Steering assist device of towing vehicle

Abstract

To provide a steering assist device of a towing vehicle which can be mounted in a narrow space and enables reduction of operator's steering force.SOLUTION: A steering assist device 30A includes: a steering shaft 10 which is connected to a front wheel 4 of a towing vehicle 1, rotated by operation of a steering 20, and includes a pinion gear 14 formed on a side surface 11a; a rack member 40 having a rack gear 41 configured to engage with the pinion gear 14 and extending along a width direction D intersecting with an axial direction of the steering shaft 10; and a steering assist unit 50A which moves the rack member 40 along the width direction D to provide rotational force around the steering shaft 10 to the steering shaft 10.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a steering assist device for a towing vehicle. [Background technology]

[0002] For example, Patent Document 1 describes a steering device equipped with a steering assist mechanism. The steering device described in Patent Document 1 has a steering shaft, an electric motor that applies a rotational torque that assists the steering torque to the steering shaft, and a speed reducer (speed reduction mechanism) that reduces the rotation of the electric motor and transmits it to the steering shaft (steering shaft). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-7407 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when applying the above-described steering assist device to a towing vehicle, space is required around the steering shaft to install a reduction mechanism. However, it has been difficult to install the above-described reduction mechanism in towing vehicles with limited space (free layout area) around the steering shaft, such as stand-on towing vehicles. In such cases, the steering force (steering force) required by the driver to rotate the steering shaft tends to be greater than in towing vehicles equipped with a reduction mechanism (e.g., sit-down towing vehicles).

[0005] An object of the present invention is to provide a steering assist device for a towing vehicle that can be installed in a small space and can reduce the steering force required by the driver. [Means for solving the problem]

[0006] (1) One aspect of the present invention is a steering assist device that includes a steering shaft that is connected to the wheels of a towing vehicle and rotates when the steering wheel is operated, with a pinion gear formed on its side, a rack member that has a rack gear that meshes with the pinion gear and extends along a predetermined direction that intersects the axial direction of the steering shaft, and a steering assist unit that applies a rotational force around the steering shaft to the steering shaft by moving the rack member along the predetermined direction.

[0007] In such a steering assist device for a towing vehicle, a rack gear of a rack member meshes with a pinion gear formed on the side of the steering shaft. By moving the rack member in a predetermined direction intersecting the axial direction of the steering shaft, the rack member applies a rotational force to the steering shaft about the steering shaft. This reduces the steering force required by the driver to rotate the steering shaft. Furthermore, since there is no need to install a reduction mechanism with multiple gears, the device configuration can be simplified and the device can be made more compact. Therefore, the steering assist device of the present invention can be installed in a small space while reducing the driver's steering force.

[0008] (2) In the above (1), the steering assist unit may include two hydraulic first pistons connected to both ends of the rack member, a hydraulic second piston that supplies hydraulic oil to the first pistons to move the first pistons along a predetermined direction, an oil reservoir disposed between the two first and second pistons to store the hydraulic oil, and an assist pedal for moving the second piston. In this configuration, when the assist pedal is operated, the second piston moves and hydraulic oil stored in the oil reservoir is supplied to the first pistons, thereby moving the rack member connected to the first piston along the predetermined direction and applying a rotational force around the steering shaft to the steering shaft. By using hydraulic pressure in this way, the rack member can be easily moved along the predetermined direction.

[0009] (3) In the above (2), the number of second pistons, oil reservoirs, and assist pedals may be two. In this configuration, when one assist pedal is operated, one second piston moves, and hydraulic oil stored in one oil reservoir is supplied to one first piston, causing the rack member to move to one side in a predetermined direction, and a rotational force on one side is applied to the steering shaft. When the other assist pedal is operated, the other second piston moves, and hydraulic oil stored in the other oil reservoir is supplied to the other first piston, causing the rack member to move to the other side in the predetermined direction, and a rotational force on the other side is applied to the steering shaft. In this way, the driver can switch the direction of the rotational force applied to the steering shaft by the rack member by switching the operation of the two assist pedals.

[0010] (4) In the above (2), the steering system may further include a flow diverter valve disposed between the oil reservoir and the two first pistons, diverting hydraulic oil stored in the oil reservoir to the two first pistons; an angle detector that detects the rotation angle and rotation direction of the steering shaft; and a control unit that switches the flow diverting direction of the flow diverter valve based on the rotation direction of the steering shaft detected by the angle detector. In this configuration, when the assist pedal is operated, the second piston moves, and hydraulic oil stored in the oil reservoir is supplied to one of the two first pistons through the flow diverter valve. At this time, when the steering wheel is operated to one side and the angle detector detects rotation of one side of the steering shaft, the flow diverter valve switches the flow diverting direction so that hydraulic oil is supplied to one of the first pistons. As a result, the rack member moves to one side in a predetermined direction, and a rotational force on one side is applied to the steering shaft. When the steering wheel is operated to the other side and the angle detector detects rotation of the other side of the steering shaft, the flow diverting direction of the flow diverter valve switches so that hydraulic oil is supplied to the other first piston. As a result, the rack member moves to the other side in the predetermined direction, and a rotational force is applied to the steering shaft in the other direction. In this way, the direction of the rotational force applied to the steering shaft is automatically determined according to the steering direction. Therefore, the driver does not need to change the direction of the rotational force applied to the steering shaft himself, reducing the burden on the driver.

