Steering device

Abstract

To provide a steering device that is able to stably support a worm shaft.SOLUTION: A steering device 10 includes: a steering mechanism 100 and a driving force applying mechanism 150 that applies a driving force for steering to the steering mechanism 100. The driving force applying mechanism 150 includes: an electric motor 180; a worm shaft 164; a coupling member 200 that couples an output rotary shaft 181 of the electric motor 180 and the worm shaft 164; and a worm wheel 163 that meshes with the worm shaft 164. The coupling member 200 includes: a first coupling member 210 fixed to an end part of the output rotary shaft 181; a second coupling member 220 fixed to an end part of the worm shaft 164; and an intermediate member 230 formed of an elastic material and interposed between the first coupling member 210 and the second coupling member 220. The elastic material has a TR10 value of -27°C or lower in a low-temperature elastic recovery test, and a TR50 value of -9°C or lower in the low-temperature elastic recovery test.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a steering device mounted on a vehicle. [Background technology]

[0002] The electric power steering device disclosed in Patent Document 1 includes an assist mechanism. The assist mechanism includes an electric motor, a power transmission joint, and a worm reduction gear. The power transmission joint connects the rotating shaft of the electric motor and a worm shaft that is an input shaft of the worm reduction gear. The power transmission joint includes a first member, a second member, and an intermediate member. The first member is fixed to a first end of the worm shaft so as to be integrally rotatable. The second member is fixed to an end of the rotating shaft of the electric motor so as to be integrally rotatable. The intermediate member is interposed between the first member and the second member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-36767 A Summary of the Invention [Problem to be solved by the invention]

[0004] The power transmission joint of the conventional electric power steering device has an intermediate member made of an elastic material, which allows the power transmission joint to transmit the rotational output of the electric motor to the worm reduction gear while absorbing vibrations and the like that occur while the vehicle is traveling with the intermediate member.

[0005] However, the elastic member forming the intermediate member is, for example, rubber or resin. Therefore, the elastic member hardens in a low-temperature environment and the reaction force increases, and as a result, it is considered that, for example, the worm shaft is less likely to change its posture and / or position to absorb shocks, etc. In this case, for example, backlash between the worm shaft and the worm wheel increases, and as a result, there is a possibility that a hitting sound is generated between the worm shaft and the worm wheel. On the other hand, if the reaction force of the intermediate member is too small, for example, when the vehicle is traveling on a rough road, the posture and / or position of the worm shaft changes greatly, and as a result, there is a possibility that a hitting sound is generated between the worm shaft and the housing that accommodates the worm shaft, etc.

[0006] The present invention was made by the inventors of the present application by focusing on the above-mentioned problem, and has an object to provide a steering device that can stably support a worm shaft. [Means for solving the problem]

[0007] A steering device according to one embodiment of the present invention is a steering device comprising a steering mechanism which steers steered wheels in response to operation of an operating member, and a driving force imparting mechanism which imparts a driving force for steering to the steering mechanism, wherein the driving force imparting mechanism comprises an electric motor, a worm shaft, a connecting member which connects an output shaft of the electric motor and the worm shaft, and a worm wheel which meshes with the worm shaft, wherein the connecting member comprises a first connecting member fixed to an end of the output shaft, a second connecting member fixed to an end of the worm shaft, and an intermediate member which is interposed between the first connecting member and the second connecting member and is made of an elastic material, wherein the elastic material has a TR10 value of -27°C or less in a low-temperature elastic recovery test, and a TR50 value of -9°C or less in the low-temperature elastic recovery test. Effect of the Invention

[0008] According to the steering device of the present invention, the worm shaft can be stably supported. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a schematic overall configuration of a steering system to which a worm reduction gear is attached. [Diagram 2] FIG. 2 is a cross-sectional view showing an internal structure of a driving force imparting mechanism according to the embodiment. [Diagram 3] FIG. 3 is a perspective view showing a schematic configuration of a connecting member according to the embodiment. [Figure 4] FIG. 4 is an exploded perspective view of a connecting member according to an embodiment. [Diagram 5] FIG. 5 is a cross-sectional view of a connecting member according to an embodiment. [Figure 6] FIG. 6 is a diagram showing temperature-shrinkage curves of material A of the intermediate member according to the embodiment and material B of the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples of the present invention. The numerical values, shapes, materials, components, component arrangement and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims showing the highest concept will be described as optional components.

