JPS6056851B2 - Bulldozer plate automatic control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic blade control device for a bulldozer.

Conventionally, a device that automatically controls the blade by detecting overload applied to the blade during pushing up work of construction vehicles, especially bulldozers, detects the rotation speed of one engine and compares the detected value with the set rotation speed. 2. One that detects the overload condition of the engine and performs control; 2. One that detects the load condition from the input/output rotation ratio of the torque converter and performs control; 3.
There is a system that detects the ground speed of the vehicle body using a Doppler radar or the like, and determines the shoe slip of the drive wheels from the ratio of the detected value to the drive wheel speed, detects the load state, and performs control.

However, in the above-mentioned devices 1 and 2, sufficient control cannot be performed when the drive wheels cause shoe slip, and in 3, the load state before the shoe slip cannot be obtained, so the engine stalls ( The engine sometimes stopped. As mentioned above, in conventional devices, the drive wheels may cause shoe slip or the engine stalls, and in such cases, the work must be interrupted, resulting in poor work efficiency.
This invention was made in view of the above-mentioned points, and is a bulldozer blade that can prevent shoe slip of the drive wheels and engine stall, and thus enables efficient blade control without interrupting work due to overload. The aim is to provide an automatic control device.

According to the present invention, in a device that detects an inclination angle of a C frame with respect to a horizontal plane and automatically controls a blade according to a deviation between the detected inclination angle and a preset inclination angle, when an overload state is entered. In other words, the minimum speed at which work can be carried out without causing shoe slips or engine stalling (hereinafter referred to as critical speed) is set in accordance with the soil quality of the work surface and the running characteristics of the vehicle for each speed stage. On the other hand, the vehicle is equipped with a Doppler radar to detect the actual speed of the vehicle, and when the detected speed becomes lower than the critical speed, an overload is detected and the blade is raised.

The present invention will be described in detail below based on an embodiment of the accompanying drawings. In FIG. 1, the blade 3 is attached to a C frame 2 whose one end is rotatably supported on the body 1 of the bulldozer.
It is attached to the tip of the car body 1 and the C frame 2.
The vertical movement is controlled by a pair of lift cylinders 4 disposed between them.

The manual operation valve 5 is for controlling the lift cylinder 4 to be extended (position 5A), retracted (position 5B), held (position 5C), floated (position 5D), etc. according to switching positions 5A to 5D. The cylinder section 6 of the operating cylinder (hereinafter referred to as slave cylinder) 6 is connected via the rod 6a.
The piston rod 6c of the slave cylinder 6 is connected to a manual operation lever 7 for raising and lowering the blade. The locking mechanism 8 is for locking the operating lever 7 during automatic blade control. As will be described later, this locking mechanism 8 is interlocked with a switch 28 for switching between manual and automatic blade control, and when the operating lever 7 is locked, the switch 28 is turned on and unlocked. It is designed to switch to the off state at times. The first solenoid valve 9 and the second solenoid valve 10 are for driving and controlling the slave cylinder 6, and the slave cylinder 6 and the hydraulic pump P2
It is connected to the pressure oil line between the . The switching is controlled accordingly. During blade manual control, the slave cylinders 6 are switched to neutral positions 9C and 10A, respectively, and are hydraulically locked at stroke positions corresponding to the neutral position 5C of the manually operated valve 5, thereby fixing the operating lever 7 and the rod 6a. . Therefore, the operator can manually control the manually operated valve 5 to a predetermined switching position using the operating lever 7. Further, during automatic control, the operation lever 7 is locked by the lock mechanism 8, and therefore the first solenoid valve 9 is in the switching position 9A, 9B.
Accordingly, the cylinder portion 6b of the slave cylinder 6 is driven to expand and contract with respect to the piston rod 6c, and the manually operated valve 5 is controlled to a predetermined switching position. The second solenoid valve 10 is for assisting the manually operated valve 5 to return automatically by the return force of the spring 5E, and when it is switched to the position 10B, the bottom side and head side chambers are connected to the tank. It is directly connected to T3 and allows the slave cylinder 6 to move freely. j The vehicle body inclination angle detector 11 is for detecting the inclination angle of the vehicle body 1 with respect to a reference horizontal plane, and is installed at approximately the center of gravity of the bulldozer vehicle body 1, and outputs a tilt detection signal e1 according to the inclination angle of the vehicle body 1. and is added to the first arithmetic unit 13.

Since the vehicle body inclination angle detector 11 is installed approximately at the center of gravity of the vehicle body 1, it is possible to accurately detect the inclination angle of the vehicle body 1 without being affected by the rotational moment due to the longitudinal inclination of the vehicle body 1. can. The cylinder stroke detector 12 is arranged in parallel with the blade lift cylinder 4, detects the stroke of the cylinder 4, outputs a cylinder stroke detection signal E2, and applies it to the calculator 13.

