Driving force transmission device

Abstract

To provide a driving force transmission device including a dog clutch avoiding complexity.SOLUTION: A driving force transmission device includes a dog gear assembly and a dog ring, configured to be rotated about a rotational axis and to be axially adjusted between an engaged state in which torque can be transmitted between the dog gear assembly and the dog ring, and a disengaged state in which torque cannot be transmitted. The dog gear assembly includes a dog gear, a retractable dog assembly configured to move to the dog gear between an extended position and a retracted position, and a control element controlling movement of the retractable dog assembly. The dog ring comprises a plurality of first dogs, the dog gear assembly comprises a plurality of second dogs, and the second dogs are engaged with the first dogs in the engaged state, and disengaged from the first dogs in the disengaged state. The second dogs include a plurality of fixed dogs mounted on the dog gear, and a plurality of retractable dogs including the retractable dog assembly.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a drivetrain. In particular, but not exclusively, the present invention relates to a drivetrain comprising a dog clutch and to a transmission system including such a drivetrain. [Background technology]

[0002] A dog clutch is a mechanism for controlling the driving connection between a gear and a drive shaft such that when the dog clutch is engaged, rotational drive is transmitted between the gear and the drive shaft, and when the dog clutch is disengaged, the gear can rotate freely about the drive shaft without transmitting rotational drive. The drive shaft can be the main or countershaft of the transmission, depending on the type of transmission. Dog clutches are typically used in drive transmission systems, e.g., dog transmissions, used in vehicles to control the transmission of drive between the engine and the wheels.

[0003] A conventional dog clutch is shown in Figures 1-3. The dog clutch includes a dog gear 2 and a dog ring 4, which are attached to a drive shaft (not shown). The dog gear 2 is free to rotate around the drive shaft, but the dog ring 4 has a number of drive formations 6 in the form of grooves on its inner circumference that engage complementary drive formations in the form of splines on the drive shaft, so that the dog ring 4 is forced to rotate with the drive shaft. The drive formations also allow the dog ring 4 to slide axially relative to the drive shaft between an engaged position in which the dog ring 4 engages with the dog gear 2 and a disengaged position in which the dog ring 4 is disengaged from the dog gear 2. This axial movement is controlled by a selector mechanism (not shown), conventionally a selector fork, for example, which engages a radial flange 12 on the outer circumference of the dog ring 4. The dog gear 2 carries a set of gear teeth 14 on its outer periphery for transmitting drive to another gear (not shown).

[0004] The dog ring 4 carries a first set of dogs 8 and the dog gear 2 carries a second set of dogs 10. The first and second dogs 8, 10 can be engaged with one another by axially moving the dog ring 4 to an engaged position, so that torque and rotational drive are transmitted between the drive shaft, the dog ring 4 and the dog gear 2. Alternatively, the dog ring 4 can be moved to a disengaged position, so that torque and rotational drive are not transmitted between the dog ring 4 and the dog gear 2. The dog gear 2 is then free to rotate about the drive shaft.

[0005] The operation of a conventional dog clutch is shown in Figures 3a-3f, in which the dog gear 2 and dog ring 4 are shown diagrammatically and in an expanded linear view to show the relative positions of the dog gear 2 and dog ring 4 during operation.

[0006] Figures 3a-3c show the relative positions of the dog gear 2 and the dog ring 4 during a gear shift as the dog ring 4 is brought into engagement with the dog gear 2 from a disengaged position. In Figure 3a, the dog ring 4 is in a disengaged position and a first dog 8 on the dog ring 4 is axially spaced from a second dog 10 on the dog gear 2. The relative rotational movement between the dog gear 2 and the dog ring 4 is indicated by the direction of the load / direction arrow A.

[0007] In Figure 3b the dog ring 4 has been partially displaced towards the engaged position and in Figure 3c the dog ring 4 has been fully displaced to the engaged position. Due to relative rotation between the dog gear 2 and the dog ring 4 the first and second sets of dogs 8, 10 now engage with each other to transmit torque and rotational drive between the dog gear 2 and the dog ring 4.

[0008] To be successfully engaged, the first and second dogs 8, 10 must mesh as shown in Figure 3c. If the dog gear 2 and dog ring 4 are not properly aligned during the axial movement of the dog ring towards the engaged position, the first and second dogs 8, 10 may contact each other before the dog clutch is fully engaged, which may result in a delayed or rejected shift. Providing a large gap between the dogs reduces this risk and increases the likelihood that the dogs will mesh properly.

[0009] However, a drawback of having a large gap between the dogs is that it can create shock loads in the transmission system when the direction of torque transmitted through the dog clutch is reversed, for example when the throttle is lifted to cause engine braking. This is shown in Figures 3d-3f. In Figure 3d, drive is transmitted through the dog clutch in a first direction, and the direction of the load is shown by load / motion arrow A. In Figures 3e and 3f, the direction of the load is reversed, causing the dog gear 2 and dog ring 4 to rotate in opposite directions until the dogs 8, 10 come into contact and transmit torque in the opposite direction, as shown in Figure 3f.

[0010] During relative rotation of the dog gear 2 and dog ring 4 from the position shown in Figure 3d to the position shown in Figure 3f, substantial rotational speed differences can occur between the components of the transmission system resulting in large shock loads as the dogs re-engage, which can lead to an unpleasant driving experience for vehicle passengers and can also cause wear or damage to the transmission system.

