Steering device

Abstract

To improve turning force transmission efficiency of a steering device.SOLUTION: A steering device 1 includes a rack shaft 10 that has a rack gear 11 formed and turns wheels 8, a pinion shaft 25 that has a pinion gear 25a, which is engaged with the rack gear 11, formed, and transmits a turning force to the rack shaft 10, and a dummy pinion shaft 60 that has a dummy gear 60a, which is engaged with the rack gear 11, formed, and rotates along with movement of the rack shaft 10, but does not transmit the turning force to the rack shaft 10.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a steer-by-wire steering control device equipped with a steering motor that applies a steering force to a rack shaft. The steering force of the steering motor is output to a pinion shaft after its rotational speed is reduced by a reduction mechanism. A pinion gear that meshes with a rack gear of the rack shaft is formed on the pinion shaft, and the steering force of the steering motor is transmitted to the rack shaft via the pinion shaft, pinion gear, and rack gear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-001562 Summary of the Invention [Problem to be solved by the invention]

[0004] In the steering control device described in Patent Document 1, a pinion gear of a pinion shaft and a rack gear of a rack shaft mesh with each other through a so-called rack-and-pinion mechanism. Because the rack gear is formed at an angle with respect to the axial direction of the rack shaft and meshes with the pinion gear, the turning force transmitted from the pinion shaft (pinion gear) to the rack shaft (rack gear) acts not only in the axial direction of the rack shaft but also in the circumferential direction of the rack shaft. This causes a loss of thrust in the axial direction of the rack shaft, which may reduce the efficiency of transmitting the turning force.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to improve the efficiency of transmission of steering force of a steering device. [Means for solving the problem]

[0006] The present invention is a steering device characterized by comprising: a rack shaft on which a rack gear is formed and which steers wheels; a first pinion shaft on which a pinion gear that meshes with the rack gear is formed and which transmits steering force to the rack shaft; and a second pinion shaft on which a gear that meshes with the rack gear is formed and which rotates in conjunction with movement of the rack shaft without transmitting steering force to the rack shaft.

[0007] In this invention, the steering device includes a second pinion shaft that is not involved in steering, and the rack gear of the rack shaft is meshed with and supported by the gear of the second pinion shaft. Therefore, even if the rack shaft receives a circumferential torsional force from the first pinion shaft, loss of axial thrust from the rack shaft is reduced, thereby improving the steering force transmission efficiency of the steering device.

[0008] Furthermore, the present invention is characterized in that the second pinion shaft is provided with a rotation angle sensor that detects the rotation angle of the second pinion shaft.

[0009] In this invention, the mountability of the rotation angle sensor is improved compared to when the rotation angle sensor is provided on the first pinion shaft.

[0010] In addition, the present invention is characterized in that the first pinion shaft and the second pinion shaft are arranged parallel to each other and overlap each other when viewed in the axial direction of the rack shaft.

[0011] In this invention, the circumferential torsional force that the rack shaft receives from the first pinion shaft and the reaction force that the rack shaft receives from the second pinion shaft are in opposite directions and cancel each other out, so loss of axial thrust from the rack shaft can be efficiently reduced. [Effects of the Invention]

[0012] According to the present invention, the efficiency of transmission of steering force of a steering device can be improved. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of a steer-by-wire system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of a rack housing, a gear housing, and a motor housing. [Figure 3] FIG. 3 is a cross-sectional schematic view of the dummy pinion shaft taken along line III-III shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0014] A steering device 1 according to an embodiment of the present invention will be described below with reference to the drawings.

[0015] Steering device 1 is capable of steer-by-wire control for steering wheels 8 in accordance with the state of operation of steering wheel 2 by a driver. As shown in Fig. 1, steering device 1 includes steering wheel 2 operated by the driver, steering shaft 3 that rotates in accordance with the steering operation by the driver, rack shaft 10 that steers wheels 8, steering motor 21 that imparts a steering force to rack shaft 10, pinion shaft 25 as a first pinion shaft that transmits the steering force to rack shaft 10, and reaction motor 51 that imparts a steering reaction force to steering shaft 3.