[0011] (5) In any of the above (2) to (4), the assist pedal may be provided so as to be movable along the vertical direction of the towing vehicle. In this configuration, when the driver operates the assist pedal with his / her foot, the driver's own weight can be effectively applied to the assist pedal.

[0012] (6) The steering system according to (1) above further includes a motor for moving the rack member in a predetermined direction, a rotation-to-linear conversion unit for converting the rotational motion of the motor into linear motion of the rack member along the predetermined direction, an angle detection unit for detecting the rotation angle and rotation direction of the steering shaft, and a control unit for controlling the rotation of the motor based on the rotation direction of the steering shaft detected by the angle detection unit. In this configuration, when the motor rotates, the rotational motion of the motor is converted into linear motion of the rack member along the predetermined direction, causing the rack member to move along the predetermined direction and applying a rotational force about the steering shaft to the steering shaft. At this time, when the steering wheel is operated to one side and the angle detection unit detects rotation of one side of the steering shaft, the motor rotates in one direction. As a result, the rack member moves to one side in the predetermined direction and a rotational force on one side is applied to the steering shaft. When the steering wheel is operated to the other side and the angle detection unit detects rotation of the other side of the steering shaft, the motor rotates in the other direction. As a result, the rack member moves to the other side in the predetermined direction and a rotational force on the other side is applied to the steering shaft. In this way, the rack member can be easily moved in a predetermined direction without using hydraulic equipment.

[0013] (7) In any of the above (1) to (6), the towing vehicle may be a stand-on towing vehicle. A stand-on towing vehicle has a smaller space (free layout area) around the steering axis than a sit-down towing vehicle. Therefore, it is particularly effective to install the steering assist device in a stand-on towing vehicle. [Effects of the Invention]

[0014] According to the present invention, the steering force required by the driver can be reduced while the device can be installed in a small space. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view showing a towing vehicle on which steering assist devices according to first to third embodiments are mounted. [Figure 2] FIG. 2 is a perspective view showing the wheels, steering shaft, and steering wheel shown in FIG. 1. [Figure 3] 1 is a cross-sectional view of the steering assist device according to the first embodiment, showing the area around a steering shaft. [Figure 4] 1 is a longitudinal sectional view of a towing vehicle including a steering assist device according to a first embodiment. [Figure 5] 1 is a block diagram showing a configuration of a steering assist device according to a first embodiment. [Figure 6] FIG. 6 is a block diagram showing the configuration of a steering assist device according to a second embodiment. [Figure 7] 7 is a flowchart showing a process executed by a control unit shown in FIG. 6. FIG. [Figure 8] FIG. 10 is a block diagram showing the configuration of a steering assist device according to a third embodiment. [Figure 9] 9 is a flowchart showing the processing of the control unit shown in FIG. 8. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted. [First embodiment]

[0017] FIG. 1 is a perspective view showing a towing vehicle equipped with steering assist devices according to first to third embodiments of the present invention. FIG. 2 is a perspective view showing the wheels, steering shaft, and steering wheel shown in FIG. 1. The steering assist device is omitted from FIGS. 1 and 2. In FIG. 2, the front of the steering wheel faces the right side of the page. In the following description, the towing vehicle 1 will be described as being placed on a horizontal plane. The direction perpendicular to the front-to-rear direction of the towing vehicle 1 in the horizontal direction is defined as the width direction D. The direction perpendicular to the front-to-rear direction and width direction D of the towing vehicle 1 is defined as the vertical direction. In the following description, the "right side" and "left side" refer to the right side and left side of the towing vehicle 1 when viewed forward from the towing vehicle 1. Furthermore, "clockwise" and "counterclockwise" refer to the direction of rotation when viewed from above. First, the configuration of the towing vehicle 1 before the steering assist device is installed will be described.

[0018] In FIG. 1, towing vehicle 1 is a small, stand-on type towing vehicle. The driver of towing vehicle 1 drives towing vehicle 1 while standing. The driver of towing vehicle 1 manually operates steering wheel 20, which will be described later, to rotate steering shaft 10 and front wheels 4, which are connected to steering wheel 20, about steering shaft 10. This steers towing vehicle 1. A feature of stand-on type towing vehicle 1 is that steering shaft 10 and steering wheel 20 are directly connected to ensure a driving position when the driver is driving while standing. Towing vehicle 1 tows, for example, a bed on which an object to be transported is loaded.

