JP6665663B2 - Gear reducer - Google Patents

Description

  The present invention relates to a gear reduction device including a worm and a wheel gear.

  Patent Literature 1 discloses a technology of a gear reduction device including a worm driven by an electric motor and a wheel gear meshing with the worm, as a part of a mechanism constituting an electric power steering device.

  In Patent Literature 1, a side driven by an electric motor among a pair of ends of a worm is rotatably supported by a first bearing in a fixed position. The other end of the worm is supported so as to be displaceable in a first direction toward the wheel gear, and is supported in a state where displacement in a second direction orthogonal to the first direction is regulated. ing.

  Further, Patent Document 1 includes an urging mechanism having a compression coil spring for applying an urging force to mesh the teeth of the worm shaft with the teeth of the wheel gear along the first direction.

  Patent Literature 2 discloses a technique related to a gear reduction device that forms a part of a mechanism that forms an electric power steering device as in Patent Literature 1. Specifically, a concave surface is formed at each of the opposite ends of the motor shaft and the worm shaft of the electric motor, and a centering means having a configuration in which a sphere is fitted into these concave surfaces is provided. A torque transmission means for transmitting the torque to the shaft is provided.

  In Patent Literature 2, the motor shaft of the electric motor is supported by ball bearings, and the end of the worm shaft opposite to the alignment means is supported by ball bearings in a fixed position.

JP 2013-87868 A JP 2000-211537 A

  A gear reduction device that drives a worm with an electric motor or the like and extracts reduction power from a wheel gear that meshes with the worm can obtain a high reduction ratio, and when the electric motor stops, a self-lock state is reached. It has a good surface against which wheel gear rotation is prevented.

  However, in the gear reduction device having this configuration, when a large load is applied, a large force acts between the worm and the wheel gear, so that the positional relationship between the worm and the wheel gear temporarily changes from an appropriate position. In some cases, the clutch slipped off, fell into an abnormal meshing state, and generated abnormal noise.

  In order to cope with such inconvenience, in the technique disclosed in Patent Document 1, the shaft end of the worm can be displaced in the direction away from the wheel gear in the second bearing when a large load is applied. It is also conceivable that abnormal engagement can be suppressed as well as suppression.

  However, since the technique of Patent Document 1 is originally intended to remove backlash, the displacement of the worm is small, and a sufficient effect cannot be expected.

  Also, in the technology disclosed in Patent Document 2, similarly to Patent Document 1, when a large load is applied, the shaft end of the worm is displaced in a direction away from the wheel gear, and the effect of excessive pressure is suppressed. It is also conceivable that abnormal meshing can be suppressed.

  However, in the technique of Patent Document 2, since the worm is centered for the purpose of securing the shaft rigidity, the displacement of the worm is small, and a sufficient effect cannot be expected.

  Furthermore, as a technology for suppressing the generation of abnormal noise, both ends of the worm are supported by bearings such as ball bearings, and when a large load is applied by applying a spring biasing force to each bearing, the worm and the bearings at both ends are used together. A configuration in which the worm is displaced so as to be separated from the wheel gear is also conceivable, but this technology is likely to cause an increase in size and has room for improvement.

  For these reasons, it is required to reduce the size of a reduction gear that does not generate abnormal noise even when a large load acts.

A feature of the present invention is a worm having a worm tooth portion at a central position of a worm shaft that rotates about a drive shaft center,
A wheel gear that meshes with the worm tooth portion is provided on the outer periphery, and a wheel gear that rotates about an output shaft center in a posture orthogonal to the drive shaft center is provided.
At the outer end portions at both ends of the worm shaft, a support shaft surface which is tapered and swells outward smoothly with reference to the drive shaft center and serves as a rotation surface around the drive shaft center is formed,
A bearing mechanism that supports both ends of the worm is configured with a bearing having an opening into which the outer end of the worm shaft is inserted,
The opening portion has a shape extending in a direction that allows displacement in a direction in which the worm tooth portion is separated from the wheel tooth portion, and a bearing surface having an inner surface shape along an outer periphery of the support shaft surface,
At least one of the pair of bearing portions includes an urging mechanism that applies an urging force in a direction in which the worm tooth portion meshes with the wheel tooth portion by contacting the outer end portion inserted into the opening. It has a point.

