JP3731282B2 - Steering control device for work vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an agricultural work vehicle for a tractor or a rice transplanter, and a work vehicle for transportation or construction such as a forklift or a bull tosa, and in particular, the operation amount of a steering wheel can be changed with respect to the operation amount of a steering operation unit It relates to what has a steering device.
[0002]
[Prior art and problems]
Conventionally, some work vehicles have a steering device that can change the operation amount of the steering wheel with respect to the operation amount of the steering operation unit in order to easily perform turning and steering during work. For example, Japanese Patent Application Laid-Open No. 8-26126 discloses a turning device for a mobile agricultural machine that increases the turning angle of the front wheel with respect to the steering amount of the steering handle when turning on a farm field.
[0003]
The turning device disclosed in the above publication includes a steering unit that discharges pressure oil from a hydraulic pump in accordance with the operation direction of the steering handle, along the oil inflow path to the power steering cylinder that steers the front wheel of the vehicle body. A first path that is supplied via the hydraulic pump and a second path that is supplied directly from the hydraulic pump to the cylinder without going through the steering unit. Is selected as an alternative set. The switching control valve is configured to switch the inflow path from the first circuit to the second circuit when the front wheel turning angle exceeds a certain angle, and the front wheel turning angle amount relative to the steering wheel steering amount is A major change.
[0004]
However, in the configuration of the hydraulic circuit of the turning device, there is a risk that the turning control valve may not return when the turning control is activated or in a state where the switching control valve is switched due to some accident. There is a problem in that the vehicle cannot be steered in the direction desired by the operator because it is not transmitted.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has taken the following technical means.
That is, in a work vehicle having a steering device (3) capable of changing the operation amount of the steering wheel (2) with respect to the operation amount of the steering operation unit (1), the pressure oil sent from the hydraulic pump (8) is discharged. The steering unit (4) that flows out the pressure oil according to the operation direction of the steering operation section (1) in order from the circuit upper side, and a part of the pressure oil that flows out from the steering unit (4) The steering wheel (2) is operated through a switching control valve (6) capable of adjusting the flow rate of the oil by switching to a state where the oil is branched to another circuit (5) or a state where all of the same pressure oil is communicated. The hydraulic actuator (7) is configured to feed to the
The vehicle has an engine rotation sensor (48) for detecting the output rotation speed of the engine (12), a shift switch (31) for detecting a shift position for traveling, and a steering angle of the steering wheel (2). A steering wheel turning angle sensor (22) to detect,
The sensor detects a state in which the engine speed is equal to or higher than a predetermined value and the traveling shift position is set to a predetermined low speed position, and further, the steering wheel (2) is operated to be equal to or higher than a predetermined value near neutral. When operated at a speed, a control unit (21) is provided that switches the switching control valve (6) to greatly change the operation amount of the steering wheel (2) relative to the operation amount of the steering operation unit (1). A steering control device for a work vehicle is provided.
[0006]
[Effects of the invention]
In the steering control device for a work vehicle configured as described above, the steering unit 4 and the switching control valve 6 are provided in series in the hydraulic circuit, and the switching control valve 6 normally has a part of the pressure oil. the smaller the operation amount of the steering wheel 2 by the hydraulic actuator 7 as the state to branch to another circuit 5, the steep turn or the like of the steering wheel 2 by the hydraulic actuator 7 as a state of communicating all of the hydraulic fluid Since the operation amount can be greatly changed, the labor involved in the steering operation can be reduced, and even if the switching control valve 6 breaks down, the operator's steering operation is always sent to the hydraulic actuator 7. Since transmission is possible, the work vehicle can be steered safely.
In particular, in this steering control device for a work vehicle, since the pressure oil flowing into the steering unit 4 is constant, the oil pressure for assisting the steering operation force of the operator is constant regardless of the state of the switching control valve 6. Thus, the operability of the steering operation unit 1 is good.
