differential device

Abstract

The differential device comprises: an input case rotatable about an axis and having an end face facing the axis; a differential gear set including a first side gear and a second side gear, each of which is rotatable about the axis, and allowing differential movement of the second side gear relative to the first side gear; claw teeth rising toward the end face on an output case or the second side gear supporting the differential gear set; a clutch structure capable of meshing with the claw teeth, and when meshed, the clutch structure couples the output case or the second side gear to the input case; A clutch component, movable in the direction of the shaft, comprising an inner end connected to the clutch structure and an outer end exposed to the outside of the input box through the end face; an armature, movable in the direction of the shaft, at least partially composed of a magnetic material, in contact with the outer end; a solenoid, supported separately from the end face in the direction of the shaft, generating a magnetic flux in the direction of the shaft to attract the armature, causing the clutch structure to engage with the claw teeth via the clutch component; and a spring, applying force to the clutch structure in a direction of disengagement from the claw teeth.

Description

Technical Field

[0001] The following disclosure relates to a differential device, and more particularly to a differential device including an actuator using an attraction solenoid and capable of operating a clutch. Background Art

[0002] When driving a four-wheeled vehicle on rough roads, transmitting driving force to all four wheels is more advantageous than driving only the front or rear wheels. On the other hand, when driving on paved, well-maintained roads, all-wheel drive (AWD) is disadvantageous from the perspective of fuel efficiency. Therefore, a drive system known as part-time AWD, which switches between two-wheel drive and all-wheel drive through deliberate driver control, is often used.

[0003] There are various combinations of transmission systems that implement part-time AWD, such as a differential gear set that allows differential motion between two axles and a clutch that temporarily couples the input shaft to the differential gear set. A device known as a free-running differential, which integrates this combination, has been proposed. Patent Document 1 discloses an example of a free-running differential.

[0004] Gear motors, hydraulics, solenoids, etc. can be used in the actuator that drives the clutch. Solenoids are particularly excellent in terms of response. In the technology disclosed in Patent Document 1, the solenoid generates magnetic flux in a manner that surrounds the core, and generates pressing force on the plunger by causing the magnetic flux to detour to the plunger, thereby driving the clutch. This type of solenoid can operate with low power consumption while having a relatively low output. On the other hand, in order to obtain a higher output, people are turning their attention to attraction-type solenoids. In an example where the differential is not a free-running differential but is used for the purpose of locking the differential, in the technologies disclosed in Patent Documents 2 and 3, the solenoid attracts the armature by excitation, and a return spring is used to pull it apart. In any example, the solenoid needs to be connected to the vehicle body side, so the differential rotates, while the solenoid and its related components are non-rotating components.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-112114

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2-286944

[0009] Patent Document 3: International Patent Application Publication WO2017 / 100550A1 Summary of the Invention

[0010] Since the clutch is also immersed in the lubricant used to lubricate the differential gear set, the viscosity of the lubricant acts as a resistance to clutch disengagement. Furthermore, when torque is applied, the friction between the engaged clutch teeth strongly hinders disengagement. Therefore, for the clutch to reliably disengage, the return spring must exert a corresponding elastic force. To counteract this reinforced return spring, the solenoid must exert sufficient thrust, which is why a solenoid with an attracting armature is advantageous. On the other hand, the armature adheres to the solenoid due to residual magnetization, so the return spring must exert a greater elastic force to remove it. Therefore, the attracting solenoid and return spring complement each other, both requiring a strong attracting solenoid and return spring.

[0011] How to manage the reaction to these forces is a technical challenge, and how to transmit the clutch force requires expert design. Furthermore, if a larger magnetic force is generated, the effects of magnetic flux leaking into the surrounding area must also be considered. For example, reducing magnetic flux leakage by increasing the core's magnetic circuit cross-sectional area inevitably results in a bulky device. In other words, in an attracting solenoid, the arrangement and support of the associated components present numerous potential technical challenges. The device disclosed below addresses these challenges.

