JP2021196044A - Ball screw device and steering device - Google Patents

Abstract

To secure circulation of air inside and outside a ball nut in a ball screw device.SOLUTION: A ball screw device includes: a screw shaft body 110 including a first screw groove 111 at an outer peripheral surface part; a ball nut 120 having a second screw groove 122 forming a rolling passage, in which balls 121 roll, with the first screw groove 111 at an inner peripheral surface part; a circulation member 124 which is inserted into an attachment hole 123 formed at an outer peripheral surface part of the ball nut 120 to form an annular passage 125 of the balls 121; a housing 140 which houses the screw shaft body 110 and the ball nut 120; and a bearing 141 which rotatably holds the ball nut 120 on the housing 140. The circulation member 124 includes a main communication hole 126 penetrating from an outer peripheral surface to an inner peripheral surface of the ball nut 120 between the annular passage 125 and the bearing 141.SELECTED DRAWING: Figure 2

Description

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

As one of the ball screw devices, a screw shaft having a spiral screw groove formed on the outer peripheral surface and a ball nut screwed into the screw groove of the screw shaft body via a plurality of balls are provided to provide a ball nut. There is a device that moves the screw shaft linearly by rotating it.

For example, Patent Document 1 describes a ball screw device provided in a steering device, and the ball nut of the ball screw device is formed with a communication hole that allows air to flow between the outer circumference and the inner circumference. There is.

Japanese Unexamined Patent Publication No. 2015-47891

However, in order to form a communication hole in the ball nut, it is necessary to cut the ball nut, which increases the manufacturing process of the ball screw device.

The present invention has been made in view of the above problems, and is a ball screw device capable of ensuring air flow between the outside and the inside of the ball nut without processing the ball nut, and a steering device provided with the ball screw device. The purpose is to provide.

In order to achieve the above object, the ball screw device, which is one of the present inventions, has a screw shaft body having a first screw groove on the outer peripheral surface portion and a rolling path in which a plurality of balls roll together with the first screw groove. A ball nut having a second screw groove on the inner peripheral surface portion, a circulation member inserted into a mounting hole formed on the outer peripheral surface portion of the ball nut to form a ring flow path of the ball, and the screw shaft body. A housing for accommodating the ball nut and a bearing for rotatably holding the ball nut with respect to the housing are provided, and the circulation member is provided from the outer peripheral surface of the ball nut between the ring flow path and the bearing. It has a main communication hole that penetrates to the inner peripheral surface.

Further, in order to achieve the above object, in the steering device which is another one of the present invention, a screw shaft body having a first screw groove on the outer peripheral surface portion and a plurality of balls roll together with the first screw groove. A ball nut having a second thread groove forming a rolling path on the inner peripheral surface portion, a circulation member inserted into a mounting hole formed on the outer peripheral surface portion of the ball nut to form a ring flow path of the ball, and the screw. The shaft body, a housing for accommodating the ball nut, a bearing for rotatably holding the ball nut with respect to the housing, and boots for sealing both ends of the screw shaft body and the housing, respectively, are provided. The circulation member includes a main communication hole penetrating from the outer peripheral surface to the inner peripheral surface of the ball nut between the ring flow path and the bearing.

According to this ball screw device, it is possible to provide a communication hole for communicating the inside and the outside of the ball nut without going through a processing step of providing a through hole in the ball nut by cutting or the like, and the ball screw device can be provided with a small number of man-hours. Can be manufactured.

Further, according to the steering device, it is possible to move air between the inside and the outside of the ball nut without providing a hole for air flow in the ball nut. Therefore, in the two spaces in the housing divided by the bearing, the ball nut, and the screw shaft body, the pressure difference generated by the boot deformed by the movement of the screw shaft body is alleviated by the through hole provided in the circulation member. It becomes possible.

It is a figure which shows the steering apparatus. It is a figure which shows the vicinity of the ball nut of a ball screw device in a partial cross section. It is a perspective view which shows the ball nut and a bearing. It is a perspective view which shows the state which the circulation member was removed from a ball nut. It is a figure which shows the steering apparatus which concerns on another Example 1. FIG. It is a figure which shows the steering apparatus which concerns on another Example 2. FIG.

Hereinafter, embodiments of the ball screw device and the steering device according to the present invention will be described with reference to the drawings. The numerical values, shapes, materials, components, positional relationships of the components, connection states, steps, the order of steps, etc. shown in the following embodiments are examples, and are not intended to limit the present invention. Further, in the following, a plurality of inventions may be described as one embodiment, but the components not described in the claims will be described as arbitrary components with respect to the claimed invention. ing. Further, the drawings are schematic views in which emphasis, omission, and ratio adjustment are appropriately performed in order to explain the present invention, and may differ from the actual shape, positional relationship, and ratio.

