Steering device

Abstract

A steering device comprises a steering shaft (1), a sector gear (5) positioned radially outward of the steering shaft (1), an intermediate shaft (2) positioned on the side opposite from the steering shaft (1) with the sector gear (5) therebetween, first and second bevel gears (42, 43) connecting the steering shaft (1) and the intermediate shaft (2), a torque sensor (8) that detects steering torque accompanying rotational force, a first electric motor (6) that imparts torque for rotational force, and a ball screw mechanism (4) that transmits thrust generated by the rotational force to the sector gear (5). The intermediate shaft (2) is provided so as to be inclined at an inclination angle (α) with respect to the steering shaft (1) by the first and second bevel gears (42, 43). The torque sensor (8) and the first electric motor (6) are provided to the steering shaft (1), and the ball screw mechanism (4) is provided to the intermediate shaft (2).

Description

[Technical field]

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

[0002] 2. Description of the Related Art As a steering device, for example, the steering device described in Patent Document 1 below is known.

[0003] The steering device of Patent Document 1 has a steering shaft to which a rotational force caused by a steering operation by a driver is input. The steering shaft is provided with a torque sensor that detects the steering torque, an electric motor that applies an assist torque to the rotational force, and a ball screw mechanism that transmits a thrust force generated by the rotational force to an output shaft.

[0004] In the steering device described in Patent Document 1, a torque sensor, an electric motor, and a ball screw mechanism are provided on the steering shaft, which increases the size of the steering device in the axial direction, and there is a risk that it may be difficult to apply such a steering device to a small truck.

[0005] The present invention has been devised in view of the conventional situation, and has as its object to provide a steering device capable of reducing the axial dimension of the steering device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-156082 A Summary of the Invention

[0007] In one embodiment of the present invention, the steering device comprises a first shaft, an output shaft located radially outward of the first shaft, a second shaft located on the opposite side of the output shaft to the first shaft, a gear mechanism connecting the first shaft and the second shaft, a torque sensor, an electric motor, and a ball screw mechanism, wherein two of the torque sensor, the electric motor, and the ball screw mechanism are provided on the first shaft, and the remaining one is provided on the second shaft.

[0008] According to the present invention, the axial dimension of the steering device can be reduced. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a top view of a steering device according to a first embodiment. [Diagram 2] 2 is a longitudinal sectional view of the steering device of the first embodiment taken along the line AA in FIG. 1. [Diagram 3] 1 is a perspective view of a steering device according to a first embodiment. [Figure 4] FIG. 6 is a top view of a steering device according to a second embodiment. [Diagram 5] 5 is a longitudinal sectional view of a steering device according to a second embodiment taken along line BB in FIG. 4. [Figure 6] FIG. 11 is a top view of a steering device according to a third embodiment. [Figure 7] FIG. 7 is a longitudinal sectional view of a steering device of a third embodiment taken along line CC in FIG. 6. [Figure 8] FIG. 13 is a top view of a steering device according to a fourth embodiment. [Figure 9] 9 is a longitudinal sectional view of a steering device according to a fourth embodiment taken along line DD in FIG. 8. [Figure 10] 9 is a partial cross-sectional view of the first electric motor and the like taken along line EE in FIG. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the steering device of the present invention will be described with reference to the drawings. The present invention is configured such that the steering device has a first shaft, which is one of the steering shaft 1 and the intermediate shaft 2, and a second shaft, which is the other of the steering shaft 1 and the intermediate shaft 2, and two of the torque sensor 8, the first electric motor 6, and the ball screw mechanism 4 are provided on the first shaft, and the remaining one is provided on the second shaft. In other words, the present invention is configured such that the steering device has a first shaft, which is one of the steering shaft 1 and the intermediate shaft 2, and a second shaft, which is the other of the steering shaft 1 and the intermediate shaft 2, and that the torque sensor 8, the first electric motor 6, and the ball screw mechanism 4 are not all provided on the first shaft or the second shaft.

[0011] [First embodiment] (Streering device configuration) FIG. 1 is a top view of the steering device of the first embodiment. FIG. 2 is a longitudinal sectional view of the steering device of the first embodiment cut along the line AA in FIG. 1. In FIG. 2, the side (upper side in the figure) linked to the steering wheel in the direction along the rotation axis P of the steering shaft 1 is described as "one end" and the side (lower side in the figure) to which the first bevel gear 42 is attached is described as "the other end". In addition, in FIG. 2, in order to simplify the drawing, cross sections of the first electric motor 6 and the first EPS controller 48 are omitted. FIG. 3 is a perspective view of the steering device of the first embodiment.

[0012] The first embodiment shows an example in which, in an axis configuration in which a first axis is a steering shaft 1 and a second axis is an intermediate shaft 2, a torque sensor 8 and a first electric motor 6 are provided on the steering shaft 1, while a ball screw mechanism 4 is provided on the intermediate shaft 2.

