Double helical type planetary gear mechanism

Abstract

To provide a double helical type planetary gear mechanism capable of suppressing the occurrence of an unbalanced load by correcting an error of a gear and a meshing deviation due to a secular change every time.SOLUTION: In the double helical type planetary gear mechanism to which a two gear sets (planetary gear mechanisms) having mutually opposite twisting directions of tooth muscles are attached in opposition to each other, there are provided a first piston 7 for pressing a fixing element on one gear set side in the direction of a rotation axis AL with the operation of hydraulic pressure, a second piston 8 for pressing a fixing element on the other gear set side in the direction of the rotation axis AL with the operation of hydraulic pressure, and a fluid pressure circuit 9 for connecting the first piston 7 and the second piston 8 in a liquid tight state that oil 13 is filled therein, and for communicating the first piston 7 and the second piston 8 with each other to press the other fixing element when a load in the direction of the rotation axis AL is applied from one fixing element to the first piston 7 or the second piston 8.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a planetary gear mechanism using a helical gear. [Background technology]

[0002] Patent Document 1 describes two sets of double helical gears (double helical gears) each made individually and adjacent to each other so that the twist directions of the teeth are opposite to each other, and describes a method of assembling the double helical gears. Specifically, the two sets of double helical gears described in Patent Document 1 are assembled by forming a first helical gear, one of which is formed integrally with a shaft, and attaching a second helical gear, the other of which is paired with the first helical gear, in close contact with the first helical gear to form a first set of double helical gears. Meanwhile, a third helical gear, one of which is formed in a second set of double helical gears, is meshed with the first helical gear, the shaft of which is fixed, under a predetermined torque, and a fourth helical gear, the other of which is paired with the third helical gear, is fitted onto the shaft formed integrally with the third helical gear and attached in close contact with the third helical gear. A cylindrical coupler is passed over the shaft of the third helical gear, the coupler is spline-fitted onto the shaft, and the fourth helical gear is meshed with the second helical gear while a predetermined torque is applied to the fourth helical gear. At the same time, the coupler is plastically deformed and parts of it are fitted into multiple grooves formed around the through hole of the fourth helical gear, thereby joining and integrating the third helical gear and the fourth helical gear. A nut is then tightened onto the shaft of the third helical gear to fix the coupler and the fourth helical gear in the axial direction, thereby assembling the second double helical gear set. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-183909 A Summary of the Invention [Problem to be solved by the invention]

[0004] A double helical gear is a gear formed by combining two helical gears whose teeth are twisted in opposite directions. It can eliminate the thrust force generated by normal helical gears, and can transmit torque smoothly with high strength. On the other hand, it is not easy to process double helical gears as a single unit, and there are problems in terms of workability and cost. Therefore, a double helical gear is sometimes manufactured by separately processing two helical gears whose teeth are twisted in opposite directions and assembling the two helical gears facing each other. However, when two helical gears are assembled in this way to form a double helical gear, an assembly error occurs in the circumferential direction when the two helical gears are assembled, and the machining error of the tooth cutting dimensions of each helical gear may accumulate in the circumferential direction. In such a case, a misalignment occurs between the two helical gears, and as a result, when the double helical gear transmits torque, a load is unevenly applied to one of the helical gears. Furthermore, if such misalignment occurs periodically, it can cause vibrations and noise.

[0005] In contrast, the double helical gear described in the above Patent Document 1 is configured to correct the above-mentioned assembly error and processing error when the double helical gear is assembled. However, the double helical gear and its assembly method described in the above Patent Document 1 cannot deal with the aging and deterioration of the double helical gear. In other words, if the double helical gear is deformed or worn due to the load applied to it during operation, the above-mentioned unbalanced load will eventually be generated on one of the helical gears. Such problems such as unbalanced load in double helical gears also occur in so-called double helical planetary gear mechanisms, which are configured by assembling two planetary gear mechanisms using helical gears facing each other so that the twist directions of the tooth traces are opposite to each other.

