Planetary gear mechanism

Abstract

This utility model relates to a planetary gear mechanism that balances the increased capacity of transmitted torque and improved NV characteristics. At least one of the multiple pinions, a first pinion (6A), is movable in the axial direction of the pinion pin (11) and is pressed in the axial direction by an elastic force (F0). At least one other second pinion is fixed in the axial direction of the pinion pin. The sun gear (2) is movable in the axial direction. When the thrust (F1) generated by the torque transmission between the sun gear (2) and the first pinion (6A) is less than the elastic force, the first pinion (6A) moves in the axial direction, thereby maintaining its meshing with the sun gear (2) and disengaging its meshing with the gear ring (4).

Description

Technical Field

[0001] This utility model relates to a planetary gear mechanism in which a plurality of pinions are arranged between a sun gear and a gear ring arranged on a concentric circle relative to the sun gear. Background Technology

[0002] As is well known, a planetary gear mechanism is a differential gear mechanism consisting of a sun gear as an external gear, a ring gear as an internal gear arranged concentrically relative to the sun gear, and multiple pinions meshing with the sun gear and ring gear, held by a planet carrier to rotate and revolve. Torque is transmitted between the sun gear, ring gear, and planet carrier through the rotation of these pinions, or through their simultaneous rotation and revolution. Under this torque transmission state, repeated meshing occurs between the sun gear and the pinions, and between the pinions and the ring gear; therefore, vibration is inevitably generated in a planetary gear mechanism due to the rotation of the pinions.

[0003] Patent Document 1 discloses a planetary gear mechanism configured to suppress resonance caused by vibrations in the pinion portion as much as possible. The planetary gear mechanism described in Patent Document 1 has multiple pinions, and the resonant frequency of the vibration system formed by these pinions and the portion of the pinion shaft supporting them varies depending on the position of the pinions. The resonant frequency, for example, is a frequency corresponding to the rigidity of the pinion shaft; therefore, in the planetary gear mechanism of Patent Document 1, the mass, thickness, etc., of the pinion shaft are varied. Thus, even if the number of pinions is increased to increase the transmittable torque, vibrations or noise generated accompanying torque transmission can be suppressed.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2009-210028

[0005] The more pinions there are, the greater the torque (i.e., torque capacity) that can be transmitted by the planetary gear mechanism. However, as described in Patent Document 1, the pinions also vibrate by rotation. Therefore, if the number of pinions is large, the initiation force (excitation force) increases accordingly, and the overall NV characteristics of the planetary gear mechanism may deteriorate. In the planetary gear mechanism described in Patent Document 1, the resonant frequencies at different points on the pinions are different, thereby preventing or suppressing the deterioration of vibration or noise caused by resonance. However, increasing the number of pinions leads to an increase in the initiation force, and there is still room for improvement in reducing the overall vibration or noise of the planetary gear mechanism and thus improving the NV characteristics. Utility Model Content

[0006] This utility model was completed with regard to the above-mentioned technical problems. Its purpose is to provide a planetary gear mechanism that can simultaneously increase torque capacity by increasing the number of pinions and improve NV characteristics by reducing the starting force.

[0007] To achieve the aforementioned objectives, this invention provides a planetary gear mechanism comprising: a sun gear, which is an external gear; a ring gear, which is an internal gear arranged concentrically relative to the sun gear; and a plurality of pinions arranged between the sun gear and the ring gear in a meshing state with the sun gear and the ring gear, and held by a planet carrier to rotate. The planetary gear mechanism is characterized in that the sun gear, the pinions, and the ring gear are helical gears; the plurality of pinions are mounted to the planet carrier via pinion pins; and at least one of the plurality of pinions, a first pinion, is movable along the axis of the pinion pin. Furthermore, the first pinion is pressed by an elastic force in the aforementioned axial direction, and at least one of the aforementioned pinions is fixed in the axial direction of the aforementioned pinion pin. Either the aforementioned sun gear or the aforementioned gear ring can move along the aforementioned axial direction. When the thrust generated by the transmission of torque between either the aforementioned sun gear or the aforementioned gear ring and the aforementioned first pinion is less than the aforementioned elastic force, the configuration is such that: the aforementioned first pinion moves along the axial direction of the aforementioned pinion pin, thereby maintaining the meshing of the aforementioned first pinion with either the aforementioned sun gear or the aforementioned gear ring, and disengaging the aforementioned first pinion from the other of the aforementioned sun gear or the aforementioned gear ring.