[0011] In addition, the drawings are schematic diagrams in which emphasis, omissions, and ratios have been appropriately adjusted in order to illustrate the present invention, and may differ from the actual shapes, positional relationships, and ratios.

[0012] (Embodiment) [1. Overview of steering system configuration] First, the overall configuration of a steering device 10 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram that shows a schematic view of the overall configuration of the steering device 10. As shown in Fig. 1, the steering device 10 according to this embodiment is a device that steers steered wheels in response to the operation of an operating member 110 such as a steering wheel.

[0013] More specifically, the steering device 10 is a power steering device that assists the driver's force to rotate an operating member 110 such as a steering wheel for steering. The steering device 10 includes a steering mechanism 100 that steers the steered wheels 300 in response to the operation of the operating member 110, and a driving force imparting mechanism 150 that imparts a driving force for steering to the steering mechanism 100. The steering mechanism 100 includes a steering shaft 130 that rotates in conjunction with the rotation of the operating member 110, a rack-and-pinion device 140 that converts the rotation of the steering shaft 130 into a reciprocating motion of a steered shaft 141, and a sensor device 120 that detects the steering torque applied by the operating member 110.

[0014] The steering shaft 130 is composed of three shafts: a column shaft 131, an intermediate shaft 132, and a pinion shaft 133. In the power steering device, the position at which the driving force imparting mechanism 150 that imparts driving force is attached is not particularly limited, but in this embodiment, it is connected to the pinion shaft 133.

[0015] The driving force imparting mechanism 150 includes an electric motor 180, and uses the electric motor 180 as a driving source to impart a driving force (assist torque) for steering to the steering shaft 130. The electric motor 180 is controlled by an ECU (Electronic Control Unit) (not shown), whereby the driving force imparted to the steering shaft 130 is appropriately adjusted.

[0016] [2. Configuration of the driving force imparting mechanism] Next, the configuration and operation of the driving force imparting mechanism 150 according to this embodiment will be described with reference to FIGS.

[0017] [2-1. Overall configuration of the driving force imparting mechanism] 2 is a cross-sectional view showing an internal structure of the driving force imparting mechanism 150 according to the embodiment. The driving force imparting mechanism 150 includes an electric motor 180, a worm shaft 164, a connecting member 200, a worm wheel 163, a housing 153, a first bearing 161, a second bearing 162, and a biasing member 170.

[0018] The housing 153 is a box-shaped structural member that houses the worm shaft 164 and the worm wheel 163. The housing 153 is provided with a hole 154 that penetrates the housing 153, and an attachment portion 156 that is disposed on the outside of the hole 154. A biasing member 170 such as a coil spring is disposed in the hole 154. A preload member 155 that pressurizes the biasing member 170 is attached to the attachment portion 156.

[0019] Hole 154 is a through hole that penetrates from the outside to the inside of housing 153 in the radial direction of first bearing 161. The shape of hole 154 is not particularly limited, but in this embodiment, it is cylindrical. Mounting portion 156 is a cylindrical portion provided coaxially with hole 154, and has a female thread on its inner circumferential surface.

[0020] Preload member 155 has a male thread on its outer periphery that screws into mounting portion 156 of housing 153, and is fixed by being screwed into mounting portion 156 to pressurize biasing member 170. The shape of preload member 155 is not particularly limited, but in this embodiment, preload member 155 is a cylindrical member.

[0021] The worm shaft 164 is rotatably supported at both ends by a first bearing 161 and a second bearing 162 within the housing 153. The worm shaft 164 is tiltably supported with respect to a rotation axis Ra, and is pressed against the worm wheel 163 via the first bearing 161 by the biasing force of a biasing member 170. The rotation axis Ra is a virtual axis that serves as the rotation center of an output rotation shaft 181 of an electric motor 180. In this embodiment, the worm shaft 164 is connected to the electric motor 180, and is repeatedly rotated, stopped, and rotated in the reverse direction around the axis.

