Stepless transmission

Abstract

A continuously variable transmission comprising first and second shafts (1, 2) and at least one auxiliary shaft (3), the auxiliary shaft (3) rotating about a rotation axis (3a) and inserted between the main shafts (1, 2), and whose rotation planes (13, 23, 31, 32) are such that tangents (TG1, TG2) at the contact points of the auxiliary shaft (3) and the main shaft (1, 2) pass through two distinct intersection points (T1, T2) of the axes of the shafts (1, 2, 3).

Description

Technical Field

[0001] The present invention generally relates to the field of motion transmission systems, and more particularly to a continuously variable gearbox for transmitting motion between two shafts.

Background Art

[0002] In mechanical applications, there is a growing worldwide need for devices such as transmissions that can connect two rotating shafts to obtain a variable transmission ratio.

[0003] Such devices are typically placed between a motor and a user and are used in a very large number of fields, from road transportation to various types of industries.

[0004] In many uses, it is preferable to be able to continuously change the transmission ratio in terms of the availability of intermediate transmission ratios between the maximum and minimum. Hereinafter, a device having such a feature is defined as a "continuously variable transmission".

[0005] In recent years, there have been different types of continuously variable transmissions.

[0006] A very widely used type is one with pulleys of varying diameters, and is transmitted by a belt that transmits motion between the two pulleys. As the disks of each pulley approach or move away from each other, the ratio at which the belt is wound on the pulley changes, and as a result, the transmission ratio also changes.

[0007] There are many types of continuously variable transmissions that utilize the rotation of two or more rigid surfaces integrated with the shaft of the shaft, operate an appropriate mechanism to move the contact point between the two surfaces, and gradually move the radius of the theoretical circle of rotation, and as a result, change the transmission ratio.

[0008] In a continuously variable transmission based on this principle, for the surfaces, it is important to have a "pure" rotation between the surfaces. The expression "pure rotation" means a rotation without a "jamming operation". Regarding the relative movement between two contacting objects, a "jamming operation" (also referred to as a "perforation operation" or a "spin operation") is a relative rotation around an axis perpendicular to the two surfaces at the contact point.

[0009] The "jamming operation" is harmful and undesirable for the following two reasons. The main reason is that it promotes the wear of the components and significantly limits the transmitted torque and the service life of the components. Another reason is that it causes wasteful losses due to friction. Regarding the transmission ratio in actual use, the contact between the two surfaces is in a theoretical kinematic operation and, necessarily, has a footprint with non-zero elongation rather than at a single point. Therefore, when away from the center of the contact area, the two components are rubbed due to the jamming operation.

Summary of the Invention

[0010] An object of the present invention is to obtain a continuously variable transmission that can continuously change the transmission ratio, for example, a continuously variable transmission in which the operation is transmitted by pure rotation without a jamming operation occurring at the contact point.

[0011] To achieve this result, the continuously variable transmission according to the present invention includes two main shafts through which the operation is transmitted so that the transmission ratio can be changed. For example, the first shaft (drive side) is connected to a motor, and the second shaft (driven side) is connected to a user.

[0012] The two main shafts are on the same plane, which is hereinafter shown as a "reference plane", and the rotation axes of the two main shafts can be inclined to each other, parallel, or coaxial.

[0013] The rotation axis of the main shaft is fixed on the reference plane and, for example, cannot move relative to the outer box or frame of the transmission. The two main shafts are also constrained so that they cannot move in a direction parallel to their rotation axes. Thus, the two main shafts can only rotate about their rotation axes.

[0014] Each main shaft is provided with a rotating surface having a profile as more appropriately described below.

[0015] There is also an auxiliary shaft that rotates about an axis on the reference plane identified by the rotation axis of the main shaft. The rotation axis of the auxiliary shaft can move along the reference plane (while remaining on the plane).

[0016] During the use of the transmission, the rotating surface of the auxiliary shaft rotates on the rotating surface of the corresponding main shaft without rubbing.

