JP6621965B1 - Transmission device and vehicle steering apparatus using the same - Google Patents

Abstract

The transmission (1) is positioned so as to be able to roll on a screw shaft (20) housed in a cylindrical housing (2) and a screw portion (22) of the screw shaft (20). A plurality of balls (30), a nut (40) connected to the screw portion (22) by the plurality of balls (30), and the nut (40) is rotatable inside the housing (2). A supporting bearing (50). The nut (40) has a large-diameter portion (44) and a small-diameter portion (45) connected to the large-diameter portion (44) in the axial direction of the screw shaft (20). The large diameter portion (44) has a circulation portion (70) on the outer peripheral surface (44a). The circulation part (70) circulates the balls (30) rolling on the screw part (22). The small diameter portion (45) has a smaller diameter than the large diameter portion (44). The bearing (50) supports the small diameter portion (45) in the nut (40).

Description

  The present invention relates to a transmission device including a ball screw that converts a rotational motion into a straight motion and / or converts a straight motion into a rotational motion, and to an improved technique of a vehicle steering device using the power transmission device.

  The ball screw includes a screw shaft, a plurality of balls, and a nut connected to the threaded portion by the plurality of balls. The plurality of balls rolling on the threaded portion circulate through a circulation passage (circulation portion) provided in the nut. A vehicle steering apparatus using such a transmission including a ball screw is known, for example, from U.S. Pat.

  In the transmission device for a vehicle steering device known from Patent Document 1, the screw shaft of the ball screw is housed in a cylindrical housing extending in the vehicle width direction, and is movable along the housing. . The steering driving force generated by the electric motor is transmitted to the nut by the pulley, and further transmitted from the nut to the screw shaft through a plurality of balls. The screw shaft slides in the housing to steer the steering wheel of the vehicle.

  One end of the nut of the ball screw has a positioning flange on the outer peripheral surface. The pulley and the bearing are fitted to the outer peripheral surface of the nut. This bearing rotatably supports the nut inside the housing. The pulley and the bearing are positioned in this order with respect to the flange, and positioning with respect to the nut is performed by a bearing lock nut screwed into the other end of the nut.

JP2015-168371A

  The nut has a relatively large diameter because it has a thread portion on the inner peripheral surface and a circulation passage for circulating a plurality of balls. For this reason, the bearing and the housing that support the nut must also have a large diameter. There is room for improvement in order to reduce the size of the entire transmission device including the housing.

  This invention makes it a subject to provide the technique which can achieve size reduction of a transmission.

According to the invention, the transmission is
A tubular housing;
A screw shaft that is housed in the housing so as to be movable along the housing, and has a threaded portion on an outer peripheral surface;
A plurality of balls positioned so as to be able to roll on the threaded portion;
A cylindrical member connected to the threaded portion by the plurality of balls, and a large-diameter portion having a circulating portion on the outer peripheral surface for circulating the plurality of balls rolling the threaded portion; A nut having a small-diameter portion that is continuous with the large-diameter portion in the axial direction of the screw shaft and has a smaller diameter than the large-diameter portion;
A bearing that rotatably supports the small diameter portion inside the housing;
A transmission member having a hub fitted to the small-diameter portion of the nut and coupled to the small-diameter portion so that rotational force can be transmitted to each other;
Only including,
The nut has a step surface that is located at a boundary between the large diameter portion and the small diameter portion and orthogonal to the center line of the nut,
The hub has a cylindrical first hub portion and a cylindrical second hub portion,
The first hub portion and the second hub portion are continuous and integrated in the axial direction of the hub,
The inner peripheral surface of the first hub portion is fitted to the small diameter portion and serrated to the small diameter portion,
The first hub and the bearing are positioned in this order in the axial direction with respect to the step surface, and the small diameter portion is moved in the axial direction by the stop member provided on the small diameter portion and the step surface. Is regulated,
The outer peripheral surface of the second hub portion is provided with a transmission portion of the transmission member,
The inner peripheral surface of the second hub part is fitted to the large diameter part,
The large-diameter portion has a pair of side surfaces and a bottom surface that are parallel to each other to form a recess that is recessed from the outer peripheral surface of the large-diameter portion toward the center of the nut,
The circulation portion is a circulation passage defined by the pair of side surfaces, the bottom surface, and the inner peripheral surface of the second hub portion.

  In the present invention, the nut of the ball screw has a small-diameter portion having a smaller diameter than the large-diameter portion in addition to the large-diameter portion having the circulation portion on the outer peripheral surface. The bearing supports the small diameter portion of the nut inside the housing. For this reason, a bearing can be made into a small diameter. Since the bearing has a small diameter, the diameter of the housing can also be reduced.

  The length of the nut is long because the small diameter portion is continuous with the large diameter portion in the axial direction of the screw shaft. However, since the cylindrical housing which accommodates the nut also accommodates the screw shaft which can move along the housing, it is inevitably long. For this reason, a transmission can be arrange | positioned in the range of the length of a housing. The housing need not be longer. In other words, the length of the cylindrical housing is skillfully utilized to reduce the diameter of the housing.

  Thus, by reducing the diameter of the bearing and the housing while maintaining the length of the housing, the entire transmission including the housing can be reduced in size.

It is sectional drawing of the transmission device by this invention. It is sectional drawing of the structure by which the nut shown in FIG. 1, the transmission member, the guide member, and the end deflector were combined. FIG. 2 is an exploded view of the nut, the transmission member, the rolling bearing, and the rolling bearing lock nut shown in FIG. 1. FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 2. FIG. 4 is an exploded view of the nut, guide member, and end deflector shown in FIG. 3. FIG. 3 is an exploded view of a subassembly and a transmission member in which the nut, the guide member, and the end deflector illustrated in FIG. 2 are combined. It is explanatory drawing explaining the concept of the circulation part shown by FIG. It is a schematic diagram of the steering device for vehicles using the transmission shown in FIG. It is sectional drawing around the guide member of the ball screw apparatus by Example 2 of this invention. It is sectional drawing around the guide member of the ball screw apparatus by Example 3 of this invention. It is sectional drawing which shows the thread part of the nut of the ball screw apparatus by Example 4 of this invention, and the thread part of a screw shaft. It is an external view of the ball screw apparatus by Example 4 of this invention, and shows the state which assembled | attached the end deflector to the nut (a screw shaft is not shown). It is an external view of the ball screw apparatus by Example 4 of this invention, and shows the state before attaching an end deflector to a nut (a screw shaft is not shown). It is a block diagram of the end deflector of the ball screw apparatus by Example 4 of this invention. It is a plane explanatory view of the nut and end deflector seen from the axial direction of the screw shaft of the ball screw device by Example 4 of the present invention. It is sectional drawing of the thread part of the screw shaft of the ball screw apparatus by Example 4 of this invention, and an end deflector. It is an operation | movement sectional drawing which shows a mode that a ball | bowl is lifted by the ball | bowl lifting part of the ball screw apparatus by Example 4 of this invention. It is explanatory drawing which carried out plane expansion | deployment seeing the thread part of the screw shaft of the ball screw apparatus by Example 4 of this invention from the radial direction.

EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated below based on an accompanying drawing.
<Example 1>

  A transmission device 1 according to a first embodiment will be described with reference to FIGS. 1 to 7. As shown in FIG. 1, the transmission device 1 includes a housing 2, a ball screw 10, a bearing 50, and a transmission member 60. The housing 2 has, for example, a cylindrical configuration extending in the vehicle width direction of the vehicle, and includes a first housing 3 and a second housing 4 connected in a straight line.

