JP2014213615A - Steering device for work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems, for example, when a new steering device for automatic steering is developed, cost is required for development, engineering, and demonstration test, and discomfort occurs during steering operation in emergency and readiness is lacked.SOLUTION: An electrically-driven power steering mechanism (EPS) is applied. A torque signal outputted from a torque sensor 22 of the EPS and a signal inputted via a CANBUS 28 from an automatic steering system are formed into a pseudo torque signal, and is outputted to the EPS and ECU 25 selectively by a controller 24 for steering. When the torque signal outputted from the torque sensor 22 is equal to or more than a predetermined value, artificial operation is performed in prior.

Description

  The present invention relates to a steering device used for a work vehicle such as a tractor, and more particularly to a steering device that enables automatic steering.

  In general, in agricultural work vehicles such as tractors, straight traveling is required in operations such as tilling, sowing, standing and painting, but it is important to perform straight traveling accurately due to unevenness of the traveling surface and reaction of the work implement. , Skill is required, and the physical and mental burden on the operator is large.

  Conventionally, various steering devices capable of automatic steering such as straight traveling have been proposed. The steering device of Patent Document 1 connects a steering motor to a steering shaft, and when the traveling direction detection sensor detects that the vehicle body traveling direction has changed from the set reference traveling direction, the steering motor is driven to perform automatic steering, When the current value of the steering motor exceeds the set current value, it is determined that the steering handle has been artificially operated, and the steering motor is brought into a freely rotating state by the steering handle.

  In the steering device of Patent Document 2, a motor is provided on a handle post, and the driving force of the motor is transmitted to a steering shaft via a friction member. In the automatic mode, the motor is driven based on a signal from a straight-ahead support controller. .

  In the steering device of Patent Document 3, a forward / reverse rotation motor is disposed on a steering post, and the forward / reverse rotation motor is interlocked with a steering shaft via an electromagnetic clutch. When switching to the automatic mode by the switch, the electromagnetic clutch is connected, and the forward / reverse rotation motor is controlled to automatically follow the far target or the trace of the work by the camera, and when the automatic mode is switched to the manual mode, the electromagnetic clutch is disconnected. It is manually steered by the steering handle.

Japanese Patent No. 4328289 JP 2010-195252 A JP 2012-23997 A

  The above-mentioned Patent Documents 1, 2, and 3 all have an electric motor attached to an existing hydraulic power steering device. However, since this is a new automatic steering device using the electric motor, its development The design and demonstration tests require a great deal of cost. Patent Document 1 requires a running direction detection sensor such as a yaw sensor, and switches between automatic steering and artificial steering according to an operation current value of a steering (electric motor). Therefore, switching between automatic steering and artificial steering is not stable. There is a risk of delay in steering operation in an emergency. In Patent Document 2, the electric motor is rotated through the friction member during the artificial operation of the steering wheel, which causes a sense of incongruity such as a heavy steering operation in an emergency. Since the thing of patent document 3 switches automatic steering and artificial steering by an electromagnetic clutch, there exists a possibility that it may lack responsiveness to artificial operation of the steering wheel at the time of an emergency.

  Accordingly, an object of the present invention is to provide a steering device for a work vehicle that solves the above-described problems by applying an existing electric power steering mechanism.

The present invention can be switched between artificial steering for steering the steering wheel (2) by manual operation of the steering wheel (15) and automatic steering for steering the steering wheel (2) by a signal from the steering system (13). In the steering device (9),
Between the steering wheel (15) and the steering wheel (2), a torque sensor (22) for detecting a steering force of the steering wheel, an electric motor (21) for generating a force for steering the steering wheel, and the An electric power steering mechanism (EPS) (20) having a control unit (25) for controlling the electric motor;
A steering controller (24) for selecting and outputting the torque signal detected by the torque sensor (22) and the signal from the steering system (13) to the control unit (25) as a pseudo torque signal is provided. ,
The steering apparatus is characterized by the above.

  When a torque signal of a predetermined value or more from the torque sensor (22) is input to the control unit (25), the torque signal is given priority over the pseudo torque signal, and the steering wheel (15) is manually operated. The steered wheel (2) is steered.

  A hydraulic power steering mechanism (19) is interposed between the electric power steering mechanism (20) and the steering wheel (2).

  Switching means (S13) for switching whether the electric power steering mechanism functions or stops is provided.

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, it does not have any influence on the structure as described in a claim by this.

  According to the first aspect of the present invention, an existing electric power steering mechanism (EPS) having an electric motor, a torque motor, and a control unit can be applied to automatic steering of a work vehicle, and a torque signal from a torque sensor and It is only necessary to add a steering controller that selects and outputs a signal from the steering system as a pseudo torque signal to the EPS control unit (ECU), greatly reducing the time and cost of development, design, demonstration test, etc. In addition, it is possible to provide a steering apparatus capable of automatic steering with high reliability and accuracy.