Further, the steering control device for the work vehicle is configured to be operable when a state in which the engine speed is equal to or greater than a certain value and a state in which the traveling shift position is set to a predetermined low speed position is detected, that is, the vehicle Since the operation of the control is restrained when traveling on the road, the safety of the vehicle is good as described above.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an agricultural tractor (hereinafter referred to as a tractor 10) which is a work vehicle will be described as an embodiment of the present invention.
The tractor 10 appropriately changes the rotational power of the engine 12 provided in the bonnet 11 at the front of the machine body by a transmission (main transmission 14 and auxiliary transmission 15) in the transmission case 13 provided behind the engine 12. The power is transmitted to the front wheels 2, 2 or the front and rear wheels 2, 2, 16, 16.
[0008]
A handle post 17 is provided at the rear of the bonnet 11, an accelerator lever 18 is provided on the side of the bonnet 11, and a steering handle 1, which is a steering operation unit, protrudes from an upper portion of the post 17. Then, the front wheels 2 and 2 are steered by a rotational operation of the steering handle 1 via a power steering device 3 which is a steering device described later. Further, below the handle post 17, brake pedals 19, 19 for braking the left and right rear wheels 16, 16 are provided. Brake sensors 20 as means for detecting the amount of depression are provided at the rotation bases of the left and right brake pedals 19, and the depression angle is detected to the controller 21 which is a controller provided below the cockpit 25. It is the structure which transmits a signal.
[0009]
The vicinity of the pilot seat 25 of the tractor 10 will be described. At the side of the pilot seat 25, a control on / off switch 26 for turning on and off the turning control for changing the operation amount of the front wheels 1 and 1 at the time of turning, and traveling A shift lever 27 for operation and a position lever 19 for changing the height of the work implement 28 are provided. In addition, a PTO on / off switch 30 is provided for selecting whether the rotation of the PTO shaft 34 at the rear of the vehicle body is forward or reverse or stop. A shift position switch 31 is provided at the rotation base of the shift lever 27, and is turned on when the lever 27 is shifted to a high speed position. Further, a potentiometer 32 for detecting the operation angle is provided at the rotation base of the position lever 19, and this detection signal is transmitted to the controller 21 together with the shift switch 31.
[0010]
The configuration of the rear part of the tractor 10 will be described. A cylinder case 35 is provided at the rear upper part of the mission case 13. The cylinder case 35 has a built-in hydraulic cylinder 36 for raising and lowering the working machine, and lift arms 37 and 37 supported on the left and right of the case 35 are vertically rotated by the expansion and contraction of the piston of the hydraulic cylinder 36. A lift arm angle sensor 38 is provided at the rotation base of the lift arm 37 on one side to indirectly detect the lift position of the work implement 28. Thus, the piston of the hydraulic cylinder 36 is extended and contracted so that the set angle of the lift arm 37 matches the operating angle of the position lever 29. Further, a three-point link mechanism comprising a top link 39 and left and right lower links 40, 40 is provided at the rear part of the mission case 13, and the working machine 28 can be connected to the rear end part of the link mechanism. In the illustrated example, a rotary work machine is connected.
[0011]
The power transmission configuration of the tractor 10 will be described with reference to FIG.
The rotational power output from the engine 12 is interrupted by the main clutch 45 and input to the forward / reverse switching device 46. Further, an engine rotation sensor 48 is provided on the output shaft 47 of the engine 12 as means for detecting the rotational speed.
The rotational power of the engine 12 input to the forward / reverse switching device 46 is switched to forward rotation or reverse rotation to change the traveling direction of the vehicle. The transmission 15 is appropriately shifted and transmitted to the rear wheel differential mechanism 49. The rotational power output from the auxiliary transmission 15 is also transmitted to the front wheel drive shaft 50.