  The ball screw 10 is a conversion mechanism that can convert rotational motion into linear motion and / or convert linear motion into rotational motion. The ball screw 10 includes a screw shaft 20, a plurality of balls 30, and a nut 40.

  The screw shaft 20 is housed in the housing 2 and is movable along the longitudinal direction of the housing 2. The screw shaft 20 includes a configuration in which both end portions are exposed from the housing 2. The screw shaft 20 has a screw portion 22 on the outer peripheral surface 21.

  The plurality of balls 30 are positioned so as to roll on the threaded portion 22.

  The nut 40 is a cylindrical member connected to the screw portion 22 of the screw shaft 20 by a plurality of balls 30. In other words, the screw portion 42 of the nut 40 and the screw portion 22 of the screw shaft 20 are opposed to each other so that the plurality of balls 30 are rolled. A space 43, that is, a thread groove 43 is formed. The nut 40 is connected to the screw portion 22 by a plurality of balls 30 that roll in the thread groove 43.

  As shown in FIGS. 1 and 2, the nut 40 has a large-diameter portion 44, a small-diameter portion 45, and a step surface 46 that are located concentrically with each other. Since the large diameter portion 44 has the circulation portion 70 on the outer peripheral surface 44a of the large diameter portion 44, the large diameter portion 44 has a relatively large diameter. That is, the outer diameter D1 of the large diameter portion 44 is larger than the outer diameter D2 of the small diameter portion 45. The circulation part 70 circulates a plurality of balls 30 rolling the screw parts 22 and 42. The detailed configuration of the circulation unit 70 will be described later.

  As shown in FIGS. 1 and 3, the small-diameter portion 45 is continuous with the large-diameter portion 44 in the axial direction of the screw shaft 20, that is, in the direction along the center line CL of the screw shaft 20. ) And a portion having a smaller diameter than the large-diameter portion 44. The center line CL of the screw shaft 20 matches the center line of the nut 40. Hereinafter, the center line CL of the screw shaft 20 is appropriately referred to as “the center line CL of the nut 40”. The outer peripheral surface 44 a of the large-diameter portion 44 and the outer peripheral surface 45 a of the small-diameter portion 45 are surfaces formed by concentric circles having a perfect circle shape with respect to the center line CL of the nut 40. The step surface 46 is a flat surface located at the boundary between the large diameter portion 44 and the small diameter portion 45 and orthogonal to the center line CL of the nut 40.

  Here, the small diameter portion 45 will be described in detail. On the outer peripheral surface 45a of the small diameter portion 45, a male serration 45b, a bearing fitting portion 45c, and a male screw 45d are provided from the step surface 46 to one end 40a (one end 40a of the nut 40) opposite to the large diameter portion 44. They are provided in this order.

  As shown in FIG. 1, the bearing 50 can rotate the small diameter portion 45 of the nut 40 to the inside of the housing 2 (inner peripheral surface 2 a of the housing 2) and move in the axial direction with respect to the housing 2. Is regulated and supported. The bearing 50 is constituted by a rolling bearing.

  As shown in FIGS. 1 and 2, the transmission member 60 can transmit a rotational force to and from the small diameter portion 45 of the nut 40. For example, a pulley, a gear, a sprocket, a shaft coupling It can be constituted by various rotating bodies such as a rotating shaft. In this embodiment, a pulley will be exemplified and described.

  As shown in FIGS. 2 and 3, the transmission member 60 has a hub 61 at the center. The hub 61 is fitted to the small diameter portion 45 of the nut 40 and is connected to the small diameter portion 45 so that rotational force can be transmitted to each other. The hub 61 includes a first hub part 62 and a second hub part 63. The first hub portion 62 and the second hub portion 63 are located concentrically with each other, and are continuous and integrated in the axial direction of the hub 61. The diameter of the inner peripheral surface 62 a of the first hub portion 62 is smaller than the diameter of the inner peripheral surface 63 a of the second hub portion 63. The boundary between the inner peripheral surface 62 a of the first hub portion 62 and the inner peripheral surface 63 a of the second hub portion 63 is connected by a hub step surface 64. The hub step surface 64 is a flat surface orthogonal to the center line CL of the nut 40.

  The first hub portion 62 is a cylindrical fitting portion that can be fitted to and connected to the outer peripheral surface 45 a of the small diameter portion 45. For example, the first hub portion 62 can be connected to the small diameter portion 45 of the nut 40 with serrations, splines, keys, bolts, or pins while restricting relative rotation. For example, the first hub portion 62 is serrated to the small diameter portion 45. More specifically, a female serration 62 b that can be connected to the male serration 45 b of the nut 40 is formed on the inner peripheral surface 62 a of the first hub portion 62.

  The second hub portion 63 is a cylindrical fitting portion that can be fitted to the outer peripheral surface 44 a of the large diameter portion 44. That is, the inner peripheral surface 63a of the second hub portion 63 is detachably fitted to the outer peripheral surface 44a of the large diameter portion 44. On the outer peripheral surface of the second hub portion 63, a transmission portion 65 (pulley belt hanging portion 65) having a transmission function with the outside is provided.

  Referring also to FIG. 1, the first hub portion 62 and the bearing 50 of the transmission member 60 are positioned in this order in the axial direction with respect to the step surface 46 of the nut 40, and the stop member 51 provided on the small diameter portion 45. The movement of the nut 40 in the axial direction is restricted by the step surface 46. This stop member 51 is configured by a rolling bearing lock nut that can be screwed into the male screw 45 d of the small diameter portion 45.

As shown in FIG. 3, the procedure for assembling the transmission member 60 and the bearing 50 to the nut 40 is as follows.
First, the hub 61 of the transmission member 60 is inserted from one end 40a of the nut 40 (transmission member assembling step). Then, the inner peripheral surface 62 a of the first hub portion 62 is fitted into the outer peripheral surface 45 a of the small diameter portion 45 while the inner peripheral surface 63 a of the second hub portion 63 is fitted into the outer peripheral surface 44 a of the large diameter portion 44. In the middle of fitting the inner peripheral surface 62a of the first hub portion 62 into the outer peripheral surface 45a of the small diameter portion 45, the female serration 62b of the first hub portion 62 is fitted and connected to the male serration 45b of the nut 40. As a result, the relative rotation of the transmission member 60 with respect to the nut 40 is restricted. Thereafter, the hub step surface 64 comes into contact with the step surface 46 of the nut 40, whereby the axial position of the transmission member 60 with respect to the nut 40 is determined.

Next, the bearing 50 is inserted from one end 40a of the nut 40 into the bearing fitting portion 45c (bearing assembling step).
Next, the stop member 51 (rolling bearing lock nut 51) is screwed into the male screw 45d from one end 40a of the nut 40 (stop member assembling step). Then, the first hub portion 62 and the bearing 50 are sandwiched in the axial direction of the nut 40 by the step surface 46 of the nut 40 and the stopper member 51. As a result, the axial positions of the transmission member 60 and the bearing 50 are determined and attached to the nut 40.
Thus, the assembly work of the transmission member 60 and the bearing 50 with respect to the nut 40 is completed.

  As is clear from the above description, the transmission member 60, the bearing 50, and the stop member 51 are simply assembled to the nut 40 in this order from one direction, so that the assembly workability is good and the number of assembly steps can be reduced.

  Next, the circulation unit 70 will be described with reference to FIGS. 2, 4 and 5. The circulation part 70 includes a large-diameter part 44 of the nut 40, a second hub part 63, a pair of guide members 80, 80, and a pair of end deflectors 90, 90.