According to this, in a situation where both ends of the worm shaft are supported by the bearing mechanism, the state in which the worm teeth mesh with the wheel teeth is maintained by the urging force of the urging mechanism. Further, since the support shaft surface of the worm shaft is formed as a rotating surface that is tapered and smoothly expands outward with respect to the drive shaft center, and the bearing surface of the bearing portion is shaped along the outer periphery of the support shaft surface, The worm shaft is supported in a centered state at both ends by the contact of the support shaft surface with the bearing surface.
When a large load acts on the wheel gear, the displacement of the worm shaft is allowed in the opening of the bearing mechanism, so that the worm tooth separates from the wheel tooth against the urging force of the urging mechanism. In this displacement, the worm tooth portion does not displace in the direction of the width of the wheel tooth portion, so that an abnormal meshing state does not occur. In particular, since this configuration does not require a bearing such as a ball bearing, the size of the apparatus does not increase.
Therefore, a reduction gear that does not generate abnormal noise even when a large load acts is configured to be small.

  In the present invention, a curvature of the support shaft surface in a direction perpendicular to the drive shaft core may be set to be larger than a curvature of the bearing surface in a direction perpendicular to the drive shaft core.

  According to this, in a state in which the spindle surface comes into contact with the bearing surface, they come into contact with each other in a relatively small area, and a gap is formed between the bearing surface and the spindle surface at the outer peripheral position of this contact region. Therefore, the posture of the worm shaft can be changed. Further, since the support shaft surface is formed as a rotation surface about the drive shaft center, the posture of the worm shaft can be smoothly changed while maintaining the centering function.

  In the present invention, a cross section orthogonal to the drive shaft core at a portion where the bearing surface is formed in at least one of the openings of any of the pair of bearing portions separates the worm from the wheel gear. The support shaft surface may be formed as a long hole extending in a possible direction, and a part of the inner surface of the opening may be formed at an end position of the long hole in the longitudinal direction.

  According to this, even when the worm is displaced in a direction away from the wheel gear, the outer end of the worm shaft is displaced along the longitudinal direction of the long hole, so that the worm tooth is in the width direction of the wheel tooth. It does not cause any inconvenience of displacement and does not fall into an abnormal meshing state.

In the present invention, a through hole is formed in one of the pair of bearing portions in a direction along the drive shaft core,
A spring material for connecting the outer end portion of the worm shaft inserted into the bearing portion and a drive shaft of an actuator for driving and rotating the worm may be disposed so as to pass through the through hole.

  According to this, the spring material is elastically deformed even when the relative position between the outer end of the worm shaft and the drive shaft of the actuator changes due to the displacement of the worm in a direction away from the wheel gear. Thereby, the driving force of the drive shaft of the actuator can be transmitted to the worm shaft.

  In the present invention, the biasing mechanism includes a contact member having a spherical contact surface that contacts the outer end portion or the support shaft surface of the worm shaft, and a spring that biases the contact member. May be.

  According to this, the contact member urged by the spring comes into contact, and the state in which the support shaft surface is brought into contact with the bearing surface by the urging force can be maintained. Further, when the worm shaft rotates, the contact member comes into contact with the outer end of the worm shaft or the outer surface of the support shaft surface, so that the worm shaft can rotate smoothly.

It is sectional drawing of a gear reduction gear. It is sectional drawing of a 1st bearing mechanism and a 2nd bearing mechanism. It is sectional drawing of the 1st bearing mechanism and the 2nd bearing mechanism at the time of load increase. FIG. 4 is a sectional view taken along line IV-IV of FIG. 3. FIG. 5 is a sectional view taken along line VV of FIG. 3. It is sectional drawing of the 1st bearing mechanism and 2nd bearing mechanism of another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Basic configuration)
As shown in FIG. 1, a worm A rotatable around a drive shaft X and a wheel gear B rotatable around an output shaft Y orthogonal to the drive shaft X are housed in a housing 1. A gear reduction device 100 is configured.

  The gear reduction device 100 is used, for example, in a vehicle such as an automobile, as a driving source for setting a seat back posture of a driver seat, operating a power slide door, and opening and closing a sunroof.

  The worm A is formed of a metal material or a resin material. The worm A has a helical worm tooth 3 centered on the drive shaft X at the center of the worm shaft 2 arranged coaxially with the drive shaft X. It has. Both ends of the worm shaft 2 are rotatably supported by the housing 1 by a bearing mechanism C.

