Worm gear reducer

Abstract

The invention provides a worm gear reducer which can suppress abnormal noise when torque is reversely input and ensure torque transmission efficiency during normal operation at a high level and easily. The worm gear (3) is provided with a biasing plate spring (6) that biases the inner diameter-side member (5) toward the worm gear (3), and the biasing plate spring (6) is disposed on the side away from the worm gear (3) in the biasing direction of the biasing plate spring (6) in a portion between the outer peripheral surface of the inner diameter-side member (5) and the inner peripheral surface of the outer diameter-side member (9), and has: a load point (P) that is a contact portion that comes into contact with the outer peripheral surface of the inner diameter-side member (5); and a fulcrum (S) that is a portion of a contact portion in contact with the inner peripheral surface of the outer diameter-side member (9) that is located closest to the load point (P), and the biasing plate spring (6) exhibits a non-linear spring characteristic in which the spring constant increases by changing the position of the fulcrum (S) so as to approach the load point (P) as the amount of deflection in the first direction increases.

Description

Technical Field

[0001] The present invention relates to a worm gear reducer that can be assembled in an electric power steering device or the like. Background Art

[0002] In the field of steering devices, electric power steering devices that use electric motors as auxiliary power sources to reduce the force required for a driver to operate a steering wheel are becoming popular.

[0003] The electric power steering device is provided with a worm gear reducer for increasing the torque of the electric motor. The worm gear reducer is provided with a housing, a worm wheel and a worm. The housing has: a worm wheel housing; and a worm housing, the worm housing having a center axis in a twisted position relative to the center axis of the worm wheel housing, and an axial middle portion opening to the worm wheel housing. The worm wheel has gear teeth on the outer peripheral surface, and is rotatably supported on the inner side of the worm wheel housing. The worm has worm teeth meshing with the gear teeth on the outer peripheral surface, and is rotatably supported on the inner side of the worm housing.

[0004] The torque of the electric motor is transmitted to the worm wheel via the worm gear, thereby being increased and then applied as auxiliary power to the steering shaft, the pinion shaft of the steering gear unit, or the rack shaft, etc., thereby reducing the force required by the driver to operate the steering wheel.

[0005] In a worm gear reducer, there is inevitable backlash at the meshing portion between the gear teeth and the worm teeth due to dimensional errors and assembly errors of the components constituting the worm gear reducer. Due to the existence of this backlash, a harsh sound of teeth clattering sometimes occurs at the meshing portion when the steering wheel's rotation direction is changed.

[0006] Japanese Patent Application Publication No. 2020-128803 describes a structure for applying force to the tip of the worm toward the worm wheel in order to suppress the occurrence of a rattling sound at the meshing portion between the gear teeth and the worm teeth. The structure comprises: an externally-fitted component externally fitted to a support bearing that supports the tip of the worm to rotate freely and is configured to be able to move forward and backward relative to the worm wheel; and a force spring disposed between the externally-fitted component and the worm housing portion.

[0007] The biasing spring is elastically deformed, and the outer fitting component is biased toward the worm wheel by the elastic restoring force of the biasing spring, thereby suppressing the backlash of the meshing part between the wheel teeth and the worm teeth, and suppressing the generation of the gear rattling sound.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2020-128803 Summary of the invention

[0011] Technical problem that the invention aims to solve

[0012] In the conventional structure described in Japanese Patent Application Laid-Open No. 2020-128803, there is room for improvement from the following aspects.

[0013] In a worm gear reducer assembled in a steering device, when a car's tires run onto a curb or the car is driving on a bad road, a large torque is sometimes inputted in the reverse direction from the tires to the worm wheel. If such a reverse input of torque occurs, a large meshing reaction force acts on the worm from the meshing portion between the worm teeth and the gear teeth, thereby increasing the elastic deformation of the force spring as the worm moves away from the worm wheel. As a result, the force spring or components around the force spring may violently collide with adjacent components, generating a harsh impact sound.

[0014] In addition, the torque inputted from the tire to the worm wheel in the reverse direction sometimes becomes torque vibration in which the rotation direction is repeatedly reversed. In this case, it is possible to repeatedly generate a knocking sound caused by the collision between the parts, a tooth-gripping sound between the worm gear and the gear teeth, that is, a rattling sound.

[0015] In order to suppress the generation of these abnormal sounds, it is required to sufficiently suppress the collision force between the components by the elastic force of the urging spring, and specifically, it is required to increase the spring constant of the urging spring.

[0016] On the other hand, it is desired that during normal operation when no torque reverse input is generated, the friction force acting on the meshing portion between the worm teeth and the wheel teeth is suppressed to a low level regardless of the worm displacement caused by the generation of the meshing reaction force, thereby being able to fully ensure the transmission efficiency of the torque from the worm to the worm wheel. To this end, it is required to suppress the force of the urging spring during normal operation to a low level, specifically, it is required to reduce the spring constant of the urging spring.

[0017] However, in the conventional structure described in Japanese Patent Application Laid-Open No. 2020-128803, since the spring constant of the biasing spring is constant, it is difficult to satisfy the above two requirements that are contradictory to each other.

[0018] An object of the present invention is to provide a worm gear reducer capable of achieving both suppression of abnormal noise generation when torque is input in reverse and ensuring torque transmission efficiency during normal operation at a high level.

[0019] Technical solutions to the problem

[0020] A worm gear reducer according to one embodiment of the present invention includes a housing, a worm wheel, a worm, a support bearing, and a biasing plate spring.

[0021] The housing has a worm wheel housing portion and a worm housing portion having a center axis in a twisted position relative to a center axis of the worm wheel housing portion, and an axial intermediate portion opens in the worm wheel housing portion.

[0022] The worm wheel has gear teeth on an outer peripheral surface and is rotatably supported inside the worm wheel housing portion.

[0023] The worm has a worm wheel meshing with the gear teeth on an outer peripheral surface, and is rotatably supported inside the worm housing portion.

[0024] The support bearing is externally fitted on the top end portion of the worm.

[0025] The urging plate spring urges an inner diameter side member toward the worm wheel side, and the inner diameter side member is the support bearing or an externally fitted member externally fitted to the support bearing.

[0026] In a worm gear reducer of one embodiment of the present invention, the force leaf spring is arranged on a side away from the worm wheel in a portion between the outer circumferential surface of the inner diameter side component and the inner circumferential surface of the outer diameter side component, in the force direction of the force leaf spring, i.e., the first direction, and the outer diameter side component is the worm housing portion or an embedded component embedded in the worm housing portion.

[0027] The biasing leaf spring has a load point as a contact portion with the outer peripheral surface of the inner diameter side member and a fulcrum as a portion of the contact portion with the inner peripheral surface of the outer diameter side member that is located closest to the load point.

[0028] The urging leaf spring exhibits the following nonlinear spring characteristics: as the deflection in the first direction increases, the position of the fulcrum changes so as to approach the load point, thereby increasing the spring constant. The increase in the spring constant as the deflection in the first direction increases may be a stepwise increase or a continuous increase.

[0029] In a worm gear reducer of one embodiment of the present invention, the force leaf spring is configured in a manner extending in a third direction that is orthogonal to both the first direction and the axial direction of the worm housing portion, i.e., the second direction, and the end on either side of the third direction is cantilevered supported on the outer diameter side component, and the end on the other side of the third direction has the load point.

[0030] In the worm gear reducer according to one aspect of the present invention, the one end portion of the biasing plate spring is cantilever-supported by the outer diameter side member using a pin disposed so as to extend in the second direction.

[0031] In the worm gear reducer according to one aspect of the present invention, the outer diameter side member is made of an aluminum alloy, and the pin is made of an iron alloy.

[0032] In a worm gear reducer of one embodiment of the present invention, the inner circumferential surface of the outer diameter side component has a main retaining portion and a secondary retaining portion. The main retaining portion is one circle larger than the outer circumferential surface of the inner diameter side component, and the inner diameter side component is arranged inside. The secondary retaining portion extends to the outer diameter side from the end of the main retaining portion on the side away from the worm wheel in the first direction, and the biasing leaf spring is arranged inside.

[0033] When observed from the second direction, the main retaining portion exists in a circumferential range that can intersect with a radial straight line L1 and a radial straight line L2, wherein the radial straight line L1 includes a vector of an engagement reaction force F1 applied to the worm from the meshing portion between the worm teeth and the wheel teeth when the worm rotates in a specified direction, and the radial straight line L2 includes a vector of an engagement reaction force F2 applied to the worm from the meshing portion when the worm rotates in a direction opposite to the specified direction.