[0006] This invention was made with an eye on the technical problems described above, and targets a so-called double helical planetary gear mechanism configured by assembling two planetary gear mechanisms using helical gears facing each other so that the twist directions of the tooth traces are opposite. The object of the invention is to provide a double helical planetary gear mechanism that is capable of correcting deviations in meshing caused by gear errors and changes over time, each time, and suppressing the occurrence of offset loads. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a motor comprising: a case fixed to a predetermined fixed portion so as to be non-rotatable; a rotating shaft which rotates when a predetermined torque is transmitted; a first sun gear formed of an externally toothed helical gear integral with the rotating shaft; a first ring gear formed of an internally toothed helical gear coaxial with the first sun gear; a first pinion formed of an externally toothed helical gear meshing with both the first sun gear and the first ring gear between the first sun gear and the first ring gear in the radial direction of the rotating shaft; and a carrier which holds the first pinion rotatably and revolvably. a second sun gear formed of an external helical gear whose tooth trace has a twist direction opposite to that of the first sun gear and which is integral with the rotating shaft and rotates integrally with the first sun gear; a second ring gear formed of an internal helical gear whose tooth trace has a twist direction opposite to that of the first ring gear and which is coaxial with the second sun gear; and a second gear set held by the carrier to be rotatable and revolvable together with the first pinion, and meshing with both the second sun gear and the second ring gear between the second sun gear and the second ring gear in the radial direction, and a second gear set having the carrier and a second pinion formed by an externally toothed helical gear having an external toothed gear with a tooth trace twisted in an opposite direction to the first pinion, the second gear set having the carrier, and the first sun gear and the second sun gear are opposed to each other in the rotational axial direction of the rotation shaft in the case, the first ring gear and the second ring gear are opposed to each other, and the first pinion and the second pinion are opposed to each other and assembled (i.e., the first gear set and the second gear set are opposed to each other on the rotation shaft in the case), and a first piston which presses the fixed element of the first gear set (i.e., the first ring gear or the first sun gear) in the direction of the rotation axis when a predetermined fluid pressure is applied thereto; and a second piston which presses the fixed element of the first gear set (i.e., the first ring gear or the first sun gear) in the direction of the rotation axis when a predetermined fluid pressure is applied thereto.The hydraulic system is characterized in that it is provided with a second piston that presses the fixed element on the second gear set side (i.e., the second ring gear or the second sun gear) in the direction of the rotation axis, and a fluid pressure circuit that connects the first piston and the second piston in a liquid-tight or airtight state filled with a predetermined working fluid, and that when a load in the direction of the rotation axis acts on the first piston or the second piston from either of the fixed elements, applies the fluid pressure, interlocks the first piston and the second piston in the direction of the rotation axis, and presses the other fixed element in the direction in which the load acts. Effect of the Invention

[0008] The double helical planetary gear mechanism of the present invention is configured by assembling two gear sets using helical gears, i.e., two planetary gear mechanisms using helical gears, so that the twist directions of the teeth are opposite to each other. At the same time, the fixed elements (i.e., the first ring gear and the second ring gear, or the first sun gear and the second sun gear, or the carrier) of the first gear set and the second gear set (i.e., the two planetary gear mechanisms) are attached to the case so as not to rotate but to be relatively movable in the direction of the rotation axis. The double helical planetary gear mechanism of the present invention is provided with a fluid pressure circuit having a first piston and a second piston. The fluid pressure circuit connects the first piston and the second piston with fluid pressure and interlocks the first piston and the second piston in the direction of the rotation axis. The first piston and the second piston generate fluid pressure by receiving loads in the direction of the rotation axis from the fixed element on the first gear set side and the fixed element on the second gear set side, respectively. At the same time, the first piston receives fluid pressure from the second piston side and presses the fixed element of the first gear set in the direction of the rotation axis. The second piston receives fluid pressure from the first piston side and presses the fixed element of the second gear set in the direction of the rotation axis. Therefore, when the double helical planetary gear mechanism of the present invention is operated under load with torque applied, if an unbalanced load (torque imbalance) occurs between the first gear set and the second gear set due to gear error, aging, or the like, a load that moves the fixed element of the gear set to which a larger torque is applied in the direction of the rotation axis, i.e., a thrust load, is generated. Then, a thrust load is applied to one piston from the fixed element of one gear set side that has received the thrust load, and the other piston presses the fixed element of the other gear set side under the fluid pressure generated by the thrust load. As a result, the unbalanced load between the first gear set and the second gear set is eliminated, and torque acts evenly between the first gear set and the second gear set. Therefore, any torque imbalance that occurs during load operation of the double helical planetary gear mechanism of the present invention can be eliminated each time, and torque can be applied evenly to the first gear set and the second gear set.