[0019] The towing vehicle 1 comprises a body 3 having a driver's cab 2, one front wheel 4 as a steering wheel provided at the front end of the body 3, two rear wheels 5 as drive wheels provided at the rear end of the body 3, and a steering device 6 connected to the front wheels 4. A coupling section 7 is formed at the rear end of the body 3 for coupling to a loading platform. A brake pedal (not shown) for stopping the towing vehicle 1 is provided below 2a of the driver's cab 2.

[0020] 2, the steering device 6 has a steering shaft 10 connected to the front wheels 4 and a steering wheel 20 connected to the steering shaft 10. The front wheels 4 and the steering shaft 10 rotate around the steering shaft 10 as the steering wheel 20 rotates around the steering shaft 10. In other words, the front wheels 4 rotate around the steering shaft 10 with the steering shaft 10 as the center of rotation.

[0021] The steering shaft 10 extends in the vertical direction of the towing vehicle 1. The steering shaft 10 has a first shaft 11, a second shaft 12, and a shaft connecting portion 13. In this example, the first shaft 11, the second shaft 12, and the shaft connecting portion 13 are arranged side by side on the same straight line in the vertical direction. The first shaft 11 is connected to the front wheels 4 via a connecting member 15. The second shaft 12 is connected to the upper end of the first shaft 11 (the end opposite the front wheels 4) via the shaft connecting portion 13. A steering 20 is connected to the upper end of the second shaft 12. When the second shaft 12 rotates around its axis by the steering 20, the first shaft 11 and the front wheels 4 rotate around the axis of the first shaft 11 via the shaft connecting portion 13.

[0022] The steering wheel 20 is an operating means by which the driver rotates the steering shaft 10 about the axis of the steering shaft 10 to perform steering operation to change the direction of travel of the towing vehicle 1. The steering wheel 20 is directly connected to the steering shaft 10 at its upper end. The steering wheel 20 has a main body 21 and two steering bars 22. The main body 21 is connected to the upper end of the steering shaft 10. The two steering bars 22 are attached to both ends of the main body 21 in the width direction D. The driver grasps these two steering bars 22 with his hands and uses his arm strength to rotate the main body 21 about the steering shaft 10. This causes the steering shaft 10, which is connected to the main body 21, to rotate. An accelerator lever 24 for moving the towing vehicle 1 forward or backward is located on the right side of the steering wheel 20.

[0023] Next, with reference to Figs. 3 to 5, a steering assist device 30A according to the first embodiment mounted on the above-described towing vehicle 1 will be described. Fig. 3 is a horizontal cross-sectional view of the steering shaft 10 and its surroundings of the steering assist device 30A. Specifically, Fig. 3 is a view in which a portion including the first shaft 11 is cut horizontally. Fig. 4 is a vertical cross-sectional view of the towing vehicle 1 including the steering assist device 30A. Fig. 5 is a block diagram showing the configuration of the steering assist device 30A. The configuration of the steering assist device 30A will be described below with reference to Figs. 3 to 5.

[0024] As shown in Figures 3 and 4, the steering assist device 30A has a steering shaft 10, a rack member 40, and a steering assist unit 50A. In addition to the above-mentioned components, the steering shaft 10 further has a pinion gear 14. The pinion gear 14 is formed on a side surface 11a of the first shaft 11. Specifically, the pinion gear 14 is formed, for example, on the side surface 11a of the first shaft 11 in the vertical center portion. The pinion gear 14 is formed on a portion of the side surface 11a of the first shaft 11 in the circumferential direction. Note that the pinion gear 14 may be formed around the entire circumference of the side surface 11a.

[0025] The rack member 40 extends along a predetermined direction intersecting the axial direction of the steering shaft 10. Here, the predetermined direction is, for example, the width direction D. When viewed from above, the rack member 40 is formed, for example, in a rectangular shape with long sides along the width direction D. The rack member 40 is provided on the front side of the steering shaft 10 in the traveling direction of the first shaft 11. The rack member 40 has a rack gear 41 that meshes with the pinion gear 14. Specifically, the rack gear 41 is formed continuously along the width direction D in the center of the rear end portion 40a of the rack member 40.

[0026] The steering assist unit 50A applies a rotational force around the steering shaft 10 to the steering shaft 10 by moving the rack member 40 along the width direction D. The steering assist unit 50A has two first pistons 51, two first cylinders 52 (cylinder tubes), two seals 53, two second pistons 54, two second cylinders 55, two oil reservoirs 56, and two assist pedals 57 (see FIG. 5).

[0027] The first pistons 51 are, for example, hydraulic pistons. As shown in FIG. 3 , the two first pistons 51 are connected to both ends of the rack member 40 in the width direction D, one on each side. In other words, the two first pistons 51 are arranged to face each other in the width direction D with the rack member 40 interposed therebetween. The two first pistons 51 are each formed, for example, in a cylindrical shape with an axis extending along the width direction D. The two first pistons 51 are each connected to the rack member 40 at an end surface 51 a facing the rack member 40 in the width direction D. The two first pistons 51 are composed of a first piston 51R connected to the right end of the rack member 40 and a first piston 51L connected to the left end of the rack member 40.

