JP2019124303A - Gear device - Google Patents

Abstract

To provide a gear device capable of improving a noise vibration while assuring its durability.SOLUTION: A driven gear 50 comprises a metallic gear 60 arranged to enable it to be displaced at an outer circumference of a balance shaft 30 in a rotating direction and having a metallic opposing gear surface 62A opposing against a driving side drive gear 21 in its rotating direction; a resin gear 70 arranged at an outer circumference of the balance shaft 30 side-by-side in an axial direction of the balance shaft 30 together with the metallic gear 60 and having a resin opposing gear surface 72A opposing against the drive gear 21 in its rotating direction, and enabled to be displaced in respect to the metallic gear 60 from an advancing position where the resin opposing gear surface 72A approaches from the metallic opposing gear surface 62A to the drive gear 21 side, to a retracting position where it approaches the metallic opposing gear surface 62A in its rotating direction and an elastic member 80 for applying a biasing force to the resin gear 70 from the retracting position to the advancing position against a rotating force of the balance shaft 30.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a gear device.

  Quietness is mentioned as the performance required by the engine. Then, in order to ensure such quietness, a gear made of resin is used as a gear which constitutes a balancer device. For example, in patent document 1, the resin gear used for the balancer shaft gear of an engine, etc., the tooth part provided at equal intervals on the perimeter is formed of resin.

JP 2012-52650 A

  By the way, in recent years, along with downsizing of an engine, a high load engine having a large input torque to a gear even with a small displacement is used. However, the resin gear as disclosed in Patent Document 1 is inferior in strength to a metal gear or the like. Therefore, there is a demand for a gear that can withstand high loads and is also excellent in noise and vibration characteristics.

  The present invention is completed based on the above circumstances, and it is an object of the present invention to provide a gear device capable of improving noise vibration characteristics while securing durability.

  The gear device according to the present invention is provided on the outer periphery of the rotary member so as to be displaceable in the rotational direction, and has a metal gear having a metal facing tooth surface facing the opposite gear on the drive side in the rotational direction; It has a resin facing tooth surface that is provided side by side in the axial direction of the metal gear and the rotating member and faces the other gear in the rotation direction, and the resin facing tooth surface is on the other gear side than the metal facing tooth surface. A resin gear capable of relative displacement with respect to the metal gear, and a retreat position from the retraction position to the retreat position from the retraction position And an elastic member for applying a biasing force of

  According to the gear device of the present invention, the resin opposing tooth surface of the resin gear in the advanced position can be meshed with the other gear by the biasing force of the elastic member, and the sound generated by the gear meshing compared to the configuration in which only the metal gear is meshed And vibration can be suppressed, and noise vibration characteristics can be improved. Further, in the gear device, for example, at high load when the input torque to the gear device is large, the pressing force of the other gear resists the biasing force of the elastic member and the resin opposing tooth surface of the resin gear is retracted from the advancing position The resin opposing tooth surface can be brought closer to the metal opposing tooth surface by displacing the resin. Therefore, in the gear device, the metal opposing tooth flank can be brought into contact with the other gear, and the load from the other gear can be received by the metal gear. Thereby, the load which the resin gear receives from the other gear can be reduced, and the durability of the resin gear can be improved. Therefore, the gear device can improve the noise vibration characteristic while securing the durability of the resin gear.

It is a side view which shows the meshing state of the driven gear of Example 1 of this invention, and a drive gear. It is an exploded perspective view showing a drive gear and a driven gear. It is a front view which shows the meshing state of a drive gear and a driven gear. It is sectional drawing which shows the AA cross section of FIG. (A) is the explanatory view seen from the axial direction explaining the meshing portion with the drive gear at the time of low load of the driven gear. (B) is the explanatory view seen from the axial direction explaining the meshing portion with the drive gear at the time of high load of the driven gear. It is sectional drawing which shows the meshing part of the driven gear and drive gear in Example 2 of this invention. FIG. 6A is a cross-sectional view showing a cross section B-B in FIG. FIG. 6 (B) is a cross-sectional view showing a cross section taken along line CC in FIG. (A) is a conceptual diagram which shows roughly the state which the drive gear and the resin gear contacted in Example 2 of this invention. (B) is a conceptual view schematically showing a state in which the resin gear and the metal gear are pushed into the drive gear and positioned at the retracted position. (A) is a cross-sectional view schematically illustrating a configuration in which a clearance is provided between an elastic member and a metal gear in another embodiment of the present invention. (B) is sectional drawing which shows the DD cross section of (A). FIG. 8 is a cross-sectional view schematically illustrating a configuration in which an elastic member is disposed between a metal gear and a balance shaft in another embodiment of the present invention.