[0012]
A front wheel drive transmission device 51 is provided on the front wheel drive shaft 50. The front wheel drive transmission device 51 has a constant speed clutch 52 and a double speed clutch 53, and both clutches 52, 53 are configured to be connected according to a command from the controller 21. That is, when the constant speed clutch 52 is connected, the peripheral speed of the front wheels 2 and 2 is substantially the same as the peripheral speed of the rear wheels 16 and 16, and when the double speed clutch 53 is connected, the peripheral speed of the front wheels 2 and 2 is the rear wheel. A small turn is possible with approximately twice the peripheral speed of 16,16. Further, when neither of the clutches 52 and 53 is connected, the tractor 10 is configured to travel in the rear wheel 2WD state. A rear wheel rotation sensor 55 is provided on the input side gear 54 of the front wheel drive transmission device 51, and a front wheel rotation sensor 57 is provided on the output side gear 56. Then, the two-wheel drive state by the rear wheel 16 is performed every certain time during traveling, and the rotational speed of the rear wheel 16 at this time is detected and compared with the rotational speed of the front wheel 2 that rotates due to the impact from the ground (front wheel rotational speed). / Rear wheel rotational speed) to detect the slip state of the tractor 10.
[0013]
Brake disks 59 are provided on the rear wheel drive shafts 58 output from the rear wheel differential mechanism 49 to the left and right. The brake discs 59 are connected to the brake pedals 19 and 19 via a link mechanism independently from each other on the left and right sides, and the brakes are applied by pressing the brake pedals 19 and 19 to apply the brakes. Thereby, in the work on the field, the rear wheel 16 of the tractor 10 can be braked only on one side to facilitate adjacent turning.
[0014]
The power steering device 3 of the tractor 10 will be described with reference to FIG. The power steering device 3 inputs a rotation operation of the steering handle 1 to the steering unit 4 via the steering shaft 60 and the like. Then, the gerotor 62 in the steering unit 4 is rotated according to the rotation of the steering shaft 60, and the hydraulic pressure of the hydraulic pump 8 assists the operating force of the steering handle 1 and flows out of the steering unit 4. It has become. A switching control valve 6 that is an oil amount adjusting means is provided on the circuit lower side of the steering unit 4.
[0015]
This switching control valve 6 has an oil chamber 70 having throttles 65 and 65 and an oil chamber 71 that is not provided with a throttle. Normally, the oil chamber 70 having the throttles 65 and 65 is operated with the steering unit 4. An oil chamber 71 that is located in communication with the hydraulic cylinder 7 and that is not provided with a throttle according to a switching command from the controller 21 is connected to the steering unit 4. In normal times, a part of the pressure oil regulated by the throttles 65 and 65 is released to the branch circuit 5 as a lubricating oil for the main clutch 45. Further, when a switching command is received from the controller 21, the total amount of oil flowing into the control valve 6 is discharged. The switching control valve 6 is urged by a spring 72 so as to switch to the oil chamber 70 having the throttles 65 and 65 as soon as the switching command is stopped. Thereby, even when the switching control valve 6 or the controller 21 is out of order, when the steering handle 1 is turned, the front wheels 2 and 2 are not greatly steered, and the tractor 10 can be steered safely. .
[0016]
Further, a hydraulic cylinder 7, which is a hydraulic actuator that steers the front wheels 2, 2, is provided via a check valve 66 on the lower side of the hydraulic circuit of the switching control valve 6. The piston of the hydraulic cylinder 7 is connected to a knuckle arm 67 that rotates the front wheels 2 and 2 via a connecting rod or the like. The knuckle arm 67 is provided with a front wheel turning angle sensor 22 that detects a rotation angle. Thus, the controller 21 is configured to detect the steering operation speed by calculating a change in the front wheel turning angle within a predetermined time. Reference numeral T denotes a hydraulic tank that also serves as the mission case 13, and R ... denotes a relief valve.
[0017]
As described above, since the hydraulic oil sent from the hydraulic pump 8 is provided in series with the steering unit 4, the switching control valve 6, and the hydraulic cylinder 7 that steers the front wheels 2, 2 in order from the transmission upper side, the switching control valve When 6 is switched to the oil chamber 71 side where the throttles 65 and 65 are not provided, the steering amount of the front wheels 2 and 2 can be greatly changed with respect to the operation amount of the steering wheel 3 as compared with the normal operation. it can. Further, even when the switching control valve 6 is normal or switched, the rotation operation of the steering handle 1 is always transmitted to the front wheels 2 and 2, so that the tractor 10 is unable to be steered. There is no. Moreover, even if the switching control valve 6 breaks down and does not operate in any case, the steering amount of the front wheels 2 is the same regardless of whether the steering handle 1 is rotated to the left or right. Absent.
