Solenoid-type clutch device

Abstract

In the present invention, a moving core is provided with a moving core body part made of a soft magnetic material, and a permanent magnet part made of a hard magnetic material. The magnetic pole direction of the permanent magnet part coincides with the magnetic pole direction of a coil when the coil is positively energized, and a stator core is not present within the moving range of the permanent magnet part. Since the moving core is provided with the permanent magnet part, a magnetic flux of the coil can be rectified by the permanent magnet part. Thus, the magnetic flux leaking to the side of a rotor made of a soft magnetic material can be reduced. Particularly, since the magnetic pole direction of the permanent magnet part coincides with the magnetic pole direction of the coil when the coil is positively energized, the rectification of the magnetic flux can be appropriately performed. Furthermore, since the moving range of the permanent magnet part includes a portion where the stator core is not present, the generation of a loop of the magnetic flux due to a magnetic field of the permanent magnet can be prevented and the reduction of an attraction force can be prevented.

Description

Solenoid clutch device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2023-138363 filed in Japan on August 28, 2023, and the contents of the original application are incorporated by reference in their entirety.

[0002] The present disclosure relates to a solenoid clutch device that switches between transmitting and not transmitting rotation of a rotating body by switching between energizing and de-energizing a coil. This disclosure can be used, for example, to switch between transmitting and not transmitting rotational power between a differential case and a drive shaft in a differential gear.

[0003] In Patent Document 1, the coil, stator core, and moving core of the solenoid device are arranged coaxially with the rotor for the advantages of ease of mounting and assembly. Generally, to mount the solenoid device coaxially with the rotor, the rotor must penetrate inside the solenoid device. Furthermore, the rotor is generally made of a soft magnetic material. Therefore, magnetic flux generated by excitation of the coil flows into the rotor, which is made of a soft magnetic material, preventing maximum utilization of the coil's magnetic flux within the solenoid device. This results in a problem of reduced attractive force of the clutch plates of the clutch device.

[0004] To prevent magnetic flux from leaking to the rotor, it is possible to provide a sufficient layer of non-magnetic material between the solenoid device and the rotor. However, this would increase the size of the solenoid device, making it difficult to install in a differential gear or the like.

[0005] Japanese Patent Application Laid-Open No. 2005-240861

[0006] In view of the above, an object of the present disclosure is to minimize leakage of magnetic flux from a solenoid device to a rotating body and to suppress a decrease in the attractive force of a clutch plate of a clutch device.

[0007] The first disclosure is a solenoid clutch device including a rotor made of a soft magnetic material that rotates about an axis, a first clutch plate that rotates integrally with the rotor, a second clutch plate that is disposed opposite the first clutch plate, a coil that is fixedly disposed on the outer periphery of the rotor, a stator core made of a soft magnetic material that is fixedly disposed on the outer periphery of the rotor and forms a magnetic circuit when the coil is energized, a moving core that is disposed on the outer periphery of the rotor, on the inner periphery of the coil and across a magnetic gap from the stator core, that forms a magnetic circuit together with the stator core when the coil is energized, and that moves in the axial direction of the rotor to narrow the magnetic gap when the coil is energized in the forward direction, a return spring that biases the stator core and the moving core in a direction separating them, and a plunger made of a non-magnetic material that transmits the movement of the moving core in the axial direction of the rotor to either the first clutch plate or the second clutch plate. Note that in this disclosure, "forward energization of the coil" refers to energization in a direction that generates magnetic flux in the coil that narrows the magnetic gap.

[0008] In a solenoid clutch device, the moving core comprises a moving core body made of a soft magnetic material and a permanent magnet part made of a hard magnetic material. The magnetic pole direction of the permanent magnet part coincides with the magnetic pole direction when the coil is positively energized, and the stator core is not present within the moving range of the permanent magnet part.

[0009] The solenoid clutch device has a permanent magnet portion in the moving core, which allows the magnetic flux of the coil to be rectified. This reduces the magnetic flux leaking to the rotating body, which is made of a soft magnetic material. In particular, the magnetic pole direction of the permanent magnet portion matches the magnetic pole direction of the coil when positive current is applied, allowing for appropriate rectification of the magnetic flux. Furthermore, because there is a portion of the stator core outside the moving range of the permanent magnet portion, the generation of a magnetic flux loop due to the magnetic field of the permanent magnet is prevented, preventing a decrease in the attractive force.

[0010] In the solenoid clutch device of the second disclosure, the permanent magnet portion is positioned on the side of the moving core closest to the magnetic gap. This allows for more optimal magnetic flux rectification by the permanent magnet portion, reducing leakage of magnetic flux to the rotating body. Furthermore, a portion of the moving core body on the magnetic gap side is interposed between the permanent magnet portion and the magnetic gap. The thickness of this portion on the magnetic gap side is a predetermined thickness determined according to the size of the magnetic gap (stroke of the moving core). For example, it is equal to or greater than the thickness of the permanent magnet portion. This prevents the moving core from being attracted to the stator core by magnetic force when the coil is not energized.

