power transmission device

Abstract

To reduce torque required to restrict or stop rotation, thereby simplifying the overall structure. [Solution] A power transmission device (1) having a sun gear (7), a ring gear (8), a pinion gear (9), and a carrier (10), wherein an input member (4) is connected to the sun gear (7), the ring gear (8) is fixed to a predetermined location (11), an output member is connected to the carrier (10), a part of the outer periphery of the pinion gear (9) forms a protrusion that protrudes toward the outer periphery of the carrier (10), an engaging portion (17) is formed on the side of the protrusion, a locking plate (18) that moves back and forth toward the side is provided integrally with a predetermined fixed portion (3) in the rotational direction of the carrier (10), and the locking plate (18) is provided with an engaged portion (19) that engages with the engaging portion (17) in the rotational direction of the pinion gear (10).

Description

[Technical Field]

[0001] The present invention relates to a device for transmitting power through a gear mechanism, and more particularly to a power transmission device mainly composed of a planetary gear mechanism equipped with a locking mechanism. [Background technology]

[0002] This type of power transmission device is described in Patent Documents 1 to 3. The devices described in Patent Documents 1 and 2 include a planetary gear mechanism disposed between independently driven left and right wheels and a rotation restriction mechanism that restricts the rotation of the planetary gear mechanism to stop the rotation of the left and right wheels. The planetary gear mechanism is composed of a sun gear, a ring gear, and a carrier that holds a pinion gear disposed between the sun gear and the ring gear. The rotation restriction mechanism disclosed is a mechanism that engages with the carrier to restrict its rotation. Patent Document 3 also describes a planetary gear mechanism that transmits motor torque to a final reduction gear via a reduction mechanism, in which the ring gear is used as an output element and a parking lock mechanism that selectively engages with the ring gear to stop the rotation of the ring gear and the wheels connected to it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-054099 [Patent Document 2] Japanese Patent Application Publication No. 2018-054098 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-040296 Summary of the Invention [Problem to be solved by the invention]

[0004] As described in Patent Documents 1 to 3, a planetary gear mechanism includes multiple rotating elements. Stopping the rotation of any one of these elements stops the rotation of the entire planetary gear mechanism, enabling a so-called parking lock. In the devices described in Patent Documents 1 and 2, a parking gear is formed on the outer periphery of the carrier, and a parking pole is engaged with it to restrict rotation. However, the configurations described in Patent Documents 1 and 2 impose a large torque on the carrier, potentially resulting in a large parking mechanism consisting of the parking gear and parking pole. In addition, since the parking mechanism is located adjacent to the axial direction of the planetary gear mechanism, the overall axial length (length along the rotational axis) of the power transmission device increases. Note that the configuration described in Patent Document 3 restricts the rotation of the ring gear using a parking mechanism located on its outer periphery, thereby reducing the number of components required to be arranged axially of the planetary gear mechanism and shortening the axial length. However, in a power transmission device in which the ring gear is a fixed element, the ring gear is originally fixed, making this configuration unsuitable for this type of power transmission device.

[0005] The present invention has been made in light of the above technical problems, and aims to provide a power transmission device that reduces the torque required to restrict or stop rotation, thereby simplifying the overall configuration. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a power transmission device having a sun gear which is an external gear, a ring gear which is an internal gear arranged concentrically with the sun gear, a pinion gear arranged between the sun gear and the ring gear while meshing with the sun gear and the ring gear, and a carrier which rotates while holding the pinion gear so that it can rotate on its own axis, wherein an input member is connected to the sun gear, the ring gear is fixed at a predetermined location, and an output member is connected to the carrier, a portion of the outer periphery of the pinion gear forms a protrusion that protrudes toward the outer periphery of the carrier, an engaging portion is formed on the side of the protrusion, a locking plate which moves back and forth toward the side is attached to a predetermined fixed portion in a state integrated with the rotational direction of the carrier, and the locking plate is provided with an engaged portion that engages with the engaging portion in the rotational direction of the pinion gear. [Effects of the Invention]