[0016] The rack shaft 10 is provided between the left and right wheels 8 of the vehicle, and the left and right wheels 8 are steered by the single rack shaft 10. The rack shaft 10 is connected to one wheel 8a via a ball joint 5a, a tie rod 6a, and a knuckle arm 7a provided at one end thereof, and is connected to the other wheel 8b via a ball joint 5b, a tie rod 6b, and a knuckle arm 7b provided at the other end thereof. A rack gear 11 is formed on the rack shaft 10. The rack gear 11 has a first rack gear 11a and a second rack gear 11b formed to be spaced apart from each other in the axial direction. The first rack gear 11a and the second rack gear 11b are formed obliquely with respect to the axial direction of the rack shaft 10, and are formed on the same plane on the rack shaft 10. The rack shaft 10 is accommodated in a cylindrical rack accommodation portion 31a of a rack housing 31 (see FIG. 2).

[0017] The driving force of steering motor 21 is transmitted to pinion shaft 25 after its rotational speed is reduced by speed reduction mechanism 22. Speed ​​reduction mechanism 22 has a first worm shaft 23 connected to output shaft 21a of steering motor 21, and a first worm wheel 24 that meshes with first worm shaft 23 and is connected to pinion shaft 25. Pinion shaft 25 is formed with pinion gear 25a that meshes with first rack gear 11a of rack shaft 10, and rack shaft 10 is connected to pinion shaft 25 via first rack gear 11a and pinion gear 25a. Pinion shaft 25 is arranged to intersect with rack shaft 10, and pinion gear 25a and first rack gear 11a mesh with each other at an angle with respect to the axial direction of rack shaft 10. Pinion shaft 25 is housed in pinion housing portion 31b (see FIG. 2) formed so as to intersect with rack housing portion 31a in rack housing 31. Reduction mechanism 22 is housed in gear housing 32 (see FIG. 2) which is provided coaxially with pinion housing portion 31b and connected to rack housing 31, and steering motor 21 is housed in motor housing 33 (see FIG. 2) which is connected to gear housing 32.

[0018] As will be described later, steering motor 21 is driven in response to the steering operation of the driver. When steering motor 21 is driven, a steering force for steering wheels 8 is applied to rack shaft 10 through pinion shaft 25. At this time, the rotation of pinion shaft 25 is converted into linear motion by pinion gear 25a and first rack gear 11a, and the linear motion of rack shaft 10 turns wheels 8 via tie rods 6a, 6b and knuckle arms 7a, 7b.

[0019] In response to the steering operation by the driver, a steering reaction force is applied by the reaction motor 51. The driving force of the reaction motor 51 has its rotational speed reduced by a second worm shaft 52 connected to an output shaft 51a of the reaction motor 51 and a second worm wheel 53 meshing with the second worm shaft 52 and connected to the steering shaft 3, and is then input to the steering shaft 3. When the reaction motor 51 is driven, a steering reaction force is applied to the steering shaft 3, thereby giving a pseudo weight to the steering wheel 2.

[0020] Steering device 1 further includes a steering controller 40 that controls the drive of steering motor 21, and a reaction force controller 50 that controls the drive of reaction force motor 51. Steering controller 40 and reaction force controller 50 are connected so that they can communicate with each other. Vehicle status information such as vehicle speed is input to steering controller 40 and reaction force controller 50, as well as detection signals from handle-side rotation angle sensor 55, which is provided on steering shaft 3 and detects the rotation angle (steering angle) of steering wheel 2, and detection signals from rack-side rotation angle sensor 56, which will be described later.

[0021] In steer-by-wire control, steering controller 40 controls steering motor 21 in accordance with the operation state of steering wheel 2 and vehicle state information, and steers wheels 8. Specifically, steering controller 40 sets a target steering angle based on the detection results of steering wheel side rotation angle sensor 55 and the vehicle speed, and controls steering motor 21 so that the steering angle of wheels 8 matches the target steering angle. Also in steer-by-wire control, reaction force controller 50 controls reaction force motor 51 in accordance with the steering state of wheels 8, and applies a steering reaction force to steering wheel 2. Reaction force controller 50 sets a target steering reaction force equivalent to the reaction force received from the road surface in response to a steering operation, and controls reaction force motor 51 so that the steering reaction force applied to steering shaft 3 matches the target steering reaction force.