[0011] In the solenoid clutch device of the third disclosure, even when the coil is de-energized with the magnetic gap narrowed by energizing the coil in a forward direction, the position of the moving core and the stator core is maintained by the magnetic force of the permanent magnet. On the other hand, when the coil is reversely energized, the repulsive force between the coil and the permanent magnet and the biasing force of the return spring cause the moving core to move in the axial direction of the rotor so as to widen the magnetic gap. Even when the coil is de-energized with the magnetic gap widened by energizing the coil in a reverse direction, the position of the moving core and the stator core is maintained by the biasing force of the return spring. In the third solenoid clutch device of the present disclosure, the magnetic gap can be maintained in both a narrowed and widened state even when the coil is de-energized.

[0012] The solenoid clutch device of the fourth disclosure has a bearing member made of a non-magnetic material interposed between the inner periphery of the moving core and the outer periphery of the rotating body. The bearing member not only supports the rotation of the rotating body but also holds the moving core.

[0013] In the solenoid clutch device of the fifth disclosure, the rotor includes a cylindrical outer rotor and a cylindrical shaft disposed on the inner periphery of the outer rotor. The solenoid clutch device of the present disclosure can be used for a variety of purposes, but the fifth solenoid clutch device can also be used when the rotor has a dual structure.

[0014] In the solenoid clutch device of the sixth disclosure, the outer rotor corresponds to a differential case of a differential device, the shaft corresponds to a drive shaft of the differential device, the first clutch plate corresponds to a first dog clutch of the differential device, and the second clutch plate corresponds to a second dog clutch of the differential device. Rotation of the differential case is transmitted to the drive shaft via a ring gear, first dog clutch, second dog clutch, pinion gear, and side gear of the differential device. The fourth solenoid clutch device of the present disclosure is suitable for use in the dog clutch of the differential device.

[0015] In the solenoid clutch device of the seventh disclosure, the differential gear is disposed in the powertrain unit, and the differential case is rotationally supported by the powertrain unit with differential case bearings. Because the differential case, which corresponds to the rotating body, is rotationally supported by the powertrain unit with the differential case bearings, excessive rotational load of the rotating body is not applied to the solenoid clutch device.

[0016] 1 is a diagram illustrating the configuration of a differential gear in which a solenoid clutch device is used; FIG. 2 is a perspective view illustrating an exploded configuration of the differential gear; FIG. 3 is a cross-sectional view illustrating a differential gear in which a solenoid clutch device is used; FIG. 4 is a perspective view illustrating a ring gear and a first dog clutch of the differential gear; FIG. 5 is a perspective view illustrating a disengaged state of the first dog clutch and a second dog clutch; FIG. 6 is a perspective view illustrating an engaged state of the first dog clutch and a second dog clutch; FIG. 7 is a perspective view illustrating an engaged state of the second dog clutch and a pinion gear; FIG. 8 is a perspective view illustrating an engaged state of the pinion gear and a side gear; FIG. 9 is a diagram illustrating rotation transmission in an engaged state of the solenoid clutch device; FIG. 10 is a diagram illustrating rotation transmission in a disengaged state of the solenoid clutch device; FIG. 11 is a cross-sectional view illustrating an engaged state of the solenoid clutch device;

[0017] An example in which the solenoid clutch device 100 of the present disclosure is used in a differential device 200 will be described below. An outline of the configuration is shown in Figure 1. The differential device 200 is used in a four-wheeled vehicle and transmits the driving force of a motor 300 to left and right tires (not shown) while allowing the left and right tires to rotate at different speeds. The motor 300 and the differential device 200 are arranged together with the solenoid clutch device 100 within a powertrain unit 400.

[0018] The motor 300 is fixed to the powertrain unit 400. The motor shaft 301 is rotatably supported by the powertrain unit 400 via a motor shaft bearing 401. The rotation of the motor shaft 301 is transmitted to the intermediate shaft 304 via meshing between a motor gear 302 and a first reduction gear 303. The intermediate shaft 304 is also rotatably supported by the powertrain unit 400 via an intermediate shaft bearing 402. Note that although the motor shaft bearing 401, intermediate shaft bearing 402, etc. are simply illustrated using symbols, various types of bearings such as ball bearings and roller bearings may be used.