[0012] In one example, a differential device comprises: an input box that is rotatable about an axis and has an end face facing the axis; a differential gear set that includes a first side gear and a second side gear that are respectively rotatable about the axis, allowing the second side gear to be differential with respect to the first side gear; claw teeth that stand upright toward the end face on an output box or the second side gear that supports the differential gear set; a clutch structure that is engageable with the claw teeth, and when engaged, the clutch structure connects the output box or the second side gear to the input The clutch member is movable in the direction of the axis, and comprises an inner end connected to the clutch structure and an outer end exposed to the outside of the input box through the end face; an armature is movable in the direction of the axis, is at least partially composed of a magnetic material, and is in contact with the outer end; a solenoid is supported in the direction of the axis separately from the end face, generates a magnetic flux in the direction of the axis to attract the armature, and causes the clutch structure to engage with the claw teeth via the clutch member; and a spring applies force to the clutch structure in a direction of disengagement from the claw teeth. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a cross-sectional view along an axis of a differential device according to an embodiment.

[0014] Figure 2A It is from Figure 1 An enlarged cross-sectional view of the actuator and its vicinity is obtained.

[0015] Figure 2B is a modified example, Figure 2A Corresponding enlarged cross-sectional view.

[0016] Figure 3A It is a partial elevation view of a structure for preventing rotation of an actuator according to one example.

[0017] Figure 3B This is a partial cross-sectional view of a structure for preventing rotation of an actuator in another example.

[0018] Figure 4 This is a partial cross-sectional view showing an example in which the actuator presses the clutch member via the plunger.

[0019] Figure 5A This is a partial cross-sectional view showing another example of the relationship between the sensor and the actuator.

[0020] Figure 5B This is another example of Figure 5A Corresponding partial cross-sectional view.

[0021] Figure 5C is an example of a contact sensor. Figure 5A Corresponding partial cross-sectional view.

[0022] Figure 6 This is a partial cross-sectional view showing an example of a clutch configured in combination with a side gear. DETAILED DESCRIPTION

[0023] Several exemplary embodiments are described below with reference to the accompanying drawings. In the following description and claims, unless otherwise specified, "axis" refers to the rotational axis of the differential device. Furthermore, "axial" refers to the direction parallel to the axis, and "radial" refers to the direction perpendicular thereto. The following description may sometimes distinguish between "right" and "left," but this is for ease of explanation only; embodiments in which the left and right are reversed are also possible.

[0024] Main reference Figure 1 The differential device can be used to transmit axle torque from the input shaft within a certain time limit while allowing differential motion between two axles rotating about axis C (this may be referred to as a free-running differential). This differential device can realize, for example, a part-time AWD vehicle, but its applications are not limited to this.

[0025] A differential device generally comprises an input case 1 that receives torque from an input shaft, a clutch 11 for operating a differential gear set 7, and an actuator 21 for driving the clutch 11. The differential device may include an output case 5 that supports the differential gear set 7 and is rotatable relative to the input case 1. The input case 1 and the output case 5 are coaxial and nested, with the former typically housing the latter, but this is not required.

[0026] The input box 1 is always drivingly connected to the input shaft, receiving torque from the input shaft and rotating about axis C. The output box 5 is equipped with claws 13 to form a clutch 11. When the clutch 11 is disengaged, the torque of the output box 5 is not transmitted, and the output box 5 can rotate freely about axis C. When the actuator 21 engages the clutch 11, the input box 1 and the output box 5 are drivingly coupled, transmitting torque and rotating together.

[0027] Or, as Figure 6 As shown, one side gear 77 of the differential gear set 7 may also have claw teeth 13 on the back side relative to the gear teeth, thereby forming a clutch 11. In this example, the differential gear set 7 is directly supported by the input case 1 without the output case 5. When the clutch 11 is engaged, the side gear 77 is coupled to the input case 1. When one side gear 77 is fixed, the other side gear 75 cannot perform differential operation. Therefore, in this example, the clutch 11 is used to lock / unlock the differential operation of the differential gear set 7. The differential device of this example may be referred to as a locking differential, etc.

[0028] Return to reference Figure 1 Input box 1 is generally cylindrical around axis C, with its interior and exterior semi-isolated by closed end faces. Input box 1 and the input shaft can be connected, for example, via a ring gear. A flange protruding radially from the cylinder can serve as a coupling for the ring gear, though other methods are also possible.