  The wheel gear B has a plurality of wheel teeth portions 6 formed on the outer periphery of a disk-shaped portion 5 that is circular with the output shaft center Y as a center. An output shaft 7 is provided. The wheel gear B is rotatably supported on the housing 1 by a bearing such as a ball bearing.

  With this configuration, when the worm A is driven and rotated by the electric motor 9 as an actuator, the wheel gear B is rotated, and deceleration power is output from the output shaft 7.

  In particular, in the gear reduction device 100, even when a load acting on the output shaft 7 increases and a large force acts in a direction to separate the worm A from the wheel gear B, generation of abnormal noise due to the action of the force is suppressed. The bearing mechanism C is configured to allow the displacement of the drive shaft core X of the worm shaft 2 in such a manner.

(Bearing mechanism)
As shown in FIGS. 1 and 2, the bearing mechanism C includes a first bearing mechanism C1 at a position (left side in FIG. 1) separated from the electric motor 9 in a direction along the drive axis X, and an electric motor at the opposite side. 9 (the right side in FIG. 1). Each bearing mechanism C includes a block-shaped bearing portion 11, and these bearing portions 11 are supported by being fitted into the housing 1.

  The outer end portions 2a at both ends of the worm shaft 2 are formed with a support shaft surface 2as which is tapered and smoothly swells outward and serves as a rotation surface around the drive shaft center X. The support surface 2as may have any shape as long as it has a centering function, but in the present embodiment, the support surface 2as formed in a hemispherical shape is shown.

  Each of the bearings 11 has an opening 11a into which the outer end 2a of the worm shaft 2 is inserted, on one end face in a direction along the drive shaft core X, and an opening 11a on the other end face. The communicating through-hole 11b is formed in a direction along the drive shaft core X. The opening 11a is provided with a bearing surface 11as having an inner shape along the outer periphery of the support shaft surface 2as.

  In particular, the curvature of the support shaft surface 2as when viewed in a direction perpendicular to the drive shaft core X is set slightly larger than the curvature of the bearing surface 11as when viewed in a direction perpendicular to the drive shaft core X. In this embodiment, since the support surface 2as is hemispherical, the radius of the support surface 2as is set smaller than the radius of the bearing surface 11as.

  As shown in FIGS. 4 and 5, in the opening 11 a formed in each bearing portion 11, a cross section in a position orthogonal to the drive shaft core X at a portion where the bearing surface 11 as is formed has a worm A. It is formed in the shape of a long hole extending in a direction in which it can be separated from the wheel gear B. Of the inner surface of the opening 11a, the above-described bearing surface 11as is provided at both ends in the longitudinal direction of the long hole (vertical ends in the figure). It is formed.

  That is, the longitudinal direction of the opening 11a is set to a direction extending along a virtual plane where the disk-shaped portion 5 of the wheel gear B is formed. Accordingly, even when the outer end 2a of the worm shaft 2 is displaced along the opening 11a, the worm tooth 3 is not displaced in the face width direction of the wheel tooth 6, so that the unbalanced engagement is suppressed. Is configured.

  As a specific configuration, as shown in FIGS. 4 and 5, the length L in the longitudinal direction of the long hole of the opening 11 a is a value sufficiently larger than the diameter of the outer end 2 a of the worm shaft 2, The width W of the opening 11a, which is orthogonal to the longitudinal direction of the long hole, is set to a value slightly larger than the diameter of the outer end 2a of the worm shaft 2.

  In the first bearing mechanism C1 and the second bearing mechanism C2, the shaft surfaces 2as formed on the pair of outer ends 2a of the worm shaft 2 are formed in the same shape. Also, the bearing surfaces 11as of the respective bearing portions 11 are formed in the same shape.

  The bearing portion 11 of the first bearing mechanism C1 includes an urging mechanism 15 for applying an urging force for bringing the worm A closer to the wheel gear B.

  The biasing mechanism 15 has a hemispherical contact surface that can contact the outer peripheral surface of the outer end 2 a of the worm shaft 2, and the contact mechanism is slidably accommodated in the guide hole 11 c of the bearing 11. It comprises a member 15a and a compression coil type spring 15b for urging the contact member 15a.

  Further, the outer end 2a of the worm shaft 2 supported by the bearing 11 of the second bearing mechanism C2 and the output shaft 9a of the electric motor 9 are connected by a spring member 17 so as to be able to transmit torque. The spring member 17 is disposed at a position where it is inserted into the through hole 11b.