[0007] According to the present invention, when the locking plate advances toward the pinion gear, the engaged portion of the locking plate engages with the engaging portion of the pinion gear. The locking plate is attached to a predetermined fixed portion so that it cannot rotate, thereby stopping the rotation of the pinion gear. The ring gear with which the pinion gear meshes is fixed in a predetermined location, ultimately stopping the rotation of the carrier and sun gear. In other words, a locked state is achieved. In this case, the torque applied to the pinion gear in stopping the rotation of the sun gear and carrier is smaller than the torque required to directly stop the rotation of the sun gear and carrier, because the pinion gear is located on the outer periphery of the sun gear and has a small diameter. This allows the locking plate, engaged portion, and engaging portion to be made smaller. Furthermore, since the locking plate can be arranged on the outer periphery of the carrier, in other words, there is no need to arrange it coaxially with the sun gear, it is possible to avoid increasing the number of parts arranged on the same axis, and to avoid or suppress an increase in the axial length of the entire device or an increase in the size of the device. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a cross-sectional view showing one embodiment of the present invention. [Figure 2] 10A and 10B are front views showing the shapes of pinion blades as engagement parts provided on the side of the pinion gear, where (a) shows a rectangular pinion blade, (b) shows a round pin-shaped pinion blade, and (c) shows an inclined rectangular pinion blade. [Figure 3] FIG. [Figure 4] FIG. 10 is a schematic front view showing a state in which the parking blade and the pinion blade are engaged with each other to stop the rotation of the pinion gear. [Figure 5] 10A and 10B are cross-sectional views showing examples of chamfers formed on a parking blade and a pinion blade. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0010] FIG. 1 is a cross-sectional view showing an example of an embodiment of the present invention. The power transmission device 1 shown here is configured as a reduction mechanism primarily comprising a single-pinion planetary gear mechanism 2. A sun gear shaft 4 is disposed in the center of a motor case 3, which houses a motor or motor-generator (hereinafter collectively referred to as the motor), a power source (not shown), so as to rotate about its central axis. The sun gear shaft 4 corresponds to the input member in this embodiment of the present invention. The sun gear shaft 4 is rotatably supported by a bearing 6 attached to a partition wall 5 provided inside the motor case 3, and a sun gear 7, which is an external gear, is disposed on the tip end portion protruding from the bearing 6. The sun gear 7 may be formed integrally with the sun gear shaft 4, or may be fitted and integrated with the sun gear shaft 4.

[0011] The planetary gear mechanism 2 is a differential gear mechanism including, as rotating elements, the sun gear 7, a ring gear 8 which is an internal gear arranged concentrically with the sun gear 7, and a carrier 10 which is arranged between the sun gear 7 and the ring gear 8 and holds a pinion gear 9 which meshes with the sun gear 7 and the ring gear 8. A cover 11 is attached to the open end of the motor case 3, and the planetary gear mechanism 2 is disposed inside a hollow space formed by the cover 11 and the partition wall 5. The carrier 10 is rotatably held by a bearing 12 fitted into the inner surface of the cover 11. A bearing 13 is fitted into the center of the carrier 10, and the tip end of the sun gear shaft 4 is rotatably supported by this bearing 13. The ring gear 8 is attached to the inner surface of the cover 11. Therefore, the planetary gear mechanism 2 constitutes a reduction mechanism with the sun gear 7 as an input element, the ring gear 8 as a fixed element (or a reaction element), and the carrier 10 as an output element. An output member (not shown) is connected to the carrier 10. The cover 11 corresponds to a predetermined portion in the embodiment of the present invention.

[0012] 1, the carrier 10 is cylindrical as a whole and has a first side wall portion 10a into which a bearing 12 is fitted on the outer periphery and a bearing 13 is fitted on the inner periphery, a second side wall portion 10b facing the first side wall portion 10a in the direction of the rotational center axis (hereinafter sometimes simply referred to as the center axis) of the planetary gear mechanism 2, and a bridge portion 10c connecting the outer peripheries of these side wall portions 10a, 10b. A plurality of bridge portions 10c are provided at regular intervals in the circumferential direction, and therefore the carrier 10 has a plurality of openings that open outward in the radial direction.

[0013] The pinion gear 9 is disposed in a position corresponding to the opening. That is, the opening is a portion where a part of the outer periphery of the pinion gear 9 protrudes toward the outer periphery of the carrier 10 in order to mesh the pinion gear 9 with the ring gear 8. The pinion gear 9 is attached to the carrier 10 by the pinion shaft 14 with a part of its outer periphery protruding toward the outer periphery of the carrier 10 in this manner. The pinion shaft 14 is attached to the carrier 10 by fitting both ends into the side wall portions 10a, 10b. A bearing 15 is fitted into the middle portion of the pinion shaft 14 in the axial direction, and by fitting the pinion gear 9 onto the outer periphery of this bearing 15, the pinion gear 9 is held by the carrier 10 so as to be able to rotate and revolve about its axis.

