JP2019100408A - Belt transmission device and steering device - Google Patents

Abstract

To provide a belt transmission device which can inhibit increase of operation sound caused by inclination of a driving pulley, and to provide a steering device.SOLUTION: A belt transmission device includes: a housing; a motor fixed to an outer surface of the housing; a cylindrical driving pulley 31 which integrally rotates with an output shaft 18a of the motor; a driven pulley rotatably supported within the housing; a belt wound around the driving pulley 31 and the driven pulley; and a joint 81 which is provided within the driving pulley 31 and couples the output shaft 18a to the driving pulley 31 in a manner that the output shaft 18a can swing along a direction in which tensile force of the belt 33 acts. The joint 81 has: a torque transmission part 83 which is supported within the driving pulley 31 so that the torque transmission part 83 can swing along a direction in which the tensile force of the belt 33 acts; and a connection part 82 which connects the torque transmission part 83 to a tip part of the output shaft 18a.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a belt transmission and a steering device.

  Conventionally, as described in, for example, Patent Document 1, electric power steering that decelerates the rotation of a motor by a belt transmission mechanism and converts the decelerated rotation into axial movement of a rack shaft by a ball screw mechanism provided on the rack shaft The device is known. The belt transmission mechanism includes a drive pulley provided on an output shaft of a motor, a driven pulley provided on a ball nut fitted to a ball screw portion of a rack shaft through a large number of balls, and a belt stretched between these pulleys And. The steering is assisted by the rack shaft moving in the axial direction with the rotation of the ball nut through the drive of the motor.

JP, 2013-159203, A (Drawing 1)

  As shown in FIG. 13, the output shaft 203 of the motor 202 is fixed to the drive pulley 201 in a press-fitted state. Therefore, the tension of the belt 204 acts on the tip end portion of the output shaft 203 via the drive pulley 201. Here, the output shaft 203 of the motor 202 is rotatably supported relative to the inner peripheral surface of the motor case 206 via the bearing 205, and between the inner ring 207 of the bearing 205 and the ball 208. There is a so-called internal clearance 210 between the outer ring 209 and the ball 208. Therefore, the output shaft 203 may tilt in the direction in which the tension F acts with the drive pulley 201 according to the internal clearance 210 of the bearing 205. When the drive pulley 201 is tilted, a situation occurs in which the belt 204 is in partial contact with the outer peripheral surface of the drive pulley 201. That is, the portion on the motor 202 side of the belt 204 is maintained in contact with the outer peripheral surface of the drive pulley 201, while the portion on the opposite side of the motor 202 of the belt 204 is separated from the outer peripheral surface of the drive pulley 201 Maintained. Due to the contact of the belt 204 against the outer peripheral surface of the drive pulley 201, the operating noise of the belt transmission mechanism may be increased.

  An object of the present invention is to provide a belt transmission and a steering device capable of suppressing an increase in operation noise caused by the inclination of a drive pulley.

  A belt transmission capable of achieving the above object has a housing, a motor fixed to the outer surface of the housing and having an output shaft inserted into the housing, and housed within the housing with the output shaft A cylindrical drive pulley that rotates integrally, a driven pulley rotatably supported inside the housing, a belt wound around the drive pulley and the driven pulley, and a drive pulley provided inside the drive pulley And a joint pivotally connecting the output shaft along the direction in which the belt tension acts on the drive pulley.

  The tension in the belt may cause the output shaft to tilt through the joint in the same direction as the tension acts. In this respect, according to the above configuration, the output shaft is swingably connected to the drive pulley through the joint. For this reason, it is suppressed that a drive pulley inclines with an output shaft. Thus, the belt is maintained in proper contact with the drive pulley. Since the situation where the belt does not hit the drive pulley is also less likely to occur, the increase in the operation noise of the belt transmission can also be suppressed.

  In the above-described belt transmission, the joint is provided with a first connecting portion supported so as to be able to swing along a direction in which the tension of the belt acts inside the driving pulley, the first connecting portion, and the first connecting portion. And a second connecting portion that connects the distal end portion of the output shaft.

  In the above-described belt transmission, the joint may be a universal joint having a first connection member and a second connection member swingably connected to each other. In this case, the first connection member is fixed to the inside of the drive pulley, and the end of the second connection member opposite to the second connection member is connected to the output shaft. Is preferred.

  In the above-described belt transmission, the first connection member has a hole opened in the axial direction and provided with a plurality of grooves extending along the axial direction in the inner circumferential surface, and the second connection is provided. The member may have a first transmission portion inserted in the hole in a retaining state, and a second transmission portion connecting the first transmission portion and the tip of the output shaft. preferable. In this case, in the first transmission portion, the outer diameter gradually increases from the tip to the base along the insertion direction with respect to the hole, and the outer diameter is bordered at a portion where the outer diameter is the largest. It is preferable to have a shape that gradually becomes smaller. In addition, the cross-sectional shape in the direction orthogonal to the axis of the first transmission portion is a polygonal shape, along a plurality of corners extending from the tip of the first transmission portion toward the base, It is preferable that an engagement peak portion fitted to the plurality of groove portions provided on the inner circumferential surface of the hole portion be provided.

