WO2020250905A1 - Steering device - Google Patents

Abstract

[Problem] To achieve a structure that can obtain sufficient steering force and ensure a failsafe operastion while using an electric motor in a region with excellent efficiency. [Solution] This steering device 1 rotationally drives ball nuts 4a, 4b with a pair of electric motors 7a, 7b via reducers 8a, 8b, and applies a steering angle to a steering wheel by pushing and pulling a tie rod 31 by displacing a ball screw shaft 3 through rotary motion of the electric motors 7a, 7b.

Description

Steering device

The present invention relates to a steering device incorporated in a steer-by-wire type steering device.

<First background technology>
Suspension devices for automobiles include an independent suspension system in which the left and right wheels are independently supported by separate suspensions, and a suspension device in which the left and right wheels are connected by a single axle and the axles are supported by the suspension. There is an axle suspension type (rigid axle type). Of these, the axle suspension type suspension system is used in large vehicles such as trucks because of its simple structure and high durability.

For large vehicles such as trucks, a cab-over type structure is adopted in which the driver's seat (cab) is placed above the power source such as the engine. In a steering device mounted on such a cab-over type vehicle, when the driver operates (rotates) the steering wheel, the rotation of the steering wheel is transmitted to the input shaft of the steering gear box by the steering shaft. .. The rotation of the input shaft is converted into a swinging motion (swinging motion) of the pitman arm by the steering gear box. The pitman arm is connected to one of a pair of steered wheels (usually the front wheels) (eg, the right front wheel) via a drag link and a knuckle arm, and one steered wheel is a tie rod and a tie rod. It is connected to the other steering wheel (for example, the left front wheel) via an arm. Therefore, when the pitman arm swings with the rotation of the steering wheel, the drag link is pushed and pulled in the front-rear direction, the knuckle arm swings, the steering angle is given to one steering wheel, and at the same time, the tie rod is released. Pushed and pulled in the width direction, the tie rod arm swings, and a steering angle is given to the other steering wheel.

In addition, the steering device incorporates a power steering device for reducing the force required for the driver to operate the steering wheel. There are two types of power steering devices: an electric type that uses an electric motor as an auxiliary power source and a hydraulic type that uses hydraulic pressure. Large vehicles such as trucks employ a hydraulic power steering device that can obtain a large auxiliary torque.

<Second background technology>

The steer-by-wire type steering device includes a steering device having a steering rod such as a steering wheel, and a steering device for imparting a steering angle to a pair of steering wheels electrically connected to the steering device. .. Of these, the steering device uses an electric motor as a power source to displace the linear motion shafts arranged in the width direction of the vehicle body in the axial direction, and is connected to both ends of the linear motion shafts in the axial direction. By pushing and pulling the tie rods to swing the knuckle arm, a steering angle is given to the pair of steering wheels.

Japanese Unexamined Patent Publication No. 2005-31998 (Patent Document 1) describes a structure that can be used as a steering device constituting a steer-by-wire type steering device. The steering device described in JP-A-2005-319988 uses a ball screw mechanism, and a rotary rack having an inner diameter side ball screw groove on the outer peripheral surface is rotationally driven by an electric motor to rotate the rotary rack and the rotary rack. A steering angle is given to the steering wheel based on the linear motion of a rack (linear motion shaft) composed of non-rotating racks connected to both ends of the wheel.

Japanese Unexamined Patent Publication No. 2005-31998

<Issues related to the first background technology>
By the way, in recent years, in order to reduce the burden on the driver, research on automatic driving technology including follow-up driving and platooning has been promoted. When the vehicle is traveling in the automatic driving mode, various sensors acquire the surrounding conditions, moving distance, moving direction, etc. of the vehicle, obtain an appropriate steering angle based on the information from these sensors, and use an actuator. Gives the steering wheel a steering angle.

In a large vehicle such as a truck, in order to realize automatic driving, it is conceivable to use a hydraulic actuator, which is an auxiliary power source of the power steering device, as an actuator for imparting a steering angle to the steering wheels. However, in reality, there arises a problem that it is difficult to finely adjust the steering angle due to the influence of play and play (dead zone) existing at the connection portion between the members constituting the steering device, and the dead zone of the hydraulic actuator. In addition, if automatic driving is realized by using the auxiliary power source of the power steering device, the steering wheel will rotate as the steering angle is adjusted while the vehicle is running in the automatic driving mode, giving the occupants of the vehicle a sense of discomfort. there is a possibility.

Therefore, in a vehicle equipped with an automatic driving mode, it is preferable to use a steering device of a steer-by-wire system in which a steering wheel is given a steering angle by using an electric motor as a drive source. The steer-by-wire type steering device is formed by electrically connecting a steering device having a steering rod such as a steering wheel and a steering device that gives a steering angle to the steering wheels by using an electric motor as a power source.

Japanese Unexamined Patent Publication No. 2005-31998 (Patent Document 1) describes a structure that can be used as a steering device constituting a steer-by-wire type steering device. The steering device described in JP-A-2005-319988 uses a ball screw device, and the ball screw shaft (rack) is rotated by a direct drive type electric motor to move the ball screw shaft in a linear motion. By causing the steering wheel to have a steering angle. Since the steering device described in Japanese Patent Application Laid-Open No. 2005-319988 uses one electric motor as a drive source, the torque range that can be output by the electric motor when incorporated in a large vehicle such as a truck is compared. There is a possibility that the target output torque is low and an efficient area cannot be used, or the steering force is insufficient, for example, it becomes difficult to give (stationary) the steering angle while the vehicle is stopped. There is. Even when applied to a large vehicle, in order to obtain sufficient steering force while using it in an efficient area, use a large electric motor with a large output (rated torque). There is a need. However, when a large electric motor having a large rated torque is used, the installation position of the electric motor is limited, which may reduce the degree of freedom in design or make it difficult to reduce the cost. Further, since the steering device described in Japanese Patent Application Laid-Open No. 2005-319988 includes only one electric motor, if the power supply to the electric motor becomes impossible, the vehicle cannot be steered.

In view of the above circumstances, the present invention has a structure of a steering device capable of obtaining a sufficient steering force and ensuring fail-safe while using the electric motor in an efficient region. The purpose is to realize.

<Issues related to the second background technology>

By the way, when the steering device is driven to give a steering angle to the steering wheels (steering is performed), the steering is performed depending on the size of the steering angle of the steering wheels, that is, the swing angle of the knuckle arm. The accompanying reaction force may be applied in the radial direction (specifically, the front-rear direction of the vehicle body) with respect to the linear motion axis. The steering reaction force in the radial direction increases as the steering angle of the steering wheel increases. When the steering reaction force is applied in the radial direction with respect to the linear motion shaft, the steering reaction force may be applied to the conversion mechanism that converts the rotational motion of the output shaft of the electric motor into the linear motion of the linear motion shaft. .. In particular, in the steering device described in Japanese Patent Application Laid-Open No. 2005-3199898, a ball screw mechanism is used as a conversion mechanism. Therefore, when the steering reaction force is applied in the radial direction with respect to the linear motion shaft, the balls constituting the ball screw mechanism are transferred to the inner diameter side ball screw groove provided on the outer peripheral surface of the rotary rack and the inner peripheral surface of the screw nut. The ball screw mechanism is strongly pressed against the outer diameter side ball screw groove provided in the above, and the life of the ball screw mechanism is shortened, or indentations are formed on the inner diameter side ball screw groove and the outer diameter side ball screw groove, resulting in abnormal noise. And vibration may occur.

In view of the above circumstances, the present invention considers that a steering reaction force in the radial direction is applied to a conversion mechanism that converts the rotational motion of the output shaft of the electric motor into the linear motion in the axial direction of the linear motion shaft. The purpose is to realize a structure of a steering device that can be prevented.

<Means for Solving the Problem Related to the First Background Technology> The steering device of the present invention has a housing and a ball screw groove on the inner diameter side on the outer peripheral surface, and can be displaced in the axial direction inside the housing. In addition, it has a ball screw shaft that is supported so that it cannot rotate, and a ball screw groove on the outer diameter side on the inner peripheral surface, and is arranged around the ball screw shaft so that it can rotate relative to the ball screw shaft. A plurality of ball nuts, a bearing device that rotatably supports the ball nuts with respect to the housing, and a ball screw groove on the inner diameter side and a ball screw groove on the outer diameter side are rotatably arranged. A plurality of balls, a plurality of electric motors, and the same number of speed reducers as the electric motor, which are applied to the ball nut after increasing the output torque of the electric motor, are provided.

The steering device of the present invention may include the same number of ball nuts as the electric motor.

The steering device of the present invention may include a pair of each of the ball nut, the bearing device, the electric motor, and the speed reducer. In this case, the ball nut, the bearing device, the electric motor, and the speed reducer are arranged one by one on both side portions of the housing with the center position in the width direction, and the ball nut and the bearing are provided. Of the device, the electric motor, and the speed reducer, it is preferable that the ball nut is arranged on the side closest to the center position in the width direction of the housing. Further, the ball nuts can be arranged adjacent to each other via the housing in a state of being separated from each other with the central position in the width direction interposed therebetween.

In the steering device of the present invention, the speed reducer can be a worm speed reducer.

In the steering device of the present invention, the housing can be made by combining a plurality of housing elements.

<Means for solving problems related to the second background technology>

The steering device of the present invention has a housing, an electric motor, a linear motion shaft supported inside the housing so as to be displaced in the axial direction, and a rotary motion of the output shaft of the electric motor. A conversion mechanism that converts the linear motion into the axial motion of the shaft, and an axial displacement and rotation are impossibly fitted to the ends of the linear motion shaft on both sides in the axial direction, and the housing is axially fitted. It is provided with a pair of guide sleeves, which are internally fitted so that they cannot be rotated.

The housing has a pair of housing-side stopper surfaces that face opposite sides with respect to the axial direction, and each of the linear motion shaft or the pair of guide sleeves has a pair of housing-side stopper surfaces. It can have shaft-side stopper surfaces facing each other. In this case, when the linear motion shaft is displaced to the limit toward one side in the axial direction, one of the pair of housing-side stopper surfaces and the pair of shaft-side stopper surfaces It is prevented that the linear motion shaft is further displaced toward one side in the axial direction due to the contact with the one shaft side stopper surface facing the one housing side stopper surface. On the other hand, when the linear motion shaft is displaced to the limit toward the other side in the axial direction, the other housing-side stopper surface of the pair of housing-side stopper surfaces and the pair of shaft-side stopper surfaces It is prevented that the linear motion shaft is further displaced toward the other side in the axial direction due to the contact with the other shaft side stopper surface facing the other housing side stopper surface.