The computing unit 13 is supplied with vehicle body tilt angle data by the tilt detection signal e1, and is supplied with lift cylinder stroke data by the stroke detection signal E2. Therefore,
The calculator 13 calculates the height of the blade 3 from the horizontal reference plane (
Blade height detection signal E corresponding to C frame inclination)
h is output. The blade height setter 16 is for presetting the height of the blade 3 with respect to the horizontal reference plane, and outputs a blade height setting signal EH according to the setting, and applies it to the second computing unit 14.

The calculator 14 calculates the deviation E1 between the height setting signal EH and the signal Eh except in the case of overload, which will be described later.

In this embodiment, the slave cylinder 6 is driven in accordance with the deviation E1, the valve 5 is switched, and the lift cylinder 4 is driven accordingly. Then, automatic control is performed so that the deviation E, is 01, that is, the current height Eh of the blade 3 matches the set height EH. The pulse control circuit 22 is the arithmetic unit 14
A pulse signal E2 having a pulse width proportional to the magnitude of the deviation signal E1 given from the deviation signal E1 is output.

2A to 2D are timing charts showing examples of the blade height setting signal EH, the blade height detection signal Eh, the deviation signal E1, and the pulse signal E2.

If the sign of the deviation signal E1 is positive, a pulse signal E2 instructing to raise the blade is output, and if it is negative, a pulse signal E2 instructing to lower the blade is output. The spool position detector 29 detects the transition position of the rod 6a of the slave cylinder 6, thereby detecting the spool position of the directional control valve 5 connected to the rod 6a, and outputs a spool position detection signal to the comparator 24. Add.

Comparator 24 connects pulse signal E2 and spool position detector 29
The deviation is compared with the actual spool position signal E7 of the directional control valve 5 detected by the dead band setting device 26.
When the deviation is larger than the dead band width E4 set in , the deviation is added to the logic circuit 25.

The logic circuit 25 outputs control signals E5 and E6 for raising and lowering the blade according to the polarity of the input deviation signal, and applies them to the solenoids 9sa and 9sb of the electromagnetic valve 9. The pulse generator 27 operates when both the control signals E, E6 are 0, that is,
When the manual operation valve 5 is in the neutral position and there is no need to raise or lower the blade 3, a signal E of a predetermined pulse width is generated.
7 to energize the solenoid 10S of the solenoid valve 10,
Switch the solenoid valve 10 to position 10B. As a result, the slave cylinder 6 becomes free, and the return spring 5E of the manually operated valve 5 quickly switches the valve 5 to the neutral position 5C. The changeover switch 28 is for switching the control of the blade 3 between manual and automatic control, and is linked to the locking mechanism 8, and is turned on when the manual operation lever 7 is locked, and the control signals E5, E6, and E7 are switched on. It can be supplied to each solenoid valve switching solenoid.

As a result, the blade 3 is set to a state where automatic control is possible. As described above, when the overload condition has not been reached, automatic control is performed so that the deviation between the blade height setting signal EH and the blade height detection signal Eh becomes O.

Next, control during overload will be explained.

The Doppler radar 23 is arranged on the bulldozer 1 so that its antenna faces the work surface at a predetermined angle.

Then, microwaves are transmitted toward the work surface via the antenna, and by receiving and detecting reflected waves, a frequency signal E3 corresponding to the ground speed of the vehicle is output. The frequency signal E3 is applied to the frequency-to-voltage conversion circuit 17 via the amplifier 15, and is converted into a voltage signal E4 corresponding to the frequency. The critical speed setter 18 is for setting the lower limit value of the critical speed, that is, the speed at which work can be performed without slipping or stalling. In other words, during civil engineering work, when the blade 3 pushes earth and dirt accumulates on the blade 3, the speed of the vehicle decreases due to the resistance, and if the vehicle continues to move forward, it will eventually become overloaded. may cause shoe slip or engine stall. Therefore, in the present invention, the lower limit of the speed at which work can be performed without shoe slipping or engine stalling is determined by the critical speed setting device 1 according to the soil work conditions and the running characteristics of the vehicle 1 for each speed stage used.
8, and when the ground speed of vehicle 1 during work falls below this critical speed, it is assumed that the vehicle is in an overload condition and the blade is raised to prevent shoe slip or engine stall. This is to remove the overload. Here, an example of how to determine the critical speed will be shown.

Consider a case where the running characteristics (relationship between vehicle speed and traction force) of the bulldozer 1 at each speed stage are as shown in FIG. 3, for example.