Preferred embodiments of the present invention are shown below.
The tooth thickness in the rotational direction of the resin gear may be larger than the tooth thickness in the rotational direction of the metal gear. As a result, even when the gear device rotates in either direction of the rotation direction, the resin gear can be made to contact the mating gear preferentially to the metal gear, and the contact of the metal gear to the mating gear can be suppressed. Noise and vibration characteristics can be improved.

  The metal gear is displaceable around the axis of the rotating member to a metal side advancing position in which the metal opposing tooth surface contacts the other gear side, and a metal side retraction position displaced in the rotation direction of the other gear. Good to be done. The metal gear may be provided with a metal-side elastic member that applies a biasing force from the metal-side retracted position to the metal-side advanced position. Thereby, the gear device can be displaced around the axis of the rotating member between the metal side advancing position where the metal opposing tooth surface contacts the other gear side and the metal side retracted position displaced in the rotation direction of the other gear. The metal gear can be relatively rotated together with the resin gear with respect to the rotating member. And since the metal opposing tooth flank can approach the other gear side at the metal side advanced position by the biasing force of the metal side elastic member, it is possible to make it difficult to cause backlash between the metal gear and the other gear.

  The elastic member may be disposed between the metal gear and the resin gear in the axial direction so as to overlap with both gears, and be engaged with both the metal gear and the resin gear. Thus, in the gear device, since the elastic member overlaps the metal gear and the resin gear in the axial direction, it is not necessary to separately provide a space for providing the elastic member in the axial direction, and space saving in the axial direction can be achieved.

Example 1
The internal combustion engine according to the first embodiment is, for example, an in-line four-cylinder reciprocating engine, and includes a crankshaft 20, a drive gear 21 on the drive side (a counterpart gear), and a balancer device 10 as shown in FIG. . The drive gear 21 is fixed to the crankshaft 20 and provided. The balancer device 10 includes a balance shaft 30 (rotation member) and a driven gear 50 (gear device). The balance shaft 30 is disposed parallel to the crankshaft 20 in the axial direction. The driven gear 50 is fixed to the balance shaft 30 and can be engaged with the drive gear 21.

  The balance shaft 30 is rotatably supported on a wall (not shown) on the crankcase side. The driven gear 50 is disposed on the balance shaft 30 at an end corresponding to the drive gear 21. The number of teeth of the driven gear 50 is set to the same number as the number of teeth of the drive gear 21. The drive gear 21 is made of metal and formed of a helical gear. The drive gear 21 includes a plurality of drive teeth 22 formed at equal intervals over the entire outer peripheral surface.

  When the crankshaft 20 rotates, the rotational force of the crankshaft 20 is transmitted to the balance shaft 30 via the drive gear 21 and the driven gear 50. The balance shaft 30 rotates with the crankshaft 20 in the opposite direction at the same speed. For this reason, the inertia force of the piston (not shown) provided on the crankshaft 20 is canceled.

Next, the detailed structure of the driven gear 50 will be described.
The driven gear 50 includes a metal gear 60, a resin gear 70, and an elastic member 80, as shown in FIG. The metal gear 60 is made of metal (for example, iron) and is configured as a helical gear. The metal gear 60 includes a main body 61 and a plurality of metal teeth 62. The main body portion 61 has a substantially disc shape having a through hole 63 at the center. The main body portion 61 is formed with a weight 64 which protrudes in a substantially arc shape in the thickness direction on one surface (surface on the left side in FIG. 2). As shown in FIG. 4, the main body portion 61 is provided with a plurality of recessed portions 65 which are recessed in the plate thickness direction on the other surface (the surface on the right side in FIG. 2). The recess 65 has a substantially arc shape along the circumferential direction, and is a portion into which a connecting portion 82 of an elastic member 80 described later is inserted. The plurality of metal teeth 62 are formed at equal intervals on the entire outer peripheral surface of the main body 61. The metal tooth portion 62 is in the shape of a helical line in the form of helical teeth. The metal tooth portion 62 has a metal facing tooth surface 62A that faces the drive gear 21 that is the mating partner in the rotational direction (arrangement direction of the metal tooth portion 62).