Specifically, the pair of housing-side stopper surfaces are provided on one side portion in the axial direction and the other side portion in the axial direction of the housing so as to face outward in the axial direction, and the pair of axial-side stoppers are provided. Each of the surfaces can be provided on each of the pair of guide sleeves so as to face inward in the axial direction. In this case, when the linear motion shaft is displaced to the limit toward one side in the axial direction, the housing-side stopper surface provided on the other side portion in the axial direction of the pair of housing-side stopper surfaces and the pair Of the guide sleeves, the shaft-side stopper surface provided on the guide sleeve on the other side in the axial direction comes into contact with the guide sleeve, and the linear motion shaft is prevented from being further displaced toward one side in the axial direction. On the other hand, when the linear motion shaft is displaced to the limit toward the other side in the axial direction, the housing-side stopper surface provided on one side portion in the axial direction of the pair of housing-side stopper surfaces and the pair of guides Of the sleeves, the shaft-side stopper surface provided on the guide sleeve on one side in the axial direction comes into contact with the sleeve, and the linear motion shaft is prevented from being further displaced toward the other side in the axial direction.

The housing has flat surface portions on the housing side at least one of the housings in relation to the circumferential direction of the inner peripheral surface of the portion that internally fits and holds each of the guide sleeves, and the outer peripheral surface of each of the guide sleeves has the said. It is possible to have a flat surface portion on the housing side and a flat surface portion on the shaft side that are close to each other or slidable.

The linear motion shaft is a ball screw shaft having an inner diameter side ball screw groove on the outer peripheral surface, and the conversion mechanism has an outer diameter side ball screw groove on the inner peripheral surface and is rotationally driven by the electric motor. A ball nut may be provided with a plurality of balls rotatably arranged between the inner diameter side ball screw groove and the outer diameter side ball screw groove. That is, the conversion mechanism can be configured by a ball screw mechanism.

In the steering device of the present invention, each of the guide sleeves can be made by combining a plurality of sleeve elements. In this case, the shim plate can be sandwiched between the sleeve element and the linear motion shaft.

In the steering device of the present invention, holding for holding grease on the outer peripheral surface of each of the guide sleeves and / or on the inner peripheral surface of the housing in which each of the guide sleeves is internally fitted and held. It can be provided with a recess.

<Effect of means to solve the problems related to the first background technology>
According to the steering device of the present invention, it is possible to obtain a sufficient steering force and ensure fail-safe while using the electric motor in an efficient region.

<Effect of means to solve problems related to the second background technology>
According to the steering device of the present invention, it is possible to prevent a steering reaction force in the radial direction from being applied to a conversion mechanism that converts the rotational motion of the output shaft of the electric motor into the axial linear motion of the linear motion shaft. Can be done.

FIG. 1 is a perspective view showing a state in which the steering device according to an example of the embodiment of the present invention is supported and fixed below the vehicle body. FIG. 2 is a perspective view showing a steering device according to an example of the embodiment of the present invention. FIG. 3 is a plan view showing a steering device according to an example of the embodiment of the present invention. FIG. 4 is a cross-sectional view taken along the line AA of FIG. FIG. 5 is a cross-sectional view taken along the line BB of FIG. FIG. 6 is an enlarged view of part C of FIG. FIG. 7 is an exploded perspective view showing a part of the constituent members of the steering device according to an example of the embodiment of the present invention. FIG. 8 is a perspective view showing a state in which the steering device according to an example of the embodiment of the present invention is supported and fixed below the vehicle body. FIG. 9 is a perspective view showing a steering device according to an example of the embodiment of the present invention. FIG. 10 is a plan view showing a steering device according to an example of the embodiment of the present invention. FIG. 11 is a cross-sectional view taken along the line AA of FIG. FIG. 12 is a cross-sectional view taken along the line BB of FIG. FIG. 13 is an enlarged view of part C of FIG. FIG. 14 is an exploded perspective view showing a part of the constituent members of the steering device according to an example of the embodiment of the present invention.

<Form for implementing means to solve the problems related to the first background technology>
An example of the embodiment of the present invention will be described with reference to FIGS. 1 to 7. The steering device 1 of this example includes a housing 2, a ball screw shaft 3, a pair of ball nuts 4a and 4b, a pair of bearing devices 5a and 5b, a plurality of balls 6, and a pair of electric motors. It includes motors 7a and 7b and a pair of speed reducers 8a and 8b.

Housing 2 is made of an iron-based alloy such as carbon steel. However, the housing 2 may be made of a light alloy such as an aluminum alloy or a synthetic resin. In this example, the housing 2 is located on a pair of small- diameter tubular portions 9a and 9b arranged on both sides in the width direction and portions adjacent to the inside (center side in the width direction) of the small- diameter tubular portions 9a and 9b, respectively. It includes a pair of actuator housing portions 10a and 10b arranged, and a connecting cylinder portion 11 for connecting the inner ends of the pair of actuator housing portions 10a and 10b in the width direction.

Unless otherwise specified, the width direction refers to the width direction (horizontal direction in FIGS. 3, 4 and 6 and front and back directions in FIG. 5) when the steering device 1 is attached to the vehicle body. Further, unless otherwise specified, the vertical direction and the front-rear direction are the vertical direction (front and back directions in FIG. 3, the vertical direction in FIGS. 4 to 6) and the front-rear direction (in the state where the steering device 1 is attached to the vehicle body). Refers to the vertical direction of FIG. 3, the front and back directions of FIGS. 4 and 6, and the horizontal direction of FIG.

Each of the small- diameter tubular portions 9a and 9b supports the axially (widthwise) side portions of the ball screw shaft 3 so that they can be displaced in the axial direction and cannot rotate. For this reason, each of the small diameter tubular portions 9a and 9b of this example has an inner peripheral surface having a non-circular cross section. Specifically, the inner peripheral surfaces of the small- diameter tubular portions 9a and 9b are partial cylinders that connect the pair of flat surface portions 12 arranged on both sides in the front-rear direction and the vertical side edges of the flat surface portions 12, respectively. It is provided with a pair of concave curved surface portions 13 having a shape. Each of the small- diameter tubular portions 9a and 9b has a stopper convex portion 14 protruding inward in the radial direction at an end portion on the inner side in the width direction of the concave curved surface portion 13. The stopper convex portion 14 has a housing-side stopper surface 15 facing outward in the width direction on an end surface on the outer side in the width direction.

Each of the actuator accommodating portions 10a and 10b includes a large-diameter tubular portion 16, a nut accommodating portion 17, and a worm accommodating portion 18.

The large diameter cylinder portion 16 is arranged adjacent to the inside of the small diameter cylinder portions 9a and 9b in the width direction, and the inner diameter dimension and the outer diameter dimension are larger than the inner diameter dimension and the outer diameter dimension of the small diameter cylinder portions 9a and 9b. It has become.

The nut accommodating portion 17 is arranged adjacent to the inside of the large diameter tubular portion 16 in the width direction. In this example, the nut accommodating portion 17 has a conical trapezoidal outer peripheral surface whose outer diameter dimension becomes smaller toward the inside in the width direction, and the inner diameter dimension is smaller than the inner diameter dimension of the large diameter tubular portion 16. ing.

The worm accommodating portion 18 has a central axis that exists at a twisted position with respect to the central axis of the large-diameter tubular portion 16, and an axial intermediate portion is open in the large-diameter tubular portion 16. In this example, the worm accommodating portion 18 is arranged above the large diameter tubular portion 16. That is, the lower portion of the axially intermediate portion of the worm accommodating portion 18 is open to the upper portion of the large diameter tubular portion 16.

The connecting tubular portion 11 has an outer diameter dimension that increases from the central position in the width direction toward both sides in the width direction, and has an outer peripheral surface having an arc-shaped bus and an inner peripheral surface having a cylindrical surface shape.

In this example, the housing 2 is formed by connecting and fixing a pair of housing elements 19a and 19b divided in the vertical direction by a plurality of bolts 20.

The ball screw shaft 3 has an inner diameter side ball screw groove 21 having an arc-shaped cross section on the outer peripheral surface of the intermediate portion in the axial direction. In addition, in FIGS. 4 and 7, the inner diameter side ball screw groove 21, the outer diameter side ball screw groove 35 and the ball 6 of the ball nuts 4a and 4b described later are omitted. The ball screw shaft 3 is supported inside the housing 2 so that its central axis is oriented in the width direction, can be displaced (sliding) in the axial direction (width direction), and cannot rotate. There is. That is, in this example, the width direction of the vehicle body and the axial direction of the ball screw shaft 3 coincide with each other. The ball screw shaft 3 of this example includes a large-diameter portion 22 and a pair of small- diameter portions 23a and 23b arranged on both sides of the large-diameter portion 22 in the width direction. The inner diameter side ball screw groove 21 is spirally formed in the axially intermediate portion of the large diameter portion 22.

Each of the pair of small diameter portions 23a and 23b has an outer peripheral surface having a non-circular cross section. Specifically, the outer peripheral surfaces of the small diameter portions 23a and 23b are a pair of flat surface portions arranged on both sides in the front-rear direction and a pair of partial cylinders connecting both vertical and vertical edges of the flat surface portions. It is provided with a convex curved surface portion of. Each of the pair of small diameter portions 23a and 23b has a screw hole 24 that opens on the outer end face in the width direction.

In this example, the ball screw shaft 3 is supported inside the housing 2 via a pair of guide sleeves 25a and 25b so that the ball screw shaft 3 can be displaced in the axial direction and cannot rotate.

Each of the guide sleeves 25a and 25b is made of a material having a small coefficient of friction with respect to the housing 2, such as a synthetic resin or a non-ferrous metal or an oil-impregnated metal having self-lubricating properties such as a copper alloy.

Each of the guide sleeves 25a and 25b has an inner peripheral surface that can be fitted onto the small diameter portions 23a and 23b of the ball screw shaft 3 without rattling and non-rotatably. Specifically, the inner peripheral surfaces of the guide sleeves 25a and 25b of this example are partial cylinders that connect a pair of flat surface portions arranged on both sides in the front-rear direction and both vertical edges of the flat surface portions. It is provided with a pair of concave curved surfaces.

Further, each of the guide sleeves 25a and 25b has an outer circumference that can be arranged (internally fitted) inside the small- diameter tubular portions 9a and 9b of the housing 2 without rattling and can be displaced (sliding) in the axial direction. Has a face. Specifically, the outer peripheral surfaces of the guide sleeves 25a and 25b of this example are portions that connect a pair of flat surface portions 26 arranged on both sides in the front-rear direction and both vertical edges of the flat surface portions 26, respectively. It includes a pair of cylindrical convex curved surface portions 27. Further, each of the guide sleeves 25a and 25b has a stopper recess 28 that is open at the inner end in the width direction and is recessed inward in the radial direction at the inner portion in the width direction of the convex curved surface portion 27. The stopper recess 28 has an axial stopper surface 29 facing inward in the width direction on an end surface on the outer side in the width direction.