[0011] Thus, in conventional dog clutches, the spacing between the dogs is selected to provide a compromise between reducing the risk of failure of the dog clutch to engage and mitigating shock loads within the drive transmission when the direction of the transmitted torque is reversed. However, such a compromise is never entirely satisfactory.

[0012] U.S. Patent Application Publication No. 2019 / 0242442A1 describes a modified dog clutch that seeks to address the shortcomings discussed above. However, the mechanism described in U.S. Patent Application Publication No. 2019 / 0242442A1 is complex and expensive to manufacture, and requires the presence of a cam groove on the power transmission shaft. This mechanism is not suitable for use in existing conventional transmission systems.

[0013] No. 4-64617 describes a dog clutch in which a dog gear comprises a number of fixed dogs and a number of retractable dogs capable of limiting the relative rotational motion between the dog gear and the dog ring when torque is reversed. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] US Patent Application Publication No. 2019 / 0242442A1 [Patent Document 2] Actual total number of employees: 4-64617 Summary of the Invention [Problem to be solved by the invention]

[0015] It is an object of the present invention to provide a drive power transmission device including a dog clutch that mitigates one or more of the above-described disadvantages while avoiding the complexities of the dog clutch described in U.S. Patent Application Publication No. 2019 / 0242442 A1. [Means for solving the problem]

[0016] According to one aspect of the present invention, there is provided a driving force transmission device including a dog clutch, the dog clutch comprising: A dog gear assembly, and Dog Ring Equipped with the dog gear assembly and the dog ring are configured for rotation about an axis of rotation and for relative axial adjustment between an engaged state in which torque may be transmitted between the dog gear assembly and the dog ring and a disengaged state in which torque may not be transmitted between the dog gear assembly and the dog ring; A dog gear assembly, Dog gear, a retractable dog assembly configured to move relative to the dog gear between an extended position and a retracted position; and A control element for controlling the movement of the retractable dog assembly Including, the dog ring includes a plurality of first dogs, the dog gear assembly includes a plurality of second dogs, the second dogs configured to engage the first dogs in an engaged state to transmit torque between the dog ring and the dog gear assembly, and configured to disengage from the first dogs in a disengaged state so that they do not transmit torque; There is provided a drive force transmission device, wherein the second dog includes a plurality of fixed dogs attached to a dog gear and a plurality of retractable dogs comprising a retractable dog assembly.

[0017] In one embodiment, each retractable dog has a torque drive surface configured to transfer torque to the dog ring when engaged with a first dog, and a cam surface configured to urge movement of the retractable dog assembly toward the retracted position when engaged with the first dog, such that relative rotation between the dog ring and the dog gear assembly causes the engaged first dog to slide on the cam surface of the engaged retractable dog, urging movement of the retractable dog assembly toward the retracted position.

[0018] When the retractable dog assembly is in the extended position and the dog clutch is engaged, the retractable dogs limit relative rotation between the dog ring and the dog gear assembly when the direction of drive force transmitted through the dog clutch is reversed. This reduces shock loads and makes the dog clutch smoother and more comfortable during operation.

[0019] When the dog clutch is changing from a disengaged to an engaged state, the retractable dog assembly, if engaged by the first dog, can be moved to a retracted position so as not to interfere with engagement of the dog clutch.

[0020] Thus, the dog clutch reduces shock loads without increasing the risk of gear rejection.

[0021] In one embodiment, the retractable dog assembly is configured for axial movement relative to the dog gear between the extended and retracted positions, and the control element is configured to control the axial movement of the retractable dog assembly. Alternatively, the retractable dog assembly may be configured for non-axial movement relative to the dog gear between the extended and retracted positions, such as through movement of the retractable dogs in a radial or circumferential direction, in which case the control element is configured to control movement of the retractable dogs in a required direction between the extended and retracted positions.

[0022] In one embodiment, the fixed dogs and the retractable dogs extend axially substantially equidistant from the dog gear when the retractable dog assembly is in the extended position, ensuring that the fixed dogs and the retractable dogs are equally capable of transmitting torque through the dog clutch.

[0023] In one embodiment, the retractable dog assembly is configured such that torque can be transmitted between the retractable dog and the first dog when the retractable dog assembly is in the extended position, and such that torque cannot be transmitted between the retractable dog and the first dog when the retractable dog assembly is in the retracted position.

[0024] In one embodiment, each retractable dog has a torque drive surface configured to transfer torque to the dog ring when engaged with a first dog, and a cam surface configured to urge movement (possibly axial movement) of the retractable dog assembly toward the retracted position when engaged with the first dog.

[0025] When the first dog engages the cam surface during engagement of the dog clutch, the relative rotation between the retractable dog and the first dog displaces the retractable dog toward a retracted position such that the retractable dog does not impede rotation of the dog ring relative to the dog gear assembly. This helps ensure that the retractable dog does not impede engagement of the dog clutch. However, when the retractable dog is in an extended position, the retractable dog can transmit torque / drive force due to engagement of the torque drive surface with the first dog.

[0026] Optionally, in one embodiment, the torque drive surface is substantially perpendicular to a cross-section of the dog clutch, enabling the dog clutch to transmit a drive force / torque.