  The resin gear 70 is configured as a helical gear as shown in FIG. The resin gear 70 includes a gear portion 71 and an insert portion 73. The gear portion 71 is in the form of a disc having a through hole at its center. The gear portion 71 has a plurality of resin tooth portions 72 formed on the entire outer peripheral surface of the annular shape. The resin tooth portion 72 is in the shape of a helical line in the form of helical teeth. The insert portion 73 is made of metal and has an annular shape. The insert portion 73 is fitted into the inner peripheral portion of the gear portion 71. The insert portion 73 has a through hole 74 at the center, and around the through hole 74, a plurality of holding portions 75 for holding an elastic member 80 described later is formed. The holding portion 75 is a through hole that penetrates in the axial direction, and has a substantially fan-shaped cross section close to a square. The holding portion 75 is formed with a convex portion 76 that protrudes in the radial direction from the wall surface on the center side.

  The tooth thickness in the rotational direction of the resin gear 70 (arrangement direction of the resin tooth portions 72) is larger than the tooth thickness in the rotational direction of the metal gear 60 (arrangement direction of the metal tooth portions 62) as shown in FIG. Further, the resin tooth portion 72 has a resin facing tooth surface 72A that faces the drive gear 21 in the rotational direction.

  The elastic member 80 is made of rubber and is elastically deformable. As shown in FIG. 2, the elastic member 80 includes a pair of elastically deformable portions 81 and 81 and a connecting portion 82. The elastically deformable portion 81 has a substantially prismatic shape that widens toward one side (the side opposite to the connecting portion of the connecting portion 82). The connecting portion 82 has a substantially arc shape, and connects the pair of elastic deformation portions 81 and 81. Specifically, the connecting portion 82 is connected to the pair of elastically deforming portions 81, 81 so as to extend from one surface (the surface on the left side in FIG. 2) in each.

Next, the assembly structure of the driven gear 50 will be described.
The plurality of elastic members 80 are assembled to the holding portion 75 of the resin gear 70, as shown in FIG. The pair of elastically deformable portions 81 is accommodated in the holding portion 75 so as to sandwich the convex portion 76 in the circumferential direction. The connecting portion 82 protrudes on one surface side of the resin gear 70 (the back surface side which is a mating surface with the metal gear 60). As shown in FIGS. 1 and 4, the resin gear 70 is provided side by side so as to substantially abut the metal gear 60 in the axial direction of the balance shaft 30. The connecting portion 82 is in the recess 65 of the metal gear 60.

  The resin gear 70 is assembled so as to be capable of relative displacement with respect to the metal gear 60 so as to have the arrangement relationship shown in FIGS. 3 and 5A. In FIG. 5, in order to make the description easy to understand, the cross section of the predetermined axial direction in which the metal gear 60 is included and the cross section of the predetermined axial direction in which the resin gear 70 is included are overlapped. . The elastic member 80 is disposed between the metal gear 60 and the resin gear 70, and is engaged with the metal gear 60 by being accommodated in the holding portion 75. The metal tooth portion 62 is accommodated within the tooth width of the resin tooth portion 72 when viewed in the axial direction of the balance shaft 30. Specifically, as viewed from the axial direction, the metal opposing tooth surface 62A is located inside of the both resin opposing tooth surfaces 72A, 72A.

  When the load of driven gear 50 is low (when the input torque from drive gear 21 is low), the amount of bending of elastic member 80 assembled to metal tooth portion 62 and resin tooth portion 72 is small, and viewed from the axial direction of balance shaft 30 The driven gear 50 is configured such that the metal tooth portion 62 fits within the tooth width of the resin tooth portion 72. The difference in tooth thickness along the rotational direction of metal tooth portion 62 and resin tooth portion 72 is determined from the relationship between the magnitude of the torque input from drive gear 21 to driven gear 50 and the amount of deflection of elastic member 80. That is, the difference in tooth thickness between the two tooth portions 62 and 72 is due to the elastic member 80 bending when the driven gear 50 is under high load (for example, when the rotational speed of the drive gear 21 is greater than 2000 rpm). The metal opposing tooth flank 62A and the resin opposing tooth flank 72A are determined to be in contact with the tooth flank 22A of the drive gear 21, as shown in FIG.

