Motorcycle frame with variable hardness

Abstract

The disclosed motorcycle frame includes a main body extending in the longitudinal direction and a pair of brackets configured to at least partially support the engine. The brackets are connected to the main body. The frame includes a pair of struts configured to be rigid during compression and free during traction. Each strut has its front end connected to the main body and its rear end connected to one of the brackets.

Description

Technical Field

[0001] The present invention relates to the field of motorcycle frames, and more particularly to the field of frames for racing motorcycles.

Background Art

[0002] The prior art includes motorcycle frames formed from aluminum or composite materials in order to balance lightness and hardness.

[0003] A motorcycle frame typically has a "U" shape or an "O" shape for connecting a steering head to a rear swing arm. Also, the frame enables the fixing of a propulsion engine. Generally, the engine is directly attached to the frame.

[0004] Some frames have an engine installed on the frame using brackets for reasons related to hardness. The brackets are connected to the frame by connecting means, and the engine is installed on the brackets. In this way, the hardness of the frame can be adjusted, and the longitudinal and lateral hardness can be optimized. In fact, the hardness of the brackets is lower than or different from that of the frame. Thereby, torsions and typical movements of the engine are only partially transmitted to the frame.

[0005] In the latter type of frame, the brackets are designed to have sufficient longitudinal hardness in order to avoid the so-called "frame closure" phenomenon, i.e., the engine moving excessively forward with respect to the steering head during braking. This phenomenon is more prominent especially in racing motorcycles such as MotoGP (trademark). In these motorcycles, the frame is greatly affected by deformation due to much more powerful braking than in normal motorcycles.

Summary of the Invention

Problems to be Solved by the Invention

[0006] To solve the problem of the "frame closure" during braking, the engine support bracket is made larger than normal. However, this increases the weight, and during cornering, the frame becomes stiffer in longitudinal deformation and more rigid in lateral deformation, resulting in a performance degradation in terms of hardness.

Means for Solving the Problem

[0007] The above-mentioned drawbacks of the prior art are solved by the motorcycle frame according to the present invention. The frame includes a main body extending in the longitudinal direction and a pair of brackets connected to the main body and configured to at least partially support the engine. The frame includes a pair of struts configured to be rigid during compression and free during traction. Each strut has a front end connected to the main body and a rear end connected to one of the brackets. The frame thus realized has higher rigidity. During braking, the mass of the engine tends to distribute a part of its weight to the bracket and a part to the strut and move forward. On the other hand, during acceleration, the strut becomes freely longer, and the engine discharges its mass only to the bracket.

Brief Description of the Drawings

[0008] The above-mentioned advantages and other advantages will become more apparent from the following description of the embodiments illustrated non - limitatively with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] The following description of one or more embodiments of the present invention refers to the accompanying drawings. The same reference numerals in the drawings identify equivalent or similar elements. The subject matter of the present invention is defined by the appended claims. The technical details, structures, or characteristics of the solutions described below can be arbitrarily combined with each other.

[0010] In FIGS. 1 and 2, reference numeral 20 indicates a frame for a motorcycle.

[0011] The frame 20 includes a main body 1 extending in the longitudinal direction L. A pair of brackets 5 configured to at least partially support an engine 30 connected to the main body 1 and schematically shown by broken lines is provided.

[0012] As shown in FIG. 2, each bracket 5 of the pair of brackets is disposed on both sides of the main body 1 with respect to the longitudinal direction L. In terms of configuration, each bracket 5 is mechanically connected to the main body 1 of the frame 20 by a connecting element 5' such as a bolt-nut connection.

[0013] Each bracket 5 is connected to the engine 30 at respective connection points 7.

[0014] Also, the engine 30 is connected to connection portions 8 and 8' (FIGS. 1 and 2). The connection portions 8 and 8' are part of the main body 1 and are distal to the steering head 6. The connection points 7 of the brackets 5 and the connection portions 8 and 8' realize the suspension attachment of the engine 30 to the body 1 of the frame.

[0015] Furthermore, the frame 20 includes at least one pair of struts 2. In particular, these struts are arranged on both sides with respect to the central plane M as shown in FIG. 2. This symmetrical arrangement can balance the load on the frame 20 mainly during deceleration and braking, as will be described later.

[0016] In particular, each of the struts 2 is configured to be highly rigid when compressed and free when in tension. In other words, each strut 2 is mainly deformed axially when subjected to a tensile load and is made to be a rigid element, i.e., a strut, when subjected to a compressive load.