[0019] The rotation of the intermediate shaft 304 is transmitted from the second reduction gear 305 to the ring gear 201 of the differential device 200. The number of teeth of the first reduction gear 303 is set to be greater than the number of teeth of the motor gear 302, and the number of teeth of the ring gear 201 is set to be greater than the number of teeth of the second reduction gear 305. Therefore, the rotation of the motor 300 is reduced before being transmitted to the differential device 200. As a result, the rotational torque transmitted to the differential device 200 is increased. Note that the ring gear 201, the second reduction gear 305, the first reduction gear 303, and the motor gear 302 are all helical gears, which increases the meshing ratio.

[0020] Next, the configuration of the differential gear 200 will be described with reference to FIGS. 2 to 8. FIG. 2 is an exploded perspective view showing the main components of the differential gear 200. As described above, the ring gear 201 rotates in response to the rotation of the motor 300. A pair of differential cases (one differential case 210 and the other differential case 211) are fixed to both sides of the ring gear 201 by welding or the like. Therefore, the one differential case 210 and the other differential case 211 rotate together with the ring gear 201. The pair of differential cases (the one differential case 210 and the other differential case 211) are rotationally supported by the powertrain unit 400 by differential case bearings 403. In this embodiment, as shown in FIG. 3, the solenoid clutch device 100 is disposed on the outer periphery of the one differential case 210, so that the one differential case 210 serves as a rotating body.

[0021] As shown in FIG. 4 , the ring gear 201 is formed with four engagement recesses 202 spaced apart in the circumferential direction. The engagement protrusions 221 of the first dog clutch 220 fit into these engagement recesses 202. As a result, the first dog clutch 220 rotates integrally with the ring gear 201. As shown in FIG. 5 , the first dog clutch 220 is ring-shaped. A large number of first dog teeth 222 are formed on the surface of the first dog clutch 220 opposite the engagement protrusions 221. A second dog clutch 230 is disposed opposite the first dog clutch 220, and the second dog clutch 230 is also ring-shaped. The second dog clutch 230 also has second dog teeth 231 that mesh with the first dog teeth 222 of the first dog clutch 220. FIG. 6 shows a state in which the first dog teeth 222 of the first dog clutch 220 and the second dog teeth 231 of the second dog clutch 230 are engaged with each other.

[0022] 7, a pair of pinion gears (one-side pinion gear 240 and the other-side pinion gear 241) are arranged on the inner periphery of the ring-shaped second dog clutch 230. The one-side pinion gear 240 and the other-side pinion gear 241 rotate together with the second dog clutch 230 via a one-side pin 242 and an other-side pin 243. In other words, the second dog clutch 230 rotates together with the pair of pinion gears arranged on the inner periphery.

[0023] The pair of pinion gears (one-side pinion gear 240 and the other-side pinion gear 241) can rotate around the one-side pin 242 and the other-side pin 243, respectively. Therefore, the pair of pinion gears can rotate around the one-side pin 242 and the other-side pin 243 while revolving together with the second dog clutch 230.

[0024] As shown in Fig. 8 , the pair of pinion gears mesh with the pair of side gears. The pair of pinion gears includes a first pinion gear 240 and an second pinion gear 241. The pair of side gears includes a first side gear 250 and an second side gear 251. Although not shown in Figs. 2 , 7 , and 8 , gear teeth are formed on the conical surfaces of the pair of pinion gears. The pair of pinion gears includes a first pinion gear 240 and an second pinion gear 241. Gear teeth are also formed on the conical surfaces of the pair of side gears that face the pair of pinion gears, and the pair of side gears transmit rotational force by meshing of their gear teeth.

[0025] Returning to FIG. 1 , the pair of side gears are respectively connected to a pair of drive shafts. The pair of drive shafts includes a first drive shaft 260 and an second drive shaft 261. Therefore, the rotational force of the motor 300 received via the ring gear 201 is transmitted to the first drive shaft 260 and the second drive shaft 261 via the differential device 200. The first drive shaft 260 is disposed on the inner periphery of the first differential case 210, which has a cylindrical shape. Therefore, for the solenoid clutch device 100, the first differential case 210 is the outer circumferential rotating body, and the first drive shaft 260 is a cylindrical shaft disposed on the inner periphery of the outer circumferential rotating body.

[0026] As shown in FIG. 1 , a sensor disk 270 is fixed to one differential case 210. Therefore, the sensor disk 270 rotates together with the ring gear 201 and one differential case 210. A position sensor 271 is arranged corresponding to this sensor disk 270. In a typical example, the position sensor 271 is provided by a magnetic sensor. An example of a magnetic sensor is a Hall sensor. The Hall sensor detects changes in magnetic flux of a magnet arranged on the sensor disk 270. In this way, the rotation direction and rotation speed of the ring gear 201 are detected. Of course, other position sensors 271, such as a resolver, can also be used. A return spring 107 is arranged on the sensor disk 270. The return spring 107 biases the first dog clutch 220 in a direction that separates it from the second dog clutch 230. The return spring 107 will be described later in connection with the solenoid clutch device 100.