[0014] Next, the locking mechanism 16 for maintaining the entire planetary gear mechanism 2 in a fixed state will be described. The locking mechanism 16 corresponds to a parking mechanism in a power transmission device 1 mounted on a vehicle, and stops rotation of an output member (not shown) by restricting the rotation of the entire planetary gear mechanism 2. In the embodiment of the present invention shown in FIG. 1, the locking mechanism 16 is configured to stop rotation of the pinion gear 9. That is, as described above, a portion of the outer periphery of each pinion gear 9 protrudes toward the outer periphery of the carrier 10, and a plurality of pinion blades 17 serving as engaging portions are arranged at regular intervals on the side of the protruding portion in the circumferential direction of the pinion gear 9. In the example shown in FIG. 1, the pinion blades 17 are essentially protrusions, and their shape can be appropriately changed as needed. For example, as shown in FIG. 2(a), the pinion blades 17 may be protrusions with a rectangular cross section that are elongated in the circumferential direction of the pinion gear 9. Alternatively, as shown in FIG. 2(b), the pinion blades 17 may be protrusions with a circular cross section, so-called round pin-like protrusions. 2(c), the pinion blade 17 may be a protrusion having a rectangular cross section, the longitudinal direction of which is inclined at a predetermined angle with respect to the circumferential direction (tangential direction) of the pinion gear 9. The reason for inclining the pinion blade 17 in this manner is to scoop up the lubricating oil that accumulates inside the motor case 3 as the pinion gear 9 rotates and revolves, thereby improving the lubrication of the bearings 6, 12, 13, etc. Therefore, the direction and angle of inclination of the pinion blade 17 can be determined appropriately based on the directions of rotation and revolution of the pinion gear 9 when the planetary gear mechanism 2 is steadily rotating.

[0015] A parking plate 18, which corresponds to a locking plate, is disposed in a position facing the side of the pinion gear 9 on which the pinion blade 17 is provided. An example of the parking plate 18 is shown in Fig. 3, and the parking plate 18 is an arc-shaped plate piece whose inner diameter is approximately the same as the outer diameter of the carrier 10. The parking plate 18 is disposed on the outer periphery of the carrier 10 and is spline-fitted to the inner surface of the motor case 3, which corresponds to a predetermined fixing portion. Therefore, the parking plate 18 moves back and forth in the central axial direction toward the pinion gear 9, with the outer periphery of the carrier 10 acting as a guide surface, and is fixed in the rotational direction.

[0016] A parking blade 19 is provided as an engaged portion on the front surface of the parking plate 18 facing the pinion gear 9. The parking blade 19 is intended to restrict the rotation of the pinion gear 9 by hooking onto the pinion blade 17 in the rotational direction. As shown in FIG. 3 as an example, the parking blade 19 has a rectangular cross-sectional protrusion extending radially outward from the inner end of the parking plate 18. That is, at least a portion of the parking blade 19 faces the pinion blade 17 in the rotational direction. When multiple parking blades 19 are provided, the spacing between the parking blades 19 is set so that when any pinion blade 17 is engaged with any parking blade 19, the other pinion blades 17 and the other parking blades 19 do not interfere with each other.

[0017] An actuator 20 is provided to move the parking plate 18 back and forth. The actuator 20 is a so-called linear actuator that moves a rod 20a back and forth using electromagnetic force, fluid pressure, or the like, and is attached to the motor case 3 so as to be located on the rear side of the parking plate 18. A pusher 20b that faces the rear side of the parking plate 18 is attached to the rod 20a. The pusher 20b and the parking plate 18 are connected via an elastic member 21 such as a coil spring. The provision of this elastic member 21 allows the parking plate 18 to move backward in a direction that compresses the elastic member 21.

[0018] Explaining the operation of the locking mechanism 16, FIG. 1 shows a state in which the pinion gear 9 is released, and the parking plate 18 is moved back by the actuator 20 in a direction away from the pinion gear 9. Therefore, the parking blade 19 provided on the parking plate 18 is separated from the pinion blade 17 provided on the pinion gear 9, and the engagement between them is released, allowing the pinion gear 9 to rotate and revolve freely. In this state, when the motor (not shown) rotates and torque is input to the sun gear 7, the carrier 10 rotates at a slower speed than the sun gear 7 because the ring gear 8 is fixed, and torque is output from the carrier 10. When the planetary gear mechanism 2 is rotating, if the pinion blade 17 has the shape shown in FIG. 2(c), the pinion blade 17 will scoop up the lubricating oil, thereby promoting lubrication of the bearings 6, 12, 13, etc.