[0029] Bushings extend axially outward from both end faces of input box 1, supporting input box 1 on gear rack 81. Bearings 83, such as roller bearings, can be interposed between input box 1 and gear rack 81. However, ball bearings or other bearing devices can also be used in place of roller bearings. An actuator 21 is positioned near one end face 3.

[0030] The output box 5 is equipped with a differential gear set 7, which can output torque to both axles while allowing for differential. Figure 1 In the illustrated example, the differential gear set 7 is of the bevel gear type, consisting of a pinion 71 rotatably supported on a pinion shaft 73 and side gears 75 and 77 meshing therewith. Of course, other suitable types, such as a face gear type or a planetary gear type, may also be employed. Since the side gears 75 and 77 are coupled to the axles, their inner surfaces may be provided with splines, but other coupling types are also possible.

[0031] The output box 5 has claws 13 at one end 9 thereof, and the claws 13 are further raised in the axial direction toward the end face 3 of the input box 1. The claws 13 constitute the clutch 11, and as already described, the clutch 11 drives the output box 5 and the input box 1 together when engaged. Figure 1 As in the example shown, the clutch structure for drivingly coupling the output case 5 and the input case 1 may be via the clutch member 15 , or may include claws corresponding to the input case 1 to constitute the claws 13 and the clutch 11 .

[0032] Combine Figure 1 , for example, refer to Figure 2A The clutch member 15 is a generally annular component loosely fitted onto the inner surface of the input housing 1 and movable in the direction of axis C. Its inner end 17 is located within the input housing 1 and connected to the clutch structure. Multiple legs protrude axially outward from the surface opposite the inner end 17, with their respective outer ends 19 exposed to the outside of the input housing 1 through the end surface 3. Through the holes defined in the end surface 3, the legs of the clutch member 15 engage with each other, enabling the clutch member 15 to transmit torque from the input housing 1 to the output housing 5.

[0033] The inner end 17 may include the second claws 14, and the claws 13 and the second claws 14 may be configured to mesh with each other, and the combination thereof constitutes the clutch 11. In this case, as described above, the clutch structure and the clutch member 15 are integrated.

[0034] Furthermore, the outer end 19 may be provided with a contact plate 27 for connection with the actuator 21. The contact plate 27 is a plate-shaped, generally continuous wheel in the circumferential direction. It may also include a portion appropriately bent and raised for fastening to the outer end 19, or may include appropriate protrusions for contact with the actuator 21. The material used for the contact plate 27 is not particularly limited, but a material different from that used for the input case 1, the clutch member 15, or the armature 23 and core 53 described later may be used.

[0035] The actuator 21 generally comprises an armature 23, a solenoid 25, and a return spring 31. The armature 23 is at least partially composed of a magnetic material and is attracted to the magnetic flux generated when the solenoid 25 is energized. The armature 23 is positioned so as to contact the outer end 19 and is capable of driving the clutch member 15 in the axial direction C. The return spring 31 urges the clutch member 15 in the opposite direction.

[0036] The solenoid 25 is annular in shape, wound around the axis C. It includes a coil 51 that generates magnetic flux in the axial direction and a core 53 that surrounds the coil 51 and guides the magnetic flux. Coil 51 is a motor coil wound with a good conductor such as copper, preferably wound in a direction that generates the strongest magnetic flux in the direction of the axis C. Core 53 can also be made of a high-permeability material such as ferrite, which can efficiently guide the magnetic flux to improve energy efficiency and reduce the adverse effects of magnetic flux leakage to the surrounding area. Core 53 surrounds most of the coil 51, but is open in the axial direction only on the surface facing the armature 23, that is, the magnetic flux is efficiently directed toward this surface.

[0037] The armature 23 has at least a radial surface 41 that receives the magnetic flux and should be attracted, which can be formed into a disk-shaped surface that is radially expanded. In order to expand the area receiving the magnetic flux, as shown in FIG. Figure 2B As shown, the core 53 may further include an inclined surface 45 that is inclined toward the core 53. The inclined surface 45 may be located not only radially inside but also radially outside. The core 53 may also have a shape that is complementary to the inclined surface.