[0028] The two first cylinders 52 are arranged to face each other in the width direction D with the rack member 40 interposed therebetween. Each of the two first cylinders 52 is formed in a cylindrical shape with an axis extending along the width direction D. The two first cylinders 52 are composed of a right-side first cylinder 52R and a left-side first cylinder 52L.

[0029] The right-side first cylinder 52R is disposed on the right side of the rack member 40. The left end of the first cylinder 52R is open. The first cylinder 52R accommodates the right end of the rack member 40 and the first piston 51R. The first cylinder 52R has a first space S1R formed therein. The first space S1R is divided into a space S11R located on the rack member 40 side with respect to the first piston 51R, and a space S12R located on the opposite side of the rack member 40. The space S12R is filled with hydraulic oil A. When hydraulic oil A is further supplied to the space S12R from a hydraulic pipe 58R (described later), the first cylinder 52R moves from the right side to the left side along the width direction D.

[0030] The left first cylinder 52L is disposed on the left side of the rack member 40. The right end of the first cylinder 52L is open. The first cylinder 52L accommodates the left end of the rack member 40 and the first piston 51L. The first cylinder 52L has a first space S1L formed therein. The first space S1L is divided into a space S11L located on the rack member 40 side with respect to the first piston 51L, and a space S12L located on the opposite side of the rack member 40. The space S12L is filled with hydraulic oil A. When hydraulic oil A is further supplied to the space S12L from a hydraulic pipe 58L (described later), the first cylinder 52L moves from left to right along the width direction D.

[0031] The two seals 53 are composed of a right seal 53R and a left seal 53L. The right seal 53R seals the gap between the right end of the rack member 40 and the radially inner side surface 52aR of the first cylinder 52R. The seal 53R is provided at the end of the first cylinder 52R on the rack member 40 side. The seal 53R is made of, for example, rubber. The left seal 53L seals the gap between the left end of the rack member 40 and the radially inner side surface 52aL of the first cylinder 52L. The seal 53L is provided at the end of the first cylinder 52L on the rack member 40 side. The seal 53L is made of the same material as the seal 53R.

[0032] The two second pistons 54 each supply hydraulic oil A to the two first pistons 51. The hydraulic oil A is oil for moving each of the two first pistons 51 along the width direction D. The two second pistons 54 are composed of a right second piston 54R and a left second piston 54L.

[0033] The right second piston 54R is provided on the right side inside the lower portion 2a of the cab 2 (see FIG. 4). The second piston 54R is housed in a second cylinder 55R (described later). The second piston 54R is formed, for example, in a cylindrical shape with an axis extending along the vertical direction. Alternatively, the second piston 54R is formed in a disk shape when viewed from above. The upper end surface of the second piston 54R is connected to an assist pedal 57R (described later). The second piston 54R supplies hydraulic oil A to the first piston 51R. Specifically, the second piston 54R supplies hydraulic oil A to a space S12R of the first piston 51R via a hydraulic pipe 58R (described later). The hydraulic oil A supplied to the space S12R moves the first piston 51R from right to left along the width direction D. As a result, the first piston 51R moves the rack member 40 from right to left along the width direction D. At this time, the pinion gear 14 formed on the side surface 11a of the first shaft 11 of the steering shaft 10 is engaged with the rack gear 41 of the rack member 40 arranged on the front side of the steering shaft 10, so that by moving the rack member 40 from the right side to the left side along the width direction D, a counterclockwise rotational force is applied to the steering shaft 10.

[0034] The left second piston 54L is configured to correspond to the right second piston 54R (not shown in FIG. 4). That is, the second piston 54L is provided on the left side inside the lower portion 2a of the cab 2. The second piston 54L is housed in a second cylinder 55L (described later). The second piston 54L is formed, for example, in a cylindrical shape whose axis extends along the vertical direction. Alternatively, the second piston 54L is formed in a disk shape when viewed from above. The upper end surface of the second piston 54L is connected to an assist pedal 57L (described later). The second piston 54L supplies hydraulic oil A to the first piston 51L. Specifically, the second piston 54L supplies hydraulic oil A to a space S12L of the first piston 51L via a hydraulic pipe 58L (described later). The hydraulic oil A supplied to the space S12L moves the first piston 51L from left to right along the width direction D. As a result, the first piston 51L moves the rack member 40 from left to left along the width direction D. At this time, the pinion gear 14 formed on the side surface 11a of the first shaft 11 of the steering shaft 10 meshes with the rack gear 41 of the rack member 40 arranged on the front side of the steering shaft 10, so that by moving the rack member 40 from left to right along the width direction D, a clockwise rotational force is applied to the steering shaft 10.

[0035] The two second cylinders 55 are composed of a right second cylinder 55R and a left second cylinder 55L. The right second cylinder 55R is formed, for example, in a cylindrical shape with an axis extending along the vertical direction. The second cylinder 55R houses a second piston 54R. The second cylinder 55R has a second space S2R formed therein. The second space S2R includes a space S21R located on the assist pedal 57R side of the second piston 54R, and a space S22R located on the opposite side of the assist pedal 57R. The space S22R is filled with hydraulic oil A.