[0017] Each strut 2 is, by construction, connected to the main body 1 at the front end portion 3 and to the corresponding bracket 5 at the rear end portion 4. The terms "front" and "rear" mean the front-rear direction of the motorcycle. The motorcycle includes a front end portion provided with a steering head 6 to which a steering member for controlling a front steering wheel (not shown) is connected, and a rear end portion extending on the opposite side of the front end portion and including a rear drive wheel (not shown).

[0018] Preferably, the front end portion 3 of the strut 2 is connected to the main body 1 near the steering head 6. Most preferably, the rear end portion 4 of the strut 2 is connected to the bracket 5 near the connection point 7 where the bracket 5 is connected to the engine 30. The rear end portion 4 of the strut 2 preferably coincides with the connection point 7.

[0019] In this way, while the pair of struts 2 absorbs the compressive load acting on the main frame 1, when a load different from the compressive load acts, the struts idle and become irrelevant. These compressive loads mainly occur during sudden deceleration or sudden braking of the motorcycle and tend to "close" the main body 1 of the frame, that is, generate angular momentum in the clockwise direction in FIG. 2. The function of the strut 2 is to increase the hardness of the bracket 5 during braking and mainly release the force applied to the portion of the main body 1 close to the steering head 6. In this way, the motorcycle is more stable during braking, and the driver can enter the corner in a more fluid and calm state.

[0020] At the same time, the pair of struts 2 is transparent under other operating conditions of the motorcycle, such as during cornering or acceleration, thereby enabling deformation of the main body 1 and the bracket 5 with respect to the main body 1. In the tensile or tangential loads generated during acceleration and / or cornering, the pair of struts 2 is neutral and allows unstable deformation of the main body 1 and the bracket 5 with respect to the main body 1.

[0021] In this way, the flexibility of the frame 20, which is particularly required during acceleration and cornering, is ensured. Due to the flexibility of this frame 20, the grip of the tire is improved, and the traction during acceleration from the corner is improved.

[0022] In terms of configuration, FIGS. 3 and 4 show the first embodiment of the strut 2, and FIGS. 5 and 6 show the second embodiment of the strut 2.

[0023] In both embodiments, the strut 2 includes a front portion 9 and a rear portion 10 that are coupled to each other. The front portion 9 is the portion facing the steering head 6, and the rear portion 10 is the portion facing the bracket 5. The two portions 9 and 10 can be arranged in reverse.

[0024] In the first embodiment, the joint between the front portion 9 and the rear portion 10 is a prismatic joint. In particular, this prismatic joint is obtained via a bush 12 screwed into the front portion 9 that forms a male element inserted into the female element of the rear portion 10.

[0025] Figure 4 shows a cross-section of Figure 3. Here, the prismatic joint can be seen. When a compressive load is applied to the ends 3 and 4 of the strut 2 connected to the main body 1 and the bracket 5 of the frame 20 respectively, the bush 12 connected to the front portion 9 tends to enter the hollow portion of the rear portion 10, i.e., the female element, until it contacts the rear wall 10" of the female element of the rear portion 10. Thereby, as shown in Figure 3, a non-compressible rigid element can be effectively realized. In this embodiment, the rear wall 10" forms a contact surface for the male element shown as the bush 12 connected to the front portion 9. In other embodiments, the bush 12 can be omitted and the male element can be formed as part of the front portion 9. When the male element abuts against the contact surface of the female element, the function of a strut with compression and hardness is obtained. On the other hand, when a tensile load that tends to move the connection points 3 and 4 away from each other acts on the strut 2, the prismatic joint of the bush 12 moves the bush 12 within the rear portion 10 and away from the rear wall 10", thereby enabling the front portion 9 to move away from the rear portion 10. Therefore, since the front portion 9 and the rear portion 10 can move freely relative to each other, the strut 2 is neutral and irrelevant to these tensile deformations.

[0026] According to a further advantageous aspect, the strut 2 comprises a ball joint 11 configured to connect to the main body 1 and / or the bracket 5 at one or both of the ends 3 and 4.

