JP7346888B2 - Steering device and ball screw device - Google Patents

Description

The present invention relates to a steering device that rotates a ball nut to move a screw shaft body in the axial direction, and a ball screw device.

One type of ball screw device includes a screw shaft with a spiral thread groove formed on the outer peripheral surface and a ball nut screwed into the thread groove of the screw shaft via a plurality of balls, and the ball nut is rotated. There is a device that moves the screw shaft in a straight line by moving the screw shaft.

For example, a ball screw device described in Patent Document 1 includes a pulley having a protrusion that protrudes radially from the outer circumferential surface of a ball nut and a groove that can fit into the protrusion. The pulley is rotated by a belt or the like, and torque is transmitted by engagement between the groove of the pulley and the protrusion of the ball nut.

Japanese Patent Application Publication No. 2006-69517

By the way, when a ball nut and a pulley are fastened together using a bolt or the like in the axial direction of a screw shaft body and torque is transmitted by the fastening force, protrusions for transmitting torque are formed on the outer peripheral surface of the ball nut using complicated machining. There is no need to provide one.

However, when connecting the ball nut and pulley in the axial direction, it takes time to align the threaded hole and through hole provided on one side of the ball nut and pulley, resulting in a longer assembly time. .

The present invention has been made in view of the above problems, and aims to provide a steering device and a ball screw device that can easily connect a ball nut and a pulley.

In order to achieve the above object, a steering device according to the present invention includes a threaded shaft body that includes a first threaded groove on an outer circumferential surface portion, and that steers a steered wheel, and a plurality of balls together with the first threaded groove. a ball nut having a second threaded groove on its inner peripheral surface that forms a rolling path for rolling; and a circulation member that is inserted into a mounting hole formed in an outer peripheral surface of the ball nut and forms a circulation path for the ball. , a pulley having an inner circumferential surface fitted to an outer circumferential surface of the ball nut and fastened to the ball nut at an axial end; a housing accommodating the screw shaft body; a driving means for rotationally driving a pulley, the circulation member includes a protrusion that protrudes beyond the outer peripheral surface of the ball nut when attached to the mounting hole, and the pulley is configured to rotate the shaft of the screw shaft body. The inner peripheral surface portion is provided with a groove portion extending in the direction, recessed in the radial direction, and having an open end for accommodating the protrusion portion.

In addition, in order to achieve the above object, a ball screw device according to another aspect of the present invention includes a screw shaft body having a first thread groove on the outer peripheral surface thereof, and a plurality of balls rolling together with the first thread groove. a ball nut having a second threaded groove on its inner peripheral surface that forms a rolling path for the ball; a circulation member that is inserted into a mounting hole formed in the outer peripheral surface of the ball nut and forms a circulation path for the ball; and a pulley having an inner circumferential surface portion that is fitted to an outer circumferential surface portion of the ball nut and is fastened to the ball nut in the axial direction of the screw shaft body, and the circulation member is mounted in the mounting hole. The pulley includes a protrusion that protrudes beyond the outer circumferential surface of the ball nut, and the pulley has a groove on the inner circumferential surface that extends in the axial direction of the screw shaft body, is recessed in the radial direction, and is open at one end to accommodate the protrusion. Be prepared.

According to the present invention, work efficiency when assembling a pulley to a ball nut can be improved.

FIG. 1 is a diagram showing a schematic configuration of a steering device according to the present embodiment. FIG. 3 is a partially cross-sectional view showing the vicinity of the ball nut according to the present embodiment. FIG. 2 is a perspective view showing the ball nut with the pulley removed according to the present embodiment. FIG. 2 is an exploded perspective view showing a ball nut, a pulley, and a circulation member according to the present embodiment. FIG. 2 is a perspective view showing a ball nut to which a pulley and a bearing are attached according to the present embodiment. FIG. 2 is a perspective view showing a ball nut to which a pulley and a bearing are attached according to the present embodiment from another direction. FIG. 3 is a plan view showing the relationship between the protrusion and the groove according to the present embodiment with the pulley in a transparent state. FIG. 7 is a plan view showing a protrusion of a different shape and a groove of a different shape with the pulley in a transparent state. FIG. 7 is a diagram showing a steering device according to another embodiment. FIG. 7 is a diagram showing a steering device according to another embodiment.

Embodiments of a steering device including a ball screw device according to the present invention will be described below with reference to the drawings. Note that the embodiments described below are all inclusive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, order of steps, etc. shown in the following embodiments are merely examples, and do not limit the present invention. Further, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the most significant concept will be described as arbitrary constituent elements.