[0027] In one embodiment, the cam surface is inclined relative to a cross-section of the dog clutch such that relative rotation of the dog ring and the dog gear assembly moves the retractable dogs toward the retracted position. In general, the cam surface is inclined relative to a cross-section of the dog clutch at an acute angle θ that is effective and different from the prior art, taking into account tolerances. In one embodiment, the cam surface is inclined relative to a cross-section of the dog clutch at an acute angle θ that is greater than 0° and less than 90°. In some cases, the angle θ is in the range of 1° to 85°, or in some cases, 5° to 85°, or in some cases, 10° to 50°, or in some cases, 20° to 40°.

[0028] In one embodiment, the retractable dogs are asymmetric and arranged in pairs, where the torque drive surface includes an outer surface of each pair of retractable dogs and the cam surface includes an inner surface of each pair of retractable dogs, and the retractable dogs forming each pair are optionally interconnected to cooperate between extended and retracted positions.

[0029] In one embodiment, the retractable dogs are disposed between adjacent fixed dogs. Optionally, each pair of retractable dogs is disposed between adjacent pairs of fixed dogs.

[0030] In one embodiment, each retractable dog passes through a pocket in the drive gear, possibly in a direction substantially parallel to the axis of rotation, which supports the retractable dog and allows the dog to move between an extended position and a retracted position, but may prevent any other movement of the dog relative to the drive gear.

[0031] In one embodiment, the retractable dog assembly includes a support element and the retractable dogs are attached to the support element. In this embodiment, the retractable dogs cooperate between an extended position and a retracted position.

[0032] Optionally, in one embodiment, the control element is configured to control the movement of the support element, and thus the control element controls the cooperation of all the retractable dogs between the extended position and the retracted position.

[0033] In another embodiment, the retractable dogs are configured to move independently of one another between the extended and retracted positions. Optionally, in one embodiment, the control element may be configured to individually control the axial movement of the retractable dogs.

[0034] In one embodiment, the control element comprises a resilient biasing means for biasing the retractable dog assembly towards the extended position. For example, the control element may comprise a spring, such as a wave spring, a helical spring, or a Belville washer, or an elastomeric element such as a rubber block, or the control element may comprise an air spring.

[0035] In an alternative embodiment, the control element comprises an actuator operable to control the movement of the retractable dog assembly, e.g., in an axial direction, between the extended and retracted positions. The actuator may, for example, be a mechanical, electrical, or hydraulic actuator that allows the position of the retractable dog assembly to be directly controlled, e.g., by a computer control system.

[0036] In one embodiment, the dog gear includes a recess that receives the retractable dog assembly to provide a compact assembly.

[0037] Optionally, in one embodiment, the dog clutch further comprises a retaining element, such as a retaining ring, that retains the retractable dog assembly within the recess.

[0038] According to another aspect of the present invention, there is provided a transmission system including a drive power transmission device according to any one of the previous statements of the present invention and a drive shaft rotatable about a shaft axis, wherein a dog gear assembly and a dog ring are configured to rotate about the shaft axis, the dog gear assembly being rotatable relative to the drive shaft and the dog ring being rotated to rotate with the drive shaft. The transmission system may be part of a drive power transmission system of a vehicle, for example, transmitting drive power between an engine and wheels.

[0039] In one embodiment, the drive shaft and the dog ring include a mutual drive structure that allows relative axial movement between the dog ring and the drive shaft and prevents relative rotation between the dog ring and the drive shaft.

[0040] Optionally, in one embodiment, the transmission system includes a selector mechanism that controls relative axial movement between the dog ring and the drive shaft between an engaged and a disengaged condition.