[0017] To simplify the description, assuming that one of the main shafts is connected to the motor and the other main shaft is connected to the user, the drive shaft transmits the rotation to the auxiliary shaft, and the field shaft transmits the rotation to the driven shaft.

[0018] Due to the tangential force due to friction at the contact point between the rotating surface of the auxiliary shaft and the rotating surface of the corresponding main shaft (this contact is always maintained by an appropriate perpendicular force), the operation can be transmitted.

[0019] The movement of the auxiliary shaft along the reference plane determines the movement of the contact point on the rotating surface. This movement changes the ratio of the radii of the rotating circles, thus changing the transmission ratio.

[0020] In particular, the rotating surface is a swivel surface obtained by an appropriate generatrix surface that rotates about the respective rotation axes of the shafts and has two surfaces (neither conical nor cylindrical, but a straight generatrix).

[0021] The rotating surfaces are arranged tangentially to each other at the contact point.

[0022] In the reference plane, for each position of the auxiliary shaft relative to the main shaft, the straight line that is the tangent line at the contact point of the generatrix curves of the rotating surfaces of the first main shaft and the auxiliary shaft passes through the intersection point of the rotation axes of the first main shaft and the auxiliary shaft. Similarly, the straight line that is the tangent line at the contact point of the generatrix curves of the rotating surfaces of the second main shaft and the auxiliary shaft passes through the intersection point of the rotation axes of the second main shaft and the auxiliary shaft.

[0023] Under the described conditions, the jamming operation can be eliminated. The profile of the generatrix curve of the rotating surface can be obtained as the geometric locus of the points satisfying the conditions (as will be detailed below with reference to the drawings).

[0024] In the continuously variable transmission according to the present invention, the intersection point of the rotation axes of the first main shaft and the auxiliary shaft and the intersection point of the rotation axes of the second main shaft and the auxiliary shaft can be identified. The solution presented as the present invention allows for many embodiments and considerable flexibility in the design of the shape.

[0025] The continuously variable transmission according to the present invention is defined in claim 1. The preferred embodiments of the present invention are defined in the dependent claims.

Brief Description of the Drawings

[0026]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 8A

Figure 8B

Figure 9A

Figure 9B

Figure 10A

Figure 10B

Best Mode for Carrying Out the Invention

[0027] Functional and structural features of some preferred embodiments of the continuously variable transmission according to the present invention will be described with reference to the drawings.

[0028] Before explaining the multiple embodiments of the present invention in detail, it should be confirmed that the present invention is not limited to a detailed structure in the application and is not limited to the configuration of the elements shown here and in the drawings. The invention can assume other embodiments that are carried out or realized in substantially different ways. It should be understood that the choice of words and terms is for the purpose of description and does not constitute a limitation.

[0029] The present invention is implemented by a number of alternative structural arrangements that appear to have different geometric designs but achieve the same type of operation.

[0030] As an example, referring to FIGS. 1A and 1B, the continuously variable transmission includes first and second shafts 1 and 2 each having a respective rotational axis 1a, 2a fixed on a reference plane P.

[0031] These main shafts 1, 2 each include main rotating surfaces 13, 23 formed as rotating entities.

[0032] The transmission further includes at least one auxiliary shaft 3 (which can also be formed by a plurality of second shaft axes 3', 3'' as shown in the examples of FIGS. 7A to 9B) that is rotatable about a rotational axis 3a and inserted between the main shafts 1, 2. The auxiliary shaft 3 includes two second rotating surfaces 31, 32. The second rotating surfaces 31, 32 are each formed as rotating entities and include two second rotating surfaces 31, 32 that are in contact with the respective main rotating surfaces of the main shafts 1, 2, and transmit the operation from one main shaft to the other main shaft.

[0033] The rotation axis 3a of the auxiliary shaft 3 can only move along the reference plane P identified by the rotation axes 1a, 2a of the two main shafts 1, 2.