Further, the drawings are schematic diagrams with appropriate emphasis, omission, and ratio adjustment in order to illustrate the present invention, and may differ from the actual shapes, positional relationships, and ratios.

FIG. 1 is a diagram showing a steering device. As shown in the figure, the steering device 100 is a power steering device that steers steered wheels 210 based on the torque generated by the driver's operation of an operating member 200 such as a steering wheel and the assist torque from the drive means 150. It includes a body 110, a ball nut 120, a pulley 130, a housing 140, and a driving means 150. In the case of the present embodiment, the steering device 100 further includes a steering shaft 160 in which a plurality of shaft bodies are connected by a universal joint and mechanically transmits the rotational torque of the operating member 200 operated by the driver to the screw shaft body 110. We are prepared.

The screw shaft body 110 is a rod-shaped member having a first screw groove 111 in a part of its outer peripheral surface. The threaded shaft body 110 provided in the steering device 100 is connected to the steered wheel 210 via the tie rod 211, and functions as a steered shaft body that steers the steered wheel 210. Further, a rack 112 is provided on the other portion of the screw shaft body 110, forming a rack and pinion mechanism that meshes with a pinion 161 provided at the tip of the steering shaft 160. The steering device 100 is a so-called electric power system in which the rotational torque transmitted through the steering shaft 160 is converted into direct motion of the screw shaft body 110, and the assist torque by the driving means 150 is converted into direct motion of the screw shaft body 110. It is a steering device.

The housing 140 is a member that accommodates the screw shaft body 110. In the case of this embodiment, the housing 140 is a member that is fixed to the vehicle body using an integrally molded bracket and guides the screw shaft body 110 housed inside in the axial direction. Housing 140 is made of, for example, an aluminum alloy. Furthermore, bellows-like tubular boots 142 made of rubber or the like are attached to both ends of the housing 140. Since both longitudinal open ends of the housing 140 are sealed by the boots 142, the housing 140 is sealed to some extent, preventing water, mud, etc. from entering inside.

FIG. 2 is a partial cross-sectional view of the vicinity of the ball nut. FIG. 3 is a perspective view showing the ball nut with the pulley removed. FIG. 4 is an exploded perspective view of the ball nut, pulley, and circulation member. The ball nut 120 is provided opposite to the first thread groove 111 provided on the screw shaft body 110, and has a second thread groove 122 that forms a rolling path along which a plurality of balls 121 roll together with the first thread groove 111. It is a cylindrical member having an inner peripheral surface. A circulation member 124 that forms a circulation path for the balls 121 is press-fitted into an attachment hole 123 formed on the outer peripheral surface of the ball nut 120 .

The mounting hole 123 provided in the ball nut 120 communicates with a rolling path formed by the first thread groove 111 and the second thread groove 122, and includes two communicating holes through which the balls 121 can pass. The circulation member 124 inserted into the attachment hole 123 is formed with a circulation path that guides the ball 121 scooped up from the rolling path in one communication hole to the other communication hole and returns to the rolling path. Note that the circulation path may be formed inside the circulation member 124, or may be formed by a groove provided at the bottom of the mounting hole 123 and a groove provided oppositely to the circulation member 124. .

When the ball nut 120 is rotated with respect to the screw shaft body 110, the circulation member 124 guides the balls 121 scooped up from the rolling path to the circulation path through one of the communication holes, and causes the balls 121 to roll through the other communication hole. It has the function of discharging into the street. By infinitely circulating the balls 121 in the rolling path via this circulation path, it is possible to convert the rotation of the ball nut 120 into linear motion of the screw shaft body 110 with low frictional resistance. The circulation member 124 includes a protrusion 125 that protrudes beyond the outer peripheral surface of the ball nut 120 when attached to the attachment hole 123. Details of the protrusion 125 will be described later.

The ball nut 120 is accommodated in the housing 140 with the screw shaft 110 pierced therethrough, and is attached to the housing 140 via a bearing 141. The ball nut 120 rotates around the axis of the screw shaft body 110 relative to the housing 140. The end surface of the ball nut 120 is provided with a plurality of second fastening holes 127 (see FIG. 2) into which fastening members 152 for fixing a pulley 130 (described later) are inserted.