[0034] The inclination angle of the radial line L2 with respect to the third direction is smaller than the inclination angle of the radial line L1 with respect to the third direction. In this case, the portion of the auxiliary retaining portion where the end of the one side of the biasing leaf spring is arranged can be arranged on the same side as the radial line L2 compared to the central axis of the worm in the third direction.

[0035] In the worm gear reducer according to one aspect of the present invention, the outer diameter side member includes a plurality of corner portions that are spaced apart from each other in the third direction as portions that come into contact with the biasing plate spring during operation.

[0036] In the worm gear reducer according to one aspect of the present invention, the biasing plate spring is configured to be able to simultaneously contact two or more corner portions among the plurality of corner portions during operation.

[0037] In the worm gear reducer according to one aspect of the present invention, the outer diameter side member includes a convex curved surface portion as a portion that comes into contact with the biasing leaf spring during operation.

[0038] A worm gear reducer according to one embodiment of the present invention is provided with an elastic clamping unit, which clamps the inner diameter side component from both sides in the third direction. The elastic clamping unit has a pair of clamping leaf springs, which are arranged on both sides of the third direction in a portion between the outer peripheral surface of the inner diameter side component and the inner peripheral surface of the outer diameter side component.

[0039] Each of the pair of clamping leaf springs exhibits a nonlinear spring characteristic in which the spring constant increases as the deflection in the third direction increases. The spring constant may increase in a stepwise or continuous manner as the deflection in the third direction increases.

[0040] The present invention can be implemented by appropriately combining the above-described various aspects within a range where no contradiction occurs.

[0041] Effects of the Invention

[0042] According to the worm gear reducer of one embodiment of the present invention, it is possible to easily achieve both suppression of abnormal noise generated when torque is input in reverse and securing torque transmission efficiency during normal operation at a high level. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a diagram showing an electric power steering system incorporating a worm gear reducer according to a first example of an embodiment of the present invention.

[0044] Figure 2 yes Figure 1 AA section view.

[0045] Figure 3 yes Figure 2 Magnified image of the upper right portion.

[0046] Figure 4 yes Figure 3 Exploded perspective view of the parts shown.

[0047] Figure 5 is from Figure 3 Remove the cover and retaining ring from Figure 3 Observation diagram on the right.

[0048] Figure 6 yes Figure 5 Enlarged view of part B.

[0049] Figure 7 yes Figure 5 Enlarged view of part C.

[0050] Figure 8 In the first case, Figure 3 Figure 2. Observation of the housing on the right side.

[0051] Fig. 9 This is a perspective view showing the support bearing, the biasing plate spring, and the elastic clamping unit removed from the first example.

[0052] Fig.10 Yes Fig. 9 The components shown in the figures are shown separated.

[0053] Fig.11 (a) is a side view of the force-applying leaf spring in the first example, Fig.11 (b) is from Fig.11 (a) is a diagram viewed from the upper side. Fig.11 (c) is from Fig.11(a) is a diagram viewed from the bottom side. Fig.11 (d) is from Fig.11 The left side of (a) is observed. Fig.11 (e) is from Fig.11 The figure observed on the right side of (a).

[0054] Fig.12 (a) is a side view of the elastic clamping unit in the first example, Fig.12 (b) is from Fig.12 (a) is a diagram viewed from the upper side. Fig.12 (c) is from Fig.12 (a) is a diagram viewed from the bottom. Fig.12 (d) is from Fig.12 The left side of (a) is observed. Fig.12 (e) is from Fig.12 The figure observed on the right side of (a).

[0055] Fig.13 (a)~ Fig.13 (d) is a diagram schematically showing a state in which the deflection amount of the biasing plate spring in the first direction increases in the first example.

[0056] Fig.14 It is a line diagram (conceptual diagram) showing the spring characteristics of the biasing plate spring in the first example.

[0057] Fig.15 (a)~ Fig.15 (c) is a diagram schematically showing a state in which the deflection amount in the third direction of the elastic clamping unit (clamping leaf spring) in the first example increases.

[0058] Fig.16 It is a line diagram (conceptual diagram) showing the spring characteristics of the elastic clamping unit (clamping leaf spring) in the first example.

[0059] Fig.17 (a)~ Fig.17 (c) is a diagram schematically showing a situation in which the deflection amount of the elastic clamping unit (clamping leaf spring) in the third direction does not change with the movement in the first direction in the first example.

[0060] Fig.18 This is a second example of an embodiment of the present invention, which is equivalent to Fig.13 Figure 2(a). DETAILED DESCRIPTION

[0061] [First example]

[0062] use Figure 1 to Figure 17 A first example of an embodiment of the present invention will be described.

[0063] (1) Worm gear reducer

[0064] The worm gear reducer of the present invention can be applied to a worm gear reducer incorporated in a part of various mechanical devices, but in this example, a case where the present invention is applied to a worm gear reducer incorporated in a part of an electric power steering device for an automobile will be described.

[0065] like Figure 1 to Figure 5 As shown, the worm gear reducer 1 of this example includes a housing 2 , a worm wheel 3 , a worm 4 , a support bearing 5 , and a biasing plate spring 6 .

[0066] The housing 2 includes: a worm wheel housing portion 8; and a worm housing portion 9 having a central axis in a twisted position relative to the central axis of the worm wheel housing portion 8, and an axial middle portion thereof opening toward the worm wheel housing portion 8. In this example, the housing 2 is made of an aluminum alloy. However, when the present invention is implemented, the material of the housing may be any material as long as the rigidity required by the housing is ensured.

[0067] The worm wheel housing portion 8 is configured in a cylindrical shape. Figure 2 In the embodiment, the central axis of the worm wheel housing portion 8 extends in the front-back direction.

[0068] The worm housing portion 9 is configured in a cylindrical shape and has openings at both ends in the axial direction. Figure 2 The central axis of the worm housing portion 9 extends in the left-right direction. The opening on one axial side of the worm housing portion 9 is blocked by a cover 10 mounted on the opening using a retaining ring 47. The opening on the other axial side of the worm housing portion 9 is blocked by an electric motor 11 fixed to the housing 2.

[0069] In addition, regarding the components including the worm housing portion 9 and the worm 4 housed in the worm housing portion 9, one side in the axial direction is Figure 2 The right side of the axis is Figure 2 on the left side of the .

[0070] The worm wheel 3 has gear teeth 12 on the outer peripheral surface. In this example, the gear teeth are composed of helical gears. The worm wheel 3 is rotatably supported inside the worm wheel storage portion 8. In this example, the worm wheel 3 is externally fixed to an axial portion of the rotating shaft rotatably supported inside the worm wheel storage portion 8 (in this example, the front side portion of the steering shaft 50 in the front-rear direction of the vehicle).

[0071] The worm 4 has worm teeth 13 meshing with the gear teeth 12 of the worm wheel 3 on the outer peripheral surface of the axial middle portion, and is rotatably supported inside the worm housing portion 9. In this example, the worm teeth 13 are threaded, and the twisting direction is the right helical direction. However, the twisting direction may also be the left helical direction.

[0072] The base end portion (the portion near the other axial end) of the worm 4 is supported by a ball bearing 14 so as to be rotatable relative to the worm housing portion 9. In this example, the outer ring of the ball bearing 14 is embedded in the worm housing portion 9 via a radial gap, and the inner ring of the ball bearing 14 is embedded in the base end portion of the worm 4 via a radial gap. Thus, the base end portion of the worm 4 is supported so as to be rotatable and swingable relative to the worm housing portion 9. The outer ring of the ball bearing 14 can also be embedded in the worm housing portion 9 by interference fit.

[0073] The structure for supporting the proximal end portion of the worm 4 so as to be rotatable and swingably displaceable relative to the worm housing portion 9 is not limited to that of this example, and various structures can be adopted.

[0074] The base end portion (the other end portion in the axial direction) of the worm 4 is connected to the top end portion (one end portion in the axial direction) of the output shaft 15 of the electric motor 11 in a manner that allows torque transmission and swing displacement, using a coupler 16. The base end portion of the worm 4 and the top end portion of the output shaft 15 of the electric motor 11 can also be connected to each other in a manner that allows torque transmission and swing displacement by spline engagement or the like.

[0075] The support bearing 5 is externally fitted on the tip end portion (one end portion in the axial direction) of the worm 4 .

[0076] In this example, the support bearing 5 is composed of a ball bearing. Figure 3 As shown, the support bearing 5 includes an inner ring 17, an outer ring 18, and a plurality of balls 19 arranged between an inner ring track provided on the outer circumferential surface of the inner ring 17 and an outer ring track provided on the inner circumferential surface of the outer ring 18. The inner ring 17 is externally fitted and fixed to the top end portion of the worm 4. In addition, when implementing the present invention, the support bearing can also be composed of other types of bearings such as roller bearings.