[0038] The armature 23 further includes an axial portion 43 for contacting the outer end 19 or the contact plate 27 to transmit the driving force. Figure 3A As shown, the axial portion 43 may also be, for example, Figure 2A 、 Figure 2B The cylindrical edge of the core 53 is formed by combining the outer periphery of the radial surface 41 and extending axially upward. This edge extends through the outer side of the core 53 to reach the outer end 19 or the contact plate 27, at least partially covering the core 53. This shape can be formed into a flat plate in one piece by stamping, making it easy to manufacture. Of course, it can also be manufactured by casting, forging, etc., or the separate axial portion 43 can be meshed with the flat radial surface 41. Even if this shape is relatively thin, it is still sufficient to drive the clutch component 15, so it is advantageous in that the cross-sectional area of ​​the core 53 can be kept constant.

[0039] Alternatively, the armature 23 may also replace the cylindrical edge, or on this basis, as Figure 4 As shown in the example, the column 49 is provided. The column 49 allows the solenoid 25 to particularly penetrate the core 53 and extend in the axial direction, and to contact the outer end 19 or the contact plate 27. The column 49 can pass through the inner side in the radial direction of the coil 51 as shown in the figure, or it can pass through the outer side. In these embodiments, the column 49 stops the armature 23 from rotating, so that the incision described later is not required. Furthermore, the column 49 can also extend in a manner that bypasses the outer circumference of the core 53. In this case, the column 49 can also be stopped by engaging with the pin 85 described later, or a separate rotation-stopping treatment can be performed.

[0040] The axial portion 43 and the column 49 may be made of the same material as the radial surface 41 or may be integral, or may be separate bodies made of non-magnetic material. When made of non-magnetic material, magnetic flux leakage can be reduced, thereby reducing its adverse effects.

[0041] Furthermore, a separate bushing may be interposed between the axial portion 43 or post 49 and the outer end 19 or contact plate 27. This bushing is annular and maintains contact between the two even when the input box 1 rotates. This bushing can also be made of a non-magnetic material, such as a resin with a low coefficient of friction, to reduce friction.

[0042] The inner circumference of core 53 is engaged with sleeve portion 57, supporting the entire actuator 21. Aside from the inner circumference, core 53 is separated from input box 1. In particular, a considerable gap is maintained between the back surface of core 53 and end face 3 of input box 1. This helps reduce magnetic flux leakage from core 53 to end face 3. To position core 53, sleeve portion 57 may also include a shoulder 59 that extends slightly radially outward. Shoulder 59 is at least sufficient to not reach the back surface of coil 51, that is, a gap is maintained radially outward of the inner circumference of coil 51.

[0043] like Figure 2A 、 Figure 4 As shown, the inner circumference of the core 53 may also be extended axially in the direction opposite to the shoulder 59. The extension may also be roughly cylindrical, usually integral with the core 53, but may also be fixed to the core 53 separately. In addition, its end may also abut against the bearing 83 to prevent it from falling off. Alternatively, in order to prevent the core 53 from falling off, the sleeve portion 57 may also be provided with an anti-falling component. This component is, for example, a ring that meshes with the sleeve portion 57, and in order to reduce the leakage of magnetic flux, it may also be made of non-magnetic material. On the other hand, the inner circumference of the core 53 may not be in contact with the sleeve portion 57. In order to reduce the contact area, the inner circumferential surface of the core 53 may also have grooves or recesses. This also helps to reduce the leakage of magnetic flux, and in addition, helps to reduce the sliding resistance between the core 53 and the sleeve portion 57.

[0044] The armature 23 can be directly engaged with the sleeve portion 57 or with the extension of the core 53. In either case, the engagement is slidable, allowing the armature 23 to move in the axial direction. Engaging the armature 23 with the core 53, which is a non-rotating member, facilitates smooth axial movement. To prevent the armature 23 from falling out, a ring 33 can be used that meshes with the core 53 or the sleeve portion 57. This ring can also be made of a non-magnetic material to reduce magnetic flux leakage.

[0045] Or, as Figure 2BAs shown, a support component 35 for supporting the core 53 and the armature 23 can be utilized. The support component 35 is, for example, roughly cylindrical, and one end thereof abuts against the bearing 83 to prevent it from falling off. The support component 35 abuts against the core 53 and both are non-rotating components, and can also prevent them from falling off. Alternatively, the support component 35 can be interference fit with the shaft sleeve portion 57, or can also have a structure that meshes with the shaft sleeve portion 57. In addition, the armature 23 can be slidably fitted on the support component 35, which helps to suppress the leakage of magnetic flux from the armature 23 to the shaft sleeve portion 57. In order to prevent the armature 23 from falling off, the support component 35 can also have an anti-falling structure, an example of which is a shorter flange formed by bending its end outward as shown in the figure. In order to reduce the leakage of magnetic flux, the support component 35 can also be made of non-magnetic material.

