JPH0790879A - Automatic blade raising and lowering control device for motor grader - Google Patents

Abstract

PURPOSE:To prevent digging-up of a road surface caused by a rear wheel slip by reducing a load by raising a blade automatically when rear wheels start to slip since an overload is imposed in finishing and shaping work of the road surface. CONSTITUTION:A car body is made to travel by driving rear wheels 12, and a road surface A is excavated, finished and shaped by a blade 9. Next, when a difference between a target finishing height and a road surface height in the present condition becomes large and excavating resistance of the blade 9 becomes large and a work load of a motor grader becomes large, the rear wheels 12 slip. Next, in this case, since front wheel rotating speed detected by a front wheel rotating speed sensor 19 becomes larger than rear wheel rotating speed detected by a rear wheel rotating speed sensor 20, a controller 15 judges that the rear wheels 12 are slipping. The controller 15 contracts left and right raising and lowering cylinders 3 and 4, and moves the blade 9 upward, and reduces the excavating resistance. Thereby, a rear wheel slip can be prevented, and the finished and shaped road surface can be prevented from being dug up by the rear wheels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic blade raising / lowering control device for automatically raising and lowering a blade of a motor grader which is a leveling finishing machine to a constant height.

[0002]

2. Description of the Related Art For example, a motor grader shown in FIG. 1 is known. That is, the drawbar 2 is swingably supported on the front end of the vehicle body 1, and the drawbar 2 and the vehicle body 1
The left and right elevating cylinders 3 and 4 and the lateral feed cylinder 5 are connected to each other, and a swing circle 6 is swingably provided on the drawbar 2 by a swing hydraulic motor 7. A blade 9 is attached to a bracket 8 of the swing circle 6 as a shift cylinder. The front wheel 11 is tilted to the left and right by a leaning cylinder (not shown), and a rear wheel 12 is provided at the rear end of the vehicle body 1.
To drive. In order to control the operation of the above-described plurality of cylinders and the swing hydraulic motor, the pressure oil discharged from the hydraulic pump is supplied to each cylinder and the swing hydraulic motor by a directional control valve. As a motor grader, there are known a motor grader provided with a scarifier at a front end portion of a vehicle body so as to be vertically movable by a cylinder for the scarifier, and a vehicle body capable of being bent by a steering cylinder.

The above-mentioned motor grader is often used for finishing and shaping a roadbed before concrete paving. The required accuracy for finishing the roadbed before paving is generally required to be finished to an absolute height of ± 10 mm, and the operator controls the directional control valve by utilizing the characteristics of the machine that the motor grader easily smoothes. Although the blade 9 is moved up and down by expanding and contracting the left and right lifting cylinders 3 and 4, the roadbed is finished and shaped to the required finishing accuracy, but this operation is very difficult and difficult, unless it is a skilled operator for more than 10 years. It is said that it cannot be done.

In order to solve this problem, various automatic blade elevating control devices have been proposed which automatically control the blade height to a constant height. This automatic blade lifting control device includes height reference members such as water strings, light projectors, and ultrasonic transmitters installed on the roadbed, and height detection members such as levers, light receivers, and ultrasonic receivers provided on the vehicle body side. And a means for automatically switching the directional control valve according to the detection of the height detecting member, etc., so that the blade height is always kept constant regardless of the vehicle height, position, inclination, behavior, etc. This is a very useful device that solves the conventional difficulty of operation by an operator.

[0005]

SUMMARY OF THE INVENTION Such an automatic blade raising / lowering control device automatically moves a blade based on the difference in height between the height reference member and the height detecting member, that is, the difference between the target finish height and the current road surface height. If the difference between the target finish height and the current road surface height is large, the excavation load by the blades becomes large and the work load of the motor grader becomes large, so that the rear wheels are dusted. In other words, after finishing the road surface, it is not necessary to refill the holes with softened loose soil.
The finished road surface is compacted by the rollers working together with the motor grader, so even if the roadbed material is flatly backfilled on the excavated road surface, compacting with the rollers creates dents due to rolling pressure and flattens it. It's not easy to do.

