shaft. In these vehicles, therefore, it is advantageous to attach the driving shaft directly to the system for transmitting the motion to the wheels, so that forward or reverse motion can be transmitted purely by varying the direction of rotation of the electric motor, without the need for the "reverse gear" components used in vehicles with internal combustion engines. However, since the auxiliary components must be driven at the same time, the problem arises of enabling them to be powered even when the electric motor reverses its direction of rotation to move the vehicle in reverse.

A possible solution to this problem is to use auxiliary components that can operate in both directions of rotation. In the case of pumps, this requires, for example, the reversal of the suction and delivery lines, provided that the pumping element, that is to say the rotor that sucks the fluid from the suction line and directs it into the delivery line, allows the reversal of motion. In most case, this solution is unfavourable in economic terms, since it requires the provision of more complex auxiliary components, to be provided specifically for electric motor vehicles. For example, in the case of pumps, reversing valves will have to be used for the suction and delivery channels.

Document <CIT> discloses a drive conversion mechanism including a rotatably mounted output shaft, a pair of output gears mounted on the output shaft so as to rotate independent of one another and relative to the output shaft and being displaced from each other axially along the output shaft, and a pair of one-way clutches arranged about the output shaft. Each clutch is connected to one of the output gears and extends about the output shaft in respective orientations that are the reverse of each other such that the one-way clutches can only drivingly engage the output shaft at alternate times, and thus not at the same time, so as to cause the output shaft to rotate in a same single direction as the output gears are driven in opposite directions relative to each other by an input train of constantly meshed input drive and idler gears.

Document <CIT> discloses a motor vehicle auxiliary unit arrangement, in which there are provided a motor vehicle auxiliary unit (<NUM>) with a transmission arrangement (<NUM>) is arranged in a drive train (<NUM>) of a motor vehicle, a transmission input member (<NUM>, <NUM>), which is connected in terms of drive to the drive train (<NUM>), and at least one transmission output member (<NUM>, <NUM>), which is connected in terms of drive to a rotary member (<NUM>) of the motor vehicle auxiliary unit (<NUM>). The transmission input member (<NUM>, <NUM>) can be driven both in a first direction of rotation and in a second direction of rotation. The transmission arrangement (<NUM>) having a first freewheel arrangement (<NUM>, <NUM>), (<NUM>) which, when the transmission input member (<NUM>, <NUM>) rotate in a first direction, provides power transmission for driving the rotary member (<NUM>) in the second direction of rotation, and a second freewheel arrangement (<NUM>) which, when the transmission input member (<NUM>, <NUM>) rotates in a second direction, transmits a force to drive the rotary member (<NUM>) in the second direction of rotation.

Consequently there is a need to enable auxiliary components similar to those used in internal combustion engine vehicles to be used in electric vehicles, thus benefiting from advantageous production costs due to the effects of scale, while also benefiting from the aforementioned advantage of having the electric motor attached directly to the system for transmitting motion to the vehicle wheels, without the need for appropriate reversing components. The aforesaid advantage relating to production costs is particularly evident in the case of electric vehicles developed from pre-existing vehicles with internal combustion engines.

The object of the present invention is to meet the aforesaid need by providing a mechanical transmission system capable of transferring a driving torque to auxiliary components of a vehicle.

This and other objects are achieved with the mechanical transmission system as claimed in the attached claims.

The transmission system according to the present invention is a system configured for transmitting a driving torque from a driving wheel to a driven output wheel.

The transmission system comprises a first transmission stage of the freewheel type, comprising a first wheel engaged with the driving wheel, a second wheel, coaxial with said first wheel, and a first coupling mechanism between the first and the second wheel. This first coupling mechanism is configured for fixing the aforesaid first and second wheels to each other, creating what is known as the engaged state, when the first wheel rotates in a first direction of rotation (known as the engagement direction), and for disengaging the first wheel from the second wheel, creating what is known as the slip state, when the first wheel rotates in a second direction of rotation (opposed to the engagement direction).