  In the above-described belt transmission, the joint includes a cylindrical first connecting member having a first flange, a cylindrical second connecting member having a second flange, the first flange, and the first flange. It may have a plate spring provided between the second flange and a plurality of bolts for fixing the plate spring to the first flange and the second flange at a plurality of points. In this case, while the first connection member is fixed inside the drive pulley, the second connection member is provided on the output shaft in a state of being provided with a gap from the inner peripheral surface of the drive pulley. Preferably, they are linked.

In the above-described belt transmission, it is preferable that an axial position of a support point of the joint with respect to the drive pulley is in a range in which the belt is hooked on the drive pulley.
The above-mentioned belt transmission is suitable for a steering device. A steering device is screwed with the above-mentioned belt transmission, a steered shaft linearly moving inside the housing, and a large number of balls on the steered shaft, and a bearing on the inner circumferential surface of the housing. Preferably, a ball nut rotatably supported is provided, and the driven pulley is integrally rotatably fitted to an outer peripheral surface of the ball nut.

  According to the belt transmission and the steering device of the present invention, it is possible to suppress an increase in operation noise caused by the inclination of the drive pulley.

The front view of 1st Embodiment which applied the belt transmission to the electric-power-steering apparatus. Sectional drawing to which the principal part of the electric-power-steering apparatus in 1st Embodiment was expanded. Sectional drawing which shows the connection part of the motor in 1st Embodiment, and the output shaft of a motor, and a drive pulley. The perspective view of the coupling in a 1st embodiment. 5 is a cross-sectional view taken along line 5-5 of FIG. 3; Sectional drawing which shows the inclination range of the coupling | joint in 1st Embodiment. Sectional drawing which shows the connection part of the said output shaft and drive pulley when the output shaft of a motor inclines in 1st Embodiment. The longitudinal cross-sectional view of the coupling | joint in 2nd Embodiment which applied the belt transmission to the electric-power-steering apparatus. 9 is a sectional view taken along line 9-9 of FIG. Sectional drawing which shows the connection part of the said output shaft and drive pulley when the output shaft of a motor inclines in 2nd Embodiment. Sectional drawing of the coupling | joint in 3rd Embodiment which applied the belt transmission to the electric-power-steering apparatus. In 3rd Embodiment, the schematic diagram which shows the connection part of the said output shaft and drive pulley when the output shaft of a motor inclines. Sectional drawing which shows the connection part of the motor and drive pulley in the conventional electric-power-steering apparatus.

First Embodiment
Hereinafter, a first embodiment in which the steering device is embodied in an electric power steering device will be described.

  As shown in FIG. 1, the electric power steering apparatus 10 has a housing 11 fixed to a vehicle body (not shown). The housing 11 is provided such that its cylindrical main body 12 extends in the left-right direction (left-right direction in FIG. 1) of the vehicle body. The rack shaft 13 is inserted into the main body 12. Wheels (turning wheels) W are connected to both ends of the rack shaft 13 via ball joints (not shown). The direction of the wheel W is changed by the rack shaft 13 moving in its own axial direction.

<First storage unit>
A first housing portion 14 is provided at a portion near the right end of the main body 12. The first housing portion 14 extends in a direction obliquely intersecting with the axial direction (left and right direction in FIG. 1) of the main body 12. The first housing portion 14 is rotatably supported in a state in which the pinion shaft 15 is inserted. The pinion teeth provided at the inner end of the pinion shaft 15 mesh with the rack teeth formed in a predetermined range near the right end of the rack shaft 13. The outer end of the pinion shaft 15 opposite to the pinion teeth is connected to the steering wheel H via a plurality of shafts (not shown). Therefore, along with the steering operation, the rack shaft 13 linearly moves along its axial direction. The torque acting on the pinion shaft 15 through the steering operation is detected by a torque sensor 16 provided in the first accommodation portion 14.

<Second container>
A second accommodation portion 17 is provided at a portion near the left end of the main body 12. The lower part of the cylindrical portion having a diameter larger than that of the main body 12 of the second housing portion 17 extends downward. A motor 18 is fixed to the right side wall 21 a at the lower part of the second housing portion 17. The output shaft 18 a of the motor 18 extends along the axis of the rack shaft 13 and is inserted inside through a hole 21 b provided in the side wall 21 a of the second accommodation portion 17. A power conversion mechanism 20 is provided inside the second housing portion 17. An output shaft 18 a of the motor 18 is connected to the power conversion mechanism 20. The power conversion mechanism 20 converts the rotational movement of the motor 18 into the linear movement of the rack shaft 13. That is, the steering operation is assisted by assisting the operation of the rack shaft 13 through the use of the rotational force of the motor 18. The motor 18 is controlled by a control device (not shown) according to the detection result of the torque sensor 16 or the like.