[0009] Therefore, according to the double helical planetary gear mechanism of the present invention, which is a so-called double helical planetary gear mechanism configured by assembling two planetary gear mechanisms (first gear set and second gear set) using helical gears facing each other so that the twist directions of the tooth traces are opposite, the gear meshing deviation due to errors in the gears or changes over time can be corrected each time, thereby suppressing the occurrence of offset load. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram for explaining the configuration of the double helical planetary gear mechanism of the present invention, and is a cross-sectional view showing the structure of the double helical planetary gear mechanism that combines two gear sets (planetary gear mechanisms), as well as a first piston, a second piston, and a fluid pressure circuit in the present invention. [Diagram 2] FIG. 2 is a diagram for explaining the configuration of the double helical planetary gear mechanism of the present invention, and is a diagram showing a schematic image of a cross section taken along line AA in FIG. [Diagram 3] FIG. 3 is a diagram for explaining the operation of the double helical planetary gear mechanism of the present invention, where (a) shows an image of a state in which torque imbalance has occurred due to gear error or deterioration over time, and (b) shows an image of a state in which the torque is balanced due to the functioning of the fluid pressure circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings. Note that the following embodiment is merely an example of a specific embodiment of the present invention, and is not intended to limit the present invention.

[0012] Figures 1 and 2 show an example of a double helical planetary gear mechanism according to an embodiment of the present invention. The double helical planetary gear mechanism 1 shown in Figures 1 and 2 is a "planetary gear mechanism using double helical gears" and is configured by assembling two "planetary gear mechanisms" made up of "helical gears" facing each other to form a "double helical gear planetary gear mechanism." Specifically, the double helical planetary gear mechanism 1 includes a case 2, a rotating shaft 3, a first gear set 4, and a second gear set 5.

[0013] The case 2 is a member that constitutes the outer shell (housing, casing) of the double helical planetary gear mechanism 1, and is fixed non-rotatably to a predetermined fixed portion such as a vehicle chassis (not shown).

[0014] The rotating shaft 3 is the "input shaft" or "output shaft" of the double helical planetary gear mechanism 1, and rotates when a predetermined torque is transmitted to it. The central axis of this rotating shaft 3 is the rotation axis AL of the double helical planetary gear mechanism 1.

[0015] The first gear set 4 is a "planetary gear mechanism made up of helical gears." The first gear set 4 is made up of a first sun gear 4a formed of an externally toothed helical gear integral with the rotating shaft 3, a first ring gear 4b formed of an internally toothed helical gear coaxial with the first sun gear 4a, a first pinion 4c formed of an externally toothed helical gear meshing with both the first sun gear 4a and the first ring gear 4b between the first sun gear 4a and the first ring gear 4b in the radial direction of the rotating shaft 3 (the vertical direction in FIG. 1), and a carrier 4d that holds the first pinion 4c so that it can rotate and revolve around its axis.

[0016] The second gear set 5 is a "planetary gear mechanism made up of helical gears." The second gear set 5 is composed of a second sun gear 5a, which is integral with the rotating shaft 3 and formed of an external tooth helical gear whose tooth trace has a twist direction opposite to that of the first sun gear 4a, and which rotates integrally with the first sun gear 4a, a second ring gear 5b, which is coaxial with the second sun gear 5a and formed of an internal tooth helical gear whose tooth trace has a twist direction opposite to that of the first ring gear 4b, a second pinion 5c, which is held rotatably and revolvably together with the first pinion 4c by the carrier 4d and meshes with both the second sun gear 5a and the second ring gear 5b between the second sun gear 5a and the second ring gear 5b in the radial direction of the rotating shaft 3, and which is formed of an external tooth helical gear whose tooth trace has a twist direction opposite to that of the first pinion 4c, and which rotates integrally with the first pinion 4c, and the above-mentioned carrier 4d.

[0017] Then, the first gear set 4 and the second gear set 5 are assembled facing each other on the rotating shaft 3 inside the case 2 to form a double helical planetary gear mechanism 1, which is a "double helical gear planetary gear mechanism." Specifically, the double helical planetary gear mechanism 1 is formed by assembling the first sun gear 4a and the second sun gear 5a facing each other, the first ring gear 4b and the second ring gear 5b facing each other, and the first pinion 4c and the second pinion 5c facing each other in the direction of the rotation axis AL inside the case 2.