[0013] The steering device is mainly composed of a steering shaft 1 connected to a steering wheel (not shown), an intermediate shaft 2 arranged radially outside the steering shaft 1, a gear mechanism 3 connecting the steering shaft 1 and the intermediate shaft 2, a ball screw mechanism 4 provided on the intermediate shaft 2, a sector gear (output shaft) 5 to which thrust from the ball screw mechanism 4 is transmitted and used for steering the steered wheels, a first electric motor 6 that imparts assist torque to the steering shaft 1, a first reduction gear 7 that decelerates the rotation of the first electric motor 6, and a torque sensor 8 that detects the steering torque associated with the rotational force input by the driver.

[0014] The steering shaft 1 is housed in a first housing 9, a partition member 10, and a second housing 11, which will be described later, except for one end thereof, and includes an input shaft 12, a first linking shaft 13, and a second linking shaft 14. One end of the input shaft 12 is linked to the steering wheel, and is used to input the steering torque of the driver. The other end of the input shaft 12 is inserted into an open recess 13a formed on one end of the first linking shaft 13. The input shaft 12 is rotatably supported by a bearing, for example, a first ball bearing 15, provided on the inner peripheral surface of the first housing 9. One end of the first linking shaft 13 is connected to the input shaft 12 via a torsion bar 16 so as to be rotatable relative to the input shaft 12, and is used to input the assist torque of the first electric motor 6, which is connected to the outer periphery via a first reduction gear 7. The first linking shaft 13 is rotatably supported by a bearing, such as a second ball bearing 17, provided on the inner periphery of the partition member 10, and a bearing, such as a third ball bearing 18, provided on the inner periphery of the second housing 11. One end of the second linking shaft 14 is fixed to the outer periphery of the other end of the first linking shaft 13, while the other end is rotatably supported by a bearing, such as a fourth ball bearing 19.

[0015] Here, for convenience of the following explanation, the direction along the rotation axis P of the steering shaft 1 is defined as the "axial direction", the direction perpendicular to the axial direction is defined as the "radial direction", and further, the direction around the steering shaft 1 is defined as the "circumferential direction".

[0016] The first housing 9 is formed in a cylindrical shape from a metal, for example, an aluminum alloy. The first housing 9 is disposed on one end side of the steering shaft 1, and is fixed to a disk-shaped partition member 10 by a plurality of (three in this embodiment) fastening members, for example, screws 20, as shown in FIG. 1. As shown in FIG. 2, the first housing 9 has a small diameter portion 9a located on one end side of the steering shaft 1, and a large diameter portion 9b formed integrally with the small diameter portion 9a and having a larger diameter than the small diameter portion 9a. The space inside the small diameter portion 9a is a bearing accommodating portion 21 that accommodates the first ball bearing 15. The space inside the large diameter portion 9b is a sensor accommodating portion 22 that accommodates the torque sensor 8.

[0017] An annular flange 9c is formed on the outer periphery of the large diameter portion 9b so as to protrude radially outward from the outer periphery. A tip end face of an annular first protrusion 10a formed on one end face of the metallic partition member 10 is abutted against a continuous annular surface on the other end side of the flange 9c. In this abutted state, the outer periphery of the peripheral wall of the large diameter portion 9b and the inner periphery of the first protrusion 10a are airtightly sealed by a ring-shaped first seal member 23.

[0018] The second housing 11 is made of metal, such as an aluminum alloy, and is configured by integrally forming a cylindrical linkage shaft side tubular portion 24 that houses the first linkage shaft 13 and the second linkage shaft 14, and a cylindrical intermediate shaft side tubular portion 25 that houses the intermediate shaft 2 equipped with the ball screw mechanism 4.

[0019] The connecting shaft side tubular portion 24 has a cylindrical tubular main body portion 24a, a first expanded diameter portion 24b that expands in diameter from one end of the tubular main body portion 24a, and a second expanded diameter portion 24c that expands in diameter from the other end of the tubular main body portion 24a and is formed with a smaller diameter than the first expanded diameter portion 24b. The space inside the first enlarged diameter portion 24b is a first reducer housing portion 26 that houses the first reducer 7. The first reducer housing portion 26 is located below the sensor housing portion 22 with the partition member 10 in between. One end of the peripheral wall of the first enlarged diameter portion 24b is butted against the other end side surface of the partition member 10, and in this butted state, the outer circumferential surface of the peripheral wall of the first enlarged diameter portion 24b and the annular second protrusion portion 10b formed to protrude from the other end side surface of the partition member 10 to the other end side are airtightly sealed by the ring-shaped second seal member 27. The second protrusion portion 10b is located radially outward from the first protrusion portion 10a.

[0020] The partition member 10 has a through hole 10c in the center thereof through which one end of the first linkage shaft 13 passes. A third protrusion 10d having an annular shape protruding toward the other end is formed in the vicinity of the through hole 10c on the surface of one end side of the partition member 10 (the upper surface in FIG. 2). A second ball bearing 17 that rotatably supports the first linkage shaft 13 is provided on the inner peripheral surface of the third protrusion 10d.

[0021] Further, a third ball bearing 18 that rotatably supports the first linking shaft 13 is provided on the inner circumferential surface of the other end of the first enlarged diameter portion 24b.

[0022] In addition, a bearing, such as a fourth ball bearing 19, that rotatably supports the second linking shaft 14 is provided on the inner circumferential surface of the second expanded diameter portion 24c and on a part of the inner circumferential surface adjacent to the second expanded diameter portion 24c in the axial direction.