<Power conversion mechanism>
As shown in FIG. 2, the power conversion mechanism 20 has a belt transmission mechanism 30 and a ball screw mechanism 40. The belt transmission mechanism 30 transmits the rotational movement of the motor 18 to the ball screw mechanism 40. The ball screw mechanism 40 converts the rotational movement of the motor 18 transmitted through the belt transmission mechanism 30 into the linear movement of the rack shaft 13.

<Ball screw mechanism>
The ball screw mechanism 40 has a ball screw portion 41 provided on the rack shaft 13, a cylindrical ball nut 42 and a large number of balls 43.

  The ball screw portion 41 is a portion on the outer peripheral surface of the rack shaft 13 in which the ball screw groove 13 a is formed. The ball screw portion 41 is provided in a fixed range directed to the right end with reference to the left end of the rack shaft 13. The ball nut 42 is screwed to the ball screw portion 41 via a large number of balls 43 so as to be movable back and forth. A ball bearing 44 is fixed to the outer peripheral surface of the ball nut 42. The ball nut 42 is rotatably supported by the ball bearing 44 with respect to the housing 11, more precisely, the inner peripheral surface of the second housing portion 17.

<Belt Transmission Mechanism>
The belt transmission mechanism 30 includes a cylindrical drive pulley 31, a cylindrical driven pulley 32 and an endless belt 33.

  The drive pulley 31 is connected to an output shaft 18 a of the motor 18 via a joint 81. The driven pulley 32 is fixed to the outer peripheral surface of the ball nut 42. The driven pulley 32 and the ball bearing 44 are adjacent to each other in the axial direction of the ball nut 42. The ball bearing 44 is provided on the side of the externally threaded portion 42a, and the driven pulley 32 is provided on the side of the collar portion 42b. The belt 33 is stretched between the drive pulley 31 and the driven pulley 32. Therefore, the rotation of the motor 18 is transmitted to the ball nut 42 via the drive pulley 31, the belt 33 and the driven pulley 32.

  The driving pulley 31 and the driven pulley 32 are toothed pulleys (timing pulleys) whose teeth are provided on their outer peripheral surfaces. Further, the belt 33 is a toothed belt (timing belt) provided with teeth on its inner circumferential surface. The number of teeth of the belt 33 is set to be a non-integer multiple with respect to the number of teeth of the drive pulley 31 and the number of teeth of the driven pulley 32 respectively.

<Fixing structure of ball bearing and driven pulley>
Next, the fixing structure of the ball bearing 44 and the driven pulley 32 will be described.
As shown in FIG. 2, in a state where the driven pulley 32 and the ball bearing 44 are fitted on the outer peripheral surface of the ball nut 42, it is provided on the outer peripheral surface of the first end (left end in FIG. 2) of the ball nut 42. The driven pulley 32 and the ball bearing 44 are respectively fixed to the ball nut 42 by tightening the lock nut 45 on the externally threaded portion 42 a. In a state where the ball bearing 44 and the driven pulley 32 are nipped by the lock nut 45 and the collar 42 b provided on the outer peripheral surface of the second end (right end in FIG. 2) in the axial direction of the ball nut 42 By being held, the positions of the ball bearing 44 and the driven pulley 32 relative to the ball nut 42 in the axial direction are restrained. Further, the axial position of the ball bearing 44 with respect to the second accommodation portion 17 is restrained by the outer ring thereof being sandwiched by the annular support members 51 and 52 in the axial direction.

<Mounting position of motor>
Next, the mounting position of the motor 18 will be described. In this example, it is possible to adjust the mounting position of the motor 18 with respect to the second housing portion 17 (more precisely, the side wall 21a thereof). As shown in FIG. 2, the adjustment direction D of the mounting position of the motor 18 is a direction along a straight line L3 orthogonal to both the axis L1 of the drive pulley 31 and the axis L2 of the driven pulley 32.

  As shown in FIG. 2, the drive pulley 31 is connected to an output shaft 18 a of the motor 18 via a joint 81. Therefore, when the mounting position of the motor 18 in the adjustment direction D is changed, the position of the drive pulley 31 in the adjustment direction D, and in turn, the inter-core distance ΔL between the drive pulley 31 and the driven pulley 32 also changes. The inter-core distance ΔL is a distance between the axis L1 of the drive pulley 31 and the axis L2 of the driven pulley 32. As the drive pulley 31 approaches the driven pulley 32, the inter-core distance ΔL decreases. As the drive pulley 31 separates from the driven pulley 32, the inter-core distance ΔL increases. That is, it is possible to adjust the inter-core distance ΔL through adjustment of the mounting position of the motor 18. In the electric power steering apparatus 10, the tension of the belt 33 is appropriately set through the adjustment of the inter-core distance ΔL from the viewpoint of securing the torque transmission efficiency of the motor 18 or the like.

<Motor>
Next, the motor 18 will be described in detail.
As shown in FIG. 3, the motor 18 has a cylindrical motor case 71, a cylindrical stator 72, two bearings 73 and 74, and a cylindrical rotor 76 in addition to the output shaft 18a.