  The large-diameter portion 44 of the nut 40 has an annular recess 47 that is recessed from the outer peripheral surface 44a of the large-diameter portion 44 over the entire circumference in the central portion in the axial direction (the direction along the center line CL of the nut 40). Hereinafter, the annular recess 47 is appropriately referred to as “annular recess 47”. The annular recess 47 is located concentrically with the large diameter portion 44. The bottom surface 47 a of the annular recess 47 is a perfect circle surface centered on the center line CL of the nut 40. The diameter D3 of the bottom surface 47a of the annular recess 47 is smaller than the outer diameter D1 of the large diameter portion 44. Thus, the portion of the nut 40 where the annular recess 47 is located is thin as much as the small diameter with respect to the large diameter portion 44. As a result, the nut 40 becomes lighter.

  The pair of guide members 80, 80 are detachable in the radial direction with respect to the bottom surface 47a of the annular recess 47, and are preferably resin molded products. The pair of guide members 80, 80 can be made of resin separately from the nut 40, and can be reduced in weight. As a result, the ball screw 10 can be further reduced in weight. The pair of guide members 80, 80 are positioned with a constant interval Le (see FIG. 4) in the circumferential direction of the annular recess 47 and extend between both axial end surfaces 47 b, 47 b of the annular recess 47. .

  Further, the pair of guide members 80, 80 has a bar-like configuration having a square cross section when viewed from the direction along the center line CL of the nut 40. More specifically, in the configuration in which the pair of guide members 80, 80 are positioned with a distance Le in the circumferential direction of the annular recess 47, the breakdown of each of the four surfaces 81 to 84 having a square cross section is as follows. The first surfaces 81 and 81 that can contact the entire surface of the bottom surface 47a and the second surfaces 82 and 82 that can contact the entire surface of the inner peripheral surface 63a of the second hub portion 63 have a distance Le. And third surfaces 83 and 83 facing each other, and fourth surfaces 84 and 84 opposite to the third surfaces 83 and 83. The first surfaces 81 and 81 are configured to have the same curved surface as the bottom surface 47 a of the annular recess 47. The second surfaces 82 and 82 are configured to have the same curved surface as the inner peripheral surface 63 a of the second hub portion 63. The third surfaces 83 and 83 and the fourth surfaces 84 and 84 are parallel to each other.

  The depth from the outer peripheral surface 44a of the large diameter portion 44 to the bottom surface 47a of the annular recess 47, that is, the depth of the annular recess 47 with respect to the large diameter portion 44 is Dp. In the configuration in which the guide member 80 is fitted in the annular recess 47, the first surface 81 has no step with respect to the outer peripheral surface 44 a of the large-diameter portion 44, and continues extremely smoothly on the outer peripheral surface 44 a of the large-diameter portion 44 (the same surface Becomes). The distance Le between the pair of guide members 80 and 80 and the depth of the annular recess 47 with respect to the large diameter portion 44 are such that the ball 30 shown in FIG. A slightly larger value).

  The pair of guide members 80, 80 have a pair of first positioning portions 86, 86 at both ends 85, 85 (both end surfaces 85, 85) in the direction along the axial direction of the nut 40. These first positioning portions 86 are arcuate protrusions when viewed from the first surface 81 side.

  On the other hand, a plurality of (for example, four) second positioning portions 44b are formed on the outer peripheral surface 44a of the large diameter portion 44. The plurality of second positioning portions 44 b have a concave configuration in which each first positioning portion 86 can be fitted from the outside of the large diameter portion 44, and is recessed from the outer peripheral surface 44 a of the large diameter portion 44. The shape of the second positioning portion 44 b is the same arc shape as the first positioning portions 86 and 86 when viewed from the outside of the large diameter portion 44.

  As shown in FIG. 5, the pair of guide members 80 and 80 are positioned on the nut 40 by the fitting relationship between each first positioning portion 86 and each second positioning portion 44 b.

  As described above, the pair of guide members 80, 80 have a pair of first positioning portions 86, 86 at both ends 55, 55 in the direction along the axial direction of the nut 40. The large-diameter portion 44 has a plurality of second positioning portions 44b in which a pair of first positioning portions 86, 86 can be fitted from the outside in the outer peripheral surface 44a. Therefore, the pair of guide members 80, 80 can be accurately and easily positioned on the nut 40 by simply fitting each first positioning portion 86 from the outside of the plurality of second positioning portions 44b. Can do. In addition, the position of the pair of guide members 80, 80 relative to the nut 40 can be reliably held.

  The second hub portion 63 covers the pair of guide members 80 and 80 while restricting the outward displacement in the configuration in which the second hub portion 63 is fitted to the large diameter portion 44. In this way, the transmission member 60 serves as a so-called cover that can cover the nut 40 while restricting the displacement of the pair of guide members 80, 80 radially outward.

  As shown in FIGS. 2 and 4, the circulating portion 70 includes a bottom surface 47 a of the annular recess 47, a pair of guide members 80 and 80 assembled to the nut 40, and an inner peripheral surface of the second hub portion 63. 63a, a circulation path defined by (enclosed), that is, a space.

  The concept of the circulation unit 70 will be described with reference to FIGS. 7 (a) to 7 (c). FIG. 7A shows the relationship between the bottom surface 47a of the annular recess 47 shown in FIG. 4 and the pair of guide members 80, 80 again. FIG. 7B schematically shows the space 71 shown in FIG. FIG. 7C schematically shows a concept in which the annular recess 47 is formed by enclosing the space 71 shown in FIG. 7B with the second hub portion 63.

  As shown in FIG. 7A, the space 71 surrounded by the bottom surface 47 a of the annular recess 47 and the third surfaces 83 and 83 of the pair of guide members 80 and 80 is referred to as “recess 71”. . The recess 71 is recessed from the outer peripheral surface 44a of the large diameter portion 44 toward the center of the nut 40, and is along the center line CL (see FIG. 3) of the nut 40. The pair of side surfaces 72, 72 of the recess 71 is constituted by the third surfaces 83, 83 of the pair of guide members 80, 80. The bottom surface 73 of the recess 71 is constituted by a part of the bottom surface 47 a of the annular recess 47. That is, it can be said that the large-diameter portion 44 forms a recess 71 that is recessed from the outer peripheral surface 44a of the large-diameter portion 44 toward the center of the nut 40, as shown in FIG. it can.

  As shown in FIG. 7C, by fitting the inner peripheral surface 63a of the second hub portion 63 to the outer peripheral surface 44a of the large-diameter portion 44, the inner peripheral surface 63a becomes the recess 71 (FIG. 7B). ))). A closed space 70 formed by surrounding the recess 71 with the inner peripheral surface 63 a is referred to as a circulation portion 70. The circulation portion 70 is a circulation passage defined by the pair of side surfaces 72, 72, the bottom surface 73, and the inner peripheral surface 63 a of the second hub portion 63. Hereinafter, the circulation unit 70 is appropriately referred to as a “circulation passage 62”. The plurality of balls 30 rolling in the thread groove 43 can circulate through the circulation passage 70.

  As shown in FIGS. 1 and 2, the pair of end deflectors 90 and 90 are members that communicate between the screw groove 43 and both ends of the circulation passage 70, and are configured by, for example, a resin molded product. . Each end deflector 90, 90 has communication holes 91, 91 communicating between the thread groove 43 and the circulation passage 70. The plurality of balls 30 rolling in the thread groove 43 can circulate through the communication holes 91 and 91 through the circulation passage 70.