Each of the guide sleeves 25a and 25b has an inner peripheral surface that is non-circularly engaged (fitted) with the outer peripheral surfaces of the small diameter portions 23a and 23b of the ball screw shaft 3 so as to be loose around the small diameter portions 23a and 23b. It is not attached and is externally fitted so that it cannot rotate relative to the small diameter portions 23a and 23b. Further, in each of the guide sleeves 25a and 25b, the flat surface portion 26 is slidably or close to the flat surface portion 12 of the small diameter tubular portions 9a and 9b, and the convex curved surface portion 27 is recessed in the small diameter tubular portions 9a and 9b. By sliding contact with or facing the curved surface portion 13, the inside of the small diameter tubular portions 9a and 9b of the housing 2 is arranged (internally fitted) without rattling and can be displaced (sliding) in the axial direction. ing. As a result, the ball screw shaft 3 is supported inside the housing 2 so as to be displaced (sliding) in the axial direction (width direction) and unable to rotate. In short, the guide sleeves 25a and 25b have a rotation stop function for preventing the ball screw shaft 3 from rotating relative to the housing 2.

In this example, each of the guide sleeves 25a and 25b is a combination of a pair of sleeve elements 46 divided in the front-rear direction. In this example, by arranging the guide sleeves 25a and 25b inside the small diameter tubular portions 9a and 9b of the housing 2, the pair of sleeve elements 46 constituting the guide sleeves 25a and 25b are separated from each other. It is preventing. Further, as will be described later, in a state where the support shaft portion 32 of the spherical joint 30 is screwed into the screw hole 24 of the ball screw shaft 3, the width direction of the guide sleeves 25a and 25b is due to the inner side surface in the width direction of the spherical joint 30. The outer end face is pressed down. That is, the guide sleeves 25a and 25b are axially (widthwise) between the stepped portion connecting the outer peripheral surface of the large diameter portion 22 of the ball screw shaft 3 and the outer peripheral surfaces of the small diameter portions 23a and 23b and the spherical joint 30. ), The guide sleeves 25a and 25b are prevented from being displaced in the axial direction (falling off from the small diameter portions 23a and 23b).

It should be noted that one or a plurality of shim plates can be sandwiched between the pair of sleeve elements 46 constituting each of the guide sleeves 25a and 25b and the small diameter portions 23a and 23b of the ball screw shaft 3.

When the ball screw shaft 3 is supported inside the housing 2 via a pair of guide sleeves 25a and 25b, the shaft-side stopper surfaces 29 of the guide sleeves 25a and 25b and the small- diameter tubular portions 9a and 9b The respective housing-side stopper surfaces 15 face each other in the width direction (axial direction). Regardless of the width direction (axial direction) position of the ball screw shaft 3 with respect to the housing 2, the shaft side stopper surface 29 of the guide sleeve 25a on one side in the width direction (left side in FIGS. 3 and 4) and the small diameter on one side in the width direction. The portion between the housing side stopper surface 15 of the tubular portion 9a, the shaft side stopper surface 29 of the guide sleeve 25b on the other side in the width direction (right side in FIGS. 3 and 4), and the small diameter tubular portion 9b on the other side in the width direction. There is a gap in the width direction at least one of the parts between the housing side stopper surface 15 and the housing side.

A pair of tie rods 31 are connected to both ends of the ball screw shaft 3 in the width direction via a spherical joint 30. That is, the male screw portions provided on the outer peripheral surfaces of the respective support shaft portions 32 of the spherical joint 30 are screwed into the screw holes 24 of the ball screw shaft 3, and are provided on the inner peripheral surfaces of the spherical joint 30. A partially convex spherical spherical engaging portion 34 provided at the base end portion (inner end portion in the width direction) of the tie rod 31 is spherically engaged with the partially concave spherical engaging recess 33.

As shown in FIG. 6, each of the pair of ball nuts 4a and 4b has an outer diameter side ball screw groove 35 having an arcuate cross-sectional shape and a spiral shape on the inner peripheral surface, and each of them has an outer diameter side ball screw groove 35. Around the ball screw shaft 3, relative rotation with respect to the ball screw shaft 3 is possible, and axial displacement is impossibly supported. In this example, the outer diameter side ball screw grooves 35 of the pair of ball nuts 4a and 4b have the same specifications (lead and lead angle). Further, in this example, each of the ball nuts 4a and 4b is rotatably supported inside the nut accommodating portion 17 of the housing 2 by using the sleeve 36 and the bearing devices 5a and 5b, respectively. Specifically, the inner ends of the sleeve 36 in the width direction are coupled and fixed to the outer ends of the ball nuts 4a and 4b in the width direction so that torque can be transmitted, and the sleeve 36 is connected and fixed in the width direction. Bearing devices 5a and 5b are arranged between the outer peripheral surface of the intermediate portion and the inner peripheral surface of the inner peripheral surface of the large-diameter tubular portion 19 of the housing 2 in the width direction. Each of the bearing devices 5a and 5b has a structure capable of bearing a radial load and a thrust load. Specifically, for example, each of the bearing devices 5a and 5b is composed of a double-row angular contact ball bearing or a double-row tapered roller bearing having a contact angle of a back combination type (DB type) fitted on the sleeve 36. can do. The sleeve 36 can also be integrally formed with the ball nuts 4a and 4b.

Each of the pair of ball nuts 4a and 4b further has a circulation mechanism (not shown) for circulating the ball 6, which will be described later. The circulation mechanism may adopt any structure of tube type, deflector type, end cap type or top type, but in order to displace the ball screw shaft 3 in the width direction with a sufficiently large force, the ball 6 From the viewpoint of ensuring a sufficient ball diameter, it is preferable to use a tube type.

Each of the pair of electric motors 7a and 7b rotationally drives the ball nuts 4a and 4b via the speed reducers 8a and 8b, respectively. In this example, the pair of electric motors 7a and 7b have the same rated output, and the speed reducers 8a and 8b have the same reduction ratio. In particular, in this example, each of the speed reducers 8a and 8b is a worm speed reducer. That is, each of the speed reducers 8a and 8b meshes with the worm wheel 37 outerly fitted to the outer end of the sleeve 36 in the width direction so as to transmit torque, and the worm of the housing 2. It is composed of a worm 38 rotatably supported inside the housing portion 18. Each of the electric motors 7a and 7b has an output shaft connected to a base end portion of the worm 38. In this example, the speed reducers 8a and 8b, which are worm speed reducers, do not have a self-locking function and have high reverse efficiency.

The speed reducers 8a and 8b are not limited to worm speed reducers as long as the output torque of the electric motors 7a and 7b can be increased and applied to the ball nuts 4a and 4b. Specifically, for example, as the speed reducers 8a and 8b, speed reducers such as a parallel shaft gear type, a friction roller type, and a belt type can also be used. As the pair of electric motors 7a and 7b, those having different rated outputs may be used, and as the speed reducers 8a and 8b, those having different types (structures) and different reduction ratios may be used. You can also do it. However, from the viewpoint of facilitating control of the electric motors 7a and 7b, a pair of electric motors 7a and 7b having the same rated output are used, and the speed reducers 8a and 8b are of the same type. It is preferable to use one having the same reduction ratio.

The steering device 1 of this example is supported below the vehicle body of a large vehicle such as a truck provided with an axle suspension type suspension device, for example. Specifically, as shown in FIG. 1, the steering device 1 inserts bolts 40 through which through holes provided in the mounting plate portion 39 of the housing 2 are inserted into the vehicle body frame 41 via a pair of leaf springs 42. By screwing into a screw hole formed in the axle 43 supported by the vehicle and further tightening the screw hole, the axle 43 is supported and fixed to the vehicle body frame 41. Each tip of the pair of tie rods 31 is swingably connected to the tip of the arm 45 of the knuckle 44. Further, each of the knuckles 44 is rotatably supported by steering wheels via hub unit bearings (not shown).

The steering device 1 is electrically combined with a steering device having a control stick such as a steering wheel via a controller (ECU) to form a steer-by-wire type steering device. When the vehicle is traveling in the normal driving mode, the controller calculates the steering angle given to the steering wheels based on the amount of operation of the steering wheel acquired by the sensor and, if necessary, the traveling speed of the vehicle. .. On the other hand, when the vehicle is traveling in the automatic driving mode, the controller determines the steering angle given to the steering wheels based on the surrounding conditions, the moving distance, the moving direction, etc. of the vehicle acquired by various sensors. calculate.

Regardless of whether the vehicle is traveling in either the normal operation mode or the automatic operation mode, the controller simultaneously energizes the electric motors 7a and 7b of the steering device 1 according to the calculated steering angle to generate the worm 38. It is driven to rotate. By rotating the worm 38, the worm wheel 37 that meshes with the worm 38 is rotated, and the ball nuts 4a and 4b coupled to the worm wheel 37 via the sleeve 36 are rotated in the same direction and at the same speed. As the ball nuts 4a and 4b rotate, the ball 6 moves between the inner diameter side ball screw groove 21 and the outer diameter side ball screw groove 35, and the ball screw shaft 3 is displaced in the width direction (axial direction). To do. When the tie rod 31 is pushed and pulled with the displacement of the ball screw shaft 3 in the width direction, the knuckle 44 is oscillated and displaced to give the steering wheel a desired steering angle.

In the steering device 1 of this example, when the ball screw shaft 3 is displaced to one side in the width direction to steer the steering wheel in a predetermined direction to the steering limit (so-called end contact), the ball screw shaft 3 is formed. The shaft-side stopper surface 29 of the guide sleeve 25b externally fitted to the small-diameter portion 23b on the other side in the width direction abuts on the housing-side stopper surface 15 of the small-diameter tubular portion 9b on the other side in the width direction in the housing 2. It is prevented that the ball screw shaft 3 is further displaced to one side in the width direction. In other words, by bringing the shaft-side stopper surface 29 of the guide sleeve 25b on the other side in the width direction into contact with the housing-side stopper surface 15 of the small-diameter tubular portion 9b on the other side in the width direction, the steering limit in the predetermined direction is set. It stipulates.

On the other hand, when the ball screw shaft 3 is displaced to the other side in the width direction to steer the steering wheel in the direction opposite to the predetermined direction to the steering limit, the small diameter portion of the ball screw shaft 3 on one side in the width direction is used. The shaft-side stopper surface 29 of the guide sleeve 25a externally fitted to the 23a abuts on the housing-side stopper surface 15 of the small-diameter tubular portion 9a on one side in the width direction of the housing 2, and the ball screw shaft 3 is further in the width direction. It is prevented from being displaced to the other side. In other words, by bringing the shaft side stopper surface 29 of the guide sleeve 25a on one side in the width direction into contact with the housing side stopper surface 15 of the small diameter tubular portion 9a on one side in the width direction, the steering limit in the direction opposite to the predetermined direction is reached. Is stipulated.