[0019] On the other hand, when the actuator 20 is operated by, for example, a parking command to keep the vehicle stopped, the rod 20a extends, and the pusher 20b and the parking plate 18 move forward toward the pinion gear 9. As a result, when the parking blade 19 provided in front of the parking plate 18 enters between the pinion blades 17 provided on the side of the pinion gear 9, the parking blade 19 and the pinion blade 17 face each other in the rotational direction, and when the pinion gear 9 rotates, they come into contact with each other as shown in FIG. 4. That is, as shown by the circle in FIG. 4, the pinion blade 17 abuts against the parking blade 19, stopping the rotation of the pinion gear 9. When the rotation of the pinion gear 9 is stopped, the carrier 10 cannot rotate, and as a result, the entire planetary gear mechanism 2 is fixed. Therefore, for example, in a vehicle, when the carrier 10 is connected to wheels (not shown) via an output member, the vehicle is maintained in a parked state.

[0020] In this case, the torque for keeping the vehicle stopped is received by motor case 3 via pinion gear 9 and parking plate 18, and stress acts on pinion blade 17 of pinion gear 9 and parking blade 19 of parking plate 18. This stress is due to the torque that tries to rotate pinion gear 9, but the torque that acts on pinion gear 9 based on the torque for keeping the vehicle stopped is small because pinion gear 9 has a small diameter and the torque is received on the outer periphery of planetary gear mechanism 2. Therefore, pinion blade 17, parking blade 19, parking plate 18, etc. are not required to have particularly high rigidity or strength, which means that these members and lock mechanism 16 can be made smaller, and further the overall configuration of power transmission device 1 can be made smaller. Furthermore, since the locking mechanism 16 can be provided on the outer periphery of the carrier 10, the number of parts arranged coaxially with the sun gear 7 does not increase. Therefore, in the embodiment of the present invention, an increase in the axial length of the power transmission device 1 can be avoided or suppressed. In other words, a power transmission device 1 with a short axial length and parking function can be obtained.

[0021] If the parking plate 18 advances toward the pinion gear 9 while the pinion gear 9 is rotating, the parking blade 19 may be repelled by the pinion blade 17, preventing the two from engaging, depending on the rotational speed of the pinion gear 9. This occurs because the elastic material 21 provided on the back side of the parking plate 18 is compressed, causing the parking plate 18 to temporarily retreat. This is to avoid shock or damage that may occur if the parking blade 19 and the pinion blade 17 suddenly engage with each other. Therefore, to ensure that the parking blade 19 temporarily repels, or so-called ratcheting, the parking blade 19 is desirably configured to convert the torque acting between the parking blade 19 and the pinion blade 17 into thrust in the axial direction. For example, as shown in FIG. 5, the corners of the parking blade 19 and the pinion blade 17 are chamfered to form chamfers C. The chamfer angle can be about 45 degrees, and by doing so, when the chamfers C come into contact with each other, an axial component force (axial thrust) is generated, which pushes back the parking blade 19 and the parking plate 18 on which it is mounted.As a result, it is possible to avoid or suppress sudden engagement between the parking blade 19 and the pinion blade 17 while the pinion gear 9 is rotating.

[0022] Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and the engaging portion and the engaged portion in the present invention do not both need to be protrusions, but one may be a convex portion and the other a concave portion. Furthermore, the planetary gear mechanism in the present invention is not limited to a single-pinion planetary gear mechanism, but may also be a double-pinion planetary gear mechanism. Furthermore, the power transmission device according to the present invention is not limited to a power transmission device mounted on a vehicle, and may be any device configured to transmit torque output from a power source such as a motor or engine to a predetermined output member. [Explanation of symbols]

[0023] 1 Power transmission device 2 Planetary gear mechanism 3 Motor case 4 Sun gear shaft 5 Bulkhead 6,12,13 Bearings 7 Sun gear 8 ring gear 9 Pinion gear 10 Carrier 10a Side wall part 10b Side wall part 10c bridge 11 Cover 14 Pinion shaft 15 Bearings 16 Locking mechanism 17 Pinion Blade 18 Parking Plate 19 Parking Blade 20 Actuator 20a rod 20b Pusher 21 Elastic material C Chanfa

Claims

[Claim 1] A power transmission device comprising: a sun gear which is an external gear; a ring gear which is an internal gear arranged concentrically with the sun gear; a pinion gear arranged between the sun gear and the ring gear while meshing with the sun gear and the ring gear; and a carrier which rotates while rotatably holding the pinion gear, an input member connected to the sun gear; The ring gear is fixed in place, an output member connected to the carrier; a part of an outer circumferential side of the pinion gear forms a protruding portion that protrudes toward an outer circumferential side of the carrier, An engagement portion is formed on a side surface of the protrusion, a locking plate that moves back and forth toward the side surface is provided integrally with a predetermined fixing portion in the rotation direction of the carrier, The locking plate is provided with an engaged portion that engages with the engaging portion in the rotation direction of the pinion gear. A power transmission device characterized by:

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