  In the driven gear 50 assembled as described above, the metal gear 60 is fixed to the balance shaft 30 such that the balance shaft 30 enters the through hole 63 as shown in FIGS. 1, 3 and 4. The resin gear 70 is rotatable in the same direction with respect to the balance shaft 30 so that the balance shaft 30 is inserted into the through hole 74.

Next, the operation of the driven gear 50 of the first embodiment will be described.
In the state before driving the engine, as shown in FIG. 5A, the driven gear 50 meshes with the drive gear 21 in a state where backlash does not occur. Some backlash may occur between the drive gear 21 and the driven gear 50. The elastic member 80 is in a natural state, and the resin facing tooth surface 72A is located at the advanced position where the resin facing tooth surface 72A is closer to and closer to the drive gear 21 than the metal facing tooth surface 62A. The metal toothed portion 62 is accommodated within the tooth width of the resin toothed portion 72 when viewed from the axial direction of the balance shaft 30, and does not contact the drive gear 21. That is, the metal gear 60 has a backlash with respect to the drive gear 21. Before the engine is driven, the resin facing tooth surface 72A of the resin gear 70 is positioned on both sides in the circumferential direction sandwiching the metal gear 60.

  After engine driving, at low load of driven gear 50 (for example, when the rotation speed of drive gear 21 is 2000 rpm or less) in which input torque from drive gear 21 is low, resin gear 70 in contact with drive gear 21 Receives the driving force from the drive gear 21 and rotates in the rotational direction (counterclockwise in FIG. 5A). The elastic member 80 rotating with the resin gear 70 rotates the metal gear 60 in the rotational direction because the connecting portion 82 presses the wall portion constituting the recess 65 of the metal gear 60 in the rotational direction. Thereby, the resin gear 70 transmits the driving force to the metal gear 60 via the elastic member 80. However, when the driven gear 50 has a low load, the amount of deflection of the elastic member 80 in the rotational direction is small, and the relative rotation in the rotational direction of the resin gear 70 with respect to the metal gear 60 is small. Therefore, the metal tooth portion 62 remains within the tooth width of the resin tooth portion 72 when viewed in the axial direction of the balance shaft 30, and does not contact the drive gear 21. That is, due to the biasing force of the elastic member 80, the resin facing tooth surface 72A is positioned at the advanced position so that the resin facing tooth surface 72A comes closer to and closer to the drive gear 21 than the metal facing tooth surface 62A. As described above, when the load of the driven gear 50 is low, only the resin gear 70 meshes with the driven gear 50 as compared with the configuration using only the metal gear 60, so that the noise vibration characteristic can be improved.

  At high load of the driven gear 50 (for example, when the rotational speed of the drive gear 21 is greater than 2000 rpm), the amount of deflection of the elastic member 80 in the rotational direction is larger than at low load. The relative rotation in the rotational direction (clockwise in FIG. 5B) also increases. Then, as shown in FIG. 5B, the resin facing tooth surface 72A opposite to the rotation direction of the resin gear 70 resists the biasing force of the elastic member 80, and the rotation direction of the metal gear 60 is opposite. It retreats to the metal opposing tooth flank 62A side. That is, the resin opposing tooth flank 72A is displaced to the retracted position approaching the metal opposing tooth flank 62A. Thereby, the resin facing tooth surface 72A and the metal facing tooth surface 62A contact the tooth surface 22A of the drive gear 21. As described above, when the torque equal to or greater than a predetermined value is input to the resin gear 70, the metal opposing tooth flank 62A is brought into contact with the tooth flank 22A of the drive gear 21 to load the load from the drive gear 21 into the metal gear. 60 can be received. Therefore, the load which resin gear 70 receives from drive gear 21 can be reduced, and the durability of resin gear 70 can be improved. Therefore, the driven gear 50 can improve the noise vibration characteristic while securing the durability of the resin gear 70.