[0022] The electric motor 180 has a motor body 185 having a stator, a rotor, etc. therein, and an output rotating shaft 181 protruding from the motor body 185. In this embodiment, the output rotating shaft 181 of the electric motor 180 and the worm shaft 164 are connected by a connecting member 200. The connecting member 200 according to this embodiment includes a first connecting member 210, a second connecting member 220, and an intermediate member 230.

[0023] The worm wheel 163 is rotatably held in the housing 153. In the present embodiment, the worm wheel 163 is connected to the pinion shaft 133, and amplifies the torque input to the worm shaft 164 to apply an assist torque to the pinion shaft 133. As shown in FIG. 2, the worm wheel 163 and the pinion shaft 133 rotate about a rotation axis Rb (virtual axis) perpendicular to the rotation axis Ra.

[0024] The first bearing 161 holds one end of the worm shaft 164 (the end in the negative X-axis direction in FIG. 2) inside the housing 153. The first bearing 161 is held so as to be reciprocable with respect to the housing 153 in a direction approaching the worm wheel 163 and a direction away from the worm wheel 163 (the Z-axis direction in FIG. 2). That is, the first bearing 161 is arranged so as to be able to tilt the worm shaft 164 with respect to the rotation axis Ra. The second bearing 162 has a structure that allows the worm shaft 164 to tilt. In this structure, the first bearing 161 is biased in the negative Z-axis direction by the biasing member 170 as shown in FIG. 2. That is, in the driving force imparting mechanism 150 according to this embodiment, the worm shaft 164 is pressed against the worm wheel 163 by the biasing force of the biasing member 170, thereby suppressing an increase in backlash, so-called an anti-backlash system (ABLS) is constructed.

[0025] For example, due to impact or vibration that the vehicle equipped with the steering device 10 receives from the road surface, an external force in the Z-axis direction acts on the worm wheel 163 to change the distance between the rotation axis Rb and the rotation axis Ra. Even in this case, in this embodiment, the biasing force of the biasing member 170 acts on the worm shaft 164 so as to press the worm shaft 164 against the worm wheel 163. That is, the biasing force of the biasing member 170 acts so as not to increase the backlash between the worm shaft 164 and the worm wheel 163. Furthermore, the connecting member 200 that connects the worm shaft 164 and the output rotating shaft 181 of the electric motor 180 includes an intermediate member 230 formed of an elastic material. This allows the torque output from the electric motor 180 to be transmitted to the worm shaft 164 while allowing the attitude and / or position of the worm shaft 164 with respect to the housing 153 to change. Hereinafter, a detailed configuration of the connecting member 200 will be described with reference to FIGS. 3 to 6.

[0026] [2-2. About the structure of connecting parts] Fig. 3 is a perspective view showing an outline of the configuration of a connecting member 200 according to an embodiment. Fig. 3 shows the connecting member 200 in a state where the worm shaft 164 is removed from the connecting member 200. Fig. 4 is an exploded perspective view of the connecting member 200 according to an embodiment. Fig. 5 is a cross-sectional view of the connecting member 200 according to an embodiment. Fig. 5 shows a cross section of the connecting member 200 in a YZ plane passing through the line VI-VI in Fig. 3. Fig. 6 is a diagram showing temperature-shrinkage curves of material A of the intermediate member 230 according to the embodiment and material B according to a comparative example.

[0027] As described above, in this embodiment, the end of the worm shaft 164 opposite to the end held by the first bearing 161 is connected to the output rotation shaft 181 of the electric motor 180 by the connecting member 200. As shown in Figs. 2 and 3, the connecting member 200 has a first connecting member 210, a second connecting member 220, and an intermediate member 230. The first connecting member 210 is fixed to an end of the output rotation shaft 181. The second connecting member 220 is fixed to an end of the worm shaft 164. The intermediate member 230 is disposed between the first connecting member 210 and the second connecting member 220. The intermediate member 230 is formed of an elastic material.