[0027] In particular, as shown in FIG. 3, the ball joints 11 are provided at each of the ends 3 and 4. In this way, the ball joints 11 can be used to prevent the lateral stiffness of the bracket 5 with respect to the main body 1 from changing. The mechanical connection portion 5' of the bracket 5 to the main body 1 of the frame 20 has a lateral stiffness that allows for a movement of the bracket 5 with respect to the main body 1 of about several degrees in the lateral direction. The bracket 5 has a tendency to bend substantially laterally with respect to the main body 1. The function of the ball joints 11 is to ensure that the struts 2 at the connection points 3 and 4 are independent of and neutral with respect to the lateral bending of the bracket 5. The effect achieved by the ball joints 11 is actually to follow the lateral displacement of the bracket 5 with respect to the main body 1 of the frame 20. Since the ball joints 11 do not transmit momentum, the influence on the lateral stiffness is nominally zero. In other words, when the motorcycle is cornering, due to the effect of the centrifugal force acting on the mass of the engine 30, the bracket 5 has a tendency to bend in a direction orthogonal to the longitudinal direction L. The ball joints 11 on the connection points 3 and 4 enable them to follow the lateral movement of the bracket 5 and ensure a constant "rigidity" with respect to the main body 1 of the frame 20 and each bracket 5.

[0028] Also, the ball joints 11 perform the same function by following the movement of the struts 2 during elongation following a deformation that tends to "release", i.e., "open" the main body 1 of the frame 20. The ball joints 11 allow for a deformation that is completely transmissive to such an opening movement. This is a result that cannot be obtained with other types of restrictions. Also, the ball joints 11 assume a case where the frame opens (intentionally) without necessarily deforming laterally.

[0029] In the alternative embodiment shown in FIGS. 5 and 6, the joint between the front portion 9 and the rear portion 10 is achieved by a joint configured to incline the longitudinal axis A1 of the front portion 9 with respect to the longitudinal axis A2 of the rear portion 10 (FIG. 6).

[0030] More specifically, the joint of FIG. 6 is obtained by a conical coupling portion in which the end portion 9' of the front portion 9 is the male-side element and the end portion 10' of the rear portion 10 is the female-side element. Embodiments where these are reversed are also possible. Also, a sealing element 15 such as an O-ring is provided. Based on the same operating principle as described above, when the end portions 3 and 4 receive a compressive load, the conical male end portion 9' tends to be inserted into the female end portion 10'. Note that due to the conical shape of this coupling portion, when the portions 9 and 10 move towards each other, the reverse tapers of the respective end portions 9' and 10' also ensure the axiality between the front portion 9 and the rear portion 10. In other words, the conical male end portion 9' and female end portion 10' tend to restore axiality when moving towards each other. Substantially, similar to the above-described embodiment, (in this case) the female end portion 10' formed by the rear portion 10 forms a contact surface (in this case, a concave conical shape) with which the male-side element formed by the end portion 9' of the front portion 9 comes into contact. The male-side element has a convex conical end face complementary to the shape of the contact surface formed by the female end portion. When the two complementary conical surfaces come into contact, that is, when the male-side element abuts against the contact surface defined at the bottom of the female-side element, the strut becomes highly rigid under compression.

[0031] On the other hand, when the conical male end portion 9' and female end portion 10' move away from each other, it becomes possible to swing the front portion 9 with respect to the rear portion 10, that is, to change the incident angle of the axis A1 with respect to the axis A2. The incident angle formed between the axis A1 and the axis A2 is 0° to 3°, particularly 0° to 2°, and more specifically less than 2°.

[0032] Also, in this solution, the strut 2 remains neutral with respect to the lateral movement of the bracket 5. When the end portions 9' and 10' are separated from each other, this is similar to the case where the two rods 9 and 10 are not in contact with each other, and thus it is not active with respect to the main body 1.

[0033] In this embodiment, since the ball joint 11 is abolished, the strut 2 is further lightened, and at the same time, self-centering is enabled by a conical end stopper that serves to "center" (restore the axiality) when the system comes into contact.

[0034] In both of the above-described embodiments, the strut 2 includes adjustment means 14 configured to adjust the length of the strut 2. In particular, the adjustment means 14 includes adjustment threaded joints 14' and 14" provided at the ends of the rear portion 10 facing the end portion 4. The threaded joints 14' engage with their respective seat portions 14". By acting on the hexagonal portion provided in the rear portion 10 at a more accessible position, the stroke of the threaded portion 14' in the seat portion 14" can be adjusted to adjust the preload of the strut 2.

[0035] A similar solution indicated by reference numeral 14 is also provided in the embodiments of FIGS. 5 and 6.

[0036] In both solutions, the stopper is adjustable (since the system does not become compressed during braking, it is the same as if it did not exist) in order to accurately establish the moment when the system comes into contact (a sharp increase in hardness) and to cancel it by moving the stopper away from the engageable area without removing the strut 2.