  The bearing 73 is fixed in a state of being press-fitted into the housing portion 72 a provided on the inner bottom surface of the first end portion (left end portion in FIG. 3) of the motor case 71. The bearing 74 is fixed in a state of being press-fitted into the housing portion 72 b provided on the inner bottom surface of the second end (right end in FIG. 3) of the motor case 71. As the bearings 73 and 74, for example, a ball bearing which is a kind of rolling bearing is employed.

  The output shaft 18 a is rotatably supported relative to the motor case 71 via two bearings 73 and 74. A first end (left end in FIG. 3) of the output shaft 18a penetrates the first end of the motor case 71 and protrudes to the outside.

The rotor 76 is fixed to the outer peripheral surface of the output shaft 18 a inside the motor case 71.
<Joint>
The first end (tip end) of the output shaft 18 a is coupled to the drive pulley 31 via a joint 81.

  As shown in FIG. 4, the joint 81 has a connecting portion 82 and a torque transmitting portion 83. The connecting portion 82 and the torque transmitting portion 83 are integrally provided. The connecting portion 82 has a cylindrical shape. The end of the connecting portion 82 opposite to the torque transmitting portion 83 is connected to the output shaft 18 a. The torque transfer unit 83 is coupled to the drive pulley 31.

  The torque transfer portion 83 is provided in a prismatic shape having a diamond shape as viewed in a direction perpendicular to the axis. The torque transfer unit 83 has a first tapered portion 84 and a second tapered portion 85. The first tapered portion 84 is a portion on the tip end side (opposite to the connecting portion 82) with reference to the vicinity of the center in the direction along the axis of the torque transmitting portion 83. The second tapered portion 85 is a portion on the base end side (the connecting portion 82 side) based on the vicinity of the center in the direction along the axis of the torque transmission portion 83.

  The first tapered portion 84 has two inclined surfaces 84a and 84b located on opposite sides of each other. The inclined surfaces 84 a and 84 b are inclined so as to approach each other as the tip end of the torque transfer unit 83 is approached. The second tapered portion 85 has two inclined surfaces 85a and 85b located on opposite sides of each other. The inclined surfaces 85 a and 85 b are inclined so as to approach each other as they go to the proximal end of the torque transfer portion 83. The inclined surface 84 a of the first tapered portion 84 and the inclined surface 85 a of the second tapered portion 85 are continuous with each other in a mutually intersecting manner. The inclined surface 84 b of the first tapered portion 84 and the inclined surface 85 b of the second tapered portion 85 are continuous with each other in a mutually intersecting manner.

  In torque transmission portion 83, as one of the two upper surfaces (upper surface in FIG. 4) orthogonal to inclined surfaces 84a and 84b and inclined surfaces 85a and 85b and opposite to each other (upper surface in FIG. 4) as a support member Ball 86 is provided.

  As shown in FIG. 5, the spherical body 86 is accommodated in the accommodation hole 87 provided in the torque transmission portion 83 in a state of retaining it. The ball 86 is provided to be reciprocally movable along the housing hole 87. A compression coil spring 88 is provided between the ball 86 and the inner bottom surface of the receiving hole 87. The ball 86 is constantly urged in the direction of coming out of the accommodation hole 87 by the elastic force of the compression coil spring 88. The movement of the spherical body 86 in the direction of coming out of the accommodation hole 87 is restricted by the spherical body 86 coming into contact with the portion of the accommodation hole 87 near the opening with a narrowed inner diameter from the inside.

  The drive pulley 31 is provided with a through hole 31 a extending in the axial direction. The cross-sectional shape of the through hole 31 a cut along the direction orthogonal to the axis of the drive pulley corresponds to the cross-sectional shape at the boundary between the first tapered portion 84 and the second tapered portion 85 in the torque transfer portion 83. It has a shape. A hemispherical recess 31 b is provided on the inner side surface of the through hole 31 a. A ball 86 is fitted in the recess 31 b. The spherical body 86 is kept pressed against the inner surface of the recess 31 b by the elastic force of the compression coil spring 88.

  In the torque transfer portion 83, the flat surface 83a where the spherical body 86 is exposed and the flat surface 83b opposite to the flat surface 83a engage with the inner side surface of the through hole 31a in the rotational direction of the drive pulley 31 without looseness. For this reason, the joint 81 including the torque transmission unit 83 and, consequently, the output shaft 18 a of the motor 18 rotate integrally with the drive pulley 31. That is, the rotational force (torque) and the rotational angle of the output shaft 18 a are transmitted to the drive pulley 31 via the joint 81.

  As shown in FIG. 6, the joint 81 swings around the ball 86 with respect to the drive pulley 31. The joint 81 can swing between the first inclined position and the second inclined position with reference to a reference position whose axis coincides with the axis of the drive pulley 31. When the joint 81 inclines from the reference position to the first inclined position, the inclined surface 85a of the torque transfer portion 83 abuts on the inner side surface (inner top surface in FIG. 6) of the through hole 31a of the drive pulley 31. The axis O1 of the joint 81 at this time is inclined at an angle α with respect to the axis O when the joint 81 is at the reference position. When the joint 81 is inclined from the reference position to the second inclined position, the inclined surface 85b of the torque transfer portion 83 abuts on the inner side surface (inner bottom surface in FIG. 6) of the through hole 31a of the drive pulley 31. The axis O2 of the joint 81 at this time is inclined at an angle α with respect to the axis O when the joint 81 is at the reference position.