[0034] Furthermore, in the reference plane P, for the main rotation surface 13 of the first main shaft 1 and the second rotation surface 31 of the corresponding auxiliary shaft 3, the line TG1 that is the tangent at the contact point P1 between the rotation surfaces 13, 31 always passes through the intersection point T1 of the rotation axis 1a of the first main shaft 1 and the rotation axis 3a of the auxiliary shaft 3. Similarly, for the rotation surfaces 23, 32, in the reference plane P, for the main rotation surface 23 of the second main shaft 2 and the second rotation surface 32 of the corresponding auxiliary shaft 3, the line TG2 that is the tangent at the contact point P2 between the rotation surfaces 23, 32 always passes through the intersection point T2 of the rotation axis 2a of the second main shaft 2 and the rotation axis 3a of the auxiliary shaft 3.

[0035] Furthermore, the intersection point T1 of the rotation axis 1a of the first main shaft 1 and the rotation axis 3a of the auxiliary shaft 3 is identified from the intersection point T2 of the rotation axis 2a of the second main shaft 2 and the rotation axis 3a of the auxiliary shaft 3.

[0036] All embodiments of the present invention generally have the following characteristics as shown above: In the reference plane P, the straight line that is the tangent of the rotation surface at the contact point always passes through the intersection point of the axes of the auxiliary shafts involved in the contact, and this intersection point is the intersection point of the rotation axis of the auxiliary shaft and the respective rotation axes of the first and second main shafts.

[0037] In this way, the second rotation surfaces 32, 32 of the auxiliary shaft 3 rotate on the respective main rotation surfaces 13, 23 of the main shafts 1, 2 without rubbing and without causing a jamming operation.

[0038] The geometric locus that satisfies the above conditions shows the generatrix curves of the rotation surfaces 13, 23, 31, 32.

[0039] As an example, the profiles of the generatrix curves of the rotating surfaces 13, 23, 31, 32 are desired to be accurately approximated and are drawn using the iterative process shown below. The process is carried out by image or analytical numerical calculations.

[0040] In the first step, together with the further described criteria, an initial profile is optionally provided as the generatrix curve of the rotating surfaces 31, 32 of the auxiliary shaft 3. In the second time, using the iterative process, the generatrix curves of the rotating surfaces 13, 23 of the main shafts 1, 2 are obtained, and the above-mentioned condition without the kinking operation can be achieved.

[0041] For illustration, referring to FIGS. 2A to 2D, the first step of the iterative process consists of providing an auxiliary shaft 3 formed as a rotating body and provided with two second rotating surfaces 31, 32 having two curved surfaces.

[0042] To identify the positions of the members of the transmission in different iterations, numerical reference numbers are appended with a character identifying the iteration (in the illustrated example, the character "A" indicates the first iteration, the character "B" indicates the first iteration, etc.). For example, reference 3A indicates the position of the auxiliary shaft 3 in the first iteration.

[0043] Referring to FIG. 2A, the iterative process is started and a straight line TG1 is drawn. The straight line TG1 passes through the point T1A at the intersection of the rotation axes 1a and 3aA (the first main shaft 1 and the auxiliary shaft 3A not shown respectively), becomes the tangent of the profile 31A, and represents the generatrix curve of the second rotating surface related to the auxiliary shaft 3A. Further, a straight line TG2 is drawn. The straight line TG2 passes through the point T2A at the intersection of the rotation axes 2a and 3aA (the second main shaft 2 and the auxiliary shaft 3A not shown respectively), becomes the tangent of the profile 32A, and represents the generatrix curve of the second rotating surface at the opposite end of the auxiliary shaft 3A. Then, at the points of the two tangents, two first contact points P1A and P2A are identified.

[0044] Two straight lines R1A and R2A are drawn perpendicular to profiles 31A and 32A at contact points P1A and P2A, respectively.

[0045] A point A, which is the intersection of the two straight lines R1A and R2A, is the center of rotation of the first cycle of the iterative process.

[0046] A small rotation around point A occurs on shaft 3A, thereby moving to point 3B (second iteration). The smaller the magnitude of the rotation adopted in each iteration, the higher the accuracy of the result.