[0022] In the steering device 1, the pinion gear 25a of the pinion shaft 25 meshes with the first rack gear 11a of the rack shaft 10 via a rack-and-pinion mechanism. As described above, the first rack gear 11a is formed at an angle with respect to the axial direction of the rack shaft 10 and meshes with the pinion gear 25a. Therefore, the turning force transmitted from the pinion shaft 25 (pinion gear 25a) to the rack shaft 10 (first rack gear 11a) acts as a torsional force not only in the axial direction of the rack shaft 10 but also in the circumferential direction of the rack shaft 10. Ball joints 5a and 5b are connected to the end of the rack shaft 10, and the ball joints 5a and 5b do not restrict torsion of the rack shaft 10. Therefore, the torsional force acting in the circumferential direction of the rack shaft 10 causes a loss of axial thrust of the rack shaft 10, which may reduce the efficiency of transmission of the turning force from the pinion shaft 25 to the rack shaft 10.

[0023] Therefore, the steering device 1 of this embodiment further includes a dummy pinion shaft 60 as a second pinion shaft on which a dummy gear 60a as a gear that meshes with the second rack gear 11b is formed. The rack shaft 10 is supported by the dummy pinion shaft 60 via the second rack gear 11b and the dummy gear 60a.

[0024] Next, the dummy pinion shaft 60 will be described in detail.

[0025] Unlike a normal pinion shaft such as pinion shaft 25 that is connected to steering motor 21 and applies a steering force to rack shaft 10, dummy pinion shaft 60 is not connected to a drive source such as a steering motor and does not transmit steering force to rack shaft 10. In other words, dummy pinion shaft 60 is not involved in steering. Although dummy pinion shaft 60 is not connected to a drive source, its configuration is the same as that of a normal pinion shaft, and a normal pinion shaft can be used as dummy pinion shaft 60. The thrust of rack shaft 10 is input to dummy pinion shaft 60 from second rack gear 11b of rack shaft 10 via dummy gear 60a, and dummy pinion shaft 60 rotates as rack shaft 10 moves. In other words, dummy pinion shaft 60 does not obstruct the axial movement of rack shaft 10.

[0026] FIG. 3 is a cross-sectional schematic diagram of the dummy pinion shaft 60, and the meshing portion between the dummy gear 60a and the second rack gear 11b is indicated by a straight line. As shown in FIG. 3, the dummy pinion shaft 60 is disposed so as to intersect with the rack shaft 10, and the dummy gear 60a and the second rack gear 11b mesh with each other at an angle with respect to the axial direction of the rack shaft 10. The dummy pinion shaft 60 is accommodated in a dummy pinion accommodating portion 31c formed in the rack housing 31 so as to intersect with the rack accommodating portion 31a (see FIG. 2). The dummy pinion shaft 60 is rotatably supported in the dummy pinion accommodating portion 31c via a bearing 65. The dummy pinion shaft 60 is disposed so as to be parallel to the pinion shaft 25 and overlap with the rack shaft 10 when viewed in the axial direction (see the pinion accommodating portion 31b and the dummy pinion accommodating portion 31c in FIG. 2). In other words, the dummy pinion shaft 60 is connected to the rack shaft 10 in the same direction as the pinion shaft 25 and spaced apart in the axial direction of the rack shaft 10 .

[0027] In this manner, the pinion shaft 25 and the dummy pinion shaft 60 are connected to the rack shaft 10, and the rack shaft 10 is supported by both of them. In other words, the rack shaft 10 is supported at both ends by the pinion gear 25a of the pinion shaft 25 and the dummy gear 60a of the dummy pinion shaft 60.

[0028] For example, when the rack shaft 10 receives a torsional force A (arrow A in FIG. 3 ) in the counterclockwise direction from the pinion gear 25a of the pinion shaft 25, the torsional force A presses the second rack gear 11b of the rack shaft 10 against the dummy gear 60a of the dummy pinion shaft 60. Then, a reaction force B (arrow B in FIG. 3 ) pushing back from the dummy gear 60a acts on the second rack gear 11b. Because the torsional force A pressing the second rack gear 11b against the dummy gear 60a and the reaction force B pushing back from the dummy gear 60a are the same in magnitude, the circumferential torsional force A received by the rack shaft 10 from the pinion shaft 25 and the reaction force B received by the dummy pinion shaft 60 cancel each other out. Therefore, even when the rack shaft 10 receives the torsional force A in the circumferential direction from the pinion shaft 25, twisting of the rack shaft 10 is suppressed. Therefore, the loss of the axial thrust of the rack shaft 10 is reduced, and the efficiency of transmission of the steering force of the steering device 1 can be improved.