  As shown in FIG. 5, the large diameter portion 44 has a pair of concave portions 48, 48 on the outer peripheral surface 44 a. The pair of recesses 48 are recessed from the outer peripheral surface 44 a of the large diameter portion 44. The pair of end deflectors 90, 90 can be individually fitted into the concave portions 48, 48 from the outside of the large diameter portion 44.

  As shown in FIGS. 2 and 5, in a configuration in which a pair of end deflectors 90 and 90 are fitted in the recesses 48 and 48, the outer surface of each end deflector 90 and 90 is in relation to the outer peripheral surface 44 a of the large diameter portion 44. Thus, there is no difference in level, and the outer surface 44a of the large-diameter portion 44 is connected very smoothly (becomes flush). The second hub portion 63 of the transmission member 60 covers the pair of end deflectors 90 and 90 together with the pair of guide members 80 and 80 while restricting the outward displacement of the pair of end deflectors 90 and 90.

  For this reason, the pair of end deflectors 90, 90 can be individually fitted into the concave portions 48, 48 provided on the outer peripheral surface 44 a of the large-diameter portion 44 from the outside of the diameter. Moreover, the pair of end deflectors 90 and 90 can be covered together with the pair of guide members 80 and 80 by effectively utilizing the transmission member 60. For this reason, a “separate member” for covering the pair of end deflectors 90, 90 is not necessary. Furthermore, since the pair of guide members 80, 80 are separate from the pair of end deflectors 90, 90, the shape can be simplified.

As is clear from the above description, the transmission member 60 has all of the following four configurations.
First, as shown in FIG. 1, the transmission member 60 is configured to be able to transmit a rotational force to the nut 40.

  Secondly, as shown in FIGS. 4 and 7, the transmission member 60 is configured to be able to define the circulation passage 70 in cooperation with the annular recess 47 and the pair of guide members 80, 80.

  Thirdly, as shown in FIGS. 2 and 4, the transmission member 60 can cover the pair of guide members 80, 80 with respect to the nut 40 while restricting the outward displacement of the diameter. (See FIG. 4).

  Fourth, as shown in FIGS. 2 and 4, the transmission member 60 is displaced radially outwardly with respect to the nut 40 together with the pair of guide members 80 and 80 and the pair of end deflectors 90 and 90. It is the structure which can be covered while regulating.

  As is apparent from the third configuration and the fourth configuration, the transmission member 60 assembled to the nut 40 is effectively utilized. The second hub portion 63 of the transmission member 60 covers the pair of guide members 80 and 80 and the pair of end deflectors 90 and 90 while restricting the radially outward displacement of the nut 40. For this reason, the pair of guide members 80, 80 and the pair of end deflectors 90, 90 are not detached from the nut 40.

  Next, the vehicle steering apparatus 100 using the transmission apparatus 1 will be exemplified and described with reference to FIG.

  The vehicle steering apparatus 100 includes both the steering system 110 and the steered power transmission mechanism 130 or only the steered power transmission mechanism 130. The steering system 110 is a system that extends from the steering wheel 111 of the vehicle to the wheels 121 and 121 (steering wheels 121 and 121). The turning power transmission mechanism 130 is configured to add turning power to the wheels 121 and 121.

  In the present embodiment, the steered power transmission mechanism 130 will be described by exemplifying an auxiliary torque mechanism that adds an auxiliary torque to the steering system 110. Hereinafter, the steered power transmission mechanism 130 is appropriately referred to as an “auxiliary torque mechanism 130”.

  The steering system 110 includes a steering wheel 111, a steering shaft 112 connected to the steering wheel 111, an input shaft 114 connected to the steering shaft 112 by a universal shaft joint 113, and a first transmission mechanism connected to the input shaft 114. 115 and a left and right (both sides in the vehicle width direction) wheel connected to both ends of the steered shaft 116 via ball joints 117 and 117, tie rods 118 and 118, and knuckle 119 and 119. 121, 121. The first transmission mechanism 115 is configured by, for example, a rack and pinion mechanism.

  According to the steering system 110, when the driver steers the steering wheel 111, the left and right wheels 121, 121 are driven by the steering torque via the first transmission mechanism 115, the steered shaft 116, and the left and right tie rods 118, 118. Can be steered.

  The auxiliary torque mechanism 130 (steering power transmission mechanism 130) includes a steering torque sensor 131, a control unit 132, an electric motor 133, and a second transmission mechanism 134. The steering torque sensor 131 detects the steering torque of the steering system 110 applied to the steering wheel 111. The control unit 132 generates a control signal based on the torque detection signal of the steering torque sensor 131. The electric motor 133 generates a motor torque (auxiliary torque) corresponding to the steering torque, that is, a driving force for turning, based on the control signal of the control unit 132. The second transmission mechanism 134 transmits the auxiliary torque generated by the electric motor 133 to the steered shaft 116.

  According to the vehicle steering device 100, the wheels 121 and 121 can be steered by the steered shaft 116 with a combined torque obtained by adding the assist torque of the electric motor 133 to the steering torque of the driver.

  The steered shaft 116 is constituted by the screw shaft 20 and is housed in the housing 2 so as to be movable in the vehicle width direction (axial direction). The first transmission mechanism 115 and the second transmission mechanism 134 are also accommodated in the housing 2.

  As shown in FIGS. 1 and 7, the second transmission mechanism 134 includes, for example, a belt transmission mechanism 150 and the ball screw 10.

  The belt transmission mechanism 150 includes a driving pulley 151 provided on the output shaft 133 a of the electric motor 133, a driven pulley 152 provided on the nut 40 of the ball screw 10, and a belt hung on the driving pulley 151 and the driven pulley 152. 153. The driven pulley 152 is a kind of the transmission member 60 of the ball screw 10. Hereinafter, the driven pulley 152 will be appropriately referred to as the “transmission member 60”.

  The ball screw 10 transmits the driving force for turning generated by the electric motor 133 (see FIG. 7), that is, auxiliary torque, to the turning shaft 116.

The above description is summarized as follows.
As shown in FIGS. 1 to 3, the transmission 1 is
A tubular housing 2;
A screw shaft 20 housed in the housing 2 so as to be movable along the housing 2 and having a screw portion 22 on the outer peripheral surface 21;
A plurality of balls 30 positioned so as to be able to roll on the threaded portion 22;
A cylindrical member connected to the screw portion 22 by the plurality of balls 30, and having a circulation portion 70 that circulates the plurality of balls 30 rolling the screw portion 22 on the outer peripheral surface 44 a. A nut 40 having a large-diameter portion 44 and a small-diameter portion 45 that is continuous with the large-diameter portion 44 in the axial direction of the screw shaft 20 and has a smaller diameter than the large-diameter portion 44;
And a bearing 50 that rotatably supports the small-diameter portion 45 inside the housing 2.

  Thus, the nut 40 of the ball screw 10 has the small diameter portion 45 having a smaller diameter than the large diameter portion 44 in addition to the large diameter portion 44 having the circulation portion 70 on the outer peripheral surface 44a. . The bearing 50 supports the small diameter portion 45 of the nut 40 inside the housing 2. For this reason, the bearing 50 can be made into a small diameter. Since the bearing 50 has a small diameter, the diameter of the housing 2 can also be reduced.

  The length of the nut 40 is longer than the large diameter portion 44 because the small diameter portion 45 is continuous in the axial direction of the screw shaft 20. However, the cylindrical housing 2 in which the nut 40 is accommodated also accommodates the screw shaft 20 that can move along the housing 2, and is inevitably long. For this reason, the transmission device 1 can be arranged in the range of the length of the housing 2. The housing 2 need not be longer. That is, the length of the cylindrical housing 2 is skillfully utilized to make the housing 2 have a small diameter.