[0077] In this example, the inner peripheral surface of the worm housing portion 9 has a small-diameter cylindrical surface portion 20 having a smaller diameter than the outer peripheral surface of the support bearing 5, that is, the outer peripheral surface of the outer ring 18, at a portion near the end portion on the axial side, and has a retaining portion 21 having a larger diameter than the small-diameter cylindrical surface portion 20 at a portion adjacent to the axial side of the small-diameter cylindrical surface portion 20. The small-diameter cylindrical surface portion 20 and the retaining portion 21 are connected via a stepped surface 22 facing the axial side. In this example, the support bearing 5 is arranged inside the retaining portion 21 so as to be movable in the radial direction.

[0078] In the following description, the urging direction of the urging plate spring 6, i.e., the direction in which the worm 4 moves forward or backward relative to the worm wheel 3 ( Figure 2 , Figure 3 as well as Figure 5 The vertical direction of the worm 4 and the worm housing portion 9 is taken as the “first direction”, and the axial direction of the worm 4 and the worm housing portion 9 is taken as the “first direction”. Figure 2 as well as Figure 3 The left and right directions, Figure 5 The front and back direction of the first direction is taken as the “second direction”, and the direction orthogonal to both the first direction and the second direction is taken as the “second direction”. Figure 2 as well as Figure 3 The table and back direction, Figure 5 The left-right direction of the worm 4 is regarded as the “third direction”. In addition, the top end of the worm 4 is equivalent to the axial direction of the worm 4 and one end of the second direction.

[0079] like Figure 5 as well as Figure 8 As shown in FIG. 1 , the retaining portion 21 of the worm housing portion 9 includes a main retaining portion 23, a secondary retaining portion 24, and a locking portion 25. The main retaining portion 23 is arranged substantially coaxially with the small-diameter cylindrical surface portion 20, and has a substantially cylindrical shape that is one circle larger than the outer peripheral surface of the support bearing 5. The secondary retaining portion 24 is formed from a side (ie, a side) of the main retaining portion 23 that is away from the worm wheel 3 in the first direction. Figure 5 as well as Figure 8 The locking portion 25 extends from an end portion of the main retaining portion 23 on the side close to the worm wheel 3 in the first direction to the outer diameter side.

[0080] The main holding portion 23 is a portion inside which the support bearing 5 is disposed so as to be movable in the radial direction. The worm speed reducer 1 of this example further includes an elastic clamping unit 7 disposed between the outer peripheral surface of the support bearing 5 and the inner peripheral surface of the main holding portion 23 .

[0081] The ends of the main holding portion 23 on both sides in the third direction are formed by a pair of flat surfaces 26 extending in the first direction (see Figure 7 ) is formed. The pair of flat surfaces 26 are portions for contacting with a pair of clamping leaf springs 41 constituting the elastic clamping unit 7. The spacing between the pair of flat surfaces 26 in the third direction is greater than the diameter of the outer peripheral surface of the support bearing 5. The length of the pair of flat surfaces 26 in the first direction is ensured to be greater than the stroke amount that the elastic clamping unit 7 can move in the first direction together with the top end of the worm 4 and the support bearing 5 during operation.

[0082] Thus, regardless of the movement of the elastic clamping unit 7 in the first direction, the pair of clamping leaf springs 41 constituting the elastic clamping unit 7 maintains a state of being in contact with the pair of flat surface portions 26 .

[0083] The portion of the main retaining portion 23 that is circumferentially offset from the pair of flat portions 26 is formed by a cylindrical surface portion 27 having a larger diameter than the outer peripheral surface of the support bearing 5. In the embodiment of the present invention, the pair of flat portions of the main retaining portion may be omitted and the main retaining portion may be formed only by the cylindrical surface portion.

[0084] In the worm gear reducer 1 of this example, when the torque is transmitted from the worm 4 to the worm wheel 3, a meshing reaction force is applied to the worm 4 from the meshing portion of the gear teeth 12 and the worm teeth 13. The meshing reaction force includes not only a first direction component but also a third direction component. In the case where the worm 4 rotates in a prescribed direction and in the case where the worm 4 rotates in a direction opposite to the prescribed direction, the directions of the third direction component in the meshing reaction force are opposite to each other. In addition, the ratio of the first direction component to the third direction component contained in the meshing reaction force is different when the worm 4 rotates in a prescribed direction and in the opposite direction.

[0085] That is, when the torque is transmitted between the worm 4 and the worm wheel 3, a force such as Figure 5 The meshing reaction force F1 or F2 shown. The meshing reaction forces F1 and F2 are directed in directions asymmetrical to each other in the third direction. This example is an example in which the torsion direction of the worm gear 13 is the right helical direction, but when the torsion direction of the worm gear 13 is the left helical direction, Figure 5 The directions of the meshing reaction forces F1 and F2 in the third direction are reversed. Figure 5 The structure of the portion shown is reversed in the third direction, i.e. Figure 5 Reverse left and right.

[0086] like Figure 5 As shown, the circumferential range of the cylindrical surface 27 of the main retaining portion 23 includes the same circumferential position as the vector of the meshing reaction forces F1 and F2 when viewed from the second direction. That is, the radial straight lines L1 and L2 including the vectors of the meshing reaction forces F1 and F2 intersect a part of the circumferential direction of the cylindrical surface 27 of the main retaining portion 23.

[0087] The auxiliary holding portion 24 is a portion in which the biasing plate spring 6 is arranged. The auxiliary holding portion 24 is on one side of the third direction ( Figure 5 and Figure 8 The auxiliary holding portion 24 has a large recess 28 that is recessed toward one side of the third direction. Figure 5 and Figure 8 The left side) portion has a small recess 29 recessed toward the side away from the worm wheel 3 in the first direction.

[0088] The auxiliary holding portion 24 has a first inclined surface portion 30 and a second inclined surface portion 31 in order from the large recess 28 side between the large recess 28 and the small recess 29. The first inclined surface portion 30 and the second inclined surface portion 31 are each composed of a plane that is inclined toward a direction away from the worm wheel 3 in the first direction as it moves toward the other side in the third direction.

[0089] like Figure 6As shown, the inclination angle θ2 of the second inclined surface portion 31 relative to the third direction is greater than the inclination angle θ1 of the first inclined surface portion 30 relative to the third direction (θ2>θ1). In this example, when viewed from the second direction, the length of the second inclined surface portion 31 is longer than the length of the first inclined surface portion 30. The large recess 28 is connected to the first inclined surface portion 30 via the first corner portion 32. The first inclined surface portion 30 is connected to the second inclined surface portion 31 via the second corner portion 33. The second inclined surface portion 31 is connected to the small recess 29 via the third corner portion 34.

[0090] That is, the first corner portion 32, the second corner portion 33, and the third corner portion 34 are oriented in the third direction away from the pin 36 disposed in the large recess 28 ( Figure 5 , Figure 6 as well as Figure 8 The first corner portion 32, the second corner portion 33 and the third corner portion 34 are sequentially arranged in a direction away from the worm wheel 3 in the first direction ( Figure 5 , Figure 6 as well as Figure 8 The first corner portion 32, the second corner portion 33 and the third corner portion 34 are sequentially arranged above the first corner portion 32, the second corner portion 33 and the third corner portion 34 separated in the third direction are the parts that the urging plate spring 6 contacts during operation.

[0091] like Figure 5 and Figure 8 As shown, the locking portion 25 is a portion for locking a part of the elastic clamping unit 7 in the circumferential direction. In the example shown in the figure, the locking portion 25 is composed of a semi-cylindrical concave surface.

[0092] In this example, the worm housing portion 9 has a partially opened recess 35 located inside the large recess 28 in the step surface 22. The end portion on the other axial side of a cylindrical pin 36 arranged in a manner extending in the second direction is embedded and supported in the recess 35 by press-fitting. The pin 36 is a component for cantilevering the force plate spring 6 in the worm housing portion. In this example, the pin 36 is made of an iron alloy. However, when implementing the present invention, the material of the pin 36 can be any material as long as the rigidity required for the pin 36 can be ensured.

[0093] The urging plate spring 6 urges the support bearing 5, which corresponds to the inner diameter side component, toward the worm wheel 3. Thus, the backlash between the gear teeth 12 and the worm teeth 13 is suppressed, thereby suppressing the occurrence of the tooth rattling sound. In addition, when implementing the present invention, an externally-fitted component externally fitted to the support bearing 5 can also be used as the inner diameter side component. That is, the externally-fitted component can also be urged toward the worm wheel side by the urging plate spring.