  In addition, during manual steering, a light steering operation assisted by an electric power steering mechanism (EPS) is possible.

  According to the second aspect of the present invention, even during automatic steering, when the operator operates the steering wheel, switching to human operation is prioritized over automatic steering, so switching to the human operation is smooth. There is no sense of incongruity, and it can respond immediately in an emergency and improve safety.

  According to the third aspect of the present invention, in addition to the electric power steering mechanism (EPS), the hydraulic power steering mechanism is provided. For example, the hydraulic power steering mechanism originally provided in a work vehicle such as a tractor is provided. It can be used as it is, and the existing EPS with insufficient assisting force can be applied to a work vehicle such as a tractor, and the steering wheel is steered by a hydraulic power steering mechanism using the EPS steering as a steering signal for automatic steering. be able to.

  According to the fourth aspect of the present invention, it is possible to switch between the mode in which the EPS is functioned and the mode in which it is stopped in the manual steering. Thus, for example, an operation similar to the conventional one using a hydraulic power steering mechanism can be performed, and can be selectively used according to the preference of the operator.

  Further, by stopping the EPS, power consumption can be saved, and even when the hydraulic power steering mechanism cannot be used due to an engine stall or the like, the EPS can function to assist the steering force.

The schematic side view which shows the tractor as a work vehicle which can apply this invention. The side view which shows the steering device. The figure which shows the circuit. The flowchart. The embodiment which changed partially is shown, (A) is a side view which shows a cabin, (B) is a side view which shows a steering device. The embodiment which changed partially is shown, (A) is a side view which shows a cabin, (B) is a side view which shows a steering device. The steering apparatus by embodiment changed partially is shown, (A) is a front view, (B) is a side view. FIG. 2 shows a partially modified embodiment, (A) is a side view showing a steering device, and (B) is an enlarged view showing an attachment portion of the steering wheel.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the tractor 1 that is a work vehicle has a body 5 that is supported by front wheels (steering wheels) 2 and a rear wheel 3, and the front portion of the body 5 is covered with a bonnet 6. An engine is disposed, and a cabin 7 is disposed at the rear thereof, and a work machine can be mounted behind the machine body 5. In the cabin 7, a steering device 9 is disposed at the front, and a driver's seat 8 (see FIG. 2) is disposed at the rear.

  In the body 5, a camera 10, an image processing board 11, an HMI (Human Machine Interface) 12, and a steering system 13 are arranged facing forward. The camera 10 can shoot a far target installed at a farm field end in the machine traveling direction or a work trace at the previous work. The image processing board 11 performs feature analysis from the video obtained from the camera 10 to obtain information necessary for straight-ahead steering, determines a steering direction, and transmits a steering signal to the steering system 13. The HMI 12 is an interface between a machine (the entire image processing system) and a driver, and displays the status of the image processing system and inputs to the system. The steering system 13 steers an electric power steering mechanism (EPS) described later by a steering signal sent from the image processing board 11 or the like.

  As shown in FIG. 2, the steering device 9 includes a steering wheel 15, a steering shaft 16, a universal link 17, and a hydraulic power steering mechanism (orbit roll) 19, and further an electric power steering mechanism (Electronic Power Steer). ; Hereinafter referred to as EPS) 20 is attached. The EPS 20 has an assist (electric) motor 21, and the power of the assist motor 21 is transmitted to the steering shaft 16 through a gear transmission such as a worm or a power transmission device such as a chain. A torsion bar is interposed in the steering shaft, and the torque sensor 22 detects the steering force, the road surface reaction force, and the steering direction of the steering wheel 15 based on the torsion amount of the torsion bar.

  The torque sensor 22 electrically detects the phase shift between the upper part and the lower part due to torsion of the torsion bar (increase / decrease in magnetic flux density) (torque sensor voltage main, torque sensor voltage sub). Control unit) 25. The EPS / ECU 25 receives not only signals from the torque sensor 22 but also other signals such as the steering angle and vehicle speed of the front wheels 2 that are the steering wheels, and further receives external signals from the steering system 13. . The EPS / ECU 25 processes various signals and outputs them to the assist motor 21. The assist motor 21 is operated with a natural feeling so that the steering force of the manual operation by the steering wheel 15 is reduced. Assist driving is performed as described above, and processing is performed by the image processing board 11 so as to face the far target or to follow the trace of the existing work.