[0027] Next, the rotation transmission of the motor 300 will be described with reference to FIG. 9 . The motor 300 can be switched between forward and reverse rotation by a control device (not shown). The forward direction of the vehicle corresponds to the forward rotation, and the reverse direction corresponds to the reverse rotation. The rotation speed of the motor 300 can also be controlled by a control device (not shown). Assume that the rotation direction R1 of the motor shaft 301 in FIG. 9 is forward rotation. In this case, the rotation direction R2 of the intermediate shaft 304 is reverse rotation, and the rotation direction R3 of the ring gear 201 is forward rotation. As described above, the output of the motor 300 is reduced by the reduction ratio between the motor gear 302 and the first reduction gear 303 and the reduction ratio between the second reduction gear and the ring gear 201. The output of the motor 300 increases the driving torque. As a result, the rotational force of the motor 300 is transmitted to the ring gear 201.

[0028] When the solenoid clutch device 100 is in the ON state, the first dog teeth 222 and the second dog teeth 231 of the first dog clutch 220 and the second dog clutch 230 are engaged with each other. Therefore, the forward rotation of the ring gear 201 is transmitted to the second dog clutch 230 via the first dog clutch 220, causing the second dog clutch 230 to rotate forward. The revolution direction R4 of the first pinion gear 240 and the second pinion gear 241, which revolve together with the second dog clutch 230, also rotates forward. The revolution of the first pinion gear 240 and the second pinion gear 241 is transmitted to the first drive shaft 260 and the second drive shaft 261 via the first side gear 250 and the second side gear 251. Therefore, the rotation direction R5 of the first drive shaft 260 and the second drive shaft 261 also rotates forward.

[0029] When the vehicle is traveling straight, the pair of pinion gears revolve without rotating, and the rotation speeds of the one-side drive shaft 260 and the other-side drive shaft 261 are equal. When the vehicle is turning, the one-side pinion gear 240 and the other-side pinion gear 241 rotate while revolving around their own axes. As a result, the rotation speed of the drive shaft located on the outside of the curve can be made higher than the rotation speed of the drive shaft located on the inside of the curve.

[0030] Next, the configuration of the solenoid clutch device 100 will be described using Figures 11 and 12. In this example, the solenoid clutch device 100 switches between engagement and disengagement of a first dog clutch 220 and a second dog clutch 230. Therefore, in this example, the first dog clutch 220 corresponds to the first clutch plate, and the second dog clutch 230 corresponds to the second clutch plate. Reference numeral 101 denotes a coil formed by winding multiple turns of copper wire insulated with an enamel coating. This coil 101 is wound around a cylindrical bobbin 102 made of a resin material. The bobbin may be made of, for example, polybutylene terephthalate (PBT).

[0031] When current is applied to the coil 101, it becomes magnetized. A stator core 103 is disposed on both sides and around the outer periphery of the coil 101 to form a magnetic circuit. The stator core 103 is made of a soft magnetic material, which has low magnetic retention and high magnetic permeability. Examples include ferrite stainless steel, permalloy, and electromagnetic steel sheet. Therefore, when the coil 101 is energized, it forms a magnetic circuit, but when the coil 101 is not energized, it is not magnetized by the coil 101. However, even when it is not energized, the stator core 103 is magnetized by the magnetic force of the permanent magnet portion 112. The position of the moving core 110 can be maintained depending on the degree of magnetization. The position of the moving core 110 will be described later.

[0032] The stator core 103 is cylindrical with an outer diameter of approximately 100 mm. Arranged opposite the stator core 103 across a magnetic gap 104 is a moving core 110. In this embodiment, the moving core 110 is composed of a moving core main body 111 made of a soft magnetic material and a permanent magnet portion 112 made of a hard magnetic material. Hard magnetic materials have a large residual magnetic flux density and function as permanent magnets.

[0033] A moving core tip portion 111A made of a soft magnetic material is disposed on the surface of moving core 110 (moving core main body portion 111) facing magnetic gap 104 with stator core 103. Moving core 110 is disposed on the inner periphery of ring-shaped stator core 103. It is also disposed on the outer periphery of one side differential case 210 that corresponds to the rotating body (particularly the outer rotating body). Moving core 110 is disposed so as to be movable in the axial direction of the rotating body (one side differential case 210).