The pulley 130 is a cylindrical member that has a cylindrical inner circumferential surface that fits into the outer circumferential surface of the ball nut 120 and is fastened to the ball nut 120 in the axial direction of the screw shaft body 110 (Y-axis direction in the figure). It is. In the case of the present embodiment, the pulley 130 includes an annular flange portion 131 that protrudes inwardly and radially at one end, and through which the screw shaft body 110 is pierced. The flange portion 131 is provided with a plurality of first fastening holes 132 into which fastening members 152 such as bolts are inserted. The first fastening hole 132 is disposed to penetrate along the rotation axis of the pulley 130 at a position corresponding to the second fastening hole 127 provided in the end surface of the ball nut 120. The groove portion 133 provided in the pulley 130 will be described later.

The pulley 130 rotates around the axis of the screw shaft body 110 due to rotational torque being transmitted from the driving means 150, and the pulley 130 rotates around the axis of the screw shaft body 110, and tightens the ball via the flange portion 131 fixed to the end surface of the ball nut 120 by the fastening force of the fastening member 152. Rotate the nut 120.

Note that the outer peripheral surface of the pulley 130 may be provided with a structure such as a groove to increase the frictional force with the belt 151.

The driving means 150 is fixed to the housing 140 and drives the pulley 130 to rotate. In the case of this embodiment, the driving means 150 includes a motor, a driving pulley 153 attached to the output shaft of the motor, and an endless belt 151 wound around the driving pulley 153 and a pulley 130 functioning as a driven pulley. It is equipped with

A ball screw device including a screw shaft body 110, a ball nut 120, and a pulley 130, and a drive means 150 including a drive pulley 153 having a smaller diameter than the pulley 130 to assist the rotational torque from the operating member 200. An assist mechanism that generates torque is configured. Specifically, the assist mechanism transmits assist torque to the screw shaft body 110 by the following operation. That is, when the drive pulley 153 is rotated by the motor, the pulley 130 is rotated via the belt 151. Since the pulley 130 has a larger diameter than the drive pulley 153, it is in a deceleration state. The ball nut 120 assembled integrally with the pulley 130 also rotates. When the ball nut 120 rotates relative to the screw shaft 110, the balls 121 receive a load (frictional force) from the ball nut 120 and the screw shaft 110 and endlessly circulate in the rolling path and the circulation path. Through this endless circulation of the balls 121, the torque applied to the ball nut 120 is converted into direct motion of the screw shaft 110, and the screw shaft 110 moves relative to the ball nut 120 in the axial direction. That is, an axial force is applied to the screw shaft body 110. The axial force applied to the screw shaft body 110 serves as an assist force to assist the driver in steering operation.

Next, a protrusion 125 that is a part of the circulation member 124 protrudes from the outer peripheral surface of the ball nut 120, and a pulley 130 that extends in the axial direction of the screw shaft body 110 and is recessed in the radial direction and accommodates the protrusion 125. The relationship with the groove portion 133 provided on the inner circumferential surface of will be explained. FIG. 5 is a perspective view showing a ball nut to which a pulley and a bearing are attached. FIG. 6 is a perspective view showing the ball nut to which the pulley and bearing are attached from another direction. FIG. 7 is a plan view showing the relationship between the protrusion and the groove when the pulley and ball nut are assembled, with the pulley seen through.

In the case of this embodiment, the protrusion 125 protrudes from the entire mounting hole 123 of the ball nut 120, as shown in FIG. That is, in the radial direction of the ball nut 120, the length of the circulation member 124 is set to be longer than the depth of the attachment hole 123 by the amount of the protrusion 125.

The groove 133 is open at one end on the bearing 141 side in the axial direction of the screw shaft body 110, and can accommodate at least a portion of the protrusion 125 of the circulation member 124 by fitting the pulley 130 into the ball nut 120. This is the part where it can be done. Further, in the circumferential direction centered on the axial direction of the screw shaft body 110, the tube axis of the first fastening hole 132 provided in the flange portion 131 with respect to at least one side wall of the groove portion 133 is set at a predetermined phase. There is. On the other hand, the tube axis of the second fastening hole 127 provided in the end face of the ball nut 120 is also set to be in the same phase as the first fastening hole 132 with respect to the protrusion 125 that abuts the side wall of the groove 133. . As a result, with the protrusion 125 accommodated in the groove 133, the pulley 130 is rotated in the circumferential direction relative to the ball nut 120 to bring the protrusion 125 and the side wall of the groove 133 into contact with each other. and the second fastening hole 127 can be easily opposed to each other. Therefore, it becomes possible to pierce the fastening member 152 into the first fastening hole 132 and screw it into the second fastening hole 127 easily, and it becomes possible to improve the work efficiency when fixing the pulley 130 to the ball nut 120. .