[0041] Some embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0042] [Figure 1] FIG. 1 is a front isometric view of a dog gear and dog ring forming part of a conventional dog clutch. [Diagram 2] FIG. 1 is a rear isometric view of a dog gear and dog ring forming part of a conventional dog clutch. [Figure 3a] 1 is an exploded schematic sectional view of a conventional dog clutch showing the relative positions of the dog gears and dog ring during operation of the dog clutch; FIG. [Figure 3b] 1 is an exploded schematic sectional view of a conventional dog clutch showing the relative positions of the dog gears and dog ring during operation of the dog clutch; FIG. [Figure 3c] 1 is an exploded schematic sectional view of a conventional dog clutch showing the relative positions of the dog gears and dog ring during operation of the dog clutch; FIG. [Figure 3d] 1 is an exploded schematic sectional view of a conventional dog clutch showing the relative positions of the dog gears and dog ring during operation of the dog clutch; FIG. [Figure 3e] 1 is an exploded schematic sectional view of a conventional dog clutch showing the relative positions of the dog gears and dog ring during operation of the dog clutch; FIG. [Figure 3f]1 is an exploded schematic sectional view of a conventional dog clutch showing the relative positions of the dog gears and dog ring during operation of the dog clutch; FIG. [Figure 4] FIG. 2 illustrates a first dog clutch according to one embodiment of the present invention, showing a front isometric view of the dog gears and dog ring. [Diagram 5] FIG. 2 illustrates a first dog clutch according to one embodiment of the present invention, showing an isometric view from the rear of the dog gears and dog ring. [Figure 6a] FIG. 2 is an exploded linear schematic diagram showing the operation of a first dog clutch according to one embodiment of the present invention; [Figure 6b] FIG. 2 is an exploded linear schematic diagram showing the operation of a first dog clutch according to one embodiment of the present invention; [Figure 6c] FIG. 2 is an exploded linear schematic diagram showing the operation of a first dog clutch according to one embodiment of the present invention; [Figure 6d] FIG. 2 is an exploded linear schematic diagram showing the operation of a first dog clutch according to one embodiment of the present invention; [Figure 6e] FIG. 2 is an exploded linear schematic diagram showing the operation of a first dog clutch according to one embodiment of the present invention; [Figure 7] FIG. 2 illustrates a first dog clutch according to one embodiment of the present invention; FIG. 3 is an exploded isometric view of the first dog clutch; [Figure 8] FIG. 2 illustrates a first dog clutch according to one embodiment of the present invention, showing an isometric front view of the dog gears. [Figure 9] FIG. 2 illustrates a first dog clutch according to one embodiment of the present invention, showing an isometric rear view of the dog gears. [Figure 10] FIG. 2 illustrates a first dog clutch according to one embodiment of the present invention, showing an isometric front view of a retractable dog assembly. [Figure 11] FIG. 2 illustrates a first dog clutch according to one embodiment of the present invention, showing an isometric rear view of a retractable dog assembly. [Figure 12] FIG. 2 illustrates a first dog clutch according to one embodiment of the present invention, showing an isometric view of a dog ring. [Figure 13] FIG. 2 illustrates a first dog clutch according to an embodiment of the present invention, showing an isometric view of a control element. [Figure 14] FIG. 2 illustrates a first dog clutch according to an embodiment of the present invention, showing an isometric view of a retaining element. [Figure 15] FIG. 2 illustrates a second dog clutch according to one embodiment of the present invention; FIG. 3 is an exploded isometric view of the second dog clutch. [Figure 16] FIG. 2 illustrates a second dog clutch according to one embodiment of the present invention, showing an isometric view from the front of the dog gears. [Figure 17] FIG. 2 is an isometric view from the rear of the dog gears showing a second dog clutch according to one embodiment of the present invention. [Figure 18] FIG. 2 illustrates a second dog clutch according to an embodiment of the present invention, showing an isometric view of a dog ring. [Figure 19] FIG. 2 illustrates a second dog clutch according to one embodiment of the present invention, showing a front isometric view of a retaining element. [Figure 20] FIG. 2 illustrates a second dog clutch according to one embodiment of the present invention, showing a rear isometric view of a retaining element. [Figure 21] FIG. 2 illustrates a second dog clutch according to one embodiment of the present invention, showing a front isometric view of a set of retractable dogs. [Figure 22] FIG. 13 illustrates a rear isometric view of a set of retractable dogs in a second dog clutch according to one embodiment of the present invention. [Diagram 23] FIG. 13 illustrates a second dog clutch according to one embodiment of the present invention, showing an isometric view of a set of springs. [Figure 24]FIG. 13 illustrates a second dog clutch according to an embodiment of the present invention, showing an isometric view of a set of retaining elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] A drive transmission including a first dog clutch 20 according to one embodiment of the present invention is shown in Figures 4 to 14. The first dog clutch 20 includes a dog gear assembly 22 and a dog ring 24 that are attached to a rotating drive shaft 26. The drive shaft 26 may be a main shaft or a counter shaft of the transmission depending on the type of transmission. The rotating drive shaft 26 carries a hub 28 that has a plurality of first drive structures 30, e.g., splines or other structures, on its outer periphery. The first drive structures 30 engage complementary second drive structures 32, e.g., grooves or other structures, on the inner periphery of the dog ring 24. The first and second drive structures force the dog ring 24 to rotate with the drive shaft 26, but allow relative axial movement between the dog ring 24 and the drive shaft 26. This axial movement is controlled by a selector mechanism 33, e.g., a selector fork that engages a radial flange 34 on the outer periphery of the dog ring 24. The dog gear assembly 22 carries a set of gear teeth 35 for transmitting driving force to another gear (not shown).

[0044] In this embodiment, the dog gear assembly 22 is mounted to a plain portion 26a of the drive shaft 26 that does not have a drive structure and is configured to rotate freely relative to the drive shaft 26. Optionally, the dog gear assembly 22 may be mounted in bearings (not shown) that allow for free rotation relative to the drive shaft 26. The dog gear assembly 22 includes a dog gear 36, a retractable dog assembly 38, a control element 40 which in this embodiment includes a wave spring, and a retaining element 42 which in this embodiment includes a spiral retaining ring.

[0045] The dog ring 24 carries a first set of dogs 44 and the dog gear assembly 22 carries a second set of dogs 46 that are engageable with the first dogs 44 to transmit rotational drive and torque between the dog ring 24 and the dog gear assembly 22. In this embodiment, the first dogs 44 and the second dogs 46 are substantially triangular in cross section and extend axially from end faces 48, 49 of the dog ring 24 and the dog gear 36, respectively. In this embodiment, the apex of the first dog 44 points radially outward and the apex of the second dog 46 points radially inward. Thus, the first and second dogs 44, 46 have complementary shapes that enable the respective faces of the dogs to transmit torque and rotational drive between the dog ring 24 and the dog gear assembly 22. However, the first and second dogs 44, 46 may have alternative cross-sectional shapes (eg, square, trapezoidal, etc.).