In short, the guide sleeves 25a and 25b have a stopper function to prevent the ball screw shaft 3 from being excessively displaced in the width direction. With such a stopper function, the ball 6 is prevented from being pressed against the end of the ball screw groove 21 on the inner diameter side of the ball screw shaft 3 or riding on the end of the ball screw groove 21 on the inner diameter side. , The widthwise inner ends of the guide sleeves 25a and 25b are prevented from colliding with the widthwise outer ends of the ball nuts 4a and 4b.

The steering device further has a reaction force applying motor that applies a reaction force corresponding to the steering amount of the control stick to the control stick. Therefore, when the driver operates the control stick while the vehicle is traveling in the normal operation mode, an operation reaction force corresponding to the amount of operation of the control stick is applied to the control stick. On the other hand, when the vehicle is traveling in the automatic driving mode, the control stick does not rotate even when the steering wheel is provided with a steering angle by the steering device 1.

As described above, in the steering device 1 of this example, the ball screw shaft 3 is driven by a pair of electric motors 7a and 7b to simultaneously rotate and drive the ball nuts 4a and 4b via the speed reducers 8a and 8b. Is configured to give a steering angle to the steering wheel by shifting the steering wheel in the width direction. Therefore, according to the steering device 1 of this example, it is not necessary to use electric motors 7a and 7b having a large output (rated torque), and each of the electric motors 7a and 7b can be output. Sufficient steering force can be obtained even when used in an efficient region where the output torque is relatively low in the torque range.

Further, since the steering device 1 of this example includes a pair of electric motors 7a and 7b, it is impossible to energize the electric motor 7a (or 7b) of any one of the pair of electric motors 7a and 7b. Even in the case of, the ball screw shaft 3 can be displaced in the width direction and the steering wheel can be provided with a steering angle by driving only the other electric motor 7b (or 7a). In this case, when the ball screw shaft 3 is displaced in the width direction by driving only the other electric motor 7b (or 7a), the outer diameter side ball screw groove of the one ball nut 4a (or 4b) is used. The ball 6 moves between the 35 and the ball screw groove 21 on the inner diameter side of the ball screw shaft 3. As a result, when one of the ball nuts 4a (or 4b) rotates, the worm wheel 37 rotates, the worm 38 that meshes with the worm wheel 37 rotates, and the output shaft of the one electric motor 7a (or 7b) rotates. Rotate. In this way, the displacement of the ball screw shaft 3 in the width direction is allowed. That is, according to the steering device 1 of this example, fail-safe can be ensured.

When steering is performed by only one electric motor 7b (or 7a), the range in which the electric motor 7b (or 7a) can be output is larger than that when steering is performed by a pair of electric motors 7a and 7b. Of these, it is necessary to use it in a region where the output torque is relatively high and the efficiency is low. Further, when steering is performed with only one electric motor 7b (or 7a), the obtained steering force is also small, and for example, it may be difficult to give (stationary) the steering angle while the vehicle is stopped. There is sex. However, even in this case, if the vehicle is moved even slightly to rotate the steering wheels, the load applied to the electric motor 7b (or 7a) can be reduced, and the steering wheels can be provided with a steering angle.

In the steering device 1 of this example, the pair of electric motors 7a and 7b are configured to displace the ball screw shaft 3 in the width direction by rotationally driving separate ball nuts 4a and 4b. There is. Therefore, in addition to being able to use small electric motors 7a and 7b having relatively small outputs, the ball screw shaft is driven by rotating one ball nut to rotate the radial dimensions of the ball nuts 4a and 4b. It can be kept small as compared with the structure in which 3 is displaced in the width direction. In short, it is possible to reduce the size of the electric actuators 47a and 47b, which are formed by combining the ball nuts 4a and 4b, the bearing devices 5a and 5b, the speed reducers 8a and 8b, and the electric motors 7a and 7b, respectively. , The degree of freedom of the installation position with respect to the width direction of the electric actuators 47a and 47b can be increased.

In the steering device 1 of this example, the pair of electric actuators 47a and 47b are arranged near the center in the width direction, specifically, on both side portions of the housing 2 with the center position in the width direction in between. In particular, in this example, among the members constituting each of the electric actuators 47a and 47b, the ball nuts 4a and 4b are arranged on the most central side in the width direction. In other words, the ball nuts 4a and 4b are arranged close to each other near the center in the width direction. Therefore, when the ball screw shafts 3 screwed into the ball nuts 4a and 4b via the ball 6 are displaced in the width direction by rotationally driving the ball nuts 4a and 4b, the ball screw shaft is displaced. A structure in which a pair of ball nuts 4a and 4b are arranged so as to be largely separated from each other in the width direction (for example, in a double pinion type power steering device), a steering wheel is applied so that an unreasonable force (force in the twisting direction) is applied to 3. Compared to the part where the steering force is input from the ball and the part where the assist force is applied by the electric motor, the force is applied near the ends on both sides of the rack shaft in the width direction). Can be done.

Further, by arranging the ball nuts 4a and 4b close to each other near the center in the width direction, the length in the width direction of the inner diameter side ball screw groove 21 provided on the outer peripheral surface of the large diameter portion 22 of the ball screw shaft 3 The ball size (formation range in the width direction) can also be shortened. Therefore, the processing cost of the ball screw groove 21 on the inner diameter side can be suppressed low, and the small diameter portions 23a and 23b can be provided on both side portions of the ball screw shaft 3 in the width direction, and the small diameter portions 23a and 23b can be provided. Guide sleeves 25a and 25b can be arranged around each of the two. In addition to the rotation stop function and the stopper function, each of the guide sleeves 25a and 25b transmits the steering reaction force applied in the radial direction of the ball screw shaft 3 to the housing 2, and the vehicle body via the housing 2. It has a function to be supported by.

In this example, the ball nuts 4a and 4b are arranged adjacent to each other via the housing 2 in a state of being separated from each other near the center in the width direction (with the center position in the width direction in between). As a result, in the housing 2, the actuator accommodating portions 10a and 10b accommodating the electric actuators 47a and 47b including the ball nuts 4a and 4b are present in the lower part of the vehicle body and around the axle 43 (for example, the oil pan 48 and the like). ) Is prevented from interfering with. However, from the viewpoint of preventing an excessive force from being applied to the ball screw shaft 3, the pair of ball nuts 4a and 4b are arranged as close as possible, most preferably adjacent to each other without the housing 2. Is preferable. In short, the pair of ball nuts 4a and 4b are arranged as close as possible to each other as long as they do not interfere with the members existing around the axle 43.

In this example, the members constituting the electric actuators 47a and 47b are directed from the center side in the width direction to the outside, and the ball nuts 4a and 4b, the bearing devices 5a and 5b, the reduction gears 8a and 8b, and the electric motor 7a. They are arranged in the order of 7b. However, if the ball nuts 4a and 4b are arranged on the most central side in the width direction, the arrangement of other members is not particularly limited. For example, the bearing devices 5a and 5b may be arranged outside the worm wheel 37 of the speed reducers 8a and 8b in the width direction. Further, the worm wheels 37 of the speed reducers 8a and 8b can be arranged around the ball nuts 4a and 4b so as to rotate integrally with the ball nuts 4a and 4b.

Further, in this example, the tie rod 31 is connected to both ends of the ball screw shaft 3 in the width direction via the spherical joint 30, and the tip of the arm 45 of the knuckle 44 is attached to the tip of the tie rod 31. It is connected so that it can swing. Therefore, when the steering device 1 of this example is driven to give a steering angle to the steering wheels (steering is performed), a reaction force due to steering is applied to the ball screw shaft 3 depending on the angle of the arm 45. On the other hand, it may be added in the radial direction (front-back direction).

Here, in this example, the ball screw shaft 3 is supported inside the housing 2 via a pair of guide sleeves 25a and 25b so that the ball screw shaft 3 can be displaced in the width direction and cannot rotate. Specifically, the guide sleeves 25a and 25b are fitted around the small diameter portions 23a and 23b without rattling, and the relative rotation with respect to the small diameter portions 23a and 23b is impossible, and the housing 2 is fitted. Inside the small- diameter tubular portions 9a and 9b, the displacement (sliding) in the axial direction is arranged (internally fitted) without rattling. Therefore, when the reaction force accompanying the steering is applied to the ball screw shaft 3 in the radial direction, the flat surface portions 26 of the guide sleeves 25a and 25b are pressed against the flat surface portions 12 of the small diameter tubular portions 9a and 9b. In short, the reaction force applied to the ball screw shaft 3 in the radial direction due to steering is transmitted to the vehicle body via the guide sleeves 25a and 25b and the housing 2, and is supported by the vehicle body. Therefore, according to the steering device 1 of this example, even when the reaction force accompanying the steering is applied in the radial direction with respect to the ball screw shaft 3, the rolling surface of the ball 6 is the ball screw shaft 3. It is possible to prevent the ball screw groove 21 on the inner diameter side and the ball screw grooves 4a and 4b on the inner diameter side from being strongly pressed against the ball screw groove 35 on the outer diameter side. As a result, it is possible to prevent the life of the ball screw mechanism including the ball screw shaft 3, the ball nuts 4a and 4b, and the ball 6 from being shortened, and the occurrence of abnormal noise and vibration.

In this example, each of the pair of guide sleeves 25a and 25b is configured by combining a pair of sleeve elements 46. Therefore, by sandwiching one or a plurality of shim plates between the sleeve element 46 and the small diameter portions 23a and 23b of the ball screw shaft 3, the outer peripheral surfaces of the guide sleeves 25a and 25b and the small diameter of the housing 2 are held. The gap between the inner peripheral surfaces of the tubular portions 9a and 9b can be adjusted. That is, the inner peripheral surfaces of the small diameter tubular portions 9a and 9b without excessively increasing the shape accuracy of the small diameter tubular portions 9a and 9b of the housing 2, the small diameter portions 23a and 23b of the ball screw shaft 3, and the guide sleeves 25a and 25b. Since the rattling of the outer peripheral surfaces of the guide sleeves 25a and 25b can be sufficiently suppressed, the cost can be reduced.

However, each of the guide sleeves 25a and 25b may be integrally formed as a whole, that is, in a tubular shape. Alternatively, each of the guide sleeves 25a and 25b can be configured by combining three or more sleeve elements.

In this example, an example in which the steering device 1 is applied to a steer-by-wire type steering device of a vehicle equipped with a leaf spring type suspension device among the axle suspension types has been described. However, the steering device of the present invention is not limited to the leaf spring type, and can be applied to a steer-by-wire type steering device of a vehicle provided with a coil spring type suspension device. Alternatively, the steering device of the present invention can also be applied to a steer-by-wire type steering device of a vehicle provided with an independent suspension type suspension device. Further, the steering device of the present invention is not limited to the steering device of a large vehicle such as a truck, and can be incorporated into a steering device for a passenger car.