[0028] The first connecting member 210 has a first fixing portion 211b into which the end of the output rotating shaft 181 is inserted and fixed, a circular first main body portion 211, and a plurality of first protrusions 212 protruding from the first main body portion 211 toward the second connecting member 220. In this embodiment, as shown in FIG. 5, four first protrusions 212 are arranged at equal intervals in the circumferential direction centered on the rotation axis Ra. A first hole 211a is provided in the first fixing portion 211b. For example, the end of the output rotating shaft 181 is press-fitted into the first hole 211a, whereby the first connecting member 210 is fixed to the end of the output rotating shaft 181. In this embodiment, the plurality of first protrusions 212 are integrally provided on the first main body portion 211 made of, for example, resin, and the first fixing portion 211b made of, for example, metal is fixed to the first main body portion 211 by a predetermined means. The first connecting member 210, which is integrally provided with the first body portion 211 made of resin and the first fixing portion 211b made of metal, can be produced by, for example, insert molding. The entire first connecting member 210 may be made of metal, or the entire first connecting member 210 may be made of resin.

[0029] The second connecting member 220 has a second fixing portion 221b into which the end of the worm shaft 164 is inserted and fixed, a circular second main body portion 221, and a plurality of second protrusions 222 protruding from the second main body portion 221 toward the first connecting member 210. In this embodiment, as shown in Figs. 4 and 5, four second protrusions 222 are arranged at equal intervals in the circumferential direction centered on the rotation axis Ra. A second hole 221a is provided in the second fixing portion 221b. For example, the worm shaft 164 is press-fitted into the second hole 221a, whereby the second connecting member 220 is fixed to the end of the worm shaft 164. In this embodiment, the plurality of second protrusions 222 are integrally provided on the second main body portion 221 made of, for example, resin, and the second fixing portion 221b made of, for example, metal is fixed to the second main body portion 221 by a predetermined means. The second connecting member 220, which is integrally provided with the second body portion 221 made of resin and the second fixing portion 221b made of metal, can be produced by, for example, insert molding. The entire second connecting member 220 may be made of metal, or the entire second connecting member 220 may be made of resin.

[0030] The intermediate member 230 includes a central portion 231a disposed at a position through which the rotation axis Ra passes, a plurality of connecting portions 231 extending from the central portion 231a in a direction perpendicular to the rotation axis Ra (radial direction), and a plurality of intermediate protrusions 232. The intermediate member 230 according to the present embodiment integrally includes the central portion 231a, the plurality of connecting portions 231, and the plurality of intermediate protrusions 232.

[0031] In this embodiment, the intermediate member 230 has four connecting portions 231. Each of the four connecting portions 231 connects a pair of intermediate protrusions 232 arranged side by side in the circumferential direction centered on the rotation axis Ra. As a result, the four pairs of intermediate protrusions 232 are arranged side by side at equal intervals in the circumferential direction centered on the rotation axis Ra. In other words, the intermediate member 230 according to this embodiment has eight intermediate protrusions 232. More specifically, the connecting portion 231 connects the ends of the pair of intermediate protrusions 232 in the positive direction of the X-axis.

[0032] Between a pair of intermediate protrusions 232 connected by the connecting portion 231, a second insertion portion 234 (see FIG. 4) into which the second protrusion 222 of the second connecting member 220 is inserted is formed. In this embodiment, the intermediate member 230 has four second insertion portions 234. Also, between two intermediate protrusions 232 that are adjacent to each other in the circumferential direction and that are not connected by the connecting portion 231, a first insertion portion 233 (see FIG. 4) into which the first protrusion 212 of the first connecting member 210 is inserted is formed. In this embodiment, the intermediate member 230 has four first insertion portions 233.

[0033] The first connecting member 210, the second connecting member 220, and the intermediate member 230 thus configured are combined to form the connecting member 200 shown in FIGS.

[0034] Specifically, when the first connecting member 210, the second connecting member 220, and the intermediate member 230 are combined, the first protrusion 212 and the second protrusion 222 are arranged in the circumferential direction with the intermediate protrusion 232 in between, as shown in Fig. 5. As a result, in the connecting member 200, the first connecting member 210 and the intermediate member 230 engage with each other in the circumferential direction, and the second connecting member 220 and the intermediate member 230 engage with each other in the circumferential direction.