  Thus, by reducing the diameter of the bearing 50 and the housing 2 while maintaining the length of the housing 2, it is possible to reduce the size of the entire transmission device 1 including the housing 2.

Further, as shown in FIGS. 1 to 3, a hub 61 that is fitted to the small diameter portion 45 of the nut 40 and is connected to the small diameter portion 45 so as to be able to transmit a rotational force to each other. And further comprising a transmission member 60,
The nut 40 has a step surface 46 positioned at the boundary between the large diameter portion 44 and the small diameter portion 45 and orthogonal to the center line CL of the nut 40.
The hub 61 and the bearing 50 are positioned in this order in the axial direction with respect to the step surface 46, and the shaft of the nut 40 is formed by the stop member 51 provided on the small diameter portion 45 and the step surface 46. Movement in the direction is restricted.

  Thus, the movement in the axial direction relative to the nut 40 can be easily restricted by a simple operation of assembling the hub 61, the bearing 50, and the stopper member 51 to the nut 40 from one direction.

Further, as shown in FIGS. 1 and 3, the bearing 50 is constituted by a rolling bearing 50,
The stop member 51 is configured by a rolling bearing lock nut 51 that can be screwed into the small diameter portion 45.

  Therefore, by simply screwing the rolling bearing lock nut 51 into the small diameter portion 45, the position of the hub 61 and the rolling bearing 50 in the axial direction with respect to the nut 40 can be accurately set regardless of the manufacturing tolerance.

Further, as shown in FIG. 3, the hub 61 includes a first hub portion 62 fitted and connected to the small diameter portion 45, and a second hub portion 63 fitted to the large diameter portion 44. And having
The first hub portion 62 and the second hub portion 63 are continuous and integrated in the axial direction of the hub 61.

  By integrating and integrating the first hub part 62 and the second hub part 63 in the axial direction of the hub 61, the inner peripheral surface 62a of the first hub part 62 and the inner peripheral surface of the second hub part 63 are integrated. A step surface 64 (hub step surface 64) can be provided at the boundary with 63a. Despite the single hub 61, a hub step surface 64 can be provided. The number of parts is small.

Furthermore, as shown in FIGS. 2, 4, and 7, the large diameter portion 44 constitutes a recess 71 that is recessed from the outer peripheral surface 44 a of the large diameter portion 44 toward the center of the nut 40. A pair of side surfaces 72, 72 and a bottom surface 73,
The circulation portion 70 is a circulation passage 70 defined by the pair of side surfaces 72, 72, the bottom surface 73, and the inner peripheral surface 63 a of the second hub portion 63.
Therefore, the circulation passage 70 can be provided with a simple configuration.

More specifically, as shown in FIG. 1 to FIG.
A tubular housing 2;
A screw shaft 20 housed in the housing 2 so as to be movable along the housing 2 and having a screw portion 22 on the outer peripheral surface 21;
A plurality of balls 30 positioned so as to be able to roll on the threaded portion 22;
A cylindrical member connected to the screw portion 22 by the plurality of balls 30, and having a circulation portion 70 that circulates the plurality of balls 30 rolling the screw portion 22 on the outer peripheral surface 44 a. A nut 40 having a large-diameter portion 44 and a small-diameter portion 45 that is continuous with the large-diameter portion 44 in the axial direction of the screw shaft 20 and has a smaller diameter than the large-diameter portion 44;
A rolling bearing 50 that rotatably supports the small diameter portion 45 in the housing 2;
A transmission member 60 constituted by a pulley 152 (driven pulley 152) having a hub 61 serrated to the small diameter portion 45 of the nut 40;
The nut 40 has a step surface 46 positioned at the boundary between the large diameter portion 44 and the small diameter portion 45 and orthogonal to the center line CL of the nut 40.
The hub 61 and the rolling bearing 50 are positioned in this order in the axial direction with respect to the step surface 46, and the bearing lock nut 51 screwed into the small diameter portion 45 and the step surface 46 (that is, The movement of the nut 40 in the axial direction is restricted by the restriction by the hub step surface 64 hitting the step surface 46),
The hub 61 is serrated and coupled to the small diameter portion 45 (a male serration 45b is connected to a female serration 62b), and a second hub portion 63 is fitted to the large diameter portion 44. Have
The first hub portion 62 and the second hub portion 63 are continuous and integrated in the axial direction of the hub 61, and
The large diameter portion 44 has a pair of side surfaces 72, 72 and a bottom surface 73 that form a recess 71 that is recessed from the outer peripheral surface 44a of the large diameter portion 44 toward the center of the nut 40,
The circulation portion 70 is a circulation passage defined by the pair of side surfaces 72, 72, the bottom surface 73, and the inner peripheral surface 63 a of the second hub portion 63.

As shown in FIG. 1 and FIG.
The transmission 1;
An electric motor 133 that generates a driving force for steering that is transmitted from the transmission member 60 to the nut 40;
The screw shaft 20 includes a steered shaft 116 that steers the steered wheels 121 and 121.

  For this reason, by transmitting the driving force for turning generated by the electric motor 133 from the transmission member 60 to the nut 40, the rotational movement of the nut 40 is converted into the straight movement of the steering shaft 116, and the steering wheel 121 is converted. , 121 can be efficiently steered.

<Example 2>
A ball screw device 200 according to the second embodiment will be described with reference to FIG. FIG. 9 is shown corresponding to FIG. In the ball screw device 200 of the second embodiment, the pair of guide members 80 and 80 of the ball screw device 10 of the first embodiment shown in FIGS. 1 to 8 is replaced with the pair of guide members 280 and 280 shown in FIG. Since the other configuration is the same as that of the first embodiment, the description is omitted.

  The first surfaces 81 and 81 of the pair of guide members 280 and 280 according to the second embodiment are separated from each other without being in contact with the outer peripheral surface 45 a of the small diameter portion 45. That is, there is a gap between the first surfaces 81 and 81 and the outer peripheral surface 45a. For this reason, it is not necessary to strictly manage the dimensions from the first surface 81, 81 to the second surface 82, 82. The management man-hour of the ball screw device 200 can be reduced. Other functions and effects are the same as those of the first embodiment.

<Example 3>
The ball screw device 300 according to the third embodiment will be described with reference to FIG. FIG. 10 is shown corresponding to FIG. In the ball screw device 300 of the third embodiment, the pair of guide members 80 and 80 of the ball screw device 10 of the first embodiment shown in FIGS. 1 to 8 is replaced with the pair of guide members 380 and 380 shown in FIG. Since the other configuration is the same as that of the first embodiment, the description is omitted.

  The first surfaces 81 and 81 and the second surfaces 82 and 82 of the pair of guide members 380 and 380 according to the third embodiment have a curved configuration that protrudes outward. More specifically, the first surfaces 81 and 81 have a curved cross-sectional configuration that is convex toward the outer peripheral surface 45 a of the small diameter portion 45. For this reason, in Example 3, only the convex tips of the curved first surfaces 81, 81 can contact the outer peripheral surface 45 a of the small diameter portion 45. The second surfaces 82, 82 have a curved cross-sectional configuration that is convex toward the inner peripheral surface 61 a of the fitting portion 61. For this reason, in Example 3, only the convex tips of the curved second surfaces 82 and 82 can contact the inner peripheral surface 61 a of the fitting portion 61. Therefore, it is not necessary to strictly manage the shapes and dimensions of the first surfaces 81, 81 and the second surfaces 82, 82. The management man-hour of the ball screw device 300 can be reduced. Other functions and effects are the same as those of the first embodiment.