[0037] In a further embodiment of the present invention, a pair of struts 2 are provided. The struts 2 are actuated by a gear mechanism connected to the handlebar and directly controlled by a driver (not shown). For example, the struts 2 are actuated by a lever on the handlebar to change the length, and thus the hardness, of the struts 2 symmetrically or asymmetrically with respect to the central plane M.

[0038] The passive asymmetric operation of the struts 2 provides non-simultaneous intervention of two struts 2 arranged on opposite sides of each other in order to generate an appropriate lateral displacement of the frame during braking.

[0039] In a further embodiment (not shown), the length (and thus the stiffness) of the strut 2 is adjusted by an actuator controlled by the control unit.

[0040] The control unit may be configured to implement control logic. This is actuated according to a series of vehicle function parameters during the operating state of the vehicle (cornering or straight). As an example, an actuator coupled to a brake line (typically the front) configured to adjust the stiffness of the strut 2 controlled by the pressure directly acting on the brake system by the driver may be mentioned.

[0041] It is obvious that modifications and variations can be applied to the present invention without departing from the scope of protection. Also, all details can be replaced by technically equivalent elements. In fact, the quantity can be changed according to technical requirements.

Description of the reference numerals

[0042] 1 Main body 2 Strut 3 Front end (of the strut) 4 Rear end (of the strut) 5 Bracket 5’ Mechanical coupling element 6 Steering head 7 Connection point 8 Frame body of the connection part 9 Front part (of the strut) 10 Rear part (of the strut) 10” Rear wall 11 Ball joint 12 Bush 14 Adjusting means A1 Front axle A2 Rear axle L Longitudinal direction M Central plane

Claims

1. A motorcycle frame (20) comprising: a main body (1) extending in a longitudinal direction (L); and a pair of brackets (5) connected to the main body (1) and configured to at least partially support an engine (30), the frame also comprising a pair of struts (2) configured to be stiff in compression and free in towing, each of the struts (2) having a front end (3) connected to the main body (1) and a rear end (4) connected to one of the brackets (5), the struts (2) having a front portion (9) connected to a rear portion (10).

2. 2. A frame (20) according to claim 1, wherein one of the front and rear portions (9) comprises a female element and the other of the front and rear portions (9) comprises a male element, the male element being slidably received within the female element such that the front and rear portions (9) are joined to one another at a joint, the female element forming an abutment surface for the male element, and the struts becoming stiff in compression when the male and female elements contact one another at the abutment surface.

3. 3. A frame (20) according to claim 1 or 2, wherein the connection between the front section (9) and the rear section (10) is a prismatic joint.

4. 4. A frame (20) according to claim 3, wherein the prismatic joint is obtained through a bush (12) threaded into the front part (9) forming the male element which is inserted into the rear part (10) forming the female element, and vice versa.

5. 5. A frame (20) according to claim 3 or 4, wherein the strut (2) comprises, at one or both of the front end (3) and the rear end (4), a ball joint (11) configured to connect to the main body (1) and / or the bracket (5).

6. 3. A frame (20) according to claim 1 or 2, wherein the front portion (9) and the rear portion (10) are connected by a joint configured to incline the longitudinal axis (A1) of the front portion (9) relative to the longitudinal axis (A2) of the rear portion (10) at an angle preferably less than 2°.

7. The joint includes a male-side element including one end portion (9') of one of the front portion (9) and the rear portion (10), and a female-side element including one end portion (10') of the other of the front portion (9) and the rear portion (10). The male-side element is inserted into the female-side element. The male-side element has a convex conical surface, and the female-side element has a concave conical surface that forms a contact portion of the convex conical surface of the male-side element. When the male-side element and the female-side element approach each other, the conical shape of the male-side element and the conical shape of the female-side element ensure the axial alignment between the front portion (9) and the rear portion (10) of the strut. The frame (20) according to claim 6.

8. The strut (2) includes adjustment means (14) configured to adjust the length of the strut (2). The frame (20) according to any one of claims 1 to 7.

9. The front end portion (3) of the strut (2) is connected to the main body (1) near the steering head (6). The frame (20) according to any one of claims 1 to 8.

10. The rear end portion (4) of the strut (2) is connected to the bracket (5) near the connection point (7) of the bracket (5) to the engine (30). The frame (20) according to any one of claims 1 to 9.

11. The strut (2) is arranged to be substantially parallel to the central plane (M) of the main body (1). The frame (20) according to any one of claims 1 to 10.

12. A motorcycle comprising an engine and the frame according to any one of claims 1 to 11 to which the engine is attached.

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