In this example, it is considered that a traction force exceeding the shoe slip limit is generated only in the first speed, and shoe slip does not occur in other speed stages. Therefore, the critical speed should be set to the speed just before exceeding the shoe slip limit in 1st gear (approximately 1.8 km Ih in this example), and the speed just before engine stall occurs in 2nd and 3rd gears. good. However, if we consider not only to prevent the engine from stalling but also to perform work more efficiently, the critical speed for 2nd and 3rd gears is the speed at which the traction force does not become too small. Moreover, it is better to set the speed at such a speed that the traction force does not become extremely large or small when the gear is down to the lower gear. That is, in the example shown in FIG. 3, the critical speed of the second speed is the intersection point P of the characteristic curve of the first speed and the characteristic curve of the second speed.
2 (approximately 2.3-'h), and the critical speed of the third speed is the speed at the intersection P3 of the characteristic curve of the second speed and the characteristic curve of the third speed (approximately 4.5-1h). And it is sufficient. Determining the critical speed in this way not only makes the work more efficient, but also makes it more economical. In other words, the fuel consumption rate is poor at speeds where the traction force is small and good at speeds where the traction force is large, so if the critical speed is set to the above value, work can be performed at a speed with a good fuel consumption rate. Incidentally, since the traction force at the shoe slip limit differs depending on the soil quality, the traction force may be investigated in advance for each work surface and the critical speed at a speed stage exceeding this traction force may be determined.

The critical speed setter 18 can be configured with one volume, for example, and in that case, the speed scale (not shown) of the setter 18 is marked with an applicable range for each speed stage (this applicable range is indicated at lower speed stages). If you display the lower speed section and the higher speed section for higher speed stages, you can set the critical speed according to the used speed stage with one volume instead of using separate volumes for each speed stage. can do.

A signal E5 having a magnitude corresponding to the critical speed output from the critical speed setter 18 and a signal E4 having a magnitude corresponding to the ground speed output from the frequency-to-voltage conversion circuit 17 are input to the comparator 19.

The comparator 19 outputs a signal E4 when the ground speed is lower than the critical speed.
, e, becomes E4 × E, that is, blade 3
When overload occurs, an overload signal E6 is output. This overload signal E6 is integrated by an integrator 20, and then applied to a clipper circuit 21, where the upper limit is cut off at a certain level, and is passed through a gate circuit 30 to an arithmetic unit 1 as an overload signal E8.
Join 4. When the computing unit 14 is not in an overload state, it outputs the deviation E1 between the blade height setting signal EH and the blade height detection signal Eh as described above, but when the above-mentioned overload signal E8 is added, the blade height The value obtained by adding the overload signal E8 to the setting signal E8 is set as the blade height setting value (EH
+E8), and as a result, the arithmetic unit 14. The deviation signal E1 outputted from the sensor becomes larger by the value indicated by the signal E8.

Therefore, the solenoid valve 9 is switched to position 9A, the rod 6a of the cylinder 6 is retracted in the direction shown by arrow A, and the solenoid valve 5 is switched to position 5.
B, the lift cylinder 4 is retracted, the blade 3 is raised, and the overload is removed. When the overload is removed, the overload signal E8 is no longer output, so the blade 3
decreases until the blade height setting signal EH and the blade height detection signal Eh become the same value. Clip circuit 21
The gate circuit 30 provided between the and the arithmetic unit 14 is
When the driving force applied to the drive wheels of the vehicle 1 exceeds a predetermined value, that is, when the accelerator (or throttle) is depressed (open) by a predetermined amount or more, conduction occurs and an overload signal is generated. can be input to the calculator 14, and when the driving force is less than a predetermined value, that is, the amount of accelerator depression (throttle opening) is less than a predetermined amount, it becomes a non-conducting state and the overload signal E8 is not applied to the calculator 14. That's what I do. This is to prevent the blade lifting operation from being performed when the vehicle speed is low based on a speed command from an accelerator pedal or the like (that is, not due to overload). As explained above, according to the present invention, the speed at which the bulldozer enters the overload state is set according to the soil quality and the running characteristics of the vehicle for each speed stage, and the actual speed of the vehicle is set as above. Since the blade is raised when the speed becomes lower than the set speed, shoe slips and engine stalls can be prevented, and dozing work can be carried out with high efficiency.

Furthermore, in the speed setting described above, one setter can be shared by all speed stages instead of using a separate setter for each speed stage, which has the effect of simplifying the setting operation. Furthermore, since the load can be removed before an overload is applied, the vehicle is not strained, and dozing work can be carried out with good fuel efficiency, so it is economical.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a timing chart explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is a graph showing the running characteristics of the vehicle.

Claims (1)

[Scope of Claims] 1. Blade state quantity setting means for setting the state quantity of the blade relative to the horizontal plane, blade state quantity detection means detecting the state quantity of the blade relative to the horizontal plane, the set state quantity of the blade and the detection means. a control means for raising and lowering the blade based on the deviation of the state quantity of the blade, a speed detection means for detecting the ground speed of the vehicle, and a speed setting for setting a predetermined minimum speed corresponding to each speed stage of the vehicle. means for comparing the detected ground speed with the set speed corresponding to the current speed range of the vehicle, and superimposing a signal on the deviation to raise the blade when the ground speed becomes smaller than the set speed; A bulldozer blade automatic control device comprising means. 2. The bulldozer blade automatic control device according to claim 1, wherein the state quantity of the blade is the height of the blade with respect to a horizontal plane. 3. The bulldozer blade automatic control device according to claim 1, wherein the state quantity of the blade is an inclination angle of a C frame to which the blade is attached with respect to a horizontal plane.