<Example 4>
A ball screw device 400 according to a fourth embodiment will be described with reference to FIGS. The ball screw device 400 according to the fourth embodiment includes a pair of end deflectors 90 and 90 of the ball screw device 10 according to the first embodiment shown in FIGS. 1 to 8 and a pair of end deflectors 470 shown in FIGS. , 470, and the other configuration is the same as that of the first embodiment, and the description thereof will be omitted.

Hereinafter, the ball screw device 400 will be described in detail.
As shown in FIGS. 1 and 11 to 13, the ball screw device 400 includes a nut 40 in which a spiral groove 42 (screw portion 42) is formed on the inner peripheral surface 41, and the nut 40. A screw shaft 20 having a spiral groove 22 (screw portion 22) formed thereon, a plurality of balls 30 rolling along the spiral groove 22, and a pair of end deflectors 470 and 470 attached to the nut 40 (only one is shown in the figure) ). In the following description, the traveling direction of the ball 30 refers to the direction in which the ball 30 enters the end deflector 470 from the spiral grooves 22 and 42.

"Nut 40"
The nut 40 is a cylindrical member and includes a spiral groove 42 that accommodates the ball 30 between the nut 30 and the spiral groove 22 of the screw shaft 20, as shown in FIG. 11. The cross-sectional shape of the spiral grooves 22 and 42 is, for example, a Gothic arc shape having pointed groove bottom portions 22a and 42a. The groove crest 22b of the spiral groove 22 and the groove crest 42b of the spiral groove 42 are separated by a distance s.

  FIG. 13A shows a state before the end deflector 470 is assembled to the nut 40. FIG.13 (b) has shown the structure which looked at the end deflector 470 shown by Fig.13 (a) from the radial outside.

  As shown in FIGS. 13A and 13B, the axis line CL direction (axis CL direction) outer side Ou refers to a direction away from the center part of the nut 40 in the axis line CL direction along the axis line CL direction. The direction inside In refers to a direction approaching the center of the nut 40 in the axis CL direction.

  The accommodating portion 48 (that is, the concave portion 48) that accommodates the end deflector 470 extends from the inner peripheral surface 41 of the nut 40 toward the outer peripheral surface 44a, and faces the first side wall surface 628 and the second side wall surface 629 that face each other. The bottom wall surface 630 (ie, the inner periphery of the fitting portion 61) formed between the edge near the outer peripheral surface 44 a of the nut 40 on the first side wall surface 628 and the edge near the outer peripheral surface 44 a of the nut 40 on the second side wall surface 629. Corresponding to the surface 61a), a first abutting surface 631 formed on the inner edge of each of the first side wall surface 628, the second side wall surface 629, and the bottom wall surface 630 in the direction of the axis CL, and the first side wall surface 628. The second side wall surface 629 and the bottom wall surface 630 are defined by the second abutting surface 632 formed on the outer edge of each of the bottom wall surfaces 630 in the direction of the axis CL.

  The first side wall surface 628, the second side wall surface 629, and the bottom wall surface 630 are formed along the axis line CL direction, and the first abutting surface 631 is formed along a surface orthogonal to the axis line CL direction. The first side wall surface 628 and the second side wall surface 629 are opposed to each other, but need not be parallel to each other. The second side wall surface 629 is formed so as to be smoothly connected to the end 22 c of the spiral groove 22. An opening of the circulation path 62 (circulation path 62) faces the first abutting surface 631. The circulation path 62 is formed in the nut 40 along the direction of the axis CL, and a similar opening is formed at the opposite end of the nut 40.

"End deflector 470"
Referring also to FIG. 11, the end deflector 470 functions to rectify the spiral movement of the ball 30 in the spiral grooves 22 and 42 and the movement in the axis CL direction in the circulation passage 62, that is, the spiral grooves 22 and 42 and the circulation passage. This is a member having a function of changing the direction of the ball 30 with respect to 62.

  14A is a perspective view of a state in which the first member 473 and the second member 474 constituting the end deflector 470 are assembled, and FIG. 14B is a state before the first member 473 and the second member 474 are assembled. FIG. 14C is a plan view of the state in which the first member 473 and the second member 474 are assembled.

  Referring mainly to FIG. 13 and FIG. 14, a passage 518 (communication hole 518) for passing the ball 30 is formed inside the end deflector 470. In the fourth embodiment, mainly from the viewpoint of moldability of the passage 518, the end deflector 470 is a first member in which a semicircular passage (referred to as a first half passage 511) having a semicircular cross section connected to the spiral groove 22 of the screw shaft 20 is formed. 473 and a second member 474 formed with a semicircular passage (referred to as a second half passage 517) having a semicircular cross section continuous with the spiral groove 22 of the nut 40. The material of the end deflector 470 is not particularly limited, and is a metal material, a synthetic resin material, or the like. When the end deflector 470 is made of, for example, a zinc material, a part can be formed by a die casting method.

  The first member 473 includes, as an outer surface substantially along the axis CL direction, a first side surface 476 formed following the first side wall surface 628, an outer surface 513A formed following the bottom wall surface 630, and the screw shaft 20. And a split surface 478 which is a surface in contact with the second member 474. An end surface of the first member 473 closer to the inner side in the axis line CL direction is formed as a to-be-abutted surface 479 that abuts against the first abutting surface 631. The end surface of the first member 473 on the outer side in the axis line CL direction is formed as a to-be-abutted surface 510 that abuts against the second abutting surface 632. A first half passage 511 that forms half of the passage 518 of the ball 30 is formed in the dividing surface 478. A part of the inner surface 477 is formed with a claw portion 475 that bulges in the radially inward direction of the axis CL and is positioned in the spiral groove 22 of the screw shaft 20. The claw portion 475 has a substantially semicircular shape with a size that does not interfere with the spiral groove 22.

  The second member 474 includes a second side surface 512 formed following the second side wall surface 629, an outer side surface 513B formed following the bottom wall surface 630, and a first member as outer surfaces generally extending along the axis CL direction. 473 and a divided surface 514 that is a surface to be contacted. The end surface of the second member 474 closer to the inner side in the axis line CL direction is formed as a butted surface 515 that abuts against the first abutting surface 631. The end surface of the second member 474 on the outer side in the axis line CL direction is formed as a to-be-abutted surface 516 that abuts against the second abutting surface 632. A second half passage 517 that forms half of the passage 71 of the ball 30 is formed in the dividing surface 514. A notch 540 is formed at the tip of the second half passage 517 so as to smoothly guide the ball 30 from the end 22 c of the spiral groove 22.

  Engaging protrusions 519 are formed on the dividing surface 514 of the second member 474, and engaging recesses 520 are formed on the dividing surface 478 of the first member 473. The first member 473 and the second member 474 are such that the engaging projection 519 snap-engages with the engaging recess 520 so that the split surfaces 478 and 514 are in contact with each other, and the two are integrated into the end deflector 470. Configure. The end surfaces 510 and 516 are continuous with each other, and the abutted surfaces 479 and 515 are also continuous with each other. In the end deflector 470, the first half passage 511 and the second half passage 517 are combined, so that the first passage 518A communicating with the spiral grooves 22 and 42 and the first passage 518A are smoothly and substantially omitted. A passage 518 is formed which includes a second passage 518B formed by changing the direction by 90 degrees and communicating with the opening of the circulation passage 62 along the direction of the axis CL. The structure for integrating the first member 473 and the second member 474 is not particularly limited to the engagement method of the engagement protrusion 519 and the engagement recess 520. Further, there may be no structure in which the first member 473 and the second member 474 are integrated.