FIG. 1 is a diagram showing a steering device. FIG. 2 is a diagram showing a partial cross section of the vicinity of the ball nut of the ball screw device. The steering device 100 is a power steering device that steers the steering wheel 210 based on the torque generated by the driver operating the operating member 200 such as the steering wheel and the assist torque by the driving means 150, and is the ball screw device 101. , A pulley 130, a drive means 150, and a boot 142. Further, the ball screw device 101 includes a ball nut 120, a circulation member 124, a screw shaft body 110, a housing 140, and a bearing 141. In the case of the present embodiment, the steering device 100 further has a steering shaft 160 in which a plurality of shaft bodies are connected by universal joints and the rotational torque of the operating member 200 operated by the driver is mechanically transmitted to the screw shaft body 110. I have.

The screw shaft body 110 is a rod-shaped member having a first screw groove 111 in a part of the outer peripheral surface portion. The screw shaft body 110 provided in the steering device 100 is connected to the steering wheel 210 via the tie rod 211, and functions as a steering shaft body for steering the steering wheel 210. Further, the screw shaft body 110 has a long rod shape, and a first screw groove 111 is provided at one end thereof, and a rack 112 is provided at the other end portion. The rack 112 provided on the screw shaft body 110 constitutes a rack and pinion mechanism that meshes with the pinion 161 provided at the tip of the steering shaft 160. In the steering device 100, the rotational torque transmitted via the steering shaft 160 is converted into the linear motion of the screw shaft body 110 by the rack and pinion mechanism, and the assist torque by the drive means 150 is the linear motion of the screw shaft body 110. It is a so-called electric power steering device that is converted to.

The housing 140 is a member that houses the screw shaft body 110, the ball nut 120, and the like. In the case of the present embodiment, the housing 140 is a member that is fixed to the vehicle body by using a bracket integrally molded on the outside and guides the screw shaft body 110 housed inside in the axial direction (Y-axis direction in the figure). be. The housing 140 is made of, for example, an aluminum alloy. Further, bellows tubular boots 142 made of rubber or the like are attached to both ends of the housing 140. Since the boots 142 are sealed between both end portions of the housing 140 in the longitudinal direction and the screw shaft body 110, the housing 140 is in a sealed state to some extent, and water, mud, etc. can enter inward. Is prevented. Since one end of the boot 142 is attached to the housing 140 and the other end is attached to the screw shaft body 110, when one boot 142 inflates due to the movement of the screw shaft body 110 with respect to the housing 140, the other boot 142 is opened. Wither, the pressure of the air inside the housing 140 changes.

FIG. 3 is a perspective view showing a ball nut and a bearing. FIG. 4 is a perspective view showing a state in which the circulation member is removed from the ball nut. The ball nut 120 is provided so as to face the first thread groove 111 provided on the screw shaft body 110, and together with the first thread groove 111, forms a rolling path on which a plurality of balls 121 roll. It is a cylindrical member having (not shown in FIG. 3) on the inner peripheral surface portion. A circulation member 124 forming the ring flow path 125 of the ball 121 is attached to the mounting hole 123 formed on the outer peripheral surface of the ball nut 120 in a press-fitted state.

The mounting hole 123 provided in the ball nut 120 is a hole into which the circulation member 124 is press-fitted, and both ends of the circulation member 124 are provided at both ends of the screw shaft body 110 in the axial direction (Y-axis direction in the drawing). There is a through hole to be fitted. The circulation member 124 inserted into the mounting hole 123 is formed with a ring flow path 125 that guides the ball 121 scooped up from the rolling path in one through hole to the other through hole and returns it to the rolling path. .. The ring flow path 125 may be formed inside the circulation member 124, or may be formed by a groove provided on the bottom surface of the mounting hole 123 and a groove provided so as to face the circulation member 124. No.

When the ball nut 120 is rotated with respect to the screw shaft body 110, the circulation member 124 guides the ball 121 scooped up from the rolling path to the ring flow path 125 through one of the through holes and rolls through the other through hole. It has the function of discharging to the flow path. By infinitely circulating the ball 121 in the rolling path through the ring flow path 125, it is possible to convert the rotation of the ball nut 120 into the linear motion of the screw shaft body 110 with low frictional resistance.