  As described above, according to the first embodiment, the driven gear 50 can cause the resin opposing tooth surface 72A of the resin gear 70 in the advanced position to mesh with the drive gear 21 by the biasing force of the elastic member 80, and the metal gear Compared with the configuration in which only the gear 60 is engaged, the noise and vibration generated by the meshing of the gears can be suppressed, and the noise and vibration characteristics can be improved. Furthermore, in the driven gear 50, for example, under high load where the input torque to the driven gear 50 is increased, the pressing force of the drive gear 21 resists the biasing force of the elastic member 80 and advances the resin facing tooth surface 72A of the resin gear 70. By displacing the position from the position to the retracted position, the resin facing tooth surface 72A can be brought closer to the metal facing tooth surface 62A. Therefore, the driven gear 50 can bring the metal facing tooth flank 62A into contact with the drive gear 21 and can receive the load from the drive gear 21 by the metal gear 60. Thereby, the load which resin gear 70 receives from drive gear 21 can be reduced, and the endurance of resin gear 70 can be improved. Therefore, the driven gear 50 can improve the noise vibration characteristic while securing the durability of the resin gear 70.

  The tooth thickness in the rotational direction of the resin gear 70 is larger than the tooth thickness in the rotational direction of the metal gear 60. Thereby, even when driven gear 50 is rotated to either side in the rotational direction, resin gear 70 can be made to contact drive gear 21 preferentially over metal gear 60, and drive gear 21 of metal gear 60 can be moved to Can be suppressed to improve the noise vibration characteristic.

  The elastic member 80 may be disposed between the metal gear 60 and the resin gear 70 in the axial direction so as to overlap with both gears, and be engaged with both the metal gear 60 and the resin gear 70. Thereby, in the driven gear 50, since the elastic member 80 overlaps the metal gear 60 and the resin gear 70 in the axial direction, it is not necessary to separately provide a space for providing the elastic member 80 in the axial direction, and space saving in the axial direction is achieved. Can.

Example 2
6 to 8 show Embodiment 2 of the present invention. The second embodiment is the same as the first embodiment except that the configurations of the driven gear 50 and the balance shaft 30 are different from the first embodiment. In the second embodiment, the same reference numerals or the same reference numerals denote the same or corresponding parts as in the first embodiment, and the redundant description will be omitted.

  The metal gear 60 includes a main body 61 and a plurality of metal teeth 62 as shown in FIGS. 6 and 7A. The main body portion 61 has a substantially disc shape having a through hole 63 at the center. The main body portion 61 is formed with a plurality of claw portions 66 extending in the plate thickness direction on one surface (surface on the left side in FIG. 7). The claw portion 66 is formed in a substantially rectangular parallelepiped shape. The metal gear 60 is displaceable around the axis of the balance shaft 30 between a metal side advancing position in which the metal facing tooth surface 62A contacts the drive gear 21 side, and a metal side retraction position displaced in the rotation direction of the drive gear 21. It is configured.

  The resin gear 70 includes a main body 71A and a plurality of resin teeth 72 as shown in FIGS. 6 and 7B. The main body portion 71A has a substantially disc shape having a through hole 74A at the center. The main body 71A has a plurality of claws 77 extending in the thickness direction on one surface (the surface on the right in FIG. 6). The claw portion 77 is formed in a substantially rectangular parallelepiped shape. The length L2 of the claw portion 77 in the lateral direction (direction orthogonal to the axial direction and the radial direction) is larger than the length L1 of the claw portion 66 in the lateral direction (direction orthogonal to the axial direction and the radial direction) . The relationship between the tooth thickness of the metal gear 60 and the tooth thickness of the resin gear 70 is the same as that of the first embodiment, and the state shown in FIG.

  The elastic member 80 is provided with a pair of elastic deformation parts 81A and 81A as shown in FIG. The elastically deformable portion 81A has a substantially prismatic shape that widens toward the one side (radially outward in FIG. 7).

  The balance shaft 30, as shown in FIGS. 6 and 7, includes a support portion 32 for supporting the metal gear 60 via the elastic member 80 and a support portion 34 for supporting the resin gear 70 via the elastic member 80. There is. The support portions 32 and 34 are formed in a ring shape, and a plurality of holding portions 33 and 35 for holding the elastic member 80 are respectively formed. The holding portions 33 and 35 are through holes penetrating in the axial direction, and the cross section thereof has a substantially fan-like shape close to a square. The metal gear 60 and the resin gear 70 are both displaceable in the rotational direction on the balance shaft 30 via the elastic member 80.