  The spring member 17 is made of a material which has a square cross section and can be elastically deformed flexibly in the bending direction. One end of the spring member 17 is inserted through a fitting hole of the outer end 2 a of the worm shaft 2, and the other end is inserted through a fitting hole of the output shaft 9 a of the electric motor 9. Note that one end of the spring member 17 may be slidably inserted into the fitting hole.

(Drive form)
Since the load acting on the output shaft 7 is low when the electric motor 9 is stopped or when the electric motor 9 is driven with a low load, the first bearing mechanism C1 uses the urging force of the urging mechanism 15 as shown in FIG. The state where the support shaft surface 2as of the worm shaft 2 abuts on the bearing surface 11as of the opening 11a of the bearing portion 11 at a position close to the wheel gear B is maintained.

  As described above, since the posture of the worm shaft 2 is determined by the urging force of the urging mechanism 15, in the second bearing mechanism C <b> 2, the support shaft surface 2 as of the worm shaft 2 The state of contact with the bearing surface 11as at a position separated from the bearing surface is maintained.

  In a state where the posture of the worm shaft 2 is determined by the urging force of the urging mechanism 15, the worm tooth portion 3 and the wheel tooth portion 6 are designed to mesh with each other in an optimal state. Further, in each of the bearing portions 11, the support shaft surface 2as of the worm shaft 2 comes into contact with the bearing surface 11as, so that the outer end portion 2a of the worm shaft 2 in each bearing portion 11 reaches an alignment state, and the worm shaft 2 (The attitude of the drive shaft center X) is stabilized.

  When the electric motor 9 is driven and the load acting on the output shaft 7 rises above a preset value, a force is exerted on the worm tooth 3 to separate it from the wheel tooth 6. As a result, the bearing 11 of the first bearing mechanism C1 is displaced against the biasing force of the spring 15b of the biasing mechanism 15 as shown in FIG. The opening 11a of the portion 11 reaches a state in which it comes into contact with the bearing surface 11as at a position where the urging mechanism 15 is provided.

  Since the attitude of the worm shaft 2 is determined in this manner, in the second bearing mechanism C2, as shown in FIG. 3, the support shaft surface 2as of the worm shaft 2 is close to the wheel gear B in the opening 11a of the bearing portion 11. The state of contact with the bearing surface 11as at the position is maintained.

  In addition, since the rotational force of the output shaft 9a of the electric motor 9 is transmitted to the outer end 2a of the worm shaft 2 by the spring member 17, the spring member 17 is elastically deformed so as to bend even when the posture of the worm shaft 2 changes. Driving is performed in the state.

  Even when the attitude of the worm shaft 2 is changed in this way, since the support shaft surface 2as of the worm shaft 2 abuts the bearing surface 11as in each of the bearing portions 11, the outer surface of the worm shaft 2 in each of the bearing portions 11 is formed. The end 2a reaches the alignment state, and the attitude of the worm shaft 2 (the attitude of the drive axis X) is stabilized.

  With such a configuration, when an excessive load acts on the output shaft 7, the worm A is displaced in a direction away from the wheel gear B. Since this displacement is performed along the opening 11a formed in the shape of a long hole, the worm tooth portion 3 does not fall into a positional relationship deviated to one side in the tooth width direction of the wheel tooth portion 6. As a result, the inconvenience of the worm tooth portion 3 and the wheel tooth portion 6 falling into an abnormal meshing state is suppressed, and no abnormal noise is generated. Note that the displacement of the worm A also suppresses the damage of the worm teeth 3 and the wheel teeth 6.

  In particular, in this configuration, although the configuration does not use a bearing such as a ball bearing, it is possible to maintain the accuracy of the drive shaft X of the worm shaft 2 at a high level, and no bearing is required. And cost reduction has been realized.

[Another embodiment]
The present invention may be configured as follows in addition to the above-described embodiment (those having the same functions as those of the embodiment are denoted by the same reference numerals and symbols as those of the embodiment).

(A) As shown in FIG. 6, the support shaft surface 2 as a tapered and smoothly swelling outward with respect to the outer end portions 2 a at both ends of the worm shaft 2, and serving as a rotation surface about the drive shaft core X. , In a shape protruding in the direction of the drive shaft center X as compared with the hemisphere.