[0008] According to this invention, when the transmitted torque is small, the first pinion, which can move along the axial direction, experiences a thrust that is smaller than the elastic force accompanying the torque transmission and moves along the axial direction. Conversely, the second pinion, fixed in the axial direction, maintains meshing with both the sun gear and the ring gear. Therefore, the first pinion can move along the axial direction via either the sun gear or the ring gear, maintaining meshing with that gear and engaging with the other gear. Thus, the first pinion does not participate in torque transmission and therefore does not become a source of vibrational force, resulting in good overall NV characteristics for the planetary gear mechanism. In this case, since the transmitted torque is small, problems such as excessive wear of the tooth surfaces are avoided. Conversely, when the transmitted torque is large, the first pinion overcomes the elastic force and moves in the opposite direction, thus meshing with both the sun gear and the ring gear, just like the second pinion. That is, all the pinions involved participate in torque transmission, thus increasing the overall torque or torque capacity that the planetary gear mechanism can transmit. As a result, the number of pinions associated with torque transmission increases or decreases depending on the transmitted torque, thus achieving both an increase in torque capacity and an improvement in NV characteristics due to a reduction in starting force. Attached Figure Description

[0009] Figure 1 This is a schematic skeleton diagram illustrating an example of a stepped pinion planetary gear mechanism according to an embodiment of the present invention.

[0010] Figure 2 This is a schematic diagram illustrating the arrangement of the pinions.

[0011] Figure 3A , Figure 3B This is a schematic cross-sectional view used to illustrate the position of the first pinion. Figure 3A This indicates the state at low torque. Figure 3B This indicates the state under high torque.

[0012] Figure 4 This is a line graph showing the sound pressure measurement results when the number of pinions is set to three and two.

[0013] Explanation of reference numerals in the attached figures

[0014] 1: Planetary gear mechanism; 2: Sun gear; 3: Rotating shaft; 4: Gear ring; 5: Fixed part; 6: Pinion; 6A: First pinion; 6B: Second pinion; 7: Planet carrier; 8: Large diameter part; 9: Small diameter part; 10: Rotating shaft; 11: Pinion pin; 12: Spring. Detailed Implementation

[0015] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the embodiments described below are merely one example of implementing the present invention and do not limit the scope of the invention.

[0016] The planetary gear mechanism in this embodiment of the invention is a gear mechanism in which multiple pinions held by a planet carrier are arranged between a sun gear and a ring gear arranged concentrically on a circle relative to the sun gear, thereby causing the sun gear and the ring gear to mesh. It is a differential gear mechanism in which the planet carrier, sun gear, and ring gear are the three rotating elements. Figure 1 As an example, a planetary gear mechanism 1, known as a stepped pinion planetary gear mechanism, is represented by a skeleton diagram.

[0017] The sun gear 2 is an external gear, integral with the designated rotating shaft 3. A gear ring 4, acting as an internal gear, is arranged on a circle concentric with the sun gear 2. Figure 1 In the example shown, the ring gear 4 is integrated with the housing or other fixed parts 5 to form a fixed element. The pinion 6 is held in place by the planet carrier 7 to enable rotation. The sun gear 2, ring gear 4, and pinion 6 described above are helical gears.