[0046] The return spring 31 can be disposed in the gap maintained between the back surface of the core 53 and the end surface 3 of the input box 1. In particular, it can be interposed between the contact plate 27 and the end surface 3. The return spring 31 can be slightly compressed in advance to bias the clutch member 15 in a direction that promotes disengagement of the clutch 11.

[0047] The return spring 31 is a component that rotates together with the contact plate 27, etc., but it is preferable that the armature 23 and the solenoid 25 are non-rotating components and are stopped from rotating. Figure 3A As shown, the core 53 may also include a pin 85 protruding radially outward, and the pin 85 engages with the gear frame 81, thereby preventing the solenoid 25 from rotating. The armature 23 may also include a structure that engages with the solenoid 25, for example, the axial portion 43 may also include a notch that engages with the pin 85. Alternatively, as Figure 3B As shown, pins 87 extending axially from the core 53 and penetrating the armature 23 can also be used. In either case, the armature 23 and solenoid 25 can be prevented from rotating by the pins 85 and 87. Pins 85 and 87 can be integral with the core 53, or they can be separate and made of non-magnetic material. When made of non-magnetic material, magnetic flux leakage can be reduced, thereby minimizing its adverse effects.

[0048] Return to reference Figure 1 Although not required, the differential device may include a device for detecting whether the clutch 11 is engaged. One example is a non-contact sensor 91. Examples of non-contact sensor 91 include, but are not limited to, sensors that detect the proximity of metal using high-frequency oscillation, non-contact sensors that detect changes in electrostatic capacitance, electric fields, or magnetic fields, and detection devices using optical units. These non-contact sensors can avoid energy loss due to contact with rotating bodies.

[0049] For example, the non-contact sensor 91 can be arranged at a position where it can detect whether the contact plate 27 is approaching. As can be understood from the above description, the contact plate 27 is exposed on the periphery in the differential device, and furthermore, moves axially in the gap between the core 53 and the input box 1, so that the non-contact sensor 91 can accurately detect without being disturbed by surrounding components. As described above, the contact plate 27 is annular, and therefore always faces the non-contact sensor 91 during rotation, and can be used for axial position detection. In addition, as described above, any material can be applied to the contact plate 27, and therefore, a material suitable for detection by the non-contact sensor 91 can be selected. Of course, other parts of the clutch component 15 can be set as the detection object instead of the contact plate 27, or as Figure 5A As shown in the example, any part of the armature 23 is used as the target. The armature 23 is a non-rotating component, so it is always opposite to the non-rotating non-contact sensor 91 and can be used for position detection. In addition, some appropriate components that facilitate detection can also be added to them.

[0050] In the above description, the non-contact sensor 91 is oriented approximately orthogonally to the component moving in the axial direction. Figure 5B As shown in the example shown, the non-contact sensor 91 can also be oriented axially. The object of detection can be either the armature 23 or, as in the example shown, the contact plate 27. In the latter case, in order to avoid interference with the armature 23 and core 53, they can also be partially removed. The armature 23 and core 53 are non-rotating components, so it is sufficient to only cut the problematic area instead of cutting the entire circumference. Of course, instead of cutting, the diameter of the contact plate 27 can also be enlarged so that it protrudes radially outward from the outer circumference of the armature 23 and core 53.

[0051] Alternatively, as shown in the example of FIG5c, a contact sensor 93 may be used instead of a non-contact sensor. For example, a mechanical push switch or pull switch may be used as the contact sensor 93. Of course, electrical, magnetic, or optical sensors may also be used. As described above, the detection target may be the armature 23 or the contact plate 27, or any other part of the clutch member 15.