In the above configuration, when the ball 30 enters the end deflector 470 as shown in FIG.
(1) A sandwiched state between the spiral groove 42 and the spiral groove 22;
(2) A sandwiched state between the spiral groove 42 and the second half passage 517 of the second member 474,
(3) The first half passage 511 of the first member 473 and the second half passage 517 of the second member 474 are sandwiched in this order.
Regarding the transition from (1) to (2), the second half passage 517 of the second member 474 is notched 540 (FIG. 14) without causing a gap or a step with respect to the end 22c of the spiral groove 22 of the nut 40. The ball 30 can be smoothly moved by making it communicate smoothly by reference. However, regarding the transition from (2) to (3), since the screw shaft 20 is a movable body with respect to the end deflector 470, the first member 473 of the end deflector 470 and the spiral groove 22 of the screw shaft 20 A gap t for avoiding contact must be set between them. Accordingly, as described above, the presence of the gap t makes it easy for the ball 30 to collide with the claw portion 475 and to generate a collision sound.

"Ball lifting part 571, 572"
In response to this problem, the end deflector 470 of the present invention includes a pair of ball lifting portions 571 and 572 (see FIGS. 16 to 18) provided across the center of the width of the spiral groove 22 of the screw shaft 20. The pair of ball lifting portions 571, 572 lifts the ball 30 from the spiral groove 22 by supporting the ball 30 at two positions spaced in the width direction of the spiral groove 22 across the width center of the spiral groove 22.

  In the fourth embodiment, the ball lifting portions 571 and 572 are formed on the first member 473. 14 to 16, the first member 473 extends along the ball traveling direction between the second member 474 and the groove crest portion 22 b of the screw shaft 20, and sandwiches the width center of the spiral groove 22 of the screw shaft 20. Are provided with a pair of thin plate portions 573 and 574 that are spaced apart in the width direction of the spiral groove 22. An inclined surface 575 is formed on the side surface of the thin plate portion 573 facing the thin plate portion 574, and an inclined surface 576 is formed on the side surface of the thin plate portion 574 facing the thin plate portion 573. The inclined surfaces 575 and 576 are inclined so as to be displaced toward the center of the width of the spiral groove 22 as they go in the radially inward direction of the screw shaft 20, and can be seen from FIGS. 17A to 17C and FIG. In this way, the distance L between each other becomes narrower toward the ball traveling direction. The inclined surfaces 575 and 576 constitute the ball lifting portions 571 and 572. As can be seen from the above, the ball lifting portions 571 and 572 are located in the radially outward direction of the axis CL with respect to the groove peak portion 22b of the spiral groove 22.

  FIGS. 17A, 17B, and 17C are action cross-sectional views showing how the ball 30 is lifted by the ball lifting portions 571, 572. FIG. 17A to 17C generally show the AA cross section, the BB cross section, and the CC cross section of FIGS. 15 and 18. In FIGS. 17A to 17C and FIG. 16, the inclined surfaces 575 and 576 are illustrated in stippling in order to make it easy to understand that the distance L between the inclined surfaces 575 and 576 is gradually reduced. It is illustrated.

  The inclined surfaces 575 and 576 may have a curved surface shape that follows the spherical surface of the ball 30 or may have a flat surface shape. As shown in FIG. 16, the distance w between the groove portion 22b of the screw shaft 20 and the thin plate portions 573 and 574 is set smaller than the distance u between the groove portion 22b of the screw shaft 20 and the ball center p. The edges of the inclined surfaces 575 and 576 closer to the inner diameter direction are located in the inner diameter direction than the ball center p. Therefore, when the ball 30 reaches the inclined surfaces 575 and 576, the inclined surfaces 575 and 576 are brought into contact with the spherical surface below the center p of the ball 30 to lift the ball 30 from both sides, and the separation distance L toward the traveling direction. As the ball becomes narrower, the ball 30 is gradually lifted.

"Action"
When the ball 30 enters the end deflector 470 from the spiral grooves 22 and 42, as shown in FIGS. 17A to 17C, the inclined surfaces 575 and 576 lift the ball 30 from both sides and move in the traveling direction. As the distance L between the inclined surfaces 575 and 576 becomes narrower, the ball 30 is gradually raised. As a result, the ball 30 enters the passage 518 in the end deflector 470 without colliding with the tip of the claw portion 475.

  If the configuration includes the pair of ball lifting portions 571 and 572 as in the fourth embodiment, the impact when contacting the lifting portions 571 and 572 is dispersed in two places. Therefore, even if a collision sound is generated when abutting against the lifting portions 571 and 572, it is smaller than a collision sound when abutting against the conventional claw portion 475. Since the lifting portions 571 and 572 are located approximately 180 degrees opposite to each other with the center p of the ball 30 in between, the behavior of the ball 30 jumping when contacting the lifting portions 571 and 572 is also suppressed.

  In addition, the ball lifting portions 571 and 572 according to the fourth embodiment are located on the outer side of the axis CL with respect to the groove peak portion 22 b of the spiral groove 22. In the structure in which the ball 30 is hit by the conventional claw portion 475, a contact avoidance gap t must be set between the claw portion 475 and the spiral groove 22, and therefore, the collision angle with respect to the ball 30 (the traveling direction of the ball 30). And the angle of intersection of the ball 30 with the tangential direction at the collision portion) increases and the collision sound tends to increase. On the other hand, if the ball lifting portions 571 and 572 are positioned in the radially outward direction of the axis CL with respect to the groove portion 22b of the spiral groove 22, any contact with the screw shaft 20 should be taken into account when lifting the ball 30. In addition, the collision angle of the ball lifting portions 571 and 572 to the ball 30 can be set very shallow. That is, it becomes possible to position the periphery of the tip of the ball lifting portions 571 and 572 substantially along the tangential direction of the spherical surface of the ball 30. As a result, the occurrence of collision noise can be almost eliminated.

  Further, the ball lifting portions 571 and 572 are inclined so as to be displaced toward the center of the width of the spiral groove 22 as they go in the radially inward direction of the screw shaft 20, and the separation distance L between them increases as they go in the ball traveling direction. If the pair of narrow inclined surfaces 575 and 576 are configured, the ball lifting portions 571 and 572 can have a simple structure, and the ball 30 can be lifted smoothly.

  Further, as in the fourth embodiment, if the first member 473 has a pair of thin plate portions 573 and 574, and the inclined surfaces 575 and 576 are formed on the thin plate portions 573 and 574, the first member 473 and the second member 473 are formed. The shape design of the end deflector 470 in the case of being divided into the members 474 is easy.

  The ball screw 10 and the vehicle steering device 100 according to the present invention are not limited to the embodiments as long as the operations and effects of the present invention are exhibited.

  For example, the transmission device 1 is not limited to the configuration used for the vehicle steering device 100, and can be used for various devices such as various industrial machines such as machine tools and transportation equipment.

  Further, for example, the vehicle steering device 100 shown in FIG. 8 may have a configuration of a steer-by-wire type steering device or an autonomous driving vehicle steering device.

  The steer-by-wire steering device mechanically separates the steering wheel 111 and the steered shaft 116, and the electric motor 133 generates steering power according to the steering amount of the steering wheel 111. Is transmitted to the steered shaft 116 by the belt transmission mechanism 150.