<Internal clearance of bearing>
Next, the internal clearances of the bearings 73 and 74 will be described.
There are so-called internal clearances in the bearings 73 and 74. The internal clearance means the amount of play between the inner ring and the ball of the bearings 73 and 74 and between the outer ring and the ball. Internal clearances include radial clearances, axial clearances, and angular clearances. The angular clearance means an amount of movement (inclination angle) when the inner ring is inclined in the axial direction in a state where the outer ring is fixed in a state before the bearings 73 and 74 are attached to the motor case 71.

<Operation of Embodiment>
Next, the operation of connecting the output shaft 18 a of the motor 18 to the drive pulley 31 via the joint 81 will be described.

  As shown in FIG. 7, the tension F of the belt 33 is appropriately set through the adjustment of the inter-core distance ΔL, and the tension F causes the drive pulley 31 and the driven pulley 32 to move in the direction approaching each other. Therefore, the first end (the left end in FIG. 7) of the output shaft 18a is directed in the same direction as the direction in which the drive pulley 31 tends to move (the direction in which the tension F acts) via the joint 81. Power acts.

  Here, internal clearances exist in the two bearings 73 and 74 that support the output shaft 18 a of the motor 18. Therefore, when the tension F of the belt 33 acts on the first end of the output shaft 18a via the joint 81, the output shaft 18a may be inclined in accordance with the internal clearance.

  As shown in FIG. 7, when the rotational position of the drive pulley 31 is in a position where the direction along the tension F of the belt 33 (vertical direction in FIG. 7) and the central axis of rotation of the joint 81 are orthogonal to each other, By the tension F of 33, the output shaft 18a is inclined to the direction (clockwise direction in FIG. 7) in which the inclined surface 85b of the torque transmission portion 83 approaches the inner side surface of the through hole 31a via the joint 81. At this time, the axis O3 of the joint 81 is inclined at an angle β (<α) with respect to the axis O when the joint 81 is at the reference position. However, since the joint 81 rotates around the ball 86 with respect to the drive pulley 31, the drive pulley 31 does not tilt together with the joint 81 and the output shaft 18a.

  Even if the drive pulley 31 inclines together with the output shaft 18a, the drive pulley 31 and the driven pulley 32 keep their axes parallel to each other, even if the tension F of the belt 33 tries to tilt together with the output shaft 18a. This is due to the following reason. That is, when the drive pulley 31 tilts together with the output shaft 18a, the circumferential length of the end t1 of the belt 33 on the side near the bearing 73 (right side in FIG. 7) is the side far from the bearing 73 on the belt 33 (FIG. It becomes longer than the circumference of the end t2 of the inner left side). Accordingly, the belt tension F1 at the end t1 becomes larger than the belt tension F2 at the end t2, so that the restoring moment of the driving pulley 31 in the direction parallel to the axis of the driven pulley 32 Occur. Therefore, even if the drive pulley 31 tilts together with the output shaft 18a, the drive pulley 31 rotates around the sphere 86 in the direction opposite to the tilt direction of the output shaft 18a by the restoring moment. As a result, the drive pulley 31 returns to a posture in which the axis thereof is parallel to the axis of the driven pulley 32. Incidentally, the drive pulley 31 is rotated by the restoring moment because the axial position of the support point Q (see FIG. 7) of the joint 81 with respect to the drive pulley 31 is within the range in which the belt 33 hangs on the drive pulley 31. .

<Effect of the embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
(1) Since the output shaft 18a is swingably connected to the drive pulley 31 via the joint 81, the tension F of the belt 33 prevents the drive pulley 31 from tilting with the output shaft 18a. Therefore, the axes of the drive pulley 31 and the driven pulley 32 are kept parallel to each other. Therefore, the belt 33 is maintained in a properly meshed state with the drive pulley 31 and the driven pulley 32. Since the situation in which the belt 33 partially contacts the drive pulley 31 is also less likely to occur, an increase in the operation noise of the belt transmission mechanism 30 can be suppressed. It is also possible to suppress uneven wear due to one side contact of the belt 33 with the drive pulley 31. By the way, when the belt 33 makes a partial contact with the outer peripheral surface of the drive pulley 31, there is a possibility that the wear of the portion of the belt 33 in contact with the drive pulley 31 may progress more than other portions.