[0023] A side portion of the second enlarged diameter portion 24c and a side portion of the cylindrical main body portion 24a adjacent to the second enlarged diameter portion 24c in the axial direction are connected to a side portion of the other end side of the intermediate shaft side cylindrical portion 25 via a connecting portion 28 at a predetermined inclination angle α. Here, the inclination angle α is an angle in the range of 30 to 60 degrees, for example, and is about 35 degrees in this embodiment. Note that the inclination angle α is not necessarily set within the above range, but is appropriately set according to the design of the vehicle in which the steering device is mounted. A space on the other end side of the connecting portion 28 of the cooperation shaft side cylindrical portion 24 communicates with a space below the connecting portion 28 of the intermediate shaft side cylindrical portion 25, and this connected space portion serves as a gear mechanism housing portion 29 that houses the gear mechanism 3. The gear mechanism accommodating portion 29 is closed by fixing a circular plate-shaped first cover member 30 to the inclined axial end face 24d of the linkage shaft side cylindrical portion 24 and the inclined axial end face 25a of the intermediate shaft side cylindrical portion 25 via fastening members (not shown), such as bolts.

[0024] The intermediate shaft side cylindrical portion 25 has a generally constant diameter along the longitudinal direction. The intermediate shaft side cylindrical portion 25 is closed by a second cover member 31 at one axial end side (diagonally upper right side in FIG. 2 ) of the rotation axis Q of the intermediate shaft 2 inclined at an inclination angle α with respect to the rotation axis P of the steering shaft 1. The second cover member 31 is formed in a bottomed cylindrical shape, and a male thread portion is formed on its outer circumferential surface. The male thread portion is screwed into a female thread portion formed on the inner circumferential surface of the intermediate shaft side cylindrical portion 25, whereby the second cover member 31 is attached and fixed to the intermediate shaft side cylindrical portion 25.

[0025] A bearing that rotatably supports the intermediate shaft 2, such as a fifth ball bearing 32, is provided on the inner circumferential surface of the second cover member 31. The fifth ball bearing 32 is fixed between the second cover member 31 and the intermediate shaft 2 by screwing the second cover member 31 into the intermediate shaft side cylindrical portion 25 in a state in which the fifth ball bearing 32 abuts against an annular projection 2a provided on the intermediate shaft 2.

[0026] Further, a portion of the inner circumferential surface of the intermediate shaft side cylindrical portion 25 adjacent to the gear mechanism accommodating portion 29 is a bearing support portion 25b formed in a reduced diameter, and a sixth ball bearing 33 that rotatably supports the intermediate shaft 2 is provided in the bearing support portion 25b. The sixth ball bearing 33 is fixed between the intermediate shaft side cylindrical portion 25 and the intermediate shaft 2 by being brought into contact with both a circular protrusion 25c provided on the intermediate shaft side cylindrical portion 25 and a stepped portion 2b provided on the intermediate shaft 2.

[0027] The space between the fifth ball bearing 32 and the sixth ball bearing 33 in the internal space of the intermediate shaft side cylindrical portion 25 serves as a ball screw mechanism accommodating portion 34 that accommodates the ball screw mechanism 4. As shown in FIG. 2, the portion of the ball screw mechanism accommodating portion 34 that faces the cooperation shaft side cylindrical portion 24 is connected to the cylindrical main body portion 24a of the cooperation shaft side cylindrical portion 24 via a substantially cylindrical output shaft peripheral wall portion 35 that surrounds the sector gear 5 that is the output shaft. The output shaft peripheral wall portion 35 is provided at a position between the first enlarged diameter portion 24b of the cooperation shaft side cylindrical portion 24 and the coupling portion 28, closer to the first enlarged diameter portion 24b. The internal space of the output shaft peripheral wall portion 35 serves as a gear accommodating portion 36 that accommodates the sector gear 5, and the gear accommodating portion 36 opens to the ball screw mechanism accommodating portion 34 of the intermediate shaft side cylindrical portion 25. The gear accommodating portion 36 and a portion of the ball screw mechanism accommodating portion 34 adjacent to the gear accommodating portion 36 are closed by attaching a plate-shaped third cover member 38 to the intermediate shaft side cylindrical portion 25 with multiple (four in this embodiment) fastening members, for example bolts 37, as shown in Figures 1 and 3.

[0028] The torque sensor 8 is mainly composed of a permanent magnet (not shown), a holder member 39, a pair of first and second yokes (not shown), a pair of first and second magnetic flux collector rings 40, 41, and a magnetic sensor (not shown). The permanent magnet, the holder member 39, the first and second yokes, and the magnetic flux collector rings 40, 41 are all arranged substantially concentrically with the rotation axis P of the steering shaft 1.

[0029] The permanent magnet is a magnetic member made of a magnetic material and formed into a substantially cylindrical shape, and attached and fixed to the outer periphery of one end of the first linking shaft 13. The permanent magnet is configured such that N poles and S poles are alternately arranged (magnetized) along the circumferential direction of the permanent magnet.

[0030] The holder member 39 is formed in a substantially cylindrical shape, and is attached and fixed to the outer periphery of the other end side of the input shaft 12 .