[0029] Furthermore, in steering device 1 of the present embodiment, twisting of rack shaft 10 is suppressed as described above, improving the tooth contact (meshing state) between first rack gear 11a of rack shaft 10 and pinion gear 25a of pinion shaft 25, thereby improving the durability of rack shaft 10 and pinion shaft 25. Furthermore, since the efficiency of transmitting the steering force is improved, steering motor 21 can be made lower output, and steering motor 21 can be made smaller.

[0030] Furthermore, in the steering device 1 of this embodiment, the pinion shaft 25 and the dummy pinion shaft 60 are arranged to be parallel to each other and to overlap when viewed in the axial direction of the rack shaft 10. Therefore, as shown in Fig. 3, a circumferential torsional force A that the rack shaft 10 receives from the pinion shaft 25 and a reaction force B that the rack shaft 10 receives from the dummy pinion shaft 60 are directed in opposite directions and cancel each other out, thereby efficiently reducing loss of the axial thrust of the rack shaft 10. Furthermore, because the first rack gear 11a and the second rack gear 11b are formed on the same plane, machining of the first rack gear 11a and the second rack gear 11b is facilitated.

[0031] Furthermore, in a conventional steering device that does not include the dummy pinion shaft 60, if the rack shaft is long, the distance between the end of the rack shaft and the rack gear (in other words, the location where the torsional force A is input to the rack shaft) becomes long, and a large torsional force A acts on the end of the rack shaft due to the moment. As a result, the degree of freedom in determining the length of the rack shaft and the position of the rack gear is low. In contrast, the steering device 1 of the present embodiment includes the dummy pinion shaft 60, which prevents the rack shaft 10 from twisting. This increases the degree of freedom in determining the length of the rack shaft 10 and the position of the rack gear 11. Note that, from the perspective of suppressing twisting of the rack shaft 10, it is preferable that the dummy pinion shaft 60 be provided at the end of the rack shaft 10, taking the above-mentioned moment into consideration. If the dummy pinion shaft 60 is provided at the end of the rack shaft 10, a bearing (not shown) or the like that rotatably supports the end of the rack shaft 10 is not required.

[0032] As shown in FIG. 3 , in the steering device 1 of this embodiment, the dummy pinion shaft 60 is provided with a rack-side rotation angle sensor 56 as a rotation angle sensor that detects the rotation angle of the dummy pinion shaft 60. By detecting the rotation angle of the dummy pinion shaft 60 with the rack-side rotation angle sensor 56, the stroke amount of the rack shaft 10 can be detected. The rack-side rotation angle sensor 56 can be used, for example, to control the steering wheel 2 to return to the neutral position. The rack-side rotation angle sensor 56 is provided at the end of the dummy pinion shaft 60 and covers the opening of the dummy pinion accommodating portion 31c. Because no drive source is connected to the dummy pinion shaft 60 (in other words, no worm shaft or worm wheel is connected), the rack-side rotation angle sensor 56 can be easily provided at the end of the dummy pinion shaft 60. This improves the mountability of the rack-side rotation angle sensor 56 compared to when the rack-side rotation angle sensor 56 is provided on the pinion shaft 25.

[0033] According to the present embodiment described above, the following effects are achieved.

[0034] The steering device 1 includes a dummy pinion shaft 60 that is not involved in steering, and the second rack gear 11b of the rack shaft 10 is meshed with and supported by a dummy gear 60a of the dummy pinion shaft 60. Therefore, even if the rack shaft 10 receives a circumferential torsional force A from the pinion shaft 25, loss of thrust from the rack shaft 10 is reduced, thereby improving the efficiency of transmission of the steering force of the steering device 1.

[0035] Next, modified examples of this embodiment will be described. The following modified examples are also within the scope of the present invention, and it is possible to combine the configurations shown in the modified examples with the configurations described in the above embodiment, or to combine the configurations described in the different modified examples below.

[0036] <Variation 1> In the above embodiment, the steering device 1 is capable of steer-by-wire control, in which the wheels 8 are steered in accordance with the state of operation of the steering wheel 2 by the driver. However, the steering device 1 is not limited to this, and may be a power steering device in which the steering wheel 2 and the rack shaft 10 are physically connected. Even in this case, the rack shaft 10 is provided with only one pinion shaft 25 that transmits the steering force, and the dummy pinion shaft 60 prevents the rack shaft 10 from twisting.