[0047] After rotation, the intersection point T1B is identified between the rotation axis 1a of the first main shaft 1 (not shown) and the rotation axis 3aB of the auxiliary shaft 3B (for example, the axis of the auxiliary shaft 3 in the second iteration). Further, the intersection point T2B is identified between the rotation axis 2a of the second shaft 2 (not shown) and the rotation axis 3aB of the auxiliary shaft 3B.

[0048] At this point, two new straight lines TG1B and TG2B are drawn passing through the above intersection points T1B and T2B and becoming the tangents to the respective second rotation surfaces 31B and 32B of the auxiliary shaft 3 (new position 3B), respectively.

[0049] And a new iteration is executed.

[0050] At the end of the iteration, the generatrix curves of the main rotation surfaces 13 and 23 of the main shafts 1 and 2 are drawn in the following manner: - The curve must connect each of the contact points P1A, P1B, P1C, etc. with respect to the main rotation surface 13 (related to the first main shaft 1) and each of the contact points P2A, P2B, P2C, etc. with respect to the main rotation surface 23 (related to the second main shaft 2).

[0051] To illustrate the tracing method, FIG. 2C shows a series of line segments located at one of the points P1A, P1B, P1C and P2A, P2B, P2C, respectively, and inclined like the respective tangents. In fact, by connecting the segments, the corresponding generatrix curve is obtained.

[0052] In summary, at the contact points P1 and P2, the profiles of the main rotation appearances 13 and 23 can be drawn with the desired accuracy, with the desired magnitude, by rotation inheritance, around the continuously changing point (instantaneous rotation center) given by the intersection of two straight lines R1 and R2 that are perpendicular to one of the tangent lines TG1 and TG2 respectively. As the number of repetitions increases, the accuracy of the profile increases.

[0053] The result can be optimized by changing the profile of the generatrix curve of the second rotation surfaces 31 and 32 of the auxiliary shaft 3 and changing the initial positions of the shafts 1 and 3 relative to each other.

[0054] In this way, the design can be optimized based on the required transmission ratio and the allowable stress of the material.

[0055] Advantageously, the radius of curvature of the generatrix curve of the second rotation surfaces 31 and 32 of the auxiliary shaft 3 on the reference plane P can be changed along this generatrix curve, and the stress at the contact point can be reduced.

[0056] The embodiments of FIGS. 1A and 1B form the basis of the above description, as clearly shown in the figures.

[0057] The same principle applied to describe the above iterative method is also applicable to other embodiments with respect to those described from FIGS. 1A to 2D and to other embodiments shown below.

[0058] For example, the rotation axis 1a of one main shaft 1 intersects the rotation axis 2a of the other main shaft 2 at a point (as illustrated in the figures from FIGS. 1A to 3B, the rotation axes 1a and 2a project onto each other), or (as illustrated in FIGS. 4A to 8B) the main shafts 1 and 2 can be arranged such that the main shafts 1 and 2 are parallel or coincident with each other.

[0059] The auxiliary shaft 3 is formed of one member or comprises two auxiliary shafts 3', 3'' which are connected to each other by engagement members 14 (advantageously gears) applied so as to maintain a constant ratio between their respective rotational speeds, as illustrated in FIGS. 7A to 9B. A similar configuration is particularly effective when the two main shafts 1, 2 are coaxial with each other (as in FIGS. 7A to 9B). The two second shafts 3', 3'' have, at their first end, respective second rotational surfaces 31, 32, while their other end is configured to connect to the other second shaft 3', 3'' (for example, as illustrated in FIGS. 7A to 9B, the first second shaft has a gear which cooperates with a complementary gear area of the next second shaft).

[0060] No. The two shafts 3', 3'' are coaxial or rotate about rotational axes 3'a, 3''a which are offset from each other (for example, as shown in FIGS. 7A to 9B). In the latter case, what has been described above in connection with the rotational axis 3a of the auxiliary shaft 3 can equally be applied to the rotational axes 3'a, 3''a of the second shafts 3', 3''.