[0034] The surface of the moving core 110 facing the magnetic gap 104 with the stator core 103 is provided by a moving core tip portion 111A made of a soft magnetic material. A permanent magnet portion 112 and the moving core tip portion 111A are arranged in this order between the moving core main body portion 111 and the magnetic gap 104 with the stator core 103. The moving core main body portion 111, the permanent magnet portion 112, and the moving core tip portion 111A are in contact with each other. In other words, the moving core main body portion 111 and the permanent magnet portion 112 are arranged in contact with each other on both sides of the permanent magnet portion 112. The moving core tip portion 111A faces the magnetic gap 104 with the stator core 103. The direction of movement of the moving core 110 is also referred to as the axial direction. The axial length of the non-existence portion 108 is longer than the axial length of the permanent magnet portion 112. The axial length of the non-existence portion 108 is longer than the axial length of the moving core tip portion 111A. The permanent magnet portion 112 is located within the axial range of the non-existence portion 108 throughout the entire range of movement of the moving core 110. As a result, the non-existence portion 108 extends throughout the entire range of movement of the permanent magnet portion 112.

[0035] The stator core 103 and coils 101 are fixedly disposed in the powertrain unit 400. In this example, a bearing member 105 is disposed between the stator core 103 and the rotor (one-side differential case 210). The bearing member 105 is made of a non-magnetic material that is not magnetized and is therefore not affected by magnetic fields. Stainless steel, for example, is used as the non-magnetic material for the bearing member 105. Therefore, the bearing member 105 and the moving core 110 are rotationally supported by the one-side differential case 210. The bearing load of the one-side differential case 210 is borne by the differential case bearing 403, and in this state, the bearing member 105 slidably supports the moving core 110. The inner diameter of the bearing member 105 is slightly larger than the outer diameter of the one-side differential case 210. The outer diameter of the one-side differential case 210 is, for example, approximately 55 millimeters.

[0036] The moving core 110 is connected to a first dog clutch 220, which corresponds to the first clutch plate, by a plunger 106 made of a non-magnetic material. The plunger 106 is made of stainless steel. The plunger 106 is formed in a cylindrical shape that covers one side differential case 210, which is a rotating body. One end face of the cylindrical plunger 106 is fixed to the first dog clutch 220, and the moving core 110 is fixed to the outer circumferential surface. However, the plunger 106 does not necessarily have to be fixed as long as it abuts against the first dog clutch 220.

[0037] FIG. 11 shows the state when the coil 101 is not energized. The first dog clutch 220 is separated from the second dog clutch 230 by the biasing force of the return spring 107. FIG. 12 shows the state when the coil 101 is energized in the positive direction from the state shown in FIG. 11 , and a magnetic circuit is formed around the coil 101 by the stator core 103 and the moving core 110. When the coil 101 is energized in the positive direction, a magnetic force acts to narrow the magnetic gap 104 present in the magnetic circuit. The magnetic force at this time is set to be larger than the biasing force of the return spring 107. Therefore, the moving core 110 moves the first dog clutch 220 via the plunger 106, and brings it into mesh with the second dog clutch 230.

[0038] 11 and 12, the portion of the stator core 103 that is within the range of movement of the permanent magnet portion 112 is cut out to form a non-existing portion 108 of the stator core 103. This is to prevent the generation of a magnetic flux loop due to the magnetic field of the permanent magnet portion 112 by configuring the magnetic circuit so that no magnetic material is present on the surface facing the permanent magnet portion 112. If a magnetic flux loop occurs, the attractive force in the magnetic gap 104 will decrease, so by providing the non-existing portion 108, it is possible to prevent the attractive force from decreasing.

[0039] FIG. 13 compares an example in which a permanent magnet portion 112 is disposed on the moving core 110 (bottom row) with an example in which a permanent magnet portion 112 is not provided (top row). The top row is the example in which a permanent magnet portion 112 is not provided. As shown in the legend on the left side of the figure, the dotted pattern on the components indicates the magnitude of the magnetic flux. As shown, the closer to black (HT), the stronger the magnetic flux, and the closer to white (LT), the weaker the magnetic flux. It can be seen that a magnetic circuit is formed between the stator core 103 and the moving core 110 when the coil 101 is energized in the forward direction. Furthermore, it can be seen that the magnetic flux passes through the magnetic gap 104, and the magnetic gap 104 attracts the moving core 110 toward the stator core 103.

[0040] However, as shown in the upper part of Figure 13, a portion of the magnetic flux flows toward the one-side differential case 210, which is the rotating body. This is because both the one-side differential case 210 and the moving core 110 are made of the same soft magnetic material. The magnetic flux that flows toward the one-side differential case 210 does not contribute at all to attracting the moving core 110. The excitation force of the coil 101 is wasted. In the illustration of Figure 13, only the one-side differential case 210 is shown as the rotating body located on the inner and outer peripheries of the rotating body. However, in reality, the one-side drive shaft 260 is located on the inner periphery of the one-side differential case 210. Because the one-side drive shaft 260 is also made of a soft magnetic material, the leakage of magnetic flux toward the rotating body becomes even greater.