[0018]
Here, the switching control valve 6 is provided on the lower side of the hydraulic circuit of the steering unit 4, but the switching control valve 6 may be provided on the upper side of the steering unit 4. Since the pressure oil flowing into the steering unit 4 is constant when the switching control valve 6 is provided on the lower side as in this embodiment, the operator's steering operation force is increased regardless of the state of the switching control valve 6. The assisting oil pressure is kept constant, which is preferable in terms of operability of the tractor 10.
[0019]
The turning control will be described. As shown in FIG. 4, the controller 7 has a CPU for processing information of various sensors and switches, a RAM for temporarily storing this information, a ROM for setting this turning control program, and the like. ing.
The input unit includes the control switch 26, brake sensors 20, 20, PTO on / off switch 30, shift position switch 31, potentiometer 32 for position lever 29, lift arm angle sensor 38, engine rotation sensor 48, front wheel rotation. A sensor 57, a rear wheel rotation sensor 55, and a front wheel turning angle sensor 22 are connected.
[0020]
In addition, the output part extends solenoids 33F and 33R of switching control valves for switching PTO excited by turning on / off of the PTO on / off switch 30 to forward rotation and reverse rotation, and a piston of a hydraulic cylinder 36 for lifting and lowering the work implement. The solenoids 41 and 42 of the proportional pressure control valve to be shortened, the solenoids 68 and 69 of the switching control valve for crimping the constant speed and double speed clutches, and the solenoid 9 of the switching control valve for adjusting the pressure oil amount of the steering unit 4 are connected. Provided.
[0021]
The operation of the turning control of the tractor 10 configured as described above will be described based on the flowchart of FIG.
First, when the engine 12 is started with the power system of the tractor 10 turned “ON”, the controller 7 reads the setting state, connection state, or detection state signal of various switches and sensors (STEP 1). Then, it is determined by the front wheel turning angle sensor 22 whether or not the steering speed of the tractor 10 is equal to or higher than a speed assumed to be a sharp turn (STEP 2). In the case of YES, next, whether the control switch 26 is turned on (STEP 3), and whether the shift position switch 31 is off, that is, is “low speed” (STEP 4), the detected value of the engine rotation sensor 48 Is stable at a certain level (STEP 5), and whether the slip is within a certain range (STEP 6). Further, the detection of the brake sensor 20 is determined to determine whether only one of the detected values is equal to or greater than a certain value (STEP 7). When all these determinations are YES, the solenoid 9 of the switching control valve 6 is energized. The switching output is turned off when the determination in STEP 3 to STEP 7 is NO, and these processes are repeated periodically.
[0022]
In STEP 5, by detecting a change in the engine speed, the operation of this control is restrained when the field is extremely uneven or on the road. In addition, by detecting the slip state in STEP 6, the control operation is controlled so that the front wheels 2 and 2 are rapidly cut and the tractor 10 does not fluctuate greatly when the field is very muddy or frozen. ing.
[0023]
FIG. 6 is a diagram showing the relationship between the turning angle (horizontal axis) of the steering handle 1 and the front wheel turning angle (vertical axis) of this turning control. Here, the front wheel steering speed is detected at the position of the dead zone near the front wheel neutral, and when the front wheel steering speed is below a certain level, the front wheels 2 and 2 are locked to the left and right locked positions (about It is configured to steer up to ± 60 degrees. Further, when the front wheel steering speed is equal to or higher than a predetermined value and the condition for switching the switching control valve 6 is satisfied, the front wheels 2 and 2 are steered to the lock position by about one rotation of the steering handle .