Therefore, the operator is always careful not to slip the vehicle when the difference between the target finish height and the current road surface height is large, and when the vehicle is about to slip, the vehicle is stopped and the target finish height is set. It is necessary to reset and give a tentative target again to restart the work, but if the tentative target is not appropriate, the vehicle slips again and the work is often redone, resulting in inefficiency and at the same time always being nervous. It was

A device for detecting the slip of the vehicle and controlling the pressing force of the blade has been proposed, but this pressing force control device for the blade lowers the pressure of the lifting cylinder when the vehicle slips to reduce the blade pressure. This device weakens the pressing force, and although this device is effective during snow removal work, it cannot be applied to road surface finishing shaping work.

That is, the above-mentioned blade pressing force control device is used for removing snow by pressing the blade against a hard pavement surface.
It is to prevent the vehicle from slipping by controlling the pressing force of the blade, and the hard pavement surface is the work reference surface for snow removal work, and even if the blade pressing force is changed, the blade against the work reference surface The position does not change. That is, the height of the blade with respect to the work reference plane does not change even if slip control is performed.

On the other hand, at the time of finishing shaping by excavation, the force applied to the blade is not always directed upward, and the shape of the load,
Depending on the size and amount of earth and sand in front of the blade, the blade reaction force can be upward, downward, or horizontal, and the method of detecting the blade pressing force / pulling force (pressure sensor method) can only be used for snow removal work, etc. Not available.

In view of the above, the present invention automatically raises the blade to prevent slippage when the rear wheels start slipping due to overload during road surface finishing and shaping work, thereby preventing overload and preventing storms on the road surface. It is an object of the present invention to provide an automatic blade raising / lowering control device for a motor grader capable of performing the above.

[0011]

In a motor grader in which a front wheel 11 and a rear wheel 12 are provided on a vehicle body 1, and a blade 9 is provided on the vehicle body 1 so as to be vertically movable by left and right lifting cylinders 3 and 4, the blades are installed on a road surface side. The height reference member 13, the height detection member 14 provided on the vehicle body 1 side, and the difference between the target finish height by the height reference member 13 and the current road surface height detected by the height detection member 14 are calculated, And the controller 15 which expands / contracts the left and right lifting cylinders 3 and 4 by the difference so that the blade 9 has a height commensurate with the target finishing height, the front wheel rotation speed sensor 19, the rear wheel rotation speed sensor 20, the front wheel rotation speed and the rear wheel rotation speed. An automatic blade lifting control for a motor grader provided with means for detecting a rear wheel slip based on a difference from the wheel rotation speed and means for lifting the blade 9 by expanding and contracting the left and right lifting cylinders 3 and 4 based on the detection signal. Apparatus.

[0012]

[Operation] When the rear wheel 12 slips, the blade 9 is automatically raised to prevent the rear wheel 12 from slipping, so that the finished and shaped road surface is not dusted by the rear wheel, and evenly finished by the roller after the road surface finish shaping. Can be compacted to

[0013]

[Example] As shown in FIG. 1, a height reference member 13, for example, an ultrasonic transmitter is installed on the road surface A, and a height detection member 14, for example, an ultrasonic receiver is provided on the vehicle body 1 side, for example, the bracket 8. Is provided, and the received signal is the controller 15
Is input to calculate the difference between the target finish height and the current road surface height. The vehicle body 1 is provided with a vehicle body inclination angle sensor 16 for detecting a longitudinal inclination angle of the vehicle body 1, and the turning circle 6 is provided with a blade inclination angle sensor 17 for detecting a lateral inclination angle of the blade 9. The turning hydraulic motor 7 is provided with a blade propulsion angle sensor 18 for detecting an angle in a direction orthogonal to the traveling direction of the blade 9,
The front wheel 11 is provided with a front wheel rotation speed sensor 19, and the rear wheel 12 is provided with a rear wheel rotation speed sensor 20, and detection signals of these sensors are input to the controller 15.

