JP2020117191A - Steering device - Google Patents

Abstract

To provide a steering device including a rack housing having high vibration rigidity.SOLUTION: A steering device 100 includes a rack housing 131 to which an electric drive source 140 is fixed and which has a substantially cylindrical shape in an overall view. The rack housing 131 includes a vibration rigidity reinforcement rib 141 which protrudes from an outer peripheral surface of the rack housing 131 at an opposite side of the electric drive source 140 with respect to a rack shaft 130 along a tangent line, extends ranging from a centroid position C of the electric drive source 140 to an attachment part 142 in an axial direction of the rack shaft 130, and is integrally molded with the rack housing 131.SELECTED DRAWING: Figure 3

Description

The present invention relates to a steering device that steers steerable wheels based on the output of an electric drive source to steer a vehicle or the like.

For example, an electric power steering apparatus may employ a structure in which the output of the motor is applied to the rack shaft as an assist torque via a reduction gear. Further, in recent years, a technique called steer-by-wire (SBW) has been drawing attention. In this technology called steer-by-wire, the steering member operated by the driver and the rack shaft are not mechanically connected, the operation state of the steering member is output as a signal, and the motor reciprocates on the rack shaft based on the signal. This is a technology for moving the steered wheels.

Patent Document 1 discloses a technique of increasing the rigidity of a housing by providing a rib on the housing that houses a torque sensor of an electric power steering device.

JP, 2018-128387, A

It is generally practiced to erect ribs perpendicular to the surface of the housing to improve the rigidity while suppressing an increase in weight. However, it has been found that when a motor used for driving the rack shaft is attached to the rack housing that accommodates the rack shaft, a problem may occur in the rack housing simply by providing a rib on the rack housing. Further, as a result of earnest research, the inventor has found that vibration generated in the motor affects the rack housing for a long period of time, causing a problem in the rack housing.

The present invention has been made in view of the above knowledge, and an object of the present invention is to provide a steering device including a rack housing having an increased vibration rigidity against vibration of a motor or the like.

In order to achieve the above object, a steering device according to one aspect of the present invention is a steering device including a rack housing having a generally cylindrical shape as a whole, to which an electric drive source for driving a rack shaft is fixed. Is projected from the outer peripheral surface of the rack housing on the side opposite to the electric drive source with respect to the rack shaft along a tangent line of the outer peripheral surface, and the electric motor is driven from the center of gravity of the electric drive source in the axial direction of the rack shaft. A vibration rigidity reinforcing rib that extends over the mounting portion of the drive source and is integrally formed with the rack housing is provided.

According to the present invention, it is possible to provide a steering device including a rack housing having high vibration rigidity.

FIG. 1 is a diagram showing a steering device according to an embodiment. FIG. 2 is a cross-sectional view showing the relationship between the speed reducer housing and the rack housing according to the embodiment. FIG. 3 is a rear view showing the relationship between the speed reducer housing and the rack housing according to the embodiment. FIG. 4 is a sectional view showing a state in which the electric drive source is attached to the rack housing. FIG. 5 is a diagram showing a steering device according to another embodiment. FIG. 6 is a diagram showing a steering device according to another embodiment.

Next, an embodiment of a steering device according to the present invention will be described with reference to the drawings. It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, connection forms, and the like shown in the following embodiments are examples and are not intended to limit the present invention. Further, among the constituent elements in the following embodiments, constituent elements not described in the independent claim showing the highest concept are described as arbitrary constituent elements.

In addition, the drawings are schematic diagrams in which the present invention is appropriately emphasized or omitted and ratios are adjusted, and may differ from actual shapes, positional relationships, and ratios.