[0052] Furthermore, in place of or in addition to any of the aforementioned sensors, another detector, such as a speed sensor, can be included as a differential device. Accordingly, contact plate 27 can also include a structure, such as notches or teeth formed on its periphery, that causes the sensor to generate pulses corresponding to the speed. Since contact plate 27 is a rotating component that rotates synchronously with input box 1, it can be used not only to determine whether clutch 11 is engaged but also to obtain information on the rotational speed.

[0053] In the differential device described herein, magnetic flux leakage from the solenoid to the input box, particularly from the back of the core to the end face of the input box, is reduced. In an attracting solenoid, the magnetic flux in this direction is greatest, strongly attracting the input box. Therefore, if the back of the core contacts the end face of the input box, energy loss due to friction is significant. Furthermore, since the input box rotates in a direction perpendicular to the magnetic flux, energy loss due to the generation of induced power also increases as the magnetic force increases. The differential device described herein suppresses these energy losses. Furthermore, since the core's cross-sectional area does not need to be increased to address magnetic flux leakage, the device can be made compact. Furthermore, since the relatively wide gap between the back of the core and the end face of the input box can be used for the return spring, the return spring has greater freedom in design, which helps ensure sufficient elastic force and extension length. Furthermore, since the contact plate is radially exposed in this gap, it is easy to detect the clutch status using a sensor, etc.

[0054] Several embodiments have been described, but corrections or modifications can be made to the embodiments based on the above disclosure.

Claims

1. A differential device comprising: The input box is rotatable about an axis and has an end surface facing the axis; a differential gear set including a first side gear and a second side gear respectively rotatable about the shaft, allowing differential movement of the second side gear relative to the first side gear; claw teeth, which stand upright toward the end surface on an output box or the second side gear supporting the differential gear set; a clutch structure capable of engaging with the claw teeth, wherein when engaged, the clutch structure couples the output box or the second side gear with the input box; a clutch member movable in the direction of the shaft, comprising an inner end connected to the clutch structure and an outer end exposed to the outside of the input box through the end surface; an armature movable in the direction of the shaft, at least partially composed of a magnetic material, in contact with the outer end; a solenoid supported in a direction of the axis away from the end surface, generating a magnetic flux in the direction of the axis to attract the armature, and causing the clutch structure to engage with the claw teeth via the clutch member; as well as a spring that applies force to the clutch structure in a direction of disengaging the claw teeth, The differential device is characterized in that: The armature includes: a radial surface extending in the radial direction to receive the magnetic flux; and an axial portion extending in the axial direction from the radial surface to the outer end, the axial portion being in contact with the outer end. The axial portion is separate from the radial surface and is made of a non-magnetic material.

2. The differential device according to claim 1, characterized in that: The axial portion has a cylinder that at least partially covers the outer circumference of the solenoid and contacts the outer end.

3. The differential device according to claim 1, wherein: The axial portion includes a post that passes through the solenoid and is connected to the outer end.

4. The differential device according to any one of claims 1 to 3, characterized in that: The input box includes a sleeve portion extending from the end surface in the direction of the axis. The solenoid includes a coil that generates the magnetic flux and a core that surrounds the coil and guides the magnetic flux. The core is slidably engaged with the sleeve portion, so that the solenoid is supported by the input box.

5. The differential device according to claim 4, characterized in that: The core includes a support portion integrally or separately fitted in the boss portion so as to be slidable, and extends in the axial direction so as to come into contact with a bearing supporting the boss portion.

6. The differential device according to claim 5, characterized in that: The armature is supported so as to be movable in the axial direction by being fitted into the support portion.

7. The differential device according to claim 4, characterized in that: The core includes a pin that stops the solenoid from rotating and extends in the radial direction or the axial direction. The armature is engaged with the pin and thereby stopped from rotating together.

8. The differential device according to any one of claims 1 to 3, characterized in that: The outer end of the clutch member includes a contact plate forming a continuous wheel around the shaft, the contact plate being arranged between the solenoid and the end surface and in contact with the armature.

9. The differential device according to claim 8, characterized in that: The spring is interposed between the end surface and the contact plate to bias the contact plate.

10. The differential device according to claim 8, characterized in that The contact plate is exposed radially outward and can be used for detection by a sensor.

11. The differential device according to any one of claims 1 to 3, characterized in that: The clutch structure is formed integrally with the clutch member so as to move together with the clutch member, and includes second claw teeth that mesh with the claw teeth.

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