[0046] The second set of dogs 46 includes a number of fixed dogs 46a extending axially from an end face 49 of the dog gear 36 and a number of retractable dogs 46b forming part of the retractable dog assembly 38. The retractable dogs 46b are attached to an annular support element 50, which in this embodiment includes an annular ring made, for example, of steel. However, the annular support element 50 may be made of other materials and may have a different shape. The retractable dogs 46b extend axially (i.e., in a direction parallel to the axis of rotation Z of the drive shaft 26) from the annular support element 50 towards the dog ring 24. In some cases, the fixed dogs and the retractable dogs extend axially a substantially equal distance D from the dog gear when the retractable dog assembly is in the extended position, as shown in FIG. 6a.

[0047] In this embodiment, the retractable dog assembly 38 includes eight retractable dogs 46b arranged in four pairs 51 of dogs. The retractable dogs 46b are aligned with pockets 52 that extend axially through the dog gear 36 and are configured to move axially with the annular support element 50 between an extended position and a retracted position, where the retractable dogs 46b extend axially beyond the end face 49 of the dog gear 36 and where the retractable dogs 46b are positioned substantially flush with or below the end face 49 of the dog gear 36. When the retractable dogs 46b are in the extended position, they can engage with the first dog 44 provided on the dog ring 24. When the retractable dogs 46b are in the retracted position, they cannot engage with the first dog 44.

[0048] The axial position of the retractable dog assembly 38 relative to the dog gear 36 is controlled by a control element 40, which in this embodiment is a resilient control element including an annular wave spring. Alternatively, the control element 40 can take a number of different forms. For example, the control element 40 can include a different resilient element, such as a Belleville spring or an air spring, or the control element 40 can include an actuator that can be pneumatically, mechanically, or electromagnetically controlled.

[0049] In this embodiment, the control element 40 includes a resilient control element that is axially compressed between an annular support element 50 and a retaining element 42. The retractable dog assembly 38, the control element 40, and the retaining element 42 are all received within an annular recess 54 in a rear face 56 of the dog gear 36. The retaining element 42 engages an inwardly facing circumferential groove 58 of the annular recess 54. The resilient control element 40 biases the retractable dog assembly 38 axially toward an extended position in which the retractable dog 46b can engage the first dog 44 on the dog ring 24.

[0050] As mentioned above, the retractable dogs 46b are arranged in pairs 51 as shown in Figs. 10 and 11. In this embodiment, each pair of retractable dogs 46b is arranged between a pair of adjacent fixed dogs 46a. In this embodiment, the two retractable dogs 46b of each pair 51 are mirror images of each other, and each individual retractable dog 46b is asymmetric. Each retractable dog 46b of each pair 51 includes an outer surface 62 and an inner surface 64, with the inner surfaces 64 of each pair facing inwardly toward each other. The outer surface 62 is designed to engage with a first dog 44 on the dog ring 24 and has a contour that is complementary to the contour of the first dog 44, which in this embodiment is set at an acute angle to the turning radius to match the triangular shape of the first dog 44. The outer surface 62 of each retractable dog 46b includes a torque driving surface configured to transmit torque to the dog ring 24 when engaged with the first dog 44.

[0051] The inner surface 64 of each retractable dog 46b includes a cam surface 68 configured to urge axial movement of the retractable dog assembly toward the retracted position when engaged with the first dog. In this embodiment, the cam surface 68 includes a beveled surface inclined at an acute angle θ with respect to a transverse plane of the dog clutch (the term "transverse plane" in this context means a plane perpendicular to the axis of rotation Z of the drive shaft 26), as shown in FIG. 6a. The acute angle θ is greater than 0° and less than 90°. Optionally, the acute angle θ is in the range of 1° to 85°, or optionally 5° to 85°, or optionally 10° to 50°, or optionally 20° to 40°, e.g., about 30°. In contrast, the outer surface 62 of each retractable dog 46b is substantially perpendicular to the transverse plane of the dog clutch.

[0052] The operation of the dog clutch will now be described with reference to Figures 6a to 6e. Figures 6a to 6c show a shifting situation in which the dog ring 24 is moved axially from a disengaged state shown in Figure 6a, through a partially engaged state shown in Figure 6b, to a fully engaged state shown in Figure 6c. Arrow A indicates the direction of relative rotation between the dog ring 24 and the dog gear assembly 22 and / or the load / torque being transmitted. In these figures, the relative rotation between the dog ring 24 and the dog ring assembly 22 is represented as a linear motion for clarity and ease of understanding, where, for example, a right hand direction represents clockwise rotation or torque and a left hand direction represents counterclockwise rotation or torque.

[0053] 6a, the dog ring 24 is disengaged from the dog gear assembly 22 in the axial direction X. Thus, the dog clutch is in a disengaged state and no load / torque is transferred between the dog ring 24 and the dog gear assembly 22. The dog ring 24 is rotating to the left (e.g., counterclockwise) relative to the dog gear assembly 22.

[0054] 6b, the dog ring 24 has been moved axially toward the dog gear assembly 22 (i.e., toward an engaged state). However, the first and second dogs 44, 46 are not yet fully engaged, so that no torque is transferred directly between the dog ring 24 and the dog gear assembly 22 at this stage.

[0055] However, one of the first dogs 44 on the dog ring 24 is engaged with one of the retractable dogs 46b of the retractable dog assembly 38. Relative rotation between the dog ring 24 and the dog gear assembly 22 causes the first dog 44 to slide over the cam surface 68 of the engaged retractable dog 46b, forcing the retractable dog assembly 38 axially inward toward the retracted position against the force of the control element 40, which in this embodiment is a compressed wave spring. This allows the dog ring 24 to continue to rotate relative to the dog gear assembly 22. As a result of the contact between the first dog 44 and the retractable dog 46b, a small amount of torque can be transmitted between the dog ring 24 and the retractable dog assembly 38.