[0031] The pair of first and second yokes are each made of a soft magnetic material and formed into a substantially cylindrical shape, and are connected to the input shaft 12 via a holder member 39, with the other end facing the permanent magnet in the radial direction. The first and second yokes are fixed to the holder member 39 by welding with an annular welding plate (not shown).

[0032] The pair of magnetic flux collecting rings 40, 41 are substantially annular rings that collect magnetic flux from the permanent magnets leaking to one end of both yokes in a predetermined range. The magnetic flux collecting ring 40 is disposed on the outer periphery of the torque sensor 8, while the magnetic flux collecting ring 41 is disposed on the inner periphery of the torque sensor 8 so as to face the magnetic flux collecting ring 40. A magnetic flux collecting portion 40a having a flat surface (not shown) is provided at a predetermined circumferential position of the magnetic flux collecting ring 40, while a magnetic flux collecting portion 41a having a flat surface (not shown) parallel to the flat surface of the magnetic flux collecting portion 40a is provided at a position of the magnetic flux collecting ring 41 facing the magnetic flux collecting portion 40a in the circumferential direction.

[0033] The magnetic sensor is composed of a Hall element (not shown) accommodated and arranged in the radial gap between the flat surface of the magnetic flux collector 40a and the flat surface of the magnetic flux collector 41a, and a connection terminal (not shown) for connecting the Hall element to a substrate (not shown). The magnetic sensor detects the magnetic flux passing between the opposing flat surfaces of the magnetic flux collectors 40a, 41a by using the Hall effect of the Hall element, and outputs a signal corresponding to the magnetic flux to the substrate (not shown). This allows the substrate to calculate the relative rotation angle between the input shaft 12 and the first linkage shaft 13, and to calculate the steering torque based on the relative rotation angle.

[0034] The gear mechanism 3 is composed of a first bevel gear 42 fixed to the outer periphery of the other end of the second cooperation shaft 14, and a second bevel gear 43 fixed to the outer periphery of the other end of the intermediate shaft 2 and meshing with the first bevel gear 42. The first bevel gear 42 has a plurality of first teeth 42a inclined toward the other end in the direction of the rotation axis P of the steering shaft 1, while the second bevel gear 43 has a plurality of second teeth 43a inclined toward the other end in the direction of the rotation axis Q of the intermediate shaft 2. The number of the first teeth 42a and the number of the second teeth 43a are set to be the same, and therefore the speed ratio of the first bevel gear 42 and the second bevel gear 43 is 1:1. The first teeth 42a and the second teeth 43a are connected to each other by meshing with each other, so that the rotation axis Q of the intermediate shaft 2 is inclined at an angle α with respect to the rotation axis P of the steering shaft 1 extending in the vertical direction.

[0035] The ball screw mechanism 4 is composed of an intermediate shaft side ball screw groove 2c which is a helical groove provided on the outer periphery of the intermediate shaft 2, a nut side ball screw groove 44a which is a helical groove provided on the inner periphery of the nut 44, and a plurality of balls 45 arranged between the ball screw grooves 2c, 44a. The balls 45 support the nut 44 so as to be rotatable relative to the intermediate shaft 2. The outer periphery of the nut 44 is in slidable contact with the inner periphery of the ball screw mechanism accommodating portion 34. This allows the nut 44 to slide along the rotation axis Q of the intermediate shaft 2 within the ball screw mechanism accommodating portion 34.

[0036] Further, a plurality of rack teeth 44b are formed on the outer periphery of the nut 44 on the sector gear 5 side. These rack teeth 44b are adapted to mesh with the teeth portion 5a of the sector gear 5.

[0037] The sector gear 5 is provided swingably within the gear housing portion 36. One axial end of the sector gear 5 is connected to a nut 44 via a toothed portion 5a, and the other axial end is linked to a steered wheel (not shown) via a pitman arm 46, a drag link (not shown), and a ball joint.

[0038] The pitman arm 46 is attached to the other end of the sector gear 5 so as to be rotatable about the rotation axis R of the sector gear 5. The pitman arm 46 is rotatable clockwise from the position shown by the solid line in Fig. 2 to a position of 90 degrees (the position of the left pitman arm 46 shown by the two-dot chain line). When the pitman arm 46 rotates, the path of the pitman arm 46 and the path of a drag ring (not shown) connected to the pitman arm 46 are designed not to interfere with parts or components located below the steering device.

[0039] The first reduction gear 7 is disposed in a first reduction gear housing portion 26 provided in the large diameter portion 9b of the linking shaft side cylindrical portion 24. The first reduction gear 7 reduces the speed of rotation from the first electric motor 6, and is composed of a worm gear formed by meshing a worm shaft (not shown) with a worm wheel 47.

[0040] The worm wheel 47 has a generally cylindrical metal core 47a and a gear forming portion 47b made of synthetic resin provided on the outer periphery of the core 47a. The gear forming portion 47b meshes with a worm formed on the worm shaft.