The ball nut 120 is housed in the housing 140 in a state where the screw shaft body 110 is pierced, and is attached to the housing 140 via a bearing 141. The ball nut 120 rotates about the axis of the screw shaft body 110 with respect to the housing 140. On the end surface of the ball nut 120, screw holes 129 into which a fastening member for fixing the pulley 130, which will be described later, is inserted are provided at a plurality of places.

The circulation member 124 includes a main communication hole 126 that penetrates from the outer peripheral surface to the inner peripheral surface that is not held by the bearing 141 of the ball nut 120. The main communication hole 126 is provided between the ring flow path 125 and the bearing 141 in a state of not communicating with the ring flow path 125 of the ball 121 provided in the circulation member 124. The main communication hole 126 ensures the flow of air outside the ball nut 120 not covered by the bearing 141 and air inside the ball nut 120 between the first thread groove 111 and the second thread groove 122. It becomes possible. Therefore, the imbalance of air pressure on both sides of the bearing 141 generated in the housing 140 due to the expansion and contraction of the boot 142 can be corrected by the main communication hole 126, and the boot 142 expands or contracts excessively. It is possible to suppress the damage of the boot 142 caused by the above.

The method for forming the main communication hole 126 is not particularly limited, but in the case of the present embodiment, the circulation member 124 is a so-called molded product manufactured by using a mold, and the main communication hole 126 is a circulation product. It is molded at the same time as the molding of the member 124. The shape of the main communication hole 126 is not particularly limited, but is a groove shape that opens toward the inner peripheral surface of the mounting hole 123 of the ball nut 120. It has the same shape as the sub-communication hole 127 (described later) shown in FIG. With this shape, the releasability of the circulation member 124 with respect to the molded mold can be enhanced, and the main communication hole 126 can be easily provided in the circulation member 124. Specific examples of the molding method of the circulation member 124 include metal injection molding (MIM: Metal Injection Molding) in which a mixture of metal powder and a binder is injected into a molding mold, resin injection molding, and the like. Can be done.

Further, in the case of the present embodiment, the circulation member 124 is provided with an auxiliary communication hole 127 penetrating from the outer peripheral surface to the inner peripheral surface of the ball nut 120 on the opposite side of the main communication hole 126 with respect to the ring flow path 125. This makes it possible to secure the air flow from the inside to the outside of the ball nut 120 even when the air flow is obstructed by the pulley 130 or the like. Further, when the circulation member 124 is a rotationally symmetric body, it can be attached to the mounting hole 123 of the ball nut 120 without worrying about the orientation of the circulation member 124.

The pulley 130 has a cylindrical inner peripheral surface portion that is fitted to the outer peripheral surface portion of the ball nut 120, and is a cylindrical member that is fastened to the ball nut 120 in the axial direction (Y-axis direction in the drawing) of the screw shaft body 110. Is. In the case of the present embodiment, the pulley 130 includes an annular flange portion 131 that protrudes inward at one end in the radial direction and through which the screw shaft body 110 is pierced. The flange portion 131 is provided with a plurality of fastening holes through which a fastening member such as a bolt is pierced. The fastening hole is arranged so as to penetrate along the rotation axis of the pulley 130 at a position corresponding to the screw hole 129 provided on the end face of the ball nut 120.

The pulley 130 rotates around the axis of the screw shaft body 110 by transmitting rotational torque from the drive means 150, and the ball nut is passed through the flange portion 131 fixed to the end face of the ball nut 120 by the fastening force of the fastening member. Rotate 120.

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

Rotational torque from the operating member 200 by a ball screw device 101 including a screw shaft body 110, a ball nut 120, a pulley 130, and a drive means 150 including a drive pulley 153 having a diameter smaller than that of the pulley 130. An assist mechanism that generates an assist torque is configured. Specifically, the assist mechanism transmits the assist torque to the screw shaft body 110 by the following operations. That is, when the drive pulley 153 is rotated by the motor, the pulley 130 rotates via the belt 151. Since the pulley 130 has a larger diameter than the drive pulley 153, it is in a decelerated state. The ball nut 120 integrally assembled with the pulley 130 also rotates. When the ball nut 120 rotates relative to the screw shaft body 110, the ball 121 receives a load (friction force) from the ball nut 120 and the screw shaft body 110 and circulates infinitely in the rolling path and the ring flow path 125. Through the infinite circulation of the ball 121, the torque applied to the ball nut 120 is converted into the linear motion of the screw shaft body 110, and the screw shaft body 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's steering operation.

