Vehicle steering system

Abstract

To provide a steering motor for use in automatic driving which is realized by mounting an electric motor in a steering column without impairing the features of a cab suspension and an adjustable steering column particular to a middle or large-size truck.SOLUTION: An underpart of a steering shaft is formed with a spline shaft. A sleeve spline of a motor sub-assembly is engaged with the underpart so that the sleeve spline can slide, and a pivot point enabling turning is formed in the motor sub-assembly. The resultant assemblage is attached to a cab rotatably. Thus, a steering column and the motor sub-assembly can turn about the pivot point. This makes it possible to perform vertical position adjustment through spline sliding and front-back position adjustment through turning adjustment with a pivot as a fulcrum.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a vehicle steering device equipped with a steering motor for automatic driving. [Background technology]

[0002] An autonomous vehicle is equipped with a "steering device for autonomous driving" in addition to the steering device used by a human driver.

[0003] Figure 1 shows an example of the steering layout of a large truck or bus to illustrate what kind of "steering device for autonomous driving" should be installed, where, and how. Large trucks and buses are equipped with adjustable column steering, which allows the steering wheel position to be adjusted 40 mm up, 28 mm forward, and 60 mm backward. There is a lever to lock or loosen the steering wheel adjustment position, a universal joint whose intersection angle changes in response to changes in the steering wheel position, and a spline shaft that expands and contracts. The steering motor for autonomous driving may be incorporated into the steering column, into the input shaft of the gearbox, or into an electromagnetic valve that drives the power steering valve.

[0004] The classification of where the electric motor is installed in electric power steering, which is widespread mainly in passenger cars, is shown in Fig. 2. There are three types: the column type, in which the electric motor is installed in the steering column, the pinion type, in which the electric motor is installed in the input part of the steering gear, and the rack type, in which the electric motor is installed in the output part of the gear.

[0005] In the case of electric power steering, adding automatic driving control to the electric motor makes it a steering system for automatic driving. However, it is difficult to apply this to large vehicles with steering axle loads exceeding 4,500 kg and reaching 5,000 kg to 6,500 kg or more. There are two ways to apply this to large vehicles: incorporating a column-type or pinion-type motor unit into the input section of the power steering, or driving the power steering directional control valve (control valve) with an electromagnetic hydraulic valve.

[0006] Fig. 1 shows an example of a research paper on "power steering with cut-off delay correction," in which a solenoid valve is used to add corrective hydraulic pressure to the power steering directional control valve. However, there are significant challenges that must be overcome to enable rotation angle control that meets the needs of autonomous driving.

[0007] Power steering is designed to respond to steering axle loads by adjusting the power piston diameter and the set hydraulic pressure (relief hydraulic pressure) to achieve a steering load that allows driving, so there is a possibility that the electric motor incorporated in the input section of the power steering can be designed to be common to medium to large trucks. Also, in the case of medium to large trucks equipped with a cab suspension, cab tilt mechanism, and adjustable steering column mechanism, it is necessary to equip the electric motor without impairing the functions. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2014-180103 A [Patent Document 2] JP 2001-301651 A [Non-patent literature]

[0009] [Non-Patent Document 1] Fujio Momiyama: History of Truck Chassis Body Technology, Automotive Technology, Vol. 64, No. 7, 2010, p. 27-p. 33. [Non-Patent Document 2] Hideyuki Takeda: Electric Power Steering, Automotive Technology, Vol. 64, No. 7, 2010. p. 58-p. 62. [Non-Patent Document 3] Fujio Momiyama et al., “Electro-Hydraulic Feedforward Control Power Steering System for Trucks and Buses”, SAE paper No. 892519. Summary of the Invention [Problem to be solved by the invention]

[0010] To provide a steering motor for automatic driving by equipping a steering column with an electric motor without impairing the functions of the cab suspension and the adjustable steering column.

[0011] Figure 2 shows an explanatory diagram of the cab suspension and adjustable steering. The cab (cabin) (3) is mounted on the frame (1) via the cab suspension (2). The position of the cab is determined by the cab hinge bracket (4) and the link lever (5). The cab (3) is structured so that the cab can be tilted (6) using the cab hinge bracket (4) as a fulcrum to improve maintenance.

[0012] The steering is laid out as follows: The integral power steering gear (7) is attached to the frame (1). Above it is the universal joint (B) (8). This part is the input shaft side of the power steering gear (7). The cab (3) is equipped with an adjustable steering column (9), below which is the universal joint (A) (10). The universal joint (A) (10) is freely rotatably connected to the universal joint (B) (8) via a telescopic spline shaft (11).

