Abstract: Correction for compensating for errors caused by the pitching movement of a vehicle is executed with high accuracy at low cost. The ground speed of the vehicle sensed by a Doppler sensor is corrected with angular velocities with respect to the center of gravity of the vehicle. In this correction, the center of rotation of the vehicle and the rotation of the Doppler sensor itself during the pitching movement of the vehicle are taken into account.

Abstract: A dozing system for a bulldozer capable of providing high operational efficiency in dozing operation and a smooth excavation face. If it is determined when operation is performed in an automatic digging mode that the load exerted on the blade is stable, a target position for the cutting edge relative to the ground is corrected to the actual position of the cutting edge at that time. According to the ratio of the amount of excavated soil loaded on the front surface of the blade to the loading capacity of the blade front surface and/or the stability of the load exerted on the blade, a switching is performed between a weight characteristic for the operation amount of the load control and a weight characteristic for the operation amount of the smoothing control.

Abstract: An extensive torsional force exerted on a vehicle body frame due to an operation of blade lift cylinders can be avoided. Determination is made to identify an occurrence condition which causes a torsional force on a vehicle body frame due to an operation of the blade lift cylinders 9. If a condition which causes a torsional force is identified, pressure oil supplied to the blade lift cylinders 9 through a lift control valve 26 is interrupted, thereby stopping the operation of the blade lift cylinders 9. Alternatively, the operation speed of the blade lift cylinders 9 may be reduced by limiting the flow rate of pressure oil supplied to the blade lift cylinders 9.

Abstract: An improved accuracy is ensured for the calculation of the travel distance of a bulldozer by obtaining the accurate vehicle speed and travel direction of the bulldozer. To this end, arrangement is made such that a check is made to determine whether actual tractive force F exerted on the blade exceeds a predetermined shoe slip threshold value F.sub.0 ; switching between vehicle speed detectors (between a Doppler sensor and Sprocket rotating speed detector) is made according to the determination so that suitable one of the vehicle speed detectors detects the vehicle speed of the bulldozer; and the vehicle speed detected by the selected vehicle speed detector is integrated, whereby the travel distance of the bulldozer is calculated.

Abstract: Smooth, effective dumping is achieved by automating. A switching point, at which a carrying mode is switched to a dumping mode during automatic driving in a dozing operation, is set beforehand. A dumping attitude of the blade is also preset for a desired traveling distance of the bulldozer from the switching point to a dumping point. The actual traveling distance of the bulldozer from the switching point is detected, based on which the blade is controlled so as to take the preset attitude.

Abstract: A dozing system that enables automatic control for all kinds of soil properties and less frequently requires manual control intervention. The system is designed such that the blade is lifted or lowered at a start of excavation in dozing operation in an automatic drive mode such that the actual cutting angle .theta. of a blade detected by an actual cutting angle detector becomes coincident with a target cutting angle (maximum cutting angle) .theta..sub.0 preset by a target cutting angle setting device.

Abstract: A tractive force control apparatus and method for preventing a torque converter from being stalled while a working machine is operated during excavation and earth carrying work using a construction machine. In this apparatus, an engine rotational speed sensor (2), a torque converter output shaft rotational speed sensor (4) and a lift combination solenoid valve (12) are connected to a control apparatus. A pilot pressure control valve (11) for a blade lift is connected to a first lift operating valve (13), and also to a second lift operating valve (14) via the lift combination solenoid valve (12). First and second hydraulic pumps (20, 21) and lift cylinders (15, 15) are connected respectively via the first and second lift operating valves (13, 14). A traction output is computed in the control apparatus (16), and, when the traction output is lower than a target level, the lift combination solenoid valve (12) is turned off to reduce a flow rate of oil to the lift cylinders (15, 15).

Abstract: During dozing operation, the amount of earth (i.e., load factor) accumulated on the front face of a blade is automatically detected independently of the operator's perception and, based on the detection, the dozing operation is automatically shifted from digging to carrying. The load factor is calculated by obtaining a horizontal reaction force and a vertical reaction force exerted on the blade during digging and by calculating the ratio of the vertical reaction force to the horizontal reaction force. When the load factor reaches a specified value, the blade is automatically controlled to incline backward to hold the earth.

Abstract: A dozing system for use in a bulldozer, which is capable of performing an automatic dozing operation, according to working conditions and soil properties in the field. In this system, data on the relationships of the actual traveling distance of the bulldozer with actual tractive force exerted on the blade, with the position of the cutting edge of the blade relative to the ground, with the ratio of the amount of excavated soil loaded on the front surface of the blade to the loading capacity of the front surface of the blade, and with the pitch angle of the blade are stored, and based on the stored data, the blade is controlled so as to assume the desired position.

Abstract: A dozing system for use in a bulldozer, having the capability of estimating a loading ratio (the ratio of soil loaded on the blade to the loading capacity of the blade) with high accuracy so that a mode shift from digging to carrying can be stably performed. Data pieces each representing the digging distance of the bulldozer and the associated loading ratio are obtained from n previous dozing operations and stored. The average of the stored data pieces obtained from n operations is calculated and according to the average, data representative of a digging distance and its associated loading ratio obtained from the present dozing operation is compensated.

Abstract: A hydraulic drive system for the pitch cylinders (4A, 4B) of a bulldozer blade apparatus can include (a) main hydraulic pumps (30A, 30B) and an assistant hydraulic pump (31) to make up the assistant hydraulic circuit, (b) variable displacement hydraulic pumps (21A, 21B), or (c) fixed displacement hydraulic pumps (30A, 30B) and a plurality of solenoid selector valves such that the pitch cylinders can be connected in series. The assistant hydraulic pump (31) is connectable to delivery lines of the main hydraulic pumps through an assistant solenoid selector valve (32) which is controlled by an external signal. The blade (10) can be formed so that a line (14) tangential to the lower edge of the curved panel of the blade is inclined rearwardly with respect to the front face (13) of the blade edge member (12). Earth-moving work can be performed by inclining the blade (10) rearwardly by an angle (.theta..sub.

Abstract: A geared steering device (30) selectively operates rightside and leftside driving mechanisms (2,3) of a crawler vehicle (1) for more efficient operation of the crawler vehicle. The geared steering device (30) comprises a power input drive element (33) for inputting a driving power from a prime mover (7), rightside and leftside steering brakes (38R, 38L), rightside and leftside direct-coupled clutches (36, 44), a turn clutch (46), three arrays of planet gear trains (40, 43 and 48), and power output shafts (32R, 32L) coupled to right and leftside steering brake hubs (34R, 34L). A control unit compares an actual steering ratio of a geared steering device (30) with a designated steering ratio, outputs control signals to respective solenoid valves for controlling the direct-coupled clutches, the turn clutch or a steering brake so as to cause the actual steering ratio to approximate the designated steering ratio.