FIG. 1 is a diagram showing the entire steering device. The steering device 100 is a device that steers a steering wheel 201, which is a so-called tire, by increasing a rotational torque that is an output of an electric drive source 140 including an electric motor by a speed reducer 150 to steer a vehicle or the like. .. In the case of the present embodiment, the steering device 100 is a device that includes the steering member 200 that is steered by the driver, and that can steer the steered wheels 201 mechanically via the steering shaft 110 and the rack shaft 130. This is a steering device that can apply a force that assists the turning of the steered wheels 201 in accordance with the steering torque generated by the driver rotating 200. The steering apparatus 100 includes a steering shaft 110 in which a plurality of shafts are connected by a universal joint, a pinion 120 connected to the tip of the steering shaft 110, a rack shaft 130 that meshes with the pinion 120, and a rack that houses the rack shaft 130. A housing 131, an electric drive source 140, a speed reducer 150 that increases the rotational torque of the electric drive source 140, a speed reducer housing 151 that houses the speed reducer 150, and a pinion shaft 160 that functions as an output shaft of the speed reducer 150. Equipped with.

FIG. 2 is a perspective view showing the rack housing 131. FIG. 3 is a plan view showing the rack housing 131 from the vibration rigidity reinforcing rib 141 side. FIG. 4 is a cross-sectional view showing a portion such as the rack housing 131 cut along a plane that includes the center of gravity of the electric drive source 140 and is perpendicular to the axis of the rack shaft 130.

The rack shaft 130 is a rod-shaped member that is long in the axial direction and has a substantially circular cross section, and is housed in the rack housing 131. Both ends of the rack shaft 130 are connected to the steered wheels 201 via tie rods (not shown). In the rack shaft 130, the rotation of the pinion 120 is converted into the reciprocating motion of the rack shaft 130 with the rotation of the steering member 200, and the rack shaft 130 moves in the axial direction, whereby the steered wheels 201 turn and the steering is controlled. It is supposed to be done.

The rack housing 131 is a member that is fixed to the vehicle body using an integrally molded bracket 136 and that guides the rack shaft 130 housed inside in the axial direction, and is one of the mechanical elements that intersect and contact the rack shaft 130. A cylindrical pinion insertion portion 132 (see FIG. 1) into which the pinion 120, which is one of the two, and a rack shaft 130 are housed, and the rack shaft 130 is housed in a substantially cylindrical rack shaft 130 so as to reciprocate in the axial direction. A portion 133 and a tubular shaft insertion portion 134 into which a part of the pinion shaft 160, which is one of the mechanical elements that mesh with the rack while intersecting with the rack shaft 130, are inserted. The rack housing 131 is formed of, for example, an aluminum alloy. Further, bellows tubular boots 135 made of rubber or the like are attached to both ends of the rack housing 131. Since both open ends of the rack housing 131 in the longitudinal direction are sealed by the boots 135, and the opening of the pinion insertion portion 132 is also sealed, the rack housing 131 is in a hermetically sealed state to some extent, and the water is inwardly sealed. , To prevent mud from entering.

As shown in FIG. 4 and the like, the rack housing 131 includes a vibration rigidity reinforcing rib 141 protruding from the outer peripheral surface of the rack housing 131 on the opposite side of the rack shaft 130 from the electric drive source 140 along a tangent line of the outer peripheral surface. ing. The rack housing 131 is provided with ribs protruding in the radial direction other than the vibration rigidity reinforcing ribs 141, but they are not shown.

As shown in FIG. 3, the vibration rigidity reinforcing rib 141 extends at least from the center of gravity C of the electric drive source 140 to the mounting portion 142 of the electric drive source 140 in the axial direction of the rack shaft 130 (Y axis in the figure). Is integrally formed with the rack housing 131. Here, the center-of-gravity position C of the electric drive source 140 refers to the center-of-gravity position of the motor, the electric drive source 140 is the motor, and the ECU (Electronic Control Unit) that controls the motor when the electric drive source 140 is composed of only the motor. When equipped, it is the position of the center of gravity of the whole.

As described above, the plate-like vibration projecting not in the radial direction (radial direction) with respect to the axis of the rack shaft housing portion 133 but in the tangential direction of the outer peripheral surface and extending from the center of gravity C of the electric drive source 140 to the mounting portion 142. By integrally providing the rigidity-enhancing ribs 141, the relatively heavy electric drive source 140 fixed to the rack housing 131 in a cantilevered state at the mounting portion 142 can resist vibration in a pendulum shape for a long period of time.