According to the invention, the second wheel of the first transmission stage is engaged with the driven output wheel.

The transmission system further comprises an intermediate driven wheel, engaged with the driving wheel, and a second transmission stage of the freewheel type. This second transmission stage comprises a third wheel, engaged with the intermediate driven wheel, a fourth wheel, coaxial with said third wheel, and a second coupling mechanism between the third and the fourth wheel. This second coupling mechanism is configured for fixing the third and fourth wheels of the aforesaid second transmission stage to each other, creating what is known as the engaged state, when the third wheel of the second transmission stage rotates in a first direction of rotation (known as the engagement direction), and for disengaging the third wheel from the fourth wheel, creating what is known as the slip state, when the third wheel of the second transmission stage rotates in a second direction of rotation (opposed to the engagement direction).

According to the invention, the fourth wheel of the second transmission stage is engaged with the driven output wheel.

Additionally, the first direction of rotation (engagement direction) of the first transmission stage and the first direction of rotation (engagement direction) of the second transmission stage are coincident directions (both clockwise or both anticlockwise).

Because of the transmission system according to the invention, the rotation of the driving wheel in one direction or the opposite direction causes the driven output wheel to always rotate in the same direction. The transmission system therefore acts as an automatic rotation inverter, such that the incoming direction of rotation (of the driving wheel) is recognized and converted into an output direction of rotation (of the driven output wheel) which is predefined and unique.

The transmission system according to the invention is applicable to electric motor vehicles. In an electric motor vehicle comprising the transmission system according to the invention, the driving shaft of the electric motor may advantageously be attached directly to the components for transmitting motion to the vehicle wheels, so that the forward or reverse motion may be transmitted to the wheels simply by reversing the direction of rotation of the driving shaft. The driving wheel of the transmission system is also driven in rotation by the driving shaft of the electric motor, and at least one auxiliary user component of the vehicle is driven in rotation by the driven output wheel of the transmission system. Thus the auxiliary component is always made to rotate in the same direction of rotation, regardless of the direction of rotation of the electric motor.

The present invention is also applicable in fields other than that of motor vehicles, being applicable to all fields (the industrial machinery field, for example) in which user elements always have to be driven in the same direction of rotation, regardless of the direction of rotation of the electric motor powering them.

These and other characteristics and advantages of the present invention will be evident from the following description of preferred embodiments, provided by way of nonlimiting example with the aid of the appended figure, in which elements indicated by the same or a similar reference numeral indicate elements that have the same or a similar function and construction, and in which:
<FIG> shows a front view of a mechanical motion transmission system according to the present invention.

A mechanical transmission system <NUM> according to an embodiment of the present invention is described below with reference to <FIG>.

The transmission system <NUM> is a gear mechanism capable of transferring a driving torque from a driving wheel <NUM> which, in turn, is driven, preferably, by a motor (not shown), such as an electric motor, to a driven output wheel <NUM> which, in turn, is capable of powering, preferably, one or more user components (not shown).

According to the invention, the transmission system <NUM> comprises a first transmission stage <NUM> of the freewheel (or overrun engagement) type, the operating principle of which is known.

This transmission stage <NUM> comprises a first wheel <NUM>, engaged with the driving wheel <NUM>, a second wheel <NUM>, coaxial with the aforesaid first wheel <NUM>, and a coupling mechanism <NUM> between the first wheel <NUM> and the second wheel <NUM>. The coupling mechanism <NUM> is configured for fixing the first wheel <NUM> and the second wheel <NUM> to each other (in what is known as the engaged state) when the first wheel <NUM> rotates in a first direction of rotation C' (called the engagement direction), and for disengaging the first wheel <NUM> from the second wheel <NUM> (in what is known as the slip state) when the first wheel <NUM> rotates in a second direction of rotation C" (opposed to the engagement direction C').