  In this alternative embodiment, the opening 11a of the bearing portion 11 is formed in a long hole shape as in the embodiment, and the curvature of the support shaft surface 2as is set to be larger than the curvature of the bearing surface 11as. In particular, although a biasing mechanism 15 having the same configuration as that of the embodiment is provided for the first bearing mechanism C1 constituting the bearing mechanism C, the position at which the support shaft surface 2as abuts on the biasing force of the biasing mechanism 15 (see FIG. The bearing surface 11as is formed only on the lower side).

  Further, in the second bearing mechanism C2 constituting the bearing mechanism C, the above-described bearing surfaces 11as are formed on both ends in the longitudinal direction of the long hole (the vertical direction in FIG. 6) as in the embodiment.

  Even with such a configuration, when the load acting on the output shaft 7 fluctuates, the outer end portion 2a of the worm shaft 2 can be supported in the centered state in the second bearing mechanism C2.

(B) The biasing mechanism 15 is provided in both the first bearing mechanism C1 and the second bearing mechanism C2. When the urging mechanism 15 is provided as described above, the first bearing mechanism C1 applies an urging force in the same direction as the embodiment so that the worm shaft 2 is maintained in the same posture as the embodiment at a low load. The second bearing mechanism C2 can be configured to apply an urging force to the opposite side.

(C) As a transmission structure for transmitting the driving force of the electric motor 9 to the worm shaft 2, a spline structure that fits between the end of the worm shaft 2 and the end of the output shaft 9a so as to freely transmit torque, a dog, and the like. By providing a structure similar to that of the clutch, the spring member 17 may not be used.

  INDUSTRIAL APPLICABILITY The present invention can be used for a gear reduction device including a worm and a wheel gear that meshes with the worm.

2 Worm shaft 2a Outer end 2as Support shaft surface 3 Worm teeth 6 Wheel teeth 9 Electric motor (actuator)
11 Bearing 11a Opening 11b Through Hole 11as Bearing Surface 15 Biasing Mechanism 15a Contact Member 15b Spring 17 Spring Material 100 Gear Reduction Device A Worm B Wheel Gear C Bearing Mechanism X Drive Shaft Center Y Output Shaft Center

Claims (5)

A worm having a worm tooth portion at a central position of a worm shaft that rotates about a drive shaft center;
A wheel gear that meshes with the worm tooth portion is provided on the outer periphery, and a wheel gear that rotates about an output shaft center in a posture orthogonal to the drive shaft center is provided.
At the outer end portions at both ends of the worm shaft, a support shaft surface which is tapered and swells outward smoothly with reference to the drive shaft center and serves as a rotation surface around the drive shaft center is formed,
A bearing mechanism that supports both ends of the worm is configured with a bearing having an opening into which the outer end of the worm shaft is inserted,
The opening portion has a shape extending in a direction that allows displacement in a direction in which the worm tooth portion is separated from the wheel tooth portion, and a bearing surface having an inner surface shape along an outer periphery of the support shaft surface,
At least one of the pair of bearing portions includes an urging mechanism that applies an urging force in a direction in which the worm tooth portion meshes with the wheel tooth portion by contacting the outer end portion inserted into the opening. Gear reducer provided.   2. The gear reduction device according to claim 1, wherein a curvature of the support shaft surface is set to be larger than a curvature of the bearing surface when viewed in a direction perpendicular to the drive shaft core.   Of the at least one of the pair of bearing portions, at least one of the openings, a cross section orthogonal to the drive shaft center at a portion where the bearing surface is formed is in a direction in which the worm can be separated from the wheel gear. 3. The gear reduction according to claim 1, wherein the shaft is formed as an elongated hole, and the shaft surface is formed at a longitudinal end position of the elongated hole in a part of an inner surface of the opening. 4. apparatus. A through hole is formed in one of the pair of bearing portions in a direction along the drive shaft core,
A spring material for connecting the outer end portion of the worm shaft inserted into the bearing portion and a drive shaft of an actuator for driving and rotating the worm is disposed so as to pass through the through hole. The gear reduction device according to claim 3.   The said urging mechanism is provided with the contact member which has a spherical contact surface which contacts the said outer end part or the said support shaft surface of the said worm shaft, and the spring which urges this contact member. The gear reduction device according to any one of claims 1 to 4.

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