[0056] 6c, the first dog 44 has rotated past the retractable dog 46b, allowing the retractable dog assembly 38 to return to the extended position under the influence of the control element 40. The first dog 44 now engages the fixed dog 46a, allowing the fixed dog 46a to transmit torque / rotational drive between the dog ring 24 and the dog gear assembly 22.

[0057] Figures 6d and 6e show a situation where the dog clutch is engaged and there is a change in direction of drive / torque transfer through the dog clutch, such as may occur in a vehicle when the throttle is closed such that the torque transferred through the dog clutch changes from forward drive to engine braking.

[0058] In Figure 6d (which is identical to Figure 6c described above), a first dog 44 on the dog ring 24 is engaged with a fixed second dog 46a on the dog gear assembly 22 to transmit drive / torque between the dog ring 24 and the dog gear assembly 22 and vice versa. In this example, the dog ring 24 transmits torque to the left (counterclockwise) to the dog gear assembly 22.

[0059] If the direction of the transmitted torque is reversed, such as when the throttle is closed or during engine braking, the dog ring 24 rotates in the opposite direction relative to the dog gear assembly 22, as shown in Figure 6d. In this example, the dog ring 24 rotates to the right (clockwise) relative to the dog gear assembly 22.

[0060] The relative rotation between the dog ring 24 and the dog gear assembly 22 is limited by the retractable dog assembly 38 being biased to the extended position by the control element 40. The dog ring 24 can only rotate a short distance (i.e., a small angle) until the first dog 44 engages the drive face of the retractable dog 46b, which is now in the extended position. The dog clutch can then transmit the rotational drive / torque in the opposite direction. Because the dog ring 24 rotates only a small distance before re-engaging with the dog gear assembly 22, the change in the relative rotational speed of the two parts of the transmission system is only small, resulting in a smooth reversal of torque.

[0061] On the other hand, the relatively large gap between the fixed second dogs 46a during shifting also reduces the risk of change rejection. The retractable second dogs 46b can retract when engaged by the first dogs, allowing the dog ring 24 to continue to rotate relative to the dog gear assembly 22 until the first dogs 44 engage the fixed second dogs 46a without impeding or blocking the shifting.

[0062] Further, as shown in FIG. 6b, the retractable dog assembly 38 is pushed (in the direction of arrow X) toward the retracted position as the first dog 44 slides over the cam surface 68 of the engaged retractable dog 46b. This motion is opposed by the operating member 40 (wave spring) which exerts a biasing force on the retractable dog assembly 38. This causes the retractable dog assembly 38 to exert a force on the first dog 44 through the cam surface 68 in a direction opposite to the direction of rotation (opposite the direction of arrow A). As a result of the contact between the first dog 44 and the retractable dog 46b, a small amount of torque is transmitted between the dog ring 24 and the retractable dog assembly 38. Thus, the relative rotational speed of the dog ring 24 and the dog gear assembly 22 is reduced by the retractable dog assembly 38 before the first dog 44 engages the fixed second dog 46a, thereby reducing the impact of the engagement.

[0063] A drive transmission including a dog clutch 120 according to a second embodiment of the present invention is shown in Figures 15 to 24. The dog clutch 120 includes a dog gear assembly 122 and a dog ring 124 that are attached to a rotating drive shaft 126. The rotating drive shaft 126 carries a hub 128 that has a plurality of first drive structures 130, e.g., splines or other structures, on its outer periphery. The splines 130 engage complementary second drive structures 132, e.g., grooves or other structures, on the inner periphery of the dog ring 124. The first and second drive structures force the dog ring 124 to rotate with the drive shaft 126, but allow relative axial movement between the dog ring 124 and the drive shaft 126. This axial movement is controlled by a selector mechanism 133, e.g., a selector fork, that engages a radial flange 134 on the outer periphery of the dog ring 124. The dog gear assembly 122 carries a set of gear teeth 135 on its outer periphery for transmitting driving force to another gear (not shown).

[0064] The dog gear assembly 122 is attached to a plain portion 126 a of a drive shaft 126 that does not have any drive structure and is configured to rotate freely relative to the drive shaft 126 .

[0065] Dog gear assembly 122 includes a dog gear 136, a retractable dog assembly 138, a control element 140 which in this embodiment includes a plurality of helical springs 140', and a retaining element 142 which in this embodiment includes a plurality of bolts 142'.

[0066] The dog ring 124 carries a first set of dogs 144 and the dog gear assembly 122 carries a second set of dogs 146 that are engageable with the first dogs 144 to transmit rotational drive and torque between the dog ring 124 and the dog gear assembly 122. In this embodiment, the first and second dogs 144, 146 are substantially triangular in cross section and extend axially from respective end faces of the dog ring 124 and the dog gear assembly 122. In this embodiment, the apex of the first dog 144 points radially outward and the apex of the second dog 146 points radially inward. Thus, the first and second dogs 144, 146 have complementary shapes that enable the respective faces of the dogs to transmit torque and rotational drive between the dog ring 124 and the dog gear assembly 122. However, the first and second dogs may have alternative cross-sectional shapes (eg, square, trapezoid, etc.).