The steering device 1 of this example includes a pair of ball nuts 4a and 4b, bearing devices 5a and 5b, electric motors 7a and 7b, and speed reducers 8a and 8b, respectively. However, the steering device of the present invention may also include three or more ball nuts and bearing devices, and three or more electric motors and speed reducers.

The technical concept regarding the means for solving the problems related to the first background technology is described below.
(1)
With the housing
A ball screw shaft having an inner diameter side ball screw groove on the outer peripheral surface and supported inside the housing so as to be displaced in the axial direction and unable to rotate.
A plurality of ball nuts having an outer diameter side ball screw groove on the inner peripheral surface and arranged around the ball screw shaft so as to be relatively rotatable with respect to the ball screw shaft.
A bearing device that rotatably supports the ball nut with respect to the housing,
A plurality of balls rotatably arranged between the inner diameter side ball screw groove and the outer diameter side ball screw groove, and
With multiple electric motors
The same number of speed reducers as the electric motor, which are applied to the ball nut after increasing the output torque of the electric motor,
A steering device.

(2)
The steering device according to (2), comprising the same number of ball nuts as the electric motor.

(3)
The steering device according to (2), further comprising a pair of each of the ball nut, the bearing device, the electric motor, and the speed reducer.

(4)
The ball nut, the bearing device, the electric motor, and the speed reducer are arranged one by one on both side portions of the housing at the center position in the width direction.
The steering device according to (3), wherein the ball nut is arranged on the side of the ball nut, the bearing device, the electric motor, and the speed reducer closest to the center position in the width direction of the housing. ..

(5)
The steering device according to (4), wherein the ball nuts are arranged adjacent to each other via the housing in a state of being separated from each other with a central position in the width direction interposed therebetween.

(6)
The steering device according to any one of (1) to (5), wherein the speed reducer is a worm speed reducer.

(7)
The steering device according to any one of (1) to (6), wherein the housing is a combination of a plurality of housing elements.

<Form for implementing means for solving problems related to the second background technology>
An example of the embodiment of the present invention will be described with reference to FIGS. 8 to 14. The steering device 1 of this example includes a housing 2, a ball screw shaft 3 which is a linear motion shaft, a pair of ball nuts 4a and 4b, a pair of bearing devices 5a and 5b, and a plurality of balls 6. It includes a pair of electric motors 7a and 7b and a pair of speed reducers 8a and 8b.

Housing 2 is made of an iron-based alloy such as carbon steel. However, the housing 2 may be made of a light alloy such as an aluminum alloy or a synthetic resin. In this example, the housing 2 is located on a pair of small- diameter tubular portions 9a and 9b arranged on both sides in the width direction and portions adjacent to the inside (center side in the width direction) of the small- diameter tubular portions 9a and 9b, respectively. It includes a pair of actuator housing portions 10a and 10b arranged, and a connecting cylinder portion 11 for connecting the inner ends of the pair of actuator housing portions 10a and 10b in the width direction.

Unless otherwise specified, the width direction refers to the width direction (horizontal direction in FIGS. 10, 11 and 13 and front and back directions in FIG. 12) when the steering device 1 is attached to the vehicle body. Further, unless otherwise specified, the vertical direction and the front-rear direction are the vertical direction (front and back directions in FIG. 10, the vertical direction in FIGS. 11 to 13) and the front-rear direction (in the state where the steering device 1 is attached to the vehicle body). Refers to the vertical direction of FIG. 10, the front and back directions of FIGS. 11 and 13, and the horizontal direction of FIG.

Each of the small- diameter tubular portions 9a and 9b supports the axially (widthwise) side portions of the ball screw shaft 3 so that they can be displaced in the axial direction and cannot rotate. For this reason, each of the small diameter tubular portions 9a and 9b of this example has an inner peripheral surface having a non-circular cross section. Specifically, the inner peripheral surfaces of the small-diameter cylindrical portions 9a and 9b are a pair of housing-side flat surface portions 12 arranged on both sides in the front-rear direction and both vertical edges of the housing-side flat surface portions 12, respectively. It is provided with a pair of concave curved surface portions 13 having a partial cylindrical shape to be connected. In this example, each of the housing-side flat surface portions 12 is composed of flat surfaces facing in the front-rear direction. Each of the small- diameter tubular portions 9a and 9b has a stopper convex portion 14 projecting inward in the radial direction at an end portion on the inner side in the width direction (axial direction) of the concave curved surface portion 13. The stopper convex portion 14 has a housing-side stopper surface 15 facing outward in the width direction (axial direction) on an end surface on the outer side in the width direction (axial direction).

As will be described later, the ball screw shaft 3 enables displacement (sliding) in the axial direction (width direction) inside the housing 2 with its central axis oriented in the width direction of the vehicle body. And, the rotation is impossiblely supported. Therefore, in this example, the width direction of the vehicle body and the axial direction of the ball screw shaft 3 coincide with each other. With respect to the ball screw shaft 3, the axial inner side means the width direction center side (inside) of the ball screw shaft 3, and the axial outer side means the width direction outer side (both sides) of the ball screw shaft 3.

Each of the actuator accommodating portions 10a and 10b includes a large-diameter tubular portion 16, a nut accommodating portion 17, and a worm accommodating portion 18.

The large diameter cylinder portion 16 is arranged adjacent to the inside of the small diameter cylinder portions 9a and 9b in the width direction, and the inner diameter dimension and the outer diameter dimension are larger than the inner diameter dimension and the outer diameter dimension of the small diameter cylinder portions 9a and 9b. It has become.

The nut accommodating portion 17 is arranged adjacent to the inside of the large diameter tubular portion 16 in the width direction. In this example, the nut accommodating portion 17 has a cone-shaped outer peripheral surface whose outer diameter dimension becomes smaller toward the inside in the width direction, and the inner diameter dimension is smaller than the inner diameter dimension of the large diameter tubular portion 16. ing.

The worm accommodating portion 18 has a central axis that exists at a twisted position with respect to the central axis of the large-diameter tubular portion 16, and an axial intermediate portion is open in the large-diameter tubular portion 16. In this example, the worm accommodating portion 18 is arranged above the large diameter tubular portion 16. That is, the lower portion of the axially intermediate portion of the worm accommodating portion 18 is open to the upper portion of the large diameter tubular portion 16.

The connecting tubular portion 11 has an outer diameter dimension that increases from the central position in the width direction toward both sides in the width direction, and has an outer peripheral surface having an arc-shaped bus and an inner peripheral surface having a cylindrical surface shape.

In this example, the housing 2 is formed by connecting and fixing a pair of housing elements 19a and 19b divided in the vertical direction by a plurality of bolts 20.

The ball screw shaft 3 is a linear motion shaft, and enables displacement (sliding) in the axial direction (width direction) inside the housing 2 with its central axis oriented in the width direction of the vehicle body. And, the rotation is impossiblely supported. The ball screw shaft 3 of this example includes a large-diameter portion 22 and a pair of small- diameter portions 23a and 23b arranged on both sides of the large-diameter portion 22 in the axial direction. Further, the ball screw shaft 3 includes an inner diameter side ball screw groove 21 formed in a spiral shape with an arc shape in an axially intermediate portion of the large diameter portion 22. In addition, in FIGS. 11 and 14, the inner diameter side ball screw groove 21, the outer diameter side ball screw groove 35 and the ball 6 of the ball nuts 4a and 4b described later are omitted.

Each of the pair of small diameter portions 23a and 23b has an outer peripheral surface having a non-circular cross section. Specifically, the outer peripheral surfaces of the small diameter portions 23a and 23b are a pair of flat surface portions arranged on both sides in the front-rear direction and a pair of partial cylinders connecting both vertical and vertical edges of the flat surface portions. It is provided with a convex curved surface portion of. Each of the pair of small diameter portions 23a and 23b has a screw hole 24 that opens on the end face on the outer side in the axial direction.

In this example, the ball screw shaft 3 is outside the end of the ball screw shaft 3 on one axial side (left side in FIGS. 10 and 11) and the other end in the axial direction (right side in FIGS. 10 and 11). An axially displaceable and non-rotatable support is provided inside the housing 2 via a pair of fitted guide sleeves 25a, 25b.

Each of the guide sleeves 25a and 25b is made of a material having a small coefficient of friction with respect to the housing 2, such as a synthetic resin or a non-ferrous metal or an oil-impregnated metal having self-lubricating properties such as a copper alloy. Each of the guide sleeves 25a and 25b has an inner peripheral surface that can be fitted onto the small diameter portions 23a and 23b of the ball screw shaft 3 without rattling and non-rotatably. Specifically, the inner peripheral surfaces of the guide sleeves 25a and 25b of this example are partial cylinders that connect a pair of flat surface portions arranged on both sides in the front-rear direction and both vertical edges of the flat surface portions. It is provided with a pair of concave curved surfaces.

Further, each of the guide sleeves 25a and 25b is arranged (internally fitted) inside the small diameter tubular portions 9a and 9b of the housing 2 so that the relative rotation with respect to the housing 2 is impossible and the displacement (sliding) in the axial direction is possible. ) Has a possible outer surface. Specifically, the outer peripheral surfaces of the guide sleeves 25a and 25b of this example have a pair of axial flat surface portions 26 arranged on both sides in the front-rear direction and both vertical edges of the axial flat surface portions 26. It is provided with a pair of convex curved surface portions 27 having a partial cylindrical shape to be connected to each other. Further, each of the guide sleeves 25a and 25b has a stopper recess 28 which is open at the axially inner end and is recessed inward in the radial direction in the axially inner portion of the convex curved surface portion 27. The stopper recess 28 has an axial stopper surface 29 facing inward in the axial direction on an end surface on the outer side in the axial direction.

Each of the guide sleeves 25a and 25b has an inner peripheral surface that is non-circularly engaged (fitted) with the outer peripheral surfaces of the small diameter portions 23a and 23b of the ball screw shaft 3 so as to be loose around the small diameter portions 23a and 23b. It is not attached and is externally fitted so that it cannot rotate relative to the small diameter portions 23a and 23b. Further, in each of the guide sleeves 25a and 25b, the shaft-side flat surface portion 26 is slidably or close to the housing-side flat surface portion 12 of the small- diameter tubular portions 9a and 9b, and the convex curved surface portion 27 is brought into contact with the small-diameter tubular portion 9a. By sliding contact or close contact with the concave curved surface portion 13 of 9b, relative rotation with respect to the housing 2 is made impossible and displacement (sliding) in the axial direction is caused inside the small diameter tubular portions 9a and 9b of the housing 2. It is arranged (internally fitted) so that it can be placed. As a result, the ball screw shaft 3 is supported inside the housing 2 so as to be displaced (sliding) in the axial direction (width direction) and unable to rotate. In short, the guide sleeves 25a and 25b have a rotation stop function for preventing the ball screw shaft 3 from rotating relative to the housing 2.