  (2) The engagement state (contact condition) of the belt 33 with the drive pulley 31 is affected by the mounting precision of the motor 18 with respect to the housing 11 as well as the internal clearances of the bearings 73 and 74 in the motor 18. For example, the influence of the accuracy of the end surface (right side surface in FIG. 2) of the side wall 21a to which the motor 18 is attached in the housing 11 and the accuracy of the end surface (left side surface in FIG. 2) attached to the side wall 21a of the housing 11 in the motor 18 It is also conceivable that the motor 18 itself is mounted inclined with respect to the axis of the driven pulley 32 (and thus the rack shaft 13). Therefore, conventionally, it has been difficult to uniformly control the contact between the belt 33 and the drive pulley 31. In this respect, according to the present embodiment, the inclination of the output shaft 18 a with respect to the drive pulley 31 is absorbed by the joint 81. Therefore, the inclination of the motor 18 with respect to the side wall 21 a of the housing 11 can be absorbed. Therefore, the contact condition between the belt 33 and the drive pulley 31 can be controlled more uniformly. Further, since it becomes difficult to be affected by the mounting accuracy of the motor 18 with respect to the housing 11, it is not necessary to strictly manage the end surface accuracy of the side wall 21a of the housing 11 and the end surface accuracy of the motor 18 on the side wall 21a side of the housing 11.

  (3) The smaller the internal clearance of the bearings 73 and 74, the harder the output shaft 18a is inclined. Therefore, in order to improve the support accuracy of the output shaft 18a in the motor 18, it is conceivable to set the internal clearance of the bearings 73 and 74 narrower. However, as the internal clearance is narrowed, the rotational resistance of the output shaft 18a increases, so the loss torque of the motor 18 increases. In this respect, according to this example, since the inclination of the output shaft 18a with respect to the drive pulley 31 is absorbed by the joint 81, the internal clearance of the bearings 73 and 74 can be secured or further enlarged. Therefore, the loss torque of the motor 18 can be suppressed from increasing. As a result, the output efficiency of the motor 18 can be secured.

Second Embodiment
Next, a second embodiment in which the steering apparatus is embodied as an electric power steering apparatus will be described. In this example, a universal joint is employed as a joint for connecting the output shaft 18 a and the drive pulley 31.

  As shown in FIG. 8, the joint 91 includes a connecting member 92 and a torque transmitting member 93. The connection member 92 and the torque transfer member 93 are swingably connected to each other. A hole 94 is provided at a first end (left end in FIG. 8) of the connecting member 92.

The torque transfer member 93 has a first transfer portion 95 and a second transfer portion 96.
The first transmission portion 95 is inserted into the hole 94 of the connecting member 92. The first transmission portion 95 has a shape in which the outer diameter gradually increases from the tip end portion 95a toward the base portion 95b, and the outer diameter gradually decreases at the boundary of the portion 95c where the outer diameter is maximum. ing.

  As shown in FIG. 9, the cross-sectional shape which cut | disconnected the 1st transmission part 95 along the direction orthogonal to the axis line has comprised hexagonal shape. On the outer peripheral surface of the first transmission portion 95, the six corner portions 97a, 97b, 97c, 97d, 97e are chamfered by chamfering each corner of the hexagon into a flat surface or a curved surface convex outward. , 97f are provided.

  The cross-sectional shape obtained by cutting the connecting member 92 in the direction orthogonal to the axis thereof has a rectangular shape corresponding to the inner shape of the through hole 31 a of the drive pulley 31. Further, the cross-sectional shape obtained by cutting the hole 94 of the connecting member 92 in the direction orthogonal to the axis thereof has a hexagonal shape corresponding to the outer shape of the first transmission portion 95. Six grooves 94 a, 94 b, 94 c, 94 d, 94 e, 94 f are provided on the inner peripheral surface of the hole 94. The grooves 94 a to 94 f extend along the axis of the connecting member 92. The grooves 94 a to 94 f are provided at equal intervals in the circumferential direction of the hole 94.

  The engagement ridges 97a to 97f of the first transmission portion 95 are fitted in the grooves 94a, 94b, 94c, 94d, 94e, 94f of the hole 94, respectively. The engagement peak portions 97a to 97f engage with the inner side surfaces of the groove portions 94a to 94f in the circumferential direction. For this reason, the torque transfer member 93 rotates integrally with the connecting member 92. In addition, the torque transfer member 93 can swing in the radial direction with respect to the connection member 92 with the first transfer portion 95 as a fulcrum. As the torque transfer member 93 swings, the engagement ridges 97 a to 97 f slide in the shapes guided by the grooves 94 a to 94 f of the hole 94.

  As shown in FIG. 8, a compression coil spring 98 is interposed between the inner bottom surface of the hole 94 and the tip 95 a of the first transmission unit 95 inside the hole 94. The compression coil spring 98 is maintained in a compressed state. The torque transfer member 93 is always urged in the direction of coming out of the hole 94 by the elastic force of the compression coil spring 98.

  A ring groove 99 is provided on the inner circumferential surface of the hole 94 over the entire circumference thereof. The ring groove 99 is located in the vicinity of the opening in the hole 94. A C ring 100 as a retaining member is fitted in the ring groove 99. The inner peripheral portion of the C-ring 100 axially abuts on a portion between the portion 95 c where the outer diameter of the first transmission portion 95 is largest and the base 95 b. As a result, the movement of the first transmission portion 95 in the direction of coming out of the hole 94 is restricted.