As a means for detecting whether or not the engine speed of STEP 5 is stable, an angle sensor for detecting the operation angle is provided at the rotation base of the accelerator lever, and the detected value is kept constant for a certain time. It is good also as a structure which detects whether it exists.
[0024]
Further, the flowchart shown in FIG. 7 is an example in the case where the oil amount adjusting means is constituted by a proportional pressure control valve that always opens a part of the oil passage. Here, in STEP 5, it is detected whether the lift arm angle is equal to or greater than a certain level, and the rise of the work implement 28 is detected. As a result, the control is operated while the work machine 28 is lowered, and this is prevented from being greatly dragged in the lateral direction and being damaged. Further, in STEP 6, the amount of depression of the brake pedal 19 is detected by detecting the angle of the brake sensors 20, 20, and the degree of opening of the proportional pressure control valve is controlled accordingly. That is, when the operator wants to turn rapidly, the brake pedal 19 of the rear wheel 16 on one side is greatly depressed, so that the proportional pressure control valve opens the oil passage according to the operation amount, and the front wheels 2 and 2 can be steered greatly. It is said. Further, when both left and right brake depressions are detected, it is determined that the brake operation is being performed on the road, and the operation of the control is checked .
In STEP 8, the steering angle of the front wheels 2 and 2 is detected in place of the steering operation speed, and when the angle exceeds a certain value, the steering amount of the front wheels 2 and 2 is increased with respect to the operation amount of the steering handle 3. It is possible. As a result, this control is also activated for an elderly or female operator who is not good at rapid steering wheel operation, and labor saving can be achieved.
[0025]
As a means for detecting the raising operation of the working machine 28 in STEP 4, the engine speed is constantly detected, and when this rotation rises rapidly, that is, when the work load is lost, the working machine 28 The rise may be detected indirectly.
In addition, although the code | symbol of the member corresponding to the structure of embodiment is attached | subjected to a claim, this invention is not limited to this embodiment by this code | symbol.
[Brief description of the drawings]
FIG. 1 is a part of a hydraulic circuit of a tractor.
FIG. 2 is an overall side view of the tractor.
FIG. 3 is a diagram showing power transmission of a tractor.
FIG. 4 is a block diagram showing connection of a controller.
FIG. 5 is a flowchart (1) of turning control.
FIG. 6 is a graph showing the relationship between the steering wheel turning angle and the front wheel cutting angle.
FIG. 7 is a flowchart (2) of turning control.
[Brief description of symbols]
1 Steering handle (steering control unit)
2 Front wheels (steering wheels)
3 Power steering device (steering device)
4 Steering unit
5 Shunt circuit
6 Switching control valve
7 Hydraulic cylinder (hydraulic actuator)
8 Hydraulic pump
12 engine
21 Controller (control unit)
22 Front wheel angle sensor
48 Engine rotation sensor

Claims (1)

In a work vehicle having a steering device (3) capable of changing the operation amount of the steering wheel (2) with respect to the operation amount of the steering operation unit (1), the hydraulic oil sent from the hydraulic pump (8) In order from the side, the steering unit (4) that discharges the pressure oil according to the operation direction of the steering operation unit (1), and a part of the pressure oil that flows out from the steering unit (4) The steering wheel (2) is steered through a switching control valve (6) capable of adjusting the flow rate of the oil by switching to a state of branching to the circuit (5) of FIG. It is configured to feed to the hydraulic actuator (7) ,
The vehicle has an engine rotation sensor (48) for detecting the output rotation speed of the engine (12), a shift switch (31) for detecting a shift position for traveling, and a steering angle of the steering wheel (2). A steering wheel turning angle sensor (22) to detect,
The sensor detects a state in which the engine speed is equal to or higher than a predetermined value and the traveling shift position is set to a predetermined low speed position, and further, the steering wheel (2) is operated to be equal to or higher than a predetermined value near neutral. When operated at a speed, a control unit (21) is provided that switches the switching control valve (6) to greatly change the operation amount of the steering wheel (2) relative to the operation amount of the steering operation unit (1). A steering control device for a work vehicle.

Images