[0018] As described above, the opposing first sun gear 4a and second sun gear 5a, first ring gear 4b and second ring gear 5b, and first pinion 4c and second pinion 5c are all formed of helical gears with teeth that twist in opposite directions. Therefore, the first sun gear 4a and second sun gear 5a form a "double helical gear sun gear" in the double helical planetary gear mechanism 1. The first ring gear 4b and second ring gear 5b form a "double helical gear ring gear" in the double helical planetary gear mechanism 1. The first pinion 4c and second pinion 5c form a "double helical gear pinion (i.e., planetary gear)" in the double helical planetary gear mechanism 1.

[0019] In addition, in the double helical planetary gear mechanism 1, any one of the first sun gear 4a and the second sun gear 5a, the first ring gear 4b and the second ring gear 5b, or the carrier 4d is attached to the case 2 as a "fixed element" of the first gear set 4 side and the second gear set 5 side so as to be non-rotatable with respect to the case 2 and relatively movable in the direction of the rotation axis. In the embodiment shown in Figs. 1 and 2, the first ring gear 4b is attached to the case 2 as a "fixed element" of the first gear set 4 side so as to be non-rotatable with respect to the case 2 and relatively movable in the direction of the rotation axis AL. In addition, the second ring gear 5b is attached to the case 2 as a "fixed element" of the second gear set 5 side so as to be non-rotatable with respect to the case 2 and relatively movable in the direction of the rotation axis AL. Specifically, the outer peripheral surface of the first ring gear 4b and the inner peripheral surface of the case 2 are spline-fitted by a ball spline 6. Similarly, the outer circumferential surface of the second ring gear 5b and the inner circumferential surface of the case 2 are spline-fitted together by a ball spline 6.

[0020] Furthermore, the double helical planetary gear mechanism 1 in the embodiment of the present invention is equipped with a first piston 7, a second piston 8, and a fluid pressure circuit 9 to correct any deviation in meshing caused by errors in each gear or changes over time, and to suppress the occurrence of offset load.

[0021] When a predetermined fluid pressure is applied, the first piston 7 presses a "fixed element" on the first gear set 4 side (the first ring gear 4b in the example shown in FIG. 1) in the direction of the rotation axis AL. In the example shown in FIG. 1, the first piston 7 is inserted into a first cylinder portion 10 formed in the side portion 2a of the case 2. The first cylinder portion 10 is formed in a position facing the tooth width portion 5d of the second ring gear 5b in the direction of the rotation axis AL on the side portion 2a. The first piston 7 can contact and press the tooth width portion 5d of the second ring gear 5b, and can also contact and press the tooth width portion 4e of the first ring gear 4b via the rod 7a. The rod 7a is disposed in a through hole 5e formed by penetrating the tooth width portion 5d of the second ring gear 5b in the direction of the rotation axis AL so as to be relatively movable in the direction of the rotation axis AL. The first piston 7 and the rod 7a move together in the direction of the rotation axis AL.

[0022] When a predetermined fluid pressure is applied, the second piston 8 presses a "fixed element" on the second gear set 5 side (the second ring gear 5b in the example shown in FIG. 1) in the direction of the rotation axis AL. In the example shown in FIG. 1, the second piston 8 is inserted into a second cylinder portion 11 formed in the side portion 2b of the case 2. The second cylinder portion 11 is formed in a position facing the tooth width portion 4e of the first ring gear 4b in the direction of the rotation axis AL on the side portion 2b. The second piston 8 can contact and press the tooth width portion 4e of the first ring gear 4, and can also contact and press the tooth width portion 5d of the second ring gear 5b via the rod 8a. The rod 8a is disposed in a through hole 4f formed by penetrating the tooth width portion 4e of the first ring gear 4b in the direction of the rotation axis AL so as to be relatively movable in the direction of the rotation axis AL. The second piston 8 and the rod 8a move together in the direction of the rotation axis AL.

[0023] The fluid pressure circuit 9 connects the first piston 7 and the second piston 8 in a liquid-tight or air-tight state filled with a predetermined working fluid. At the same time, when a load in the direction of the rotation axis AL acts on the first piston 7 or the second piston 8 from one of the "fixed elements" (the first ring gear 4b or the second ring gear 5b in the example shown in FIG. 1), the fluid pressure circuit 9 applies fluid pressure to interlock the first piston 7 and the second piston 8 in the direction of the rotation axis AL. By interlocking the first piston 7 and the second piston 8, the other "fixed element" (the second ring gear 5b or the first ring gear 4b in the example shown in FIG. 1) is pressed in the direction in which the load acts.