  The elastic member (metal gear side elastic member) 80 is fixed to the holding part 33 of the support part 32, as shown to FIG. 6, FIG. 7 (A). The metal gear 60 is assembled to the balance shaft 30 via the elastic member 80 such that the claws 66 are disposed between the elastic deformation portions 81A and 81A. The elastic member 80 is being fixed to the holding part 35 of the support part 34, as shown to FIG. 6, FIG. 7 (B). The resin gear 70 is assembled to the balance shaft 30 via the elastic member 80 such that the claws 77 are disposed between the elastic deformation portions 81A and 81A. The lateral length L1 of the claw portion 66 is smaller than the lateral length L2 of the claw portion 77, and as shown in FIG. 7, a clearance is generated between the claw portion 66 and the elastic member 80, There is no clearance between the claws 77 and the elastic member 80. A clearance smaller than the clearance generated between the claw portion 66 and the elastic member 80 may be generated between the claw portion 77 and the elastic member 80. The difference between the lateral length L1 of the claw portion 66 and the lateral length L2 of the claw portion 77 is the relationship between the magnitude of the torque input from the drive gear 21 to the driven gear 50 and the amount of deflection of the elastic member 80. It is determined from That is, as shown in FIG. 8B, the lengths L1 and L2 face the resin opposing tooth surface 62A at the time of high load of the driven gear 50 (for example, when the rotation speed of the drive gear 21 is larger than 2000 rpm). Tooth surface 72A is determined to be in contact with tooth surface 22A of drive gear 21.

Next, the operation of the driven gear 50 of the second embodiment will be described.
In the state before driving the engine, as shown in FIG. 8A, in the natural state of the elastic member 80, the metal tooth portion 62 is within the tooth width of the resin tooth portion 72 when viewed from the axial direction of the balance shaft 30. And is not in contact with the drive gear 21.

  After engine driving, at low load of driven gear 50 (for example, when the rotation speed of drive gear 21 is 2000 rpm or less) in which input torque from drive gear 21 is low, resin gear 70 in contact with drive gear 21 Receives the driving force from the drive gear 21 and rotates in the rotational direction (left direction in FIG. 8A). As the resin gear 70 rotates, the balance shaft 30 and the metal gear 60 rotate in the rotational direction. However, since the clearance is generated between the claws 66 of the metal gear 60 and the elastic member 80, the relative rotation in the rotational direction of the resin gear 70 with respect to the metal gear 60 is small when the driven gear 50 is loaded. Therefore, the metal tooth portion 62 remains within the tooth width of the resin tooth portion 72 when viewed from the axial direction of the balance shaft 30, and the elastic member 80 resists the rotational force of the balance shaft 30 and the metal facing tooth surface 62A. Is positioned at a separated position relatively separated from the drive gear 21 side. Thereby, the noise vibration characteristic can be improved. The power transmission route includes the drive gear 21, the resin gear 70, the elastic member 80 held by the support portion 32, the balance shaft 30, the elastic member 80 held by the support portion 34, and the metal gear 60 in this order.

  At high load of the driven gear 50 (for example, when the number of revolutions of the drive gear 21 is greater than 2000 rpm), the amount of deflection in the rotational direction of the elastic members 80 respectively assembled to the support portion 34 becomes larger than at low load. . The resin facing tooth surface 72A opposite to the rotation direction of the resin gear 70 resists the biasing force of the elastic member 80 and retracts to the metal facing tooth surface 62A opposite to the rotation direction of the metal gear 60. By doing this, as shown in FIG. 8B, the metal opposing tooth surface 62A comes into contact with the tooth surface 22A of the drive gear 21 as well as the resin opposing tooth surface 72A. After the drive gear 21 contacts both the resin gear 70 and the metal gear 60, both gears are synchronously displaced in the rotational direction and reach the retracted position. Specifically, the metal gear 60 is displaced to the metal side retracted position. As described above, the driven gear 50 can improve the noise vibration characteristics while securing the durability of the resin gear 70 as in the first embodiment.

  As shown in FIG. 8, the displacement amount of the resin gear 70 with respect to the balance shaft 30 is A, which corresponds to the deflection amount of the elastic member 80 held by the holding portion 35. The displacement amount of the metal gear 60 with respect to the balance shaft 30 is B, which corresponds to the deflection amount of the elastic member 80 held by the holding portion 33. The difference between the displacement amount A of the resin gear 70 and the displacement amount B of the metal gear 60 corresponds to the length L3 along the circumferential direction of the clearance formed between the claw portion 66 and the elastic member 80. Further, since the metal gear 60 can approach the drive gear 21 by a distance corresponding to the displacement amount B, the backlash can be reduced.