[0041] The first electric motor 6 is connected to the first linkage shaft 13 via the first reduction gear 7, and is configured as a three-phase AC brushless motor that applies an assist torque to the first linkage shaft 13 according to the amount of torsion of the torsion bar 16. As shown in FIG. 1, the first electric motor 6 is configured integrally with a first EPS controller 48 that controls the first electric motor 6 based on the steering torque from the torque sensor 8. The first electric motor 6 is accommodated in a motor housing 49, and the motor housing 49 is attached and fixed to a worm shaft housing 50 formed integrally with the first housing 9. The first electric motor 6 has a motor shaft (not shown), and one axial end of the motor shaft is connected to a worm shaft (not shown). The first electric motor 6 and the first EPS controller 48 are provided at a position higher than the sector gear 5 and lower than the driving floor (not shown).

[0042] In this steering device, when the driver turns the steering wheel, the input shaft 12 rotates and the torsion bar is twisted, and the elastic force of the torsion bar rotates the first and second linked shafts 13, 14. The rotational force of the first and second linked shafts 13, 14 is transmitted to the intermediate shaft 2 through the meshing of the first bevel gear 42 and the second bevel gear 43. As the intermediate shaft 2 rotates, the nut 44 moves in the direction of the rotation axis Q of the intermediate shaft 2, causing the sector gear 5 to rotate. As a result, the pitman arm 46 is pulled in the vehicle body width direction, changing the direction of the steered wheels.

[0043] In the first embodiment, an example of manual driving in which steering force from the driver is input to the steering shaft 1 is disclosed, but by enlarging the size of the first electric motor 6, the present invention can be applied to a steering device for automatic driving.

[0044] [Advantages of the First Embodiment] As described above, in the first embodiment, the sector gear 5 is disposed on the radially outer side of the steering shaft 1, and the steering shaft 1 and the intermediate shaft 2 are connected to each other via the first and second bevel gears 42, 43, so that the intermediate shaft 2 is disposed on the opposite side of the steering shaft 1 with the sector gear 5 interposed therebetween. More specifically, the intermediate shaft 2 is inclined at an inclination angle α with respect to the steering shaft 1 by the first and second bevel gears 42, 43. In such a configuration of the steering shaft 1 and the intermediate shaft 2, the torque sensor 8 and the first electric motor 6 are provided on the steering shaft 1, while the ball screw mechanism 4 is provided on the intermediate shaft 2.

[0045] Therefore, the axial length of the ball screw mechanism 4, including the stroke of the nut 44, is not added to the steering shaft 1, so that the axial dimension of the steering device can be reduced compared to the conventional configuration in which the torque sensor, the first electric motor, and the ball screw mechanism are all provided on the steering shaft. Such a steering device is particularly effective for small trucks.

[0046] In the steering device of the prior art, a torque sensor, a ball screw mechanism, and a first electric motor (a first reduction gear connected to the first electric motor) are arranged in this order from one end of the steering shaft. There is no space between one end of the steering shaft and the torque sensor to provide the first reduction gear. In addition, since it is necessary to ensure the deflection angle of the sector gear accompanying the movement of the nut of the ball screw mechanism, it is not possible to ensure a space for arranging the first reduction gear between the torque sensor and the ball screw mechanism without increasing the axial dimension of the steering device. Furthermore, since the design from the sector gear to the steered wheels is also fixed, the steering shaft and the sector gear have a fixed positional relationship. For these reasons, in the prior art, in order to arrange the first electric motor while maintaining the positional relationship between the steering shaft and the sector gear, the first electric motor, more specifically, the first reduction gear connected to the first electric motor must be arranged at the other end (lower) of the steering shaft.

[0047] However, if the first reduction gear is disposed at the other end of the steering shaft, there is a risk that the drag link connected to the pitman arm will interfere with the motor housing when the pitman arm rotates.

[0048] Furthermore, the first electric motor provided at the other end of the steering shaft is easily exposed to water and small stones that seep into the underside of the vehicle from the road surface, which may cause an electrical failure of the first electric motor or damage to the motor housing.

[0049] In contrast, in the first embodiment, the first electric motor 6 is provided at a position higher than the sector gear 5. In other words, the first electric motor 6 is provided at a position very far away from the pitman arm 46 and the drag link. This makes it possible to prevent the drag link from damaging the motor housing 49 and the first EPS controller 48 when the pitman arm 46 rotates.

[0050] Furthermore, since the first electric motor 6 is positioned higher than the sector gear 5, water and pebbles from the road surface are less likely to reach the first electric motor 6, thereby improving robustness against water and pebbles and suppressing electrical failure of the first electric motor 6 and damage to the motor housing 49 and first EPS controller 48.

[0051] Furthermore, when the first electric motor 6 is disposed higher than the sector gear 5 in this manner, the minimum ground clearance standard, which indicates the vertical distance between the road surface and the lowest part of the vehicle, can be easily achieved.

[0052] In addition, in the steering device of the conventional technology, a ball screw mechanism is provided on the steering shaft, and the teeth of the sector gear mesh with the rack teeth of the nut of the ball screw mechanism. As described above, the steering shaft and the sector gear have a fixed positional relationship, so there was a problem that it was difficult to increase the outer diameter of the ball screw mechanism, which requires a relatively high rigidity to transmit thrust to the sector gear.