FIG. 3 is a control circuit diagram. The controller 15 receives a blade left raising / lowering signal, a blade right raising / lowering signal, a drawbar left / right lateral feed signal, a turning signal, and a blade left / right moving signal, and An automatic control signal is input from the automatic button 22 and a blade inclination angle signal is input from the blade inclination angle setting device 23, and the controller 15 supplies the pressure oil discharged from the hydraulic pump 24 to each cylinder and the swing hydraulic motor based on the input signal. An electric signal is output to the directional control valve, for example, the solenoid of the proportional solenoid valve 30.

The proportional solenoid valve 30 includes a first proportional solenoid valve 30-1 for supplying pressure oil to the left lift cylinder 3, a second proportional solenoid valve 30-2 for supplying pressure oil to the right lift cylinder 4, and a lateral feed cylinder. A third proportional solenoid valve 30-3 for supplying pressure oil to 5,
Fourth proportional solenoid valve 3 for supplying pressure oil to the shift cylinder 10
0-4, a fifth proportional solenoid valve 30-5 for supplying pressure oil to the swing hydraulic motor 7 is provided, and first to fifth proportional solenoid valves 30-1 to 30-1
By sending an energization signal from the controller 15 to 30-5 and switching it, the pressure oil discharged from the hydraulic pump 24 is transferred to each cylinder,
Supply to the swing hydraulic motor 7. The first to fifth proportional solenoid valves 30-1 to 30-5 are switched by a stroke proportional to the energization amount so that the opening area (supply flow rate) is proportional to the energization amount.

Next, the operation will be described. When the operation lever 21 is operated to input various signals to the controller 15, the solenoid of the solenoid proportional valve 30 is energized based on the input signals to operate each cylinder and the turning hydraulic motor 7. The operation lever 21 is composed of a left-right lift lever, a horizontal feed lever, a blade left-right movement lever, and a turning lever lever.

When an automatic control signal is input from the automatic button 22 and a blade inclination angle is input to the controller 15 from the blade inclination angle setting device 23, the controller 15 causes the first and second solenoid proportional valves 30-1 and 30-2. The solenoid of is energized to expand and contract the left and right lifting cylinders 3 and 4, thereby raising and lowering the blade 9 to a height corresponding to the target finishing height of the blade 9, and at the same time, setting the blade inclination angle to the set blade inclination angle. .

In this state, the rear wheels 12 are driven to drive the vehicle body to excavate the road surface A by the blades 9 for finishing shaping. At this time, when the difference between the target finish height and the current road surface height is large and the excavation resistance of the plate 9 is large and the work load of the motor grader becomes large, the rear wheels 12 slip. When the rear wheel 12 slips, the front wheel rotation speed detected by the front wheel rotation speed sensor 19 becomes smaller than the rear wheel rotation speed detected by the rear wheel rotation speed sensor 20, so that the controller 1
5 judges that the rear wheel 12 is slipping.

That is, unlike the wheel loader and the like, the motor grader has the front wheels 11 as the driven wheels and the vehicle speed can be accurately known, but the rear wheels 12 are the driving wheels and the rear wheels 1 when slipping.
Even if 2 is rotating, it cannot be said that there is a vehicle speed. Taking advantage of this property, it is possible to directly know whether or not the rear wheel 12 is slipping by comparing the rotational speeds of the front wheel 11 and the rear wheel 12.

When the controller 15 determines that the rear wheel is slipping, the solenoids of the first and second proportional solenoid valves 30-1 and 30-2 are energized to contract the left and right lifting cylinders 3 and 4 and move the blade 9 upward. . As a result, the excavation resistance of the blade 9 is reduced and the work load of the motor grader is reduced, so that the rear wheel 12 does not slip and the controller 1
When it is determined that the rear wheel 5 does not slip, the energization of the solenoids of the first and second proportional solenoid valves 30-1 and 30-2 is stopped and the blade 9 is stopped.