[0094] The urging plate spring 6 is disposed as a whole inside the worm housing portion 9. Figure 5As shown, the urging leaf spring 6 is arranged on the side away from the worm wheel 3 in the first direction in the portion between the outer peripheral surface of the support bearing 5 and the retaining portion 21, and the retaining portion 21 is arranged on the inner peripheral surface of the worm housing portion 9 corresponding to the outer diameter side member. More specifically, the urging leaf spring 6 is arranged on the inner side of the auxiliary retaining portion 24 constituting the retaining portion 21.

[0095] In addition, when implementing the present invention, an inner fitting member that is fitted into the worm housing portion may be used as the outer diameter side member. That is, the inner peripheral surface of the inner fitting member may be provided with the holding portion 21 .

[0096] In this example, the urging leaf spring 6 has: a load point P, which is a contact portion that contacts the outer peripheral surface of the support bearing 5; and a fulcrum S, which is a portion of the contact portion that contacts the retaining portion 21 that is located closest to the load point P (see Fig.13 (a)). In addition, the urging plate spring 6 exhibits the following nonlinear spring characteristics: as the deflection amount related to the first direction increases, the position of the fulcrum S changes so as to approach the load point P, thereby increasing the spring constant.

[0097] In this example, if Fig.11 (a)~ Fig.11 As shown in (e), the urging plate spring 6 comprises: a strip plate portion 38 having a rectangular flat plate shape with a large aspect ratio; a base plate portion 39 extending from the base end side of the strip plate portion 38 in the longitudinal direction ( Fig.11 The edge portion of (a) on the right side) is directed toward one side in the thickness direction ( Fig.11 and the folded back plate portion 40, which is from the top side of the length direction of the plate portion 38 ( Fig.11 The end edge portion of the left side of (a) is folded back 180 degrees to one side in the thickness direction, and the top end side portion of the folded back plate portion 40 overlaps with the top end side portion of the belt plate portion 38.

[0098] In this example, the urging plate spring 6 is made of a metal plate such as an iron alloy. However, when the present invention is implemented, the urging plate spring 6 may be made of any material as long as the spring rigidity required for the urging plate spring 6 is ensured.

[0099] like Figure 5 As shown, the biasing plate spring 6 is arranged in a state of being extended in the third direction, and the end on either side in the third direction (in this example, the end on one side in the third direction) is cantilever-supported by the worm housing portion 9, and the end on the other side in the third direction (in this example, the end on the other side in the third direction) has a load point P (refer to Fig.13 (a)).

[0100] In this example, the end portion of the biasing plate spring 6 on one side in the third direction is cantilever-supported by the worm housing portion 9 using a pin 36 disposed so as to extend in the second direction.

[0101] More specifically, the biasing leaf spring 6 is disposed around the worm reducer 1 as follows in the unloaded state, that is, when the torque transmitted from the worm 4 to the worm wheel 3 is zero and the meshing reaction forces F1 and F2 applied to the tip of the worm 4 are zero.

[0102] The base end of the substrate portion 39 elastically contacts the bottom of the large recess 28 constituting the auxiliary holding portion 24. The side surface ( Figure 5 The lower side surface of the strip plate portion 38 is in elastic contact with the outer peripheral surface of the pin 36. The other side surface ( Figure 5 The upper side surface of the folded-back plate portion 40 is in elastic contact with the first corner portion 32 constituting the auxiliary holding portion 24. Figure 5 The lower side surface of the support bearing 5 is in elastic contact with an end portion of the outer peripheral surface of the support bearing 5 on the side away from the worm wheel 3 in the first direction.

[0103] In this example, the folded plate portion 40 is provided at the portion of the urging plate spring 6 that contacts the outer peripheral surface of the support bearing 5. Therefore, based on the presence of the folded plate portion 40, the size of the radial gap between the portion of the outer peripheral surface of the support bearing 5 that contacts the urging spring 6 and the retaining portion 21 can be adjusted to an appropriate size.

[0104] The strip plate portion 38 does not contact the second corner portion 33 and the third corner portion 34 , and a gap exists between the strip plate portion 38 and the second corner portion 33 and the third corner portion 34 .

[0105] In this state, the urging plate spring 6 elastically urges the support bearing 5 toward the worm wheel 3 side with the contact portion with the first corner portion 32 as the fulcrum S and the contact portion with the outer peripheral surface of the support bearing 5 as the load point P (see Fig.13 (a)).

[0106] In this example, the biasing plate spring 6 is held in the use position by the friction force acting on the contact portion between the worm housing portion 9 and the pin 36. The load point P is arranged at substantially the same position as the third corner portion 34 of the auxiliary holding portion 24 in the third direction.

[0107] In this example, when the meshing reaction force F1 or F2 applied to the tip of the worm 4 increases, the pressing force applied from the support bearing 5 to the load point P of the biasing plate spring 6 increases, and the deflection amount of the biasing plate spring 6 (belt plate portion 38) in the first direction increases. Fig.13 (a)~ Fig.13(d) is a diagram schematically showing a situation where the deflection amount increases.

[0108] In this example, when the deflection amount of the urging plate spring 6 in the first direction increases, the elastic contact position of the urging plate spring 6 with respect to the auxiliary holding portion 24 is adjusted according to Fig.13 (a)~ Fig.13 That is, the position of the fulcrum S of the urging leaf spring 6 changes stepwise in the direction approaching the load point P. As a result, the spring constant of the urging leaf spring 6 is as follows: Fig.14 (Conceptual diagram) shows a gradual increase.

[0109] More specifically, when the deflection amount of the urging plate spring 6 in the first direction increases, the elastic contact position of the urging plate spring 6 with respect to the auxiliary retaining portion 24 changes from Fig.13 The first corner 32 (one part) shown in (a) is changed to Fig.13 The first corner 32 and the second corner 33 (two locations) shown in (b) are then changed to Fig.13 The second corner 33 (one part) shown in (c) is then changed to Fig.13 The second corner portion 33 and the third corner portion 34 (two locations) shown in (d) of FIG. 1 . That is, in this example, the biasing plate spring 6 is configured to be able to contact two or more corner portions among the plurality of corner portions simultaneously during operation.

[0110] like Fig.13 As shown in (a), when the urging plate spring 6 is in elastic contact with only the first corner portion 32 (one location), the fulcrum S of the urging plate spring 6 is the contact portion with the first corner portion 32. Fig.14 In this example, during normal operation without reverse input of torque, the deflection of the urging leaf spring 6 in the first direction is suppressed to be small, and the urging leaf spring 6 always contacts the first corner 32.

[0111] like Fig.13 As shown in (b), in the state where the urging plate spring 6 is in elastic contact with the first corner portion 32 and the second corner portion 33 (two locations), and as shown in Fig.13 When the urging plate spring 6 is in elastic contact with only the second corner portion 33 (one portion) as shown in (c), the fulcrum S of the urging plate spring 6 is the contact portion with the second corner portion 33. Fig.14 As shown, the spring constant of the urging plate spring 6 in this state (second stage) is larger, specifically, larger than that in the first stage.

[0112] like Fig.13As shown in (d), when the urging plate spring 6 elastically contacts the second corner portion 33 and the third corner portion 34 (two locations), the urging plate spring 6 cannot further increase the deflection amount in the first direction, and is in a so-called bottoming state.

[0113] In this example, the spring constant of the urging leaf spring 6 changes in two stages according to the deflection amount of the urging leaf spring 6 in the first direction. Specifically, the spring constant of the urging leaf spring 6 increases from a smaller value (first stage) to a larger value (second stage) as the deflection amount of the urging leaf spring 6 in the first direction increases.

[0114] According to the worm gear reducer 1 of this example, when the mechanical device (in this example, an automobile) assembled with the worm gear reducer 1 is working, even if a large torque is reversely input to the worm gear reducer 1 from a portion located on the downstream side of the worm gear reducer 1 in the power transmission direction (in this example, the tire), the occurrence of abnormal noise can be efficiently suppressed based on the presence of the force-applying leaf spring 6.

[0115] More specifically, by inputting a large torque (including torque vibration) in the reverse direction to the worm gear reducer 1, the deflection amount of the biasing plate spring 6 in the first direction can be increased to about Fig.13 The spring constant of the urging plate spring 6 before the state shown in (d) is set to a large value (second stage). Therefore, the momentum of the urging plate spring 6 colliding with the third corner portion 34 can be effectively suppressed by the large elastic force of the urging plate spring 6.