  As shown in FIG. 3, in addition to the EPS / ECU 25, a steering controller 24 including a multiplexer is provided. The steering controller 24 outputs a signal from the torque sensor 22 directly to the EPS / ECU 25. Then, it is selected whether to output to the EPS • ECU via a signal processed by a microcomputer 26 in the steering controller 24. A signal from the steering system 13 is input to the microcomputer 26 via a CAN BUS 28 and a CAN transceiver 29, and the torque sensor voltage (main, sub) from the torque sensor 22 and the steering angle of the front wheels 2 are detected. A signal (front wheel angle) from the potentiometer 30 is input. Further, the microcomputer 26 outputs a signal for switching between a direct input of a torque sensor to the EPS / ECU 25 and a straight steering signal input from the microcomputer 26, and an ON / OFF switching signal of the EPS 20 is output. The EPS / ECU 25 and the steering controller (multiplexer) 24 communicate with a power source, and the potentiometer 30 communicates with an analog current. In addition, an automatic switch for selecting whether or not to operate an automatic mode for performing straight-ahead steering based on the steering system 13, a changeover switch for switching an automatic control pattern, and an EPS20 function when an operator manually operates the steering wheel. And a switch for switching whether to directly apply an artificial operation force without functioning.

  In other words, the electric power steering mechanism 20 that is commercially available for automobiles or buggies can be applied, and is attached to the steering device 9 having the existing hydraulic power steering mechanism 19. At this time, a steering controller 24 composed of a multiplexer having a microcomputer 26 is interposed in the input circuit from the torque sensor 22 to the EPS / ECU 25 to assist the artificial steering of the steering wheel 15 based on the signal from the input torque sensor 22. The normal mode and the automatic mode based on the straight steering signal (pseudo torque signal) from the microcomputer 26 based on the steering system 13 are switched.

  Next, the operation based on the above configuration will be described with reference to FIG. First, when the start of the tractor 1 is started, the steering system 13 is initialized (S1). The tractor 1 is in a travelable state, and the forward angle from the potentiometer 30 and the voltage (main, sub) from the torque sensor 22 are converted into digital and analog by the D / A circuit 27, and the signal from the microcomputer 26 is converted. Smoothed (S2). It is determined whether or not there is a manual input (artificial steering) from the steering wheel 15 (S3). When there is no manual input, that is, when the input from the EPS torque sensor 22 is less than a predetermined value, data from the CAN BUS 28, for example, whether automatic control is ON or OFF, the rotational direction and rotational speed of the aircraft based on the steering system 13 are acquired. (S4). It is determined whether automatic control is ON or OFF (S5). If ON, the steering controller (multiplexer) 24 is switched to the microcomputer 26 side (S6).

  A control pattern by the pattern changeover switch is determined (S7). In the case of torque designation control (S8), a pseudo torque signal such as a straight steering signal from the CAN BUS 28 is output to the EPS / ECU 25 as it is (S9). When the control pattern is angle designation control (S10), for example, an instruction angle of a steering angle for straight-ahead steering is received from the CAN BUS 28, and an actual angle of the front wheel is received from the potentiometer 30, and the difference between these two angles is received. Accordingly, the output torque is determined, and the output torque is output to the EPS • ECU 25 as a pseudo torque signal (S9). Based on the pseudo torque signal of the EPS / ECU 25, the assist motor 21 is driven, the EPS 20 is operated, and is automatically controlled through the universal link 17 and the hydraulic power steering mechanism 19, for example, so that the machine body goes straight.

  On the other hand, when the automatic switch is OFF in step S5 or in the automatic control described above, the operator manually operates the steering wheel 15 by, for example, emergency avoidance or the like. Is input, the steering controller (multiplexer) 24 is switched to the EPS torque sensor side (S11). At this time, the data in step S4 is set to neutral in the rotational direction and rotational speed 0 so as not to suddenly steer when returning to automatic control (S12).

  Then, it is determined whether the assist mode at the time of artificial steering by the operation of the steering wheel 15 is the combined mode in which the EPS 20 functions or the single mode in which the EPS does not function (S13). In the combined mode, the assist motor 21 is driven by a sensor signal (voltage main, sub) from the torque sensor 22, and the aircraft traveling direction is operated by a light steering force. In the case of the single mode, an operation stop signal is output to the EPS / ECU 25 (S14), and the EPS 20 is stopped. Even in this state, the force for manipulating by the steering wheel 15 acts on the hydraulic power steering mechanism 19 via the steering shaft 16 and the universal link 17, and the front wheel 2 is steered.

  Therefore, existing EPS 20, which has been proven and reliable in buggy vehicles, can be used as it is with some modifications to add the steering controller 24, and a new dedicated automatic steering drive device has been developed and designed. Thus, it is possible to obtain a highly reliable and highly accurate automatic steering drive device. In the above existing EPS, the assist force is insufficient and it is difficult to apply it to a tractor alone. However, by connecting to the existing hydraulic power steering mechanism (orbit roll) 19, the EPS 20 is connected like a pilot signal. The above-mentioned orbit roll is operated by the automatic control of the EPS, so that even a tractor or the like having a large ground resistance can be automatically controlled.