[0024] Specifically, the fluid pressure circuit 9 is composed of the first piston 7, the second piston 8, the first cylinder portion 10, the second cylinder portion 11, and the flow path 12. The flow path 12 connects the first cylinder portion 10 and the second cylinder portion 11 in a liquid-tight or air-tight state. A predetermined working fluid is filled in the first cylinder portion 10, the second cylinder portion 11, and the flow path 12. In the example shown in FIG. 1, oil 13 is filled as the working oil that generates hydraulic pressure. Therefore, in the fluid pressure circuit 9, when the first ring gear 4b (or the second ring gear 5b) moves in the direction of the rotation axis AL and a load in the direction of the rotation axis AL acts on the first piston 7 (or the second piston 8) in response to the movement, the oil 13 in the fluid pressure circuit 9, i.e., the oil 13 in the first cylinder portion 10, the second cylinder portion 11, and the flow path 12, is compressed, and hydraulic pressure corresponding to the magnitude of the load is generated. The generated hydraulic pressure acts on the second piston 8 (or the first piston 7) and presses the second ring gear 5b (or the first ring gear 4b) in the direction of the rotation axis AL. Therefore, when an unbalanced load is generated between the first gear set 4 and the second gear set 5 and a load is applied from one of the ring gears 4b (or 5b) to one of the pistons 7 (or 8), the first piston 7 and the second piston 8 move in conjunction with each other, and the one piston 8 (or 7) presses the other ring gear 5b (or 4b). As a result, the unbalanced load between the first gear set 4 and the second gear set 5 is eliminated, and torque acts evenly on the first gear set 4 and the second gear set 5.

[0025] In the double helical planetary gear mechanism 1 configured as described above, it is preferable that the first pinion 4c and the second pinion 5c constituting the "planetary gear" are provided in multiple sets at equal intervals in the circumferential direction of the case 2, in consideration of the balance in the rotational direction of the double helical planetary gear mechanism 1. For example, four sets of pinions 4c, 5c may be assembled at a 90° pitch in the circumferential direction of the case 2. In the example shown in Fig. 2, three sets of pinions 4c, 5c are assembled at a 120° pitch in the circumferential direction of the case 2.

[0026] 1 and 2, the first gear set 4 and the second gear set 5 are each a "single pinion type planetary gear", but in the double helical planetary gear mechanism 1 according to the embodiment of the present invention, the first gear set 4 and the second gear set 5 may each be configured as a "double pinion type planetary gear mechanism". In other words, the first pinion 4c and the second pinion 5c may each be configured as a "double pinion" pair.

[0027] Although not specifically indicated by reference numerals, each rotating and sliding portion of the double helical planetary gear mechanism 1 is provided with a designated bearing, and each rotating member is rotatably supported by these bearings.

[0028] As described above, the double helical planetary gear mechanism 1 in the embodiment of the present invention is configured by assembling two gear sets 4, 5 using helical gears so that the twist directions of the tooth traces are opposite to each other. In addition, the fixed elements of the first gear set 4 and the second gear set 5 (the first ring gear 4b and the second ring gear 5b in the example shown in Figs. 1 and 2) are attached to the case 2 so as to be non-rotatable and relatively movable in the direction of the rotation axis AL. The double helical planetary gear mechanism 1 in the embodiment of the present invention is provided with a fluid pressure circuit 9 having a first piston 7 and a second piston 8. The fluid pressure circuit 9 connects the first piston 7 and the second piston 8 by fluid pressure and moves the first piston 7 and the second piston 8 in the direction of the rotation axis AL. The first piston 7 and the second piston 8 receive loads in the direction of the rotation axis AL from the fixed element (first ring gear 4b) on the first gear set 4 side and the fixed element (second ring gear 5b) on the second gear set 5 side, respectively, to generate fluid pressure. At the same time, the first piston 7 receives fluid pressure from the second piston 8 side and presses the fixed element of the first gear set 4 in the direction of the rotation axis AL. The second piston 8 receives fluid pressure from the first piston 7 side and presses the fixed element of the second gear set 5 in the direction of the rotation axis AL.

[0029] In the double helical planetary gear mechanism 1 configured as described above, when the gears are operated under load with torque applied, if a misalignment of the gears occurs due to, for example, gear error or deterioration over time, the first ring gear 4b or the second ring gear 5b moves left or right in the direction of the rotation axis AL. As a result, as shown in Fig. 3(a), the transmission torques of the first gear set 4 and the second gear set 5 change, and a torque imbalance (offset load) occurs between the first gear set 4 and the second gear set 5. This generates a load that moves the first ring gear 4b on the side of the first gear set 4 to which a larger torque is applied, in the direction of the rotation axis AL, i.e., a thrust load.

