JPH05239850A - Preventive method of slip of wheel loader - Google Patents

Abstract

PURPOSE:To avoid a large slip by controlling clutch pressure by detecting a slip from the difference of the number of revolution of left and right driving wheels and releasing the control or clutch pressure to the operation of a working machine, by which the slip is released when the working machine is operated. CONSTITUTION:Detecting signals from an engine revolution detector 2 detecting the number of revolution of an engine 3, a variable-speed position sensor 4 sensing the variable-speed position of a transmission 5, the output revolution detector 6 of the transmission 5, a working-machine operational position sensor 7, driving-wheel revolution detectors 9a, 9b detecting each number of revolution of left and right driving wheels 10a, 10b, and the bottom-pressure detector 11 of a boom cylinder 12 are input to a CPU 13 respectively, and a specified control signal is output to a clutch controller 14. When a slip is detected from the difference of the number of revolution of the left and right driving wheels 10a, 10b, clutch pressure is controlled instantaneously, and the state of the slip is released. The control of clutch pressure is released by the operation of a working machine, by which the slip is released when the working machine is worked, thus quickly returning the state of the slip a normal state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel loader slip prevention method.

[0002]

2. Description of the Related Art A conventional wheel loader slip prevention method is disclosed in Japanese Patent Publication No. 64-4013. This conventional slip prevention method is based on an input signal from a work machine load detection sensor. The slip control device performs information processing, and outputs a work machine control command signal and a vehicle traction force control command signal when a vehicle slip occurs.
The output signal of this causes the working machine to perform a correction operation in the load reducing direction. In addition to the above-mentioned conventional techniques, there is a method of preventing traction control so that a predetermined tire acceleration is obtained as a method for preventing a vehicle starting slip.

[0003]

Of the above-mentioned conventional techniques,
In the former case, work machine control and traction force control are performed at the same time by detecting work machine load and traction force system load, which may cause the work machine to move against the operator's intention or reduce traction force more than necessary. There is a problem that the workability is deteriorated by. On the other hand, slips during wheel loader work occur due to the relationship between load, road surface conditions, and traction force, and it is basically necessary to stop the tire rotation immediately when slip is detected and wait for a change in conditions. The idea is different from the latter case of technology. The engine output control has a slow response, and it takes 0.5 to 1.
It takes 0 seconds and is not effective. After all, the above conventional slip prevention method cannot reliably prevent a large slip such as a side cut that causes a large degree of tire damage, and the operator's skill is unskilled. In the case of slipping on the ground, the slip could not be stopped quickly.

The present invention has been made in view of the above points, and an object of the present invention is to provide a slip prevention method for a wheel loader that can solve the above-mentioned conventional problems.

[0005]

In order to achieve the above object, a method for preventing slippage of a wheel loader according to the present invention detects a slip due to a rotational speed difference between left and right driving wheels and its variation. The clutch pressure is controlled so that the clutch will be in a half-clutch state by the detection, and the slip is detected when the indexing force exceeds the set value, and the bottom pressure of the boom cylinder is set when the work machine is operated. When it exceeds the value and when the engine speed falls below the set value, release the half clutch state,
Further, the excavation resistance during the excavation work is detected, and the clutch pressure control according to the variation of the excavation resistance is performed.

[0006]

[Operation] When slip is detected from the difference in the rotational speeds of the left and right drive wheels, the clutch pressure is immediately controlled, and the slip state is released without reducing the load on the work equipment. Further, the clutch pressure control is released by the operation of the work machine such that the slip is released during the operation of the work machine, and the normal state is quickly restored. Furthermore, the risk of slip is predicted in advance from the fluctuation of the excavation resistance during excavation work, and clutch control is performed according to the degree of danger.

[0007]

EXAMPLES Examples of the present invention will be described with reference to the drawings. In the figure, 1 is a wheel loader, 2 is an engine speed detector for detecting the number of revolutions of the engine 3, 4 is a shift position detector for detecting the shift position of the transmission 5, and 6 is for the transmission 5. An output shaft rotational speed detector for detecting the rotational speed of the output shaft, 7 is a working machine operating position detector such as a limit switch for detecting the operating position of the working machine operating device 8, 9a,
Reference numeral 9b is a left / right drive wheel rotation speed detector that detects the respective rotation speeds of the left and right drive wheels 10a and 10b, and 11 is a bottom pressure detector that detects the pressure in the bottom chamber of the boom cylinder 12. And 13 is each of the above detectors 2, 4, 6, 7, 9
It is a CPU (central control arithmetic unit) which inputs detection signals from a, 9b and 11 and outputs a predetermined control signal to the clutch control device 14. An embodiment of the slip prevention method in the wheel loader as described above will be described based on the flowchart shown in FIG. First, the gear shift position detector 4 detects the gear shift position while the wheel loader 1 is running,
The CPU 13 determines whether or not the traveling direction is forward (step 1). When it is determined in step 1 that the wheel loader 1 is in the forward traveling state, the traction force pressure at that time, the horizontal resistance R _h ,
The vertical resistance R _v is calculated by the CPU 13 from the vehicle weight W, the vehicle speed V, and the road friction resistance μs (step 2). Then, the clutch pressure control according to the vertical resistance is performed based on the calculation result in step 2 (step 3). The clutch pressure P'at this time has a magnitude corresponding to the output torque at this time. That is, assuming that the radius of the drive wheels 10a and 10b is r, the output torque is represented by F · r.
-R is shown by the equation (1), and the target clutch pressure P'is shown by the equation (2).