Further, the protrusion amount (length) of the vibration rigidity reinforcing rib 141 is not particularly limited, but it is desirable that the vibration rigidity reinforcing rib 141 protrudes beyond the rack shaft housing portion 133 in the protruding direction of the vibration rigidity reinforcing rib 141. As a result, the vibration rigidity of the rack housing 131 can be increased. Further, when a heat source such as an engine is present on the side opposite to the electric drive source 140 with respect to the vibration rigidity reinforcing rib 141, the vibration rigidity reinforcing rib 141 causes the heat generation source to move. It is possible to block the heat radiation from the electric drive source 140 and suppress the heat absorption of the electric drive source 140. This makes it possible to protect the electric drive source 140 by suppressing an increase in heat of the electric drive source 140.

In the case of the present embodiment, one end of the vibration rigidity reinforcing rib 141 in the axial direction of the rack shaft 130 is one of the mechanical elements that integrally protrude in the radial direction from the rack housing 131 and mesh with the rack provided on the rack shaft 130. It is integrally connected to a shaft insertion portion 134 as a protruding accommodating portion that accommodates a certain pinion shaft 160. Thus, in the axial direction of the rack shaft 130, the end of the vibration rigidity reinforcing rib 141 is firmly connected to the shaft insertion portion 134 integrated with the rack housing 131, so that stress is applied near the end of the vibration rigidity reinforcing rib 141. The vibration rigidity of the rack housing 131 can be enhanced without concentration.

Further, in the case of the present embodiment, the vibration rigidity reinforcing rib 141 projects in both directions from the rack housing 131 along the tangent line of the outer peripheral surface of the rack housing 131. In this way, the rack housing 131 is provided with the vibration rigidity reinforcing ribs 141 protruding on both sides in the tangential direction, whereby the vibration rigidity can be further increased. The vibration rigidity reinforcing ribs 141 projecting to both sides at the tangent of the rack housing 131 are formed in a single plate shape, so that the vibration rigidity can be increased while avoiding interference with other structures in the vehicle. Becomes Further, heat reflection may be enhanced by, for example, processing for reducing the surface roughness.

Further, the vibration rigidity reinforcing rib 141 includes a taper portion 143 along which the protrusion amount from the rack housing 131 gradually decreases as the distance from the center of gravity C of the electric drive source 140 increases along the axial direction of the rack shaft 130. According to this, it is possible to avoid concentration of stress on the end portion of the vibration rigidity reinforcing rib 141 in the axial direction of the rack shaft 130. The start position of the taper is located outside the region from the center of gravity C of the electric drive source 140 to the mounting portion 142 in the axial direction of the rack housing 131. By arranging the tapered portion 143 in this manner, the rigidity of the rack housing 131 can be maintained in a high state.

The electric drive source 140 is an electric drive source that generates assist torque. An electric drive source ECU may be attached to the electric drive source 140, and a torque suitable for assisting is output based on the torque applied by the steering member 200 and the information on the vehicle speed. In the case of the present embodiment, the rotation axis M of the electric drive source 140 is arranged parallel to or substantially parallel to the extending direction of the rack shaft 130. As a result, the amount of protrusion of the electric drive source 140 from the rack housing 131 in the direction perpendicular to the extending direction of the rack shaft 130 can be suppressed, and the steering device 100 in the engine room can be made compact. it can.

The speed reducer 150 is a device that reduces the rotational speed of the output shaft of the electric drive source 140 by means of gears and outputs a torque inversely proportional to the speed reduction to the pinion shaft 160. In the case of the present embodiment, the speed reducer 150 employs a worm speed reducer including a worm shaft (not shown) connected to the output shaft of the electric drive source 140 and a worm wheel that is an output gear that meshes with the worm shaft. ..