[0116] Furthermore, by Fig.13 The state shown in (d) of FIG. 1 is to reverse the rotation direction of the worm 4, thereby reducing the deflection amount of the urging plate spring 6 in the first direction to about Fig.13 The spring constant of the urging plate spring 6 before the state shown in (a) is set to a small value (first stage). Therefore, by reducing the urging force of the urging plate spring 6, the momentum of the wheel teeth 12 and the worm teeth 13 colliding with the reversal of the rotation direction of the worm 4 can be effectively suppressed.

[0117] That is, even when the torque inputted in the reverse direction to the worm gear reducer 1 becomes torque vibration, the hitting sound and the rattling sound between the gear teeth 12 and the worm teeth 13, which are repeatedly generated due to the collision between the biasing plate spring 6 and the third corner portion 34, can be effectively suppressed.

[0118] In this example, during normal operation when no reverse input of torque is generated, the deflection amount of the force plate spring 6 in the first direction becomes small, so that the spring constant of the force plate spring 6 can be made small (first stage). Therefore, during normal operation, regardless of the displacement of the worm 4 caused by the meshing reaction forces F1 and F2, the friction force acting on the meshing portion between the gear teeth 12 and the worm teeth 13 can be suppressed to a small value, and the torque transmission efficiency from the worm 4 to the worm wheel 3 can be fully ensured.

[0119] In short, according to the worm gear reducer 1 of this example, it is possible to achieve both suppression of the generation of abnormal noise when torque is input in the reverse direction and securing the torque transmission efficiency during normal operation at a high level.

[0120] The force of the urging plate spring 6 urging the support bearing 5 toward the worm wheel 3, that is, the force acting on the load point P, is Fig.13 The force acting on the bottoming state as shown in (d) is relative to Fig.13 The force in the initial state shown in (a) can be set to any multiple, but it is preferably set to 3 times or more.

[0121] In this example, the corners that serve as the fulcrum S of the urging leaf spring 6 are the first corner 32 and the second corner 33. However, when implementing the present invention, the number of corners can be increased compared to this example, so that the spring constant of the urging leaf spring 6 can be changed to three or more stages.

[0122] When the present invention is implemented, the shape of the biasing plate spring may be different from that of this example.

[0123] In the structure of this example, the pin 36 is made of an iron alloy, and the housing 2 including the worm housing portion 9 is made of an aluminum alloy. The worm housing portion 9 made of an aluminum alloy has good machinability, and it is easy to perform a cutting process for forming the holding portion 21 in the forming process. In addition, the pin 36 made of an iron alloy is not only easy to obtain, but also has little effect on the spring characteristics of the urging plate spring 6 due to dimensional changes. In addition, since the urging spring is a leaf spring, that is, the urging plate spring 6, it is easy to assemble it to the use location.

[0124] By combining these, the inter-core adjustment mechanism of the worm wheel 3 and the worm 4 can be realized with high accuracy, so that the function of the above-mentioned biasing plate spring 6 can be easily exerted well.

[0125] In this example, the biasing plate spring 6 is arranged to be extended in the third direction, and the entire spring is arranged inside the worm housing portion 9. Figure 5 As shown in FIG. 1 , the urging plate spring 6 can be assembled with the end portion on one axial side of the worm housing portion 9 facing forward. Therefore, the urging plate spring 6 can be assembled easily.

[0126] Although different from the structure of the present invention, it is also possible to adopt a structure in which the base end and the middle part of the force leaf spring are arranged outside the worm housing portion, and only the top end of the force leaf spring is inserted into the inside of the worm housing portion, and the outer peripheral surface of the inner diameter side component such as the support bearing is pressed by the top end. However, in this case, it is necessary to form a through hole, a cutout, etc. for inserting the top end of the force leaf spring in a part of the worm housing portion, so there are problems such as an increase in the cost for forming the through hole or the cutout, or the through hole or the cutout makes it impossible to set the part of the worm housing portion to achieve airtightness.

[0127] Furthermore, before being set in the use position, there is a possibility that a portion of the biasing spring disposed outside the worm housing portion collides with surrounding objects and is damaged.

[0128] On the other hand, in the structure of this example, since the entire urging plate spring 6 is arranged inside the worm housing portion 9, all the above-mentioned problems can be avoided.

[0129] The elastic clamping means 7 clamps the support bearing 5 corresponding to the inner diameter side member from both sides in a third direction orthogonal to both the first direction of the urging direction of the urging plate spring 6 and the second direction of the axial direction of the worm housing portion 9 .

[0130] The elastic clamping unit 7 has a pair of clamping leaf springs 41, which are arranged on both sides of the third direction in a portion between the outer peripheral surface of the support bearing 5 and the retaining portion 21 provided on the inner peripheral surface of the worm housing portion 9 corresponding to the outer diameter side member. Each clamping leaf spring 41 constituting the pair of clamping leaf springs 41 exhibits nonlinear spring characteristics, that is, the spring constant increases as the deflection amount in the third direction increases.

[0131] In this example, if Fig.12 (a)~ Fig.12 As shown in (e), the elastic clamping unit 7 is composed of a metal leaf spring having a notched cylindrical shape (C-shaped) as a whole. A pair of clamping leaf springs 41 constitute the circumferential side portions of the elastic clamping unit 7. The elastic clamping unit 7 has a circumferential connecting portion 42, which connects the circumferential ends of the pair of clamping leaf springs 41 on the side close to the worm wheel 3 to each other in the circumferential direction. Fig.12 In (a), the dotted line α represents the boundary line between the pair of clamping leaf springs 41 and the circumferential connecting portion 42 .

[0132] In this example, each of the pair of clamping leaf springs 41 includes a first portion 43 constituting a circumferential middle portion and a second portion 44 constituting both circumferential side portions. Fig.12 In (a), the dotted line β represents the boundary line between the first portion 43 and the second portion 44 .

[0133] The first portion 43 has a partial cylindrical shape bent along the outer peripheral surface of the support bearing 5. The second portions 44 each have a partial cylindrical shape bent along the outer peripheral surface of the support bearing 5, and are smoothly continuous with the first portion 43. That is, when viewed from the axial direction of the worm 4, the first portion 43 and the second portion 44 are connected so that the circumferential ends of the radially inner side surfaces have a common tangent to each other, and are connected so that the circumferential ends of the radially outer side surfaces have a common tangent to each other.

[0134] The curvature radius R1 of the radially inner side surface of the first portion 43 in the free state is larger than the curvature radius Rs of the outer peripheral surface of the support bearing 5 (see Figure 5 ) is smaller (R1<Rs). The curvature radius R2 of the radially inner side surface of the second portion 44 in the free state is larger than the curvature radius R1 of the radially inner side surface of the first portion 43 in the free state (R2>R1). In this example, the curvature radius R2 is made equal to the curvature radius Rs of the outer peripheral surface of the support bearing 5 (R2=Rs). However, when implementing the present invention, the curvature radius R2 can also be made slightly larger or smaller than the curvature radius Rs.

[0135] In this example, in each of the pair of clamping leaf springs 41, residual stress is applied to the first portion 43, which corresponds to the portion in contact with the retaining portion 21 disposed on the inner peripheral surface of the worm housing portion 9. As a result, it is easy to ensure the durability of the first portion 43, which is likely to have a larger elastic deformation amount during operation than other portions. In the case of implementing the present invention, the application of the residual stress can also be omitted.

[0136] The circumferential connecting portion 42 has a partial cylindrical shape bent along the outer peripheral surface of the support bearing 5, and is smoothly continuous with respect to each clamping leaf spring 41 constituting the pair of clamping leaf springs 41. That is, when viewed from the axial direction of the worm 4, the clamping leaf spring 41 and the circumferential connecting portion 42 are connected in a manner that the circumferential ends of the radially inner side surfaces have a common tangent to each other, and are connected in a manner that the circumferential ends of the radially outer side surfaces have a common tangent to each other.

[0137] In this example, the curvature radius Rj of the radially inner side surface of the circumferential connecting portion 42 in the free state is made equal to the curvature radius R2 of the radially inner side surface of the second portion 44 in the free state (Rj=R2).

[0138] When the present invention is implemented, the circumferential connection portion can be omitted, that is, the pair of clamping leaf springs 41 can be separated from each other.

[0139] In this example, the elastic clamping unit 7 has a circumferential positioning piece 45 that engages with the worm housing portion 9 in the circumferential direction.

[0140] In this example, two circumferential positioning pieces 45 are provided at a circumferentially separated position in the circumferential middle portion of the circumferential connecting portion 42. The two circumferential positioning pieces 45 are provided so as to protrude radially outward from the circumferential middle portion of the circumferential connecting portion 42.