Furthermore, by making a part of the circulation member 124 attached to the outer circumferential surface of the ball nut 120 protrude from the outer circumferential surface of the ball nut 120, there is no need to process the outer circumferential surface of the ball nut 120 to provide a positioning protrusion. It becomes possible to process the nut 120 easily. Further, since at least a portion of the press-fitted circulation member 124 is covered by the pulley 130, the pulley 130 functions to prevent the circulation member 124 from coming off.

In the case of the present embodiment, the protruding portion 125 abuts both the first side wall 135 and the second side wall 136 (see FIG. 7) facing each other of the groove portion 133 when the pulley 130 is attached to the ball nut 120. As a result, the pulley 130 and the ball nut 120 are in a state where they do not move relative to each other in the circumferential direction, and the fastening member 152 can be inserted into the first fastening hole 132 and easily screwed into the second fastening hole 127 in a stable state. Become.

Further, the second side wall 136 that is one side wall of the groove portion 133 functions as a first inclined surface portion that gradually moves away from the first side wall 135 that is the other side wall as it goes toward the opening of the groove portion 133, that is, as it goes toward the bearing 141. There is. Furthermore, the protruding portion 125 includes a second inclined surface portion 128 that contacts a second side wall 136 that functions as an inclined surface portion, and an end portion 129 that contacts the other side wall of the groove portion 133. As a result, when the pulley 130 is fitted into the ball nut 120, the second side wall 136 functioning as the first inclined surface portion and the second inclined surface portion 128 come into surface contact, and the protruding portion 125 is attached to the first side wall 135 on the opposite side. It is possible to guide the relative rotation of the pulley 130 with respect to the ball nut 120 so that the distal end 129 of the ball nut 120 comes into contact with the ball nut 120 . Therefore, even if the pulley 130 is fitted into the ball nut 120 without worrying too much about the exact position of the groove 133 relative to the protrusion 125, it is possible to easily match the phase of the first fastening hole 132 with the second fastening hole 127. This improves work efficiency.

In addition, the ball nut 120 is a cylinder whose outer circumferential surface is a perfect circle with no irregularities on the end side where the pulley 130 is fitted rather than the mounting hole 123 where the circulation member 124 is installed in the axial direction of the screw shaft body 110. A fitting surface portion 126 is provided. On the other hand, the inner circumferential surface of the pulley 130 on the side opposite to the open end of the groove section 133 (on the flange section 131 side) can be fitted with the first fitting surface section 126, and has a perfectly circular inner circumferential surface without unevenness. A second fitting surface portion 134 that is cylindrical is provided. By fitting the first fitting surface portion 126 with no unevenness and the second fitting surface portion 134 with no unevenness, the ball nut 120 and the pulley 130 can be coaxially arranged with high precision, and the It becomes possible to match the rotation axis of the ball nut 120 with high precision.

Note that the present invention is not limited to the above embodiments. For example, the embodiments of the present invention may be realized by arbitrarily combining the components described in this specification or by excluding some of the components. The present invention also includes modifications obtained by making various modifications to the above-described embodiments that a person skilled in the art can conceive without departing from the gist of the present invention, that is, the meaning of the words written in the claims. It will be done.

For example, the protrusion 125 does not need to protrude over the entire mounting hole 123, and may protrude from a portion of the circulation member 124 as shown in FIG. In this case, the portions of the circulation member 124 other than the protruding portion 125 may be arranged flush with the outer circumferential surface of the ball nut 120 or at a position recessed from the outer circumferential surface of the ball nut 120. Further, the shape of the protruding portion 125 may be any shape such as not only a cylindrical shape but also a wedge shape.

Further, the shape of the groove portion 133 is not particularly limited, and the first side wall 135 and the second side wall 136 facing each other may both be inclined as shown in FIG. 8 .

Further, as shown in FIG. 9, in the steering device 100, the operating member 200 and the screw shaft body 110 are not mechanically connected, and the rotation angle of the operating member 200 is read by a sensor or the like, and the rotation angle of the operating member 200 is read based on the signal from the sensor or the like. It may be a so-called SBW (Steer By Wire System) in which the screw shaft body 110 reciprocates by the rotation of the ball nut 120 and steers the steered wheels 210.

Furthermore, as shown in FIG. 10, the steering device 100 may be an automatic steering device that does not include the operating member 200, the steering shaft 160, etc. and is steered by a computer.