[0013] When the cab (3) is tilted (6), the cab (3) rotates together with the link lever (5) around the cab hinge bracket (4), and the steering side rotates around the universal joint (B) (8). The fulcrum of the cab hinge bracket (4) and the fulcrum of the universal joint (B) (8) are not in the same position, and the supporting load of the link lever (5) changes with the change in the cab tilt angle, causing the lever angle to sink and rise as it rotates. Therefore, a telescopic spline shaft (11) is provided between the universal joint (B) (8) and the universal joint (A) (10) on the steering side to absorb the positional deviation. At the same time, it is designed to absorb the stroke change of the cab suspension.

[0014] Since the cab is mounted on the frame via springs, the cab becomes unstable due to changes in acceleration during acceleration / deceleration and turning. To stabilize this, the cab is supported as shown in Figure 5, and this function has been patented in Patent Document 1.

[0015] The steering layout in Figure 3 is incorporated into the cab suspension (2) and adjustable steering column (9) in Figure 2. FIG. 4 is an explanatory diagram of classification of motor mounting positions of electric power steering, and the mounting positions are classified into column type, pinion type, and rack type. Fig. 5 is an explanatory diagram of electric power steering from Patent Document 1, and Fig. 6 is an explanatory diagram of cab suspension from Patent Document 2. If you try to install a steering motor as shown in Fig. 5 following the column type shown in Fig. 4, the adjustable steering function will not be established. [Means for solving the problem]

[0016] In order to solve the above problems, the present invention provides a "steering motor assembly" by arranging a worm gear on the output shaft of a steering motor, and providing a spline sleeve (female spline) at the center of a worm wheel gear that meshes with the worm gear to form an integral part with the steering motor, and further providing a spline (male spline) on the steering shaft of the "steering column assembly" to fit axially with the female spline on the motor side, so that the spline fit between the steering shaft and the worm wheel gear slides axially, making it possible to adjust the steering wheel in the up and down directions.

[0017] In addition, in the present invention, a tilt pivot is provided on the upper part of the "steering motor assembly." The "steering column assembly" is attached with the male spline of the "steering column assembly" fitted into the female spline of the "steering motor assembly" so as to be rotatable around this pivot.

[0018] A steering column bracket with a vertically long hole is welded to the top of the steering column. The adjustable steering pin and lever are passed through the vertically long hole and the horizontally long hole in the steering bracket that protrudes from the instrument panel side of the cab, and then fastened in place.

[0019] The vertical position can be adjusted along the vertical slots, and the tilt position can be adjusted along the horizontal slots and around the tilt pivot. The position adjustment diagram is shown in Figure 9. This layout makes it possible to install the steering motor without interfering with the function of the adjustable steering column.

[0020] Furthermore, the shaft of the steering motor is made into a sleeve spline (female spline), and a spline (male spline) is provided on the steering shaft, which fits axially with the female spline on the motor side. The spline fit between the steering shaft and steering motor slides axially, allowing the steering wheel to be adjusted up and down. The position adjustment diagram is shown in Figure 9. This layout makes it possible to install the steering motor without interfering with the function of the adjustable steering column. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a model explanatory diagram of a document in which an electronic hydraulic valve is added to a directional control valve of a hydraulic power steering to improve steering response. [Diagram 2] FIG. 2 is an explanatory diagram of the relationship between the cab suspension and the adjustable steering column. [Diagram 3] FIG. 2 is an explanatory diagram of a steering layout of a truck bus. [Figure 4] A diagram showing the classification of motor mounting positions for electric power steering [Diagram 5] FIG. 1 is an explanatory diagram of the electric power steering disclosed in Patent Document 1. [Figure 6] FIG. 1 is an explanatory diagram of a cab suspension disclosed in Patent Document 2. [Figure 7] FIG. 1 is an explanatory diagram of a steering layout in which an electric motor is attached without interfering with the function of an adjustable steering column (in the case of a worm gear steering motor). [Figure 8] 4 is an explanatory diagram of a cross section of a motor and a tilt lock mechanism. FIG. [Figure 9] 4 is an explanatory diagram of a tilt mechanism and a slide mechanism for adjusting the handle position. FIG. [Figure 10] FIG. 1 is an explanatory diagram of a steering layout in which an electric motor is attached without interfering with the function of an adjustable steering column (in the case of a sleeve spline steering motor). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows the steering layout of a large truck equipped with a cab suspension. It is quoted from Non-Patent Document 1. The set relief pressure is 150 kg / cm 2 It uses high-pressure integral power steering that reaches The diameter of the power cylinder corresponds to the size of the steering axle load, and the power ratio is set so that the steering wheel can be operated as lightly as in a passenger car.