[0061] More specifically, the intersection point T1 of the rotational axis 1a of the first main shaft 1 and the rotational axis 3'a of the corresponding second shaft 3' (for example, the second shaft on the first main shaft 1) is identified from the intersection point T2 of the rotational axis 2a of the second main shaft 2 and the rotational axis 3''a of the corresponding second shaft 3'' (for example, the second shaft on the second main shaft 2).

[0062] Furthermore, the auxiliary shaft 3 (or the second shafts 3', 3'') can be of the male type or of the female type. In the latter case, the second rotational surfaces 31, 32 face the rotational axis of the auxiliary shaft 3, while in the male type they face outwards, with the respective main rotational surfaces 13, 23 facing the rotational axis of the auxiliary shaft 3.

[0063] For the main shafts 1, 2 and their respective main rotational surfaces 13, 23, the contact point can face the rotational axis or face outwards.

[0064] As an example, the following cases are identified: - In FIGS. 1A to 1B, 6A to 7B, and 9A to 9B, the main shafts 1, 2 are of a female configuration (each having a concave main rotating surface 13, 23), and the auxiliary shaft 3 is of a male configuration. - In FIGS. 3A to 3B, 8A to 8B, and 10A to 10B, the main shafts 1, 2 are of a male configuration, and the auxiliary shaft 3 is of a female configuration. - In FIGS. 4A to 5B, both the main shafts 1, 2 and the auxiliary shaft 3 are of a female configuration.

[0065] Solutions involving a female type of auxiliary shaft 3 are preferred because the pressure between the surfaces in the contact zone is reduced.

[0066] Furthermore, from the perspective that the main rotating surfaces 13, 23 are equal and have a shape like a mirror image of each other, and at the same time, the second rotating surfaces 31, 32 are also equal and have a shape like a mirror image of each other (symmetric drawings), or all the main and second rotating surfaces 13, 23, 32, 32 have different shapes from each other (asymmetric drawings), the configuration can be symmetric or asymmetric. As illustrated in the drawings, an asymmetric structural arrangement is shown in FIGS. 5A, 5B (apart from such features, the rest is the same as the arrangement in FIGS. 4A and 4B, having parallel main shafts and a female auxiliary shaft). In any case, the structural arrangements shown here can be implemented in a symmetric or asymmetric form.

[0067] If the configuration is symmetric, the transmission ratio changes proportionally with respect to others between the maximum and minimum values. In this case, when the auxiliary shaft 3 is in the central position, the transmission ratio becomes equal to 1.

[0068] In an asymmetric design, there is an advantage that the transmission ratio changes non - proportionally with respect to others between the maximum and minimum values. Thus, in many applications, an asymmetric design is more appropriate. For example, the structural arrangement shown in FIGS. 5A and 5B has a transmission ratio that varies between approximately 1.2 and 5 in response to the requirements shown in the automotive industry.

[0069] There are many possible combinations, including the possibility of obtaining an anti - metric design as shown in FIGS. 6A and 6B.

[0070] From a practical point of view, a configuration with a female auxiliary shaft has the advantage that when it has a rotating circle with an outer diameter larger than the outer diameter of the drive shaft, it has a lower rotational speed than the drive shaft itself. This feature is preferable for defining the bearing that supports the auxiliary shaft 3.

[0071] In a structural arrangement with two second shafts 3', 3'', these shafts 3', 3'' can be connected by a gear 14, and the gear 14 has a given transmission ratio different from one another (as illustrated in FIGS. 7A to 9B). In this way, a wide range of transmission ratios of the transmission can be obtained.

[0072] In some cases, as schematically shown in FIGS. 9A and 9B, two distinguishable auxiliary shafts can also be employed. This arrangement is similar to that of FIGS. 7A and 7B, but there are two distinguishable auxiliary shafts 3 formed from (instead of one) two second shafts (shown by reference numerals 3', 3'' in the lower part of each figure and identified by reference numerals 3''', 3'''' in the upper part).

[0073] Regarding the description, in FIGS. 9A and 9B above, all other reference numerals similar to those in FIGS. 7A and 7B are omitted.