[0067] The second set of dogs 146 includes a plurality of fixed dogs 146a extending axially from an end face 147 of the dog gear 136 and a plurality of retractable dogs 146b that form part of the retractable dog assembly 138. The retractable dogs 146b are separated from one another and extend axially (i.e., in a direction parallel to the axis of rotation Z of the drive shaft 126) from the annular support element 150 towards the dog ring 124.

[0068] In this embodiment, the retractable dog assembly 138 includes eight retractable dogs 146b arranged in four pairs 151 of dogs. Each retractable dog 146b is aligned with a respective pocket 152 axially extending through the dog gear 136 and is configured to move axially between an extended position and a retracted position, where in the extended position the retractable dogs 146b extend axially beyond the end face 147 of the dog gear 136 and where in the retracted position the retractable dogs 146b are positioned substantially flush with or below the end face of the dog gear 136. When in the extended position, the retractable dogs 146b can engage with a first dog 144 provided on the dog ring 124. When in the retracted position, the retractable dogs 146b cannot engage with the first dog 144.

[0069] The retractable dog 146b is supported by an annular support element 150, which in this embodiment comprises an annular ring made, for example, of steel. However, the annular support element 150 may be made of other materials and may have a different shape. The control element 140 comprises a set of helical springs 140', which are compressed between the retractable dog 146b and the annular support element 150 and provide an axial force biasing the retractable dog 146b towards the extended position. The annular support element 150 is attached to the dog gear 136 by a retaining element 142, which in this embodiment comprises a number of bolts 142' which pass through bolt holes 153 in the annular support element 150 and engage threaded bores 155 in the rear face 156 of the dog gear 136.

[0070] The axial position of the retractable dog 146b relative to the dog gear 136 is controlled by a control element 140, which in this example includes a plurality of helical springs 140'. Alternatively, the control element 140 can take a number of different forms. For example, the control element 140 can include a different elastic element, such as an air spring, or the control element 140 can include one or more actuators that can be pneumatically, mechanically, or electromagnetically controlled.

[0071] In this embodiment, the control element 140, the annular support element 150, and the retaining element 142 are all received within an annular recess 154 in a rear face 156 of the dog gear 136. The helical spring 140' axially biases the retractable dog 146b toward an extended position in which the retractable dog 146b can engage the first dog 144 on the dog ring 124.

[0072] As mentioned above, the retractable dogs 146b are arranged in pairs 151 as shown in Figs. 15, 21 and 22. In this embodiment, the two retractable dogs 146b of each pair 151 are mirror images of each other, and each individual retractable dog 146b is asymmetric. Both retractable dogs 146b of each pair 151 include an outer edge 162 and an inner edge 164, with the inner edges 164 of each pair facing inwardly toward each other. The outer edge 162 has a complementary contour designed to engage with the first dog 144 on the dog ring 124 and set at an acute angle to the turning radius to match the triangular shape of the first dog 144 in this embodiment. The outer surface 162 of each retractable dog 146b includes a torque driving surface 166 configured to transmit torque to the dog ring when engaged with the first dog.

[0073] An inner surface 164 of each retractable dog 146b includes a cam surface 168 configured to urge axial movement of the retractable dog assembly toward the retracted position upon engagement with the first dog. In this embodiment, the cam surface 168 includes a beveled surface inclined at an acute angle relative to the transverse plane of the dog clutch (the term "transverse plane" in this context means a plane perpendicular to the axis of rotation Z of the drive shaft 126). In contrast, an outer surface 162 of each retractable dog 146b is substantially perpendicular to the transverse plane of the dog clutch.

[0074] The operation of the second dog clutch is similar to that of the first dog clutch described above with reference to Figures 6a to 6e, with the only significant difference being that the retractable dog 146b can move axially independently of each other between an extended position and a retracted position when engaged by the first dog.

[0075] Similar to the first dog clutch described above, in the second dog clutch, the first dog 144 is biased towards the extended position by the force of the control element 140 (a helical spring). As a result of contact between the first dog 144 and the retractable dog 146b, a small amount of torque is transferred between the dog ring 124 and the retractable dog assembly 138. Thus, the relative rotational speed of the dog ring 124 is slowed by the retractable dog assembly 138 before the first dog 144 engages with the fixed second dog 146a, thereby reducing the shock of engagement.

[0076] Various modifications of the first and second dog clutches are possible, some of which are described below.

[0077] In the two embodiments described above, the control elements 40, 140 which axially bias the retractable dog assemblies 38, 138 were wave springs and helical springs respectively, however other types of resilient members (such as rubber blocks) and actuators could alternatively be used.

[0078] Further, in the above two embodiments, an annular member having a circular outer periphery is used as the dog ring 24, 124. Alternatively, sliding dogs having a different outer periphery shape (e.g., having a radial drive configuration) may be used or another gear adjacent to the dog gear assembly 22, 122, provided that the dogs are also rotated with the drive shaft, are axially slidable relative to the drive shaft, and have dogs that are axially movable to engage and disengage with the second dogs 44, 46, 144, 146 of the dog gear assembly, and the dogs engage with each other to transmit the torque and rotation of the drive shaft to the dog gear assembly 22, 122.

[0079] It is also possible to configure the retractable dog assembly for non-axial movement relative to the dog gear between the extended and retracted positions, such as through movement in a radial or circumferential direction.