[0041] In contrast, as shown in the lower part of Figure 13, when a permanent magnet portion 112 is provided, the magnetic flux of the coil 101 is rectified by the permanent magnet portion 112. This is because the magnetic pole direction of the permanent magnet portion 112 matches the magnetic pole direction of the coil 101 when current is forwardly applied. Although the magnetic flux leaking to the one side differential case 210 is not zero, it is significantly reduced compared to the upper part. Also, as described above, the portion facing the permanent magnet portion 112 is the non-existence portion 108 of the stator core 103. Therefore, no magnetic flux loops due to the permanent magnet portion 112 are generated in the non-existence portion 108.

[0042] As can be seen from Figure 13, it is desirable to reduce the magnetic flux leaking toward the one-side differential case 210, which is the rotating body. To achieve this, it is desirable to position the permanent magnet portion 112 closer to the magnetic gap 104. In other words, the thickness of the moving core tip portion 111A of the moving core 110 (moving core main body portion 111) is determined by how the magnetic force of the permanent magnet portion 112 is utilized. In this embodiment, the permanent magnet portion 112 is also used to maintain the position of the moving core 110.

[0043] As described above, when the coil 101 shown in FIG. 11 is not energized, the first dog clutch 220 is separated from the second dog clutch 230 by the biasing force of the return spring 107. On the other hand, when the coil 101 is energized in the forward direction from the state shown in FIG. 11 , the magnetic gap 104 narrows, and the first dog clutch 220 transitions to an engaged state with the second dog clutch 230, as shown in FIG. 12 . Even if the coil 101 is de-energized in this state, the state shown in FIG. 12 can be maintained by the magnetic force of the permanent magnet portion 112. That is, in this embodiment, both the disengaged state of the first dog clutch 220 and the second dog clutch 230 shown in FIG. 11 and the engaged state of the first dog clutch 220 and the second dog clutch 230 shown in FIG. 12 can be maintained without energizing the coil 101.

[0044] In this embodiment, to switch from the engaged state shown in Fig. 12 to the disengaged state shown in Fig. 11, reverse current is passed through the coil 101. Reverse current is passed through the coil 101 with the positive and negative poles reversed compared to forward current. When reverse current is passed through the coil 101, the excitation force generated in the coil 101 repels the magnetic force of the permanent magnet portion 112, widening the magnetic gap 104. Once the magnetic gap 104 has widened, that state is maintained by the biasing force of the return spring 107.

[0045] Therefore, the relationship between the biasing force of the return spring 107 and the magnetic force of the permanent magnet portion 112 is as follows: When the magnetic gap 104 is narrowed and the first dog clutch 220 and the second dog clutch 230 are engaged, the magnetic force of the permanent magnet portion 112 is greater than the biasing force of the return spring 107. Conversely, when the magnetic gap 104 is widened and the first dog clutch 220 and the second dog clutch 230 are disengaged, the biasing force of the return spring 107 is greater than the magnetic force of the permanent magnet portion 112. In other words, in the engaged state, the attractive force due to the magnetic force of the permanent magnet portion 112 is greater than the biasing force of the return spring 107. Conversely, in the disengaged state, the biasing force of the return spring 107 is greater than the attractive force due to the magnetic force of the permanent magnet portion 112. The thickness of the moving core tip portion 111A described above is determined so as to set the magnetic force of the permanent magnet portion 112 in this manner. In this embodiment, the thickness of moving core tip portion 111A is set to be equal to or greater than the thickness of permanent magnet portion 112. In other words, moving core tip portion 111A having a predetermined thickness is interposed on the magnetic gap 104 side of permanent magnet portion 112 to adjust the magnetic force of permanent magnet portion 112.

[0046] Thus, in this embodiment, by arranging the permanent magnet portion 112 in an appropriate position on the moving core 110, the excitation force when the coil 101 is positively energized can be utilized most efficiently. FIG. 14 shows the relationship between stroke and attractive force for the upper and lower examples of FIG. 13. Note that the attractive force FA in FIG. 14 is the attractive force generated in the magnetic gap 104 when the coil 101 is positively energized. The upper example is shown by solid line A, and the lower example is shown by solid line B. As shown, the solid lines A and B indicate the same behavior as the solenoid clutch device 100. However, the solid line B in the lower example exhibits a higher attractive force than the solid line A at all strokes ST.

[0047] In this embodiment, the permanent magnet portion 112 is used, so that the first dog clutch 220 and the second dog clutch 230 can be transitioned from a disengaged state to an engaged state with a high attractive force. Furthermore, in this embodiment, the engaged state can be maintained. In other words, in this example, the coil 101 required to generate sufficient attractive force for engagement can be made smaller.