  As shown in FIG. 10, the connecting member 92 is fixed in a state of being fitted into the inner peripheral surface of the through hole 31 a of the drive pulley 31. Further, a second transmission portion 96 which is an end portion of the torque transmission member 93 on the opposite side to the connection member 92 is coupled to the tip end portion of the output shaft 18a so as to be integrally rotatable. Therefore, the joint 91 and thus the output shaft 18 a of the motor 18 rotate integrally with the drive pulley 31. That is, the rotational force (torque) of the output shaft 18 a is transmitted to the drive pulley 31 via the joint 91.

<Operation and Effect of Second Embodiment>
As shown in FIG. 10, the tension F of the belt 33 causes the output shaft 18a to tilt in the same direction (upward direction in FIG. 10) as the tension F acts via the joint 91. At this time, the torque transfer member 93 tilts in the same direction as the direction in which the tension F acts on the connecting member 92, with the first transfer portion 95 as a fulcrum. Therefore, the drive pulley 31 does not tilt together with the output shaft 18a, and the drive pulley 31 and the driven pulley 32 keep their axes parallel to each other. Therefore, according to the present embodiment, the same effects as (1) to (3) in the first embodiment can be obtained.

Third Embodiment
Next, a third embodiment in which the steering apparatus is embodied in an electric power steering apparatus will be described. In this example, a leaf spring coupling is employed as a joint that connects the output shaft 18 a and the drive pulley 31.

As shown in FIG. 11, the joint 111 includes a first connection member 112, a second connection member 113, and a multilayer leaf spring 114.
The first connecting member 112 has a cylindrical insertion portion 115 and an annular plate-like flange 116. The flange 116 is provided on the outer peripheral surface at one end of the insertion portion 115. The flange 116 is provided with two bolt insertion holes 117 (only one is shown in FIG. 11) and two relief holes 118 (only one is shown in FIG. 11). The bolt insertion holes 117 and the relief holes 118 are alternately provided at equal intervals in the circumferential direction of the flange 116.

  The second connection member 113 has the same configuration as the first connection member 112. That is, the second connection member 113 also has the insertion portion 119 and the flange 120. The flange 120 is provided with two bolt insertion holes 121 and two relief holes 122.

  The first connecting member 112 and the second connecting member 113 are provided such that their flanges 116 and 120 face each other in the axial direction. The bolt insertion holes 117 and 121 and the relief holes 122 and 118 of the two flanges 116 and 120 face each other in the axial direction.

  The multilayer leaf spring 114 is provided between the flange 116 of the first connecting member 112 and the flange 120 of the second connecting member 113. The multilayer leaf spring 114 is formed by superposing a plurality of leaf springs 114a. Four holes 123 (only two are shown in FIG. 11) are provided on the peripheral edge portion of the multilayer leaf spring 114 at intervals of 90 degrees in the circumferential direction. Four annular spacers 124 (eight in total) are interposed between the flange 116 and the multilayer leaf spring 114 and between the flange 120 and the multilayer leaf spring 114, respectively. The spacers 124 are provided at positions corresponding to the holes 123 of the multilayer leaf spring 114.

  The first connecting member 112, the second connecting member 113, and the multilayer leaf spring 114 are fixed to each other by a reamer bolt 125 and a nut 126. The shaft portion of the reamer bolt 125 is passed through the bolt insertion holes 117 and 121 of the flanges 116 and 120, the spacer 124, the multilayer leaf spring 114, and the relief holes 118 and 122 of the flanges 116 and 120.

  The joint 111 is provided inside the through hole 31 a of the drive pulley 31. The outer peripheral surface of the flange 116 in the first connection member 112 is fixed to the inner peripheral surface of the through hole 31 a of the drive pulley 31. For this reason, the first connection member 112 is rotatable integrally with the drive pulley 31. On the other hand, between the outer peripheral surface of multilayer leaf spring 114 and the inner peripheral surface of through hole 31a, and between the outer peripheral surface of flange 120 in the second connecting member 113 and the inner peripheral surface of through hole 31a. , A gap is provided. The output shaft 18 a of the motor 18 is fixed to the insertion portion 119 of the second connection member 113 in a state of being inserted. Therefore, the rotational force of the output shaft 18 a of the motor 18 is transmitted to the drive pulley 31 via the joint 111. That is, the output shaft 18 a rotates integrally with the drive pulley 31.

<Operation and Effect of Third Embodiment>
As schematically shown in FIG. 12, the tension F of the belt 33 causes the output shaft 18a to tilt in the same direction (clockwise in FIG. 12) as the tension F acts via the joint 111. At this time, the joint 111 moves with the drive pulley 31 in the direction in which the tension F acts, and the second connection member 113 is inclined with the output shaft 18 a against the elastic force of the multilayer leaf spring 114 along with the movement. Do. Therefore, the drive pulley 31 does not tilt together with the output shaft 18a, and the drive pulley 31 and the driven pulley 32 keep their axes parallel to each other. Therefore, according to the present embodiment, the same effects as (1) to (3) in the first embodiment can be obtained.