The steering device 100 described in the above embodiment includes the rack housing 131 that is sufficiently lightweight and compact, yet can sufficiently withstand the vibration of the electric drive source 140 attached to the rack housing 131. Therefore, it is possible to provide the steering device 100 that has high durability and can contribute to weight reduction of the vehicle. In addition, since the vibration rigidity reinforcing rib 141 does not project in the radial direction, the area occupied by the entire rack housing 131 can be made compact and interference with other structures in the vehicle can be avoided.

The present invention is not limited to the above embodiment. For example, another embodiment realized by arbitrarily combining the constituent elements described in this specification or excluding some of the constituent elements may be an embodiment of the present invention. Further, the present invention also includes modified examples obtained by applying various modifications that those skilled in the art can think of to the above-described embodiment without departing from the gist of the present invention, that is, the scope of the wording described in the claims. Be done.

For example, the case where one end of the vibration rigidity reinforcing rib 141 is connected to the shaft insertion portion 134 and the other end is provided with the tapered portion 143 in the axial direction of the rack shaft 130 has been described. Both ends may be connected to a protruding accommodating portion such as the shaft insertion portion 134. Further, the tapered portions 143 may be provided at both ends of the vibration rigidity reinforcing rib 141 without connecting the vibration rigidity reinforcing rib 141 to the projecting accommodating portion.

Further, although the substantially flat plate-shaped vibration-stiffness reinforcing rib 141 is illustrated in the above-described embodiment, the vibration-stiffness reinforcing rib 141 may be provided with a rib protruding from the surface of the vibration-stiffness reinforcing rib 141.

Further, in the steering device 100, as shown in FIG. 5, the steering member 200 and the rack shaft 130 are not mechanically connected to each other, and the rotation angle of the steering member 200 is read by a sensor or the like, and based on the signal of the sensor or the like. A so-called SBW (Steer By Wire System) in which the rack shaft 130 reciprocates by the rotation of the pinion shaft 160 and steers the steered wheels 201 may be used.

Further, as shown in FIG. 6, the steering device 100 may be an unmanned steering device that does not include the steering member 200, the steering shaft 110, etc., and is steered by a computer.

The present invention relates to a steering device for a vehicle or the like, which is a steering device capable of assisting a steering force by a person, an SBW in which a steering member and a steered wheel are not mechanically connected and electrically steered, and an unmanned steering device. It is available for

100... Steering device, 110... Steering shaft, 120... Pinion, 130... Rack shaft, 131... Rack housing, 132... Pinion insertion part, 133... Rack shaft accommodation part, 134... Shaft insertion part, 135... Boots, 136... Bracket , 140... Electric drive source, 141... Vibration rigidity reinforcing ribs, 142... Mounting portion, 143... Tapered portion, 150... Reduction gear, 151... Reduction gear housing, 160... Pinion shaft, 200... Steering member, 201... Steering wheel

Claims (5)

A steering device comprising a rack housing of a generally cylindrical shape to which an electric drive source for driving a rack shaft is fixed,
The rack housing is
The electric drive source protrudes from the outer peripheral surface of the rack housing on the side opposite to the electric drive source with respect to the rack shaft, along a tangent line of the outer peripheral surface, and from the center of gravity of the electric drive source in the axial direction of the rack shaft. A steering device including a vibration rigidity reinforcing rib that extends over the mounting portion of the rack housing and is integrally formed with the rack housing. The one end portion of the vibration rigidity reinforcing rib in the axial direction of the rack shaft is connected to a protruding accommodating portion that integrally protrudes radially from the rack housing and accommodates a mechanical element different from the rack shaft. Steering device. The vibration rigidity reinforcing rib is
The steering device according to claim 1, wherein the steering device projects in both directions from the rack housing along a tangent line of an outer peripheral surface of the rack housing. The vibration rigidity reinforcing rib is
The steering device according to claim 1, further comprising a taper portion in which an amount of protrusion from the rack housing gradually decreases as the distance from the center of gravity of the electric drive source increases along the axial direction of the rack shaft. The tapered portion is
The steering apparatus according to claim 4, wherein the steering device is arranged outside an area from a center of gravity of the electric drive source to a mounting portion of the electric drive source in an axial direction of the rack shaft.

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