[0053] In contrast, in the first embodiment, the intermediate shaft 2 is inclined at an inclination angle α with respect to the steering shaft 1, and further, the teeth 5a of the sector gear 5 mesh with the rack teeth 44b of the nut 44 of the ball screw mechanism 4 outside the linking shaft side cylindrical portion 24.

[0054] Therefore, the outer diameter of the ball screw mechanism 4 can be increased and the degree of freedom in designing the ball screw mechanism 4 can be improved without being restricted by the positional relationship between the steering shaft 1 and the sector gear 5. Furthermore, the steering device having the configuration of the first embodiment can be applied not only to small trucks but also to large trucks.

[0055] [Second embodiment] Fig. 4 is a top view of the steering device of the second embodiment, and Fig. 5 is a longitudinal sectional view of the steering device of the second embodiment taken along line BB in Fig. 4.

[0056] The second embodiment shows an example in which, in a shaft configuration in which the first shaft is the steering shaft 1 and the second shaft is the intermediate shaft 2, a torque sensor 8 is provided on the steering shaft 1, while a ball screw mechanism 4 and a first electric motor 6 are provided on the intermediate shaft 2. That is, the second embodiment shows an example in which the first electric motor 6 provided on the steering shaft 1 in the first embodiment is provided on the intermediate shaft 2. Accordingly, the first reducer accommodating portion 26 of the first embodiment is eliminated, and the axial dimension of the first enlarged diameter portion 24b of the linkage shaft side cylindrical portion 24 is shorter than that of the first embodiment.

[0057] The second cover member 31 has a circular shaft through hole 31a formed in its center, and a small diameter end portion 2d of the intermediate shaft 2 formed in a stepped diameter reducing shape passes through this shaft through hole 31a. A worm wheel 47 constituting a part of the first reducer 7 is attached and fixed to the outer periphery of the small diameter end portion 2d protruding outward from the second cover member 31. The first reducer accommodating portion 26 of the second embodiment that accommodates the first reducer 7 is closed by attaching a cup-shaped closing member 51 to the outer periphery of the intermediate shaft side cylindrical portion 25.

[0058] [Effects of the second embodiment] In the second embodiment, in an axial configuration in which the intermediate shaft 2 is inclined relative to the steering shaft 1 by the first and second bevel gears 42, 43, a torque sensor 8 is provided on the steering shaft 1, while a ball screw mechanism 4 and a first electric motor 6 are provided on the intermediate shaft 2.

[0059] Therefore, since the first reducer 7 is not disposed inside the first enlarged diameter portion 24b, the axial dimension of the steering device can be reduced more than in the first embodiment by shortening the axial dimension of the first enlarged diameter portion 24b.

[0060] In the second embodiment, since the ball screw mechanism 4 and the first electric motor 6 are provided on the intermediate shaft 2, the ball screw mechanism 4 can be decelerated by shortening the lead of the intermediate shaft side ball screw groove 2c and the nut side ball screw groove 44a of the ball screw mechanism 4, and the assist force to the intermediate shaft 2 can be increased. In addition, by shortening the lead, the assist force by the first electric motor 6 can be reduced by the shortened lead, and the first electric motor 6 can be made smaller. Furthermore, by increasing the speed ratio of the first and second bevel gears 42, 43 by the shortened lead, the total speed ratio from the input shaft 12 to the sector gear 5 can be kept constant, thereby improving the degree of freedom in designing the reduction ratio of the ball screw mechanism 4 and the speed ratio of the first and second bevel gears 42, 43.

[0061] [Third embodiment] Fig. 6 is a top view of the steering device of the third embodiment, and Fig. 7 is a longitudinal sectional view of the steering device of the third embodiment taken along line CC in Fig. 6.

[0062] The third embodiment is a combination of the configuration of the steering device of the first embodiment and the configuration of the steering device of the second embodiment. That is, in the third embodiment, a torque sensor 8 and a first electric motor 6 are provided on the steering shaft 1, while a ball screw mechanism 4 and a second electric motor 52 having a configuration similar to that of the first electric motor 6 are provided on the intermediate shaft 2.

[0063] The first electric motor 6 is arranged so that the second EPS controller 53 is located on the rear side (the back side in FIG. 7) of the first housing 9 and the connecting shaft side cylindrical portion 24 when viewed from the direction of the rotation axis R of the sector gear 5 as shown in FIG. 7. [Effects of the third embodiment] In the third embodiment, in an axial configuration in which the intermediate shaft 2 is inclined at an inclination angle α relative to the steering shaft 1 by the first and second bevel gears 42, 43, a torque sensor 8 and a first electric motor 6 are provided on the steering shaft 1, while a ball screw mechanism 4 and a second electric motor 52 are provided on the intermediate shaft 2.

[0064] Therefore, a larger assist torque can be supplied compared to the first and second embodiments by the two motors, the first and second electric motors 6, 52. Even if one of the first and second electric motors 6, 52 breaks down, the other of the first and second electric motors 6, 52 can continue to operate the steering device.