  As described above, according to the second embodiment, the metal gear 60 has the metal-side advanced position where the metal facing tooth surface 62A contacts the drive gear 21 side, and the metal-side retracted position displaced in the rotation direction of the drive gear 21. And is displaceable about the axis of the rotating member. The metal gear 60 is provided with an elastic member 80 for applying a biasing force from the metal side retracted position to the metal side advanced position. Thereby, the driven gear 50 can be displaced around the axis of the rotating member to the metal side advancing position where the metal facing tooth surface 62A contacts the drive gear 21 side, and the metal side retraction position displaced in the rotation direction of the drive gear 21. Therefore, the metal gear 60 can be rotated relative to the resin gear 70 with respect to the rotating member. Then, since the metal opposing tooth surface 62A can approach the drive gear 21 side at the metal side advancing position by the biasing force of the elastic member 80, it is difficult to cause backlash between the metal gear 60 and the drive gear 21. Can.

Other Embodiments
The present invention is not limited to the embodiments described above with reference to the drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the first embodiment, as shown in FIG. 9, the driven gear 50 may be configured such that the elastic member 80 is held with respect to the metal gear 60 through a predetermined clearance. The elastic member 80 is held by the holding portion 67 of the metal gear 60 and the holding portion 78 of the resin gear 70. The size of the relative rotation of the metal gear 60 with respect to the resin gear 70 may be adjusted by changing the size of the clearance provided between the elastic member 80 and the metal gear 60.
(2) In the first embodiment, as shown in FIG. 10, in the driven gear 50, the elastic member 80 is not engaged with the metal gear 60, and is formed on the support portion 34 of the balance shaft 30 as in the second embodiment. It may be configured to be held by the holding unit 35. Even with such a configuration, the driven gear 50 can improve the noise vibration characteristic while securing the durability of the resin gear 70 as in the first and second embodiments.
(3) In the first and second embodiments described above, the driven gear 50 rotates in a predetermined rotational direction (for example, counterclockwise in FIG. 3), but rotates in the opposite direction (for example, clockwise in FIG. 3) The same effects as those described above can be achieved.
(4) In the first and second embodiments, each of the gears 21, 60 and 70 is a helical gear, but may be a gear such as a spur gear instead of the helical gear.
(5) In the above-described first and second embodiments, the present invention can be widely applied not only to the balancer device but also to other power transmission devices of the internal combustion engine.

21 ... Drive gear (other gear)
22A: Tooth surface 30: Balance shaft (rotating member)
50 ... driven gear (gear unit)
DESCRIPTION OF SYMBOLS 60 ... Metal gear 62A ... Metal opposing tooth surface 70 ... Resin gear 72A ... Resin opposing tooth surface 80, 83 ... Elastic member (metal gear side elastic member)

Claims (4)

A metal gear provided on the outer periphery of the rotating member so as to be displaceable in the rotational direction, and having a metal opposing tooth surface facing the driving counterpart gear in the rotational direction;
It has a resin opposing tooth surface which is provided on the outer periphery of the rotating member in the axial direction of the metal gear and the rotating member and has a resin opposing tooth surface facing the other gear in the rotational direction, and the resin opposing tooth surface is the metal opposing tooth A resin gear that is relatively displaceable with respect to the metal gear from an advanced position in close contact with the mating gear side from a surface to a retracted position approaching the metal opposing tooth surface in the rotational direction;
A gear device comprising: an elastic member which applies an urging force from the retracted position to the advanced position to the resin gear.   The gear device according to claim 1, wherein a tooth thickness in a rotational direction of the resin gear is larger than a tooth thickness in a rotational direction of the metal gear. The metal gear is displaceable around the axis of the rotating member to a metal side advancing position in which the metal opposing tooth surface contacts the other gear side, and a metal side retraction position displaced in the rotation direction of the other gear. And
The gear device according to claim 1 or 2, further comprising a metal-side elastic member that applies an urging force from the metal-side retracted position to the metal-side advanced position to the metal gear.   The elastic member is disposed between the metal gear and the resin gear in the axial direction so as to overlap with both gears, and engaged with both the metal gear and the resin gear. The gear device according to claim 2.

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