[0074] By employing two auxiliary shafts, the number of contact points can be doubled, and the transmitted torque can be doubled while the overall external dimensions are equal. Furthermore, since the radial components of the forces transmitted by the two shafts can be balanced respectively, this arrangement has a favorable effect in determining the efficiency and the dimensions of the bearings of the main shaft.

[0075] As described above, an important aspect to be considered in the design is to limit partial stress in the contact zone where rotation allowing transmission movement occurs. From this perspective, to the extent possible, the respective pairs of principal surfaces of the rotation surfaces at each contact point are such that they widen the footprint of the contact zone (since there is deformation due to stress, actually, it is not clearly a single point).

[0076] Regarding this point, it should be remembered that the principal curves of the surface are on two mutually orthogonal planes. Further, since the axis of the main shaft is inclined with respect to the axis of the auxiliary shaft, the two rotating surfaces in contact are on the same plane at each contact point.

[0077] Since there are two tangent surfaces, clearly there are four principal curves. It should always be understood that the comparison of curves is only made between the curve of the surface and the corresponding curve of the other surface in contact (for example, only within each plane where there is a principal curve). Therefore, no comparison is made for curved surfaces on different planes (however, this will no longer be described to avoid overloading the description).

[0078] (As described above) the curves of the two surfaces in contact need to be close to each other and have values with opposite signs. This condition can be obtained, for example, by dealing with those clearly positioned with corresponding curves to each other, such as a concave surface and a convex surface having slightly different radii, or two saddle surfaces.

[0079] From this perspective, a "female" solution (having, for example, a male auxiliary shaft and a female main shaft, etc.) is preferred, and as schematically shown in FIGS. 1A to 1B, 3A to 3B, 6A to 10B, the curves of the rotating surfaces in contact with each other have opposite signs in each plane (for example, one surface has a concave profile and the other surface has a convex profile).

[0080] As a different aspect, the curves of the rotating surfaces in contact with each other can also have the same sign in one of the two planes, such as in the conventional solutions of logarithmic CVT transmissions or in the embodiments schematically shown in FIGS. 4A to 4B (for example, the junction between two convex profiles).

[0081] If rotating surfaces with close radii and opposite signs are adopted, when the loaded contact footprints increase and equal forces are applied, partial stress can be reduced.

[0082] However, the method of adopting rotating surfaces with close radii and opposite signs cannot be practiced beyond a certain range. Because if the radii of the two surfaces are actually equal and have opposite signs, the two surfaces will partially or completely correspond to each other, and instead of rotating, they will engage without rotating.

[0083] Furthermore, as described above, since no jamming operation occurs, the present invention has the feature that it can promote the formation of a larger contact footprints without causing wear or abrasion damage.

[0084] This advantage is due to the fact that the two contacting surfaces do not have a rotational element about an axis perpendicular to the two surfaces at the contact point in relative motion, but rather a pure rotational motion. Thus, in the vicinity of the contact point (even when slightly away from the outside of the contact point), homologous points belonging to the two surfaces have equal speeds.

[0085] Various embodiments of a system for supporting and moving an auxiliary shaft 3 that can be incorporated into the continuously variable transmission according to the present invention will be described below. FIGS. 10A and 10B schematically show one such embodiment. In this embodiment, the main shafts 1 and 2 are arranged inclined to each other, and the auxiliary shaft 3 is of the female type. It goes without saying that the support and movement system is related to the two main shafts 1 and 2 and the auxiliary shaft 3 (including pairs of second shafts 3' and 3'').

[0086] The main shafts 1, 2 are advantageously attached to the case or frame 20 by means of bearings 1b, 2b. Thus, such main shafts 1, 2 rotate only about their axes of rotation 1a, 2a.

[0087] With respect to the axis of rotation 3a of the auxiliary shaft 3 which moves only on the reference plane P, the auxiliary shaft 3 is advantageously attached to a moving body or slide 5 (for example, using two bearings 3b) which moves along the reference plane P.

[0088] In FIGS. 10A and 10B, since it is necessary to actually attach the bearings 3b, the shaft 3 is, as an example, divided into two parts which are firmly connected to each other.