[0035] More specifically, for example, when the output rotating shaft 181 of the electric motor 180 is not rotating, the first protrusion 212 and the intermediate protrusion 232 adjacent to each other in the circumferential direction are in contact with each other, and the second protrusion 222 and the intermediate protrusion 232 adjacent to each other in the circumferential direction are in contact with each other. That is, as shown in Fig. 5, at least a part of the first side surface 212a, which is the side surface in the circumferential direction of the first protrusion 212, and at least a part of the intermediate first side surface 232a, which is the side surface of the intermediate protrusion 232 facing the first protrusion 212, are in a state of pressing against each other. Also, at least a part of the second side surface 222a, which is the side surface in the circumferential direction of the second protrusion 222, and at least a part of the intermediate second side surface 232b, which is the side surface of the intermediate protrusion 232 facing the second protrusion 222, are in a state of pressing against each other.

[0036] In the connecting member 200 according to the present embodiment, the first protrusion 212, the intermediate protrusion 232, and the second protrusion 222, which are in a state of pressing against each other in the circumferential direction as described above, are arranged continuously in the circumferential direction as shown in FIG. 5. In addition, the elastic material forming the intermediate protrusion 232 has lower rigidity (in other words, is more easily elastically deformed) than the material (e.g., resin) forming the first protrusion 212 and the material (e.g., resin) forming the second protrusion 222. Therefore, when the output rotating shaft 181 of the electric motor 180 rotates, the intermediate protrusion 232 connects the first protrusion 212 and the second protrusion 222 in the circumferential direction while expanding and contracting the circumferential width between the first protrusion 212 and the second protrusion 222. In addition, when the attitude and / or position of the worm shaft 164 relative to the housing 153 changes, such as when the worm shaft 164 tilts with respect to the rotation axis Ra, the intermediate protrusion 232 connects the first protrusion 212 and the second protrusion 222 in the circumferential direction while deforming between the first protrusion 212 and the second protrusion 222. In this manner, the connecting member 200 has the intermediate member 230 formed from an elastic material, and thus the torque generated by the rotation of the output rotating shaft 181 of the electric motor 180 can be smoothly transmitted to the worm shaft 164 .

[0037] In the connecting member 200 configured as described above, rubber is used as the elastic material forming the intermediate member 230. In the present embodiment, hydrogenated nitrile rubber that satisfies predetermined conditions is used as the elastic material forming the intermediate member 230.

[0038] Specifically, material A, which is the elastic material forming intermediate member 230, has the properties that the TR10 value in the low-temperature elastic recovery test is −27° C. or less, and the TR50 value in the low-temperature elastic recovery test is −9° C. or less, as shown in FIG. 6, for example.

[0039] The low-temperature elastic recovery test is a test to determine the temperature at which a rubber test piece, which has been stretched and frozen at a low temperature, recovers its elasticity as the temperature rises and reaches a certain shrinkage percentage. The low-temperature elastic recovery test is specified, for example, in JIS K6261. Specifically, "the TR10 value in the low-temperature elastic recovery test is -27°C or less" means that the temperature at which the elasticity recovers with the temperature rise and the shrinkage percentage reaches 10 percent after the test piece is stretched and cooled to -70°C is -27°C or less. "The TR50 value in the low-temperature elastic recovery test is -9°C or less" means that the temperature at which the elasticity recovers with the temperature rise and the shrinkage percentage reaches 50 percent after the test piece is stretched and cooled to -70°C is -9°C or less. The "shrinkage percentage" is a numerical value calculated by dividing the length shrunk with the temperature rise by the length stretched before cooling.

[0040] That is, the intermediate member 230 of the connecting member 200 according to this embodiment is made of an elastic material that does not harden even at low temperatures, in other words, an elastic material that has high cold resistance.

[0041] More specifically, material A, which is an elastic material forming the intermediate member 230, is hydrogenated nitrile rubber having a relatively small acrylonitrile content (%). That is, the hydrogenated nitrile rubber adopted as the elastic material has a relatively small acrylonitrile content (%), and thus can exhibit the above-mentioned characteristics.