  Further, according to the joint 111, the rotational force of the output shaft 18a is transmitted while absorbing the eccentricity and deflection error generated between the output shaft 18a and the drive pulley 31 using the flexibility of the multilayer plate spring 114. can do.

<Other Embodiments>
The embodiments may be modified as follows.
-In 2nd Embodiment, although the cross-sectional shape which cut | disconnected the 1st transmission part 95 along the direction orthogonal to the axis line had comprised hexagonal shape, the said cross-sectional shape should just be a polygon.

  In the first to third embodiments, an example of the electric power steering apparatus that assists the operation of the rack shaft 13 which linearly moves in conjunction with the steering operation using the rotational force of the motor 18 is exemplified. It can also be applied to by-wire (SBW). The steer-by-wire is a steering device that does not have a mechanical connection between the steering wheel and the steered wheels, and transmits an operation of the steering wheel to the steering actuator by an electrical signal. The steering actuator includes, for example, a belt transmission mechanism 30 and a ball screw mechanism 40 as a power conversion mechanism 20 that converts the motor, the rotational movement of the motor into a linear movement of a steering shaft (ball screw shaft). When the present invention is embodied as a steer-by-wire, it can be embodied not only as a front wheel steering device but also as a rear wheel steering device or a four-wheel steering device (4WS).

  11: housing (component of belt transmission), 13: rack shaft (steered shaft), 18: motor (component of belt transmission), 18a: output shaft, 31: drive pulley, 32: driven pulley, 33 ... Belt, 30 ... Belt transmission mechanism (component of belt transmission), 42 ... Ball nut, 43 ... Ball, 44 ... Ball bearing, 81, 91, 111 ... Joint, 82 ... Coupling part (second coupling part) 83: torque transmission part (first connection part) 92: connection member (first connection member) 93: torque transmission member (second connection member) 94a, 94b, 94c, 94d, 94e, 94f ... groove portion 94 hole portion 95 first transmission portion 96 second transmission portion 97a, 97b, 97c, 97d, 97e 97f engagement peak portion 112 first coupling member 113 ... second connecting member, 114 ... many Leaf springs, 114a ... plate spring, 116 ... flange (first flange), 120 ... flange (second flange), 125 ... bolts.

Claims (7)

With the housing,
A motor having an output shaft fixed to the outer surface of the housing and inserted into the interior of the housing;
A cylindrical drive pulley housed inside the housing and rotating integrally with the output shaft;
A driven pulley rotatably supported inside the housing;
A belt wound around the drive pulley and the driven pulley;
And a joint provided inside the drive pulley and pivotally connecting the output shaft to the drive pulley along a direction in which the tension of the belt acts. In the belt transmission according to claim 1,
The joint is a first connection portion swingably supported along a direction in which the tension of the belt acts inside the drive pulley.
A belt transmission comprising a first connection portion and a second connection portion connecting the tip end portion of the output shaft. In the belt transmission according to claim 1,
The joint is a universal joint having a first connecting member and a second connecting member pivotally connected to each other,
The belt transmission according to claim 1, wherein the first connection member is fixed to the inside of the drive pulley, and an end of the second connection member opposite to the second connection member is connected to the output shaft. In the belt transmission according to claim 3,
The first connection member has a hole which is opened in the axial direction and provided with a plurality of grooves extending in the axial direction on the inner circumferential surface,
The second connection member has a first transmission portion inserted in the hole in a retaining state, and a second transmission portion connecting the first transmission portion and the tip of the output shaft. And
The outer diameter of the first transmission portion gradually increases from the tip end toward the base along the insertion direction with respect to the hole, and the outer diameter gradually decreases at a portion where the outer diameter is the largest. Have the following
The cross-sectional shape in the direction orthogonal to the axis of the first transmission portion is polygonal, and the holes are formed along a plurality of corners extending from the tip of the first transmission portion toward the base. A belt transmission comprising an engagement peak portion fitted to the plurality of groove portions provided on an inner circumferential surface of the portion. In the belt transmission according to claim 1,
The joint is a tubular first connection member having a first flange;
A tubular second connecting member having a second flange;
A leaf spring provided between the first flange and the second flange;
And a plurality of bolts for fixing the plate spring to the first flange and the second flange at a plurality of points,
The first connection member is fixed to the inside of the drive pulley, while the second connection member is connected to the output shaft in a state of being provided with a gap from the inner circumferential surface of the drive pulley. Belt drive. The belt transmission according to any one of claims 1 to 5.
An axial position of a supporting point of the joint with respect to the drive pulley, wherein the belt is in a range in which the belt hangs on the drive pulley. The belt transmission according to any one of claims 1 to 6.
A steered shaft linearly moving inside the housing;
And a ball nut which is screwed to the steering shaft via a large number of balls and rotatably supported with respect to the inner circumferential surface of the housing via a bearing.
The steering apparatus, wherein the driven pulley is integrally rotatably mounted on an outer peripheral surface of the ball nut.