Depending on the condition of the road surface A, the blade 9
When the height of the road surface, that is, the height of the current road surface is different from the target finishing height, the controller 15 determines that the blade 9 is high or low according to the received signal of the height detection member 14, and the first and second proportional electromagnetic fields are thereby determined. The solenoids of the valves 30-1 and 30-2 are energized to expand and contract the left and right lifting cylinders 3 and 4 to move the blade 9 up and down, and the received signal of the height detection member 14 determines the current road surface height to be the target finish height. If it coincides with, the energization of the solenoids of the first and second proportional solenoid valves 30-1, 30-2 is stopped and the blade 9 is held at that height.

The vehicle body inclination angle from the vehicle body inclination angle sensor 16 and the blade propulsion angle from the blade propulsion angle sensor 18 are input to the controller 15 to correct the inclination angle control of the blade 9. In other words, the inclination angle of the vehicle body 1 in the front-rear direction and the inclination angle of the blade 9 in the left-right direction differ depending on the propulsion angle of the blade 9, and therefore the blade 9 is corrected based on the detected angle to set the inclination angle of the blade 9.

After the road surface is finished and shaped as described above, it is compacted by the roller, again shaped by the motor grader and compacted by the roller. This operation is repeated a plurality of times to finish and shape the road surface to a predetermined height.

The controller 15 calculates the slip ratio of the rear wheels based on the difference between the front wheel rotation speed and the rear wheel rotation speed, and raises the blade 9 so that the target finishing height is set according to the calculated slip ratio. Alternatively, the original target finishing height may be automatically restored by decreasing the slip ratio.

It is also possible to provide an actuator for stopping the cylinder, decelerating the vehicle speed, or giving a warning when the slip ratio exceeds a certain value, and each function can be simultaneously generated.

In another embodiment, it can be used to prevent slippage during work of a scarifier, ripper, etc. other than a grader blade. Scalifier, ripper, etc. are used to dig up stones embedded in the ground, but when digging up due to the shape of the work machine, the rivers try to dig up stones, etc. Not only will this cause damage to the vehicle and rippers, but also shorten the service life. In addition, it is impossible to prevent slippage by simultaneously inputting a signal to the controller with a potentiometer or the like that knows the depth of the ripper and the scarifier to know the rotation angle of the link.

[0027]

When the rear wheel 12 slips, the blade 9
Is automatically raised to prevent the rear wheel 12 from slipping,
There is no need for the rear wheels to raise the finished road surface,
Rollers can evenly roll after finishing the road surface.

[Brief description of drawings]

FIG. 1 is a front view of a motor grader showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a defect in a conventional example.

FIG. 3 is a control circuit diagram of the present invention.

[Explanation of symbols]

1 ... vehicle body, 3 ... left lifting cylinder, 4 ... right lifting cylinder,
9 ... Blade, 11 ... Front wheel, 12 ... Rear wheel, 13 ... Height reference member, 14 ... Height detection member, 15 ... Controller, 1
9 ... Front wheel rotation sensor, 20 ... Rear wheel rotation sensor.

Claims (1)

[Claims] 1. A motor grader in which a front wheel 11 and a rear wheel 12 are provided on a vehicle body 1, and a blade 9 is provided on the vehicle body 1 so as to be vertically movable by left and right lifting cylinders 3, 4, and a height reference member installed on a road surface side. 13, the height detection member 14 provided on the vehicle body 1 side, and the difference between the target finish height by the height reference member 13 and the current road surface height detected by the height detection member 14 is calculated, and the difference is calculated. A controller 15 for expanding and contracting the left and right lifting cylinders 3, 4 to adjust the blade 9 to a height corresponding to the target finishing height, and a front wheel rotation speed sensor 19
A rear wheel rotation speed sensor 20; a means for detecting a rear wheel slip based on the difference between the front wheel rotation speed and the rear wheel rotation speed; An automatic blade lifting control device for a motor grader, which is provided with a means for lifting.