[0018] Each pinion 6 is an integrated structure in which the large-diameter portion 8, which meshes with the sun gear 2, and the small-diameter portion 9, which has a smaller diameter than the large-diameter portion 8 and meshes with the ring gear 4, are arranged on the same axis. The planet carrier 7 is connected to other rotating shafts 10, so the pinions 6 can rotate on their own axis and revolve around the sun gear. Furthermore, either the sun gear 2 or the planet carrier 7 serves as an input element, and the other as an output element. The planetary gear mechanism 1 described here has three pinions 6, such as... Figure 2 As shown, these small gears 6 are arranged at equal intervals in the circumferential direction. Figure 2 In the diagram, a circle represents the pinion 6, which has a large diameter portion 8 and a small diameter portion 9. Furthermore, the sun gear 2 is a small dimension capable of moving along its axial direction to absorb machining and assembly errors. Therefore, the sun gear 2 corresponds to "either the sun gear or the gear ring" in the embodiments of this invention, and the gear ring 4 corresponds to "the other one of the sun gear and the gear ring".

[0019] The pinion 6 includes a first pinion 6A movable along the axial direction and a second pinion 6B fixed relative to the axial direction. The pinions 6A and 6B are held by the planet carrier 7 via pinions mounted on the planet carrier 7. Wherein, as Figure 3A , Figure 3B As shown, the first pinion 6A is engaged with the pinion pin 11 in a manner that allows it to move along its axial direction. Furthermore, a force-applying axial direction force is applied between the first pinion 6A and the pinion pin 11 to the first pinion 6A. Figure 3A , Figure 3BThe spring 12 (to the left) exerts a spring force. The direction of this spring force is opposite to the direction of the axial meshing reaction force generated between the large diameter portion 8 of the pinion 6A and the tooth surface of the sun gear 2 when torque is transmitted from the sun gear 2 to the planet carrier 7. Alternatively, conversely, the direction of this spring force is opposite to the axial meshing reaction force generated between the large diameter portion 8 of the pinion 6A and the tooth surface of the sun gear 2 when torque is transmitted from the planet carrier 7 to the sun gear 2.

[0020] Next, taking the case where the sun gear 2 is used as the input element and the planet carrier 7 is used as the output element to transmit torque as an example, the function of the above-mentioned planetary gear mechanism 1 will be explained. Figure 3A and Figure 3B A schematic cross-sectional view showing the first planetary gear 6A described above. Figure 3A This indicates the case where the transmitted torque is small. Figure 3B This indicates a case where the transmitted torque is large. The sun gear 2, ring gear 4, and pinion 6 are all helical gears, thus generating a thrust (meshing reaction force) of corresponding magnitude at their respective meshing points.

[0021] When the torque transmitted between the sun gear 2 and the first pinion 6A is small, such as Figure 3A As shown, the meshing reaction force F1 is smaller than the elastic force F0 of spring 12. In other words, Figure 3A This indicates a torque transmission state where the meshing reaction force F1 is smaller than the elastic force F0. In this case, the first pinion 6A transmits torque through the elastic force of the spring 12 to... Figure 3A Move to the left.

[0022] The tooth surfaces of the first pinion 6A and the ring gear 4 are inclined relative to their axial direction, and the ring gear 4 is fixed relative to the axial direction. Therefore, when the first pinion 6A moves along the axial direction, the tooth surfaces that are in contact to transmit torque separate from each other, and the tooth surfaces on their opposite sides contact each other. That is, the first pinion 6A moves along the axial direction to the extent that backlash is eliminated. As a result, no torque is transmitted between the ring gear 4 and the first pinion 6A. Furthermore, as described above, the sun gear 2 can move along the axial direction to the extent that it can absorb errors in machining, assembly, etc., so the meshing between the first pinion 6A and the sun gear 2 is maintained.