According to the ball screw device 101 and the steering device 100 shown in the above embodiments, the main communication hole 126 that communicates the inside and the outside of the ball nut 120 is formed in the circulation member 124. Therefore, it is possible to form a flow path of air flowing inside and outside the ball nut 120 through the main communication hole 126 of the circulation member 124. This makes it possible to move air in the axial direction of the screw shaft body 110 inside the housing 140. Specifically, when the air flow on the outside of the ball nut 120 is obstructed by the bearing 141 or the like, air can be drawn into the inside of the ball nut 120 through the main communication hole 126. On the contrary, when the air flow inside the ball nut 120 is obstructed by the balls 121 or grease, the air can be pushed out of the ball nut 120 through the main communication hole 126.

Further, since the main communication hole 126 is integrally formed with the circulation member 124 together with the ring flow path 125, no special step for processing the main communication hole 126 is required.

The present invention is not limited to the above embodiment. For example, another embodiment realized by arbitrarily combining the components described in the present specification and excluding some of the components may be the embodiment of the present invention. The present invention also includes modifications obtained by making various modifications that can be conceived by those skilled in the art within the scope of the gist of the present invention, that is, the meaning indicated by the wording described in the claims, with respect to the above-described embodiment. Will be.

For example, the case where one main communication hole 126 is provided in the circulation member 124 has been described, but a plurality of main communication holes 126 may be provided in the circulation member 124 in order to secure a large number of air flow paths. Similarly, the circulation member 124 may be provided with sub-communication holes 127 at a plurality of locations.

Further, the shape of the main communication hole 126 and the sub-communication hole 127 is not a groove shape that opens toward the inner circumference of the mounting hole 123, but is a tubular having no opening other than the openings at both ends in the air flow direction. It doesn't matter. Further, the cross-sectional shapes of the main communication hole 126 and the sub-communication hole 127 that are orthogonal to the air flow direction do not have to be the same.

Further, the main communication hole 126 and the sub communication hole 127 may be curved or bent as well as straight in the air flow direction.

Further, as shown in FIG. 5, 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 used as a signal of the sensor or the like. Based on this, the screw shaft body 110 may be reciprocated by the rotation of the ball nut 120 to steer the steering wheel 210, so-called SBW (Steer By Wall System).

Further, as shown in FIG. 6, the steering device 100 may be an automatic steering device that does not include an operating member 200, a steering shaft 160, or the like, and is steered by a computer.

The present invention is a steering device for a vehicle or the like, which is a steering device capable of assisting a steering force by a person, an SBW in which an operating member and a steering wheel are not mechanically connected and are electrically steered, and an automatic steering device. It can be used for such purposes.

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

100 ... Steering device, 101 ... Ball screw device, 110 ... Shaft body, 111 ... First screw groove, 112 ... Rack, 120 ... Ball nut, 121 ... Ball, 122 ... Second screw groove, 123 ... Mounting hole, 124 ... Circulation member, 125 ... Ring flow path, 126 ... Main communication hole, 127 ... Sub communication hole, 129 ... Screw hole, 130 ... Pulley, 131 ... Flange, 140 ... Housing, 141 ... Bearing, 142 ... Boot, 150 ... Drive means , 151 ... Belt, 153 ... Drive pulley, 160 ... Steering shaft, 161 ... Pinion, 200 ... Operating member, 210 ... Steering wheel, 211 ... Tie rod

Claims (5)

A screw shaft body having a first screw groove on the outer peripheral surface,
A ball nut having a second thread groove on the inner peripheral surface portion that forms a rolling path through which a plurality of balls roll together with the first thread groove.
A circulation member that is inserted into a mounting hole formed in the outer peripheral surface of the ball nut to form a ring flow path of the ball.
The screw shaft, the housing for accommodating the ball nut, and
A bearing that rotatably holds the ball nut against the housing.
The circulation member is
A ball screw device provided with a main communication hole penetrating from the outer peripheral surface to the inner peripheral surface of the ball nut between the ring flow path and the bearing. The ball screw device according to claim 1, wherein the main communication hole has a groove shape that opens toward the inner peripheral surface of the mounting hole of the ball nut. The ball screw device according to claim 1 or 2, wherein the main communication hole does not communicate with the ring flow path of the circulation member. The circulation member is
The ball screw device according to any one of claims 1 to 3, further comprising an auxiliary communication hole penetrating from the outer peripheral surface to the inner peripheral surface of the ball nut on the opposite side of the main communication hole with respect to the ring flow path. The ball screw device according to any one of claims 1 to 4.
Boots that seal between both ends of the screw shaft and the housing, respectively.
A steering device equipped with.

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