Grease is filled between the guide sleeves 25a and 25b and the small- diameter tubular portions 9a and 9b of the housing 2, so that the outer peripheral surfaces of the guide sleeves 25a and 25b and the inner peripheral surfaces of the small- diameter tubular portions 9a and 9b Lubrication of the sliding contact part is planned. Therefore, the outer peripheral surfaces of the guide sleeves 25a and 25b and / or the inner peripheral surfaces of the small- diameter tubular portions 9a and 9b of the housing 2 may be provided with holding recesses for holding grease. The holding recess can be formed, for example, by a recess extending in the axial direction or the circumferential direction.

In this example, each of the guide sleeves 25a and 25b is a combination of a pair of sleeve elements 46 divided in the front-rear direction. In this example, by arranging the guide sleeves 25a and 25b inside the small diameter tubular portions 9a and 9b of the housing 2, the pair of sleeve elements 46 constituting the guide sleeves 25a and 25b are separated from each other. It is preventing. Further, as will be described later, in a state where the support shaft portion 32 of the spherical joint 30 is screwed into the screw hole 24 of the ball screw shaft 3, the axial inner surface of the spherical joint 30 allows the guide sleeves 25a and 25b to be axially oriented. The outer end face is pressed down. That is, the guide sleeves 25a and 25b are axially (widthwise) between the stepped portion connecting the outer peripheral surface of the large diameter portion 22 of the ball screw shaft 3 and the outer peripheral surfaces of the small diameter portions 23a and 23b and the spherical joint 30. ), The guide sleeves 25a and 25b are prevented from being displaced in the axial direction (falling off from the small diameter portions 23a and 23b).

It should be noted that one or a plurality of shim plates can be sandwiched between the pair of sleeve elements 46 constituting each of the guide sleeves 25a and 25b and the small diameter portions 23a and 23b of the ball screw shaft 3.

When the ball screw shaft 3 is supported inside the housing 2 via a pair of guide sleeves 25a and 25b, the shaft-side stopper surfaces 29 of the guide sleeves 25a and 25b and the small- diameter tubular portions 9a and 9b The respective housing-side stopper surfaces 15 face each other in the axial direction (width direction). Regardless of the axial position of the ball screw shaft 3 with respect to the housing 2, the axial stopper surface 29 of the guide sleeve 25a on one side in the axial direction (left side in FIGS. 10 and 11) and the small diameter tubular portion 9a on one side in the axial direction. The housing-side stopper between the housing-side stopper surface 15 and the axial-side stopper surface 29 of the guide sleeve 25b on the other side in the axial direction (right side of FIGS. 10 and 11) and the small-diameter tubular portion 9b on the other side in the axial direction. There is an axial gap in at least one of the intermediate portions with the surface 15.

A pair of tie rods 31 are connected to the ends of the ball screw shaft 3 on both sides in the axial direction via spherical joints 30, respectively. That is, the male screw portions provided on the outer peripheral surfaces of the support shaft portions 32 of the spherical joint 30 are screwed into the screw holes 24 of the ball screw shaft 3 and provided on the inner peripheral surfaces of the spherical joint 30. A partially convex spherical spherical engaging portion 34 provided at the base end portion (inner end in the axial direction) of the tie rod 31 is spherically engaged with the partially concave spherical engaging recess 33.

Each of the pair of ball nuts 4a and 4b has an outer diameter side ball screw groove 35 formed in a spiral shape with an arc shape on the inner peripheral surface, and around the ball screw shaft 3. It is arranged so that it can rotate relative to the ball screw shaft 3. In this example, the outer diameter side ball screw grooves 35 of the pair of ball nuts 4a and 4b have the same specifications (lead and lead angle). Further, in this example, each of the ball nuts 4a and 4b is rotatably supported inside the nut accommodating portion 17 of the housing 2 by using the sleeve 36 and the bearing devices 5a and 5b, respectively. Specifically, the axially inner end of the sleeve 36 is coupled and fixed to the axially outer ends of the ball nuts 4a and 4b so that torque can be transmitted, and the sleeve 36 is axially connected and fixed. Bearing devices 5a and 5b are arranged between the outer peripheral surface of the intermediate portion and the inner peripheral surface of the inner peripheral surface of the large-diameter tubular portion 19 of the housing 2 in the width direction. Each of the bearing devices 5a and 5b has a structure capable of bearing a radial load and a thrust load. Specifically, for example, each of the bearing devices 5a and 5b can be configured by a double-row angular contact ball bearing or a double-row tapered roller bearing having a back surface combination type (DB type) contact angle. The sleeve 36 can also be integrally formed with the ball nuts 4a and 4b.

Each of the pair of ball nuts 4a and 4b further has a circulation mechanism (not shown) for circulating the ball 6, which will be described later. The circulation mechanism may have any structure of tube type, deflector type, end cap type or top type, but in order to displace the ball screw shaft 3 in the axial direction with a sufficiently large force, the ball 6 From the viewpoint of ensuring a sufficient ball diameter, it is preferable to use a tube type.

Each of the pair of electric motors 7a and 7b rotationally drives the ball nuts 4a and 4b via the speed reducers 8a and 8b, respectively. In this example, the pair of electric motors 7a and 7b have the same rated output, and the speed reducers 8a and 8b have the same reduction ratio. In particular, in this example, each of the speed reducers 8a and 8b is a worm speed reducer. That is, each of the speed reducers 8a and 8b meshes with the worm wheel 37 which is outerly fitted to the axially outer end of the sleeve 36 so as to be able to transmit torque, and the worm of the housing 2. It is composed of a worm 38 rotatably supported inside the housing portion 18. Each of the electric motors 7a and 7b has an output shaft connected to a base end portion of the worm 38. In this example, the speed reducers 8a and 8b, which are worm speed reducers, do not have a self-locking function and have high reverse efficiency.

The speed reducers 8a and 8b are not limited to worm speed reducers as long as the output torque of the electric motors 7a and 7b can be increased and applied to the ball nuts 4a and 4b. Specifically, for example, as the speed reducers 8a and 8b, speed reducers such as a parallel shaft gear type, a friction roller type, and a belt type can also be used. As the pair of electric motors 7a and 7b, those having different rated outputs may be used, and as the speed reducers 8a and 8b, those having different types (structures) and different reduction ratios may be used. You can also do it. However, from the viewpoint of facilitating control of the electric motors 7a and 7b, a pair of electric motors 7a and 7b having the same rated output are used, and the speed reducers 8a and 8b are of the same type. It is preferable to use one having the same reduction ratio.

The steering device 1 of this example is supported below the vehicle body of a large vehicle such as a truck provided with an axle suspension type suspension device, for example. Specifically, as shown in FIG. 8, the steering device 1 inserts bolts 40 through which through holes provided in the mounting plate portion 39 of the housing 2 are inserted into the vehicle body frame 41 via a pair of leaf springs 42. By screwing into a screw hole formed in the axle 43 supported by the vehicle and further tightening the screw hole, the axle 43 is supported and fixed to the vehicle body frame 41. Each tip of the pair of tie rods 31 is swingably connected to the tip of the arm 45 of the knuckle 44. Further, each of the knuckles 44 is rotatably supported by steering wheels via hub unit bearings (not shown).

The steering device 1 is electrically combined with a steering device having a control stick such as a steering wheel via a controller (ECU) to form a steer-by-wire type steering device. When the vehicle is traveling in the normal driving mode, the controller calculates the steering angle given to the steering wheels based on the amount of operation of the steering wheel acquired by the sensor and, if necessary, the traveling speed of the vehicle. .. On the other hand, when the vehicle is traveling in the automatic driving mode, the controller determines the steering angle given to the steering wheels based on the surrounding conditions, the moving distance, the moving direction, etc. of the vehicle acquired by various sensors. calculate.

Regardless of whether the vehicle is traveling in either the normal operation mode or the automatic operation mode, the controller simultaneously energizes the electric motors 7a and 7b of the steering device 1 according to the calculated steering angle to generate the worm 38. It is driven to rotate. By rotating the worm 38, the worm wheel 37 that meshes with the worm 38 is rotated, and the ball nuts 4a and 4b coupled to the worm wheel 37 via the sleeve 36 are rotated in the same direction and at the same speed. As the ball nuts 4a and 4b rotate, the ball 6 moves between the inner diameter side ball screw groove 21 and the outer diameter side ball screw groove 35, and the ball screw shaft 3 is displaced in the axial direction (width direction). To do. In short, in this example, the speed reducers 8a and 8b, the ball nuts 4a and 4b, and the ball 6 convert the rotational movement of the output shafts of the electric motors 7a and 7b into the linear movement of the ball screw shaft 3 which is the linear movement shaft. A conversion mechanism is configured. When the tie rod 31 is pushed and pulled along with the axial displacement of the ball screw shaft 3, the knuckle 44 is oscillated and displaced to give the steering wheel a desired steering angle.

In the steering device 1 of this example, when the ball screw shaft 3 is displaced to one side in the axial direction to steer the steering wheel in a predetermined direction to the steering limit (so-called end contact), the ball screw shaft 3 is formed. The shaft-side stopper surface 29 of the guide sleeve 25b externally fitted to the small-diameter portion 23b on the other side in the axial direction abuts on the housing-side stopper surface 15 of the small-diameter tubular portion 9b on the other side in the axial direction in the housing 2. It is prevented that the ball screw shaft 3 is further displaced to one side in the axial direction. In other words, the steering limit in the predetermined direction is set by bringing the shaft-side stopper surface 29 of the guide sleeve 25b on the other side in the axial direction into contact with the housing-side stopper surface 15 of the small-diameter tubular portion 9b on the other side in the axial direction. It stipulates.

On the other hand, when the steering wheel is steered to the steering limit in the direction opposite to the predetermined direction by shifting the ball screw shaft 3 to the other side in the axial direction, the small diameter portion of the ball screw shaft 3 on one side in the axial direction The shaft-side stopper surface 29 of the guide sleeve 25a externally fitted to the 23a abuts on the housing-side stopper surface 15 of the small-diameter tubular portion 9a on one side in the axial direction of the housing 2, and the ball screw shaft 3 is further axially oriented. It is prevented from being displaced to the other side. In other words, by bringing the shaft side stopper surface 29 of the guide sleeve 25a on one side in the axial direction into contact with the housing side stopper surface 15 of the small diameter tubular portion 9a on one side in the axial direction, the steering limit in the direction opposite to the predetermined direction is reached. Is stipulated.