[0048] As shown in Figure 9, in the engaged state, the rotation of the motor 300 is transmitted to the one-side drive shaft 260 and the other-side drive shaft 261 via the differential 200. On the other hand, in the disengaged state, as shown in Figure 10, the transmission of rotation R5 of the one-side drive shaft 260 and the other-side drive shaft 261 ends at the second dog clutch 230. As a result, in the disengaged state, the rotation is not transmitted to the motor 300. Since a counter electromotive force is generated when the motor 300 is rotated, the first dog clutch 220 and the second dog clutch 230 are disengaged when the vehicle is allowed to inertial travel. When the motor 300 is used for regenerative braking or power generation, the first dog clutch 220 and the second dog clutch 230 are engaged.

[0049] While the above is a preferred example of the present disclosure, the present disclosure can be modified in various ways. For example, the bearing member 105 is desirable for supporting the moving core 110, but it can be eliminated. Eliminating the bearing member 105 allows the solenoid clutch device 100 to be made smaller.

[0050] In this embodiment, the first dog clutch 220 and the second dog clutch 230 are engaged by energizing the coil 101 in a forward direction. In this embodiment, even if the coil 101 is subsequently de-energized, the engaged state is maintained by the magnetic force of the permanent magnet portion 112. This is a desirable example, as it is possible to maintain both the engaged and disengaged states without energizing the coil 101. Alternatively, it is possible to maintain the engaged state by the magnetic force of the coil 101 by adjusting the magnetic force of the permanent magnet portion 112 to be smaller or by adjusting the thickness of the moving core tip portion 111A to be larger.

[0051] In addition, in the solenoid clutch device 100 of this embodiment, the movement of the moving core 110 can be transmitted to either the first clutch plate or the second clutch plate, and the movement of the moving core 110 can be used to engage the first clutch plate and the second clutch plate, or to disengage them.

[0052] In this embodiment, the solenoid clutch device 100 is used to engage the first dog clutch 220 and the second dog clutch 230. Alternatively or in addition to this, the solenoid clutch device 100 can be used for other purposes in the differential device 200. For example, the solenoid clutch device 100 can be used as a limited slip differential device that is used in situations where one of the drive shafts is unable to rotate due to tire slip.

[0053] Furthermore, the solenoid clutch device 100 of this embodiment is not limited to use in the differential device 200. As long as the solenoid clutch device 100 is disposed on the outer periphery of a rotating body made of a soft magnetic material, it can be used in a wide range of applications, not just as a differential device 200.

[0054] Furthermore, the materials and sizes described above are merely examples and can be selected appropriately depending on the required performance. The disclosure in this specification and drawings is not limited to the exemplified embodiments. The disclosure encompasses the exemplified embodiments and modifications thereto by those skilled in the art.

[0055] (Disclosure of Technical Ideas) This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be described in a multiple dependent form, in which the subsequent clause alternatively refers to the preceding clause. Furthermore, some clauses may be described in a multiple dependent form, in which the subsequent clause refers to another multiple dependent clause. The clauses described in these multiple dependent forms define multiple technical ideas.

[0056] (Technical Idea 1) A rotating body made of soft magnetic material that rotates around an axis, a first clutch plate that rotates integrally with the rotating body, a second clutch plate that is arranged opposite the first clutch plate, a coil that is fixedly arranged on the outer periphery of the rotating body, a stator core made of soft magnetic material that is fixedly arranged on the outer periphery of the rotating body and that forms a magnetic circuit when the coil is energized, a moving core that is arranged on the outer periphery of the rotating body, with a magnetic gap between it and the stator core, that forms a magnetic circuit together with the stator core when the coil is energized, and that moves in the axial direction of the rotating body to narrow the magnetic gap when the coil is energized in the forward direction, a return spring that urges the stator core and the moving core in a direction that separates them from each other, and a plunger made of a non-magnetic material that transmits the movement of the moving core in the axial direction of the rotating body to either the first clutch plate or the second clutch plate, the moving core comprising a moving core main body portion made of soft magnetic material and a permanent magnet portion made of hard magnetic material, A solenoid clutch device in which the magnetic pole direction of the permanent magnet portion coincides with the magnetic pole direction when the coil is positively energized, and the stator core is not present within the movement range of the permanent magnet portion.

[0057] (Technical Idea 2) A solenoid clutch device according to Technical Idea 1, wherein the permanent magnet portion is positioned on the side of the moving core closer to the magnetic gap, and the moving core tip portion of the moving core body is interposed between the permanent magnet portion inside the moving core and the magnetic gap, and the thickness of this moving core tip portion is a predetermined thickness determined according to the size of the magnetic gap.