[0023] exist Figure 2The first pinion 6A, which does not participate in torque transmission, is represented by a dashed line. Therefore, when the transmitted torque is low, the two other pinions 6B, acting as the second pinion, transmit the torque. Thus, the number of pinions 6 that generate the starting force Fb associated with torque transmission is reduced to two, thereby reducing the overall vibration and noise of the planetary gear mechanism 1. That is, the NV characteristics become better, or at least their deterioration is suppressed. Furthermore, since the torque to be transmitted in the planetary gear mechanism 1 is relatively small, even with a smaller number of pinions 6 involved in torque transmission, excessive wear and other adverse conditions are not particularly likely to occur.

[0024] On the other hand, when the torque to be transmitted is large, it becomes Figure 3B The state shown is as follows. In this case, due to the large transmitted torque, the meshing reaction force F2 generated on the meshing tooth surface of the sun gear 2 and the first pinion 6A is greater than the elastic force F0 of the spring 12. Therefore, the first pinion 6A... Figure 3B The gear moves to the right. This position in the axial direction is the same as the position of the second pinion 6B, so the small diameter portion 9 of the first pinion 6B meshes with the gear ring 4. As a result, all three pinions 6 participate in the transmission of torque, thus enabling the transmission of large torques without obstruction.

[0025] The experimental results conducted to confirm the improvement effect of the NV characteristics of the embodiments of this utility model are shown below. Figure 4 The sound pressure measurement results shown here pertain to the aforementioned stepped pinion planetary gear mechanism, configured with three pinions, switching between three and two pinions for torque transmission. With all three pinions transmitting torque, the overall sound pressure of the planetary gear mechanism, i.e., the sound pressure sum, is represented by line L3. Conversely, with torque transmitted via two pinions, the sound pressure sum is shown by line L2. Based on these measurements, it is confirmed that fewer pinions transmitting torque result in lower vibration or noise, particularly significantly reducing resonance from one rotational vibration. This frequency is the lowest among the frequencies representing the peak value of the sound pressure sum, a vibration easily felt by occupants in a vehicle; therefore, the excellent improvement in NV characteristics achieved by the embodiment of this invention is evident.

[0026] The embodiments of this utility model have been described above, but this utility model is not limited to the above-described embodiments and can be implemented by appropriate modifications within the scope of the purpose of this utility model. For example, the spring 12 can be any elastic component capable of applying an axial force to the first planetary gear 6A, so conventionally known suitable spring components such as helical springs and disc springs can be used. In addition, the elastic force does not need to be a pressing force, but can also be a tensile force, so the position of the elastic body is not limited to the above-described positions. Figure 1 , Figure 3A , Figure 3B The position is shown. Furthermore, the number of pinions is not limited; there can be multiple pinions. In addition, besides the stepped pinion type planetary gear mechanism, the planetary gear mechanism of this invention can also be a single pinion type, a double pinion type, a Ravina type, or other forms of planetary gear mechanism. Moreover, in this invention, any one of the sun gear, ring gear, and planet carrier can be used as the input element, output element, or reaction force element; the reaction force element is also not fixed.

Claims

1. A planetary gear mechanism, comprising: a sun gear, which is an external gear; The gear ring is an internal gear arranged on a concentric circle relative to the sun gear; And a plurality of pinions, which are configured to mesh with the sun gear and the ring gear between the sun gear and the ring gear, and are held by the planet carrier to rotate, wherein, The sun gear, the pinion, and the ring gear are all composed of helical gears. The plurality of pinions are mounted to the planetary carrier via pinion pins. At least one of the plurality of pinions, the first pinion, is movable along the axial direction of the pinion pin and is pressed by an elastic force in the axial direction. At least one of the plurality of pinions, the second pinion, is fixed in the axial direction of the pinion pin. Either the sun gear or the gear ring can move along the axial direction. When the thrust generated by the torque transmission between the sun gear and the ring gear and the first pinion is less than the elastic force, the configuration is such that: the first pinion moves along the axial direction of the pinion pin, thereby maintaining the meshing of the first pinion with either the sun gear or the ring gear, and disengaging the first pinion from the other of the sun gear and the ring gear.

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