[0036] The left second cylinder 55L has a configuration corresponding to the right second cylinder 55R (not shown in FIG. 4). That is, the second cylinder 55L is formed, for example, in a cylindrical shape with an axis extending along the vertical direction. The second cylinder 55L accommodates the second piston 54L. The second cylinder 55L has a second space S2L formed therein. The second space S2L includes a space S21L located on the assist pedal 57L side of the second piston 54L, and a space S22L located on the opposite side of the assist pedal 57L. The space S22L is filled with hydraulic oil A.

[0037] The two oil reservoirs 56 are composed of a right oil reservoir 56R and a left oil reservoir 56L. The right oil reservoir 56R is disposed between the first piston 51R and the second piston 54R. Specifically, the oil reservoir 56R includes a space S12R of the first cylinder 52R, a space S22R of the second cylinder 55R, and a hydraulic pipe 58R. The hydraulic pipe 58R is disposed between the first cylinder 52R and the second cylinder 55R. One end 58aR of the hydraulic pipe 58R is connected to the end of the first cylinder 52R opposite the rack member 40 (see FIG. 3). The other end 58bR of the hydraulic pipe 58R is connected to the end of the second cylinder 55R opposite the assist pedal 57R. The hydraulic pipe 58R is filled with hydraulic oil A.

[0038] The left oil reservoir 56L has a configuration corresponding to the right oil reservoir 56R (not shown in FIG. 4). That is, the left oil reservoir 56L is disposed between the first piston 51L and the second piston 54L. Specifically, the oil reservoir 56L includes a space S12L of the first cylinder 52L, a space S22L of the second cylinder 55L, and a hydraulic pipe 58L. The hydraulic pipe 58L is disposed between the first cylinder 52L and the second cylinder 55L. One end 58aL of the hydraulic pipe 58L is connected to the end of the first cylinder 52L opposite the rack member 40 (see FIG. 3). The other end 58bL of the hydraulic pipe 58L is connected to the end of the second cylinder 55L opposite the assist pedal 57L. The hydraulic pipe 58L is filled with hydraulic oil A.

[0039] The two assist pedals 57 are, for example, foot pedals. The two assist pedals 57 include a right assist pedal 57R and a left assist pedal 57L. The right assist pedal 57R is an assist pedal for turning left. The left assist pedal 57L is an assist pedal for turning right.

[0040] The right assist pedal 57R is connected to the upper end of the second piston 54R. The assist pedal 57R is provided so as to be movable in the vertical direction of the towing vehicle 1. The assist pedal 57R has a support portion 571R and a pedal portion 572R. The support portion 571R extends vertically upward from the second piston 54R. The pedal portion 572R is formed, for example, in the shape of a rectangular plate extending horizontally. The pedal portion 572R is connected to the upper end of the support portion 571R at the center of the pedal portion 572R.

[0041] The left assist pedal 57L is configured to correspond to the right assist pedal 57R (not shown in FIG. 4). That is, the left assist pedal 57L is connected to the upper end of the second piston 54L. The assist pedal 57L is provided so as to be movable along the vertical direction of the towing vehicle 1. The assist pedal 57L has a support portion 571L and a pedal portion 572L. The support portion 571L extends vertically upward from the second piston 54L. The pedal portion 572L is formed, for example, in the shape of a rectangular plate extending horizontally. The pedal portion 572L is connected to the upper end of the support portion 571L at the center of the pedal portion 572L.

[0042] Next, the operating principle of the steering assist device according to the first embodiment will be described. To rotate the steering wheel 20 counterclockwise, the driver presses the right assist pedal 57R downward. When the right assist pedal 57R is pressed downward, the right second piston 54R moves downward, and hydraulic oil A stored in the right oil reservoir 56R is supplied to the right first piston 51R. Specifically, as the second piston 54R moves downward, hydraulic oil A stored in the space S22R of the second cylinder 55R is pushed into the hydraulic pipe 58R, and hydraulic oil A stored in the hydraulic pipe 58R is supplied to the space S12R of the first cylinder 52R. This causes the rack member 40 to move leftward along the width direction D, and a counterclockwise rotational force is applied to the steering shaft 10.

[0043] On the other hand, to rotate the steering wheel 20 clockwise, the driver presses the left assist pedal 57L downward. When the left assist pedal 57L is pressed downward, the left second piston 54L moves downward, and hydraulic oil A stored in the left oil reservoir 56L is supplied to the left first piston 51L. Specifically, as the second piston 54L moves downward, hydraulic oil A stored in the space S22L of the second cylinder 55L is pushed into the hydraulic pipe 58L, and hydraulic oil A stored in the hydraulic pipe 58L is supplied to the space S12L of the first cylinder 52L. As a result, the rack member 40 moves to the right along the width direction D, and a clockwise rotational force is applied to the steering shaft 10.