[0089] On the slide 5, one or more Operation means 10 act to press the auxiliary shaft 3 against the main shafts 1 and 2, generating a force perpendicular to the rotating surfaces 13, 23 at the contact points P1, P2 between the main rotating surfaces 13, 23 and the corresponding second rotating surfaces 31, 32.

[0090] In particular, the bearings 3b allow the auxiliary shaft 3 to rotate only about the axis of rotation of the bearing and do not allow other movements or rotations with respect to the slide 5.

[0091] The slide 5 is constrained to move only on the reference plane P.

[0092] For this purpose, the slide 5 can comprise two planes or skids (not shown) which face each other, are located on each side with respect to the reference plane P, and are parallel to each other. Such skids are in contact with two planes or guides (not shown) parallel to the reference plane P which are integrated with the outer frame 20, with an appropriately small play. The skids are appropriately lubricated and, in this way, move on the guides. The two guides integrated with the outer frame 20 cause the slide 5 to move only on the reference plane P.

[0093] More specifically, the coupling of the skid and the guide locks three of the six degrees of freedom of the slide 5, in particular the translation in the direction perpendicular to the reference plane P and the rotation about two orthogonal axes in the plane of the reference plane P.

[0094] It should be emphasized that if the skid and the guide rub against each other, they deviate from the purpose of the mechanical efficiency of the system. This is because the relative movement of these surfaces only serves to allow the definition of the transmission ratio. Instead, in the kinematic system that defines the transmission of motion, no rubbing occurs.

[0095] Operation To implement the means 10, there are two hydraulic cylinders connected to the slide 5 and connected to the external frame 20 at the opposite ends. Two hydraulic cylinders having axes along the reference plane P press the slide 5 in the direction of the main shafts 1, 2, and maintain the contact of the second rotating surfaces 31, 32 of the auxiliary shaft 3 with the main rotating surfaces 13, 23 of the corresponding main shafts. At the contact points of these rotating surfaces, the required vertical force is applied, and the force is transmitted by friction. Generate a tangential force.

[0096] By using hydraulic cylinders or other devices that can advantageously define the generated force, the vertical force applied at the contact points P1, P2 can be corrected as a function of the torque to be transmitted. In this way, the mechanical efficiency in transmission can be improved.

[0097] In the theoretical kinematic operation, no rubbing occurs in the device, but losses occur (energy loss) in the rotation of the shaft bearings and the surfaces that transmit the motion (losses due to rotational friction).

[0098] As the force applied between the contacting surfaces increases, these losses increase. Therefore, adding a vertical force greater than the force required to obtain the tangential force in the engagement direction by friction, with an appropriate margin, to transmit the required torque is meaningless and harmful.

[0099] As a result, it is highly desirable that the force applied between the rotating surfaces can be changed as a function of the transmitted torque.

[0100] By having two distinguishable hydraulic cylinders, the vertical forces applied to the two contact surfaces P1, P2 can be adjusted individually and arbitrarily.

[0101] According to other embodiments (not shown), the two hydraulic cylinders can be replaced with other devices capable of generating the necessary vertical force between the rotating surfaces. For example, instead of or in combination with the hydraulic cylinders, springs with pre-applied weights can be used.

[0102] As already described, by moving the auxiliary shaft 3, the positions of the contact points P1, P2 between the main rotating surface 13 and the second rotating surface 31, and between the main rotating surface 23 and the second rotating surface 32 can be changed respectively, thereby adjusting the gear ratio.

[0103] According to a preferred embodiment (as illustrated in FIGS. 10A and 10B), a hydraulic cylinder 8 with one end attached to the slide 5 and the other end attached to the case 20 is used to move the slide 5 along the reference surface P, that is, the slide 5 is moved along the reference surface P by the locus and / or inclination of the hydraulic cylinder 8 to adjust the gear ratio.

[0104] As an embodiment not shown, instead of the hydraulic cylinder, for example, an electric actuator or a manual lever can also be applied.