According to the operating principle of the freewheel transmission, it should be noted, for the sake of completeness, that the aforementioned slip state is also present, as is known, when the first wheel <NUM> rotates in the first direction of rotation C' and the second wheel <NUM> also rotates in the first direction of rotation C', but more rapidly than the first.

In other words, the first freewheel transmission stage <NUM> is configured for transmitting the driving torque from the first wheel <NUM> to the second wheel <NUM> in the first direction of rotation C' (engagement direction), while it becomes disengaged if the direction of rotation of the first wheel <NUM> is reversed, or if the second wheel <NUM> starts to rotate in the first direction of rotation C' more rapidly than the first wheel <NUM>.

The second wheel <NUM> of the first freewheel transmission stage <NUM> is engaged with the driven output wheel <NUM>.

Consequently the driving torque is transmitted from the driving wheel <NUM> to the driven output wheel <NUM> through the first freewheel transmission stage <NUM> when the driving wheel <NUM> rotates in a direction A opposed to the engagement direction C' of the first transmission stage <NUM>. Conversely, there is no transmission of the driving torque to the driven output wheel <NUM> through the first transmission stage <NUM> when the driving wheel <NUM> rotates in a direction B identical to the engagement direction C' of the first transmission stage <NUM>.

It is also evident that the transmission of the driving torque from the driving wheel <NUM> to the driven output wheel <NUM> through the first transmission stage <NUM> causes a rotation of the driven output wheel <NUM> only in a direction of rotation D identical to the direction of rotation A of the driving wheel <NUM>.

According to the invention, the transmission system <NUM> further comprises an intermediate driven wheel <NUM>, engaged with the driving wheel <NUM>, and a second transmission stage <NUM> of the freewheel (or overrun engagement) type, similar to the first transmission stage <NUM> described above. Therefore, the second transmission stage <NUM> also comprises a third wheel <NUM> and a fourth wheel <NUM>, coaxial with the third wheel <NUM>, and a second coupling mechanism <NUM> between the third wheel <NUM> and the fourth wheel <NUM>.

The third wheel <NUM> of the second transmission stage <NUM> is engaged with the intermediate driven wheel <NUM>, which therefore acts as an idle wheel; in other words it causes the third wheel <NUM> of the second transmission stage <NUM> to rotate in the opposite direction to the driving wheel <NUM>.

Similarly to what has been illustrated for the first transmission stage <NUM>, the second coupling mechanism <NUM> between the third wheel <NUM> and the fourth wheel <NUM> of the second transmission stage <NUM> is configured for fixing the third wheel <NUM> and the fourth wheel <NUM> to each other (in what is known as the engaged state) when the third wheel <NUM> rotates in a first direction of rotation G' (called the engagement direction), and for disengaging the third wheel <NUM> from the fourth wheel <NUM> (in what is known as the slip state) when the third wheel <NUM> rotates in a second direction of rotation G" (opposed to the engagement direction G').

In this case also, according to the operating principle of the freewheel transmission, it should be noted that the aforementioned slip state is also present, as is known, when the third wheel <NUM> rotates in the first direction of rotation G' and the fourth wheel <NUM> also rotates in the first direction of rotation G', but more rapidly than the first.

According to the invention, the first direction of rotation C' (that is to say the engagement direction) of the first transmission stage <NUM> and the first direction of rotation G' (that is to say the engagement direction) of the second transmission stage <NUM> are coincident directions; that is to say, they are both clockwise or both anticlockwise. With particular reference to the embodiment of <FIG> , the aforesaid engagement directions C', G' are anticlockwise.

According to the invention, the fourth wheel <NUM> of the second freewheel transmission stage <NUM> is engaged with the driven output wheel <NUM>.

Consequently, the driving torque is transmitted from the driving wheel <NUM> to the driven output wheel <NUM> through the intermediate driven wheel <NUM> and the second freewheel transmission stage <NUM> when the driving wheel <NUM> rotates in a direction B identical to the engagement direction G' of the second transmission stage <NUM>. Conversely, there is no transmission of the driving torque to the driven output wheel <NUM> through the second transmission stage <NUM> when the driving wheel <NUM> rotates in a direction A opposed to the engagement direction G' of the second transmission stage <NUM>.