[0030] The thrust load is applied to the first piston 7 from the first ring gear 4b on the first gear set 4 side, and the second piston 8 presses the second ring gear 5b on the second gear set 5 side by receiving the hydraulic pressure generated by the thrust load. As a result, as shown in (b) of Fig. 3, the torque imbalance between the first gear set 4 and the second gear set 5 is eliminated, and the torque acts evenly between the first gear set 4 and the second gear set 5. Therefore, the offset load generated during the loaded operation of the double helical planetary gear mechanism 1 can be eliminated each time, and the torque can be applied evenly to the first gear set 4 and the second gear set 5.

[0031] Therefore, according to the above-described embodiment of the present invention, the so-called double helical planetary gear mechanism 1 is configured by assembling "two planetary gear mechanisms using helical gears," i.e., the first gear set 4 and the second gear set 5, opposed to each other so that the twist directions of the teeth are opposite, and it is possible to correct gear errors and deviations in meshing due to changes over time each time and suppress the occurrence of offset load. [Explanation of symbols]

[0032] 1. Double helical planetary gear mechanism 2 Cases 2a (case) side 2b (case) side 3 Rotation Axis 4 1st gear set 4a 1st sun gear (of 1st gear set) 4b 1st ring gear (of 1st gear set) 4c 1st pinion (of 1st gear set) 4d (Common to 1st and 2nd gear sets) Carrier 4e (first gear set) tooth width section 4f (1st gear set) through hole 5 1st gear set 5a 2nd sun gear (of 2nd gear set) 5b 2nd ring gear (of 2nd gear set) 5c (2nd gear set) 2nd pinion 5d (2nd gear set) tooth width 5e (2nd gear set) through hole 6 Ball spline 7 First piston 7a (First piston) rod 8 Second piston 8a (Second piston) rod 9 Fluid pressure circuits 10 First cylinder section 11 Second cylinder section 12 Flow Path 13 Oil (working fluid) AL Rotation axis

Claims

[Claim 1] A case that is fixed so that it cannot rotate, A rotating shaft that rotates when a predetermined torque is transmitted thereto; a first gear set including: a first sun gear formed of an externally toothed helical gear integral with the rotating shaft; a first ring gear formed of an internally toothed helical gear coaxial with the first sun gear; a first pinion formed of an externally toothed helical gear meshing with both the first sun gear and the first ring gear between the first sun gear and the first ring gear in the radial direction of the rotating shaft; and a carrier that holds the first pinion rotatably and revolvably; a second sun gear which is integral with the rotating shaft and is formed of an external helical gear whose teeth have a twist direction opposite to that of the first sun gear and rotates integrally with the first sun gear; a second ring gear which is coaxial with the second sun gear and is formed of an internal helical gear whose teeth have a twist direction opposite to that of the first ring gear; a second pinion which is held rotatably and revolvably by the carrier, which meshes with both the second sun gear and the second ring gear between the second sun gear and the second ring gear in the radial direction, which is formed of an external helical gear whose teeth have a twist direction opposite to that of the first pinion and rotates integrally with the first pinion, and the carrier; The first sun gear and the second sun gear are opposed to each other in a rotational axial direction of the rotation shaft in the case, the first ring gear and the second ring gear are opposed to each other, and the first pinion and the second pinion are opposed to each other and assembled together; a double helical planetary gear mechanism in which any one set of the first sun gear and the second sun gear, or the first ring gear and the second ring gear, or the carrier is attached to the case as a fixed element of the first gear set side and the second gear set side so as to be unrotatable with respect to the case and to be relatively movable in the direction of the rotation axis, a first piston that presses the fixed element of the first gear set in the direction of the rotation axis when a predetermined fluid pressure is applied to the first piston; a second piston that presses the fixed element of the second gear set in the direction of the rotation axis by the action of the fluid pressure; a fluid pressure circuit that connects the first piston and the second piston in a liquid-tight or airtight state filled with a predetermined working fluid, and that, when a load in the rotation axis direction acts on the first piston or the second piston from either one of the fixed elements, moves the first piston and the second piston in conjunction with each other to press the other fixed element. A double helical planetary gear mechanism.

Images