[0023] The steering column can be adjusted 40mm up, 28mm forward, and 60mm backward. Lowering the lever on the left side of the column locks it in place, and raising it loosens it. The front-to-back position can be adjusted by tilting the column using the lower pivot bolt as a fulcrum, and the steering column is supported at the lower pivot so that it can slide up and down, allowing the vertical position to be adjusted.

[0024] A spline shaft is attached to the bottom of the steering column via a universal joint, and is slidably fitted with a sleeve spline from the power steering side. This adjustable steering adjustment margin and positional changes between the frame side and the cab side due to the cab suspension are absorbed by the sliding of the spline in this part.

[0025] Figure 4 shows the classification of the mounting position of the electric motor of electric power steering that is widespread in passenger cars. It is quoted from Non-Patent Document 2. It is classified into a column type in which the motor is attached to the steering column, a pinion type in which the motor is attached to the pinion part of the rack-and-pinion steering, and a rack type in which the motor is attached to the rack part of the rack-and-pinion steering.

[0026] The column and pinion types have the motor attached to the input side of the steering wheel, while the rack type is attached to the output side. If it is attached to the input side, a motor that can handle the load reduced through the gear ratio is sufficient, but if it is attached to the output side, a motor that can handle the load corresponding to the steering shaft load is required. Installing it on the input side has the advantage that the same motor can be used for vehicles with different steering shaft loads.

[0027] Figure 1 shows an example of correcting the movement of a hydraulic power steering control valve by applying corrective hydraulic pressure to the control valve via a solenoid valve. This is quoted from Non-Patent Document 3. It is possible to apply this example to autonomous driving by developing it further and moving the control valve with corrective hydraulic pressure from a solenoid valve, but there are some challenges to overcome.

[0028] From Figures 1 and 3, it is determined that the steering device for automatic driving should be an electric motor, and that the best place to install it is the steering column. When installing it on the steering column, it needs to be installed in a way that does not interfere with the function of the adjustable steering column and cab suspension in Figure 3.

[0029] Figure 2 is an explanatory diagram of the relationship between the cab suspension and the adjustable steering column. It explains the technical points that must be considered when attaching an electric motor for autonomous driving to the steering column.

[0030] The cab (3) is mounted on the frame (1) via the cab suspension (2). The position of the cab is determined by the cab hinge bracket (4) and the link lever (5). The cab (3) is structured so that the cab can be tilted (6) using the cab hinge bracket (4) as a fulcrum to improve maintenance.

[0031] The steering is laid out as follows: The integral power steering gear (7) is attached to the frame (1). Above it is the universal joint (B) (8). This part is the input shaft side of the power steering gear (7). The cab (3) is equipped with an adjustable steering column (9), below which is the universal joint (A) (10). The universal joint (A) (10) is freely rotatably connected to the universal joint (B) (8) via a telescopic spline shaft (11).

[0032] When the cab (3) is tilted (6), the cab (3) rotates around the cab hinge bracket (4) as a fulcrum, and the steering side rotates around the universal joint (B) (8) as a fulcrum. Since the fulcrum of the cab hinge bracket (4) and that of the universal joint (B) (8) are not in the same position, a telescopic spline shaft (11) is provided between the universal joint (B) (8) and the universal joint (A) (10) on the steering side to absorb the positional deviation. At the same time, the positional relationship between the universal joint (A) and the universal joint (B) is determined so that the stroke change of the cab suspension can be absorbed and the change in the spline shaft sliding length caused by the deviation between the tilt fulcrum of the cab and the tilt fulcrum of the steering column during the cab tilt, and the change in the spline sliding length caused by the change in the deflection of the cab suspension during the cab tilt state can be absorbed.

[0033] Figure 5 shows a column-type electric power steering system from Patent Document 1. The worm gear wheel of the steering shaft is fixed and meshed with the worm gear of the electric motor. If this system were to be installed in the steering layout of Figures 1 and 4 as shown above, the function of the adjustable steering column would be lost.