It is also evident that the transmission of the driving torque from the driving wheel <NUM> to the driven output wheel <NUM> through the intermediate driven wheel <NUM> and the second transmission stage <NUM> causes a rotation of the driven output wheel <NUM> only in a direction of rotation D opposed to the direction of rotation B of the driving wheel <NUM>.

Because of the transmission system <NUM> as a whole, therefore, the rotation of the driving wheel <NUM> in a direction A or in the opposite direction B causes the driven output wheel <NUM> to always rotate in the same direction D. This direction coincides with the direction of rotation A of the driving wheel <NUM> in the embodiment shown in <FIG> , but could alternatively coincide with the direction of rotation B by reversing the engagement direction of both of the transmission stages <NUM> and <NUM>.

According to the embodiment of the invention shown in <FIG> , the coupling mechanisms <NUM> and <NUM> of the freewheel transmission stages <NUM> and <NUM> are what are known as shape coupling mechanisms, of a known type, each of which comprises a first and second pawl <NUM>, <NUM>, respectively, said first and second pawl being hinged on the first and third wheel <NUM>, <NUM> of the transmission stage, respectively. This first and second pawl <NUM>, <NUM> are configured for bearing against a first and second set of teeth 17a, 24a formed in the second and fourth wheel <NUM>, <NUM>, respectively, if the first and third wheel <NUM>, <NUM> rotate in the engagement direction of rotation C', G' (in other words, in the anticlockwise direction, in the embodiment of <FIG>), so that the first and third wheel <NUM>, <NUM> drive the second and fourth wheel <NUM>, <NUM> in rotation, respectively. Conversely, if the first and third wheel <NUM>, <NUM> rotate in the direction of rotation C", G", opposed to the engagement direction C', G', the first and second pawl <NUM>, <NUM> slide over the first and second set of teeth 17a, 24a, respectively, and jumps from one tooth to another, so that the first and third wheel <NUM>, <NUM> do not drive the second and fourth wheel <NUM>, <NUM> in rotation, respectively, and the second and fourth wheel therefore remain idle. Additionally, a first and a second spring <NUM>, <NUM> act on the first and second pawl <NUM>, <NUM>, respectively, so as to push the first and second pawl against the first and second set of teeth 17a, 24a, respectively, and then return the first and second pawls into the seats 17b, 24b between one tooth and another. Alternatively, the first and second pawls, instead of being hinged and impelled by a spring, are attached in a fixed manner to the first and third wheel <NUM>, <NUM>, respectively and are made of elastic material, so as to return automatically into the seats 17b, 24b between one tooth and another after sliding over a tooth 17a, 24a.

For the sake of completeness, it should be noted that the coupling mechanism <NUM>, <NUM> described above also causes the pawls <NUM>, <NUM> to slide and jump from one tooth to another when the first and third wheel <NUM>, <NUM> rotate in the engagement direction C', G' and the second and fourth wheel <NUM>, <NUM> rotate in the same direction of rotation C', G' more rapidly than the first and third wheel <NUM>, <NUM>.

According to further embodiments of the invention (not shown), the coupling mechanisms of the freewheel transmission stages may be constructed in other known ways. For example, coupling mechanisms known as friction couplings may be used. An example of such a coupling mechanism, which is known, is the cam-type freewheel, based on the use of contact bodies called cams, which, being positioned between an inner first wheel and an outer second wheel of the transmission stage, engage in suitable surfaces of the wheels, called tracks, in such a way that the frictional forces exchanged with them allow the relative motion of the two wheels in one direction and make them fixed in the other direction. A further example of a friction coupling mechanism is the roller freewheel, which uses rollers housed between an inner first wheel and an outer second wheel of the transmission stage. For each roller, the outer profile of the inner wheel has an ascending ramp. When the direction of rotation of the outer wheel lies in the ascending direction of the ramp, the rollers tend to move outwards, locking the outer wheel to the inner wheel by friction. In the opposite direction, the rollers are pressed into corresponding seats, and do not interfere with the relative motion of the two wheels.