[0044] In this way, by switching the operation of the two assist pedals 57, the driver can switch the direction of the rotational force that the rack member 40 applies to the steering shaft 10. [Actions and Effects of the First Embodiment]

[0045] As described above, in the first embodiment, the rack gear 41 of the rack member 40 meshes with the pinion gear 14 formed on the side surface of the steering shaft 10. As a result, by moving the rack member 40 in the width direction D intersecting the axial direction of the steering shaft 10, the rack member 40 applies a rotational force to the steering shaft 10 about the steering shaft 10. As a result, the steering force required by the driver to rotate the steering shaft 10 can be reduced. Furthermore, since there is no need to install a speed reduction mechanism having multiple gears, the configuration of the device can be simplified and the device can be made smaller. Therefore, the steering assist device 30A can be installed in a small space while reducing the steering force required by the driver.

[0046] In particular, when the steering shaft 10 is rotated in one direction while the towing vehicle 1 is stopped, the reaction force that rotates the steering shaft 10 in the opposite direction is greater than when the towing vehicle 1 is moving. In other words, when the towing vehicle 1 is stopped, the steering force required to rotate the steering shaft 10 in one direction is greater than when the towing vehicle 1 is moving. In such cases, the steering assist device 30A is particularly effective.

[0047] Moreover, in the first embodiment, there are provided two hydraulic first pistons 51 connected to both ends of the rack member 40, a hydraulic second piston 54 that supplies hydraulic oil A to the first pistons 51 for moving the first pistons 51 along the width direction D, an oil reservoir 56 that is disposed between the two first pistons 51 and the second pistons 54 and that stores the hydraulic oil A, and an assist pedal 57 that moves the second piston 54. With this configuration, when the assist pedal 57 is operated, the second piston 54 moves and the hydraulic oil A stored in the oil reservoir 56 is supplied to the first pistons 51, thereby moving the rack member 40 connected to the first pistons 51 along the width direction D and applying a rotational force around the steering shaft 10 to the steering shaft 10. By using hydraulic pressure in this manner, the rack member 40 can be easily moved along the width direction D.

[0048] In the first embodiment, the number of second pistons 54, oil reservoirs 56, and assist pedals 57 is two. With this configuration, as described above, the driver can switch the direction of the rotational force that the rack member 40 applies to the steering shaft 10 by switching the operation of the two assist pedals 57.

[0049] Furthermore, in the first embodiment, the assist pedal 57 is provided so as to be movable in the vertical direction of the towing vehicle 1. This allows the weight of the driver to be effectively applied to the assist pedal 57 when the driver operates the assist pedal 57 with his / her foot while standing.

[0050] In the first embodiment, the towing vehicle 1 is a stand-on towing vehicle. A stand-on towing vehicle has a smaller space (free layout area) around the steering shaft than a sit-down towing vehicle. Therefore, it is particularly effective to install the steering assist device 30A in a stand-on towing vehicle 1. [Second embodiment]

[0051] Fig. 6 is a block diagram showing the configuration of a steering assist device according to the second embodiment. In Fig. 6, the steering assist device 30B of the second embodiment is different from the steering assist device 30A of the first embodiment in the configuration of the steering assist unit 50B. The configuration of the steering assist device 30B is the same as that of the steering assist device 30A of the first embodiment, except for the steering assist unit 50B.

[0052] The steering assist unit 50B differs from the steering assist unit 50A of the first embodiment in the following two points. The first point is that there is only one second piston 54, one oil reservoir 56, and one assist pedal 57. The second point is that the steering assist unit 50B has a flow dividing valve 61, an angle detection unit 62, and a control unit 63.

[0053] The flow dividing valve 61 is disposed between the two first pistons 51 and one oil reservoir 56. The flow dividing valve 61 divides the hydraulic oil A stored in the oil reservoir 56 into the two first pistons 51. The angle detecting unit 62 detects the rotation angle and rotation direction of the steering shaft 10. The angle detecting unit 62 is, for example, an angle sensor. The control unit 63 is configured as a computer device including a CPU, RAM, ROM, input / output interface, etc. The control unit 63 switches the flow dividing direction of the flow dividing valve 61 based on the rotation direction of the steering shaft 10 detected by the angle detecting unit 62.

[0054] FIG. 7 is a flowchart showing the processing executed by the control unit 63. The control unit 63 first acquires the rotation direction of the steering shaft 10 from the angle detection unit 62 (step S101). Next, the control unit 63 determines whether the rotation direction of the steering shaft 10 is counterclockwise (step S102). When the control unit 63 determines that the rotation direction of the steering shaft 10 is counterclockwise, the control unit 63 switches the flow diversion direction of the flow diversion valve 61 so that the hydraulic oil A is supplied to the right-side first piston 51R (step S103). When the control unit 63 determines that the rotation direction of the steering shaft 10 is not counterclockwise (clockwise), the control unit 63 switches the flow diversion direction of the flow diversion valve 61 so that the hydraulic oil A is supplied to the left-side first piston 51L (step S104). After executing the processing of either step S103 or S104, the control unit 63 executes the above-described step S101 again.