[0065] [Fourth embodiment] Fig. 8 is a top view of the steering device of the fourth embodiment. Fig. 9 is a longitudinal sectional view of the steering device of the fourth embodiment taken along line DD in Fig. 8. Fig. 10 is a partial sectional view of the first electric motor 6 etc. taken along line EE in Fig. 8.

[0066] As shown in Fig. 9, in the fourth embodiment, an intermediate shaft 2 is connected to a steering shaft 1 via a gear mechanism 3 so as to be perpendicular to the steering shaft 1. A torque sensor 8 and a ball screw mechanism 4 are provided on the steering shaft 1, while a first electric motor 6 is provided on the intermediate shaft 2. In the fourth embodiment, the partition member 10 of the first to third embodiments is eliminated, and a first housing 9 is directly attached to a cooperation shaft side cylindrical portion 24 by bolts 20. Furthermore, the cooperation shaft side cylindrical portion 24 is formed separately from the intermediate shaft side cylindrical portion 25.

[0067] In the fourth embodiment, the first housing 9 further has a medium diameter portion 9d located between the small diameter portion 9a and the large diameter portion 9b, and the space inside this medium diameter portion 9d serves as a sensor accommodating portion 22 that accommodates the torque sensor 8.

[0068] The cooperation shaft side tubular portion 24 is generally cylindrical, and a part of the outer periphery bulges outward in the radial direction to form an output shaft peripheral wall portion 35. The output shaft peripheral wall portion 35 opens into the inside of the cooperation shaft side tubular portion 24. In the output shaft peripheral wall portion 35, the sector gear 5 is disposed with the teeth portion 5a facing the second cooperation shaft 14, and the teeth portion 5a mesh with the rack teeth 44b of the nut 44 of the ball screw mechanism 4 provided around the second cooperation shaft 14.

[0069] A cooperation-shaft-side ball screw groove 14a, which constitutes a part of the ball screw mechanism 4, is formed on the outer circumferential surface of the second cooperation shaft 14 in the axial center portion.

[0070] Further, a generally annular bearing holding member 55 that holds a bearing, for example, a seventh ball bearing 54, is provided inside one end of the cooperation shaft side cylindrical portion 24. A male thread is formed on the outer circumferential surface of the bearing holding member 55, and this male thread is screwed into a female thread formed on the inner circumferential surface of one end of the cooperation shaft side cylindrical portion 24, thereby attaching and fixing the bearing holding member 55 to the cooperation shaft side cylindrical portion 24. The bearing holding member 55 has a shaft through hole 55a formed in the center, and the steering shaft 1 extends axially through this shaft through hole 55a.

[0071] As shown in FIG. 9, a reduced-diameter portion 24e is formed at the other end of the connecting shaft side cylindrical portion 24, and a bearing, such as an eighth ball bearing 70, that rotatably supports the second connecting shaft 14 is provided on the inner circumferential surface of this reduced-diameter portion 24e.

[0072] The intermediate shaft side cylindrical portion 25 has a first cylindrical portion 56 that accommodates a portion of the second linking shaft 14, and a second cylindrical portion 57 that is formed integrally with the first cylindrical portion 56 and accommodates a portion of the intermediate shaft 2.

[0073] One end of the first cylindrical portion 56 serves as a support portion on which the connecting shaft side cylindrical portion 24 is placed, while the other end is formed to have a smaller diameter than the one end and serves as a portion coupled to the second cylindrical portion 57. An end portion 56a of the first cylindrical portion 56 that is not coupled to the second cylindrical portion 57 is inclined radially outward.

[0074] The second cylindrical portion 57 has an annular protrusion 57a ​​formed on its inner circumferential surface, and one end of an outer race 58a of a bearing that rotatably supports the intermediate shaft 2, for example, a ninth ball bearing 58, abuts against the annular protrusion 57a. With one end of the outer race 58a abutting against the annular protrusion 57a, the outer race 58a is fixed to the second cylindrical portion 57 by pressing the other end of the outer race 58a toward one axial end of the intermediate shaft 2 by a first retaining ring 59 provided on the inner periphery of the second cylindrical portion 57. Moreover, one end of the inner race 58b of the ninth ball bearing 58 abuts against a step 2e formed at a position near the axial center of the intermediate shaft 2. The inner race 58b is fixed to the intermediate shaft 2 by pressing the other end of the inner race 58b toward one axial end of the intermediate shaft 2 with a second retaining ring 60 provided on the outer periphery of the intermediate shaft 2 while the inner race 58b is in contact with the step portion 2e of the intermediate shaft 2.

[0075] The second bevel gear 43 is attached and fixed to the small diameter end portion 2d on one axial end side of the intermediate shaft 2 so as to be perpendicular to the first bevel gear 42. The first teeth portion 42a of the first bevel gear 42 and the second teeth portion 43a of the second bevel gear 43 mesh with each other, so that the rotation axis Q of the intermediate shaft 2 and the rotation axis P of the steering shaft 1 are perpendicular to each other.

[0076] The inside of the blocking member 51 forms a first reducer accommodating section 26 that accommodates a first reducer 7 that reduces the rotation speed of the first electric motor 6. A part of the outer periphery of the blocking member 51 communicates with a worm shaft accommodating section 61 (described later) that is provided in the worm shaft housing 50 shown in FIG.