In short, the guide sleeves 25a and 25b have a stopper function to prevent the ball screw shaft 3 from being excessively displaced in the axial direction. With such a stopper function, the ball 6 is prevented from being pressed against the end of the ball screw groove 21 on the inner diameter side of the ball screw shaft 3 or riding on the end of the ball screw groove 21 on the inner diameter side. , The axially inner ends of the guide sleeves 25a and 25b are prevented from colliding with the axially outer ends of the ball nuts 4a and 4b.

The steering device further has a reaction force applying motor that applies a reaction force corresponding to the steering amount of the control stick to the control stick. Therefore, when the driver operates the control stick while the vehicle is traveling in the normal operation mode, an operation reaction force corresponding to the amount of operation of the control stick is applied to the control stick. On the other hand, when the vehicle is traveling in the automatic driving mode, the control stick does not rotate even when the steering wheel is provided with a steering angle by the steering device 1.

As described above, in the steering device 1 of this example, the ball screw shaft 3 is driven by a pair of electric motors 7a and 7b to simultaneously rotate and drive the ball nuts 4a and 4b via the speed reducers 8a and 8b. Is configured to give a steering angle to the steering wheel by shifting the steering wheel in the axial direction. Therefore, according to the steering device 1 of this example, it is not necessary to use electric motors 7a and 7b having a large output (rated torque), and each of the electric motors 7a and 7b can be output. Sufficient steering force can be obtained even when used in an efficient region where the output torque is relatively low in the torque range.

Further, since the steering device 1 of this example includes a pair of electric motors 7a and 7b, it is impossible to energize the electric motor 7a (or 7b) of any one of the pair of electric motors 7a and 7b. Even in the case of, the ball screw shaft 3 can be displaced in the axial direction and the steering wheel can be provided with a steering angle by driving only the other electric motor 7b (or 7a). In this case, when the ball screw shaft 3 is displaced in the axial direction by driving only the other electric motor 7b (or 7a), the outer diameter side ball screw groove of the one ball nut 4a (or 4b) is used. The ball 6 moves between the 35 and the ball screw groove 21 on the inner diameter side of the ball screw shaft 3. As a result, when one of the ball nuts 4a (or 4b) rotates, the worm wheel 37 rotates, the worm 38 that meshes with the worm wheel 37 rotates, and the output shaft of the one electric motor 7a (or 7b) rotates. Rotate. In this way, the axial displacement of the ball screw shaft 3 is allowed. That is, according to the steering device 1 of this example, fail-safe can be ensured.

When steering is performed by only one electric motor 7b (or 7a), the range in which the electric motor 7b (or 7a) can be output is larger than that when steering is performed by a pair of electric motors 7a and 7b. Of these, it is necessary to use it in a region where the output torque is relatively high and the efficiency is low. Further, when steering is performed with only one electric motor 7b (or 7a), the obtained steering force is also small, and for example, it may be difficult to give (stationary) the steering angle while the vehicle is stopped. There is sex. However, even in this case, if the vehicle is moved even slightly to rotate the steering wheels, the load applied to the electric motor 7b (or 7a) can be reduced, and the steering wheels can be provided with a steering angle.

In the steering device 1 of this example, each of the pair of electric motors 7a and 7b is configured to rotationally drive separate ball nuts 4a and 4b to displace the ball screw shaft 3 in the axial direction. There is. Therefore, in addition to being able to use small electric motors 7a and 7b having relatively small outputs, the ball screw shaft is driven by rotating one ball nut to rotate the radial dimensions of the ball nuts 4a and 4b. It can be kept small as compared with the structure in which 3 is displaced in the axial direction. In short, it is possible to reduce the size of the electric actuators 47a and 47b, which are formed by combining the ball nuts 4a and 4b, the bearing devices 5a and 5b, the speed reducers 8a and 8b, and the electric motors 7a and 7b, respectively. , The degree of freedom in the installation position of the electric actuators 47a and 47b in the axial direction (width direction) can be increased.

In the steering device 1 of this example, the pair of electric actuators 47a and 47b are arranged near the center in the width direction, specifically, on both side portions of the housing 2 with the center position in the width direction in between. In particular, in this example, among the members constituting each of the electric actuators 47a and 47b, the ball nuts 4a and 4b are arranged on the most central side in the width direction. In other words, the ball nuts 4a and 4b are arranged close to each other near the center in the width direction. Therefore, by rotationally driving the ball nuts 4a and 4b, the ball screw shaft 3 screwed into each of the ball nuts 4a and 4b via the ball 6 is displaced in the axial direction. A structure in which a pair of ball nuts 4a and 4b are arranged so as to be largely separated from each other in the width direction (for example, in a double pinion type power steering device), a steering wheel is applied so that an unreasonable force (force in the twisting direction) is applied to 3. Compared to the part where the steering force is input from the ball and the part where the assist force is applied by the electric motor, the force is applied near the ends on both sides of the rack shaft in the width direction). Can be done.

Further, by arranging the ball nuts 4a and 4b close to each other near the center in the width direction, the length in the axial direction of the inner diameter side ball screw groove 21 provided on the outer peripheral surface of the large diameter portion 22 of the ball screw shaft 3 The ball size (formation range in the axial direction) can also be shortened. Therefore, the processing cost of the ball screw groove 21 on the inner diameter side can be suppressed low, and the small diameter portions 23a and 23b can be provided on both side portions of the ball screw shaft 3 in the axial direction, and the small diameter portions 23a and 23b can be provided. Guide sleeves 25a and 25b can be arranged around the respective guide sleeves 25a and 25b. In addition to the rotation stop function and the stopper function, each of the guide sleeves 25a and 25b transmits the steering reaction force applied in the radial direction of the ball screw shaft 3 to the housing 2, and the vehicle body via the housing 2. It has a function to be supported by.

In this example, the ball nuts 4a and 4b are arranged close to each other near the center in the width direction, but separated from each other. As a result, in the housing 2, the actuator accommodating portions 10a and 10b accommodating the electric actuators 47a and 47b including the ball nuts 4a and 4b are present in the lower part of the vehicle body and around the axle 43 (for example, the oil pan 48 and the like). ) Is prevented from interfering with. However, from the viewpoint of preventing an excessive force from being applied to the ball screw shaft 3, it is preferable to arrange the pair of ball nuts 4a and 4b as close to each other as possible, most preferably adjacent to each other. In short, the pair of ball nuts 4a and 4b are arranged as close as possible to each other as long as they do not interfere with the members existing around the axle 43.

In this example, the members constituting the electric actuators 47a and 47b are directed from the center side in the width direction to the outside, and the ball nuts 4a and 4b, the bearing devices 5a and 5b, the reduction gears 8a and 8b, and the electric motor 7a. They are arranged in the order of 7b. However, if the ball nuts 4a and 4b are arranged on the most central side in the width direction, the arrangement of other members is not particularly limited. For example, the bearing devices 5a and 5b may be arranged outside the worm wheel 37 of the speed reducers 8a and 8b in the width direction. Further, the worm wheels 37 of the speed reducers 8a and 8b can be arranged around the ball nuts 4a and 4b so as to rotate integrally with the ball nuts 4a and 4b.

Further, in this example, the tie rod 31 is connected to both ends of the ball screw shaft 3 in the axial direction via the spherical joint 30, and the tip of the arm 45 of the knuckle 44 is connected to the tip of the tie rod 31. It is connected so that it can swing. Therefore, when the steering device 1 of this example is driven to give a steering angle to the steering wheels (steering is performed), a reaction force due to steering is applied to the ball screw shaft 3 depending on the angle of the arm 45. On the other hand, it may be added in the radial direction (front-back direction).

Here, in this example, the pair of shaft-side flat surface portions 26 arranged on the front and rear side portions of the outer peripheral surfaces of the pair of guide sleeves 25a and 25b are provided on the small- diameter tubular portions 9a and 9b of the housing 2, respectively. It is in sliding contact with or close to the flat surface portion 12 on the housing side arranged on both front and rear portions of the inner peripheral surface. Therefore, when the reaction force due to the steering is applied to the ball screw shaft 3 in the radial direction, the shaft-side flat surface portions 26 of the guide sleeves 25a and 25b are pressed against the housing-side flat surface portions 12 of the small- diameter tubular portions 9a and 9b. In short, the reaction force applied to the ball screw shaft 3 in the radial direction due to steering is transmitted to the vehicle body via the guide sleeves 25a and 25b and the housing 2, and is supported by the vehicle body. Therefore, according to the steering device 1 of this example, it is possible to prevent the steering reaction force in the radial direction from being applied to the conversion mechanism including the reduction gears 8a and 8b, the ball nuts 4a and 4b, and the ball 6. it can. Specifically, even when a reaction force due to steering is applied in the radial direction with respect to the ball screw shaft 3, the rolling surface of the ball 6 is the ball screw groove 21 on the inner diameter side of the ball screw shaft 3 and the ball nut. It is possible to prevent the ball screw groove 35 on the outer diameter side of 4a and 4b from being strongly pressed. As a result, it is possible to prevent the life of the ball screw mechanism including the ball screw shaft 3, the ball nuts 4a and 4b, and the ball 6 from being shortened, and the occurrence of abnormal noise and vibration.

As described above, in this example, the housing-side flat surface portions 12 arranged on the front and rear side portions of the inner peripheral surfaces of the small- diameter tubular portions 9a and 9b of the housing 2 and the pair of guide sleeves 25a and 25b, respectively. A pair of shaft-side flat surface portions 26 arranged on both front and rear portions of the outer peripheral surface are in sliding contact with each other or are in close contact with each other. As a result, a rotation stop function for preventing the ball screw shaft 3 from rotating relative to the housing 2 is realized, and a reaction force applied to the ball screw shaft 3 in the radial direction due to steering is applied to the conversion mechanism. Is being prevented.

However, from the surface that realizes the rotation stop function, the inner peripheral surfaces of the small diameter tubular portions 9a and 9b of the housing 2 and the outer peripheral surfaces of the pair of guide sleeves 25a and 25b are non-circularly fitted. It's enough. Further, when a steering reaction force in the radial direction is applied to the ball screw shaft 3, a pair of guide sleeves and front and rear side portions of the inner peripheral surfaces of the small diameter tubular portions 9a and 9b of the housing 2 come into contact with each other. The front and rear side portions of the outer peripheral surfaces of 25a and 25b do not necessarily have to be flat surfaces as long as they are in sliding contact with each other or are in close contact with each other. That is, the steering device of the present invention has a flat surface portion on the housing side at at least one position with respect to the circumferential direction of the inner peripheral surface of the portion of the housing that internally fits and holds each of the pair of guide sleeves. In addition, each outer peripheral surface of the pair of guide sleeves can be configured to have a shaft-side flat surface portion that is close to the housing-side flat surface portion or that can be slidably opposed to the housing-side flat surface portion. In this case, the front and rear side portions of the outer peripheral surfaces of the pair of guide sleeves are slidably contacted or close to the front and rear side portions of the inner peripheral surface of the portion of the housing that internally fits and holds each of the pair of guide sleeves. Make them face each other. Specifically, for example, the outer circumferences of the pair of guide sleeves are formed on concave curved surfaces provided on both front and rear portions of the inner peripheral surface of the portion of the housing that internally fits and holds each of the pair of guide sleeves. Convex curved surfaces provided on both front and rear portions of the surface can be slidably contacted or close to each other.