The present invention relates to a steering device for a vehicle, etc., which is capable of assisting human steering force, an SBW in which the operating member and the steered wheels are not mechanically connected, and are electrically steered, and an automatic steering device. It can be used for etc.

The ball screw device can also be used in an electric brake device that converts the rotation of a motor into linear motion that drives a caliper.

DESCRIPTION OF SYMBOLS 100... Steering device, 110... Screw shaft body, 111... First thread groove, 112... Rack, 120... Ball nut, 121... Ball, 122... Second thread groove, 123... Mounting hole, 124... Circulation member, 125... Projection part, 126... First fitting surface part, 127... Second fastening hole, 128... Second inclined surface part, 129... End part, 130... Pulley, 131... Flange part, 132... First fastening hole, 133... Groove part, 134... Second fitting surface part, 135... First side wall, 136... Second side wall, 140... Housing, 141... Bearing, 142... Boot, 150... Drive means, 151... Belt, 152... Fastening member, 153... Drive pulley , 160...Steering shaft, 161...Pinion, 200...Operation member, 210...Steered wheel, 211...Tie rod

Claims (6)

a screw shaft body having a first screw groove on its outer peripheral surface and steering a steered wheel;
a ball nut having a second threaded groove on its inner peripheral surface that forms a rolling path along which a plurality of balls roll together with the first threaded groove;
a circulation member that is inserted into a mounting hole formed on the outer peripheral surface of the ball nut and forms a circulation path for the ball;
a pulley having an inner circumferential surface portion that fits into the outer circumferential surface portion of the ball nut, and is fastened to the ball nut at an axial end portion;
a housing that accommodates the screw shaft;
a driving means fixed to the housing and rotationally driving the pulley;
The pulley is provided with a first fastening hole through which the fastening member is penetrated,
A second fastening hole into which the fastening member for fixing the pulley is inserted is provided in an axial end surface of the ball nut,
The circulation member is
comprising a protrusion that protrudes beyond the outer circumferential surface of the ball nut when attached to the mounting hole;
The pulley is
a groove portion extending in the axial direction of the screw shaft body, recessed in the radial direction, and having an open end at one end for accommodating the protrusion portion ;
By accommodating the protrusion, the groove portion allows the phase of the tube axis of the first fastening hole and the tube axis of the second fastening hole to be in the same phase in a circumferential direction centered on the axial direction of the screw shaft body. The steering device is set to The ball nut is
In the axial direction of the screw shaft body, a first fitting surface portion having a cylindrical outer circumferential surface is provided on the end side of the position where the circulation member is attached,
The pulley is
The steering device according to claim 1, further comprising a second fitting surface portion having a cylindrical inner peripheral surface that fits into the first fitting surface portion. The protruding portion is
The steering device according to claim 1 or 2, wherein the pulley contacts at least one of opposing side walls of the groove when the pulley is attached to the ball nut. The groove portion is
One side wall includes a first inclined surface part that moves away from the other side wall as it goes toward the opening of the groove part,
The protruding portion is
a second inclined surface portion that comes into contact with the first inclined surface portion;
The steering device according to any one of claims 1 to 3, further comprising an end portion that abuts the other side wall of the groove portion. The protruding portion is
The steering device according to any one of claims 1 to 4, wherein the ball nut protrudes throughout the mounting hole. a screw shaft body having a first thread groove on its outer peripheral surface;
a ball nut having a second threaded groove on its inner peripheral surface that forms a rolling path along which a plurality of balls roll together with the first threaded groove;
a circulation member that is inserted into a mounting hole formed on the outer peripheral surface of the ball nut and forms a circulation path for the ball;
a pulley having an inner circumferential surface part fitted to an outer circumferential surface part of the ball nut and fastened to the ball nut in the axial direction of the screw shaft body,
The pulley is provided with a first fastening hole through which the fastening member is penetrated,
A second fastening hole into which the fastening member for fixing the pulley is inserted is provided in an axial end surface of the ball nut,
The circulation member is
comprising a protrusion that protrudes beyond the outer circumferential surface of the ball nut when attached to the mounting hole;
The pulley is
a groove portion extending in the axial direction of the screw shaft body, recessed in the radial direction, and having an open end at one end for accommodating the protrusion portion ;
By accommodating the protrusion, the groove portion allows the phase of the tube axis of the first fastening hole and the tube axis of the second fastening hole to be in the same phase in a circumferential direction centered on the axial direction of the screw shaft body. A ball screw device that is set to

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