[0105] Different aspects and embodiments of the continuously variable transmission according to the present invention have been described so far. It is understood that each embodiment can be combined with any other embodiment. Furthermore, the present invention is not limited to what has been described and can be modified within the scope defined by the claims.

Claims

1. First and second shafts (1, 2) arranged on a reference plane (P) and each provided with a main rotating surface (13, 23) formed as a rotating body, At least one auxiliary shaft (3, 3', 3''), Comprising, The main rotating surfaces (13, 23) are defined by a generatrix surface, The auxiliary shafts (3, 3', 3'') rotate around their respective rotation axes (3a, 3'a, 3''a), are inserted between the main shafts (1, 2), and are each formed as a rotating body, and each has two second rotating surfaces (31, 32) that contact the main rotating surfaces (13, 23) of the main shafts (1, 2), thereby transmitting motion from one main shaft to the other main shaft, The auxiliary shafts (3, 3', 3'') are configured such that their rotation axes (3a, 3'a, 3''a) move only along the reference plane (P) defined by the rotation axes (1a, 2a) of the two main shafts (1, 2), The main rotating surfaces (13, 23) are: - In the reference plane (P), at the contact point (P1) between the contact surfaces (13, 31), the line (TG1) that is the tangent to the main rotating surface (13) of the first main shaft (1) and the second rotating surface (31) of the corresponding auxiliary shaft (3) passes through the intersection point (T1) of the rotation axis (1a) of the first shaft (1) and the rotation axis (3a) of the auxiliary shaft 3, - In the reference plane (P), at the contact point (P2) between the contact surfaces (23, 32), the line (TG2) that is the tangent to the main rotating surface (23) of the second main shaft (2) and the second rotating surface (32) of the corresponding auxiliary shaft (3) passes through the intersection point (T2) of the rotation axis (2a) of the second shaft (2) and the rotation axis (3a) of the auxiliary shaft 3 Formed as, The second rotating surfaces (31, 32) of the auxiliary shaft (3) rotate on the respective main rotating surfaces (13, 23) of the main shafts (1, 2) without rubbing and jamming in all operating states. A continuously variable transmission characterized by this.

2. The continuously variable transmission according to claim 1, wherein the rotation axes (1a, 2a) of the main shafts (1, 2) are parallel but not coaxial.

3. The continuously variable transmission according to claim 1, wherein the rotation axis (1a) of the main shaft (1) intersects the rotation axis (2a) of the main shaft (2) at a point.

4. The continuously variable transmission according to any one of claims 1 to 3, wherein the main rotating surfaces (13, 23) of the main shafts (1, 2) are different from each other.

5. The auxiliary shaft (3) comprises two second shafts (3') and (3'') connected to each other by an engagement member (14), and the engagement member (14) is applied such that the respective rotational speeds of the second shafts (3', 3'') are maintained at a constant ratio. The continuously variable transmission according to any one of claims 1 to 4.

6. The auxiliary shaft (3) is supported by a slide (5) that moves along a reference plane (P), and one or more actuating means (10) operate such that the auxiliary shaft (3) is pressed against the main shafts (1, 2), and at the contact points (P1, P2) between the main rotating surfaces (13, 23) and the corresponding second rotating surfaces (31, 32), a force perpendicular to these rotating surfaces (13, 23, 31, 32) is generated. The continuously variable transmission according to any one of claims 1 to 5.

7. The actuating means (10) is connected to the slide (5) at a first end and fixed to an external frame (20) at a second end, and is a pair of a hydraulic actuator and / or a spring connected to a frame (20) that houses the slide (5) and at least a part of the main shafts (1, 2). The continuously variable transmission according to claim 6.

8. The actuating means (10) is individually adjustable, and using the auxiliary shaft (3), the perpendicular force applied to the main rotating surfaces (13, 23) changes according to the transmitted torque and can be individually adjusted at each of the two contact points (P1, P2). The continuously variable transmission according to claim 6 or 7.

9. The adjustment of the transmission ratio is performed by moving the slide (5) along the reference plane (P) using a hydraulic cylinder (8). The continuously variable transmission according to any one of claims 6 to 8.

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