In this example, each of the pair of guide sleeves 25a and 25b is configured by combining a pair of sleeve elements 46. Therefore, by sandwiching one or a plurality of shim plates between the sleeve element 46 and the small diameter portions 23a and 23b of the ball screw shaft 3, the outer peripheral surfaces of the guide sleeves 25a and 25b and the small diameter of the housing 2 are held. The gap between the inner peripheral surfaces of the tubular portions 9a and 9b can be adjusted. That is, the inner peripheral surfaces of the small diameter tubular portions 9a and 9b without excessively increasing the shape accuracy of the small diameter tubular portions 9a and 9b of the housing 2, the small diameter portions 23a and 23b of the ball screw shaft 3, and the guide sleeves 25a and 25b. Since the rattling of the outer peripheral surfaces of the guide sleeves 25a and 25b can be sufficiently suppressed, the cost can be reduced.

However, each of the guide sleeves 25a and 25b may be integrally formed as a whole, that is, in a tubular shape. Alternatively, each of the guide sleeves 25a and 25b can be configured by combining three or more sleeve elements.

In this example, an example in which the steering device 1 is applied to a steer-by-wire type steering device of a vehicle equipped with a leaf spring type suspension device among the axle suspension types has been described. However, the steering device of the present invention is not limited to the leaf spring type, and can be applied to a steer-by-wire type steering device of a vehicle provided with a coil spring type suspension device. Alternatively, the steering device of the present invention can also be applied to a steer-by-wire type steering device of a vehicle provided with an independent suspension type suspension device. Further, the steering device of the present invention is not limited to the steering device of a large vehicle such as a truck, and can be incorporated into a steering device for a passenger car.

The steering device 1 of this example includes a pair of ball nuts 4a and 4b, bearing devices 5a and 5b, electric motors 7a and 7b, and speed reducers 8a and 8b, respectively. However, the steering device of the present invention may also include three or more ball nuts and bearing devices, and three or more electric motors and speed reducers. Alternatively, the steering device of the present invention may be configured such that one ball nut is rotationally driven by a plurality of electric motors. That is, the output torque of the plurality of electric motors can be increased by the speed reducer provided for each electric motor, and then applied to one ball nut. Alternatively, when the steering device of the present invention is implemented, as a conversion mechanism for converting the rotational motion of the output shaft of the electric motor into the linear motion of the linear motion shaft, a rack and pinion mechanism or a sliding screw is used instead of the ball screw mechanism. A mechanism, a planetary roller screw mechanism, or the like can also be adopted.

The technical concept relating to the means for solving the problem related to the second background technology is described below.
(1)
With the housing
With an electric motor
Inside the housing, a linear motion shaft supported for axial displacement,
A conversion mechanism that converts the rotary motion of the output shaft of the electric motor into a linear motion in the axial direction of the linear motion shaft, and
Of the linear motion shafts, the ends on both sides in the axial direction are externally fitted so as not to be displaced and rotated in the axial direction with respect to the linear motion shaft, and the housing can be rotated in the axial direction. A pair of guide sleeves that are impossible to fit inside,
A steering device.

(2)
The housing has a pair of housing-side stopper surfaces that face opposite to each other in the axial direction, and each of the linear motion shaft or the pair of guide sleeves has a pair of housing-side stopper surfaces. It has a pair of shaft-side stopper surfaces facing each other.
When the linear motion shaft is displaced to the limit toward one side in the axial direction, one of the pair of housing-side stopper surfaces and the one of the pair of shaft-side stopper surfaces One of the shaft-side stopper surfaces facing the housing-side stopper surface comes into contact with each other to prevent the linear motion shaft from being further displaced toward one side in the axial direction, and the linear motion shaft is displaced to the other side in the axial direction. When displaced to the limit toward, the other housing-side stopper surface of the pair of housing-side stopper surfaces and the other of the pair of shaft-side stopper surfaces facing the other housing-side stopper surface. The steering device according to (1), wherein the linear motion shaft is prevented from being further displaced toward the other side in the axial direction due to contact with the shaft side stopper surface of the above.

(3)
The pair of housing-side stopper surfaces are provided on one side portion in the axial direction and the other side portion in the axial direction of the housing so as to face outward in the axial direction.
Each of the pair of shaft-side stopper surfaces is provided on each of the pair of guide sleeves so as to face inward in the axial direction.
When the linear motion shaft is displaced to the limit toward one side in the axial direction, the housing-side stopper surface provided on the other side portion in the axial direction and the pair of guide sleeves of the pair of housing-side stopper surfaces Of these, the shaft-side stopper surface provided on the guide sleeve on the other side in the axial direction is in contact with the shaft-side stopper surface to prevent the linear motion shaft from being further displaced toward one side in the axial direction, and the linear motion shaft is displaced. When displaced to the limit toward the other side in the axial direction, the housing side stopper surface provided on one side portion in the axial direction of the pair of housing side stopper surfaces and the axial one side of the pair of guide sleeves. The steering device according to (2), wherein the linear motion shaft is prevented from being further displaced toward the other side in the axial direction due to contact with the shaft side stopper surface provided on the guide sleeve.

(4)
The housing side flat surface portion is provided at least at one position in the circumferential direction of the inner peripheral surface of the portion of the housing that internally fits and holds each of the guide sleeves.
The steering device according to any one of (1) to (3), wherein each outer peripheral surface of the guide sleeve has a flat surface portion on the housing side and a flat surface portion on the shaft side that is close to each other or can be slidably contacted.

(5)
The linear motion shaft is a ball screw shaft having an inner diameter side ball screw groove on the outer peripheral surface.
The conversion mechanism has an outer diameter side ball screw groove on the inner peripheral surface and is rotationally driven by the electric motor, and between the inner diameter side ball screw groove and the outer diameter side ball screw groove. The steering device according to any one of (1) to (4), comprising a plurality of balls rotatably arranged on the ball.

(6)
The steering device according to any one of (1) to (5), wherein each of the guide sleeves is a combination of a plurality of sleeve elements.

(7)
A holding recess for holding grease is provided on the outer peripheral surface of each of the guide sleeves and / or the inner peripheral surface of the portion of the housing that internally fits and holds each of the guide sleeves. The steering device according to any one of 1) to (6).

<Explanation of Codes Related to FIGS. 1 to 7>
1 Steering device 2 Housing 3 Ball screw shaft 4a, 4b Ball nut 5a, 5b Bearing device 6 Ball 7a, 7b Electric motor 8a, 8b Reducer 9a, 9b Small diameter cylinder 10a, 10b Actuator housing 11 Connecting cylinder 12 Flat Surface part 13 Concave curved surface part 14 Stopper convex part 15 Housing side stopper surface 16 Large diameter cylinder part 17 Nut accommodating part 18 Warm accommodating part 19a, 19b Housing element 20 Bolt 21 Inner diameter side ball screw groove 22 Large diameter part 23a, 23b Small diameter part 24 Screw hole 25a, 25b Guide sleeve 26 Flat surface 27 Convex curved surface 28 Stopper recess 29 Shaft side stopper surface 30 Spherical joint 31 Tie rod 32 Support shaft 33 Engagement recess 34 Spherical engagement 35 Outer diameter side ball screw groove 36 Sleeve 37 Worm wheel 38 Warm 39 Mounting plate 40 Bolt 41 Body frame 42 Leaf spring 43 Axle 44 Knuckle 45 Arm 46 Sleeve element 47a, 47b Electric actuator 48 Oil pan

<Explanation of symbols relating to FIGS. 8 to 14> 1 Steering device 2 Housing 3 Ball screw shaft 4a, 4b Ball nut 5a, 5b Bearing device 6 Ball 7a, 7b Electric motor 8a, 8b Reducer 9a, 9b Small diameter cylinder 10a 10b Actuator accommodating part 11 Connecting cylinder part 12 Housing side flat surface part 13 Concave curved surface part 14 Stopper convex part 15 Housing side stopper surface 16 Large diameter cylinder part 17 Nut accommodating part 18 Worm accommodating part 19a, 19b Housing element 20 Bolt 21 Inner diameter side Ball screw groove 22 Large diameter part 23a, 23b Small diameter part 24 Screw hole 25a, 25b Guide sleeve 26 Shaft side flat surface part 27 Convex curved surface part 28 Stopper recess 29 Shaft side stopper surface 30 Spherical joint 31 Tie rod 32 Support shaft part 33 Engagement recess 34 Spherical engagement part 35 Outer diameter side ball screw groove 36 Sleeve 37 Worm wheel 38 Warm 39 Mounting plate part 40 Bolt 41 Body frame 42 Leaf spring 43 Axle 44 Knuckle 45 Arm 46 Sleeve element 47a, 47b Electric actuator 48 Oil pan

Claims (7)

1. With the housing
   A ball screw shaft having an inner diameter side ball screw groove on the outer peripheral surface and supported inside the housing so as to be displaced in the axial direction and unable to rotate.
   A plurality of ball nuts having an outer diameter side ball screw groove on the inner peripheral surface and arranged around the ball screw shaft so as to be relatively rotatable with respect to the ball screw shaft.
   A bearing device that rotatably supports the ball nut with respect to the housing,
   A plurality of balls rotatably arranged between the inner diameter side ball screw groove and the outer diameter side ball screw groove, and
   With multiple electric motors
   The same number of speed reducers as the electric motor, which are applied to the ball nut after increasing the output torque of the electric motor,
   A steering device.
2. The steering device according to claim 1, further comprising the same number of ball nuts as the electric motor.
3. The steering device according to claim 2, further comprising a pair of each of the ball nut, the bearing device, the electric motor, and the speed reducer.
4. The ball nut, the bearing device, the electric motor, and the speed reducer are arranged one by one on both side portions of the housing at the center position in the width direction.
   The steering device according to claim 3, wherein the ball nut is arranged on the side of the ball nut, the bearing device, the electric motor, and the speed reducer closest to the center position in the width direction of the housing. ..
5. The steering device according to claim 4, wherein the ball nuts are arranged adjacent to each other via the housing in a state where the ball nuts are separated from each other with a central position in the width direction interposed therebetween.
6. The steering device according to any one of claims 1 to 5, wherein the speed reducer is a worm speed reducer.
7. The steering device according to any one of claims 1 to 6, wherein the housing is a combination of a plurality of housing elements.

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