  The automatic driving vehicle steering apparatus completely eliminates the steering wheel 111, the steering shaft 112, the universal shaft joint 113, the input shaft 114, and the first transmission mechanism 115 in the steering system 110, and the electric motor 133. The second transmission mechanism 134 is provided. By transmitting the power for steering generated by the electric motor 133 to the steering shaft 116 by the belt transmission mechanism 150 without steering by the driver, the wheels 121 and 121 can be automatically steered.

  Further, the bearing 50 shown in FIG. 1 is not limited to a rolling bearing, and may be a sliding bearing, for example. The stop member 51 may be configured to restrict the movement of the bearing 50 in the axial direction of the nut 40, and may be, for example, a configuration of a retaining ring.

  Further, the transmission member 60 shown in FIG. 1 may be configured to transmit the rotational force to and from the nut 40. For example, a hollow input shaft or output shaft included in various drive sources such as an electric motor or an engine can be used as the transmission member 60.

  Further, the recess 71 for constituting a part of the circulation portion 70 shown in FIG. 7 includes a part of the bottom surface 47a of the annular recess 47 of the large diameter portion 44 and the third surface of the pair of guide members 80 and 80. The space surrounded by 83 and 83 is not limited, and may be any configuration as long as it is recessed from the outer peripheral surface 44a of the large diameter portion 44 toward the center of the nut 40, for example.

In the fourth embodiment, the ball lifting portions 571 and 572 are formed on the first member 473 side, but may be formed on the second member 474 side.
Further, the end deflector 470 is not divided into the first member 473 and the second member 474, and may be integrally formed as a whole.
Furthermore, if the ball 30 can be smoothly guided to the passage 518 in the end deflector 470 by the ball lifting portions 571 and 572, the claw portion 475 protruding in the spiral groove 22 may be omitted.

  The transmission device 10 and the vehicle steering device 100 of the present invention are suitable for being mounted on an automobile.

DESCRIPTION OF SYMBOLS 1 Transmission device 2 Housing 10 Ball screw 20 Screw shaft 21 Outer peripheral surface of screw shaft 22 Screw portion 30 Ball 40 Nut 41 Inner peripheral surface of nut 42 Screw portion 44 Large diameter portion 44a Outer surface of large diameter portion 45 Small diameter portion 45a Small diameter portion Outer peripheral surface 45b male serration 45d male screw 46 stepped surface 50 bearing (rolling bearing)
51 Stopping member (Lock nut for rolling bearing)
60 Transmission member 61 Hub 62 First hub 62b Female serration 62b
63 2nd hub part 63a Inner peripheral surface of 2nd hub part 70 Circulation part (circulation passage)
DESCRIPTION OF SYMBOLS 71 Recessed part 72 Pair of side surface of recessed part 73 Bottom face of recessed part 100 Vehicle steering device 111 Steering wheel 116 Steering shaft 121 Steering wheel 133 Electric motor 150 Belt transmission mechanism 151 Drive pulley 152 Driven pulley 153 Belt CL Centerline of screw shaft (Nut centerline)
D1 Outer diameter of large diameter part D2 Outer diameter of small diameter part D3 Diameter of bottom surface of annular recess

Claims (5)

A tubular housing;
A screw shaft that is housed in the housing so as to be movable along the housing, and has a threaded portion on an outer peripheral surface;
A plurality of balls positioned so as to be able to roll on the threaded portion;
A cylindrical member connected to the threaded portion by the plurality of balls, a large-diameter portion having an outer peripheral surface that circulates the plurality of balls rolling the threaded portion; A nut having a small-diameter portion that is continuous with the large-diameter portion in the axial direction of the screw shaft and has a smaller diameter than the large-diameter portion;
A bearing that rotatably supports the small diameter portion inside the housing;
A transmission member having a hub fitted to the small-diameter portion of the nut and coupled to the small-diameter portion so that rotational force can be transmitted to each other;
Only including,
The nut has a step surface that is located at a boundary between the large diameter portion and the small diameter portion and orthogonal to the center line of the nut,
The hub has a cylindrical first hub portion and a cylindrical second hub portion,
The first hub portion and the second hub portion are continuous and integrated in the axial direction of the hub,
The inner peripheral surface of the first hub portion is fitted to the small diameter portion and serrated to the small diameter portion,
The first hub and the bearing are positioned in this order in the axial direction with respect to the step surface, and the nut is moved in the axial direction by the stop member provided on the small diameter portion and the step surface. Regulated,
The outer peripheral surface of the second hub portion is provided with a transmission portion of the transmission member,
An inner peripheral surface of the second hub portion is fitted to the large diameter portion,
The large-diameter portion has a pair of mutually parallel side surfaces and a bottom surface that form a recess that is recessed from the outer peripheral surface of the large-diameter portion toward the center of the nut,
The circulation portion is a circulation passage defined by the pair of side surfaces, the bottom surface, and the inner peripheral surface of the second hub portion.
A transmission device characterized by that. The bearing is constituted by a rolling bearing,
The transmission device according to claim 1 , wherein the stopper member is configured by a rolling bearing lock nut that can be screwed into the small diameter portion. A tubular housing;
A screw shaft that is housed in the housing so as to be movable along the housing, and has a threaded portion on an outer peripheral surface;
A plurality of balls positioned so as to be able to roll on the threaded portion;
A cylindrical member connected to the threaded portion by the plurality of balls, and a large-diameter portion having a circulating portion on the outer peripheral surface for circulating the plurality of balls rolling the threaded portion; A nut having a small-diameter portion that is continuous with the large-diameter portion in the axial direction of the screw shaft and has a smaller diameter than the large-diameter portion;
A rolling bearing that rotatably supports the small diameter portion in the housing;
A transmission member constituted by a pulley having a hub serrated to the small diameter portion of the nut;
Including
The nut has a step surface that is located at a boundary between the large diameter portion and the small diameter portion and orthogonal to the center line of the nut,
The hub has a cylindrical first hub portion and a cylindrical second hub portion,
The first hub portion and the second hub portion are continuous and integrated in the axial direction of the hub,
An inner peripheral surface of the first hub portion is fitted to the small diameter portion and is serrated to the small diameter portion,
The first hub and the rolling bearing are positioned in this order in the axial direction with respect to the step surface, and a bearing lock nut screwed into the small-diameter portion and the step surface are provided in the axial direction of the nut. Is restricted from moving to
The outer peripheral surface of the second hub portion is provided with a transmission portion of the transmission member,
The inner peripheral surface of the second hub part is fitted to the large diameter part,
The large-diameter portion has a pair of parallel side surfaces and a bottom surface that form a recess that is recessed from the outer peripheral surface of the large-diameter portion toward the center of the nut,
The circulation portion is a circulation passage defined by the pair of side surfaces, the bottom surface, and an inner peripheral surface of the second hub portion.
A transmission device characterized by that. The large diameter portion has a pair of recesses on the outer peripheral surface,
A pair of end deflectors that can be individually fitted to the pair of recesses from the outside of the diameter, further comprising:
The pair of end deflectors communicates between a thread groove in a portion where the screw shaft and the nut face each other, and both ends of the circulation passage.
Each of the pair of end deflectors includes a pair of ball lifting portions provided across a width center of the screw portion of the screw shaft,
Each of the pair of ball lifting portions lifts the ball from the screw portion by supporting the ball at two locations spaced in the width direction across the width center of the screw portion.
The transmission device according to any one of claims 1 to 3 . A transmission device according to any one of claims 1 to 4 ,
An electric motor that generates a driving force for steering transmitted from the transmission member to the nut;
A turning shaft configured by the screw shaft to steer a wheel for turning;
A vehicle steering apparatus.

Images