[0055] In the configuration of the steering assist device 30B of the second embodiment described above, when the assist pedal 57 is operated, the second piston 54 moves, and the hydraulic oil A stored in the oil reservoir 56 is supplied to either the right-side first piston 51R or the left-side first piston 51L through the flow diverter valve 61. At this time, when the steering wheel 20 is rotated counterclockwise and the angle detection unit 62 detects the counterclockwise rotation of the steering shaft 10, the flow diverter valve 61 switches its flow diverting direction so that the hydraulic oil A is supplied to the right-side first piston 51R. As a result, the rack member 40 moves to the left in the width direction D, and a counterclockwise rotation force is applied to the steering shaft 10. On the other hand, when the steering wheel 20 is rotated clockwise and the angle detection unit 62 detects the clockwise rotation of the steering shaft 10, the flow diverter valve 61 switches its flow diverting direction so that the hydraulic oil A is supplied to the left-side first piston 51L. As a result, the rack member 40 moves to the right in the width direction D, and a clockwise rotational force is applied to the steering shaft 10. In this way, the direction of the rotational force applied to the steering shaft 10 is automatically determined according to the operating direction of the steering wheel 20. Therefore, the driver does not need to change the direction of the rotational force applied to the steering shaft 10 himself, and the burden on the driver is reduced. [Third embodiment]

[0056] Fig. 8 is a block diagram showing the configuration of a steering assist device according to the third embodiment. In Fig. 8, the steering assist device 30C differs from the steering assist devices 30A and 30B of the first and second embodiments mainly in that a steering assist unit 50C does not have a hydraulic device. The configuration other than the steering assist unit 50C is the same as that of the steering assist devices 30A and 30B of the first and second embodiments. Therefore, the configuration of the steering assist unit 50C will be described below.

[0057] The steering assist unit 50C has a motor 71, a rotary-to-linear converter 72, an angle detector 73, and a controller 74. The motor 71 is a drive source for moving the rack member 40 in the width direction D via the rotary-to-linear converter 72. The motor 71 is, for example, a power steering motor. The motor 71 has a rotary shaft 71a that rotates under the control of the controller 74. The rotary shaft 71a extends, for example, along the vertical direction of the towing vehicle 1 and is disposed in front of the rack member 40.

[0058] The rotary-to-linear converter 72 converts the rotational motion of the motor 71 into linear motion along the width direction D of the rack member 40. The rotary-to-linear converter 72 has, for example, a pinion gear 75 and a rack gear 76. The pinion gear 75 is connected to a rotary shaft 71a of the motor 71. The rack gear 76 is formed, for example, at a front end 40b (see FIG. 3) of the rack member 40 so as to be continuous with the front end 40b along the width direction D. That is, the rack gear 76 is formed at the end of the rack member 40 opposite the rack gear 41. The rack gear 76 meshes with the pinion gear 75 connected to the rotary shaft 71a of the motor 71. This converts the rotational motion of the rotary shaft 71a of the motor 71 into linear motion along the width direction D of the rack member 40. Specifically, when the rotary shaft 71a of the motor 71 rotates clockwise, the rack member 40 moves from the right side to the left side along the width direction D, and a counterclockwise rotational force is applied to the steering shaft 10. Conversely, when the rotary shaft 71a of the motor 71 rotates counterclockwise, the rack member 40 moves from left to right along the width direction D, and a clockwise rotation force is applied to the steering shaft 10.

[0059] The angle detection unit 73 has the same configuration as the angle detection unit 62 of the second embodiment. The control unit 74 has the same configuration as the control unit 63 of the second embodiment. The control unit 74 controls the rotation of the motor 71 based on the rotation direction of the steering shaft 10 detected by the angle detection unit 73.

[0060] FIG. 9 is a flowchart showing the processing of the control unit 74. The control unit 74 first acquires the rotation direction of the steering shaft 10 from the angle detection unit 73 (step S111). Next, the control unit 74 determines whether the rotation direction of the steering shaft 10 is counterclockwise (step S112). When the control unit 74 determines that the rotation direction of the steering shaft 10 is counterclockwise, it rotates the rotating shaft 71a of the motor 71 clockwise (step S113). This causes the rack member 40 to move from the right side to the left side, and a counterclockwise rotation force is applied to the steering shaft 10. When the control unit 74 determines that the rotation direction of the steering shaft 10 is clockwise, it rotates the rotating shaft 71a of the motor 71 counterclockwise (step S114). This causes the rack member 40 to move from the left side to the right side, and a clockwise rotation force is applied to the steering shaft 10. After executing the process of either step S113 or S114, the control unit 74 executes the above-mentioned step S111 again.