[0042] For example, when a low-temperature elastic recovery test is performed on material B, which has a higher acrylonitrile content (%) than material A, the TR10 value in the low-temperature elastic recovery test is greater than −27° C., and the TR50 value in the low-temperature elastic recovery test is greater than −9° C., as shown in Fig. 6. In other words, when a member made of material A and a member made of material B are frozen and then thawed, the member made of material A can recover its elasticity at a lower temperature.

[0043] In this manner, in the present embodiment, the intermediate member 230 interposed between the first connecting member 210 and the second connecting member 220 in the connecting member 200 is formed of an elastic material that is difficult to harden even at low temperatures. This makes it possible to suppress an increase in reaction force due to hardening of the intermediate member 230, for example, when the vehicle equipped with the steering device 10 is placed in a low-temperature environment. As a result, for example, when the worm wheel 163 is displaced in the vertical direction (Z-axis direction) relative to the housing 153, the movement of the worm shaft 164 following the displacement is unlikely to be hindered by the intermediate member 230. That is, the intermediate member 230 can deform in a low-temperature environment so as not to hinder the change in attitude and / or position of the worm shaft 164 for absorbing shocks and the like. This suppresses the occurrence of problems (such as hitting sounds between the worm shaft 164 and the worm wheel 163) caused by an increase in backlash between the worm shaft 164 and the worm wheel 163.

[0044] In this way, according to the steering device 10 according to the present embodiment, the worm shaft 164 can be supported stably.

[0045] Here, if the elastic material forming the intermediate member 230 is too soft at low temperatures, the intermediate member 230 may lose at least a part of its function of being interposed between the first connecting member 210 and the second connecting member 220 and supporting the worm shaft 164. Therefore, it is preferable that material A, which is the elastic material forming the intermediate member 230, has the characteristics that the TR10 value in the low-temperature elastic recovery test is -35°C or more and the TR50 value in the low-temperature elastic recovery test is -15°C or more. In other words, it is preferable that the TR10 value of material A is -27°C or less and -35°C or more, and the TR50 value is -9°C or less and -15°C or more.

[0046] This prevents the amount of change in the attitude and / or position of the worm shaft 164 from becoming excessively large due to the intermediate member 230 being too soft (too low rigidity) when, for example, a vehicle equipped with the steering device 10 is placed in a low-temperature environment. As a result, for example, when the vehicle is traveling on a rough road, problems caused by an increase in backlash between the worm shaft 164 and the worm wheel 163, or hitting noise between the worm shaft 164 and the housing 153 that accommodates the worm shaft 164, etc. are more reliably prevented.

[0047] As described above, a structure including an intermediate member 230 formed of an elastic material that satisfies at least the above-mentioned predetermined conditions (TR10 value being greater than -27°C and TR50 value being greater than -9°C) is particularly useful when including a biasing member 170.

[0048] Specifically, the steering device 10 according to this embodiment is provided with a biasing member 170 that biases the end of the worm shaft 164 opposite the end to which the second connecting member 220 is fixed in a direction toward the worm wheel 163.

[0049] That is, in this embodiment, as described above, a structure is adopted in which one end of the worm shaft 164 is biased toward the worm shaft 164 while allowing some degree of change in the attitude and / or position of the worm shaft 164. In such a structure, the intermediate member 230 is formed from an elastic material that satisfies the above-mentioned predetermined conditions, so that the intermediate member 230 can deform so as to stably support the attitude and / or position of the worm shaft 164 even when the temperature becomes low.

[0050] [3. Modifications] The steering device according to the present invention has been described above based on the embodiment. However, the present invention is not limited to the above embodiment. As long as it does not deviate from the spirit of the present invention, various modifications conceivable by a person skilled in the art to the above embodiment, or a form constructed by combining multiple components described above, are also included within the scope of the present invention.

[0051] For example, the number of first protrusions 212 of the first connecting member 210 included in the connecting member 200 is not limited to four. The number of first protrusions 212 may be one or more. The number of second protrusions 222 of the second connecting member 220 may be one or more, and the number of intermediate protrusions 232 of the intermediate member 230 may be two or more. However, it is preferable that the first protrusions 212, the intermediate protrusions 232, and the second protrusions 222 are arranged in this order over the entire circumferential area of ​​the connecting member 200 (see FIG. 5). In other words, when the number of first protrusions 212 is N (N is an integer equal to or greater than 1), it is preferable that the number of second protrusions 222 is N and the number of intermediate protrusions 232 is 2N.