Claims

1. A driving force transmission device including a dog clutch, the dog clutch comprising: A dog gear assembly, and Dog Ring Equipped with the dog gear assembly and the dog ring are configured for rotation about an axis of rotation and for relative axial adjustment between an engaged state in which torque may be transmitted between the dog gear assembly and the dog ring and a disengaged state in which torque may not be transmitted between the dog gear assembly and the dog ring; The dog gear assembly is Dog gear, a retractable dog assembly provided on the dog gear and configured to move relative to the dog gear between an extended position and a retracted position; and A control element for controlling the movement of the retractable dog assembly Including, the dog ring includes a plurality of first dogs, the dog gear assembly includes a plurality of second dogs, the second dogs configured to engage with the first dogs in the engaged state to transmit torque between the dog ring and the dog gear assembly, and configured to disengage from the first dogs in the disengaged state; the second dogs include a plurality of fixed dogs attached to the dog gear and a plurality of retractable dogs forming the retractable dog assembly, the dog clutch having a transverse surface, each retractable dog having a torque drive surface disposed perpendicular to the transverse surface configured to transmit torque to the dog ring when the torque drive surface engages the first dog, and a cam surface inclined relative to the transverse surface configured to urge movement of the retractable dog assembly toward the retracted position when the cam surface engages the first dog; whereby, when the first dog is engaged with the cam surface, relative rotation between the dog ring and the dog gear assembly causes the engaged first dog to slide on the cam surface of the engaged retractable dog, urging movement of the retractable dog assembly toward the retracted position relative to the dog gear.

2. 2. The drive power transmission device of claim 1, wherein the retractable dog assembly is configured for axial movement relative to the dog gear between an extended position and a retracted position, and the control element controls the axial movement of the retractable dog assembly.

3. 3. The drive transmission device of claim 2, wherein said fixed dog and said retractable dog extend axially substantially equidistant from said dog gear when said retractable dog assembly is in said extended position.

4. 4. The drive force transmission device according to claim 1, wherein the retractable dog assembly is configured such that torque can be transmitted between the retractable dog and the first dog when the retractable dog assembly is in the extended position, and such that torque cannot be transmitted between the retractable dog and the first dog when the retractable dog assembly is in the retracted position.

5. 5. A drive transmission device according to claim 1, wherein the torque driving surface is substantially perpendicular to the transverse plane of the dog clutch.

6. 6. A drive force transmission device according to claim 1, wherein the cam surface is inclined at an acute angle θ with respect to the transverse plane of the dog clutch, the acute angle θ being greater than 0° and less than 90°, and optionally the acute angle θ being in the range of 1° to 85°, or optionally 5° to 85°, or optionally 10° to 50°, or optionally 20° to 40°.

7. 7. A drive force transmission device as claimed in any one of claims 1 to 6, wherein the retractable dogs are arranged in pairs, the torque drive surface includes an outer surface of each pair of retractable dogs, and the cam surface includes an inner surface of each pair of retractable dogs.

8. 8. The drive transmission device of claim 7, wherein each pair of retractable dogs is disposed between adjacent fixed dogs.

9. 9. A drive transmission device as claimed in any one of claims 1 to 8, wherein each retractable dog passes through a pocket in the dog gear.

10. 10. A drive force transmission device according to claim 1, wherein the retractable dog assembly comprises a support element, the retractable dog being attached to the support element, and optionally the control element being configured to control the movement of the support element.

11. 10. A drive force transmission device according to claim 1, wherein the retractable dogs are configured to move independently of one another between the extended position and the retracted position, and optionally the control element is configured to control the movement of the retractable dogs.

12. 12. A drive transmission device as claimed in any preceding claim, wherein the control element comprises resilient biasing means for biasing the retractable dog assembly towards the extended position.

13. 12. A drive transmission device as claimed in any preceding claim, wherein the control element comprises an actuator operable to control movement of the retractable dog assembly between the extended position and the retracted position.

14. 14. A drive transmission device as claimed in any one of claims 1 to 13, wherein the dog gear includes a recess for receiving the retractable dog assembly, and optionally further comprises a retaining element for retaining the retractable dog assembly within the recess.

15. 15. The drive transmission device of claim 1, wherein the first dogs are substantially triangular in cross section perpendicular to the axis of rotation and extend axially from respective end faces of the dog ring, with apexes of the first dogs pointing radially outward, the retractable dogs include outer surfaces, the outer surfaces of the retractable dogs having a contour designed to engage the first dogs on the dog ring and complementary to the contour of the first dogs and set at an acute angle to a radius of rotation to match the triangular shape of the first dogs, and the outer surface of each retractable dog includes a torque drive surface configured to transmit torque to the dog ring when engaged with a first dog.

16. 16. A transmission system comprising a drive force transmission device according to any one of claims 1 to 15 and a drive shaft rotatable about a shaft axis, wherein the dog gear assembly and the dog ring are configured to rotate about the shaft axis, the dog gear assembly is rotatable relative to the drive shaft, and the dog ring is configured to rotate together with the drive shaft.

17. 17. The transmission system of claim 16, wherein the drive shaft and the dog ring include a mutual drive structure that allows relative axial movement between the dog ring and the drive shaft and prevents relative rotation between the dog ring and the drive shaft, and optionally includes a selector mechanism that controls the relative axial movement between the dog ring and the drive shaft.

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