[0037] <Variation 2> In the above embodiment, the pinion shaft 25 and the dummy pinion shaft 60 are arranged parallel to each other and overlap when viewed in the axial direction of the rack shaft 10, and the dummy pinion shaft 60 is arranged at the end of the rack shaft 10. However, the arrangement of the dummy pinion shaft 60 is not limited to the above. The dummy pinion shaft 60 does not necessarily have to be arranged parallel to the pinion shaft 25, and may be arranged so as not to overlap when viewed in the axial direction of the rack shaft 10 (in other words, at a position offset circumferentially from the rack shaft 10). Furthermore, the dummy pinion shaft 60 does not have to be arranged at the end of the rack shaft 10.

[0038] <Variation 3> In the above embodiment, the rack gear 11 of the rack shaft 10 has a first rack gear 11a and a second rack gear 11b that are formed apart from each other in the axial direction. In other words, two gears are formed as the rack gear 11 on the rack shaft 10. However, this is not limiting, and the first rack gear 11a and the second rack gear 11b may be formed continuously. In other words, a single gear may be formed as the rack gear 11 on the rack shaft 10.

[0039] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0040] The steering device 1 includes a rack shaft 10 having a rack gear 11 formed thereon and steering the wheels 8, a pinion shaft 25 serving as a first pinion shaft having a pinion gear 25a meshing with the rack gear 11 and transmitting a steering force to the rack shaft 10, and a dummy pinion shaft 60 serving as a second pinion shaft having a dummy gear 60a meshing with the rack gear 11 and rotating in accordance with the movement of the rack shaft 10 without transmitting a steering force to the rack shaft 10.

[0041] In this configuration, the steering device 1 is provided with a dummy pinion shaft 60 that is not involved in steering, and the rack gear 11 of the rack shaft 10 is meshed with and supported by a dummy gear 60a of the dummy pinion shaft 60. Therefore, even if the rack shaft 10 receives a circumferential torsional force A from the pinion shaft 25, loss of the axial thrust of the rack shaft 10 is reduced, and the steering device 1 can improve its steering force transmission efficiency.

[0042] In addition, in the steering device 1, the dummy pinion shaft 60 is provided with a rack-side rotation angle sensor 56 as a rotation angle sensor that detects the rotation angle of the dummy pinion shaft 60.

[0043] In this configuration, the rack-side rotation angle sensor 56 can be more easily mounted than when the rack-side rotation angle sensor 56 is provided on the pinion shaft 25 .

[0044] In addition, in the steering device 1, the pinion shaft 25 and the dummy pinion shaft 60 are arranged parallel to each other and overlap each other when viewed in the axial direction of the rack shaft 10.

[0045] In this configuration, the circumferential torsional force A that the rack shaft 10 receives from the pinion shaft 25 and the reaction force B that the rack shaft 10 receives from the dummy pinion shaft 60 are in opposite directions and cancel each other out, so that the loss of the axial thrust of the rack shaft 10 can be efficiently reduced.

[0046] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0047] 1...Steering device, 8, 8a, 8b...Wheel, 8a...Wheel, 8b...Wheel, 10...Rack shaft, 11...Rack gear, 25...Pinion shaft (first pinion shaft), 25a...Pinion gear, 56...Rack side rotation angle sensor (rotation angle sensor), 60...Dummy pinion shaft (second pinion shaft), 60a...Dummy gear (gear)

Claims

1. A steering device, a rack shaft on which a rack gear is formed and which steers the wheels; a first pinion shaft having a pinion gear meshing with the rack gear and transmitting a steering force to the rack shaft; a second pinion shaft having a gear that meshes with the rack gear and that rotates in accordance with movement of the rack shaft without transmitting steering force to the rack shaft.

2. 2. The steering device according to claim 1, A steering device, wherein the second pinion shaft is provided with a rotation angle sensor that detects a rotation angle of the second pinion shaft.

3. 2. The steering device according to claim 1, A steering device, wherein the first pinion shaft and the second pinion shaft are arranged parallel to each other and overlap each other when viewed in the axial direction of the rack shaft.

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