[0141] More specifically, the two circumferential positioning pieces 45 are formed by bending a pair of tongue pieces radially outward, and the pair of tongue pieces are provided by forming an H-shaped through hole in the circumferential middle portion of the circumferential connecting portion 42. The circumferential positioning piece 45 is a portion for circumferentially positioning and rotationally stopping the elastic clamping unit 7 by engaging with the locking portion 25 of the retaining portion 21 in the circumferential direction.

[0142] When implementing the present invention, when circumferential positioning pieces are provided, the shape, number and circumferential position of the circumferential positioning pieces may also be different from those in this example. In addition, the circumferential positioning pieces may also be provided in a manner that is circumferentially engaged with an inner diameter side component formed by a support bearing or an externally embedded component externally embedded in the support bearing.

[0143] In this example, the circumferential connecting portion 42 has a low rigidity portion 57 in the circumferential middle portion, specifically, the low rigidity portion 57 is provided between the two circumferential positioning pieces 45, and the rigidity of the low rigidity portion 57 is lower than that of the circumferential side portions of the circumferential connecting portion 42 and the pair of clamping leaf springs 41 in the remaining circumferential portion. In this example, in order to reduce the rigidity of the low rigidity portion 57, a rectangular through hole 58 is formed in the circumferential portion where the low rigidity portion 57 is located, thereby reducing the section modulus of the circumferential portion. The low rigidity portion 57 is provided to reduce the interaction between the pair of clamping leaf springs 41 by reducing the flexural resistance of the low rigidity portion 57.

[0144] In the case of implementing the present invention, when the low rigidity portion is provided at the circumferential connecting portion, the low rigidity portion may be provided at a circumferential position different from that in the present example, or at a plurality of positions separated along the circumferential direction, or over the entire circumferential length. In the case of implementing the present invention, the low rigidity portion may be omitted from being provided at the circumferential connecting portion.

[0145] When the present invention is implemented, as a means for reducing the rigidity of the low rigidity portion, a means different from the present example may be adopted, such as reducing the plate thickness of the low rigidity portion.

[0146] In this example, the elastic clamping unit 7 has an axial positioning piece 46 that engages with the support bearing 5 in the axial direction.

[0147] In this example, two axial positioning pieces 46 are provided circumferentially spaced apart on each of the pair of clamping leaf springs 41. More specifically, the axial positioning pieces 46 are bent radially inward from the axial end of each circumferential middle portion of the second portion 44.

[0148] In the case of implementing the present invention, when an axial positioning piece is provided, the shape, number, circumferential position and axial position of the axial positioning piece may also be different from those in this example. In addition, the axial positioning piece may also be provided in a manner of engaging with an inner diameter side component composed of a worm housing portion or an embedded component embedded in the worm housing portion in the axial direction.

[0149] like Figure 5 As shown, the elastic clamping unit 7 is arranged between the outer peripheral surface of the support bearing 5 and the holding portion 21 arranged on the inner peripheral surface of the worm housing portion 9. Specifically, the elastic clamping unit 7 is externally fitted to the support bearing 5 and arranged inside the main holding portion 23 constituting the holding portion 21.

[0150] In this state, the two circumferential positioning pieces 45 of the elastic clamping unit 7 are arranged on the inner side of the stopper 25 constituting the holding portion 21, so as to be circumferentially engaged with the stopper 25. Thus, the elastic clamping unit 7 is positioned in the circumferential direction, so that the pair of clamping leaf springs 41 constituting the elastic clamping unit 7 are arranged on both sides of the third direction in the portion between the outer circumferential surface of the support bearing 5 and the main holding portion 23.

[0151] In this example, a gap in the first direction and a gap in the third direction are provided between the two circumferential positioning pieces 45 and the stopper 25. Thus, slight displacement of the two circumferential positioning pieces 45 relative to the stopper 25 in the first direction and the third direction is allowed when working.

[0152] In this example, the first direction dimensions of the two circumferential positioning pieces 45 are set in such a manner that the intrusion amount of the two circumferential positioning pieces 45 relative to the locking portion 25 in the first direction is always fully ensured regardless of whether the elastic clamping unit 7 moves in the first direction together with the top end portion of the worm 4 and the supporting bearing 5 during operation.

[0153] The axial positioning pieces 46 of the elastic clamping unit 7 are brought into contact with the axial side surfaces of the outer ring 18 of the support bearing 5, thereby being axially engaged with the outer ring 18. Thus, the elastic clamping unit 7 is positioned relative to the support bearing 5 in the axial direction.

[0154] Furthermore, each of the clamping leaf springs 41 constituting the pair of clamping leaf springs 41 is arranged in the surrounding portion as follows in a state where the meshing reaction forces F1 and F2 are zero.

[0155] The circumferential center of the radially outer side surface of the first portion 43 is Fig.15 The second portion 44 is in contact with the flat surface 26 constituting the main retaining portion 23 at the point Q1 shown in (a). The circumferentially outer end of the radially inner side surface of each second portion 44, that is, the end of the second portion 44 on the side away from the first portion 43 in the circumferential direction, is Fig.15The first portion 43 contacts the outer peripheral surface of the support bearing 5 at point Q2 shown in (a). The radially inner side surface of the first portion 43 does not contact the outer peripheral surface of the support bearing 5, and a gap exists between the radially inner side surface of the first portion 43 and the outer peripheral surface of the support bearing 5.

[0156] The radially outer side surfaces of the second portions 44 do not contact the main retaining portion 23, and there is a gap between the radially outer side surfaces of the second portions 44 and the main retaining portion 23. That is, the clamping leaf spring 41 is only at one location ( Fig.15 The point Q1 shown in (a) of FIG. 1 is in contact with the main holding portion 23, and only at two locations ( Fig.15 Point Q2) shown in (a) is in contact with the outer peripheral surface of the support bearing 5.

[0157] When the meshing reaction forces F1 and F2 are zero, each of the pair of clamping leaf springs 41 generates initial deflection in the third direction. Thus, even when the meshing reaction forces F1 and F2 are zero, the support bearing 5 can be prevented from shaking in the third direction inside the main retaining portion 23. However, from the viewpoint of reducing the friction force of the pair of clamping leaf springs 41 on the flat surface 26 when the meshing reaction forces F1 and F2 are zero, it is preferable to set the initial deflection in the third direction as small as possible.

[0158] Of the pair of clamping leaf springs 41, the one located on the other side ( Figure 5 The second portion 44 of the clamping leaf spring 41 on the left side of the pair of clamping leaf springs 41, which is located away from the worm wheel 3, intersects the radial straight line L1 including the vector of the meshing reaction force F1 when viewed from the second direction. Figure 5 The second portion 44 of the clamping leaf spring 41 on the right side of the meshing plate (on the right side) which is away from the worm wheel 3 intersects the radial straight line L2 including the vector of the meshing reaction force F2 when viewed from the second direction.

[0159] In the above state, the elastic clamping unit 7 clamps the support bearing 5 from both sides in the third direction using the pair of clamping leaf springs 41. This suppresses the momentum of the tip of the worm 4 when it moves in the third direction, thereby suppressing the generation of abnormal noise.

[0160] In the structure of this example, in order to enable the tip of the worm 4 to move forward and backward relative to the worm wheel 3 in the first direction, the main retaining portion 23 arranged around the support bearing 5 is formed to be larger than the outer peripheral surface of the support bearing 5. Therefore, the tip of the worm 4 can also move in the third direction.

[0161] On the other hand, the meshing reaction forces F1 and F2 acting on the worm 4 include not only the first direction component but also the third direction component. The direction of the third direction component is reversed according to the rotation direction of the worm 4. Therefore, if the top end of the worm 4 is allowed to move in the third direction without resistance, the outer peripheral surface of the support bearing 5 will violently collide with the main retaining portion 23 in the third direction due to the third direction component of the meshing reaction forces F1 and F2 acting on the worm 4, which is likely to cause abnormal noises such as harsh hitting sounds and rattling sounds.

[0162] In the structure of this example, in order to suppress the generation of such abnormal noise, the support bearing 5 is clamped from both sides of the third direction by a pair of clamping leaf springs 41 constituting the elastic clamping unit 7. Thus, the generation of abnormal noise is suppressed by suppressing the momentum of the top end of the worm 4 when moving in the third direction.