[0058] (Technical Idea 3) A solenoid clutch device according to Technical Idea 1 or Technical Idea 2, in which when current is passed through the coil in a forward direction to narrow the magnetic gap, even when the coil is de-energized, the positions of the moving core and the stator core are maintained by the magnetic force of the permanent magnet portion, and when current is passed through the coil in a reverse direction, the repulsive force between the coil and the permanent magnet portion and the biasing force of the return spring cause the moving core to move in the axial direction of the rotating body so as to widen the magnetic gap, and when current is passed through the coil in a reverse direction to widen the magnetic gap, even when the coil is de-energized, the positions of the moving core and the stator core are maintained by the biasing force of the return spring.

[0059] (Technical Idea 4) A solenoid clutch device according to any one of Technical Ideas 1 to 3, wherein a bearing member made of a non-magnetic material is interposed between the inner periphery of the moving core and the outer periphery of the rotating body.

[0060] (Technical Idea 5) A solenoid clutch device according to any one of Technical Ideas 1 to 4, wherein the rotating body comprises a cylindrical outer rotating body and a cylindrical shaft arranged on the inner periphery of the outer rotating body.

[0061] (Technical Idea 6) A solenoid clutch device according to Technical Idea 5, wherein the outer rotating body corresponds to a differential case of a differential device, the shaft corresponds to a drive shaft of the differential device, the first clutch plate corresponds to a first dog clutch of the differential device, and the second clutch plate corresponds to a second dog clutch of the differential device, and rotation of the differential case is transmitted to the drive shaft via a ring gear of the differential device, the first dog clutch, the second dog clutch, a pinion gear, and a side gear.

[0062] (Technical Concept 7) A solenoid clutch device according to Technical Concept 6, wherein the differential gear is disposed in a power train unit, and the differential case is rotationally supported by the power train unit through a differential case bearing.

Claims

a stator core made of a soft magnetic material and arranged to be fixed to the outer periphery of the rotor, and configured to form a magnetic circuit when the coil is energized; a moving core arranged on the outer periphery of the rotor, on the inner periphery of the coil and on the outer periphery of the rotor, with a magnetic gap between the stator core and the moving core, configured to form a magnetic circuit together with the stator core when the coil is energized, and moving in the axial direction of the rotor so as to narrow the magnetic gap when the coil is energized; a return spring that biases the stator core and the moving core in a direction separating them from each other; and a plunger made of a non-magnetic material that transmits the axial movement of the moving core of the rotor to either the first clutch plate or the second clutch plate, the moving core comprising a moving core main body made of a soft magnetic material and a permanent magnet portion made of a hard magnetic material, A solenoid clutch device, characterized in that a magnetic pole direction of the permanent magnet portion coincides with a magnetic pole direction when a positive current is applied to the coil, and the stator core is not present within a moving range of the permanent magnet portion.

2. A solenoid clutch device as described in claim 1, wherein the permanent magnet portion is disposed on the side of the moving core closer to the magnetic gap, and the tip portion of the moving core body is interposed between the internal permanent magnet portion of the moving core and the magnetic gap, and the thickness of the tip portion of the moving core is a predetermined thickness determined according to the size of the magnetic gap.

3. A solenoid clutch device as described in claim 2, wherein when current is passed through the coil in a forward direction to narrow the magnetic gap, even when the coil is de-energized, the positions of the moving core and the stator core are maintained by the magnetic force of the permanent magnet portion, and when current is passed through the coil in a reverse direction, the repulsive force between the coil and the permanent magnet portion and the biasing force of the return spring cause the moving core to move in the axial direction of the rotating body so as to widen the magnetic gap, and when current is passed through the coil in a reverse direction to widen the magnetic gap, even when the coil is de-energized, the positions of the moving core and the stator core are maintained by the biasing force of the return spring.

4. A solenoid clutch device according to claim 1 or 2, wherein a bearing member made of a non-magnetic material is interposed between the inner periphery of said moving core and the outer periphery of said rotor.

5. A solenoid clutch device according to claim 1 or 2, wherein the rotor comprises a cylindrical outer rotor and a cylindrical shaft disposed on the inner circumference of the outer rotor.

6. A solenoid clutch device as described in claim 5, wherein the outer peripheral rotor corresponds to a differential case of a differential device, the shaft corresponds to a drive shaft of the differential device, the first clutch plate corresponds to a first dog clutch of the differential device, and the second clutch plate corresponds to a second dog clutch of the differential device, and rotation of the differential case is transmitted to the drive shaft via a ring gear, the first dog clutch, the second dog clutch, a pinion gear, and a side gear of the differential device.

7. A solenoid clutch device according to claim 6, wherein said differential gear is disposed in a power train unit, and said differential case is rotationally supported by said power train unit through a differential case bearing.

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