[0034] Fig. 6 is an explanation of the cab suspension in Patent Document 2. The cab is placed on top of an air spring placed on a frame, which causes nodding, or rocking, of the cab back and forth, and rolling, or rocking, of the cab. The arrangement of the link lever 4 and air spring 8 to suppress nodding, and the arrangement of the damper 7 to suppress rolling, have been patented.

[0035] Figure 7 is an explanatory diagram of a steering layout in which an electric motor is installed without interfering with the function of an adjustable steering column. The steering wheel (1) and steering shaft (2) are connected in a general structure in which they are fitted with a taper and straight serration and fixed with a nut. Two bearings (4) are secured to the shaft with a snap ring (5), and the steering shaft is housed in the steering column (3).

[0036] A steering column bracket (13) with upper and lower long holes for adjusting the vertical position is welded to the steering column (3). The bracket (13) is fixed to the dashboard (15) by an adjustable steering pin (16) in the front and rear long holes opened in the steering bracket (14), but the fixing position can be adjusted by the upper and lower long holes on the column bracket side and the front and rear long holes on the steering bracket side.

[0037] The lower part of the steering shaft is a splined shaft (6), on which the electric motor subassembly consisting of the electric motor (8), worm gear (18), worm wheel gear (7), and motor housing (9) is slidably fitted by a sleeve spline that passes through the worm wheel gear (7). This sliding allows the vertical position of the steering wheel to be adjusted (Vs). The motor housing (9) is rotatably attached to the steering tilt pivot (17), allowing the position to be adjusted in the angular direction (Ta).

[0038] The vertical long holes in the steering column bracket (13) are overlapped with the front-rear long holes in the steering bracket (14), and an adjustable steering pin and lever are passed through them and screwed down, allowing the position to be adjusted up and down and fore and aft and then fixed in place.

[0039] Figure 8 explains the cross section of the motor, the cross section of the pivot bolt, and the tilt lock. The motor (8) is connected to a worm gear (18), which meshes with the worm gear wheel gear (7), and the rotation from the motor (8) is transmitted to the spline shaft (6) which is spline-fitted to the center of the worm gear wheel gear (7).

[0040] Viewed from the arrow B in FIG. 7 (right side in FIG. 8) shows the state in which the steering column bracket (13) is placed in the steering bracket (14) and then tightened and fixed with the adjustable steering pin and lever.

[0041] Figure 9 explains the operation of the tilt mechanism and slide function for adjusting the handle position. The figure on the left shows the neutral state, the figure in the middle shows the up and down sliding when tilted backward, and the figure on the right shows the up and down sliding when tilted forward.

[0042] FIG. 10 shows a structure in which the rotating shaft of the electric motor (steering motor) body (8) is a sleeve spline (7) that does not use a worm gear, instead being configured to be coaxially fitted to the spline shaft (6) on the steering shaft (2) side, from the worm gear type electric motor (steering motor) in FIG. 7, thereby enabling vertical adjustment (telescopic adjustment) of the steering wheel. [Explanation of symbols]

[0043] (1)…Steering wheel, (2) Steering shaft, (3)…Steering column, (4) Bearings, (5)…Snap ring, (6) Spline shaft, (7)…Worm wheel gear, (8) Electric motor, (9) Motor housing, (13)…Steering column bracket, (14)…Steering bracket, (15)…Dashboard, (16)…Adjustable steering pin, (17)…Steering tilt pivot, (18)…Worm gear.

Claims

1. An adjustable steering column device that can adjust the position of the steering wheel in the up-down and front-to-back directions, in which the lower part of the steering shaft is constructed of a spline shaft, into which the sleeve spline of the worm wheel gear of the motor subassembly is slidably fitted, and the motor subassembly is provided with a rotatable pivot point and rotatably attached to the cab side, thereby allowing the steering column and motor subassembly to rotate around this fulcrum, thereby enabling up-down position adjustment by spline sliding and front-to-rear position adjustment by rotational adjustment around the pivot part as a fulcrum.

2. An adjustable steering column device that can adjust the position of the steering wheel in the up-down and front-to-back directions, in which the lower part of the steering shaft is constructed of a spline shaft, into which the sleeve spline of the motor subassembly is slidably fitted, and the motor subassembly is provided with a rotatable pivot point and rotatably attached to the cab side, thereby allowing the steering column and motor subassembly to rotate around this fulcrum, thereby enabling up-down position adjustment by spline sliding and front-to-rear position adjustment by rotational adjustment around the pivot part as a fulcrum.

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