[0163] In this example, if the meshing reaction force F1 or F2 applied to the tip of the worm 4 increases, the support bearing 5 acts on one side ( Figure 5 left side) or the other side ( Figure 5 The pressing force of the clamping leaf spring 41 in the third direction (on the right side) increases. As a result, the deflection amount of the clamping leaf spring 41 in the third direction increases. Fig.15 (a)~ Fig.15 (c) is a diagram schematically showing a situation where the deflection amount increases.

[0164] In this example, as the deflection amount of the clamping leaf spring 41 in the third direction increases, the distance W in the first direction between the contact portion (point Q2) of the radial inner side surfaces of the two second portions 44 with respect to the outer peripheral surface of the support bearing 5 is increased as follows: Fig.15 (a)~ Fig.15 In addition, Fig.15 As shown in (c), if the first portion 43 of the clamping leaf spring 41 is clamped between the flat portion 26 of the main retaining portion 23 and the outer peripheral surface of the support bearing 5, the clamping leaf spring 41 cannot further increase the deflection amount in the third direction, and becomes a so-called bottoming state.

[0165] In this example, until the bottoming state is reached, the distance W is continuously reduced as the deflection amount of the clamping leaf spring 41 in the third direction increases, so that the spring constant of the clamping leaf spring 41 is as follows: Fig.16 (Conceptual diagram) shows that it increases continuously.

[0166] Therefore, the urging operation of the urging plate spring 6 on the tip end portion of the worm 4 and the support bearing 5 can be smoothed, and the momentum of collision between components in the third direction can be easily suppressed around the tip end portion of the worm 4 .

[0167] That is, the spring constant of the clamping leaf spring 41 is small in the stage (low load region) where the deflection amount in the third direction is small, so in this stage, the friction force acting between the clamping leaf spring 41 and the flat surface 26 of the main holding portion 23, and the friction force acting between the clamping leaf spring 41 and the outer peripheral surface of the support bearing 5 are reduced. Therefore, the movement of the top end portion of the worm 4 and the support bearing 5 in the first direction can be smoothed. Therefore, the urging action of the urging leaf spring 6 on the top end portion of the worm 4 and the support bearing 5 can be smoothed accordingly.

[0168] On the other hand, the spring constant of the clamping leaf spring 41 increases in the stage where the deflection amount in the third direction increases (high load region), so the larger elastic force of the clamping leaf spring 41 can effectively suppress the Fig.15 The momentum of the movement of the support bearing 5 in the third direction before the bottoming state shown in (c) is reduced. Thus, the occurrence of the collision sound when the bottoming is reached can be effectively suppressed.

[0169] Furthermore, by Fig.15 The state shown in (c) reverses the rotation direction of the worm 4, thereby reducing the deflection amount of the clamping leaf spring 41 in the third direction to about Fig.15 The spring constant of the clamping leaf spring 41 before the state shown in (a) is reduced. Therefore, the momentum of the collision between the gear teeth 12 and the worm teeth 13 caused by the reversal of the rotation direction of the worm 4 can be effectively suppressed by reducing the force of the clamping leaf spring 41. As a result, the generation of the tooth-smashing sound between the gear teeth 12 and the worm teeth 13 can be effectively suppressed.

[0170] In this example, the curvature radius of the radially inner surface of the second portion 44 constituting the circumferential side portions of the clamping leaf spring 41 is made constant, but when implementing the present invention, the curvature radius of the radially inner surface of the second portion can also be changed in stages or continuously in the circumferential direction.

[0171] In this example, the portion of the main holding portion 23 with which each of the pair of clamping leaf springs 41 elastically contacts is formed by the flat surface portion 26 extending in the first direction. Fig.17 (a)~ Fig.17 As shown in (c), even when the elastic clamping unit 7 moves in the first direction, the deflection amount in the third direction of the pair of clamping leaf springs 41, that is, the interval W does not change, and the spring constant of each clamping leaf spring 41 constituting the pair of clamping leaf springs 41 can be kept constant. Therefore, with respect to the force applying leaf spring 6 and the elastic clamping unit 7, stable spring characteristics can be ensured.

[0172] In the case of implementing the present invention, the length of the pair of flat surfaces 26 in the first direction can also be made smaller than the stroke amount by which the elastic clamping unit 7 can move in the first direction together with the top end of the worm 4 and the support bearing 5 during operation, that is, when a large meshing reaction force is applied to the worm 4, the elastic contact portion of the clamping leaf spring 41 with respect to the main retaining portion 23 goes over the cylindrical surface portion 27 from the flat surface portion 26. In this case, while the contact portion exists on the flat surface portion 26, the spring constant of the clamping leaf spring 41 can also be kept constant.

[0173] In this example, when viewed from the second direction, radial lines L1 and L2 including the vectors of the meshing reaction forces F1 and F2 intersect a portion of the circumferential direction of the cylindrical surface portion 27 of the main retaining portion 23. Figure 5 The second portion 44 of the clamping leaf spring 41 on the left side of the meshing plate spring 41, which is away from the worm wheel 3, intersects the radial straight line L1 including the vector of the meshing reaction force F1 when viewed from the second direction.

[0174] In addition, of the pair of clamping leaf springs 41, the one located on one side in the third direction ( Figure 5 The second portion 44 of the clamping leaf spring 41 on the right side of the meshing plate (on the right side) which is away from the worm wheel 3 intersects the radial straight line L2 including the vector of the meshing reaction force F2 when viewed from the second direction.

[0175] Therefore, during operation, even if the support bearing 5 tends to move in the direction of the meshing reaction force F1, the momentum of the movement can be suppressed by the elastic force of the second portion 44 of the clamping leaf spring 41 located on one side in the third direction and away from the worm wheel 3. Furthermore, the meshing reaction force F1 can be supported by the cylindrical surface portion 27 of the main retaining portion 23.

[0176] During operation, even if the support bearing 5 tends to move in the direction of the meshing reaction force F2, the momentum of the movement can be suppressed by the elastic force of the second portion 44 of the clamping leaf spring 41 located on the other side in the third direction and away from the worm wheel 3. Furthermore, the meshing reaction force F2 can be supported by the cylindrical surface portion 27 of the main retaining portion 23.

[0177] In this example, if Figure 5 As shown, when viewed from the second direction, the cylindrical surface 27 of the main retaining portion 23 exists in the circumferential range that can intersect the radial lines L1 and L2 containing the vectors of the meshing reaction forces F1 and F2, but the inclination angle of the radial line L2 with respect to the third direction is smaller than the inclination angle of the radial line L1 with respect to the third direction. Therefore, the radial line L2 side of the cylindrical surface 27 in the third direction ( Figure 5The circumferential end edge E2 is arranged on the side of the radial straight line L1 ( Figure 5 The circumferential end edge E1 of the worm wheel 3 is located on the left side of the worm wheel 3 in the first direction. Figure 5 on the lower side).

[0178] Therefore, in the main retaining portion 23, the first direction is from the side away from the worm wheel 3 ( Figure 5 as well as Figure 8 In the auxiliary retaining portion 24 in which the end portion thereof protrudes toward the outer diameter side, the large recessed portion 28 as a portion for arranging one end portion of the biasing plate spring 6 and the pin 36 is arranged on the same side as the radial straight line L2 than the center axis of the worm 4 in the third direction ( Figure 5 on the right side of the ).

[0179] This is similar to the case where the large recess 28 is disposed on the same side as the radial line L1 in the third direction ( Figure 5 Compared with the case of the left side of the main holding portion 23, the large recess 28 can be arranged at a position close to the worm wheel 3 in the first direction. That is, by adopting such an arrangement, the width dimension of the entire holding portion 21 including the main holding portion 23 and the auxiliary holding portion 24 in the first direction can be minimized.

[0180] In the case of implementing the present invention, the spring characteristics of each clamping leaf spring constituting a pair of clamping leaf springs may also be linear.

[0181] In the structure of this example, the urging plate spring 6 for urging the support bearing 5 toward the worm wheel 3 in the first direction and the elastic clamping unit 7 for clamping the support bearing 5 from both sides in the third direction are manufactured as independent components. Therefore, unlike the case where the urging plate spring and the elastic clamping unit are manufactured as an integral component, the spring characteristics of the urging plate spring 6 and the elastic clamping unit 7 can be set without interfering with each other. Therefore, the degree of freedom in designing the urging plate spring 6 and the elastic clamping unit 7 can be increased.

[0182] (2) Electric power steering

[0183] like Figure 1 As shown, the electric power steering device 48 of this example includes a steering wheel 49 , a steering shaft 50 , a steering column 51 , a pair of universal joints 52 a and 52 b , an intermediate shaft 53 , a steering gear unit 54 , the worm gear reducer 1 of this example, and an electric motor 11 .