[0052] The position of the connecting portion 231 (see FIG. 4) in the intermediate member 230 does not have to be the end in the positive direction of the X-axis. For example, the connecting portion 231 may connect the ends of a pair of middle protrusions 232 in the negative direction of the X-axis. That is, the connecting portion 231 may be disposed at the end in the negative direction of the X-axis in the intermediate member 230. In this case, a first insertion portion into which the first protrusion 212 of the first connecting member 210 is inserted is formed between the pair of middle protrusions 232 connected by the connecting portion 231. In addition, a second insertion portion into which the second protrusion 222 of the second connecting member 220 is inserted is formed between two middle protrusions 232 that are adjacent to each other in the circumferential direction and that are not connected by the connecting portion 231.

[0053] There is no particular limitation on the type of the biasing member 170 included in the steering device 10. The biasing member 170 may be a spring such as a coil spring, a leaf spring, or a spiral spring, or may be an elastic body such as a block-shaped rubber. The steering device 10 does not need to be provided with the biasing member 170. Even if the steering device 10 does not have the biasing member 170, the worm shaft 164 supported by the first bearing 161 and the second bearing 162 is allowed to change in attitude and / or position. Therefore, by forming the intermediate member 230 from an elastic material that satisfies the above-mentioned predetermined conditions, the steering device 10 can stably support the worm shaft 164. [Industrial Applicability]

[0054] The steering device according to the present invention is useful as a steering device that steers steered wheels in response to the operation of an operating member, and can be employed, for example, as a steering device for vehicles such as automobiles, agricultural machines, or construction machines. [Explanation of symbols]

[0055] 10: steering device, 100: steering mechanism, 110: operating member, 120: sensor device, 130: steering shaft, 131: column shaft, 132: intermediate shaft, 133: pinion shaft, 140: rack and pinion device, 141: steered shaft, 150: driving force imparting mechanism, 153: housing, 154: hole portion, 155: preload member, 156: mounting portion, 161: first bearing, 162: second bearing, 163: worm wheel, 164: worm shaft, 170: biasing member, 180: electric motor, 181: output rotating shaft, 185: motor body, 200: connecting member, 210: first connecting member, 211: first main body portion, 211a: first hole, 211b: first fixing portion, 212: first protrusion, 212a: first side surface, 220: second connecting member, 221: second main body portion, 221a: second hole, 221b: second fixing portion, 222: second protrusion, 222a: second side surface, 230: intermediate member, 231: connecting portion, 231a: central portion, 232: intermediate protrusion, 232a: intermediate first side surface, 232b: intermediate second side surface, 233: first insertion portion, 234: second insertion portion, 300: steered wheel, A, B: material, Ra, Rb: rotating shaft

Claims

1. A steering device including a steering mechanism for steering a steered wheel in response to an operation of an operating member, and a driving force imparting mechanism for imparting a driving force for steering to the steering mechanism, The driving force imparting mechanism includes: The electric motor includes an electric motor, a worm shaft, a connecting member that connects an output rotation shaft of the electric motor and the worm shaft, and a worm wheel that meshes with the worm shaft, The connecting member is A first connecting member fixed to an end of the output rotating shaft; A second connecting member fixed to an end of the worm shaft; an intermediate member formed of an elastic material and interposed between the first connecting member and the second connecting member; The elastic material has a TR10 value of −27° C. or less in a low-temperature elastic recovery test, and a TR50 value of −9° C. or less in the low-temperature elastic recovery test. Steering gear.

2. The elastic material has a TR10 value of −35° C. or more in the low-temperature elastic recovery test, and a TR50 value of −15° C. or more in the low-temperature elastic recovery test. The steering system according to claim 1.

3. Further, a biasing member is provided that biases an end portion of the worm shaft opposite to an end portion to which the second connecting member is fixed in a direction approaching the worm wheel.

3. A steering device according to claim 1 or 2.

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