[0077] The worm shaft housing 50 has a cylindrical shaft tubular portion 50a and a conical tapered portion 50b formed integrally with the shaft tubular portion 50a and formed in a conical tapered shape that gradually expands in diameter toward the first electric motor 6. The space inside the shaft tubular portion 50a and the conical tapered portion 50b forms a worm shaft accommodating portion 61 that accommodates a worm shaft 62. One axial end portion 50c of the conical tapered portion 50b is fixed to the outer periphery of a stepped reduced diameter portion 49a formed in the motor housing 49 in a stepped reduced diameter shape. A ring-shaped fourth seal member 63 provides an airtight seal between the inner circumferential surface of the axial end portion 50c and the outer circumferential surface of the stepped reduced diameter portion 49a.

[0078] The opening on the other axial end side of the shaft cylindrical portion 50a is closed by a breather valve 64 that allows air within the worm shaft housing 50 to escape to the outside.

[0079] The worm shaft 62 is made of a metal material and is formed into a generally cylindrical shape. One end of the worm shaft 62 is fixed to the motor shaft 65, while the other end is disposed in the worm shaft housing 61 so as to be located near the breather valve 64. The worm shaft 62 has a cylindrical shaft portion 62a and a helical tooth portion 62b formed on the outer periphery of the shaft portion 62a and continuing in a helical shape. The helical tooth portion 62b meshes with the gear forming portion 47b of the worm wheel 47 of the first reduction gear 7.

[0080] As shown in FIG. 10, a bearing, for example a deep groove ball bearing 66, for supporting the worm shaft 62 rotatably is provided on the outer periphery of one axial end of the worm shaft 62.

[0081] A tenth ball bearing 67, which rotatably supports the worm shaft 62, is provided on the outer periphery of the other axial end of the worm shaft 62. The tenth ball bearing 67 is supported by a bearing support member 68 provided between the worm shaft 62 and the breather valve 64. More specifically, the bearing support member 68 has a circular recess 68a formed on a surface facing the other axial end of the worm shaft 62, and the tenth ball bearing 67 is supported by the bearing holding member 68 by fitting the tenth ball bearing 67 into this circular recess 68a. The outer periphery of the bearing holding member 68 and the inner periphery of the shaft cylindrical portion 50a are airtightly sealed by a ring-shaped fifth seal member 69.

[0082] [Effects of the fourth embodiment] In the fourth embodiment, in an axial configuration in which the intermediate shaft 2 is perpendicular to the steering shaft 1 by the first and second bevel gears 42, 43, a torque sensor 8 and a ball screw mechanism 4 are provided on the steering shaft 1, while a first electric motor 6 is provided on the intermediate shaft 2.

[0083] Therefore, since the first electric motor 6 is not disposed on the steering shaft 1, the axial dimension of the steering device can be reduced by the amount of the first electric motor 6 compared to the steering device of the prior art.

[0084] In the above first to third embodiments, an example has been described in which the intermediate shaft 2 is inclined at the inclination angle α with respect to the steering shaft 1 by the first and second bevel gears 42, 43. However, an example in which the intermediate shaft 2 is shifted so as to be parallel to the steering shaft 1 by a pair of spur gears can also be applied to the present invention.

Claims

1. A steering device that transmits a rotational force to a steered wheel, A first axis; an output shaft located radially outward of the first shaft; a second shaft located on the opposite side of the first shaft across the output shaft; a gear mechanism connecting the first shaft and the second shaft; a torque sensor for detecting a steering torque associated with the rotational force; a first electric motor that applies a torque to the rotational force; a ball screw mechanism that transmits a thrust generated by the rotational force to the output shaft; Equipped with two of the torque sensor, the first electric motor, and the ball screw mechanism are provided on one of the first shaft and the second shaft, and the remaining one is provided on the other of the first shaft and the second shaft; the gear mechanism includes a first bevel gear fixed to an outer periphery of the first shaft and a second bevel gear fixed to an outer periphery of the second shaft, A steering device, wherein the second axis is inclined at a predetermined inclination angle that is an acute angle with respect to the first axis.

2. 2. The steering device according to claim 1, the first shaft is a steering shaft connected to a steering wheel, the second shaft is an intermediate shaft connected to the output shaft, the torque sensor and the first electric motor are provided on the steering shaft, The steering device according to claim 1, wherein the ball screw mechanism is provided on the intermediate shaft.

3. 2. The steering device according to claim 1, the first shaft is a steering shaft connected to a steering wheel, the second shaft is an intermediate shaft connected to the output shaft, The torque sensor is provided on the steering shaft, A steering device according to claim 1, wherein the first electric motor and the ball screw mechanism are provided on the intermediate shaft.

4. 2. The steering device according to claim 1, A second electric motor is further provided to apply a torque to the rotational force. the first shaft is a steering shaft connected to a steering wheel, the second shaft is an intermediate shaft connected to the output shaft, the torque sensor and the first electric motor are provided on the steering shaft, The second electric motor and the ball screw mechanism are provided on the intermediate shaft.

5. In the steering device according to any one of claims 2 to 4, A steering device according to claim 1, wherein the first electric motor is provided at a position higher than the output shaft.

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