[0184] The steering wheel 49 is supported and fixed to the rear end of the steering shaft 50. The steering shaft 50 is rotatably supported inside a steering column 51, which is supported by the vehicle body. The top end of the steering shaft 50 is connected to a pinion shaft 55 of a steering gear unit 54 via a universal joint 52a on the rear side, an intermediate shaft 53, and a universal joint 52b on the front side.

[0185] Therefore, when the driver rotates the steering wheel 49, the rotation of the steering wheel 49 is transmitted to the pinion shaft 55 via the steering shaft 50, the pair of universal joints 52a, 52b, and the intermediate shaft 53. The rotation of the pinion shaft 55 is converted into a linear motion of a rack shaft (not shown) of the steering gear unit 54 meshing with the pinion shaft 55. As a result, the pair of tie rods 56 are pushed and pulled, thereby giving a steering angle corresponding to the rotation operation amount of the steering wheel 49 to the left and right steering wheels.

[0186] The electric power steering system 48 of this example is configured to reduce the force required for the driver to operate the steering wheel 49 by increasing the auxiliary power of the electric motor 11 through the worm gear reducer 1 and applying the increased auxiliary power to the tip of the steering shaft 50 .

[0187] When the present invention is implemented, the worm gear reducer 1 and the electric motor 11 can be arranged at a position where auxiliary power is applied to the pinion shaft or the rack shaft of the steering gear unit.

[0188] [Second example]

[0189] use Fig.18 A second example of the embodiment of the present invention will be described.

[0190] In this example, the portion of the auxiliary holding portion 24a with which the biasing plate spring 6 elastically contacts is formed as the convex curved surface portion 37. In the structure of this example adopting such a structure, as the deflection amount of the biasing plate spring 6 in the first direction increases, the biasing plate spring 6 bends along the convex curved surface portion 37. Therefore, the position of the fulcrum S of the biasing plate spring 6 can be continuously changed in the direction approaching the load point P, and the spring constant of the biasing plate spring 6 can be continuously, specifically, quadratically increased.

[0191] The other structures and effects of the second example are the same as those of the first example.

[0192] The present invention can be implemented by appropriately combining the configurations of the various examples of the embodiments of the present invention described above within a range where no contradiction occurs.

[0193] Description of Reference Numerals

[0194] 1 Worm gear reducer

[0195] 2 Housing

[0196] 3 Worm gear

[0197] 4 Worm

[0198] 5 Support bearing

[0199] 6 Force leaf spring

[0200] 7 Elastic clamping unit

[0201] 8 Worm gear storage area

[0202] 9 Worm storage area

[0203] 10 Cover

[0204] 11 Electric Motor

[0205] 12 teeth

[0206] 13 Worm teeth

[0207] 14 Ball bearings

[0208] 15 Output shaft

[0209] 16 Coupler

[0210] 17 Inner Circle

[0211] 18 Outer ring

[0212] 19 Ball

[0213] 20 Small diameter cylindrical surface

[0214] 21. Maintaining part

[0215] 22 Step surface

[0216] 23 Main holding part

[0217] 24, 24a auxiliary holding portion

[0218] 25 Stopper

[0219] 26 Flat surface

[0220] 27 Cylindrical face

[0221] 28 large recesses

[0222] 29 small recesses

[0223] 30 First inclined face

[0224] 31 Second inclined face

[0225] 32 First corner

[0226] 33 Second corner

[0227] 34 Third corner

[0228] 35 recess

[0229] 36 Pins

[0230] 37 Convex face

[0231] 38 Strip plate

[0232] 39 Substrate Department

[0233] 40 Fold back plate

[0234] 41 Clamping leaf spring

[0235] 42 Circumferential connection

[0236] 43 Part 1

[0237] 44 Part 2

[0238] 45 Circumferential positioning piece

[0239] 46 Axial positioning piece

[0240] 47 Retaining ring

[0241] 48 Electric power steering

[0242] 49 Steering Wheel

[0243] 50 Steering shaft

[0244] 51 Steering column

[0245] 52a, 52b universal joint

[0246] 53 Intermediate shaft

[0247] 54 Steering gear unit

[0248] 55 Pinion shaft

[0249] 56 Tie rod

[0250] 57 Low rigidity part

[0251] 58 holes

Claims

1. A worm gear reducer, characterized in that: have: a housing having a worm wheel housing portion and a worm housing portion, the worm housing portion having a center axis in a twisted position relative to a center axis of the worm wheel housing portion, and an axial middle portion of the worm housing portion opening toward the worm wheel housing portion; a worm wheel having gear teeth on an outer peripheral surface and rotatably supported inside the worm wheel housing portion; a worm having worm teeth meshing with the gear teeth on an outer peripheral surface and rotatably supported inside the worm housing portion; a support bearing, the support bearing being externally embedded in a top end portion of the worm; and a biasing leaf spring that biases an inner diameter side component toward the worm wheel side, wherein the inner diameter side component is the support bearing or an externally fitted component externally fitted to the support bearing, The urging plate spring is arranged on a side away from the worm wheel in a first direction, i.e., in a portion between an outer peripheral surface of the inner diameter side component and an inner peripheral surface of the outer diameter side component, and the outer diameter side component is the worm housing portion or an embedded component embedded in the worm housing portion. The urging leaf spring has: a load point as a contact portion contacting the outer peripheral surface of the inner diameter side member; and a fulcrum as a portion of the contact portion contacting the inner peripheral surface of the outer diameter side member that is located closest to the load point, and The biasing plate spring exhibits a nonlinear spring characteristic in which the position of the fulcrum changes so as to approach the load point as the deflection amount in the first direction increases, thereby increasing the spring constant.

2. The worm gear reducer according to claim 1, characterized in that: The force leaf spring is configured in a manner extending in a third direction that is orthogonal to both the first direction and the axial direction of the worm housing portion, i.e., the second direction, and the end on either side of the third direction is cantilevered supported on the outer diameter side component, and the end on the other side of the third direction has the load point.

3. The worm gear reducer according to claim 2, characterized in that: The one end portion of the biasing plate spring is cantilever-supported by the outer diameter side member using a pin disposed so as to extend in the second direction.

4. The worm gear reducer according to claim 3, characterized in that: The outer diameter side member is made of an aluminum alloy, and the pin is made of an iron alloy.

5. The worm gear reducer according to claim 2, characterized in that: The inner peripheral surface of the outer diameter side member has a main retaining portion and a secondary retaining portion. The main retaining portion is larger than the outer peripheral surface of the inner diameter side component and the inner diameter side component is arranged inside. The auxiliary holding portion extends outwardly from an end of the main holding portion on a side away from the worm wheel in the first direction, and the biasing leaf spring is arranged inside. When viewed from the second direction, the main retaining portion exists in a circumferential range that can intersect with a radial straight line (L1) and can intersect with a radial straight line (L2), the radial straight line (L1) containing a vector of a meshing reaction force (F1) applied to the worm from a meshing portion between the worm tooth and the gear tooth when the worm rotates in a predetermined direction, and the radial straight line (L2) containing a vector of a meshing reaction force (F2) applied to the worm from the meshing portion when the worm rotates in a direction opposite to the predetermined direction, The inclination angle of the radial straight line (L2) relative to the third direction is smaller than the inclination angle of the radial straight line (L1) relative to the third direction, The portion of the auxiliary holding portion where the one end of the biasing plate spring is arranged is arranged on the same side as the radial straight line (L2) relative to the central axis of the worm in the third direction.

6. The worm gear reducer according to claim 2, characterized in that: The outer diameter side member includes a plurality of corner portions that are spaced apart from each other in the third direction as portions that come into contact with the biasing leaf spring during operation.

7. The worm gear reducer according to claim 6, characterized in that: The biasing plate spring is configured to be able to simultaneously contact two or more corner portions among the plurality of corner portions during operation.

8. The worm gear reducer according to claim 2, characterized in that: The outer diameter side member includes a convex curved surface portion as a portion that contacts the biasing leaf spring during operation.

9. The worm gear reducer according to any one of claims 1 to 8, characterized in that: The worm gear reducer includes an elastic clamping unit that clamps the inner diameter side member from both sides in a third direction that is orthogonal to both the first direction and the axial direction of the worm housing portion, that is, the second direction. The elastic clamping unit includes a pair of clamping leaf springs, the pair of clamping leaf springs being arranged on both sides of the third direction in a portion between the outer peripheral surface of the inner diameter side member and the inner peripheral surface of the outer diameter side member. Each of the pair of clamping leaf springs exhibits a nonlinear spring characteristic in which a spring constant increases as the deflection amount in the third direction increases.

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