The wheels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the transmission system <NUM> are preferably gear wheels with external teeth 11a, 13a, 14a, 18a, 20a, 21a, 25a (shown purely schematically in the figures). In this case, the overall transmission ratio of the transmission system is defined by the ratio between the number of teeth of the driving wheel <NUM> and the number of teeth of the driven output wheel <NUM>.

Alternatively, the wheels are non-toothed wheels (known as friction wheels), in which transmission takes place by the friction developed in the coupling.

The transmission system <NUM> according to the present invention acts as an automatic rotation inverter, such that the incoming direction of rotation A or B (of the driving wheel <NUM>) is recognized and converted into an output direction of rotation D (of the driven output wheel <NUM>) which is predefined and unique.

The transmission system <NUM> proposed by the present invention may therefore be advantageously used for transferring the driving torque generated by an electric motor to a user component, by driving the driving wheel <NUM> of the transmission system <NUM> by means of the driving shaft of the electric motor and powering the user component by means of the driven output wheel <NUM> of the transmission system <NUM>, with the result that the user component is always driven in the same direction of rotation, regardless of the direction of rotation of the motor.

A particular application of the transmission system that has been described is therefore an application to electric motor vehicles, in which, because of this transmission system, the driving shaft of the electric motor may advantageously be attached directly to the components for transmitting motion to the vehicle wheels (so that the forward or reverse motion may be transmitted to the wheels simply by reversing the direction of rotation of the driving shaft), while the auxiliary components (such as hydraulic pumps, cooling pumps, air conditioning compressors, etc.) can be driven so that they always rotate in the same direction of rotation, independently of the direction of rotation of the electric motor.

Other examples of application may be provided, for example in the field of industrial machinery driven by electric motors.

Claim 1:
Transmission system for transmitting a driving torque from a driving wheel (<NUM>) to a driven output wheel (<NUM>),
wherein it comprises a first transmission stage (<NUM>) of the freewheel type, comprising a first wheel (<NUM>) engaged with the driving wheel (<NUM>), a second wheel (<NUM>) coaxial with said first wheel (<NUM>), and a first coupling mechanism (<NUM>) between the first wheel (<NUM>) and the second wheel (<NUM>) configured for fixing said first wheel (<NUM>) and second wheel (<NUM>) to each other when the first wheel (<NUM>) rotates in a first direction of rotation (C') and for disengaging the first wheel (<NUM>) from the second wheel (<NUM>) when the first wheel (<NUM>) rotates in a second direction of rotation (C"), wherein said second wheel (<NUM>) of the first transmission stage (<NUM>) is engaged with the driven output wheel (<NUM>),
and wherein it comprises an intermediate driven wheel (<NUM>), engaged with the driving wheel (<NUM>), and a second transmission stage (<NUM>) of the freewheel type, comprising a third wheel (<NUM>) engaged with the intermediate driven wheel (<NUM>), a fourth wheel (<NUM>) coaxial with said third wheel (<NUM>), and a second coupling mechanism (<NUM>) between the third wheel (<NUM>) and the fourth wheel (<NUM>) configured for fixing the third wheel (<NUM>) and the fourth wheel (<NUM>) to each other when the third wheel (<NUM>) rotates in a first direction of rotation (G') and for disengaging the third wheel (<NUM>) from the fourth wheel (<NUM>) when the third wheel (<NUM>) rotates in a second direction of rotation (G"), wherein said fourth wheel (<NUM>) of the second transmission stage (<NUM>) is engaged with the driven output wheel (<NUM>), and wherein the first direction of rotation (C') of the first transmission stage (<NUM>) and the first direction of rotation (G') of the second transmission stage (<NUM>) are coincident directions.