[0061] In the configuration of the steering assist device 30C of the third embodiment described above, when the rotation shaft 71a of the motor 71 rotates, the rotation-to-linear conversion unit 72 converts the rotational motion of the motor 71 into linear motion of the rack member 40 along the width direction D. As a result, the rack member 40 moves along the width direction D, and a rotational force about the steering shaft 10 is applied to the steering shaft 10. At this time, when the steering wheel 20 is operated counterclockwise and the angle detection unit 73 detects the counterclockwise rotation of the steering shaft 10, the rotation shaft 71a of the motor 71 rotates clockwise. As a result, the rack member 40 moves from right to left along the width direction D, and a counterclockwise rotational force is applied to the steering shaft 10. When the steering wheel 20 is operated clockwise and the angle detection unit 73 detects the clockwise rotation of the steering shaft 10, the rotation shaft 71a of the motor 71 rotates counterclockwise. As a result, the rack member 40 moves from left to right along the width direction D, and a clockwise rotational force is applied to the steering shaft 10. In this way, even without using hydraulic equipment, the rack member 40 can be easily moved along the width direction D. Even in this case, since there is no need to install a speed reduction mechanism with multiple gears, the configuration of the device can be simplified and the device can be made smaller. [Variations]

[0062] Although the first to third embodiments have been described above, one aspect of the present invention is not limited to these embodiments. The above embodiments and each configuration are not limited to the shapes described above, and various shapes can be applied. Some of the configurations in the above embodiments can be omitted as appropriate without departing from the gist of one aspect of the present invention. For example, the steering assist units 50A to 50C may not have the first piston 51 or the motor 71, and the rack member 40 may be moved along the width direction D by another mechanism.

[0063] The assist pedal 57 in the first and second embodiments does not have to be arranged so as to be movable along the vertical direction of the towing vehicle 1, but may be arranged so as to be movable along a direction inclined relative to the vertical direction of the towing vehicle 1.

[0064] The right assist pedal 57R in the first embodiment may be an assist pedal for turning right, and the left assist pedal 57L may be an assist pedal for turning left.

[0065] The angle detection units 62, 73 in the second and third embodiments do not have to be angle sensors, and the rotation angle and rotation direction may be calculated based on data acquired by other means. The rotation-to-linear conversion unit 72 does not have to have the pinion gear 75 and the rack gear 76, and may be configured with another mechanism. The towing vehicle 1 does not have to be a stand-on type, and may be a sit-down type towing vehicle. Even in this case, the effects of one aspect of the present invention can be achieved. [Explanation of symbols]

[0066] 1...towing vehicle, 10...steering shaft, 11a...side, 14...pinion gear, 20...steering, 30A, 30B, 30C...steering assist device, 40...rack member, 41...rack gear, 50A, 50B, 50C...steering assist unit, 51, 51R, 51L...first piston, 54, 54R, 54L...second piston, 56, 56R, 56L...oil reservoir, 57, 57R, 57L...assist pedal, 61...flow diverter valve, 62, 73...angle detection unit, 63, 74...control unit, 71...motor, 72...rotation-to-linear conversion unit, A...hydraulic oil, D...width direction (predetermined direction).

Claims

1. a steering shaft connected to the wheels of the towing vehicle and rotated by steering operation, the steering shaft having a pinion gear formed on its side; a rack member having a rack gear that meshes with the pinion gear and that extends along a predetermined direction that intersects with the axial direction of the steering shaft; a steering assist unit that applies a rotational force about the steering shaft to the steering shaft by moving the rack member along the predetermined direction.

2. The steering assist unit is two hydraulic first pistons connected to both ends of the rack member, one each; a hydraulic second piston that supplies hydraulic oil to the first piston to move the first piston along the predetermined direction; an oil reservoir disposed between the two first pistons and the second piston and configured to store the hydraulic oil; an assist pedal for moving the second piston; The steering assist device for a towing vehicle according to claim 1.

3. The number of the second pistons, the oil reservoirs, and the assist pedals is two. The steering assist device for a towing vehicle according to claim 2.

4. a flow dividing valve disposed between the oil reservoir and the two first pistons, which divides the hydraulic oil stored in the oil reservoir into the two first pistons; an angle detection unit that detects the rotation angle and rotation direction of the steering shaft; a control unit that switches the flow dividing direction of the flow dividing valve based on the rotation direction of the steering shaft detected by the angle detection unit, The steering assist device for a towing vehicle according to claim 2.

5. 3. The steering assist device for a towing vehicle according to claim 2, wherein the assist pedal is provided so as to be movable along the vertical direction of the towing vehicle.

6. a motor for moving the rack member in the predetermined direction; a rotation-to-linear conversion unit that converts the rotational motion of the motor into linear motion of the rack member along the predetermined direction; an angle detection unit that detects the rotation angle and rotation direction of the steering shaft; 2. The steering assist device for a towing vehicle according to claim 1, further comprising: a control unit that controls rotation of the motor based on the rotation direction of the steering shaft detected by the angle detection unit.

7. 2. The steering assist device for a towing vehicle according to claim 1, wherein the towing vehicle is a stand-on type towing vehicle.

Images