[0008]

[Equation 1]

The clutch pressure control according to the vertical resistance Rv is performed by the equation (2). Here, μs is a friction coefficient of the road surface, which is an unknown value, but is treated as a constant value in consideration of the actual operating site situation. Then, the traction force F is calculated, and this traction force F is set to a certain set traction force (set traction force) F _o.
(Step 4), and if the result is larger than F _o , then the horizontal resistance R _h is calculated and this horizontal resistance R _h is calculated.
Is compared with the set horizontal resistance _Rho (step 5), and if the result is larger than this, the work implement operating position detector 7
It is detected whether or not the work implement is in operation by a detection signal from the drive wheel 10 (step 6).
The slips a and 10b are detected (step 7). Conditions for this slip detection (half clutch pressure control ON condition)
From the above, forward, F> F _o , R _h > R _ho ,
In addition, the boom is not raised and the tilt is not operated, the average speed of the left and right drive wheels 10a and 10b is equal to or higher than the set value V _o Km / h, the left / right speed ratio is 2 or more, or the left / right speed difference is differentiated. | The set value is α _o | or more. Here, the half-clutch pressure control OFF condition is as follows: (1) The boom bottom pressure is the set value P _BO K when the work machine is operated (boom up, tilt operation).
g / cm ² or more, (2) engine speed is set value E o vp
It is less than or equal to m. Half-clutch control is performed by clutch pressure control according to the conditions at the time of slip detection (step 8). Then, the operator loosens the accelerator to reduce the engine speed, and compares the engine speed with the set value E _o (step 9). Here, when the engine speed is higher than the set value E _o , the operator operates the work machine (step 10), and the half clutch pressure control OFF condition,
That is, when the boom bottom pressure is equal to or higher than the set value and the engine speed is equal to or lower than the set value, the clutch pressure control (half clutch) is turned off (step 11), and the original traveling state is restored. Of the above steps, if No in Steps 4, 5 and 7, the process returns to the front side of Step 1. If Yes in step 6, the process similarly returns to the front side of step 1. Further, in the case of No in step 9, the half clutch in step 11 is turned off. If the work load is small in step 10, the process returns to step 8. From the above, the slip control conditions in the slip prevention method for the wheel loader according to the present invention are (1) left and right drive wheels 10a, 10
Slip is detected from the rotation speed difference of b and its fluctuation,
(2) Engine speed, gear shifting operation, traction force and excavation horizontal resistance from the output shaft rpm of the transmission are equal to or greater than set values, (3) Boom up, tilt, work machine limit switch to work equipment Is to detect that you are not operating. Also, (1) engine speed, gear change of transmission,
Calculate the horizontal excavation resistance from the output shaft speed of the operating transmission,
(2) The vertical excavation resistance is calculated from the horizontal excavation resistance and the boom bottom pressure. When the vertical excavation resistance is large, the slip risk is low. Therefore, when the excavation vertical pressure is high, the slip risk is high. Is large, and therefore the clutch pressure is reduced to perform slip risk predictive clutch control. Further, when the above slip control condition is satisfied, the clutch pressure is set to a half clutch state to prevent slip. Slip control is used when the transmission shifts to a mode other than forward, the engine speed is reduced by the operator's operation, the traction force is reduced, and the boom is raised and tilted to enter the work machine operation state. It will be canceled. The figure shows the speed of the tire when slip is detected, and the horizontal line in the figure shows the slip amount. The figure shows the clutch command pressure P ', and the figure shows the clutch pressure. The clutch command pressure P'is controlled in step 3 according to the magnitude of the vertical resistance Rv, and the vertical resistance Rv constantly detects the bottom pressure of the boom cylinder by the bottom pressure detector 11. Therefore, when the vertical resistance Rv is low as shown in the figure and the risk of slip is high, the reaction immediately occurs when the slip occurs, and the slip detection S ₁ immediately starts the clutch slip S ₂ and the slip amount S ₃
Can be reduced.

[0010]

According to the present invention, it is possible to surely prevent a large slip such as a side cut which causes a great degree of tire damage. In addition, even if the operator's skill is unskilled and a pushing force is applied to the bucket so that the front wheel floats during excavation, the slip can be quickly stopped. Then, the risk of slip can be predicted in advance from fluctuations in excavation resistance during excavation work, and clutch pressure control can be performed according to the degree of danger.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention.

FIG. 2 is a configuration explanatory view showing a wheel loader and each detector.

FIG. 3 is a tire velocity diagram when a slip occurs.

FIG. 4 is a clutch command pressure diagram when a slip occurs.

FIG. 5 is a clutch pressure diagram when a slip occurs.

FIG. 6 is a diagram showing a change in vertical resistance acting on a work machine.

[Explanation of symbols]

1 wheel loader, 2 engine speed detector, 3
Engine, 4 shift position detector, 5 transmission, 6 output shaft rotation speed detector, 7 working machine operating position detector, 8 working machine operating device, 9a, 9b drive wheel rotation speed detector, 10
a, 10b Drive wheel, 11 Bottom pressure detector, 12 Boom cylinder, 13 CPU, 14 Clutch control device.

Claims (1)

[Claims] 1. A slip is detected based on a difference between the rotational speeds of the left and right driving wheels and its variation, and the clutch pressure is controlled so that a half-clutch state is obtained by detecting the slip. The slip is detected by an index force. Occurs when the work machine is operated, the bottom pressure of the boom cylinder exceeds the set value, and the engine speed falls below the set value. A method for preventing slipping of a wheel loader, which comprises releasing, and further detecting excavation resistance during excavation work, and performing clutch pressure control according to fluctuations in the excavation resistance.