  When the steering operation is performed artificially, the steering operation can be performed with priority over the automatic steering, and the emergency response can be immediately and without a sense of incongruity, and the safety and feeling can be improved.

  At the time of artificial steering operation, the electric power steering mechanism (EPS) 20 can be selected between a function mode (combination mode) and a stop mode (single mode), and the steering feeling is changed according to the driver's preference. be able to. In the combined mode, the steering force is assisted by the EPS 20, and the steering operation can be performed lightly. In the single mode, the steering operation similar to that of an ordinary tractor can be performed by the hydraulic power steering mechanism 19 without excessively reducing the steering operation.

  In the single mode in which the EPS 20 does not function, the EPS can be stopped to reduce power consumption, and even when the hydraulic power steering mechanism cannot be used at the time of stall, the steering force can be assisted by the EPS 20.

  Next, a partially modified embodiment will be described. In FIG. 5, the EPS 20 and the hydraulic power steering mechanism (orbit roll) 19 are arranged adjacent to each other on the same axis. Thereby, it can comprise with the minimum number of parts, and can be simplified. Further, the EPS 20 and the orbit roll 19 can be unitized to form a steering assembly, which can be used for other models.

  If the assist (electric) motor 21 of the EPS 20 protrudes toward the driver's seat, the arrangement structure is simple, but the operator's foot space is limited. FIG. 6 shows the EPS 20 assist motor 21 oriented in a direction other than the driver's seat side, for example, the hood direction (front direction), and does not impair the foot space.

  FIG. 7 shows an embodiment in which the horizontal axis 40 is arranged on a plane orthogonal to the steering shaft 16 and the EPS 20 and the orbit roll 19 are arranged at both ends on the horizontal axis 40. The horizontal shaft 40 is interlocked with the steering shaft 16 and the bevel gear 41 at the center thereof, and the assist motor 21 of the EPS 20 is disposed downward with respect to the EPS 20. Thereby, the EPS motor 21 and the orbit roll 19 are disposed sideways in front of the driver's seat and the EPS motor 21 is directed downward, so that the operator's feet can be widened.

  FIG. 8 shows the attachment of the steering wheel 15. A spline and a plurality of detent grooves 45 are formed in the shaft 42 of the steering wheel 15, and a cylindrical boss 46 is fixed to the upper portion of the steering shaft 16 of the EPS 20. A detent 47 is disposed on the boss 46, and the steering wheel 15 can be moved in the vertical direction, and the detent 47 is engaged with one of the plurality of detent grooves 45 and positioned. The wheel shaft 42 and the boss 46 rotate together by a spline. Thereby, the EPS 20 is fixedly attached to the tractor body, but the steering wheel 15 can be adjusted and moved in the axial direction, becomes telescopic steering, and can take an appropriate driving posture according to the physique of the driver.

  Note that the EPS 20 including the assist motor 21 may be disposed in the steering column cover so as not to be exposed to mud or water. Further, by disposing the EPS 20 above the orbit roll 19, even if oil leaks from the orbit roll 19, the oil is not applied to the EPS 20. As shown in FIG. 2, the orbit roll 19 can be connected to the steering shaft 16 via the universal link 17, and the orbit roll 19 that may generate noise can be disposed outside the cabin 7. Thereby, the noise in a cabin can be reduced.

1 Work vehicle (tractor)
2 Steering wheel (front wheel)
5 Airframe 9 Steering device 15 Steering wheel 16 Steering shaft 19 Hydraulic power steering mechanism (orbit roll)
20 Electric power steering mechanism (EPS)
21 Electric (Assist) Motor 22 Torque Sensor 24 Steering Controller (Multiplexer)
25 Control unit (EPS / ECU)
26 Microcomputer

Claims (4)

In a steering device that can be switched between artificial steering for steering the steering wheel by manual operation of the steering wheel and automatic steering for steering the steering wheel by a signal from the steering system,
An electric motor having a torque sensor for detecting a steering force of the steering wheel, an electric motor for generating a force for steering the steering wheel, and a control unit for controlling the electric motor between the steering wheel and the steering wheel. Through the power steering mechanism,
A steering controller that selects and outputs the torque signal detected by the torque sensor and the signal from the steering system as a pseudo torque signal to the control unit;
A steering device characterized by that. When a torque signal of a predetermined value or more is input to the control unit, the steering wheel is steered by an artificial operation of the steering wheel in preference to the pseudo torque signal.
The steering apparatus according to claim 1. A hydraulic power steering mechanism is interposed between the electric power steering mechanism and the steering wheel.
The steering apparatus according to claim 1 or 2. Comprising a switching means for switching the electric power steering mechanism to function or stop.
The steering device according to any one of claims 1 to 3.

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